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Sample records for 234u 235u 236u

  1. Determination of 234U/238U, 235U/238U and 236U/238U isotope ratios in urine using sector field inductively coupled plasma mass spectrometry.

    PubMed

    Xiao, Ge; Jones, Robert L; Saunders, David; Caldwell, Kathleen L

    2014-12-01

    Quantification of the isotopic composition of uranium in urine at low levels of concentration is important for assessing both military and civilian populations' exposures to uranium. However, until now there has been no convenient, precise method established for rapid determination of multiple uranium isotope ratios. Here, the authors report a new method to measure (234)U/(238)U, (235)U/(238)U and (236)U/(238)U. It uses solid-phase chelation extraction (via TRU columns) of actinides from the urine matrix, followed by measurement using a magnetic sector field inductively coupled plasma mass spectrometer (SF-ICP-MS-Thermo Element XR) equipped with a high-efficiency nebulizer (Apex PFA microflow) and coupled with a membrane desolvating nebulizer system (Aridus II™). This method provides rapid and reliable results and has been used successfully to analyse Certified Reference Materials. PMID:24563523

  2. Neutron Capture Cross Sections of 236U and 234U

    NASA Astrophysics Data System (ADS)

    Rundberg, R. S.; Bredeweg, T. A.; Bond, E. M.; Haight, R. C.; Hunt, L. F.; Kronenberg, A.; O'Donnell, J. M.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2006-03-01

    Accurate neutron capture cross sections of the actinide elements at neutron energies up to 1 MeV are needed to better interpret archived nuclear test data, for post-detonation nuclear attribution, and the Advanced Fuel Cycle Initiative. The Detector for Advance Neutron Capture Experiments, DANCE, has unique capabilities that allow the differentiation of capture gamma rays from fission gamma rays and background gamma rays from scattered neutrons captured by barium isotopes in the barium fluoride scintillators. The DANCE array has a high granularity, 160 scintillators, high efficiency, and nearly 4-π solid angle. Through the use of cuts in cluster multiplicity and calorimetric energy the capture gamma-rays are differentiated from other sources of gamma rays. The preliminary results for the capture cross sections of 236U are in agreement with the ENDF/B-VI evaluation. The preliminary results for 234U lower are than ENDF/B-VI evaluation and are closer to older evaluations.

  3. Neutron Capture Cross Sections of 236U and 234U

    SciTech Connect

    Rundberg, R. S.; Bredeweg, T. A.; Bond, E. M.; Haight, R. C.; Hunt, L. F.; O'Donnell, J. M.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Kronenberg, A.

    2006-03-13

    Accurate neutron capture cross sections of the actinide elements at neutron energies up to 1 MeV are needed to better interpret archived nuclear test data, for post-detonation nuclear attribution, and the Advanced Fuel Cycle Initiative. The Detector for Advance Neutron Capture Experiments, DANCE, has unique capabilities that allow the differentiation of capture gamma rays from fission gamma rays and background gamma rays from scattered neutrons captured by barium isotopes in the barium fluoride scintillators. The DANCE array has a high granularity, 160 scintillators, high efficiency, and nearly 4-{pi} solid angle. Through the use of cuts in cluster multiplicity and calorimetric energy the capture gamma-rays are differentiated from other sources of gamma rays. The preliminary results for the capture cross sections of 236U are in agreement with the ENDF/B-VI evaluation. The preliminary results for 234U lower are than ENDF/B-VI evaluation and are closer to older evaluations.

  4. Neutron-induced fission cross section measurements for uranium isotopes 236U and 234U at LANSCE

    NASA Astrophysics Data System (ADS)

    Laptev, A. B.; Tovesson, F.; Hill, T. S.

    2013-04-01

    A well established program of neutron-induced fission cross section measurement at Los Alamos Neutron Science Center (LANSCE) is supporting the Fuel Cycle Research program (FC R&D). The incident neutron energy range spans from sub-thermal up to 200 MeV by combining two LANSCE facilities, the Lujan Center and the Weapons Neutron Research facility (WNR). The time-of-flight method is implemented to measure the incident neutron energy. A parallel-plate fission ionization chamber was used as a fission fragment detector. The event rate ratio between the investigated foil and a standard 235U foil is converted into a fission cross section ratio. In addition to previously measured data new measurements include 236U data which is being analyzed, and 234U data acquired in the 2011-2012 LANSCE run cycle. The new data complete the full suite of Uranium isotopes which were investigated with this experimental approach. Obtained data are presented in comparison with existing evaluations and previous data.

  5. IUPAC-IUGS status report on the half-lives of 238U, 235U and 234U

    NASA Astrophysics Data System (ADS)

    Villa, I. M.; Bonardi, M. L.; De Bièvre, P.; Holden, N. E.; Renne, P. R.

    2016-01-01

    The current state of knowledge on the half-lives of the long-lived U radionuclides has been reviewed by the IUPAC-IUGS joint Task Group "Isotopes in Geosciences". 238U is assigned a half-life of (4.4683 ± 0.0096) Ga, i.e. a decay constant λ238 = (0.155125 ± 0.000333) Ga-1. The coverage factor is k = 2 for this and all other estimates presented here. The 238U half-life can be used as a reference for the half-lives/decay constants of all other isotopic geochronometers. A revision of the half-life of 235U based on intercomparison of natural geological samples is premature. The improved repeatability of mass spectrometric measurements has revealed Type B uncertainties that had been dismissed as subordinate in the past. The combined uncertainty of these as yet incompletely charted and quantified sources of Type B uncertainty may be no smaller than the currently accepted uncertainty of the α counting experiments. A provisional value for the 234U half-life can be calculated with the assumption of secular equilibrium in the analyzed natural samples. This assumption has not yet been verified independently and its metrological traceability appears sub-optimum. A Type B evaluation suggests that the ca. 0.17% offset between the N(234U)/N(238U) number-ratios of the natural samples used to estimate the 235U half-life and those of the four samples used to estimate the 234U half-life should be compounded into the standard measurement uncertainty of the latter. The resulting provisional uncertainty interval (k = 2) for the 234U half-life is (244.55-247.77) ka, corresponding to λ234 = (2.8203-2.8344) Ma-1.

  6. 206Pb-230Th-234U-238U and 207Pb-235U geochronology of Quaternary opal, Yucca Mountain, Nevada

    USGS Publications Warehouse

    Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.

    2000-01-01

    U–Th–Pb isotopic systems have been studied in submillimeter-thick outermost layers of Quaternary opal occurring in calcite–silica fracture and cavity coatings within Tertiary tuffs at Yucca Mountain, Nevada, USA. These coatings preserve a record of paleohydrologic conditions at this site, which is being evaluated as a potential high-level nuclear waste repository. The opal precipitated from groundwater is variably enriched in 234U (measured 234U/238U activity ratio 1.124–6.179) and has high U (30–313 ppm), low Th (0.008–3.7 ppm), and low common Pb concentrations (measured 206Pb/204Pb up to 11,370). It has been demonstrated that the laboratory acid treatment used in this study to clean sample surfaces and to remove adherent calcite, did not disturb U–Th–Pb isotopic systems in opal. The opal ages calculated from 206Pb∗/238U and 207Pb∗/235U ratios display strong reverse discordance because of excess radiogenic 206Pb∗ derived from the elevated initial 234U. The data are best interpreted using projections of a new four-dimensional concordia diagram defined by 206Pb∗/238U, 207Pb∗/235U, 234U/238Uactivity, and 230Th/238Uactivity. Ages and initial 234U/238U activity ratios have been calculated using different projections of this diagram and tested for concordance. The data are discordant, that is observed 207Pb∗/235U ages of 170 ± 32 (2σ) to 1772 ± 40 ka are systematically older than 230Th/U ages of 34.1 ± 0.6 to 452 ± 32 ka. The age discordance is not a result of migration of uranium and its decay products under the open system conditions, but a consequence of noninstantaneous growth of opal. Combined U–Pb and 230Th/U ages support the model of slow mineral deposition at the rates of millimeters per million years resulting in layering on a scale too fine for mechanical sampling. In this case, U–Pb ages provide more accurate estimates of the average age for mixed multiage samples than 230Th/U ages, because ages based on shorter

  7. Analysis of prompt fission neutrons in 235U(nth,f) and fission fragment distributions for the thermal neutron induced fission of 234U

    NASA Astrophysics Data System (ADS)

    Al-Adili, A.; Tarrío, D.; Hambsch, F.-J.; Göök, A.; Jansson, K.; Solders, A.; Rakopoulos, V.; Gustafsson, C.; Lantz, M.; Mattera, A.; Oberstedt, S.; Prokofiev, A. V.; Vidali, M.; Österlund, M.; Pomp, S.

    2016-06-01

    This paper presents the ongoing analysis of two fission experiments. Both projects are part of the collaboration between the nuclear reactions group at Uppsala and the JRC-IRMM. The first experiment deals with the prompt fission neutron multiplicity in the thermal neutron induced fission of 235U(n,f). The second, on the fission fragment properties in the thermal fission of 234U(n,f). The prompt fission neutron multiplicity has been measured at the JRC-IRMM using two liquid scintillators in coincidence with an ionization chamber. The first experimental campaign focused on 235U(nth,f) whereas a second experimental campaign is foreseen later for the same reaction at 5.5 MeV. The goal is to investigate how the so-called sawtooth shape changes as a function of fragment mass and excitation energy. Some harsh experimental conditions were experienced due to the large radiation background. The solution to this will be discussed along with preliminary results. In addition, the analysis of thermal neutron induced fission of 234U(n,f) will be discussed. Currently analysis of data is ongoing, originally taken at the ILL reactor. The experiment is of particular interest since no measurement exist of the mass and energy distributions for this system at thermal energies. One main problem encountered during analysis was the huge background of 235U(nth,f). Despite the negligible isotopic traces in the sample, the cross section difference is enormous. Solution to this parasitic background will be highlighted.

  8. Uranium ((234)U, (235)U and (238)U) contamination of the environment surrounding phosphogypsum waste heap in Wiślinka (northern Poland).

    PubMed

    Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

    2015-08-01

    The aim of this work was to determine the uranium concentration ((234)U, (235)U and (238)U) and values of the activity ratio (234)U/(238)U in soil samples collected near phosphogypsum waste heap in Wiślinka (northern Poland). On the basis of the studies it was found that the values of the (234)U/(238)U activity ratio in the analyzed soils collected in the vicinity of phosphogypsum dump in Wiślinka are in most cases close to one and indicate the phosphogypsum origin of the analyzed nuclides. The obtained results of uranium concentrations are however much lower than in previous years before closing of the phosphogypsum stockpile. After this process and covering the phosphogypsum stockpile in Wiślinka with sewage sludge, phosphogypsum particles are successfully immobilized. In the light of the results the use of phosphate fertilizers seems to be a major problem. Prolonged and heavy rains can cause leaching accumulated uranium isotopes in the phosphogypsum stockpile, which will be washed into the Martwa Wisła and on the fields in the immediate vicinity of this storage.

  9. Uranium ((234)U, (235)U and (238)U) contamination of the environment surrounding phosphogypsum waste heap in Wiślinka (northern Poland).

    PubMed

    Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

    2015-08-01

    The aim of this work was to determine the uranium concentration ((234)U, (235)U and (238)U) and values of the activity ratio (234)U/(238)U in soil samples collected near phosphogypsum waste heap in Wiślinka (northern Poland). On the basis of the studies it was found that the values of the (234)U/(238)U activity ratio in the analyzed soils collected in the vicinity of phosphogypsum dump in Wiślinka are in most cases close to one and indicate the phosphogypsum origin of the analyzed nuclides. The obtained results of uranium concentrations are however much lower than in previous years before closing of the phosphogypsum stockpile. After this process and covering the phosphogypsum stockpile in Wiślinka with sewage sludge, phosphogypsum particles are successfully immobilized. In the light of the results the use of phosphate fertilizers seems to be a major problem. Prolonged and heavy rains can cause leaching accumulated uranium isotopes in the phosphogypsum stockpile, which will be washed into the Martwa Wisła and on the fields in the immediate vicinity of this storage. PMID:25913057

  10. Ground water contamination with (238)U, (234)U, (235)U, (226)Ra and (210)Pb from past uranium mining: cove wash, Arizona.

    PubMed

    Dias da Cunha, Kenya Moore; Henderson, Helenes; Thomson, Bruce M; Hecht, Adam A

    2014-06-01

    The objectives of the study are to present a critical review of the (238)U, (234)U, (235)U, (226)Ra and (210)Pb levels in water samples from the EPA studies (U.S. EPA in Abandoned uranium mines and the Navajo Nation: Red Valley chapter screening assessment report. Region 9 Superfund Program, San Francisco, 2004, Abandoned uranium mines and the Navajo Nation: Northern aum region screening assessment report. Region 9 Superfund Program, San Francisco, 2006, Health and environmental impacts of uranium contamination, 5-year plan. Region 9 Superfund Program, San Franciso, 2008) and the dose assessment for the population due to ingestion of water containing (238)U and (234)U. The water quality data were taken from Sect. "Data analysis" of the published report, titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah-Navajo Lands 1994-2000, Project Atlas. Total uranium concentration was above the maximum concentration level for drinking water (7.410-1 Bq/L) in 19 % of the water samples, while (238)U and (234)U concentrations were above in 14 and 17 % of the water samples, respectively. (226)Ra and (210)Pb concentrations in water samples were in the range of 3.7 × 10(-1) to 5.55 × 102 Bq/L and 1.11 to 4.33 × 102 Bq/L, respectively. For only two samples, the (226)Ra concentrations exceeded the MCL for total Ra for drinking water (0.185 Bq/L). However, the (210)Pb/(226)Ra ratios varied from 0.11 to 47.00, and ratios above 1.00 were observed in 71 % of the samples. Secular equilibrium of the natural uranium series was not observed in the data record for most of the water samples. Moreover, the (235)U/(total)U mass ratios ranged from 0.06 to 5.9 %, and the natural mass ratio of (235)U to (total)U (0.72 %) was observed in only 16 % of the water samples, ratios above or below the natural ratio could not be explained based on data reported by U.S. EPA. In addition, statistical evaluations showed no correlations among the distribution of the radionuclide concentrations

  11. Occurrence of natural radioactivity in public water supplies in Germany: (238)U, (234)U, (235)U, (228)RA, (226)RA, (222)RN, (210)PB, (210)PO and gross alpha activity concentrations.

    PubMed

    Beyermann, M; Bünger, T; Schmidt, K; Obrikat, D

    2010-09-01

    The Federal Office for Radiation Protection performed a representative survey on the radiological quality of drinking water in Germany. The aim of this study was to determine regional variations of natural radionuclide concentrations and to estimate radiation exposures caused by drinking water consumption. The study includes analyses of the natural radionuclides (238)U, (234)U, (235)U, (228)Ra, (226)Ra, (222)Rn, (210)Pb, (210)Po and of gross alpha activity concentrations in drinking water from 564 public water supplies. This represents 3 % of all German water supplies providing about 37 Mio. inhabitants. Results on ranges, medians and distributions of radionuclide concentrations of drinking water as well as age-dependent ingestion and inhalation doses estimated for members of the public are presented. Generally, the dose due to uranium isotopes is negligibly low. Radiation exposures are predominantly caused by (222)Rn, (228)Ra, (210)Po and (210)Pb. The ingestion dose deduced for adults (>17 a) and infants (0-1 a) is dominated by (222)Rn and (228)Ra, respectively. A gross alpha activity analysis procedure using liquid scintillation counting has been tested. Measured gross alpha activities values were found to be well related to the summarised activities of (238)U, (234)U, (226)Ra and (210)Po.

  12. Fission cross sections of some thorium, uranium, neptunium and plutonium isotopes relative to /sup 235/U

    SciTech Connect

    Meadows, J W

    1983-10-01

    Earlier results from the measurements, at this Laboratory, of the fission cross sections of /sup 230/Th, /sup 232/Th, /sup 233/U, /sup 234/U, /sup 236/U, /sup 238/U, /sup 237/Np, /sup 239/Pu, /sup 240/Pu, and /sup 242/Pu relative to /sup 235/U are reviewed with revisions to include changes in data processing procedures, alpha half lives and thermal fission cross sections. Some new data have also been included. The current experimental methods and procedures and the sample assay methods are described in detail and the sources of error are presented in a systematic manner. 38 references.

  13. Isotopic composition ( 238U/ 235U) of some commonly used uranium reference materials

    NASA Astrophysics Data System (ADS)

    Condon, Daniel J.; McLean, Noah; Noble, Stephen R.; Bowring, Samuel A.

    2010-12-01

    We have determined 238U/ 235U ratios for a suite of commonly used natural (CRM 112a, SRM 950a, and HU-1) and synthetic (IRMM 184 and CRM U500) uranium reference materials by thermal ionisation mass-spectrometry (TIMS) using the IRMM 3636 233U- 236U double spike to accurately correct for mass fractionation. Total uncertainty on the 238U/ 235U determinations is estimated to be <0.02% (2σ). These natural 238U/ 235U values are different from the widely used 'consensus' value (137.88), with each standard having lower 238U/ 235U values by up to 0.08%. The 238U/ 235U ratio determined for CRM U500 and IRMM 184 are within error of their certified values; however, the total uncertainty for CRM U500 is substantially reduced (from 0.1% to 0.02%). These reference materials are commonly used to assess mass-spectrometer performance and accuracy, calibrate isotope tracers employed in U, U-Th and U-Pb isotopic studies, and as a reference for terrestrial and meteoritic 238U/ 235U variations. These new 238U/ 235U values will thus provide greater accuracy and reduced uncertainty for a wide variety of isotopic determinations.

  14. Geochemistry of speleothem records from southern Illinois: Development of (234U)/(238U) as a proxy for paleoprecipitation

    USGS Publications Warehouse

    Zhou, Juanzuo; Lundstrom, C.C.; Fouke, B.; Panno, S.; Hackley, K.; Curry, B.

    2005-01-01

    Natural waters universally show fractionation of uranium series (U-series) parent-daughter pairs, with the disequilibrium between 234U and 238U (234U)/(238U) commonly used as a tracer of groundwater flow. Because speleothems provide a temporal record of geochemical variations in groundwater precipitating calcite, (234U)/(238U) variations in speleothems provide a unique method of investigating water-rock interaction processes over millennium time scales. We present high precision Thermal Ionization Mass Spectrometric (TIMS) U-series analyses of speleothems and drip waters from Fogelpole Cave in southern Illinois. Data from all speleothems from the cave show an inverse correlation between (234U)/(238U) and U concentration, following the pattern observed in groundwaters globally. Within a 65-cm-long stalagmite, concordant 234U-238 U-230Th and 235U-231Pa ages for 5 samples indicate accurate chronology from 78.5 ka to 30 ka. Notably, (234U)/(238U)o which differs from most speleothems by having (234U)/(238U)o <1, positively correlates with speleothem growth rate. We generalize this to the observation that speleothems globally show (234U)/ (238U)o deviating farther from secular equilibrium at lower growth rates and approaching secular equilibrium at higher grow rates. Based on the Fogelpole observations, we suggest that groundwater (234U)/(238U) is controlled by the U oxidation state, the U concentration of the water and the fluid velocity. A transport model whereby U-series nuclides react and exchange with mineral surfaces can reproduce the observed trend between growth rate and (234U)/(238U)o. Based on this result, we suggest that (234U)/(238U)o in speleothems may record changes in hydrologic flux with time and thus could provide a useful proxy for long term records of paleoprecipitation. ?? 2005 Elsevier B.V. All rights reserved.

  15. Fissile Nuclei Rotation Effect in 235U(n,γf) Process

    NASA Astrophysics Data System (ADS)

    Danilyan, Gevorg; Granz, Peter; Klenke, Jens; Krakhotin, Vyacheslav; Kuznetsov, Valery; Mezei, Ferenz; Novitsky, Vadim; Pavlov, Valery; Russina, Margarita; Shatalov, Pavel; Wilpert, Thomas

    2009-01-01

    A small shift of an angular distribution of prompt γ-rays relative to the fission axis of 236U* 235U(n,γf) process is presented. This effect has been observed in the experiment at BER-II reactor of BENSC/HMI (Berlin). The sign of the shift depends on the direction of the incident neutron beam polarization. This phenomena can be explained by the rotation of fissile nucleus 236U*, like the effect that has been observed recently at ILL in ternary fission of 235U by cold polarized neutrons. The main surprise of this result is the detection of scission gamma-rays radiated by a fissile nucleus during the time interval of the order of 10-21 s before or after the moment of the neck rupture. Detailed measurements of trigger γ-rays energy dependence are in progress at the neutron beam "MEPHISTO" of FRM-II reactor (Garching).

  16. A laboratory study of the transfer of 234U and 238U during water-rock interactions in the Carnmenellis granite (Cornwall, England) and implications for the interpretation of field data.

    PubMed

    Bonotto, D M; Andrews, J N; Darbyshire, D P

    2001-06-01

    Laboratory time-scale experiments were conducted on gravels from the Carnmenellis granite, Cornwall, England, with the purpose of evaluating the release of natural uranium isotopes to the water phase. The implications of these results for the production of enhanced 234U/235U activity ratios in Cornish groundwaters are discussed. It is suggested that the 234U/238U lab data can be used to interpret activity ratios from Cornwall, even when the observed inverse relationship between dissolved U and 234U/235U in leachates/etchates is taken into account.

  17. Natural Isotopic Fractionation of 238U/235U in the Water Column of the Black Sea

    NASA Astrophysics Data System (ADS)

    Romaniello, S. J.; Brennecka, G.; Anbar, A. D.; Colman, A. S.

    2009-12-01

    The natural fractionation of long-lived uranium isotopes (238U, 235U) is being explored as a paleoredox proxy. While uranium behaves conservatively in oxic seawater, it is readily removed to sediments under reducing conditions. Measurements of δ238/235U in black shales and marine sediments deposited under sulfidic conditions suggest that uranium removed in such environments is isotopically heavy. However, this fractionation process has not been directly demonstrated in a present-day marine environment, nor is the specific mechanism of fractionation known. The euxinic water column of the Black Sea provides an ideal laboratory for studying uranium isotope fractionation. Uranium in Black Sea sediments is 0.35-0.84‰ heavy in δ238/235U relative to open ocean seawater (Weyer et al. 2008). We therefore expect that dissolved uranium in the Black Sea water column should be correspondingly light. Furthermore, direct measurements of δ238/235U versus depth could be used in combination with sediment δ238/235U to infer the dominant locations of U removal and constrain specific mechanisms of fractionation. Here we present the first δ238/235U depth profile from the water column of the Black Sea. The measurements were made on a Neptune MC-ICP-MS, using a 236U-233U double spike to correct for instrumental mass bias, following preconcentration and purification with UTEVA resin. With this method, we are able to measure δ238/235U with a 2σ precision of 0.07‰ on 100 ng samples. Our results show that δ238/235U decreases monotonically with depth (Fig. 1). At the surface, δ238/235U values are similar to those in the open ocean. At 2000m, δ238/235U is 0.28‰ lighter than open ocean seawater, while uranium concentrations are depleted by ~44% relative to conservative mixing. As expected, δ238/235U in the water column is always lighter than the underlying sediments, confirming that 238U is preferentially removed to marine sediments under sulfidic conditions. Fig 1. (left) Depth

  18. Remeasurement of (234)U Half-Life.

    PubMed

    Varga, Zsolt; Nicholl, Adrian; Wallenius, Maria; Mayer, Klaus

    2016-03-01

    The half-life of (234)U has been measured using a novel approach. In this method, a uranium material was chemically purified from its thorium decay product at a well-known time. The ingrowth of the (230)Th daughter product in the material was followed by measuring the accumulated (230)Th daughter product relative to its parent (234)U nuclide using inductively coupled plasma mass spectrometry. Then, the (234)U decay constant and the respective half-life could be calculated using the radioactive decay equations based on the n((230)Th)/n((234)U) amount ratio. The obtained (234)U half-life is 244 900 ± 670 years (k = 1), which is in good agreement with the previously reported results in the literature with comparable uncertainty. The main advantages of the proposed method are that it does not require the assumption of secular equilibrium between (234)U and (238)U. Moreover, the calculation is independent from the (238)U half-life value and its uncertainty. The suggested methodology can also be applied for the remeasurement of the half-lives of several other long-lived radionuclides. PMID:26823129

  19. Natural fractionation of 238U/235U

    NASA Astrophysics Data System (ADS)

    Weyer, S.; Anbar, A. D.; Gerdes, A.; Gordon, G. W.; Algeo, T. J.; Boyle, E. A.

    2008-01-01

    The isotopic composition of U in nature is generally assumed to be invariant. Here, we report variations of the 238U/235U isotope ratio in natural samples (basalts, granites, seawater, corals, black shales, suboxic sediments, ferromanganese crusts/nodules and BIFs) of ∼1.3‰, exceeding by far the analytical precision of our method (≈0.06‰, 2SD). U isotopes were analyzed with MC-ICP-MS using a mixed 236U-233U isotopic tracer (double spike) to correct for isotope fractionation during sample purification and instrumental mass bias. The largest isotope variations found in our survey are between oxidized and reduced depositional environments, with seawater and suboxic sediments falling in between. Light U isotope compositions (relative to SRM-950a) were observed for manganese crusts from the Atlantic and Pacific oceans, which display δ238U of -0.54‰ to -0.62‰ and for three of four analyzed Banded Iron Formations, which have δ238U of -0.89‰, -0.72‰ and -0.70‰, respectively. High δ238U values are observed for black shales from the Black Sea (unit-I and unit-II) and three Kupferschiefer samples (Germany), which display δ238U of -0.06‰ to +0.43‰. Also, suboxic sediments have slightly elevated δ238U (-0.41‰ to -0.16‰) compared to seawater, which has δ238U of -0.41 ± 0.03‰. Granites define a range of δ238U between -0.20‰ and -0.46‰, but all analyzed basalts are identical within uncertainties and slightly lighter than seawater (δ238U = -0.29‰). Our findings imply that U isotope fractionation occurs in both oxic (manganese crusts) and suboxic to euxinic environments with opposite directions. In the first case, we hypothesize that this fractionation results from adsorption of U to ferromanganese oxides, as is the case for Mo and possibly Tl isotopes. In the second case, reduction of soluble UVI to insoluble UIV probably results in fractionation toward heavy U isotope compositions relative to seawater. These findings imply that variable

  20. Relative {sup 235}U(n,{gamma}) and (n,f) cross sections from {sup 235}U(d,p{gamma}) and (d,pf)

    SciTech Connect

    Allmond, J.M.; Bernstein, L.A.; Beausang, C.W.; Phair, L.; Bleuel, D.L.; Burke, J.T.; Escher, J.E.; Evans, K.E.; Goldblum, B.L.; Hatarik,, R.; Jeppesen, H.B.; Rasmussen, J.O.

    2009-01-01

    The internal surrogate ratio method allows for the determination of an unknown cross section, such as (n,{gamma}), relative to a better-known cross section, such as (n,f), by measuring the relative exit-channel probabilities of a surrogate reaction that proceeds through the same compound nucleus. The validity of the internal surrogate ratio method is tested by comparing the relative gamma and fission exit-channel probabilities of a {sup 236}U* compound nucleus, formed in the {sup 235}U(d,p) reaction, to the known {sup 235}U(n,{gamma}) and (n,f) cross sections. A model-independent method for measuring the gamma-channel yield is presented and used.

  1. Radioisotope dilution analyses of geological samples using 236U and 229Th

    USGS Publications Warehouse

    Rosholt, J.N.

    1984-01-01

    The use of 236U and 229Th in alpha spectrometric measurements has some advantages over the use of other tracers and measurement techniques in isotope dilution analyses of most geological samples. The advantages are: (1) these isotopes do not occur in terrestrial rocks, (2) they have negligible decay losses because of their long half lives, (3) they cause minimal recoil contamination to surface-barrier detectors, (4) they allow for simultaneous determination of the concentration and isotopic composition of uranium and thorium in a variety of sample types, and (5) they allow for simple and constant corrections for spectral inferences, 0.5% of the 238U activity is subtracted for the contribution of 235U in the 236U peak and 1% of the 229Th activity is subtracted from the 230Th activity. Disadvantages in using 236U and 229Th are: (1) individual separates of uranium and thorium must be prepared as very thin sources for alpha spectrometry, (2) good resolution in the spectrometer system is required for thorium isotopic measurements where measurement times may extend to 300 h, and (3) separate calibrations of the 236U and 229Th spike solution with both uranium and thorium standards are required. The use of these tracers in applications of uranium-series disequilibrium studies has simplified the measurements required for the determination of the isotopic composition of uranium and thorium because of the minimal corrections needed for alpha spectral interferences. ?? 1984.

  2. 232Th, 233Pa, and 234U capture cross-section measurements in moderated neutron flux

    NASA Astrophysics Data System (ADS)

    Bringer, O.; Isnard, H.; AlMahamid, I.; Chartier, F.; Letourneau, A.

    2008-07-01

    The Th-U cycle was studied through the evolution of a 100 μg 232Th sample irradiated in a moderated neutron flux of 8.010 14 n/cm 2/s, intensity close to that of a thermal molten salt reactor. After 43 days of irradiation and 6 months of cooling, a precise mass spectrometric analysis, using both TIMS and MC-ICP-MS techniques, was performed, according to a rigorous methodology. The measured thorium and uranium isotopic ratios in the final irradiated sample were then compared with integral simulations based on evaluated data; an overall good agreement was seen. Four important thermal neutron-capture cross-sections were also extracted from the measurements, 232Th (7.34±0.21 b), 233Pa (38.34±1.78 b), 234U (106.12±3.34 b), and 235U (98.15±11.24 b). Our 232Th and 235U results confirmed existing values whereas the cross-sections of 233Pa and 234U (both key parameters) have been redefined.

  3. /sup 235/U and /sup 239/Pu sample-mass determinations and intercomparisons

    SciTech Connect

    Poenitz, W.P.; Meadows, J.W.

    1983-11-01

    The masses of fifteen /sup 235/U samples obtained from seven laboratories were determined and intercompared. The present results indicate that sample masses are well enough known (+- 0.3%) for the required high-accuracy-fission cross-section measurements. A comparison of four /sup 239/Pu samples indicates problems in the order of 1 to 3% which are more likely, to be related to counting efficiencies than to sample masses. The half-life of /sup 234/U was determined as (2.457 +- 0.005) . 10/sup 5/ yrs. 27 references.

  4. Identification of a shape isomer in 235U.

    PubMed

    Oberstedt, A; Oberstedt, S; Gawrys, M; Kornilov, N

    2007-07-27

    The shape isomer in 235U has been searched for in a neutron-induced fission experiment on 234U, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above 100 micros are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies En=0.95 and 1.27 MeV the isomeric fission half-life could be determined to be T1/2=(3.6+/-1.8) ms. The corresponding cross section was determined to sigmaif=(10+/-8) microb. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time. PMID:17678355

  5. Anthropogenic 236U at Rocky Flats, Ashtabula river harbor, and Mersey estuary: three case studies by sector inductively coupled plasma mass spectrometry.

    PubMed

    Ketterer, M E; Hafer, K M; Link, C L; Royden, C S; Hartsock, W J

    2003-01-01

    236U (t(1/2)=2.3 x 10(7) y) is formed as a result of thermal neutron capture by (235)U. In naturally occurring U ores, where a high neutron flux is present from spontaneous fission of (238)U, (236)U/(238)U atom ratios are approximately 10(-4) ppm. In the natural Earth's crust, unaffected by nuclear fallout, these ratios are expected to be on the order of 10(-8) ppm. Reactor-irradiated U, however, exhibits high (236)U/(238)U atom ratios approaching 10(4) ppm. As a result, the presence of very small quantities of reactor-irradiated U will significantly enhance the "background" (236)U/(238)U atom ratio. When sufficiently elevated (236)U/(238)U ratios are present, the determination of (236)U/(238)U by rapid inductively coupled plasma mass spectrometric (ICPMS) methods is attractive. We have used sector ICPMS at medium resolving power (R=3440) to measure (236)U/(238)U atom ratios with a determination limit of 0.2 ppm. The limiting factors in the measurement are the (235)U(1)H(+) isobar and background signal at m/z 236 arising from the (238)U(+) peak tail. Based upon the analysis of replicates and considerations of possible systematic errors, uncertainties of +/-5% are found for (236)U/(238)U atom ratios of 1-100 ppm. This procedure has been demonstrated in studies of anthropogenic (236)U in the environment at three locations: (a) offsite soils from the vicinity of the Rocky Flats Environmental Technology site (Golden, Colorado, USA); (b) sediments from the Ashtabula River (Ohio, USA); and (c) sediments from the Mersey estuary (Liverpool, UK). In each of these three locations, definite plumes of elevated (236)U/(238)U are identified and characterized. Maximum (236)U/(238)U atom ratios observed in RFETS-vicinity soils, the Ashtabula River, and the Mersey Estuary are 2.8, 140, and 4.4 ppm, respectively. PMID:12691718

  6. Evaluating 238U/235U in U-bearing accessory minerals

    NASA Astrophysics Data System (ADS)

    Hiess, J.; Condon, D. J.; Noble, S. R.; McLean, N.; Bowring, S. A.; Mattinson, J. M.

    2010-12-01

    U-daughter (U-Pb, Pb-Pb, and U-series) geochronology and cosmochronology utilize the absolute value of the present day 238U/235U ratio to calculate and compare dates. For decades, this value has been assumed to be invariant and equal to 137.88, but recent experiments indicate that there is potential for ‘per mil level’ variation in 238U/235U in natural materials, hypothesized to be the result of redox reactions. These studies have largely focused on materials formed in low-temperature environments (e.g. speleothems, corals) and U ore deposits. At present there are no published high-precision high-accuracy 238U/235U data for U-bearing accessory minerals commonly used for U-Pb geochronology. We present accurate and precise 238U/235U determinations for a suite of common U-bearing accessory minerals (zircon, monazite etc.), from a variety of geological environments and ages. Measurements have been made by thermal ionization mass spectrometry, accurately correcting for mass fractionation using the IRMM 3636 233U-236U double spike. Accessory mineral 238U/235U ratios are generally lower than the ‘consensus’ value of 137.88. Systematic discordance has been observed in 238U/206Pb and 235U/207Pb dates obtained for closed-system minerals, and has been used to reassess the relative decay constants of 238U and 235U (Mattinson, 2000, 2010; Schoene et al., 2006). However, these attempts assumed values (i.e., 137.88 or 137.80) for all present-day 238U/235U ratios. Our new determination of coupled 238U/206Pb, 235U/207Pb and 238U/235U measurements on the same closed system zircons, all traceable to SI units, permit further refinement of λ238U/λ235U estimates. Mattinson J.M. 2000. Revising the "gold standard" - the Uranium decay constants of Jaffey et al., 1971. EOS, AGU Fall meeting Supplement Abstract V61A-02. Mattinson J.M. 2010. Analysis of the relative decay constants of 235U and 238U by multi-step CA-TIMS measurements of closed-system natural zircon samples. Chemical

  7. Evaluation of 235U decay data.

    PubMed

    Xiaolong, Huang; Baosong, Wang

    2009-09-01

    Evaluation of the complete decay scheme and data for (235)U including new measurements are presented in this report; literature data available up to June 2008 are included. The half-life is determined to be (7.04+/-0.01) x 10(8) yr. All known measured gamma-ray absolute intensities have been examined; the gamma-ray emission probability of the reference gamma-ray line of 185.72 keV is recommended to be 57.0+/-0.3%. The calculated internal conversion coefficients and their uncertainties have been used to obtain the complete decay intensity balance. The other decay characteristics are calculated using the ENSDF analysis program. Finally the new decay scheme for (235)U is presented.

  8. First 236U data from the Arctic Ocean and use of 236U/238U and 129I/236U as a new dual tracer

    NASA Astrophysics Data System (ADS)

    Casacuberta, N.; Masqué, P.; Henderson, G.; Rutgers van-der-Loeff, M.; Bauch, D.; Vockenhuber, C.; Daraoui, A.; Walther, C.; Synal, H.-A.; Christl, M.

    2016-04-01

    The first dataset of 236U/238U in the water column of the Arctic Ocean (AO) is presented and shows the widest range of ratios reported so far in the open ocean, from (5 ± 5) to (3840 ± 260) ×10-12. Surface samples and depth profiles were collected during two GEOTRACES expeditions in 2011-2012 and analyzed for the concentrations of 236U and 129I, with the aim of investigating whether the combination of 236U/238U and 129I/236U can be used as a new oceanographic tool in the AO. Results show that the distributions of the 236U/238U and 129I/236U atomic ratios are consistent with the different water masses in the AO. High 236U/238U and 129I/236U ratios in the upper water column (> 2000 ×10-12 and >200, respectively) illustrate the penetration of Atlantic waters (AW) into the AO. Lower values were found in Pacific waters (PW) and deep waters of the AO. Rivers seem to represent a temporally and spatially-constrained third anthropogenic source of 236U but more data are needed to confirm this. In a simple mixing model, the combination of 236U/238U and 129I/236U reveals a high contribution (>99%) of natural background waters (pre-nuclear era) in the deep and bottom waters of the Amerasian basin, indicating an apparent water mass renewal time of >1000 years. Despite the relatively high apparent age of the Amerasian Basin deep waters, this work shows the potential of using the dual-tracer approach as a new oceanographic tool in the Arctic Ocean.

  9. First results on 236U levels in global fallout.

    PubMed

    Sakaguchi, A; Kawai, K; Steier, P; Quinto, F; Mino, K; Tomita, J; Hoshi, M; Whitehead, N; Yamamoto, M

    2009-07-01

    The global fallout (236)U level in soil was deduced from measurements of (236)U, (239+240)Pu and (137)Cs in surface soils which are solely influenced by global fallout. A total of 12 soil cores from the depths of 0-10, 0-20 and 0-30 cm were collected at a flat forest area in Japan. Concentrations of (239+240)Pu and (238)U were determined by alpha-particle spectrometry, while the (236)U/(238)U ratio was measured with accelerator mass spectrometry (AMS). Consistent (236)U/(239)Pu ratios between 0.212 and 0.253 were found. Using this ratio, the total global fallout of (236)U on the earth is estimated to be as much as ca. 900 kg. This knowledge will contribute to the promotion of research on U isotopes, including (236)U, for the fields of geo-resources, waste management and geochemistry. PMID:19406452

  10. First results on 236U levels in global fallout.

    PubMed

    Sakaguchi, A; Kawai, K; Steier, P; Quinto, F; Mino, K; Tomita, J; Hoshi, M; Whitehead, N; Yamamoto, M

    2009-07-01

    The global fallout (236)U level in soil was deduced from measurements of (236)U, (239+240)Pu and (137)Cs in surface soils which are solely influenced by global fallout. A total of 12 soil cores from the depths of 0-10, 0-20 and 0-30 cm were collected at a flat forest area in Japan. Concentrations of (239+240)Pu and (238)U were determined by alpha-particle spectrometry, while the (236)U/(238)U ratio was measured with accelerator mass spectrometry (AMS). Consistent (236)U/(239)Pu ratios between 0.212 and 0.253 were found. Using this ratio, the total global fallout of (236)U on the earth is estimated to be as much as ca. 900 kg. This knowledge will contribute to the promotion of research on U isotopes, including (236)U, for the fields of geo-resources, waste management and geochemistry.

  11. 238U/235U determinations of some commonly used reference materials and U-bearing accessory minerals (Invited)

    NASA Astrophysics Data System (ADS)

    Condon, D.; Noble, S.; McLean, N.; Bowring, S. A.

    2009-12-01

    We have determined 238U/235U ratios for a suite of commonly used natural (CRM 112a, SRM 950a, HU-1) and synthetic (IRMM 184 and CRM U500) uranium reference materials in addition to several U-bearing accessory phases (zircon and monazite) by thermal ionisation mass-spectrometry (TIMS) using the IRMM 3636 233U-236U double spike to accurately correct for mass fractionation. The 238U/235U values for the natural uranium reference materials differ, by up to 0.1%, from the widely used ‘consensus’ value (137.88) with all having 238U/235U values less than 137.88. Similarly, initial 238U/235U data from zircon and monazite yield 238U/235U values that are lower than the ‘consensus’ value. The data obtained from U-bearing minerals is used to assess how the uncertainty in the 238U/235U ratio contributes to the systematic discordance observed in 238U/206Pb and 235U/207Pb dates (Mattinson, 2000; Schoene et al., 2006) which has traditionally been wholly attributed to error in the U decay constants. The 238U/235U determinations made on the synthetic reference materials yield results that are considerably more precise and accurate than the certified values (0.02% vs. 0.1% for CRM U500). The calibration of isotopic tracers used for U-daughter geochronology that are partially based upon these reference materials, and the resultant age determinations, will benefit from increased accuracy and precision. Mattinson, J.M., 2000. Revising the “gold standard”—the uranium decay constants of Jaffey et al., 1971. Eos Trans. AGU, Spring Meet. Suppl., Abstract V61A-02. Schoene B., Crowley J.L., Condon D.C., Schmitz M.D., Bowring S.A., 2006, Reassessing the uranium decay constants for geochronology using ID-TIMS U-Pb data. Geochimica et Cosmochimica Acta 70: 426-445

  12. 234U and 230Th determination by FIA-ICP-MS and application to uranium-series disequilibrium in marine samples.

    PubMed

    Godoy, Maria Luiza D P; Godoy, José Marcus; Kowsmann, Renato; Dos Santos, Guaciara M; Petinatti da Cruz, Rosana

    2006-01-01

    A 234U and 230Th determination method based on an extraction chromatographic separation on a flow injection system coupled to a quadruple ICP-MS was developed. Two-milliliter UTEVA (Eichrom Co.) cartridges were applied as separation tool and 236U and 229Th as spikes. Loading and washing steps were carried out in 3 M HNO3 solution and 0.05 M ammonium oxalate applied to elute both uranium and thorium. The method was applied initially to the IAEA-327 soil reference sample and NIST SRM 4357 ocean sediment reference material, with the obtained 234U and 230Th concentrations in agreement with the reference levels. Samples from a deep-sea sediment core (2450 m water depth) were analyzed and based on 230Th/234U dating, a mean sedimentation rate of 3.3 cm ky(-1) was calculated. Samples from two sediment layers were also dated by 14C-AMS and the observed ages agree with the 230Th/234U results. PMID:16545893

  13. High-precision determination of {sup 234}U/{sup 238}U activity ratios in natural waters and carbonates by ICPMS

    SciTech Connect

    Ketterer, M.E.; Khourey, C.J.

    1998-12-31

    A method has been developed for precise measurement of {sup 234}U/{sup 238}U activity ratios in natural waters and carbonates using quadrupole inductively coupled plasma mass spectrometry. A recovery of 80--85% of seawater U is achieved by Fe(III) coprecipitation followed by extraction chromatography with a supported dipentyl pentane phosphonate material; 90--95% of U is recovered from carbonates, which are dissolved in HNO{sub 3} and subjected to the same extraction chromatographic preparation. Isotopic measurements are made via recirculating pneumatic nebulization of small volumes of solutions containing 0.5--5 mg/L U. {sup 234}U/{sup 235}U is measured as a proxy for determination of {sup 234}U/{sup 238}U; iridium is added to sample solutions and the ion ratio {sup 191}Ir{sup 40}Ar{sup +}/{sup 193}Ir{sup 40}Ar{sup +} is measured for internal mass discrimination correction {sup 234}U/{sup 238}U activity ratios in the range 1.143--1.154 are observed for 13 seawater and contemporary corals, in agreement with the established marine {sup 234}U/{sup 238}U activity ratio. For samples sizes of 5--25 {micro}g U, ICPMS uncertainties of {+-} 0.2--0.5% relative, 2{theta} standard error, approach those obtained for < 0.1 {micro}g U by thermal ionization mass spectrometry. Measurements of {sup 234}U/{sup 238}U activity ratios in bottled waters, Lake Erie surface waters, mollusk fossils, and fertilizers are also demonstrated.

  14. Assessment of uranium exposure from total activity and 234U:238U activity ratios in urine.

    PubMed

    Nicholas, T; Bingham, D

    2011-03-01

    Radiation workers at Atomic Weapons Establishment (AWE) are monitored for uranium exposure by routine bioassay sampling (primarily urine sampling). However, the interpretation of uranium in urine and faecal results in terms of occupational intakes is difficult because of the presence of uranium due to intakes from environmental (dietary) sources. For uranium in urine data obtained using current analytical techniques at AWE, the mean, median and standard deviation of excreted uranium concentrations were 0.006, 0.002 and 0.012 μg per g creatinine, respectively. These values are consistent with what might be expected from local dietary intakes and the knowledge that occupational exposures at AWE are likely to be very low. However, some samples do exceed derived investigation levels (DILs), which have been set up taking account of the likely contribution from environmental sources. We investigate how the activity and isotopic composition of uranium in the diet affects the sensitivity of uranium in urine monitoring for occupational exposures. We conclude that DILs based on both total uranium in urine activity and also (234)U:(238)U ratios are useful given the likely variation in dietary contribution for AWE workers. Assuming a background excretion rate and that the enrichment of the likely exposure is known, it is possible to assess exposures using (234)U:(238)U ratios and/or total uranium activity. The health implications of internalised uranium, enriched to <5-8 % by mass (235)U, centre on its nephrotoxicity; the DILs for bioassay samples at AWE are an order of magnitude below the conservative recommendations made by the literature. PMID:21036806

  15. Assessment of uranium exposure from total activity and 234U:238U activity ratios in urine.

    PubMed

    Nicholas, T; Bingham, D

    2011-03-01

    Radiation workers at Atomic Weapons Establishment (AWE) are monitored for uranium exposure by routine bioassay sampling (primarily urine sampling). However, the interpretation of uranium in urine and faecal results in terms of occupational intakes is difficult because of the presence of uranium due to intakes from environmental (dietary) sources. For uranium in urine data obtained using current analytical techniques at AWE, the mean, median and standard deviation of excreted uranium concentrations were 0.006, 0.002 and 0.012 μg per g creatinine, respectively. These values are consistent with what might be expected from local dietary intakes and the knowledge that occupational exposures at AWE are likely to be very low. However, some samples do exceed derived investigation levels (DILs), which have been set up taking account of the likely contribution from environmental sources. We investigate how the activity and isotopic composition of uranium in the diet affects the sensitivity of uranium in urine monitoring for occupational exposures. We conclude that DILs based on both total uranium in urine activity and also (234)U:(238)U ratios are useful given the likely variation in dietary contribution for AWE workers. Assuming a background excretion rate and that the enrichment of the likely exposure is known, it is possible to assess exposures using (234)U:(238)U ratios and/or total uranium activity. The health implications of internalised uranium, enriched to <5-8 % by mass (235)U, centre on its nephrotoxicity; the DILs for bioassay samples at AWE are an order of magnitude below the conservative recommendations made by the literature.

  16. Excess of (236)U in the northwest Mediterranean Sea.

    PubMed

    Chamizo, E; López-Lora, M; Bressac, M; Levy, I; Pham, M K

    2016-09-15

    In this work, we present first (236)U results in the northwestern Mediterranean. (236)U is studied in a seawater column sampled at DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (Ligurian Sea, 43°25'N, 07°52'E). The obtained (236)U/(238)U atom ratios in the dissolved phase, ranging from about 2×10(-9) at 100m depth to about 1.5×10(-9) at 2350m depth, indicate that anthropogenic (236)U dominates the whole seawater column. The corresponding deep-water column inventory (12.6ng/m(2) or 32.1×10(12) atoms/m(2)) exceeds by a factor of 2.5 the expected one for global fallout at similar latitudes (5ng/m(2) or 13×10(12) atoms/m(2)), evidencing the influence of local or regional (236)U sources in the western Mediterranean basin. On the other hand, the input of (236)U associated to Saharan dust outbreaks is evaluated. An additional (236)U annual deposition of about 0.2pg/m(2) based on the study of atmospheric particles collected in Monaco during different Saharan dust intrusions is estimated. The obtained results in the corresponding suspended solids collected at DYFAMED station indicate that about 64% of that (236)U stays in solution in seawater. Overall, this source accounts for about 0.1% of the (236)U inventory excess observed at DYFAMED station. The influence of the so-called Chernobyl fallout and the radioactive effluents produced by the different nuclear installations allocated to the Mediterranean basin, might explain the inventory gap, however, further studies are necessary to come to a conclusion about its origin.

  17. Excess of (236)U in the northwest Mediterranean Sea.

    PubMed

    Chamizo, E; López-Lora, M; Bressac, M; Levy, I; Pham, M K

    2016-09-15

    In this work, we present first (236)U results in the northwestern Mediterranean. (236)U is studied in a seawater column sampled at DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (Ligurian Sea, 43°25'N, 07°52'E). The obtained (236)U/(238)U atom ratios in the dissolved phase, ranging from about 2×10(-9) at 100m depth to about 1.5×10(-9) at 2350m depth, indicate that anthropogenic (236)U dominates the whole seawater column. The corresponding deep-water column inventory (12.6ng/m(2) or 32.1×10(12) atoms/m(2)) exceeds by a factor of 2.5 the expected one for global fallout at similar latitudes (5ng/m(2) or 13×10(12) atoms/m(2)), evidencing the influence of local or regional (236)U sources in the western Mediterranean basin. On the other hand, the input of (236)U associated to Saharan dust outbreaks is evaluated. An additional (236)U annual deposition of about 0.2pg/m(2) based on the study of atmospheric particles collected in Monaco during different Saharan dust intrusions is estimated. The obtained results in the corresponding suspended solids collected at DYFAMED station indicate that about 64% of that (236)U stays in solution in seawater. Overall, this source accounts for about 0.1% of the (236)U inventory excess observed at DYFAMED station. The influence of the so-called Chernobyl fallout and the radioactive effluents produced by the different nuclear installations allocated to the Mediterranean basin, might explain the inventory gap, however, further studies are necessary to come to a conclusion about its origin. PMID:27262827

  18. 31 CFR 540.315 - Uranium-235 (U235).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Uranium-235 (U235). 540.315 Section... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY HIGHLY ENRICHED URANIUM (HEU) AGREEMENT ASSETS CONTROL REGULATIONS General Definitions § 540.315 Uranium-235 (U235). The term uranium-235 or U235 means the...

  19. 31 CFR 540.315 - Uranium-235 (U235).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Uranium-235 (U235). 540.315 Section... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY HIGHLY ENRICHED URANIUM (HEU) AGREEMENT ASSETS CONTROL REGULATIONS General Definitions § 540.315 Uranium-235 (U235). The term uranium-235 or U235 means the...

  20. 31 CFR 540.315 - Uranium-235 (U235).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Uranium-235 (U235). 540.315 Section... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY HIGHLY ENRICHED URANIUM (HEU) AGREEMENT ASSETS CONTROL REGULATIONS General Definitions § 540.315 Uranium-235 (U235). The term uranium-235 or U235 means the...

  1. 31 CFR 540.315 - Uranium-235 (U235).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Uranium-235 (U235). 540.315 Section... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY HIGHLY ENRICHED URANIUM (HEU) AGREEMENT ASSETS CONTROL REGULATIONS General Definitions § 540.315 Uranium-235 (U235). The term uranium-235 or U235 means the...

  2. 31 CFR 540.315 - Uranium-235 (U235).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Uranium-235 (U235). 540.315 Section... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY HIGHLY ENRICHED URANIUM (HEU) AGREEMENT ASSETS CONTROL REGULATIONS General Definitions § 540.315 Uranium-235 (U235). The term uranium-235 or U235 means the...

  3. Methods for spectral interference corrections for direct measurements of 234U and 230Th in materials by gamma-ray spectrometry.

    PubMed

    Yücel, H; Solmaz, A N; Köse, E; Bor, D

    2010-03-01

    When the high-resolution gamma-ray spectrometry was used in the analysis of (234)U and (230)Th in samples, there is a much more need to correct for the measured activity results of (234)U and (230)Th mainly due to self-absorption effects and the interfering lines from (226)Ra, (235)U, (238)U and their decay products that often might be present in the samples. Therefore, in the present study, the methods for the spectral interference corrections for the analytical peaks of (234)U and (230)Th are suggested to take into account the contributions of the overlapping gamma rays to these peaks. For the method validation, direct gamma-ray spectrometric measurements were carried out using certified reference materials (CRM) by use of a 76.5 % n-type Ge detector. The activities measured for the CRM samples were corrected for spectral interferences, self-absorption and true coincidence-summing (TCS) effects. The obtained results indicate that ignoring of the contribution of the interference gamma rays to the main analytical peak at 53.2 keV of (234)U leads to a lager systematic error of 87.3-90.4 % for the measured activities of (234)U, and similarly if one ignores the contributions of the interference gamma rays to the main analytical peak at 67.7 keV of (230)Th, this leads to a much smaller systematic error of 2.1-2.7 % for the activities of (230)Th. Therefore, the required correction factors for spectral interferences to the analytical peaks of (234)U and (230)Th are not negligible and thus they should also be considered besides necessary self-absorption factors to determine more accurate activities in the samples. On the other hand, it is estimated that although the TCS effects on the main analytical peaks of both (234)U and (230)Th are negligibly small, those TCS correction factors for their interference gamma rays to these peaks should be taken into account when direct measurements are performed in a close-counting geometry condition. Otherwise, the resulted activities

  4. Reaction paths and host phases of uranium isotopes (235U; 238U), Saanich Inlet

    NASA Astrophysics Data System (ADS)

    Amini, M.; Holmden, C. E.; Francois, R. H.

    2009-12-01

    In recent times, Uranium has become increasingly the focus of stable isotope fractionation studies. Variations in 238U/235U have been reported as a result of redox reactions [1,2] from the nuclear field shift effect [3], and a mass-dependent, microbially-mediated, kinetic isotope effect [4]. The 238U/235U variability caused by changes in environmental redox conditions leads to an increase in the 238U/235U ratios of the reduced U species sequestered into marine sediments. This points to U isotope variability as a new tool to study ancient ocean redox changes. However, the process by which reduced sediments become enriched in the heavy isotopes of U is not yet known, and hence the utility of 238U/235U as a redox tracer remains to be demonstrated. In order to further constrain sedimentary U enrichment and related isotope effect, we are investigating U isotopic compositions of water samples and fresh surface sediment grab samples over a range of redox conditions in the seasonally anoxic Saanich Inlet, on the east coast of Vancouver Island. U was sequentially extracted from sediments in order to characterize specific fractions for their isotopic composition. The measurements were carried out by MC-ICPMS using 233U/236U-double spike technique. The data are reported as δ238U relative to NBL 112a with a 238U/235U ratio of 137.88 (2sd). External precision is better than 0.10‰ (2sd). Fifteeen analyses of seawater yielded δ238U of -0.42±0.08‰ (2sd). The results for the water samples indicate a homogenous δ238U value throughout the Saanich Inlet water column that matches the global seawater signature. All of the water samples from above and below average -0.42±0.05‰ (2sd). In contrast, a plankton net sample yielded a distinctly different, (about 0.5‰ lighter) isotope value. Bacterial reduction experiments [4] have also shown isotope enrichment factors of about -0.3‰. In addition, metal isotope fractionation occurs during adsorption with the light isotope being

  5. Observations of 231Pa/ 235U disequilibrium in volcanic rocks

    NASA Astrophysics Data System (ADS)

    Pickett, David A.; Murrell, Michael T.

    1997-04-01

    We present here the first survey of ( 231Pa/ 235U) ratios in volcanic rocks; such measurements are made possible by new mass spectrometric techniques. The data place new constraints on the timing and extent of magma source and evolutionary processes, particularly due to the sensitivity of the 231Pa- 235U pair and its intermediate time scale ( 231Pat 1/2 = 33 ky). ( 231Pa/ 235U) is found to vary widely, from 0.2 in carbonatites to 1.1-2.9 in basalts and 0.9-2.2 in arcs. Substantial Pa enrichment is nearly ubiquitous, suggestive of the relative incompatibility of Pa, qualitatively consistent with available partitioning data. The level of 231Pa- 235U disequilibrium typically far exceeds that of 230Th- 238U and is comparable to 226Ra- 230Th. The high ( 231Pa/ 235U) ratios in MORB and other basalts reflect a large degree of discrimination between two incompatible elements, posing challenges for modelling of melt generation and migration. Fundamental differences in ( 231Pa/ 235U) among different basaltic environments are likely related to contrasts in melting zone conditions (e.g., melting rate). Strong ( 231Pa/ 235U) disequilibria in continental basalts, for which ( 230Th/ 238U) disequilibria are small or absent, demonstrate that Pa-U fractionation is possible in both garnet and spinel mantle stability fields. In arcs, correlation of ( 231Pa/ 235U) and ( 230Th/ 238U) is consistent with U enrichment via slab-derived fluids, a process which is additional to the still dominant Pa enrichment. An important new constraint is provided by the observation that the near-equilibrium ( 230Th/ 238U) common to arcs and continental basalts is not typically accompanied by near-equilibrium ( 231Pa/ 235U), arguing against the influence of long magma history, crustal material, or equilibrium mantle sources in affecting decay-series ratios. Small sample sets from two silicic centers illustrate: (1) recent, rapid U enrichment in the magma chamber (El Chichón); and (2) the failure of

  6. Mass and abundance 236U sensitivities at CIRCE

    NASA Astrophysics Data System (ADS)

    De Cesare, M.; De Cesare, N.; D'Onofrio, A.; Fifield, L. K.; Gialanella, L.; Terrasi, F.

    2015-10-01

    The actinides (e.g. 236U and xPu isotopes) are present in environmental samples at the ultra trace level since atmospheric tests of NWs (Nuclear Weapons) performed in the past, deliberate dumping of nuclear waste, nuclear fuel reprocessing, on a large scale and operation of NPPs (Nuclear Power Plants) on a small scale have led to the release of a wide range of radioactive nuclides in the environment. Their detection requires the most sensitive AMS (Accelerator Mass Spectrometry) techniques and at the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy, an upgraded actinide AMS system, based on a 3-MV pelletron tandem accelerator, has been operated. In this paper the progress made in order to push the 236U mass sensitivity and 236U/238U isotopic ratio down to the natural levels is reported. A uranium contamination mass of about 0.05 μg and a 236U/238U isotopic ratio sensitivities at the level of 3.2 × 10-13 are presently achievable.

  7. Cleanup levels for Am-241, Pu-239, U-234, U-235 & U-238 in soils at the Rocky Flats Environmental Technology Site

    SciTech Connect

    Roberts, R.; Colby, B.; Brooks, L.; Slaten, S.

    1997-07-03

    This presentation briefly outlines a cleanup program at a Rocky Flats site through viewgraphs and an executive summary. Exposure pathway analyses to be performed are identified, and decontamination levels are listed for open space and office worker exposure areas. The executive summary very briefly describes the technical approach, RESRAD computer code to be used for analyses, recommendations for exposure levels, and application of action levels to multiple radionuclide contamination. Determination of action levels for surface and subsurface soils, based on radiation doses, is discussed. 1 tab.

  8. Comparative study of different analytical methods for the determination of 238U, 234U, 235U, 230Th and 232Th in NORM samples (Southern Catalonia).

    PubMed

    Mola, M; Palomo, M; Peñalver, A; Borrull, F; Aguilar, C

    2013-01-01

    Uranium and thorium isotopes from sludge samples taken from an area of influence of a dicalcium phosphate factory, located close to the Ebro River reservoir in Flix, and from mineral raw materials (coal and phosphate) which were deposited in Tarragona Harbour (Catalonia) have been measured. To do that, several procedures to determine these isotopes have been applied and compared in terms of accuracy, precision and total analysis time. In particular, digestion procedures, such as one based on conventional acidic digestion or another based on the use of microwave digestion, have been tested. Moreover, different radiochemical separation procedures have been applied. In this regard, one method based on liquid-liquid extraction using TBP/Xylene and another based on the use of extraction chromatography using UTEVA resins have been compared. Firstly, the different proposed methods were tested by analyzing a phosphogypsum sediment and a moss-soil sample from two different intercomparison exercises. The microwave digestion - UTEVA method provided the best results (recoveries higher than 82% for uranium and thorium isotopes) and was then applied to the NORM samples. The obtained results showed that the higher uranium and thorium activities values were found in phosphate raw material and in the more superficial samples located in sludge sediments next to the dicalcium phosphate factory.

  9. Accurate fast method with high chemical yield for determination of uranium isotopes (234U, 235U, 238U) in granitic samples using alpha spectroscopy

    NASA Astrophysics Data System (ADS)

    Guirguis, Laila A.; Farag, Nagdy M.; Salim, Adham K.

    2015-03-01

    The present study aims to use the α-spectroscopy at Nuclear Materials Authority (NMA) of Egypt. A radiochemical technique for analysis uranium isotopes was carried out for ten mineralized granitic samples together with the International standards RGU-1 (IAEA) and St4 (NMA). Several steps of sample preparation, radiochemical separation and source preparation were performed before analysis. Uranium was separated from sample matrix with 0.2 M TOPO in cyclohexane as an extracting agent with a chemical yield 98.95% then uranium was purified from lanthanides and actinides present with 0.2 M TOA in xylene as an extracting agent. The pure fraction was electrodeposited on a mirror-polished copper disc from buffer solution (NaHSO4+H2SO4+NH4OH). Rectangle pt-electrode with an anode-cathode distance of 2 cm was used. Current was 900 mA and the electrodeposition time reach up to 120 min. The achieved results show that the chemical yield ranged between 87.9±6.8 and 98±8.6.

  10. Comparative study of different analytical methods for the determination of 238U, 234U, 235U, 230Th and 232Th in NORM samples (Southern Catalonia).

    PubMed

    Mola, M; Palomo, M; Peñalver, A; Borrull, F; Aguilar, C

    2013-01-01

    Uranium and thorium isotopes from sludge samples taken from an area of influence of a dicalcium phosphate factory, located close to the Ebro River reservoir in Flix, and from mineral raw materials (coal and phosphate) which were deposited in Tarragona Harbour (Catalonia) have been measured. To do that, several procedures to determine these isotopes have been applied and compared in terms of accuracy, precision and total analysis time. In particular, digestion procedures, such as one based on conventional acidic digestion or another based on the use of microwave digestion, have been tested. Moreover, different radiochemical separation procedures have been applied. In this regard, one method based on liquid-liquid extraction using TBP/Xylene and another based on the use of extraction chromatography using UTEVA resins have been compared. Firstly, the different proposed methods were tested by analyzing a phosphogypsum sediment and a moss-soil sample from two different intercomparison exercises. The microwave digestion - UTEVA method provided the best results (recoveries higher than 82% for uranium and thorium isotopes) and was then applied to the NORM samples. The obtained results showed that the higher uranium and thorium activities values were found in phosphate raw material and in the more superficial samples located in sludge sediments next to the dicalcium phosphate factory. PMID:22742771

  11. High-Resolution Inductively Coupled Plasma Optical Emission Spectrometry for (234)U/(238)Pu Age Dating of Plutonium Materials and Comparison to Sector Field Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Krachler, Michael; Alvarez-Sarandes, Rafael; Rasmussen, Gert

    2016-09-01

    Employing a commercial high-resolution inductively coupled plasma optical emission spectrometry (HR-ICP-OES) instrument, an innovative analytical procedure for the accurate determination of the production age of various Pu materials (Pu powder, cardiac pacemaker battery, (242)Cm heat source, etc.) was developed and validated. This undertaking was based on the fact that the α decay of (238)Pu present in the investigated samples produced (234)U and both mother and daughter could be identified unequivocally using HR-ICP-OES. Benefiting from the high spectral resolution of the instrument (<5 pm) and the isotope shift of the emission lines of both nuclides, (234)U and (238)Pu were selectively and directly determined in the dissolved samples, i.e., without a chemical separation of the two analytes from each other. Exact emission wavelengths as well as emission spectra of (234)U centered around λ = 411.590 nm and λ = 424.408 nm are reported here for the first time. Emission spectra of the isotopic standard reference material IRMM-199, comprising about one-third each of (233)U, (235)U, and (238)U, confirmed the presence of (234)U in the investigated samples. For the assessment of the (234)U/(238)Pu amount ratio, the emission signals of (234)U and (238)Pu were quantified at λ = 424.408 nm and λ = 402.148 nm, respectively. The age of the investigated samples (range: 26.7-44.4 years) was subsequently calculated using the (234)U/(238)Pu chronometer. HR-ICP-OES results were crossed-validated through sector field inductively coupled plasma mass spectrometry (SF-ICPMS) analysis of the (234)U/(238)Pu amount ratio of all samples applying isotope dilution combined with chromatographic separation of U and Pu. Available information on the assumed ages of the analyzed samples was consistent with the ages obtained via the HR-ICP-OES approach. Being based on a different physical detection principle, HR-ICP-OES provides an alternative strategy to the well-established mass

  12. High-Resolution Inductively Coupled Plasma Optical Emission Spectrometry for (234)U/(238)Pu Age Dating of Plutonium Materials and Comparison to Sector Field Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Krachler, Michael; Alvarez-Sarandes, Rafael; Rasmussen, Gert

    2016-09-01

    Employing a commercial high-resolution inductively coupled plasma optical emission spectrometry (HR-ICP-OES) instrument, an innovative analytical procedure for the accurate determination of the production age of various Pu materials (Pu powder, cardiac pacemaker battery, (242)Cm heat source, etc.) was developed and validated. This undertaking was based on the fact that the α decay of (238)Pu present in the investigated samples produced (234)U and both mother and daughter could be identified unequivocally using HR-ICP-OES. Benefiting from the high spectral resolution of the instrument (<5 pm) and the isotope shift of the emission lines of both nuclides, (234)U and (238)Pu were selectively and directly determined in the dissolved samples, i.e., without a chemical separation of the two analytes from each other. Exact emission wavelengths as well as emission spectra of (234)U centered around λ = 411.590 nm and λ = 424.408 nm are reported here for the first time. Emission spectra of the isotopic standard reference material IRMM-199, comprising about one-third each of (233)U, (235)U, and (238)U, confirmed the presence of (234)U in the investigated samples. For the assessment of the (234)U/(238)Pu amount ratio, the emission signals of (234)U and (238)Pu were quantified at λ = 424.408 nm and λ = 402.148 nm, respectively. The age of the investigated samples (range: 26.7-44.4 years) was subsequently calculated using the (234)U/(238)Pu chronometer. HR-ICP-OES results were crossed-validated through sector field inductively coupled plasma mass spectrometry (SF-ICPMS) analysis of the (234)U/(238)Pu amount ratio of all samples applying isotope dilution combined with chromatographic separation of U and Pu. Available information on the assumed ages of the analyzed samples was consistent with the ages obtained via the HR-ICP-OES approach. Being based on a different physical detection principle, HR-ICP-OES provides an alternative strategy to the well-established mass

  13. Neutron-induced fission cross section of {sup 234}U and {sup 237}Np measured at the CERN Neutron Time-of-Flight (n{sub T}OF) facility

    SciTech Connect

    Paradela, C.; Duran, I.; Tarrio, D.; Alvarez, H.; Tassan-Got, L.; Berthier, B.; Ferrant, L.; Isaev, S.; Le Naour, C.; Stephan, C.; Trubert, D.; David, S.; Abbondanno, U.; Fujii, K.; Milazzo, P. M.; Moreau, C.; Aerts, G.

    2010-09-15

    A high-resolution measurement of the neutron-induced fission cross section of {sup 234}U and {sup 237}Np has been performed at the CERN Neutron Time-of-Flight facility. The cross sections have been determined in a wide energy range from 1 eV to 1 GeV using the evaluated {sup 235}U cross section as reference. In these measurements the energy determination for the {sup 234}U resonances could be improved, whereas previous discrepancies for the {sup 237}Np resonances were confirmed. New cross-section data are provided for high neutron energies that go beyond the limits of prior evaluations, obtaining important differences in the case of {sup 237}Np.

  14. Nuclear excitation by electronic transition of 235U

    DOE PAGES

    Chodash, P. A.; Norman, E. B.; Burke, J. T.; Casperson, R. J.; Fisher, S. E.; Holliday, K. S.; Jeffries, J. R.; Wakeling, M. A.; Wilks, S. C.

    2016-03-11

    Here, nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that can occur in isotopes containing a low-lying nuclear excited state. Over the past 40 yr, several experiments have attempted to measure NEET of 235U and those experiments have yielded conflicting results.

  15. 234U /238U and 230Th /234U activity ratios in mineral phases of a lateritic weathered zone

    NASA Astrophysics Data System (ADS)

    Lowson, Richard T.; Short, Stephen A.; Davey, Brian G.; Gray, David J.

    1986-08-01

    A selective phase extraction procedure was developed for the identification of the significant phases of a typical deep soil profile sampled in the vicinity of the Ranger No. 1 uranium ore body, Alligator Rivers region, N.T., Australia. The significant phases were identified as amorphous iron oxide, crystalline iron oxide and a clay/quartz resistate. The distribution of 238U, 234U, 230Th and 226Ra between the phases was measured. The results indicated that the amorphous iron oxide phase is in adsorption/desorption equilibrium with the ground water. The crystalline iron oxide phase contains a chemical control, the kinetics of which are commensurate with or less than the half-life of 230Th (7.52 × 10 4 y). The clay/quartz resistate is enriched in 238U descendants in such a way that they are not readily accessible to the ground water.

  16. Impact of the 235U Covariance Data in Benchmark Calculations

    SciTech Connect

    Leal, Luiz C; Mueller, Don; Arbanas, Goran; Wiarda, Dorothea; Derrien, Herve

    2008-01-01

    The error estimation for calculated quantities relies on nuclear data uncertainty information available in the basic nuclear data libraries such as the U.S. Evaluated Nuclear Data File (ENDF/B). The uncertainty files (covariance matrices) in the ENDF/B library are generally obtained from analysis of experimental data. In the resonance region, the computer code SAMMY is used for analyses of experimental data and generation of resonance parameters. In addition to resonance parameters evaluation, SAMMY also generates resonance parameter covariance matrices (RPCM). SAMMY uses the generalized least-squares formalism (Bayes method) together with the resonance formalism (R-matrix theory) for analysis of experimental data. Two approaches are available for creation of resonance-parameter covariance data. (1) During the data-evaluation process, SAMMY generates both a set of resonance parameters that fit the experimental data and the associated resonance-parameter covariance matrix. (2) For existing resonance-parameter evaluations for which no resonance-parameter covariance data are available, SAMMY can retroactively create a resonance-parameter covariance matrix. The retroactive method was used to generate covariance data for 235U. The resulting 235U covariance matrix was then used as input to the PUFF-IV code, which processed the covariance data into multigroup form, and to the TSUNAMI code, which calculated the uncertainty in the multiplication factor due to uncertainty in the experimental cross sections. The objective of this work is to demonstrate the use of the 235U covariance data in calculations of critical benchmark systems.

  17. Extreme fractionation of 234U 238U and 230Th 234U in spring waters, sediments, and fossils at the Pomme de Terre Valley, southwestern Missouri

    USGS Publications Warehouse

    Szabo, B. J.

    1982-01-01

    Isotopic fractionation as great as 1600% exists between 234U and 238U in spring waters, sediments, and fossils in the Pomme de Terre Valley, southwestern Missouri. The activity ratios of 234U 238U in five springs range from 7.2 to 16 in water which has been discharged for at least the past 30,000 years. The anomalies in 234U 238U ratio in deep water have potential usefulness in hydrologic investigations in southern Missouri. Clayey units overlying the spring bog sediments of Trolinger Spring are enriched in 230Th relative to their parent 234U by as much as 720%. The results indicate that both preferential displacement via alpha recoil ejection and the preferential emplacement via recoiling and physical entrapment are significant processes that are occurring in the geologic environment. ?? 1982.

  18. Activity ratios of (234)U/(238)U and (226)Ra/(228)Ra for transport mechanisms of elevated uranium in alluvial aquifers of groundwater in south-western (SW) Punjab, India.

    PubMed

    Kumar, A; Karpe, R K; Rout, S; Gautam, Y P; Mishra, M K; Ravi, P M; Tripathi, R M

    2016-01-01

    The concentrations of total dissolved uranium (U), its isotopic composition ((234)U, (235)U, (238)U) and two long lived Ra isotopes ((226)Ra and (228)Ra) in alluvial aquifers of groundwater were determined to investigate the groundwater flow pattern in the south-western (SW) Punjab, India. Particular attention was given to the spatial variability of activity ratios (ARs) of (234)U/(238)U and (226)Ra/(228)Ra to predict the possible sources and supply process of U into the water from the solid phase. The measured groundwater (234)U/(238)U ARs were ∼1 or >1 in the shallow zone (depth < 30 m) with high U concentration and <1 in the deeper zone (depth > 30 m) with relatively low U concentration. The simultaneous elevated U concentration and (234)U/(238)U ARs in waters were possibly due to differences in imprints of rock-water interactions under hydrologic conditions. However, (234)U/(238)U ARs < 1 clearly indicate the lack of recharge from surface water to groundwater leading to (234)U deficit in groundwater. This deficit might be also attributed to alpha recoil processes under strong dissolution. Overall, the decreasing pattern of (234)U/(238)U ARs observed from SE to SW or NW ward clearly indicates a groundwater flow paths from SE to SW/NW. Similarly, (226)Ra/(238)U ARs < 1 for all water samples reflect that the precursor (238)U is fairly mobile relative to (226)Ra. This might be due to unusually high amount of (238)U in groundwaters and subsequently the different geochemistry of the two isotopes. On the other hand, (226)Ra/(228)Ra ARs in groundwaters varied widely and observed about 50-300 times higher than (238)U/(232)Th ARs in granitic rocks or soils. Such elevation in ARs might be attributed to different dissolution properties of their parents during water-rock interactions or lattice damage during decay or local enrichments of uranium in the aquifers. PMID:26555366

  19. Activity ratios of (234)U/(238)U and (226)Ra/(228)Ra for transport mechanisms of elevated uranium in alluvial aquifers of groundwater in south-western (SW) Punjab, India.

    PubMed

    Kumar, A; Karpe, R K; Rout, S; Gautam, Y P; Mishra, M K; Ravi, P M; Tripathi, R M

    2016-01-01

    The concentrations of total dissolved uranium (U), its isotopic composition ((234)U, (235)U, (238)U) and two long lived Ra isotopes ((226)Ra and (228)Ra) in alluvial aquifers of groundwater were determined to investigate the groundwater flow pattern in the south-western (SW) Punjab, India. Particular attention was given to the spatial variability of activity ratios (ARs) of (234)U/(238)U and (226)Ra/(228)Ra to predict the possible sources and supply process of U into the water from the solid phase. The measured groundwater (234)U/(238)U ARs were ∼1 or >1 in the shallow zone (depth < 30 m) with high U concentration and <1 in the deeper zone (depth > 30 m) with relatively low U concentration. The simultaneous elevated U concentration and (234)U/(238)U ARs in waters were possibly due to differences in imprints of rock-water interactions under hydrologic conditions. However, (234)U/(238)U ARs < 1 clearly indicate the lack of recharge from surface water to groundwater leading to (234)U deficit in groundwater. This deficit might be also attributed to alpha recoil processes under strong dissolution. Overall, the decreasing pattern of (234)U/(238)U ARs observed from SE to SW or NW ward clearly indicates a groundwater flow paths from SE to SW/NW. Similarly, (226)Ra/(238)U ARs < 1 for all water samples reflect that the precursor (238)U is fairly mobile relative to (226)Ra. This might be due to unusually high amount of (238)U in groundwaters and subsequently the different geochemistry of the two isotopes. On the other hand, (226)Ra/(228)Ra ARs in groundwaters varied widely and observed about 50-300 times higher than (238)U/(232)Th ARs in granitic rocks or soils. Such elevation in ARs might be attributed to different dissolution properties of their parents during water-rock interactions or lattice damage during decay or local enrichments of uranium in the aquifers.

  20. sup 235 U accountability measurements on small samples

    SciTech Connect

    Sigg, R.A.

    1991-01-01

    Savannah River Site (SRS) is improving uranium accountability at its fuel fabrication facility through measurements of {sup 235}U in samples taken from uranium/aluminum alloy melts. Since area personnel desired a method that would minimize mixed waste, low volume samples are prepared from dissolutions of production melt grab samples. The solution assay monitor (SAM) analyzes for {sup 235}U gamm-rays by using a high-efficiency germanium well detector. The detector's high counting efficiency permits analysis of small samples (7 mL) from these dissolutions, and the counting geometry minimizes sample geometry uncertainties. Counting each sample for thirty minutes delivers excellent precision across the calibration range of 3 to 12 g uranium per liter. As shown by interlaboratory calibration, the gamma-ray spectrometer provides overall (counting, calibration, geometric,...) uncertainties less than 0.7% one sigma. Gamma-rays from a reference source, used to provide live-time corrections, are collimated to avoid absorption by the sample in the detector well. Since sample masses are small, minor self-attenuation corrections are calculated from chemical composition data rather than determined in separate transmission measurements. This avoids employing short-lived transmission sources for self-attenuation corrections.

  1. {sup 235}U accountability measurements on small samples

    SciTech Connect

    Sigg, R.A.

    1991-12-31

    Savannah River Site (SRS) is improving uranium accountability at its fuel fabrication facility through measurements of {sup 235}U in samples taken from uranium/aluminum alloy melts. Since area personnel desired a method that would minimize mixed waste, low volume samples are prepared from dissolutions of production melt grab samples. The solution assay monitor (SAM) analyzes for {sup 235}U gamm-rays by using a high-efficiency germanium well detector. The detector`s high counting efficiency permits analysis of small samples (7 mL) from these dissolutions, and the counting geometry minimizes sample geometry uncertainties. Counting each sample for thirty minutes delivers excellent precision across the calibration range of 3 to 12 g uranium per liter. As shown by interlaboratory calibration, the gamma-ray spectrometer provides overall (counting, calibration, geometric,...) uncertainties less than 0.7% one sigma. Gamma-rays from a reference source, used to provide live-time corrections, are collimated to avoid absorption by the sample in the detector well. Since sample masses are small, minor self-attenuation corrections are calculated from chemical composition data rather than determined in separate transmission measurements. This avoids employing short-lived transmission sources for self-attenuation corrections.

  2. Status of 236U analyses at ETH Zurich and the distribution of 236U and 129I in the North Sea in 2009

    NASA Astrophysics Data System (ADS)

    Christl, Marcus; Casacuberta, Nuria; Lachner, Johannes; Maxeiner, Sascha; Vockenhuber, Christof; Synal, Hans-Arno; Goroncy, Ingo; Herrmann, Jürgen; Daraoui, Abdelouahed; Walther, Clemens; Michel, Rolf

    2015-10-01

    Compact, low energy accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for the analysis of heavy and long lived radionuclides. In this study, we will first focus on the analytical capabilities of the compact AMS system TANDY, mainly for 236U analyses, and then present a new dual tracer approach, that combines 129I and 236U. The measured 129I/236U ratios of samples collected in the North Sea in 2009 are in reasonable agreement with the expectations from documented or estimated releases from the two major nuclear reprocessing plants located at Sellafield (GB) and La Hague (F), suggesting that the 129I/236U ratio can be used as a water mass tag in the North Atlantic region. However, our results indicate that, in contrast to 129I, additional contributions of bomb produced 236U cannot be neglected in the North Sea region. This complicates the simple and straight forward use of the 129I/236U ratio as a quantitative tool for the calculation of transport times of North Sea water in the Arctic Ocean.

  3. Measurement of 235U(n,n'γ) and 235U(n,2nγ) reaction cross sections

    NASA Astrophysics Data System (ADS)

    Kerveno, M.; Thiry, J. C.; Bacquias, A.; Borcea, C.; Dessagne, P.; Drohé, J. C.; Goriely, S.; Hilaire, S.; Jericha, E.; Karam, H.; Negret, A.; Pavlik, A.; Plompen, A. J. M.; Romain, P.; Rouki, C.; Rudolf, G.; Stanoiu, M.

    2013-02-01

    The design of generation IV nuclear reactors and the studies of new fuel cycles require knowledge of the cross sections of various nuclear reactions. Our research is focused on (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data for reactions and isotopes of interest for transmutation or advanced reactors. The present work studies the 235U(n,n'γ) and 235U(n,2nγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments were performed with the Geel electron linear accelerator GELINA, which delivers a pulsed white neutron beam. The time characteristics enable measuring neutron energies with the time-of-flight (TOF) technique. The neutron induced reactions [in this case inelastic scattering and (n,2n) reactions] are identified by on-line prompt γ spectroscopy with an experimental setup including four high-purity germanium (HPGe) detectors. A fission ionization chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods are presented and the model calculations performed with the TALYS-1.2 code are discussed.

  4. Aspects Of The Coriolis Interaction In 235U

    SciTech Connect

    Ward, D.; Clark, R.M.; Cromaz, M.; Deleplanque, M.A.; Diamond, R.M.; Fallon, P.; Lee, I.Y.; Macchiavelli, A.O.; Stephens, F.S.; Lane, G.J.; Goergen, A.; Svensson, C.E.; Vetter, K.; Cline, D.; Hayes, A.B.; Teng, R.; Wu, C.-Y.; Nakatsukasa, T.

    2005-04-05

    We have performed three separate experiments at LBNL's 88-Inch Cyclotron over a period of several years in which 235U (thick target) was Coulomb-excited. It involved stand-alone experiments with Gammasphere and with the 8PI Spectrometer using 136Xe beams at 720 MeV, and a CHICO-Gammasphere experiment with an 40Ar beam at 180 MeV. In addition to extending the known negative-parity bands to high spin, we have assigned levels in some seven positive-parity bands which are in some cases ( e.g. [631]1/2, [624]7/2 and [622]5/2) strongly populated by E3 excitation. The CHICO data has been analyzed to extract E2 and E3 matrix elements from the observed yields. Additionally, many E1 and M1 matrix elements could be extracted from the {gamma}-ray branching ratios.

  5. Impact of the 235U series on doses from intakes of natural uranium and decay progeny.

    PubMed

    Lowe, L M

    1997-10-01

    The doses from 235U series radionuclides have often been ignored in dose assessments involving natural uranium and progeny. This is due to the relatively low abundance of 235U in natural uranium (less than 5% on an activity basis). However, inclusion of the 235U series radionuclides, especially 227Ac and 231Pa, in dose calculations can have a substantial impact on estimated inhalation doses.

  6. Impact of the 235U series on doses from intakes of natural uranium and decay progeny.

    PubMed

    Lowe, L M

    1997-10-01

    The doses from 235U series radionuclides have often been ignored in dose assessments involving natural uranium and progeny. This is due to the relatively low abundance of 235U in natural uranium (less than 5% on an activity basis). However, inclusion of the 235U series radionuclides, especially 227Ac and 231Pa, in dose calculations can have a substantial impact on estimated inhalation doses. PMID:9314233

  7. 234U /238U and 230Th /234U activity ratios in the colloidal phases of aquifers in lateritic weathered zones

    NASA Astrophysics Data System (ADS)

    Short, Stephen A.; Lowson, Richard T.; Ellis, John

    1988-11-01

    A procedure was developed for comparing solute and colloid phases of groundwaters in contact with uranium ore bodies at Nabarlek and Koongarra in the Alligator Rivers region, Northern Territory, Australia. Single-pass ultrafiltration of large volumes with cut-offs of 18 nm and 1 μm was used. Colloids were composed of Fe and Si species with sorbed U and U daughters. Uranium isotopes were mostly present as soluble species. Thorium was significantly associated with the colloids. The 234U /238U activity ratios (ARs) were similar in solute and colloid phases close to the ore bodies but further down-gradient colloids were generally more depleted of 234U than the solute. The 230Th /234U ARs rose from very low values for both solute and colloid phases close to the ore bodies through several orders of magnitude to much higher values further down-gradient. Colloid 230Th /234U ARs were always significantly greater than solute ARs. Results were consistent with a systematic leaching of U from colloids going down-gradient and very little mobilization of ore-body 230Th relative to U. Ubiquitous complexed 232Th appeared to suppress the solubility of 230Th.

  8. sup 234 U/ sup 238 U and sup 230 Th/ sup 234 U activity ratios in the collidal phases of aquifers in lateritic weathered zones

    SciTech Connect

    Short, S.A.; Lowson, R.T. ); Ellis, J. )

    1988-11-01

    A procedure was developed for comparing solute and colloid phases of groundwaters in contact with uranium ore bodies at Nabarlek and Koongarra in the Alligator Rivers region, Northern Territory, Australia. Single-pass ultrafiltration of large volumes with cut-offs of 18 nm and 1 {mu}m was used. Colloids were composed of Fe and Si species with sorbed U and U daughters. Uranium isotopes were mostly present as soluble species. Thorium was significantly associated with the colloids. The {sup 234}U/{sup 238}U activity ratios (ARs) were similar in solute and colloid phases close to the ore bodies but further down-gradient colloids were generally more depleted of {sup 234}U than the solute. The {sup 230}Th/{sup 234}U ARs rose from very low values for both solute and colloid phases close to the ore bodies through several orders of magnitude to much higher values further down-gradient. Colloid {sup 230}Th/{sup 234}U ARs were always significantly greater than solute ARs. Results were consistent with a systematic leaching of U from colloids going down-gradient and very little mobilization of ore body. {sup 230}Th relative to U. Ubiquitous complexes {sup 232}Th appeared to suppress the solubility of {sup 230}Th.

  9. Determination of the isotopic ratio 236U/ 238U in Austrian water samples

    NASA Astrophysics Data System (ADS)

    Srncik, M.; Steier, P.; Wallner, G.

    2010-04-01

    236U with a half life of 2.3 × 10 7 years is naturally produced in ultra-trace amounts ( 236U/ 238U < 10 -10) in ores, soils and rocks, while a huge amount has been produced in nuclear power plants and possibly nuclear weapons tests by man. Thus, anthropogenic uranium may cause a significant measurement background for geological applications of natural 236U. To investigate this background, water samples from rivers, creeks and wells were collected in the alpine region of Forstau (Salzburg, Austria) and from surrounding areas. Thin sources for alpha spectrometry were prepared by anion exchange and co-precipitation with NdF 3 to determine the 238U concentration. These filters were reprocessed for the analysis of the isotopic ratio 236U/ 238U by AMS. The special aim was the characterization of the 236U/ 238U ratio in natural waters and the investigation of contributions from anthropogenic sources. Our measurements of 236U in Austrian water samples from wells, rivers and creeks show the first data on the spreading of anthropogenic 236U in the general environment far from local contamination sources.

  10. Measurement of (233)U/(234)U ratios in contaminated groundwater using alpha spectrometry.

    PubMed

    Harrison, Jennifer J; Payne, Timothy E; Wilsher, Kerry L; Thiruvoth, Sangeeth; Child, David P; Johansen, Mathew P; Hotchkis, Michael A C

    2016-01-01

    The uranium isotope (233)U is not usually observed in alpha spectra from environmental samples due to its low natural and fallout abundance. It may be present in samples from sites in the vicinity of nuclear operations such as reactors or fuel reprocessing facilities, radioactive waste disposal sites or sites affected by clandestine nuclear operations. On an alpha spectrum, the two most abundant alpha emissions of (233)U (4.784 MeV, 13.2%; and 4.824 MeV, 84.3%) will overlap with the (234)U doublet peak (4.722 MeV, 28.4%; and 4.775 MeV, 71.4%), if present, resulting in a combined (233+234)U multiplet. A technique for quantifying both (233)U and (234)U from alpha spectra was investigated. A series of groundwater samples were measured both by accelerator mass spectrometry (AMS) to determine (233)U/(234)U atom and activity ratios and by alpha spectrometry in order to establish a reliable (233)U estimation technique using alpha spectra. The Genie™ 2000 Alpha Analysis and Interactive Peak Fitting (IPF) software packages were used and it was found that IPF with identification of three peaks ((234)U minor, combined (234)U major and (233)U minor, and (233)U major) followed by interference correction on the combined peak and a weighted average activity calculation gave satisfactory agreement with the AMS data across the (233)U/(234)U activity ratio range (0.1-20) and (233)U activity range (2-300 mBq) investigated. Correlation between the AMS (233)U and alpha spectrometry (233)U was r(2) = 0.996 (n = 10). PMID:26359847

  11. Measurement of (233)U/(234)U ratios in contaminated groundwater using alpha spectrometry.

    PubMed

    Harrison, Jennifer J; Payne, Timothy E; Wilsher, Kerry L; Thiruvoth, Sangeeth; Child, David P; Johansen, Mathew P; Hotchkis, Michael A C

    2016-01-01

    The uranium isotope (233)U is not usually observed in alpha spectra from environmental samples due to its low natural and fallout abundance. It may be present in samples from sites in the vicinity of nuclear operations such as reactors or fuel reprocessing facilities, radioactive waste disposal sites or sites affected by clandestine nuclear operations. On an alpha spectrum, the two most abundant alpha emissions of (233)U (4.784 MeV, 13.2%; and 4.824 MeV, 84.3%) will overlap with the (234)U doublet peak (4.722 MeV, 28.4%; and 4.775 MeV, 71.4%), if present, resulting in a combined (233+234)U multiplet. A technique for quantifying both (233)U and (234)U from alpha spectra was investigated. A series of groundwater samples were measured both by accelerator mass spectrometry (AMS) to determine (233)U/(234)U atom and activity ratios and by alpha spectrometry in order to establish a reliable (233)U estimation technique using alpha spectra. The Genie™ 2000 Alpha Analysis and Interactive Peak Fitting (IPF) software packages were used and it was found that IPF with identification of three peaks ((234)U minor, combined (234)U major and (233)U minor, and (233)U major) followed by interference correction on the combined peak and a weighted average activity calculation gave satisfactory agreement with the AMS data across the (233)U/(234)U activity ratio range (0.1-20) and (233)U activity range (2-300 mBq) investigated. Correlation between the AMS (233)U and alpha spectrometry (233)U was r(2) = 0.996 (n = 10).

  12. Discrete deexcitations in 235U from Nuclear Resonance Fluorescence

    NASA Astrophysics Data System (ADS)

    Kwan, E.; Howell, C. R.; Raut, R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Adekola, A. S.; Hammond, S. L.; Karwowski, H. J.; Pedroni, R.; Kelley, J. H.

    2010-11-01

    Systematics of the even-even rare-earth nuclei suggest a concentration of M1 excitations peaking around 3 MeV with a ∑B(M1) strength of ˜3μN^2. In addition, a linear dependence on the square of the ground-state deformation was observed in the systematics of the ∑B(M1) strengths. The actinide region is interesting for investigation of the ``scissors'' mode of M1 excitations because it has neutron-rich nuclei with large deformations. Evidence of M1 resonances concentrated around 2.0-2.5 MeV were found in ^238U & ^232Th. A research program has been initiated at TUNL to measure dipole transitions in the actinide using HIγS. Nearly monoenergic & circular polarized γ-ray beams below 3.0 MeV was used to measure transitions in ^235U. More than 20 transitions were observed. The integrated cross sections, B(M1) strengths & branching transitions intensities will be presented and compared with previous measurements.

  13. Determination of 235U/238U atom ratio in uranium samples using liquid scintillation counting (LSC).

    PubMed

    Alamelu, D; Aggarwal, S K

    2009-01-15

    A correlation has been developed for the determination of (235)U/(238)U atom ratio in uranium samples using liquid scintillation counting (LSC). The (235)U/(238)U atom ratio determined by thermal ionization mass spectrometry (TIMS) was correlated to the ratio of (i) alpha-count rate and (ii) Cerenkov count rate due to (234 m)Pa in the sample; both measured by LSC. This correlation is linear over the range of (235)U/(238)U atom ratio encountered in the nuclear fuel samples, i.e. the low enriched uranium (LEU) samples with (235)U<20 atom%. The methodology based on this correlation will be useful for the quick determination and verification of (235)U/(238)U atom ratios in fuel samples using cost effective technique of LSC. PMID:19064080

  14. On the Use of 233U-236U Double-Spike for TIMS Measurements of Uranium Isotopes: A Simulation Study

    SciTech Connect

    Williams, R W

    2004-03-17

    Synthetic ion beams with instantaneous and temporal characteristics appropriate to thermal ionization mass spectrometry (TIMS) were mathematically generated and analyzed to determine the effects of using a mixed {sup 233}U-{sup 236}U spike (double-spike) in the analysis of uranium isotopes. The instantaneous beam characteristics are the intensities (e.g., counts per second) modeled with a Poisson distribution plus a component of random noise that simulates the detection processes. Several beam intensity and mass fractionation vs. time functions were modeled to simulate a range of sample sizes and the commonly employed methods of data collection. These beam profiles were also generated with different noise levels, and signal-to-noise vs. analytical precision diagrams are presented. Modeling focused on natural uranium, where {sup 238}U/{sup 235}U = 137.88, and on the ability of a given method to determine precisely and accurately small variations in this ratio. Practical limits on precision were determined to be 20-30 ppm, which is consistent with precision seen for other elements by state-of-the-art TIMS. The TIMS total evaporation method was compared directly with the double-spike method. While similar analytical precisions are obtained with either method, the double-spike method of correcting for analytical bias gives more accurate results. The results of a total evaporation analysis will deviate from true by more than the analytical precision if as little as 0.05% of the signal is not integrated, whereas the accuracy and precision of the double-spiked analyses are always linked.

  15. A comparison of fallout (236)U and (239)Pu uptake by Australian vegetation.

    PubMed

    Froehlich, M B; Dietze, M M A; Tims, S G; Fifield, L K

    2016-01-01

    The isotopes (236)U and (239)Pu, both produced during nuclear weapons tests carried out in the 1950s and 1960s, are present in the environment and may be used as tracers for soil erosion studies. Although these radionuclides occur only at ultra-trace levels in nature, they can be readily measured by accelerator mass spectrometry with the 14UD heavy ion accelerator at the Australian National University. We have analysed a series of vegetation samples for their (236)U and (239)Pu concentration and compared the results with those found in the surrounding soil. (236)U could be measured in all collected samples whereas (239)Pu could not be detected in several vegetation samples due to its very low concentration, although it was readily detectable in the soil. We find that, relative to plutonium, (236)U is preferentially taken up by plants with enrichment factors ((236)U/(239)Pu)veg/((236)U/(239)Pu)soil that range between 7 and 52 in the present study. PMID:26141188

  16. A comparison of fallout (236)U and (239)Pu uptake by Australian vegetation.

    PubMed

    Froehlich, M B; Dietze, M M A; Tims, S G; Fifield, L K

    2016-01-01

    The isotopes (236)U and (239)Pu, both produced during nuclear weapons tests carried out in the 1950s and 1960s, are present in the environment and may be used as tracers for soil erosion studies. Although these radionuclides occur only at ultra-trace levels in nature, they can be readily measured by accelerator mass spectrometry with the 14UD heavy ion accelerator at the Australian National University. We have analysed a series of vegetation samples for their (236)U and (239)Pu concentration and compared the results with those found in the surrounding soil. (236)U could be measured in all collected samples whereas (239)Pu could not be detected in several vegetation samples due to its very low concentration, although it was readily detectable in the soil. We find that, relative to plutonium, (236)U is preferentially taken up by plants with enrichment factors ((236)U/(239)Pu)veg/((236)U/(239)Pu)soil that range between 7 and 52 in the present study.

  17. Recent measurements of 234U/238U isotope ratio in spring waters from the Hadzici area.

    PubMed

    Vidic, Alfred; Ilić, Zorana; Benedik, Ljudmila

    2013-06-01

    The Hadzici area has become interesting for investigation since depleted uranium ammunition had been employed in 1995 during the NATO air strike campaign in Bosnia and Herzegovina. The purpose of this study is to determine uranium concentration and (234)U/(238)U activity ratio in the spring waters of this area and to investigate their relationship, as well as spatial variations. The spring water samples were taken at 18 sites in total. For the determination of uranium radioisotopes, radiochemical separation procedure followed by alpha-particle spectrometry was applied. Uranium concentration in analyzed waters range from 0.15 to 1.12 μg/L. Spring waters from carbonate based sediments have a lower uranium concentration of between 0.15 and 0.43 μg/L, in comparison to waters sampled within sandstone-based sediments ranging from 0.53 to 1.12 μg/L. Dissolved uranium shows significant spatial variability and correlation with bedrock type confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The majority of the analyzed waters have a (234)U/(238)U activity ratio ranging from 1.02 to 1.90, of which half of the results range between 1.02 and 1.16. No apparent depleted uranium (DU) contamination was observed, as (234)U/(238)U activity ratio is dependent on geochemical conditions in the environment. Even though the tested spring waters demonstrate significant variability in uranium concentration, (234)U/(238)U activity ratio and (234)U excess, waters with similar uranium isotopic signatures are observable within the region. The guidelines on the spatial redistribution of dissolved uranium (corresponding to (238)U mass concentration), along with (234)U/(238)U activity ratios were provided by the Inverse Distance Weighting (IDW) method. Waters having similar isotopic signature have been delineated.

  18. Recent measurements of 234U/238U isotope ratio in spring waters from the Hadzici area.

    PubMed

    Vidic, Alfred; Ilić, Zorana; Benedik, Ljudmila

    2013-06-01

    The Hadzici area has become interesting for investigation since depleted uranium ammunition had been employed in 1995 during the NATO air strike campaign in Bosnia and Herzegovina. The purpose of this study is to determine uranium concentration and (234)U/(238)U activity ratio in the spring waters of this area and to investigate their relationship, as well as spatial variations. The spring water samples were taken at 18 sites in total. For the determination of uranium radioisotopes, radiochemical separation procedure followed by alpha-particle spectrometry was applied. Uranium concentration in analyzed waters range from 0.15 to 1.12 μg/L. Spring waters from carbonate based sediments have a lower uranium concentration of between 0.15 and 0.43 μg/L, in comparison to waters sampled within sandstone-based sediments ranging from 0.53 to 1.12 μg/L. Dissolved uranium shows significant spatial variability and correlation with bedrock type confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The majority of the analyzed waters have a (234)U/(238)U activity ratio ranging from 1.02 to 1.90, of which half of the results range between 1.02 and 1.16. No apparent depleted uranium (DU) contamination was observed, as (234)U/(238)U activity ratio is dependent on geochemical conditions in the environment. Even though the tested spring waters demonstrate significant variability in uranium concentration, (234)U/(238)U activity ratio and (234)U excess, waters with similar uranium isotopic signatures are observable within the region. The guidelines on the spatial redistribution of dissolved uranium (corresponding to (238)U mass concentration), along with (234)U/(238)U activity ratios were provided by the Inverse Distance Weighting (IDW) method. Waters having similar isotopic signature have been delineated. PMID:23410592

  19. First measurements of (236)U concentrations and (236)U/(239)Pu isotopic ratios in a Southern Hemisphere soil far from nuclear test or reactor sites.

    PubMed

    Srncik, M; Tims, S G; De Cesare, M; Fifield, L K

    2014-06-01

    The variation of the (236)U and (239)Pu concentrations as a function of depth has been studied in a soil profile at a site in the Southern Hemisphere well removed from nuclear weapon test sites. Total inventories of (236)U and (239)Pu as well as the (236)U/(239)Pu isotopic ratio were derived. For this investigation a soil core from an undisturbed forest area in the Herbert River catchment (17°30' - 19°S) which is located in north-eastern Queensland (Australia) was chosen. The chemical separation of U and Pu was carried out with a double column which has the advantage of the extraction of both elements from a relatively large soil sample (∼20 g) within a day. The samples were measured by Accelerator Mass Spectrometry using the 14UD pelletron accelerator at the Australian National University. The highest atom concentrations of both (236)U and (239)Pu were found at a depth of 2-3 cm. The (236)U/(239)Pu isotopic ratio in fallout at this site, as deduced from the ratio of the (236)U and (239)Pu inventories, is 0.085 ± 0.003 which is clearly lower than the Northern Hemisphere value of ∼0.2. The (236)U inventory of (8.4 ± 0.3) × 10(11) at/m(2) was more than an order of magnitude lower than values reported for the Northern Hemisphere. The (239)Pu activity concentrations are in excellent agreement with a previous study and the (239+240)Pu inventory was (13.85 ± 0.29) Bq/m(2). The weighted mean (240)Pu/(239)Pu isotopic ratio of 0.142 ± 0.005 is slightly lower than the value for global fallout, but our results are consistent with the average ratio of 0.173 ± 0.027 for the southern equatorial region (0-30°S).

  20. Chronology of Pu isotopes and 236U in an Arctic ice core.

    PubMed

    Wendel, C C; Oughton, D H; Lind, O C; Skipperud, L; Fifield, L K; Isaksson, E; Tims, S G; Salbu, B

    2013-09-01

    In the present work, state of the art isotopic fingerprinting techniques are applied to an Arctic ice core in order to quantify deposition of U and Pu, and to identify possible tropospheric transport of debris from former Soviet Union test sites Semipalatinsk (Central Asia) and Novaya Zemlya (Arctic Ocean). An ice core chronology of (236)U, (239)Pu, and (240)Pu concentrations, and atom ratios, measured by accelerator mass spectrometry in a 28.6m deep ice core from the Austfonna glacier at Nordaustlandet, Svalbard is presented. The ice core chronology corresponds to the period 1949 to 1999. The main sources of Pu and (236)U contamination in the Arctic were the atmospheric nuclear detonations in the period 1945 to 1980, as global fallout, and tropospheric fallout from the former Soviet Union test sites Novaya Zemlya and Semipalatinsk. Activity concentrations of (239+240)Pu ranged from 0.008 to 0.254 mBq cm(-2) and (236)U from 0.0039 to 0.053 μBq cm(-2). Concentrations varied in concordance with (137)Cs concentrations in the same ice core. In contrast to previous published results, the concentrations of Pu and (236)U were found to be higher at depths corresponding to the pre-moratorium period (1949 to 1959) than to the post-moratorium period (1961 and 1962). The (240)Pu/(239)Pu ratio ranged from 0.15 to 0.19, and (236)U/(239)Pu ranged from 0.18 to 1.4. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of nuclear atmospheric testing (1952 to 1962). To the best knowledge of the authors the present work is the first publication on biogeochemical cycles with respect to (236)U concentrations and (236)U/(239)Pu atom ratios in the Arctic and in ice cores.

  1. Determination of 235U/238U Ratio on Urine by ICP-MS

    SciTech Connect

    Collins, L; Gobaleza, A; Langston, R; Radev, R; Than, C; Wong, C; Wood-Zika, A

    2011-10-19

    LLNL Internal Dosimetry Program - The new procedure satisfies the requirement to determine {sup 235}U/{sup 238}U ratio in bioassay urine samples. MDA - The L{sub C} and MDA{sub 95} for {sup 235}U are well below the required detection limit of 0.00035 {mu}g/L. Turn around time - Analysis of 10 samples plus 2 QCs can be completed in one work day (8 hours).

  2. Feasibility of using 236U to reconstruct close-in fallout deposition from the Hiroshima atomic bomb.

    PubMed

    Sakaguchi, A; Kawai, K; Steier, P; Imanaka, T; Hoshi, M; Endo, S; Zhumadilov, K; Yamamoto, M

    2010-10-15

    The first results on the feasibility of using (236)U to reconstruct the level and spatial distribution of close-in fallout deposition from the Hiroshima A-bomb are reported, coupled with the use of global fallout (137)Cs and (239+240)Pu. The results for global fallout (236)U in soil samples (0-30cm) from Ishikawa prefecture showed that the deposition density of (236)U from the global fallout can be accurately evaluated using AMS. All deposited (236)U, (137)Cs and (239+240)Pu appeared to have been recovered using 30-cm cores. It was also noted from the depth profiles for (236)U/(239+240)Pu and (236)U/(137)Cs ratios that the downward behavior of (236)U in the soil was apparently similar to that of (239+240)Pu, while the (137)Cs was liable to be retained in upper layers compared with (236)U and (239+240)Pu. The accumulated levels were 1.78×10(13)atomsm(-2) for (236)U, 4340Bqm(-2) for (137)Cs and 141Bqm(-2) for (239+240)Pu. The ratios of (236)U/(137)Cs and (236)U/(239+240)Pu were (4.10±0.12)×10(9) and (1.26±0.04)×10(11)atomsBq(-1), respectively. Results of (236)U, (137)Cs and (239+240)Pu measurements for the seven soil cores (0-30cm) from Hiroshima were discussed on the basis of ratios of (236)U/(137)Cs and (236)U/(239+240)Pu by comparing with those from the background area in Ishikawa, indicating that the global fallout dominates the current level of (236)U accumulation in soil in the Black-rain area around Hiroshima after the Hiroshima bomb, and the contribution of the close-in fallout (236)U produced by the Hiroshima A-bomb seems difficult to observe.

  3. Feasibility of using 236U to reconstruct close-in fallout deposition from the Hiroshima atomic bomb.

    PubMed

    Sakaguchi, A; Kawai, K; Steier, P; Imanaka, T; Hoshi, M; Endo, S; Zhumadilov, K; Yamamoto, M

    2010-10-15

    The first results on the feasibility of using (236)U to reconstruct the level and spatial distribution of close-in fallout deposition from the Hiroshima A-bomb are reported, coupled with the use of global fallout (137)Cs and (239+240)Pu. The results for global fallout (236)U in soil samples (0-30cm) from Ishikawa prefecture showed that the deposition density of (236)U from the global fallout can be accurately evaluated using AMS. All deposited (236)U, (137)Cs and (239+240)Pu appeared to have been recovered using 30-cm cores. It was also noted from the depth profiles for (236)U/(239+240)Pu and (236)U/(137)Cs ratios that the downward behavior of (236)U in the soil was apparently similar to that of (239+240)Pu, while the (137)Cs was liable to be retained in upper layers compared with (236)U and (239+240)Pu. The accumulated levels were 1.78×10(13)atomsm(-2) for (236)U, 4340Bqm(-2) for (137)Cs and 141Bqm(-2) for (239+240)Pu. The ratios of (236)U/(137)Cs and (236)U/(239+240)Pu were (4.10±0.12)×10(9) and (1.26±0.04)×10(11)atomsBq(-1), respectively. Results of (236)U, (137)Cs and (239+240)Pu measurements for the seven soil cores (0-30cm) from Hiroshima were discussed on the basis of ratios of (236)U/(137)Cs and (236)U/(239+240)Pu by comparing with those from the background area in Ishikawa, indicating that the global fallout dominates the current level of (236)U accumulation in soil in the Black-rain area around Hiroshima after the Hiroshima bomb, and the contribution of the close-in fallout (236)U produced by the Hiroshima A-bomb seems difficult to observe. PMID:20797770

  4. 234U/238U as a ground-water tracer, SW Nevada-SE California

    USGS Publications Warehouse

    Ludwig, K. R.; Peterman, Z.E.; Simmons, K.R.; Gutentag, E.D.

    1993-01-01

    The 234U/238U ratio of uranium in oxidizing ground waters is potentially an excellent ground-water tracer because of its high solubility and insensitivity to chemical reactions. Moreover, recent advances in analytical capability have made possible very precise uranium-isotopic analyses on modest (approx.100 ml) amounts of normal ground water. Preliminary results on waters from SW Nevada/Se California indicate two main mixing trends, but in detail indicate significant complexity requiring three or more main components.

  5. Round-robin 230Th–234U age dating of bulk uranium for nuclear forensics

    DOE PAGES

    Gaffney, Amy M.; Hubert, Amélie; Kinman, William S.; Magara, Masaaki; Okubo, Ayako; Pointurier, Fabien; Schorzman, Kerri C.; Steiner, Robert E.; Williams, Ross W.

    2015-07-30

    In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. As a result, these model ages are concordant with to slightly older than the known production age of NBL U050.

  6. Fractionation of 238U/235U by reduction during low temperature uranium mineralisation processes

    NASA Astrophysics Data System (ADS)

    Murphy, Melissa J.; Stirling, Claudine H.; Kaltenbach, Angela; Turner, Simon P.; Schaefer, Bruce F.

    2014-02-01

    Investigations of ‘stable’ uranium isotope fractionation during low temperature, redox transformations may provide new insights into the usefulness of the 238U/235U isotope system as a tracer of palaeoredox processes. Sandstone-hosted uranium deposits accumulate at an oxidation/reduction interface within an aquifer from the low temperature reduction of soluble U(VI) complexes in groundwaters, forming insoluble U(IV) minerals. This setting provides an ideal environment in which to investigate the effects of redox transformations on 238U/235U fractionation. Here we present the first coupled measurements of 238U/235U isotopic compositions and U concentrations for groundwaters and mineralised sediment samples from the same redox system in the vicinity of the high-grade Pepegoona sandstone-hosted uranium deposit, Australia. The mineralised sediment samples display extremely variable 238U/235U ratios (herein expressed as δUCRM145238, the per-mil deviation from the international NBL standard CRM145). The majority of mineralised sediment samples have δUCRM145238 values between -1.30±0.05 and 0.55±0.12‰, spanning a ca. 2‰ range. However, one sample has an unusually light isotopic composition of -4.13±0.05‰, which suggests a total range of U isotopic variability of up to ca. 5‰, the largest variation found thus far in a single natural redox system. The 238U/235U isotopic signature of the mineralised sediments becomes progressively heavier (enriched in 238U) along the groundwater flow path. The groundwaters show a greater than 2‰ variation in their 238U/235U ratios, ranging from δUCRM145238 values of -2.39±0.07 to -0.71±0.05‰. The majority of the groundwater data exhibit a clear systematic relationship between 238U/235U isotopic composition and U concentration; samples with the lowest U concentrations have the lowest 238U/235U ratios. The preferential incorporation of 238U during reduction of U(VI) to U(IV) and precipitation of uranium minerals leaves

  7. U-Pb chronology of the Solar System's oldest solids with variable 238U/ 235U

    NASA Astrophysics Data System (ADS)

    Amelin, Yuri; Kaltenbach, Angela; Iizuka, Tsuyoshi; Stirling, Claudine H.; Ireland, Trevor R.; Petaev, Michail; Jacobsen, Stein B.

    2010-12-01

    Accurate determination of the absolute ages of the oldest Solar System objects — chondrules and Ca-Al-rich inclusions (CAIs), requires knowledge of their 238U/ 235U ratios. This ratio was assumed to be invariant in all U-Pb dating of meteorites so far, but the recent discovery of U isotope variations in CAIs (Brennecka et al., 2010a) shows that this assumption is invalid. We present the first combined high-precision U and Pb isotopic data for a CAI, and U isotopic data for chondrules and whole rock fractions of the Allende meteorite. The Pb-Pb isochron age of the CAI SJ101 is 4567.18 ± 0.50 Ma, calculated using the measured 238U/ 235U = 137.876 ± 0.043 (2σ), reported relative to 238U/ 235U = 137.837 of the CRM 145 standard. Our best current estimate of the average terrestrial value is: 238U/ 235U = 137.821 ± 0.014.The error in the age includes uncertainties in the Pb-Pb isochron intercept and in the 238U/ 235U ratio. Allende bulk rock and chondrules have 238U/ 235U = 137.747 ± 0.017 (2σ), distinctly lower than the CAI. The difference in the 238U/ 235U ratio of 0.129 ± 0.046 (2σ) between the CAI and chondrules and bulk meteorite increases the 207Pb- 206Pb age difference by ~ 1.4 Ma, and eliminates apparent disagreement between the CAI-chondrule formation time interval determinations with the U-Pb and extinct nuclide ( 26Al- 26Mg and 182Hf- 182W) data. We discuss standardisation of 238U/ 235U measurements for U-Pb geochronology and cosmochronology, elemental and isotopic fractionation induced by intensive acid leaching, ages of CAIs in the context of 238U/ 235U variability, and possible causes of U isotopic variations in CAIs and meteorites.

  8. Method for (236)U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry.

    PubMed

    Qiao, Jixin; Hou, Xiaolin; Steier, Peter; Nielsen, Sven; Golser, Robin

    2015-07-21

    An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of (236)U in 10 L seawater samples. (238)U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after an effective iron hydroxide coprecipitation. Accelerator mass spectrometry (AMS) was applied for quantifying the (236)U/(238)U ratio, and inductively coupled plasma mass spectrometry (ICPMS) was used to determine the absolute concentration of (238)U; thus, the concentration of (236)U can be calculated. The key experimental parameters affecting the analytical effectiveness were investigated and optimized in order to achieve high chemical yields and simple and rapid analysis as well as low procedure background. Besides, the operational conditions for the target preparation prior to the AMS measurement were optimized, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80-100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional manual methods for (236)U determination in its tracer application. PMID:26105019

  9. Magmatic Processes at Loihi Seamount Inferred From 226Ra-230Th-234U-238U Disequilibria

    NASA Astrophysics Data System (ADS)

    Pietruszka, A. J.; Hauri, E. H.; Garcia, M. O.

    2001-12-01

    We have conducted a detailed study of the U-series isotope geochemistry of young tholeiitic, transitional and alkalic Loihi basalts to examine the melt generation process during the preshield stage of a Hawaiian volcano. A previous study (Sims et al. 1999; GCA, v. 63) of two dredged lavas from the deep flanks of Loihi found a higher (230Th/238U) activity ratio in an alkalic basalt (1.07) compared to a tholeiitic basalt (1.04). This difference suggests that the tholeiitic basalt may have formed at a higher rate of mantle upwelling than the alkalic basalt. Our samples were collected from surface lava flows at Loihi's summit and along the volcano's south rift zone by submersible. Analyses were preformed using high-precision plasma ionization mass spectrometry. The samples display a relatively large range in the amount of excess 226Ra (0-13%) that extends to much lower values than observed at Kilauea Volcano (11-12%). The low (226Ra/230Th) ratios of Loihi lavas probably result from post-eruptive decay of 226Ra and imply eruption ages of 0-12 kyr. All of the Loihi samples (including the 1996 lava) have small amounts of excess 234U (0.2-0.8%). The most likely source for (234U/238U)>1 at Loihi is seawater, which has (234U/238U)=1.14. Since all of the samples were fresh, hand-picked glasses, these elevated (234U/238U) ratios may have resulted from the assimilation of a seawater-derived component within Loihi's magmatic plumbing system rather than post-eruptive U addition. The range of (230Th/238U) that we measured is 1.01-1.07, which is larger than the previous range known for Loihi. Mass balance calculations using the measured (234U/238U) ratios suggest that 1-6% of the U in the samples that we analyzed is ultimately derived from seawater. Correcting the 230Th-238U disequilibria of the Loihi lavas for this seawater-derived U results in a narrower range in the amount of excess 230Th (6-9%) with no significant differences between tholeiitic, transitional or alkalic basalts

  10. Isotope ratios of (235)U/(238)U and (137)Cs/(235)U in black rain streaks on plaster wall caused by fallout of the Hiroshima atomic bomb.

    PubMed

    Shizuma, Kiyoshi; Endo, Satoru; Fujikawa, Yoko

    2012-02-01

    Radiological investigations of fallout from the atomic bomb detonated over Hiroshima city on 6 August 1945 are important to estimate doses for inhabitants. The authors have analyzed the concentrations of (137)Cs, (235)U, and (238)U in streaks of black rain caused by the atomic bomb using gamma-ray spectroscopy and the ICP-QMS method. The black rain streaks were deposited on a plaster wall of a house located 3.7 km west of the hypocenter that has been kept in the same condition as after the rainfall. Cesium-137 ((137)Cs) was detected from black streak samples. Concentration of (137)Cs in the black rain streaks is twice as high as fallout deposition on the ground in this area. A (235)U/(238)U atom ratio of 0.00887 was found, which is higher than the natural ratio, reflecting the fact that the atomic bomb "Little Boy" used enriched uranium as fuel. The ratio (137)Cs/(235)U was determined to be 0.0091, which is about eight times higher than the estimated ratio of 0.00113 based on the fission yield.

  11. Behavior of 234U, 238U and 226Ra in shallow aquifers of Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Méjean, P.; Pinti, D. L.; Ghaleb, B. G.; Larocque, M.

    2012-12-01

    A study was initiated in order to quantify the groundwater resources available in two different hydrogeological systems. The first is the Bécancour basin located between Montréal and Québec. Groundwater flow in shallower sands intercalated with clays of the Holocene Champlain Sea and fractured carbonates of Ordovician age of the St. Lawrence Lowlands. The second is composed of unconfined and/or buried fluvioglacial deposits (eskers) produced during the Holocene deglaciation (ca. 8,000 yrs ago) in the region of Amos, Abitibi-Temiscamingue. Presence of uranium and radium is dependent of the redox conditions and the physical/lithological characteristic of aquifers. 234U/238U activity ratios can give precious information on the infiltration conditions at the recharge or the water-rock interactions. 226Ra can allow obtaining residence time in young groundwater thanks to its half-life of 2,622 yrs. In Bécancour basin, there is a clear decreasing trend of the 234U/238U activity ratio along the flow path, from a maximum of 3.12 measured close to the recharge (Appalachian Mts.) to a value of 1.14, on the plain close to the St. Lawrence River (discharge). This trend cannot be related to the radioactive decay of the 234U compared to that of 238U because this would mean a water residence time of 106 yrs timescale, while waters are young and they show the occurrence of tritiogenic 3He. There is a clear relation between the alkalinity of waters (and the HCO3- content) and the 234U/238U activity ratio, suggesting that the mobility of uranium might be related to HCO3- and CO32- ions complex, inducing higher mobility of 234U compared to 238U after its expulsion into water by induced α-recoil. In the region of Amos, Abitibi, preliminary results were obtained on freshwater samples collected in the semi-confined St-Mathieu de Berry, the buried one of Barraute and the unconfined moraine of Harricana. Three samples were collected in a confined saline aquifer in the fractured

  12. European roe deer antlers as an environmental archive for fallout (236)U and (239)Pu.

    PubMed

    Froehlich, M B; Steier, P; Wallner, G; Fifield, L K

    2016-01-01

    Anthropogenic (236)U and (239)Pu were measured in European roe deer antlers hunted between 1955 and 1977 which covers and extends beyond the period of intensive nuclear weapons testing (1954-1962). The antlers were hunting trophies, and hence the hunting area, the year of shooting and the approximate age of each animal is given. Uranium and plutonium are known to deposit in skeletal tissue. Since antler histology is similar to bone, both elements were expected in antlers. Furthermore, roe deer shed their antlers annually, and hence antlers may provide a time-resolved environmental archive for fallout radionuclides. The radiochemical procedure is based on a Pu separation step by anion exchange (Dowex 1 × 8) and a subsequent U purification by extraction chromatography using UTEVA(®). The samples were measured by Accelerator Mass Spectrometry at the VERA facility (University of Vienna). In addition to the (236)U and (239)Pu concentrations, the (240)Pu/(239)Pu isotopic ratios were determined with a mean value of 0.172 ± 0.023 which is in agreement with the ratio of global fallout (∼0.18). Rather high (236)U/(238)U ratios of the order of 10(-6) were observed. These measured ratios, where the (236)U arises only from global fallout, have implications for the use of the (236)U/(238)U ratio as a fingerprint for nuclear accidents or releases from nuclear facilities. Our investigations have shown the potential to use antlers as a temporally resolved archive for the uptake of actinides from the environment.

  13. European roe deer antlers as an environmental archive for fallout (236)U and (239)Pu.

    PubMed

    Froehlich, M B; Steier, P; Wallner, G; Fifield, L K

    2016-01-01

    Anthropogenic (236)U and (239)Pu were measured in European roe deer antlers hunted between 1955 and 1977 which covers and extends beyond the period of intensive nuclear weapons testing (1954-1962). The antlers were hunting trophies, and hence the hunting area, the year of shooting and the approximate age of each animal is given. Uranium and plutonium are known to deposit in skeletal tissue. Since antler histology is similar to bone, both elements were expected in antlers. Furthermore, roe deer shed their antlers annually, and hence antlers may provide a time-resolved environmental archive for fallout radionuclides. The radiochemical procedure is based on a Pu separation step by anion exchange (Dowex 1 × 8) and a subsequent U purification by extraction chromatography using UTEVA(®). The samples were measured by Accelerator Mass Spectrometry at the VERA facility (University of Vienna). In addition to the (236)U and (239)Pu concentrations, the (240)Pu/(239)Pu isotopic ratios were determined with a mean value of 0.172 ± 0.023 which is in agreement with the ratio of global fallout (∼0.18). Rather high (236)U/(238)U ratios of the order of 10(-6) were observed. These measured ratios, where the (236)U arises only from global fallout, have implications for the use of the (236)U/(238)U ratio as a fingerprint for nuclear accidents or releases from nuclear facilities. Our investigations have shown the potential to use antlers as a temporally resolved archive for the uptake of actinides from the environment. PMID:26119579

  14. Verification of 235U mass content in nuclear fuel plates by an absolute method

    NASA Astrophysics Data System (ADS)

    El-Gammal, W.

    2007-01-01

    Nuclear Safeguards is referred to a verification System by which a State can control all nuclear materials (NM) and nuclear activities under its authority. An effective and efficient Safeguards System must include a system of measurements with capabilities sufficient to verify such NM. Measurements of NM using absolute methods could eliminate the dependency on NM Standards, which are necessary for other relative or semi-absolute methods. In this work, an absolute method has been investigated to verify the 235U mass content in nuclear fuel plates of Material Testing Reactor (MTR) type. The most intense gamma-ray signature at 185.7 keV emitted after α-decay of the 235U nuclei was employed in the method. The measuring system (an HPGe-spectrometer) was mathematically calibrated for efficiency using the general Monte Carlo transport code MCNP-4B. The calibration results and the measured net count rate were used to estimate the 235U mass content in fuel plates at different detector-to-fuel plate distances. Two sets of fuel plates, containing natural and low enriched uranium, were measured at the Fuel Fabrication Facility. Average accuracies for the estimated 235U masses of about 2.62% and 0.3% are obtained for the fuel plates containing natural and low enriched uranium; respectively, with a precision of about 3%.

  15. The SOFIA experiment: Measurement of 236U fission fragment yields in inverse kinematics

    NASA Astrophysics Data System (ADS)

    Grente, L.; Taïeb, J.; Chatillon, A.; Martin, J.-F.; Pellereau, É.; Boutoux, G.; Gorbinet, T.; Bélier, G.; Laurent, B.; Alvarez-Pol, H.; Ayyad, Y.; Benlliure, J.; Caamaño, M.; Audouin, L.; Casarejos, E.; Cortina-Gil, D.; Farget, F.; Fernández-Domínguez, B.; Heinz, A.; Jurado, B.; Kelić-Heil, A.; Kurz, N.; Lindberg, S.; Löher, B.; Nociforo, C.; Paradela, C.; Pietri, S.; Ramos, D.; Rodriguez-Sanchez, J.-L.; Rodríguez-Tajes, C.; Rossi, D.; Schmidt, K.-H.; Simon, H.; Tassan-Got, L.; Törnqvist, H.; Vargas, J.; Voss, B.; Weick, H.; Yan, Y.

    2016-06-01

    The SOFIA (Studies On FIssion with Aladin) experiment aims at measuring fission-fragments isotopic yields with high accuracy using inverse kinematics at relativistic energies. This experimental technique allows to fully identify the fission fragments in nuclear charge and mass number, thus providing very accurate isotopic yields for low energy fission of a large variety of fissioning systems. This report focuses on the latest results obtained with this set-up concerning electromagnetic-induced fission of 236U.

  16. Crustal subsidence rate off Hawaii determined from 234U/238U ages of drowned coral reefs

    USGS Publications Warehouse

    Ludwig, K. R.; Szabo, B. J.; Moore, J.G.; Simmons, K.R.

    1991-01-01

    A series of submerged coral reefs off northwestern Hawaii was formed during (largely glacial) intervals when the rate of local sea-level rise was less than the maximum upward growth rate of the reefs. Mass-spectrometric 234U/238U ages for samples from six such reefs range from 17 to 475 ka and indicate that this part of the Hawaiian Ridge has been subsiding at a roughly uniform rate of 2.6 mm/yr for the past 475 ka. The 234U/238U ages are in general agreement with model ages of reef drowning (based on estimates of paleo-sea-level stands derived from oxygen-isotope ratios of deep-sea sediments), but there are disagreements in detail. The high attainable precision (??10 ka or better on samples younger than ~800 ka), large applicable age range, relative robustness against open-system behavior, and ease of analysis for this technique hold great promise for future applications of dating of 50-1000 ka coral. -Authors

  17. 230Th-234U Model-Ages of Some Uranium Standard Reference Materials

    SciTech Connect

    Williams, R W; Gaffney, A M; Kristo, M J; Hutcheon, I D

    2009-05-28

    The 'age' of a sample of uranium is an important aspect of a nuclear forensic investigation and of the attribution of the material to its source. To the extent that the sample obeys the standard rules of radiochronometry, then the production ages of even very recent material can be determined using the {sup 230}Th-{sup 234}U chronometer. These standard rules may be summarized as (a) the daughter/parent ratio at time=zero must be known, and (b) there has been no daughter/parent fractionation since production. For most samples of uranium, the 'ages' determined using this chronometer are semantically 'model-ages' because (a) some assumption of the initial {sup 230}Th content in the sample is required and (b) closed-system behavior is assumed. The uranium standard reference materials originally prepared and distributed by the former US National Bureau of Standards and now distributed by New Brunswick Laboratory as certified reference materials (NBS SRM = NBL CRM) are good candidates for samples where both rules are met. The U isotopic standards have known purification and production dates, and closed-system behavior in the solid form (U{sub 3}O{sub 8}) may be assumed with confidence. We present here {sup 230}Th-{sup 234}U model-ages for several of these standards, determined by isotope dilution mass spectrometry using a multicollector ICP-MS, and compare these ages with their known production history.

  18. Potential sources affecting the activity concentrations of 238U, 235U, 232Th and some decay products in lettuce and wheat samples.

    PubMed

    Jeambrun, M; Pourcelot, L; Mercat, C; Boulet, B; Pelt, E; Chabaux, F; Cagnat, X; Gauthier-Lafaye, F

    2012-11-01

    The activity concentrations of radionuclides within the uranium and thorium series were determined in wheat and lettuce at five sites in France, and in their respective potential sources: crop soils of wheat and crop soils and irrigation waters of lettuce. These data were used to calculate concentration ratios and to enrich the database supported by the technical report series N°472 of the IAEA (2010). For wheat and lettuce, the activity concentrations were in the same range for all radionuclides studied, except for (210)Pb, which had higher activity concentrations in wheat, ranging between 1.3 and 11 Bq kg(−1) (fresh weight) as compared to 0.4 and 0.7 Bq kg(−1) (fresh weight) for lettuce. For wheat, the range of activity concentrations (mBq kg(−1); fresh weight) decreased as (210)Pb > (226)Ra (56–1511) ≈ (228)Ra (86–769) > (228)Th (19–176) ≈ (238)U (11–169) ≈ (234)U (12–150) ≈ (230)Th (9.08–197.18) ≈ (232)Th (8.61–121.45) > (235)U (0.53–7.9). For lettuce, it decreased as (228)Ra (<320–1221) > (210)Pb (409–746) > (226)Ra (30–599) ≈ (228)Th (<29–347) > (238)U (8–120) ≈ (234)U (8–121) ≈ (230)Th (5.21–134.63) ≈ (232)Th (5.25–156.99) > (235)U (0.35–5.63). The species differences may reflect different plant physiologies. Through the study of activity ratios of wheat and lettuce in relation with those of the various radionuclide sources it has been possible to highlight the contribution of the main sources of natural radionuclides. Indeed, irrigation water when the uranium concentration is enhanced (>30 mBq L(−1)) contributed significantly to the activity concentration of uranium in lettuces. Concerning the high activity concentrations of (210)Pb, it could be explained by atmospheric particle deposition. The effect of soil particles resuspension and their adhesion to the plant surface seemed to be important in some cases. The soil-to-plant transfer factors were calculated for lettuce and wheat. The values were

  19. Bomb fall-out 236U as a global oceanic tracer using an annually resolved coral core

    PubMed Central

    Winkler, Stephan R.; Steier, Peter; Carilli, Jessica

    2012-01-01

    Anthropogenic 236U (t½=23.4 My) is an emerging isotopic ocean tracer with interesting oceanographic properties, but only with recent advances in accelerator mass spectrometry techniques is it now possible to detect the levels from global fall-out of nuclear weapons testing across the water column. To make full use of this tracer, an assessment of its input into the ocean over the past decades is required. We captured the bomb-pulse of 236U in an annually resolved coral core record from the Caribbean Sea. We thereby establish a concept which gives 236U great advantage – the presence of reliable, well-resolved chronological archives. This allows studies of not only the present distribution pattern, but gives access to the temporal evolution of 236U in ocean waters over the past decades. PMID:23564966

  20. Bomb fall-out 236U as a global oceanic tracer using an annually resolved coral core

    NASA Astrophysics Data System (ADS)

    Winkler, Stephan R.; Steier, Peter; Carilli, Jessica

    2012-12-01

    Anthropogenic 236U (t½=23.4 My) is an emerging isotopic ocean tracer with interesting oceanographic properties, but only with recent advances in accelerator mass spectrometry techniques is it now possible to detect the levels from global fall-out of nuclear weapons testing across the water column. To make full use of this tracer, an assessment of its input into the ocean over the past decades is required. We captured the bomb-pulse of 236U in an annually resolved coral core record from the Caribbean Sea. We thereby establish a concept which gives 236U great advantage - the presence of reliable, well-resolved chronological archives. This allows studies of not only the present distribution pattern, but gives access to the temporal evolution of 236U in ocean waters over the past decades.

  1. Differential Die-Away Analysis for detection of 235U in metallic matrix

    NASA Astrophysics Data System (ADS)

    Kashyap, Yogesh; Agrawal, Ashish; Roy, Tushar; Sarkar, P. S.; Shukla, Mayank; Patel, Tarun; Sinha, Amar

    2016-01-01

    Differential Die-Away Analysis is a powerful tool for detecting small quantity of fissile material even if it is shielded or placed in non-fissile matrix. The technique can be used to monitor and characterize fissile content for nuclear waste assay. In this paper, we have discussed the application of differential die away technique for detection of small quantity of fissile material in nuclear waste assay. Feasibility experiments to optimize various parameters have been carried out for detection of 235U in metallic matrix and reported in this paper. A minimum quantity of 1 g of 235U in 150 kg of metallic matrix has been detected in the experimental configuration being reported.

  2. The 235U Prompt Fission Neutron Spectrum in the BR1 Reactor at SCK•CEN

    NASA Astrophysics Data System (ADS)

    Wagemans, Jan; Malambu, Edouard; Borms, Luc; Fiorito, Luca

    2016-02-01

    The BR1 research reactor at SCK•CEN has a spherical cavity in the graphite above the reactor core. In this cavity an accurately characterised Maxwellian thermal neutron field is present. Different converters can be loaded in the cavity in order to obtain other types of neutron (and gamma) irradiation fields. Inside the so-called MARK III converter a fast 235U(n,f) prompt fission neutron field can be obtained. With the support of MCNP calculations, irradiations in MARK III can be directly related to the pure 235U(n,f) prompt fission neutron spectrum. For this purpose MARK III spectrum averaged cross sections for the most relevant fluence dosimetry reactions have been determined. A calibration factor for absolute measurements has been determined applying activation dosimetry following ISO/IEC 17025 standards.

  3. Critical mass experiment using {sup 235}U foil-SiO{sub 2}-polyethylene plates

    SciTech Connect

    Sanchez, R.; Kimpland, R.; Butterfield, K.; Jaegers, P.; Casson, W.

    1998-12-31

    Fissile material in waste is frequently encountered in decontamination and decommissioning activities. Thousands of drums containing radioactive waste are stored in storage facilities throughout the US Department of Energy (DOE) complex. The amount of fissile material in each drum is generally small because of the criticality safety limits that have been calculated using neutron transport computer codes such as MCNP, KENO, or ONEDANT. No experimental critical data are available to ensure the correctness of the calculations for those systems containing fissile material ({sup 235}U, {sup 233}U, and {sup 239}Pu) in contact with matrix material (Al{sub 2}O{sub 3}, CaO, MgO, and SiO{sub 2}) in the drums. The purpose of the {sup 235}U foil-SiO{sub 2}-polyethylene experiment is to provide experimental data to validate the computer transport codes and the cross-section data.

  4. Calculation and measurement of 235U and 238U fussion counter assembly detection efficiency

    NASA Astrophysics Data System (ADS)

    Swinhoe, M. T.; Jarvis, O. N.

    1984-04-01

    The detection efficiencies of two fission counter assemblies ( 235U and 238U) designed to measure the neutron flux at JET, have been determined for monoenergetic and radioactive neutron sources. The results are in good agreement with calculations using Monte Carlo neutron transport codes, when care is used in setting up the computer models. The mean difference between calculation and experiment is (7±7%).

  5. Mass-spectrometric 230Th-234U-238U dating of the Devils Hole calcite vein

    USGS Publications Warehouse

    Ludwig, K. R.; Simmons, K.R.; Szabo, B. J.; Winograd, I.J.; Landwehr, J.M.; Riggs, A.C.; Hoffman, R.J.

    1992-01-01

    The Devils Hole calcite vein contains a long-term climatic record, but requires accurate chronologic control for its interpretation. Mass-spectrometric U-series ages for samples from core DH-11 yielded 230Th ages with precisions ranging from less than 1,000 years (2??) for samples younger than ???140 ka (thousands of years ago) to less than 50,000 years for the oldest samples (???566 ka). The 2348U/238U ages could be determined to a precision of ???20,000 years for all ages. Calcite accumulated continuously from 566 ka until ???60 ka at an average rate of 0.7 millimeter per 103 years. The precise agreement between replicate analyses and the concordance of the 230Th/238U and 234U/238U ages for the oldest samples indicate that the DH-11 samples were closed systems and validate the dating technique in general.

  6. Resonance analysis and evaluation of the sup 235 U neutron induced cross sections

    SciTech Connect

    Leal, L.C.

    1990-06-01

    Neutron cross sections of fissile nuclei are of considerable interest for the understanding of parameters such as resonance absorption, resonance escape probability, resonance self-shielding,and the dependence of the reactivity on temperature. In the present study, new techniques for the evaluation of the {sup 235}U neutron cross sections are described. The Reich-Moore formalism of the Bayesian computer code SAMMY was used to perform consistent R-matrix multilevel analyses of the selected neutron cross-section data. The {Delta}{sub 3}-statistics of Dyson and Mehta, along with high-resolution data and the spin-separated fission cross-section data, have provided the possibility of developing a new methodology for the analysis and evaluation of neutron-nucleus cross sections. The results of the analysis consists of a set of resonance parameters which describe the {sup 235}U neutron cross sections up to 500 eV. The set of resonance parameters obtained through a R-matrix analysis are expected to satisfy statistical properties which lead to information on the nuclear structure. The resonance parameters were tested and showed good agreement with the theory. It is expected that the parametrization of the {sub 235}U neutron cross sections obtained in this dissertation represents the current state of art in data as well as in theory and, therefore, can be of direct use in reactor calculations. 44 refs., 21 figs., 8 tabs.

  7. Rates of silicate dissolution in deep-sea sediment: In situ measurement using 234U/238U of pore fluids

    SciTech Connect

    Maher, Katharine; DePaolo, Donald J.; Lin, Jo Chiu-Fang

    2004-11-22

    Bulk dissolution rates for sediment from ODP Site 984A in the North Atlantic are determined using the 234U/238U activity ratios of pore water, bulk sediment, and leachates. Site 984A is one of only several sites where closely spaced pore water samples were obtained from the upper 60 meters of the core; the sedimentation rate is high (11 15 cm/ka), hence the sediments in the upper 60 meters are less than 500 ka old. The sediment is clayey silt and composed mostly of detritus derived from Iceland with a significant component of biogenic carbonate (up to 30 percent).The pore water 234U/238U activity ratios are higher than seawater values, in the range of 1.2 to 1.6, while the bulk sediment 234U/238U activity ratios are close to 1.0. The 234U/238U of the pore water reflects a balance between the mineral dissolution rate and the supply rate of excess 234U to the pore fluid by a-recoil injection of 234Th. The fraction of 238U decays that result in a-recoil injection of 234U to pore fluid is estimated to be 0.10 to 0.20 based on the 234U/238U of insoluble residue fractions. The calculated bulk dissolution rates, in units of g/g/yr are in the range of 4 x 10-7 to 2 x 10-6 yr-1. There is significant down-hole variability in pore water 234U/238U activity ratios (and hence dissolution rates) on a scale of ca. 10 m. The inferred bulk dissolution rate constants are 100 to 104 times slower than laboratory-determined rates, 100 times faster than rates inferred for older sediments based on Sr isotopes, and similar to weathering rates determined for terrestrial soils of similar age. The results of this study suggest that U isotopes can be used to measure in situ dissolution rates in fine-grained clastic materials. The rate estimates for sediments from ODP Site 984 confirm the strong dependence of reactivity on the age of the solid material: the bulk dissolution rate (Rd) of soils and deep-sea sediments can be approximately described by the expression Rd >> 0.1 Age-1 for ages

  8. Isotope fractionation of 238U and 235U during biologically-mediated uranium reduction

    NASA Astrophysics Data System (ADS)

    Stirling, Claudine H.; Andersen, Morten B.; Warthmann, Rolf; Halliday, Alex N.

    2015-08-01

    A series of laboratory-controlled microbial experiments using gram-negative sulphate-reducing bacteria (Desulfovibrio brasiliensis) inoculated with natural uranium were performed to investigate 238U/235U fractionation during bacterially-mediated U reduction. Control experiments, without bacteria to drive U reduction, were conducted in parallel. Paired measurements of 238U/235U and U concentration for both the residual growth medium solution and the accumulated biologically-mediated precipitate were obtained using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The control experiments show that only minor (<0.1‰), if any 238U/235U fractionation occurs during co-precipitation with calcite. This implies that carbonate sediments are capable of faithfully recording the signature of the global ocean during Earth's major climatic events, including oxygenation and de-oxygenation transitions in the marine environment. The results for the microbial experiments demonstrate that the 238U/235U composition of the unreacted growth medium containing U(VI) is isotopically lighter than the composition of the U(IV)-bearing precipitate as U(VI) is consumed, in agreement with field-based observations of microbially-mediated U reduction. Uranium isotopic shifts of up to 0.8‰ were observed between the liquid and solid phases. These observations can be modelled using a Rayleigh distillation approach describing kinetic uptake in a closed system, which yields a fractionation factor α of 0.99923 ± 0.00004 (ε = -0.77 ± 04‰) for U(VI)-U(IV) reduction mediated by the D. brasiliensis microbe. This fractionation behaviour is consistent with that observed in field-based redox environments, which give rise to similar α values. Competing processes such as U co-precipitation (e.g. adsorption) may act to lower the apparent value for α and possibly play a secondary role both in the microbial experiments of this study and in natural U reduction settings where

  9. Gamma-ray spectrometer measurement of 238U/235U in uranium ore from a natural reactor at Oklo, Gabon

    USGS Publications Warehouse

    Moxham, Robert M.

    1976-01-01

    About 20 years ago, Kuroda theorized that a high-grade uranium deposit emplaced about 2x109 years ago could achieve criticality and sustain a nuclear chain reaction, given a sufficient thickness of high-grade ore and an appropriate water content. Such a natural reactor was found in 1972 at the Oklo deposit, Gabon. The ore contains as much as 60 percent uranium, but the isotopic abundance of 235U is as little as 0.4 percent in contrast to the normal abundance of 0.7110 percent 235U. A sample from the Oklo deposit containing about 0.51 atom percent 235U (by mass spectrometer) was analyzed by a gamma-ray spectrometer system, using a high-purity planar germanium detector. The 235U was determined from its daughter's (234Th) 63.3 keV photopeak; the 235U was determined from its 143.8 and 163.4 keV photopeaks. The ratios of these photopeaks were compared with that from a standard having normal uranium isotopic content; the resulting calculations give a 235U abundance of 0.54 atom percent in the Oklo sample. The gamma-ray spectrum also contains lines from five other isotopes in the uranium series, which indicate the Oklo sample to be at or near secular equilibrium, as the time elapsed since the nuclear reaction ended was sufficient to permit the daughters to achieve equilibrium.

  10. 230Th-234U Age-Dating Uranium by Mass Spectrometry

    SciTech Connect

    Williams, R W; Gaffney, A M

    2012-04-18

    This is the standard operating procedure used by the Isotope Ratio Mass Spectrometry Group of the Chemical Sciences Division at LLNL for the preparation of a sample of uranium oxide or uranium metal for {sup 230}Th-{sup 234}U age-dating. The method described here includes the dissolution of a sample of uranium oxide or uranium metal, preparation of a secondary dilution, spiking of separate aliquots for uranium and thorium isotope dilution measurements, and purification of uranium and thorium aliquots for mass spectrometry. This SOP may be applied to uranium samples of unknown purity as in a nuclear forensic investigation, and also to well-characterized samples such as, for example, U{sub 3}O{sub 8} and U-metal certified reference materials. The sample of uranium is transferred to a quartz or PFA vial, concentrated nitric acid is added and the sample is heated on a hotplate at approximately 100 C for several hours until it dissolves. The sample solution is diluted with water to make the solution approximately 4 M HNO{sub 3} and hydrofluoric acid is added to make it 0.05 M HF. A secondary dilution of the primary uranium solution is prepared. Separate aliquots for uranium and thorium isotope dilution measurements are taken and spiked with {sup 233}U and {sup 229}Th, respectively. The spiked aliquot for uranium isotope dilution analysis is purified using EiChrom UTEVA resin. The spiked aliquot for thorium isotope dilution analysis is purified by, first, a 1.8 mL AG1x8 resin bed in 9 M HCl on which U adsorbs and Th passes through; second, adsorbing Th on a 1 mL AG1x8 resin bed in 8 M HNO{sub 3} and then eluting it with 9 M HCl followed by 0.1 M HCl + 0.005 M HF; and third, by passing the Th through a final 1.0 mL AG1x8 resin bed in 9 M HCl. The mass spectrometry is performed using the procedure 'Th and U Mass Spectrometry for {sup 230}Th-{sup 234}U Age Dating'.

  11. Fission yields of In isotopes in the thermal neutron fission of235U

    NASA Astrophysics Data System (ADS)

    Shmid, M.; Engler, G.

    1983-03-01

    Fission yields of124 132In in the thermal neutron fission of235U were determined for the first time. Charge displacements ΔZ= Z p- Z UCD were calculated for the corresponding mass chains. Both fission yields and charge displacement values were compared with those obtained by systematics by Wahl et al. and Wolfsberg. It was found that the fission yields of the In isotopes obey the gaussian distribution. The displacement function of Wolfsberg seems to give the better representation of the experimental results. Half-lives of124 131In were determined from beta decay curves.

  12. Moderation control in low enriched {sup 235}U uranium hexafluoride packaging operations and transportation

    SciTech Connect

    Dyer, R.H.; Kovac, F.M.; Pryor, W.A.

    1993-12-31

    Moderation control is the basic parameter for ensuring nuclear criticality safety during the packaging and transport of low {sup 235}U enriched uranium hexafluoride before its conversion to nuclear power reactor fuel. Moderation control has permitted the shipment of bulk quantities in large cylinders instead of in many smaller cylinders and, therefore, has resulted in economies without compromising safety. Overall safety and uranium accountability have been enhanced through the use of the moderation control. This paper discusses moderation control and the operating procedures to ensure that moderation control is maintained during packaging operations and transportation.

  13. Moderation control in low enriched {sup 235}U uranium hexafluoride packaging operations and transportation

    SciTech Connect

    Dyer, R.H.; Kovac, F.M.; Pryor, W.A.

    1993-10-01

    Moderation control is the basic parameter for ensuring nuclear criticality safety during the packaging and transport of low {sup 235}U enriched uranium hexafluoride before its conversion to nuclear power reactor fuel. Moderation control has permitted the shipment of bulk quantities in large cylinders instead of in many smaller cylinders and, therefore, has resulted in economies without compromising safety. Overall safety and uranium accountability have been enhanced through the use of the moderation control. This paper discusses moderation control and the operating procedures to ensure that moderation control is maintained during packaging operations and transportation.

  14. Transition from Asymmetric to Symmetric Fission in the 235U(n,f) Reaction

    SciTech Connect

    Younes, W; Becker, J A; Bernstein, L A; Garrett, P E; McGrath, C A; McNabb, D P; Nelson, R O; Johns, G D; Wilburn, W S; Drake, D M

    2001-07-19

    Prompt {gamma} rays from the neutron-induced fission of {sup 235}U have been studied using the GEANIE spectrometer situated at the LANSCE/WNR ''white'' neutron facility. Gamma-ray production cross sections for 29 ground-state-band transitions in 18 even-even fission fragments were obtained as a function of incident neutron energy, using the time-of-flight technique. Independent yields were deduced from these cross sections and fitted with standard formulations of the fragment charge and mass distributions to study the transition from asymmetric to symmetric fission. The results are interpreted in the context of the disappearance of shell structure at high excitation energies.

  15. Critical mass experiment using {sup 235}U foils and lucite plates

    SciTech Connect

    Sanchez, R.; Butterfield, K.; Kimpland, R.; Jaegers, P.

    1998-09-01

    This experiment demonstrated how the neutron multiplication of a system increases as moderated material is placed between highly enriched uranium foils. In addition, this experiment served to demonstrate the hand-stacking technique and approach to criticality be remote operation. This experiment was designed by McLaughlin in the mid-seventies as part of the criticality safety course that is taught at the Los Alamos Critical Experiments Facility. The H/{sup 235}U ratio for this experiment was 215, which is the ratio at which the minimum critical mass for this configuration occurs.

  16. Collinear cluster tripartition channel in the reaction {sup 235}U(n{sub th}, f)

    SciTech Connect

    Pyatkov, Yu. V.; Kamanin, D. V.; Kopach, Yu. N.; Alexandrov, A. A.; Alexandrova, I. A.; Borzakov, S. B.; Voronov, Yu. N.; Zhuchko, V. E.; Kuznetsova, E. A. Panteleev, Ts.; Tyukavkin, A. N.

    2010-08-15

    Investigation of the {sup 235}U(n{sub th}, f) reaction using the miniFOBOS double-arm time-of-flight spectrometer of fission fragments confirmed manifestations of the earlier unknown many-body, at least ternary, decay involving almost collinear decay-product escape, which were first observed in the spontaneous fission of {sup 252}Cf(sf). The use of variables sensitive to the nuclear charge of fission fragments allowed the reliability of identification of decay events to be increased and new decay modes to be revealed.

  17. U-234/U-238 ratio: Qualitative estimate of groundwater flow in Rocky Flats monitoring wells

    SciTech Connect

    Laul, J.C.

    1994-02-01

    Groundwater movement through various pathways is the primary mechanism for the transport of radionuclides and trace elements in a water/rock interaction. About three dozen wells, installed in the Rocky Flats Plant (RFP) Solar Evaporation Ponds (SEP) area, are monitored quarterly to evaluate the extent of any lateral and downgradient migration of contaminants from the Solar Evaporation Ponds: 207-A; 207-B North, 207-B Center, and 207-B South; and 207-C. The Solar Ponds are the main source for the various contaminants: radionuclides (U-238, U-234, Pu-239, 240 and Am-241); anions; and trace metals to groundwaters. The U-238 concentrations in Rocky Flats groundwaters vary from <0.2 to 69 pCi/I (IpCi = 3 ug). However, the activity U-234/U-238 ratios are low and range mostly 1.2 to 2.7. The low activity ratios can be interpreted to suggest that the groundwaters are moving slow (

  18. Mass estimates of very small reactor cores fueled by Uranium-235, U-233 and Cm-245

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.; Lipinski, Ronald J.

    2001-02-01

    This paper explores the possibility of manufacturing very small reactors from U-235, U-233 and Cm-245. Pin type reactor systems fueled with uranium or curium metal zirconium hydride (UZrH or CmZrH) are compared with similar designs using U-235. Criticality measurements of homogeneous water uranium systems, suggest that reactor subsystem masses have a broad minimum for hydrogen-to-uranium atom ratios that vary from 25-250. This paper compares the masses of metal-hydride fueled reactor systems that use U-235, U-233, and Cm-245 fuel with hydrogen-to-metal atom ratios from 20-300 when cooled by gas (HeXe), liquid metal (Na), and water. The results indicate that water cooled reactors in general have the smallest reactor subsystem mass. For gas and liquid-metal cooled reactors U-233 subsystems have total masses that are about 1/2 those of similarly designed U-235 fuel reactors. Reactor subsystems consisting of 11.2% enriched Cm-245 (balance Cm-244) that can be obtained from fuel reprocessing have system masses comparable to that of U-233. The smallest reactor subsystem masses were on the order of 60-80 kg for U-233 fueled water cooled reactors. .

  19. New precision measurements of the 235U(n,γ) cross section.

    PubMed

    Jandel, M; Bredeweg, T A; Bond, E M; Chadwick, M B; Couture, A; O'Donnell, J M; Fowler, M; Haight, R C; Kawano, T; Reifarth, R; Rundberg, R S; Ullmann, J L; Vieira, D J; Wouters, J M; Wilhelmy, J B; Wu, C Y; Becker, J A

    2012-11-16

    The neutron capture cross section of (235)U was measured for the neutron incident energy region between 4 eV and 1 MeV at the DANCE facility at the Los Alamos Neutron Science Center with an unprecedented accuracy of 2-3% at 1 keV. The new methodology combined three independent measurements. In the main experiment, a thick actinide sample was used to determine neutron capture and neutron-induced fission rates simultaneously. In the second measurement, a fission tagging detector was used with a thin actinide sample and detailed characteristics of the prompt-fission gamma rays were obtained. In the third measurement, the neutron scattering background was characterized using a sample of (208)Pb. The relative capture cross section was obtained from the experiment with the thick (235)U sample using a ratio method after the subtraction of the fission and neutron scattering backgrounds. Our result indicates errors that are as large as 30% in the 0.5-2.5 keV region, in the current knowledge of neutron capture as embodied in major nuclear data evaluations. Future modifications of these databases using the improved precision data given herein will have significant impacts in neutronics calculations for a variety of nuclear technologies.

  20. R-matrix analysis of the /sup 235/U neutron cross sections

    SciTech Connect

    Leal, L.C.; de Saussure, G.; Perez, R.B.

    1988-01-01

    The ENDFB-V representation of the /sup 235/U neutron cross sections in the resolved resonance region is unsatisfactory: below 1 eV the cross sections are given by ''smooth files'' (file 3) rather than by resonance parameters; above 1 eV the single-level formalism used by ENDFB-V necessitates a structured file 3 contribution consisting of more than 1300 energy points; furthermore, information on level-spins has not been included. Indeed the ENDFB-V /sup 235/U resonance region is based on an analysis done in 1970 for ENDFB-III and therefore does not include the results of high quality measurements done in the past 18 years. The present paper presents the result of an R-matrix multilevel analysis of recent measurements as well as older data. The analysis also extends the resolved resonance region from its ENDFB-V upper limit of 81 eV to 110 eV. 13 refs., 2 figs., 1 tab

  1. Consistent Data Assimilation of Actinide Isotopes: 235U and 239Pu

    SciTech Connect

    G. Palmiottti; H. Hiruta; M. Salvatores

    2011-09-01

    In this annual report we illustrate the methodology of the consistent data assimilation that allows to use the information coming from integral experiments for improving the basic nuclear parameters used in cross section evaluation. A series of integral experiments were analyzed using the EMPIRE evaluated files for {sup 235}U, {sup 238}U, and {sup 239}Pu. Inmost cases the results have shown quite large worse results with respect to the corresponding existing evaluations available for ENDF/B-VII. The observed discrepancies between calculated and experimental results were used in conjunction with the computed sensitivity coefficients and covariance matrix for nuclear parameters in a consistent data assimilation. Only the GODIVA and JEZEBEL experimental results were used, in order to exploit information relative to the isotope of interest that are, in this particular case: {sup 235}U and {sup 239}Pu. The results obtained by the consistent data assimilation indicate that with reasonable modifications (mostly within the initial standard deviation) it is possible to eliminate the original large discrepancies on the K{sub eff} of the two critical configurations. However, some residual discrepancy remains for a few fission spectral indices that are, most likely, to be attributed to the detector cross sections.

  2. 234U/238U evidence for local recharge and patterns of groundwater flow in the vicinity of Yucca Mountain, Nevada, USA

    USGS Publications Warehouse

    Paces, J.B.; Ludwig, K. R.; Peterman, Z.E.; Neymark, L.A.

    2002-01-01

    Uranium concentrations and 234U/238U ratios in saturated-zone and perched ground water were used to investigate hydrologic flow and downgradient dilution and dispersion in the vicinity of Yucca Mountain, a potential high-level radioactive waste disposal site. The U data were obtained by thermal ionization mass spectrometry on more than 280 samples from the Death Valley regional flow system. Large variations in both U concentrations (commonly 0.6-10 ??g 1-1) and 234U/238U activity ratios (commonly 1.5-6) are present on both local and regional scales; however, ground water with 234U/238U activity ratios from 7 up to 8.06 is restricted largely to samples from Yucca Mountain. Data from ground water in the Tertiary volcanic and Quaternary alluvial aquifers at and adjacent to Yucca Mountain plot in 3 distinct fields of reciprocal U concentration versus 234U/238U activity ratio correlated to different geographic areas. Ground water to the west of Yucca Mountain has large U concentrations and moderate 234U/238U whereas ground water to the east in the Fortymile flow system has similar 234U/238U, but distinctly smaller U concentrations. Ground water beneath the central part of Yucca Mountain has intermediate U concentrations but distinctive 234U/238U activity ratios of about 7-8. Perched water from the lower part of the unsaturated zone at Yucca Mountain has similarly large values of 234U/238U. These U data imply that the Tertiary volcanic aquifer beneath the central part of Yucca Mountain is isolated from north-south regional flow. The similarity of 234U/238U in both saturated- and unsaturated-zone ground water at Yucca Mountain further indicates that saturated-zone ground water beneath Yucca Mountain is dominated by local recharge rather than regional flow. The distinctive 234U/238U signatures also provide a natural tracer of downgradient flow. Elevated 234U/238U in ground water from two water-supply wells east of Yucca Mountain are interpreted as the result of induced

  3. Investigating Prompt Fission Neutron Emission from 235U(n,f) in the Resolved Resonance Region

    NASA Astrophysics Data System (ADS)

    Göök, Alf; Hambsch, Franz-Josef; Oberstedt, Stephan

    2016-03-01

    Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.

  4. High-Resolution Correlated Fission Product Measurements of 235U (nth , f) with SPIDER

    NASA Astrophysics Data System (ADS)

    Shields, Dan; Spider Team

    2015-10-01

    The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) has obtained high-resolution, moderate-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (ν), and total kinetic energy (TKE). These data will be some of the first of their kind available to nuclear data evaluations. An overview of the SPIDER detector, analytical method, and preliminary results for 235U (nth , f) will be presented. LA-UR-15-20130 This work benefited from the use of the LANSCE accelerator facility and was performed under the auspices of the US Department of Energy by Los Alamos Security, LLC under Contract DE-AC52-06NA25396.

  5. ({sup 234}U/{sup 238}U) activity ratios in freshwaters as tracers of hydrological processes: The Strengbach watershed (Vosges, France)

    SciTech Connect

    Riotte, J.; Chabaux, F.

    1999-05-01

    ({sup 234}U/{sup 238}U) and {sup 87}Sr/{sup 86}Sr isotopic ratios, as well as major and trace (U, Ba, Sr, Rb) element concentrations were analyzed in dissolved loads of the Strengback stream (Vosges, France) in order to constrain the sources of U isotopes ({sup 234}U--{sup 238}U) to river waters. The variations of the ({sup 234}U/{sup 238}U) activity ratios along the stream indicate a clear dependence between the ({sup 234}U/{sup 238}U) activity ratios of the surface waters and the different types of rocks forming the watershed, with near equilibrium values for the waters draining granites and high ({sup 234}U/{sup 238}U) disequilibria (1.4) for those flowing over carbonates. The high ({sup 234}U/{sup 238}U) disequilibria are related to a supply of {sup 234}U-enriched groundwaters located within the carbonate rocks. The ({sup 234}U/{sup 238}U) activity ratios of the waters at the outlet of the catchment collecting the sources of the stream on the granitic lithology, decrease from 1.02 to 0.96 when the discharge of the stream increases. Such a tendency requires mixing between a water body enriched in {sup 234}U which weathered the granitic bed rock at secular equilibrium, and a water with a ({sup 234}U/{sup 238}U) activity ratio below unity representing a mobilization of U from material that has already been weathered. Comparison of the geochemical characteristics of waters collected during the year and those collected during a flood event, reveals the involvement of two different weathered end-members, depending on the hydrological conditions: during the year, the dissolved U transported by the river originates from bed-rock and deep horizons of the weathering profile, whereas a significant part of U, during the flood event, is supplied by superficial horizons of soils, probably complexes by organic colloids. These results outline the potential of ({sup 234}U/{sup 238}U) activity ratios to investigate hydrological processes and emphasize that their use as tracers

  6. 238U/235U variations in meteorites: extant 247Cm and implications for Pb-Pb dating.

    PubMed

    Brennecka, G A; Weyer, S; Wadhwa, M; Janney, P E; Zipfel, J; Anbar, A D

    2010-01-22

    The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAIs) of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409 +/- 0.039 and 137.885 +/- 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAIs, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of 238U/235U in CAIs were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial 247Cm/235U ratio of approximately 1.1 x 10(-4) to 2.4 x 10(-4).

  7. Combined 238U/235U and Pb Isotopics of Planetary Core Material: The Absolute Age of the IVA Iron Muonionalusta

    NASA Astrophysics Data System (ADS)

    Brennecka, G. A.; Amelin, Y.; Kleine, T.

    2016-08-01

    We report a measured 238U/235U for the IVA iron Muonionalusta. This measured value requires an age correction of ~7 Myr to the previously published Pb-Pb age. This has major implications for our understanding of planetary core formation and cooling.

  8. Surrogate Reactions in the Actinide Region

    SciTech Connect

    Burke, J T; Bernstein, L A; Scielzo, N D; Bleuel, D L; Lesher, S R; Escher, J; Ahle, L; Dietrich, F S; Hoffman, R D; Norman, E B; Sheets, S A; Phair, L; Fallon, P; Clark, R M; Gibelin, J; Jewett, C; Lee, I Y; Macchiavelli, A O; McMahan, M A; Moretto, L G; Rodriguez-Vieitez, E; Wiedeking, M; Lyles, B F; Beausang, C W; Allmond, J M; Ai, H; Cizewski, J A; Hatarik, R; O'Malley, P D; Swan, T

    2008-01-30

    Over the past three years we have studied various surrogate reactions (d,p), ({sup 3}He,t), ({alpha},{alpha}{prime}) on several uranium isotopes {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U. An overview of the STARS/LIBERACE surrogate research program as it pertains to the actinides is discussed. A summary of results to date will be presented along with a discussion of experimental difficulties encountered in surrogate experiments and future research directions.

  9. Diagenesis of fossil coral skeletons: Correlation between trace elements, textures, and [sup 234]U/[sup 238]U

    SciTech Connect

    Bar-Matthews, M.; Wasserburg, G.J.; Chen, J.H. )

    1993-01-01

    A comparative study of Pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographic and trace element analyses on a suite of Pleistocene samples that had previously been studied from [sup 234]U, [sup 230]Th, and U-[sup 230]Th ages (Chen et al. 1991). Evidence of a range of diagenetic changes can be recognized by optical (OM) and scanning electron microscopy (SEM). Using an electron microprobe and SEM, concentrations of Na, S, Sr, and Mg were measured. No other trace elements were detected. Na, S, and Mg contents of the matrix, the fibrous micropores, and radiating needles are highly variable and well correlated. High concentrations of Na, S, and Mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores, and the lowest value in the radiating needles. The reason for the correlations of Na, S, and Mg and crystal chemistry and the response to diagenesis of these trace elements is not understood. The average concentrations of Na, S, and Mg for each sample, when plotted against the whole coral initial [delta][sup 234]U, are generally correlated (Chen et al., 1991). As all these diagenetic changes involve the recystallization and deposition of aragonite, the authors infer that the geologic site of diagenesis both for forming the secondary aragonitic phases and for the enhancement of the [sup 234]U content in the fossil corals was the marine environment. It is possible that the textural and Na, S, and Mg trace element contents of fossil corals be used to ascertain the reliability of fossil coral skeletons for U-[sup 230]Th dating. The basic problem of identifying a priori unaltered coral skeletons for [sup 230]Th dating is not yet resolved. 64 refs., 16 figs., 5 tabs.

  10. Determination of 235U enrichment with a large volume CZT detector

    NASA Astrophysics Data System (ADS)

    Mortreau, Patricia; Berndt, Reinhard

    2006-01-01

    Room-temperature CdZnTe and CdTe detectors have been routinely used in the field of Nuclear Safeguards for many years [Ivanov et al., Development of large volume hemispheric CdZnTe detectors for use in safeguards applications, ESARDA European Safeguards Research and Development Association, Le Corum, Montpellier, France, 1997, p. 447; Czock and Arlt, Nucl. Instr. and Meth. A 458 (2001) 175; Arlt et al., Nucl. Instr. and Meth. A 428 (1999) 127; Lebrun et al., Nucl. Instr. and Meth. A 448 (2000) 598; Aparo et al., Development and implementation of compact gamma spectrometers for spent fuel measurements, in: Proceedings, 21st Annual ESARDA, 1999; Arlt and Rudsquist, Nucl. Instr. and Meth. A 380 (1996) 455; Khusainov et al., High resolution pin type CdTe detectors for the verification of nuclear material, in: Proceedings, 17th Annual ESARDA European Safeguards Research and Development Association, 1995; Mortreau and Berndt, Nucl. Instr. and Meth. A 458 (2001) 183; Ruhter et al., UCRL-JC-130548, 1998; Abbas et al., Nucl. Instr. and Meth. A 405 (1998) 153; Ruhter and Gunnink, Nucl. Instr. and Meth. A 353 (1994) 716]. Due to their performance and small size, they are ideal detectors for hand-held applications such as verification of spent and fresh fuel, U/Pu attribute tests as well as for the determination of 235U enrichment. The hemispherical CdZnTe type produced by RITEC (Riga, Latvia) [Ivanov et al., 1997] is the most widely used detector in the field of inspection. With volumes ranging from 2 to 1500 mm 3, their spectral performance is such that the use of electronic processing to correct the pulse shape is not required. This paper reports on the work carried out with a large volume (15×15×7.5 mm 3) and high efficiency hemispherical CdZnTe detector for the determination of 235U enrichment. The measurements were made with certified uranium samples whose enrichment ranging from 0.31% to 92.42%, cover the whole range of in-field measurement conditions. The interposed

  11. Neutron experiments at Portsmouth for measuring flow and {sup 235}U content in UF{sub 6} gas

    SciTech Connect

    Stromswold, D C; Reeder, P L; Peurrung, A J

    1997-04-01

    The Portsmouth Gaseous Diffusion Plant produces enriched uranium for use in commercial power reactors. The plant also aids disposal of excess high-enrichment uranium (HEU) by blending it with lower-enrichment material. Experiments were conducted to test two neutron-based methods for monitoring the down-blending of HEU. Results of the initial experiments showed that gas (on-off) could be detected, but that additional tests and data are needed to quantify the flow velocity and {sup 235}U content. The experiments used a {sup 252}Cf neutron source to induce fission in a small fraction of the {sup 235}U contained in the UF{sub 6} gas. The first method measured the attenuation of neutrons passing through the low-pressure UF{sub 6} gas in a 7.6-cm diameter pipe. The concept was based on the fact that some of the thermal neutrons are absorbed by {sup 235}U, thus changing the observed count rate. The second method, tested on a 20-cm diameter pipe where gas pressure was higher, used a modulated neutron flux to induce fission in the {sup 235}U. Modulation was achieved by moving a neutron source. During both experiments, plant monitoring equipment showed that light gases (freon, oxygen, and nitrogen) were present in widely varying amounts, along with the UF{sub 6} gas. These gases may have affected the experimental results, at least to the extent that they replaced UF{sub 6}. This report also contains results of computer simulations and tests performed on the electronics after the experiments were completed at Portsmouth. Recommendations are made for follow-on work to measure the flow velocity and {sup 235}U content.

  12. Mass dependence of fragment angular distributions in the fission of 232Th and 236U induced by polarized photons

    NASA Astrophysics Data System (ADS)

    Steiper, F.; Frommhold, Th.; Henkel, W.; Jung, A.; Kneissl, U.; Stock, R.

    1993-10-01

    Near-barrier fission of 232Th and 236U induced by linearly polarized photons has been investigated. The experiments have been carried out at the "off-axis" bremsstrahlung facility of the Giessen 65 MeV electron linac. Fragment angular, mass and energy distributions have been measured simultaneously allowing the investigation of correlations between these fragment characteristics. A consistent assignment of the quantum numbers Jπ and K for the fussion channels involved in the fission process is proposed. For the first time, the polar anisotropies and azimuthal asymmetries of the fission fragment angular distributions W( θ, φ) have been investigated as a function of the fragment masses. The results are discussed in the framework of the double-humped fission barrier concept and the so-called "multi-exit fission channel" model. Additionally, angular distributions of heavy and light fission fragments from photofission of 236U have been analyzed for a possible asymmetry with respect to θ = 90°.

  13. Sequential injection method for rapid and simultaneous determination of 236U, 237Np, and Pu isotopes in seawater.

    PubMed

    Qiao, Jixin; Hou, Xiaolin; Steier, Peter; Golser, Robin

    2013-11-19

    An automated analytical method implemented in a novel dual-column tandem sequential injection (SI) system was developed for simultaneous determination of (236)U, (237)Np, (239)Pu, and (240)Pu in seawater samples. A combination of TEVA and UTEVA extraction chromatography was exploited to separate and purify target analytes, whereupon plutonium and neptunium were simultaneously isolated and purified on TEVA, while uranium was collected on UTEVA. The separation behavior of U, Np, and Pu on TEVA-UTEVA columns was investigated in detail in order to achieve high chemical yields and complete purification for the radionuclides of interest. (242)Pu was used as a chemical yield tracer for both plutonium and neptunium. (238)U was quantified in the sample before the separation for deducing the (236)U concentration from the measured (236)U/(238)U atomic ratio in the separated uranium target using accelerator mass spectrometry. Plutonium isotopes and (237)Np were measured using inductively coupled plasma mass spectrometry after separation. The analytical results indicate that the developed method is robust and efficient, providing satisfactory chemical yields (70-100%) of target analytes and relatively short analytical time (8 h/sample). PMID:24134480

  14. (236)U and (239,)(240)Pu ratios from soils around an Australian nuclear weapons test site.

    PubMed

    Tims, S G; Froehlich, M B; Fifield, L K; Wallner, A; De Cesare, M

    2016-01-01

    The isotopes (236)U, (239)Pu and (240)Pu are present in surface soils as a result of global fallout from nuclear weapons tests carried out in the 1950's and 1960's. These isotopes potentially constitute artificial tracers of recent soil erosion and sediment movement. Only Accelerator Mass Spectrometry has the requisite sensitivity to measure all three isotopes at these environmental levels. Coupled with its relatively high throughput capabilities, this makes it feasible to conduct studies of erosion across the geographical extent of the Australian continent. In the Australian context, however, global fallout is not the only source of these isotopes. As part of its weapons development program the United Kingdom carried out a series of atmospheric and surface nuclear weapons tests at Maralinga, South Australia in 1956 and 1957. The tests have made a significant contribution to the Pu isotopic abundances present in the region around Maralinga and out to distances ∼1000 km, and impact on the assessment techniques used in the soil and sediment tracer studies. Quantification of the relative fallout contribution derived from detonations at Maralinga is complicated owing to significant contamination around the test site from numerous nuclear weapons safety trials that were also carried out around the site. We show that (236)U can provide new information on the component of the fallout that is derived from the local nuclear weapons tests, and highlight the potential of (236)U as a new fallout tracer. PMID:26141189

  15. (236)U and (239,)(240)Pu ratios from soils around an Australian nuclear weapons test site.

    PubMed

    Tims, S G; Froehlich, M B; Fifield, L K; Wallner, A; De Cesare, M

    2016-01-01

    The isotopes (236)U, (239)Pu and (240)Pu are present in surface soils as a result of global fallout from nuclear weapons tests carried out in the 1950's and 1960's. These isotopes potentially constitute artificial tracers of recent soil erosion and sediment movement. Only Accelerator Mass Spectrometry has the requisite sensitivity to measure all three isotopes at these environmental levels. Coupled with its relatively high throughput capabilities, this makes it feasible to conduct studies of erosion across the geographical extent of the Australian continent. In the Australian context, however, global fallout is not the only source of these isotopes. As part of its weapons development program the United Kingdom carried out a series of atmospheric and surface nuclear weapons tests at Maralinga, South Australia in 1956 and 1957. The tests have made a significant contribution to the Pu isotopic abundances present in the region around Maralinga and out to distances ∼1000 km, and impact on the assessment techniques used in the soil and sediment tracer studies. Quantification of the relative fallout contribution derived from detonations at Maralinga is complicated owing to significant contamination around the test site from numerous nuclear weapons safety trials that were also carried out around the site. We show that (236)U can provide new information on the component of the fallout that is derived from the local nuclear weapons tests, and highlight the potential of (236)U as a new fallout tracer.

  16. Characterization of 235U Targets for the Development of a Secondary Neutron Fluence Standard

    NASA Astrophysics Data System (ADS)

    Heyse, J.; Anastasiou, M.; Eykens, R.; Moens, A.; Plompen, A. J. M.; Schillebeeckx, P.; Sibbens, G.; Vanleeuw, D.; Wynants, R.

    2014-05-01

    The MetroFission project, a Joint Research Project within the European Metrology Research Program (EMRP), aims at addressing a number of metrological problems involved in the design of proposed Generation IV nuclear reactors. As part of this project a secondary neutron fluence standard is being developed and tested at the neutron time-of-flight facility GELINA of the JRC Institute for Reference Materials and Measurements (IRMM). This secondary standard will help to reach the neutron cross section measurement uncertainties required for the design of new generation power plants and fuel cycles. Such a neutron fluence device contains targets for which the neutron induced cross section is considered to be a standard. A careful preparation and characterization of these samples is an essential part of its development. In this framework a set of 235U targets has been produced by vacuum deposition of UF4 on aluminum backings by the target preparation laboratory at IRMM. These targets have been characterized for both their total mass and mass distribution over the sample area.

  17. Crustal subsidence rate off Hawaii determined from sup 234 U/ sup 238 U ages of drowned coral reefs

    SciTech Connect

    Ludwig, K.R.; Szabo, B.J.; Simmons, K.R. ); Moore, J.G. )

    1991-02-01

    A series of submerged coral reefs off northwestern Hawaii was formed during (largely glacial) intervals when the rate of local sea-level rise was less than the maximum upward growth rate of the reefs. Mass-spectrometric {sup 234}U/{sup 238}U ages for samples from six such reefs range from 17 to 475 ka and indicate that this part of the Hawaiian Ridge has been subsiding at a roughly uniform rate of 2.6 mm/yr for the past 475 ka. The {sup 234}U/{sup 238}U ages are in general agreement with model ages of reef drowning (based on estimates of paleo-sea-level stands derived from oxygen-isotope ratios of deep-sea sediments), but there are disagreements in detail. The high attainable precision ({plus minus}10 ka or better on samples younger than {approximately}800 ka), large applicable age range, relative robustness against open-system behavior, and ease of analysis for this technique hold great promise for future applications of dating of 50-1,000 ka coral.

  18. 234U and 238U concentration in brine from geopressured aquifers of the northern Gulf of Mexico basin

    USGS Publications Warehouse

    Kraemer, T.F.

    1981-01-01

    The 234U and 238U concentration in brine from six Gulf Coast geopressured aquifers has been determined. The results reveal very low uranium concentrations (from 0.003 to 0.03 ??g/l) and uranium activity ratios slightly greater than unity (from 1.06 to 1.62). Reducing conditions within the aquifers are responsible for the low uranium concentrations. The uranium activity ratios observed are well below those calculated using theoretical considerations of alpha-particle recoil effects. This can be explained by interference with alpha-recoil nuclides entering the liquid phase as a result of quartz overgrowths on sand grains and high-temperature re-equilibration that tends to minimize the effects of the alpha-recoil process. The fact that the uranium activity ratios of the brines are slightly greater than unity instead of the equilibrium value of 1.000 indicates that either the alpha particle recoil blocking and re-equlibration effects are not complete or that another process is operative that enriches the fluid in excess 234U by selectively removing uranium from radiation induced damage sites in the mineral (sand grain) matrix. ?? 1981.

  19. Measurements of /sup 234/U, /sup 238/U and /sup 230/Th in excreta of uranium-mill crushermen

    SciTech Connect

    Fisher, D.R.; Jackson, P.O.; Brodacynski, G.G.; Scherpelz, R.I.

    1982-07-01

    Uranium and thorium levels in excreta of uranium mill crushermen who are routinely exposed to airborne uranium ore dust were measured. The purpose was to determine whether /sup 230/Th was preferentially retained over either /sup 234/U or /sup 238/U in the body. Urine and fecal samples were obtained from fourteen active crushermen with long histories of exposure to uranium ore dust, plus four retired crushermen and three control individuals for comparison. Radiochemical procedures were used to separate out the uranium and thorium fractions, which were then electroplated on stainless steel discs and assayed by alpha spectrometry. Significantly greater activity levels of /sup 234/U and /sup 238/U were measured in both urine and fecal samples obtained from uranium mill crushermen, indicating that uranium in the inhaled ore dust was cleared from the body with a shorter biological half-time than the daughter product /sup 230/Th. The measurements also indicated that uranium and thorium separate in vivo and have distinctly different metabolic pathways and transfer rates in the body. The appropriateness of current ICRP retention and clearance parameters for /sup 230/Th in ore dust is questioned.

  20. Calculation of resonance self-shielding for {sup 235}U from 0 to 2250 eV

    SciTech Connect

    Leal, L.C.; Larson, N.M.; Derrien, H.; Santos, G.R.

    1998-08-01

    Over the years, the evaluated {sup 235}U cross sections in the resolved energy range have been extensively revised. A major accomplishment was the first evaluation released to the ENDF/B-VI library. In that evaluation, the low energy range bound was lowered to 10{sup {minus}5} eV, and the upper limit raised to 2,250 eV. Several high-resolution measurements in conjunction with the Bayesian computer code SAMMY were used to perform the analysis of the {sup 235}U resonance parameters. SAMMY uses the Reich-Moore formalism, which is adequate for representing neutron cross sections of fissile isotopes, and a generalized least-squares (Bayes) technique for determining the energy-dependence of the neutron cross sections. Recently a re-evaluation of the {sup 235}U cross section in the resolved resonance region was completed. This evaluation has undergone integral tests in various laboratories throughout the USA and abroad. The evaluation has been accepted for inclusion in ENDF/B-VI release 5. The intent of this work is to present results of calculations of self-shielded fission rates carried out with these resonance parameters and to compare those fission rates with experimental data. Results of this comparison study provide an assessment of the resonance parameters with respect to the calculation of self-shielded group cross sections.

  1. Coupling groundwater residence time and 234U/238U isotopic ratios in a granitic catchment (Vosges, Eastern France)

    NASA Astrophysics Data System (ADS)

    Viville, Daniel; Aquilina, Luc; Ackerer, Julien; Chatton, Eliot; Labasque, Thierry; Pierret, Marie-Claire; Granet, Mathieu; Perrone, Thierry; Chabaux, François

    2016-04-01

    Weathering processes are active in surface waters but groundwater also represents no neglectable chemical fluxes. As residence-time in groundwater are high, silicate weathering might take place and control Si, Ca and C fluxes. Weathering processes can be deduced from U isotopic ratios but the kinetics of these processes remain relatively poorly constrained. In order to better characterize these processes, we have coupled residence-times deduced from anthropogenic gases (CFC and SF6) analysis and 234U/238U isotopic ratios determination. Samples were collected in the Strengbach catchment (Hydro-geochemical Observatory OHGE, Vosges, eastern France). Two campaigns were carried out in May and August 2015 during two highly contrasted hydro-climatic periods. Both springs and boreholes down to 80 m depth have been sampled. A very clear geochemical distinction is observed between groundwater from surface springs and deeper groundwater from boreholes. Springs show much lower residence-time (few years) and specific chemical composition. Deeper groundwater have residence-time of several decades and different geochemical composition. A clear SF6 production is observed with increasing SF6 concentrations with residence-time. The campaign of May is characterized by highly groundwater levels and spring fluxes. All groundwater show very low residence time, except in the boreholes at depth greater than 40 m. Conversely, during low groundwater-level period in August, the residence times are much higher and CFC concentrations indicate a large mixing process between surface groundwater and deeper levels. The 234U/238U isotopic ratios confirm this vertical zonation in the boreholes, with much higher activity ratios in the deep ground-waters from borehole than in the surface and spring waters; Such high U activity ratios are indicative of long water-rock interactions, which is consistent with the long residence times deducted from the CFC and SF6 data.

  2. Measurements of absolute delayed neutron yield and group constants in the fast fission of {sup 235}U and {sup 237}Np

    SciTech Connect

    Loaiza, D.J.; Brunson, G.; Sanchez, R.; Butterfield, K.

    1998-03-01

    The delayed neutron activity resulting from the fast induced fission of {sup 235}U and {sup 237}Np has been studied. The six-group decay constants, relative abundances, and absolute yield of delayed neutrons from fast fission of {sup 235}U and {sup 237}Np were measured using the Godiva IV fast assembly at the Los Alamos Critical Experiments Facility. The absolute yield measured for {sup 235}U was 0.0163 {+-} 0.0008 neutron/fission. This value compares very well with the well-established Keepin absolute yield of 0.0165 {+-} 0.0005. The absolute yield value measured for {sup 237}Np was 0.0126 {+-} 0.0007. The measured delayed neutron parameters for {sup 235}U are corroborated with period (e-folding time) versus reactivity calculations.

  3. 238U-234U activity ratio as tracer of waterpathway within the watershed substratum: evidence of U data from the Strengbach and Ringelbach research catchments (Vosges , France)

    NASA Astrophysics Data System (ADS)

    Chabaux, F.; Schaffhausen, Th.; Pierret, M.-C.; Ambroise, B.

    2012-04-01

    U activity ratios were measured in spring and source waters collected in two small research watersheds developed on granitic bedrocks in Vosges Mountains (Eastern France), i.e., the Strengbach (http://ohge.u-strasbg.fr) and the Ringelbach catchments. The data indicates a clear relationship between the emerging altitude of sources/springs in each slope of the watersheds, and the intensity of 234U-238U activity ratios in the waters. Such a relationship can be readily explained through a scenario assuming that U mobilization in these waters and their 234U enrichment (consequence of the alpha recoil process) are controlled by the duration of the water-pathway within the substratum of the watershed: longer water pathway within the watershed, longer duration of water-rock interaction and hence higher 234U enrichment in the source/spring waters. The immediate consequence of such an interpretation is that (234U/238U) activity ratio in surface waters, at least at the scale of such small and elemental watersheds, might be a geochemical tracer useful to constrain a key hydrological parameter which controls, at least partly, the nature and the intensity of water-rock interactions in the watershed, namely the water pathway within the watershed substratum. The data also suggests that U activity ratios could be also very relevant to constrain the contribution of deep waters within surface waters. Future developments in this domain will certainly confirm the interest of U activity ratio as hydrological tracer of the water-rock interactions.

  4. 234U/238U isotope data from groundwater and solid-phase leachate samples near Tuba City Open Dump, Tuba City, Arizona

    USGS Publications Warehouse

    Johnson, Raymond H.; Horton, Robert J.; Otton, James K.; Ketterer, Michael K.

    2012-01-01

    This report releases 234U/238U isotope data, expressed as activity ratios, and uranium concentration data from analyses completed at Northern Arizona University for groundwater and solid-phase leachate samples that were collected in and around Tuba City Open Dump, Tuba City, Arizona, in 2008.

  5. Current Issues in Nuclear Data Evaluation Methodology: {sup 235}U Prompt Fission Neutron Spectra and Multiplicity for Thermal Neutrons

    SciTech Connect

    Trkov, A.; Capote, R.; Pronyaev, V.G.

    2015-01-15

    Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the {sup 235}U are discussed. The inconsistency between the experimental differential and integral data is addressed. By using differential data as ”shape data” good consistency was achieved between available sets of differential data. Integral dosimetry data have been used to define the PFNS slope at high outgoing neutron energies, where the quality of the differential data is poor. The inclusion into the fit of measured integral (spectrum-averaged) cross sections had a very small impact in the region where differential PFNS data are abundant and accurate, but removed the discrepancy with integral data at higher neutron emission energies. All experimental data are consistently fitted giving a PFNS average energy of 2.008 MeV. The impact on criticality prediction of the newly evaluated PFNS was tested. The highly enriched {sup 235}U solution assemblies with high leakage HEU-SOL-THERM-001 and HEU-SOL-THERM-009 benchmarks are the most sensitive to the PFNS. Criticality calculations for those solutions show a significant increase in reactivity if the average neutron energy of the fission neutrons is reduced from the ENDF/B-VI.5 value of 2.03 MeV. The proposed reduction of the PFNS average energy by 1.1% can be compensated by reducing the average number of neutrons per fission ν{sup ¯} at the thermal energy to the Gwin et al. measured value. The simple least-squares PFNS fit was confirmed by a more sophisticated combined fit of differential PFNS data for {sup 233,235}U, {sup 239}Pu and {sup 252}Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

  6. Energy dependence of mass, charge, isotopic, and energy distributions in neutron-induced fission of 235U and 239Pu

    NASA Astrophysics Data System (ADS)

    Pasca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kim, Y.

    2016-05-01

    The mass, charge, isotopic, and kinetic-energy distributions of fission fragments are studied within an improved scission-point statistical model in the reactions 235U+n and 239Pu+n at different energies of the incident neutron. The charge and mass distributions of the electromagnetic- and neutron-induced fission of 214,218Ra, 230,232,238U are also shown. The available experimental data are well reproduced and the energy-dependencies of the observable characteristics of fission are predicted for future experiments.

  7. Fission Fragment Angular Distribution measurements of 235U and 238U at CERN n_TOF facility

    NASA Astrophysics Data System (ADS)

    Leal-Cidoncha, E.; Durán, I.; Paradela, C.; Tarrío, D.; Leong, L. S.; Tassan-Got, L.; Audouin, L.; Altstadt, S.; Andrzejewski, J.; Barbagallo, M.; Bécares, V.; Bečvář, F.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dzysiuk, N.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Ganesan, S.; García, A. R.; Giubrone, G.; Gómez-Hornillos, M. B.; Gonçalves, I. F.; González-Romero, E.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Gurusamy, P.; Hernández-Prieto, A.; Jenkins, D. G.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karadimos, D.; Kivel, N.; Koehler, P.; Kokkoris, M.; Krtička, M.; Kroll, J.; Lampoudis, C.; Langer, C.; Lederer, C.; Leeb, H.; Lo Meo, S.; Losito, R.; Mallick, A.; Manousos, A.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Meaze, M.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Mondelaers, W.; Pavlik, A.; Perkowski, J.; Plompen, A.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego, A.; Robles, M. S.; Roman, F.; Rubbia, C.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Tagliente, G.; Tain, J. L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Versaci, R.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiß, C.; Wright, T.; Žugec, P.

    2016-03-01

    Neutron-induced fission cross sections of 238U and 235U are used as standards in the fast neutron region up to 200 MeV. A high accuracy of the standards is relevant to experimentally determine other neutron reaction cross sections. Therefore, the detection effciency should be corrected by using the angular distribution of the fission fragments (FFAD), which are barely known above 20 MeV. In addition, the angular distribution of the fragments produced in the fission of highly excited and deformed nuclei is an important observable to investigate the nuclear fission process. In order to measure the FFAD of neutron-induced reactions, a fission detection setup based on parallel-plate avalanche counters (PPACs) has been developed and successfully used at the CERN-n_TOF facility. In this work, we present the preliminary results on the analysis of new 235U(n,f) and 238U(n,f) data in the extended energy range up to 200 MeV compared to the existing experimental data.

  8. A generalized method for characterization of 235U and 239Pu content using short-lived fission product gamma spectroscopy

    NASA Astrophysics Data System (ADS)

    Knowles, Justin; Skutnik, Steven; Glasgow, David; Kapsimalis, Roger

    2016-10-01

    Rapid nondestructive assay methods for trace fissile material analysis are needed in both nuclear forensics and safeguards communities. To address these needs, research at the Oak Ridge National Laboratory High Flux Isotope Reactor Neutron Activation Analysis facility has developed a generalized nondestructive assay method to characterize materials containing fissile isotopes. This method relies on gamma-ray emissions from short-lived fission products and makes use of differences in fission product yields to identify fissile compositions of trace material samples. Although prior work has explored the use of short-lived fission product gamma-ray measurements, the proposed method is the first to provide a complete characterization of isotopic identification, mass ratios, and absolute mass determination. Successful single fissile isotope mass recoveries of less than 6% recovery bias have been conducted on standards of 235U and 239Pu as low as 12 ng in less than 10 minutes. Additionally, mixtures of fissile isotope standards containing 235U and 239Pu have been characterized as low as 198 ng of fissile mass with less than 7% recovery bias. The generalizability of this method is illustrated by evaluating different fissile isotopes, mixtures of fissile isotopes, and two different irradiation positions in the reactor. It is anticipated that this method will be expanded to characterize additional fissile nuclides, utilize various irradiation facilities, and account for increasingly complex sample matrices.

  9. A generalized method for characterization of 235U and 239Pu content using short-lived fission product gamma spectroscopy

    DOE PAGES

    Knowles, Justin R.; Skutnik, Steven E.; Glasgow, David C.; Kapsimalis, Roger J.

    2016-06-23

    Rapid non-destructive assay methods for trace fissile material analysis are needed in both nuclear forensics and safeguards communities. To address these needs, research at the High Flux Isotope Reactor Neutron Activation Analysis laboratory has developed a generalized non-destructive assay method to characterize materials containing fissile isotopes. This method relies on gamma-ray emissions from short-lived fission products and capitalizes off of differences in fission product yields to identify fissile compositions of trace material samples. Although prior work has explored the use of short-lived fission product gamma-ray measurements, the proposed method is the first to provide a holistic characterization of isotopic identification,more » mass ratios, and absolute mass determination. Successful single fissile isotope mass recoveries of less than 6% error have been conducted on standards of 235U and 239Pu as low as 12 nanograms in less than 10 minutes. Additionally, mixtures of fissile isotope standards containing 235U and 239Pu have been characterized as low as 229 nanograms of fissile mass with less than 12% error. The generalizability of this method is illustrated by evaluating different fissile isotopes, mixtures of fissile isotopes, and two different irradiation positions in the reactor. Furthermore, it is anticipated that this method will be expanded to characterize additional fissile nuclides, utilize various irradiation sources, and account for increasingly complex sample matrices.« less

  10. Comparative measurement of prompt fission γ -ray emission from fast-neutron-induced fission of 235U and 238U

    NASA Astrophysics Data System (ADS)

    Lebois, M.; Wilson, J. N.; Halipré, P.; Oberstedt, A.; Oberstedt, S.; Marini, P.; Schmitt, C.; Rose, S. J.; Siem, S.; Fallot, M.; Porta, A.; Zakari, A.-A.

    2015-09-01

    Prompt fission γ -ray (PFG) spectra have been measured in a recent experiment with the novel directional fast-neutron source LICORNE at the ALTO facility of the IPN Orsay. These first results from the facility involve the comparative measurement of prompt γ emission in fast-neutron-induced fission of 235U and 238U . Characteristics such as γ multiplicity and total and average radiation energy are determined in terms of ratios between the two systems. Additionally, the average photon energies were determined and compared with recent data on thermal-neutron-induced fission of 235U . PFG spectra are shown to be similar within the precision of the present measurement, suggesting that the extra incident energy does not significantly impact the energy released by prompt γ rays. The origins of some small differences, depending on either the incident energy or the target mass, are discussed. This study demonstrates the potential of the present approach, combining an innovative neutron source and new-generation detectors, for fundamental and applied research on fission in the near future.

  11. Mass Yields and Average Total Kinetic Energy Release in Fission for 235U, 238U, and 239Pu

    NASA Astrophysics Data System (ADS)

    Duke, Dana

    2015-10-01

    Mass yield distributions and average total kinetic energy (TKE) in neutron induced fission of 235U, 238U, and 239Pu targets were measured with a gridded ionization chamber. Despite decades of fission research, our understanding of how fragment mass yields and TKE depend on incident neutron energy is limited, especially at higher energies (above 5-10 MeV). Improved accuracy in these quantities is important for nuclear technology as it enhances our simulation capabilities and increases the confidence in diagnostic tools. The data can also guide and validate theoretical fission models where the correlation between the fragment mass and TKE is of particular value for constraining models. The Los Alamos Neutron Science Center - Weapons Neutron Research (LANSCE - WNR) provides a neutron beam with energies from thermal to hundreds of MeV, well-suited for filling in the gaps in existing data and exploring fission behavior in the fast neutron region. The results of the studies on target nuclei 235U, 238U, and 239Pu will be presented with a focus on exploring data trends as a function of neutron energy from thermal through 30 MeV. Results indicate clear evidence of structure due to multi-chance fission in the TKE . LA-UR-15-24761.

  12. Fission Product Yields for 14 MeV Neutrons on 235U, 238U and 239Pu

    NASA Astrophysics Data System (ADS)

    Mac Innes, M.; Chadwick, M. B.; Kawano, T.

    2011-12-01

    We report cumulative fission product yields (FPY) measured at Los Alamos for 14 MeV neutrons on 235U, 238U and 239Pu. The results are from historical measurements made in the 1950s-1970s, not previously available in the peer reviewed literature, although an early version of the data was reported in the Ford and Norris review. The results are compared with other measurements and with the ENDF/B-VI England and Rider evaluation. Compared to the Laurec (CEA) data and to ENDF/B-VI evaluation, good agreement is seen for 235U and 238U, but our FPYs are generally higher for 239Pu. The reason for the higher plutonium FPYs compared to earlier Los Alamos assessments reported by Ford and Norris is that we update the measured values to use modern nuclear data, and in particular the 14 MeV 239Pu fission cross section is now known to be 15-20% lower than the value assumed in the 1950s, and therefore our assessed number of fissions in the plutonium sample is correspondingly lower. Our results are in excellent agreement with absolute FPY measurements by Nethaway (1971), although Nethaway later renormalized his data down by 9% having hypothesized that he had a normalization error. The new ENDF/B-VII.1 14 MeV FPY evaluation is in good agreement with our data.

  13. The use of k0-NAA for the determination of the n( 235U)/ n( 238U) isotopic ratio in samples containing uranium

    NASA Astrophysics Data System (ADS)

    Farina Arboccò, F.; Vermaercke, P.; Sneyers, L.; Soares Leal, A.; Gonçalves Bouças, J.

    2010-10-01

    In the analysis of rare earth elements in samples containing uranium by k0-neutron activation analysis fission of 235U was considered an undesired phenomenon until the "fission k0-factors" were introduced to account for natural-U fission interferences. In this work, by using a reverse perspective of the problem, the observed 235U-fission and 238U activation products (along with the k0-factors) were used to obtain information about the n( 235U)/ n( 238U) isotopic ratio in the samples. The relevant formulae and data-filtering algorithm were implemented in a home-made computer software, allowing automated evaluation and selection of unbiased data. Two radioisotopes ( 131I and 140La) were demonstrated to be reliable candidates for n( 235U)/ n( 238U) determination in environmental samples. The accuracy of this method was determined using several isotopic standards varying from a depleted to a highly enriched 235U content. An overall 2.31±0.03% overestimation of the isotopic ratio was observed (within 95% confidence level). Definition: n(X) refers to the isotopic abundance of isotope X

  14. Uranium half-lives: a critical review

    SciTech Connect

    Holden, N.E.

    1981-01-01

    The experimental data are evaluated and values for the spontaneous fission half-life of /sup 238/U and the total half-lives for /sup 232/U, /sup 233/U, /sup 234/U, /sup 235/U, /sup 236/U, and /sup 238/U are recommended. Also the variation of the isotopic abundance of /sup 234/U in nature and the error involved in the assumption of secular equilibrium between /sup 234/U and /sup 238/U in the determination of the specific activity of natural uranium samples are discussed. The recommended half-life values and 95% confidence limits are: /sup 238/U spontaneous fission: 8.09 +- 0.26 x 10/sup 15/ years; /sup 232/U total: 69.8 +- 1.0 years; /sup 233/U total: 1.592 +- 0.002 x 10/sup 5/ years; /sup 234/U total: 2.454 +- 0.006 x 10/sup 5/ years; /sup 235/U total: 7.037 +- 0.011 x 10/sup 8/ years; /sup 236/U total: 2.342 +- 0.003 x 10/sup 7/ years /sup 238/U total: 4.468 +- 0.005 x 10/sup 9/ years.

  15. Early diagenesis of travertine deposits from the Tibetan Plateau - implications for 230Th/234U dating and palaeoenvironmental reconstruction

    NASA Astrophysics Data System (ADS)

    Wang, Zhijun; Meyer, Michael; Hoffmann, Dirk; Spötl, Christoph; Aldenderfer, Mark; Sanders, Diethard

    2014-05-01

    Travertine is calcium carbonate precipitated from hydrothermal springs. These terrestrial carbonate deposits can be used as high-resolution archives for reconstructing palaeoclimatic and palaeoenvironmental change and are also suitable for uranium-series disequilibrium (230Th/234U) dating. In many instances such spring deposits are associated with archaeological remains (e.g. stone artifacts and other traces of prehistoric human activity) and are therefore of interest for palaeoclimatologists and archaeologists alike. However, travertines are often affected by early diagenesis that can impact on the closed-system U-series behavior and on their geochemical signature. Hence, careful evaluation of the travertine microfabrics is required before these types of hot spring deposits can be accurately dated and used for paleoenviromental reconstruction. The Tibetan plateau hosts numerous hydrothermal spring deposits that occur along neotectonic faults. In this study, samples were collected from two archaeological travertine sites, i.e. Chusang and Tirthapuri, located in southern and western Tibet, respectively. Microscopic analysis of thin sections reveals a wide variety of crystal fabrics, including micrite, microspar and sparite, the latter can be composed of columnar or mosaic crystals, respectively. Areas where dendritic crystals are preserved are identified in our micrographs as well. Many of the Chusang and Tirthapuri travertine samples are porous. Drusy sparite is rimming most of the pore walls and a complex succession of secondary calcite phases precipitated in these pore spaces as well. The different generations of pore cement comprise micrite and sparite that can be laminated or fibrous in character and show sometimes evidence of an aragonite precursor. Detrital material like quartz, feldspar and other grains as well as humic and fulvic acids have been washed into the travertine pores too. Based on our microscopic analysis a complex growth history can be

  16. 238U-234U-230Th disequilibrium in hydrogenous oceanic Fe-Mn crusts: Palaeoceanographic record or diagenetic alteration?

    USGS Publications Warehouse

    Chabaux, F.; O'Nions, R. K.; Cohen, A.S.; Hein, J.R.

    1997-01-01

    A detailed TIMS study of (234Uexc/238U), (230Th/232Th), and Th/U ratios have been performed on the outermost margin of ten hydrogenous Fe-Mn crusts from the equatorial Pacific Ocean and west-central Indian Ocean. Th/U concentration ratios generally decrease from the crust's surface down to 0.5-1 mm depth and growth rates estimated by uranium and thorium isotope ratios are significantly different in Fe-Mn crusts from the Peru Basin and the west-central Indian Ocean. Fe-Mn crusts from the same geographical area define a single trend in plots of Ln (234Uexc/238U) vs. Ln(230Th/232Th) and Th/U ratios vs. age of the analysed fractions. Results suggest that (1) hydrogenous Fe-Mn crusts remain closed-systems after formation, and consequently (2) the discrepancy observed between the 230Th and 234U chronometers in Fe-Mn crusts, and the variations of the Th/U ratios through the margin of Fe-Mn crusts, are not due to redistribution of uranium and thorium isotopes after oxyhydroxide precipitation, but rather to temporal variations of both Th/U and initial thorium activity ratios recorded by the Fe-Mn layers. Implications of these observations for determination of Fe-Mn crust growth-rates are discussed. Variations of both Th/U and initial Th activity ratios in Fe-Mn crusts might be related to changes in particle input to seawater and/or changes in ocean circulation during the last 150 ka. Copyright ?? 1997 Elsevier Science Ltd.

  17. Use of 234U and 238U isotopes to identify fertilizer-derived uranium in the Florida Everglades

    USGS Publications Warehouse

    Zielinski, R.A.; Simmons, K.R.; Orem, W.H.

    2000-01-01

    Surface water and peat in the northern Everglades have very low natural concentrations of U and are therefore sensitive to the addition of small amounts of U from anthropogenic sources such as fertilizer. Peat samples collected along a nutrient gradient in the northern Everglades have unusually high concentrations of U (> 1 ??g/g, dry basis) and also have a distinctive 234U/238U activity ratio (AR). AR values for U-enriched peat fall in the narrow range of AR values for commercial phosphate fertilizer (1.00 ??0.05) In contrast, AR values for low-U peat from background sites exceed 1.05. The spatial distribution of anomalous U concentration, and of fertilizer-like AR values in peat, parallel a previously documented pattern of P enrichment These results strongly suggest that some of the U in nutrient-impacted peatlands is fertilizer-derived. Agricultural drainage water sampled in the northern Everglades has high concentrations of dissolved U (0.3-2.4 ??g/1) compared to surface water from background sites ( 1.05). Synoptic sampling of surface water along drainage canals indicate that Lake Okeechobee, and some drainage from agricultural fields, are sources of dissolved U, whereas wetlands farther downstream act as sinks for U. Historically cultivated agricultural soft has only a marginally elevated (+0.2 ??g/g) average concentration of U compared to nearby uncultivated soil and incorporates only 20% of the U from an aqueous solution that was slurried with the soil. In contrast, a similar experiment with fresh Everglades peat indicated uptake of 90% of the added U. These experiments support the proposed removal of U from agricultural fields and concentration of U in downstream peatlands. The methodology of this study can be used to describe the behavior of fertilizer-derived U in other low-U environments.

  18. Analysis of Fragment Mass Distribution in Asymmetric Area at Fission of {sup 235}U Induced by Thermal Neutrons

    SciTech Connect

    Pikul, V.P.; Koblik, Yu.N.; Khugaev, A.V.; Yuldashev, B.S.; Jovliev, U.Yu.; Muminov, A.I.; Pavliy, K.V.; Nasirov, A.K.

    2005-02-01

    The fragment mass yields in fission of {sup 235}U induced by thermal neutrons for A=145 - 160 and E{sub K}=50 - 75 MeV were measured using a mass spectrometer. The fine structure is observed at A=153, 154 and E{sub K}=50 - 60 MeV. The obtained results were described in the framework of a model based on the dinuclear system concept. The analyzed correlation between the total kinetic energy and mass distribution of fission fragments is connected with the shell structure of the formed fragments of fission. From this correlation and the time dependence of the calculated mass distribution of the binary reaction products, one can conclude that the descent time from a saddle point to a scission point for the more deformed fragments is longer than that for fragments of more compact shape.

  19. Study of Photon Strength Function of Actinides: the Case of (235)U, (238)Np and (241)Pu

    SciTech Connect

    Guerrero, C.; Koehler, Paul Edward; N_TOF collaboration,

    2011-01-01

    The decay from excited levels in medium and heavy nuclei can be described in a statistical approach by means of Photon Strength Functions and Level Density distributions. The study of electromagnetic cascades following neutron capture based on the use of high efficiency detectors has been shown to be well suited for probing the properties of the Photon Strength Function of heavy (high level density) and/or radioactive (high background) nuclei. In this work we have investigated for the first time the validity of the recommended PSF of actinides, in particular {sup 235}U, {sup 238}Np and {sup 241}Pu. Our study includes the search for resonance structures in the PSF below Sn and draws conclusions regarding their existence and their characteristics in terms of energy, width and electromagnetic nature.

  20. Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers

    NASA Astrophysics Data System (ADS)

    Bhatia, C.; Fallin, B.; Howell, C.; Tornow, W.; Gooden, M.; Kelley, J.; Arnold, C.; Bond, E.; Bredeweg, T.; Fowler, M.; Moody, W.; Rundberg, R.; Rusev, G.; Vieira, D.; Wilhelmy, J.; Becker, J.; Macri, R.; Ryan, C.; Sheets, S.; Stoyer, M.; Tonchev, A.

    2014-05-01

    To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced γ-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.

  1. Multilevel fitting of {sup 235}U resonance data sensitive to Bohr-and Brosa-fission channels

    SciTech Connect

    Moore, M.S.

    1995-05-01

    The recent determination of the K, J dependence of the neutron induced fission cross section of {sup 235}U by the Dubna group has led to a renewed interest in the mechanism of fission from saddle to scission. The K quantum numbers designate the so-called Bohr fission channels, which describe the fission properties at the saddle point. Certain other fission properties, e.g., the fragment mass and kinetic-energy distribution, are related to the properties of the scission point. The neutron energy dependence of the fragment kinetic energies has been measured by Hambsch et al., who analyzed their data according to a channel description of Brosa et al. How these two channel descriptions, the saddle-point Bohr channels and the scission-point Brosa channels, relate to one another is an open question, and is the subject matter of the present paper. We use the correlation coefficient between various data sets, in which variations are reported from resonance to resonance, as a measure of both-the statistical reliability of the data and of the degree to which different scission variables relate to different Bohr channels. We have carried out an adjustment of the ENDF/B-VI multilevel evaluation of the fission cross section of {sup 235}U, one that provides a reasonably good fit to the energy dependence of the fission, capture, and total cross sections below 100 eV, and to the Bohr-channel structure deduced from an earlier measurement by Pattenden and Postma. We have also further explored the possibility of describing the data of Hambsch et al. in the Brosa-channel framework with the same set of fission-width vectors, only in a different reference system. While this approach shows promise, it is clear that better data are also needed for the neutron energy variation of the scission-point variables.

  2. Reactive transport of uranium in a groundwater bioreduction study: Insights from high-temporal resolution 238U/235U data

    NASA Astrophysics Data System (ADS)

    Shiel, A. E.; Johnson, T. M.; Lundstrom, C. C.; Laubach, P. G.; Long, P. E.; Williams, K. H.

    2016-08-01

    We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical investigation during field-scale biostimulation and desorption experiments. This investigation was carried out in the uranium-contaminated alluvial aquifer of the Rifle field research site. In this well-characterized setting, a more comprehensive understanding of U isotope geochemistry is possible. Our results indicate that U isotope fractionation is consistently observed across multiple experiments at the Rifle site. Microbially-mediated reduction is suggested to account for most or all of the observed fractionation as abiotic reduction has been demonstrated to impart much smaller, often near-zero, isotopic fractionation or isotopic fractionation in the opposite direction. Data from some time intervals are consistent with a simple model for transport and U(VI) reduction, where the fractionation factor (ε = +0.65‰ to +0.85‰) is consistent with experimental studies. However, during other time intervals the observed patterns in our data indicate the importance of other processes in governing U concentrations and 238U/235U ratios. For instance, we demonstrate that departures from Rayleigh behavior in groundwater systems arise from the presence of adsorbed species. We also show that isotope data are sensitive to the onset of oxidation after biostimulation ends, even in the case where reduction continues to remove contaminant uranium downstream. Our study and the described conceptual model support the use of 238U/235U ratios as a tool for evaluating the efficacy of biostimulation and potentially other remedial strategies employed at Rifle and other uranium-contaminated sites.

  3. Process for producing enriched uranium having a {sup 235}U content of at least 4 wt. % via combination of a gaseous diffusion process and an atomic vapor laser isotope separation process to eliminate uranium hexafluoride tails storage

    DOEpatents

    Horton, J.A.; Hayden, H.W. Jr.

    1995-05-30

    An uranium enrichment process capable of producing an enriched uranium, having a {sup 235}U content greater than about 4 wt. %, is disclosed which will consume less energy and produce metallic uranium tails having a lower {sup 235}U content than the tails normally produced in a gaseous diffusion separation process and, therefore, eliminate UF{sub 6} tails storage and sharply reduce fluorine use. The uranium enrichment process comprises feeding metallic uranium into an atomic vapor laser isotope separation process to produce an enriched metallic uranium isotopic mixture having a {sup 235} U content of at least about 2 wt. % and a metallic uranium residue containing from about 0.1 wt. % to about 0.2 wt. % {sup 235} U; fluorinating this enriched metallic uranium isotopic mixture to form UF{sub 6}; processing the resultant isotopic mixture of UF{sub 6} in a gaseous diffusion process to produce a final enriched uranium product having a {sup 235}U content of at least 4 wt. %, and up to 93.5 wt. % or higher, of the total uranium content of the product, and a low {sup 235}U content UF{sub 6} having a {sup 235}U content of about 0.71 wt. % of the total uranium content of the low {sup 235}U content UF{sub 6}; and converting this low {sup 235}U content UF{sub 6} to metallic uranium for recycle to the atomic vapor laser isotope separation process. 4 figs.

  4. Process for producing enriched uranium having a .sup.235 U content of at least 4 wt. % via combination of a gaseous diffusion process and an atomic vapor laser isotope separation process to eliminate uranium hexafluoride tails storage

    DOEpatents

    Horton, James A.; Hayden, Jr., Howard W.

    1995-01-01

    An uranium enrichment process capable of producing an enriched uranium, having a .sup.235 U content greater than about 4 wt. %, is disclosed which will consume less energy and produce metallic uranium tails having a lower .sup.235 U content than the tails normally produced in a gaseous diffusion separation process and, therefore, eliminate UF.sub.6 tails storage and sharply reduce fluorine use. The uranium enrichment process comprises feeding metallic uranium into an atomic vapor laser isotope separation process to produce an enriched metallic uranium isotopic mixture having a .sup.235 U content of at least about 2 wt. % and a metallic uranium residue containing from about 0.1 wt. % to about 0.2 wt. % .sup.235 U; fluorinating this enriched metallic uranium isotopic mixture to form UF.sub.6 ; processing the resultant isotopic mixture of UF.sub.6 in a gaseous diffusion process to produce a final enriched uranium product having a .sup.235 U content of at least 4 wt. %, and up to 93.5 wt. % or higher, of the total uranium content of the product, and a low .sup.235 U content UF.sub.6 having a .sup.235 U content of about 0.71 wt. % of the total uranium content of the low .sup.235 U content UF.sub.6 ; and converting this low .sup.235 U content UF.sub.6 to metallic uranium for recycle to the atomic vapor laser isotope separation process.

  5. SAS2H input for computing core activities of 4.5, 5.0, and 5.5 weight % {sup 235}U fuel for Sequoyah Nuclear Plant

    SciTech Connect

    Hermann, O.W.

    1994-08-01

    Sequoyah Nuclear Plant core activities at initial fuel enrichments of 4.5, 5.0, and 5.5 wt% {sup 235}U, required in nuclear safety evaluations, were computed by the SAS2H analysis sequence and the ORIGEN-S code within the SCALE-4.2 code system.

  6. Uranium 238U/235U isotope ratios as indicators of reduction: results from an in situ biostimulation experiment at Rifle, Colorado, U.S.A.

    PubMed

    Bopp, Charles John; Lundstrom, Craig C; Johnson, Thomas M; Sanford, Robert A; Long, Philip E; Williams, Kenneth H

    2010-08-01

    The attenuation of groundwater contamination via chemical reaction is traditionally evaluated by monitoring contaminant concentration through time. However, this method can be confounded by common transport processes (e.g., dilution, sorption). Isotopic techniques bypass the limits of concentration methods, and so may provide improved accuracy in determining the extent of reaction. We apply measurements of 238U/235U to a U bioremediation field experiment at the Rifle Integrated Field Research Challenge Site in Rifle, Colorado. An array of monitoring and injection wells was installed on a 100 m2 plot where U(VI) contamination was present in the groundwater. Acetate-amended groundwater was injected along an up-gradient gallery to encourage the growth of dissimilatory metal reducing bacteria (e.g., Geobacter species). During amendment, U concentration dropped by an order of magnitude in the experiment plot. We measured 238U/235U in samples from one monitoring well by MC-ICP-MS using a double isotope tracer method. A significant approximately 1.00 per thousand decrease in 238U/235U occurred in the groundwater as U(VI) concentration decreased. The relationship between 238U/235U and concentration corresponds approximately to a Rayleigh distillation curve with an effective fractionation factor (alpha) of 1.00046. We attribute the observed U isotope fractionation to a nuclear field shift effect during enzymatic reduction of U(VI)(aq) to U(IV)(s).

  7. Towards A Modern Calibration Of The 238U/235U Paleoredox Proxy: Apparent Uranium Isotope Fractionation Factor During U(VI)-U(IV) Reduction In The Black Sea

    NASA Astrophysics Data System (ADS)

    Rolison, J. M.; Stirling, C. H.; Middag, R.; Rijkenberg, M. J. A.; De Baar, H. J. W.

    2015-12-01

    The isotopic compositions of redox-sensitive metals, including uranium (U), in marine sediments have recently emerged as powerful diagnostic tracers of the redox state of the ancient ocean-atmosphere system. Interpretation of sedimentary isotopic information requires a thorough understating of the environmental controls on isotopic fractionation in modern anoxic environments before being applied to the paleo-record. In this study, the relationship between ocean anoxia and the isotopic fractionation of U was investigated in the water column and sediments of the Black Sea. The Black Sea is the world's largest anoxic basin and significant removal of U from the water column and high U accumulation rates in modern underlying sediments have been documented. Removal of U from the water column occurs during the redox transition of soluble U(VI) to relatively insoluble U(IV). The primary results of this study are two-fold. First, significant 238U/235U fractionation was observed in the water column of the Black Sea, suggesting the reduction of U induces 238U/235U fractionation with the preferential removal of 238U from the aqueous phase. Second, the 238U/235U of underlying sediments is related to the water column through the isotope fractionation factor of the reduction reaction but is influenced by mass transport processes. These results provide important constraints on the use of 238U/235U as a proxy of the redox state of ancient oceans.

  8. Biological availability of (238)U, (234)U and (226)Ra for wild berries and meadow grasses in natural ecosystems of Belarus.

    PubMed

    Sokolik, G A; Ovsiannikova, S V; Voinikava, K V; Ivanova, T G; Papenia, M V

    2014-01-01

    This work is devoted to investigation of behavior of (234)U, (238)U and (226)Ra by determining the soil to plant transfer under different natural conditions such as forest or swamped areas and meadow lands with different soil types. The paper summarizes the data on investigation of uranium and radium uptake by wild berries and natural meadow grasses in the typical conditions of Belarus. Parameters characterizing the biological availability of (234)U, (238)U and (226)Ra for bilberry (Vaccinium myrtillus), lingonberry (Vaccinium viti-idaea), blueberry (Vaccinium iliginosum) and cranberry (Vaccinium oxycoccus palustris) as well as for widely occurring mixed meadow vegetation, which belongs to the sedge-grass or grass-sedge associations and forbs, have been established. In the sites under investigation, the deposition levels of (238+239+240)Pu were less than 0.37 kBq m(-2) and (137)Cs deposition ranged between less than 0.37 and 37 kBq m(-2). It was found that activity concentrations of radionuclides in berries varied in the ranges of 0.037-0.11 for (234)U, 0.036-0.10 for (238)U and 0.11-0.43 Bq kg(-1) for (226)Ra, but in the mixed meadow grasses they were 0.32-4.4, 0.24-3.9 and 0.14-6.9 Bq kg(-1) accordingly. The (234)U/(238)U activity ratios were 1.02 ± 0.01 for wild berries, 1.20 ± 0.09 for underground meadow grasses and 1.02 ± 0.02 for proper soils. The concentration ratios (CRs, dry weight basis) of (234)U and (238)U for mixed meadow grasses were 0.036-0.42 and 0.041-0.46 respectively. The correspondent geometric means (GM) were 0.13 and 0.15 with geometric standard deviations (GSD) of 2.4. The CRs of (226)Ra for meadow grasses were 0.031-1.0 with GM 0.20 and GSD 2.6. The CRs of (234)U, (238)U and (226)Ra for wild berries ranged within 0.0018-0.008 (GM is 0.0034, GSD is 1.8), 0.0018-0.008 (GM is 0.0035, GSD is 1.8) and 0.005-0.033 (GM is 0.016, GSD is 2.1) accordingly. The highest CR values of uranium for mixed meadow grasses were found in the

  9. Biological availability of (238)U, (234)U and (226)Ra for wild berries and meadow grasses in natural ecosystems of Belarus.

    PubMed

    Sokolik, G A; Ovsiannikova, S V; Voinikava, K V; Ivanova, T G; Papenia, M V

    2014-01-01

    This work is devoted to investigation of behavior of (234)U, (238)U and (226)Ra by determining the soil to plant transfer under different natural conditions such as forest or swamped areas and meadow lands with different soil types. The paper summarizes the data on investigation of uranium and radium uptake by wild berries and natural meadow grasses in the typical conditions of Belarus. Parameters characterizing the biological availability of (234)U, (238)U and (226)Ra for bilberry (Vaccinium myrtillus), lingonberry (Vaccinium viti-idaea), blueberry (Vaccinium iliginosum) and cranberry (Vaccinium oxycoccus palustris) as well as for widely occurring mixed meadow vegetation, which belongs to the sedge-grass or grass-sedge associations and forbs, have been established. In the sites under investigation, the deposition levels of (238+239+240)Pu were less than 0.37 kBq m(-2) and (137)Cs deposition ranged between less than 0.37 and 37 kBq m(-2). It was found that activity concentrations of radionuclides in berries varied in the ranges of 0.037-0.11 for (234)U, 0.036-0.10 for (238)U and 0.11-0.43 Bq kg(-1) for (226)Ra, but in the mixed meadow grasses they were 0.32-4.4, 0.24-3.9 and 0.14-6.9 Bq kg(-1) accordingly. The (234)U/(238)U activity ratios were 1.02 ± 0.01 for wild berries, 1.20 ± 0.09 for underground meadow grasses and 1.02 ± 0.02 for proper soils. The concentration ratios (CRs, dry weight basis) of (234)U and (238)U for mixed meadow grasses were 0.036-0.42 and 0.041-0.46 respectively. The correspondent geometric means (GM) were 0.13 and 0.15 with geometric standard deviations (GSD) of 2.4. The CRs of (226)Ra for meadow grasses were 0.031-1.0 with GM 0.20 and GSD 2.6. The CRs of (234)U, (238)U and (226)Ra for wild berries ranged within 0.0018-0.008 (GM is 0.0034, GSD is 1.8), 0.0018-0.008 (GM is 0.0035, GSD is 1.8) and 0.005-0.033 (GM is 0.016, GSD is 2.1) accordingly. The highest CR values of uranium for mixed meadow grasses were found in the

  10. Investigating Uranium Mobility Using Stable Isotope Partitioning of 238U/235U and a Reactive Transport Model

    NASA Astrophysics Data System (ADS)

    Bizjack, M.; Johnson, T. M.; Druhan, J. L.; Shiel, A. E.

    2015-12-01

    We report a numerical reactive transport model which explicitly incorporates the effectively stable isotopes of uranium (U) and the factors that influence their partitioning in bioactive systems. The model reproduces trends observed in U isotope ratios and concentration measurements from a field experiment, thereby improving interpretations of U isotope ratios as a tracer for U reactive transport. A major factor contributing to U storage and transport is its redox state, which is commonly influenced by the availability of organic carbon to support metal-reducing microbial communities. Both laboratory and field experiments have demonstrated that biogenic reduction of U(VI) fractionates the stable isotope ratio 238U/235U, producing an isotopically heavy solid U(IV) product. It has also been shown that other common reactive transport processes involving U do not fractionate isotopes to a consistently measurable level, which suggests the capacity to quantify the extent of bioreduction occurring in groundwater containing U using 238U/235U ratios. A recent study of a U bioremediation experiment at the Rifle IFRC site (Colorado, USA) applied Rayleigh distillation models to quantify U stable isotope fractionation observed during acetate amendment. The application of these simplified models were fit to the observations only by invoking a "memory-effect," or a constant source of low-concentration, unfractionated U(VI). In order to more accurately interpret the measured U isotope ratios, we present a multi-component reactive transport model using the CrunchTope software. This approach is capable of quantifying the cycling and partitioning of individual U isotopes through a realistic network of transport and reaction pathways including reduction, oxidation, and microbial growth. The model incorporates physical heterogeneity of the aquifer sediments through zones of decreased permeability, which replicate the observed bromide tracer, major ion chemistry, U concentration, and U

  11. Study on the radioactivity and soil-to-plant transfer factor of (226)Ra, (234)U and (238)U radionuclides in irrigated farms from the northwestern Saudi Arabia.

    PubMed

    Al-Hamarneh, Ibrahim F; Alkhomashi, N; Almasoud, Fahad I

    2016-08-01

    The present study addresses the soil-to-plant transfer factors (TFs) of (226)Ra, (234)U and (238)U for 13 types of vegetables and agricultural crops planted under semi-arid environment in the northwestern part of Saudi Arabia. Crop plants along with plant-growing soils were collected from selected farms, which are irrigated from the non-renewable Saq aquifer, and investigated for their radioactivity content by means of alpha spectrometry after applying a radiochemical separation procedure. Hence, TF data for plant roots, green parts (stem and leaves) and fruits were calculated and contrasted to those reported in the literature. Substantial differences were observed in the TFs of Ra and U radioisotopes among plant species. In crop fruits, eggplant exhibited the highest uptake of (226)Ra (TF value of 0.11), while beans (0.16) have the highest TF for (234)U and (238)U. The geometric mean TF values indicated that the crop roots tend to accumulate Ra and U about four to six-folds higher than fruits. The relation between TF values and soil concentrations showed a weak correlation. Activity ratios between radionuclides in crop plants indicated the preferential translocation of U in fruits than Ra even though Ra is more available for root uptake. The fruit/root (F/R) ratios obtained for the investigated plants shown that pepper had the smallest F/R ratios (0.07 ± 0.01, 0.12 ± 0.02 and 0.11 ± 0.02 for (226)Ra, (234)U and (238)U, respectively), while the highest F/R ratios were observed in potatoes (0.71 ± 0.15, 0.44 ± 0.10 and 0.40 ± 0.08 for (226)Ra, (234)U and (238)U, respectively). The TF and F/R ratios data of natural radionuclides in the study region can hopefully improve the scientific knowledge for future studies. PMID:27108351

  12. Determination of Nuclear Charge Distributions of Fission Fragments from ^{235}U (n_th, f) with Calorimetric Low Temperature Detectors

    NASA Astrophysics Data System (ADS)

    Grabitz, P.; Andrianov, V.; Bishop, S.; Blanc, A.; Dubey, S.; Echler, A.; Egelhof, P.; Faust, H.; Gönnenwein, F.; Gomez-Guzman, J. M.; Köster, U.; Kraft-Bermuth, S.; Mutterer, M.; Scholz, P.; Stolte, S.

    2016-08-01

    Calorimetric low temperature detectors (CLTD's) for heavy-ion detection have been combined with the LOHENGRIN recoil separator at the ILL Grenoble for the determination of nuclear charge distributions of fission fragments produced by thermal neutron-induced fission of ^{235}U. The LOHENGRIN spectrometer separates fission fragments according to their mass-to-ionic-charge ratio and their kinetic energy, but has no selectivity with respect to nuclear charges Z. For the separation of the nuclear charges, one can exploit the nuclear charge-dependent energy loss of the fragments passing through an energy degrader foil (absorber method). This separation requires detector systems with high energy resolution and negligible pulse height defect, as well as degrader foils which are optimized with respect to thickness, homogeneity, and energy loss straggling. In the present, contribution results of test measurements at the Maier Leibnitz tandem accelerator facility in Munich with ^{109}Ag and ^{127}I beams with the aim to determine the most suitable degrader material, as well as measurements at the Institut Laue-Langevin will be presented. These include a systematic study of the quality of Z-separation of fission fragments in the mass range 82le A le 132 and a systematic measurement of ^{92}Rb fission yields, as well as investigations of fission yields toward the symmetry region.

  13. Yields of short-lived fission products produced following {sup 235}U(n{sub th},f)

    SciTech Connect

    Tipnis, S.V.; Campbell, J.M.; Couchell, G.P.; Li, S.; Nguyen, H.V.; Pullen, D.J.; Schier, W.A.; Seabury, E.H.; England, T.R.

    1998-08-01

    Measurements of gamma-ray spectra, following the thermal neutron fission of {sup 235}U have been made using a high purity germanium detector at the University of Massachusetts Lowell (UML) Van de Graaff facility. The gamma spectra were measured at delay times ranging from 0.2 s to nearly 10thinsp000 s following the rapid transfer of the fission fragments with a helium-jet system. On the basis of the known gamma transitions, forty isotopes have been identified and studied. By measuring the relative intensities of these transitions, the relative yields of the various precursor nuclides have been calculated. The results are compared with the recommended values listed in the ENDF/B-VI fission product data base (for the lifetimes and the relative yields) and those published in the Nuclear Data Sheets (for the beta branching ratios). This information is particularly useful for the cases of short-lived fission products with lifetimes of the order of fractions of a second or a few seconds. Independent yields of many of these isotopes have rather large uncertainties, some of which have been reduced by the present study. {copyright} {ital 1998} {ital The American Physical Society}

  14. Preliminary results on ^241,243Am and ^235U (n,γ) cross sections measured at DANCE

    NASA Astrophysics Data System (ADS)

    Jandel, M.; Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Macri, R. A.; Wu, C.-Y.; Becker, J. A.

    2006-10-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL) was used for neutron capture cross sections measurements. Its high granularity of 160 BaF2 detectors allows for highly efficient detection of prompt gamma-rays following a neutron capture. DANCE is located on the 20.26 m neutron flight path 14 at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center (LANSCE). The moderated production target provides neutrons in the 0.02 eV - 500 keV energy range. An analysis of neutron capture measurements on ^241,243Am and ^235U targets will be presented. The experiments were carried out using a customized Parallel-Plate Avalanche Counter (PPAC) detector installed in the center of the DANCE array. The PPAC was used as a fission-tagging detector to separate (n,γ) from (n,fission) events. Preliminary results of (n,γ) cross sections will be presented and compared with the available evaluated data for neutron energies from 0.02 eV to 1 keV. Additional neutron capture measurements with DANCE will be briefly discussed.

  15. On monitoring anthropogenic airborne uranium concentrations and (235)U/(238)U isotopic ratio by Lichen - bio-indicator technique.

    PubMed

    Golubev, A V; Golubeva, V N; Krylov, N G; Kuznetsova, V F; Mavrin, S V; Aleinikov, A Yu; Hoppes, W G; Surano, K A

    2005-01-01

    Lichens are widely used to assess the atmospheric pollution by heavy metals and radionuclides. However, few studies are available in publications on using lichens to qualitatively assess the atmospheric pollution levels. The paper presents research results applying epiphytic lichens as bio-monitors of quantitative atmospheric contamination with uranium. The observations were conducted during 2.5 years in the natural environment. Two experimental sites were used: one in the vicinity of a uranium contamination source, the other one - at a sufficient distance away to represent the background conditions. Air and lichens were sampled at both sites monthly. Epiphytic lichens Hypogimnia physodes were used as bio-indicators. Lichen samples were taken from various trees at about 1.5m from the ground. Air was sampled with filters at sampling stations. The uranium content in lichen and air samples as well as isotopic mass ratios (235)U/(238)U were measured by mass-spectrometer technique after uranium pre-extraction. Measured content of uranium were 1.45 mgkg(-1) in lichen at 2.09 E-04 microgm(-3) in air and 0.106 mgkg(-1) in lichen at 1.13 E-05 microgm(-3) in air. The relationship of the uranium content in atmosphere and that in lichens was determined, C(AIR)=exp(1.1 x C(LICHEN)-12). The possibility of separate identification of natural and man-made uranium in lichens was demonstrated in principle.

  16. Calculation of the absolute detection efficiency of a moderated /sup 235/U neutron detector on the Tokamak Fusion Test Reactor

    SciTech Connect

    Ku, L.P.; Hendel, H.W.; Liew, S.L.

    1989-02-01

    Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated /sup 235/U neutron detector which is used on the TFTR as a part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semi-empirical model based on matching the calculational results with a small set of experiments produces good agreement (+-15%) for a wide range of source energies and geometries. 20 refs., 6 figs., 4 tabs.

  17. Design of a high-flux epithermal neutron beam using 235U fission plates at the Brookhaven Medical Research Reactor.

    PubMed

    Liu, H B; Brugger, R M; Rorer, D C; Tichler, P R; Hu, J P

    1994-10-01

    Beams of epithermal neutrons are being used in the development of boron neutron capture therapy for cancer. This report describes a design study in which 235U fission plates and moderators are used to produce an epithermal neutron beam with higher intensity and better quality than the beam currently in use at the Brookhaven Medical Research Reactor (BMRR). Monte Carlo calculations are used to predict the neutron and gamma fluxes and absorbed doses produced by the proposed design. Neutron flux measurements at the present epithermal treatment facility (ETF) were made to verify and compare with the computed results where feasible. The calculations indicate that an epithermal neutron beam produced by a fission-plate converter could have an epithermal neutron intensity of 1.2 x 10(10) n/cm2.s and a fast neutron dose per epithermal neutron of 2.8 x 10(-11) cGy.cm2/nepi plus being forward directed. This beam would be built into the beam shutter of the ETF at the BMRR. The feasibility of remodeling the facility is discussed.

  18. Direct uranium isotope ratio analysis of single micrometer-sized glass particles

    PubMed Central

    Kappel, Stefanie; Boulyga, Sergei F.; Prohaska, Thomas

    2012-01-01

    We present the application of nanosecond laser ablation (LA) coupled to a ‘Nu Plasma HR’ multi collector inductively coupled plasma mass spectrometer (MC-ICP-MS) for the direct analysis of U isotope ratios in single, 10–20 μm-sized, U-doped glass particles. Method development included studies with respect to (1) external correction of the measured U isotope ratios in glass particles, (2) the applied laser ablation carrier gas (i.e. Ar versus He) and (3) the accurate determination of lower abundant 236U/238U isotope ratios (i.e. 10−5). In addition, a data processing procedure was developed for evaluation of transient signals, which is of potential use for routine application of the developed method. We demonstrate that the developed method is reliable and well suited for determining U isotope ratios of individual particles. Analyses of twenty-eight S1 glass particles, measured under optimized conditions, yielded average biases of less than 0.6% from the certified values for 234U/238U and 235U/238U ratios. Experimental results obtained for 236U/238U isotope ratios deviated by less than −2.5% from the certified values. Expanded relative total combined standard uncertainties Uc (k = 2) of 2.6%, 1.4% and 5.8% were calculated for 234U/238U, 235U/238U and 236U/238U, respectively. PMID:22595724

  19. Direct uranium isotope ratio analysis of single micrometer-sized glass particles.

    PubMed

    Kappel, Stefanie; Boulyga, Sergei F; Prohaska, Thomas

    2012-11-01

    We present the application of nanosecond laser ablation (LA) coupled to a 'Nu Plasma HR' multi collector inductively coupled plasma mass spectrometer (MC-ICP-MS) for the direct analysis of U isotope ratios in single, 10-20 μm-sized, U-doped glass particles. Method development included studies with respect to (1) external correction of the measured U isotope ratios in glass particles, (2) the applied laser ablation carrier gas (i.e. Ar versus He) and (3) the accurate determination of lower abundant (236)U/(238)U isotope ratios (i.e. 10(-5)). In addition, a data processing procedure was developed for evaluation of transient signals, which is of potential use for routine application of the developed method. We demonstrate that the developed method is reliable and well suited for determining U isotope ratios of individual particles. Analyses of twenty-eight S1 glass particles, measured under optimized conditions, yielded average biases of less than 0.6% from the certified values for (234)U/(238)U and (235)U/(238)U ratios. Experimental results obtained for (236)U/(238)U isotope ratios deviated by less than -2.5% from the certified values. Expanded relative total combined standard uncertainties U(c) (k = 2) of 2.6%, 1.4% and 5.8% were calculated for (234)U/(238)U, (235)U/(238)U and (236)U/(238)U, respectively.

  20. Uranium concentrations and /sup 234/U//sup 238/U activity ratios in fault-associated groundwater as possible earthquake precursors

    SciTech Connect

    Finkel, R.C.

    1981-05-01

    In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and /sup 234/U//sup 238/U activity ratios have been monitored on a monthly or bimonthly basis in water from 24 wells and springs associated with Southern California fault zones. Uranium concentrations vary from 0.002 ppb at Indian Canyon Springs on the San Jacinto fault to 8.3 ppb at Lake Hughes well on the San Andreas fault in the Palmdale area. /sup 234/U//sup 238/U activity ratios vary from 0.88 at Agua Caliente Springs on the Elsinore fault to 5.4 at Niland Slab well on the San Andreas fault in the Imperial Valley. There was one large earthquake in the study area during 1979, the 15 October 1979 M = 6.6 Imperial Valley earthquake. Correlated with this event, uranium concentrations varied by a factor of more than 60 and activity ratios by a factor of 3 at the Niland Slab site, about 70 km from the epicenter. At the other sites monitored, uranium concentrations varied in time, but with no apparent pattern, while uranium activity ratios remained essentially constant throughout the monitoring period.

  1. Abundance of low-energy gamma rays in the decay of 238U, 234U, 230Th, 227Ac, 226Ra and 214Pb

    NASA Astrophysics Data System (ADS)

    Komura, K.; Yamamoto, M.; Ueno, K.

    1990-11-01

    Abundance of low-energy gamma rays emitted from 238U (49.5 keV), 227Ac (50.0 keV), 234U (53.2 keV), 214Pb (53.2 keV), 230Th (67.7 and 143.9 keV) and 226Ra (186 keV) was determined using a high-purity Ge low energy photon spectrometer. The results are: 49.5 keV (238U): 0.059±0.002%, 50.0 keV (227Ac): 8.18±0.17%, 53.2 keV (234U): 0.156±0.006%, 53.2 keV (214Pb): 0.927±0.025%, 67.7 keV (230Th): 0.463±0.012%, 143.9 keV (230Th): 0.078±0.007%, 186.0 keV (226Ra): 3.688±0.099%.

  2. Delayed Fission Gamma-ray Characteristics of Th-232 U-233 U-235 U-238 and Pu-239

    SciTech Connect

    Lane, Taylor; Parma, Edward J.

    2015-08-01

    Delayed fission gamma-rays play an important role in determining the time dependent ioniz- ing dose for experiments in the central irradiation cavity of the Annular Core Research Reactor (ACRR). Delayed gamma-rays are produced from both fission product decay and from acti- vation of materials in the core, such as cladding and support structures. Knowing both the delayed gamma-ray emission rate and the time-dependent gamma-ray energy spectrum is nec- essary in order to properly determine the dose contributions from delayed fission gamma-rays. This information is especially important when attempting to deconvolute the time-dependent neutron, prompt gamma-ray, and delayed gamma-ray contribution to the response of a diamond photo-conducting diode (PCD) or fission chamber in time frames of milliseconds to seconds following a reactor pulse. This work focused on investigating delayed gamma-ray character- istics produced from fission products from thermal, fast, and high energy fission of Th-232, U-233, U-235, U-238, and Pu-239. This work uses a modified version of CINDER2008, a transmutation code developed at Los Alamos National Laboratory, to model time and energy dependent photon characteristics due to fission. This modified code adds the capability to track photon-induced transmutations, photo-fission, and the subsequent radiation caused by fission products due to photo-fission. The data is compared against previous work done with SNL- modified CINDER2008 [ 1 ] and experimental data [ 2 , 3 ] and other published literature, includ- ing ENDF/B-VII.1 [ 4 ]. The ability to produce a high-fidelity (7,428 group) energy-dependent photon fluence at various times post-fission can improve the delayed photon characterization for radiation effects tests at research reactors, as well as other applications.

  3. Searches for T-odd correlations in the emission of prompt neutrons in the polarized-neutron-induced fission of 235U nuclei

    NASA Astrophysics Data System (ADS)

    Danilyan, G. V.; Klenke, J.; Krakhotin, V. A.; Novitsky, V. V.; Pavlov, V. S.; Shatalov, P. B.

    2010-07-01

    The results of an experiment aimed at searches for formally T-odd correlations in the angular distribution of prompt neutrons from the fission of 235U nuclei are presented. The experiment was performed in the MEPHISTO polarized cold-neutron beam from the Munich FRMII reactor. The correlation coefficient proved to be (-3.5 ± 3.4) × 10-5 for a three-vector correlation (TRI effect) and (-5.0 ± 3.4) × 10-5 for a five-vector correlation (ROT effect). This means that no significant effects were discovered within the measurement errors. A comparison with the analogous effects in the ternary fission of 235U nuclei was performed. The values of the corresponding correlations in the angular distribution of prompt fission gamma rays were refined.

  4. Uranium 238U/235U isotope ratios as indicators of reduction: Results from an in situ biostimulation experiment at Rifle, Colorado, USA

    SciTech Connect

    Bopp IV, C.J.; Lundstrom, C.C.; Johnson, T.M.; Sanford, R.A.; Long, P.E.; Williams, K.H.

    2010-02-01

    The attenuation of groundwater contamination via chemical reaction is traditionally evaluated by monitoring contaminant concentration through time. However, this method can be confounded by common transport processes (e.g. dilution, sorption). Isotopic techniques bypass the limits of concentration methods, and so may provide improved accuracy in determining the extent of reaction. We apply measurements of {sup 238}U/{sup 235}U to a U bioremediation field experiment at the Rifle Integrated Field Research Challenge Site in Rifle, Colorado (USA). An array of monitoring and injection wells was installed on a 100 m{sup 2} plot where U(VI) contamination was present in the groundwater. Acetate-amended groundwater was injected along an up-gradient gallery to encourage the growth of dissimilatory metal reducing bacteria (e.g. Geobacter species). During amendment, U concentration dropped by an order of magnitude in the experiment plot. We measured {sup 238}U/{sup 235}U in samples from one monitoring well by MC-ICP-MS using a double isotope tracer method. A significant {approx}1.00{per_thousand} decrease in {sup 238}U/{sup 235}U occurred in the groundwater as U(VI) concentration decreased. The relationship between {sup 238}U/{sup 235}U and concentration corresponds approximately to a Rayleigh distillation curve with an effective fractionation factor ({alpha}) of 1.00046. We attribute the observed U isotope fractionation to a nuclear field shift effect during enzymatic reduction of U(VI){sub (aq)} to U(IV){sub (s)}.

  5. Measurement of {sup 235}U content and flow of UF{sub 6} using delayed neutrons or gamma rays following induced fission

    SciTech Connect

    Stromswold, D.C.; Peurrung, A.J.; Reeder, P.L.; Perkins, R.W.

    1996-06-01

    Feasibility experiments conducted at Pacific Northwest National Laboratory demonstrate that either delayed neutrons or energetic gamma rays from short-lived fission products can be used to monitor the blending of UF{sub 6} gas streams. A {sup 252}Cf neutron source was used to induce {sup 235}U fission in a sample, and delayed neutrons and gamma rays were measured after the sample moved {open_quotes}down-stream.{close_quotes} The experiments used a UO{sub 2} powder that was transported down the pipe to simulate the flowing UF{sub 6} gas. Computer modeling and analytic calculation extended the test results to a flowing UF{sub 6} gas system. Neutron or gamma-ray measurements made at two downstream positions can be used to indicate both the {sup 235}U content and UF{sub 6} flow rate. Both the neutron and gamma-ray techniques have the benefits of simplicity and long-term reliability, combined with adequate sensitivity for low-intrusion monitoring of the blending process. Alternatively, measuring the neutron emission rate from (a, n) reactions in the UF{sub 6} provides an approximate measure of the {sup 235}U content without using a neutron source to induce fission.

  6. Feasibility study of 235U and 239Pu characterization in radioactive waste drums using neutron-induced fission delayed gamma rays

    NASA Astrophysics Data System (ADS)

    Nicol, T.; Pérot, B.; Carasco, C.; Brackx, E.; Mariani, A.; Passard, C.; Mauerhofer, E.; Collot, J.

    2016-10-01

    This paper reports a feasibility study of 235U and 239Pu characterization in 225 L bituminized waste drums or 200 L concrete waste drums, by detecting delayed fission gamma rays between the pulses of a deuterium-tritium neutron generator. The delayed gamma yields were first measured with bare samples of 235U and 239Pu in REGAIN, a facility dedicated to the assay of 118 L waste drums by Prompt Gamma Neutron Activation Analysis (PGNAA) at CEA Cadarache, France. Detectability in the waste drums is then assessed using the MCNPX model of MEDINA (Multi Element Detection based on Instrumental Neutron Activation), another PGNAA cell dedicated to 200 L drums at FZJ, Germany. For the bituminized waste drum, performances are severely hampered by the high gamma background due to 137Cs, which requires the use of collimator and shield to avoid electronics saturation, these elements being very penalizing for the detection of the weak delayed gamma signal. However, for lower activity concrete drums, detection limits range from 10 to 290 g of 235U or 239Pu, depending on the delayed gamma rays of interest. These detection limits have been determined by using MCNPX to calculate the delayed gamma useful signal, and by measuring the experimental gamma background in MEDINA with a 200 L concrete drum mock-up. The performances could be significantly improved by using a higher interrogating neutron emission and an optimized experimental setup, which would allow characterizing nuclear materials in a wide range of low and medium activity waste packages.

  7. Isotopic compositions of (236)U and Pu isotopes in "black substances" collected from roadsides in Fukushima prefecture: fallout from the Fukushima Dai-ichi nuclear power plant accident.

    PubMed

    Sakaguchi, Aya; Steier, Peter; Takahashi, Yoshio; Yamamoto, Masayoshi

    2014-04-01

    Black-colored road dusts were collected in high-radiation areas in Fukushima Prefecture. Measurement of (236)U and Pu isotopes and (134,137)Cs in samples was performed to confirm whether refractory elements, such as U and Pu, from the fuel core were discharged and to ascertain the extent of fractionation between volatile and refractory elements. The concentrations of (134,137)Cs in all samples were exceptionally high, ranging from 0.43 to 17.7 MBq/kg, respectively. (239+240)Pu was detected at low levels, ranging from 0.15 to 1.14 Bq/kg, and with high (238)Pu/(239+240)Pu activity ratios of 1.64-2.64. (236)U was successfully determined in the range of (0.28 to 6.74) × 10(-4) Bq/kg. The observed activity ratios for (236)U/(239+240)Pu were in reasonable agreement with those calculated for the fuel core inventories, indicating that trace amounts of U from the fuel cores were released together with Pu isotopes but without large fractionation. The quantities of U and (239+240)Pu emitted to the atmosphere were estimated as 3.9 × 10(6) Bq (150 g) and 2.3 × 10(9) Bq (580 mg), respectively. With regard to U, this is the first report to give a quantitative estimation of the amount discharged. Appreciable fractionation between volatile and refractory radionuclides associated with the dispersal/deposition processes with distance from the Fukushima Dai-ichi Nuclear Power Plant was found.

  8. Fission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on 239Pu, 235U, 238U

    NASA Astrophysics Data System (ADS)

    Selby, H. D.; Mac Innes, M. R.; Barr, D. W.; Keksis, A. L.; Meade, R. A.; Burns, C. J.; Chadwick, M. B.; Wallstrom, T. C.

    2010-12-01

    where the present results are about 4%-relative higher for neutrons incident on 239Pu and 235U. Additionally, our results illustrate the importance of representing the incident energy dependence of fission product yields over the fast neutron energy range for high-accuracy work, for example the 147Nd from neutron reactions on plutonium. An upgrade to the ENDF library, for ENDF/B-VII.1, based on these and other data, is described in a companion paper to this work.

  9. 234U/238U isotope ratios in groundwater from Southern Nevada: a comparison of alpha counting and magnetic sector ICP-MS.

    PubMed

    Cizdziel, James; Farmer, Dennis; Hodge, Vernon; Lindley, Kazumasa; Stetzenbach, Klaus

    2005-11-01

    The 234U/238U activity ratio (AR) is extensively used as a geochemical tool to investigate movement and flow relationships in major hydrological units, information that is particularly important when considering nuclear waste disposal. It is usually determined by radiochemical separation and concentration of U, followed by energy-specific alpha particle counting. Alternatively, sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) can be used to measure U isotopic signatures directly in groundwater samples. Here, we compare the two methods for samples of spring and groundwater from southern Nevada. Results for samples stripped from stainless steel disks, previously used for alpha counting, and for splits of groundwater samples show good agreement between the methods. However, SF-ICP-MS is faster, requires much less sample, and produces essentially no waste. We demonstrate applicability of the SF-ICP-MS method for groundwater collected from over 25 wells on and near the Nevada Test Site during 2003. Uranium concentrations ranged from 0.17 to 9.87 ppb with a mean of 2.9 ppb, while 234U/238U AR values ranged from 1.9 to 11.5 with a mean of 4.3. Groundwater collected from deep wells in the northern part of the study area tended to have moderate to high U concentrations and AR values, possibly representative of older volcanic-type waters, whereas groundwater from wells in the Fortymile Wash area had relatively low AR and U concentrations, suggesting younger waters with a possible local recharge component.

  10. Trace element distribution and 235U/238U ratios in Euphrates waters and in soils and tree barks of Dhi Qar province (southern Iraq).

    PubMed

    Riccobono, Francesco; Perra, Guido; Pisani, Anastasia; Protano, Giuseppe

    2011-09-01

    To assess the quality of the environment in southern Iraq after the Gulf War II, a geochemical survey was carried out. The survey provided data on the chemistry of Euphrates waters, as well as the trace element contents, U and Pb isotopic composition, and PAH levels in soil and tree bark samples. The trace element concentrations and the (235)U/(238)U ratio values in the Euphrates waters were within the usual natural range, except for the high contents of Sr due to a widespread presence of gypsum in soils of this area. The trace element contents in soils agreed with the common geochemistry of soils from floodplain sediments. Some exceptions were the high contents of Co, Cr and Ni, which had a natural origin related to ophiolitic outcrops in the upper sector of the Euphrates basin. The high concentrations of S and Sr were linked to the abundance of gypsum in soils. A marked geochemical homogeneity of soil samples was suggested by the similar distribution pattern of rare earth elements, while the (235)U/(238)U ratio was also fairly homogeneous and within the natural range. The chemistry of the tree bark samples closely reflected that of the soils, with some notable exceptions. Unlike the soils, some tree bark samples had anomalous values of the (235)U/(238)U ratio due to mixing of depleted uranium (DU) with the natural uranium pool. Moreover, the distribution of some trace elements (such as REEs, Th and Zr) and the isotopic composition of Pb in barks clearly differed from those of the nearby soils. The overall results suggested that significant external inputs occurred implying that once formed the DU-enriched particles could travel over long distances. The polycyclic aromatic hydrocarbon concentrations in tree bark samples showed that phenanthrene, fluoranthene and pyrene were the most abundant components, indicating an important role of automotive traffic.

  11. Monte Carlo cross section testing for thermal and intermediate {sup 235}U/{sup 238}U critical assemblies, ENDF/B-V vs ENDF/B-VI

    SciTech Connect

    Weinman, J.P.

    1997-06-01

    The purpose of this study is to investigate the eigenvalue sensitivity to changes in ENDF/B-V and ENDF/B-VI cross section data sets by comparing RACER vectorized Monte Carlo calculations for several thermal and intermediate spectrum critical experiments. Nineteen Oak Ridge and Rocky Flats thermal solution benchmark critical assemblies that span a range of hydrogen-to-{sup 235}U (H/U) concentrations (2052 to 27.1) and above-thermal neutron leakage fractions (0.555 to 0.011) were analyzed. In addition, three intermediate spectrum critical assemblies (UH3-UR, UH3-NI, and HISS-HUG) were studied.

  12. Preliminary evaluation of the /sup 235/U(n,f) cross-section from 100 keV to 20 MeV

    SciTech Connect

    Bhat, M.R.

    1983-01-01

    A preliminary evaluation of the fission cross-section of /sup 235/U from 100 keV to 20 MeV is described. Variance-covariance matrices for a number of experimental data sets were constructed and used to evaluate the fission cross-section following a Bayesian procedure. The evaluated fission cross-section is compared with experimental data including the /sup 252/Cf fission neutron spectrum averages and some of the problems encountered in carrying out the fit are discussed.

  13. Analysis of 236U and plutonium isotopes, 239,240Pu, on the 1 MV AMS system at the Centro Nacional de Aceleradores, as a potential tool in oceanography

    NASA Astrophysics Data System (ADS)

    Chamizo, Elena; López-Lora, Mercedes; Villa, María; Casacuberta, Núria; López-Gutiérrez, José María; Pham, Mai Khanh

    2015-10-01

    The performance of the 1 MV AMS system at the CNA (Centro Nacional de Aceleradores, Seville, Spain) for 236U and 239,240Pu measurements has been extensively investigated. A very promising 236U/238U abundance sensitivity of about 3 × 10-11 has been recently achieved, and background figures for 239Pu of about 106 atoms were reported in the past. These promising results lead to the use of conventional low energy AMS systems for the analysis of 236U and 239Pu and its further application in environmental studies. First 236U results obtained on our AMS system for marine samples (sediments and water) are presented here. Results of two new IAEA reference materials (IAEA-410 and IAEA-412, marine sediments from Pacific Ocean) are reported. The obtained 236U/239Pu atom ratios, of 0.12 and 0.022, respectively, show a dependency with the contamination source (i.e. local fallout from the US tests performed at the Bikini Atoll and general fallout). The results obtained for a third IAEA reference material (IAEA-381, seawater from the Irish Sea), are also presented. In the following, the uranium and plutonium isotopic compositions obtained on a set of 5 intercomparison seawater samples from the Arctic Ocean provided by the ETH Zürich are discussed. By comparing them with the obtained results on the 600 kV AMS facility Tandy at the ETH Zürich, we demonstrate the solidity of the CNA technique for 236U/238U determinations at, at least, 7 × 10-10 level. Finally, these results are discussed in their environmental context.

  14. Preliminary Report on the Population of the 235U T1/2=25-Minute Isomer by the (Nu,Nu'Gamma)Reaction

    SciTech Connect

    Younes, W; Britt, H C; Becker, J A; Bernstein, L A; Garrett, P E; McGrath, C A; McNabb, D P; Nelson, R O; Devlin, M; Fotiades, N

    2002-10-09

    The population cross section of the T{sub 1/2} = 25-minute, E{sub x} = 76.8-keV isomer in {sup 235}U via the {sup 235}U(n,n{prime}{gamma}) reaction has been estimated in the E{sub n} = 2.1-20-MeV range. Gamma rays populating both isomer and ground states were detected using the GEANIE spectrometer at the LANSCE/WNR ''white-source'' neutron facility. Partial {gamma}-ray cross sections were obtained as a function of incident neutron energy, using {gamma}-ray spectroscopy and the time-of-flight technique. A correction for unobserved transitions was applied to the measured partial cross sections using the Hauser-Feshbach code GNASH to produce population cross sections for the isomer- and ground-state levels. The deduced isomer population cross section at E{sub n} = 2.1 MeV is 1.1(1) b, and the isomer-to-ground state population ratio decreases from 0.9 to 0.06 over the E{sub n} = 2.1-20-MeV range. The details of the measurement and recommendations to improve the current results are discussed.

  15. True ternary fission, the collinear decay into fragments of similar size in the 252Cf(sf) and 235U(nth, f) reactions

    NASA Astrophysics Data System (ADS)

    von Oertzen, W.; Nasirov, A. K.

    2014-06-01

    The collinear cluster decay in 252Cf(sf, fff), with three cluster fragments of different masses (e.g. 132Sn, 52-48Ca, 68-72Ni), which has been observed by the FOBOS group in JINR, has established a new decay mode of heavy nuclei, the collinear cluster tripartition (CCT). The same type of ternary fission decay has been observed in the reaction 235U(nth, fff). This kind of “true ternary fission” of heavy nuclei has been predicted many times in theoretical works during the last decades. In the present note we discuss true ternary fission (TFFF) into three nuclei of almost equal size (e.g. Z=98→Zi=32, 34, 32) in the same systems. The possible fission channels are predicted from potential-energy (PES) calculations. These PES's show pronounced minima for several ternary fragmentation decays, e.g. for 252Cf(sf) and for 235U(nth, f). They suggest the existence of a variety of collinear ternary fission modes. The TFFF-decays chosen in this letter have very similar dynamical features as the previously observed collinear CCT-decays. The data obtained in the above mentioned experiments allow us to extract the yield for these TFFF-decays in both systems by using specific gates on the measured parameters. These yields are a few 1.0ṡ10-6/(binary fission).

  16. Actinides AMS at CIRCE and 236U and Pu measurements of structural and environmental samples from in and around a mothballed nuclear power plant

    NASA Astrophysics Data System (ADS)

    De Cesare, M.; Fifield, L. K.; Sabbarese, C.; Tims, S. G.; De Cesare, N.; D'Onofrio, A.; D'Arco, A.; Esposito, A. M.; Petraglia, A.; Roca, V.; Terrasi, F.

    2013-01-01

    Accelerator mass spectrometry (AMS) is presently the most sensitive technique for the measurement of long-lived actinides, e.g. 236U and 239Pu. A new actinide line is in operation at the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy. Using the actinide line a uranium mass sensitivity of around 4 μg has been reached measuring with a 16-strip silicon detector, and a 239Pu background level of below 0.1 fg has been obtained. In this work we also discuss preliminary results for environmental and structural samples from in and around the Garigliano nuclear power plant (GNPP), presently in the decommissioning phase. Measurements on environmental samples from the vicinity of the plant allow the assessment of contamination, if any, over the years. Measurements of structural samples from the plant are relevant to the optimization of the decommissioning program for the GNPP.

  17. Measurement of Uranium Isotope Ratios in Keratinous Materials: A Noninvasive Bioassay for Special Nuclear Material.

    PubMed

    Brockman, John D; Brown, John W N; Morrell, Jonathan S; Robertson, J David

    2016-09-01

    Hair, toenail, and fingernail are noninvasive, integrative biological monitors routinely used to assess mineral intake.1-4 In this study, we demonstrate the feasibility of distinguishing between exposure to natural, depleted, and enriched U by measuring the (235)U/(238)U, (234)U/(238)U, and (236)U/(238)U ratios in the hair, fingernails, and toenails of occupationally exposed workers and control volunteers. The exposure history of cases and controls to non-natural U was assessed through voluntary self-reporting using a simple questionnaire. The measured U isotope ratios and U concentration in the hair, toenail, and fingernail of cases were compared to a nonexposed control group. No difference was observed in the uranium concentration between the two groups. Significant differences between the cases and the control group were observed in the (235)U/(238)U and (236)U/(238)U isotope ratios but not the (234)U/(238)U. This is the first time that hair, fingernail, and toenail have been demonstrated to be sensitive to occupational exposure to enriched and depleted U, a result with significant implications for proliferation compliance monitoring. PMID:27484415

  18. Surrogate measurement of the {sup 238}Pu(n,f) cross section

    SciTech Connect

    Ressler, J. J.; Burke, J. T.; Escher, J. E.; Bernstein, L. A.; Bleuel, D. L.; Casperson, R. J.; Gostic, J.; Henderson, R.; Scielzo, N. D.; Thompson, I. J.; Wiedeking, M.; Angell, C. T.; Goldblum, B. L.; Munson, J.; Basunia, M. S.; Phair, L. W.; Beausang, C. W.; Hughes, R. O.; Hatarik, R.; Ross, T. J.

    2011-05-15

    The neutron-induced fission cross section of {sup 238}Pu was determined using the surrogate ratio method. The (n,f) cross section over an equivalent neutron energy range 5-20 MeV was deduced from inelastic {alpha}-induced fission reactions on {sup 239}Pu, with {sup 235}U({alpha},{alpha}{sup '}f) and {sup 236}U({alpha},{alpha}{sup '}f) used as references. These reference reactions reflect {sup 234}U(n,f) and {sup 235}U(n,f) yields, respectively. The deduced {sup 238}Pu(n,f) cross section agrees well with standard data libraries up to {approx}10 MeV, although larger values are seen at higher energies. The difference at higher energies is less than 20%.

  19. Effects of Neutron Emission on Fragment Mass and Kinetic Energy Distribution from Thermal Neutron-Induced Fission of {sup 235}U

    SciTech Connect

    Montoya, M.; Rojas, J.; Saetone, E.

    2007-10-26

    The mass and kinetic energy distribution of nuclear fragments from thermal neutron-induced fission of {sup 235}U(n{sub th},f) have been studied using a Monte-Carlo simulation. Besides reproducing the pronounced broadening in the standard deviation of the kinetic energy at the final fragment mass number around m = 109, our simulation also produces a second broadening around m = 125. These results are in good agreement with the experimental data obtained by Belhafaf et al. and other results on yield of mass. We conclude that the obtained results are a consequence of the characteristics of the neutron emission, the sharp variation in the primary fragment kinetic energy and mass yield curves. We show that because neutron emission is hazardous to make any conclusion on primary quantities distribution of fragments from experimental results on final quantities distributions.

  20. Critical experiments with 4. 31 wt % /sup 235/U-enriched UO/sub 2/ rods in highly borated water lattices

    SciTech Connect

    Durst, B.M.; Bierman, S.R.; Clayton, E.D.

    1982-08-01

    A series of critical experiments were performed with 4.31 wt % /sup 235/U enriched UO/sub 2/ fuel rods immersed in water containing various concentrations of boron ranging up to 2.55 g/l. The boron was added in the form of boric acid (H/sub 3/BO/sub 3/). Critical experimental data were obtained for two different lattice pitches wherein the water-to-uranium oxide volume ratios were 1.59 and 1.09. The experiments provide benchmarks on heavily borated systems for use in validating calculational techniques employed in analyzing fuel shipping casks and spent fuel storage systems that may utilize boron for criticality control.

  1. Fission-fragment angular distributions and total kinetic energies for /sup 235/U(n,f) from. 18 to 8. 83 MeV

    SciTech Connect

    Meadows, J.W.; Budtz-Joergensen, C.

    1982-01-01

    A gridded ion chamber was used to measure the fission fragment angular distribution and total kinetic energy for the /sup 235/U(n,f) reaction from 0.18 to 8.81 MeV neutron energy. The anisotropies are in generally good agreement with earlier measurements. The average total kinetic energy is approx. 0.2 MeV greater than the thermal value at neutron energies < 2 MeV and shows a sudden decrease of approx. 0.8 MeV between 4 and 5 MeV neutron energy, well below the (n, n'f) threshold. Possible causes of this decrease are a change in the mass distribution or decreased shell effects in the heavy fragment.

  2. Exploratory study of fission product yields of neutron-induced fission of 235U , 238U , and 239Pu at 8.9 MeV

    NASA Astrophysics Data System (ADS)

    Bhatia, C.; Fallin, B. F.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.; Arnold, C. W.; Bond, E.; Bredeweg, T. A.; Fowler, M. M.; Moody, W.; Rundberg, R. S.; Rusev, G. Y.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Macri, R.; Ryan, C.; Sheets, S. A.; Stoyer, M. A.; Tonchev, A. P.

    2015-06-01

    Using dual-fission chambers each loaded with a thick (200 -400 -mg /c m2) actinide target of 235 ,238U or 239Pu and two thin (˜10 -100 -μ g /c m2) reference foils of the same actinide, the cumulative yields of fission products ranging from 92Sr to 147Nd have been measured at En= 8.9 MeV . The 2H(d ,n ) 3He reaction provided the quasimonoenergetic neutron beam. The experimental setup and methods used to determine the fission product yield (FPY) are described, and results for typically eight high-yield fission products are presented. Our FPYs for 235U(n ,f ) , 238U(n ,f ) , and 239Pu(n ,f ) at 8.9 MeV are compared with the existing data below 8 MeV from Glendenin et al. [Phys. Rev. C 24, 2600 (1981), 10.1103/PhysRevC.24.2600], Nagy et al. [Phys. Rev. C 17, 163 (1978), 10.1103/PhysRevC.17.163], Gindler et al. [Phys. Rev. C 27, 2058 (1983), 10.1103/PhysRevC.27.2058], and those of Mac Innes et al. [Nucl. Data Sheets 112, 3135 (2011), 10.1016/j.nds.2011.11.009] and Laurec et al. [Nucl. Data Sheets 111, 2965 (2010), 10.1016/j.nds.2010.11.004] at 14.5 and 14.7 MeV, respectively. This comparison indicates a negative slope for the energy dependence of most fission product yields obtained from 235U and 239Pu , whereas for 238U the slope issue remains unsettled.

  3. The Role of Plants in the 238U-234U Disequilibria of Stream Waters: The Example of the Strengbach Watershed (Vosges, France)

    NASA Astrophysics Data System (ADS)

    Pierret, M.; Chbaaux, F.

    2004-12-01

    Recent TIMS or MC ICPMS analyses of U disequilibria in the dissolved load of stream and river waters have confirmed the potential of the U activity ratio in river waters as a specific tracer of chemical fluxes coming from rocks and soils (e.g., 1). These precise measurements have also outlined that occurrence of U activity ratios lower than one in dissolved load of river waters is not exceptional, especially at the scale of small watersheds. Such U values pose in turn the question of the real mechanisms controlling the supply of 234U-238U isotopes to the freshwaters. In order to address this question U activity ratios, Sr isotope ratios and the concentrations of major and some trace elements were analyzed in the different compartments of a small granitic watershed: the Strengbach environmental observatory (Vosges, France) ( http://ohge.u-strasbg.fr). In addition of the different streamwaters draining this watershed, the main horizons of weathering profiles, the associated soil solutions and the main tree species growing around were analyzed. The data confirm that the Strengbach stream water samples have generally U activity ratios lower than one and point out that soils solutions display a similar range of U and Sr variations. By contrast, tree and plant samples define different trends of variation in a plot of U activity ratios against Sr isotope ratios with, above all, U activity ratios systematically greater than one. These data show that trees and plants collected during this work cannot directly pomp their nutriments from soils and soil solutions sampled here, i.e. gravity solutions. They also suggest that, in this watershed, the plants, especially trees, play a central role in the weathering processes of rocks and minerals, and control a large part of the geochemical signature of the water samples collected on this watershed, including their U activity ratios. 1Riotte J and Chabaux F. (1999) GCA 63, 1263-1275.

  4. 234U/238U and δ87Sr in peat as tracers of paleosalinity in the Sacramento-San Joaquin Delta of California, USA

    USGS Publications Warehouse

    Drexler, Judith Z.; Paces, James B.; Alpers, Charles N.; Windham-Myers, Lisamarie; Neymark, Leonid; Bullen, Thomas D.; Taylor, Howard E.

    2013-01-01

    The purpose of this study was to determine the history of paleosalinity over the past 6000+ years in the Sacramento-San Joaquin Delta (the Delta), which is the innermost part of the San Francisco Estuary. We used a combination of Sr and U concentrations, d87Sr values, and 234U/238U activity ratios (AR) in peat as proxies for tracking paleosalinity. Peat cores were collected in marshes on Browns Island, Franks Wetland, and Bacon Channel Island in the Delta. Cores were dated using 137Cs, the onset of Pb and Hg contamination from hydraulic gold mining, and 14C. A proof of concept study showed that the dominant emergent macrophyte and major component of peat in the Delta, Schoenoplectus spp., incorporates Sr and U and that the isotopic composition of these elements tracks the ambient water salinity across the Estuary. Concentrations and isotopic compositions of Sr and U in the three main water sources contributing to the Delta (seawater, Sacramento River water, and San Joaquin River water) were used to construct a three-end-member mixing model. Delta paleosalinity was determined by examining variations in the distribution of peat samples through time within the area delineated by the mixing model. The Delta has long been considered a tidal freshwater marsh region, but only peat samples from Franks Wetland and Bacon Channel Island have shown a consistently fresh signal (<0.5 ppt) through time. Therefore, the eastern Delta, which occurs upstream from Bacon Channel Island along the San Joaquin River and its tributaries, has also been fresh for this time period. Over the past 6000+ years, the salinity regime at the western boundary of the Delta (Browns Island) has alternated between fresh and oligohaline (0.5-5 ppt).

  5. Spatially-Resolved Analyses of Aerodynamic Fallout from a Uranium-Fueled Nuclear Test

    DOE PAGES

    Lewis, L. A.; Knight, K. B.; Matzel, J. E.; Prussin, S. G.; Zimmer, M. M.; Kinman, W S; Ryerson, F. J.; Hutcheon, I. D.

    2015-07-28

    The fiive silicate fallout glass spherules produced in a uranium-fueled, near-surface nuclear test were characterized by secondary ion mass spectrometry, electron probe microanalysis, autoradiography, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Several samples display compositional heterogeneity suggestive of incomplete mixing between major elements and natural U (238U/235U = 0.00725) and enriched U. Samples exhibit extreme spatial heterogeneity in U isotopic composition with 0.02 < 235U/238U < 11.84 among all five spherules and 0.02 < 235U/238U < 7.41 within a single spherule. Moreover, in two spherules, the 235U/238U ratio is correlated with changes in major element composition, suggesting the agglomeration ofmore » chemically and isotopically distinct molten precursors. Two samples are nearly homogenous with respect to major element and uranium isotopic composition, suggesting extensive mixing possibly due to experiencing higher temperatures or residing longer in the fireball. Linear correlations between 234U/238U, 235U/238U, and 236U/238U ratios are consistent with a two-component mixing model, which is used to illustrate the extent of mixing between natural and enriched U end members.« less

  6. Spatially-resolved analyses of aerodynamic fallout from a uranium-fueled nuclear test.

    PubMed

    Lewis, L A; Knight, K B; Matzel, J E; Prussin, S G; Zimmer, M M; Kinman, W S; Ryerson, F J; Hutcheon, I D

    2015-10-01

    Five silicate fallout glass spherules produced in a uranium-fueled, near-surface nuclear test were characterized by secondary ion mass spectrometry, electron probe microanalysis, autoradiography, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Several samples display compositional heterogeneity suggestive of incomplete mixing between major elements and natural U ((238)U/(235)U = 0.00725) and enriched U. Samples exhibit extreme spatial heterogeneity in U isotopic composition with 0.02 < (235)U/(238)U < 11.84 among all five spherules and 0.02 < (235)U/(238)U < 7.41 within a single spherule. In two spherules, the (235)U/(238)U ratio is correlated with changes in major element composition, suggesting the agglomeration of chemically and isotopically distinct molten precursors. Two samples are nearly homogenous with respect to major element and uranium isotopic composition, suggesting extensive mixing possibly due to experiencing higher temperatures or residing longer in the fireball. Linear correlations between (234)U/(238)U, (235)U/(238)U, and (236)U/(238)U ratios are consistent with a two-component mixing model, which is used to illustrate the extent of mixing between natural and enriched U end members. PMID:26225462

  7. Spatially-resolved analyses of aerodynamic fallout from a uranium-fueled nuclear test.

    PubMed

    Lewis, L A; Knight, K B; Matzel, J E; Prussin, S G; Zimmer, M M; Kinman, W S; Ryerson, F J; Hutcheon, I D

    2015-10-01

    Five silicate fallout glass spherules produced in a uranium-fueled, near-surface nuclear test were characterized by secondary ion mass spectrometry, electron probe microanalysis, autoradiography, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Several samples display compositional heterogeneity suggestive of incomplete mixing between major elements and natural U ((238)U/(235)U = 0.00725) and enriched U. Samples exhibit extreme spatial heterogeneity in U isotopic composition with 0.02 < (235)U/(238)U < 11.84 among all five spherules and 0.02 < (235)U/(238)U < 7.41 within a single spherule. In two spherules, the (235)U/(238)U ratio is correlated with changes in major element composition, suggesting the agglomeration of chemically and isotopically distinct molten precursors. Two samples are nearly homogenous with respect to major element and uranium isotopic composition, suggesting extensive mixing possibly due to experiencing higher temperatures or residing longer in the fireball. Linear correlations between (234)U/(238)U, (235)U/(238)U, and (236)U/(238)U ratios are consistent with a two-component mixing model, which is used to illustrate the extent of mixing between natural and enriched U end members.

  8. Trace metal cycling and 238U/235U in New Zealand's fjords: Implications for reconstructing global paleoredox conditions in organic-rich sediments

    NASA Astrophysics Data System (ADS)

    Hinojosa, Jessica L.; Stirling, Claudine H.; Reid, Malcolm R.; Moy, Christopher M.; Wilson, Gary S.

    2016-04-01

    Reconstructing the history of ocean oxygenation provides insight into links between ocean anoxia, biogeochemical cycles, and climate. Certain redox-sensitive elements respond to changes in marine oxygen content through phase shifts and concomitant isotopic fractionation, providing new diagnostic proxies of past ocean hypoxia. Here we explore the behavior and inter-dependence of a suite of commonly utilized redox-sensitive trace metals (U, Mo, Fe, and Mn) and the emerging "stable" isotope system of U (238U/235U, or δ238U) in New Zealand fjords. These semi-restricted basins have chemical conditions spanning the complete redox spectrum from fully oxygenated to suboxic to intermittently anoxic/euxinic. In the anoxic water column, U and Mo concentrations decrease, while Fe and Mn concentrations increase. Similarly, signals of past euxinic conditions can be found by U, Mo, Fe, and Mn enrichment in the underlying sediments. The expected U isotopic shift toward a lower δ238U in the anoxic water column due to U(VI)-U(IV) reduction is not observed; instead, water column δ238U profiles are consistent in fjords of all oxygen content, falling within previously reported ranges for open ocean seawater (δ238U = -0.42 ± 0.07‰). Additionally, surface sediment δ238U results show evidence for competing U isotope fractionation processes. One site indicates increased export of 238U from seawater to the underlying sediments (fractionation between aqueous seawater U and particulate sediment U, or ΔU(aq)-U(solid) = -0.25‰), consistent with redox-driven fractionation. Another site suggests potential U(VI) adsorption-driven fractionation, reflecting increased export of 235U from seawater to sediments (ΔU(aq)-U(solid) = 0.25‰). We discuss several potential factors that could alter δ238U in waters and sediments beyond redox-driven shifts, including adsorption to organic matter in waters of high primary productivity, reaction rates for competing processes of U adsorption and

  9. Determination of Fission Product Yields of 235U, 238U and 239Pu for Neutron Energies from 0.5 to 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, Matthew; Arnold, Charles; Becker, John; Bhatia, Chitra; Bhike, Megha; Fallin, Brent; Fowler, Malcolm; Howell, Calvin; Kelley, John; Stoyer, Mark; Tonchev, Anton; Tornow, Werner; Viera, David; Wilhelmy, Jerry

    2013-10-01

    A joint TUNL-LANL-LLNL collaboration has been formed to study the issue of possible energy dependences for fission product isotopes. Work has been carried out at the TUNL 10 MV Tandem accelerator which produces nearly mono-energetic neutrons via either 2H(d,n)3He,3H(d,n)4He, or 3H(p,n)3He reactions. Three dual fission ionization chambers dedicated to 235U, 238U and 239Pu thick target foils and thin monitor foils respectively, were exposed to the neutron beams. After irradiation, thick target foils were gamma counted over a period of 1-2 months and characteristic gamma rays from fission products were recorded using HPGe detectors at TUNL's low background counting area. Using the dual fission chambers fission product yields relative to total number of fissions were determined at a high precision of 2-3% as well as absolute fission product yields at a lower precision of 5-6%. Results will be presented for a number of fission product isotopes at 1.38, 4.6 and 14.8 MeV as well as preliminary results at 9 MeV.

  10. Energy Dependence of Neutron-Induced Fission Product Yields of 235U, 238U and 239Pu Between 0.5 and 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, Matthew; Tornow, Werner; Tonchev, Anton; Vieira, Dave; Wilhelmy, Jerry; Arnold, Charles; Fowler, Malcolm; Stoyer, Mark

    2014-09-01

    Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements have been performed. The energy dependence of a number of cumulative fission products between 0.5 and 14.8 MeV have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of activation utilizing specially designed dual-fission chambers and γ-ray counting. The dual-fission chambers are back-to-back ionization chambers encasing a target with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the fission rate in the activation target with no reference to the fission cross-section, reducing uncertainties. γ-ray counting was performed on well-shield HPGe detectors over a period of 2 months per activation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 4.6 and 14.8 MeV.

  11. Determination of Fission Product Yields of 235U, 238U and 239Pu for Neutron Energies from 0.5 to 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, Matthew; Arnold, Charles; Becker, John; Bhatia, Chitra; Bhike, Megha; Fowler, Malcolm; Howell, Calvin; Kelley, John; Stoyer, Mark; Tonchev, Anton; Tornow, Werner; Vieira, Dave; Wilhelmy, Jerry

    2014-03-01

    A joint TUNL-LANL-LLNL collaboration has been formed to study the issue of possible energy dependences for certain fission product isotopes. Work has been carried out at the TUNL 10 MV Tandem accelerator which produces nearly mono-energetic neutrons via either 2H(d,n)3He,3H(d,n)4He,or3H(p,n)3He reactions. Three dual fission ionization chambers dedicated to 235U, 238U and 239Pu thick target foils and thin monitor foils respectively, were exposed to the neutron beams. After irradiation, thick target foils were gamma counted over a period of 1-2 months and characteristic gamma rays from fission products were recorded using HPGe detectors at TUNL's low background counting area. Using the dual fission chambers, relative fission product yield were determined at a high precision of 2-3 % as well as absolute fission product yields at a lower precision of 5-6 %. Preliminary results will be presented for a number of fission product isotopes over the incident neutron energy range of 0.5 to 14.8 MeV.

  12. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    PubMed

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel. PMID:27081973

  13. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for 235U (n ,fission) at Thermal and Fast Neutron Energies

    NASA Astrophysics Data System (ADS)

    Sonzogni, A. A.; McCutchan, E. A.; Johnson, T. D.; Dimitriou, P.

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 235U 235 fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of 86Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  14. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    PubMed

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  15. Coulomb and even-odd effects in cold and super-asymmetric fragmentation for thermal neutron induced fission of 235U

    NASA Astrophysics Data System (ADS)

    Montoya, M.

    2016-07-01

    Even-odd effects of the maximal total kinetic energy (Kmax) as a function of charge (Z) and mass (A) of fragments from thermal neutron induced fission of actinides are questioned by other authors. In this work, visiting old results on thermal neutron induced fission of 235U, those even-odd effects are reconfirmed. The cases seeming to contradict even-odd effects are interpreted with the Coulomb effect hypothesis. According to Coulomb effect hypothesis, Kmax is equal to the Coulomb interaction energy of the most compact scission configuration. As a consequence, between two isobaric charge splits with similar Q-values, the more asymmetrical one will get the more compact scission configuration and then it will reach the higher Kmax-value. In some cases, the more asymmetrical charge split corresponds, by coincidence, to an odd charge split; consequently its higher Kmax-value may be misinterpreted as anti-even-odd effect. Another experimental result reported in the literature is the increasing of even-odd effects on charge distribution on the more asymmetrical fragmentations region. In this region, the difference between Kmax and Q-values increases with asymmetry, which means that the corresponding scission configuration needs higher total deformation energy to occur. Higher deformation energy of the fragments implies lower free energy to break nucleon pairs. Consequently, in the asymmetric fragmentation region, the even-odd effects of the distribution of proton number and neutron number must increase with asymmetry.

  16. Tracing and Apportioning Sources of Uranium to the Hanford Reach of the Columbia River Using Uranium Isotopes

    NASA Astrophysics Data System (ADS)

    Christensen, J. N.; Dresel, P. E.; Conrad, M. E.; Patton, G. W.; Depaolo, D. J.

    2004-12-01

    The U.S. Department of Energy's Hanford Site is situated along an unimpounded portion of the Columbia River, the highest discharge volume river west of the continental divide. Decades of nuclear related activities have left significant local contamination (e.g. nitrate, U, tritium, Cr6+, 99Tc) in the vadose zone and groundwater within the site. Some of this contamination has reached the Columbia River, and there remains the potential for further contaminant migration to the river. We collected and analyzed samples of Columbia River water for U and Sr isotopes in coordination with the ongoing sampling and monitoring of the river. The U and Sr isotopic data allow us to evaluate sources of U (e.g. natural background, Hanford related, agricultural runoff) and their relative contributions to the river's U budget. The data also provide constraints on the flux of contaminant U from the Hanford Site to the river. We analyzed two sample traverses across the Columbia, one near the Vernita Bridge, upstream from Hanford Site contamination, and a second about 5 km downstream of the Hanford Site. An island divides the downstream traverse into western (main channel) and eastern portions. Filtered (0.45 micron) water samples were analyzed for U isotopic composition (including 236U, one marker of spent U fuel) and U concentration, as well as 87Sr/86Sr and Sr concentration. The samples from the upstream traverse had no detectible 236U (236U/238U < 2x10-8), one marker of spent U fuel, natural 238U/235U, uniform (234U/238U, 87Sr/86Sr, U and Sr concentrations. In contrast, the downstream traverse showed variation in all of these parameters. Concentrations of U are 0.5 ppb to 1.2 ppb and are all well below the EPA MCL of 30 ppb for drinking water. In the western channel, measured 236U/238U is 3.4x10-5 to < 2x10-8, with a co-variation in 238U/235U toward enriched ratios. This correlation is consistent with the U isotopic compositions of a groundwater sample from the environs of a former

  17. Thallium, uranium, and {sup 235}U/{sup 238}U ratios in the digestive gland of American lobster (Homarus americanus) from an industrialized harbor

    SciTech Connect

    Chou, C.L.; Uthe, J.F.

    1995-01-01

    Only a few studies have concentrated on elements such as thallium (TI). Uranium (U) has been studied as a radionuclide of concern in food and the environment. Foodstuffs contain 10-100 ng U{center_dot}{sup -1} with vegetables and cereals contributing most heavily to the daily intake of ca 1.5 ug U. Between 10-30% of ingested U is absorbed, with most being stored in bone. Rainbow trout (onchorynchus mykiss) and longnose sucker (Catostomus catostomus) from a lake with naturally high radioactivity contained < 5 ng U{center_dot}g{sup -1} in the flesh. Trout bone contained 40 ng U{center_dot}g{sup -1}. Higher tissue U concentrations occurred in fish from areas receiving U mining wastes. Bioconcentration factors for bone and flesh were estimated to be low, 118 and 14.7, respectively. This paper describes the Inductively coupled plasma-mass spectrometry (ICP-MS) determination of Tl and U in digestive gland tissue from lobsters captured in the vicinity of Belledune Harbor, New Brunswick, Canada. The harbor is the site of a lead smelter, a fertilizer plant, and a coal-fired power station (the latter due to enter production in late 1993) and thus has the potential of adding significant amounts of Tl to the local marine environment. The accumulation of Tl from water by marine shellfish is low, at least for bivalves, and the accumulated Tl is eliminated in a number of days when the animals are transferred to clean water. Bioconcentration factors for U in finfish ranged from 0.4-17 for larger species. However, because of the high concentrations of various trace elements in lobster digestive gland, its desirability as a foodstuff, and its relatively large size (approximately 20% of the edible tissue yield), we have investigated Tl and U concentrations and {sup 235U}/{sup 238U} ratios in it. 15 refs., 1 fig., 3 tabs.

  18. Procedures for the use of Lexan and Makrofol SSNTDs in the detection of environmental concentrations of {sup 235}U and {sup 239}Pu

    SciTech Connect

    Henderson, C.L.

    1993-03-01

    Solid State Nuclear Track Detectors are used to study a variety of atomic particles. Polycarbonate SSNTD is used to study environmental concentrations of {sup 235}U and {sup 239}Pu in human urine and feces through fission track analysis. The samples of interest are deposited upon a Lexan slide, covered with a piece of Makrofol and exposed to a neutron fluence of 1.1 X 10{sup 17}. The fissile isotopes in the sample fission and the resulting fission fragments pass through either the surface of the Lexan or the surface of the Makrofol. The positive Coulombic attraction of the ionized fission fragments causes the electrons of the polycarbonate lattice to move towards the path of these particles, resulting in the breakage of chemical bonds in the lattice. The detector is then chemically etched in 6.5 N KOH that preferentially dissolves the damaged polycarbonate left in the path of the fission fragment. The chemically etched fission tracks are permanent records of the path of the fission fragment. The etched fission tracks in Lexan are optically counted using a microscope and the fission tracks in Makrofol are counted using a Spark Chamber. The amount of fissile material in the original sample can be calculated from the number of fission tracks. This paper presents further details of procedures for etching fission tracks in Lexan and Makrofol and for operating a Spark Chamber to count etched fission tracks in Makrofol. The physics of fission track formation in dielectric detectors is also discussed, as well as the physics of the Spark Chamber.

  19. Simulated (n,f) cross section of isomeric 235m-U

    SciTech Connect

    Becker, J; Britt, H; Younes, W

    2003-12-18

    The neutron-induced fission cross section on the {sup 235}U, T{sub 1/2} {approx} 26 min isomer has been deduced for incident neutron energies in the range E{sub n}=0.1-2.5 MeV, using the surrogate-reaction technique. In this technique, {sup 236}U fission probabilities measured in the {sup 234}U(t, pf) reaction have been converted into {sup 235}U(n,f) and {sup 235m}U(n,f) cross sections, using reaction theory to compensate for the differences in angular-momentum and parity distributions in the fissioning systems, transferred by the (t,p) and neutron-induced reactions. Based on the comparison between the {sup 235}U(n,f) cross section extracted in this work and independent experimental data, the deduced {sup 235m}U(n,f) cross section is believed to be reliable to 20% below E{sub n} {approx} 0.5 MeV and 10% at higher energies. The surrogate-reaction technique, its validation in the case of the {sup 235}U(n,f) cross section, and the deduced {sup 235m}U(n,f) cross section are discussed. Validation of this method allows (n,f) cross sections for many short-lived nuclei, as well as isomeric nuclei, to be extracted from measured fission probabilities.

  20. "Stable" Isotope Fractionation of Uranium: Implications for Geochemical Cycling and Geochronology

    NASA Astrophysics Data System (ADS)

    Stirling, C. H.; Andersen, M. B.; Warthmann, R.; Halliday, A. N.

    2007-12-01

    Uranium is the heaviest naturally occurring element. It has three natural radioactive isotopes, 238U, 235U and 234U and is thus widely utilized for geochronology, and two oxidation states, insoluble U(IV) and soluble U(VI). Mass-dependent thermodynamic isotopic fractionation between 235U and 238U (and 234U and 238U), which scales with δM/M2, is not normally considered significant given the small ~1% difference in mass. It is therefore usual to assume that 238U/235U is constant in nature and presently equal to 137.88 throughout the entire solar system. Importantly, isotopic fractionation of the very heavy elements has recently been investigated for mercury and thallium in the context of mass-independent nuclear field shift effects (Schauble 2007, GCA 71, 2170-2189), which do not scale with δM/M2, and are predicted to have permil-level effects on the heavy masses, including uranium. Uranium is thus emerging as a potentially significant element for monitoring biological pathways and redox processes occurring during the transition between the U(IV) and U(VI) oxidation states. We have developed experimental protocols for the precise measurement of 238U/235U and 238U/234U by multiple-collector ICPMS (MC-ICPMS) to investigate "stable" isotope fractionation in uranium. Using a Nu Plasma MC-ICPMS, concentrated solutions are measured at high signal intensity to enable simultaneous data collection on a stable multiple-Faraday array in place of the usual electron multiplier configuration. Using these protocols and a high-purity 233U-236U double-spike to internally monitor instrumental mass fractionation, we are able to resolve variations in 238U/235U and 238U/234U at the 0.4 and 0.3 epsilon level (2σ; 1 ɛ = 1 part in 10,000), respectively. Terrestrial and meteoritic samples formed in high-temperature environments show no variability in 238U/235U at the 1-ɛ level. In contrast, measurements for samples formed in low- temperature environments reveal permil-level natural

  1. Study on Prompt Fission Neutron Spectra and Associated Covariances for 235U(nth,f) and 239Pu(nth,f)

    NASA Astrophysics Data System (ADS)

    Berge, L.; Litaize, O.; Serot, O.; Jean, C. De Saint; Archier, P.; Peneliau, Y.

    normalization of experimental spectra, and the uncertainty on the energy-dependent neutron detection efficiency. We show the resulting PFNS and associated covariance matrix in the case of thermal neutron-induced fission of 235U and 239Pu.

  2. NUSIMEP-7: uranium isotope amount ratios in uranium particles.

    PubMed

    Truyens, J; Stefaniak, E A; Aregbe, Y

    2013-11-01

    The Institute for Reference Materials and Measurements (IRMM) has extensive experience in the development of isotopic reference materials and the organization of interlaboratory comparisons (ILC) for nuclear measurements in compliance with the respective international guidelines (ISO Guide 34:2009 and ISO/IEC 17043:2010). The IRMM Nuclear Signatures Interlaboratory Measurement Evaluation Program (NUSIMEP) is an external quality control program with the objective of providing materials for measurements of trace amounts of nuclear materials in environmental matrices. Measurements of the isotopic ratios of the elements uranium and plutonium in small amounts, typical of those found in environmental samples, are required for nuclear safeguards and security, for the control of environmental contamination and for the detection of nuclear proliferation. The measurement results of participants in NUSIMEP are evaluated according to international guidelines in comparison to independent external certified reference values with demonstrated metrological traceability and uncertainty. NUSIMEP-7 focused on measurements of uranium isotope amount ratios in uranium particles aiming to support European Safeguards Directorate General for Energy (DG ENER), the International Atomic Energy Agency's (IAEA) network of analytical laboratories for environmental sampling (NWAL) and laboratories in the field of particle analysis. Each participant was provided two certified test samples: one with single and one with double isotopic enrichment. These NUSIMEP test samples were prepared by controlled hydrolysis of certified uranium hexafluoride in a specially designed aerosol deposition chamber at IRMM. Laboratories participating in NUSIMEP-7 received the test samples of uranium particles on two graphite disks with undisclosed isotopic ratio values n((234)U)/n((238)U), n((235)U)/n((238)U) and n((236)U)/n((238)U). The uranium isotope ratios had to be measured using their routine analytical

  3. NUSIMEP-7: uranium isotope amount ratios in uranium particles.

    PubMed

    Truyens, J; Stefaniak, E A; Aregbe, Y

    2013-11-01

    The Institute for Reference Materials and Measurements (IRMM) has extensive experience in the development of isotopic reference materials and the organization of interlaboratory comparisons (ILC) for nuclear measurements in compliance with the respective international guidelines (ISO Guide 34:2009 and ISO/IEC 17043:2010). The IRMM Nuclear Signatures Interlaboratory Measurement Evaluation Program (NUSIMEP) is an external quality control program with the objective of providing materials for measurements of trace amounts of nuclear materials in environmental matrices. Measurements of the isotopic ratios of the elements uranium and plutonium in small amounts, typical of those found in environmental samples, are required for nuclear safeguards and security, for the control of environmental contamination and for the detection of nuclear proliferation. The measurement results of participants in NUSIMEP are evaluated according to international guidelines in comparison to independent external certified reference values with demonstrated metrological traceability and uncertainty. NUSIMEP-7 focused on measurements of uranium isotope amount ratios in uranium particles aiming to support European Safeguards Directorate General for Energy (DG ENER), the International Atomic Energy Agency's (IAEA) network of analytical laboratories for environmental sampling (NWAL) and laboratories in the field of particle analysis. Each participant was provided two certified test samples: one with single and one with double isotopic enrichment. These NUSIMEP test samples were prepared by controlled hydrolysis of certified uranium hexafluoride in a specially designed aerosol deposition chamber at IRMM. Laboratories participating in NUSIMEP-7 received the test samples of uranium particles on two graphite disks with undisclosed isotopic ratio values n((234)U)/n((238)U), n((235)U)/n((238)U) and n((236)U)/n((238)U). The uranium isotope ratios had to be measured using their routine analytical

  4. ZPR-3 Assembly 6F : A spherical assembly of highly enriched uranium, depleted uranium, aluminum and steel with an average {sup 235}U enrichment of 47 atom %.

    SciTech Connect

    Lell, R. M.; McKnight, R. D; Schaefer, R. W.; Nuclear Engineering Division

    2010-09-30

    Over a period of 30 years, more than a hundred Zero Power Reactor (ZPR) critical assemblies were constructed at Argonne National Laboratory. The ZPR facilities, ZPR-3, ZPR-6, ZPR-9 and ZPPR, were all fast critical assembly facilities. The ZPR critical assemblies were constructed to support fast reactor development, but data from some of these assemblies are also well suited for nuclear data validation and to form the basis for criticality safety benchmarks. A number of the Argonne ZPR/ZPPR critical assemblies have been evaluated as ICSBEP and IRPhEP benchmarks. Of the three classes of ZPR assemblies, engineering mockups, engineering benchmarks and physics benchmarks, the last group tends to be most useful for criticality safety. Because physics benchmarks were designed to test fast reactor physics data and methods, they were as simple as possible in geometry and composition. The principal fissile species was {sup 235}U or {sup 239}Pu. Fuel enrichments ranged from 9% to 95%. Often there were only one or two main core diluent materials, such as aluminum, graphite, iron, sodium or stainless steel. The cores were reflected (and insulated from room return effects) by one or two layers of materials such as depleted uranium, lead or stainless steel. Despite their more complex nature, a small number of assemblies from the other two classes would make useful criticality safety benchmarks because they have features related to criticality safety issues, such as reflection by soil-like material. ZPR-3 Assembly 6 consisted of six phases, A through F. In each phase a critical configuration was constructed to simulate a very simple shape such as a slab, cylinder or sphere that could be analyzed with the limited analytical tools available in the 1950s. In each case the configuration consisted of a core region of metal plates surrounded by a thick depleted uranium metal reflector. The average compositions of the core configurations were essentially identical in phases A - F. ZPR-3

  5. ZPR-3 Assembly 12 : A cylindrical assembly of highly enriched uranium, depleted uranium and graphite with an average {sup 235}U enrichment of 21 atom %.

    SciTech Connect

    Lell, R. M.; McKnight, R. D.; Perel, R. L.; Wagschal, J. J.; Nuclear Engineering Division; Racah Inst. of Physics

    2010-09-30

    Over a period of 30 years, more than a hundred Zero Power Reactor (ZPR) critical assemblies were constructed at Argonne National Laboratory. The ZPR facilities, ZPR-3, ZPR-6, ZPR-9 and ZPPR, were all fast critical assembly facilities. The ZPR critical assemblies were constructed to support fast reactor development, but data from some of these assemblies are also well suited for nuclear data validation and to form the basis for criticality safety benchmarks. A number of the Argonne ZPR/ZPPR critical assemblies have been evaluated as ICSBEP and IRPhEP benchmarks. Of the three classes of ZPR assemblies, engineering mockups, engineering benchmarks and physics benchmarks, the last group tends to be most useful for criticality safety. Because physics benchmarks were designed to test fast reactor physics data and methods, they were as simple as possible in geometry and composition. The principal fissile species was {sup 235}U or {sup 239}Pu. Fuel enrichments ranged from 9% to 95%. Often there were only one or two main core diluent materials, such as aluminum, graphite, iron, sodium or stainless steel. The cores were reflected (and insulated from room return effects) by one or two layers of materials such as depleted uranium, lead or stainless steel. Despite their more complex nature, a small number of assemblies from the other two classes would make useful criticality safety benchmarks because they have features related to criticality safety issues, such as reflection by soil-like material. ZPR-3 Assembly 12 (ZPR-3/12) was designed as a fast reactor physics benchmark experiment with an average core {sup 235}U enrichment of approximately 21 at.%. Approximately 68.9% of the total fissions in this assembly occur above 100 keV, approximately 31.1% occur below 100 keV, and essentially none below 0.625 eV - thus the classification as a 'fast' assembly. This assembly is Fast Reactor Benchmark No. 9 in the Cross Section Evaluation Working Group (CSEWG) Benchmark Specifications

  6. Overview of Uranium Isotopic Reference Materials at IRMM

    NASA Astrophysics Data System (ADS)

    Alonso-Munoz, A.; Richter, S.; Eykens, R.; Aregbe, Y.; Kuehn, H.; Verbruggen, A.

    2007-12-01

    For many applications in the geological sciences, in particular in geochemistry research, isotope ratio measurements play a significant role. For instance, in geochronology isotope abundances of uranium and its daughter products thorium and lead have been used since more than five decades to determine the age of various samples of geological interest. However, in order to validate mass spectrometric measurement procedures and to calibrate detector systems, suitable isotope reference materials are needed. IRMM is a well recognized provider for nuclear isotope reference materials to the nuclear industry and nuclear safeguards authorities, which can also be used for geological applications. This paper gives an overview of isotope reference materials for uranium prepared and certified at IRMM. These materials are synthetic isotope reference materials prepared based on proven methods of purifying and mixing highly enriched oxides. Firstly, a set of 10 mixtures of 233U, 235U and 238U was made in which the 235U/238U ratios were kept at 1:1 and the 233U/235U ratios varied from 1.0 to 10-6 (IRMM-072). This set is ideal for checking the linearity response of detectors used in isotope mass spectrometry. Recently, after the IRMM-072 series was exhausted, it has been replaced by the IRMM-073 and IRMM-074 series. Secondly the double spike IRMM-3636 with a 233U/236U ratio of 1:1 was prepared which allows internal mass fractionation correction for high precision 235U/238U ratio measurements. The 234U abundance of this double spike material is low enough to allow an accurate and precise correction of 234U/238U ratios, even for measurements of close to equilibrium uranium samples.

  7. The Surrogate Method: Past, Present and Future

    SciTech Connect

    Lesher, S R; Bernstein, L A; Burke, J T; Lyles, B F; Clark, R M; Fallon, P; Phair, L

    2008-01-09

    The STARS/LiBerACE collaboration has been exploring the surrogate technique with success in the actinide region. This method uses a direct reaction to measure the decay probability of the same compound nucleus produced via a neutron-induced channel. This paper serves as an overview of these activities. Using the STARS array at 88-inch Cyclotron at Lawrence Berkeley National Laboratory we have explored the following surrogate reactions: {sup 234}U({alpha}, {alpha}{prime}f), {sup 235}U({sup 3}He, {alpha}f), {sup 236}U({alpha}, {alpha}{prime}f), {sup 238}U ({alpha},{alpha}{prime}f), {sup 238}U({sup 3}He,{alpha}f), {sup 238}U({sup 3}He, tf) surrogates for {sup 233}U(n,f), {sup 233}U(n,f), {sup 235}U(n,f), {sup 237}U(n,f), {sup 236}U(n,f), and {sup 237}Np(n,f), respectively.

  8. (238)U/(235)U isotope ratios of crustal material, rivers and products of hydrothermal alteration: new insights on the oceanic U isotope mass balance.

    PubMed

    Noordmann, Janine; Weyer, Stefan; Georg, R Bastian; Jöns, Svenja; Sharma, Mukul

    2016-01-01

    In this study, the U isotope composition, n((238)U)/n((235)U), of major components of the upper continental crust, including granitic rocks of different age and post-Archaean shales, as well as that of rivers (the major U source to the oceans) was investigated. Furthermore, U isotope fractionation during the removal of U at mid-ocean ridges, an important sink for U from the oceans, was investigated by the analyses of hydrothermal water samples (including low- and high-temperature fluids), low-temperature altered basalts and calcium carbonate veins. All analysed rock samples from the continental crust fall into a limited range of δ(238)U between -0.45 and -0.21 ‰ (relative to NBL CRM 112-A), with an average of -0.30 ± 0.15 ‰ (2 SD, N = 11). Despite differences in catchment lithologies, all major rivers define a relatively narrow range between -0.31 and -0.13 ‰, with a weighted mean isotope composition of -0.27 ‰, which is indistinguishable from the estimate for the upper continental crust (-0.30 ‰). Only some tributary rivers from the Swiss Alps display a slightly larger range in δ(238)U (-0.29 to +0.01 ‰) and lower U concentrations (0.87-3.08 nmol/kg) compared to the investigated major rivers (5.19-11.69 nmol/kg). These findings indicate that only minor net U isotope fractionation occurs during weathering and transport of material from the continental crust to the oceans. Altered basalts display moderately enriched U concentrations (by a factor of 3-18) compared to those typically observed for normal mid-ocean ridge basalts. These, and carbonate veins within altered basalts, show large U isotope fractionation towards both heavy and light U isotope compositions (ranging from -0.63 to +0.27 ‰). Hydrothermal water samples display low U concentrations (0.3-1 nmol/kg) and only limited variations in their U isotope composition (-0.43 ± 0.25 ‰) around the seawater value. Nevertheless, two of the investigated fluids display

  9. (238)U/(235)U isotope ratios of crustal material, rivers and products of hydrothermal alteration: new insights on the oceanic U isotope mass balance.

    PubMed

    Noordmann, Janine; Weyer, Stefan; Georg, R Bastian; Jöns, Svenja; Sharma, Mukul

    2016-01-01

    In this study, the U isotope composition, n((238)U)/n((235)U), of major components of the upper continental crust, including granitic rocks of different age and post-Archaean shales, as well as that of rivers (the major U source to the oceans) was investigated. Furthermore, U isotope fractionation during the removal of U at mid-ocean ridges, an important sink for U from the oceans, was investigated by the analyses of hydrothermal water samples (including low- and high-temperature fluids), low-temperature altered basalts and calcium carbonate veins. All analysed rock samples from the continental crust fall into a limited range of δ(238)U between -0.45 and -0.21 ‰ (relative to NBL CRM 112-A), with an average of -0.30 ± 0.15 ‰ (2 SD, N = 11). Despite differences in catchment lithologies, all major rivers define a relatively narrow range between -0.31 and -0.13 ‰, with a weighted mean isotope composition of -0.27 ‰, which is indistinguishable from the estimate for the upper continental crust (-0.30 ‰). Only some tributary rivers from the Swiss Alps display a slightly larger range in δ(238)U (-0.29 to +0.01 ‰) and lower U concentrations (0.87-3.08 nmol/kg) compared to the investigated major rivers (5.19-11.69 nmol/kg). These findings indicate that only minor net U isotope fractionation occurs during weathering and transport of material from the continental crust to the oceans. Altered basalts display moderately enriched U concentrations (by a factor of 3-18) compared to those typically observed for normal mid-ocean ridge basalts. These, and carbonate veins within altered basalts, show large U isotope fractionation towards both heavy and light U isotope compositions (ranging from -0.63 to +0.27 ‰). Hydrothermal water samples display low U concentrations (0.3-1 nmol/kg) and only limited variations in their U isotope composition (-0.43 ± 0.25 ‰) around the seawater value. Nevertheless, two of the investigated fluids display

  10. Preliminary results of calculations for heavy-water nuclear-power-plant reactors employing 235U, 233U, and 232Th as a fuel and meeting requirements of a nonproliferation of nuclear weapons

    NASA Astrophysics Data System (ADS)

    Ioffe, B. L.; Kochurov, B. P.

    2012-02-01

    A physical design is developed for a gas-cooled heavy-water nuclear reactor intended for a project of a nuclear power plant. As a fuel, the reactor would employ thorium with a small admixture of enriched uranium that contains not more than 20% of 235U. It operates in the open-cycle mode involving 233U production from thorium and its subsequent burnup. The reactor meets the conditions of a nonproliferation of nuclear weapons: the content of fissionable isotopes in uranium at all stages of the process, including the final one, is below the threshold for constructing an atomic bomb, the amount of product plutonium being extremely small.

  11. Preliminary results of calculations for heavy-water nuclear-power-plant reactors employing {sup 235}U, {sup 233}U, and {sup 232}Th as a fuel and meeting requirements of a nonproliferation of nuclear weapons

    SciTech Connect

    Ioffe, B. L.; Kochurov, B. P.

    2012-02-15

    A physical design is developed for a gas-cooled heavy-water nuclear reactor intended for a project of a nuclear power plant. As a fuel, the reactor would employ thorium with a small admixture of enriched uranium that contains not more than 20% of {sup 235}U. It operates in the open-cycle mode involving {sup 233}U production from thorium and its subsequent burnup. The reactor meets the conditions of a nonproliferation of nuclear weapons: the content of fissionable isotopes in uranium at all stages of the process, including the final one, is below the threshold for constructing an atomic bomb, the amount of product plutonium being extremely small.

  12. Indirect Determination of the 230Th(n,f) and 231Th(n,f) Cross Sections for Thorium-Based Nuclear Energy Systems

    SciTech Connect

    Stroberg, S.R.; Allmond, J.M.; Angell, C.; Bernstein, L.A.; Bleuel, D.L.; Burke, J.T.; Gibelin, J.; Phair, L.; Scielzo, N.D.; Swanberg, E.; Wiedeking, M.; Norman, E.B.; Goldblum, Bethany

    2009-09-11

    The Surrogate Ratio Method (SRM) was employed in the first experimental determination of the 231Th(n,f) cross section, relative to the 235U(n,f) cross section, over an equivalent neutron energy range of 360 keV to 10 MeV. The 230Th(n,f) cross section was also deduced using the SRM, relative to the 234U(n,f) cross section, over an equivalent neutron energy range of 220 keV to 25 MeV. The desired compound nuclei were populated using (3He,3He) and (3He) reactions on targets of 232Th and 236U and relative fission decay probabilities were measured. The surrogate 230,231Th(n,f) cross sections were compared to cross section evaluations and directly-measured experimental data, where available.

  13. Benchmarking the External Surrogate Ratio Method using the (alpha,alpha' f) reaction at STARS

    SciTech Connect

    Lesher, S R; Bernstein, L A; Ai, H; Beausang, C W; Bleuel, D; Burke, J T; Clark, R M; Fallon, P; Gibelin, J; Lee, I Y; Lyles, B F; Macchiavelli, A O; McMahan, M A; Moody, K J; Norman, E B; Phair, L; Rodriguez-Vieitez, E; Wiedeking, M

    2008-01-09

    We measured the ratio of the fission probabilities of {sup 234}U* relative to {sup 236}U* formed via an ({alpha},{alpha}{prime}) direct reactions using the STARS array at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This ratio has a shape similar to the ratio of neutron capture probabilities from {sup 233}U(n; f) and {sup 235}U(n; f), indicating the alpha reactions likely formed a compound nucleus. This result indicates that the ratios of fission exit channel probabilities for two actinide nuclei populated via ({alpha}, {alpha}{prime}) can be used to determine an unknown fission cross section relative to a known one. The validity of the External Surrogate Ratio Method (ESRM) is tested and the results support the conclusions of Burke et al. [1].

  14. Recommended Method To Account For Daughter Ingrowth For The Portsmouth On-Site Waste Disposal Facility Performance Assessment Modeling

    SciTech Connect

    Phifer, Mark A.; Smith, Frank G. III

    2013-06-21

    A 3-D STOMP model has been developed for the Portsmouth On-Site Waste Disposal Facility (OSWDF) at Site D as outlined in Appendix K of FBP 2013. This model projects the flow and transport of the following radionuclides to various points of assessments: Tc-99, U-234, U-235, U-236, U-238, Am-241, Np-237, Pu-238, Pu-239, Pu-240, Th-228, and Th-230. The model includes the radioactive decay of these parents, but does not include the associated daughter ingrowth because the STOMP model does not have the capability to model daughter ingrowth. The Savannah River National Laboratory (SRNL) provides herein a recommended method to account for daughter ingrowth in association with the Portsmouth OSWDF Performance Assessment (PA) modeling.

  15. Prompt fission neutron spectra from fission induced by 1 to 8 MeV neutrons on {sup 235}U and {sup 239}Pu using the double time-of-flight technique

    SciTech Connect

    Noda, S.; Haight, R. C.; Nelson, R. O.; Devlin, M.; O'Donnell, J. M.; Chatillon, A.; Granier, T.; Belier, G.; Taieb, J.; Kawano, T.; Talou, P.

    2011-03-15

    Prompt fission neutron spectra from {sup 235}U and {sup 239}Pu were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg {sup 235}U and 90 mg {sup 239}Pu detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced {gamma}-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.

  16. Investigation of (235)U, (226)Ra, (232)Th, (40)K, (137)Cs, and heavy metal concentrations in Anzali international wetland using high-resolution gamma-ray spectrometry and atomic absorption spectroscopy.

    PubMed

    Zare, Mohammad Reza; Kamali, Mahdi; Fallahi Kapourchali, Maryam; Bagheri, Hashem; Khoram Bagheri, Mahdi; Abedini, Ali; Pakzad, Hamid Reza

    2016-02-01

    Measurements of natural radioactivity levels and heavy metals in sediment and soil samples of the Anzali international wetland were carried out by two HPGe-gamma ray spectrometry and atomic absorption spectroscopy techniques. The concentrations of (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs in sediment samples ranged between 1.05 ± 0.51-5.81 ± 0.61, 18.06 ± 0.63-33.36 ± .0.34, 17.57 ± 0.38-45.84 ± 6.23, 371.88 ± 6.36-652.28 ± 11.60, and 0.43 ± 0.06-63.35 ± 0.94 Bq/kg, while in the soil samples they vary between 2.36-5.97, 22.71-38.37, 29.27-42.89, 472.66-533, and 1.05-9.60 Bq/kg for (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs, respectively. Present results are compared with the available literature data and also with the world average values. The radium equivalent activity was well below the defined limit of 370 Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. Heavy metal concentrations were found to decrease in order as Fe > Mn > Sr > Zn > Cu > Cr > Ni > Pb > Co > Cd. These measurements will serve as background reference levels for the Anzali wetland. PMID:26490904

  17. Investigation of (235)U, (226)Ra, (232)Th, (40)K, (137)Cs, and heavy metal concentrations in Anzali international wetland using high-resolution gamma-ray spectrometry and atomic absorption spectroscopy.

    PubMed

    Zare, Mohammad Reza; Kamali, Mahdi; Fallahi Kapourchali, Maryam; Bagheri, Hashem; Khoram Bagheri, Mahdi; Abedini, Ali; Pakzad, Hamid Reza

    2016-02-01

    Measurements of natural radioactivity levels and heavy metals in sediment and soil samples of the Anzali international wetland were carried out by two HPGe-gamma ray spectrometry and atomic absorption spectroscopy techniques. The concentrations of (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs in sediment samples ranged between 1.05 ± 0.51-5.81 ± 0.61, 18.06 ± 0.63-33.36 ± .0.34, 17.57 ± 0.38-45.84 ± 6.23, 371.88 ± 6.36-652.28 ± 11.60, and 0.43 ± 0.06-63.35 ± 0.94 Bq/kg, while in the soil samples they vary between 2.36-5.97, 22.71-38.37, 29.27-42.89, 472.66-533, and 1.05-9.60 Bq/kg for (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs, respectively. Present results are compared with the available literature data and also with the world average values. The radium equivalent activity was well below the defined limit of 370 Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. Heavy metal concentrations were found to decrease in order as Fe > Mn > Sr > Zn > Cu > Cr > Ni > Pb > Co > Cd. These measurements will serve as background reference levels for the Anzali wetland.

  18. Use of {sup 59}Ni, {sup 99}Tc, and {sup 236}U to monitor the release of radionuclides from objects containing spent nuclear fuel dumped in the Kara Sea

    SciTech Connect

    Mount, M.E.; Layton, D.W.; Lynn, N.M.; Hamilton, T.F.

    1998-04-01

    Between 1965 and 1981, five objects - six naval reactor pressure vessels (RPVs) from four former Soviet Union submarines and a special containers from the icebreaker Lenin, each of which contained damaged spent nuclear fuel (SNF) - were dumped in a variety of containments, using a number of sealing methods, at four sites in the Kara Sea. All objects were dumped at sites that varied in depth from 12 to 300 m. This paper examines the use of the long-lived radionuclides {sup 59}Ni, {sup 99}Tc, and {sup 236}U encased within these objects to monitor the breakdown of the containments due to corrosion. Included are discussions of the radionuclide inventory and their release rate model, the estimated radionuclide mass in a typical seawater sample, and the potential for radionuclide measurement via Accelerator Mass Spectrometry (AMS).

  19. Separation Of Uranium And Plutonium Isotopes For Measurement By Multi Collector Inductively Coupled Plasma Mass Spectroscopy

    SciTech Connect

    Martinelli, R E; Hamilton, T F; Williams, R W; Kehl, S R

    2009-03-29

    Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with {sup 233}U and {sup 242}Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA{reg_sign} column coupled to a UTEVA{reg_sign} column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of {sup 234}U/{sup 235}U, {sup 238}U/{sup 235}U, {sup 236}U/{sup 235}U, and {sup 240}Pu/{sup 239}Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.

  20. Isotopic Analysis of Uranium in NIST SRM Glass by Femtosecond Laser Ablation

    SciTech Connect

    Duffin, Andrew M.; Hart, Garret L.; Hanlen, Richard C.; Eiden, Gregory C.

    2013-05-19

    We employed femtosecond Laser Ablation Multicollector Inductively Coupled Mass Spectrometry for the 11 determination of uranium isotope ratios in a series of standard reference material glasses (NIST 610, 612, 614, and 12 616). This uranium concentration in this series of SRM glasses is a combination of isotopically natural uranium in 13 the materials used to make the glass matrix and isotopically depleted uranium added to increase the uranium 14 elemental concentration across the series. Results for NIST 610 are in excellent agreement with literature values. 15 However, other than atom percent 235U, little information is available for the remaining glasses. We present atom 16 percent and isotope ratios for 234U, 235U, 236U, and 238U for all four glasses. Our results show deviations from the 17 certificate values for the atom percent 235U, indicating the need for further examination of the uranium isotopes in 18 NIST 610-616. Our results are fully consistent with a two isotopic component mixing between the depleted 19 uranium spike and natural uranium in the bulk glass.

  1. Uranium isotopes (U-234/U-238) in rivers of the Yukon Basin (Alaska and Canada) as an aid in identifying water sources, with implications for monitoring hydrologic change in arctic regions

    USGS Publications Warehouse

    Kraemer, Thomas F.; Brabets, Timothy P.

    2012-01-01

    The ability to detect hydrologic variation in large arctic river systems is of major importance in understanding and predicting effects of climate change in high-latitude environments. Monitoring uranium isotopes (234U and 238U) in river water of the Yukon River Basin of Alaska and northwestern Canada (2001–2005) has enhanced the ability to identify water sources to rivers, as well as detect flow changes that have occurred over the 5-year study. Uranium isotopic data for the Yukon River and major tributaries (the Porcupine and Tanana rivers) identify several sources that contribute to river flow, including: deep groundwater, seasonally frozen river-valley alluvium groundwater, and high-elevation glacial melt water. The main-stem Yukon River exhibits patterns of uranium isotopic variation at several locations that reflect input from ice melt and shallow groundwater in the spring, as well as a multi-year pattern of increased variability in timing and relative amount of water supplied from higher elevations within the basin. Results of this study demonstrate both the utility of uranium isotopes in revealing sources of water in large river systems and of incorporating uranium isotope analysis in long-term monitoring of arctic river systems that attempt to assess the effects of climate change.

  2. Radionuclide concentrations in benthic invertebrates from Amchitka and Kiska Islands in the Aleutian Chain, Alaska.

    PubMed

    Burger, Joanna; Gochfeld, Michael; Jewett, Stephen C

    2007-05-01

    Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for

  3. Radionuclide concentrations in benthic invertebrates from Amchitka and Kiska Islands in the Aleutian Chain, Alaska.

    PubMed

    Burger, Joanna; Gochfeld, Michael; Jewett, Stephen C

    2007-05-01

    Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for

  4. New measurements of (n,γ) and (n,fission) cross sections and capture-to-fission ratios for ^233,235U and ^239Pu using the DANCE 4π BaF2 array

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.; Jandel, M.; Fowler, M. M.; Bond, E. M.; Haight, R. C.; Keksis, A. L.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Becker, J. A.; Parker, W. E.; Wu, C. Y.; Baker, J. D.; McGrath, C. A.

    2009-10-01

    Accurate neutron nuclear data are important to many issues in stockpile stewardship, nuclear reactor design and re-certification, nuclear non-proliferation and nuclear forensics. Of particular interest are the production and destruction reactions for all of the major and most of the minor actinides. The competition between capture and fission in many of the actinides presents both an obstacle and an opportunity for large γ detector arrays such as DANCE. Additional instrumentation is required to deconvolve the two contributions to the total observed γ-ray spectrum. However, conducting a simultaneous measurement can simplify background treatment and other sources of systematic uncertainty. An outline of the current experimental program will be presented along with results from neutron capture measurements on ^233,235U and ^239Pu.

  5. Use of 234U and 238U isotopes to evaluate contamination of near-surface groundwater with uranium-mill effluent: A case study in south-central Colorado, U.S.A.

    USGS Publications Warehouse

    Zielinski, R.A.; Chafin, D.T.; Banta, E.R.; Szabo, B. J.

    1997-01-01

    The 234U/238U alpha activity ratio (AR) was determined in 47 samples of variably uraniferous groundwater from the vicinity of a uranium mill near Canon City, Colorado. The results illustrate that uranium isotopes can be used to determine the distribution of uranium contamination in groundwater and to indicate processes such as mixing and chemical precipitation that affect uranium concentrations. Highly to moderately contaminated groundwater samples collected from the mill site and land immediately downgradient from the mill site contain more than 100 ??g/l of dissolved uranium and typically have AR values in the narrow range of 1.0-1.06. Other samples from the shallow alluvial aquifer farther downgradient from the mill contain 10-100 ??g/1 uranium and plot along a broad trend of increasing AR (1.06-1.46) with decreasing uranium concentration. The results are consistent with mixing of liquid mill waste (AR ??? 1.0) with alluvial groundwater of small, but variable, uranium concentrations and AR of 1.31.5. In the alluvial aquifer, the spatial distribution of wells with AR values less than 1.3 is consistent with previous estimates of the probable distribution of contamination, based on water chemistry and hydrology. Wells more distant from the area of probable contamination have AR values that are consistently greater than 1.3 and are indicative of little or no contamination. The methodology of this study can be extended usefully to similar sites of uranium mining, milling, or processing provided that local geohydrologic settings promote uranium mobility and that introduced uranium contamination is isotopically distinct from that of local groundwater.

  6. ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS

    SciTech Connect

    Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

    2009-09-03

    Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for

  7. Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, M.; Arnold, C.; Bredeweg, T.; Vieira, D.; Wilhelmy, J.; Tonchev, A.; Stoyer, M.; Bhike, M.; Krishichayan, F.; Tornow, W.; Fowler, M.

    2015-10-01

    Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and ?-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. ?-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of 2 months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. These results are compared to previous measurements and theoretical estimates. This work was performed under the auspices of the USDoE by Los Alamos National Security, LLC under Contract DE-AC52-06NA25396.

  8. New measurements of (n,γ) and (n,fission) cross sections and capture-to-fission ratios for ^233,235U and ^239Pu using the DANCE 4π BaF2 array

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.; Jandel, M.; Fowler, M. M.; Bond, E. M.; Haight, R. C.; Keksis, A. L.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Slemmons, A. K.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Becker, J. A.; Wu, C. Y.; Baker, J. D.; McGrath, C. A.

    2010-11-01

    Accurate neutron-induced reaction data are important to many issues in stockpile stewardship, nuclear reactor design and re-certification, nuclear non-proliferation and nuclear forensics. Of particular interest are the production and destruction reactions for all of the major and most of the minor actinides, including both neutron-induced capture and fission. The competition between capture and fission presents both an obstacle and an opportunity for large γ detector arrays such as the DANCE array (Detector for Advanced Neutron Capture Experiments), which cannot clearly differentiate γ-rays resulting from the two exit channels. With the addition of a high efficiency, 4π fission-tagging detector it is possible to deconvolve the two contributions to the total γ-ray spectrum. Using these tools we are able to conduct simultaneous fission/capture measurements which can simplify background treatment and other sources of systematic uncertainty. An outline of the current experimental program will be presented along with results from neutron capture measurements on ^233,235U and ^239Pu.

  9. Porosity of the melting zone and variations in the solid mantle upwelling rate beneath Hawaii: Inferences from {sup 238}U-{sup 230}Th-{sup 226}Ra and {sup 235}U-{sup 231}Pa disequilibria

    SciTech Connect

    Sims, K.W.W.; DePaolo, D.J.; Murrell, M.T.; Baldridge, W.S.; Goldstein, S.; Clague, D.; Jull, M.

    1999-12-01

    Measurements of {sup 238}U-{sup 230}Th-{sup 226}Ra and {sup 235}U-{sup 231}Pa disequilibria in a suite of tholeiitic-to-basanitic lavas provide estimates of porosity, solid mantle upwelling rate and melt transport times beneath Hawaii. The observation that ({sup 230}Th/{sup 238}U) {gt} 1 indicates that garnet is required as a residual phase in the magma sources for all of the lavas. Both chromatographic porous flow and dynamic melting of a garnet peridotite source can adequately explain the combined U-Th-Ra and U-Pa data for these Hawaiian basalts. For chromatographic porous flow, the calculated maximum porosity in the melting zone ranges from 0.3--3% for tholeiites and 0.1--1% for alkali basalts and basanites, and solid mantle upwelling rates range from 40 to 100 cm/yr for tholeiites and from 1 to 3 cm/yr for basanites. For dynamic melting, the escape or threshold porosity is 0.5--2% for tholeiites and 0.1--0.8% for alkali basalts and basanites, and solid mantle upwelling rates range from 10 to 30 cm/yr for tholeiites and from 0.1 to 1 cm/yr for basanites. Assuming a constant melt productivity, calculated total melt fractions range from 15% for the tholeiitic basalts to 3% for alkali basalts and basanites.

  10. Neutron Total Cross Sections of {sup 235}U From Transmission Measurements in the Energy Range 2 keV to 300 keV and Statistical Model Analysis of the Data

    SciTech Connect

    Derrien, H.; Harvey, J.A.; Larson, N.M.; Leal, L.C.; Wright, R.Q.

    2000-05-01

    The average {sup 235}U neutron total cross sections were obtained in the energy range 2 keV to 330 keV from high-resolution transmission measurements of a 0.033 atom/b sample.1 The experimental data were corrected for the contribution of isotope impurities and for resonance self-shielding effects in the sample. The results are in very good agreement with the experimental data of Poenitz et al.4 in the energy range 40 keV to 330 keV and are the only available accurate experimental data in the energy range 2 keV to 40 keV. ENDF/B-VI evaluated data are 1.7% larger. The SAMMY/FITACS code 2 was used for a statistical model analysis of the total cross section, selected fission cross sections and data in the energy range 2 keV to 200 keV. SAMMY/FITACS is an extended version of SAMMY which allows consistent analysis of the experimental data in the resolved and unresolved resonance region. The Reich-Moore resonance parameters were obtained 3 from a SAMMY Bayesian fits of high resolution experimental neutron transmission and partial cross section data below 2.25 keV, and the corresponding average parameters and covariance data were used in the present work as input for the statistical model analysis of the high energy range of the experimental data. The result of the analysis shows that the average resonance parameters obtained from the analysis of the unresolved resonance region are consistent with those obtained in the resolved energy region. Another important result is that ENDF/B-VI capture cross section could be too small by more than 10% in the energy range 10 keV to 200 keV.

  11. NEUTRON TOTAL CROSS SECTIONS OF 235U FROM TRANSMISSION MEASUREMENTS IN THE ENERGY RANGE 2 keV to 300 keV AND STATISTICAL MODEL ANALYSIS OF THE DATA

    SciTech Connect

    Derrien, H.

    2000-05-22

    The average {sup 235}U neutron total cross sections were obtained in the energy range 2 keV to 330 keV from high-resolution transmission measurements of a 0.033 atom/b sample. The experimental data were corrected for the contribution of isotope impurities and for resonance self-shielding effects in the sample. The results are in very good agreement with the experimental data of Poenitz et al. in the energy range 40 keV to 330 keV and are the only available accurate experimental data in the energy range 2 keV to 40 keV. ENDF/B-VI evaluated data are 1.7% larger. The SAMMY/FITACS code was used for a statistical model analysis of the total cross section, selected fission cross sections and {alpha} data in the energy range 2 keV to 200 keV. SAMMY/FITACS is an extended version of SAMMY which allows consistent analysis of the experimental data in the resolved and unresolved resonance region. The Reich-Moore resonance parameters were obtained from a SAMMY Bayesian fits of high resolution experimental neutron transmission and partial cross section data below 2.25 keV, and the corresponding average parameters and covariance data were used in the present work as input for the statistical model analysis of the high energy range of the experimental data. The result of the analysis shows that the average resonance parameters obtained from the analysis of the unresolved resonance region are consistent with those obtained in the resolved energy region. Another important result is that ENDF/B-VI capture cross section could be too small by more than 10% in the energy range 10 keV to 200 keV.

  12. Determination of (226)Ra, (232)Th, (40)K, (235)U and (238)U activity concentration and public dose assessment in soil samples from bauxite core deposits in Western Cameroon.

    PubMed

    Mekongtso Nguelem, Eric Jilbert; Moyo Ndontchueng, Maurice; Motapon, Ousmanou

    2016-01-01

    Determination of activity concentrations in twenty five (25) soil samples collected from various points in bauxite ore deposit in Menoua Division in Western of Cameroon was done using gamma spectrometry based Broad Energy Germanium (BEGe6530) detector. The average terrestrial radionuclides of (40)K, (226)Ra, (232)Th, (235)U and (238)U were measured as 671 ± 272, 125 ± 58, 157 ± 67, 6 ± 3 and 99 ± 69 Bq kg(-1), respectively. The observed activity concentrations of radionuclides were compared with other published values in the world. The outdoor absorbed dose rate in air varied from 96.1 to 321.2 nGy h(-1) with an average of 188.2 ± 59.4 nGy h(-1). The external annual effective dose rate and external hazard index were estimated as 0.23 ± 0.07 mSv year(-1) for outdoor, 0.92 ± 0.29 mSv year(-1) for indoor and 1.13 for the external hazard index, respectively. These radiological safe parameters were relatively higher than the recommended safe limits of UNSCEAR. Consequently, using of soil as building material might lead to an increase the external exposure to natural radioactivity and future applications research need to be conducted to have a global view of radioactivity level in the area before any undergoing bauxite ore exploitation. PMID:27536536

  13. Beta and gamma decay heat measurements between 0.1s - 50,000s for neturon fission of {sup 235}U, {sup 238}U and {sup 239}Pu. Progress report, June 1, 1992--December 31, 1994

    SciTech Connect

    Schier, W.A.; Couchell, G.P.

    1997-05-01

    In the investigations reported here, a helium-jet/tape-transport system was used for the rapid transfer of fission products to a low-background environment where their aggregate beta and gamma-ray spectra were measured as a function of delay time after neutron induced fission of {sup 235}U, {sup 238}U and {sup 239}Pu. Beta and gamma-ray energy distributions have been deduced for delay times as short as 0.2 s and extending out to 100,000s. Instrumentation development during the initial phase of the project included: (1) assembly and characterization of a NaI(Tl) spectrometer for determining aggregate gamma-ray energy distributions, (2) development and characterization of a beta spectrometer (having excellent gamma-ray rejection) for measuring aggregate beta-particle energy distributions, (3) assembly and characterization of a Compton-suppressed HPGe spectrometer for determining gamma-ray intensities of individual fission products to deduce fission-product yields. Spectral decomposition and analysis codes were developed for deducing energy distributions from measured aggregate beta and gamma spectra. The aggregate measurements in the time interval 0.2 - 20s after fission are of special importance since in this region data from many short-lived nuclei are missing and summation calculations in this region rely on model calculations for a large fraction of their predicted beta and gamma decay heat energy spectra. Comparison with ENDF/B-VI fission product data was performed in parallel with the measurements through a close collaboration with Dr. T. England at LANL, assisted by one of our graduate students. Such aggregate measurements provide tests of the Gross Theory of beta decay used to calculated missing contributions to this data base. Fission-product yields deduced from the HPGe studies will check the accuracy of the semi-empirical Gaussian dispersion model used presently by evaluators in the absence of measured yields.

  14. Application of Inductively Coupled Plasma Mass Spectrometry to the determination of uranium isotope ratios in individual particles for nuclear safeguards

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao Zhi; Esaka, Fumitaka; Esaka, Konomi T.; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Watanabe, Kazuo

    2007-10-01

    The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the 235U/ 238U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the 235U/ 238U isotope ratio was within 4.2%. Although the analysis of 234U/ 238U and 236U/ 238U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards.

  15. Test and evaluation results of the /sup 252/Cf shuffler at the Savannah River Plant

    SciTech Connect

    Crane, T.W.

    1981-03-01

    The /sup 252/Cf Shuffler, a nondestructive assay instrument employing californium neutron source irradiation and delayed-neutron counting, was developed for measuring /sup 235/U content of scrap and waste items generated at the Savannah River Plant (SRP) reactor fuel fabrication facility. The scrap and waste items include high-purity uranium-aluminum alloy ingots as well as pieces of castings, saw and lathe chips from machining operations, low-purity items such as oxides of uranium or uranium intermixed with flux materials found in recovery operations, and materials not recoverable at SRP such as floor sweepings or residues from the uranium scrap recovery operation. The uranium contains about 60% /sup 235/U with the remaining isotopes being /sup 236/U, /sup 238/U, and /sup 234/U in descending order. The test and evaluation at SRP concluded that the accuracy, safety, reliability, and ease of use made the /sup 252/Cf Shuffler a suitable instrument for routine use in an industrial, production-oriented plant.

  16. Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, M. E.; Arnold, C. W.; Becker, J. A.; Bhatia, C.; Bhike, M.; Bond, E. M.; Bredeweg, T. A.; Fallin, B.; Fowler, M. M.; Howell, C. R.; Kelley, J. H.; Krishichayan; Macri, R.; Rusev, G.; Ryan, C.; Sheets, S. A.; Stoyer, M. A.; Tonchev, A. P.; Tornow, W.; Vieira, D. J.; Wilhelmy, J. B.

    2016-01-01

    Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varying degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma

  17. Energy dependence of fission product yields from 235U, 238U and 239Pu for incident neutron energies between 0.5 and 14.8 MeV

    DOE PAGES

    Gooden, M. E.; Arnold, C. W.; Becker, J. A.; Bhatia, C.; Bhike, M.; Bond, E. M.; Bredeweg, T. A.; Fallin, B.; Fowler, M. M.; Howell, C. R.; et al

    2016-01-06

    In this study, Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varyingmore » degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual

  18. ZPR-3 Assembly 11 : A cylindrical sssembly of highly enriched uranium and depleted uranium with an average {sup 235}U enrichment of 12 atom % and a depleted uranium reflector.

    SciTech Connect

    Lell, R. M.; McKnight, R. D.; Tsiboulia, A.; Rozhikhin, Y.; National Security; Inst. of Physics and Power Engineering

    2010-09-30

    Over a period of 30 years, more than a hundred Zero Power Reactor (ZPR) critical assemblies were constructed at Argonne National Laboratory. The ZPR facilities, ZPR-3, ZPR-6, ZPR-9 and ZPPR, were all fast critical assembly facilities. The ZPR critical assemblies were constructed to support fast reactor development, but data from some of these assemblies are also well suited for nuclear data validation and to form the basis for criticality safety benchmarks. A number of the Argonne ZPR/ZPPR critical assemblies have been evaluated as ICSBEP and IRPhEP benchmarks. Of the three classes of ZPR assemblies, engineering mockups, engineering benchmarks and physics benchmarks, the last group tends to be most useful for criticality safety. Because physics benchmarks were designed to test fast reactor physics data and methods, they were as simple as possible in geometry and composition. The principal fissile species was {sup 235}U or {sup 239}Pu. Fuel enrichments ranged from 9% to 95%. Often there were only one or two main core diluent materials, such as aluminum, graphite, iron, sodium or stainless steel. The cores were reflected (and insulated from room return effects) by one or two layers of materials such as depleted uranium, lead or stainless steel. Despite their more complex nature, a small number of assemblies from the other two classes would make useful criticality safety benchmarks because they have features related to criticality safety issues, such as reflection by soil-like material. ZPR-3 Assembly 11 (ZPR-3/11) was designed as a fast reactor physics benchmark experiment with an average core {sup 235}U enrichment of approximately 12 at.% and a depleted uranium reflector. Approximately 79.7% of the total fissions in this assembly occur above 100 keV, approximately 20.3% occur below 100 keV, and essentially none below 0.625 eV - thus the classification as a 'fast' assembly. This assembly is Fast Reactor Benchmark No. 8 in the Cross Section Evaluation Working Group

  19. Applications of New Synthetic Uranium Reference Materials for Research in Geochemistry

    NASA Astrophysics Data System (ADS)

    Richter, Stephan; Alonso, Adolfo; Aregbe, Yetunde; Eykens, Roger; Jacobsson, Ulf; Kuehn, Heinz; Verbruggen, Andre; Weyer, Stefan

    2010-05-01

    For many applications in geochemistry research isotope ratio measurements play a significant role. In geochronology isotope abundances of uranium and its daughter products thorium and lead are being used to determine the age and history of various samples of geological interest. For measuring the isotopic compositions of these elements by mass spectrometry, suitable isotope reference materials are needed to validate measurement procedures and to calibrate multi-collector and ion counting detector systems. IRMM is a recognized provider for nuclear isotope reference materials to the nuclear industry and nuclear safeguards authorities, which are also being applied widely for geochemical applications. Firstly, the double spike IRMM-3636 with a 233U/236U ratio of 1:1 was prepared which allows internal mass fractionation correction for high precision 235U/238U ratio measurements. The 234U abundance of this double spike material is low enough to allow an accurate and precise correction of 234U/238U ratios, even for measurements of close to equilibrium uranium samples. The double spike IRMM-3636 is offered in 3 concentrations: 1mg/g, 0.1mg/g and 0.005mg/g. Secondly, the 236U single spike IRMM-3660 was prepared and is offered in 3 concentrations: 1mg/g, 0.1mg/g and 0.01mg/g. Thirdly, a "Quad"-isotope reference material, IRMM-3101, has been prepared which is characterized by 233U/235U/236U/238U=1/1/1/1. This material is useful for checking Faraday cup efficiencies and inter-calibration of MIC (multiple ion counting) detectors. The quad-IRM is offered in 3 concentrations: 1mg/g, 0.1mg/g and 0.01mg/g. As one example for the significant influence of synthetic reference materials for geochemical research, the IRMM-074 series of gravimetrically prepared uranium mixtures for linearity testing of secondary electron multipliers (SEMs) has been applied for the redetermination of the secular equilibrium 234U/238U value and the 234U half-life by Cheng et al (2009). Due to the use of

  20. Optimized Chemical Separation and Measurement by TE TIMS Using Carburized Filaments for Uranium Isotope Ratio Measurements Applied to Plutonium Chronometry.

    PubMed

    Sturm, Monika; Richter, Stephan; Aregbe, Yetunde; Wellum, Roger; Prohaska, Thomas

    2016-06-21

    An optimized method is described for U/Pu separation and subsequent measurement of the amount contents of uranium isotopes by total evaporation (TE) TIMS with a double filament setup combined with filament carburization for age determination of plutonium samples. The use of carburized filaments improved the signal behavior for total evaporation TIMS measurements of uranium. Elevated uranium ion formation by passive heating during rhenium signal optimization at the start of the total evaporation measurement procedure was found to be a result from byproducts of the separation procedure deposited on the filament. This was avoided using carburized filaments. Hence, loss of sample before the actual TE data acquisition was prevented, and automated measurement sequences could be accomplished. Furthermore, separation of residual plutonium in the separated uranium fraction was achieved directly on the filament by use of the carburized filaments. Although the analytical approach was originally tailored to achieve reliable results only for the (238)Pu/(234)U, (239)Pu/(235)U, and (240)Pu/(236)U chronometers, the optimization of the procedure additionally allowed the use of the (242)Pu/(238)U isotope amount ratio as a highly sensitive indicator for residual uranium present in the sample, which is not of radiogenic origin. The sample preparation method described in this article has been successfully applied for the age determination of CRM NBS 947 and other sulfate and oxide plutonium samples. PMID:27240571

  1. Optimized Chemical Separation and Measurement by TE TIMS Using Carburized Filaments for Uranium Isotope Ratio Measurements Applied to Plutonium Chronometry.

    PubMed

    Sturm, Monika; Richter, Stephan; Aregbe, Yetunde; Wellum, Roger; Prohaska, Thomas

    2016-06-21

    An optimized method is described for U/Pu separation and subsequent measurement of the amount contents of uranium isotopes by total evaporation (TE) TIMS with a double filament setup combined with filament carburization for age determination of plutonium samples. The use of carburized filaments improved the signal behavior for total evaporation TIMS measurements of uranium. Elevated uranium ion formation by passive heating during rhenium signal optimization at the start of the total evaporation measurement procedure was found to be a result from byproducts of the separation procedure deposited on the filament. This was avoided using carburized filaments. Hence, loss of sample before the actual TE data acquisition was prevented, and automated measurement sequences could be accomplished. Furthermore, separation of residual plutonium in the separated uranium fraction was achieved directly on the filament by use of the carburized filaments. Although the analytical approach was originally tailored to achieve reliable results only for the (238)Pu/(234)U, (239)Pu/(235)U, and (240)Pu/(236)U chronometers, the optimization of the procedure additionally allowed the use of the (242)Pu/(238)U isotope amount ratio as a highly sensitive indicator for residual uranium present in the sample, which is not of radiogenic origin. The sample preparation method described in this article has been successfully applied for the age determination of CRM NBS 947 and other sulfate and oxide plutonium samples.

  2. Preparation of actinide specimens for the US/UK joint experiment in the Dounreay Prototype Fast Reactor

    SciTech Connect

    Quinby, T C; Adair, H L; Kobisk, E H

    1982-05-01

    A joint research program involving the United States and the United Kingdom was initiated about four years ago for the purpose of studying the fuel behavior of higher actinides using in-core irradiation in the fast reactor at Dounreay, Scotland. Simultaneously, determination of integral cross sections of a wide variety of higher actinide isotopes (physics specimens) was proposed. Coincidental neutron flux and energy spectral measurements were to be made using vanadium encapsulated dosimetry materials in the immediate region of the fuel pellets and physics samples. The higher actinide samples chosen for the fuel study were /sup 241/Am and /sup 244/Cm in the forms of Am/sub 2/O/sub 3/, Cm/sub 2/O/sub 3/, and Am/sub 6/Cm(RE)/sub 7/O/sub 21/, where (RE) represents a mixture of lanthanides. Milligram quantities of actinide oxides of /sup 248/Cm, /sup 246/Cm, /sup 244/Cm, /sup 243/Cm, /sup 243/Am, /sup 241/Am, /sup 244/Pu, /sup 242/Pu, /sup 241/Pu, /sup 240/Pu, /sup 239/Pu, /sup 238/Pu, /sup 237/Np, /sup 238/U, /sup 236/U, /sup 235/U, /sup 234/U, /sup 233/U, /sup 232/Th, /sup 230/Th, and /sup 231/Pa were encapsulated to obtain nuclear cross section and reaction rate data for these materials.

  3. Value of burnup credit beyond actinides

    SciTech Connect

    Lancaster, D.; Fuentes, E.; Kang, Chi

    1997-12-01

    DOE has submitted a topical report to the NRC justifying burnup credit based only on actinide isotopes (U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, and Am-241). When this topical report is approved, it will allow a great deal of the commercial spent nuclear fuel to be transported in significantly higher capacity casks. A cost savings estimate for shipping fuel in 32 assembly (burnup credit) casks as opposed to 24 assembly (non-burnup credit) casks was previously presented. Since that time, more detailed calculations have been performed using the methodology presented in the Actinide-Only Burnup Credit Topical Report. Loading curves for derated casks have been generated using actinide-only burnup credit and are presented in this paper. The estimates of cost savings due to burnup credit for shipping fuel utilizing 32, 30, 28, and 24 assembly casks where only the 24 assembly cask does not burnup credit have been created and are discussed. 4 refs., 2 figs.

  4. Applications of New Synthetic Uranium Reference Materials for Geochemistry Research (Invited)

    NASA Astrophysics Data System (ADS)

    Richter, S.; Weyer, S.; Alonso, A.; Aregbe, Y.; Kuehn, H.; Eykens, R.; Verbruggen, A.; Wellum, R.

    2009-12-01

    For many applications in geochemistry research isotope ratio measurements play a significant role. In geochronology isotope abundances of uranium and its daughter products thorium and lead are being used to determine the age and history of various samples of geological interest. For measuring the isotopic compositions of these elements by mass spectrometry, suitable isotope reference materials are needed to validate measurement procedures and to calibrate multi-collector and ion counting detector systems. IRMM is a recognized provider for nuclear isotope reference materials to the nuclear industry and nuclear safeguards authorities, which are also being applied widely for geochemical applications. The preparation of several new synthetic uranium reference materials at IRMM during the recent five years has provided significant impacts on geochemical research. As an example, the IRMM-074 series of gravimetrically prepared uranium mixtures for linearity testing of secondary electron multipliers (SEMs) has been applied for the redetermination of the secular equilibrium 234U/238U value and the 234U half-life by Cheng et al (2009). Due to the use of IRMM-074, results with smaller uncertainties were obtained, which are shifted by about 0.04% compared to the commonly used values published earlier by Cheng et al. in 2000. This has a significant impact for U isotope measurements in geochemistry.. As a further example, the new double spike IRMM-3636 with a 233U/236U ratio of 1:1 and an expanded uncertainty as low as 0.016% (coverage factor k=2, 95% confidence level) was prepared gravimetrically. This double spike allows internal mass fractionation correction for high precision 235U/238U ratio measurements of close to natural samples. Using the new double spike IRMM-3636, the 235U/238U ratios for several commonly used natural U standard materials from NIST/NBL and IRMM, such as e.g. NBS960 (=NBL CRM-112a), NBS950a,b and IRMM-184, have been re-measured with improved precision

  5. Report on 238Pu(n,x) surrogate cross section measurement

    SciTech Connect

    Burke, J T; Ressler, J J; Henderson, R A; Scielzo, N D; Escher, J E; Thompson, I J; Gostic, J; Bleuel, D; Weideking, M; Bernstein, L A

    2010-03-31

    The goal of this year's effort is to measure the {sup 238}Pu(n,f) and {sup 238}Pu(n,2n) cross section from 100 keV to 20 MeV. We designed a surrogate experiment that used the reaction {sup 239}Pu(a,a{prime}x) as a surrogate for {sup 238}Pu(n,x). The experiment was conducted using the STARS/LIBERACE experimental facility located at the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory in January 2010. A description of the experiment and status of the data analysis is given. In order to obtain a reliable {sup 238}Pu(n,x) cross section we designed the experiment using the surrogate ratio technique. This technique allows one to measure a desired, unknown, cross section relative to a known cross section. In the present example, the {sup 238}Pu(n,x) cross section of interest is determined relative to the known {sup 235}U(n,x) cross section. To increase confidence in the results, and to reduce overall uncertainties, we are also determining the {sup 238}Pu(n,x) cross section relative to the known {sup 234}U(n,x) cross section. The compound nuclei of interest for this experiment were produced using inelastic alpha scattering. For example, {sup 236}U(a,a{prime}x) served as a surrogate for {sup 235}U(n,x); analogous reactions were considered for the other cross sections. Surrogate experiments determine the probabilities for the decay of the compound nuclei into the various channels of interest (fission, gamma decay) by measuring particle-fission (p-f) or particle?gamma (p?g) reaction spectra. By comparing the decay probabilities associated with the unknown cross section to that of a known cross section it is possible to obtain the ratio of these cross sections and thus determine the unknown, desired cross section.

  6. The use of secondary ion mass spectrometry in forensic analyses of ultra-small samples

    NASA Astrophysics Data System (ADS)

    Cliff, John

    2010-05-01

    less than 300 picograms of bacteria. Perhaps the most successful application of SIMS for forensic purposes to date is in the field of nuclear forensics. An example that has been used by laboratories associated with the International Atomic Energy Agency is the examination of environmental samples for enriched uranium particles indicative of clandestine weapons production activities.. The analytical challenge in these types of measurements is to search complex environmental matrices for U-bearing particles which must then be analyzed for 234U, 235U, and 236U content with high precision and accuracy. Older-generation SIMS instruments were hampered by small geometries that made resolution of significant interferences problematic. In addition, automated particle search software was proprietary and difficult to obtain. With the development of new search software, the IMS 1280 is capable of searching a sample in a matter of hours, flagging U-bearing particles for later analyses, and providing a rough 235U content. Particles of interest can be revisited for high precision analyses, and all U-isotopes can be measured simultaneously in multicollector mode, dramatically improving analysis time and internal precision. Further, the large geometry of the instrument allows complete resolution of isobaric interferences that have traditionally limited SIMS analyses of difficult samples. Examples of analyses of micron-sized standard particles indicate that estimates of 235U enrichment can be obtained with an external relative precision of 0.1% and 234U and 236U contents can be obtained with a relative precision of less than 1%. Analyses of 'real' samples show a dramatic improvement in the data quality obtained compared with small-geometry SIMS instruments making SIMS the method of choice for these high-profile samples when accurate, precise, and rapid results are required.

  7. Variation of uranium isotopic composition in soil within the JCO grounds from the 30 September 1999 criticality accident at JCO, Tokai-mura, Japan.

    PubMed

    Yamamoto, Masayoshi; Kawabata, Yoshiko; Murata, Yoshimasa; Komura, Kazuhisa

    2002-08-01

    Following the 30 September 1999 criticality accident at JCO, 29 surface and 3 core soil samples were collected inside and outside the JCO grounds to evaluate possible contamination by 235U-enriched uranium (18.8%) being handled at the time of the accident. Uranium (234U, 235U, and 238U) and thorium (228Th, 230Th, and 232Th) isotopes were determined by alpha-spectrometry and ICP-MS after radiochemical separation. Concentrations of 238U and 234U ranged from 11.3 to 63.5 and 11.6 to 360 mBq g(-1), respectively. Higher amounts of 238U and/or 234U were found in the vicinity of the uranium conversion building. The calculated 234U/235U activity ratios ranged from a 1.0 radioactive equilibrium value to an unusually high 5.7 value. Several of the soil samples showed considerably higher 235U/238U atomic ratios (1.06-4.37%) than 0.725% for natural uranium. Based on the assumption that measured U-series nuclides in soil samples taken from the JCO grounds were almost at radioactive equilibrium up to 230Th, excess uranium could be calculated for each sample. The results suggest that the excess uranium in the soils have lower 235U/238U atomic ratios (a few %) than the 18.8% enrichment of the precipitation tank uranium.

  8. High-precision measurements of uranium and thorium isotopic ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS)

    NASA Astrophysics Data System (ADS)

    Wang, Lisheng; Ma, Zhibang; Duan, Wuhui

    2015-04-01

    Isotopic compositions of U-Th and 230Th dating have been widely used in earth sciences, such as chronology, geochemistry, oceanography and hydrology. In this study, five ages of different carbonate samples were measured using 230Th dating technique with U-Th high-precision isotopic measurements by multi-collector inductively coupled plasma mass spectrometry, in Uranium-series Chronology Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences.In this study, the precision and accuracy of uranium isotopic composition were estimated by measuring the uranium ratios of NBS-CRM 112A, NBS-CRM U500 and HU-1. The mean measured ratios, 234U/238U = 52.86 (±0.04) × 10-6 and δ234U = -38.36 (±0.77) × 10-3 for NBS-CRM 112A, 234U/238U = 10.4184 (±0.0001) × 10-3, 236U/238U = 15.43 (±0.01) × 10-4 and 238U/235U = 1.00021 (±0.00002) for NBS-CRM U500, 234U/238U = 54.911 (±0.007) and δ234U = -1.04 (±0.13) × 10-3 for HU-1 (95% confidence levels). The U isotope data for standard reference materials are in excellent agreement with previous studies, further highlighting the reliability and analytical capabilities of our technique. We measured the thorium isotopic ratios of three different thorium standards by MC-ICPMS. The three standards (Th-1, Th-2 and Th-3) were mixed by HU-1 and NBS 232Th standard, with the 230Th/232Th ratios from 10-4 to 10-6. The mean measured atomic ratios, 230Th/232Th = 2.1227 (±0.0024) × 10-6, 2.7246 (±0.0026) × 10-5, and 2.8358 (±0.0007) × 10-4 for Th-1, Th-2 and Th-3 (95% confidence levels), respectively. Using this technique, the following standard samples were dated by MC-ICPMS. Sample RKM-4, collected from Babardos Kendal Hill terrace, was used during the first stage of the Uranium-Series Intercomparison Project (USIP-I). Samples 76001, RKM-5 and RKM-6 were studied during the second stage of the USIP program (USIP-II). Sample 76001 is a laminated flowstone, collected from Sumidero Terejapa, Chiapas, Mexico, and samples

  9. Identifying the sources of subsurface contamination at the Hanford Site in Washington using high-precision uranium isotopic measurements.

    PubMed

    Christensen, John N; Dresel, P Evan; Conrad, Mark E; Maher, Kate; DePaolo, Donald J

    2004-06-15

    In the mid-1990s, a groundwater plume of uranium (U) was detected in monitoring wells in the B-BX-BY Waste Management Area at the Hanford Site in Washington. This area has been used since the late 1940s to store high-level radioactive waste and other products of U fuel-rod processing. Using multiple-collector ICP source magnetic sector mass spectrometry, high-precision uranium isotopic analyses were conducted of samples of vadose zone contamination and of groundwater. The isotope ratios 236U/238U, 234U/238U, and 238U/235U are used to distinguish contaminant sources. On the basis of the isotopic data, the source of the groundwater contamination appears to be related to a 1951 overflow event at tank BX-102 that spilled high-level U waste into the vadose zone. The U isotopic variation of the groundwater plume is a result of mixing between contaminant U from this spill and natural background U. Vadose zone U contamination at tank B-110 likely predates the recorded tank leak and can be ruled out as a significant source of groundwater contamination, based on the U isotopic composition. The locus of vadose zone contamination is displaced from the initial locus of groundwater contamination, indicating that lateral migration in the vadose zone was at least 8 times greater than vertical migration. The time evolution of the groundwater plume suggests an average U migration rate of approximately 0.7-0.8 m/day showing slight retardation relative to a groundwater flow of approximately 1 m/day.

  10. Airborne Plutonium and non-natural Uranium from the Fukushima DNPP found at 120 km distance a few days after reactor hydrogen explosions.

    PubMed

    Shinonaga, Taeko; Steier, Peter; Lagos, Markus; Ohkura, Takehisa

    2014-04-01

    Plutonium (Pu) and non-natural uranium (U) originating from the Fukushima Daiichi Nuclear Power Plant (FDNPP) were identified in the atmosphere at 120 km distance from the FDNPP analyzing the ratio of number of atoms, following written as n(isotope)/n(isotope), of Pu and U. The n((240)Pu)/n((239)Pu), n((241)Pu)/n((239)Pu), n((234)U)/n((238)U), n((235)U)/n((238)U) and n((236)U)/n((238)U) in aerosol samples collected before and after the FDNPP incident were analyzed by accelerator mass spectrometry (AMS) and inductively coupled plasma mass spectrometry (ICPMS). The activity concentrations of (137)Cs and (134)Cs in the same samples were also analyzed by gamma spectrometry before the destructive analysis. Comparing the time series of analytical data on Pu and U obtained in this study with previously reported data on Pu, U, and radioactive Cs, we concluded that Pu and non-natural U from the FDNPP were transported in the atmosphere directly over a 120 km distance by aerosol and wind within a few days after the reactor hydrogen explosions. Effective dose of Pu were calculated using the data of Pu: (130 ± 21) nBq/m(3), obtained in this study. We found that the airborne Pu contributes only negligibly to the total dose at the time of the incident. However the analytical results show that the amount of Pu and non-natural U certainly increased in the environment after the incident.

  11. OSMOSE program : statistical review of oscillation measurements in the MINERVE reactor R1-UO2 configuration.

    SciTech Connect

    Stoven, G.; Klann, R.; Zhong, Z.; Nuclear Engineering Division

    2007-08-28

    The OSMOSE program is a collaboration on reactor physics experiments between the United States Department of Energy and the France Commissariat Energie Atomique. At the working level, it is a collaborative effort between the Argonne National Laboratory and the CEA Cadarache Research Center. The objective of this program is to measure very accurate integral reaction rates in representative spectra for the actinides important to future nuclear system designs, and to provide the experimental data for improving the basic nuclear data files. The main outcome of the OSMOSE measurement program will be an experimental database of reactivity-worth measurements in different neutron spectra for the heavy nuclides. This database can then be used as a benchmark to verify and validate reactor analysis codes. The OSMOSE program (Oscillation in Minerve of isotopes in Eupraxic Spectra) aims at improving neutronic predictions of advanced nuclear fuels through oscillation measurements in the MINERVE facility on samples containing the following separated actinides: {sup 232}Th, {sup 233}U, {sup 234}U, {sup 235}U, {sup 236}U, {sup 238}U, {sup 237}Np, {sup 238}Pu, {sup 239}Pu, {sup 240}Pu, {sup 241}Pu, {sup 242}Pu, {sup 241}Am, {sup 243}Am, {sup 244}Cm, and {sup 245}Cm. The first part of this report provides an overview of the experimental protocol and the typical processing of a series of experimental results which is currently performed at CEA-Cadarache. In the second part of the report, improvements to this technique are presented, as well as the program that was created to process oscillation measurement results from the MINERVE facility in the future.

  12. Determining a self-consistent set of physical constants for use in geochronology

    NASA Astrophysics Data System (ADS)

    McLean, N. M.; Condon, D. J.; Bowring, S. A.

    2012-12-01

    It is widely recognized that the accuracy of isotopic dates depends on the accuracy of decay constants, which link the relative abundance of parent and daughter isotopes to the passage of time. While precise first-principles measurements of some decay constants exist (e.g. λ238U [1]), others have been measured less precisely (e.g. λ235U [1], λɛ and λβ for 40K [2]) and have been partially (e.g. λɛ and λβ for 40K [3]) or completely (e.g. λ234U, λ230Th [4], λ187Re [5], λ176Lu [6]) calibrated against more precise decay constants utilizing systems closed with respect to both chronometers. Thus, the uncertainties of many decay constants used in modern geochronology are based upon the same underlying data and are therefore correlated. These correlations (systematic uncertainties) must be considered when comparing or combining data from multiple isotopic chronometers, and quantitative results require an estimate of this correlation. However, the relationships between dates determined with different chronometers are not limited to decay constant inter-calibration. Ar-Ar dating also requires a fluence monitor of known date, which has been estimated using U-Pb data [3]. Mineral isotope ratios for other systems are typically measured against a well-characterized tracer solution (e.g. 202Pb-205Pb-233U-235U) or standard whose isotopic composition (IC) can be traced back to first-principles isotopic and purity measurements of elemental standards (e.g. NBS 981 Pb or IRMM 3636 U). These standards can influence the calculation of dates from multiple chronometers in multiple ways: for instance, the IRMM 3636 233U-236U solution could be used to (1) calibrate multiple U-Pb tracer parameters, used to calculate 206Pb/238U dates, as well as (2) determine 238U/235U ratios of accessory minerals, used to calculate 207Pb/206Pb dates, and (3) calibrate multiple U-Th tracer parameters, used to determine U-series disequilibrium dates and λ234U and λ 230Th relative to λ 238U [4

  13. Precise determination of U isotopic compositions in low concentration carbonate samples by MC-ICP-MS.

    PubMed

    Wang, Ruo-Mei; You, Chen-Feng

    2013-03-30

    We developed a fast and simple analytical procedure for precise determination of U isotopic compositions in low concentration natural samples. The main advantage of the new method is that it requires only 12ng U and can obtain all U isotopic ratios without using spike. Five carbonate reference materials (JCp-1, RKM-4, RKM-5, GBW04412 and GBW04413) and 3 international standards with different matrices (IAPSO, IRMM-3184 and CRM-U010) were analyzed for ((234)U/(238)U) and (238)U/(235)U ratios by MC-ICPMS. Using our method, the results for these standards are in close agreement with the certified values, 1.144 ± 0.004, 0.966 ± 0.004 and 0.990 ± 0.003 for ((234)U/(238)U) and 137.72 ± 0.13, 137.64 ± 0.15 and 98.63 ± 0.04 for (238)U/(235)U, in IAPSO, IRMM-3184 and CRM-U010, respectively. The long-term reproducibility of ((234)U/(238)U) and (238)U/(235)U is 0.970 ± 0.002 and 137.56 ± 0.09; 1.144 ± 0.004 and 137.72 ± 0.13, respectively, for in-house U solution and IAPSO. The new ((234)U/(238)U) results for carbonates show much better precision than previous studies and also reflect their age variability. The obtained (238)U/(235)U ratios, representing the first measurements in these carbonate specimens, are rather constant. The method described here requires only 12 ng of U for analysis and can be completed in 5.2 min. The approach provides a fast method to measure ((234)U/(238)U) and (238)U/(235)U ratios in sample matrices commonly encountered in studies of chemical weathering, oceanography and paleoclimatology. PMID:23598194

  14. Enhanced techniques for the measurement of ultra-low level (pg and fg) actinide analysis by ICP-MS for forensic and geologic applications

    NASA Astrophysics Data System (ADS)

    Pollington, A. D.; Kinman, W.; Hanson, S. K.

    2014-12-01

    Recent advances in mass spectrometry have led to an improved ability to measure high precision isotope ratios at increasingly low analyte concentrations. Combining techniques for enhanced ionization with better counting of small ion beams, we routinely measure isotope ratios on 100's of pg uranium samples and ≤10 pg plutonium samples with relative standard deviations of 1‰ on major isotope ratios and 10‰ on minor ratios achievable. With slightly larger samples (≤1 ng total U), these precisions can be as low as 0.01‰ (10 ppm) and 1‰ respectively. These techniques can be applied to both nuclear forensics questions where only a small amount of sample is available, as well as geologic questions such as U-Pb or U-Th disequilibrium geochronology from either single small crystals, or microsampled domains from within a heterogeneous sample. The analytical setup is a Cetac Aridus II desolvating nebulizer interfaced with a ThermoScientific Neptune Plus equipped with a jet-type sample cone and x-type skimmer cone. The combination of the desolvating nebulizer with the enhanced cone setup leads to an increase in sensitivity on the order of 10x that of a standard glass spray chamber (~1000V/ppm U). The Neptune Plus is equipped with 9 Faraday cups and 5 electron multipliers (two behind RPQ energy filters for improved abundance sensitivtiy). This allows for the simultaneous collection of all isotopes of either U or Pu with a combination of Faraday cups (e.g., 235U and 238U) and electron multipliers (e.g., 234U and 236U) with other configurations also available (e.g., 235U and 238U can instead be measured on electron multipliers in small samples). As sample sizes get small, the contributions from environmental blanks, as well as interfering species, become increasing concerns. In this study, we will present data on efforts to minimize the contribution of environmental U using scaled down chemical procedures as well as the effect of polyatomic species on the precision

  15. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    DOE PAGES

    Kayzar, Theresa M.; Williams, Ross W.

    2015-09-26

    The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing.

  16. A more accurate and penetrating method to measure the enrichment and mass of UF6 storage containers using passive neutron self-interrogation

    SciTech Connect

    Menlove, Howard O; Swinhoe, Martyn T; Miller, Karen A

    2010-01-01

    This paper describes an unattended mode neutron measurement that can provide the enrichment of the uranium in UF{sub 6} cylinders. The new passive neutron measurement provides better penetration into the uranium mass than prior gamma-ray enrichment measurement methods. The Passive Neutron Enrichment Monitor (PNEM) provides a new measurement technique that uses passive neutron totals and coincidence counting together with neutron self-interrogation to measure the enrichment in the cylinders. The measurement uses the neutron rates from two detector pods. One of the pods has a bare polyethylene surface next to the cylinder and the other polyethylene surface is covered with Cd to prevent thermal neutrons from returning to the cylinder. The primary neutron source from the enriched UF{sub 6} is the alpha-particle decay from the {sub 234}U that interacts with the fluorine to produce random neutrons. The singles neutron counting rate is dominated by the {sub 234}U neutrons with a minor contribution from the induced fissions in the {sub 235}U. However, the doubles counting rate comes primarily from the induced fissions (i.e., multiplication) in the {sub 235}U in enriched uranium. The PNEM concept makes use of the passive neutrons that are initially produced from the {sub 234}U reactions that track the {sub 235}U enrichment during the enrichment process. The induced fission reactions from the thermal-neutron albedo are all from the {sub 235}U and provide a measurement of the {sub 235}U. The Cd ratio has the desirable feature that all of the thermal-neutron-induced fissions in {sub 235}U are independent of the original neutron source. Thus, the ratio is independent of the uranium age, purity, and prior reactor history.

  17. Stand Up of Uranium Capability for Swipe Analysis

    SciTech Connect

    Matthew Watrous; Anthony Appelhans; Robert Hague; Tracy Houghton; John Olson

    2013-11-01

    swipe material at nanogram (~2 x 10-9 g) levels for a typical sample, a level easily detected with ICPMS. The abundance of the isotopes ranges over 4 orders of magnitude for the naturally occurring 234U, 235U and 238U and a goal was set to be able to detect the presence of 236U at 6 orders of magnitude lower than the 238U. The 236U measurement is particularly important because the presence of 236U is a strong indicator that the uranium as been in a nuclear reactor. To demonstrate these capabilities the following sample types were used: blank swipe material, blank process reagents, swipe material spiked with a natural abundance U isotope standard, swipe material spiked with an environmental standard (Columbia River sediment), and swipes taken at various locations within the processing laboratories and the INL environment. This report summarizes the method used to extract the U from the swipe material, the ICPMS analyses that demonstrate the limit of detection (LOD) and the limit of quantification (LOQ) for the U isotopes of interest, the precision of the measured isotope ratios and the dependence of precision on the quantity of U present, and the method proposed to determine if an off-normal ratio is statistically relevant.

  18. Use of uranium isotopes as a temporal and spatial tracer of nuclear contamination in the environment.

    PubMed

    Tortorello, R; Widom, E; Renwick, W H

    2013-10-01

    The Fernald Feed Materials Production Center (FFMPC) was established in 1951 to process natural uranium (U) ore, enriched uranium (EU) and depleted uranium (DU). This study tests the utility of U isotopic ratios in sediment cores and lichens as indicators of the aerial extent, degree and timing of anthropogenic U contamination, using the FFMPC as a test case. An 80-cm-long sediment core was extracted from an impoundment located approximately 6.7 km southwest of the FFMPC. Elemental concentrations of thorium (2.7-6.2 μg g(-1)) and U (0.33-1.33 μg g(-1)) as well as major and minor U isotopes were analyzed in the core. The lack of measurable (137)Cs in the deepest sample as well as a natural (235)U/(238)U signature and no measurable (236)U, are consistent with pre-FFMPC activity. Anomalously elevated U with respect to Th concentrations occur in seven consecutive samples immediately above the base of the core (62-76 cm depth). Samples with elevated U concentrations also show variable (235)U/(238)U (0.00645-0.00748), and all contain measurable (236)U ((236)U/(238)U = 2.1 × 10(-6)-3.6 × 10(-5)). Correspondence between the known releases of U dust from the FFMPC through time and variations in sediment core U concentrations, (235)U/(238)U and (236)U/(238)U ratios provide evidence for distinct releases of both DU and EU. Furthermore, these relationships demonstrate that the sediment core serves as a robust archive of past environmental U contamination events. Samples in the upper 40 cm display natural (235)U/(238)U, but measurable (236)U/(238)U ((236)U/(238)U = 5.68 × 10(-6)-1.43 × 10(-5)), further indicating the continued presence of anthropogenic U in present-day sediment. Three local lichen samples were also analyzed, and all display either EU or DU signatures coupled with elevated (236)U/(238)U, recording airborne U contamination from the FFMPC.

  19. Concentration of natural radionuclides in raw water and packaged drinking water and the effect of water treatment.

    PubMed

    Manu, Anitha; Santhanakrishnan, V; Rajaram, S; Ravi, P M

    2014-12-01

    The raw water (RW) samples collected from natural sources are subjected to water treatment process, including reverse osmosis (RO), and are packed in bottles as packaged drinking water (PDW). Raw water (21 samples) taken from deep wells of Chennai and Secunderabad which are used in the production of PDW, were analysed for (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb activity concentrations. Activity Concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in PDW were also analysed. The mean activity concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb in RW at Chennai were 12.1, ≤1.3, 7.1, 2.6, 27.5, and 16.3 mBq/L respectively. The mean activity concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb in RW at Secunderabad were found to be 40.9, 1.7, 41.5 84.5, 100.1, and 17.0 mBq/L respectively. The mean concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in PDW at Chennai were found to be ≤1.3, ≤1.3, ≤1.3, ≤0.2, ≤1.7, 28.0 and 1.2 mBq/L at Secunderabad were found to be ≤1.3, ≤1.3, 1.7, 4.3, 5.0 and 28.1 mBq/L. The study indicated a considerable reduction in the concentration of natural radionuclides due to water treatment. The reduction ratios of RW to PDW for (234)U, (238)U, (226)Ra, (228)Ra were 97, 96, 94 and 95%. In case of (210)Pb, the PDW showed higher concentration of (210)Pb than RW. This was due to its in growth from (222)Rn which was not removed in the RO process.

  20. Concentration of natural radionuclides in raw water and packaged drinking water and the effect of water treatment.

    PubMed

    Manu, Anitha; Santhanakrishnan, V; Rajaram, S; Ravi, P M

    2014-12-01

    The raw water (RW) samples collected from natural sources are subjected to water treatment process, including reverse osmosis (RO), and are packed in bottles as packaged drinking water (PDW). Raw water (21 samples) taken from deep wells of Chennai and Secunderabad which are used in the production of PDW, were analysed for (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb activity concentrations. Activity Concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in PDW were also analysed. The mean activity concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb in RW at Chennai were 12.1, ≤1.3, 7.1, 2.6, 27.5, and 16.3 mBq/L respectively. The mean activity concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra and (210)Pb in RW at Secunderabad were found to be 40.9, 1.7, 41.5 84.5, 100.1, and 17.0 mBq/L respectively. The mean concentrations of (234)U, (235)U, (238)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in PDW at Chennai were found to be ≤1.3, ≤1.3, ≤1.3, ≤0.2, ≤1.7, 28.0 and 1.2 mBq/L at Secunderabad were found to be ≤1.3, ≤1.3, 1.7, 4.3, 5.0 and 28.1 mBq/L. The study indicated a considerable reduction in the concentration of natural radionuclides due to water treatment. The reduction ratios of RW to PDW for (234)U, (238)U, (226)Ra, (228)Ra were 97, 96, 94 and 95%. In case of (210)Pb, the PDW showed higher concentration of (210)Pb than RW. This was due to its in growth from (222)Rn which was not removed in the RO process. PMID:25223293

  1. Stream sediment sampling and analysis. Final report

    SciTech Connect

    Means, J.L.; Voris, P.V.; Headington, G.L.

    1986-04-01

    The objectives were to sample and analyze sediments from upstream and downstream locations (relative to the Goodyear Atomic plant site) of three streams for selected pollutants. The three streams sampled were the Scioto River, Big Beaver Creek, and Big Run Creek. Sediment samples were analyzed for EPA's 129 priority pollutants (Clean Water Act) as well as isotopic uranium (/sup 234/U, /sup 235/U, and /sup 238/U) and technetium-99.

  2. Verification of 235U enrichment of fresh VVER-440 fuel assemblies.

    PubMed

    Almási, I; Nguyen, C T; Zsigrai, J; Lakosi, L; Hlavathy, Z; Nagy, P; Buglyó, N

    2012-10-01

    Enrichment of uniformly and non-uniformly enriched ("profiled") fuel assemblies in a range of 1.6-4.4% was verified by gamma-ray spectrometry at a nuclear power plant (NPP). HPGe detectors and a CdZnTe (CZT) detector, the latter fitting into the central tube of the assemblies, were used for obtaining information from outer and inner fuel rods. A procedure which has minimal impact on the NPP work was developed for verifying freshly arrived assemblies under normal operational conditions, and is now in routine use.

  3. ORALLOY (93.15 235U) METAL ANNULI WITH BERYLLIUM CORE

    SciTech Connect

    John D. Bess; Leland M. Montierth; Raymond L. Reed; John T. Mihalczo

    2010-09-01

    A variety of critical experiments were constructed of enriched uranium metal during the 1960s and 1970s at the Oak Ridge Critical Experiments Facility (ORCEF) in support of criticality safety operations at the Y-12 Plant. The purposes of these experiments included the evaluation of storage, casting, and handling limits for the Y-12 Plant and providing data for verification of calculation methods and cross-sections for nuclear criticality safety applications. These included solid cylinders of various diameters, annuli of various inner and outer diameters, two and three interacting cylinders of various diameters, and graphite and polyethylene reflected cylinders and annuli. Of the hundreds of delayed critical experiments, two were performed that consisted of uranium metal annuli with a solid beryllium metal core. The outer diameter of the annuli was approximately 13 or 15 inches with an inner diameter of 7 inches. The diameter of the core was approximately 7 inches. The critical height of the configurations was approximately 5 and 4 inches, respectively. The uranium annuli consisted of multiple stacked rings with diametral thicknesses of approximately 2 inches apiece and varying heights. The 15-inch experiment was performed on June 4, 1963, and the 13-inch experiment on July 12, 1963 by J. T. Mihalczo and R. G. Taylor (Ref. 1) with accompanying logbook. Both detailed and simplified model specifications are provided in this evaluation. Both of these fast-spectra experiments were determined to represent acceptable benchmarks. The calculated eigenvalues for both the detailed and simple models are within approximately 0.6% of the benchmark values, but significantly greater than 3s from the benchmark value because the uncertainty in the benchmark is very small: <±0.0004 (1s). There is significant variability between results using different neutron cross section libraries, the greatest being a ?keff of ~0.67%. Unreflected and unmoderated experiments with the same highly enriched uranium metal parts were performed at the Oak Ridge Critical Experiments Facility in the 1960s and are evaluated in HEU MET FAST 051. Thin graphite reflected (2 inches or less) experiments also using the same highly enriched uranium metal parts are evaluated in HEU MET FAST 071. Polyethylene-reflected configurations are evaluated in HEU-MET-FAST-076. A stack of highly enriched metal discs with a thick beryllium reflector is evaluated in HEU-MET-FAST-069.

  4. ORALLOY (93.2 235U) METAL CYLINDER WITH BERYLLIUM TOP REFLECTOR

    SciTech Connect

    John D. Bess; Leland M. Montierth; Raymond Reed; John T. Mihalczo

    2010-09-01

    A variety of critical experiments were constructed of enriched uranium metal during the 1960s and 1970s at the Oak Ridge Critical Experiments Facility (ORCEF) in support of criticality safety operations at the Y-12 Plant. The purposes of these experiments included the evaluation of storage, casting, and handling limits for the Y-12 Plant and providing data for verification of calculation methods and cross-sections for nuclear criticality safety applications. These included solid cylinders of various diameters, annuli of various inner and outer diameters, two and three interacting cylinders of various diameters, and graphite and polyethylene reflected cylinders and annuli. Of the hundreds of delayed critical experiments, one experiment was comprised of a stack of approximately 7-inch-diameter metal discs. The bottom of the stack consisted of uranium with an approximate height of 4-1/8 inches. The top of the stack consisted of beryllium with an approximate height of 5-9/16 inches. This experiment was performed on August 20, 1963 by J. T. Mihalczo and R. G. Taylor (Ref. 1) with accompanying logbook. Both detailed and simplified model specifications are provided in this evaluation. This fast-spectra experiment was determined to represent an acceptable benchmark. The calculated eigenvalues for both the detailed and simple models are within approximately 0.5% of the benchmark values, but significantly greater than 3s from the benchmark value because the uncertainty in the benchmark is very small: ±0.0002 (1s). There is significant variability between results using different neutron cross section libraries, the greatest being a ?keff of ~0.65% . Unreflected and unmoderated experiments with the same highly enriched uranium metal parts were performed at the Oak Ridge Critical Experiments Facility in the 1960s and are evaluated in HEU MET FAST 051. Thin graphite reflected (2 inches or less) experiments also using the same highly enriched uranium metal parts are evaluated in HEU MET FAST 071. Polyethylene-reflected configurations are evaluated in HEU-MET-FAST-076. Highly enriched metal annuli with beryllium cores are evaluated in HEU-MET-FAST-059.

  5. 235U Holdup Measurements in Three 321-M Exhaust HEPA Banks

    SciTech Connect

    Dewberry, R

    2005-02-24

    The Analytical Development Section of Savannah River National Laboratory (SRNL) was requested by the Facilities Disposition Division to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers holdup measurements of uranium residue in three HEPA filter exhaust banks of the 321-M facility. Each of the exhaust banks has dimensions near 7' x 14' x 4' and represents a complex holdup problem. A portable HPGe detector and EG&G Dart system that contains the high voltage power supply and signal processing electronics were used to determine highly enriched uranium (HEU) holdup. A personal computer with Gamma-Vision software was used to control the Dart MCA and to provide space to store and manipulate multiple 4096-channel {gamma}-ray spectra. Some acquisitions were performed with the portable detector configured to a Canberra Inspector using NDA2000 acquisition and analysis software. Our results for each component uses a mixture of redundant point source and area source acquisitions that yielded HEU contents in the range of 2-10 grams. This report discusses the methodology, non-destructive assay (NDA) measurements, assumptions, and results of the uranium holdup in these items. This report includes use of transmission-corrected assay as well as correction for contributions from secondary area sources.

  6. Inorganic, radioisotopic and organic analysis of 241-AP-101 tank waste

    SciTech Connect

    SK Fiskum; PR Bredt; JA Campbell; LR Greenwood; OT Farmer; GJ Lumetta; GM Mong; RT Ratner; CZ Soderquist; RG Swoboda; MW Urie; JJ Wagner

    2000-06-28

    Battelle received five samples from Hanford waste tank 241-AP-101, taken at five different depths within the tank. No visible solids or organic layer were observed in the individual samples. Individual sample densities were measured, then the five samples were mixed together to provide a single composite. The composite was homogenized and representative sub-samples taken for inorganic, radioisotopic, and organic analysis. All analyses were performed on triplicate sub-samples of the composite material. The sample composite did not contain visible solids or an organic layer. A subsample held at 10 C for seven days formed no visible solids. The characterization of the 241-AP-101 composite samples included: (1) Inductively-coupled plasma spectrometry for Ag, Al, Ba, Bi, Ca, Cd, Cr, Cu, Fe, K, La, Mg, Mn, Na, Nd, Ni, P, Pb, Pd, Ru, Rh, Si, Sr, Ti, U, Zn, and Zr (Note: Although not specified in the test plan, As, B, Be, Co, Li, Mo, Sb, Se, Sn, Tl, V, W, and Y were also measured and reported for information only) (2) Radioisotopic analyses for total alpha and total beta activities, {sup 3}H, {sup 14}C, {sup 60}Co, {sup 79}Se, {sup 90}Sr, {sup 99}Tc as pertechnetate, {sup 106}Ru/Rh, {sup 125}Sb, {sup 134}Cs, {sup 137}Cs, {sup 152}Eu, {sup 154}Eu, {sup 155}Eu, {sup 238}Pu, {sup 239+240}Pu, {sup 241}Am, {sup 242}Cm, and {sup 243+244}Cm; (3) Inductively-coupled plasma mass spectrometry for {sup 237}Np, {sup 239}Pu, {sup 240}Pu, {sup 99}Tc, {sup 126}Sn, {sup 129}I, {sup 231}Pa, {sup 233}U, {sup 234}U, {sup 235}U, {sup 236}U, {sup 238}U, {sup 241}AMU, {sup 242}AMU, {sup 243}AMU, As, B, Be, Ce, Co, Cs, Eu, I, Li, Mo, Pr, Rb, Sb, Se, Ta, Te, Th, Tl, V, and W; (4) total U by kinetic phosphorescence analysis; (5) Ion chromatography for Cl, F, NO{sub 2}, NO{sub 3}, PO{sub 4}, SO{sub 4}, acetate, formate, oxalate, and citrate; (6) Density, inorganic carbon and organic carbon by two different methods, mercury, free hydroxide, ammonia, and cyanide. The 241-AP-101 composite met all

  7. Topical report on actinide-only burnup credit for PWR spent nuclear fuel packages. Revision 1

    SciTech Connect

    None, None

    1997-04-01

    A methodology for performing and applying nuclear criticality safety calculations, for PWR spent nuclear fuel (SNF) packages with actinide-only burnup credit, is described. The changes in the U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, and Am-241 concentration with burnup are used in burnup credit criticality analyses. No credit for fission product neutron absorbers is taken. The methodology consists of five major steps. (1) Validate a computer code system to calculate isotopic concentrations of SNF created during burnup in the reactor core and subsequent decay. A set of chemical assay benchmarks is presented for this purpose as well as a method for assessing the calculational bias and uncertainty, and conservative correction factors for each isotope. (2) Validate a computer code system to predict the subcritical multiplication factor, k{sub eff}, of a spent nuclear fuel package. Fifty-seven UO{sub 2}, UO{sub 2}/Gd{sub 2}O{sub 3}, and UO{sub 2}/PuO{sub 2} critical experiments have been selected to cover anticipated conditions of SNF. The method uses an upper safety limit on k{sub eff} (which can be a function of the trending parameters) such that the biased k{sub eff}, when increased for the uncertainty is less than 0.95. (3) Establish bounding conditions for the isotopic concentration and criticality calculations. Three bounding axial profiles have been established to assure the ''end effect'' is accounted for conservatively. (4) Use the validated codes and bounding conditions to generate package loading criteria (burnup credit loading curves). Burnup credit loading curves show the minimum burnup required for a given initial enrichment. The utility burnup record is compared to this requirement after the utility accounts for the uncertainty in its record. Separate curves may be generated for each assembly design, various minimum cooling times and burnable absorber histories. (5) Verify that SNF assemblies meet the package loading criteria

  8. Evaluation of the uranium double spike technique for environmental monitoring

    SciTech Connect

    Hemberger, P.H.; Rokop, D.J.; Efurd, D.W.; Roensch, F.R.; Smith, D.H.; Turner, M.L.; Barshick, C.M.; Bayne, C.K.

    1998-01-01

    Use of a uranium double spike in analysis of environmental samples showed that a {sup 235}U enrichment of 1% ({sup 235}U/{sup 238}U = 0.00732) can be distinguished from natural ({sup 235}U/{sup 238}U = 0.00725). Experiments performed jointly at Los Alamos National Laboratory (LANL) and Oak Ridge National Laboratory (ORNL) used a carefully calibrated double spike of {sup 233}U and {sup 236}U to obtain much better precision than is possible using conventional analytical techniques. A variety of different sampling media (vegetation and swipes) showed that, provided sufficient care is exercised in choice of sample type, relative standard deviations of less than {+-} 0.5% can be routinely obtained. This ability, unavailable without use of the double spike, has enormous potential significance in the detection of undeclared nuclear facilities.

  9. Modern Measurements of Uranium Decay Rates

    NASA Astrophysics Data System (ADS)

    Parsons-Moss, T.; Faye, S. A.; Williams, R. W.; Wang, T. F.; Renne, P. R.; Mundil, R.; Harrison, M.; Bandong, B. B.; Moody, K.; Knight, K. B.

    2015-12-01

    It has been widely recognized that accurate and precise decay constants (λ) are critical to geochronology as highlighted by the EARTHTIME initiative, particularly the calibration benchmarks λ235U and λ238U. [1] Alpha counting experiments in 1971[2] measured λ235U and λ238U with ~0.1% precision, but have never been independently validated. We are embarking on new direct measurements of λ235U, λ238U, λ234Th, and λ234U using independent approaches for each nuclide. For the measurement of λ235U, highly enriched 235U samples will be chemically purified and analyzed for U concentration and isotopic composition by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Thin films will be electrodeposited from these solutions and the α activity will be measured in an α-γ coincidence counting apparatus, which allows reduced uncertainty in counting efficiency while achieving adequate counting statistics. For λ238U measurement we will measure ingrowth of 234Th in chemically purified, isotopically enriched 238U solutions, by quantitatively separating the Th and allowing complete decay to 234U. All of the measurements will be done using MC-ICP-MS aiming at 0.05% precision. This approach is expected to result in values of λ238U with less than 0.1% uncertainty, if combined with improved λ234Th measements. These will be achieved using direct decay measurements with an E-∆E charged particle telescope in coincidence with a gamma detector. This system allows measurement of 234Th β-decay and simultaneous detection and identification of α particles emitted by the 234U daughter, thus observing λ234U at the same time. The high-precision λ234U obtained by the direct activity measurements can independently verify the commonly used values obtained by indirect methods.[3] An overarching goal of the project is to ensure the quality of results including metrological traceability in order to facilitate implementation across diverse disciplines. [1] T

  10. Precise and accurate measurement of U and Th isotopes via ICP-MS using a single solution

    NASA Astrophysics Data System (ADS)

    Mertz-Kraus, R.; Sharp, W. D.; Ludwig, K. R.

    2012-04-01

    , allowing the sample's 238U/235U ratio to be measured. In step 3, we monitor peak-tails at half-mass positions (229.5, 231.5, 234.5) and on mass 237 while aspirating sample solution. Tail measurement requires a distinct cup configuration to maintain 238U in the cups; however, no sample is consumed during automated cup reconfiguration. We monitor the accuracy of 234U/238U ratios using CRM 145, which gives a weighted mean atom ratio of (5.2846 ± 0.0029) - 10-5 (all errors 2σ), consistent with published and reference values. The reproducibility of 230Th/238U ratios is monitored using the Schwartzwalder Mine secular-equilibrium standard (SM). We detect no bias in 230Th/238U or 234U/238U ratios measured for SM at beam intensities ranging over a factor of four, consistent with accurate correction for IC yields. Aladdin's cave coral (AC-1) was analyzed to check our ICP-MS method (and the preceding purification by ion exchange) on a carbonate and yields a mean age of 125.43 ± 0.38 ka, in agreement with published values. We are currently applying the method to corals, speleothems, pedogenic coatings, and tufas.

  11. Improving the Sensitivity of Uranium Isotope Ratio Measurements

    NASA Astrophysics Data System (ADS)

    Friedrich, J.; Snow, J.

    2003-12-01

    Accurate and precise measurements of natural and anthropogenic 235/238 U isotope ratios are important for a range of investigations where the amount of sample is extremely restricted and/or the analyte is only present in ultra-trace quantities. Examples include biological, cosmochemical, environmental, geological, and radiological studies. We have developed and validated a novel method using our Nu Instruments Nu Plasma Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) and a 233U, 236U mixed double spike for the measurement of 235U/238U ratios. Our multi-dynamic technique employs the installed quadrupole zoom optics and fixed positioning of the ion counting detectors such that rather than the commonly used mass dispersion of 1 or 2, we utilize a mass dispersion of 1.5. Using this configuration, we can simultaneously monitor the 235U and 238U ion beams in the first cycle followed by a second cycle that simultaneously monitors the 233U and 236U beams. This innovative approach allows us to correct for the considerable, but consistent, instrumental mass fractionation and ion-counter amplification bias within each sequence. Since we were hesitant to use a U500 (235U, 238U equal atom) solution for spike calibration because of possible enriched U laboratory and instrumentation contamination, we used a U960 (terrestrial 235U/238U) solution for isotopic calibration of the spike. This standardization corrected for the small amounts of 235U and 238U in the spike solution by using a U960 standard solution. With a mean intraday 2-sigma precision of 1.5 permil and an overall 2-sigma precision of 2.25 permil using individual sample sizes of 350 pg (8.8 x10 E11 atoms), we are confident our technique will be useful for identifying U isotopic anomalies present in many sample types.

  12. Evaluating the potential of the MegaSIMS for nuclear forensics

    NASA Astrophysics Data System (ADS)

    Boehnke, P.; McKeegan, K. D.; Coath, C. D.; Hutcheon, I. D.; Steele, R. C.; Harrison, M.

    2013-12-01

    Nuclear forensics investigates the illicit movement of nuclear materials. Measurements of uranium isotopic compositions are an important key as they permit provenance tracing and determination of intended use. Traditional secondary ion mass spectrometers (SIMS) are incapable of resolving 235UH from 236U due to the high mass resolving power (MRP ~38,000) needed, significantly limiting their ability to accurately measure 236U/235U, particularly for highly enriched uranium. This limitation can significantly inhibit the ability to establish details about enrichment processes. The MegaSIMS is a unique combination of SIMS and accelerator mass spectrometry (AMS) and allows for molecular interference free measurements, while retaining the spatial resolution and ease of sample preparation common in SIMS analyses. The instrument was primarily designed to measure the oxygen isotope composition of the solar wind [1] and its capability for measuring high mass elements has not been evaluated previously. We evaluated the potential of the MegaSIMS by measuring 236U/235U without hydride interference. While preliminary results show abundance sensitivity of ~E-9 and an MRP of ~1,200 at the high mass side of 238 amu, precision is limited by the detector geometry and slow magnet switching. Future work will include developing electrostatic peak switching as well as refining the measurement precision and abundance sensitivity of the MegaSIMS for nuclear forensics. [1] McKeegan, Kallio, Heber, Jarzebinski, Mao, Coath, Kunihiro, Wiens, Nordholt, Moses Jr., Reisenfeld, Jurewicz, and Burnett, 2011. Science. 332, 1528-1532.

  13. Variations in the uranium isotopic compositions of uranium ores from different types of uranium deposits

    NASA Astrophysics Data System (ADS)

    Uvarova, Yulia A.; Kyser, T. Kurt; Geagea, Majdi Lahd; Chipley, Don

    2014-12-01

    Variations in 238U/235U and 234U/238U ratios were measured in uranium minerals from a spectrum of uranium deposit types, as well as diagenetic phosphates in uranium-rich basins and peraluminous rhyolites and associated autunite mineralisation from Macusani Meseta, Peru. Mean δ238U values of uranium minerals relative to NBL CRM 112-A are 0.02‰ for metasomatic deposits, 0.16‰ for intrusive, 0.18‰ for calcrete, 0.18‰ for volcanic, 0.29‰ for quartz-pebble conglomerate, 0.29‰ for sandstone-hosted, 0.44‰ for unconformity-type, and 0.56‰ for vein, with a total range in δ238U values from -0.30‰ to 1.52‰. Uranium mineralisation associated with igneous systems, including low-temperature calcretes that are sourced from U-rich minerals in igneous systems, have low δ238U values of ca. 0.1‰, near those of their igneous sources, whereas uranium minerals in basin-hosted deposits have higher and more variable values. High-grade unconformity-related deposits have δ238U values around 0.2‰, whereas lower grade unconformity-type deposits in the Athabasca, Kombolgie and Otish basins have higher δ238U values. The δ234U values for most samples are around 0‰, in secular equilibrium, but some samples have δ234U values much lower or higher than 0‰ associated with addition or removal of 234U during the past 2.5 Ma. These δ238U and δ234U values suggest that there are at least two different mechanisms responsible for 238U/235U and 234U/238U variations. The 234U/238U disequilibria ratios indicate recent fluid interaction with the uranium minerals and preferential migration of 234U. Fractionation between 235U and 238U is a result of nuclear-field effects with enrichment of 238U in the reduced insoluble species (mostly UO2) and 235U in oxidised mobile species as uranyl ion, UO22+, and its complexes. Therefore, isotopic fractionation effects should be reflected in 238U/235U ratios in uranium ore minerals formed either by reduction of uranium to UO2 or chemical

  14. Regenerated Uranium Separation in Matched Abundance Ratio Cascade with Additional Product Flow

    NASA Astrophysics Data System (ADS)

    Maslyukov, E. V.; Palkin, V. A.

    2016-09-01

    This paper addresses known methods used to purify regenerated uranium in single and double cascades. A new method for separating regenerated uranium has been developed that enables a significant reduction of the concentration of 232,234U in the additional product flow. Matched abundance ratio cascades (M*-cascades) with different key components and additional product flow are used in the new method. Main product flow of the M*-cascade contains low enriched regenerated uranium. It can be used for reactor fuel production. Purified product can be enriched in the ordinary cascade in compliance with the requirements of ASTM C 996-10 set for isotopes 232,234U in low enriched commercial uranium, which is usually produced from the natural one. Computer experiment based on the new method has been performed. The experiment shows that the best cascade with the maximum flow of the enriched purified product is M*-cascade with key components 232,236U.

  15. Improving Precision and Accuracy of Isotope Ratios from Short Transient Laser Ablation-Multicollector-Inductively Coupled Plasma Mass Spectrometry Signals: Application to Micrometer-Size Uranium Particles.

    PubMed

    Claverie, Fanny; Hubert, Amélie; Berail, Sylvain; Donard, Ariane; Pointurier, Fabien; Pécheyran, Christophe

    2016-04-19

    The isotope drift encountered on short transient signals measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) is related to differences in detector time responses. Faraday to Faraday and Faraday to ion counter time lags were determined and corrected using VBA data processing based on the synchronization of the isotope signals. The coefficient of determination of the linear fit between the two isotopes was selected as the best criterion to obtain accurate detector time lag. The procedure was applied to the analysis by laser ablation-MC-ICPMS of micrometer sized uranium particles (1-3.5 μm). Linear regression slope (LRS) (one isotope plotted over the other), point-by-point, and integration methods were tested to calculate the (235)U/(238)U and (234)U/(238)U ratios. Relative internal precisions of 0.86 to 1.7% and 1.2 to 2.4% were obtained for (235)U/(238)U and (234)U/(238)U, respectively, using LRS calculation, time lag, and mass bias corrections. A relative external precision of 2.1% was obtained for (235)U/(238)U ratios with good accuracy (relative difference with respect to the reference value below 1%). PMID:27031645

  16. Polyatomic interferences on high precision uranium isotope ratio measurements by MC-ICP-MS: Applications to environmental sampling for nuclear safeguards

    DOE PAGES

    Pollington, Anthony D.; Kinman, William S.; Hanson, Susan K.; Steiner, Robert E.

    2015-09-04

    Modern mass spectrometry and separation techniques have made measurement of major uranium isotope ratios a routine task; however accurate and precise measurement of the minor uranium isotopes remains a challenge as sample size decreases. One particular challenge is the presence of isobaric interferences and their impact on the accuracy of minor isotope 234U and 236U measurements. Furthermore, we present techniques used for routine U isotopic analysis of environmental nuclear safeguards samples and evaluate polyatomic interferences that negatively impact accuracy as well as methods to mitigate their impacts.

  17. Measurements of natural uranium concentration and isotopic composition with permil-level precision by inductively coupled plasma-quadrupole mass spectrometry

    NASA Astrophysics Data System (ADS)

    Shen, Chuan-Chou; Lin, Huei-Ting; Chu, Mei-Fei; Yu, Ein-Fen; Wang, Xianfeng; Dorale, Jeffrey A.

    2006-09-01

    A new analytical technique using inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) has been developed that produces permil-level precision in the measurement of uranium concentration ([U]) and isotopic composition (δ234U) in natural materials. A 233U-236U double spike method was used to correct for mass fractionation during analysis. To correct for ratio drifting, samples were bracketed by uranium standard measurements. A sensitivity of 6-7 × 108 cps/ppm was generated with a sample solution uptake rate of 30 μL/min. With a measurement time of 15-20 min, standards of 30-ng uranium produced a within-run precision better than 3‰ (±2 R.S.D.) for δ234U and better than 2‰ for [U]. Replicate measurements made on standards show that a between-run reproducibility of 3.5‰ for δ234U and 2‰ for [U] can be achieved. ICP-QMS data of δ234U and [U] in seawater, coral, and speleothem materials are consistent with the data measured by other ICP-MS and TIMS techniques. Advantages of the ICP-QMS method include low cost, easy maintenance, simple instrumental operation, and few sample preparation steps. Sample size requirements are small, such as 10-14 mg of coral material. The results demonstrate that this technique can be applied to natural samples with various matrices.

  18. Initial Report for the Aquifer Background Study: Summary of Uranium and Plutonium Data from INEEL Groundwater Samples

    SciTech Connect

    Robert C. Roback; Don L. Koeppen

    2003-06-01

    As part of the “Aquifer Background Study,” Los Alamos National Laboratory (LANL) under contract with the Idaho National Engineering and Environmental Laboratory (INEEL) has undertaken a study to determine uranium and plutonium abundances and isotopic composition in groundwater samples collected at the INEEL. To date, four samples have been analyzed for uranium and plutonium and an additional nine samples have been analyzed for uranium. It is expected that several more samples will be analyzed for this study. This report summarizes the results from this initial set of samples. Of the 13 samples analyzed for uranium, four samples have 238U/235U ratios that differ from the natural value of 137.88. These four samples and two additional samples also contain 236U at 3-sigma level above detection limits. The presence of 236U and the non-natural 238U/235U ratios unequivocally indicate the presence of anthropic uranium in four of the samples. A small component of anthropic uranium is also present in two additional samples with positive 236U detection but natural 238U/235U isotope ratios. Two of the samples with anthropic uranium, as well as two samples with no detectable anthropic uranium were analyzed for plutonium. No plutonium was detected in these four samples at detection limits of approximately 5E7 239Pu atoms for three of the samples and approximately 1E8 239Pu atoms for the forth sample. These detection limits correspond to (239+240)Pu activity ratios (assuming a 240Pu/239Pu atom ratio of 0.18) of 0.002 and 0.004 pCi/L respectively.

  19. Simultaneous {sup 233}U and{sup 235}U characterization through the assay of delayed neutron temporal behavior

    SciTech Connect

    Sellers, M. T.; Corcoran, E. C.; Kelly, D. G.

    2012-07-01

    Aqueous solutions containing dissolved uranium-233 and uranium-235 were irradiated for 60's in the SLOWPOKE-2 reactor at the Royal Military College of Canada. The temporal behavior of the delayed neutrons produced was recorded by the Facility's Delayed Neutron Counting (DNC) system. The percentage of uranium-233 as a function of total fissile mass present in each sample ranged from 0 to 100% and was predicted by the DNC system with average absolute errors of {+-} 4%. Future work will upgrade the system electronics and software to reduce both uncertainties in timings and electrical noise. Mixture analysis will also be expanded to include plutonium-239 and fissile materials contained in non-aqueous matrices. (authors)

  20. Evaluation of {sup 235}U, {sup 238}U, {sup 6}Li, and {sup 27}Al Cross Sections

    SciTech Connect

    Chandler, J.R.

    2001-05-17

    Good nuclear data are essential for accurate prediction of reactor parameters. Several cross section libraries are currently available for use with GLASS physics calculations. In recent Mark 15 and Mark 22 studies, cross section data were developed to provide more accurate buckling calculations for Mark 15 and Mark 22 charges. This report documents evaluation of these new data for universal application.

  1. The Current State of Genetics Training in Psychiatric Residency: Views of 235 U.S. Educators and Trainees

    ERIC Educational Resources Information Center

    Hoop, Jinger G.; Savla, Gauri; Roberts, Laura Weiss; Zisook, Sidney; Dunn, Laura B.

    2010-01-01

    Objective: As researchers make progress in understanding genetic aspects of mental illness and its treatment, psychiatrists will increasingly need to understand and interpret genetic information specific to psychiatric disorders. Little is known about the extent to which residency programs are preparing psychiatrists for this new role. This study…

  2. Commissioning the NIFFTE Time Projection Chamber: Towards the 238U / 235U (n, f) Cross-section Ratio

    NASA Astrophysics Data System (ADS)

    Meharchand, R.; Asner, D. M.; Baker, R. G.; Bundgaard, J.; Burgett, E.; Cunningham, M.; Deaven, J.; Duke, D. L.; Greife, U.; Grimes, S.; Heffner, M.; Hill, T.; Isenhower, D.; Klay, J. L.; Kleinrath, V.; Kornilov, N.; Laptev, A. B.; Loveland, W.; Massey, T. N.; Qu, H.; Ruz, J.; Sangiorgio, S.; Seilhan, B.; Snyder, L.; Stave, S.; Tatishvili, G.; Thornton, R. T.; Tovesson, F.; Towell, D.; Towell, R. S.; Watson, S.; Wendt, B.; Wood, L.

    2014-05-01

    The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration is developing a Time Projection Chamber (TPC) to measure neutron-induced fission cross sections with unprecedented accuracy. Modifying TPC technology for nuclear physics applications is a challenging endeavor, and frequent testing and evaluation is required to ensure that all components are behaving as expected. In-beam tests of the NIFFTE TPC at the Los Alamos Neutron Science Center (LAN-SCE) commenced in 2010. An overview of the NIFFTE TPC experiments performed at LANSCE will be presented, along with preliminary performance results.

  3. Determination of the 235U Mass and Enrichment within Small UF6 Cylinders via a Neutron Coincidence Well Counting System

    SciTech Connect

    McElroy, Robert Dennis; Croft, Dr. Stephen; Young, Brian M; Venkataraman, Ram

    2011-01-01

    The construction of three new uranium enrichment facilities in the United States has sparked renewed interest in the development and enhancement of methods to determine the enrichment and fissile mass content of UF6 cylinders. We describe the design and examine the expected performance of a UF6 bottle counter developed for the assay of Type 5A cylinders. The counter, as designed and subsequently constructed, is a tall passive neutron well counter with a clam-shell configuration and graphite end plugs operated in fast neutron mode. Factory performance against expectation is described. The relatively high detection efficiency and effectively 4 detection geometry provide a near-ideal measurement configuration, making the UF6 bottle counter a valuable tool for the evaluation of the neutron coincidence approach to UF6 cylinder assay. The impacts of non-uniform filling, voids, enrichment, and mixed enrichments are examined

  4. HEU age determination

    SciTech Connect

    Moorthy, A.R.; Kato, W.Y.

    1995-08-01

    A technique has been developed to determine the Highly Enriched Uranium (HEU) Age which is defined as the time since the HEU was produced in an enrichment process. The HEU age is determined from the ratios of relevant uranium parents and their daughters viz {sup 230}Th/{sup 234}U and {sup 231}Pa/{sup 235}U. Uranium isotopes are quantitatively measured by their characteristic gammas and their daughters by alpha spectroscopy. In some of the samples where HEU is enriched more than 99%, the only mode of HEU age determination is by the measurement of {sup 231}Pa since there is negligible quantity of {sup 230}Th due to very low atom concentrations of {sup 234}U in the sample. In this paper we have presented data and methodology of finding the age of two HEU samples.

  5. Initiation of nuclear reactions in femtosecond laser plasma

    SciTech Connect

    Golovinski, P. A.; Mikhin, E. A.

    2013-01-15

    Mechanisms of electron interaction with a nucleus via a direct electron-nucleus collision and via bremsstrahlung generated in electron scattering on a nucleus in a femtosecond laser plasma are considered. The description of this interaction is simplified substantially by using the instantaneous-impact and equivalent-photon approximations. The yields of photons, electron-positron pairs, and products of nuclear reactions initiated by a laser pulse for some nuclei are calculated. In particular, this is done for {sup 235}U, {sup 236}U, {sup 238}U, and {sup 232}Th fission in a laser field of intensity 10{sup 20} to 10{sup 22} W/cm{sup 2}.

  6. Neutron-Induced Fission Measurements at the Dance and Lsds Facilities at Lanl

    NASA Astrophysics Data System (ADS)

    Jandel, M.; Bredeweg, T. A.; Bond, E. M.; Chadwick, M. B.; Couture, A.; O'Donnell, J. M.; Fowler, M. M.; Haight, R. C.; Hayes-Sterbenz, A. C.; Rundberg, R. S.; Rusev, G. Y.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wu, C. Y.; Becker, J. A.; Alexander, C. W.; Belier, G.

    2014-09-01

    New results from neutron-induced fission measurements performed at the Detector for Advanced Neutron Capture Experiments (DANCE) and Lead Slowing Down Spectrometer (LSDS) are presented. New correlated data on promptfission γ-ray (PFG) distributions were measured using the DANCE array for resonant neutron-induced fission of 233U, 235U and 239Pu. The deduced properties of PFG emission are presented using a simple parametrization. An accurate knowledge of fission γ-ray spectra enables us to analyze the isomeric states of 236U created after neutron capture on 235U. We briefly discuss these new results. Finally, we review details and preliminary results of the challenging 237U(n,f) cross section measurement at the LSDS facility.

  7. Age of the moon: an isotopic study of uranium-thorium-lead systematics of lunar samples.

    PubMed

    Tatsumoto, M; Rosholt, J N

    1970-01-30

    Concentrations of U, Th, and Pb in Apollo 11 samples studied are low (U. 0.16 to 0.87; Th, 0.53 to 3.4; Pb, 0.29 to 1.7, in ppm) but the extremely radiogenic lead in samples allows radiometric dating. The fine dust and the breccia have a concordant age of 4.66 billion years on the basis of (207)Pb/(206)Pb, (206)Pb/(238)U, (207)Pb/(235U), and(208)Pb/(232)Th ratios. This age is comparable with the age of meteorites and with the age generally accepted for the earth. Six crystalline and vesicular samples are distinctly younger than the dust and breccia. The (238)U/(235)U ratio is the same as that in earth rocks, and (234)U is in radioactive equilibrium with parent (238)U.

  8. Age of the moon: An isotopic study of uranium-thorium-lead systematics of lunar samples

    USGS Publications Warehouse

    Tatsumoto, M.; Rosholt, J.N.

    1970-01-01

    Concentrations of U, Th, and Pb in Apollo 11 samples studied are low (U. 0.16 to 0.87; Th, 0.53 to 3.4; Pb, 0.29 to 1.7, in ppm) but the extremely radiogenic lead in samples allows radiometric dating. The fine dust and the breccia have a concordant age of 4.66 billion years on the basis of 207Pb/206Pb, 206Pb/238U, 207Pb/235U, and 208Pb/232Th ratios. This age is comparable with the age of meteorites and with the age generally accepted for the earth. Six crystalline and vesicular samples are distinctly younger than the dust and breccia. The 238U/235U ratio is the same as that in earth rocks, and 234U is in radioactive equilibrium with parent 238U.

  9. UDATE1: A computer program for the calculation of uranium-series isotopic ages

    USGS Publications Warehouse

    Rosenbauer, R.J.

    1991-01-01

    UDATE1 is a FORTRAN-77 program with an interface for an Apple Macintosh computer that calculates isotope activities from measured count rates to date geologic materials by uranium-series disequilibria. Dates on pure samples can be determined directly by the accumulation of 230Th from 234U and of 231Pa from 235U. Dates for samples contaminated by clays containing abundant natural thorium can be corrected by the program using various mixing models. Input to the program and file management are made simple and user friendly by a series of Macintosh modal dialog boxes. ?? 1991.

  10. HEU age determination

    SciTech Connect

    Moorthy, A.R.; Kato, W.Y.

    1994-12-31

    A criteria that a sample of highly enriched uranium (HEU) had come from a weapons stockpile and not newly produced in an enrichment plant is to show that the HEU had been produced a significant time in the past. The time since the HEU has produced in an enrichment plant is defined as the age of the HEU in this paper. The HEU age is determined by measuring quantitatively the daughter products {sup 230}Th and {sup 231}Pa of {sup 234}U and {sup 235}U, respectively, by first chemical separation of the thorium and protactinium and then conducting alpha spectrometry of the daughter products.

  11. Electron spin resonance (ESR) dating of hominid-bearing deposits in the Caverna delle Fate, Ligure, Italy

    NASA Astrophysics Data System (ADS)

    Falgueres, Christophe; Yokoyama, Yuji; Bibron, Roland

    1990-07-01

    Stalagmitic floors interstratified with Mousterian deposits from the Caverna delle Fate (Italy) have been dated by the electron spin resonance (ESR) method. Three samples dated fall between 60,000 and 74,000 yr and indicate the age of the Mousterian deposits. They are in good agreement with ages determined by nondestructive γ-ray spectrometry of the human remains from 231Pa/ 235U and 230Th /234U ratios, which are, respectively, 75,000 -14,000+21,000 and 82,000 -25,000+36,000 yr. These dates are consistent with the morphological characteristics of the bones as Neanderthal remains.

  12. The alpha-recoil effects of uranium in the Oklo reactor

    NASA Astrophysics Data System (ADS)

    Sheng, Z. Z.; Kuroda, P. K.

    1984-12-01

    A series of acid-leaching experiments have been carried out on a sample of uranium ore from reactor zone number 10 of the Oklo mines in Gabon. Anomalously high U-234/U-238 ratios were observed accompanied by modestly increased U-235/U-238 ratios in uranium fractions. These results, which can be interpreted as being due to the alpha-recoil effects of U-238 and Pu-239, provide a convenient way of calculating the conversion factor (the fraction of uranium atoms converted to plutonium) of the natural reactors from radiochemical data, obviating the necessity for mass-spectrometric measurements.

  13. Desert varnish: potential for age dating via uranium-series isotopes

    SciTech Connect

    Knauss, K.G.; Ku, T.L.

    1980-01-01

    Trace metals and natural radioisotopes are measured in an unusually thick and presumed ancient desert varnish from the Colorado Plateau in Utah. Uranium and thorium concentrations in the sequence: varnish-altered rind-heartrock (Shinarump formation sandstone) indicate that uranium with little accompanying thorium is derived from external sources. The varnish forms a closed system for /sup 230/Th and /sup 231/Pa with equilibrium values for both /sup 230/Th//sup 234/U and /sup 231/Pa//sup 235/U. Selective leaching of the ferromanganese oxides followed by analysis of both the leachate and silicate residue is proposed to allow age determinations.

  14. Desert varnish: potential for age dating via uranium-series isotopes

    SciTech Connect

    Knauss, K.G.; Ku, T.L.

    1980-01-01

    Trace metals and natural radioisotopes are measured in an unusually thick and presumed ancient desert varnish from the Colorado Plateau in Utah. Uranium and thorium concentrations in the sequence: varnish--altered rind--heartrock (Shinarump formation sandstone) indicate that uranium with little accompanying thorium is derived from external sources. The varnish forms a closed system for /sup 230/Th and /sup 231/Pa with equilibrium values for both /sup 230/Th//sup 234/U and /sup 231/Pa//sup 235/U. Selective leaching of the ferromanganese oxides followed by analysis of both the leachate and silicate residue is proposed to allow age determinations.

  15. Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters.

    PubMed

    Boulyga, Sergei F; Prohaska, Thomas

    2008-01-01

    This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten

  16. Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters.

    PubMed

    Boulyga, Sergei F; Prohaska, Thomas

    2008-01-01

    This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten

  17. Depth distributions of uranium-236 and cesium-137 in the Japan/East Sea; toward the potential use as a new oceanic circulation tracer

    NASA Astrophysics Data System (ADS)

    Sakaguchi, A.; Kadokura, A.; Steier, P.; Takahashi, Y.; Shizuma, K.; Yamamoto, M.

    2012-04-01

    137Cs (T1/2=30.2 y) has been spread all over the world as a fission product of atmospheric nuclear weapons tests in the 1960s. This nuclide has been used as a powerful tool for oceanography due to the well-defined origin and conservative behaviour in water . However, the number of atoms has decayed already to one thirds compared with its initial levels, and it will become more difficult to measure. In this situation, we focus on 236U (T1/2=2.342-107 y) as a candidate for a new isotopic tracer for oceanography. The detection of 236U in the environment has become possible only recently, by the development of measuring techniques with high sensitivity based on AMS. Our group showed that global fallout from bomb tests contains 236U, which might be produced as nuclear reactions of 235U(n,γ) and/or 238U(n,3n). So 236U has been therefore globally distributed in the surface environment. Thus, 236U has a similar potential as a tracer for environmental dynamics as 137Cs, especially for oceanography. In this study, a comprehensive attempt was made to measure the concentration of 236U in marine samples such as water, suspended solid and bottom sediments to clarify the environmental behaviour of this isotope. Furthermore, the discussion of the circulation of deep and bottom water in "Miniature Ocean", the Japan Sea, has been attempted. Bottom sediments (4 sites) and seawater samples (7 sites) were collected from the Japan Sea. The sediment core was cut into 1 cm segments from the surface to 5 cm in depth within a few hours after the sampling. About 20 L of seawater samples were collected from some depths in each site, and immediately after the sampling, the water was filtered with 0.45 μm pore-size membrane-filters. After the appropriate pre-treatment for each sample, uranium isotope and 137Cs were measured with AMS and Ge-detector, respectively. 236U was successfully detected for all seawater samples, and 236U/238U atom ratios in seawater were in the range of (0

  18. OSMOSE experiment representativity studies.

    SciTech Connect

    Aliberti, G.; Klann, R.; Nuclear Engineering Division

    2007-10-10

    The OSMOSE program aims at improving the neutronic predictions of advanced nuclear fuels through measurements in the MINERVE facility at the CEA-Cadarache (France) on samples containing the following separated actinides: Th-232, U-233, U-234, U-235, U-236, U-238, Np-237, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, Am-241, Am-243, Cm-244 and Cm-245. The goal of the experimental measurements is to produce a database of reactivity-worth measurements in different neutron spectra for the separated heavy nuclides. This database can then be used as a benchmark for integral reactivity-worth measurements to verify and validate reactor analysis codes and integral cross-section values for the isotopes tested. In particular, the OSMOSE experimental program will produce very accurate sample reactivity-worth measurements for a series of actinides in various spectra, from very thermalized to very fast. The objective of the analytical program is to make use of the experimental data to establish deficiencies in the basic nuclear data libraries, identify their origins, and provide guidelines for nuclear data improvements in coordination with international programs. To achieve the proposed goals, seven different neutron spectra can be created in the MINERVE facility: UO2 dissolved in water (representative of over-moderated LWR systems), UO2 matrix in water (representative of LWRs), a mixed oxide fuel matrix, two thermal spectra containing large epithermal components (representative of under-moderated reactors), a moderated fast spectrum (representative of fast reactors which have some slowing down in moderators such as lead-bismuth or sodium), and a very hard spectrum (representative of fast reactors with little moderation from reactor coolant). The different spectra are achieved by changing the experimental lattice within the MINERVE reactor. The experimental lattice is the replaceable central part of MINERVE, which establishes the spectrum at the sample location. This configuration

  19. Isotopic Systematics (U, nitrate and Sr) of the F-Area Acidic Contamination Plume at the Savannah River Site: Clues to Contaminant History and Mobility

    NASA Astrophysics Data System (ADS)

    Christensen, J. N.; Conrad, M. E.; Bill, M.; Denham, M.; Wan, J.; Rakshit, S.; Stringfellow, W. T.; Spycher, N.

    2010-12-01

    Seepage basins in the F-Area of the Savannah River Site were used from 1955 to 1989 for the disposal of low-level radioactive acidic (ave. pH ˜2.9) waste solutions from site operations involving irradiated uranium billets and other materials used in the production of radionuclides. These disposal activities resulted in a persistent acidic groundwater plume (pH as low as 3.2) beneath the F-Area including contaminants such as tritium, nitrate, 90Sr, 129I and uranium and that has impinged on surface water (Four Mile Branch) about 600 m from the basins. After cessation of disposal in 1989, the basins were capped in 1991. Since that time, remediation has consisted of a pump-and-treat system that has recently been replaced with in situ treatment using a funnel-and-gate system with injection of alkaline solutions in the gates to neutralize pH. In order to delineate the history of contamination and the current mobility and fate of contaminants in F-Area groundwater, we have undertaken a study of variations in the isotopic compositions of U (234U/238U, 235U/238U, 236U/238U), Sr (87Sr/86Sr) and nitrate (δ15N, δ18O) within the contaminant plume. This data can be used to trace U transport within the plume, evaluate chemical changes of nitrate, and potentially track plume/sediment chemical interaction and trace the migration of 90Sr. We have analyzed a suite of groundwater samples from monitoring wells, as well as pore-water samples extracted from aquifer sediment cores to map out the isotopic variation within the plume. The isotopic compositions of U from well samples and porewater samples are all consistent with the variable burn-up of depleted U. The variation in U isotopic composition requires at least three different endmembers, without any significant influence of background natural U. The δ15N and δ18O of nitrate from F-Area plume groundwater are distinct both from natural and unaltered synthetic nitrate, and likely represents fractionation due to waste volume

  20. Determination of Reportable Radionuclides for DWPF Sludge Batch 3 (Macrobatch 4)

    SciTech Connect

    Bannochie, C

    2005-05-01

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that ''The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115''. As part of the strategy to meet WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report (WQR). However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, IAEA Safeguards Reporting for HLW, requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The Defense Waste Processing Facility (DWPF) is receiving radioactive sludge slurry from High Level Waste Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the previous contents of Tank 40 (Sludge Batch 2) and the sludge that was transferred to Tank 40 from Tank 51. The blend of sludge from Tank 51 and Tank 40 defines Macrobatch 4 (also referred to as Sludge Batch 3). This report develops the list of reportable radionuclides and associated activities and determines the radionuclide activities as a function of time. The DWPF will use this list and the activities as one of the inputs for the

  1. Performance testing of the upgraded uranium isotopics multi-group analysis code MGAU

    NASA Astrophysics Data System (ADS)

    Berlizov, A. N.; Gunnink, R.; Zsigrai, J.; Nguyen, C. T.; Tryshyn, V. V.

    2007-06-01

    The paper describes recent developments of the MGAU (Multi-Group Analysis for Uranium) method, which resulted in the creation of an upgraded version 4.0 of the MGAU code. The major improvements concerned the procedure of the intrinsic efficiency calibration, particularly in the 120-205 keV region. The results of the tests carried out with the use of certified reference uranium isotopic materials SRM 969 and CRM 146 showed a significantly improved performance of the upgraded MGAU code for the accurate characterization of 235U and 234U abundances. The relative systematic biases of the abundances measured were evaluated not to exceed 1% and 3% over the concentration intervals 0.32-93.2 and 0.002-0.98 mass% for 235U and 234U, respectively. The influence of an up to 4-5 mm steel equivalent absorber and sample thickness on the measurement results was found to be much smaller than in previous versions of the code.

  2. Non-destructive determination of uranium, thorium and 40K in tobacco and their implication on radiation dose levels to the human body.

    PubMed

    Landsberger, S; Lara, R; Landsberger, S G

    2015-11-01

    The naturally occurring radionuclides of (235)U, (238)U and (232)Th and their daughter products are a potential major source of anthropogenic radiation to tobacco smokers. Often overlooked is the presence of (40)K in tobacco and its implication to radiation dose accumulation in the human body. In this study, these three radiation sources have been determined in four typical US cigarettes using neutron activation analysis (NAA). The NAA reactions of (238)U(n,γ)(239)U, (232)Th(n,γ)(233)Th and (41)K(n,γ)(42)K were used to determine (235)U, (238)U and (232)Th and (40)K, respectively. The activity of (238)U can easily be determined by epithermal NAA of the (238)U(n,γ)(239)U reaction, and the activity of (235, 234)U can easily be deduced. Using isotopic ratios, the activity due to (40)K was found by the determined concentrations of (41)K (also by epithermal neutrons) in the bulk material. Each gram of total potassium yields 30 Bq of (40)K. The annual effective dose for smokers using 20 cigarettes per day was calculate to be 14.6, 137 and 9 μSv y(-1) for (238,235,) (234)U, (232)Th and (40)K, respectively. These values are significantly lower that the dose received from (210)Po except for (232)Th.

  3. Estimation of (n,f) Cross-Sections by Measuring Reaction Probability Ratios

    SciTech Connect

    Plettner, C; Ai, H; Beausang, C W; Bernstein, L A; Ahle, L; Amro, H; Babilon, M; Burke, J T; Caggiano, J A; Casten, R F; Church, J A; Cooper, J R; Crider, B; Gurdal, G; Heinz, A; McCutchan, E A; Moody, K; Punyon, J A; Qian, J; Ressler, J J; Schiller, A; Williams, E; Younes, W

    2005-04-21

    Neutron-induced reaction cross-sections on unstable nuclei are inherently difficult to measure due to target activity and the low intensity of neutron beams. In an alternative approach, named the 'surrogate' technique, one measures the decay probability of the same compound nucleus produced using a stable beam on a stable target to estimate the neutron-induced reaction cross-section. As an extension of the surrogate method, in this paper they introduce a new technique of measuring the fission probabilities of two different compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. This method was benchmarked in this report by measuring the probability of deuteron-induced fission events in coincidence with protons, and forming the ratio P({sup 236}U(d,pf))/P({sup 238}U(d,pf)), which serves as a surrogate for the known cross-section ratio of {sup 236}U(n,f)/{sup 238}U(n,f). IN addition, the P({sup 238}U(d,d{prime}f))/P({sup 236}U(d,d{prime}f)) ratio as a surrogate for the {sup 237}U(n,f)/{sup 235}U(n,f) cross-section ratio was measured for the first time in an unprecedented range of excitation energies.

  4. Uranium beam characterization at CIRCE for background and contamination determinations.

    PubMed

    De Cesare, M; De Cesare, N; D'Onofrio, A; Fifield, L K; Gialanella, L; Terrasi, F

    2015-09-01

    The Accelerator Mass Spectrometry (AMS) is the most sensitive technique, compared either to the Inductively Coupled Plasma (ICP-MS) or Thermal Ionization (TI-MS) mass spectrometer, for the actinide (e.g. (236)U, (x)Pu isotopes) measurements. They are present in environmental samples at the ultra trace level since atmospheric tests of Nuclear Weapons (NWs) performed in the past, deliberate dumping of nuclear waste, nuclear fuel reprocessing, on a large scale, and operation of Nuclear Power Plants (NPPs), on a small scale, have led to the release of a wide range of radioactive nuclides in the environment. At the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy, an upgraded actinide AMS system, based on a 3-MV pelletron tandem accelerator, has been developed and routinely operated. At CIRCE a charge state distribution as a function of terminal voltage, the beam emittance, measured in the 20° actinides dedicated beam line, as well as the energy and position validation of the U ions were performed in order to determine the best measurement conditions. A (236)U/(238)U isotopic ratio background level of about 5×10(-12) or 3×10(-13), depending on the Time of Flight-Energy (TOF-E) configurations, as well as the spatial distribution of the (235)U, (238)U interferences ions and a (236)U contamination mass of about 0.5 fg have been determined. PMID:26103623

  5. Certification of the Uranium Isotopic Ratios in Nbl Crm 112-A, Uranium Assay Standard (Invited)

    NASA Astrophysics Data System (ADS)

    Mathew, K. J.; Mason, P.; Narayanan, U.

    2010-12-01

    Isotopic reference materials are needed to validate measurement procedures and to calibrate multi-collector ion counting detector systems. New Brunswick Laboratory (NBL) provides a suite of certified isotopic and assay standards for the US and international nuclear safeguards community. NBL Certified Reference Material (CRM) 112-A Uranium Metal Assay Standard with a consensus value of 137.88 for the 238U/235U ratio [National Bureau of Standards -- NBS, currently named National Institute for Standards and Technology, Standard Reference Material (SRM) 960 had been renamed CRM 112-A] is commonly used as a natural uranium isotopic reference material within the earth science community. We have completed the analytical work for characterizing the isotopic composition of NBL CRM 112-A Uranium Assay Standard and NBL CRM 145 (uranyl nitrate solution prepared from CRM 112-A). The 235U/238U isotopic ratios were characterized using the total evaporation (TE) and the modified total evaporation (MTE) methods. The 234U/238U isotope ratios were characterized using a conventional analysis technique and verified using the ratios measured in the MTE analytical technique. The analysis plan for the characterization work was developed such that isotopic ratios that are traceable to NBL CRM U030-A are obtained. NBL is preparing a certificate of Analysis and will issue a certificate for Uranium Assay and Isotopics. The results of the CRM 112-A certification measurements will be discussed. These results will be compared with the average values from Richter et al (2010). A comparison of the precision and accuracy of the measurement methods (TE, MTE and Conventional) employed in the certification will be presented. The uncertainties in the 235U/238U and 234U/238U ratios, calculated according to the Guide to the Expression of Uncertainty in Measurements (GUM) and the dominant contributors to the combined standard uncertainty will be discussed.

  6. Calculation of K{sub {infinity}} for homogeneous {sup 235}U metal mixtures: Will the real K{sub {infinity}} please stand up?

    SciTech Connect

    Jordan, W.C.; Petrie, L.M.; Wright, R.Q.; Parks, C.V.

    1997-06-01

    This paper very briefly analyzes a journal article about calculating k{sub {infinity}} for metals mixed with uranium 235, and compares the article results with other calculation methods. The article suggested that continuous energy cross sections gave more accurate results than groupwise cross sections. The mixtures described in the article were dry, fast systems with several unusual characteristics; however, the majority of multigroup libraries used for analysis were developed for well moderated thermal systems. The results of calculations performed using several different codes and cross sections for three uranium/metal mixtures are presented in this paper. 1 tab.

  7. Determination of (235)U, (239)Pu, (240)Pu, and (241)Am in a nuclear bomb particle using a position-sensitive α-γ coincidence technique.

    PubMed

    Peräjärvi, Kari A; Ihantola, Sakari; Pöllänen, Roy C; Toivonen, Harri I; Turunen, Jani A

    2011-02-15

    A nuclear bomb particle containing 1.6 ng of Pu was investigated nondestructively with a position-sensitive α detector and a broad-energy HPGe γ-ray detector. An event-mode data acquisition system was used to record the data. α-γ coincidence counting was shown to be well suited to nondestructive isotope ratio determination. Because of the very small background, the 51.6 keV γ rays of (239)Pu and the 45.2 keV γ rays of (240)Pu were identified, which enabled isotopic ratio calculations. In the present work, the (239)Pu/((239)Pu+(240)Pu) atom ratio was determined to be 0.950 ± 0.010. The uncertainties were much smaller than in the previous more conventional nondestructive studies on this particle. Obtained results are also in good agreement with the data from the destructive mass spectrometric studies obtained previously by other investigators.

  8. A refined model for 235U( n,f) prompt fission neutron multiplicity and spectrum calculation with validation in integral benchmarks

    NASA Astrophysics Data System (ADS)

    Tudora, Anabella; Morillon, B.; Hambsch, F.-J.; Vladuca, G.; Oberstedt, S.

    2005-06-01

    The prompt fission neutron multiplicity and spectra of the n+U235 reaction are calculated for the first time with a refined model that takes into account the entire fission fragment range with a point-by-point treatment. At higher incident neutron energies, the treatment of neutrons evaporated prior to scission is improved by the use of the ( n,xn) spectra obtained in the frame of the cross-section calculation (compound nucleus and pre-equilibrium mechanisms). The new prompt fission neutron multiplicity and spectra up to 30 MeV incident neutron energy, included in the U-235 BRC/JEFF3.1t evaluation, lead to very good K results with the fast and thermal integral benchmarks.

  9. Characterization of Nuclear Fuel using Multivariate Statistical Analysis

    SciTech Connect

    Robel, M; Robel, M; Robel, M; Kristo, M J; Kristo, M J

    2007-11-27

    Various combinations of reactor type and fuel composition have been characterized using principle components analysis (PCA) of the concentrations of 9 U and Pu isotopes in the 10 fuel as a function of burnup. The use of PCA allows the reduction of the 9-dimensional data (isotopic concentrations) into a 3-dimensional approximation, giving a visual representation of the changes in nuclear fuel composition with burnup. Real-world variation in the concentrations of {sup 234}U and {sup 236}U in the fresh (unirradiated) fuel was accounted for. The effects of reprocessing were also simulated. The results suggest that, 15 even after reprocessing, Pu isotopes can be used to determine both the type of reactor and the initial fuel composition with good discrimination. Finally, partial least squares discriminant analysis (PSLDA) was investigated as a substitute for PCA. Our results suggest that PLSDA is a better tool for this application where separation between known classes is most important.

  10. Discrimination of source reactor type by multivariate statistical analysis of uranium and plutonium isotopic concentrations in unknown irradiated nuclear fuel material.

    PubMed

    Robel, Martin; Kristo, Michael J

    2008-11-01

    The problem of identifying the provenance of unknown nuclear material in the environment by multivariate statistical analysis of its uranium and/or plutonium isotopic composition is considered. Such material can be introduced into the environment as a result of nuclear accidents, inadvertent processing losses, illegal dumping of waste, or deliberate trafficking in nuclear materials. Various combinations of reactor type and fuel composition were analyzed using Principal Components Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLSDA) of the concentrations of nine U and Pu isotopes in fuel as a function of burnup. Real-world variation in the concentrations of (234)U and (236)U in the fresh (unirradiated) fuel was incorporated. The U and Pu were also analyzed separately, with results that suggest that, even after reprocessing or environmental fractionation, Pu isotopes can be used to determine both the source reactor type and the initial fuel composition with good discrimination.

  11. Uranium from German Nuclear Power Projects of the 1940s— A Nuclear Forensic Investigation

    PubMed Central

    Mayer, Klaus; Wallenius, Maria; Lützenkirchen, Klaus; Horta, Joan; Nicholl, Adrian; Rasmussen, Gert; van Belle, Pieter; Varga, Zsolt; Buda, Razvan; Erdmann, Nicole; Kratz, Jens-Volker; Trautmann, Norbert; Fifield, L Keith; Tims, Stephen G; Fröhlich, Michaela B; Steier, Peter

    2015-01-01

    Here we present a nuclear forensic study of uranium from German nuclear projects which used different geometries of metallic uranium fuel.3b,d, 4 Through measurement of the 230Th/234U ratio, we could determine that the material had been produced in the period from 1940 to 1943. To determine the geographical origin of the uranium, the rare-earth-element content and the 87Sr/86Sr ratio were measured. The results provide evidence that the uranium was mined in the Czech Republic. Trace amounts of 236U and 239Pu were detected at the level of their natural abundance, which indicates that the uranium fuel was not exposed to any major neutron fluence. PMID:26501922

  12. Alpha particle induced gamma yields in uranium hexafluoride

    NASA Astrophysics Data System (ADS)

    Croft, Stephen; Swinhoe, Martyn T.; Miller, Karen A.

    2013-01-01

    Fluorine has a relatively large (α,n) production cross-section in the MeV range, the energy range of interest for special nuclear materials. In the uranium fuel cycle enriched UF6 in particular is a reasonably prolific source of (α,n) neutrons because along with 235U, 234U becomes enriched and it has a relatively short half-life. This enables the mass content of storage cylinders containing UF6 to be verified by neutron counting methods. In association with such measurements high resolution gamma-ray spectrometry (HRGS) measurements using a high-purity Ge detector are often undertaken to determine the 235U enrichment based off the intensity of the direct 186 keV line. The specific (α,n) neutron production, neutrons per second per gram of U, is sensitive to the relative isotopic composition, particularly the 234U concentration, and the traditional gross neutron counting approach is needed to quantitatively interpret the data. In addition to F(α,n) neutrons, α-induced reaction γ-rays are generated, notably at 110, 197, 582, 891, 1236 and 1275 keV. If one could observe 19F(α,xγ) gamma-lines in the HRGS spectra the thought was that perhaps the α-activity could be estimated directly, and in turn the 234U abundance obtained. For example, by utilizing the ratio of the detected 197-186 keV full energy peaks. However, until now there has been no readily available estimate of the expected strength of the reaction gamma-rays nor any serious consideration as to whether they might be diagnostic or not. In this work we compute the thick target yields of the chief reaction gamma-rays in UF6 using published thin target data. Comparisons are made to the neutron production rates to obtain γ/n estimates, and also to the 235U decay line at 186 keV which we take as a fiducial line. It is shown that the reaction gamma-rays are produced but are far too weak for practical safeguards purposes. Now that the underlying numerical data is readily available however, it can be used to

  13. Simultaneous determination of the quantity and isotopic ratios of uranium in individual micro-particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS).

    PubMed

    Park, Jong-Ho; Choi, Eun-Ju

    2016-11-01

    A method to determine the quantity and isotopic ratios of uranium in individual micro-particles simultaneously by isotope dilution thermal ionization mass spectrometry (ID-TIMS) has been developed. This method consists of sequential sample and spike loading, ID-TIMS for isotopic measurement, and application of a series of mathematical procedures to remove the contribution of uranium in the spike. The homogeneity of evaporation and ionization of uranium content was confirmed by the consistent ratio of n((233)U)/n((238)U) determined by TIMS measurements. Verification of the method was performed using U030 solution droplets and U030 particles. Good agreements of resulting uranium quantity, n((235)U)/n((238)U), and n((236)U)/n((238)U) with the estimated or certified values showed the validity of this newly developed method for particle analysis when simultaneous determination of the quantity and isotopic ratios of uranium is required.

  14. Multiple ion counting ICPMS double spike method for precise U isotopic analysis at ultra-trace levels

    NASA Astrophysics Data System (ADS)

    Snow, Jonathan E.; Friedrich, Jon M.

    2005-04-01

    Of the various methods for the measurement of the isotopic composition of U in solids and solutions, few offer both sensitivity and precision. In recent years, the use of ICPMS technology for this determination has become increasingly prevalent. Here we describe a method for the determination of the 235U/238U ratio in very small quantities (<=350 pg) with an accuracy of better than 3[per mille sign]. We measured several terrestrial standard materials and repeated analyses of the U960 isotopic composition standard. We used a 233U/236U double spike, with multiple ion counting on an unmodified Nu Instruments multicollector ICPMS and a non-standard detector configuration that allows an approximately 20-fold sensitivity gain over the best conventional techniques. This technique shows promise for the detection of isotopic tracers in the environment (for example anthropogenic 238U) at very extreme dilutions, or in cases where the total amount of analyte is necessarily limited.

  15. MANTRA: An Integral Reactor Physics Experiment to Infer Actinide Capture Cross-sections from Thorium to Californium with Accelerator Mass Spectrometry

    SciTech Connect

    G. Youinou; C. McGrath; G. Imel; M. Paul; R. Pardo; F. Kondev; M. Salvatores; G. Palmiotti

    2011-08-01

    The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectrometry technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm and 248Cm.

  16. AN INTEGRAL REACTOR PHYSICS EXPERIMENT TO INFER ACTINIDE CAPTURE CROSS-SECTIONS FROM THORIUM TO CALIFORNIUM WITH ACCELERATOR MASS SPECTROMETRY

    SciTech Connect

    G. Youinou; M. Salvatores; M. Paul; R. Pardo; G. Palmiotti; F. Kondev; G. Imel

    2010-04-01

    The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor (ATR) at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectroscopy (AMS) technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am and 248Cm.

  17. Simultaneous determination of the quantity and isotopic ratios of uranium in individual micro-particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS).

    PubMed

    Park, Jong-Ho; Choi, Eun-Ju

    2016-11-01

    A method to determine the quantity and isotopic ratios of uranium in individual micro-particles simultaneously by isotope dilution thermal ionization mass spectrometry (ID-TIMS) has been developed. This method consists of sequential sample and spike loading, ID-TIMS for isotopic measurement, and application of a series of mathematical procedures to remove the contribution of uranium in the spike. The homogeneity of evaporation and ionization of uranium content was confirmed by the consistent ratio of n((233)U)/n((238)U) determined by TIMS measurements. Verification of the method was performed using U030 solution droplets and U030 particles. Good agreements of resulting uranium quantity, n((235)U)/n((238)U), and n((236)U)/n((238)U) with the estimated or certified values showed the validity of this newly developed method for particle analysis when simultaneous determination of the quantity and isotopic ratios of uranium is required. PMID:27591656

  18. The Characterization of Biotic and Abiotic Media Upgradient and Downgradient of the Los Alamos Canyon Weir

    SciTech Connect

    P.R. Fresquez

    2006-01-15

    As per the Mitigation Action Plan for the Special Environmental Analysis of the actions taken in response to the Cerro Grande Fire, sediments, vegetation, and small mammals were collected directly up- and downgradient of the Los Alamos Canyon weir, a low-head sediment control structure located on the northeastern boundary of Los Alamos National Laboratory, to determine contaminant impacts, if any. All radionuclides ({sup 3}H, {sup 137}Cs, {sup 238}Pu, {sup 239,240}Pu, {sup 90}Sr, {sup 241}Am, {sup 234}U, {sup 235}U and {sup 238}U) and trace elements (Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, and Tl) in these media were low and most were below regional upper level background concentrations (mean plus three sigma). The very few constituents that were above regional background concentrations were far below screening levels (set from State and Federal standards) for the protection of the human food chain and the terrestrial environment.

  19. Certified Reference Material IAEA-446 for radionuclides in Baltic Sea seaweed.

    PubMed

    Pham, M K; Benmansour, M; Carvalho, F P; Chamizo, E; Degering, D; Engeler, C; Gascó, C; Gwynn, J P; Harms, A V; Hrnecek, E; Ibanez, F L; Ilchmann, C; Ikaheimonen, T; Kanisch, G; Kloster, M; Llaurado, M; Mauring, A; Møller, B; Morimoto, T; Nielsen, S P; Nies, H; Norrlid, L D R; Pettersson, H B L; Povinec, P P; Rieth, U; Samuelsson, C; Schikowski, J; Silobritiene, B V; Smedley, P A; Suplinska, M; Vartti, V-P; Vasileva, E; Wong, J; Zalewska, T; Zhou, W

    2014-05-01

    A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The (40)K, (137)Cs, (234)U and (239+240)Pu radionuclides were certified for this material, and information values for 12 other radionuclides ((90)Sr, (99)Tc, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (230)Th, (232)Th, (235)U, (238)U, (239)Pu and (240)Pu) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes.

  20. Certified Reference Material IAEA-446 for radionuclides in Baltic Sea seaweed.

    PubMed

    Pham, M K; Benmansour, M; Carvalho, F P; Chamizo, E; Degering, D; Engeler, C; Gascó, C; Gwynn, J P; Harms, A V; Hrnecek, E; Ibanez, F L; Ilchmann, C; Ikaheimonen, T; Kanisch, G; Kloster, M; Llaurado, M; Mauring, A; Møller, B; Morimoto, T; Nielsen, S P; Nies, H; Norrlid, L D R; Pettersson, H B L; Povinec, P P; Rieth, U; Samuelsson, C; Schikowski, J; Silobritiene, B V; Smedley, P A; Suplinska, M; Vartti, V-P; Vasileva, E; Wong, J; Zalewska, T; Zhou, W

    2014-05-01

    A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The (40)K, (137)Cs, (234)U and (239+240)Pu radionuclides were certified for this material, and information values for 12 other radionuclides ((90)Sr, (99)Tc, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (230)Th, (232)Th, (235)U, (238)U, (239)Pu and (240)Pu) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes. PMID:24291528

  1. Uranium isotopic ratio determination in urine using flow-injection ICP-MS: a tool for emergency monitoring.

    PubMed

    Godoy, Maria Luiza D P; Julião, Ligia M Q C; Godoy, José Marcus

    2009-02-01

    An inductively coupled plasma mass spectrometry-based method is presented aimed at total uranium concentration and atomic ratio determination. The method includes flow-injection uranium separation based on TRU Eichrom extraction chromatographic cartridges. The method was tested with urine interlaboratorial exercise samples and certified reference materials (NBL-CRM-U020A and NBL-CRM-U050) providing reliable results. The proposed methodology was also applied to urine samples obtained after an incident at a nuclear facility. The obtained (235)U/(238)U and (234)U/(238)U atomic ratios in the urine of an exposed worker were equal to those observed for an enriched uranium solution from the same origin.

  2. Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412).

    PubMed

    Pham, M K; van Beek, P; Carvalho, F P; Chamizo, E; Degering, D; Engeler, C; Gascó, C; Gurriaran, R; Hanley, O; Harms, A V; Herrmann, J; Hult, M; Ikeuchi, Y; Ilchmann, C; Kanisch, G; Kis-Benedek, G; Kloster, M; Laubenstein, M; Llaurado, M; Mas, J L; Nakano, M; Nielsen, S P; Osvath, I; Povinec, P P; Rieth, U; Schikowski, J; Smedley, P A; Suplinska, M; Sýkora, I; Tarjan, S; Varga, B; Vasileva, E; Zalewska, T; Zhou, W

    2016-03-01

    The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: (40)K, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (234)U, (238)U, (239)Pu, (239+240)Pu and (241)Am for IAEA-410 and (40)K, (137)Cs, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (235)U, (238)U, (239)Pu, (240)Pu and (239+240)Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training.

  3. Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412).

    PubMed

    Pham, M K; van Beek, P; Carvalho, F P; Chamizo, E; Degering, D; Engeler, C; Gascó, C; Gurriaran, R; Hanley, O; Harms, A V; Herrmann, J; Hult, M; Ikeuchi, Y; Ilchmann, C; Kanisch, G; Kis-Benedek, G; Kloster, M; Laubenstein, M; Llaurado, M; Mas, J L; Nakano, M; Nielsen, S P; Osvath, I; Povinec, P P; Rieth, U; Schikowski, J; Smedley, P A; Suplinska, M; Sýkora, I; Tarjan, S; Varga, B; Vasileva, E; Zalewska, T; Zhou, W

    2016-03-01

    The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: (40)K, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (234)U, (238)U, (239)Pu, (239+240)Pu and (241)Am for IAEA-410 and (40)K, (137)Cs, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (235)U, (238)U, (239)Pu, (240)Pu and (239+240)Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training. PMID:26631455

  4. Natural and man-made radioactivity in soils and plants around the research reactor of Inshass.

    PubMed

    Higgy, R H; Pimpl, M

    1998-12-01

    The specific radioactivities of the U-series, 232Th, 137Cs and 40K were measured in soil samples around the Inshass reactor in Cairo, using a gamma-ray spectrometer with a HpGe detector. The alpha activity of 238U, 234U and 235U was measured in the same soil samples by surface barrier detectors after radiochemical separation and the obtained results were compared with the specific activities determined by gamma-measurements. The alpha-activity of 238Pu, 239+240Pu, 241Am, 242Cm and 244Cm was measured after radiochemical separation by surface barrier detectors for both soil and plant samples. Then beta-activity of 241Pu was measured using liquid scintillation spectrometry. PMID:9776618

  5. Concentrations of Radionuclides and Trace Elements in Soils and Vegetation Around the DARHT Facility during 2004

    SciTech Connect

    P.R. Fresquez

    2004-10-01

    Samples of soil, sediment, and unwashed overstory and understory vegetation were collected at four locations around the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory (LANL). All samples were analyzed for concentrations of {sup 3}H, {sup 137}Cs, {sup 90}Sr, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, {sup 234}U, {sup 235}U, {sup 238}U, Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, and Tl. These results, which represent five years since the start of operations, were compared with baseline statistical reference level (BSRL) data established over a four-year-long preoperational period prior to DARHT operations, and to LANL and U.S. Environmental Protection Agency Screening Action Levels (SALs). Most radionuclides and trace elements in soil, sediment, and vegetation were below BSRL values and those soils/sediments that were above BSRLs were far below SALs.

  6. Protactinium-231 measurement and application to a uranium series transport model

    NASA Astrophysics Data System (ADS)

    Golian, C.; Nightingale, T.; Airey, P. L.

    1984-06-01

    Precise measurements of small deviations of 230Th/ 234U and 231Pa/ 235U contribute to the modelling of the geochemical transport of uranium series nuclides. The use of alpha-spectrometry to measure the second-order daughter product 227Th was the analytical technique chosen. It was thereby assumed that the intermediate 227Ac is immobile. Complete methematical expressions for the count rate in various regions of the spectrum have been developed. They allow calculation of the initial yield from the cumulative counts of 227Th and the interfering 223Ra. 224Ra and 212Bi for extended time periods. The resulting increase in precision is particularly useful at low levels. The approach to modelling the transport of uranium series nuclides down-gradient of deposits within the Alligator Rivers Uranium Province of the Northern Territory of Australia is outlined. Some preliminary data are presented which call into question the assumption of the immobility of the 227Ac.

  7. Production of monodisperse uranium oxide particles and their characterization by scanning electron microscopy and secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Erdmann, N.; Betti, M.; Stetzer, O.; Tamborini, G.; Kratz, J. V.; Trautmann, N.; van Geel, J.

    2000-10-01

    Secondary ion mass spectrometry (SIMS) can be confidently used to measure uranium isotopic ratios in single particles. Dense particles of known isotopic composition and size allow the precision and the accuracy of the applied procedure to be estimated. These particles can be obtained by dissolving standard reference uranium materials, nebulizing the solution in droplets of proper diameter and collecting the particles after the desolvation and calcination of the droplets. A new instrumental set up, based on a commercial vibrating orifice aerosol generator to generate monodisperse droplets of the solutions from four uranium oxide reference materials, is described. The droplets were dried and calcined in a sequence of three furnaces. The morphology of the monodisperse uranium oxide particles was studied by scanning electron microscopy. It was observed that the particles were nearly spherical and consisted of dense material. Their diameter distribution evidenced the presence of two populations mainly, the first showing a narrow distribution with a maximum centered at approximately 1 μm. The first statistical moment ratios between the two populations remained practically constant at 1.24±0.01. This demonstrated that the second population was due to the formation of one particle from two droplets of solution (theoretical double mass≡diameter ratio of 2=1.26). Secondary ion mass spectrometry was used to verify the isotopic composition of the produced particles. Typical accuracies of better than 0.4% for 235U/ 238U and a few percent for the minor isotopes have been achieved. For the determination of the 236U content, the signal at mass M=239 (due to 238UH +) was used to correct the 235UH + contribution to 236U at mass M=236, greatly improving the accuracy of the 236/238 ratio with increasing enrichment of the 235U isotope.

  8. Radionuclide Transport in Fracture-Granite Interface Zones

    SciTech Connect

    Hu, Q; Mori, A

    2007-09-12

    In situ radionuclide migration experiments, followed by excavation and sample characterization, were conducted in a water-conducting shear zone at the Grimsel Test Site (GTS) in Switzerland to study diffusion paths of radionuclides in fractured granite. In this work, we employed a micro-scale mapping technique that interfaces laser ablation sampling with inductively coupled plasma-mass spectrometry (LA/ICP-MS) to measure the fine-scale (micron-range) distribution of actinides ({sup 234}U, {sup 235}U, and {sup 237}Np) in the fracture-granite interface zones. Long-lived {sup 234}U, {sup 235}U, and {sup 237}Np were detected in flow channels, as well as in the adjacent rock matrix, using the sensitive, feature-based mapping of the LA/ICP-MS technique. The injected sorbing actinides are mainly located within the advective flowing fractures and the immediately adjacent regions. The water-conducting fracture studied in this work is bounded on one side by mylonite and the other by granitic matrix regions. These actinides did not penetrate into the mylonite side as much as the relatively higher-porosity granite matrix, most likely due to the low porosity, hydraulic conductivity, and diffusivity of the fracture wall (a thickness of about 0.4 mm separates the mylonite region from the fracture) and the mylonite region itself. Overall, the maximum penetration depth detected with this technique for the more diffusive {sup 237}Np over the field experimental time scale of about 60 days was about 10 mm in the granitic matrix, illustrating the importance of matrix diffusion in retarding radionuclide transport from the advective fractures. Laboratory tests and numerical modeling of radionuclide diffusion into granitic matrix was conducted to complement and help interpret the field results. Measured apparent diffusivity of multiple tracers in granite provided consistent predictions for radionuclide transport in the fractured granitic rock.

  9. Isotopic Evidence for Reductive Immobilization of Uranium Across a Roll-Front Mineral Deposit.

    PubMed

    Brown, Shaun T; Basu, Anirban; Christensen, John N; Reimus, Paul; Heikoop, Jeffrey; Simmons, Ardyth; Woldegabriel, Giday; Maher, Kate; Weaver, Karrie; Clay, James; DePaolo, Donald J

    2016-06-21

    We use uranium (U) isotope ratios to detect and quantify the extent of natural U reduction in groundwater across a roll front redox gradient. Our study was conducted at the Smith Ranch-Highland in situ recovery (ISR) U mine in eastern Wyoming, USA, where economic U deposits occur in the Paleocene Fort Union formation. To evaluate the fate of aqueous U in and adjacent to the ore body, we investigated the chemical composition and isotope ratios of groundwater samples from the roll-front type ore body and surrounding monitoring wells of a previously mined area. The (238)U/(235)U of groundwater varies by approximately 3‰ and is correlated with U concentrations. Fluid samples down-gradient of the ore zone are the most depleted in (238)U and have the lowest U concentrations. Activity ratios of (234)U/(238)U are ∼5.5 up-gradient of the ore zone, ∼1.0 in the ore zone, and between 2.3 and 3.7 in the down-gradient monitoring wells. High-precision measurements of (234)U/(238)U and (238)U/(235)U allow for development of a conceptual model that evaluates both the migration of U from the ore body and the extent of natural attenuation due to reduction. We find that the premining migration of U down-gradient of the delineated ore body is minimal along eight transects due to reduction in or adjacent to the ore body, whereas two other transects show little or no sign of reduction in the down-gradient region. These results suggest that characterization of U isotopic ratios at the mine planning stage, in conjunction with routine geochemical analyses, can be used to identify where more or less postmining remediation will be necessary.

  10. Isotopic Evidence for Reductive Immobilization of Uranium Across a Roll-Front Mineral Deposit.

    PubMed

    Brown, Shaun T; Basu, Anirban; Christensen, John N; Reimus, Paul; Heikoop, Jeffrey; Simmons, Ardyth; Woldegabriel, Giday; Maher, Kate; Weaver, Karrie; Clay, James; DePaolo, Donald J

    2016-06-21

    We use uranium (U) isotope ratios to detect and quantify the extent of natural U reduction in groundwater across a roll front redox gradient. Our study was conducted at the Smith Ranch-Highland in situ recovery (ISR) U mine in eastern Wyoming, USA, where economic U deposits occur in the Paleocene Fort Union formation. To evaluate the fate of aqueous U in and adjacent to the ore body, we investigated the chemical composition and isotope ratios of groundwater samples from the roll-front type ore body and surrounding monitoring wells of a previously mined area. The (238)U/(235)U of groundwater varies by approximately 3‰ and is correlated with U concentrations. Fluid samples down-gradient of the ore zone are the most depleted in (238)U and have the lowest U concentrations. Activity ratios of (234)U/(238)U are ∼5.5 up-gradient of the ore zone, ∼1.0 in the ore zone, and between 2.3 and 3.7 in the down-gradient monitoring wells. High-precision measurements of (234)U/(238)U and (238)U/(235)U allow for development of a conceptual model that evaluates both the migration of U from the ore body and the extent of natural attenuation due to reduction. We find that the premining migration of U down-gradient of the delineated ore body is minimal along eight transects due to reduction in or adjacent to the ore body, whereas two other transects show little or no sign of reduction in the down-gradient region. These results suggest that characterization of U isotopic ratios at the mine planning stage, in conjunction with routine geochemical analyses, can be used to identify where more or less postmining remediation will be necessary. PMID:27203292

  11. Isotopic evidence for reductive immobilization of uranium across a roll-front mineral deposit

    DOE PAGES

    Brown, Shaun T.; Basu, Anirban; Christensen, John N.; Reimus, Paul; Heikoop, Jeffrey; Simmons, Ardyth; Woldegabriel, Giday; Maher, Kate; Weaver, Karrie; Clay, James; et al

    2016-05-20

    We use uranium (U) isotope ratios to detect and quantify the extent of natural U reduction in groundwater across a roll front redox gradient. Our study was conducted at the Smith Ranch-Highland in situ recovery (ISR) U mine in eastern Wyoming, USA, where economic U deposits occur in the Paleocene Fort Union formation. To evaluate the fate of aqueous U in and adjacent to the ore body, we investigated the chemical composition and isotope ratios of groundwater samples from the roll-front type ore body and surrounding monitoring wells of a previously mined area. The 238U/235U of groundwater varies by approximatelymore » 3‰ and is correlated with U concentrations. Fluid samples down-gradient of the ore zone are the most depleted in 238U and have the lowest U concentrations. Activity ratios of 234U/238U are ~5.5 up-gradient of the ore zone, ~1.0 in the ore zone, and between 2.3 and 3.7 in the down-gradient monitoring wells. High-precision measurements of 234U/238U and 238U/235U allow for development of a conceptual model that evaluates both the migration of U from the ore body and the extent of natural attenuation due to reduction. We find that the premining migration of U down-gradient of the delineated ore body is minimal along eight transects due to reduction in or adjacent to the ore body, whereas two other transects show little or no sign of reduction in the down-gradient region. Lastly, these results suggest that characterization of U isotopic ratios at the mine planning stage, in conjunction with routine geochemical analyses, can be used to identify where more or less postmining remediation will be necessary.« less

  12. Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

    SciTech Connect

    Smith, Leon E.; Jordan, David V.; Orton, Christopher R.; Misner, Alex C.; Mace, Emily K.

    2010-08-01

    Pacific Northwest National Laboratory (PNNL) is developing the concept of an automated UF6 cylinder verification station that would be located at key measurement points to positively identify each cylinder, measure its mass and enrichment, store the collected data in a secure database, and maintain continuity of knowledge on measured cylinders until the arrival of International Atomic Energy Agency (IAEA) inspectors. At the center of this unattended system is a hybrid enrichment assay technique that combines the traditional enrichment-meter method (based on the 186 keV peak from 235U) with non-traditional neutron-induced high-energy gamma-ray signatures (spawned primarily by 234U alpha emissions and 19F(alpha, neutron) reactions). Previous work by PNNL provided proof-of-principle for the non-traditional signatures to support accurate, full-volume interrogation of the cylinder enrichment, thereby reducing the systematic uncertainties in enrichment assay due to UF6 heterogeneity and providing greater sensitivity to material substitution scenarios. The work described here builds on that preliminary evaluation of the non-traditional signatures, but focuses on a prototype field system utilizing NaI(Tl) and LaBr3(Ce) spectrometers, and enrichment analysis algorithms that integrate the traditional and non-traditional signatures. Results for the assay of Type-30B cylinders ranging from 0.2 to 4.95 wt% 235U, at an AREVA fuel fabrication plant in Richland, WA, are described for the following enrichment analysis methods: 1) traditional enrichment meter signature (186 keV peak) as calculated using a square-wave convolute (SWC) algorithm; 2) non-traditional high-energy gamma-ray signature that provides neutron detection without neutron detectors and 3) hybrid algorithm that merges the traditional and non-traditional signatures. Uncertainties for each method, relative to the declared enrichment for each cylinder, are calculated and compared to the uncertainties from an attended

  13. U-isotopes and (226)Ra as tracers of hydrogeochemical processes in carbonated karst aquifers from arid areas.

    PubMed

    Guerrero, José Luis; Vallejos, Ángela; Cerón, Juan Carlos; Sánchez-Martos, Francisco; Pulido-Bosch, Antonio; Bolívar, Juan Pedro

    2016-07-01

    Sierra de Gádor is a karst macrosystem with a highly complex geometry, located in southeastern Spain. In this arid environment, the main economic activities, agriculture and tourism, are supported by water resources from the Sierra de Gádor aquifer system. The aim of this work was to study the levels and behaviour of some of the most significant natural radionuclides in order to improve the knowledge of the hydrogeochemical processes involved in this groundwater system. For this study, 28 groundwater and 7 surface water samples were collected, and the activity concentrations of the natural U-isotopes ((238)U, (235)U and (234)U) and (226)Ra by alpha spectrometry were determined. The activity concentration of (238)U presented a large variation from around 1.1 to 65 mBq L(-1). Elevated groundwater U concentrations were the result of oxidising conditions that likely promoted U dissolution. The PHREEQC modelling code showed that dissolved U mainly existed as uranyl carbonate complexes. The (234)U/(238)U activity ratios were higher than unity for all samples (1.1-3.8). Additionally, these ratios were in greater disequilibrium in groundwater than surface water samples, the likely result of greater water-rock contact time. (226)Ra presented a wide range of activity concentrations, (0.8 up to about 4 × 10(2) mBq L(-1)); greatest concentrations were detected in the thermal area of Alhama. Most of the samples showed (226)Ra/(234)U activity ratios lower than unity (median = 0.3), likely the result of the greater mobility of U than Ra in the aquifer system. The natural U-isotopes concentrations were strongly correlated with dissolution of sulphate evaporites (mainly gypsum). (226)Ra had a more complex behaviour, showing a strong correlation with water salinity, which was particularly evident in locations where thermal anomalies were detected. The most saline samples showed the lowest (234)U/(238)U activity ratios, probably due to fast uniform bulk mineral dissolution

  14. In situ Th and U isotope determinations of low-U geological samples using laser ablation single-collector sector-field ICPMS

    NASA Astrophysics Data System (ADS)

    Mertz-Kraus, R.; Jochum, K. P.; Sharp, W. D.; Stoll, B.; Weis, U.; Andreae, M. O.

    2009-12-01

    In situ spatially resolved U-series dating of geological and biological silicates, phosphates and carbonates (e.g., bone, speleothem, coral, and pedogenic silica and carbonate), facilitates measurement of the rates of natural processes (e.g., precipitation, crystallization) during the past 500,000 years. We present a LA-ICPMS technique for precise and accurate determination of Th and U isotopic ratios applicable to samples with U concentrations as low as 0.4 µg/g. Previously, in situ U-series determinations have been done using multi-collector ICPMS. We use a single-collector sector-field ICPMS connected to a 213 Nd:YAG laser ablation system. Precision and accuracy were determined for different matrices, such as synthetic NIST SRM 612, diverse silicate MPI-DING and USGS reference glasses, 91500 zircon, and a travertine previously analyzed by TIMS.230Th and 234U (~0.00001 to 0.0001 µg/g), required laser tracks up to 1800 µm long, rastering over a 400 x 400 µm square and measurement times of 5 to 25 minutes. We applied corrections for background (< 0.2 cps), the tails of 232Th, 235U and 238U peaks on 230Th and 234U (0.1 to 6 cps corresponding to a proportion of 0.3 to 30 % of the measured peak for 232Th and 238U concentrations of 0.003 to 10 µg/g), instrumental mass fractionation (~1 % per atomic mass unit), and differences in element sensitivity of Th and U using the certified values of the reference glasses.230Th/238U and 234U/238U determinations varies between 1.6 and 5 % depending on the extent of peak tailing corrections. We obtained 230Th/238U = 1.65 x 10-5 and 234U/238U = 5.29 x 10-5 for BCR-2G (1.7 µg/g U, 5.9 µg/g Th) which agree within 2 % and 4 %, respectively, with TIMS values (Matthews et al., 2008). For the travertine (2.5 µg/g U, 0.003 µg/g Th) the mean values for four scans (~0.14 mg sample each) are 230Th/238U = 2.47 x 10-5 and 234U/238U = 7.49 x 10-5, within 2 % of TIMS values. Matthews K. et al. (2008), Evaluation of Solid Geologic

  15. U-isotopes and (226)Ra as tracers of hydrogeochemical processes in carbonated karst aquifers from arid areas.

    PubMed

    Guerrero, José Luis; Vallejos, Ángela; Cerón, Juan Carlos; Sánchez-Martos, Francisco; Pulido-Bosch, Antonio; Bolívar, Juan Pedro

    2016-07-01

    Sierra de Gádor is a karst macrosystem with a highly complex geometry, located in southeastern Spain. In this arid environment, the main economic activities, agriculture and tourism, are supported by water resources from the Sierra de Gádor aquifer system. The aim of this work was to study the levels and behaviour of some of the most significant natural radionuclides in order to improve the knowledge of the hydrogeochemical processes involved in this groundwater system. For this study, 28 groundwater and 7 surface water samples were collected, and the activity concentrations of the natural U-isotopes ((238)U, (235)U and (234)U) and (226)Ra by alpha spectrometry were determined. The activity concentration of (238)U presented a large variation from around 1.1 to 65 mBq L(-1). Elevated groundwater U concentrations were the result of oxidising conditions that likely promoted U dissolution. The PHREEQC modelling code showed that dissolved U mainly existed as uranyl carbonate complexes. The (234)U/(238)U activity ratios were higher than unity for all samples (1.1-3.8). Additionally, these ratios were in greater disequilibrium in groundwater than surface water samples, the likely result of greater water-rock contact time. (226)Ra presented a wide range of activity concentrations, (0.8 up to about 4 × 10(2) mBq L(-1)); greatest concentrations were detected in the thermal area of Alhama. Most of the samples showed (226)Ra/(234)U activity ratios lower than unity (median = 0.3), likely the result of the greater mobility of U than Ra in the aquifer system. The natural U-isotopes concentrations were strongly correlated with dissolution of sulphate evaporites (mainly gypsum). (226)Ra had a more complex behaviour, showing a strong correlation with water salinity, which was particularly evident in locations where thermal anomalies were detected. The most saline samples showed the lowest (234)U/(238)U activity ratios, probably due to fast uniform bulk mineral dissolution

  16. Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

    SciTech Connect

    Burke, J T; Bernstein, L A; Escher, J; Ahle, L; Church, J A; Dietrich, F S; Moody, K J; Norman, E B; Phair, L; Fallon, P; Clark, R M; Deleplanque, M A; Descovich, M; Cromaz, M; Lee, I Y; Macchiavelli, A O; McMahan, M A; Moretto, L G; Rodriguez-Vieitez, E; Stephens, F S; Ai, H; Beausang, C; Cridder, B

    2005-12-29

    The authors have deduced the cross section for {sup 237}U(n,f) over an equivalent neutron energy range from 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: {sup 238}U({alpha},{alpha}{prime}f) and {sup 236}U({alpha},{alpha}{prime}f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup 235}U(n,f). Scattered alpha particles were detected in a fully depleted segmented silicon telescope array (STARS) over an angle range of 35{sup o} to 60{sup o} with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between 106{sup o} and 131{sup o}.

  17. The production of Neptunium-236g.

    PubMed

    Jerome, S M; Ivanov, P; Larijani, C; Parker, D J; Regan, P H

    2014-12-01

    Radiochemical analysis of (237)Np is important in a number of fields, such as nuclear forensics, environmental analysis and measurements throughout the nuclear fuel cycle. However analysis is complicated by the lack of a stable isotope of neptunium. Although various tracers have been used, including (235)Np, (239)Np and even (236)Pu, none are entirely satisfactory. However, (236g)Np would be a better candidate for a neptunium yield tracer, as its long half-life means that it is useable as both a radiometric and mass spectrometric measurements. This radionuclide is notoriously difficult to prepare, and limited in scope. In this paper, we examine the options for the production of (236g)Np, based on work carried out at NPL since 2011. However, this work was primarily aimed at the production of (236)Pu, and not (236g)Np and therefore the rate of production are based on the levels of (236)Pu generated in the irradiation of (i) (238)U with protons, (ii) (235)U with deuterons, (iii) (236)U with protons and (iv) (236)U with deuterons. The derivation of a well-defined cross section is complicated by the relevant paucity of information on the variation of the (236m)Np:(236g)Np production ratio with incident particle energy. Furthermore, information on the purity of (236g)Np so produced is similarly sparse. Accordingly, the existing data is assessed and a plan for future work is presented.

  18. Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

    SciTech Connect

    Burke, J T; Bernstein, L A; Escher, J; Ahle, L; Church, J A; Dietrich, F; Moody, K J; Norman, E B; Phair, L W; Fallon, P; Clark, R; Delaplanque, M; Descovich, M; Cromaz, M; Lee, I Y; Macchiavelli, A O; McMahan, M A; Moretto, L G; Rodriguez-Vieitez, E; Stephens, F S

    2005-08-16

    The authors have deduced the {sup 237}U(n,f) cross-section over an equivalent neutron energy range of 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He{sup 2+} beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions {sup 238}U({alpha},{alpha}'f) and {sup 236}U({alpha},{alpha}'f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup 235}U(n,f). The energies of the scattered alpha particles were detected in a fully depleted segmented silicon telescope array (STARS) over an angle range of 35{sup o} to 60{sup o} with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between 106{sup o} to 131{sup o}.

  19. Dynamical approach to isotopic-distribution of fission fragments from actinide nuclei

    NASA Astrophysics Data System (ADS)

    Ishizuka, Chikako; Chiba, Satoshi; Karpov, Alexander V.; Aritomo, Yoshihiro

    2016-06-01

    Measurements of the isotope distribution of fission fragments, often denoted as the primary fission yield (pre-neutron yield) or independent fission yield (post-neutron yield) are still challenging at low excitation energies, so that it is important to investigate it within a theory. Such quantities are vital for applications as well. In this study, fragment distributions from the fission of U isotopes at low excitation energies are studied using a dynamical model. The potential energy surface is derived from the two center shell model including the shell and pairing corrections. In order to calculate the charge distribution of fission fragments, we introduce a new parameter ηZ as the charge asymmetry, in addition to three parameters describing a nuclear shape, z as the distance between two centers of mass, δ as fragment deformation, and ηA as the mass asymmetry. Using this model, we calculated the isotopic distribution of 236U for the n-induced process 235U + n → 236U at low excitation energies. As a result, we found that the current model can well reproduce isotopic fission-fragment distribution which can be compared favorably with major libraries.

  20. Uranium-series dating of actinide decay series mobility at Pena Blanca

    SciTech Connect

    Dixon, P.R.; Goldstein, S.J.; Murrell, M.T.

    1997-12-31

    Studies of U-series disequilibria near uranium ore deposits can provide valuable information on the mobility of actinides and their daughters over the range of timescales needed to assess the stability of proposed waste repositories. We have applied highly sensitive TIMS methods to obtain 238U-234U-230Th dates for three whole rock samples within a {approximately}30 in long fracture emanating into surrounding tuff from the deposit at Pena Blanca, Mexico. The 238U-234U-230Th data lie on a whole-rock isochron that requires closed-system behavior for the last 380 ka. Preliminary 231Pa-235U data for the U-rich vein also indicates closed system behavior for at least the last 100 ka. In contrast, 226Ra/230Th activity ratios range from 0.76-0.99 which indicates more recent Ra mobility within the fracture most likely due to surface water infiltration. Our results require uranium, thorium and protactinium stability despite recent radium mobility and provide important constraints on repository stability over {approximately}100 ka timescales.

  1. HEU age determination

    SciTech Connect

    Moorthy, A.R.; Kato, W.Y.

    1997-07-01

    A new technique has been developed to determine the age of highly enriched uranium (HEU) in solids. Uranium age is defined as the time since the uranium-containing material was last subjected to a process capable of separating uranium from its radioactive-decay daughters. [Most chemical processing, uranium enrichment, volatilization processes, and phase transformations (especially relevant for uranium hexafluoride) can result in separation of the uranium parent material from the decay-product daughters.] Determination of the uranium age, as defined here, may be relevant in verifying arms-control agreements involving uranium-containing nuclear weapons. The HEU age is determined from the ratios of relevant uranium daughter isotopes and their parents, viz {sup 230}Th/{sup 234}U and {sup 231}Pa/{sup 235}U. Uranium isotopes are quantitatively measured by their characteristic gamma rays and their daughters by alpha spectroscopy. In some of the samples, where HEU is enriched more than 99%, the only mode of HEU age determination is by the measurement of {sup 231}Pa since there is negligible quantity of {sup 230}Th due to very low atom concentrations of {sup 234}U in the samples. In this report the methodology and the data for determining the age of two HEU samples are presented.

  2. Isotopic and Geochemical Tracers for U(VI) Reduction and U Mobility at an in Situ Recovery U Mine.

    PubMed

    Basu, Anirban; Brown, Shaun T; Christensen, John N; DePaolo, Donald J; Reimus, Paul W; Heikoop, Jeffrey M; Woldegabriel, Giday; Simmons, Ardyth M; House, Brian M; Hartmann, Matt; Maher, Kate

    2015-05-19

    In situ recovery (ISR) uranium (U) mining mobilizes U in its oxidized hexavalent form (U(VI)) by oxidative dissolution of U from the roll-front U deposits. Postmining natural attenuation of residual U(VI) at ISR mines is a potential remediation strategy. Detection and monitoring of naturally occurring reducing subsurface environments are important for successful implementation of this remediation scheme. We used the isotopic tracers (238)U/(235)U (δ(238)U), (234)U/(238)U activity ratio, and (34)S/(32)S (δ(34)S), and geochemical measurements of U ore and groundwater collected from 32 wells located within, upgradient, and downgradient of a roll-front U deposit to detect U(VI) reduction and U mobility at an ISR mining site at Rosita, TX, USA. The δ(238)U in Rosita groundwater varies from +0.61‰ to -2.49‰, with a trend toward lower δ(238)U in downgradient wells. The concurrent decrease in U(VI) concentration and δ(238)U with an ε of 0.48‰ ± 0.08‰ is indicative of naturally occurring reducing environments conducive to U(VI) reduction. Additionally, characteristic (234)U/(238)U activity ratio and δ(34)S values may also be used to trace the mobility of the ore zone groundwater after mining has ended. These results support the use of U isotope-based detection of natural attenuation of U(VI) at Rosita and other similar ISR mining sites.

  3. Development of the NIST bone ash standard reference material for environmental radioactivity measurement.

    PubMed

    Lin, Z; Inn, K G; Altzitzoglou, T; Arnold, D; Cavadore, D; Ham, G J; Korun, M; Wershofen, H; Takata, Y; Young, A

    1998-01-01

    The bone ash standard reference material (SRM), a blend of 4% contaminated human bone and 96% diluent bovine bone, has been developed for radiochemical method validation and quality control for radio-bone analysis. The massic activities of 90Sr, 226Ra, 230Th, 232Th, 234U, 235U, 238U, 238Pu, (239 + 240)Pu and (243 + 244)Cm were certified using a variety of radiochemical procedures and detection methods. Measurements confirmed undetectable radionuclide heterogeneity down to a sample size of 5 g. thereby implying adequate blending of particulate materials with dilution factors of up to 17,900. The results among most of the intercomparison laboratories and their methods were consistent. Disequilibrium was observed for decay chains: 234U(0.67 mBq/g)-230Th(0.47 mBq/g)-226Ra(15.1 mBq/g)-210Pb(23 mBq/g)-210Po(13 mBq/g) and 232Th(0.99 mBq/g)-228 Ra(6.1 mBq/g)-228Th(7.1 mBq/g). The disequilibria were the results of mixing occupationally contaminated human bone with natural bovine bone and the fractionation during internal biological processes. The massic activity of 210Pb, 228Th and 241Am were not certified because of insufficient 228Ra and 241Pu data and lack of knowledge in how 222Rn and its daughters will be fractionated in the SRM bottle over time.

  4. Radiological impacts of natural radioactivity in Abu-Tartor phosphate deposits, Egypt.

    PubMed

    Khater, A E; Higgy, R H; Pimpl, M

    2001-01-01

    Phosphate and environmental samples were collected from Abu Tartor phosphate mine and the surrounding region. The activity concentration of 226Ra (238U) series, 232Th series and 40K were measured using a gamma-ray spectrometer. The activities of uranium isotopes (238U, 235U and 234U) and 210Pb were measured using an alpha spectrometer and a low-background proportional gas counting system, respectively, after radiochemical separation. The results are discussed and compared with the levels in phosphate rocks from different countries. It seems that the Abu Tartor phosphate deposit has the lowest radioactivity level of exploited phosphate of sedimentary origin. 226Ra/238U, 210Pb/226Ra, 234U/238U and 226Ra/228Ra activity ratios were calculated and are discussed. The radioactivity levels in the surrounding region and the calculated exposure dose (nGy/h) will be considered as a pre-operational baseline to estimate the possible radiological impacts due to mining, processing and future phosphate industrial activities. To minimize these impacts, the processing wastes should be recycled to the greatest possible extent.

  5. Uranium Isotope Fractionation During Coprecipitation with Aragonite and Calcite

    NASA Astrophysics Data System (ADS)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2014-12-01

    Natural variations in the 238U/235U ratio of marine carbonates may provide a useful way of constraining past variations in ocean redox conditions. However, before applying this novel redox proxy, it is essential to explore possible isotopic fractionation during U coprecipitation with aragonite and calcite. We investigated these effects in laboratory experiments. Aragonite and calcite coprecipitation experiments were conducted at pH 8.5±0.1 using a constant addition method [1]. More than 90% of the U was incorporated into the solid phase at the end of each experiment. Samples were purified using UTEVA chemistry and δ238/235U was measured using 233U-236U double-spike MC-ICP-MS with a precision of ±0.10‰ [2]. The aragonite experiment demonstrated a 238U/235U Rayleigh fractionation factor of α=1.00008±0.00002 with the 238U preferentially incorporated. In contrast, the calcite experiment demonstrated no resolvable U isotope fractionation (α=1.00001±0.00003). To determine if U isotopes are affected during the early diagenetic conversion of aragonite to calcite, natural carbonate samples were collected along an aragonite-calcite transition across a single coral head in the Key Largo limestone, and characterized for U concentration and δ238/235U [3]. We found that the mean δ238/235U in aragonite (-0.33±0.07‰ 2se) was slightly heavier than that in calcite (-0.37±0.02‰ 2se). Further work is needed to address the mechanisms leading to differential isotopic fractionation of U(VI) during incorporation into aragonite and calcite. Possible drivers include differences in coordination in the crystal structure or equilibrium isotopic fractionation between various aqueous U(VI) species prior to incorporation. [1] Reeder et al. (2001) GCA 65, 3491-3503. [2] Weyer et al., (2008) GCA 72, 345-359. [3] Gill et al., (2008) GCA 72, 4699-4722.

  6. Uranium Isotopes in Calcium Carbonate: A Possible Proxy for Paleo-pH and Carbonate Ion Concentration?

    NASA Astrophysics Data System (ADS)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2015-12-01

    Natural variations of 238U/235U in marine carbonates are being explored as a paleoredox proxy. However, in order for this proxy to be robust, it is important to understand how pH and alkalinity affect the fractionation of 238U/235U during coprecipitation with calcite and aragonite. Recent work suggests that the U/Ca ratio of foraminiferal calcite may vary with seawater [CO32-] concentration due to changes in U speciation[1]. Here we explore analogous isotopic consequences in inorganic laboratory co-precipitation experiments. Uranium coprecipitation experiments with calcite and aragonite were performed at pH 8.5 ± 0.1 and 7.5 ± 0.1 using a constant addition method [2]. Dissolved U in the remaining solution was periodically collected throughout the experiments. Samples were purified with UTEVA resin and 238U/235U was determined using a 233U-236U double-spike and MC-ICP-MS, attaining a precision of ± 0.10 ‰ [3]. Small but resolvable U isotope fractionation was observed in aragonite experiments at pH ~8.5, preferentially enriching heavier U isotopes in the solid phase. 238U/235U of the dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00002 - 1.00009. In contrast, no resolvable U isotope fractionation was detected in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among dissolved U species is the most likely mechanism driving these isotope effects. Our quantitative model of this process assumes that charged U species are preferentially incorporated into CaCO3 relative to the neutral U species Ca2UO2(CO3)3(aq), which we hypothesize to have a lighter equilibrium U isotope composition than the charged U species. According to this model, the magnitude of U isotope fractionation should scale with the fraction of the neutral U species in the solution, in agreement with our experimental results. These findings suggest that U isotope variations in

  7. General Constraints on Cross Sections Deduced from Surrogate Reactions

    SciTech Connect

    Younes, W

    2003-08-14

    Cross sections that cannot be measured in the laboratory, e.g. because the target lifetime is too short, can be inferred indirectly from a different reaction forming the same compound system, but with a more accessible beam/target combination (the ''surrogate-reaction'' technique). The reactions share the same compound system and a common decay mechanism, but they involve different formation processes. Therefore, an implicit constraint is imposed on the inferred cross section deduced from the measured surrogate-reaction data, through the common decay mechanism. In this paper, the mathematical consequences of this implicit constraint are investigated. General formulas are derived from upper and lower bounds on the inferred cross section, estimated from surrogate data in a procedure which does not require any modeling of the common decay process. As an example, the formulas developed here are applied to the case of the {sup 235}U(n,f) cross section, deduced from {sup 234}U(t,pf) surrogate data. The calculated bounds are not very tight in this particular case. However, by introducing a few qualitative assumptions about the physics of the fission process, meaningful bounds on the deduced cross section are obtained. Upper and lower limits for the cross-section ratio of the (n,f) reaction on the {sup 235}U isomer at E{sub x} = 77 eV relative to the (n,f) reaction on the ground state are also calculated. The generalization of this technique to other surrogate reactions is discussed.

  8. Isotopic determination of uranium in Picomole and Subpicomole quantities

    SciTech Connect

    Chen, J.H.; Wasserburg, G.J.

    1981-11-01

    A procedure for the separation of U and measurement of U isotopes in meteoritic, lunar, and terrestrial samples is described. Accurate /sup 238/U//sup 235/U ratios and U concentration measurements can be done on a routine basis at the level of approx. 10/sup -13/ mol of U by isotope dilution using a double tracer composed of /sup 233/U and /sup 236/U. Precise determination of the number of U atoms in a sample can be done at the level of 10/sup 8/-10/sup 9/ atoms. The technique involves careful control of the chemical procedures to eliminate laboratory contamination and precise calibration of the mass spectrometer in order to obtain high reproducibility. The /sup 238/U//sup 235/U ratios were measured on a wide variety of samples which include: (1) bulk meteorites; (2) lunar samples; (3) coarse-grained Ca-Al-Ti-rich inclusions; and (4) fine-grained Al-Mg-Na-rich inclusions from the Allende meteorite; and (5) phosphates from three meteorites. The results show the same isotopic values within limits of errors as that measured on normal terrestrial U to within 4%. All of the analyzed meteorite samples are very ancient and several of them show large fractionations of U relative to Th and Nd. These data imply that /sup 247/Cm was not abundant in the early solar system (/sup 247/Cm//sup 235/U much less than 4 x 10/sup -3/) and that the last major r process terminated at approx. 10/sup 8/ years prior to the formation of the solar system.

  9. U-Pb ages of uraniferous opals and implications for the history of beryllium, fluorine, and uranium mineralization at Spor Mountain, Utah

    USGS Publications Warehouse

    Ludwig, K. R.; Lindsey, D.A.; Zielinski, R.A.; Simmons, K.R.

    1980-01-01

    The U-Pb isotope systematics of uraniferous opals from Spor Mountain, Utah, were investigated to determine the suitability of such material for geochronologic purposes, and to estimate the timing of uranium and associated beryllium and fluorine mineralization. The results indicate that uraniferous opals can approximate a closed system for uranium and uranium daughters, so that dating samples as young as ???1 m.y. should be possible. In addition, the expected lack of initial 230Th and 231Pa in opals permits valuable information on the initial 234U/238U to be obtained on suitable samples of ???10 m.y. age. The oldest 207Pb/235U apparent age observed, 20.8 ?? 1 m.y., was that of the opal-fluorite core of a nodule from a beryllium deposit in the Spor Mountain Formation. This age is indistinguishable from that of fission-track and K-Ar ages from the host rhyolite, and links the mineralization to the first episode of alkali rhyolite magmatism and related hydrothermal activity at Spor Mountain. Successively younger ages of 13 m.y. and 8-9 m.y. on concentric outer zones of the same nodule indicate that opal formed either episodically or continuously for over 10 m.y. Several samples of both fracture-filling and massive-nodule opal associated with beryllium deposits gave 207Pb/235U apparent ages of 13-16 m.y., which may reflect a restricted period of mineralization or perhaps an averaging of 21- and <13-m.y. periods of opal growth. Several samples of fracture-filling opal in volcanic rocks as young as 6 m.y. gave 207Pb/235U ages of 3.4-4.8 m.y. These ages may reflect hot-spring activity after the last major eruption of alkali rhyolite. ?? 1980.

  10. Measurements of (234)U and (238)U in hair, urine, and drinking water among drilled bedrock well water users for the evaluation of hair as a biomonitor of uranium intake.

    PubMed

    Israelsson, Axel; Pettersson, Håkan

    2014-08-01

    Hair is evaluated and compared with urine as a biomonitor for human intake of uranium. Concentrations of U and U and the activity ratio between them are measured in the hair, urine, and drinking water of 24 drilled bedrock well water users in Östergötland, Sweden. The samples are measured with α-spectrometry after radiochemical preparation using liquid-liquid separation with tributylphosphate. The results show that there is a stronger correlation between the uranium concentrations in the drinking water of each subject and the hair of the subject (r = 0.50) than with the urine (r = 0.21). There is also a stronger correlation between the activity ratios of water and hair (r = 0.91) than between water and urine (r = 0.56). These results imply that hair may serve as a robust indicator of chronic uranium intake. One obvious advantage over sampling urine is that hair samples reflect a much longer excretion period: weeks compared to days. The absorbed fraction of uranium, the f value, is calculated as the ratio between the excreted amount of uranium in urine and hair per day and the daily drinking water intake of uranium. The f values stretch from 0.002 to 0.10 with a median of 0.023.

  11. DETERMINATION OF REPORTABLE RADIONUCLIDES FOR DWPF SLUDGE BATCH 6 (MACROBATCH 7)

    SciTech Connect

    Bannochie, C.; Diprete, D.

    2011-06-01

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that 'The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115'. As part of the strategy to comply with WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report (WQR). However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that may meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, International Atomic Energy Agency (IAEA) Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The DWPF is receiving radioactive sludge slurry from HLW Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the heel from Sludge Batch 5 (SB5) with H-Canyon Np transfers completed after the start of processing SB5, and Sludge Batch 6 (SB6) that was transferred to Tank 40 from Tank 51. The blend of sludge in Tank 40 is also referred to as Macrobatch 7 (MB7). This report develops the list of reportable radionuclides and associated activities as a function of time. The DWPF will use this list and the activities as one of the

  12. DETERMINATION OF REPORTABLE RADIONUCLIDES FOR DWPF SLUDGE BATCH 7B (MACROBATCH 9)

    SciTech Connect

    Crawford, C. L.; Diprete, D. P.

    2014-05-01

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that “The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115”. As part of the strategy to comply with WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report (WQR). However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that may meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, International Atomic Energy Agency (IAEA) Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu- 242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The DWPF is receiving radioactive sludge slurry from HLW Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the heel from Sludge Batch 7a (SB7a) and Sludge Batch 7b (SB7b) that was transferred to Tank 40 from Tank 51. The blend of sludge in Tank 40 is also referred to as Macrobatch 9 (MB9). This report develops the list of reportable radionuclides and associated activities as a function of time. The DWPF will use this list and the activities as one of the inputs for the development of the Production Records that relate to

  13. Determination Of Reportable Radionuclides For DWPF Sludge Batch 7B (Macrobatch 9)

    SciTech Connect

    Crawford, C. L.; DiPrete, D. P.

    2013-08-22

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that “The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115”. As part of the strategy to comply with WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report (WQR). However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that may meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, International Atomic Energy Agency (IAEA) Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The DWPF is receiving radioactive sludge slurry from HLW Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the heel from Sludge Batch 7a (SB7a) and Sludge Batch 7b (SB7b) that was transferred to Tank 40 from Tank 51. The blend of sludge in Tank 40 is also referred to as Macrobatch 9 (MB9). This report develops the list of reportable radionuclides and associated activities as a function of time. The DWPF will use this list and the activities as one of the inputs for the development of the Production Records that relate to

  14. Results of Characterization and Retrieval Testing on Tank 241-C-110 Heel Solids

    SciTech Connect

    Callaway, William S.

    2013-09-30

    dissolution tests. Most of the {sup 99}Tc and {sup 137}Cs present in the initial heel solids composites was removed in the water dissolution tests. The estimated activities/weights of {sup 129}I, {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U in the dry residual solids were <25% of the weights/activities in the initial composite solids. Gibbsite and nordstrandite [both Al(OH){sub 3}] were the major solid phases identified in the solids remaining after completion of the dissolution tests. Chemical analysis indicated that the residual solids may have contained up to 62 wt% Al(OH){sub 3}. Significant quantities of unidentified phosphate-, iron-, bismuth-, silicon-, and strontium- bearing species were also present in the residual solids. The reference density of gibbsite (and nordstrandite) is 2.42 g/mL. The measured density of the residual solids, 2.65 g/mL, would be a reasonable value for solids containing gibbsite as the major component with minor quantities of other, higher density solids. Sieve analysis indicated that 22.2 wt% of the residual solids were discrete particles >710 μm in size, and 77.8 wt% were particulates <710 μm in size. Light-scattering measurements suggested that nearly all of the <710-μm particulates with diameters >12 μm were weakly bound aggregates of particles with diameters <2 μm. The <710-μm residual solids settled very slowly when dispersed in reagent water. The physical appearance of a suspension containing ≈0.4 vol% of the solids in pure water changed very little over a period of 46.5 hours. It should be noted that the distribution of particle sizes in the residual solids and the observed settling behavior were both strongly influenced by the procedures followed in the dissolution tests.

  15. DETERMINATION OF REPORTABLE RADIONUCLIDES FOR DWPF SLUDGE BATCH 5 (MACROBATCH 6)

    SciTech Connect

    Bannochie, C.; Bibler, N.; Diprete, D.

    2010-02-04

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that ''The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115''. As part of the strategy to comply with WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report (WQR). However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that may meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, International Atomic Energy Agency (IAEA) Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The DWPF is receiving radioactive sludge slurry from HLW Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the heel from Tank 40 (Sludge Batch 4 (SB4)), Sludge Batch 5 (SB5) that was transferred to Tank 40 from Tank 51, and H-Canyon Np transfers completed after the start of processing. The blend of sludge in Tank 40 is also referred to as Macrobatch 6 (MB6). This report develops the list of reportable radionuclides and associated activities and determines the radionuclide activities as a function of time. The DWPF will use

  16. DETERMINATION OF REPORTABLE RADIONUCLIDES FOR DWPF SLUDGE BATCH 4 MACROBATCH 5

    SciTech Connect

    Bannochie, C; Ned Bibler, N; David Diprete, D

    2008-05-30

    The Waste Acceptance Product Specifications (WAPS)1 1.2 require that 'The Producer shall report the inventory of radionuclides (in Curies) that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115'. As part of the strategy to meet WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type, all radionuclides (with half-lives greater than 10 years) that have concentrations greater than 0.01 percent of the total inventory from time of production through the 1100 year period from 2015 through 3115. The initial listing of radionuclides to be included is based on the design-basis glass as identified in the Waste Form Compliance Plan (WCP)2 and Waste Form Qualification Report (WQR)3. However, it is required that this list be expanded if other radionuclides with half-lives greater than 10 years are identified that may meet the greater than 0.01% criterion for Curie content. Specification 1.6 of the WAPS, International Atomic Energy Agency (IAEA) Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, U-238, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete set of reportable radionuclides must also include this set of U and Pu isotopes. The DWPF is receiving radioactive sludge slurry from HLW Tank 40. The radioactive sludge slurry in Tank 40 is a blend of the previous contents of Tank 40 (Sludge Batch 3) and the sludge that was transferred to Tank 40 from Tank 51. The blend of sludge from Tank 51 and Tank 40 defines Sludge Batch 4 (also referred to as Macrobatch 5 (MB5)). This report develops the list of reportable radionuclides and associated activities and determines the radionuclide activities as a function of time. The DWPF will use this list and the activities as one of

  17. Uranium and radium diffusion in organic-rich sediments (sapropels)

    NASA Astrophysics Data System (ADS)

    Gourgiotis, A.; Reyss, J.-L.; Frank, N.; Guihou, A.; Anagnostou, C.

    2011-09-01

    Among the late Quaternary Mediterranean sapropels, the S5 (125 ka) is one of the best preserved due to its high organic carbon content that has limited postdepositional oxidation. The high uranium content in this sapropel, >40 dpm g-1, makes this layer interesting for studying uranium series disequilibrium in organic-rich sediments. For this reason, the present work provides isotopic measurements of the U decay series in a S5 sapropel by applying more precise mass spectrometric methods, TIMS/MC-ICPMS, and gamma spectrometry. Assuming that U in the sapropel mostly originated from seawater the (234U/238U), (230Th/238U), (226Ra/230Th) and (231Pa/235U) activity ratios show systematic deviations from the theoretical values for a closed-system evolution of the U series over the 125 ka since sapropel formation. The radiogenic 234Urad and 226Ra show clear evidence of migration in the sapropel with modeled diffusion coefficients of (7.1 ± 1.1) × 10-12 cm2 s-1 and (1.6 ± 0.2) × 10-10 cm2 s-1, respectively. The diffusion of 234Urad cannot explain the high (230Th/238U) and (231Pa/235U) activity ratios observed in the sapropel. Two possible mechanisms or a combination of both are proposed for explaining the irregular (230Th/238U) and (231Pa/235U) activity profiles in sapropel S5. The first one is an enhanced export flux of 230Thxs and 231Paxs excesses exceeding the production rate in seawater, during the time of sapropel formation, and the second one is diffusion of authigenic Uauth in the sapropel. However, the ambiguous determination of 230Thxs and 231Paxs in the sapropel and the poorly understood processes that might lead to Uauth migration in anoxic sediments still limit a final explanation for the deviation of (230Th/238U) and (231Pa/235U) activity ratios from their expected theoretical values.

  18. Theoretical studies of {sup 238}U-{sup 230}Th-{sup 226}Ra and {sup 235}U-{sup 231}Pa disequilibria in young lavas produced by mantle melting

    SciTech Connect

    Zou, H.; Zindler, A.

    2000-05-01

    This paper provides ready-to-use equations to describe variations in uranium-series (U-series) disequilibrium as a function of elemental distribution coefficients, melting porosity, melting rate, and melting time. The effects of these melting parameters on U-series disequilibria are quantitatively evaluated in both an absolute and relative sense. The importance of net elemental fractionation and ingrowth of daughter nuclides are also described and compared in terms of their relative contributions to total U-series disequilibrium. In addition, the authors compare the production of U-series disequilibrium during mantle melting to trace element fractionations produced by melting in a similar context. Trace element fractionations depend externally on the degree to which a source is melted, whereas U-series disequilibrium depends upon both the degree and rate of melting. In contrast to previous models, their approach to modeling U-series disequilibrium during dynamic melting collapses simply to a description of trace element behavior during dynamic melting when the appropriate decay terms are omitted. Their formulation shows that extremely small degrees of melting, sometimes called upon to explain observed extents of U-series disequilibrium, are not always required.

  19. SPECT Imaging of Mice with 99mTc-Radiopharmaceuticals Obtained from 99Mo Produced by 100Mo(n,2n)99Mo and Fission of 235U

    NASA Astrophysics Data System (ADS)

    Hashimoto, Kazuyuki; Nagai, Yasuki; Kawabata, Masako; Sato, Nozomi; Hatsukawa, Yuichi; Saeki, Hideya; Motoishi, Shoji; Ohta, Masayuki; Konno, Chikara; Ochiai, Kentaro; Kawauchi, Yukimasa; Ohta, Akio; Shiina, Takayuki; Takeuchi, Nobuhiro; Ashino, Hiroki; Nakahara, Yuto

    2015-04-01

    The distribution of 99mTc-radiopharmaceutical in mouse was determined by single photon emission computed tomography (SPECT) for the first time using 99mTc, which was separated by thermochromatography from 99Mo produced via the 100Mo(n,2n)99Mo reaction with accelerator neutrons. The SPECT image was comparable to that obtained using the fission product 99Mo. Radionuclidic and radiochemical purities of the separated 99mTc and its aluminum concentration met the United States Pharmacopeia regulatory requirements for 99mTc from the fission product 99Mo. These results provide important evidence that the 99mTc-radiopharmaceutical formulated using the (n,2n) 99Mo can be a promising substitute for the fission product 99Mo. The current and forthcoming problem of ensuring a reliable and constant supply of 99Mo in Japan can be partially mitigated.

  20. Dose distributions in a human head phantom for neutron capture therapy using moderated neutrons from the 2.5 MeV proton-7Li reaction or from fission of 235U

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenichi; Kobayashi, Tooru; Sakurai, Yoshinori; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

    2001-10-01

    The feasibility of neutron capture therapy (NCT) using an accelerator-based neutron source of the 7Li(p,n) reaction produced by 2.5 MeV protons was investigated by comparing the neutron beam tailored by both the Hiroshima University radiological research accelerator (HIRRAC) and the heavy water neutron irradiation facility in the Kyoto University reactor (KUR-HWNIF) from the viewpoint of the contamination dose ratios of the fast neutrons and the gamma rays. These contamination ratios to the boron dose were estimated in a water phantom of 20 cm diameter and 20 cm length to simulate a human head, with experiments by the same techniques for NCT in KUR-HWNIF and/or the simulation calculations by the Monte Carlo N-particle transport code system version 4B (MCNP-4B). It was found that the 7Li(p,n) neutrons produced by 2.5 MeV protons combined with 20, 25 or 30 cm thick D2O moderators of 20 cm diameter could make irradiation fields for NCT with depth-dose characteristics similar to those from the epithermal neutron beam at the KUR-HWNIF.

  1. Natural radionuclide mobility and its influence on U-Th-Pb dating of secondary minerals from the unsaturated zone at Yucca Mountain, Nevada

    USGS Publications Warehouse

    Neymark, L.A.; Amelin, Y.V.

    2008-01-01

    Extreme U and Pb isotope variations produced by disequilibrium in decay chains of 238U and 232Th are found in calcite, opal/chalcedony, and Mn-oxides occurring as secondary mineral coatings in the unsaturated zone at Yucca Mountain, Nevada. These very slowly growing minerals (mm my-1) contain excess 206Pb and 208Pb formed from excesses of intermediate daughter isotopes and cannot be used as reliable 206Pb/238U geochronometers. The presence of excess intermediate daughter isotopes does not appreciably affect 207Pb/235U ages of U-enriched opal/chalcedony, which are interpreted as mineral formation ages. Opal and calcite from outer (younger) portions of coatings have 230Th/U ages from 94.6 ?? 3.7 to 361.3 ?? 9.8 ka and initial 234U/238U activity ratios (AR) from 4.351 ?? 0.070 to 7.02 ?? 0.12, which indicate 234U enrichment from percolating water. Present-day 234U/238U AR is ???1 in opal/chalcedony from older portions of the coatings. The 207Pb/235U ages of opal/chalcedony samples range from 0.1329 ?? 0.0080 to 9.10 ?? 0.21 Ma, increase with microstratigraphic depth, and define slow long-term average growth rates of about 1.2-2.0 mm my-1, in good agreement with previous results. Measured 234U/238U AR in Mn-oxides, which pre-date the oldest calcite and opal/chalcedony, range from 0.939 ?? 0.006 to 2.091 ?? 0.006 and are >1 in most samples. The range of 87Sr/86Sr ratios (0.71156-0.71280) in Mn-oxides overlaps that in the late calcite. These data indicate that Mn-oxides exchange U and Sr with percolating water and cannot be used as a reliable dating tool. In the U-poor calcite samples, measured 206Pb/207Pb ratios have a wide range, do not correlate with Ba concentration as would be expected if excess Ra was present, and reach a value of about 1400, the highest ever reported for natural Pb. Calcite intergrown with opal contains excesses of both 206Pb and 207Pb derived from Rn diffusion and from direct ??-recoil from U-rich opal. Calcite from coatings devoid of opal

  2. Uranium and plutonium total half-lives and for the spontaneous fission branch

    SciTech Connect

    Holden, N.E.

    1985-01-01

    The long-lived nuclides of the uranium and plutonium elements are of interest for their use in nuclear reactors, as well as in certain safeguard applications, e.g., alpha counting is often used to determine the amount of material present. The total half-life and the half-life for spontaneous fission are evaluated for these various long-lived nuclides of interest. The various experiments have been reanalyzed and recommended values are presented for /sup 232,233,234/U, /sup 235,236,238/U, and for /sup 236,238,239,240,241,242,244/Pu. These values improve upon preliminary estimates previously presented, in particular with respect to the uncertainties reported. The /sup 234/U half-life of 2.456 +- 0.005 x 10/sup 5/ years impacts directly on the 2200 meters/second fission cross section of /sup 235/U, since earlier measurements used values of 2.47 to 2.5 x 10/sup 5/ years and obtained correspondingly lower cross sections. In a similar manner, the /sup 239/Pu half-life is 1.25% lower than earlier estimates, which results in a 1.25% increase in the 2200 m/s fission cross section for /sup 239/Pu in some earlier cross section measurements. The total half-lives for the uranium nuclides were reviewed some time ago. At that time, the only spontaneous fission value which was evaluated was /sup 238/U. Recently, the uranium and plutonium nuclides were reviewed for both total and fission half-lives. The general procedure followed in this paper has been to review each of the experiments and revise the published values for the latest estimates of the various parameters used by the original authors. For the case of the total half-lives of uranium, only differences from the original work have been discussed. 120 refs., 23 tabs.

  3. First data on the uranium content in water of the Yenisei River basin in the area affected by the operation of Rosatom plants

    NASA Astrophysics Data System (ADS)

    Bolsunovskii, A. Ya.; Zhizhaev, A. M.; Saprykin, A. I.; Degermendzhi, A. G.; Rubailo, A. I.

    2011-07-01

    This study is devoted to investigating the content of uranium isotopes in water of the Yenisei River and its tributaries within the territories affected by the operation of Rosatom plants (mining chemical combine, and electrochemical plant). Long-term monitoring of the 238U content by mass spectrometry carried out in two institutes of the Siberian Branch of the Russian Academy of Sciences first revealed the multiple excess of 238U over the background content in different areas of the Yenisei River basin, such as the region of the Yenisei River near the effluents of the mining and chemical combine (MCC), and the territories of the Bol'shaya Tel' and Kan rivers. In these regions, the 238U content in water reaches 2.1-4.0 μg/l, which exceeds its content upstream from the MCC (0.3-0.6 μg/l) by almost an order of magnitude. The studies of the isotopic composition of uranium in water samples, which were carried out at the Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, showed the presence of a technogenic isotope of uranium 236U in the samples from the Bolshaya Tel' River and revealed the deviation of the isotope ratio 238U/235U (167 ± 3 and 177 ± 3) from the equilibrium natural ratio (238U/235U = 138). These facts attest to the technogenic origin of part of the uranium in water of the Bol'shaya Tel' River connected with the activity of MCC. The excess uranium content in the Kan River requires additional studies to ascertain the fraction of uranium of technogenic origin connected with the activity of the electrochemical plant (ECP) (Fig. 1, Table 4).

  4. Radiation Doses to Members of the U.S. Population from Ubiquitous Radionuclides in the Body: Part 1, Autopsy and In Vivo Data

    SciTech Connect

    Watson, David J.; Strom, Daniel J.

    2011-02-25

    This paper is part one of a three-part series investigating annual effective doses to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling 222Rn, 220Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. The goal of part one of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the 238U series (14 nuclides), the actinium series (headed by 235U; 11 nuclides), and the 232Th series (11 nuclides); primordial radionuclides 87Rb and 40 K; cosmogenic and fallout radionuclides 14C and 3H; and purely anthropogenic radionuclides 137Cs-137mBa, 129I, and 90Sr-90Y. Measurements judged to be relevant were available for only 15 of these radionuclides: 238U, 235U, 234U, 232Th, 230Th, 228Th, 228Ra, 226Ra, 210Pb, 210Po, 137Cs, 87Rb, 40K, 14C, and 3H. Recent and relevant measurements were not available for 129I and 90Sr-90Y. A total of 11,714 radionuclide concentration measurements were found in one or more tissues or organs from 14 States. Data on age, sex, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements so that variability in data sets is confounded with measurement uncertainty. The following papers detail how these shortcomings are overcome to achieve the goals of the three-part series.

  5. Actinides in deer tissues at the rocky flats environmental technology site.

    PubMed

    Todd, Andrew S; Sattelberg, R Mark

    2005-11-01

    Limited hunting of deer at the future Rocky Flats National Wildlife Refuge has been proposed in U.S. Fish and Wildlife planning documents as a compatible wildlife-dependent public use. Historically, Rocky Flats site activities resulted in the contamination of surface environmental media with actinides, including isotopes of americium, plutonium, and uranium. In this study, measurements of actinides [Americium-241 (241Am); Plutonium-238 (238Pu); Plutonium-239,240 (239,240Pu); uranium-233,244 (233,234U); uranium-235,236 (235,236U); and uranium-238 (238U)] were completed on select liver, muscle, lung, bone, and kidney tissue samples harvested from resident Rocky Flats deer (N = 26) and control deer (N = 1). In total, only 17 of the more than 450 individual isotopic analyses conducted on Rocky Flats deer tissue samples measured actinide concentrations above method detection limits. Of these 17 detects, only 2 analyses, with analytical uncertainty values added, exceeded threshold values calculated around a 1 x 10(-6) risk level (isotopic americium, 0.01 pCi/g; isotopic plutonium, 0.02 pCi/g; isotopic uranium, 0.2 pCi/g). Subsequent, conservative risk calculations suggest minimal human risk associated with ingestion of these edible deer tissues. The maximum calculated risk level in this study (4.73 x 10(-6)) is at the low end of the U.S. Environmental Protection Agency's acceptable risk range. PMID:16639905

  6. Analysis of Savannah Survey Sediment Collections of 30 Sep 04

    SciTech Connect

    Wimer, N; Hutcheon, I; Esser, B; Ramon, E

    2004-12-03

    This report summarizes laboratory radiochemical analyses of sediment samples collected by the Defense Threat Reduction Agency during the DoD Savannah Survey operations of Sep 04. The analytic goal was to determine if Wassaw Sound sediment collections of 30 Sep 04 display evidence for local anthropogenic uranium, as distinct from the recognized regional background stemming from the Savannah River Site (SRS). Radiochemical methods were selected to maximize detection sensitivity for such anthropogenic uranium. Within the suite of twelve collections, there would be evidence for a localized source if individual collections were to differ from the population as a whole. If in fact non-natural uranium were observed, definitive determination of whether the source was SRS effluent or a localized release would likely involve additional field sampling. These collections were logged by the LLNL Forensics Science Center, photographed, and laboratory chain-of-custody was begun. The inventory received at LLNL is reported in Table 1. The separate collections were not assigned any relative priority among them. LLNL has separately reviewed detailed records of the item in question, and determined what materials are involved and what radiochemical assays are of value. Attempting quantitative estimates of source-item material release, transport, and collection levels would be quite uncertain. Rather, present assays examine for departure from natural background isotopic compositions. To summarize the findings, analyses for all collections displayed natural uranium isotopic composition--considering the {sup 238}U/{sup 235}U and {sup 236}U/{sup 235}U ratios--within measurement uncertainties, which were quite low. No one collection or set of collections stood apart from the others in its uranium isotopes. These {sup 238}U/{sup 235}U data uncertainty levels also determined with 99.5% confidence (a three-standard-deviation determination) that no more than 0.46% of the total uranium present

  7. Capture and fission with DANCE and NEUANCE

    NASA Astrophysics Data System (ADS)

    Jandel, M.; Baramsai, B.; Bond, E.; Rusev, G.; Walker, C.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M. M.; Hayes, A.; Kawano, T.; Mosby, S.; Stetcu, I.; Taddeucci, T. N.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.

    2015-12-01

    A summary of the current and future experimental program at DANCE is presented. Measurements of neutron capture cross sections are planned for many actinide isotopes with the goal to reduce the present uncertainties in nuclear data libraries. Detailed studies of capture gamma rays in the neutron resonance region will be performed in order to derive correlated data on the de-excitation of the compound nucleus. New approaches on how to remove the DANCE detector response from experimental data and retain the correlations between the cascade gamma rays are presented. Studies on 235U are focused on quantifying the population of short-lived isomeric states in 236U after neutron capture. For this purpose, a new neutron detector array NEUANCE is under construction. It will be installed in the central cavity of the DANCE array and enable the highly efficient tagging of fission and capture events. In addition, developments of fission fragment detectors are also underway to expand DANCE capabilities to measurements of fully correlated data on fission observables.

  8. Capture and fission with DANCE and NEUANCE

    DOE PAGES

    Jandel, M.; Baramsai, B.; Bond, E.; Rusev, G.; Walker, C.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M. M.; Hayes, A.; et al

    2015-12-23

    A summary of the current and future experimental program at DANCE is presented. Measurements of neutron capture cross sections are planned for many actinide isotopes with the goal to reduce the present uncertainties in nuclear data libraries. Detailed studies of capture gamma rays in the neutron resonance region will be performed in order to derive correlated data on the de-excitation of the compound nucleus. New approaches on how to remove the DANCE detector response from experimental data and retain the correlations between the cascade gamma rays are presented. Studies on 235U are focused on quantifying the population of short-lived isomericmore » states in 236U after neutron capture. For this purpose, a new neutron detector array NEUANCE is under construction. It will be installed in the central cavity of the DANCE array and enable the highly efficient tagging of fission and capture events. In addition, developments of fission fragment detectors are also underway to expand DANCE capabilities to measurements of fully correlated data on fission observables.« less

  9. Applications of high resolution ICP-AES in the nuclear industry

    SciTech Connect

    Johnson, S.G.; Giglio, J.J.; Goodall, P.S.; Cummings, D.G.

    1998-07-01

    Application of high resolution ICP-AES to selected problems of importance in the nuclear industry is a growing field. The advantages in sample preparation time, waste minimization and equipment cost are considerable. Two examples of these advantages are presented in this paper, burnup analysis of spent fuel and analysis of major uranium isotopes. The determination of burnup, an indicator of fuel cycle efficiency, has been accomplished by the determination of {sup 139}La by high resolution inductively coupled plasma atomic emission spectroscopy (HR-ICP-AES). Solutions of digested samples of reactor fuel rods were introduced into a shielded glovebox housing an inductively coupled plasma (ICP) and the resulting atomic emission transmitted to a high resolution spectrometer by a 31 meter fiber optic bundle. Total and isotopic U determination by thermal ionization mass spectrometry (TIMS) is presented to allow for the calculation of burnup for the samples. This method of burnup determination reduces the time, material, sample handling and waste generated associated with typical burnup determinations which require separation of lanthanum from the other fission products with high specific activities. Work concerning an alternative burnup indicator, {sup 236}U, is also presented for comparison. The determination of {sup 235}U:{sup 238}U isotope ratios in U-Zr fuel alloys is also presented to demonstrate the versatility of HR-ICP-AES.

  10. SOFIA, a Next-Generation Facility for Fission Yields Measurements and Fission Study. First Results and Perspectives

    NASA Astrophysics Data System (ADS)

    Audouin, L.; Pellereau, E.; Taieb, J.; Boutoux, G.; Béliera, G.; Chatillon, A.; Ebran, A.; Gorbinet, T.; Laurent, B.; Martin, J.-F.; Tassan-Got, L.; Jurado, B.; Alvarez-Pol, H.; Ayyad, Y.; Benlliure, J.; Caamano, M.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Paradela, C.; Rodriguez-Sanchez, J.-L.; Vargas, J.; Casarejos, E.; Heinz, A.; Kelic-Heil, A.; Kurz, N.; Nociforo, C.; Pietri, S.; Prochazka, A.; Rossi, D.; Schmidt, K.-H.; Simon, H.; Voss, B.; Weick, H.; Winfield, J. S.

    2015-10-01

    Fission fragments play an important role in nuclear reactors evolution and safety. However, fragments yields are poorly known : data are essentially limited to mass yields from thermal neutron-induced fissions on a very few nuclei. SOFIA (Study On FIssion with Aladin) is an innovative experimental program on nuclear fission carried out at the GSI facility, which aims at providing isotopic yields on a broad range of fissioning systems. Relativistic secondary beams of actinides and pre-actinides are selected by the Fragment Separator (FRS) and their fission is triggered by electromagnetic interaction. The resulting excitation energy is comparable to the result of an interaction with a low-energy neutron, thus leading to useful data for reactor simulations. For the first time ever, both fission fragments are completely identified in charge and mass in a new recoil spectrometer, allowing for precise yields measurements. The yield of prompt neutrons can then be deduced, and the fission mechanism can be ascribed, providing new constraints for fission models. During the first experiment, all the technical challenges were matched : we have thus set new experimental standards in the measurements of relativistic heavy ions (time of flight, position, energy loss).This communication presents a first series of results obtained on the fission of 238U; many other fissioning systems have also been measured and are being analyzed presently. A second SOFIA experiment is planned in September 2014, and will be focused on the measurement of the fission of 236U, the analog of 235U+n.

  11. Rapid determination of uranium isotopes in urine by inductively coupled plasma-mass spectrometry.

    PubMed

    Shi, Y; Dai, X; Collins, R; Kramer-Tremblay, S

    2011-08-01

    Following a radiological or nuclear emergency involving uranium exposure, rapid analytical methods are needed to analyze the concentration of uranium isotopes in human urine samples for early dose assessment. The inductively coupled plasma mass spectrometry (ICP-MS) technique, with its high sample throughput and high sensitivity, has advantages over alpha spectrometry for uranium urinalysis after minimum sample preparation. In this work, a rapid sample preparation method using an anion exchange chromatographic column was developed to separate uranium from the urine matrix. A high-resolution sector field ICP-MS instrument, coupled with a high sensitivity desolvation sample introduction inlet, was used to determine uranium isotopes in the samples. The method can analyze up to 24 urine samples in two hours with the limits of detection of 0.0014, 0.10, and 2.0 pg mL(-1) for (234)U, (235)U, and (238)U, respectively, which meet the requirement for isotopic analysis of uranium in a radiation emergency.

  12. An alternative procedure for uranium analysis in drinking water using AQUALIX columns: application to varied French bottled waters.

    PubMed

    Bouvier-Capely, C; Bonthonneau, J P; Dadache, E; Rebière, F

    2014-01-01

    The general population is chronically exposed to uranium ((234)U, (235)U, and (238)U) and polonium ((210)Po) mainly through day-to-day food and beverage intake. The measurement of these naturally-occurring radionuclides in drinking water is important to assess their health impact. In this work the applicability of calix[6]arene-derivatives columns for uranium analysis in drinking water was investigated. A simple and effective method was proposed on a specific column called AQUALIX, for the separation and preconcentration of U from drinking water. This procedure is suitable for routine analysis and the analysis time is considerably shortened (around 4h) by combining the separation on AQUALIX with fast ICP-MS measurement. This new method was tested on different French bottled waters (still mineral water, sparkling mineral water, and spring water). Then, the case of simultaneous presence of uranium and polonium in water was considered due to interferences in alpha spectrometry measurement. A protocol was proposed using a first usual step of spontaneous deposition of polonium on silver disc in order to separate Po, followed by the uranium extraction on AQUALIX column before alpha spectrometry counting.

  13. Radionuclides in Small Mammals Collected at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility during 2001-- 2003

    SciTech Connect

    P.R. Fresquez

    2005-01-20

    Rodents are effective indicators of environmental contamination and the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility Mitigation Action Plan specifies the (radionuclide) comparison of small mammals to baseline levels to determine if there are any impacts as a result of operations. Consequently, samples of (whole body) field mice (Peromyscus spp.) were collected from within the grounds of the DARHT facility at Los Alamos National Laboratory, Technical Area 15, from 2001 through 2003. Samples were analyzed for {sup 3}H, {sup 137}Cs, {sup 90}Sr, {sup 241}Am, {sup 238}Pu, {sup 239,240}Pu, {sup 234}U, {sup 235}U, and {sup 238}U. Results, which represent three years since the start of operations in 2000, were compared with baseline statistical reference level (BSRL) data established over a four-year-long preoperational period. Most radionuclides in mice were either at nondetectable levels or within BSRLs. The few radionuclides that were above BSRLs included U isotopes; and the ratios of some samples indicated depleted U sources. Although the amounts of U in some samples were just above BSRLs, and since depleted U is less soluble and less toxic (chemical and radioactive) than naturally occurring U, the very small levels in the mice collected around the DARHT facility grounds are unlikely to pose a threat to predators that feed upon them.

  14. In-beam studies of high-spin states of actinide nuclei

    SciTech Connect

    Stoyer, M.A. . Nuclear Science Div. California Univ., Berkeley, CA . Dept. of Chemistry)

    1990-11-15

    High-spin states in the actinides have been studied using Coulomb- excitation, inelastic excitation reactions, and one-neutron transfer reactions. Experimental data are presented for states in {sup 232}U, {sup 233}U, {sup 234}U, {sup 235}U, {sup 238}Pu and {sup 239}Pu from a variety of reactions. Energy levels, moments-of-inertia, aligned angular momentum, Routhians, gamma-ray intensities, and cross-sections are presented for most cases. Additional spectroscopic information (magnetic moments, M{sub 1}/E{sub 2} mixing ratios, and g-factors) is presented for {sup 233}U. One- and two-neutron transfer reaction mechanisms and the possibility of band crossings (backbending) are discussed. A discussion of odd-A band fitting and Cranking calculations is presented to aid in the interpretation of rotational energy levels and alignment. In addition, several theoretical calculations of rotational populations for inelastic excitation and neutron transfer are compared to the data. Intratheory comparisons between the Sudden Approximation, Semi-Classical, and Alder-Winther-DeBoer methods are made. In connection with the theory development, the possible signature for the nuclear SQUID effect is discussed. 98 refs., 61 figs., 21 tabs.

  15. Radionuclide Concentration in Soils and Vegetation at Low-Level Radioactive Waste Disposal Area G during 2005

    SciTech Connect

    P.R. Fresquez; M.W. McNaughton; M.J. Winch

    2005-10-01

    Soil samples were collected at 15 locations and unwashed overstory and understory vegetation samples were collected from up to nine locations within and around the perimeter of Area G, the primary disposal facility for low-level radioactive solid waste at Los Alamos National Laboratory (LANL). Soil and plant samples were also collected from the proposed expansion area west of Area G for the purpose of gaining preoperational baseline data. Soil and plant samples were analyzed for radionuclides that have shown a history of detection in past years; these included {sup 3}H, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, {sup 234}U, {sup 235}U, and {sup 238}U for soils and {sup 3}H, {sup 238}Pu, and {sup 239,240}Pu for plants. As in previous years, the highest levels of {sup 3}H in soils and vegetation were detected at the south portion of Area G near the {sup 3}H shafts; whereas, the highest concentrations of the Pu isotopes were detected in the northern and northeastern portions near the pads for transuranic waste. All concentrations of radionuclides in soils and vegetation, however, were still very low (pCi range) and far below LANL screening levels and regulatory standards.

  16. An alternative procedure for uranium analysis in drinking water using AQUALIX columns: application to varied French bottled waters.

    PubMed

    Bouvier-Capely, C; Bonthonneau, J P; Dadache, E; Rebière, F

    2014-01-01

    The general population is chronically exposed to uranium ((234)U, (235)U, and (238)U) and polonium ((210)Po) mainly through day-to-day food and beverage intake. The measurement of these naturally-occurring radionuclides in drinking water is important to assess their health impact. In this work the applicability of calix[6]arene-derivatives columns for uranium analysis in drinking water was investigated. A simple and effective method was proposed on a specific column called AQUALIX, for the separation and preconcentration of U from drinking water. This procedure is suitable for routine analysis and the analysis time is considerably shortened (around 4h) by combining the separation on AQUALIX with fast ICP-MS measurement. This new method was tested on different French bottled waters (still mineral water, sparkling mineral water, and spring water). Then, the case of simultaneous presence of uranium and polonium in water was considered due to interferences in alpha spectrometry measurement. A protocol was proposed using a first usual step of spontaneous deposition of polonium on silver disc in order to separate Po, followed by the uranium extraction on AQUALIX column before alpha spectrometry counting. PMID:24274286

  17. Evaluation of the diffuse contamination of soils caused by residues coming from the large scale production of phosphate fertilisers

    NASA Astrophysics Data System (ADS)

    Martinez, M. J.; Perez-Sirvent, C.; Martinez-Lopez, S.; Bolivar, J. P.; Mosqueda, F.; Vaca, F.; Garcia-Tenorio, R.

    2012-04-01

    The obtaining of phosphate fertilizers results in large amounts of residues that are frequently accumulated in deposits or pools occupying a wide area. These residues are acidic, and contain variable amounts of trace elements and radionuclides. The potentially polluting agents can be leached by rainwater, and so transferred to the surface waters and then to the groundwater after soil infiltration. Since the distribution and thickness of the residue deposits are variable, the contaminants cannot be easily traced back to a single, well defined source, and so a diffuse contamination (nonpoint source pollution) of the surrounding soils and waters occurs. This communication reports the results obtained in the study of soils close to the phosphogypsum deposits placed near Rio Tinto (Huelva, Spain). The zone is affected not only by the mentioned residues but also by the tides due to the vicinity of the sea. The samples studied had a low organic content and a low acidity with average values of 30 mS/cm for the EC. The mineralogical study allowed illite, goethite, quartz, gypsum and kaolinite to be identified as the main mineralogical components. Although the arsenic level was relatively high (about 600 mg/Kg) the data proved that this element is not mobilized into water. Analytical data for 238U , 234U, 235U, 228Th, 230Th, 232Th, 226Ra, 228Ra, 210Po, 40K , 137Cs were also obtained.

  18. Levels of depleted uranium in Kosovo soils.

    PubMed

    Sansone, U; Stellato, L; Jia, G; Rosamilia, S; Gaudino, S; Barbizzi, S; Belli, M

    2001-01-01

    The United Nations Environment Programme (UNEP) has performed a field survey at 11 sites located in Kosovo, where depleted uranium (DU) ammunitions were used by the North Atlantic Treaty Organization (NATO) during the last Balkans conflict (1999). Soil sampling was performed to assess the spread of DU ground contamination around and within the NATO target sites and the migration of DU along the soil profile. The 234U/238U and 235U/238U activity concentration ratios have been used as an indicator of natural against anthropogenic sources of uranium. The results show that levels of 238U activity concentrations in soils above 100 Bq x kg(-1) can be considered a 'tracer' of the presence of DU in soils. The results also indicate that detectable ground surface contamination by DU is limited to areas within a few metres from localised points of concentrated contamination caused by penetrator impacts. Vertical distribution of DU along the soil profile is measurable up to a depth of 10-20 cm. This latter aspect is of particular relevance for the potential risk of future contamination of groundwater.

  19. Determination of total content and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes by ICP-QMS.

    PubMed

    Godoy, Maria Luiza Duarte Pinto; Godoy, José Marcus; Roldão, Luiz Alfredo; Tauhata, Luiz

    2009-08-01

    The aim of this work was to determine the concentrations and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes. An analytical method was developed with a plutonium and uranium separation procedure based on extraction chromatography (using 2mL TEVA and UTEVA columns) and detection with a quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with a membrane desolvation system. Starting from blank swipes, the background equivalent concentration (BEC) was 8fg for (239)Pu and 1ng (238)U. The method was successfully applied to certified reference materials as well as to round robin samples obtained in the framework of the inter-laboratory exercise program, promoted by the Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC), together with the US Department of Energy (USDOE). After the introduction of an additional ion-exchange separation step, the methodology was applied to the IAEA-384 sediment reference sample with precise and accurate total plutonium and uranium, (240)Pu/(239)Pu, (241)Pu/(239)Pu, (234)U/(238)U and (235)U/(238)U atomic ratio results. PMID:19500890

  20. Rapid determination of uranium isotopes in urine by inductively coupled plasma-mass spectrometry.

    PubMed

    Shi, Y; Dai, X; Collins, R; Kramer-Tremblay, S

    2011-08-01

    Following a radiological or nuclear emergency involving uranium exposure, rapid analytical methods are needed to analyze the concentration of uranium isotopes in human urine samples for early dose assessment. The inductively coupled plasma mass spectrometry (ICP-MS) technique, with its high sample throughput and high sensitivity, has advantages over alpha spectrometry for uranium urinalysis after minimum sample preparation. In this work, a rapid sample preparation method using an anion exchange chromatographic column was developed to separate uranium from the urine matrix. A high-resolution sector field ICP-MS instrument, coupled with a high sensitivity desolvation sample introduction inlet, was used to determine uranium isotopes in the samples. The method can analyze up to 24 urine samples in two hours with the limits of detection of 0.0014, 0.10, and 2.0 pg mL(-1) for (234)U, (235)U, and (238)U, respectively, which meet the requirement for isotopic analysis of uranium in a radiation emergency. PMID:21709502

  1. Radionuclide Concentrations in Soils and Vegetation at Low-Level Radioactive Waste Disposal Area G during the 1997 Growing Season

    SciTech Connect

    L. Naranjo, Jr.; P. R. Fresquez; R. J. Wechsler

    1998-08-01

    Soil and overstory and understory vegetation (washed and unwashed) collected at eight locations within and around Area G-a low-level radioactive solid-waste disposal facility at Los Alamos National Laboratory-were analyzed for 3H, 238Pu, 239Pu, 137CS, 234U, 235U, 228AC, Be, 214Bi, 60Co, 40& 54Mn, 22Na, 214Pb and 208Tl. In general, most radionuclide concentrations, with the exception of 3Ef and ~9Pu, in soils and overstory and understory vegetation collected from within and around Area G were within upper (95'%) level background concentrations. Although 3H concentrations in vegetation from most sites were significantly higher than background (>2 pCi mL-l), concentrations decreased markedly in comparison to last year's results. The highest `H concentration in vegetation was detected from a juniper tree that was growing over tritium shaft /+150; it contained 530,000 pCi 3H mL-l. Also, as in the pas~ the transuranic waste pad area contained the highest levels of 239Pu in soils and in understory vegetation as compared to other areas at Area G.

  2. Radionuclide concentrations in soils and vegetation at radioactive-waste disposal Area G during the 1996 growing season. Progress report

    SciTech Connect

    Fresquez, P.R.; Vold, E.L.; Naranjo, L. Jr.

    1997-07-01

    Soil and overstory and understory vegetation (washed and unwashed) collected at eight locations within and around Area G--a low-level radioactive solid-waste disposal facility at Los Alamos National laboratory--were analyzed for {sup 3}H, {sup 90}Sr, {sup 238}Pu, {sup 239}Pu, {sup 137}Cs, {sup 234}U, {sup 235}U, {sup 238}U, {sup tot}U, {sup 228}Ac, {sup 214}Bi, {sup 60}Co, {sup 40}K, {sup 54}Mn, {sup 22}Na, {sup 214}Pb, and {sup 208}Tl. Also, heavy metals (Ag, As, Ba, Be, Cd, Cr, Hg, Ni, Pb, Sb, Se, and Tl) in soil and vegetation were determined. In general, most radionuclide concentrations, with the exception of {sup 3}H and {sup 239}Pu, in soils and washed and unwashed overstory and understory vegetation collected from within and around Area G were within upper limit background concentrations. Tritium was detected as high as 14,744 pCi mL{sup {minus}1} in understory vegetation collected from transuranic (TRU) waste pad {number_sign}4, and the TRU waste pad area contained the highest levels of {sup 239}Pu in soils and in understory vegetation as compared to other areas at Area G.

  3. Prompt Fission Neutron Spectra of Actinides

    SciTech Connect

    Capote, R; Chen, Y J; Hambsch, F J; Kornilov, N V; Lestone, J P; Litaize, O; Morillon, B; Neudecker, D; Oberstedt, S; Ohsawa, T; Smith, D. L.

    2016-01-01

    The energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) “Evaluation of Prompt Fission Neutron Spectra of Actinides”was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS data are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data

  4. Comment on "Radiocarbon Calibration Curve Spanning 0 to 50,000 Years B.P. Based on Paired 230Th/234U/238U and 14C Dates on Pristine Corals" by R.G. Fairbanks, R. A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T. P. Guilderson, T. W. Fairbanks, A. L. Bloom, P

    SciTech Connect

    Reimer, P J; Baillie, M L; Bard, E; Beck, J W; Blackwell, P G; Buck, C E; Burr, G S; Edwards, R L; Friedrich, M; Guilderson, T P; Hogg, A G; Hughen, K A; Kromer, B; McCormac, G; Manning, S; Reimer, R W; Southon, J R; Stuiver, M; der Plicht, J v; Weyhenmeyer, C E

    2005-10-02

    Radiocarbon calibration curves are essential for converting radiocarbon dated chronologies to the calendar timescale. Prior to the 1980's numerous differently derived calibration curves based on radiocarbon ages of known age material were in use, resulting in ''apples and oranges'' comparisons between various records (Klein et al., 1982), further complicated by until then unappreciated inter-laboratory variations (International Study Group, 1982). The solution was to produce an internationally-agreed calibration curve based on carefully screened data with updates at 4-6 year intervals (Klein et al., 1982; Stuiver and Reimer, 1986; Stuiver and Reimer, 1993; Stuiver et al., 1998). The IntCal working group has continued this tradition with the active participation of researchers who produced the records that were considered for incorporation into the current, internationally-ratified calibration curves, IntCal04, SHCal04, and Marine04, for Northern Hemisphere terrestrial, Southern Hemisphere terrestrial, and marine samples, respectively (Reimer et al., 2004; Hughen et al., 2004; McCormac et al., 2004). Fairbanks et al. (2005), accompanied by a more technical paper, Chiu et al. (2005), and an introductory comment, Adkins (2005), recently published a ''calibration curve spanning 0-50,000 years''. Fairbanks et al. (2005) and Chiu et al. (2005) have made a significant contribution to the database on which the IntCal04 and Marine04 calibration curves are based. These authors have now taken the further step to derive their own radiocarbon calibration extending to 50,000 cal BP, which they claim is superior to that generated by the IntCal working group. In their papers, these authors are strongly critical of the IntCal calibration efforts for what they claim to be inadequate screening and sample pretreatment methods. While these criticisms may ultimately be helpful in identifying a better set of protocols, we feel that there are also several erroneous and misleading statements made by these authors which require a response by the IntCal working group. Furthermore, we would like to comment on the sample selection criteria, pretreatment methods, and statistical methods utilized by Fairbanks et al. in derivation of their own radiocarbon calibration.

  5. Benchmark Evaluation of the NRAD Reactor LEU Core Startup Measurements

    SciTech Connect

    J. D. Bess; T. L. Maddock; M. A. Marshall

    2011-09-01

    The Neutron Radiography (NRAD) reactor is a 250-kW TRIGA-(Training, Research, Isotope Production, General Atomics)-conversion-type reactor at the Idaho National Laboratory; it is primarily used for neutron radiography analysis of irradiated and unirradiated fuels and materials. The NRAD reactor was converted from HEU to LEU fuel with 60 fuel elements and brought critical on March 31, 2010. This configuration of the NRAD reactor has been evaluated as an acceptable benchmark experiment and is available in the 2011 editions of the International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP Handbook) and the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP Handbook). Significant effort went into precisely characterizing all aspects of the reactor core dimensions and material properties; detailed analyses of reactor parameters minimized experimental uncertainties. The largest contributors to the total benchmark uncertainty were the 234U, 236U, Er, and Hf content in the fuel; the manganese content in the stainless steel cladding; and the unknown level of water saturation in the graphite reflector blocks. A simplified benchmark model of the NRAD reactor was prepared with a keff of 1.0012 {+-} 0.0029 (1s). Monte Carlo calculations with MCNP5 and KENO-VI and various neutron cross section libraries were performed and compared with the benchmark eigenvalue for the 60-fuel-element core configuration; all calculated eigenvalues are between 0.3 and 0.8% greater than the benchmark value. Benchmark evaluations of the NRAD reactor are beneficial in understanding biases and uncertainties affecting criticality safety analyses of storage, handling, or transportation applications with LEU-Er-Zr-H fuel.

  6. Effect of Radium mobility on the U-Pb systematic and age determination of uraninite.

    NASA Astrophysics Data System (ADS)

    Deloule, Etienne; Brouand, Marc

    2014-05-01

    The U-Pb radio chronometer is commonly used to date the formation of uraninite, a major component of uranium deposit. Uraninite was first used in 1905, when Rutherford determines ages up to 500 Ma in using their He/U ratio, and in 1907 when Boltwood determine the first U-Pb ages (413-535 Ma). During the last decade, in situ U-Pb datation on Uraninite has been developed, either in using 'chemical ages' with the determination by EMP of U and Pb contents, either in using 'isotopic ages' with the determination of Pb and U isotopic ratios and contents by SIMS, providing a large amount of age from archean up to Cenozoic ages. It is noticeable that the determination of chemical age relies on the assumption that the U-Pb system stay closed over time. This assumption can be supported by many isotopic measurements providing concordant or close to concordance 238U-206Pb and 235U-207Pb ages. However, during the last year, SIMS U-Pb age determination on Uraninite from the Imouraren (Niger) uranium deposit provides contrasted results. On one hand, samples provide concordant U-Pb ages with an average value of 99 ±2 Ma. On the other hand, samples provide largely discordant ages, with 207Pb/206Pb ages up to 340 Ma. Duplicated measurements and careful data examination allowed us to discard any common lead contamination as a source of discordance. Therefore we set the in situ measurement of the U series nuclides 238U - 234U - 230Th - 226Ra. The high transmission at high mass resolution of the CRPG -Cameca IMS 1270 ion microprobe allowed us to get significant secondary beam intensities for the smaller isotopes and to determine the activity ratios with a few % precision. These measurements points out that 234U and 230Th are at equilibrium with 238U, when 226Ra may be largely depleted, up to 50%. This points out that in the geological context of the deposit, hydrothermal fluids may leach Ra. To explain the observed discordant ages, Ra should have been lost during a large amount of time

  7. Uranium and Strontium Isotopic Study of the Hydrology of the Alluvial Aquifer at the Rifle Former U Mine Tailings Site, Colorado

    NASA Astrophysics Data System (ADS)

    Christensen, J. N.; Shiel, A. E.; Conrad, M. E.; Williams, K. H.; Dong, W.; Tokunaga, T. K.; Wan, J.; Long, P. E.; Hubbard, S. S.

    2014-12-01

    The Rifle Site consists of a floodplain along the Colorado River that was remediated through the removal of surface material underlying former uranium-vanadium mill tailings. The semi-arid (precip. = ~30 cm/year) catchment for the site has an area of ~1km2. The Rifle Site provides an excellent field laboratory for the study of the fluxes of water and carbon from the vadose zone to groundwater (LBNL SFA2.0, http://esd.lbl.gov/research/projects/sssfa2/). A network of monitoring wells, particularly a set instrumented in the vadose zone, provide the opportunity to closely sample groundwater and vadose zone porewater both in space and time. In order to better understand the spatial and temporal variation of vadose zone interaction with groundwater within the Rifle floodplain and provide constraints for a Rifle hydrological model, we have analyzed the Sr isotopic compositions, 234U/238U activity ratios, and d238U of groundwater, vadose zone porewater (sampled through depth-distributed lysimeters) and surface water including the Colorado River. Significant contrasts in 87Sr/86Sr and 234U/238U allow the identification of different sources contributing to Rifle groundwater, while d238U provides an additional tracer and insights into redox processes. Vadose zone porewater is characterized by high 87Sr/86Sr and Sr concentrations and falls at one end of a mixing line with Rifle groundwater, while upgradient groundwater with lower 87Sr/86Sr and Sr concentrations falls at the other end. A mixing model using vadose zone porewater and upgradient groundwater as endmembers suggests that the contribution of vertical recharge through the floodplain increases to ~20% systematically across the floodplain towards the Colorado River. An exception to this pattern is a well located 150m from the river with recent high U concentrations (>300 ppb) and U and Sr isotopic compositions consistent with a 38% vadose zone contribution. U and Sr isotopes show that an irrigation-return ditch that cuts

  8. A Record of Uranium-Series Transport in Fractured, Unsaturated Tuff at Nopal I, Sierra Peña Blanca, Chihuahua, Mexico

    NASA Astrophysics Data System (ADS)

    Denton, J.; Goldstein, S. J.; Paviet, P.; Nunn, A. J.; Amato, R. S.; Hinrichs, K. A.

    2015-12-01

    In this study we utilize U-series disequilibria measurements to investigate mineral fluid interactions and the role fractures play in the geochemical evolution of an analogue for a high level nuclear waste repository, the Nopal I uranium ore deposit. Samples of fracture-fill materials have been collected from a vertical drill core and surface fractures. High uranium concentrations in these materials (12-7700 ppm) indicate U mobility and transport from the deposit in the past. U concentrations generally decrease with horizontal distance away from the ore deposit but show no trend with depth. Isotopic activity ratios indicate a complicated geochemical evolution in terms of the timing and extent of actinide mobility, possibly due to changing environmental (redox) conditions over the history of the deposit. 234U/238U activity ratios are generally distinct from secular equilibrium and indicate some degree of open system U behavior during the past 1.2 Ma. However, calculated closed system 238U-234U-230Th model ages are generally >313 ka and >183 ka for the surface fracture and drill core samples respectively, suggesting closed system behavior for U and Th over this most recent time period. Whole rock isochrons drawn for the drill core samples show that at two of three depths fractures have remained closed with respect to U and Th mobility for >200 ka. However, open system behavior for U in the last 350 ka is suggested at 67 m depth. 231Pa/235U activity ratios within error of unity suggest closed system behavior for U and Pa for at least the past 185 ka. 226Ra/230Th activity ratios are typically <1 (0.7-1.2), suggesting recent (<8 ka) radium loss and mobility due to ongoing fluid flow in the fractures. Overall, the mainly closed system behavior of U-Th-Pa over the past ~200 ka provides one indicator of the geochemical immobility of these actinides over long time-scales for potential nuclear waste repositories sited in fractured, unsaturated tuff.

  9. Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data.

    PubMed

    Watson, David J; Strom, Daniel J

    2011-04-01

    This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with

  10. Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data.

    PubMed

    Watson, David J; Strom, Daniel J

    2011-04-01

    This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with

  11. U-Pb ages of secondary silica at Yucca Mountain, Nevada: Implications for the paleohydrology of the unsaturated zone

    USGS Publications Warehouse

    Neymark, L.A.; Amelin, Y.; Paces, J.B.; Peterman, Z.E.

    2002-01-01

    Uranium, Th and Pb isotopes were analyzed in layers of opal and chalcedony from individual mm- to cm-thick calcite and silica coatings at Yucca Mountain, Nevada, USA, a site that is being evaluated for a potential high-level nuclear waste repository. These calcite and silica coatings on fractures and in lithophysal cavities in Miocene-age tuffs in the unsaturated zone (UZ) precipitated from descending water and record a long history of percolation through the UZ. Opal and chalcedony have high concentrations of U (10 to 780 ppm) and low concentrations of common Pb as indicated by large values of 206Pb/204Pb (up to 53,806), thus making them suitable for U-Pb age determinations. Interpretations of U-Pb isotope systems in opal samples at Yucca Mountain are complicated by the incorporation of excess 234U at the time of mineral formation, resulting in reverse discordance of U-Pb ages. However, the 207PB/235U ages are much less affected by deviation from initial secular equilibrium and provide reliable ages of most silica deposits between 0.6 and 9.8 Ma. For chalcedony subsamples showing normal age discordance, these ages may represent minimum times of deposition. Typically, 207Pb/235U ages are consistent with the microstratigraphy in the mineral coating samples, such that the youngest ages are for subsamples from outer layers, intermediate ages are from inner layers, and oldest ages are from innermost layers. 234U and 230Th in most silica layers deeper in the coatings are in secular equilibrium with 238U, which is consistent with their old age and closed system behavior during the past -0.5 Ma. The ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from lithophysal cavities in the welded part of the Topopah Spring Tuff yield slow long-term average growth rates of 1 to 5 mm/Ma. These data imply that the deeper parts of the UZ at Yucca Mountain maintained long-term hydrologic stability

  12. U-Pb Ages of Secondary Silica at Yucca Mountain, Nevada: Implications for the Paleohydrology of the Unsaturated Zone

    SciTech Connect

    L.A. Neymark; Y. Amelin; J.B. Paces; Z.E. Peterman

    2001-08-20

    U, Th, and Pb isotopes were analyzed in layers of opal and chalcedony from individual millimeter- to centimeter-thick calcite and silica coatings at Yucca Mountain, Nevada, USA, a site that is being evaluated for a potential high-level nuclear waste repository. These calcite and silica coatings on fractures and in lithophysal cavities in Miocene-age tuffs in the unsaturated zone (UZ) precipitated from descending water and record a long history of percolation through the UZ. Opal and chalcedony have high concentrations of U (10 to 780 ppm) and low concentrations of common Pb as indicated by large values of {sup 206}Pb/{sup 204}Pb (up to 53,806), thus making them suitable for U-Pb age determinations. Interpretations of U-Pb isotopes in opal samples at Yucca Mountain are complicated by the incorporation of excess {sup 234}U at the time of mineral formation, resulting in reverse discordance of U-Pb ages. However, the {sup 207}Pb/{sup 235}U ages are much less affected by deviation from initial secular equilibrium and provide reliable ages of most silica deposits between 0.6 and 9.8 Ma. For chalcedony subsamples showing normal age discordance, these ages may represent minimum times of deposition. Typically, {sup 207}Pb/{sup 235}U ages are consistent with the microstratigraphy in the mineral coating samples, such that the youngest ages are for subsamples from outer layers, intermediate ages are from inner layers, and oldest ages are from innermost layers. {sup 234}U and {sup 230}Th in most silica layers deeper in the coatings are in secular equilibrium with {sup 238}U, which is consistent with their old age and closed system behavior during the past 0.5 m.y. U-Pb ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from lithophysal cavities in the welded part of the Topopah Spring Tuff yield slow long-term average depositional rates of 1 to 5 mm/m.y. These data imply that the deeper

  13. Highly enriched isotope samples of uranium and transuranium elements for scientific investigation

    NASA Astrophysics Data System (ADS)

    Vesnovskii, Stanislav P.; Polynov, Vladimir N.; Danilin, Lev. D.

    1992-02-01

    The paper describes the production of highly enriched isotopes of uranium, plutonium, americium and curium by electromagnetic separation for scientific and applied researches in physics, chemistry, geology, medicine, biology and other fields. Using the equipment described, the isotopes are produced in quantities sufficient to set up nuclear physical experiments, to produce nuclear reference materials and standard sources for calibration of radiometrical and mass spectrometrical equipment, in radionuclide metrology, etc. For the following isotopes the indicated degrees of isotopic enrichment were achieved: 233U - 99.97%; 235U - 99.97%; 236U - 98.0%; 238U - 99.997%; 238Pu - 99.6%; 239Pu - 99.9977%; 240Pu - 99.9-100%; 241Pu - 96.998%; 242Pu - 97.8-99.96%; 244Pu - 96.7%; 241Am - 99.6%; 242Am - 73.6%; 243Am - 99.2-99.94%; 243Cm - 99.99%; 245Cm - 99.998%; 246Cm - 99.8%; 247Cm - 90%; 248Cm - 97%. Methods for preparing layers of highly enriched isotopes on various substances are presented: - electrochemical deposition of transuranic elements from aqueous-organic and organic media and vacuum spraying: - the method of foil and coating formation via compounds in the vapour phase; - the method of fabrication of layers of transuranic elements on superthin (1-2 μm) metal substrates with additional isolating polymer-metal coatings (0.2-0.4 μm), that substantially decrease material transfer from the active layer and increase safety of product handling.

  14. Analysis of the Reuse of Uranium Recovered from the Reprocessing of Commercial LWR Spent Fuel

    SciTech Connect

    DelCul, Guillermo Daniel; Trowbridge, Lee D; Renier, John-Paul; Ellis, Ronald James; Williams, Kent Alan; Spencer, Barry B; Collins, Emory D

    2009-02-01

    This report provides an analysis of the factors involved in the reuse of uranium recovered from commercial light-water-reactor (LWR) spent fuels (1) by reenrichment and recycling as fuel to LWRs and/or (2) by recycling directly as fuel to heavy-water-reactors (HWRs), such as the CANDU (registered trade name for the Canadian Deuterium Uranium Reactor). Reuse is an attractive alternative to the current Advanced Fuel Cycle Initiative (AFCI) Global Nuclear Energy Partnership (GNEP) baseline plan, which stores the reprocessed uranium (RU) for an uncertain future or attempts to dispose of it as 'greater-than-Class C' waste. Considering that the open fuel cycle currently deployed in the United States already creates a huge excess quantity of depleted uranium, the closed fuel cycle should enable the recycle of the major components of spent fuel, such as the uranium and the hazardous, long-lived transuranic (TRU) actinides, as well as the managed disposal of fission product wastes. Compared with the GNEP baseline scenario, the reuse of RU in the uranium fuel cycle has a number of potential advantages: (1) avoidance of purchase costs of 11-20% of the natural uranium feed; (2) avoidance of disposal costs for a large majority of the volume of spent fuel that is reprocessed; (3) avoidance of disposal costs for a portion of the depleted uranium from the enrichment step; (4) depending on the {sup 235}U assay of the RU, possible avoidance of separative work costs; and (5) a significant increase in the production of {sup 238}Pu due to the presence of {sup 236}U, which benefits somewhat the transmutation value of the plutonium and also provides some proliferation resistance.

  15. Analysis of HEU samples from the ULBA Metallurgical Plant

    SciTech Connect

    Gift, E.H.

    1995-05-01

    In early March 1994, eight highly enriched uranium (HEU) samples were collected from materials stored at the Ulba Metallurgical Plant in Oskamen (Ust Kamenogorsk), Kazakhstan. While at the plant site, portions of four samples were dissolved and analyzed by mass spectrograph at the Ulba analytical laboratory by Ulba analysts. Three of these mass spectrograph solutions and the eight HEU samples were subsequently delivered to the Y-12 Plant for complete chemical and isotopic analyses. Chemical forms of the eight samples were uranium metal chips, U0{sub 2} powder, uranium/beryllium oxide powder, and uranium/beryllium alloy rods. All were declared by the Ulba plant to have a uranium assay of {approximately}90 wt % {sup 235}U. The uranium/beryllium powder and alloy samples were also declared to range from about 8 to 28 wt % uranium. The chemical and uranium isotopic analyses done at the Y-12 Plant confirm the Ulba plant declarations. All samples appear to have been enriched using some reprocessed uranium, probably from recovery of uranium from plutonium production reactors. As a result, all samples contain some {sup 236}U and {sup 232}U and have small but measurable quantities of plutonium. This plutonium could be the result of either contamination carried over from the enrichment process or cross-contamination from weapons material. It is not the result of direct reactor exposure. Neither the {sup 232}U nor the plutonium concentrations are sufficiently high to provide a significant industrial health hazard. Both are well within established or proposed acceptance criteria for storage at Y-12. The trace metal analyses showed that, with the exception of beryllium, there are no trace metals in any of these HEU samples that pose a significant health hazard.

  16. PRELIMINARY CROSS SECTION AND NU-BAR COVARIANCES FOR WPEC SUBGROUP 26

    SciTech Connect

    ROCHMAN,D.

    2007-01-31

    We report preliminary cross section covariances developed for the WPEC Subgroup 26 for 45 out of 52 requested materials. The covariances were produced in 15- and 187-group representations as follows: (1) 36 isotopes ({sup 16}O, {sup 19}F, {sup 23}Na, {sup 27}Al, {sup 28}Si, {sup 52}Cr, {sup 56,56}Fe, {sup 58}Ni, {sup 90,91,92,94}Zr, {sup 166,167,168,170}Er, {sup 206,207,208}Pb, {sup 209}Bi, {sup 233,234,236}U, {sup 237}Np, {sup 238,240,241,242}Pu, {sup 241,242m,243}Am, {sup 242,243,244,245}Cm) were evaluated using the BNL-LANL methodology. For the thermal region and the resolved and unresolved resonance regions, the methodology has been based on the Atlas-Kalman approach, in the fast neutron region the Empire-Kalman method has been used; (2) 6 isotopes ({sup 155,156,157,158,160}Gd and {sup 232}Th) were taken from ENDF/B-VII.0; and (3) 3 isotopes ({sup 1}H, {sup 238}U and {sup 239}Pu) were taken from JENDL-3.3. For 6 light nuclei ({sup 4}He, {sup 6,7}Li, {sup 9}Be, {sup 10}B, {sup 12}C), only partial cross section covariance results were obtained, additional work is needed and they do not report the results here. Likewise, the cross section covariances for {sup 235}U, which they recommend to take from JENDL-3.3, will be included once the multigroup processing is successfully completed. Covariances for the average number of neutrons per fission, total {nu}-bar, are provided for 10 actinides identified as priority by SG26. Further work is needed to resolve some of the issues and to produce covariances for the full set of 52 materials.

  17. A comparative experimental study of gross alpha methods in natural waters.

    PubMed

    Montaña, M; Fons, J; Corbacho, J A; Camacho, A; Zapata-García, D; Guillén, J; Serrano, I; Tent, J; Baeza, A; Llauradó, M; Vallés, I

    2013-04-01

    The aim of the present work was to compare the results obtained with gross alpha methods such as evaporation, co-precipitation and total evaporation by liquid scintillation counting and to check whether these results are representative of the real total alpha activity concentration on the sample. The study was carried out on eight natural waters with very different radioactive characteristics. For all the samples uranium ((238)U, (235)U, and (234)U), radium ((226)Ra and (224)Ra), (210)Po, and (232)Th isotopes were also assayed by using radiochemical separation and alpha spectrometry in order to determine the sum of the activities of these alpha emitters. Precision (expressed as relative standard deviation) was below 28% for evaporation and below 18% for co-precipitation. In the case of total by liquid scintillation counting it was below 10% for samples with Total Alpha activity above 0.1 Bq/L (this value is about three times the MDA). Furthermore, for most of the studied waters, the Total Alpha activity and the gross alpha activity determined by the three methods were comparable. The obtained bias by the evaporation, co-precipitation, and total evaporation by liquid scintillation counting methods was lower than 40%, 25% and 20%, respectively. The ANOVA test was applied to find out if there was significant variability among the methods. For the samples with the most common radiochemical characteristics there were no significant differences among the three studied methods. However differences were detected for samples with a high saline content or with a very low activity level. PMID:23220539

  18. Neanderthal skeleton from Tabun: U-series data by gamma-ray spectrometry.

    PubMed

    Schwarcz, H P; Simpson, J J; Stringer, C B

    1998-12-01

    The Neanderthal hominid Tabun C1, found in Israel by Garrod & Bate, was attributed to either layer B or C of their stratigraphic sequence. We have used gamma-ray spectrometry to determine the 230Th/234U and 231Pa/235U ratios of two bones from this skeleton, the mandible and a femur. The ages calculated from these ratios depend on the uranium uptake history of the bones. Assuming a model of early U (EU) uptake the age of the Tabun C1 mandible is 34+/-5 ka. The EU age of the femur is 19+/-2 ka. The femur may have experienced continuous (linear) U uptake which would give an age of 33+/-4 ka, in agreement with the mandible's EU age, but implies marked inhomogeneity in U uptake history at the site. These new age estimates for the skeleton suggest that it was younger than deposits of layer C. This apparent age is less than those of other Neanderthals found in Israel, and distinctly younger than the ages of the Skhul and Qafzeh burials. This suggests that Neanderthals did not necessarily coexist with the earliest modern humans in the region. All of the more complete Neanderthal fossils from Israel are now dated to the cool period of the last glacial cycle, suggesting that Neanderthals may have arrived in this region as a result of the southward expansion of their habitable range. The young age determined for the Tabun skeleton would suggest that Neanderthals survived as late in the Levant as they did in Europe.

  19. Neanderthal skeleton from Tabun: U-series data by gamma-ray spectrometry.

    PubMed

    Schwarcz, H P; Simpson, J J; Stringer, C B

    1998-12-01

    The Neanderthal hominid Tabun C1, found in Israel by Garrod & Bate, was attributed to either layer B or C of their stratigraphic sequence. We have used gamma-ray spectrometry to determine the 230Th/234U and 231Pa/235U ratios of two bones from this skeleton, the mandible and a femur. The ages calculated from these ratios depend on the uranium uptake history of the bones. Assuming a model of early U (EU) uptake the age of the Tabun C1 mandible is 34+/-5 ka. The EU age of the femur is 19+/-2 ka. The femur may have experienced continuous (linear) U uptake which would give an age of 33+/-4 ka, in agreement with the mandible's EU age, but implies marked inhomogeneity in U uptake history at the site. These new age estimates for the skeleton suggest that it was younger than deposits of layer C. This apparent age is less than those of other Neanderthals found in Israel, and distinctly younger than the ages of the Skhul and Qafzeh burials. This suggests that Neanderthals did not necessarily coexist with the earliest modern humans in the region. All of the more complete Neanderthal fossils from Israel are now dated to the cool period of the last glacial cycle, suggesting that Neanderthals may have arrived in this region as a result of the southward expansion of their habitable range. The young age determined for the Tabun skeleton would suggest that Neanderthals survived as late in the Levant as they did in Europe. PMID:9929173

  20. Fission Fragment Yield, Cross Section and Prompt Neutron and Gamma Emission Data from Actinide Isotopes

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; Oberstedt, S.; Al-Adili, A.; Brys, T.; Billnert, R.; Matei, C.; Oberstedt, A.; Salvador-Castiñeira, P.; Tudora, A.; Vidali, M.

    2014-05-01

    Recent experimental investigations on major and minor actinides at the JRC-IRMM are presented. Fission-fragment distributions of isotopes with vibrational resonances in the sub-threshold fission cross section, i. e. 234,238U, have been measured. For 234U, the impact of an increased neutron multiplicity for the heavy fragments with higher incident neutron energies has been studied as observed in experiment and also recently theoretically predicted. The impact is found to be noticeable on post-neutron mass yields, which are the relevant quantities for a-priori waste assessments. The fission cross sections for 240,242Pu at threshold and in the plateau region are being investigated within the ANDES project. The results show some discrepancies to the ENDF/B-VII.1 evaluation mainly for 242Pu around 1 MeV, where the evaluation exhibits a resonance-like structure not observed so clearly in the present work. The requested target accuracy in design studies of innovative reactor concepts like Gen-IV is in the range of a few percent. In order to be able to respond to requests for measurements of prompt neutron and γ-ray emission in fission JRC-IRMM has also invested in setting up a neutron and γ-ray detector array. The neutron array is called SCINTIA and has so far been tested with 252Cf(SF). For γ-ray multiplicity and spectrum measurements of 252Cf(SF) and 235U(nth, f) lanthanum- and cerium-halide detectors were successfully used.

  1. The use of non-destructive passive neutron measurement methods in dismantling and radioactive waste characterization

    SciTech Connect

    Jallu, F.; Allinei, P. G.; Bernard, P.; Loridon, J.; Soyer, P.; Pouyat, D.; Torreblanca, L.; Reneleau, A.

    2011-07-01

    The cleaning up and dismantling of nuclear facilities lead to a great volume of technological radioactive wastes which need to be characterized in order to be sent to the adequate final disposal or interim storage. The control and characterization can be performed with non-destructive nuclear measurements such as gamma-ray spectrometry. Passive neutron counting is an alternative when the alpha-gamma emitters cannot be detected due to the presence of a high gamma emission resulting from fission or activation products, or when the waste matrix is too absorbing for the gamma rays of interest (too dense and/or made of high atomic number elements). It can also be a complement to gamma-ray spectrometry when two measurement results must be confronted to improve the confidence in the activity assessment. Passive neutron assays involve the detection of spontaneous fission neutrons emitted by even nuclides ({sup 238}Pu, {sup 240}Pu, {sup 242}Pu, {sup 242}Cm, {sup 244}Cm...) and neutrons resulting from ({alpha}, n) reactions with light nuclides (O, F, Be...). The latter is conditioned by the presence of high {alpha}-activity radionuclides ({sup 234}U, {sup 238}Pu, {sup 240}Pu, {sup 241}Am...) and low-Z elements, which depends on the chemical form (metallic, oxide or fluorine) of the plutonium or uranium contaminant. This paper presents the recent application of passive neutron methods to the cleaning up of a nuclear facility located at CEA Cadarache (France), which concerns the Pu mass assessment of 2714 historic, 100 litre radioactive waste drums produced between 1980 and 1997. Another application is the dismantling and decommissioning of an uranium enrichment facility for military purposes, which involves the {sup 235}U and total uranium quantifications in about a thousand, large compressors employed in the gaseous diffusion enrichment process. (authors)

  2. INDEPENDENT VERIFICATION SURVEY REPORT FOR EXPOSURE UNITS Z2-24, Z2-31, Z2-32, AND Z2-36 IN ZONE 2 OF THE EAST TENNESSEE TECHNOLOGY PARK OAK RIDGE, TENNESSEE

    SciTech Connect

    2013-10-10

    The U.S. Department of Energy (DOE) Oak Ridge Office of Environmental Management selected Oak Ridge Associated Universities (ORAU), through the Oak Ridge Institute for Science and Education (ORISE) contract, to perform independent verification (IV) at Zone 2 of the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee. ORAU has concluded IV surveys, per the project-specific plan (PSP) (ORAU 2013a) covering exposure units (EUs) Z2-24, -31, -32, and -36. The objective of this effort was to verify the following. • Target EUs comply with requirements in the Zone 2 Record of Decision (ROD) (DOE 2005), as implemented by using the dynamic verification strategy presented in the dynamic work plan (DWP) (BJC 2007) • Commitments in the DWP were adequately implemented, as verified via IV surveys and soil sampling The Zone 2 ROD establishes maximum remediation level (RLmax) values and average RL (RLavg) values for the primary contaminants of concern (COCs) U-234, U-235, U-238, Cs-137, Np-237, Ra-226, Th-232, arsenic, mercury, and polychlorinated biphenyls (PCBs). Table 1.1 lists Zone 2 COCs with associated RLs. Additional radiological and chemical contaminants were also identified during past characterization and monitoring actions, though the ROD does not present RLs for these potential contaminants. IV activities focused on the identification and quantification of ROD-specific COCs in surface soils, but also generated data for other analytes to support future decisions. ORAU personnel also reviewed EU-specific phased construction completion reports (PCCRs) to focus IV activities and identify potential judgmental sample locations, if any.

  3. Simultaneous determination of gross alpha, gross beta and ²²⁶Ra in natural water by liquid scintillation counting.

    PubMed

    Fons, J; Zapata-García, D; Tent, J; Llauradó, M

    2013-11-01

    The determination of gross alpha, gross beta and (226)Ra activity in natural waters is useful in a wide range of environmental studies. Furthermore, gross alpha and gross beta parameters are included in international legislation on the quality of drinking water [Council Directive 98/83/EC]. In this work, a low-background liquid scintillation counter (Wallac, Quantulus 1220) was used to simultaneously determine gross alpha, gross beta and (226)Ra activity in natural water samples. Sample preparation involved evaporation to remove (222)Rn and its short-lived decay daughters. The evaporation process concentrated the sample ten-fold. Afterwards, a sample aliquot of 8 mL was mixed with 12 mL of Ultima Gold AB scintillation cocktail in low-diffusion vials. In this study, a theoretical mathematical model based on secular equilibrium conditions between (226)Ra and its short-lived decay daughters is presented. The proposed model makes it possible to determine (226)Ra activity from two measurements. These measurements also allow determining gross alpha and gross beta simultaneously. To validate the proposed model, spiked samples with different activity levels for each parameter were analysed. Additionally, to evaluate the model's applicability in natural water, eight natural water samples from different parts of Spain were analysed. The eight natural water samples were also characterised by alpha spectrometry for the naturally occurring isotopes of uranium ((234)U, (235)U and (238)U), radium ((224)Ra and (226)Ra), (210)Po and (232)Th. The results for gross alpha and (226)Ra activity were compared with alpha spectrometry characterization, and an acceptable concordance was obtained. PMID:23415246

  4. The low-level radioactivity ocean sediment standard reference material

    SciTech Connect

    Inn, K.G.W.; Lin, Z.; Liggett, W.S.; Krey, P.W.

    1995-12-31

    Over the past decades, on the order of 10{sup 15} Becquerel nuclear waste have been stored in the oceans. Potential contamination of the oceans from leaking nuclear waste has caused world wide concern. Currently, early warning of ocean contamination near the waste dumping sites rely on monitoring systems being set up by different countries and agencies. Because the determination of low-level radioactivity in ocean sediment is a difficult technical task, a basis for measurement quality assurance, methods verification, and data comparability is needed. The recently certified NIST ocean sediment Standard Reference Material (SRM-4355) is a composite of 1% contaminated Irish Sea sediment and 99% of Chesapeake Bay sediment by weight. The sediments were blended, pulverized to a median particle size of 8 {mu}m, and reblended to achieve acceptable sample homogeneity. A statistical assessment of the intercomparison results from 19 laboratories has shown the material to be homogeneous down to 10 grams. The certified radionuclide concentration range from 0.4 to 230 mBq/g. A variety of radiochemical procedures and detection techniques have been used in the measurements to minimize possible systematic bias. Twelve radionuclides including {sup 40}K, {sup 90}Sr, {sup 137}Cs, {sup 226}Ra, {sup 228}Th, {sup 230}Th, {sup 232}Th, {sup 234}U, {sup 235}U, {sup 238}U, {sup 238}Pu, and {sup (239+240)}Pu were certified. The mean values were reported for an additional 10 uncertified radionuclides: {sup 129}I, {sup 155}Eu, {sup 210}Po, {sup 210}Pb, {sup 212}Pb, {sup 214}Pb, {sup 214}Bi, {sup 228}Ra, {sup 237}Np, and {sup 241}Am. The standard reference material in unit quantities of about 100 gram each will be available by the end of 1995.

  5. Investigating Pu and U isotopic compositions in sediments: a case study in Lake Obuchi, Rokkasho Village, Japan using sector-field ICP-MS and ICP-QMS.

    PubMed

    Zheng, Jian; Yamada, Masatoshi

    2005-08-01

    The objectives of the present work were to study isotope ratios and the inventory of plutonium and uranium isotope compositions in sediments from Lake Obuchi, which is in the vicinity of several nuclear fuel facilities in Rokkasho, Japan. Pu and its isotopes were determined using sector-field ICP-MS and U and its isotopes were determined with ICP-QMS after separation and purification with a combination of ion-exchange and extraction chromatography. The observed (240)Pu/(239)Pu atom ratio (0.186 +/- 0.016) was similar to that of global fallout, indicating that the possible early tropospheric fallout Pu did not deliver Pu from the Pacific Proving Ground to areas above 40 degrees N. The previously reported higher Pu inventory in the deep water area of Lake Obuchi could be attributed to the lateral transportation of Pu deposited in the shallow area which resulted from the migration of deposited global fallout Pu from the land into the lake by river runoff and from the Pacific Ocean by tide movement and sea water scavenging, as well as from direct soil input by winds. The (235)U/(238)U atom ratios ranged from 0.00723 to 0.00732, indicating the natural origin of U in the sediments. The average (234)U/(238)U activity ratio of 1.11 in a sediment core indicated a significant sea water U contribution. No evidence was found for the release of U containing wastes from the nearby nuclear facilities. These results will serve as a reference baseline on the levels of Pu and U in the studied site so that any further contamination from the spent nuclear fuel reprocessing plants, the radioactive waste disposal and storage facilities, and the uranium enrichment plant can be identified, and the impact of future release can be rapidly assessed. PMID:16049580

  6. Determination of elemental impurities and U and O isotopic compositions with a view to identify the geographical and industrial origins of uranium ore concentrates

    NASA Astrophysics Data System (ADS)

    Salaun, A.; Hubert, A.; Pointurier, F.; Aupiais, J.; Pili, E.; Richon, P.; Fauré, A.; Diallo, S.

    2012-12-01

    First events of illicit trafficking of nuclear and radiological materials occurred 50 years ago. Nuclear forensics expertise are aiming at determining the use of seized material, its industrial history and provenance (geographical area, place of production or processing), at assisting in the identification and dismantling of illicit trafficking networks. This information is also valuable in the context of inspections of declared facilities to verify the consistency of operator's declaration. Several characteristics can be used to determine the origin of uranium ore concentrates such as trace elemental impurity patterns (Keegan et al., 2008 ; Varga et al., 2010a, 2010b) or uranium, oxygen and lead isotopic compositions (Tamborini et al., 2002a, 2002b ; Wallenius et al., 2006; Varga et al., 2009). We developed analytical procedures for measuring the isotopic compositions of uranium (234U/238U and 235U/238U) and oxygen (18O/16O) and levels of elemental impurities (e.g. REE, Th) from very small amounts of uranium ore concentrates (or yellow cakes). Micrometer particles and few milligrams of material are used for oxygen isotope measurements and REE determination, respectively. Reference materials were analyzed by mass spectrometry (TIMS, SF-ICP-MS and SIMS) to validate testing protocols. Finally, materials of unknown origin were analyzed to highlight significant differences and determine whether these differences allow identifying the origin of these ore concentrates. References: Keegan, E., et al. (2008). Applied Geochemistry 23, 765-777. Tamborini, G., et al. (2002a). Analytical Chemistry 74, 6098-6101. Tamborini, G., et al. (2002b). Microchimica Acta 139, 185-188. Varga, Z., et al. (2009). Analytical Chemistry 81, 8327-8334. Varga, Z., et al. (2010a). Talanta 80, 1744-1749. Varga, Z., et al. (2010b). Radiochimica Acta 98, 771-778 Wallenius, M., et al. (2006). Forensic Science International 156, 55-62.

  7. Comparison of Grab, Air, and Surface Results for Radiation Site Characterization

    NASA Astrophysics Data System (ADS)

    Glassford, Eric Keith

    2011-12-01

    The use of proper sampling methods and sample types for evaluating sites believed to be contaminated with radioactive materials is necessary to avoid misrepresenting conditions at the site. This study was designed to investigate if the site characterization, based upon uranium contamination measured in different types of samples, is dependent upon the mass of the sample collected. A bulk sample of potentially contaminated interior dirt was collected from an abandoned metal processing mill that rolled uranium between 1948 and 1956. The original mill dates from 1910 and has a dirt floor. The bulk sample was a mixture of dirt, black and yellow particles of metal dust, and small fragments of natural debris. Small mass (approximately 0.75 grams (g)) and large mass (approximately 70g) grab samples were prepared from the bulk sample material to simulate collection of a "grab" type sample. Air sampling was performed by re-suspending a portion of the bulk sample material using a vibration table to simulate airborne contamination that might be present during site remediation. Additionally, samples of removable contaminated surface dust were collected on 47 mm diameter filter paper by wiping the surfaces of the exposure chamber used to resuspend the bulk material. Certified reference materials, one containing a precisely known quantity of U 3O8 and one containing a known quantity of natural uranium, were utilized to calibrate the gamma spectrometry measurement system. Non-destructive gamma spectrometry measurements were used to determine the content of uranium-235 (235U) at 185 keV and 143 keV, thorium-234 (234Th) at 63 keV, and protactinium-234m (234mPa) at 1001 keV in each sample. Measurement of natural uranium in small, 1 g samples is usually accomplished by radiochemical analysis in order to measure alpha particles emitted by 238U, 235U, and 234U. However, uranium in larger bulk samples can also be measured non-destructively using gamma spectrometry to detect the low

  8. Measurements of ²³⁶U in ancient and modern peat samples and implications for postdepositional migration of fallout radionuclides.

    PubMed

    Quinto, Francesca; Hrnecek, Erich; Krachler, Michael; Shotyk, William; Steier, Peter; Winkler, Stephan R

    2013-05-21

    (236)U was analyzed in an ombrotrophic peat core representing the last 80 years of atmospheric deposition and a minerotrophic peat sample from the last interglacial period. The determination of (236)U at levels of 10(7) atoms/g was possible by using ultraclean laboratory procedures and accelerator mass spectrometry. The vertical profile of the (236)U/(238)U isotopic ratio along the ombrotrophic peat core represents the first observation of the (236)U bomb peak in a terrestrial environment. A constant level of anthropogenic (236)U with an average (236)U/(238)U isotopic ratio of (1.24 ± 0.08) × 10(-6) in the top layers of the core was observed. Comparing the abundances of the global fallout derived (236)U and (239)Pu along the peat core, the post depositional migration of plutonium clearly exceeds that of uranium. However, the cumulative (236)U/(239)Pu ratio of 0.62 ± 0.31 is in agreement with previous studies on the global fallout uranium and plutonium. In the interglacial peat samples a (236)U/(238)U isotopic ratio of (3.3 ± 0.7) × 10(-12) was detected; although this measurement is an upper limit, it constitutes a significant step forward in the experimental determination of the natural (236)U abundance and represents a true background sample for the ombrotrophic peat core.

  9. Uranium series disequilibria in ground waters from a fractured bedrock aquifer (Morungaba Granitoids--Southern Brazil): implications to the hydrochemical behavior of dissolved U and Ra.

    PubMed

    Reyes, Erika; Marques, Leila S

    2008-10-01

    Activity concentrations of dissolved (234)U, (238)U, (226)Ra and (228)Ra were determined in ground waters from two deep wells drilled in Morungaba Granitoids (Southern Brazil). Sampling was done monthly for little longer than 1 year. Significant disequilibrium between (238)U, (234)U and (226)Ra were observed in all samples. The variation of (238)U and (234)U activity concentrations and (234)U/(238)U activity ratios is related to seasonal changes. Although the distance between the two wells is short (about 900 m), systematic differences of activity concentrations of U isotopes, as well as of (234)U/(238)U, (226)Ra/(234)U and (228)Ra/(226)Ra activity ratios were noticed, indicating distinct host rock-water interactions. Slightly acidic ground water percolation through heterogeneous host rock, associated with different recharge processes, may explain uranium and radium isotope behavior.

  10. Determination the total neutron yields of several semiconductor compounds using various alpha emitters

    NASA Astrophysics Data System (ADS)

    Abdullah, Ramadhan Hayder; Sabr, Barzan Nehmat

    2016-03-01

    In the present work, the cross-sections of (α,n) reactions available in the literature as a function of α-particle energies for light and medium elements have been rearranged for α-particle energies from near threshold up to 10 MeV in steps of (0.050MeV) using the (Excel and Matlab) computer programs. The obtained data were used to calculate the neutron yields (n/106α) using the quick basic-computer program (Simpson Rules). The stopping powers of alpha particle energies from near threshold to 10 MeV for light and medium elements such as (nat.Be,10B,11B,13C,14N,nat.O,nat.F,nat.Mg,nat.Al,29Si,30Si, nat.P and 46.48Ti) have been calculated using the Zeigler formula. The kinetic energies (Tα) and the branching ratios of each α-emitters such as (211Bi, 210Po, 211Po, 215Po, 217At, 218Rn, 219Rn, 222Rn, 224Ra, 226Ra, 215Th, 228Th, 232U, 234U, 236U, 238U, 238Pu, 239Pu, 241Am, 245Es, 252Fm, 254Fm, 256Fm, 257Fm and 257Md) are taken into consideration to calculate the mean kinetic energy . The polynomial expressions were used to fitting the calculated weighted average of neutron yields (n/106α) for natural light and medium elements such as (Be, B, C, N, O, F, Mg, Al, Si, P and Ti) to determine the adopted neutron yields from the best fitting equation with minimum (CHISQ) at mean kinetic energies of various α-emitters. The total neutron yields (n/s/gx/ppmi) of the mentioned natural light and medium elements have been calculated using the adopted neutron yields (n/106α) from the fitting equations at mean kinetic energies of various α-emitters. The total neutron yields (n/s/gα-emitters/gcompounds) of semiconductor compounds such as (AlN, AlP, BN, BP, SiC, TiO2, BeSiN2, MgCN2, MgSiN2 and MgSiP2) have been calculated by mixing (1gram) of compounds with (1gram) of pure α-emitters using the quick basic computer program. The aim of the present work is to constructed and fabricate the neutron sources theoretically

  11. URANIUM-SERIES DISEQUILIBRIUM IN TUFF AND GRANITE:HYDROGEOLOGICAL IMPLICATIONS

    SciTech Connect

    M. Gasscoyne; N.H. Miller

    2000-10-27

    Uranium occurs naturally at trace levels in the major rock-forming minerals (quartz, feldspars, micas) in volcanic and plutonic rocks and is concentrated in accessory minerals (zircon, sphene, apatite). It may attain concentrations as high as 1000 ppm in the accessory minerals. Radiometric age determinations on zircon and sphene have shown that uranium migration from these minerals is generally negligible over prolonged periods of geologic time. Zircon grains separated from highly weathered igneous rocks have been found to retain most of their uranium. In contrast, the uranium fixed onto mineral grain boundaries or present in less-resistant minerals such as biotite or hornblende can be readily leached by groundwater. The ubiquitous presence of uranium in a rock makes it an ideal ''natural analogue'' for understanding the mobility of uranium at a potential site for nuclear fuel waste disposal and one that is easily overlooked in the search for suitable analogues for a disposal site. Several of the intermediate radionuclides in the decay series of the two long-lived isotopes of uranium ({sup 238}U and {sup 235}U) have half-lives greater than one year and are, therefore, of geological interest. In a sealed rock mass with no water-rock interactions, all intermediate radionuclides attain radioactive equilibrium with one another within a maximum 1-2 million years. Because rocks of the Yucca Mountain area and the Canadian Shield (both potential sites for nuclear waste disposal in the United States and Canadian programs, respectively) are considerably older, this condition (known as secular equilibrium) should exist in these rocks, and all daughter/parent radionuclide activity ratios should equal unity (1.000). If the ratios are found not to equal unity, then the rock has been disturbed, probably by groundwater transport of more soluble radionuclides into or away from the rock. How recently this migration has occurred can be determined from the half-life of the

  12. Measurements with the high flux lead slowing-down spectrometer at LANL

    NASA Astrophysics Data System (ADS)

    Danon, Y.; Romano, C.; Thompson, J.; Watson, T.; Haight, R. C.; Wender, S. A.; Vieira, D. J.; Bond, E.; Wilhelmy, J. B.; O'Donnell, J. M.; Michaudon, A.; Bredeweg, T. A.; Schurman, T.; Rochman, D.; Granier, T.; Ethvignot, T.; Taieb, J.; Becker, J. A.

    2007-08-01

    A Lead Slowing-Down Spectrometer (LSDS) was recently installed at LANL [D. Rochman, R.C. Haight, J.M. O'Donnell, A. Michaudon, S.A. Wender, D.J. Vieira, E.M. Bond, T.A. Bredeweg, A. Kronenberg, J.B. Wilhelmy, T. Ethvignot, T. Granier, M. Petit, Y. Danon, Characteristics of a lead slowing-down spectrometer coupled to the LANSCE accelerator, Nucl. Instr. and Meth. A 550 (2005) 397]. The LSDS is comprised of a cube of pure lead 1.2 m on the side, with a spallation pulsed neutron source in its center. The LSDS is driven by 800 MeV protons with a time-averaged current of up to 1 μA, pulse widths of 0.05-0.25 μs and a repetition rate of 20-40 Hz. Spallation neutrons are created by directing the proton beam into an air-cooled tungsten target in the center of the lead cube. The neutrons slow down by scattering interactions with the lead and thus enable measurements of neutron-induced reaction rates as a function of the slowing-down time, which correlates to neutron energy. The advantage of an LSDS as a neutron spectrometer is that the neutron flux is 3-4 orders of magnitude higher than a standard time-of-flight experiment at the equivalent flight path, 5.6 m. The effective energy range is 0.1 eV to 100 keV with a typical energy resolution of 30% from 1 eV to 10 keV. The average neutron flux between 1 and 10 keV is about 1.7 × 109 n/cm2/s/μA. This high flux makes the LSDS an important tool for neutron-induced cross section measurements of ultra-small samples (nanograms) or of samples with very low cross sections. The LSDS at LANL was initially built in order to measure the fission cross section of the short-lived metastable isotope of U-235, however it can also be used to measure (n, α) and (n, p) reactions. Fission cross section measurements were made with samples of 235U, 236U, 238U and 239Pu. The smallest sample measured was 10 ng of 239Pu. Measurement of (n, α) cross section with 760 ng of Li-6 was also demonstrated. Possible future cross section measurements

  13. ENDF/B-VII.1 Neutron Cross Section Data Testing with Critical Assembly Benchmarks and Reactor Experiments

    SciTech Connect

    Kahler, A.; Macfarlane, R E; Mosteller, R D; Kiedrowski, B C; Frankle, S C; Chadwick, M. B.; Mcknight, R D; Lell, R M; Palmiotti, G; Hiruta, h; Herman, Micheal W; Arcilla, r; Mughabghab, S F; Sublet, J C; Trkov, A.; Trumbull, T H; Dunn, Michael E

    2011-01-01

    The ENDF/B-VII.1 library is the latest revision to the United States' Evaluated Nuclear Data File (ENDF). The ENDF library is currently in its seventh generation, with ENDF/B-VII.0 being released in 2006. This revision expands upon that library, including the addition of new evaluated files (was 393 neutron files previously, now 423 including replacement of elemental vanadium and zinc evaluations with isotopic evaluations) and extension or updating of many existing neutron data files. Complete details are provided in the companion paper [1]. This paper focuses on how accurately application libraries may be expected to perform in criticality calculations with these data. Continuous energy cross section libraries, suitable for use with the MCNP Monte Carlo transport code, have been generated and applied to a suite of nearly one thousand critical benchmark assemblies defined in the International Criticality Safety Benchmark Evaluation Project's International Handbook of Evaluated Criticality Safety Benchmark Experiments. This suite covers uranium and plutonium fuel systems in a variety of forms such as metallic, oxide or solution, and under a variety of spectral conditions, including unmoderated (i.e., bare), metal reflected and water or other light element reflected. Assembly eigenvalues that were accurately predicted with ENDF/B-VII.0 cross sections such as unrnoderated and uranium reflected (235)U and (239)Pu assemblies, HEU solution systems and LEU oxide lattice systems that mimic commercial PWR configurations continue to be accurately calculated with ENDF/B-VII.1 cross sections, and deficiencies in predicted eigenvalues for assemblies containing selected materials, including titanium, manganese, cadmium and tungsten are greatly reduced. Improvements are also confirmed for selected actinide reaction rates such as (236)U; (238,242)Pu and (241,243)Am capture in fast systems. Other deficiencies, such as the overprediction of Pu solution system critical eigenvalues

  14. ENDF/B-VII.1 Neutron Cross Section Data Testing with Critical Assembly Benchmarks and Reactor Experiments

    SciTech Connect

    G. Palmiotti

    2011-12-01

    The ENDF/B-VII.1 library is the latest revision to the United States' Evaluated Nuclear Data File (ENDF). The ENDF library is currently in its seventh generation, with ENDF/B-VII.0 being released in 2006. This revision expands upon that library, including the addition of new evaluated files (was 393 neutron files previously, now 418 including replacement of elemental vanadium and zinc evaluations with isotopic evaluations) and extension or updating of many existing neutron data files. Complete details are provided in the companion paper [1]. This paper focuses on how accurately application libraries may be expected to perform in criticality calculations with these data. Continuous energy cross section libraries, suitable for use with the MCNP Monte Carlo transport code, have been generated and applied to a suite of nearly one thousand critical benchmark assemblies defined in the International Criticality Safety Benchmark Evaluation Project's International Handbook of Evaluated Criticality Safety Benchmark Experiments. This suite covers uranium and plutonium fuel systems in a variety of forms such as metallic, oxide or solution, and under a variety of spectral conditions, including unmoderated (i.e., bare), metal reflected and water or other light element reflected. Assembly eigenvalues that were accurately predicted with ENDF/B-VII.0 cross sections such as unmoderated and uranium reflected 235U and 239Pu assemblies, HEU solution systems and LEU oxide lattice systems that mimic commercial PWR configurations continue to be accurately calculated with ENDF/B-VII.1 cross sections, and deficiencies in predicted eigenvalues for assemblies containing selected materials, including titanium, manganese, cadmium and tungsten are greatly reduced. Improvements are also confirmed for selected actinide reaction rates such as 236U capture. Other deficiencies, such as the overprediction of Pu solution system critical eigenvalues and a decreasing trend in calculated eigenvalue for

  15. ENDF/B-VII.1 Neutron Cross Section Data Testing with Critical Assembly Benchmarks and Reactor Experiments

    SciTech Connect

    Kahler, A.C.; Herman, M.; Kahler,A.C.; MacFarlane,R.E.; Mosteller,R.D.; Kiedrowski,B.C.; Frankle,S.C.; Chadwick,M.B.; McKnight,R.D.; Lell,R.M.; Palmiotti,G.; Hiruta,H.; Herman,M.; Arcilla,R.; Mughabghab,S.F.; Sublet,J.C.; Trkov,A.; Trumbull,T.H.; Dunn,M.

    2011-12-01

    The ENDF/B-VII.1 library is the latest revision to the United States Evaluated Nuclear Data File (ENDF). The ENDF library is currently in its seventh generation, with ENDF/B-VII.0 being released in 2006. This revision expands upon that library, including the addition of new evaluated files (was 393 neutron files previously, now 423 including replacement of elemental vanadium and zinc evaluations with isotopic evaluations) and extension or updating of many existing neutron data files. Complete details are provided in the companion paper [M. B. Chadwick et al., 'ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data,' Nuclear Data Sheets, 112, 2887 (2011)]. This paper focuses on how accurately application libraries may be expected to perform in criticality calculations with these data. Continuous energy cross section libraries, suitable for use with the MCNP Monte Carlo transport code, have been generated and applied to a suite of nearly one thousand critical benchmark assemblies defined in the International Criticality Safety Benchmark Evaluation Project's International Handbook of Evaluated Criticality Safety Benchmark Experiments. This suite covers uranium and plutonium fuel systems in a variety of forms such as metallic, oxide or solution, and under a variety of spectral conditions, including unmoderated (i.e., bare), metal reflected and water or other light element reflected. Assembly eigenvalues that were accurately predicted with ENDF/B-VII.0 cross sections such as unmoderated and uranium reflected {sup 235}U and {sup 239}Pu assemblies, HEU solution systems and LEU oxide lattice systems that mimic commercial PWR configurations continue to be accurately calculated with ENDF/B-VII.1 cross sections, and deficiencies in predicted eigenvalues for assemblies containing selected materials, including titanium, manganese, cadmium and tungsten are greatly reduced. Improvements are also confirmed for

  16. Measurements of daily urinary uranium excretion in German peacekeeping personnel and residents of the Kosovo region to assess potential intakes of depleted uranium (DU).

    PubMed

    Oeh, U; Priest, N D; Roth, P; Ragnarsdottir, K V; Li, W B; Höllriegl, V; Thirlwall, M F; Michalke, B; Giussani, A; Schramel, P; Paretzke, H G

    2007-08-01

    Following the end of the Kosovo conflict, in June 1999, a study was instigated to evaluate whether there was a cause for concern of health risk from depleted uranium (DU) to German peacekeeping personnel serving in the Balkans. In addition, the investigations were extended to residents of Kosovo and southern Serbia, who lived in areas where DU ammunitions were deployed. In order to assess a possible DU intake, both the urinary uranium excretion of volunteer residents and water samples were collected and analysed using inductively coupled plasma-mass spectrometry (ICP-MS). More than 1300 urine samples from peacekeeping personnel and unexposed controls of different genders and age were analysed to determine uranium excretion parameters. The urine measurements for 113 unexposed subjects revealed a daily uranium excretion rate with a geometric mean of 13.9 ng/d (geometric standard deviation (GSD)=2.17). The analysis of 1228 urine samples from the peacekeeping personnel resulted in a geometric mean of 12.8 ng/d (GSD=2.60). It follows that both unexposed controls and peacekeeping personnel excreted similar amounts of uranium. Inter-subject variation in uranium excretion was high and no significant age-specific differences were found. The second part of the study monitored 24 h urine samples provided by selected residents of Kosovo and adjacent regions of Serbia compared to controls from Munich, Germany. Total uranium and isotope ratios were measured in order to determine DU content. (235)U/(238)U ratios were within +/-0.3% of the natural value, and (236)U/(238)U was less than 2 x 10(-7), indicating no significant DU in any of the urine samples provided, despite total uranium excretion being relatively high in some cases. Measurements of ground and tap water samples from regions where DU munitions were deployed did not show any contamination with DU, except in one sample. It is concluded that both peacekeeping personnel and residents serving or living in the Balkans

  17. ENDF/B-VII.1 Neutron Cross Section Data Testing with Critical Assembly Benchmarks and Reactor Experiments

    NASA Astrophysics Data System (ADS)

    Kahler, A. C.; MacFarlane, R. E.; Mosteller, R. D.; Kiedrowski, B. C.; Frankle, S. C.; Chadwick, M. B.; McKnight, R. D.; Lell, R. M.; Palmiotti, G.; Hiruta, H.; Herman, M.; Arcilla, R.; Mughabghab, S. F.; Sublet, J. C.; Trkov, A.; Trumbull, T. H.; Dunn, M.

    2011-12-01

    The ENDF/B-VII.1 library is the latest revision to the United States' Evaluated Nuclear Data File (ENDF). The ENDF library is currently in its seventh generation, with ENDF/B-VII.0 being released in 2006. This revision expands upon that library, including the addition of new evaluated files (was 393 neutron files previously, now 423 including replacement of elemental vanadium and zinc evaluations with isotopic evaluations) and extension or updating of many existing neutron data files. Complete details are provided in the companion paper [M. B. Chadwick et al., "ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data," Nuclear Data Sheets, 112, 2887 (2011)]. This paper focuses on how accurately application libraries may be expected to perform in criticality calculations with these data. Continuous energy cross section libraries, suitable for use with the MCNP Monte Carlo transport code, have been generated and applied to a suite of nearly one thousand critical benchmark assemblies defined in the International Criticality Safety Benchmark Evaluation Project's International Handbook of Evaluated Criticality Safety Benchmark Experiments. This suite covers uranium and plutonium fuel systems in a variety of forms such as metallic, oxide or solution, and under a variety of spectral conditions, including unmoderated (i.e., bare), metal reflected and water or other light element reflected. Assembly eigenvalues that were accurately predicted with ENDF/B-VII.0 cross sections such as unmoderated and uranium reflected 235U and 239Pu assemblies, HEU solution systems and LEU oxide lattice systems that mimic commercial PWR configurations continue to be accurately calculated with ENDF/B-VII.1 cross sections, and deficiencies in predicted eigenvalues for assemblies containing selected materials, including titanium, manganese, cadmium and tungsten are greatly reduced. Improvements are also confirmed for selected

  18. Precision and accuracy of decay constants and age standards

    NASA Astrophysics Data System (ADS)

    Villa, I. M.

    2011-12-01

    40 years of round-robin experiments with age standards teach us that systematic errors must be present in at least N-1 labs if participants provide N mutually incompatible data. In EarthTime, the U-Pb community has produced and distributed synthetic solutions with full metrological traceability. Collector linearity is routinely calibrated under variable conditions (e.g. [1]). Instrumental mass fractionation is measured in-run with double spikes (e.g. 233U-236U). Parent-daughter ratios are metrologically traceable, so the full uncertainty budget of a U-Pb age should coincide with interlaboratory uncertainty. TIMS round-robin experiments indeed show a decrease of N towards the ideal value of 1. Comparing 235U-207Pb with 238U-206Pb ages (e.g. [2]) has resulted in a credible re-evaluation of the 235U decay constant, with lower uncertainty than gamma counting. U-Pb microbeam techniques reveal the link petrology-microtextures-microchemistry-isotope record but do not achieve the low uncertainty of TIMS. In the K-Ar community, N is large; interlaboratory bias is > 10 times self-assessed uncertainty. Systematic errors may have analytical and petrological reasons. Metrological traceability is not yet implemented (substantial advance may come from work in progress, e.g. [7]). One of the worst problems is collector stability and linearity. Using electron multipliers (EM) instead of Faraday buckets (FB) reduces both dynamic range and collector linearity. Mass spectrometer backgrounds are never zero; the extent as well as the predictability of their variability must be propagated into the uncertainty evaluation. The high isotope ratio of the atmospheric Ar requires a large dynamic range over which linearity must be demonstrated under all analytical conditions to correctly estimate mass fractionation. The only assessment of EM linearity in Ar analyses [3] points out many fundamental problems; the onus of proof is on every laboratory claiming low uncertainties. Finally, sample

  19. Concentrations of Radionuclides and Trace Elements in Environmantal Media arond te Dual-Axis Radiographic Hydrodynamic Test Facilit at Los Alamos National Laboratory during 2005

    SciTech Connect

    G.J.Gonzales; P.R. Fresquez; C.D.Hathcock; D.C. Keller

    2006-05-15

    The Mitigation Action Plan (MAP) for the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory requires that samples of biotic and abiotic media be collected after operations began to determine if there are any human health or environmental impacts. The DARHT facility is the Laboratory's principal explosive test facility. To this end, samples of soil and sediment, vegetation, bees, and birds were collected around the facility in 2005 and analyzed for concentrations of {sup 3}H, {sup 137}Cs, {sup 90}Sr, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, {sup 234}U, {sup 235}U, {sup 238}U, Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Bird populations have also been monitored. Contaminant results, which represent up to six sample years since the start of operations, were compared with (1) baseline statistical reference levels (BSRLs) established over a four-year preoperational period before DARHT facility operations, (2) screening levels (SLs), and (3) regulatory standards. Most radionuclides and trace elements were below BSRLs and those few samples that contained radionuclides and trace elements above BSRLs were below SLs. Concentrations of radionuclides and nonradionuclides in biotic and abiotic media around the DARHT facility do not pose a significant human health hazard. The total number of birds captured and number of species represented were similar in 2003 and 2004, but both of these parameters increased substantially in 2005. Periodic interruption of the scope and schedule identified in the MAP generally should have no impact on meeting the intent of the MAP. The risk of not sampling one of the five media in any given year is that if a significant impact to contaminant levels were to occur there would exist a less complete understanding of the extent of the change to the baseline for these media and to the ecosystem as a whole. Since the MAP is a requirement that was established under the regulatory framework of the

  20. Analysis of the Younger Dryas Impact Layer

    SciTech Connect

    Firestone, Richard B.; West, Allen; Revay, Zsolt; Hagstrum, Jonathon T,; Belgya, Thomas; Hee, Shane S. Que; Smith, Alan R.

    2010-02-27

    We have uncovered a thin layer of magnetic grains and microspherules, carbon spherules, and glass-like carbon at nine sites across North America, a site in Belgium, and throughout the rims of 16 Carolina Bays. It is consistent with the ejecta layer from an impact event and has been dated to 12.9 ka BP coinciding with the onset of Younger Dryas (YD) cooling and widespread megafaunal extinctions in North America. At many locations the impact layer is directly below a black mat marking the sudden disappearance of the megafauna and Clovis people. The distribution pattern of the Younger Dryas boundary (YDB) ejecta layer is consistent with an impact near the Great Lakes that deposited terrestrial-like ejecta near the impact site and unusual, titanium-rich projectile-like ejecta further away. High water content associated with the ejecta, up to 28 at. percent hydrogen (H), suggests the impact occurred over the Laurentide Ice Sheet. YDB microspherules and magnetic grains are highly enriched in TiO{sub 2}. Magnetic grains from several sites are enriched in iridium (Ir), up to 117 ppb. The TiO{sub 2}/FeO, K/Th, TiO{sub 2}/Zr, Al{sub 2}O{sub 3}/FeO+MgO, CaO/Al{sub 2}O{sub 3}, REE/ chondrite, FeO/MnO ratios and SiO{sub 2}, Na{sub 2}O, K{sub 2}O, Cr{sub 2}O{sub 3}, Ni, Co, U, Th and other trace element abundances are inconsistent with all terrestrial and extraterrestrial (ET) sources except for KREEP, a lunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus (P), and other incompatible elements including U and Th. Normal Fe, Ti, and {sup 238}U/{sup 235}U isotopic abundances were found in the magnetic grains, but {sup 234}U was enriched over equilibrium values by 50 percent in Murray Springs and by 130 percent in Belgium. 40K abundance is enriched by up to 100 percent in YDB sediments and Clovis chert artifacts. Highly vesicular carbon spherules containing nanodiamonds, glass-like carbon, charcoal and soot found in large quantities in the YDB layer are

  1. RAPID DETERMINATION OF ACTINIDES IN URINE BY INDUCTIVELY-COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY: A HYBRID APPROACH

    SciTech Connect

    Maxwell, S.; Jones, V.

    2009-05-27

    A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are split between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. 239Pu, 242Pu, 237Np, 243Am, 234U, 235U and 238U were measured by ICP-MS, while 236Pu, 238Pu, 239Pu, 241Am, 243Am and 244Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead

  2. Ambient environmental profile for the Savannah River Site.

    PubMed

    Rollins, Eugene M

    2008-07-01

    One of the steps that has been taken to expedite the radiation dose reconstruction process is the development of "site profiles." These reports, one of which has been prepared for each of the major U.S. Department of Energy nuclear sites, include detailed assessments of the dose rates at a given site due to on-site exposures. Presented in this paper is a summary of the development of the ambient environmental dose profile for the Savannah River Site (SRS) for specific time periods from 1951-2001. Internal doses were estimated based on the radionuclide concentrations in the atmosphere due to individual facility releases and the resuspension of radioactive materials from the soil. External doses were estimated on the basis of releases of noble gases and contributions from ambient background radiation, which had been elevated due to various on-site activities. Although the annual environmental reports for the SRS served as a major resource for this effort, considerable work was required to access these data in terms of the accompanying dose rates. This was due, for example, to the confounding effects of nuclear weapons testing, lack of spatial and radionuclide resolution, and insensitivity of sampling methods to radionuclides important to dose. To overcome these problems, methods were developed to use well-documented source terms from reports published by others, coupled with historical meteorological records, to estimate specific airborne concentrations for radionuclides such as 3H, 41Ar, 131I, 234U, 235U, 238U, 238Pu, 239Pu, and 240Pu. Airborne concentration calculations included spatial and release height considerations for source terms at eight different production facilities. The resulting estimates then were used to derive annual intakes based on an assumed individual breathing rate of 2,400 m3 y(-1). Annual intakes resulting from resuspension of radionuclides from soil were based on maximum soil concentrations located in appropriate areas. This being

  3. Variations in Cenozoic seawater uranium reconstructed from well preserved aragonitic fossil corals

    NASA Astrophysics Data System (ADS)

    Gothmann, A. O.; Higgins, J. A.; Bender, M. L.; Stolarski, J.; Adkins, J. F.; McKeon, R. E.; Farley, K. A.; Wang, X.; Planavsky, N.

    2015-12-01

    U/Ca ratios were measured in a subset (n ≈ 30) of well preserved scleractinian fossil corals previously described by Gothmann et al. (2015) in order to investigate Cenozoic changes in seawater [U]. He/U dating studies and measurements of 234U/238U and δ238/235U provide constraints on fossil coral U preservation. He/U ages also demonstrate the ability of well preserved coral aragonite to retain most of its radiogenic He over million year timescales. We find that fossil coral U/Ca has increased by a factor of ~4 between the Early Cenozoic and today. This number is calculated from the change in seawater [Ca2+] implied by brine inclusions and other proxies, and the assumption that the U/Ca in shallow water corals equals the seawater ratio. The change cannot be attributed to a dependence of coral U uptake on seawater pH or [CO32-] (e.g., Inoue et al., 2011), which would lead to a decrease in U/Ca going forward in time. Instead, we suggest that seawater [U] has increased since the Early Cenozoic. Possible explanations for the inferred change include: (1) a small decrease in uranium uptake in suboxic and anoxic sediments over the Cenozoic, (2) a decrease in the rate of low-temperature hydrothermal alteration, and associated U uptake, over the Cenozoic, and (3) a decrease in U removal from seawater resulting from an increase in UO2-CO3 complexation, as originally suggested by Broecker (1971). References: Broecker, W. S. (1971) A Kinetic Model for the Chemical Composition of Sea Water. Quaternary Research, 1, 188-207. Gothmann, A.M., Stolarski, J., Adkins, J.F., Dennis, K.J., Schrag, D.P., Schoene, B., Bender, M.L. (2015) Fossil corals as an archive of secular variations in seawater chemistry. Geochimica et Cosmochimica Acta, 160, 188-208. Inoue, M., Suwa, R., Suzuki, A., Sakai, K., and Kawahata, H., (2011) Effects of seawater pH on growth and skeletal U/Ca ratios of Acropora digitifera coral polyps. Geophysical Research Letters 38, 12801-12804.

  4. Recent fission cross section standards measurements

    SciTech Connect

    Wasson, O.A.

    1985-01-01

    The /sup 235/U(n,f) reaction is the standard by which most neutron induced fission cross sections are determined. Most of these cross sections are derived from relatively easy ratio measurements to /sup 235/U. However, the more difficult /sup 235/U(n,f) cross section measurements require the use of advanced neutron detectors for the determination of the incident neutron fluence. Examples of recent standard cross section measurements are discussed, various neutron detectors are described, and the status of the /sup 235/U(n,f) cross section standard is assessed. 23 refs., 8 figs., 4 tabs.

  5. Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137

    PubMed Central

    Sakaguchi, Aya; Kadokura, Akinobu; Steier, Peter; Takahashi, Yoshio; Shizuma, Kiyoshi; Hoshi, Masaharu; Nakakuki, Tomoeki; Yamamoto, Masayoshi

    2012-01-01

    We present a feasibility study for using 236U as an oceanic circulation tracer based on depth profiles of 236U and 137Cs in the Japan/East Sea. The concentration of the predominantly anthropogenic 236U, measured with Accelerator Mass Spectrometry (AMS), decreased from (13±3)×106 atom/kg in surface water to (1.6±0.3)×106 atom/kg close to the sea floor (2800 m). The profile has a smooth trend with depth and concentration values are generally proportional to that of 137Cs for the same water samples, but with a slightly lower ratio of 137Cs/236U below 2000 m. The cumulative inventory of dissolved 236U in the water column was estimated to be (13.7±0.9)×1012 atom/m2, which is similar to the global-fallout level (17.8×1012 atom/m2) in Japan. Additional analyses of suspended solids (SS) and bottom sediments yielded negligible amounts of 236U. Our results suggest that 236U behaves as a conservative nuclide in seawater, with potential advantages over other tracers of oceanic circulation. PMID:23564965

  6. Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Aya; Kadokura, Akinobu; Steier, Peter; Takahashi, Yoshio; Shizuma, Kiyoshi; Hoshi, Masaharu; Nakakuki, Tomoeki; Yamamoto, Masayoshi

    2012-06-01

    We present a feasibility study for using 236U as an oceanic circulation tracer based on depth profiles of 236U and 137Cs in the Japan/East Sea. The concentration of the predominantly anthropogenic 236U, measured with Accelerator Mass Spectrometry (AMS), decreased from (13±3)×106 atom/kg in surface water to (1.6±0.3)×106 atom/kg close to the sea floor (2800 m). The profile has a smooth trend with depth and concentration values are generally proportional to that of 137Cs for the same water samples, but with a slightly lower ratio of 137Cs/236U below 2000 m. The cumulative inventory of dissolved 236U in the water column was estimated to be (13.7±0.9)×1012 atom/m2, which is similar to the global-fallout level (17.8×1012 atom/m2) in Japan. Additional analyses of suspended solids (SS) and bottom sediments yielded negligible amounts of 236U. Our results suggest that 236U behaves as a conservative nuclide in seawater, with potential advantages over other tracers of oceanic circulation.

  7. Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137.

    PubMed

    Sakaguchi, Aya; Kadokura, Akinobu; Steier, Peter; Takahashi, Yoshio; Shizuma, Kiyoshi; Hoshi, Masaharu; Nakakuki, Tomoeki; Yamamoto, Masayoshi

    2012-06-01

    We present a feasibility study for using (236)U as an oceanic circulation tracer based on depth profiles of (236)U and (137)Cs in the Japan/East Sea. The concentration of the predominantly anthropogenic (236)U, measured with Accelerator Mass Spectrometry (AMS), decreased from (13±3)×10(6) atom/kg in surface water to (1.6±0.3)×10(6) atom/kg close to the sea floor (2800 m). The profile has a smooth trend with depth and concentration values are generally proportional to that of (137)Cs for the same water samples, but with a slightly lower ratio of (137)Cs/(236)U below 2000 m. The cumulative inventory of dissolved (236)U in the water column was estimated to be (13.7±0.9)×10(12) atom/m(2), which is similar to the global-fallout level (17.8×10(12) atom/m(2)) in Japan. Additional analyses of suspended solids (SS) and bottom sediments yielded negligible amounts of (236)U. Our results suggest that (236)U behaves as a conservative nuclide in seawater, with potential advantages over other tracers of oceanic circulation.

  8. Constrains on the Uranium Isotopic Composition of Seawater and Implications for Coral U/Th Geochronology

    NASA Astrophysics Data System (ADS)

    Chutcharavan, P. M.; Dutton, A.; Ellwood, M. J.

    2015-12-01

    Coral U-series geochronology is an important tool for calibrating records of sea level change during the late Quaternary and coral 14C dates for the radiocarbon timescale. However, coralline aragonite is highly susceptible to diagenesis, and samples must be carefully screened to ensure a specimen is unaltered. One method used to accept or reject U-series ages is the initial coral 234U/238U activity ratio, which reflects the 234U/238U activity of seawater at the time of coral skeleton formation. Due to the long residence time of uranium in the ocean (~400,000 years), researchers often assume that seawater 234U/238U has remained constant throughout the late Pleistocene. Coral specimens whose U-series ages yield an initial 234U/238U value that is significantly different than modern seawater are considered altered. Several studies have demonstrated that coral initial 234U/238U and, hence, seawater 234U/238U may have varied significantly on glacial-interglacial timescales, but the cause of this variability is subject to debate. To evaluate the pattern and mechanisms of 234U/238U variability in seawater over the last glacial cycle, we draw upon a compilation of U-series measurements of shallow and deep water corals to better define the observed variability. Observed trends from the coral record will be assessed using a simple two-box model of the ocean to determine how changes to the ocean's uranium isotope budget during glacial cycles can explain shifts in seawater 234U/238U. An improved understanding the evolution of seawater 234U/238U composition will enable more robust interpretations of both closed-system and open-system ages for corals. Such interpretations of U-series ages are essential to the development of robust chronologies for climate and sea level change and for improving the calibration of the radiocarbon timescale.

  9. U-series constraints on the Holocene human presence in the Cuatro Cienegas basin, Mexico

    NASA Astrophysics Data System (ADS)

    Noble, S. R.; Felstead, N.; Gonzalez, S.; Leng, M. J.; Metcalfe, S. E.; Patchett, P. J.

    2010-12-01

    U-series tufa ages dating a human trackway have been obtained, part of a larger Late Pleistocene - Recent palaeoclimate and human occupation study of the Cuatro Cienegas basin, NE Mexico. Our analytical approach, including tracer calibration, couples aspects of what we consider best practice in the U-series community with our U-Pb experiences which includes the EarthTime U-Pb tracer calibration exercise. The recently discovered trackway is near a small hydrothermal pool within the basin [1], an ecologically highly significant oasis in the Chihuahuan desert. The oasis comprises >200 freshwater hydrothermal pools and a river system, and the related ecosystem hosts >70 endemic species[2]. Pools are fed by waters that circulate a deep karstic system and that originate in the surrounding upper Jurassic-lower Cretaceous Sierra Madre Oriental mountains (>3000m) [3]. The area hosted nomadic hunter-gatherers during the Holocene, and possibly as early as Late Pleistocene (~12 ka BP). Despite the basin's ecological significance, only three palaeoenvironmental studies have been published to date, and limited geochronological constraints are available. A pollen study of drill core through peats and tufas proximal to the pools suggested a long period of climatic stability and biogeographic isolation[4], a notion supported by the large number of endemic species, but other palynological and plant macrofossil data suggest that large climatic changes occurred post Late Pleistocene [5]. The 10 m long in situ trackway is preserved in tufa and five samples from the uppermost surfaces were analysed to date the footprints. The tufas comprise clean carbonate with no petrographic evidence of replacement and little contaminant detrital material (on some exposed upper surfaces). Powdered tufa was processed following [6-8], and analysed by TIMS (Triton, U) and MC-ICP-MS (Th, Nu HR), although our future analyses will primarily be obtained on a Neptune. Samples were spiked with a 229Th/236U

  10. Uranium-234 anomalies in corals older than 150,000 years

    SciTech Connect

    Bard, E. Columbia Univ., Palisades, NY ); Fairbanks, R.G.; Zindler, A. ); Hamelin, B. Univ. Aix-Marseille III ); Hoang, C.T. )

    1991-08-01

    The authors present new precise U-Th ages of well-preserved coral specimens collected from the island of Barbados, West Indies, and the atoll of Mururoa, French Polynesia. Their new data confirm the ages attributed to oxygen isotope stage 7 in the framework of the Milankovitch theory. By using thermal ionization mass spectrometry (TIMS), it is also possible to quantify precisely the [sup 234]U/[sup 238]U ratios in corals. Samples older than 150 kyr B.P. are shown to be characterized by significant excesses of [sup 234]U relative to the uranium isotopic composition expected if the corals grew in present-day sea water. Assuming that the [sup 230]Th-ingrowth ages are accurate, these anomalies translate into high initial [sup 234]U/[sup 238]U ratios: about 1.2 at 200 kyr and up to 1.5 at about 450 kyr B.P. They propose that the anomalies result from both diagenetic addition and replacement of U and possibly from global changes in the [sup 234]U/[sup 238]U composition of the sea water through time. The [sup 234]U anomalies cast doubt on the accuracy of the classical [sup 230]Th-ingrowth dating method in old corals, and in particular for the use of measured [sup 234]U/[sup 238]U ratios alone to date corals older than 150 kyr.

  11. Nuclear Volume-Dependent Fractionation of Uranium Isotopes

    NASA Astrophysics Data System (ADS)

    Weyer, S.; Schauble, E. A.; Anbar, A. D.

    2007-12-01

    Chemical reactions can fractionate isotopes because the magnitudes of equilibrium and rate constants are subtly sensitive to nuclear mass. Geoscientists have exploited this fact to learn about modern environmental processes and past environmental conditions by precisely measuring variations in the isotope compositions of a wide range of elements in natural materials. Here we present evidence from natural terrestrial samples that processes related to ¡°nuclear volume¡± rather than ¡°nuclear mass¡± significantly fractionate the isotope composition of the heaviest primordial element ¨C uranium. The isotopic composition of U in nature is generally assumed to be invariant. Here, we report variations of the 238U/235U isotope ratio in natural samples (basalts, granites, seawater, corals, black shales, suboxic sediments, ferro-manganese crusts/nodules and BIFs), which span a range of δ238U values of ~ 1.3 ‰, exceeding by far the analytical precision of our method (¡Ö 0.06‰, 2SD, based on replicate measurements of individual samples). The largest isotope variations found in our survey are between oxidized and reduced depositional environments, with seawater and suboxic sediments falling in between. U isotopes were analyzed with MC-ICP-MS. A mixed 236U-233U isotopic tracer (double spike) was used to correct for isotope fractionation during sample purification and instrumental mass bias. Sediments formed in oxic environments, such as manganese crusts from the Atlantic and Pacific oceans, display δ238U of -0.54 to -0.62 ‰, slightly lighter than that of seawater (-0.41 ‰). However, sediments from reducing environments, such as black shales from the Black Sea (unit I and unit II) and the Cariaco basin, display heavy U isotope compositions with δ238U of up to +0.43 ‰ (0.84 ‰ heavier than seawater). Uranium enrichment in these sediments probably occurred during the reduction of soluble U(VI) (from seawater) to insoluble U(IV). Intriguingly, isotope

  12. Application of diode lasers to the isotopically selective determination of uranium in oxides by optogalvanic spectroscopy

    NASA Astrophysics Data System (ADS)

    Young, J. P.; Barshick, C. M.; Shaw, R. W.; Ramsey, J. M.

    1995-04-01

    We have observed isotopically selective diode laser-excited optogalvanic effects in uranium at 778.42 and 776.10 nm. The samples were natural abundance uranium oxide, as well as depleted (0.3% 235U), natural (0.7% 235U) and enriched (9.75% 235U) uranium metal or powders. The measurements were carried out in a demountable-cathode glow discharge cell. Preliminary evaluations of precision for uranium isotopic ratios measured using this technique suggest that it should have broad analytical applications for uranium and other amenable actinides or lanthanides.

  13. Reactor Physics and Criticality Benchmark Evaluations for Advanced Nuclear Fuel - Final Technical Report

    SciTech Connect

    William Anderson; James Tulenko; Bradley Rearden; Gary Harms

    2008-09-11

    The nuclear industry interest in advanced fuel and reactor design often drives towards fuel with uranium enrichments greater than 5 wt% 235U. Unfortunately, little data exists, in the form of reactor physics and criticality benchmarks, for uranium enrichments ranging between 5 and 10 wt% 235U. The primary purpose of this project is to provide benchmarks for fuel similar to what may be required for advanced light water reactors (LWRs). These experiments will ultimately provide additional information for application to the criticality-safety bases for commercial fuel facilities handling greater than 5 wt% 235U fuel.

  14. Design for an upgrade of the gas-jet type ISOL at KUR

    NASA Astrophysics Data System (ADS)

    Taniguchi, A.; Tanigaki, M.; Ohkubo, Y.

    2013-12-01

    In order to increase the amount of 235U in the target chamber for KUR-ISOL, the thicknesses of the 235U target and its protective Al covering were reexamined and optimized by calculating the ranges of typical fission products in the target chamber with a SRIM code. It was found that the 235U target could be thickened by up to 6 times of the present target for heavy fission products. Our future plan of relocating the target chamber to another irradiation port at KUR is also described.

  15. On the valency state of radiogenic lead in zircon and its consequences

    SciTech Connect

    Kramers, J.; Frei, R; Newville, M.; Kober, B.; Villa, I.

    2009-03-23

    In zircon U-Pb systematics, extreme robustness up to the temperatures of granulite facies and anatexis contrasts with apparently easy loss of radiogenic Pb at low temperatures, often without any metamorphic event being in evidence. Here we propose that this paradoxical behaviour can be understood with the hypothesis that radiogenic Pb in zircon is tetravalent. We review data and arguments in favour of this hypothesis. Diffusion profiles calculated for Pb{sup 2+} in a 25 {micro}m radius zircon xenocryst in a melt at 1000 C, combined with the incompatibility of Pb{sup 2+}, or for a zircon core inside a younger zircon rim at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during the final evaporation steps. The distribution of residual Pb in a leached titanite, revealed by PIXE, is similar to that of Ti. Lastly, XANES spectra of a 1 Ga old titanite (predominantly radiogenic Pb) and an Alpine one (predominantly common Pb) are significantly different, although the former does not resemble that of PbO{sub 2}. The arguments why radiogenic Pb should be tetravalent are based on analogies with studies relating to the tetravalent state of {sup 234}Th and the hexavalent state of {sup 234}U, which show that {alpha}-recoil in silicates generates a strongly oxidizing environment at the site where the recoiling nucleus comes to rest. Further, a zircon grain, being small, should remain highly oxidizing in its interior by the constant loss of {beta}-particles, maintaining the 4+ state of radiogenic Pb. From its effective ion radius, similar to that of Zr{sup 4+}, and its charge, Pb{sup 4+} has to be compatible in the zircon lattice. Also, by analogy with U{sup 4+}, Th{sup 4+} and Hf{sup 4+}, its diffusivity should be several

  16. REPORTABLE RADIONUCLIDES IN DWPF SLUDGE BATCH 7A (MACROBATCH 8)

    SciTech Connect

    Reboul, S.; Diprete, D.; Click, D.; Bannochie, C.

    2011-12-20

    The Waste Acceptance Product Specifications (WAPS) 1.2 require that the waste producer 'shall report the curie inventory of radionuclides that have half-lives longer than 10 years and that are, or will be, present in concentrations greater than 0.05 percent of the total inventory for each waste type indexed to the years 2015 and 3115.' As part of the strategy to meet WAPS 1.2, the Defense Waste Processing Facility (DWPF) will report for each waste type all radionuclides that have half-lives longer than 10 years and contribute greater than 0.01 percent of the total curie inventory from the time of production through the 1100 year period from 2015 through 3115. The initial list of radionuclides to be reported is based on the design-basis glass identified in the Waste Form Compliance Plan (WCP) and Waste Form Qualification Report. However, it is required that the list be expanded if other radionuclides with half-lives greater than 10 years are identified that meet the 'greater than 0.01% of the curie inventory' criterion. Specification 1.6 of the WAPS, International Atomic Energy Agency Safeguards Reporting for High Level Waste (HLW), requires that the ratio by weights of the following uranium and plutonium isotopes be reported: U-233, U-234, U-235, U-236, and U-238; and Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Therefore, the complete list of reportable radionuclides must also include these sets of U and Pu isotopes - and the U and Pu isotopic mass distributions must be identified. The DWPF receives HLW sludge slurry from Savannah River Site (SRS) Tank 40. For Sludge Batch 7a (SB7a), the waste in Tank 40 contained a blend of the heel from Sludge Batch 6 (SB6) and the Sludge Batch 7 (SB7) material transferred to Tank 40 from Tank 51. This sludge blend is also referred to as Macrobatch 8. Laboratory analyses of a Tank 40 sludge sample were performed to quantify the concentrations of pertinent radionuclides in the SB7a waste. Subsequently, radiological decay and in

  17. Radioactivity in the Kuwait marine environment--Baseline measurements and review.

    PubMed

    Uddin, S; Aba, A; Fowler, S W; Behbehani, M; Ismaeel, A; Al-Shammari, H; Alboloushi, A; Mietelski, J W; Al-Ghadban, A; Al-Ghunaim, A; Khabbaz, A; Alboloushi, O

    2015-11-30

    The Arabian Gulf region is moving towards a nuclear energy option with the first nuclear power plant now operational in Bushehr, Iran, and others soon to be constructed in Abu Dhabi and Saudi Arabia. Radiological safety is becoming a prime concern in the region. This study compiles available data and presents recent radionuclide data for the northern Gulf waters, considered as pre-nuclear which will be a valuable dataset for future monitoring work in this region. Radionuclide monitoring in the marine environment is a matter of prime concern for Kuwait, and an assessment of the potential impact of radionuclides requires the establishment and regular updating of baseline levels of artificial and natural radionuclides in various environmental compartments. Here we present baseline measurements for (210)Po, (210)Pb, (137)Cs, (90)Sr, and (3)H in Kuwait waters. The seawater concentration of (3)H, (210)Po, (210)Pb, (137)Cs, and (90)Sr vary between 130-146, 0.48-0.68, 0.75-0.89, 1.25-1.38 and 0.57-0.78 mBq L(-1), respectively. The (40)K concentration in seawater varies between 8.9-9.3 Bq L(-1). The concentration of (40)K, total (210)Pb, (137)Cs, (90)Sr, (226)Ra, (228)Ra, (238)U, (235)U, (234)U, (239+240)Pu and (238)Pu were determined in sediments and range, respectively, between 353-445, 23.6-44.3, 1.0-3.1, 4.8-5.29, 17.3-20.5, 15-16.4, 28.7-31.4, 1.26-1.30, 29.7-30.0, 0.045-0.21 and 0.028-0.03 Bq kg(-1) dry weight. Since, radionuclides are concentrated in marine biota, a large number of marine biota samples covering several trophic levels, from microalgae to sharks, were analyzed. The whole fish concentration of (40)K, (226)Ra, (224)Ra, (228)Ra, (137)Cs, (210)Po and (90)Sr range between 230-447, 0.7-7.3, <0.5-6.6, <0.5-15.80, <0.17, 0.88-4.26 and 1.86-5.34 Bq kg(-1) dry weight, respectively. (210)Po was found to be highly concentrated in several marine organisms with the highest (210)Po concentration found in Marica marmorata (193.5-215.6 Bq kg(-1) dry weight). (210)Po in

  18. Sharpening the U-Th Chronometer: Progress and Outlook

    NASA Astrophysics Data System (ADS)

    McLean, N. M.; Condon, D. J.; Henderson, G. M.; Richards, D. A.; Noble, S.; Mason, A.

    2013-12-01

    Uranium is incorporated into a variety of natural materials when they form, including carbonates like speleothems and corals. The two most abundant naturally occurring uranium isotopes, 238U and 235U, decay to 206Pb and 207Pb over long timescales with half-lives of 4.5 and 0.7 billion years respectively, but transition through several intermediate daughter isotopes with shorter half-lives first. Fractionation between these daughter isotopes, including 234U, 230Th, and 231Pa, and their parent isotopes, followed by their time-dependent return to secular equilibrium over the course of up to ~800 kyr, forms the basis for U-series geochronology, and allows speleothems and corals to be precisely dated. These carbonates often additionally incorporate chemical and isotopic signatures (e.g., trace elements, δ18O and δ13C) from the environment in which they form, and thus are some of the best dated paleoclimate archives, offering clues about past and future conditions for life on Earth. Over the past decade, the analytical precision of U-series isotope measurements has improved dramatically, largely due to the steadily increasing sensitivity of multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Analytical uncertainties in U-Th dates now approach or are better than 0.1% (2σ), for instance ×100 years for a speleothem or coral that is 130 kyr old (Cheng et al., 2013). However, the accuracy of U-series dates also depends on the accuracy of tracer calibrations, reference solutions and data reduction protocols, which has not kept pace in many laboratories. This means that dates measured in different labs, while impressively precise, may not be directly comparable. To address issues of inter-laboratory bias and improve the accuracy and inter-comparability of U-Th dates, we have instigated work in three related directions. First, we report on the mixing of three synthetic U-Th age solutions, created by combining high-purity mono-isotopic solutions to

  19. CHEMICAL DIFFERENCES BETWEEN SLUDGE SOLIDS AT THE F AND H AREA TANK FARMS

    SciTech Connect

    Reboul, S.

    2012-08-29

    The primary source of waste solids received into the F Area Tank Farm (FTF) was from PUREX processing performed to recover uranium and plutonium from irradiated depleted uranium targets. In contrast, two primary sources of waste solids were received into the H Area Tank Farm (HTF): a) waste from PUREX processing; and b) waste from H-modified (HM) processing performed to recover uranium and neptunium from burned enriched uranium fuel. Due to the differences between the irradiated depleted uranium targets and the burned enriched uranium fuel, the average compositions of the F and H Area wastes are markedly different from one another. Both F and H Area wastes contain significant amounts of iron and aluminum compounds. However, because the iron content of PUREX waste is higher than that of HM waste, and the aluminum content of PUREX waste is lower than that of HM waste, the iron to aluminum ratios of typical FTF waste solids are appreciably higher than those of typical HTF waste solids. Other constituents present at significantly higher concentrations in the typical FTF waste solids include uranium, nickel, ruthenium, zinc, silver, cobalt and copper. In contrast, constituents present at significantly higher concentrations in the typical HTF waste solids include mercury, thorium, oxalate, and radionuclides U-233, U-234, U-235, U-236, Pu-238, Pu-242, Cm-244, and Cm-245. Because of the higher concentrations of Pu-238 in HTF, the long-term concentrations of Th-230 and Ra-226 (from Pu-238 decay) will also be higher in HTF. The uranium and plutonium distributions of the average FTF waste were found to be consistent with depleted uranium and weapons grade plutonium, respectively (U-235 comprised 0.3 wt% of the FTF uranium, and Pu-240 comprised 6 wt% of the FTF plutonium). In contrast, at HTF, U-235 comprised 5 wt% of the uranium, and Pu-240 comprised 17 wt% of the plutonium, consistent with enriched uranium and high burn-up plutonium. X-ray diffraction analyses of various FTF

  20. Radioactivity in the Kuwait marine environment--Baseline measurements and review.

    PubMed

    Uddin, S; Aba, A; Fowler, S W; Behbehani, M; Ismaeel, A; Al-Shammari, H; Alboloushi, A; Mietelski, J W; Al-Ghadban, A; Al-Ghunaim, A; Khabbaz, A; Alboloushi, O

    2015-11-30

    The Arabian Gulf region is moving towards a nuclear energy option with the first nuclear power plant now operational in Bushehr, Iran, and others soon to be constructed in Abu Dhabi and Saudi Arabia. Radiological safety is becoming a prime concern in the region. This study compiles available data and presents recent radionuclide data for the northern Gulf waters, considered as pre-nuclear which will be a valuable dataset for future monitoring work in this region. Radionuclide monitoring in the marine environment is a matter of prime concern for Kuwait, and an assessment of the potential impact of radionuclides requires the establishment and regular updating of baseline levels of artificial and natural radionuclides in various environmental compartments. Here we present baseline measurements for (210)Po, (210)Pb, (137)Cs, (90)Sr, and (3)H in Kuwait waters. The seawater concentration of (3)H, (210)Po, (210)Pb, (137)Cs, and (90)Sr vary between 130-146, 0.48-0.68, 0.75-0.89, 1.25-1.38 and 0.57-0.78 mBq L(-1), respectively. The (40)K concentration in seawater varies between 8.9-9.3 Bq L(-1). The concentration of (40)K, total (210)Pb, (137)Cs, (90)Sr, (226)Ra, (228)Ra, (238)U, (235)U, (234)U, (239+240)Pu and (238)Pu were determined in sediments and range, respectively, between 353-445, 23.6-44.3, 1.0-3.1, 4.8-5.29, 17.3-20.5, 15-16.4, 28.7-31.4, 1.26-1.30, 29.7-30.0, 0.045-0.21 and 0.028-0.03 Bq kg(-1) dry weight. Since, radionuclides are concentrated in marine biota, a large number of marine biota samples covering several trophic levels, from microalgae to sharks, were analyzed. The whole fish concentration of (40)K, (226)Ra, (224)Ra, (228)Ra, (137)Cs, (210)Po and (90)Sr range between 230-447, 0.7-7.3, <0.5-6.6, <0.5-15.80, <0.17, 0.88-4.26 and 1.86-5.34 Bq kg(-1) dry weight, respectively. (210)Po was found to be highly concentrated in several marine organisms with the highest (210)Po concentration found in Marica marmorata (193.5-215.6 Bq kg(-1) dry weight). (210)Po in

  1. Radionuclides, Heavy Metals, and Polychlorinated Biphenyls in Soils Collected Around the Perimeter of Low-Level Radioactive Waste Disposal Area G during 2006

    SciTech Connect

    P. R. Fresquez

    2007-02-28

    Twenty-one soil surface samples were collected in March around the perimeter of Area G, the primary disposal facility for low-level radioactive solid waste at Los Alamos National Laboratory (LANL). Three more samples were collected in October around the northwest corner after elevated tritium levels were detected on an AIRNET station located north of pit 38 in May. Also, four soil samples were collected along a transect at various distances (48, 154, 244, and 282 m) from Area G, starting from the northeast corner and extending to the Pueblo de San Ildefonso fence line in a northeasterly direction (this is the main wind direction). Most samples were analyzed for radionuclides ({sup 3}H, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, {sup 234}U, {sup 235}U, and {sup 238}U), inorganic elements (Al, Ba, Be, Ca, Cr, Co, Cu, Fe, Mg, Mn, Ni, K, Na, V, Hg, Zn, Sb, As, Cd, Pb, Se, Ag, and Tl) and polychlorinated biphenyl (PCB) concentrations. As in previous years, the highest levels of {sup 3}H in soils (690 pCi/mL) were detected along the south portion of Area G near the {sup 3}H shafts; whereas, the highest concentrations of {sup 241}Am (1.2 pCi/g dry) and the Pu isotopes (1.9 pCi/g dry for {sup 238}Pu and 5 pCi/g dry for {sup 239,240}Pu) were detected along the northeastern portions near the transuranic waste pads. Concentrations of {sup 3}H in three soil samples and {sup 241}Am and Pu isotopes in one soil sample collected around the northwest corner in October increased over concentrations found in soils collected at the same locations earlier in the year. Almost all of the heavy metals, with the exception of Zn and Sb in one sample each, in soils around the perimeter of Area G were below regional statistical reference levels (mean plus three standard deviations) (RSRLs). Similarly, only one soil sample collected on the west side contained PCB concentrations--67 {micro}g/kg dry of aroclor-1254 and 94 {micro}g/kg dry of aroclor-1260. Radionuclide and inorganic element

  2. Effect of precipitation, sorption and stable of isotope on maximum release rates of radionuclides from engineered barrier system (EBS) in deep repository.

    PubMed

    Malekifarsani, A; Skachek, M A

    2009-10-01

    shown that the concentrations of the following radionuclides are limited by solubility and precipitate around the waste and buffer: U, Np, Ra, Sm, Zr, Se, Tc, and Pd. The Sensitivity of maximum release rates in case precipitation shows that some nuclides such as Cs-135, Nb-94, Nb-93 m, Zr-93, Sn-126, Th-230, Pu-240, Pu-242, Pu-239, Cm-245, Am-243, Cm-245, U-233, Ac-227, Pb-210, Pa-231 and Th-229 are very little changed in case the maximum release rate from EBS corresponding to eliminate precipitation in buffer material. Some nuclides such as Se-79, Tc-99, Pd-107, Th-232, U-236, U-233, Ra-226, Np-237 U-235, U-234, and U-238 are virtually changed in the maximum release rate compared to case that taking account precipitation. In Sensitivity of maximum release rates in case to taking account stable isotopes (according to the table of inventory) there are only some nuclides with their stable isotopes in the vitrified waste. And calculation shows that Pd-107 and Se-79 are very increase in case eliminate stable isotope. The Sensitivity of maximum release rates in case retardation with sorption shows that some nuclides such as Pu-240, Pu-241, Pu-239, Cm-245, Am-241, Cm-246, and Am-243 are increased in some time in case maximum release rate from EBS corresponding to eliminate retardation in buffer material. Some nuclides such as U-235, U-233 and U-236 have a little decrease in case maximum release because their parents have short live and before decay to their daughter will released from the EBS. If the characteristic time taken for a nuclide to diffuse across the buffer exceeds its half-life, then the release rate of that nuclide from the EBS will be attenuated by radioactive decay. Thus, the retardation of the diffusion process due to sorption tends to reduce the release rates of short-lived nuclides more effectively than for the long-lived ones. For example, release rates of Pu-240, Cm-246 and Am-241, which are relatively short-lived and strongly sorbing, are very small

  3. A convenient method for discriminating between natural and depleted uranium by gamma-ray spectrometry.

    PubMed

    Shoji, M; Hamajima, Y; Takatsuka, K; Honoki, H; Nakajima, T; Kondo, T; Nakanishi, T

    2001-08-01

    A convenient method for discriminating between natural and depleted uranium reagent was developed by measuring and analyzing the gamma-ray spectra of some reagents with no standard source. The counting rates (R) of photoelectric peaks of gamma-rays from nuclides with the same radioactivity divided by their emission probability (B) are expressed as a function of gamma-ray energy. The radioactivities of 234Th and 234mPa and 21.72 times that of 235U are equal to the radioactivity of 235U in natural uranium. Therefore, the plot of 21.72-fold R/B for 235U should be on a curve fitted to the points for 234Th and 234mPa in natural uranium. Depleted uranium with a 235U isotopic composition of less than 0.68% could be discriminated from natural uranium in the case of a reagent containing 4.0 g of uranium.

  4. A convenient method for discriminating between natural and depleted uranium by gamma-ray spectrometry.

    PubMed

    Shoji, M; Hamajima, Y; Takatsuka, K; Honoki, H; Nakajima, T; Kondo, T; Nakanishi, T

    2001-08-01

    A convenient method for discriminating between natural and depleted uranium reagent was developed by measuring and analyzing the gamma-ray spectra of some reagents with no standard source. The counting rates (R) of photoelectric peaks of gamma-rays from nuclides with the same radioactivity divided by their emission probability (B) are expressed as a function of gamma-ray energy. The radioactivities of 234Th and 234mPa and 21.72 times that of 235U are equal to the radioactivity of 235U in natural uranium. Therefore, the plot of 21.72-fold R/B for 235U should be on a curve fitted to the points for 234Th and 234mPa in natural uranium. Depleted uranium with a 235U isotopic composition of less than 0.68% could be discriminated from natural uranium in the case of a reagent containing 4.0 g of uranium. PMID:11393763

  5. Method for radioactivity monitoring

    DOEpatents

    Umbarger, C. John; Cowder, Leo R.

    1976-10-26

    The disclosure relates to a method for analyzing uranium and/or thorium contents of liquid effluents preferably utilizing a sample containing counting chamber. Basically, 185.7-keV gamma rays following .sup.235 U alpha decay to .sup.231 Th which indicate .sup.235 U content and a 63-keV gamma ray doublet found in the nucleus of .sup.234 Pa, a granddaughter of .sup.238 U, are monitored and the ratio thereof taken to derive uranium content and isotopic enrichment .sup.235 U/.sup.235 U + .sup.238 U) in the liquid effluent. Thorium content is determined by monitoring the intensity of 238-keV gamma rays from the nucleus of .sup.212 Bi in the decay chain of .sup.232 Th.

  6. Origin of uranium isotope variations in early solar nebula condensates

    PubMed Central

    Tissot, François L. H.; Dauphas, Nicolas; Grossman, Lawrence

    2016-01-01

    High-temperature condensates found in meteorites display uranium isotopic variations (235U/238U), which complicate dating the solar system’s formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide 247Cm (t1/2 = 15.6 My) into 235U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of 235U reaching ~+6% relative to average solar system composition, which can only be due to the decay of 247Cm. This allows us to constrain the 247Cm/235U ratio at solar system formation to (1.1 ± 0.3) × 10−4. This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture. PMID:26973874

  7. Origin of uranium isotope variations in early solar nebula condensates.

    PubMed

    Tissot, François L H; Dauphas, Nicolas; Grossman, Lawrence

    2016-03-01

    High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

  8. Origin of uranium isotope variations in early solar nebula condensates.

    PubMed

    Tissot, François L H; Dauphas, Nicolas; Grossman, Lawrence

    2016-03-01

    High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture. PMID:26973874

  9. Conceptual Ideas for New Nondestructive UF6 Cylinder Assay Techniques

    SciTech Connect

    Miller, Karen A.

    2012-05-02

    Nondestructive assay (NDA) measurements of uranium cylinders play an important role in helping the International Atomic Energy Agency (IAEA) safeguard uranium enrichment plants. Traditionally, these measurements have consisted of a scale or load cell to determine the mass of UF{sub 6} in the cylinder combined with a gamma-ray measurement of the 186 keV peak from {sup 235}U to determine enrichment. More recently, Los Alamos National Laboratory (LANL) and Pacific Northwest National Laboratory (PNNL) have developed systems that exploit the passive neutron signal from UF{sub 6} to determine uranium mass and/or enrichment. These include the Uranium Cylinder Assay System (UCAS), the Passive Neutron Enrichment Meter (PNEM), and the Hybrid Enrichment Verification Array (HEVA). The purpose of this report is to provide the IAEA with new ideas on technologies that may or may not be under active development but could be useful for UF{sub 6} cylinder assay. To begin, we have included two feasibility studies of active interrogation techniques. There is a long history of active interrogation in the field of nuclear safeguards, especially for uranium assay. Both of the active techniques provide a direct measure of {sup 235}U content. The first is an active neutron method based on the existing PNEM design that uses a correlated {sup 252}Cf interrogation source. This technique shows great promise for UF{sub 6} cylinder assay and is based on advanced technology that could be implemented in the field in the near term. The second active technique is nuclear resonance fluorescence (NRF). In the NRF technique, a bremsstrahlung photon beam could be used to illuminate the cylinder, and high-resolution gamma-ray detectors would detect the characteristic de-excitation photons. The results of the feasibility study show that under certain measurement geometries, NRF is impractical for UF6 cylinder assay, but the 'grazing transmission' and 'secant transmission' geometries have more potential

  10. U-Sr isotopic speedometer: Fluid flow and chemical weatheringrates inaquifers

    SciTech Connect

    Maher, Kate; DePaolo, Donald J.; Christensen, John N.

    2005-12-27

    Both chemical weathering rates and fluid flow are difficultto measure in natural systems. However, these parameters are critical forunderstanding the hydrochemical evolution of aquifers, predicting thefate and transport of contaminants, and for water resources/water qualityconsiderations. 87Sr/86Sr and (234U/238U) activity ratios are sensitiveindicators of water-rock interaction, and thus provide a means ofquantifying both flow and reactivity. The 87Sr/86Sr values in groundwaters are controlled by the ratio of the dissolution rate to the flowrate. Similarly, the (234U/238U) ratio of natural ground waters is abalance between the flow rate and the dissolution of solids, andalpha-recoil loss of 234U from the solids. By coupl