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Sample records for 234u 235u 238u

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

    NASA Astrophysics Data System (ADS)

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

    2000-09-01

    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/ 238U activity, and 230Th/ 238U activity. 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-lived isotopes are

  3. 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.

  4. 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

  5. Redundant 230Th/ 234U/ 238U, 231Pa/ 235U and 14C dating of fossil corals for accurate radiocarbon age calibration

    NASA Astrophysics Data System (ADS)

    Chiu, Tzu-Chien; Fairbanks, Richard G.; Mortlock, Richard A.; Cao, Li; Fairbanks, Todd W.; Bloom, Arthur L.

    2006-09-01

    230Th/ 234U/ 238U dating of fossil corals by mass spectrometry is remarkably precise, but some samples exposed to freshwater over thousands of years may gain and/or lose uranium and/or thorium and consequently yield inaccurate ages. Although a δ 234U initial value equivalent to modern seawater and modern corals has been an effective quality control criterion, for samples exposed to freshwater but having δ 234U initial values indistinguishable from modern seawater and modern corals, there remains a need for additional age validation in the most demanding applications such as the 14C calibration (Fairbanks et al., 2005. Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/ 234U/ 238U and 14C dates on pristine corals. Quaternary Science Reviews 24(16-17), 1781-1796). In this paper we enhance screening criteria for fossil corals older than 30,000 years BP in the Fairbanks0805 radiocarbon calibration data set (Fairbanks et al., 2005) by measuring redundant 230Th/ 234U/ 238U and 231Pa/ 235U dates via multi-collector magnetic sector inductively coupled plasma mass spectrometry (MC-MS-ICPMS) using techniques described in Mortlock et al. (2005. 230Th/ 234U/ 238U and 231Pa/ 235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry. Geochimica et Cosmochimica Acta 69(3), 649-657.). In our present study, we regard paired 231Pa/ 235U and 230Th/ 234U/ 238U ages concordant when the 231Pa/ 235U age (±2 σ) overlaps with the associated 230Th/ 234U/ 238U age (±2 σ). Out of a representative set of 11 Fairbanks0805 (Fairbanks et al., 2005) radiocarbon calibration coral samples re-measured in this study, nine passed this rigorous check on the accuracy of their 230Th/ 234U/ 238U ages. The concordancy observed between 230Th/ 234U/ 238U and 231Pa/ 235U dates provides convincing evidence to support closed system behavior of these fossil corals and validation of their 230Th/ 234U/ 238U

  6. Determination of 234U/238U, 235U/238U and 236U/238U Isotope Ratios in Urine Using Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS)

    PubMed Central

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

    2016-01-01

    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 we report a new method to measure 234U/238U, 235U/238U and 236U/238U. 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 introduction system (Aridus II™). This method provides rapid and reliable results, and has been used successfully to analyze Certified Reference Materials (CRM). PMID:24563523

  7. 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

  8. 230Th/ 234U/ 238U and 231Pa/ 235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Mortlock, Richard A.; Fairbanks, Richard G.; Chiu, Tzu-chien; Rubenstone, James

    2005-02-01

    The 230Th/ 234U/ 238U age dating of corals via alpha counting or mass spectrometry has significantly contributed to our understanding of sea level, radiocarbon calibration, rates of ocean and climate change, and timing of El Nino, among many applications. Age dating of corals by mass spectrometry is remarkably precise, but many samples exposed to freshwater yield inaccurate ages. The first indication of open-system 230Th/ 234U/ 238U ages is elevated 234U/ 238U initial values, very common in samples older than 100,000 yr. For samples younger than 100,000 yr that have 234U/ 238U initial values close to seawater, there is a need for age validation. Redundant 230Th/ 234U/ 238U and 231Pa/ 235U ages in a single fossil coral fragment are possible by Multi-Collector Magnetic Sector Inductively Coupled Plasma Mass Spectrometry (MC-MS-ICPMS) and standard anion exchange column chemistry, modified to permit the separation of uranium, thorium, and protactinium isotopes from a single solution. A high-efficiency nebulizer employed for sample introduction permits the determination of both 230Th/ 234U/ 238U and 231Pa/ 235U ages in fragments as small as 500 mg. We have obtained excellent agreement between 230Th/ 234U/ 238U and 231Pa/ 235U ages in Barbados corals (30 ka) and suggest that the methods described in this paper can be used to test the 230Th/ 234U/ 238U age accuracy. Separate fractions of U, Th, and Pa are measured by employing a multi-dynamic procedure, whereby 238U is measured on a Faraday cup simultaneously with all minor isotopes measured with a Daly ion counting detector. The multi-dynamic procedure also permits correcting for both the Daly to Faraday gain and for mass discrimination during sample analyses. The analytical precision of 230Th/ 234U/ 238U and 231Pa/ 235U dates is generally better than ±0.3% and ±1.5%, respectively (2 Relative Standard deviation [RSD]). Additional errors resulting from uncertainties in the decay constant for 231Pa and from undetermined

  9. 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

  10. 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.

  11. Concentrations of 238U, 234U, 235U, 232Th, 230Th, 228Th, 226Ra, 228Ra, 224Ra, 210Po, 210Pb and 212Pb in drinking water in Italy: reconciling safety standards based on measurements of gross alpha and beta.

    PubMed

    Jia, Guogang; Torri, Giancarlo; Magro, Leandro

    2009-11-01

    Some important naturally occurring alpha- and beta-radionuclides in drinking water samples collected in Italy were determined and the radiological quality evaluated. The mean activity concentrations (mBqL(-1)) of the radionuclides in the water samples were almost in the order: 26+/-36 ((234)U)>21+/-30 ((238)U)>8.9+/-15 ((226)Ra)>4.8+/-6.3 ((228)Ra)>4.0+/-4.1 ((210)Pb)>3.2+/-3.7 ((210)Po)>2.7+/-1.2 ((212)Pb)>1.4+/-1.8 ((224)Ra)> 1.1+/-1.3 ((235)U)>0.26+/-0.39 ((228)Th)>0.0023+/-0.0009 ((230)Th)>0.0013+/-0.0006 ((232)Th). The mean estimated dose (microSvyr(-1)) to an adult from the water intake was in this order: 2.8+/-3.3 ((210)Po)>2.4+/-3.2 ((228)Ra)>2.1+/-2.1 ((210)Pb)>1.8+/-3.1 ((226)Ra)>0.94+/-1.30 ((234)U)>0.70+/-0.98 ((238)U)>0.069+/-0.087 ((224)Ra)>0.036+/-0.044 ((235)U)>0.014+/-0.021 ((228)Th)>0.012+/-0.005 ((212)Pb)>0.00035+/-0.00029 ((230)Th)>0.00022+/-0.00009 ((232)Th). It is obvious that (210)Po, (228)Ra, (210)Pb and (226)Ra are the most important dose contributors in the drinking water intake. As far as the seventeen brands of analysed drinking water were concerned, the committed effective doses were in the range of 2.81-38.5 microSvyr(-1), all well below the reference level of the committed effective dose (100 microSvyr(-1)) recommended by the WHO. These data throw some light on the scale of the radiological impact on the public from some naturally occurring radionuclides in drinking water, and can also serve as a comparison for the dose contribution from artificial radionuclides released to the environment as a result of human practices. Based on the radionuclide composition in the analysed waters, comment was made on the new screening level for gross alpha activity in guidelines for drinking-water quality recommended by the WHO, 2004. PMID:19635638

  12. 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

  13. (234)U/(238)U signatures associated with uranium ore bodies: part 3 Koongarra.

    PubMed

    Lowson, Richard T

    2013-04-01

    The Koongarra ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located ∼30 m below the surface. The (234)U/(238)U activity ratios (AR) for the ground water and the amorphous phase of the solid have been analysed for the ore zone and dispersion halo as a function of depth. The results display a (234)U/(238)U AR signature with depth which may be common to all U ore bodies. The (234)U/(238)U AR is depressed below secular equilibrium in the weathered material above the redox front; rises significantly above secular equilibrium in the vicinity of the redox front; and is followed by a gradual decrease with depth below the redox front. The amplitude of the profile is a function of local conditions. A model is proposed for the signature in which oxidising waters preferentially leach the (234)U sites at the redox front due to preconditioning of the (234)U sites by α recoil during the decay of (23)(8)U to (23)(4)U. Mass balance requires the solid material left behind the redox front to have a (234)U/(238)U AR reduced below 1. Local second order effects may be superimposed on the signature. The signature may have application to calibrating scenarios for nuclear waste repositories, assisting in understanding historical climates, economic evaluation of U ore bodies and U exploration. PMID:23142336

  14. 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.

  15. Toward epsilon levels of measurement precision on 234U/238U by using MC-ICPMS

    NASA Astrophysics Data System (ADS)

    Andersen, M. B.; Stirling, C. H.; Potter, E.-K.; Halliday, A. N.

    2004-10-01

    Variations in 234U/238U have wide-ranging applications as tracers for ground- and river-water fluxes and is an essential component in U-series dating. Analytical developments for measuring 234U/238U have progressed from direct alpha-counting, with precisions at the percent level, to thermal ionization and multiple-collector inductively coupled plasma mass spectrometry (TIMS and MC-ICPMS, respectively) isotopic measurement techniques. However, 234U/238U is difficult to measure with better than permil precision because of the small atomic ratios for most geological samples (~10-4 range). Using a Nu Instruments Nu Plasma MC-ICPMS, we have developed two analytical techniques for the precise measurement of 234U/238U: (1) a conventional standard-bracketing protocol using multiple Faraday cups and electron multipliers with ion counting capabilities (FM) and (2) a standard-bracketing Faraday cup protocol (FF). Both are capable of measuring 234U/238U with precisions at the epsilon level (1 epsilon = 1 part in 104): (1) The conventional standard-bracketing FM measurements are conducted as static measurements with the minor 234U isotope measured in a conventional discrete dynode electron multiplier (SEM) equipped with ion counter and a retardation filter. The Faraday-multiplier gain is measured using bracketing measurements of the U metal standard CRM-145. The external reproducibility of 234U/238U (reformulated into [delta]-notation as [delta]234U), interspersed with frequent measurements of the gain, is at the +/-0.6[per mille sign] level (2[sigma]) for both uraninite and carbonate standards, takes ~75 min and consumes ~120 ng of U per measurement. (2) The static standard-bracketing FF protocol measures all three natural U isotopes in Faraday collectors. This is not usually possible using a standard multiple-Faraday array due to the large differences in the abundances of naturally occurring U isotopes. In our study, this is achieved by replacing the standard 1011 [Omega

  16. (234)U/(238)U signatures associated with uranium ore bodies: part 2 Manyingee.

    PubMed

    Lowson, Richard T; McIntyre, Mark G

    2013-04-01

    The Manyingee ore body is a roll-front U ore body located at depth in the Cretaceous sandstone sediments of a Proterozoic palaeo valley. It is located in a confined aquifer. The aquifer is recharged 4 km upstream by the Ashburton River. Groundwater samples were collected at and up to 4.7 km downstream of the ore body. The ground water (234)U/(238)U activity ratios (AR) were elevated to 1.86 in the vicinity of the ore body and then declined to 1.06 over the 4.7 km transect. The elevated (234)U/(238)U ARs are attributed to selective leaching of (234)U sites by oxidising waters, with α recoil as a necessary precursor to produce activated (234)U sites. Direct ejection into another phase following α recoil is considered to be a minor contributor to (234)U -(238)U disequilibrium in this environment. The profile is considered to be typical of the (234)U/(238)U AR profile at and down gradient of the redox front of a U ore body. PMID:23182403

  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. PMID:23410592

  18. The Application of 238U/235U as a Redox-Proxy for Past Ocean Chemistry

    NASA Astrophysics Data System (ADS)

    Andersen, M. B.; Westermann, S.; Bahniuk, A.; Vasconcelos, C.; McKenzie, J. A.; Föllmi, K. B.; Vance, D.

    2014-12-01

    The recent discovery of significant variation in 238U/235U caused by redox change at the surface Earth has led to its use to extract information on the oxygenation state of ancient oceans from marine sediments [e.g. 1]. Recent studies have focused on improving the understanding of the 238U/235U signature in modern marine carbonates [2] and black shales [3] to improve the robustness of this tracer. To further advance its use we have focused on improving our understanding of 238U/235U systematics in modern dolomite, another commonly occurring rock-type in the geological record, before turning to 238U/235U signatures in ancient sediments. The measured dolomite samples, precipitated in modern environments of coastal hypersaline lagoons in Brazil, all exhibit 238U/235U values that deviate from the seawater composition [3]. Observed values are both lighter (ca. 130 ppm; as also observed in dolomite from tidal-ponds on Bahamas [2]) and heavier (50-180 ppm). These distinct 238U/235U values for different dolomite-precipitates likely attest to the particular formation style, as well as early diagenetic processes. We use such modern settings to discuss the utility of 238U/235U in ancient sediments, the singularity of any observed 238U/235U signal, its relation to global ocean chemistry and potential diagenetic overprinting. These constraints are then used to evaluate a well-preserved marine carbonate section [4] and published black shale 238U/235U data [1], both deposited during the Oceanic Anoxic Event 2 (93 Ma). We discuss the capabilities of both the carbonate and black shale section for retaining information on the 238U/235U composition in the ocean during OAE 2. [1] Montoya-Pino et al. (2010) Geology, 38, 315-318 [2] Romaniello et al. (2013) 362, 305-316 [3] Andersen et al. (2014) EPSL, 400, 184-194 [4] Westermann et al. (2010) Cret. Res., 31, 500-514

  19. Precise determination of the open ocean 234U/238U composition

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Uranium has a long residence time in the open oceans, and therefore, its salinity-normalized U concentration and 234U/238U activity ratio (expressed herein as δ234U, the ‰ deviation from secular equilibrium) are assumed to be uniform. The marine 234U/238U activity ratio is currently in radioactive disequilibrium and shows a ˜15% excess of 234U with respect to the secular equilibrium value due to continuous input from riverine sources. Knowledge of the marine δ234U, and how it has evolved through the Quaternary, is important for validating age accuracy in the U series dating of marine carbonates, which is increasingly relied upon for providing a chronological basis in paleoclimate research. However, accurate and precise measurements of δ234U are technically difficult. Thus, existing compilations of the open ocean δ234U value vary by up to ˜10‰, and the assumed uniformity in the oceanic δ234U remains to be confirmed. Using MC-ICPMS techniques and a suite of multiple Faraday cups instead of the typical configurations based on a combined Faraday cup-multiplier array, a long-term reproducibility of better than ±0.3‰ (2σ) is achieved for δ234U measurements. Applying these very high precision techniques to open ocean seawater samples, an average δ234U of 146.8 ± 0.1‰ (2σm, n = 19) is obtained. These high-precision seawater measurements yield an external reproducibility of better than ±0.4‰ (2σ) and show that the open oceans have a uniform δ234U on the sub-‰ level. These new data constrain the vertical mixing time of the open oceans to less than 1000 years.

  20. 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

  1. Uranium isotope systematics of ferromanganese crusts in the Pacific Ocean: Implications for the marine 238U/235U isotope system

    NASA Astrophysics Data System (ADS)

    Goto, Kosuke T.; Anbar, Ariel D.; Gordon, Gwyneth W.; Romaniello, Stephen J.; Shimoda, Gen; Takaya, Yutaro; Tokumaru, Ayaka; Nozaki, Tatsuo; Suzuki, Katsuhiko; Machida, Shiki; Hanyu, Takeshi; Usui, Akira

    2014-12-01

    Variations of 238U/235U ratio (δ238U) in sedimentary rocks have been proposed as a possible proxy for the paleo-oceanic redox conditions, although the marine δ238U system is not fully understood. Here we investigate the spatial variation of δ238U in modern ferromanganese (Fe-Mn) crusts by analyzing U isotopes in the surface (0-3 mm depth) layer of 19 Fe-Mn crusts collected from 6 seamounts in the Pacific Ocean. δ238U values in the surface layers show little variation and range from -0.59‰ to -0.69‰. The uniformity of δ238U values is consistent with the long residence time of U in modern seawater, although the δ238U values are lighter than that of present-day seawater by ∼0.24‰. The light δ238U values are consistent with the isotope offset observed in previously reported adsorption experiment of U to Mn oxide. These results indicate that removal of U from seawater to Mn oxide is responsible for the second largest U isotope fractionation in the modern marine system, and could contribute to isotopically heavy U to seawater. Depth profiles of U isotopes (δ234U and δ238U) in two Fe-Mn crusts (MR12-03_D06-R01 and MC10_CB07_B), dated by Os isotope stratigraphy, were investigated to reconstruct the evolution of the oceanic redox state during the Cenozoic. The δ238U depth profiles show very limited ranges (-0.57‰ to -0.67‰ for MR12-03_D06-R01 and -0.56‰ to -0.69‰ for MC10_CB07_B), and have values that are similar to those of the surface layers of Fe-Mn crusts. The absence of any resolvable variation in the δ238U depth profiles may suggest that the relative amounts of oxic and reducing U sinks have not varied significantly over the past 45 Myr. However, the δ234U depth profiles of the same samples show evidence for the possible redistribution of 234U after deposition. Therefore, the depth profile of δ238U in Fe-Mn crusts may have been also overprinted by later chemical exchange with pore-water or seawater, and may not reflect the paleo

  2. 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.

  3. 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.

  4. 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 λ238U235U 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

  5. 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).

  6. 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.

  7. 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.

  8. Natural Variation of 238U/235U in Geo- and Cosmochemistry

    NASA Astrophysics Data System (ADS)

    Weyer, S.; Brennecka, G.; Montoya Pino, C.; Noordmann, J.; Schauble, E. A.; Wadhwa, M.; Anbar, A. D.

    2009-12-01

    The ratio of the two primordial U isotopes has long been assumed to be invariant (i.e. 238U/235U = 137.88, [1]) in the Solar [1, 2]. Due to analytical improvements, small (‰-range) U isotope variations can now be detected in both terrestrial [3, 4, 5] and meteoritic materials [6]. Uranium isotope variations on Earth are produced by chemical reactions, analogous to stable isotope fractionation, although U has no stable isotopes. The range of U isotope variations observed thus far on Earth exceeds 1‰ and is mostly driven by nuclear field shift effects, which depend on nuclear volume rather than mass [7]. The strongest isotope fractionation appears to occur between oxidized and reduced U species (UVI and UIV). As a result, oxic environments (e.g., seawater) are enriched in the light U isotope, 235U, while anoxic sediments (e.g., from the Black Sea) are enriched in the heavy U isotope, 238U [4]. This redox-sensitive behavior of U isotope compositions makes the 238U/235U ratio promising for use as a paleo-redox proxy. In paleoceanography, 238U/235U ratios can be used to estimate the extent of seafloor anoxia. During periods of enhanced global ocean anoxia (e.g., during the mid-Cretaceous oceanic anoxic event OAE-2) heavy U was preferentially buried into anoxic sediments. Accordingly, sea water and all oceanic sinks became depleted in heavy U. We used this shift in U isotope compositions to estimate a three times enhancement of anoxic environments in the oceans during OAE-2 compared to today [8]. In meteoritic materials, 238U/235U variations may be produced by (1) chemical reactions (2) nucleosynthetic anomalies and/or (3) decay of the short-lived extant 247Cm (half life = 15.6 Ma) to 235U. We investigated the U isotope composition of calcium aluminum-rich inclusions (CAIs). The Pb-Pb ages of CAIs define the age of the Solar System, as they represent the first solids to condense from the cooling protoplanetary disk. The investigated CAIs from the Allende meteorite

  9. Studies of Neutron-Induced Fission of 235U, 238U, and 239Pu

    NASA Astrophysics Data System (ADS)

    Duke, Dana; TKE Team

    2014-09-01

    A Frisch-gridded ionization chamber and the double energy (2E) analysis method were used to study mass yield distributions and average total kinetic energy (TKE) release from neutron-induced fission of 235U, 238U, and 239Pu. Despite decades of fission research, little or no TKE data exist for high incident neutron energies. Additional average TKE information at incident neutron energies relevant to defense- and energy-related applications will provide a valuable observable for benchmarking simulations. The data can also be used as inputs in theoretical fission models. The Los Alamos Neutron Science Center-Weapons Neutron Research (LANSCE - WNR) provides a neutron beam 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 238U, 235U, and 239Pu will be presented. LA-UR-14-24921.

  10. 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

  11. 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

  12. 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

  13. Greenland meltwater impacts on the 234U/238U composition of seawater, the role of subglacial residence time.

    NASA Astrophysics Data System (ADS)

    Arendt, C. A.; Aciego, S.; Sims, K. W. W.; Stevenson, E. I.

    2014-12-01

    The chemical composition of seawater depends on the sources and sinks of the constituent elements, including those derived from continental weathering and transported by rivers. Glacial melt rivers compose a significant percentage of contributing water in the high latitudes, and potentially impact the overall composition of seawater. The magnitude of the chemical changes glacial melt can have on adjacent seawater depends on the composition of glacial melt, which is directly influenced by the subglacial residence time of meltwater. Long residence times correlate to subglacial water with both high cation concentrations and 234U/238U isotopic compositions. Thus, the residence time of subglacial water and corresponding subglacial geochemistry impacts the 234U/238U composition of proximal seawater and potentially global seawater. To test the influence of subglacial water residence times on seawater chemistry we examined the U-series composition of four outlet glaciers directly connected to the Southern Greenland Ice Sheet located near Narsarsuaq, Ilulissat, Nuuk and Kulusuk, and adjacent seawater at each site. All outlet glaciers in this study are located within three of the five primary drainage basins beneath the Greenland Ice Sheet, each in varying stages of subglacial hydrologic evolution, resulting in unique chemical compositions of meltwater draining from each location. At these four locations we found subglacial water residence time values of 10-1000 years. In regions where the U concentration, 234U/238U isotopic composition and residence times were high (1.01 ppb, 1.263 and ~1,000 years in Narsarsuaq) the adjacent seawater 234U/238U composition was elevated (1.152) compared to regions where the U concentration, 234U/238U isotopic composition and residence times were low (0.05 ppb, 1.008 and ~10 years in Illulisat) the adjacent seawater 234U/238U composition remained around the assumed seawater average (1.145). Through this study we observed a direct impact of

  14. 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

  15. 234U/238U activity ratio disequilibrium technique for studying uranium mobility in the Opalinus Clay at Mont Terri, Switzerland.

    PubMed

    Pekala, M; Kramers, J D; Waber, H N

    2010-06-01

    Mobility of naturally occurring 238U and 234U radionuclides was studied in a low permeability, reducing claystone formation (Opalinus Clay) near its contact with an overlying oxidising aquifer (Dogger Limestones) at Mont Terri, Switzerland. Our data point to a limited redistribution of U in some of the studied samples. Observed centimetre-scale U mobility is explained by slow diffusive transport of 234U in the pore waters of the Opalinus Clay driven by spatially variable in situ supply (by alpha-recoil) of 234U from the rock matrix. Metre-scale mobility is interpreted as a result of infiltration of meteoric water into the overlying aquifer which developed gradients of U concentration across the two rock formations. This triggered a slow in-diffusion of U with (234U/238U)>1 into the Opalinus Clay as attested by a clear-cut pattern of decreasing bulk rock (234U/238U) inwards the Opalinus Clay, away from the Dogger Limestones. PMID:20189405

  16. 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

  17. High Precision Measurements of 235U/238U Isotopic Fractionations Resulting From Uranium Reduction Induced by Zero Valent Iron

    NASA Astrophysics Data System (ADS)

    Rademacher, L.; Lundstrom, C.; Johnson, T.

    2003-12-01

    Uranium is a widespread natural and anthropogenic contaminant in surface and subsurface waters. Like several other inorganic contaminants, uranium is mobile under oxidizing conditions but may be immobilized by chemical reduction. U(VI) moves with groundwater as (UO2)2+ and as soluble complexes with carbonate, phosphate, and fluoride. In many groundwater systems, uranium undergoes chemical reduction to U(IV), which is insoluble and immobile. Therefore, understanding the extent of reduction is essential for predicting the mobility of uranium in groundwater. Mass dependent isotopic fractionations of redox sensitive contaminants frequently found in groundwater (including chromate, selenate, and nitrate) have proven exceptionally useful for estimating the rate and extent of reduction and immobilization. Until recently, however, analytical limitations have prevented these techniques from being applied to heavier redox sensitive elements, such as uranium. The advent of highly sensitive multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) enables high precision measurements of previously undetected variations in many elements. Laboratory reduction experiments with zero valent iron (ZVI) were performed in a controlled environment to test the hypothesis that uranium isotopes, specifically 235U/238U, behave similarly to other redox sensitive contaminants and produce a mass dependent fractionation during the transformation between valence states. Because of the large abundance differences between 235U and 238U, initial experiments used U500, an enriched uranium standard with approximately equal parts 235U and 238U. Results suggest that the highly sensitive MC-ICP-MS distinguishes 235U/238Uvariations to approximately + 0.02per mil. Measured isotopic fractionations between the 235U/238U of the initial and final experimental solutions (~70% reduced) are approximately 1.1 per mil, and increase with decreasing concentration. Measured variations in 235U/238U

  18. Fragment Characteristics from Photofission of 234U and 238U Induced by 6.0 - 9.0 Mev Bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Göök, A.; Barday, R.; Chernykh, M.; Eckardt, C.; Enders, J.; Neumann-Cosel, P. Von; Poltoratska, Y.; Wagner, M.; Richter, A.; Oberstedt, S.; Hambsch, F.-J.; Oberstedt, A.

    2011-10-01

    As a preparatory experiment for a search for parity violation in photofission, fission of 238U and 234U induced by 6 - 9 MeV bremsstrahlung has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber fission fragment energy and mass distributions have been determined by means of the double kinetic energy technique. The experiment was performed in order to test the ionization chamber's performance in a bremsstrahlung environment. Results on the fission fragment characteristics from the 238U(γ,f) reaction are found to be in good agreement with literature values. In addition results on fission fragment mass and energy distributions from the 234U(γ,f) reaction are presented for the first time in this energy region.

  19. 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.

  20. 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.

  1. 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

  2. 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). PMID:20044543

  3. 238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb Dating

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    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 × 10-4 to 2.4 × 10-4.

  4. A modern framework for the interpretation of 238U/235U in studies of ancient ocean redox

    NASA Astrophysics Data System (ADS)

    Andersen, M. B.; Romaniello, S.; Vance, D.; Little, S. H.; Herdman, R.; Lyons, T. W.

    2014-08-01

    The abundance and isotope composition of redox sensitive elements in ancient sediments are increasingly used to understand the past ocean's geochemical state and the oxygenation history of the Earth. The redox transition of uranium (U) from soluble U+6 to relatively insoluble U+4 and its subsequent incorporation into reduced sediments has been used to deduce the redox state of the oceans in the past. Furthermore, recent analytical improvements have revealed significant 238U/235U fractionation during this redox transition, offering the potential for U isotopes to act as a redox proxy. However, the development of U isotopes as a geochemical tracer requires that U isotope systematics associated with redox changes, are well-characterized. This study focuses on U isotopes in recent sediments from the two largest modern anoxic ocean basins, the Black Sea and the Cariaco Basin, with the aim of advancing our understanding of the U isotope systematics in reducing marine environments. These anoxic sediments have high U accumulation rates and high 238U/235U ratios relative to seawater, in general agreement with a process that accumulates reduced U with a heavy isotopic composition. Using Al and Ca concentrations to correct for detrital and biogenic carbonate-bound U, we estimate the reduced authigenic U accumulated in the sediments and its 238U/235U. These results highlight the importance of isotopic mass balance constraints during diffusive transport and reaction of U from seawater and through pore-water, affecting the observed 238U/235U in sediments. Using these constraints, the average percentages of U depletion from top to bottom of the water column can be estimated, assuming batch-removal of U into anoxic sediments in a restricted basin. Using this framework, 238U/235U in modern anoxic sediments from the Black Sea imply U depletions in the water column of ∼30%, which is close to the observed ∼40% U depletion in the modern Black Sea water column at these depths

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

    SciTech Connect

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

    1992-10-09

    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 yielding {sup 230}Th ages with precisions ranging from less than 1,000 years (2{sigma}) for samples younger than {approximately}140 ka (thousands of years ago) to less than 50,000 years for the oldest samples ({approximately}566 ka). The {sup 234}U/{sup 238}U ages could be determined to a precision of {approximately}20,000 years for all ages. Calcite accumulated continuously from 566 ka until {approximately}60 ka at an average rate of 0.7 millimeter per 10{sup 3} years. The precise agreement between replicate analyses and the concordance of the {sup 230}Th/{sup 238}U and {sup 234}U/{sup 238}U ages for the oldest samples indicate that the DH-11 samples were closed systems and validate the dating technique in general.

  6. Behavior of isotope (18O/16O, 234U/238U) systems during the formation of uranium deposits of the "sandstone" type

    NASA Astrophysics Data System (ADS)

    Golubev, V. N.; Dubinina, E. O.; Chernyshev, I. V.; Ikonnikova, T. A.

    2016-01-01

    The uneven character of the distribution of 18O/16O and 234U/238U values was established in the vertical cross section of the productive sequence of the Dybryn uranium deposit (Vitim uranium-ore region, Buryatia). Both a deficiency and an excess of 234U in relation to the equilibrium 234U/238U ratio in the vertical sequence may provide evidence for the extremely low rate of the infiltration water flow. The behavior of oxygen isotope characteristics for different size fractions of terrigenous rocks provides evidence for active uranium redistribution and openness of the isotope system of this element during interaction of terrigenous-sedimentary rocks with infiltration waters.

  7. On the Search for Nuclear Resonance Fluorescence Signatures of 235U and 238U above 3 MeV

    SciTech Connect

    Warren, Glen A.; Caggiano, Joseph A.; Bertozzi, William; Korbly, Steve; Ledoux, Robert; Park, William H.

    2010-02-01

    Nuclear resonance fluorescence is a physical process that provides an isotope-specific signature that could be used for the identification and characterization of materials. The technique involves the detection of prompt discrete-energy photons emitted from a sample that is exposed to MeV-energy photons. Potential applications of the technique range from detection of high explosives to characterization of special nuclear materials such as 235U. Pacific Northwest National Laboratory and Passport Systems have collaborated to conduct a pair of measurements to search for a nuclear resonance fluorescence response of 235U above 3 MeV and of 238U above 5 MeV using an 8 g sample of highly enriched uranium and a 90 g sample of depleted uranium. No new signatures were observed. The minimum detectable integrated cross section for 235U is presented.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Novel method to study neutron capture of 235U and 238U simultaneously at keV energies.

    PubMed

    Wallner, A; Belgya, T; Bichler, M; Buczak, K; Dillmann, I; Käppeler, F; Lederer, C; Mengoni, A; Quinto, F; Steier, P; Szentmiklosi, L

    2014-05-16

    The neutron capture cross sections of the main uranium isotopes, (235)U and (238)U, were measured simultaneously for keV energies, for the first time by combining activation technique and atom counting of the reaction products using accelerator mass spectrometry. New data, with a precision of 3%-5%, were obtained from mg-sized natural uranium samples for neutron energies with an equivalent Maxwell-Boltzmann distribution of kT ∼ 25 keV and for a broad energy distribution peaking at 426 keV. The cross-section ratio of (235)U(n,γ)/(238)U(n,γ) can be deduced in accelerator mass spectrometry directly from the atom ratio of the reaction products (236)U/(239)U, independent of any fluence normalization. Our results confirm the values at the lower band of existing data. They serve as important anchor points to resolve present discrepancies in nuclear data libraries as well as for the normalization of cross-section data used in the nuclear astrophysics community for s-process studies. PMID:24877933

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Explaining discrepant depth profiles of {sup 234}U/{sup 238}U and {sup 230}Th{sub exc} in Mn-crusts

    SciTech Connect

    Neff, U.; Bollhoefer, A.; Frank, N.; Mangini, A.

    1999-08-01

    Manganese encrustations are an important archive for the reconstruction of deep ocean circulation in the past. However, because of discordant growth rates derived from the decrease of the activity ratios of {sup 234}U/{sup 238}U and of {sup 230}Th{sub exc} with depth, their dating via the measurement of depth profiles of {sup 230}Th and {sup 231}Pa has been recently put into question (Chabaux et al., 1997). In this study the authors present high precision depth profiles of uranium and thorium isotopes (TIMS) of a hydrogenous Mn-crust from the South China Sea. Indeed, the depth profiles of {sup 234}U/{sup 238}U and {sup 238}Th{sub exc} deliver very different growth rates of 8.80 {+-} 1.20 and 2.64 {+-} 0.12 mm/Ma, respectively. The authors solve this discrepancy with a simple model which assumes exchange of uranium adsorbed in the Mn-crust with uranium dissolved in the pore water. The best agreement to the data is obtained applying an exchange coefficient of 5 {times} 10{sup {minus}6} [a{sup {minus}1}]. Application of this model to the data set of Chabaux et al. (1997), reproduces very well their profiles of the {delta}{sup 234}U. The authors conclude that {sup 234}U/{sup 238}U dating of Mn-encrustations is not reliable because of open-system conditions for uranium.

  3. Measurement of electrofission cross sections and photofission yields of sup 235 U and sup 238 U in the energy region 1. 33--4. 32 GeV

    SciTech Connect

    Arakelyan, E.A.; Bayatyan, G.L.; Grigoryan, N.K.; Knyazyan, S.G.; Margaryan, A.T.; Marikyan, G.G. )

    1989-05-01

    Measurements of the electrofission cross sections and photofission yields in the nuclei {sup 235}U and {sup 238}U are reported for electron and bremsstrahlung spectrum energies in the region 1--5 GeV. The data were obtained in experiments with a multiwire low-pressure chamber for detection of fission fragments.

  4. Fragment characteristics from fission of 238U and 234U induced by 6.5-9.0 MeV bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Göök, A.; Chernykh, M.; Eckardt, C.; Enders, J.; von Neumann-Cosel, P.; Oberstedt, A.; Oberstedt, S.; Richter, A.

    2011-02-01

    Fission of 238U and 234U induced by bremsstrahlung of 6.5-9.0 MeV endpoint energy has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber, fission-fragment energy and mass distributions have been determined by means of the double kinetic-energy technique. Results on the fission-fragment characteristics from U238(γ,f) are in agreement with results from the literature. In addition fission-fragment mass and energy distributions from U234(γ,f) are presented for the first time in this energy region. An analysis of fission modes within the Brosa model has been performed. The relative yield of the S1 mode was found to be (13±3)% in 234U and (35±2)% in 238U.

  5. 234U/238U Disequilibria along sedimentary discontinuities in a deep formation: late diagenetic U-relocation processes vs. large scale fluid circulation evidence ?

    NASA Astrophysics Data System (ADS)

    Deschamps, P.; Hillaire-Marcel, C.; Michelot, J.-L.; Doucelance, R.; Ghaleb, B.

    2003-04-01

    This work is part of geological investigations undertaken by the French Agency for Nuclear Waste Management (ANDRA) in order to study the safety of radioactive waste repository in deep geological clay layers. The target formation, from Mesozoic sedimentary rocks of the eastern Paris basin (France), is a thick (130--145 m), 400--500 m deep, Callovo-Oxfordian argilite unit, that is over- and underlain by Oxfordian and Bathonian limestones, respectively. Borehole core samples have been analysed for their uranium content and 234U/238U isotopic composition in order to examine the state of radioactive equilibrium existing between these two radionuclides naturally occurring in the rock. Any observations of disequilibrium should allow i) to document the mobility of these actinides in such deposits, and ii) to constrain the time scale of the geological phenomena responsible for it. Highly precise and accurate (234U/238U) analyses were obtained using Multiple Collector Inductively Coupled Plasma Mass Spectrometry. The overall reproducibility, including both chemical separation and spectrometric measurement, is about 0.15% (2σ). Most samples of the target formation and its bounding rocks display secular equilibrium. However, in the Bathonian formation near the interface with the argilite layer, significant (234U/238U) disequilibria are observed along sub-horizontal sedimentary discontinuities, identified as styloliths, indicating that the process involved has been active during the last Ma. Isotopic and elemental compositions of uranium have been determined along a transect, perpendicular to a major discontinuity. The transect exhibits a symmetric pattern relative to this discontinuity with: (1) an increase of the U-concentration towards the stylolitic joint and (2) a sharp transition between significant (234U/238U) < 1 disequilibria in the stylolith to an excess of 234U ((234U/238U) = 1.05) in the vicinity of the joint, followed by a smooth decrease of the activity ratio

  6. 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.

  7. 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

  8. 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. PMID:16083999

  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. 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.

  11. 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)}.

  12. Quantification of 235U and 238U activity concentrations for undeclared nuclear materials by a digital gamma-gamma coincidence spectroscopy.

    PubMed

    Zhang, Weihua; Yi, Jing; Mekarski, Pawel; Ungar, Kurt; Hauck, Barry; Kramer, Gary H

    2011-06-01

    The purpose of this study is to investigate the possibility of verifying depleted uranium (DU), natural uranium (NU), low enriched uranium (LEU) and high enriched uranium (HEU) by a developed digital gamma-gamma coincidence spectroscopy. The spectroscopy consists of two NaI(Tl) scintillators and XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The results demonstrate that the spectroscopy provides an effective method of (235)U and (238)U quantification based on the count rate of their gamma-gamma coincidence counting signatures. The main advantages of this approach over the conventional gamma spectrometry include the facts of low background continuum near coincident signatures of (235)U and (238)U, less interference from other radionuclides by the gamma-gamma coincidence counting, and region-of-interest (ROI) imagine analysis for uranium enrichment determination. Compared to conventional gamma spectrometry, the method offers additional advantage of requiring minimal calibrations for (235)U and (238)U quantification at different sample geometries. PMID:21411329

  13. 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

  14. 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

  15. 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%.

  16. 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.

  17. 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. PMID:21774965

  18. Giant resonance for the actinide nuclei: Photoneutron and photofission cross sections for /sup 235/U, /sup 236/U, /sup 238/U, and /sup 232/Th

    SciTech Connect

    Caldwell, J.T.; Dowdy, E.J.; Berman, B.L.; Alvarez, R.A.; Meyer, P.

    1980-04-01

    The photoneutron cross sections sigma (..gamma..,n) and sigma (..gamma..,2n), and total photofission cross sections sigma (..gamma..,F) have been measured for /sup 235/U, /sup 236/U, /sup 238/U, and /sup 232/Th from threshold to 18.3 MeV using monoenergetic photons from the annihilation in flight of fast positrons and neutron-multiplicity detection in an efficient 4..pi.. neutron detector. Use of the ring-ratio technique allowed both the average photofission neutron energy for each nucleus to be obtained as a function of photon energy and, for /sup 236/U and /sup 238/U, the determination of the partial cross sections for first-chance sigma (..gamma.., f ) and second-chance sigma (..gamma..,n f ) photofission as well. Information extracted from the data includes integrated cross sections and their moments, giant-resonance parameters, deformation and radius parameters, and relative and absolute neutron and fission probabilities.

  19. Comparison of the (p,xn) cross sections from /sup 238/U, /sup 235/U, and /sup 232/Th targets irradiated with 200-MeV protons

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1982-01-01

    We have measured absolute cross sections for (p,xn) reactions (x ranges from 0 to 8) from /sup 238/U, /sup 235/U, and /sup 232/Th targets irradiated with 200-MeV protons at the Brookhaven AGS Linac injector. Chemical yields were determined by using /sup 239/Np and /sup 233/Pa as tracers. Yield patterns obtained in this work can be compared to the experimental results and theoretical calculations from earlier work, and they are consistent within the framework of intranuclear cascade followed by neutron evaporation and fission competition.

  20. Product yields of sup 235 U, sup 238 U, sup 237 Np, and sup 239 Pu by photofission reactions with 20-, 30-, and 60-MeV Bremsstrahlung

    SciTech Connect

    Kase, T.; Yamadera, A.; Nakamura, T. ); Shibata, S. ); Fujiwara, I. )

    1992-08-01

    This paper reports that as a basic study of photonuclear transmutation of actinides in high-level radioactive wastes using electron-produced bremsstrahlung, the absolute yields of cumulative mass distributions and the transmutation rate of {sup 235}U, {sup 238}U, {sup 237}Np, and {sup 239}Pu by photofission reactions induced by 20-, 30-, and 60-MeV bremsstrahlung were measured. The results of mass yield distributions and transmutation yields agree well with other experimental results and those calculated using photofission cross sections, respectively. The transmutation efficiency per electron increases about one order of magnitude with electron energy from 20 to 60 MeV.

  1. 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.

  2. 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. PMID:16227084

  3. Characterisation of airborne uranium and thorium contamination in northern England through measurement of U, Th and 235U/238U in tree bark.

    PubMed

    Bellis, D J; Ma, R; McLeod, C W

    2001-02-01

    Samples of tree bark were collected from four locations in Northern England (a typical rural site, a coal-fired power station, a uranium (isotopic) enrichment plant and a nuclear fuel fabrication facility), to assess the nature and extent of airborne uranium and thorium contamination. The U and Th concentrations of bark were determined by inductively coupled plasma mass spectrometry after conventional nebulisation of bark digests, whilst measurement of 235U/238U isotopic ratio utilised high efficiency nebulisation. Uranium concentrations varied between and within the sites (range, 0.01-12 micrograms g-1), with maximum values recorded within 1 km of the nuclear fuel fabrication plant (Springfields). In comparison, the concentration of Th in bark was low (mean, 0.018 microgram g-1) at all sites with the exception of the area affected by coal combustion (0.2-0.8 microgram g-1). The U/Th ratio varied from 0.5 to 3900 compared with the average crustal ratio of 0.3. Low values (< 2) were recorded at the 'coal' and 'rural' sites whilst Capenhurst and Springfields showed high values indicating the relative magnitude of uranium elevation. Significant enrichment of the natural 235U/238U ratio (0.00725) was observed near the nuclear installations, in particular, the enrichment plant (Capenhurst). PMID:11354728

  4. [Determination of 235U/238U isotope ratios in camphor tree bark samples by MC-ICP-MS after separation of uranium from matrix elements].

    PubMed

    Wang, Xiao-Ping; Zhang, Ji-Long

    2007-07-01

    Twelve camphor (cinnamomum camphora) tree bark samples were collected from Hiroshima and Kyoto, and the matrix element composition and morphology of the outer surface of these camphor tree bark samples were studied by EDXS and SEM respectively. After a dry decomposition, DOWEX 1-X8 anion exchange resin was used to separate uranium from matrix elements in these camphor tree bark samples. Finally, 235U/238 U isotope ratios in purified uranium solutions were determined by MC-ICP-MS. It was demonstrated that the outer surface of these camphor tree bark samples is porous and rough, with Al, Ca, Fe, K, Mg, Si, C, O and S as its matrix element composition. Uranium in these camphor tree bark samples can be efficiently separated and quantitatively recovered from the matrix element composition. Compared with those collected from Kyoto, the camphor tree bark samples collected from Hiroshima have significantly higher uranium contents, which may be due to the increased aerosol mass concentration during the city reconstruction. Moreover, the 235 U/23.U isotope ratios in a few camphor tree bark samples collected from Hiroshima are slightly higher than 0.007 25. PMID:17944430

  5. Determination of transfer time for sediments in alluvial plains using 238U-234U-230Th disequilibria: The case of the Ganges river system

    NASA Astrophysics Data System (ADS)

    Chabaux, François; Blaes, Estelle; Granet, Mathieu; Roupert, Raphaël di Chiara; Stille, Peter

    2012-11-01

    An approach to deriving the transfer time of sediments within alluvial plains by using the variation of the U-series nuclides in sediments collected along rivers is presented in this article and discussed in the light of new data from samples from different locations within the Ganges watershed and its outlet. These data indicate that the upstream-downstream variation of 238U-234U-230Th disequilibria in the sediments, with different variation trends for suspended and coarse-grained sediments, is probably a general feature of all Himalayan rivers flowing across the Indo-Gangetic plain. The data therefore confirm the occurrence of very different transfer times within the plain, depending on the sediments granulometry, with much shorter transfer time for the fine-grained (a few ky or less) than for the coarse-grained sediments (100 ky or more). A new solving approach, using a parallel stochastic Quantum-behaved Particle Swarm Optimization (p-QPSO), has been developed for identifying the unknown parameters of the model necessary for the determination of the transfer time. The data of sediments collected at the Ganges outlet show significant variations of the 234U/230Th activity ratios for the fine-grained sediment end-member collected in 2004 and 2008. Such variations indicate that the fine-grained sediments transit quickly (a year or less) within the plain. The highly variable activity ratios might be the result of quickly changing weathering intensities. Conversely, the U-Th variations observed for the 2004 and 2008 bedload from the Ganges basin cannot result from a short sedimentary transfer time. They probably result from the dredge sampling procedure, which might be influenced by local placer effects controlling the abundance of U and Th carrying minerals. Dredging may not allow the sampling of a representative bedload, hence it may cause an artificial mineralogical and, therefore, an U-Th variability for bedload sediments collected at different periods. At this

  6. The 238U/235U isotope ratio of the Earth and the solar system: Constrains from a gravimetrically calibrated U double spike and implications for absolute Pb-Pb ages

    NASA Astrophysics Data System (ADS)

    Weyer, Stefan; Noordmann, Janine; Brennecka, Greg; Richter, Stephan

    2010-05-01

    The ratio of 238U and 235U, the two primordial U isotopes, has been assumed to be constant on Earth and in the solar system. The commonly accepted value for the 238U/235U ratio, which has been used in Pb-Pb dating for the last ~ 30 years, was 137.88. Within the last few years, it has been shown that 1) there are considerable U isotope variations (~1.3‰) within terrestrial material produced by isotope fractionation during chemical reactions [1-3] and 2) there are even larger isotope variations (at least 3.5‰) in calcium-aluminum-rich inclusions (CAIs) in meoteorites that define the currently accepted age of the solar system [4]. These findings are dramatic for geochronology, as a known 238U/235U is a requirement for Pb-Pb dating, the most precise dating technique for absolute ages. As 238U/235U variations can greatly affect the reported absolute Pb-Pb age, understanding and accurately measuring variation of the 238U/235U ratio in various materials is critical, With these new findings, the questions also arises of "How well do we know the average U isotope composition of the Earth and the solar system?" and "How accurate can absolute Pb-Pb ages be?" Our results using a gravimetrically calibrated 233U/236U double spike IRMM 3636 [5] indicate that the U standard NBL 950a, which was commonly used to define the excepted "natural" 238U/235U isotope ratio, has a slightly lower 238U/235U of 137.836 ± 0.024. This value is indistinguishable from the U isotope compositions for NBL 960 and NBL112A, which have been determined by several laboratories, also using the newly calibrated U double spike IRMM 3636 [6]. These findings provide new implications about the average U isotope composition of the Earth and the solar system. Basalts display a very tight range of U isotope variations (~0.25-0.32‰ relative to SRM 950a). Their U isotope composition is also very similar to that of chondrites [4], which however appear to show a slightly larger spread. Accepting terrestrial

  7. 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.

  8. 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).

  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. 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.

  11. Experimental Determination of the Ratio of {sup 238}U Capture to {sup 235}U Fission in LEU-HTR Pebble-Bed Configurations

    SciTech Connect

    Koeberl, O.; Chawla, R.

    2004-01-15

    The shift toward low-enrichment uranium (LEU) fuel for gas-cooled high-temperature reactors (HTRs) has revealed a lack of experimental data for validating neutronics codes that are used for the design and licensing of such systems. In the framework of the LEU-HTR experimental program at the PROTEUS critical facility, the safety-related effects of accidental moderation increase (ingress of water or other hydrogeneous compounds) in pebble-bed HTR core configurations employing low-enriched (16.7%) fuel were investigated. An important neutron balance component in this context is the integral reaction rate ratio of {sup 238}U capture (C{sub 8}) relative to {sup 235}U fission (F{sub 5}).It was necessary to develop new experimental techniques for the accurate measurement of C{sub 8}/F{sub 5} in the doubly heterogeneous fuel pebbles. These have involved the utilization of specially prepared particle foils on the one hand and the counting of whole fuel pebbles on the other. Core-center measurements employing both experimental methods have been carried out in two different HTR-PROTEUS configurations (with and without accidental moderation increase simulation, respectively). In each case, satisfactory agreement was obtained between the experimental results based on the two techniques. By carrying out a comparison of particle-foil C{sub 8}/F{sub 5} measurements in the PROTEUS reactor's thermal column with the results of standard foil-activation measurement techniques, the systematic uncertainty (1{sigma}) of the core-center measurements could be reduced by {approx}0.6%, yielding a net experimental error of {+-}1% with either of the new methods. A comparison of the experimental results with calculations based on the MICROX-2/TWODANT codes in conjunction with JEF-1 cross sections has indicated that this calculational route overpredicts the core-center C{sub 8}/F{sub 5} value by {approx}2.5% in both the investigated configurations.

  12. 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.

  13. 235U, 238U, 232Th, 40K and 137Cs activity concentrations in marine sediments along the northern coast of Oman Sea using high-resolution gamma-ray spectrometry.

    PubMed

    Zare, Mohammad Reza; Mostajaboddavati, Mojtaba; Kamali, Mahdi; Abdi, Mohammad Reza; Mortazavi, Mohammad Seddigh

    2012-09-01

    The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine (235)U, (238)U, (232)Th, (40)K and (137)Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of (235)U, (238)U, (232)Th, (40)K and (137)Cs in sediment samples ranged between 1.01 and 2.87 Bq/kg, 11.83 and 22.68 Bq/kg, 10.7 and 25.02 Bq/kg, 222.89 and 535.07 Bq/kg and 0.14 and 2.8 Bq/kg, respectively. 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. PMID:22717321

  14. 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.

  15. Absolute photofission cross section of sup 197 Au, @Pb, sup 209 Bi, sup 232 Th, sup 238 U, and sup 235 U nuclei by 69-MeV monochromatic and polarized photons

    SciTech Connect

    Martins, J.B.; Moreira, E.L.; Tavares, O.A.P.; Vieira, J.L. Centro Brasileiro de Pesquisas Fisicas-CBPF, Rua Dr. Xavier Sigaud 150, 22290 Rio de Janeiro-RJ, ); Casano, L.; D'Angelo, A.; Schaerf, C. Istituto Nazionale di Fisica Nucleare-INFN, Sezione di Roma 2, Roma, ); Terranova, M.L. Istituto Nazionale di Fisica Nucleare-INFN, Sezione di Roma 2, Roma, Italy); Babusci, D. ); Girolami, B. Istituto Nazionale di Fisica Nuclea

    1991-07-01

    Absolute cross-section measurements for the photofission reactions of {sup 197}Au, {sup nat}Pb, {sup 209}Bi, {sup 232}Th, {sup 238}U, and {sup 235}U nuclei have been performed at an incident photon energy of 69 MeV using monochromatic and polarized photon beams and dielectric fission-track detectors. Nuclear fissility values have been obtained and results are in agreement with those from other laboratories, although in some cases discrepancies are observed between one other. For nuclei in the region of the actinides the fissility result is {approx gt}0.4, while for Au, Pb, and Bi nuclei it only is {similar to}10{sup {minus}3}--10{sup {minus}2}. Results have been interpreted in terms of the primary Levinger's quasideuteron nuclear photoabsorption followed by a mechanism of evaporation-fission competition for the excited nuclei. Shell effects have been taken into account, and they are clearly manifested when fissility is evaluated. The influence of photon polarization on photofission of {sup 238}U also has been investigated, and results have shown isotropy in the fragment azimuthal distribution.

  16. 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.

  17. Dynamics of melt generation beneath mid-ocean ridge axes: Theoretical analysis based on [sup 238]U-[sup 230]Th-[sup 226]Ra and [sup 235]U-[sup 231]Pa disequilibria

    SciTech Connect

    Zhenwei Qin )

    1993-04-01

    Although slow melting favors the generation of basaltic melt from a mantle matrix with large radioactive disequilibrium between two actinide nuclides (McKenzie, 1985a), it results in long residence time in a magma chamber, during which the disequilibrium may be removed. An equilibrium melting model modified after McKenzie (1985a) is presented here which suggests that, for a given actinide parent-daughter pair, there exists a specific melting rate at which disequilibrium between these two nuclides reaches its maximum. This melting rate depends on the decay constant of the daughter nuclide concerned and the magma chamber volume scaled to that of its source. For a given scaled chamber size, large radioactive disequilibrium between two actinide nuclides in basalts will be observed if the melting rate is such that the residence time of the magma in the chamber is comparable to the mean life of the daughter nuclide. With a chamber size 1% in volume of the melting source, the melting rates at which maximum disequilibrium in basalts is obtained are 10[sup [minus]7], 2 [times] 10[sup [minus]7], and 3 [times] 10[sup [minus]6] y[sup [minus]1], respectively for [sup 238]U-[sup 230]Th, [sup 235]U-[sup 231]Pa, and [sup 230]Th-[sup 226]Ra. This implies that, while large disequilibrium between [sup 238]U-[sup 230]Th and between [sup 235]U-[sup 231]Pa may occur together, large [sup 230]Th-[sup 226]Ra disequilibrium will not coexist with large [sup 238]U-[sup 230]Th disequilibrium, consistent with some observations. The active mantle melting zone which supplies melt to a ridge axis is inferred to be only about 10 km thick and 50 km wide. The fraction of melt present in such a mantle source at any time is about 0.01 and 0.04, respectively, if melting rate is 10[sup [minus]7] and 10[sup [minus]6] y[sup [minus]1]. The corresponding residence time of the residual melt in the matrix is 10[sup 5] and 4 [times] 10[sup 4] y. 27 refs., 3 figs.

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

    SciTech Connect

    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.

    2010-12-15

    over to the ENDF/B-VII.0 library, except for {sup 99}Mo where the present results are about 4%-relative higher for neutrons incident on {sup 239}Pu and {sup 235}U. 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 {sup 147}Nd 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

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

    DOE PAGESBeta

    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

  4. Neutron induced fission of 234U

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; Al-Adili, A.; Oberstedt, S.; Pomp, S.

    2012-02-01

    The fission fragment properties of 234U(n,f) were investigated as a function of incident neutron energy from 0.2 MeV up to 5 MeV. The fission fragment mass, angular distribution and kinetic energy were measured with a double Frisch-grid ionization chamber using both analogue and digital data acquisition techniques. The reaction 234U(n,f) is relevant, since it involves the same compound nucleus as formed after neutron evaporation from highly excited 236U*, the so-called second-chance fission of 235U. Experimental data on fission fragment properties like fission fragment mass and total kinetic energy (TKE) as a function of incident neutron energy are rather scarce for this reaction. For the theoretical modelling of the reaction cross sections for Uranium isotopes this information is a crucial input parameter. In addition, 234U is also an important isotope in the Thorium-based fuel cycle. The strong anisotropy of the angular distribution around the vibrational resonance at En = 0.77 MeV could be confirmed using the full angular range. Fluctuations in the fragment TKE have been observed in the threshold region around the strong vibrational resonance at En = 0.77 MeV. The present results are in contradiction with corresponding literature values. Changes in the mass yield around the vibrational resonance and at En = 5 MeV relative to En = 2 MeV show a different signature. The drop in mean TKE around 2.5 to 3 MeV points to pair breaking as also observed in 235,238U(n,f). The measured two-dimensional mass yield and TKE distribution have been described in terms of fission modes. The yield of the standard 1 (S1) mode shows fluctuations in the threshold of the fission cross section due to the influence of the resonance and levels off at about 20% yield for higher incident neutron energies. The S2 mode shows the respective opposite behaviour. The mean TKE of both modes decreases with En. The decrease in mean TKE overrules the increase in S1 yield, so the mean TKE is dropping

  5. 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

  6. 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

  7. Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments

    SciTech Connect

    Bros, R.; Gauthier-Lafaye, F.; Stille, P.; Turpin, L.; Holliger, Ph.

    1993-03-01

    It is generally accepted that uranium and most of the fission products, with the exception of the alkalis, alkaline earths and rare gases, remained in the irradiated uranium oxides during the nuclear reactions that took place 2.0 Ga ago in the Oklo uranium deposit (Gabon). New isotope investigations show that clay minerals from argillaceous rocks neighboring the natural fission reactor 10 at Oklo have depleted {sup 235}U with {sup 235}U/{sup 238}U ratios ranging between 0.00560 and the common natural value of 0.00725. One sample, however, is enriched in {sup 235}U with a {sup 235}U/{sup 238}U ratio of 0.007682. Leach experiments of this sample with dilute 1N HCl revealed that the {sup 235}U enrichment is actually restricted to the insoluble residue ({sup 235}U/{sup 238}U = 0.010511), whereas the leachate remains depleted in {sup 235}U. This unique discovery of very enriched uranium, together with samarium, neodymium, rubidium, and strontium isotopic analyses, indicate that a small amount of plutonium could have been more mobile than uranium in the reactor 10, and it is suggested that plutonium was incorporated in the crystallographic structure of clay minerals such as the chlorites. 28 refs., 3 figs., 1 tab.

  8. Prompt γ-rays from the Fast Neutron Induced Fission on 235,238U and 232Th

    NASA Astrophysics Data System (ADS)

    Lebois, M.; Wilson, J. N.; Halipré, P.; Leniau, B.; Matea, I.; Oberstedt, A.; Oberstedt, S.; Verney, D.

    Preliminary results from the first experiment using the LICORNE neutron source at the IPN Orsay are presented. Prompt fission gamma rays from fast-neutron induced fission of 238U, 232Th and 235U were detected. Thick samples of around 50 g of 238U and 232Th are used for the first part of the experiment. An ionisation chamber containing ∼ 10 mg samples of 238U and 235U to provide a fission trigger is used for the second part of the experiment. Gamma rays have been detected using 17 high efficiency BaF2 detectors and 6 LaBr3 scintillator detectors.

  9. Disequilibrium of the 238U series in basalt

    USGS Publications Warehouse

    Somayajulu, B.L.K.; Tatsumoto, M.; Rosholt, J.N.; Knight, R.J.

    1966-01-01

    Radioisotope analyses of basalt samples from Hawaii, Japan, and Iwo Jima show that: (1) 234U and 238U are virtually in radioactive equilibrium, (2) 230Th exceeds equilibrium values in all these samples, (3) 210Pb concentrations range from 10-200% of the equilibrium values and average 30% deficient, and (4) 226Ra is probably not in equilibrium with 234U. The source regions of the basalts or magma forming processes are open systems, chemically. The enrichment of some of the uranium-daughter nuclides is insufficient to account for the excess 206Pb in volcanic rocks. The isotopic composition of lead and specific activity of 210Pb in sublimates from Showa-shinzan, Japan are also reported. ?? 1966.

  10. 226Ra/238U disequilibrium in an upland organic soil exhibiting elevated natural radioactivity.

    PubMed

    Dowdall, Mark; O'Dea, John

    2002-01-01

    This paper presents the results of a study into the anomalous 226Ra/238U disequilibrium (226Ra/238U of 0.5-9) exhibited by an upland organic soil in Co. Donegal, Ireland. Radiochemical speciation of 226Ra, 238U and 225Ra indicates that in this organic soil the high 226Ra/238U ratio is due to loss of 235U relative to 226Ra via oxidation and mobilisation of 238U in the upper layers of the soil and subsequent loss in solution. At the lower, more reducing depths of the soil profile, 238U and 226Ra are essentially in equilibrium. Loss of 238U appears to occur primarily from the easily oxidised organic and iron oxide fractions of the soil, samples exhibiting high 226Ra/238U ratios displaying significantly lower 238U levels in these fractions than samples whose ratio is below the average value for the soil of the valley. Selective enrichment of 226Ra by plants or preferential leaching of 226Ra from the underlying rock is not supported by the results of this study. PMID:11848154

  11. Difficulties in using 234u/238u ratios to detect enriched or depleted uranium.

    PubMed

    Fleischer, Robert L

    2008-03-01

    Uranium that is highly enriched in U (HEU) is also often also enriched in U because it too is a lower-mass isotope than U and thus its concentration would be preferentially increased in any mass-sensitive enrichment process. Thus the ratio U/U might be regarded as a surrogate for U/U-the usual measure of enrichment. For this reason it has been suggested that U/U measurements be used to detect contamination by HEU. The purpose of this Note is to point out that, because of alpha-recoil effects, U/U varies widely in natural systems, and for this reason it would not be a dependable indicator of the presence of HEU. The same variations would cause U/U ratios to be doubtful indicators of depleted uranium. PMID:18301103

  12. Background reduction in 236U/238U measurements

    NASA Astrophysics Data System (ADS)

    Buompane, Raffaele; De Cesare, Mario; De Cesare, Nicola; Di Leva, Antonino; D'Onofrio, Antonio; Fifield, L. Keith; Fröhlich, Michaela; Gialanella, Lucio; Marzaioli, Fabio; Sabbarese, Carlo; Terrasi, Filippo; Tims, Stephen; Wallner, Anton

    2015-10-01

    The measurements of actinide isotopic ratios, in particular 236U/238U, in environmental samples requires high sensitivity. In particular, special effort must be devoted to the suppression of interfering nuclides, such as 235,238U, when measuring 236U. At the AMS facility of CIRCE, isotopic ratios down to ∼10-10 are currently measured using a gas E - ΔE detector. In order to push this limit lower towards natural levels, a time-of-flight system is used, featuring a micro-channel plate start detector and a Si stop detector. As the mass resolution of the latter is limited by the layout, an attempt to reduce the abundant isotope interference by other means has been undertaken. In this study, we report preliminary results on the characterization of the presence of molecular interferences when using UO-, UC- and UC2- as injected molecular ions. In particular the possibility to stabilize the current yield from carbide cathodes has been investigated: it was found that the best cathode preparation procedure is obtained pressing U salts baked at 800 °C mixed with graphite and Al powder. Moreover, the 238U background in 236U measurements is strongly reduced injecting UC- ions, as verified using a time-of-flight detection system. On the other hand, 235U interference is larger with respect to UO- injection, but this increase is smaller than expected on the basis of abundances of 13C and 17O in UC and UC2 molecules on one side and UO, on the other.

  13. Band structure of 235U

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Over a period of several years we have performed three separate experiments at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron in which 235U (thick target) was Coulomb-excited. The program involved stand-alone experiments with Gammmasphere and with the 8pi Spectrometer using 136Xe beams at 720 MeV, and a CHICO-Gammasphere experiment with a 40Ca beam at 184 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 have been analyzed to extract E2 and E3 matrix elements from the observed yields. Additionally, many M1 matrix elements could be extracted from the γ-ray branching ratios. A number of new features have emerged, including the unexpected attenuation of magnetic transitions between states of the same Nilsson multiplet, the breakdown of Coriolis staggering at high spin, and the effect of E3 collectivity on Coriolis interactions.

  14. 238U, and its decay products, in grasses from an abandoned uranium mine

    NASA Astrophysics Data System (ADS)

    Childs, Edgar; Maskall, John; Millward, Geoffrey

    2016-04-01

    Bioaccumulation of radioactive contaminants by plants is of concern particularly where the sward is an essential part of the diet of ruminants. The abandoned South Terras uranium mine, south west England, had primary deposits of uraninite (UO2) and pitchblende (U3O8), which contained up to 30% uranium. When the mine was active uranium and radium were extracted but following closure it was abandoned without remediation. Waste rock and gangue, consisting of inefficiently processed minerals, were spread around the site, including a field where ruminants are grazed. Here we report the activity concentrations of 238U, 235U 214,210Pb, and the concentrations of selected metals in the soils, roots and leaves of grasses taken from the contaminated field. Soil samples were collected at the surface, and at 30 cm depth, using an auger along a 10-point transect in the field from the foot of a waste heap. Whole, individual grass plants were removed with a spade, ensuring that their roots were intact. The soils and roots and grass leaves were freeze-dried. Activity concentrations of the radionuclides were determined by gamma spectroscopy, following 30 days incubation for development of secular equilibrium. Dried soils, roots and grasses were also digested in aqua regia and the concentrations of elements determined by ICP techniques. Maximum activity concentrations of 238U, 235U, 214Pb and 210Pb surface soils were 63,300, 4,510, 23,300 and 49,400 Bq kg‑1, respectively. The mean 238U:235U ratio was 11.8 ± 1.8, an order of magnitude lower than the natural value of 138, indicating disequilibrium within the decay chain due to mineral processing. Radionuclides in the roots had 5 times lower concentration and only grass leaves in the vicinity of the waste heap had measureable values. The mean soil to root transfer factor for 238U was 36%, the mean root to leaf was 3% and overall only 0.7% of 238U was transferred from the soil to the leaves. The roots contained 0.8% iron, possibly as

  15. Absolute photofission cross sections for /sup 235,238/U in the energy range 11. 5--30 MeV

    SciTech Connect

    Ries, H.; Mank, G.; Drexler, J.; Heil, R.; Huber, K.; Kneissl, U.; Ratzek, R.; Stroeher, H.; Weber, T.; Wilke, W.

    1984-06-01

    Absolute photofission cross sections of /sup 235/U and /sup 238/U have been measured with quasimonoenergetic photons from e/sup +/ annihilation and direct fragment detection between 11.5 and 30 MeV. The results obtained in the energy range of the giant dipole resonance (up to 18 MeV) are compared with those from previous experiments.

  16. 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

  17. 238U-230Th equilibrium in arc magmas and implications for the time scales of mantle metasomatism

    NASA Astrophysics Data System (ADS)

    Reubi, Olivier; Sims, Kenneth W. W.; Bourdon, Bernard

    2014-04-01

    Large excesses of 238U and 226Ra relative to 230Th characterize many arc magmas and are commonly interpreted to represent recent addition of slab-derived fluid to the mantle wedge beneath the arc. A significant proportion of arc magmas are, however, in 238U-230Th radioactive equilibrium. This is generally thought to result from “buffering” of the young slab fluid U-series signal by a sediment component in secular equilibrium. Here we present new 238U-230Th-226Ra and 235U-231Pa measurements for historic andesites from Volcán de Colima, Mexico. In all lavas (230Th/238U) are in equilibrium, whereas (231Pa/235U) and (226Ra/230Th) are significantly greater than one. These data demonstrate that arc magmas with (230Th/238U) equilibrium can have significant 231Pa and 226Ra excesses, precluding ageing of the magmas in the crust as the cause of 230Th/238U equilibrium. Quantitative modeling of metasomatic and melting processes further indicates that addition of sediment melts to a depleted mantle wedge produces significant 230Th excesses and that 238U excesses induced by recent addition of fluids derived from the altered oceanic crust are not sufficient to compensate these 230Th excesses. U-series activity ratios in Colima magmas are best explained by models in which the metasomatised mantle returns to secular equilibrium before melting, implying a time lag ⩾350 kyr, with subsequent production of 231Pa and 226Ra excesses by in-growth during melting rather than by addition of slab fluids. Investigation of a global compilation of U-series data in arc magma indicates that our model proposed for Colima applies to most arc magmas in or near (230Th-238U) equilibrium. The time lag between mantle metasomatism and melting appears to vary between hundreds years to more than 350 kyr in subduction zones. We posit that the absence of U/Th elemental fractionation during melting of arc sources in (230Th/238U) equilibrium reflects a higher fO2 compared to MORB sources that yield

  18. Enrichment Monitor for 235U Fuel Tubes

    SciTech Connect

    Winn, W.G.

    2001-08-22

    This report describes the performance of this prototype y-monitor of 235 Uranium enrichment. In this proposed method y-rates associated with 235U and 232U are correlated with enrichment. Instrumentation for appraising fuel tubes with this method has been assembled and tested.

  19. /sup 238/U issues resolved and unresolved

    SciTech Connect

    de Saussure, G.; Smith, A.B.

    1982-01-01

    The interaction of 1 eV to 20 MeV neutrons with /sup 238/U is discussed with emphasis on recently resolved and remaining issues relevant to both application need and physical understanding. The apparent inability of older /sup 238/U evaluations to predict the measured /sup 238/U capture rate in thermal critical lattices has stimulated several recent precise measurements of the /sup 238/U cross sections, reanalysis of older data, and improved evaluations. The recent evaluations predict satisfactorily the /sup 238/U capture rate in thermal critical lattices. In the region from 1.5 to 4 keV there are differences of the order of 15%, sometimes larger, between the values of the neutron widths of the main resonances reported by several experimenters or obtained by different evaluators. Above 4 keV there are only sparse results of resonance analysis and most evaluations adopt a statistical treatment of the resonance structure. Some factors affecting the determination of the average properties of the resonance parameters are discussed. Above the inelastic-scattering threshold, energy-averaged neutron total, scattering, capture and fission cross sections are reviewed in a unified manner integrating measurement, calculation and evaluation. (n;n') and (n;2n') energy-transfer mechanisms are addressed. Particular attention is given to neutron capture, stressing precisions consistent with applied need. Fission properties are discussed including: prompt and delayed fission-neutron spectra and nubar, and fission-product yields. Physical understanding is assayed, with attention to compound-nucleus and direct-reaction mechanisms, and applications impact is illustrated in the context of fast-breeder-reactor performance. 95 references.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Investigation of n+238U Fission Observables

    NASA Astrophysics Data System (ADS)

    Litaize, O.; Serot, O.; Regnier, D.; Manailescu, C.

    2014-04-01

    The prompt fission observables related to the 238U(n,f) reaction were investigated through a Monte Carlo simulation. Two models were tested in the FIFRELIN Monte Carlo code to simulate the de-excitation of the primary fission fragments. In the first one, prompt neutrons are emitted before prompt gammas and a Weisskopf model is used for neutrons while a level-density plus gamma-strength function statistical model is used for gammas. In the second one, an Hauser-Feshbach statistical model is used for the n/γ coupled emission using neutron-transmission coefficients provided by TALYS-1.4 and gamma-transmission coefficients calculated as in the previous model.

  5. Fixation of radionuclides in the 238U decay series in the vicinity of mineralized zones: 1. The Austatom Uranium Prospect, Northern Territory, Australia

    NASA Astrophysics Data System (ADS)

    Shirvington, P. J.

    1983-03-01

    The minimum age of a zone of secondary uranium mineralization, located at the Austatom Prospect in the Alligator Rivers region of Australia, is estimated to be 3.6 × 10 5y. This is derived from a geochronological model based on retarded leaching of 234U with respect to 238U and on ratios within the ore of these members of the 238U decay series. Although kaolinite is a dominant mineral in the weathered schist-host-rocks, retarded dissolution of 234U occurs only in the presence of the clay minerals illite and montmorillonite. In their absence the reverse occurs. A model is proposed to explain the results. Ratios of 230Th to 238U indicate that the mineralization has probably remained stationary within the weathered schist for at least 1 to 2 × 10 5y. Future use of clay minerals as buffers in radioactive waste repositories is supported by the excellent long-term retention obtained for oxidized uranium, probably due in part to isomorphic substitution into the clay crystal lattice.

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers

    USGS Publications Warehouse

    Swarzenski, P.; Campbell, P.; Porcelli, D.; McKee, B.

    2004-01-01

    Natural concentrations of 238U and ??234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (???1 m) zones of Fe(III) - and, to a lesser degree, Mn(IV) - reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ??234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ??234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ??234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface

  12. 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 (

  13. Multimode approximation for {sup 238}U photofission at intermediate energies

    SciTech Connect

    Demekhina, N. A.; Karapetyan, G. S.

    2008-01-15

    The yields of products originating from {sup 238}U photofission are measured at the bremsstrahlung endpoint energies of 50 and 3500 MeV. Charge and mass distributions of fission fragments are obtained. Symmetric and asymmetric channels in {sup 238}U photofission are singled out on the basis of the model of multimode fission. This decomposition makes it possible to estimate the contributions of various fission components and to calculate the fissilities of {sup 238}U in the photon-energy regions under study.

  14. Multimode approximation for {sup 238}U photofission at intermediate energies

    SciTech Connect

    Demekhina, N. A. Karapetyan, G. S.

    2008-01-15

    The yields of products originating from {sup 238}U photofission are measured at the Bremsstrahlung endpoint energies of 50 and 3500 MeV. Charge and mass distributions of fission fragments are obtained. Symmetric and asymmetric channels in {sup 238}U photofission are singled out on the basis of the model of multimode fission. This decomposition makes it possible to estimate the contributions of various fission components and to calculate the fissilities of {sup 238}U in the photon-energy regions under study.

  15. Neutron capture therapy with sup 235 U seeds

    SciTech Connect

    Liu, H.B.; Brugger, R.M.; Shih, J.A. )

    1992-05-01

    A combination of brachytherapy and neutron capture therapy has been evaluated using {sup 235}U metal seeds and external neutron beam irradiation. When thermal neutrons are absorbed by {sup 235}U, high-energy neutrons and gamma rays are produced and some of these deposit energy in surrounding tissue. A Monte Carlo program, using the code MCNP, has been used to evaluate two sizes of {sup 235}U seeds in a water phantom. The results of flux suppression around the seeds and dose distributions are illustrated and discussed. The results show that high doses can be delivered in a relatively short time by using {sup 235}U seeds with neutron capture therapy. This therapy with multiple needles or seeds can be envisioned as a substitute for traditional brachytherapy to give an effective killing dose.

  16. Towards the high-accuracy determination of the 238U fission cross section at the threshold region at CERN - n_TOF

    NASA Astrophysics Data System (ADS)

    Diakaki, M.; Audouin, L.; Berthoumieux, E.; Calviani, M.; Colonna, N.; Dupont, E.; Duran, I.; Gunsing, F.; Leal-Cidoncha, E.; Le Naour, C.; Leong, L. S.; Mastromarco, M.; Paradela, C.; Tarrio, D.; Tassan-Got, L.; Aerts, G.; Altstadt, S.; Alvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Badurek, G.; Barbagallo, M.; Baumann, P.; Becares, V.; Becvar, F.; Belloni, F.; Berthier, B.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calvino, F.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Cennini, P.; Cerutti, F.; Chiaveri, E.; Chin, M.; Cortes, G.; Cortes-Giraldo, M. A.; Cosentino, L.; Couture, A.; Cox, J.; David, S.; Dillmann, I.; Domingo-Pardo, C.; Dressler, R.; Dridi, W.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Finocchiaro, P.; Fraval, K.; Fujii, K.; Furman, W.; Ganesan, S.; Garcia, A. R.; Giubrone, G.; Gomez-Hornillos, M. B.; Goncalves, I. F.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gurusamy, P.; Haight, R.; Heil, M.; Heinitz, S.; Igashira, M.; Isaev, S.; Jenkins, D. G.; Jericha, E.; Kadi, Y.; Kaeppeler, F.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Kivel, N.; Kokkoris, M.; Konovalov, V.; Krticka, M.; Kroll, J.; Lampoudis, C.; Langer, C.; Lederer, C.; Leeb, H.; Lo Meo, S.; Losito, R.; Lozano, M.; Manousos, A.; Marganiec, J.; Martinez, T.; Marrone, S.; Massimi, C.; Mastinu, P.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Mondelaers, W.; Moreau, C.; Mosconi, M.; Musumarra, A.; O'Brien, S.; Pancin, J.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perkowski, J.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, L.; Poch, A.; Pretel, C.; Praena, J.; Quesada, J.; Rauscher, T.; Reifarth, R.; Riego, A.; Roman, F.; Rudolf, G.; Rubbia, C.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tavora, L.; Terlizzi, R.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Versaci, R.; Vermeulen, M. J.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Wallner, A.; Walter, S.; Ware, T.; Weigand, M.; Weiß, C.; Wiesher, M.; Wisshak, K.; Wright, T.; Zugec, P.

    2016-03-01

    The 238U fission cross section is an international standard beyond 2 MeV where the fission plateau starts. However, due to its importance in fission reactors, this cross-section should be very accurately known also in the threshold region below 2 MeV. The 238U fission cross section has been measured relative to the 235U fission cross section at CERN - n_TOF with different detection systems. These datasets have been collected and suitably combined to increase the counting statistics in the threshold region from about 300 keV up to 3 MeV. The results are compared with other experimental data, evaluated libraries, and the IAEA standards.

  17. Isotopic distributions and elemental yields for the photofission of /sup 235,238/U with 12--30-MeV bremsstrahlung

    SciTech Connect

    De Frenne, D.; Thierens, H.; Proot, B.; Jacobs, E.; De Gelder, P.; De Clercq, A.

    1984-05-01

    Combining independent yields directly measured or calculated from the charge distribution, the Kr, Rb, Sr, Sn, Sb, Te, Xe, Cs, and Ba isotopic distributions were investigated for the 12--30-MeV bremsstrahlung-induced photofission of /sup 235/U. At the same bremsstrahlung endpoint energies the Rb, Sn, Sb, Te, I, and Xe isotopic distributions were studied for the photofission of /sup 238/U. For both fissioning systems the tin distributions were significantly broader than all other distributions. From the elemental yields the proton odd-even effects were calculated as a function of Z. They turned out to be almost zero.

  18. Prompt fission γ-rays from the reactions 252Cf(SF) and 235U(nth, f) - new data

    NASA Astrophysics Data System (ADS)

    Oberstedt, S.; Belgya, T.; Billnert, R.; Bryś, T.; Geerts, W.; Hambsch, F.-J.; Kis, Z.; Martinez, T.; Oberstedt, A.; Szentmiklosi, L.; Vidali, M.

    2013-12-01

    We present new spectral data of prompt γ-ray emission from the spontaneous fission of 252Cf. This work was performed in direct response to an OECD/NEA high priority data request. We discuss the impact of our new data on evaluated nuclear data tables not only for this nuclide, but also for 238U and 241Pu, which are always produced in a reactor. Furthermore, we will show results from our investigation of prompt γ-ray emission from the reaction 235 U(nth, f), measured in at the Centre for Energy Research of the Hungarian Academy of Sciences in Budapest, Hungary. Spectral data obtained with three different detectors are consistent and led to an uncertainty on total energy and multiplicity considerably smaller than requested by the OECD/NEA.

  19. sup 238 U- and sup 232 Th-series chronology of phonolite fractionation at Mount Erebus, Antarctica

    SciTech Connect

    Reagan, M.K. ); Volpe, A.M. ); Cashman, K.V. )

    1992-03-01

    Uranium, thorium, radium, and barium abundances and {sup 234}U/{sup 238}U and {sup 230}Th/{sup 232}Th isotopic ratios determined by thermal ionization mass spectrometry and ({sup 228}Th)/({sup 232}Th) activity ratios determined by alpha spectrometry are used to date anorthoclase growth and infer magma chamber residence times of phonolites erupted in 1984 and 1988 from Mount Erebus, Antarctica. The 1984 and 1988 glasses have slightly different ({sup 230}Th)/({sup 232}Th) ratios but both have a 10% excess of ({sup 230}Th) over ({sup 238}U) and equilibrium ({sup 228}Th) values. By comparing these data and Pb-isotopic data reported in SUN and HANSON (1975) to similar data for oceanic basalts, the duration of differentiation from basanite to phonolite is limited to less than 150,000 years. The anorthoclase separates have ({sup 230}Th)/({sup 238}U) ratios exceeding those of the associated glasses but have ({sup 230}Th)/({sup 232}Th) ratios like those of the glasses. Both glasses are depleted in {sup 226}Ra with respect to {sup 230}Th by about 25%, whereas associated anorthoclase separates have extreme excesses of {sup 226}Ra over {sup 230}Th and ({sup 228}Th)/({sup 232}Th) = 2.2. On a plot of ({sup 226}Ra)/Ba vs. ({sup 230}Th)/BA, the glass-anorthoclase pairs produce isochrons averaging 2,380 y, which represents the average age of anorthoclase growth in the shallow magma system at Erebus. The implied residence time of phonolite magmas in the shallow magma chamber system of Erebus is about 3,000 y. Final crystal growth occurred after intrusion into the convecting lava lake less than decades before eruption.

  20. Gamma-ray spectroscopy of the ^238U shape isomer.

    NASA Astrophysics Data System (ADS)

    Hauschild, K.; Bauer, R. W.; Becker, J. A.; Bernstein, L. A.; Britt, H. C.; Younes, W.; Fotiades, N.

    1997-04-01

    The γ--rays de--exciting the fission isomers ^236U and ^238U are very different despite similar excitation energies, lifetimes and low--lying yrast structures. The predominant γ--ray decay branch for ^236U^m is a 1.783 MeV E1 transition (J. Schirmer, et al., Phys. Rev. Lett. 63), 2196 (1989); and Refs. therein., while ^238U^m is depopulated by a 2.513 MeV E2 γ-ray (J. Kantele, et al., Phys. Rev. C 29), 1693 (1984); and Refs. therein.. Approximately 65% of the γ--branch de-exciting ^238U^m remains to be identified. To determine the multipolarity of the remaining γ-branch out of ^238U^m we used the Gammasphere array at LBNL and the ^238U(d,pn) reaction at Ed = 20 MeV. A search for excited states in the 2^nd well has also been conducted. Preliminary results will be presented, and the γ--decay of the shape isomers discussed in context with the recent A ~190 SD decay--out results (T. L. Khoo, et al., Phys. Rev. Lett. 76), 1583 (1996); A. Lopez-Martens, et al., Phys. Lett. B380, 18 (1996); K. Hauschild, et al., submitted to Phys. Rev. C (1996)..

  1. 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.

  2. 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.

  3. Independent isomeric yield ratios and primary angular momenta in the photofission of /sup 235,238/U with 12--30-MeV bremsstrahlung

    SciTech Connect

    De Frenne, D.; Proot, B.; Thierens, H.; De Gelder, P.; Jacobs, E.; De Clercq, A.

    1984-05-01

    The independent isomeric yield ratios for /sup 129/Sn, /sup 130/Sb, /sup 131/Sn, /sup 132/Sb, /sup 133/Te, and /sup 136/I for the photofission of /sup 235/U with 12--30-MeV bremsstrahlung and for /sup 126/Sb, /sup 129/Sn, /sup 130/Sb, /sup 131/Sn, /sup 132/Sb, /sup 133/Te, and /sup 136/I for the photofission of /sup 238/U have been determined using radiochemical techniques and gamma spectrometry of fission product catcher foils and irradiated uranium samples. The root-mean-square values of the primary angular momenta of the corresponding fission fragments, J/sub rms/, were calculated with the statistical procedure of Huizenga and Vandenbosch and with the more elaborate deexcitation model of Min and Martinot. Both procedures gave, except for /sup 130/Sb, almost the same J/sub rms/ values. Our experimental results show a near independency of J/sub rms/ on the spin and excitation energy of the compound nucleus. An increase of the J/sub rms/ values with the excitation energy of the fragments is observed. In addition, a significant proton odd-even effect on the J/sub rms/ values is present for the photofission of /sup 235/U as well as /sup 238/U. Our experimental photofission results show a qualitative agreement with the theoretical calculations of Dietrich and Zielinska-Pfabe.

  4. Nuclear excitation by electronic transition of 235U

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Background: 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. Purpose: An experiment was performed to determine whether NEET of 235U occurs and to determine its excitation rate. Method: A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 790 mJ and a pulse width of 9 ns was used to generate a uranium plasma. The plasma was collected on a catcher plate and electrons from the catcher plate were accelerated and focused onto a microchannel plate detector. An observation of a decay with a 26-min half-life would suggest the creation of Um235 and the possibility that NEET of 235U occurred. Results: A 26-min decay consistent with the decay of Um235 was not observed and there was no evidence that NEET occurred. An upper limit for the NEET rate of 235U was determined to be λNEET<1.8 ×10-4 s-1, with a confidence level of 68.3%. Conclusions: The upper limit determined from this experiment is consistent with most of the past measurements. Discrepancies between this experiment and past measurements can be explained by assuming that past experiments misinterpreted the data.

  5. Nuclear excitation by electronic transition of 235U

    DOE PAGESBeta

    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.

  6. 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.

  7. 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.

  8. 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.

  9. Production of heavy isotopes in transfer reactions by collisions of {sup 238}U+{sup 238}U

    SciTech Connect

    Feng Zhaoqing; Jin Genming; Li Junqing

    2009-12-15

    The dynamics of transfer reactions in collisions of two very heavy nuclei {sup 238}U+{sup 238}U is studied within the dinuclear system (DNS) model. Collisions of two actinide nuclei form a superheavy composite system during a very short time, in which a large number of charge and mass transfers may take place. Such reactions have been investigated experimentally as an alternative way for the production of heavy and superheavy nuclei. The role of collision orientation in the production cross sections of heavy nuclides is analyzed systematically. Calculations show that the cross sections decrease drastically as the charged numbers of the heavy fragments increase. The transfer mechanism is favorable to synthesizing heavy neutron-rich isotopes, such as nuclei around the subclosure at N=162 from No (Z=102) to Db (Z=105)

  10. Improvements in 230Th dating, 230Th and 234U half-life values, and U-Th isotopic measurements by multi-collector inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cheng, Hai; Lawrence Edwards, R.; Shen, Chuan-Chou; Polyak, Victor J.; Asmerom, Yemane; Woodhead, Jon; Hellstrom, John; Wang, Yongjin; Kong, Xinggong; Spötl, Christoph; Wang, Xianfeng; Calvin Alexander, E.

    2013-06-01

    We have developed techniques for measuring 234U and 230Th on Faraday cups with precisions of 1-3 epsilon units (1 ɛ-unit=1 part in 104) using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Using a Thermo-Scientific Neptune with desolvation nebulization, we obtained ionization/transmission efficiencies of 1-2% for both U and Th. We set up protocols to correct for tailing, prepared U and Th gravimetric standards, tested a Th mass fractionation correction procedure based on U isotopes, and identified natural calcite samples likely to be in U-Th isotopic secular equilibrium. The measured atomic ratios, 234U/238U=54.970 (±0.019)×10-6 and 230Th/238U=16.916 (±0.018)×10-6, for these calcite samples were identical within errors (quoted 2σ uncertainties calculated combining all sources of error). Half-life values calculated from these ratios are consistent with previous values, but have much smaller errors: 245,620±260 a for 234U and 75,584±110 a for 230Th (quoted 2σ uncertainties calculated using all sources of error). In calculating a 230Th age, some of the systematic errors included in estimating the full error in the half-lives effectively cancel. Removing these uncertainties (uncertainty in the 238U half-life value, uncertainty in our gravimetric uranium and thorium standards, and uncertainty in the absolute isotopic composition of the uranium standard), yields effective uncertainties for the purposes of 230Th dating of ±70 a for the 234U half-life value and ±30 a for the 230Th half-life value. Under ideal circumstances, with our methods, the 2σ uncertainty in age, including uncertainty in half-life values is ±10 a at 10 ka, ±100 a at 130 ka, ±300 a at 200 ka, ±1 ka at 300 ka, ±2 ka at 400 ka, ±6 ka at 500 ka, and ±12 ka at 600 ka. The isotopic composition of a sample with an age <800 ka can clearly be resolved from the isotopic composition of a sample in secular equilibrium, assuming closed system behavior. Using these

  11. Reexamining the heavy-ion reactions 238U+238U and 238U+248Cm and actinide production close to the barrier

    NASA Astrophysics Data System (ADS)

    Kratz, J. V.; Schädel, M.; Gäggeler, H. W.

    2013-11-01

    Recent theoretical work has renewed interest in radiochemically determined isotope distributions in reactions of 238U projectiles with heavy targets that had previously been published only in parts. These data are being reexamined. The cross sections σ(Z) below the uranium target have been determined as a function of incident energy in thick-target bombardments. These are compared to predictions by a diffusion model whereby consistency with the experimental data is found in the energy intervals 7.65-8.30 MeV/u and 6.06-7.50 MeV/u. In the energy interval 6.06-6.49 MeV/u, the experimental data are lower by a factor of 5 compared to the diffusion model prediction indicating a threshold behavior for massive charge and mass transfer close to the barrier. For the intermediate energy interval, the missing mass between the primary fragment masses deduced from the generalized Qgg systematics including neutron pair-breaking corrections and the centroid of the experimental isotope distributions as a function of Z have been used to determine the average excitation energy as a function of Z. From this, the Z dependence of the average total kinetic-energy loss (TKEL¯) has been determined. This is compared to that measured in a thin-target counter experiment at 7.42 MeV/u. For small charge transfers, the values of TKEL¯ of this work are typically about 30 MeV lower than in the thin-target experiment. This difference is decreasing with increasing charge transfer developing into even slightly larger values in the thick-target experiment for the largest charge transfers. This is the expected behavior which is also found in a comparison of the partial cross sections for quasielastic and deep-inelastic reactions in both experiments. The cross sections for surviving heavy actinides, e.g., 98Cf, 99Es, and 100Fm indicate that these are produced in the low-energy tails of the dissipated energy distributions, however, with a low-energy cutoff at about 35 MeV. Excitation functions show

  12. Evaluation of the /sup 238/U neutron total cross section

    SciTech Connect

    Smith, A.; Poenitz, W.P.; Howerton, R.J.

    1982-12-01

    Experimental energy-averaged neutron total cross sections of /sup 238/U were evaluated from 0.044 to 20.0 MeV using regorous numerical methods. The evaluated results are presented together with the associated uncertainties and correlation matrix. They indicate that this energy-averaged neutron total cross section is known to better than 1% over wide energy regions. There are somwewhat larger uncertainties at low energies (e.g., less than or equal to 0.2 MeV), near 8 MeV and above 15 MeV. The present evaluation is compard with values given in ENDF/B-V.

  13. Interaction times in the {sup 136}Xe+{sup 136}Xe and {sup 238}U+{sup 238}U reactions with a quantum master equation

    SciTech Connect

    Sargsyan, V. V.; Kanokov, Z.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2009-10-15

    Using the reduced-density-matrix formalism, the interaction time of two heavy nuclei is studied. In the reactions {sup 136}Xe+{sup 136}Xe and {sup 238}U+{sup 238}U, the mean interaction time and variance of interaction time distribution are calculated and compared with those of other treatments.

  14. Potential human health risk by 234,238U and 210Po due to consumption of fish from the "Luis L. Leon" reservoir (Northern Mexico)

    NASA Astrophysics Data System (ADS)

    Luna-Porres, M. Y.; Rodríguez-Villa, M. A.; Herrera-Peraza, E.; Cabral-Lares, M.; Renteria-Villalobos, M.; Montero-Cabrera, M. E.

    2014-07-01

    The Conchos River is one of the most important in northern Mexico and the main surface waterway in the arid state of Chihuahua. The Luis L. Leon dam produces the Luis L. Leon Reservoir, which is the last major reservoir before the Conchos River enters the Rio Grande at the Texas-Chihuahua border. Activity concentrations (AC) of 234,238U and 210Po in fillet and liver of three stocked fish species (Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus), as well as in water from the Luis L. Leon reservoir were determined. 238U and 234U ACs in fillet samples showed values of 0.007-0.014 and 0.01-0.02 Bq kg-1 wet weight (ww), respectively. Liver samples for Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus species, present 210Po AC of 1.16-3.26 0.70-1.13 and 0.93-1.37 Bqṡkg-1 ww. The elemental Bioaccumulation Factor (BAF) for fish tissues respect to their concentrations in water was determined. Lepomis cyanellus species showed the highest BAF for total uranium in fillet, with value 1.5. The annual effective dose for uranium in adults by fish consumption in this work ranged from 4.46×10-3 to 3.68×10-2 μSvṡyear-1. The difference in concentrations of uranium in fillet among the studied species is likely primarily due to their differences in diet and habitat.

  15. 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.

  16. 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.

  17. 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

  18. Heavy actinide cross sections in the /sup 238/U + /sup 248/Cm reaction

    SciTech Connect

    Kratz, J V; Bruechle, W; Gaeggeler, H

    1981-01-01

    Cross sections for the production of Cf, Es, Fm, and Md isotopes in the reactions of 7.4 MeV/u /sup 238/U-ions with /sup 248/Cm targets are presented and discussed. Cross sections for the formation of heavy actinides in the reactions of 7.5 MeV/u /sup 136/Xe and /sup 238/U-projectiles with /sup 238/U-targets are presented for comparison. (WHK)

  19. Neutron Induced Capture and Fission Processes on 238U

    NASA Astrophysics Data System (ADS)

    Oprea, Cristiana; Oprea, Alexandru

    2016-03-01

    Nuclear data on Uranium isotopes are of crucial interest for new generation of nuclear reactors. Processes of interest are the nuclear reactions induced by neutrons and in this work mainly the capture and the fission process on 238U will be analyzed in a wide energy interval. For slow and resonant neutrons the many levels Breit - Wigner formalism is necessary. In the case of fast and very fast neutrons up to 200 MeV the nuclear reaction mechanism implemented in Talys will be used. The present evaluations are necessary in order to obtain the field of neutrons in the design of nuclear reactors and they are compared with experimental data from literature obtained from capture and (n,xn) processes.

  20. Collision dynamics of two 238U atomic nuclei.

    PubMed

    Golabek, Cédric; Simenel, Cédric

    2009-07-24

    Collisions of actinide nuclei form, during very short times of few 10;{-21} s, the heaviest ensembles of interacting nucleons available on Earth. Such collisions have been proposed as an alternative way to produce heavy and superheavy elements. They are also used to produce superstrong electric fields by the huge number of interacting protons to test spontaneous positron-electron (e;{+}e;{-}) pair emission predicted by the quantum electrodynamics theory. The time-dependent Hartree-Fock theory is used to study collision dynamics of two 238U atomic nuclei. In particular, the role of nuclear deformation on collision time and on reaction mechanisms such as nucleon transfer is emphasized. The highest collision times (approximately 4 x 10;{-21} s at 1200 MeV) should allow experimental signature of spontaneous e;{+}e;{-} emission in case of bare uranium ions. Surprisingly, we also observe ternary fission due to purely dynamical effects. PMID:19659346

  1. Collision Dynamics of Two {sup 238}U Atomic Nuclei

    SciTech Connect

    Golabek, Cedric; Simenel, Cedric

    2009-07-24

    Collisions of actinide nuclei form, during very short times of few 10{sup -21} s, the heaviest ensembles of interacting nucleons available on Earth. Such collisions have been proposed as an alternative way to produce heavy and superheavy elements. They are also used to produce superstrong electric fields by the huge number of interacting protons to test spontaneous positron-electron (e{sup +}e{sup -}) pair emission predicted by the quantum electrodynamics theory. The time-dependent Hartree-Fock theory is used to study collision dynamics of two {sup 238}U atomic nuclei. In particular, the role of nuclear deformation on collision time and on reaction mechanisms such as nucleon transfer is emphasized. The highest collision times (approx4x10{sup -21} s at 1200 MeV) should allow experimental signature of spontaneous e{sup +}e{sup -} emission in case of bare uranium ions. Surprisingly, we also observe ternary fission due to purely dynamical effects.

  2. 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

  3. Studying Nuclear Level Densities of 238U in the Nuclear Reactions within the Macroscopic Nuclear Models

    NASA Astrophysics Data System (ADS)

    Razavi, Rohallah; Rahmatinejad, Azam; Kakavand, Tayeb; Taheri, Fariba; Aghajani, Maghsood; Khooy, Asghar

    2016-02-01

    In this work the nuclear level density parameters of 238U have been extracted in the back-shifted Fermi gas model (BSFGM), as well as the constant temperature model (CTM), through fitting with the recent experimental data on nuclear level densities measured by the Oslo group. The excitation functions for 238U(p,2nα)233Pa, and 238U(p,4n)235Np reactions and the fragment yields for the fragments of the 238U(p,f) reaction have been calculated using obtained level density parameters. The results are compared to their corresponding experimental values. It was found that the extracted excitation functions and the fragment yields in the CTM coincide well with the experimental values in the low-energy region. This finding is according to the claim made by the Oslo group that the extracted level densities of 238U show a constant temperature behaviour.

  4. Fission fragment angular distributions for 11B and 19F+238U systems

    NASA Astrophysics Data System (ADS)

    Karnik, A.; Kailas, S.; Chatterjee, A.; Navin, A.; Shrivastava, A.; Singh, P.; Samant, M. S.

    1995-12-01

    The fission fragment angular distributions were measured at energies above the fusion barrier, for the systems 11B and 19F + 238U. An analysis of the present data along with those already available for the systems 6,7Li, 12C, and 16O + 238U was made in terms of the saddle-point statistical model. While the anisotropies were ``normal'' for 6,7Li, 11B, 12C+238U systems, the ones for 16O and 19F+238U systems were found to be ``anomalous.'' The entrance channel mass asymmetry dependence of the anisotropies as observed here is consistent with the expectations of preequilibrium fission dynamics. This result emphasizes the importance of preequilibrium fission in heavy-ion induced fusion-fission reactions.

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

    DOE PAGESBeta

    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. 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.

  7. U-Pb systems and U isotopic composition of the sandstone-hosted paleovalley Dybryn uranium deposit, Vitim uranium district, Russia

    NASA Astrophysics Data System (ADS)

    Golubev, V. N.; Chernyshev, I. V.; Chugaev, A. V.; Eremina, A. V.; Baranova, A. N.; Krupskaya, V. V.

    2013-11-01

    The isotopic (U-Pb, 238U-235U, 234U-238U) and chemical study of whole-rock samples and finegrained fractions of rocks in a vertical section of the terrigenous sequence at the Dybryn uranium deposit in the Khiagda ore field shows that a wide U-Pb isotopic age range (26.9-6.5 Ma) is caused by oxidation and disturbance of the U-Pb isotopic system in combination with protracted uranium ore deposition. The oxidation of rocks resulted in the loss of uranium relative to lead and eventually to an overestimated 206Pb/238U age at sites with a low U content. The 238U/235U ratios in the studied samples are within the range of 137.74-137.88. Samples with a high uranium content are characterized by a decreasing 238U/235U ratio with a decrease in 207Pb/235U and 206Pb/238U ages. A nonequilibrium 234U/238U ratio in most studied samples furnishes evidence for young (<1.5 Ma) transformation of the Miocene uranium ore, which is responsible for uranium migration and its redeposition.

  8. Measurements of nuclear reaction cross sections for 183, 184W + 238U near the interaction barrier

    NASA Astrophysics Data System (ADS)

    Himmele, G.; Backe, H.; Butler, P. A.; Habs, D.; Metag, V.; Specht, H. J.; Wilhelmy, J. B.

    1983-08-01

    The cross sections for inelastic scattering, nucleon transfer and transfer-induced fission have been measured for 184W + 238U as a function of bombarding energy near the interaction barrier. The inelastic scattering cross section for 183W + 238U has also been measured at one energy. The two- nucleon and one-nucleon transfer cross sections, for neutron stripping at least, are similar in magnitude which suggests a substantial enhancement for the two-nucleon transfers. The probabilities for fission following the transfer reactions show in some cases strong dependence on bombarding energy, which demonstrates that simultaneous Coulomb excitation plays an important part in transfer reactions between very heavy ions.

  9. Photofission of {sup 238}U in the giant-resonance region

    SciTech Connect

    Dzhilavyan, L. Z. Nedorezov, V. G.

    2013-12-15

    Data on cross sections for the reaction {sup 238}U(γ,F) in the giant-resonance region were analyzed in connection with the preparation of new experiments aimed at studying {sup 238}U photofission—in particular, in beams of photons from in-flight positron annihilation on internal targets of positron storage rings. These data were taken from measurements also performed with annihilation photons but from positron beams external to the accelerators used. The procedures applied in such measurements and based both on processing the multiplicity of detected neutrons and on detecting fission fragments were also analyzed.

  10. Determination of 90Sr / 238U ratio by double isotope dilution inductively coupled plasma mass spectrometer with multiple collection in spent nuclear fuel samples with in situ 90Sr / 90Zr separation in a collision-reaction cell

    NASA Astrophysics Data System (ADS)

    Isnard, H.; Aubert, M.; Blanchet, P.; Brennetot, R.; Chartier, F.; Geertsen, V.; Manuguerra, F.

    2006-02-01

    Strontium-90 is one of the most important fission products generated in nuclear industry. In the research field concerning nuclear waste disposal in deep geological environment, it is necessary to quantify accurately and precisely its concentration (or the 90Sr / 238U atomic ratio) in irradiated fuels. To obtain accurate analysis of radioactive 90Sr, mass spectrometry associated with isotope dilution is the most appropriated method. But, in nuclear fuel samples the interference with 90Zr must be previously eliminated. An inductively coupled plasma mass spectrometer with multiple collection, equipped with an hexapole collision cell, has been used to eliminate the 90Sr / 90Zr interference by addition of oxygen in the collision cell as a reactant gas. Zr + ions are converted into ZrO +, whereas Sr + ions are not reactive. A mixed solution, prepared from a solution of enriched 84Sr and a solution of enriched 235U was then used to quantify the 90Sr / 238U ratio in spent fuel sample solutions using the double isotope dilution method. This paper shows the results, the reproducibility and the uncertainties that can be obtained with this method to quantify the 90Sr / 238U atomic ratio in an UOX (uranium oxide) and a MOX (mixed oxide) spent fuel samples using the collision cell of an inductively coupled plasma mass spectrometer with multiple collection to perform the 90Sr / 90Zr separation. A comparison with the results obtained by inductively coupled plasma mass spectrometer with multiple collection after a chemical separation of strontium from zirconium using a Sr spec resin (Eichrom) has been performed. Finally, to validate the analytical procedure developed, measurements of the same samples have been performed by thermal ionization mass spectrometry, used as an independent technique, after chemical separation of Sr.

  11. Investigation of 234U(n,f) as a Function of Incident Neutron Energy

    NASA Astrophysics Data System (ADS)

    Al-Adili, A.; Hambsch, F.-J.; Oberstedt, S.; Pomp, S.

    2011-10-01

    Measurements of the reaction 234U(n,f) have been performed at incident neutron energies from 0.2 MeV to 5 MeV at the 7 MV Van De Graaf accelerator at IRMM. A twin Frisch-grid ionization chamber was used for fission-fragment detection. Parallel digital and analogue data acquisitions were applied in order to compare the two techniques. First results on the angular anisotropy and preliminary mass distributions are presented along with a first comparison between the two techniques.

  12. Fission decay of the giant quadrupole resonance for /sup 234/U

    SciTech Connect

    Arruda-Neto, J.D.T.; Berman, B.L.; Herdade, S.B.; Nascimento, I.C.

    1981-06-01

    The electrofission cross section for /sup 234/U from 5.5 to 25.4 MeV has been measured. From a combined analysis of it and the previously measured photofission cross section, using virtual-photon spectra calculated in the distorted-wave Born approximation, the E2 photofission cross section has been determined. Parameters of the fission-decay branch of the giant quadrupole resonance for this nucleus have been obtained. A comparison of the E2 and E1 integrated photofission cross sections for the even uranium isotopes shows that the E1 fission channel increases in strength more rapidly with fissility than does the E2 channel.

  13. Resource Note on Photofission of Nuclei for {sup 235}U and {sup 239}Pu Detection

    SciTech Connect

    Nieto, Michael Martin

    2004-11-15

    Open-source data exist, in widely scattered places, on photofission of the important nuclear isotopes {sup 235}U and {sup 239}Pu. These data are useful for studies aimed at detecting these materials at ports of entry. An introductory survey is given to access that data.

  14. Study of fusion-fission dynamics in 19F+238U reaction

    NASA Astrophysics Data System (ADS)

    Dubey, R.; Sugathan, P.; Jhingan, A.; Kaur, Gurpreet; Mukul, Ish; Siwal, Davinder; Saneesh, N.; Banerjee, Tathagata; Yadav, Abhishek; Thakur, Meenu; Mahajan, Ruchi; Chaterjee, M. B.

    2016-05-01

    Mass angle distribution measurements for 19F+238U reaction were carried out around the sub barrier energies. Mass angle correlation has not been observed at above and below the fusion barrier in present reaction. This infer the minimal presence of non compound like events at these bombarding energies range.

  15. Daily intakes of 232Th and 238U in Japanese males.

    PubMed

    Shiraishi, K; Igarashi, Y; Takaku, Y; Masuda, K; Yoshimizu, K; Nishimura, Y; Hongo, S; Yamaguchi, H

    1992-08-01

    Diet samples were collected by a duplicate portion method from 31 locations in Japan and were analyzed by inductively coupled plasma mass spectrometry. Average daily intakes per adult male were estimated at 1.7 mBq for 232Th and 8.8 mBq for 238U. PMID:1399617

  16. 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.

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

    DOE PAGESBeta

    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.

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

    DOE PAGESBeta

    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

  19. 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

  20. 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.

  1. 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.

  2. Fissile Nuclei Rotation Effect in {sup 235}U(n,{gamma}f) Process

    SciTech Connect

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

    2009-01-28

    A small shift of an angular distribution of prompt {gamma}-rays relative to the fission axis of {sup 236}U* {sup 235}U(n,{gamma}f) 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 {sup 236}U*, like the effect that has been observed recently at ILL in ternary fission of {sup 235}U 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{sup -21} s before or after the moment of the neck rupture. Detailed measurements of trigger {gamma}-rays energy dependence are in progress at the neutron beam 'MEPHISTO' of FRM-II reactor (Garching)

  3. 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.

  4. A new experimental proposal for {sup 235}U PFNS to answer a fifty years old question

    SciTech Connect

    Kornilov, N.; Massey, T.; Grimes, S.; Voinov, A.

    2011-07-01

    The Prompt Fission Neutron Spectrum (PFNS) from {sup 235}U(n,f) is very important for various nuclear applications. It has been investigated in different experiments. In spite of {approx}50 years of experimental efforts, a continuing conflict exists at thermal neutron energy. Microscopic experimental PFNS cannot describe macroscopic data. In this report we discuss the current status of this problem and suggest a new experiment, which could possibly resolve this problem. (authors)

  5. Exploring the multihumped fission barrier of 238U via sub-barrier photofission

    NASA Astrophysics Data System (ADS)

    Csige, L.; Filipescu, D. M.; Glodariu, T.; Gulyás, J.; Günther, M. M.; Habs, D.; Karwowski, H. J.; Krasznahorkay, A.; Rich, G. C.; Sin, M.; Stroe, L.; Tesileanu, O.; Thirolf, P. G.

    2013-04-01

    The photofission cross section of 238U was measured at sub-barrier energies as a function of the γ-ray energy using a monochromatic, high-brilliance, Compton-backscattered γ-ray beam. The experiment was performed at the High Intensity γ-ray Source (HIγS) facility at beam energies between Eγ=4.7 MeV and 6.0 MeV and with ˜3% energy resolution. Indications of transmission resonances have been observed at γ-ray beam energies of Eγ=5.1 MeV and 5.6 MeV with moderate amplitudes. The triple-humped fission barrier parameters of 238U have been determined by fitting empire-3.1 nuclear reaction code calculations to the experimental photofission cross section.

  6. Solubility of 238U radionuclide from various types of soil in synthetic gastrointestinal fluids using "US in vitro" digestion method

    NASA Astrophysics Data System (ADS)

    Rashid, Nur Shahidah Abdul; Sarmani, Sukiman; Majid, Amran Ab.; Mohamed, Faizal; Siong, Khoo Kok

    2015-04-01

    238U radionuclide is a naturally occuring radioactive material that can be found in soil. In this study, the solubility of 238U radionuclide obtained from various types of soil in synthetic gastrointestinal fluids was analysed by "US P in vitro" digestion method. The synthetic gastrointestinal fluids were added to the samples with well-ordered, mixed throughly and incubated according to the human physiology digestive system. The concentration of 238U radionuclide in the solutions extracted from the soil was measured using Induced Coupling Plasma Mass Spectrometer (ICP-MS). The concentration of 238U radionuclide from the soil samples in synthetic gastrointestinal fluids showed different values due to different homogenity of soil types and chemical reaction of 238U radionuclide. In general, the solubility of 238U radionuclide in gastric fluid was higher (0.050 - 0.209 ppm) than gastrointestinal fluids (0.024 - 0.050 ppm). It could be concluded that the US P in vitro digestion method is practicle for estimating the solubility of 238U radionuclide from soil materials and could be useful for monitoring and risk assessment purposes applying to environmental, health and contaminated soil samples.

  7. Cross Sections and Yields for the Photo-Fission Productions of {sup 238}U

    SciTech Connect

    Badamsambuu, J.; Khuukhenkhuu, G.; Norov, N.; Zuzaan, P.; Belov, A. G.; Gangrsky, Yu. P.

    2009-03-31

    The yields and reaction cross-sections of {sup 92}Sr, {sup 97}Zr, {sup 97}Nb and {sup 135}I at the photofission of {sup 238}U were measured. These fission-fragments have some peculiarities in nuclear structure or in practical using. The measurements were performed on the bremsstrahlung of FLNR JINR microtron, in the electron energy range 10-22 MeV. The activation method with Ge(Li)--detector was used in these measurements.

  8. /sup 230/Th - /sup 238/U disequilibrium systematics in young volcanic rocks

    SciTech Connect

    Newman, S.

    1983-01-01

    Radioactive disequilibrium between /sup 230/Th (t/sub .5/ = 75,200 years) and its parent, /sup 238/U, has two major applications to the study of young volcanic rocks: 1) geochronology and 2) geochemical tracer studies. Geochronological investigations include both the dating of young (< approx.250,000 year-old) lavas by the internal isochron method and the study of the temporal evolution of magma systems feeding volcanoes. Older, K-Ar-dated lavas from Mauna Kea, Hawaii and Marion Island (Prince Edward hot spot) exhibit constant initial (/sup 230/Th//sup 232/Th) (activity) ratios for the past 100,000-275,000 years. At Mt. Shasta, California, a general decrease in (/sup 230/Th//sup 232/Th)/sub 0/ through time, with evidence of possible mixing corroborated by other geochemical data, is observed. Geochemical tracer studies depend on the observations that Th/U and (/sup 230/Th//sup 238/U) can be changed by such processes as partial melting, mixing, or fluid transport, whereas (/sup 230/Th//sup 232/Th) can only be modified by mixing or the passage of time. The (/sup 230/Th//sup 238/U) ratio can be used to identify possible petrogenetic processes. All lavas exhibit (/sup 230/Th//sup 238/U) greater than or equal to 1 except for some from the Aleutians and Marianas. These observations suggest that subduction-related volcanism is the only type in which U may behave as a more incompatible element than Th, although it need not (Cascades). Recent vapor transport of U or retention of Th may explain the U-enrichment in island arc lavas.

  9. Effect of /sup 235/U concentration on fast neutron space and time eigenvalues and eigenfunctions in uranium

    SciTech Connect

    Mohan, R.; Ahmed, F.; Kothari, L.S.

    1985-05-01

    The results of a detailed study of a fast neutron diffusion length and pulsed problem in depleted and enriched subcritical uranium assemblies (0.2 to 4% /sup 235/U) are reported. The multigroup space- and time-dependent equations are solved using the eigenfunction expansion method. The effect of /sup 235/U concentration on space (diffusion length problem) and time (pulsed problem) eigenvalues and eigenfunctions, particularly on the ''discrete'' eigenvalue and eigenfunction, is discussed. The approach to equilibrium (both in space and in time) of fast neutrons changes with changing /sup 235/U concentration.

  10. 238U- 230Th- 226Ra disequilibrium in young Mt. Shasta andesites and dacites

    NASA Astrophysics Data System (ADS)

    Volpe, Alan M.

    1992-11-01

    The paper describes 238U-series nuclides and 230Th/ 232Th ratios measured by mass spectrometry in mineral separates of young Mt. Shasta andesites and dacites. The results constrain the timing of recent calc-alkaline magma fractionation at this volcano. Hotlum, Misery Hill and Black Butte rocks show small, < 13% 230Th- 238U and < 6% 226Ra- 230Th, disequilibria. Plagioclase have 7-26% 226Ra excesses, magnetite and groundmass have 4-5% 226Ra deficits, and pyroxenes have equilibrium ( 226Ra/ 230Th) activity ratios. Internal ( 230Th)-( 238U)and Ba-normalized ( 226Ra)-( 230Th) isotope diagrams for Hotlum and Black Butte dacites suggest that closed-system Th-U and Ra-Th fractionation occurred less than 10,000 years ago. Significant 226Ra- 230Th disequilibria in the Black Butte dacite strongly suggests that this rock erupted more recently than 9400 years ago. Results for Hotlum andesites suggest a longer pre-eruption crystal residence time compared to the dacites. There may also have been recent open Ra-Th system changes in the melt composition. Initial Th/U ratios for the rocks are low (2.43-2.57), similar to those in mid-ocean ridge basalts (MORB), and preclude significant assimilation of crust with markedly different Th-U composition.

  11. Studies of positron electron pair production in {sup 238}U + {sup 232}Th

    SciTech Connect

    Ahmad, I.; Back, B.B.; Betts, R.R.

    1995-08-01

    Following the non-observation of sharp sum-energy lines in our earlier {sup 238}U + {sup 181}Ta measurements, it was decided to pursue measurements of the {sup 238}U + {sup 232}Th system which, in the previously published work, showed the most striking evidence for near-equal-energy back-to-back pairs leading to sharp sum-energy lines. Following the refurbishing of the APEX silicon arrays and extensive tests of the rotating target wheel assembly, a major positron run took place in November 1994. Rolled 1-mg/cm{sub 2} {sup 232}Th targets were bombarded with 5.95-MeV/u {sup 238}U. The target rotation allowed up to 2 pnA of beam to be used without serious deterioration of the targets. Over 300,000 pairs were accumulated, representing an order-of-magnitude improvement in statistics over the previously published results. Preliminary analysis shows no evidence for the sharp lines at a cross section level orders of magnitude below those previously reported. The analysis of these data is currently being completed in preparation for publication.

  12. Potential human health risk by metal(loid)s, 234,238U and 210Po due to consumption of fish from the "Luis L. Leon" Reservoir (Northern México).

    PubMed

    Luna-Porres, Mayra Y; Rodríguez-Villa, Marco A; Herrera-Peraza, Eduardo F; Renteria-Villalobos, Marusia; Montero-Cabrera, María E

    2014-07-01

    Concentrations of As, Cu, Fe, Hg, Pb and Zn and activity concentrations from 234,238U and 210Po in water, fillet, liver and gills were determined in three stocked fish species from the Luis L. Leon reservoir, located in Northern Mexico. The considered species were Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus. 238U and 234U activity concentration (AC) in fillet samples showed values of 0.007-0.014 and 0.01-0.02 Bq∙kg-1 wet weight (ww), respectively. Liver samples for L. cyanellus, C. carpio and I. furcatus present 210Po AC of 1.16-3.26, 0.70-1.13 and 0.93-1.37 Bq∙kg-1 ww. Arsenic, mercury and lead concentration intervals in fillet samples were 0.13-0.39, 0.005-0.126 and 0.009-0.08 mg∙kg-1 ww, respectively, while in gill samples they were 0.11-0.43, 0.002-0.039 and 0.02-0.26 mg∙kg-1 ww. The elemental Bioaccumulation Factor (BAF) for fish tissues with respect to their concentrations in water was determined. L. cyanellus showed the highest BAF values for As and total U, being BAFAs = 37 and 40 L∙kg-1 in fillet and gills, respectively, and BAFU total = 1.5 L∙kg-1 in fillet. I. furcatus showed the highest BAF values for Hg and Pb, being BAFHg = 40 and 13 L∙kg-1 in fillet and gills, and BAFPb = 6.5 and 22 L∙kg-1 in fillet and gills, respectively. Some metal(loid) concentrations are slightly higher than European regulations for fish fillets. The difference in concentrations of metal(loid)s in fillet among the studied species is probably due to their differences in diet and habitat. PMID:24968208

  13. Adiabatic and coupled channels calculations for near barrier fusion of 16O +238U using realistic nucleon-nucleon interaction

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Seif, W. M.; Botros, M. M.

    2016-04-01

    We investigate the fusion cross-section and the fusion barrier distribution of 16O +238U at near- and sub-barrier energies. We use an interaction potential generated by the semi-microscopic double folding model-based on density dependent (DD) form of the realistic Michigan-three-Yukawa (M3Y) Reid nucleon-nucleon (NN) interaction. We studied the role of both the static and dynamic deformations of the target nucleus on the fusion process. Rotational and vibrational degrees of freedom of 238U-nucleus are considered. We found that the deformation and the octupole vibrations in 238U enhance its sub-barrier fusion cross-section. The signature of the the octupole vibrational modes of 238U appears clearly in its fusion barrier distribution profile.

  14. Generation of 238U Covariance Matrices by Using the Integral Data Assimilation Technique of the CONRAD Code

    NASA Astrophysics Data System (ADS)

    Privas, E.; Archier, P.; Bernard, D.; De Saint Jean, C.; Destouche, C.; Leconte, P.; Noguère, G.; Peneliau, Y.; Capote, R.

    2016-02-01

    A new IAEA Coordinated Research Project (CRP) aims to test, validate and improve the IRDF library. Among the isotopes of interest, the modelisation of the 238U capture and fission cross sections represents a challenging task. A new description of the 238U neutrons induced reactions in the fast energy range is within progress in the frame of an IAEA evaluation consortium. The Nuclear Data group of Cadarache participates in this effort utilizing the 238U spectral indices measurements and Post Irradiated Experiments (PIE) carried out in the fast reactors MASURCA (CEA Cadarache) and PHENIX (CEA Marcoule). Such a collection of experimental results provides reliable integral information on the (n,γ) and (n,f) cross sections. This paper presents the Integral Data Assimilation (IDA) technique of the CONRAD code used to propagate the uncertainties of the integral data on the 238U cross sections of interest for dosimetry applications.

  15. 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.

  16. Use of integral experiments for the assessment of the 235U capture cross section within the CIELO Project

    NASA Astrophysics Data System (ADS)

    Ichou, Raphaelle; Leclaire, Nicolas; Leal, Luiz; Ivanov, Evgeny

    2016-03-01

    A new 235U capture cross-section evaluation, evaluated by ORNL and the CEA Bruyères-le-Châtel (BRC) has been proposed within the CIELO project. IRSN, who participates in the CIELO project, contributes with data testing and has carried out benchmark calculations using few benchmarks, extracted from the ICSBEP database, for testing the new 235U evaluation. The benchmarks have been selected by privileging the experiments showing small experimental uncertainties and a significant sensitivity to 235U capture cross-section. The keff calculations were performed with both the MCNP 6 code and the 5.C.1 release of the MORET 5 code, using the ENDF/B-VII.1 library for all isotopes except 235U, for which both the ENDF/B-VII.1 and the new 235U evaluation was used. The benchmark selection allowed highlighting a significant effect on keff of the new 235U capture cross-section. The results of this data testing, provided as input for the evaluators, are presented here.

  17. Fragment mass and kinetic energy distributions for the photofission of sup 234 U with 12-, 15-, and 20-MeV bremsstrahlung

    SciTech Connect

    Verboven, M.; Jacobs, E.; Piessens, M.; Pomme, S.; De Frenne, D.; De Clercq, A. )

    1990-07-01

    Energy correlation measurements were performed for the photofission of {sup 234}U with bremsstrahlung with endpoint energy 12, 15, and 20 MeV. Overall fragment provisional and postneutron masses, and postneutron and preneutron kinetic energies, are deduced. The behavior of the fragment mass and total kinetic energy with changing {sup 234}U compound nucleus excitation energy is studied.

  18. 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'.

  19. 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.

  20. Are 0. 1%-accurate gamma-ray assays possible for /sup 235/U solutions

    SciTech Connect

    Parker, J.L.

    1983-01-01

    The factors influencing the accuracy of passive gamma-ray assay of uniform, homogeneous solution samples have been studied in some detail, particularly for the assay of /sup 235/U in uranium solutions. Factors considered are the overall long-term electronic stability, the information losses caused by the rate-related electronic processes of pulse pileup and dead-time, and the self-attenuation of gamma rays within the samples. Both experimental and computational studies indicate that gamma-ray assay procedures for solution samples of moderate size (from approx. 10 to perhaps a few hundred milliliters) are now capable of accuracies approaching 0.1% in many practical cases.

  1. Attempt to confirm superheavy element production in the 48Ca +238U reaction

    SciTech Connect

    Gregorich, K.E.; Loveland, W.; Peterson, D.; Zielinski, P.M.; Nelson, S.L.; Chung, Y.H.; Dullmann, Ch.E.; Folden III, C.M.; Aleklett,K.; Eichler, R.; Hoffman D.C.; Omtvedt, J.P.; Pang, G.K.; Schwantes,J.M.; Soverna, S.; Sprunger, P.; Sudowe, R.; Wilson, R.E.; Nitsche, H.

    2005-03-24

    An attempt to confirm production of superheavy elements in the reaction of 48Ca beams with actinide targets has been performed using the 238U(48Ca,3n)283112 reaction. Two 48Ca projectile energies were used, that spanned the energy range where the largest cross sections have been reported for this reaction. No spontaneous fission events were observed. No alpha decay chains consistent with either reported or theoretically predicted element 112 decay properties were observed. The cross section limits reached are significantly smaller than the recently reported cross sections.

  2. ^238U Fission Ion Chamber for Neutron Dosimetry at the 88-Inch Cyclotron

    NASA Astrophysics Data System (ADS)

    Wilson, Brent; McMahan, Peggy; Barquest, Brad; Johnson, Mike

    2007-10-01

    Efficiency measurements have been conducted for a commercial ^238U fission ion chamber, to be used for neutron dosimetry at the 88-Inch Cyclotron at LBNL. Fast, quasi-monoenergetic neutrons in the energy range of 5 to 30 MeV are under development at the facility through deuteron break-up, for radiation effects testing and cross-section measurements for a variety of applications. Through comparisons with absolute fluxes obtained using activation foils, and energy spectra obtained using the time-of-flight method, efficiency for both monoenergetic and white spectrum neutrons can be calculated.

  3. Fusion-Fission In The {sup 86}Kr+{sup 238}U Reaction

    SciTech Connect

    Lipoglavsek, M.; Hansen, E. Lindbo; Petrovic, T.; Vencelj, M.; Bark, R. A.; Gueorguieva, E. A.; Lawrie, J. J.; Lieder, E.; Lieder, R.; Mullins, S. M.; Ntshangase, S. S.; Papka, P.

    2008-05-12

    The {sup 86}Kr+{sup 238}U reaction has been studied at krypton beam energies about 30 MeV above the Coulomb barrier. Reaction products were detected by an array of 32 photovoltaic cells coupled to the AFRODITE {gamma}-ray detector array at iThemba LABS. A symmetric fission component has been observed at about 600 MeV total kinetic energy. This could possibly be due to fusion-fission with a cross section of 35{+-}20 mb.

  4. 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

  5. Prompt Fission Neutron Experiments on 235U(n,f) and 252Cf(SF)

    NASA Astrophysics Data System (ADS)

    Göök, A.; Hambsch, F.-J.; Oberstedt, S.; Vidali, M.

    For nuclear modeling and improved evaluation of nuclear data knowledge about fluctuations of the prompt neutron multiplicity as a function of incident neutron energy is requested for the major actinides 235U and 239Pu. Experimental investigations of the prompt fission neutron emission in resonance neutron induced fission on 235U are taking place at the GELINA facility of the IRMM. The experiment employs an array of neutron scintillation-detectors (SCINTIA) in conjunction with a newly designed 3D position sensitive twin Frisch-grid ionization chamber. A preparatory experiment on prompt fission neutron emission in 252Cf(SF) was undertaken to verify analysis procedures relevant for the implementation of the SCINTIA neutron detector array. The available literature data on the TKE dependence of the multiplicity show strong deviations. Therefore, effort was focused on investigating experimental factors in low efficiency neutron counting experiments that may lead to faulty determination of this dependence. Taking these factors into account a result that agree well with data from high efficiency neutron counting experiments is obtained.

  6. Petrogenesis and 230Th-238U disequilibrium at Mt. Shasta, California, and in the Cascades

    NASA Astrophysics Data System (ADS)

    Newman, Sally; MacDougall, J. Douglas; Finkel, Robert C.

    1986-06-01

    Petrogenesis at Mt. Shasta is dominated by mixing of magmas and/or assimilation of wall rock, as is shown by petrographic, major and trace element chemistry, and 238U-230Th disequilibrium data. At least three end- members are involved in these mixing processes. Lavas of very young Cascades lavas, from Mt. Garibaldi in the north to Lassen Peak in the south, are characterized by a large range of thorium isotopic ratios, although series of samples from single volcanoes are characterized by approximately constant (230Th/232Th). There is a monotonic decrease in this ratio from Crater Lake south through Lassen Peak, perhaps reflecting increasing thickness of the underlying crust. Th/U fractionation in Cascades lavas, as evidenced by (230Th/238U)≥ 1, is in the opposite sense to that in most island arc lavas. This trend suggests that fluid transport, which is thought to produce uranium enrichment in island arc, is lacking or somehow modified in the petrogenesis of the Cascades lavas.

  7. Depth profile of 236U/238U in soil samples in La Palma, Canary Islands

    PubMed Central

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

    2011-01-01

    The vertical distribution of the 236U/238U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the 240Pu/239Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA® Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1x2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios 236U/238U, 240Pu/239Pu and 236U/239Pu, respectively. The 236U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio 240Pu/239Pu indicated a global fallout signature we assume the same origin as the probable source for 236U. Our measured 236U/239Pu value of around 0.2 is within the expected range for this contamination source. PMID:21481502

  8. On the overestimation of {sup 238}U resonance capture by equivalence theory

    SciTech Connect

    Zhang, Q.; Wu, H.; Cao, L.; Zheng, Y.

    2013-07-01

    Extensive analyses of resonance calculation based on equivalence theory have indicated that the resonance capture of {sup 238}U is usually overestimated in a heterogeneous system. We evaluate the overestimation by generating the multi-group absorption cross sections of {sup 238}U in a PWR pin cell problem using Dancoff method with equivalence theory and other rigorous methods. The integral resonance reaction rate over resolved resonance range obtained by an integration procedure based on Narrow Resonance (NR) approximation shows that rational approximation of neutron escape probability is not the primary contributor to the overestimation, and that preserving reaction rate within rational approximation is theoretically superior to pursuing accurate escape probability. It is also implied by our results and analysis that the main contributors are the constant distribution assumption of total cross section and the NR approximation. Consequently, a two-dimensional geometry dependent resonance integral table based on the homogeneous and heterogeneous components of background cross section is suggested as an alternative to the legacy one-dimensional on the sum of the two components. (authors)

  9. Physics of Neutron Interactions with 238U: New Developments and Challenges

    NASA Astrophysics Data System (ADS)

    Capote, R.; Trkov, A.; Sin, M.; Herman, M.; Daskalakis, A.; Danon, Y.

    2014-04-01

    The latest release of the EMPIRE-3.1 system (codename Rivoli) is being used in the advanced modeling of neutron induced reactions on the 238U nucleus with the aim of improving our knowledge of neutron scattering. The reaction model includes: (i) a new rotational-vibrational dispersive optical model potential coupling the low-lying collective bands of vibrational character observed in even-even actinides, (ii) the Engelbrecht-Weidenmüller transformation allowing for inclusion of compound-direct interference effects enhanced by a dispersive treatment of the optical model potential, (iii) a multi-humped fission barrier with absorption in the secondary well as described within the optical model for fission, and (iv) a modified Lorentzian model (MLO) of the radiative strength function. Impact of the advanced modeling on elastic and inelastic scattering cross section is being assessed by both comparison with selected microscopic experimental data and integral criticality benchmarks (e.g. FLATTOP, JEMIMA and BIGTEN assemblies). Benchmark calculations provide feedback to improve the reaction modeling and reduce both model and model-parameters uncertainties. Additionally, neutron scattering yields on 238U measured accurately at RPI by the time-of-flight technique at 29, 60, 112 and 153 degrees have been used as a further constraint on the incident energy dependence of elastic and inelastically scattered neutrons. Improvement of scattering cross sections in existing libraries is discussed.

  10. Photofission product yields of 238U and 239Pu with 22-MeV bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Wen, Xianfei; Yang, Haori

    2016-06-01

    In homeland security and nuclear safeguards applications, non-destructive techniques to identify and quantify special nuclear materials are in great demand. Although nuclear materials naturally emit characteristic radiation (e.g. neutrons, γ-rays), their intensity and energy are normally low. Furthermore, such radiation could be intentionally shielded with ease or buried in high-level background. Active interrogation techniques based on photofission have been identified as effective assay approaches to address this issue. In designing such assay systems, nuclear data, like photofission product yields, plays a crucial role. Although fission yields for neutron-induced reactions have been well studied and readily available in various nuclear databases, data on photofission product yields is rather scarce. This poses a great challenge to the application of photofission techniques. In this work, short-lived high-energy delayed γ-rays from photofission of 238U were measured in between linac pulses. In addition, a list-mode system was developed to measure relatively long-lived delayed γ-rays from photofission of 238U and 239Pu after the irradiation. Time and energy information of each γ-ray event were simultaneously recorded by this system. Cumulative photofission product yields were then determined using the measured delayed γ-ray spectra.

  11. 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.

  12. High accuracy 235U(n,f) data in the resonance energy region

    NASA Astrophysics Data System (ADS)

    Paradela, C.; Duran, I.; Tassan-Got, L.; Audouin, L.; Berthier, B.; Isaev, S.; Le Naour, C.; Stephan, C.; Tarrío, D.; Abbondanno, U.; Aerts, G.; Álvarez-Pol, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Badurek, G.; Baumann, P.; Becvar, F.; Berthoumieux, E.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Domingo-Pardo, C.; Dridi, W.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fujii, K.; Furman, W.; Gonçalves, I. F.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Guerrero, C.; Gunsing, F.; Haight, R.; Heil, M.; Igashira, M.; Jericha, E.; Kadi, Y.; Kaeppeler, F.; Karadimos, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Konovalov, V.; Krticka, M.; Lampoudis, C.; Lederer, C.; Leeb, H.; Lindote, A.; Lukic, S.; Marganiec, J.; Martinez, T.; Marrone, S.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Pancin, S., J.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Praena, J.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Savvidis, I.; Tagliente, G.; Tain, J. L.; Tavora, L.; Terlizzi, R.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Weiss, C.; Wiesher, M.; Wisshak, K.

    2016-03-01

    The 235U neutron-induced cross section is widely used as reference cross section for measuring other fission cross sections, but in the resonance region it is not considered as an IAEA standard because of the scarce experimental data covering the full region. In this work, we deal with a new analysis of the experimental data obtained with a detection setup based on parallel plate ionization chambers (PPACs) at the CERN n_TOF facility in the range from 1 eV to 10 keV. The relative cross section has been normalised to the IAEA value in the region between 7.8 and 11 eV, which is claimed as well-known. Comparison with the ENDF/B-VII evaluation and the IAEA reference file from 100 eV to 10 keV are provided.

  13. 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.

  14. Measurements of γ-ray Energy and Multiplicity from 235U(nthermal) using STEFF

    NASA Astrophysics Data System (ADS)

    Pollitt, A. J.; Smith, A. G.; Tsekhanovich, I.; Dare, J. A.; Murray, L.

    2015-05-01

    The amount of energy carried by γ-rays during the fission process is an important consideration when developing new reactor designs. Many studies of γ-ray energy and multiplicity, from a multitude of fissioning systems, were measured during the 1970s. However the data from such experiments largely underestimates the heating effect caused by γ-rays in the structure of a reactor. It is therefore essential to obtain more accurate measurements of the energy carried during γ-ray emission. As such, the OECD Nuclear Energy Agency has put out a high priority request [1] for measurements of the mean γ-ray energy and multiplicity to an accuracy better than 7.5 percent from several fissioning systems; including 235U(nthermal). Measurements of the rays from these fissioning nuclei were performed with the SpecTrometer for Exotic Fission Fagments (STEFF).

  15. 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

  16. T-REX Design Considerations for Detection of Concealed 238U

    SciTech Connect

    Pruet, J; McNabb, D P

    2006-02-07

    Here they outline considerations that might inform choices for the design of a laser/linac-based light source used to detect {sup 238}U via excitation of the resonance at 680.11 keV in this isotope. They assume that the principal concern is speed of interrogation and not, e.g., how much radiological dose is imparted during a scan. It is found that if the photon detectors used in the system have an energy resolution better than or comparable to that of the interrogation beam, then to a first approximation the light source should be designed to have the highest possible specific fluence (photons per unit energy per unit time). there is also a weak dependence of scan time on the number of photons emitted per pulse of the light source. A simple formula describing the tradeoff between specific fluence and number of photons per pulse is presented.

  17. Photon scattering on /sup 238/U and the interpretation of near-threshold photofission resonances

    SciTech Connect

    Birenbaum, Y.; Alarcon, R.; Hoblit, S.D.; Laszewski, R.M.; Nathan, A.M.

    1987-10-01

    Cross sections for photon elastic scattering have been measured for /sup 238/U between 4.8 and 6.4 MeV with an energy resolution of about 50 keV. These data have been used along with existing photofission data to infer the total photoabsorption cross section sigma/sub T/ and the fission transmission coefficient T/sub f/ below neutron threshold. We find that the inferred sigma/sub T/ varies smoothly with energy and generally follows the extrapolated tail of the giant dipole resonance, and that T/sub f/ shows a broad bump between 5.6 and 5.9 MeV. These results strongly support the contention that resonances seen in near-threshold photofission cross sections are due to the fission and not the photon channel .

  18. Radiative capture of fast neutrons by /sup 165/Ho and /sup 238/U

    SciTech Connect

    McDainels, D K; Varghese, P; Drake, D M; Arthur, E; Lindholm, A; Bergqvist, I; Krumlinde, J

    1982-04-01

    Radiative capture of fast neutrons by the deformed nuclei /sup 165/Ho and /sup 238/U was measured over the 7- to 15-MeV incident neutron energy range. The ..gamma..-ray detector was a large NaI(T1) anti-Compton spectrometer, and time-of-flight techniques were used to suppress background. The total radiative capture cross section exhibits an energy dependence that clearly indicates the importance of the direct-semidirect reaction mechanism. Theoretical calculations compare favorably with experimental observations. However, the shapes of the observed ..gamma..-ray spectra differ from those calculated, indicating problems in estimating the distribution of single-particle strength for these deformed nuclei.

  19. Evaluation of 238U Resonance Parameters from 0 to 20 keV

    NASA Astrophysics Data System (ADS)

    Derrien, H.; Courcelle, A.; Leal, L. C.; Larson, N.; Santamarina, A.

    2005-05-01

    The neutron resonance parameters of 238U were obtained in the energy range 0 to 20 keV from a sequential SAMMY analysis of the most recent high-resolution neutron transmission and neutron capture cross-section measurements. Special care was taken in the analysis of the lowest s-wave resonances leading to resonance parameters slightly different from those of ENDF/B-VI (Moxon-Sowerby resonance parameters). The resolved-resonance range was extended to 20 keV, taking advantage of the high-resolution neutron transmission data of Harvey and neutron capture data of Macklin et al. Preliminary integral tests were performed with the new resonance parameters; thermal low-enriched benchmark calculations show an improvement of the keff prediction, mainly due to a 1.5% decrease of the capture cross section at 0.0253 eV and about a 0.4% decrease of the effective shielded resonance capture integral.

  20. Evaluation of 238U Resonance Parameters from 0 to 20 keV

    SciTech Connect

    Derrien, H.; Leal, L.C.; Larson, N.; Courcelle, A.; Santamarina, A.

    2005-05-24

    The neutron resonance parameters of 238U were obtained in the energy range 0 to 20 keV from a sequential SAMMY analysis of the most recent high-resolution neutron transmission and neutron capture cross-section measurements. Special care was taken in the analysis of the lowest s-wave resonances leading to resonance parameters slightly different from those of ENDF/B-VI (Moxon-Sowerby resonance parameters). The resolved-resonance range was extended to 20 keV, taking advantage of the high-resolution neutron transmission data of Harvey and neutron capture data of Macklin et al. Preliminary integral tests were performed with the new resonance parameters; thermal low-enriched benchmark calculations show an improvement of the keff prediction, mainly due to a 1.5% decrease of the capture cross section at 0.0253 eV and about a 0.4% decrease of the effective shielded resonance capture integral.

  1. Structure of N{>=}126 nuclei produced in fragmentation of {sup 238}U

    SciTech Connect

    Al-Dahan, N.; Podolyak, Zs.; Regan, P. H.; Steer, S. J.; Alkhomashi, N.; Gelletly, W.; Walker, P. M.; Farrelly, G.; Deo, A. Y.; Cullen, I. J.; Swan, T.; Bacelar, A. M. Denis; Gorska, M.; Pietri, S. B.; Gerl, J.; Domingo-Pardo, C.; Wollersheim, H. J.; Boutachkov, P.; Farinon, F.; Geissel, H.

    2009-01-28

    The nuclear structure of neutron-rich N{>=}126 nuclei have been investigated following their production via relativistic projectile fragmentation of a E/A = 1 GeV {sup 238}U beam on a Be target. The cocktail of secondary beam products were separated and identified using the GSI FRagment Separator (FRS). The nuclei of interest were implanted in a high-granularity active stopper detector set-up consisting of 6 double sided silicon strip detectors. The associated gamma-ray transitions were detected with the RISING array, consisting of 15 Euroball cluster Ge-detectors. Time-correlated gamma decays from individually identified nuclear species have been recorded, allowing the clean identification of isomeric decays.

  2. Multidimensional Skyrme-density-functional study of the spontaneous fission of 238U

    DOE PAGESBeta

    Sadhukhan, J.; Mazurek, K.; Dobaczewski, J.; Nazarewicz, W.; Sheikh, J. A.; Baran, A.

    2015-01-01

    We determined the spontaneous fission lifetime of 238U by a minimization of the action integral in a three-dimensional space of collective variables. Apart from the mass-distribution multipole moments Q20 (elongation) and Q30 (left–right asymmetry), we also considered the pairing-fluctuation parameter λ2 as a collective coordinate. The collective potential was obtained self-consistently using the Skyrme energy density functional SkM*. The inertia tensor was obtained within the nonperturbative cranking approximation to the adiabatic time-dependent Hartree–Fock–Bogoliubov approach. As a result, the pairing-fluctuation parameter λ2 allowed us to control the pairing gap along the fission path, which significantly changed the spontaneous fission lifetime.

  3. Studies of positron electron pair production in {sup 238}U + {sup 181}Ta

    SciTech Connect

    Ahmad, I.; Back, B.B.; Betts, R.R.

    1995-08-01

    Following the completion of APEX in late 1993, a two-week run on the {sup 238}U + {sup 181}Ta system at 6.1 and 6.3 MeV/u with 1 mg/cm{sup 2} targets provided, for the first time, data in which the expected sharp sum-energy lines should appear. Data from previous experiments show evidence for sharp sum-energy lines at 625, 748 and 805 keV, observed at bombarding energies from 5.9 to 6.3 MeV/u. The 625- and 809-keV lines display the characteristics of equal-energy back-to-back emission whereas the 748-keV line shows a rather different behavior. In our measurements, average beam currents of 2-3 pnA from the ATLAS accelerator were used to bombard 1-mg/cm{sup 2} rolled {sup 181}Ta targets, the energy loss in which corresponds to the ranges of bombarding energies over which the sharp sum-energy lines were previously reported. A run at 5.95 MeV/u for {sup 238}U + {sup 181}Ta followed in May 1994. These data were analyzed extensively. Sum-energy spectra measured in coincidence with scattered ions in the range 20{degrees} < {theta} < 68{degrees}. No evidence is found for the sharp sum-energy lines reported previously and, depending on the scenario assumed for the production mechanism and kinematics of the pairs, upper limits on cross sections at the 90% confidence limit range from 10-100 times smaller than the values that can be deduced from the earlier reports. We are in the process of refining the data analysis and simulations of the apparatus in order to finalize these numbers for publication.

  4. Neutron capture cross section measurements for 238U in the resonance region at GELINA

    NASA Astrophysics Data System (ADS)

    Kim, H. I.; Paradela, C.; Sirakov, I.; Becker, B.; Capote, R.; Gunsing, F.; Kim, G. N.; Kopecky, S.; Lampoudis, C.; Lee, Y.-O.; Massarczyk, R.; Moens, A.; Moxon, M.; Pronyaev, V. G.; Schillebeeckx, P.; Wynants, R.

    2016-06-01

    Measurements were performed at the time-of-flight facility GELINA to determine the 238U(n, γ) cross section in the resonance region. Experiments were carried out at a 12.5 and 60m measurement station. The total energy detection principle in combination with the pulse height weighting technique was applied using C6D6 liquid scintillators as prompt γ-ray detectors. The energy dependence of the neutron flux was measured with ionisation chambers based on the 10B(n, α) reaction. The data were normalised to the isolated and saturated 238U resonance at 6.67 eV. Special procedures were applied to reduce bias effects due to the weighting function, normalization, dead time and background corrections, and corrections related to the sample properties. The total uncertainty due to the weighting function, normalization, neutron flux and sample characteristics is about 1.5%. Resonance parameters were derived from a simultaneous resonance shape analysis of the GELINA capture data and transmission data obtained previously at a 42m and 150m station of ORELA. The parameters of resonances below 500 eV are in good agreement with those resulting from an evaluation that was adopted in the main data libraries. Between 500 eV and 1200 eV a systematic difference in the neutron width is observed. Average capture cross section data were derived from the experimental capture yield in the energy region between 3.5 keV and 90 keV. The results are in good agreement with an evaluated cross section resulting from a least squares fit to experimental data available in the literature prior to this work. The average cross section data derived in this work were parameterised in terms of average resonance parameters and included in a least squares analysis together with other experimental data reported in the literature.

  5. Cross sections for {sup 238}U(n,n{sup '}{gamma}) and {sup 238}U(n,2n{gamma}) reactions at incident neutron energies between 5 and 14 MeV

    SciTech Connect

    Hutcheson, A.; Crowell, A. S.; Fallin, B.; Howell, C. R.; Kwan, E.; Tonchev, A. P.; Tornow, W.; Angell, C.; Karwowski, H. J.; Becker, J. A.; Macri, R. A.; Dashdorj, D.; Fotiades, N.; Kawano, T.; Nelson, R. O.; Kelley, J. H.; Pedroni, R. S.

    2009-07-15

    Precision measurements of {sup 238}U(n,n{sup '}{gamma}) and {sup 238}U(n,2n{gamma}) partial cross sections have been performed at Triangle Universities Nuclear Laboratory (TUNL) to improve crucial data needed for testing nuclear reaction models in the actinide mass region. A pulsed and monoenergetic neutron beam was used in combination with high-resolution {gamma}-ray spectroscopy to obtain partial cross sections for incident neutron energies between 5 and 14 MeV. {gamma}-ray yields were measured with high-purity germanium clover and planar detectors. Measured partial cross-section data are compared with previous results using white and monoenergetic neutron beams and calculations from the GNASH and TALYS Hauser-Feshbach statistical-model codes. Present experimental results are in fair to good agreement with most of the existing data for the {sup 238}U(n,n{sup '}{gamma}) reaction. However, significant discrepancies are observed for the {sup 238}U(n,2n{gamma}) reaction.

  6. Angular correlations in emission of prescission neutrons from {sup 235}U fission induced by slow polarized neutrons

    SciTech Connect

    Danilyan, G. V.; Wilpert, T.; Granz, P.; Krakhotin, V. A.; Mezei, F.; Novitsky, V. V.; Pavlov, V. S.; Russina, M. V.; Shatalov, P. B.

    2008-12-15

    A new approach to searching for and studying scission neutrons, which is based on the analysis of specific angular correlations in nuclear fission induced by polarized neutrons, is described and used to evaluate the fraction of scission neutrons in the total number of prompt neutrons of {sup 235}U fission emitted perpendicularly to the fission axis.

  7. 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

  8. Studies on radionuclides 228Ra, 238U, 228Th and 40K in selected seaweeds of coastal Tamil Nadu, India.

    PubMed

    Saroja, P Mary; Immanuel, G; Raj, G Allen Gnana; Selvan, K Esai

    2012-09-01

    Studies on natural and anthropogenic radioactivity assume greater importance in the context of human health and development. Hence two species of seaweeds viz: Gracilaria edulis and Ulva lactuca, from three high background radiation areas (Arockiapuram, Kadiapattinam and Kurumpanai) on the southwest coast of Tamil Nadu, and Mandapam as low background radiation area of the southeast coast of Tamil Nadu were studied for variations in activity concentration of 228Ra, 40K, 238U and 228Th. Among these radionuclides, 40K recorded significant inter-species variation while 238 U and 228Th showed significant association. The overall mean concentration of radionuclides was found high in G. edulis (5.31,57.49,36.05,356.55 Bq kg(-1) for 228Ra, 40K, 238U, 228Th respectively), while the mean concentrations for U. lactuca were 4.88, 42.35, 34.40,347.70 Bqkg(-1) for 228Ra, 40K, 238U, 228Th respectively. The mean concentration of radionuclides was uniformly found low during northeast monsoon season in both the seaweed species. PMID:23734458

  9. Effects of nuclear orientation on fusion and fission process for reactions using {sup 238}U target nucleus

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Makii, H.; Nagame, Y.; Watanabe, Y.; Ohtsuki, T.; Hirose, K.; Hofmann, S.

    2010-06-01

    Fission fragment mass distributions in the reaction of {sup 30}Si+{sup 238}U were measured at the energies around the Coulomb barrier. At the above-barrier energies, the mass distribution showed Gaussian shape. At the sub-barrier energies, asymmetric fission mode peaked at A{sub L}/A{sub H}approx =90/178 was observed. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections produced by {sup 30}Si+{sup 238}U. The cross-section for {sup 263}Sg at the above-barrier energy agree with the statistical model calculation which assumes that the measured fission cross-sections are equal to the fusion cross-sections, whereas the one for {sup 264}Sg measured at the sub-barrier energy is smaller than the calculation, indicating the presence for quasifission. The fragment mass distributions are compared to those for {sup 36}S+{sup 238}U and {sup 40}Ar+{sup 238}U.

  10. Time-dependent Hartree-Fock calculations for multinucleon transfer and quasifission processes in the 238U+64Ni reaction

    NASA Astrophysics Data System (ADS)

    Sekizawa, Kazuyuki; Yabana, Kazuhiro

    2016-05-01

    Background: Multinucleon transfer (MNT) and quasifission (QF) processes are dominant processes in low-energy collisions of two heavy nuclei. They are expected to be useful to produce neutron-rich unstable nuclei. Nuclear dynamics leading to these processes depends sensitively on nuclear properties such as deformation and shell structure. Purpose: We elucidate reaction mechanisms of MNT and QF processes involving heavy deformed nuclei, making detailed comparisons between microscopic time-dependent Hartree-Fock (TDHF) calculations and measurements for the 238U+64Ni reaction. Methods: Three-dimensional Skyrme-TDHF calculations are performed. Particle-number projection method is used to evaluate MNT cross sections from the TDHF wave function after collision. Results: Fragment masses, total kinetic energy (TKE), scattering angle, contact time, and MNT cross sections are investigated for the 238U+64Ni reaction. They show reasonable agreements with measurements. At small impact parameters, collision dynamics depends sensitively on the orientation of deformed 238U. In tip (side) collisions, we find a larger (smaller) TKE and a shorter (longer) contact time. In tip collisions, we find a strong influence of quantum shells around 208Pb. Conclusions: It is confirmed that the TDHF calculations reasonably describe both MNT and QF processes in the 238U64Ni reaction. Analyses of this system indicate the significance of the nuclear structure effects such as deformation and quantum shells in nuclear reaction dynamics at low energies.

  11. 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

  12. Potential Human Health Risk by Metal(loid)s, 234,238U and 210Po due to Consumption of Fish from the “Luis L. Leon” Reservoir (Northern México)

    PubMed Central

    Luna-Porres, Mayra Y.; Rodríguez-Villa, Marco A.; Herrera-Peraza, Eduardo F.; Renteria-Villalobos, Marusia; Montero-Cabrera, María E.

    2014-01-01

    Concentrations of As, Cu, Fe, Hg, Pb and Zn and activity concentrations from 234,238U and 210Po in water, fillet, liver and gills were determined in three stocked fish species from the Luis L. Leon reservoir, located in Northern Mexico. The considered species were Lepomis cyanellus, Cyprinus carpio and Ictalurus furcatus. 238U and 234U activity concentration (AC) in fillet samples showed values of 0.007–0.014 and 0.01–0.02 Bq∙kg−1 wet weight (ww), respectively. Liver samples for L. cyanellus, C. carpio and I. furcatus present 210Po AC of 1.16–3.26, 0.70–1.13 and 0.93–1.37 Bq∙kg−1 ww. Arsenic, mercury and lead concentration intervals in fillet samples were 0.13–0.39, 0.005–0.126 and 0.009–0.08 mg∙kg−1 ww, respectively, while in gill samples they were 0.11–0.43, 0.002–0.039 and 0.02–0.26 mg∙kg−1 ww. The elemental Bioaccumulation Factor (BAF) for fish tissues with respect to their concentrations in water was determined. L. cyanellus showed the highest BAF values for As and total U, being BAFAs = 37 and 40 L∙kg−1 in fillet and gills, respectively, and BAFU total = 1.5 L∙kg−1 in fillet. I. furcatus showed the highest BAF values for Hg and Pb, being BAFHg = 40 and 13 L∙kg−1 in fillet and gills, and BAFPb = 6.5 and 22 L∙kg−1 in fillet and gills, respectively. Some metal(loid) concentrations are slightly higher than European regulations for fish fillets. The difference in concentrations of metal(loid)s in fillet among the studied species is probably due to their differences in diet and habitat. PMID:24968208

  13. 238U-230Th crystallization ages for the oldest domes of the Mono Craters, eastern California

    NASA Astrophysics Data System (ADS)

    Marcaida, M.; Vazquez, J. A.

    2014-12-01

    The Mono Craters volcanic chain is one of the youngest areas of rhyolitic volcanism in the Mono Lake-Long Valley region of eastern California. Located just south of Mono Lake, the Mono Craters comprise at least 28 individual domes and flows (numbered 3-30, north to south); however, the timing and frequency of eruptions remain poorly resolved. The earliest signs of volcanic activity are preserved as numerous tephra layers (Ashes 1-19, top to bottom) in the late Pleistocene Wilson Creek formation of ancestral Mono Lake, which indicate that rhyolitic volcanism from Mono Craters began by at least ca. 62 ka [1]. Although the current chronology indicates that most of the Mono Craters are younger than ca. 20 ka [2-4], similar compositions of titanomagnetite from both pumice and lava potentially correlate several Wilson Creek tephras to porphyritic biotite-bearing domes 11, 24, and 19 of the Mono Craters [5], suggesting that multiple domes in the Mono Craters chain reflect volcanism older than ca. 20 ka. Ash 3 is correlated to dome 11 based on similar ca. 20 ka ages and titanomagnetite compositions [6]. More recently, we performed ion microprobe 238U-230Th dating of unpolished rims of allanite and zircon from domes 24 and 19, yielding isochron ages of ca. 38 ka and ca. 42 ka, respectively. The age of dome 24 is consistent with the ca. 38 ka age of its potential correlative tephra layers [1, 5], indicating that dome 24 is likely the extrusive equivalent of Ashes 9-10. Dome 19 has titanomagnetite crystals with similar bimodal chemistry to titanomagnetites from Ash 15 [5]. The age of dome 19 is indistinguishable from the 238U-230Th age of Ash 15 [1], which erupted during a prominent geomagnetic excursion, originally designated as the "Mono Lake" excursion. Combining geochronological and titanomagnetite compositional data confirms that Ash 15 and its extrusive equivalent, dome 19, erupted during the Laschamp excursion. [1] Vazquez, J.A. and Lidzbarski, M.I. (2012) EPSL 357

  14. Prompt fission neutron spectra of n+235U above the (n,nf) fission threshold

    NASA Astrophysics Data System (ADS)

    Shu, Neng-Chuan; Jia, Min; Chen, Yong-Jing; Liu, Ting-Jin

    2015-05-01

    Calculations of prompt fission neutron spectra (PFNS) from the 235U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n,xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n,xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n,nf) or (n,2nf) reactions influences the PFNS shape, and the neutron spectra of the (n,xnf) fission-channel are soft compared with the neutron spectra of the (n,f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. Supported by National Natural Science Foundation of China (11205246, 91126010, U1230127, 91226102), IAEA CRP (15905), and Defense Industrial Technology Development Program (B0120110034)

  15. Dynamics of neutron-induced fission of 235U using four-dimensional Langevin equations

    NASA Astrophysics Data System (ADS)

    Pahlavani, M. R.; Mirfathi, S. M.

    2015-08-01

    Background: Langevin equations have been suggested as a key approach to the dynamical analysis of energy dissipation in excited nuclei, formed during heavy-ion fusion-fission reactions. Recently, a few researchers theoretically reported investigations of fission for light nuclei in a low excitation energy using the Langevin approach, without considering the contribution of pre- and post-scission particles and γ -ray emission. Purpose: We study the dynamical evolution of mass distribution of fission fragments, and neutron and γ -ray multiplicity for 236U as compound nuclei that are constructed after fusion of a neutron and 235U. Method: Energy dissipation of the compound nucleus through fission is calculated using the Langevin dynamical approach combined with a Monte Carlo method. Also the shape of the fissioning nucleus is restricted to "funny hills" parametrization. Results: Fission fragment mass distribution, neutron and γ -ray multiplicity, and the average kinetic energy of emitted neutrons and γ rays at a low excitation energy are calculated using a dynamical model, based on the four-dimensional Langevin equations. Conclusions: The theoretical results show reasonable agreement with experimental data and the proposed dynamical model can well explain the energy dissipation in low energy induced fission.

  16. Fission Fragment Charge and Mass Distributions from Intermediate-Energy Reactions of 238-U Projectiles

    NASA Astrophysics Data System (ADS)

    Souliotis, G. A.; Loveland, W.; Zyromski, K. E.; Wozniak, G. J.; Morrissey, D. J.; Aleklett, Kjell

    1999-10-01

    The charge, mass and velocity distributions of fission fragments from the interaction of 20 MeV/nucleon 238-U projectiles with 27-Al and 208-Pb have been measured using the MSU A1200 fragment separator. The observed distributions from the U+Al reaction are consistent with fission following fusion-like events giving rise to products that are very n-deficient relative to the line of beta-stability. However, the distributions from the U+Pb reaction are consistent with fission following quasielastic or deep-inelastic collisions, resulting in fragments that are neutron rich. Substantial yields of very n-rich nuclei are observed. Estimates of rates of important n-rich nuclides from a typical second generation projectile-fragmentation (PF) facility are given. Finally, the importance of the present cross section data for the planning of next generation intermediate-energy PF facilities able to produce short-lived neutron-rich radioactive beams by fission of heavy projectiles is discussed.

  17. Unusual 232Th and 238U contamination on some road surfaces in Taoyuan, Taiwan.

    PubMed

    Chang, W P; Nabyvanets, Y B; Jen, M H

    2001-06-01

    At least eight bustling streets or approximately 3-5% of all the road surface of civilian utility in the downtown area of Taoyuan City, Taiwan, were inadvertently found to contain unusual levels of radioactivity during a routine environmental radiation surveillance in mid-1994. Crushed rock debris and coarse sands separated from the asphalt pavement were identified to be the source of excessive radioactivity. By employing gamma spectrometry, we have measured 232Th activity (via 228Ac) and mU activity (via 214Bi) in some of the samples to be up to about 4,000 and 1,000 Bq kg(-1), respectively. The dose rate on the road surface reached about 1.3 microSv h(-1), as compared with the background level of 0.08 microSv h(-1) in much of Taiwan. This unusual radioactivity was due to accidental mixing of road construction materials with materials enriched 232Th and 238U. PMID:11388731

  18. Prompt fission neutron spectra in fast-neutron-induced fission of 238U

    NASA Astrophysics Data System (ADS)

    Desai, V. V.; Nayak, B. K.; Saxena, A.; Suryanarayana, S. V.; Capote, R.

    2015-07-01

    Prompt fission neutron spectrum (PFNS) measurements for the neutron-induced fission of 238U are carried out at incident neutron energies of 2.0, 2.5, and 3.0 MeV, respectively. The time-of-flight technique is employed to determine the energy of fission neutrons. The prompt fission neutron energy spectra so obtained are analyzed using Watt parametrization to derive the neutron multiplicity and average prompt fission neutron energy. The present experimental PFNS data are compared with the evaluated spectra taken from the ENDF/B-VII.1 library and the predictive calculations carried out using the empire-3.2 (Malta) code with built-in Los Alamos (LA) and Kornilov PFNS models. The sensitivity of the empire-3.2 LA model-calculated PFNS to the nuclear level density parameter of the average fission fragment and to the total kinetic energy is investigated. empire-3.2 LA model PFNS calculations that use Madland 2006-recommended values [D. G. Madland, Nucl. Phys. A 772, 113 (2006), 10.1016/j.nuclphysa.2006.03.013] of the total kinetic energy and the level density parameter a =A /(10 ±0.5 ) compare very well to measured data at all incident neutron incident energies.

  19. Retardation of 238U and 232Th decay chain radionuclides in Long Island and Connecticut aquifers

    NASA Astrophysics Data System (ADS)

    Copenhaver, Sally A.; Krishnaswami, S.; Turekian, Karl K.; Epler, Nathan; Cochran, J. K.

    1993-02-01

    Knowledge of the ability of an aquifer to retard the groundwater transport of toxic or radioactive ions can be inferred from the analysis of groundwater for the radionuclides of the 238U- and 232Th-decay chains. Groundwaters of varying chemical composition were analyzed from wells in Long Island, New York, and Connecticut. Aquifer lithologies are arkose, quartz sandstone, granite, and glacial drift. Adsorption ( k1) and desorption ( k2) coefficients for Ra and Pb were calculated using 222Rn activity as a measure of the supply of other α-recoil nuclides. Laboratory tests of the validity of this assumption were made by measuring the flux of 224Ra and 222Rn from aquifer solids. The ratio k 1/k 2 is the distribution coefficient, K, which is effectively equal to R ƒ, the retardation factor. The average value of K for Ra is 6 × 10 2 in Long Island aquifers and 5 × 10 4 in Connecticut. The distribution coefficient for Pb is 10 4 in Long Island and 10 5 in Connecticut. Results from this and other studies reveal a strong dependence of retardation on pH, ƒ O 2, and ionic strength that tends to overwhelm any dependence of retardation on lithology.

  20. 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.

  1. Review of PGDP assessment of criticality safety problems in increasing product assay to 5 wt % /sup 235/U

    SciTech Connect

    Petrie, L.M.; Turner, J.C.; Stewart, G.B.

    1985-02-01

    Paducah Gaseous Diffusion Plant (PGDP) performed an evaluation of the PGDP facilities to determine the feasibility of increasing product assay from 2.0 wt % to 5.0 wt % /sup 235/U and to determine the impact of this increase on plant criticality safety; their conclusions are reported in KY-710. This report critiques the methods used and conclusions reached in KY-710. 4 figures, 5 tables.

  2. Field analyses of (238)U and (226)Ra in two uranium mill tailings piles from Niger using portable HPGe detector.

    PubMed

    Déjeant, Adrien; Bourva, Ludovic; Sia, Radia; Galoisy, Laurence; Calas, Georges; Phrommavanh, Vannapha; Descostes, Michael

    2014-11-01

    The radioactivities of (238)U and (226)Ra in mill tailings from the U mines of COMINAK and SOMAÏR in Niger were measured and quantified using a portable High-Purity Germanium (HPGe) detector. The (238)U and (226)Ra activities were measured under field conditions on drilling cores with 600s measurements and without any sample preparation. Field results were compared with those obtained by Inductive Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and emanometry techniques. This comparison indicates that gamma-ray absorption by such geological samples does not cause significant deviations. This work shows the feasibility of using portable HPGe detector in the field as a preliminary method to observe variations of radionuclides concentration with the aim of identifying samples of interest. The HPGe is particularly useful for samples with strong secular disequilibrium such as mill tailings. PMID:25036918

  3. Revisiting the {sup 238}U Thermal Capture Cross Section and Gamma-Ray Emission Probabilities from {sup 239}Np Decay

    SciTech Connect

    Trkov, A.; Molnar, G.L.; Revay, Zs.; Mughabghab, S.F.; Firestone, R.B.; Pronyaev, V.G.; Nichols, A.L.; Moxon, M.C

    2005-07-15

    The precise value of the thermal capture cross section of {sup 238}U is uncertain, and evaluated cross sections from various sources differ by more than their assigned uncertainties. A number of the original publications have been reviewed to assess the discrepant data, corrections were made for more recent standard cross sections and other constants, and one new measurement was analyzed. Because of the strong correlations in activation measurements, the gamma-ray emission probabilities from the {beta}{sup -} decay of {sup 239}Np were also analyzed. As a result of the analysis, a value of 2.683 {+-} 0.012 b was derived for the thermal capture cross section of {sup 238}U. A new evaluation of the gamma-ray emission probabilities from {sup 239}Np decay was also undertaken.

  4. Light nuclides produced in the proton-induced spallation of {sup 238}U at 1 GeV

    SciTech Connect

    Ricciardi, M.V.; Armbruster, P.; Enqvist, T.; Kelic, A.; Rejmund, F.; Schmidt, K.-H.; Yordanov, O.; Benlliure, J.; Pereira, J.; Bernas, M.; Mustapha, B.; Stephan, C.; Tassan-Got, L.

    2006-01-15

    The production of light and intermediate-mass nuclides formed in the reaction {sup 1}H+{sup 238}U at 1 GeV was measured at the Fragment Separator at GSI, Darmstadt. The experiment was performed in inverse kinematics, by shooting a 1 A GeV {sup 238}U beam on a thin liquid-hydrogen target. A total of 254 isotopes of all elements in the range 7{<=}Z{<=}37 were unambiguously identified, and the velocity distributions of the produced nuclides were determined with high precision. The results show that the nuclides are produced in a very asymmetric binary decay of heavy nuclei originating from the spallation of uranium. All the features of the produced nuclides merge with the characteristics of the fission products as their mass increases.

  5. Solubility of {sup 238}U radionuclide from various types of soil in synthetic gastrointestinal fluids using “US in vitro” digestion method

    SciTech Connect

    Rashid, Nur Shahidah Abdul; Sarmani, Sukiman; Majid, Amran Ab.; Mohamed, Faizal; Siong, Khoo Kok

    2015-04-29

    238U radionuclide is a naturally occuring radioactive material that can be found in soil. In this study, the solubility of 238U radionuclide obtained from various types of soil in synthetic gastrointestinal fluids was analysed by “US P in vitro” digestion method. The synthetic gastrointestinal fluids were added to the samples with well-ordered, mixed throughly and incubated according to the human physiology digestive system. The concentration of 238U radionuclide in the solutions extracted from the soil was measured using Induced Coupling Plasma Mass Spectrometer (ICP-MS). The concentration of 238U radionuclide from the soil samples in synthetic gastrointestinal fluids showed different values due to different homogenity of soil types and chemical reaction of 238U radionuclide. In general, the solubility of 238U radionuclide in gastric fluid was higher (0.050 – 0.209 ppm) than gastrointestinal fluids (0.024 – 0.050 ppm). It could be concluded that the US P in vitro digestion method is practicle for estimating the solubility of 238U radionuclide from soil materials and could be useful for monitoring and risk assessment purposes applying to environmental, health and contaminated soil samples.

  6. Production of unknown neutron-rich isotopes in 238U collisions at near-barrier energy

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Li, Zhuxia; Zhang, Yingxun; Wang, Ning; Li, Qingfeng; Shen, Caiwan; Wang, Yongjia; Wu, Xizhen

    2016-08-01

    The production cross sections for primary and residual fragments with charge number from Z =70 to 120 produced in the collision of 238U at 7.0 MeV/nucleon are calculated by the improved quantum molecular dynamics (ImQMD) model incorporated with the statistical evaporation model (hivap code). The calculation results predict that about 60 unknown neutron-rich isotopes from elements Ra (Z =88 ) to Db (Z =105 ) can be produced with the production cross sections above the lower bound of 10-8 mb in this reaction. And almost all of the unknown neutron-rich isotopes are emitted at the laboratory angles θlab≤60°. Two cases, i.e., the production of the unknown uranium isotopes with A ≥244 and that of rutherfordium with A ≥269 , are investigated to understand the production mechanism of unknown neutron-rich isotopes. It is found that for the former case the collision time between two uranium nuclei is shorter and the primary fragments producing the residues have smaller excitation energies of ≤30 MeV and the outgoing angles of those residues cover a range of 30°-60°. For the latter case, a longer collision time is needed for a large number of nucleons being transferred and thus it results in higher excitation energies and smaller outgoing angles of primary fragments, and eventually results in a very small production cross section for the residues of Rf with A ≥269 which have a small interval of outgoing angles of θlab=40°-50°.

  7. 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

  8. Giant resonances in {sup 238}U within the quasiparticle random-phase approximation with the Gogny force

    SciTech Connect

    Peru, S.; Gosselin, G.; Martini, M.; Dupuis, M.; Hilaire, S.

    2011-01-15

    Fully consistent axially-symmetric deformed quasiparticle random-phase approximation (QRPA) calculations have been performed, using the same Gogny D1S effective force for both the Hartree-Fock-Bogolyubov mean field and QRPA matrix. New implementation of this approach leads to the applicability of QRPA to heavy deformed nuclei. Giant resonances and low-energy collective states for monopole, dipole, quadrupole, and octupole modes are predicted for the heavy deformed nucleus {sup 238}U and compared with experimental data.

  9. Measurement of evaporation residue cross-sections of the reaction 30Si + 238U at subbarrier energies

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nagame, Y.; Tsukada, K.; Tsuruta, K.; Hofmann, S.; Hessberger, F. P.; Ackermann, D.; Heinz, S.; Khuyagbaatar, J.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mazzocco, M.; Schoett, H. J.; Antalic, S.; Saro, S.; Comas, V. F.; Heredia, J. A.

    2007-02-26

    The reaction 30Si + 238U {yields} 268Sg* was studied at beam energies close to the Coulomb barrier. At the above barrier energy of Ec.m. = 144.0 MeV (center-of-mass energy at half thickness of the target), we measured three decay chains of 263Sg produced by evaporation of five neutrons. The cross-section was (67{sub -37}{sup +67}) pb. At subbarrier energy of Ec.m. = 133.0 MeV we measured three spontaneously fissioning nuclei which we assigned to the isotope 264Sg. The half-life of (120{sub -44}{sup +126}) ms was determined. The production cross-section was (10{sub -6}{sup +10}) pb, which is about four orders magnitude larger than the calculation based on the one-dimensional barrier penetration model in the fusion process, showing fusion enhancement caused by the prolate deformation of 238U. At Ec.m. = 128.0 MeV an upper cross-section limit of 15 pb was measured. Compared to excitation functions measured for the lighter system 16O + 238U {yields} 254Fm*, a reduction of the fusion probability was observed at low beam energies indicating increasing competition from quasifission processes.

  10. Advances in Multicollector ICPMS for precise and accurate isotope ratio measurements of Uranium isotopes

    NASA Astrophysics Data System (ADS)

    Bouman, C.; Lloyd, N. S.; Schwieters, J.

    2011-12-01

    The accurate and precise determination of uranium isotopes is challenging, because of the large dynamic range posed by the U isotope abundances and the limited available sample material. Various mass spectrometric techniques are used for the measurement of U isotopes, where TIMS is the most accepted and accurate one. Multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) can offer higher productivity compared to TIMS, but is traditionally limited by low efficiency of sample utilisation. This contribution will discuss progress in MC-ICPMS for detecting 234U, 235U, 236U and 238U in various uranium reference materials from IRMM and NBL. The Thermo Scientific NEPTUNE Plus with Jet Interface offers a modified dry plasma ICP interface using a large interface pump combined with a special set of sample and skimmer cones giving ultimate sensitivity for all elements across the mass range. For uranium, an ion yield of > 3 % was reported previously [1]. The NEPTUNE Plus also offers Multi Ion Counting using discrete dynode electron multipliers as well as two high abundance-sensitivity filters to discriminate against peak tailing effects on 234U and 236U originating from the major uranium beams. These improvements in sensitivity and dynamic range allow accurate measurements of 234U, 235U and 236U abundances on very small samples and at low concentration. In our approach, minor U isotopes 234U and 236U were detected on ion counters with high abundance sensitivity filters, whereas 235U and 238U were detected on Faraday Cups using a high gain current amplifier (10e12 Ohm) for 235U. Precisions and accuracies for 234U and 236U were down to ~1%. For 235U, subpermil levels were reached.

  11. Investigation of the effects of nuclear level density parameters on the cross sections for the 234U(γ,f) reaction

    NASA Astrophysics Data System (ADS)

    Pekdogan, Hakan; Aydin, Abdullah; Hakki Sarpun, Ismail

    2015-07-01

    In this study, we have investigated the effects of nuclear level density parameters on the cross sections for the 234U(γ,f) reaction up to 20 MeV. The cross sections on 234U(γ,f) reaction were calculated for different level density models using the TALYS 1.6 code. First, it was determined the level density model that was the closest to the experimental data. Secondly, cross sections obtained for different level density parameters of this model were compared with experimental data from the EXFOR database. Thus it was determined the best level density parameter fit to experimental data.

  12. 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.

  13. Basic characterization of highly enriched uranium by gamma spectrometry

    NASA Astrophysics Data System (ADS)

    Nguyen, Cong Tam; Zsigrai, József

    2006-05-01

    Gamma-spectrometric methods suitable for the characterization of highly enriched uranium samples encountered in illicit trafficking of nuclear materials are presented. In particular, procedures for determining the 234U, 235U, 238U, 232U and 236U contents and the age of highly enriched uranium are described. Consequently, the total uranium content and isotopic composition can be calculated. For determining the 238U and 232U contents a low-background chamber was used. In addition, age dating of uranium was also performed using low-background spectrometry.

  14. Analysis and comparison of monoenergetic fast neutron fluence determination using 238U samples at different positions with respect to the neutron source.

    PubMed

    Zhang, Guohui; Liu, Xiang; Gao, Zhiqi; Wu, Hao; Liu, Jiaming

    2012-05-01

    Using two (238)U samples placed in a gridded ionization chamber and a parallel-plate fission chamber, fluence of monoenergetic fast neutrons was determined. Four runs of measurements were performed. Analysis showed that although the neutron fluences for the two (238)U samples differ by 20-33 times in the present work, the fluences at the position of the sample in the gridded ionization chamber determined by the two ways are in agreement within experimental uncertainties. PMID:22398325

  15. 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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the 235U 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 235U 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 νbar 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 233,235U, 239Pu and 252Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

  18. 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. PMID:25944955

  19. 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. PMID:25909757

  20. 238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

    USGS Publications Warehouse

    Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

    2014-01-01

    Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

  1. Experimental Cross Sections for Reactions of Heavy Ions and 208Pb, 209Bi, 238U, and 248Cm Targets

    SciTech Connect

    Patin, Joshua B.

    2002-05-24

    The study of the reactions between heavy ions and {sup 208}Pb, {sup 209}Bi, {sup 238}U, and {sup 248} Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the {sup 238}U({sup 18}O,xn){sup 256-x}Fm, {sup 238}U({sup 22}Ne,xn){sup 260-x}No, and {sup 248}Cm({sup 15}N,xn){sup 263-x}Lr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The {sup 208}Pb({sup 48}Ca,xn){sup 256-x}No, {sup 208}Pb({sup 50}Ti,xn){sup 258-x}Rf, {sup 208}Pb({sup 51}V,xn){sup 259-x}Db, {sup 209}Bi({sup 50}Ti,xn){sup 259-x}Db, and {sup 209}Bi({sup 51}V,xn){sup 260-x}Sg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics.

  2. Calculations of Neutron- and Proton-Induced Reactions up to 200 MeV for Target 238U

    SciTech Connect

    Yu Hongwei; Zhao Zhixiang; Cai Chonghai

    2005-05-24

    The calculations of neutron- and proton-induced reaction up to 200 MeV for target 238U are performed; the calculated results are generally in good agreement with experimental data, and the physics is rational. The theoretical framework consists of the spherical optical model, intranuclear cascade mechanism for nucleon emission based on empirical formula, preequilibrium emission theory based on exciton model, evaporation model, and Hauser-Feshbach statistical theory with a width fluctuation correction. The fission widths are calculated using the Bohr-Wheeler formula.

  3. Fusion Probability in the Reactions {sup 58}Fe+{sup 244}Pu and {sup 64}Ni+{sup 238}U

    SciTech Connect

    Knyazheva, G. N.; Bogachev, A. A.; Itkis, I. M.; Itkis, M. G.; Kozulin, E. M.

    2010-04-30

    Mass-energy distributions, as well as capture cross-section of fission-like fragments for the reactions {sup 64}Ni+{sup 238}U and {sup 58}Fe+{sup 244}Pu leading to the formation of superheavy compound system with Z = 120 and N 182 at energies near the Coulomb barrier have been measured. Fusion-fission cross sections were estimated from the analysis of mass and total kinetic energy distributions. It was found that the fusion probability is about one order of magnitude higher for the reaction {sup 58}Fe+{sup 244}Pu than that for the reaction with {sup 64}Ni-ions.

  4. Neutron-deficient N{approx_equal}126 nuclei produced in 238U fragmentation: population of high-spin states

    SciTech Connect

    Podolyak, Zs.; Regan, P. H.; Walker, P. M.; Pearson, C. J.; Valiente-Dobon, J. J.; Gerl, J.; Hellstroem, M.; Becker, F.; Gorska, M.; Kelic, A.; Kopatch, Y.; Mandal, S.; Schmidt, K.-H.; Wollersheim, H. J.; Banu, A.; Geissel, H.; Grawe, H.; Kojouharov, I.; Lozeva, R.; Portillo, M.

    2006-04-26

    The population of metastable states produced in relativistic-energy fragmentation of a 238U beam has been measured. For states with high angular momentum, I=17({Dirac_h}/2{pi}) and I=21.5({Dirac_h}/2{pi}), a higher population than expected has been observed, with the discrepancy increasing with angular momentum. By considering two sources for the angular momentum, related to single-particle and collective motions, a much improved description of the experimental results can be obtained. In addition, new results on the structure of 208Fr, 211Ra and 216Ac are reported.

  5. Gamma Emission Spectra from Neutron Resonances in 234,236,238U Measured Using the Dance Detector at Lansce

    NASA Astrophysics Data System (ADS)

    Ullmann, J. L.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wouters, J. M.; Wilhelmy, J. B.; Wu, C. Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

    2013-03-01

    An accurate knowledge of the radiative strength function and level density is needed to calculate of neutron-capture cross sections. An additional constraint on these quantities is provided by measurements of γ-ray emission spectra following capture. We present γ-emission spectra from several neutron resonances in 234,236,238U, measured using the DANCE detector at LANSCE. The measurements are compared to preliminary calculations of the cascade. It is observed that the generalized Lorentzian form of the E1 strength function cannot reproduce the shape of the emission spectra, but a better description is made by adding low-lying M1 Lorentzian strength.

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

    DOE PAGESBeta

    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

  7. Measurements of the /sup 235/U(n,f) standard cross section at the National Bureau of Standards

    SciTech Connect

    Johnson, R.G.; Carlson, A.D.; Wasson, O.A.; Duvall, K.C.; Behrens, J.W.; Meier, M.M.; Patrick, B.D.; Dias, M.S.

    1988-01-01

    The primary mission of the Neutron Interactions and Dosimetry Group at the National Bureau of Standards (NBS) is the measurement of the standard neutron cross sections. The group has had a long-term program for the measurement of one of the most important of these cross sections---the neutron-induced fission cross section of /sup 235/U. Since the ENDF/B-VI evaluation has been recently released, it is appropriate to review the measurements of the /sup 235/U(n,f) cross section which have been made at the NBS using accelerator-based neutron sources. In the 0.1--20 MeV region where this cross section is a standard, six separate measurements of the differential cross section, using a variety of techniques have been made. Both the NBS 150-MeV Electron Linac and the 3-MV Positive Ion Accelerator have been used as neutron sources. Two of the measurements are relative to the H(n,p) cross section while the remainder are absolute. These measurements will be reviewed and compared to ENDF/B-VI. The current status of this program and possible future improvements will be discussed. 11 refs., 3 figs., 1 tab.

  8. A GENERALIZED METHOD FOR CHARACTERIZATION OF 235U AND 239PU CONTENT USING SHORT-LIVED FISSION PRODUCT GAMMA SPECTROSCOPY

    SciTech Connect

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

    2016-01-01

    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, 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. 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.

  9. Primordial radioactivity ((238)U, (232)Th and (40)K) measurements for soils of Ludhiana district of Punjab, India.

    PubMed

    Badhan, K; Mehra, R

    2012-11-01

    The aim of the present work was to study the activity concentration and absorbed gamma dose rates due to primordial radionuclides ((238)U, (232)Th and (40)K) for the soil of different villages of Ludhiana district of Punjab, India using a high-purity germanium detector based on high resolution gamma-ray spectrometry. The average activity concentrations of (238)U, (232)Th and (40)K in the soil samples have been found to be 28.58, 50.95 and 569.59 Bq kg(-1), respectively, which gives the total gamma dose rate contribution of 68.50 nGy h(-1). To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the external hazard index, the absorbed dose rate and the effective dose rate have been calculated. The calculated radium equivalent activity values are on the lower side of the recommended safe limit value of 370 Bq kg(-1) by Organization of Economic and Control Department. The calculated value of external health hazard index is lower than unity. PMID:22899219

  10. Internal [sup 238]U-series systematics of pumice from the November 13, 1985, eruption of Nevado de Ruiz, Colombia

    SciTech Connect

    Schaefer, S.J.; Williams, S.N. ); Sturchio, N.C. ); Murrell, M.T. )

    1993-03-01

    High-precision mass spectrometer and alpha scintillation measurements of [sup 238]U-series nuclides were obtained for whole-rock pumice and constituent mineral and glass separates to help interpret the timing and nature of magmatic processes that led up to the 1985 eruption of Nevado de Ruiz volcano. Internal isochron diagrams for [sup 226]Ra/Ba vs. [sup 230]Th/Ba and [sup 230]Th/[sup 232]Th vs. [sup 238]U/[sup 232]Th show that data define linear arrays, indicating an average crystallization age of 6.1 [+-] 0.5 ka (Ra-Th isochron) and 7 [+-] 6 ka (Th-U isochron). Stratigraphic, petrographic geochemical, repose time, and eruption volume data for the Holocene eruptive sequence of Nevado del Ruiz indicate that significant changes occurred in the subvolcanic magma chamber between eruptions R9 ([approx]8.6 ka) and R8 ([approx]3.0 ka). This coincides with the average crystallization age derived from the U-series data and may represent the injection of a new batch (or batches) of mantle-derived magma into the subvolcanic magma chamber. 26 refs., 4 figs., 2 tabs.

  11. Isotopic Compositions of Uranium Reference Materials

    NASA Astrophysics Data System (ADS)

    Jacobsen, B.; Borg, L. E.; Williams, R. W.; Brennecka, G.; Hutcheon, I. D.

    2009-12-01

    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 238U/235U, as well as the minor isotopes of U. Differences of ~1.3‰ are now being observed in 238U/235U 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 238U/235U ratios were measured with a TRITON TIMS using a mixed 233U-236U isotopic tracer to correct for instrument fractionation. This tracer was extremely pure and resulted in only very minor corrections on the measured 238U/235U ratios of ~0.03. The values obtained for 238U/235U 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. Our 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 238U/235U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for 234U/235U are: SRM950a = (7.437 ± 0.043)x10-3 (n=18), and CRM112a = (7.281 ± 0.050)x10-3 (n=16), both of which are in good agreement with published values. The value for 236U/235U in SRM950a was determined to be (8.48 ± 2.63)x10-6, whereas 236U was not detected in CRM112a. We are currently obtaining the U isotopic composition of

  12. 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

  13. Photofission and photoneutron cross sections and photofission neutron multiplicities for /sup 233/U, /sup 234/U, /sup 237/Np, and /sup 239/Pu

    SciTech Connect

    Berman, B.L.; Caldwell, J.T.; Dowdy, E.J.; Dietrich, S.S.; Meyer, P.; Alvarez, R.A.

    1986-12-01

    The photonuclear cross sections for /sup 233/U, /sup 234/U, /sup 237/Np, and /sup 239/Pu have been measured from threshold up to 18 MeV. The source of radiation was the monoenergetic photon beam from the annihilation in flight of fast positrons. The branching among the neutron-producing reaction channels was determined by measuring the photofission prompt neutron multiplicities nu-bar/sub p/. One interesting result is the complete absence of any (..gamma..,2n) cross section for /sup 233/U and /sup 234/U. The values of nu-bar/sub p/(E) for /sup 234/U agree with those measured with neutrons incident on /sup 233/U. The parameters of the giant dipole resonance deduced from the total photonuclear cross sections show that these nuclei have large static deformations, as expected. The integrated photofission cross sections are large (as are the absolute fission probabilities), and account for 60% to 80% of the total photonuclear absorption strength.

  14. 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.

  15. Rotation of Nuclei as Observed in Ternary Fission of the Reaction 235U(nth,f) Induced by Polarized Neutron

    NASA Astrophysics Data System (ADS)

    Gönnenwein, F.; Gagarski, A.; Guseva, I.; Petrov, G.; Sokolov, V.; Zavarukhkina, T.; Mutterer, M.; Nesvizhevski, V.; Bunakov, V.; Kadmensky, S.

    2007-05-01

    Ternary fission of the standard reaction 235U(nth,f) induced by cold polarized neutrons has been investigated. Fission fragments and light charged particles were recorded in coincidence. Following cold neutron capture the compound nucleus 236U* has spin 3- or 4-. At the saddle point of the fissioning 236U* nucleus these states are collective. They are expected to retain a sizable collectivity down to the scission point. In fact, a collective rotation has been sensed by the shift in the angular distribution of the light charged particles which depends on the orientation of neutron polarization. Direct observation of the rotation of 236U* excited in a cold neutron reaction is reported here for the first time. It is proposed to call the new phenomenon the "ROT-effect".

  16. Investigation of the maximum accessible kinetic energy of fragments in the neutron-induced fission of {sup 238}U nuclei

    SciTech Connect

    Khryachkov, V. A. Bondarenko, I. P.; Ivanova, T. A.; Kuzminov, B. D.; Semenova, N. N.; Sergachev, A. I.

    2013-03-15

    The masses, total kinetic energies (TKE), and emission angles of fragments originating from the fission of {sup 238}U nuclei that was induced by 5- and 6.5-MeV neutrons were measured by using digital methods for processing signals. A detailed analysis of the shape of digital signals made it possible to reduce substantially the contribution of fragments whose TKE values were distorted because of a superimposition of signals from recoil protons and from alpha particles produced in the spontaneous decay of uranium. The total statistics exceeded two million events for either neutron energy, and this permitted performing a detailed analysis of fission-fragment yields in the region of the highest attainable TKE values. An analysis of fragment yields made it possible to draw specific conclusions on the structure of the potential surface of fissile nuclei.

  17. Most probable charge of fission products in 24 MeV proton induced fission of {sup 238}U

    SciTech Connect

    Kudo, H.; Maruyama, M.; Tanikawa, M.; Shinozuka, T.; Fujioka, M.

    1998-01-01

    The charge distributions of fission products in 24 MeV proton-induced fission of {sup 238}U were measured by the use of an ion-guide isotope separator on line. The most probable charge (Z{sub p}) of the charge distribution was discussed in view of the charge polarization in the fission process. It was found that Z{sub p} mainly lies on the proton-rich side in the light mass region and on the proton-deficient side in the heavy mass region compared with the postulate of the unchanged charge distribution. The charge polarization was examined with respect to production Q values. {copyright} {ital 1998} {ital The American Physical Society}

  18. Photofission of sup 238 U with monochromatic gamma rays in the energy range 11--16 MeV

    SciTech Connect

    Wilke, W.; Kneissl, U.; Weber, T. ); Stroeher, H. ); Cardman, L.S.; Debevec, P.T.; Hoblit, S.D.; Jones, R.T.; Nathan, A.M. Department of Physics, University of Illinois at Urbana-Champaign, Champaign, IL )

    1990-11-01

    We have measured the angular and mass distributions of the fragments from photofission of {sup 238}U using tagged photons with energies between 11 and 16 MeV. The fission fragments were detected by a 4{pi} arrangement of position-sensitive parallel-plate avalanche counters. Anisotropic angular distributions have been observed for the first time in the energy range where second-chance fission becomes energetically possible. A consistent assignment of {ital J}{sup {pi}} and {ital K} for the fission channels in {sup 237}U has been deduced from a combined analysis of ({gamma},{ital nf}) and ({ital e},{ital e}{prime}{ital f}) data. A clear relationship between the anisotropies and the fragment mass asymmetry has also been established. This correlation, together with the energy dependence of the angular distribution parameters, points to a possible interpretation of the results in terms of a recent theoretical model incorporating multiple exit channels in fission.

  19. 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.

  20. 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.

  1. Measurement of the U-238/U-235 (n,f) cross-section ratio with the NIFFTE Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Meharchand, Rhiannon; Niffte Collaboration

    2013-10-01

    Nuclear data play a fundamental role in energy and defense related applications. In recent years, understanding of these systems has become dependent upon advanced simulation and modeling, where uncertainties in nuclear data propagate into calculated performance parameters. It is important therefore that nuclear data uncertainties are minimized and well-understood. To this end, the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration is developing a Time Projection Chamber (TPC) to measure energy-differential (n,f) cross sections with unprecedented precision. (n,f) cross-section measurements with the NIFFTE TPC take place at the Los Alamos Neutron Science Center (LANSCE) WNR facility, a spallation neutron source which provides a neutron spectrum ranging from hundreds of keV to hundreds of MeV. During the 2012 LANSCE run cycle, data were collected on several actinide samples, including U-238 and U-235. These data, along with those collected during the 2013 LANSCE run cycle, will be used to deduce a U-238/U-235 (n,f) cross-section ratio, to benchmark TPC performance, and to provide high-quality data to the community. A brief overview of the NIFFTE TPC and preliminary analysis of the U-238/U-235 (n,f) ratio data will be presented. This work was performed under the auspices of the U.S. Department of Energy by Los Alamos National Security, LLC under contract DE-AC52-06NA25396 and by Lawrence Livermore National Security, LLC under contract DE-AC52-07NA27344. LA-UR-13-24779.

  2. Isotopic production cross sections of spallation-evaporation residues from reactions of {sup 238}U(1A GeV) with deuterium

    SciTech Connect

    Casarejos, E.; Benlliure, J.; Pereira, J.; Armbruster, P.; Enqvist, T.; Schmidt, K.-H.; Bernas, M.; Mustapha, B.; Rejmund, F.; Stephan, C.; Taieb, J.; Tassan-Got, L.; Boudard, A.; Legrain, R.; Leray, S.; Volant, C.; Wlazlo, W.

    2006-10-15

    Isotopic production cross sections and momentum distributions of 602 residual nuclei produced in the collision of {sup 238}U(1A GeV) with deuterium have been measured. These data are relevant for a better understanding of spallation reactions for use as neutron sources for accelerator-driven systems or to produce radioactive nuclear beams. Access to primary residue production makes it possible to study the main reaction mechanisms involved: intranuclear cascade, particle evaporation, and fission. The characteristics of the reaction investigated and the high fissility of the {sup 238}U and the dinucleon projectile system are discussed and compared with other available experimental data.

  3. Fusion and direct reactions around the barrier for the systems {sup 7,9}Be,{sup 7}Li+{sup 238}U

    SciTech Connect

    Raabe, R.; Angulo, C.; Charvet, J. L.; Jouanne, C.; Nalpas, L.; Figuera, P.; Pierroutsakou, D.; Romoli, M.; Sida, J. L.

    2006-10-15

    We present new cross section data for the complete fusion of the weakly bound systems {sup 7,9}Be and {sup 7}Li on {sup 238}U at energies around the Coulomb barrier. In the same measurement, yields for direct processes and incomplete fusion are detected. For all systems, a suppression of the complete fusion cross section around and above the barrier is observed. At energies below the barrier, the fusion of the {sup 7}Be+{sup 238}U system shows no enhancement with respect to simple model predictions.

  4. 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

  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. Predicted yields of new neutron-rich isotopes of nuclei with Z=64-80 in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-05-15

    The production cross sections of new neutron-rich isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U at bombarding energy E{sub c.m.}=189 MeV close to the Coulomb barrier.

  7. Mass transfer during the prefission step in the 17.0-MeV/u {sup 132}Xe+ {sup 238}U interaction

    SciTech Connect

    Savovic, S.; Djordjevich, A.; Jokic, S.; Khan, E. U.

    2011-05-15

    The process of mass transfer is investigated occurring during the first of two steps of the 17.0-MeV/u {sup 132}Xe + {sup 238}U heavy-ion reaction. Mass of the projectile-like nucleus after the first reaction step has been determined by the Fokker-Planck equation. Results have been compared with previously reported measurements.

  8. 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.

  9. 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.

  10. Angular-anisotropy coefficients for fragment originating from the resonance-neutron-induced fission of {sup 235}U oriented nuclei

    SciTech Connect

    Tambovtsev, D. I.

    2008-04-15

    Statistical distributions of the coefficients measured for the angular distribution of fragments originating from the fission of {sup 235}U oriented nuclei that was induced by resonance neutrons obtained by using booster targets at the electron accelerator in Harwell and at a pulsed reactor in Dubna were approximated by a curve that was calculated under the assumption of a normal distribution of partial-wave fission amplitudes. A cutoff from below at a level of one-half of the average partial-wave width was introduced in this distribution. The calculation was performed with allowance for the K = 0, 1 and 2 channels for J = 3 and the K = 1 and 2 channels for J =4. The contributions of the K channels to the total probability were in the ratio 0.15 : 0.53 : 0.32 for J = 3 and in the ratio 0.625 : 0.375 for J = 4. A strong suppression of the K = 0 channel in the J = 3 spin subsystem in contrast to the situation observed in photofission can be interpreted as an indication of the possible partial conservation of K in resonance states formed from the entrance channel, which features only maximum values of K equal to J and J - 1.

  11. Dipole strength in the {sup 235}U(gamma,gamma{sup '}) reaction up to 2.8 MeV

    SciTech Connect

    Yevetska, O.; Enders, J.; Fritzsche, M.; Neumann-Cosel, P. von; Romig, C.; Savran, D.; Sonnabend, K.; Oberstedt, S.; Richter, A.

    2010-04-15

    Spectra of the {sup 235}U(gamma,gamma{sup '}) reaction were measured at the S-DALINAC at bremsstrahlung end-point energies E{sub 0}=3.5 and 4.4 MeV and scattering angles of 90 deg. and 135 deg. with respect to the beam axis. Discrete transitions are observed at excitation energies below 2.3 MeV only. The deduced cross sections are in rough agreement with the findings of Bertozzi et al. [Phys. Rev. C 78, 041601(R) (2008)] except for the most prominent transition, where the present result is lower by a factor of about 2. Evidence for unresolved dipole strength is found in the spectra by means of a fluctuation analysis, which was carried out up to an excitation energy of 2.8 MeV. If this unresolved strength exhibits the same ratio of E1/M1 cross sections as observed in the even-mass neighbor {sup 236}U, then the energy centroid E{sub x}=2.5(3) MeV and total strength SIGMAB(M1)arrow up=3.6(1.3)mu{sub N}{sup 2} of the M1 part are in good agreement with the systematics of the scissors mode in even-even actinide nuclei.

  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. 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.

  14. 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.

    2016-03-01

    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 82≤ A ≤ 132 and a systematic measurement of ^{92} Rb fission yields, as well as investigations of fission yields toward the symmetry region.

  15. 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. PMID:7869995

  16. Gamma-Ray Emission Spectra as a Constraint on Calculations of 234 , 236 , 238U Neutron-Capture Cross Sections

    NASA Astrophysics Data System (ADS)

    Ullmann, J. L.; Krticka, M.; Kawano, T.; Bredeweg, T. A.; Baramsai, B.; Couture, A.; Haight, R. C.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Wu, C. Y.; Chyzh, A.

    2015-10-01

    Calculations of the neutron-capture cross section at low neutron energies (10 eV through 100's of keV) are very sensitive to the nuclear level density and radiative strength function. These quantities are often poorly known, especially for radioactive targets, and actual measurements of the capture cross section are usually required. An additional constraint on the calculation of the capture cross section is provided by measurements of the cascade gamma spectrum following neutron capture. Recent measurements of 234 , 236 , 238U(n, γ) emission spectra made using the DANCE 4 π BaF2 array at the Los Alamos Neutron Science Center will be presented. Calculations of gamma-ray spectra made using the DICEBOX code and of the capture cross section made using the CoH3 code will also be presented. These techniques may be also useful for calculations of more unstable nuclides. This work was performed with the support of the U.S. Department of Energy, National Nuclear Security Administration by Los Alamos National Security, LLC (Contract DE-AC52-06NA25396) and Lawrence Livermore National Security, LLC (Contract DE-AC52-07NA2734).

  17. Retardation of [sup 238]U and [sup 232]Th decay chain radionuclides in Long Island and Connecticut aquifers

    SciTech Connect

    Copenhaver, S.A.; Krishnaswami, S.; Turekian, K.K. ); Epler, N.; Cochran, J.K. )

    1993-02-01

    Knowledge of the ability of an aquifer to retard the groundwater transport of toxic or radioactive ions can be inferred from the analysis of groundwater for the radionuclides of the [sup 238]U- and [sup 232]Th-decay chains. Groundwaters of varying chemical composition were analyzed from wells in Long Island, New York, and Connecticut. Aquifer lithologies are arkose, quartz sandstone, granite, and glacial drift. Adsorption (k[sub 1]) and desorption (k[sub 2]) coefficients for Ra and Pb were calculated using [sup 222]Rn activity as a measure of the supply of other [alpha]-recoil nuclides. Laboratory tests of the validity of this assumption were made by measuring the flux of [sup 224]Ra and [sup 222]Rn from aquifer solids. The ratio k[sub 1]/k[sub 2] is the distribution coefficient, K, which is effective equal to R[sub f], the retardation factor. The average value of K for Ra is 6 [times] 10[sup 2] in Long Island aquifers and 5 [times] 10[sup 4] in Connecticut. The distribution coefficient for Pb is 10[sup 4] in Long Island and 10[sup 5] in Connecticut. Results from this and other studies reveal a strong dependence of retardation on pH, f[sub o[sub 2

  18. The CIELO Collaboration: Neutron Reactions on 1H, 16O, 56Fe, 235,238U, and 239Pu

    NASA Astrophysics Data System (ADS)

    Chadwick, M. B.; Dupont, E.; Bauge, E.; Blokhin, A.; Bouland, O.; Brown, D. A.; Capote, R.; Carlson, A.; Danon, Y.; De Saint Jean, C.; Dunn, M.; Fischer, U.; Forrest, R. A.; Frankle, S. C.; Fukahori, T.; Ge, Z.; Grimes, S. M.; Hale, G. M.; Herman, M.; Ignatyuk, A.; Ishikawa, M.; Iwamoto, N.; Iwamoto, O.; Jandel, M.; Jacqmin, R.; Kawano, T.; Kunieda, S.; Kahler, A.; Kiedrowski, B.; Kodeli, I.; Koning, A. J.; Leal, L.; Lee, Y. O.; Lestone, J. P.; Lubitz, C.; MacInnes, M.; McNabb, D.; McKnight, R.; Moxon, M.; Mughabghab, S.; Noguere, G.; Palmiotti, G.; Plompen, A.; Pritychenko, B.; Pronyaev, V.; Rochman, D.; Romain, P.; Roubtsov, D.; Schillebeeckx, P.; Salvatores, M.; Simakov, S.; Soukhovitskiı˜, E. Sh.; Sublet, J. C.; Talou, P.; Thompson, I.; Trkov, A.; Vogt, R.; van der Marck, S.

    2014-04-01

    CIELO (Collaborative International Evaluated Library Organization) provides a new working paradigm to facilitate evaluated nuclear reaction data advances. It brings together experts from across the international nuclear reaction data community to identify and document discrepancies among existing evaluated data libraries, measured data, and model calculation interpretations, and aims to make progress in reconciling these discrepancies to create more accurate ENDF-formatted files. The focus will initially be on a small number of the highest-priority isotopes, namely 1H, 16O, 56Fe, 235,238U, and 239Pu. This paper identifies discrepancies between various evaluations of the highest priority isotopes, and was commissioned by the OECD's Nuclear Energy Agency WPEC (Working Party on International Nuclear Data Evaluation Co-operation) during a meeting held in May 2012. The evaluated data for these materials in the existing nuclear data libraries - ENDF/B-VII.1, JEFF-3.1, JENDL-4.0, CENDL-3.1, ROSFOND, IRDFF 1.0 - are reviewed, discrepancies are identified, and some integral properties are given. The paper summarizes a program of nuclear science and computational work needed to create the new CIELO nuclear data evaluations.

  19. 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.

  20. 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.

  1. 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.

  2. The Investigation of the Doppler-Effect of the α-Value of 235U and 239Pu for Different Temperatures

    NASA Astrophysics Data System (ADS)

    Grigoriev, Yu. V.; Kitaev, V. Ya.; Sinitsa, V. V.; Mezentseva, Zh. V.; Faikov-Stanczyk, H.; Janeva, N. B.

    2005-05-01

    The time-of-flight spectra for γ -ray multiplicities from 1 to 15 were measured on the 122-m flight path of the IBR-30 pulsed neutron booster using the 16-section liquid scintillation detector for thin metallic radiator-samples of 235U (0.25 mm) and 239Pu (0.3 mm) at the presence of 235U and 239Pu filter-samples with a thickness of 0.5 mm at two temperatures (100 K and 293 K). Multiplicity spectra, Doppler-coefficients of the capture, fission cross-sections, and alpha values (their ratio) were determined from the time-of-flight spectra for above-mentioned temperatures.

  3. Validating the ENDF-B/VII{sup 235}U(n{sub th},f) prompt fission neutron spectrum using updated dosimetry cross sections (IRDFF)

    SciTech Connect

    Capote, R.; Zolotarev, K. I.; Pronyaev, V. G.; Trkov, A.

    2012-07-01

    The International Reactor Dosimetry File IRDF-2002 released in 2004 by the IAEA contains cross-section data and corresponding uncertainties for 66 dosimetry reactions. New cross-section evaluations have become available recently that re-define some of these dosimetry reactions for reactor applications including: 1) high fidelity evaluation work undertaken by one of the authors (KIZ); 2) evaluations from the ENDF/B-VII libraries that cover reactions within the International Evaluation of Neutron Cross-Section Standards; and 3) evaluations from JENDL-3.1 and JENDL-4 libraries. Overall, 37 new evaluations of dosimetry reactions have been assessed to determine whether they should be adopted to update and improve IRDF-2002. A new dosimetry library (International Reactor Dosimetry File for Fission and Fusion - IRDFF) was assembled based on new evaluations combined with selected IRDF-2002 evaluations. A grand-total of 74 dosimetry reactions are included into the IRDFF dosimetry library available at www-nds.iaea.org/IRDFFI. The assembled library was used to validate the {sup 235}U(n{sub th},f) ENDF-B/VII.0 prompt fission neutron spectrum. An excellent average C/E value of 1.002 +/- 0.02 is achieved for reactions with mean neutron energy of the integrated response (E50%) lower than 11 MeV. C/E data for reactions with E50%-response higher than 11 MeV decreases up to 0.8. We conclude that the ENDF-B/VII.0 {sup 235}U(n{sub th},f) prompt fission neutron spectrum from 1-11 MeV is validated within quoted uncertainties by available integral measurements in {sup 235}U(n{sub th},f) neutron field. Further investigations for high-threshold reactions are needed and new measurements of spectrum average cross sections for those reactions in the {sup 235}U(n{sub th},f) neutron field are recommended. (authors)

  4. Low-energy fission investigated in reactions of 750 AMeV238U-ions with Pb and Be targets. I. Nuclear charge distributions

    NASA Astrophysics Data System (ADS)

    Armbruster, P.; Bernas, M.; Czajkowski, S.; Geissel, H.; Aumann, T.; Dessagne, Ph.; Donzaud, C.; Hanelt, E.; Heinz, A.; Hesse, M.; Kozhuharov, C.; Miehe, Ch.; Münzenberg, G.; Pfützner, M.; Schmidt, K.-H.; Schwab, W.; Stéphan, C.; Sümmerer, K.; Tassan-Got, L.; Voss, B.

    1996-12-01

    Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile238U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the238U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magnetic field for the U/Pb-system, or by peripheral nuclear interactions for the U/Be-system.

  5. Electromagnetic dissociation of {sup 238}U in heavy-ion collisions at 120 MeV/A

    SciTech Connect

    Justice, M.L.

    1991-04-01

    This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A {sup 238}U beam incident on five targets: {sup 9}Be, {sup 27}Al, {sup nat}Cu, {sup nat}Ag, and {sup nat}U. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution of the giant quadrupole resonance to the EMD cross sections. The specific exit channel which was looked at was projectile fission. The two fission fragments were detected in coincidence by an array of solid-state {Delta}E-E detectors, allowing the changes of the fragments to be determined to within {plus_minus} .5 units. The events were sorted on the basis of the sums of the fragments` charges, acceptance corrections were applied, and total cross sections for the most peripheral events were determined. Electromagnetic fission at the beam energy of this experiment always leads to a true charge sum of 92. Due to the imperfect resolution of the detectors, charge sums of 91 and 93 were included in order to account for all of the electromagnetic fission events. The experimentally observed cross sections are due to nuclear interaction processes as well as electromagnetic processes. Under the conditions of this experiment, the cross sections for the beryllium target are almost entirely due to nuclear processes. The nuclear cross sections for the other four targets were determined by extrapolation from the beryllium data using a geometrical scaling model. After subtraction of the nuclear cross sections, the resulting electromagnetic cross sections are compared to theoretical calculations based on the equivalent photon approximation. Systematic uncertainties are discussed and suggestions for improving the experiment are given.

  6. Electromagnetic dissociation of sup 238 U in heavy-ion collisions at 120 MeV/A

    SciTech Connect

    Justice, M.L.

    1991-04-01

    This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A {sup 238}U beam incident on five targets: {sup 9}Be, {sup 27}Al, {sup nat}Cu, {sup nat}Ag, and {sup nat}U. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution of the giant quadrupole resonance to the EMD cross sections. The specific exit channel which was looked at was projectile fission. The two fission fragments were detected in coincidence by an array of solid-state {Delta}E-E detectors, allowing the changes of the fragments to be determined to within {plus minus} .5 units. The events were sorted on the basis of the sums of the fragments' charges, acceptance corrections were applied, and total cross sections for the most peripheral events were determined. Electromagnetic fission at the beam energy of this experiment always leads to a true charge sum of 92. Due to the imperfect resolution of the detectors, charge sums of 91 and 93 were included in order to account for all of the electromagnetic fission events. The experimentally observed cross sections are due to nuclear interaction processes as well as electromagnetic processes. Under the conditions of this experiment, the cross sections for the beryllium target are almost entirely due to nuclear processes. The nuclear cross sections for the other four targets were determined by extrapolation from the beryllium data using a geometrical scaling model. After subtraction of the nuclear cross sections, the resulting electromagnetic cross sections are compared to theoretical calculations based on the equivalent photon approximation. Systematic uncertainties are discussed and suggestions for improving the experiment are given.

  7. Isotopic production cross sections and recoil velocities of spallation-fission fragments in the reaction {sup 238}U(1A GeV)+d

    SciTech Connect

    Pereira, J.; Benlliure, J.; Casarejos, E.; Armbruster, P.; Enqvist, T.; Schmidt, K.-H.; Bernas, M.; Mustapha, B.; Rejmund, F.; Stephan, C.; Taieeb, J.; Tassan-Got, L.; Boudard, A.; Legrain, R.; Leray, S.; Volant, C.; Wlazlo, W.

    2007-01-15

    Fission fragments of 1A GeV{sup 238}U nuclei interacting with a deuterium target have been investigated with the Fragment Separator (FRS) at Gesellschaft fuer Schwerionenforschung (GSI) by measuring their isotopic production cross sections and velocities. Results, along with those obtained recently for spallation-evaporation fragments, provide a comprehensive analysis of the spallation nuclear productions in this reaction. Details about the experimental performance, data reduction and results are presented.

  8. High-resolution photofission measurements in /sup 238/U and /sup 232/Th. Progress report, June 1, 1979-February 10, 1980. [5 to 12 MeV

    SciTech Connect

    Lancman, H.

    1980-02-01

    High-intensity proton beams have been used to generate gamma rays of well-defined and variable energy from the (p,..gamma..) reaction on a number of targets. Spectra of photofission fragments of /sup 238/U and /sup 232/Th have been measured at gamma ray energies from 5.8 to 11.5 MeV. The photofission cross sections have been determined and preliminary values of barrier parameters, derived by fitting the data to model predictions.

  9. High-resolution photofission measurements in /sup 238/U and /sup 232/Th. Progress report, June 1, 1980-February 10, 1981

    SciTech Connect

    Lancman, H.

    1981-02-01

    Intense proton beam currents from the Dynamitron at Brooklyn College have been used to generate gamma rays of variable energy from a number of (p,..gamma..) resonances in various nuclei. Spectra of photofission fragments of /sup 238/U and /sup 232/Th have been measured with an average gamma ray energy resolution of approx. 300 eV. Structure in the photofission cross section of /sup 232/Th was observed at approx. 6176 keV.

  10. Angular correlations of projectilelike and fission fragments in the reaction [sup 16]O+[sup 238]U at 110 MeV

    SciTech Connect

    Pagano, A.; Aiello, S.; De Filippo, E.; Lanzano, G.; Lo Nigro, S.; Milone, C. ); Mermaz, M.C. )

    1994-08-01

    In-plane and out-of-plane angular correlations of fission fragments detected in coincidence with projectilelike residues produced in the nuclear collisions [sup 16]O+[sup 238]U at 110 MeV have been investigated. The data present the essential features of a targetlike sequential fission process. A quantitative description of the experimental angular anisotropies requires the storage in the fissioning nucleus of a mean angular momentum in agreement with a dominant mass transfer mechanism.

  11. Assessment of annual effective dose from 238U and 226Ra due to consumption of foodstuffs by inhabitants of Tehran city, Iran.

    PubMed

    Hosseini, T; Fathivand, A A; Abbasisiar, F; Karimi, M; Barati, H

    2006-01-01

    The concentrations of (238)U and (226)Ra were determined in different foodstuffs purchased from markets in Tehran. Determinations of the radionuclides have been carried out using alpha spectrometry technique, on samples of egg, lentil, potato, rice, soya, spinach, tea and wheat. Average concentrations of natural radionuclides and foodstuff consumption rate were used to assess annual intake and based on intake values, the annual effective ingestion dose has been estimated for Tehran city residents. The measurement results show that soya has the maximum concentration of (238)U equal to 15.6 +/- 2.6 mBq kg(-1) and tea has the maximum concentration of (226)Ra equal to 1153.3 +/- 265.3 mBq kg(-1). Besides, the maximum annual effective dose from (238)U and (226)Ra were assessed to be 2.88 x 10(-2) +/- 7.20 x 10(-3) and 2.15 +/- 0.54 muSv, respectively, from wheat samples. PMID:16547147

  12. Determination of cross sections for the 238U(n,3n)236U reaction induced by 14-MeV neutrons with accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Wang, Xianggao; Jiang, Shan; He, Ming; Dong, Kejun; Xiao, Caijing; Hu, Yueming; You, Qubo; Chen, Hongtao; Hou, Long; Yu, WeiXiang; Ruan, Xichao

    2013-01-01

    The cross sections of the 238U(n,3n)236U reaction induced by neutrons with energies around 14 MeV were determined using a combination of the activation technique and accelerator mass spectrometry (AMS) at the China Institute of Atomic Energy (CIAE). U3O8 samples were irradiated for 198 h by neutrons produced by the 3H(d,n)4He reaction on a 600-kV neutron generator at CIAE. Neutron flux was continuously determined by the activation of flux monitors, Co foils, closely attached to the sample. To accurately determine the long half-life product 236U, an AMS procedure was established with a sensitivity of about 10-11 for 236U/238U. As a result, the cross sections of 238U(n,3n)236U for the incident neutron energies of (14.18±0.30) and (14.65±0.40) MeV were obtained to be (489.3±48.0) and (556.7±27.8) mb, respectively.

  13. Suitable gamma energy for gamma-spectrometric determination of (238)U in surface soil samples of a high rainfall area in India.

    PubMed

    Lenka, P; Jha, S K; Gothankar, S; Tripathi, R M; Puranik, V D

    2009-06-01

    The paper presents a systematic study on suitability of various gamma lines for monitoring of (238)U activity in soil samples around a uranium mineralized zone of Kylleng Pyndengsohiong Mawthabah (Domiasiat), Meghalaya in India. The area lies in a plateau region which recieves the highest average annual rainfall (12,000mm) in the world. The geochemical behaviour of the uranium and its daughter products at such wet climatic conditions imposes restrictions to assess (238)U through gamma lines of radon decay products. Soil samples were collected from nine locations around the uranium mineralization zone for analysis. The ratio of the concentration of uranium obtained from gamma energies of radium daughter products to the 63.29keV of (234)Th was found to vary from 1.01 to 2.07, which indicates a pronounced disequilibrium between uranium and radium daughters. The results obtained from various gamma energies were validated from the data generated by Instrumental Neutron Activation Analysis (INAA) technique. The (238)U activities from the two analytical methods show a well fitted regression line with correlation coefficient 0.99 which validates the reliability of 63.29keV energy for estimation of uranium in such conditions. PMID:19375833

  14. Calculated gamma-ray spectra for keV neutron capture in /sup 240/Pu, /sup 242/Pu, and /sup 238/U

    SciTech Connect

    Reffo, G.; Fabbri, F.; Kappeler, F.; Wisshak, K.

    1983-03-01

    Capture gamma-ray spectra of /sup 240/Pu, /sup 242/Pu, and /sup 238/U were calculated in the framework of the spherical optical model and the statistical model. A consistent set of input parameters was determined from available experimental information or from model-guided systematics. The complete gamma-ray cascades were calculated considering all possible transitions up to multiplicity seven. All experimental information on level schemes and gamma-ray transition probabilities of the compound nuclei was explicitly included as input. The capture gamma-ray spectra were used to correct experimental data for the capture cross sections of /sup 240/Pu and /sup 242/Pu from a relative measurement using a Moxon-Rae detector with a graphite converter and with /sup 197/Au and /sup 238/U as standards. This correction is required to take into account that the detector efficiency is not exactly proportional to the gamma-ray energy. The resulting correction factors proved to be negligible for measurements relative to /sup 238/U; whereas, they are about 3% if gold is used as a standard.

  15. Measurement of (238)U, (228)Ra, (226)Ra, (40)K and (137)Cs in foodstuffs samples collected from coastal areas of China.

    PubMed

    Tuo, Fei; Zhang, Qing; Zhou, Qiang; Xu, Cuihua; Zhang, Jing; Li, Wenhong; Zhang, Jianfeng; Su, Xu

    2016-05-01

    This study represents a total of 245 samples collected. The activities of (238)U, (228)Ra, (226)Ra, (40)K and (137)Cs were determined in samples of vegetables, tea, cereal (rice, wheat and corn), meat, poultry, freshwater product, seafood and seaweed that collected from the 30km safety zone of the Nuclear Power Plants (NPPs) area. All the samples radionuclide activities were quantified by using High Purity Germanium (HPGe) gamma spectrometry. The geometric mean concentrations (Bqkg(-1) wet weight) for (238)U, (228)Ra, (226)Ra, (40)K, and (137)Cs in all investigated foodstuffs samples, are 0.13, 0.16, 0.11, 68 and 0.02, respectively. The arithmetic mean concentrations (Bqkg(-1) wet weight) for (238)U, (228)Ra, (226)Ra, (40)K, and (137)Cs in all investigated foodstuffs samples, are 0.34, 0.65, 0.32, 111 and 0.09, respectively. Results of this study were compared with others, the measured values are the same with those of a previous investigation. Radiation doses due to the consumption of these foodstuffs to humans are estimated to comprise around 37-46% of the annual dose limit for public. PMID:26926376

  16. Determination of total and isotopic uranium and total thorium in soils by inductively coupled plasma-mass spectrometry

    SciTech Connect

    Bolin, R.N.

    1995-12-31

    Inductively coupled plasma-mass spectrometry (ICP-MS), using standard sample introduction by peristaltic pumping, is presented as a method to determine total and isotopic uranium ({sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U) and thorium ({sup 232}Th) in soil samples. Initial sample preparation consists of oven drying to determine moisture content, and grinding and mixing the soil to make it homogeneous. This is followed by a nitric/hydrofluoric acid digestion to bring the uranium into solution. Bismuth ({sup 209}Bi) is added prior to digestion to monitor for losses due to sample preparation and analysis. An addition digestion, using nitric/perchloric acid is performed if the total thorium concentration is required on the sample. The uranium and thorium content of this solution and the {sup 235}U/{sup 238}U ratio are measured on an initial pass through the ICP-MS. The total uranium measurement is based on the {sup 238}U isotope measurement with correction for the presence of the U isotopes. To determine the concentration of the less abundant {sup 234}U and {sup 236}U isotopes, the digestate is further concentrated by using a solid phase extraction column (TRU.Spec by EiChrom Industries, Inc.) before a second pass through the ICP-MS.

  17. Incomplete-fusion reactions for {gamma}-ray spectroscopy: Application to the study of high-spin states in {sup 234}U

    SciTech Connect

    Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; McGoram, T. R.; Poletti, A. R.

    1999-09-02

    Incomplete-fusion reactions occur when breakup of the projectile results in only part of the beam particle fusing with the target, the remnant being emitted with an energy equivalent to the beam velocity. Such reactions have been demonstrated to populate slightly neutron-rich nuclei compared to conventional fusion-evaporation reactions, opening possibilities for the study of nuclei along the neutron-rich side of the line of stability. Results from a study of {sup 211}Po are presented to illustrate the use of incomplete-fusion reactions for {gamma}-ray spectroscopy. New results from a test-run which populated high-spin states in {sup 234}U via the {sup 232}Th({sup 9}Be,{alpha}3n) reaction are also presented. An interesting feature of the latter reaction is that the high fission probabilities for the compound nuclei which follow complete fusion, results in the residues from incomplete fusion forming the dominant residue channels.

  18. Determination of Background Uranium Concentration in the Snake River Plain Aquifer under the Idaho National Engineering and Environmental Laboratory's Radioactive Waste Management Complex

    SciTech Connect

    Molly K. Leecaster; L. Don Koeppen; Gail L. Olson

    2003-06-01

    Uranium occurs naturally in the environment and is also a contaminant that is disposed of at the Radioactive Waste Management Complex (RWMC) at the Idaho National Engineering and Environmental Laboratory. To determine whether uranium concentrations in the Snake River Plain Aquifer, which underlies the laboratory, are elevated as a result of migration of anthropogenic uranium from the Subsurface Disposal Area in the RWMC, uranium background concentrations are necessary. Guideline values are calculated for total uranium, 234U, 235U, and 238U from analytical results from up to five datasets. Three of the datasets include results of samples analyzed using isotope dilution thermal ionization mass spectrometry (ID-TIMS) and two of the datasets include results obtained using alpha spectrometry. All samples included in the statistical testing were collected from aquifer monitoring wells located within 10 miles of the RWMC. Results from ID-TIMS and alpha spectrometry are combined when the data are not statistically different. Guideline values for total uranium were calculated using four of the datasets, while guideline values for 234U were calculated using only the alpha spectrometry results (2 datasets). Data from all five datasets were used to calculate 238U guideline values. No limit is calculated for 235U because the ID-TIMS results are not useful for comparison with routine monitoring data, and the alpha spectrometry results are too close to the detection limit to be deemed accurate or reliable for calculating a 235U guideline value. All guideline values presented represent the upper 95% coverage 95% confidence tolerance limits for background concentration. If a future monitoring result is above this guideline, then the exceedance will be noted in the quarterly monitoring report and assessed with respect to other aquifer information. The guidelines (tolerance limits) for total U, 234U, and 238U are 2.75 pCi/L, 1.92 pCi/L, and 0.90 pCi/L, respectively.

  19. Determination of {sup 230}Th, {sup 234}U, {sup 239}Pu, and {sup 240}Pu in soils by ICP-MS using flow-injection preconcentration

    SciTech Connect

    Hollenbach, M.; Grohs, J.; Mamich, S.; Kroft, M.

    1995-12-31

    The US Department of Energy needs improved analytical methods for alpha-emitting radionuclides to support environmental restoration and waste management projects. Inductively coupled plasma-mass spectrometry (ICP-MS) has been used successfully to measure radionuclides with relatively long half-lives; however, ICP-MS used with conventional sample introduction techniques lacks the sensitivity or selectivity to measure shorter-lived radionuclides at levels important for environmental monitoring. New methods were developed for measuring {sup 230}Th, {sup 234}U, {sup 239}Pu, and {sup 240}Pu in soils. Samples are dried, ground, and dissolved by fusion. A flow injection (FI) analysis system is used to separate and concentrate the analytes by solid-phase extraction. The FI eluent is pumped directly into the nebulizer of the ICP-MS. The use of FI resulted in greater sensitivity and freedom from interferences when compared with direct aspiration. Detection limits are improved by approximately a factor of 20. The detection limits are approximately 3 Bq/kg (4 ng/kg) for {sup 230}Th, 0.6 Bq/kg (3 ng/kg) for {sup 234}U, 0.4 Bq/kg (0.2 ng/kg) for {sup 239}Pu, and 2 Bq/kg (0.3 ng/kg) for {sup 240}Pu. The FI-ICP-MS methods are faster, less labor intensive, and generate less laboratory waste than traditional radiochemical methods. The FI-ICP-MS gives individual results for {sup 239}Pu and {sup 240}Pu which cannot be resolved by the usual radiochemical method. The accuracy of the methods was verified by analyzing reference soils.

  20. A model study on the absorbed dose of radiation following respiratory intake of 238U3O8 aerosols.

    PubMed

    Canepa, Carlo

    2014-12-01

    Aerosols of depleted uranium oxides, formed upon high-energy impact of shells on hard targets during military operations, are able to disperse, reach the alveolar region of the lungs and be absorbed and distributed throughout various parts of the body. The absorbed particles are subjected to clearance in the upper respiratory tract, distribution to other body districts, dissolution and excretion. While the soluble forms of uranium are known to deliver a small dose of radiation to the body due to their homogeneous distribution and the low specific activity of (238)U, ceramic particles exhibit a low dissolution rate and irradiate a limited volume of tissue for a long time with alpha particles with an energy of 4.267 MeV. The extent of the irradiated tissues depends on the radius of the particles and the total intake of uranium oxides. For the measured intake of U3O8 of a war veteran (15.51 μg) the number of particles ranges from 5.56×10(4) to 6.95×10(6) for sizes of 0.4-2.0 μm. Modelling the distribution of the particles between two compartments of the body, the averaged dose absorbed in 20 y by tissues surrounding the particles and within the range of the alpha particles varies from 6.8 mGy to 0.85 Gy for lungs and 8.1 mGy to 1.0 Gy for the lymph nodes, respectively. Correspondingly, due to the clearance and redistribution, the mass irradiated by 2.0-μm particles falls in 20 y from 6.06 mg to 0.94 μg in the lungs and grows from 0 to 1.0 mg in the lymph nodes. The estimated rate of formation of hydroxyl radicals upon radiolysis of water in the lungs and lymph nodes is 5.17×10(4) d(-1) per cell after 1 y. PMID:24578528

  1. Spectroscopic study of the 64,66,68Ni isotopes populated in 64Ni + 238U collisions

    NASA Astrophysics Data System (ADS)

    Broda, R.; Pawłat, T.; Królas, W.; Janssens, R. V. F.; Zhu, S.; Walters, W. B.; Fornal, B.; Chiara, C. J.; Carpenter, M. P.; Hoteling, N.; Iskra, Ł. W.; Kondev, F. G.; Lauritsen, T.; Seweryniak, D.; Stefanescu, I.; Wang, X.; Wrzesiński, J.

    2012-12-01

    Excited states in 64Ni, 66Ni, and 68Ni were populated in quasielastic and deep-inelastic reactions of a 430-MeV 64Ni beam on a thick 238U target. Level schemes including many nonyrast states were established up to respective excitation energies of 6.8, 8.2, and 7.8 MeV on the basis of γ-ray coincidence events measured with the Gammasphere array. Spin-parity assignments were deduced from an angular-correlation analysis and from observed γ-decay patterns, but information from earlier γ-spectroscopy and nuclear-reaction studies was used as well. The spin assignments for nonyrast states were supported further by their observed population pattern in quasielastic reactions selected through a cross-coincidence technique. Previously established isomeric-state decays in 66Ni and 68Ni were verified and delineated more extensively through a delayed-coincidence analysis. A number of new states located above these long-lived states were identified. Shell-model calculations were carried out in the p3/2f5/2p1/2g9/2 model space with two effective interactions using a 56Ni core. Satisfactory agreement between experimental and computed level energies was achieved, even though the calculations indicate that all the states are associated with rather complex configurations. This complexity is illustrated through the discussion of the structure of the negative-parity states and of the M1 decays between them. The best agreement between data and calculations was achieved for 68Ni, the nucleus where the calculated states have the simplest structure. In this nucleus, the existence of two low-spin states reported recently was confirmed as well. Results of the present study do not indicate any involvement of collective degrees of freedom and confirm the validity of a shell-model description in terms of neutron excitations combined with a closed Z = 28 proton shell. Further improvements to the calculations are desirable.

  2. Distribution of uranium isotopes in surface water of the Llobregat river basin (Northeast Spain).

    PubMed

    Camacho, A; Devesa, R; Vallés, I; Serrano, I; Soler, J; Blázquez, S; Ortega, X; Matia, L

    2010-12-01

    A study is presented on the distribution of (234)U, (238)U, (235)U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261mBqL(-1). The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The (234)U/(238)U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of (234)U/(238)U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found. PMID:20870317

  3. Investigating Uranium Isotopic Distributions in Environmental Samples Using AMS and MC-ICPMS

    SciTech Connect

    Buchholz, B A; Brown, T A; Hamilton, T F; Hutcheon, I D; Marchetti, A A; Martinelli, R E; Ramon, E C; Tumey, S J; Williams, R W

    2005-12-09

    Major, minor, and trace uranium isotopes were measured at Lawrence Livermore National Laboratory in environmentally acquired samples using different instruments to span large variations in concentrations. Multi-collector inductively-coupled plasma mass spectrometry (MC-ICPMS) can be used to measure major and minor isotopes: {sup 238}U, {sup 235}U, {sup 234}U and {sup 236}U. Accelerator mass spectrometry (AMS) can be used to measure minor and trace isotopes: {sup 234}U, {sup 236}U, and {sup 233}U. The main limit of quantification for minor or trace uranium isotopes is the abundance sensitivity of the measurement technique; i.e., the ability to measure a minor or trace isotope of mass M in the presence of a major isotope at M{+-}1 mass units. The abundance sensitivity for {sup 236}U/{sup 235}U isotope ratio measurements using MC-ICPMS is around {approx}2x10{sup -6}. This compares with a {sup 236}U/{sup 235}U abundance sensitivity of {approx}1x10{sup -7} for the current AMS system, with the expectation of 2-3 orders of magnitude improvement in sensitivity with the addition of another high energy filter. Comparing {sup 236}U/{sup 234}U from MC-ICPMS and AMS produced agreement within {approx}10% for samples at {sup 236}U levels high enough to be measurable by both techniques.

  4. Investigating uranium isotopic distributions in environmental samples using AMS and MC-ICPMS

    NASA Astrophysics Data System (ADS)

    Buchholz, B. A.; Brown, T. A.; Hamilton, T. F.; Hutcheon, I. D.; Marchetti, A. A.; Martinelli, R. E.; Ramon, E. C.; Tumey, S. J.; Williams, R. W.

    2007-06-01

    Major, minor and trace uranium isotopes were measured at Lawrence Livermore National Laboratory in environmentally acquired samples using different instruments to span large variations in concentrations. Multi-collector inductively-coupled plasma mass spectrometry (MC-ICPMS) can be used to measure major and minor isotopes: 238U, 235U, 234U and 236U. Accelerator mass spectrometry (AMS) can be used to measure minor and trace isotopes: 234U, 236U and 233U. The main limit of quantification for minor or trace uranium isotopes is the abundance sensitivity of the measurement technique; i.e. the ability to measure a minor or trace isotope of mass M in the presence of a major isotope at M ± 1 mass units. The abundance sensitivity for 236U/235U isotope ratio measurements using MC-ICPMS is around ∼2 × 10-6. This compares with a 236U/235U abundance sensitivity of ∼1 × 10-7 for the current AMS system, with the expectation of 2-3 orders of magnitude improvement in sensitivity with the addition of another high energy filter. Comparing 236U/234U from MC-ICPMS and AMS produced agreement within ∼10% for samples at 236U levels high enough to be measurable by both techniques.

  5. Certification of a new series of gravimetrically prepared synthetic reference materials for n( 236U)/ n( 238U) isotope ratio measurements

    NASA Astrophysics Data System (ADS)

    Richter, Stephan; Alonso, Adolfo; Aregbe, Yetunde; Eykens, Roger; Jacobsson, Ulf; Kehoe, Frances; Kuehn, Heinz; Verbruggen, Andre; Wellum, Roger

    2010-04-01

    A new series of gravimetrically prepared synthetic isotope reference materials, the so-called IRMM-075 series, with n( 236U)/ n( 238U) isotope ratios varying from 10 -4 to 10 -9 has been prepared and certified. This series is suited for calibration of n( 236U)/ n( 238U) measurements made by various mass spectrometric techniques such as TIMS (Thermal Ionization Mass Spectrometry), ICPMS (Inductively Coupled Plasma Mass Spectrometry), AMS (Accelerator Mass Spectrometry) and RIMS (Resonance Ionization Mass Spectrometry). Natural uranium with low 236U isotope abundance and highly enriched 236U were both purified using well proven chemical methodology. The oxides were calcined into U 3O 8 in an oven installed in a glove-box with controlled humidity. Primary solutions of the same concentration were prepared by dissolving the oxides of 236U and natural U. From the 236U solution a series of four dilutions was made by weighing. Weighed amounts of the dilutions of 236U and weighed amounts of natural U were mixed to form a set of n( 236U)/ n( 238U) mixtures at a concentration of 1 mg U g -1. Verification of the mixtures IRMM-075/1-6 was performed by TIMS measurements using Faraday collectors and a secondary electron multiplier in combination with an energy filter for improved abundance sensitivity. The results agreed well with the certified values obtained from the gravimetrical mixing calculations. The uncertainties of the calculated isotopic ratios are significantly lower compared to typical uncertainties from mass spectrometric techniques such as TIMS and ICPMS and in particular to AMS and RIMS. The methods for the preparation and mixing of the IRMM-075/1-6 series are described and the certification and verification procedures are reported.

  6. Resolving the early chronology of Mono Craters volcanism with combined 238U-230Th and 40Ar/39Ar dating

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Calvert, A. T.; Marcaida, M.; Mangan, M.; Lidzbarski, M. I.; Stelten, M. E.

    2013-12-01

    California's largest locus of Pleistocene-Holocene rhyolitic volcanism is the Mono Lake-Long Valley region of eastern California. The Mono Craters chain marks the northern portion of this locus, and is composed of at least 28 individual domes of high-silica rhyolite. The record of Holocene volcanism at Mono Craters is relatively well constrained by tephrostratigraphy and radiocarbon dating. However, the timing and frequency of late Pleistocene dome emplacement is poorly resolved, with most of the chronology based on hydration-rind dating of obsidian. A well-exposed archive of late Pleistocene volcanism from Mono Craters is recorded by tephra beds (ashes numbered 1-19, youngest to oldest) of the informal Wilson Creek formation that accumulated in ancestral Mono Lake. To resolve a precise chronology for late Pleistocene volcanism at Mono Craters and tune the time-series of explosive volcanism preserved by Wilson Creek tephras, we performed ion microprobe 238U-230Th dating of allanite and zircon together with laser-fusion 40Ar/39Ar dating of sanidine from rhyolite domes that yield the oldest hydration rind ages and have relatively subdued morphology. Sanidine from multiple domes, including both hornblende-biotite and fayalite-bearing rhyolite types, yield 40Ar/39Ar ages up to ca. 25 ka. Ion microprobe analyses of unpolished rims on indium-mounted allanite and zircon crystals yield U-Th isochron ages that are indistinguishable from their associated sanidine 40Ar/39Ar ages. However, the interiors of sectioned allanite crystals yield model U-Th ages that may be up to 30 kyr older than their rims. Rims on allanite and zircon from ashes 7-19 in the lower portion of the Wilson Creek stratigraphy yield isochron ages of ca. 27-62 ka [1], which are supported by ages from magnetostratigraphy [2]. Ash 3 contains titanomagnetites that are compositionally distinct from other Wilson Creek tephras, but match those in the hornblende-biotite rhyolite of dome 11. Rims on allanite and

  7. Violence of heavy-ion reactions from neutron multiplicity: 11 to 20A-italic MeV /sup 20/Ne+ /sup 238/U

    SciTech Connect

    Jahnke, U.; Ingold, G.; Hilscher, D.; Lehmann, M.; Schwinn, E.; Zank, P.

    1986-07-14

    The suitability of the neutron multiplicity as a gauge for the violence of medium-energy heavy-ion reactions is investigated for the first time. For this purpose the number of neutrons emitted from fission reactions induced by 220-, 290-, and 400-MeV /sup 20/Ne on /sup 238/U is registered event-by-event with a large 4..pi.. scintillator tank. It is shown that the neutron multiplicity is indeed closely related to the two quantities characterizing the violence: the induced total intrinsic excitation and the linear momentum transfer.

  8. Accurate measurements of fission-fragment yields in 234,235,236,238U(γ,f) with the SOFIA set-up

    NASA Astrophysics Data System (ADS)

    Chatillon, A.; Taïeb, J.; Martin, J.-F.; Pellereau, E.; Boutoux, G.; Gorbinet, T.; Grente, L.; 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.; Rodrìguez-Tajes, C.; Rossi, D.; Schmidt, K.-H.; Simon, H.; Tassan-Got, L.; Törnqvist, H.; Vargas, J.; Voss, B.; Weick, H.; Yan, Y.

    2016-03-01

    SOFIA (Studies On Fission with Aladin) is a new experimental set-up dedicated to accurate measurement of fission-fragments isotopic yields. It is located at GSI, the only place to use inverse kinematics at relativistic energies in order to study the (γ,f) electromagnetic-induced fission. The SOFIA set-up is a large-acceptance magnetic spectrometer, which allows to fully identify both fission fragments in coincidence on the whole fission-fragment range. This paper will report on fission yields obtained in 234,235,236,238U(γ,f) reactions.

  9. Peripheral interactions in the collision of [sup 16]O+[sup 238]U at 110. 4 MeV bombarding energy

    SciTech Connect

    Pagano, A.; Aiello, S.; De Filippo, E.; Lanzano, G.; Lo Nigro, S.; Milone, C.; Blancato, G.; Di Marco, G. ); Mermaz, M.C. )

    1993-03-01

    Inclusive and semiexclusive elemental production cross sections of projectilelike fragments emerging in the collision [sup 16]O+[sup 238]U at 110.4 MeV have been investigated. Energy spectra and angular distributions of projectile residues with charge from [ital Z]=3 to [ital Z]=8 have been measured. It has been found that, as expected, the dominant reaction mechanism in the peripheral collisions is a mass transfer from projectile to target mainly dominated by a transfer of an [alpha] particle. The in-plane coincidences between projectilelike and fission fragments suggest that 14% of the total fission cross section is associated with the fission of a targetlike nucleus.

  10. Azimuthal distributions of fission fragments and. alpha. particles emitted in the reactions sup 36 Ar+ sup 238 U at E / A =20 and 35 MeV and sup 14 N+ sup 238 U at E / A =50 MeV

    SciTech Connect

    Tsang, M.B.; Kim, Y.D.; Carlin, N.; Chen, Z.; Gelbke, C.K.; Gong, W.G.; Lynch, W.G.; Murakami, T.; Nayak, T.; Ronningen, R.M.; Xu, H.M.; Zhu, F. Department of Physics Astronomy, Michigan State University, East Lansing, MI ); Sobotka, L.G.; Stracener, D.W.; Sarantites, D.G.; Majka, Z.; Abenante, V. )

    1990-07-01

    Azimuthal correlations between coincident fission fragments and {alpha} particles were measured for the reactions {sup 36}Ar+{sup 238}U at {ital E}/{ital A}=20 and 35 MeV and {sup 14}N+{sup 238}U at {ital E}/{ital A}=50 MeV. At all energies, coplanar emission is enhanced. The azimuthal distributions for fission fragments and {alpha} particles are decoupled using a simple parametrization. Both azimuthal distributions are highly anisotropic at lower incident energies; these anisotropies decrease with energy. At the highest incident energies, energetic {alpha} particles emitted at large transverse momenta appear to be more suited than fission fragments to tag the orientation of the entrance channel reaction plane.

  11. Isotopic evidence for reductive immobilization of uranium across a roll-front mineral deposit

    DOE PAGESBeta

    Brown, Shaun T.; Basu, Anirban; Christensen, John N.; Reimus, Paul; Heikoop, Jeffrey; Simmons, Ardyth; Woldegabriel, Giday; Maher, Kate; Weaver, Karrie; Clay, James; et al

    2016-06-21

    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 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. 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

  13. Use of delayed gamma rays for active non-destructive assay of 235U irradiated by pulsed neutron source (plasma focus)

    NASA Astrophysics Data System (ADS)

    Andola, Sanjay; Niranjan, Ram; Kaushik, T. C.; Rout, R. K.; Kumar, Ashwani; Paranjape, D. B.; Kumar, Pradeep; Tomar, B. S.; Ramakumar, K. L.; Gupta, S. C.

    2014-07-01

    A pulsed neutron source based on plasma focus device has been used for active interrogation and assay of 235U by monitoring its delayed high energy γ-rays. The method involves irradiation of fissile material by thermal neutrons obtained after moderation of a burst of neutrons emitted upon fusion of deuterium in plasma focus (PF) device. The delayed gamma rays emitted from the fissile material as a consequence of induced fission were detected by a large volume sodium iodide (NaI(Tl)) detector. The detector is coupled to a data acquisition system of 2k input size with 2k ADC conversion gain. Counting was carried out in pulse height analysis mode for time integrated counts up to 100 s while the temporal profile of delayed gamma has been obtained by counting in multichannel scaling mode with dwell time of 50 ms. To avoid the effect of passive (natural) and active (from surrounding materials) backgrounds, counts have been acquired for gamma energy between 3 and 10 MeV. The lower limit of detection of 235U in the oxide samples with this set-up is estimated to be 14 mg.

  14. Initial Design Calculations for a Detection System that will Observe Resonant Excitation of the 680 keV state in 238U

    SciTech Connect

    Pruet, J; Hagmann, C

    2007-01-26

    We present calculations and design considerations for a detection system that could be used to observe nuclear resonance fluorescence in {sup 238}U. This is intended as part of an experiment in which a nearly monochromatic beam of light incident on a thin foil of natural uranium resonantly populates the state at 680 keV in {sup 238}U. The beam of light is generated via Compton upscattering of laser light incident on a beam of relativistic electrons. This light source has excellent energy and angular resolution. In the current design study we suppose photons emitted following de-excitation of excited nuclei to be observed by a segmented array of BGO crystals. Monte Carlo calculations are used to inform estimates for the design and performance of this detector system. We find that each detector in this array should be shielded by about 2 cm of lead. The signal to background ratio for each of the BGO crystals is larger than ten. The probability that a single detector observes a resonant photon during a single pulse of the light source is near unity.

  15. Determination of (238)U, (232)Th and (40)K activity concentrations in riverbank soil along the Chao Phraya river basin in Thailand.

    PubMed

    Santawamaitre, T; Malain, D; Al-Sulaiti, H A; Bradley, D A; Matthews, M C; Regan, P H

    2014-12-01

    The activity concentrations of (238)U, (232)Th and (40)K in riverbank soil along the Chao Phraya river basin was determined through gamma-ray spectrometry measurements made using a hyper-pure germanium detector in a low background configuration. The ranges of activity concentrations of (238)U, (232)Th and (40)K were found to be 13.9 ↔ 76.8, 12.9 ↔ 142.9 and 178.4 ↔ 810.7 Bq kg(-1), respectively. The anthropogenic radionuclide, (137)Cs, was not observed in statistically significant amounts above the background level in the current study. The absorbed gamma dose rate in air at 1 m above the ground surface, the outdoor annual effective dose equivalent, the values of the radium equivalent activity and the external hazard index associated with all the soil samples in the present work were evaluated. The results indicate that the radiation hazard from primordial radionuclides in all soil samples from the area studied in this current work is not significant. PMID:25195170

  16. 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.

  17. Measurements of yields of fission products in the reaction of {sup 238}U with high-energy p, d and n beams

    SciTech Connect

    Nolen, J.A.; Ahmad, I.; Back, B.B.

    1995-08-01

    An experiment was performed at the Michigan State University cyclotron to determine the yields of neutron-rich fission products in the reaction of {sup 238}U with 100-MeV neutrons, 200-MeV deuterons and 200-MeV protons. Several 1-mm-thick {sup 238}U foils were irradiated for 100-second intervals sequentially for each configuration and the ten spectra were added for higher statistics. The three successive spectra, each for a 40 s period, were accumulated for each sample. Ten foils were irradiated. Successive spectra allowed us to determine approximate half-lives of the gamma peaks. Several arrangements, which were similar to the setup we plan to use in our radioactive beam proposal, were used for the production of fission products. For the high-energy neutron irradiation, U foils were placed after a 5-inch-long, 1-inch-diameter Be cylinder which stopped the 200-MeV deuteron beam generating 100-MeV neutrons. Arrangements for deuteron irradiation included direct irradiation of U foils, placing U foils after different lengths of (0.5 inch, 1.0 inch and 1.5 inch) 2-inch diameter U cylinder. Since the deuteron range in uranium is 17 mm, some of the irradiations were due to the secondary neutrons from the deuteron-induced fission of U. Similar arrangements were also used for the 200-MeV proton irradiation of the {sup 238}U foils. In all cases, several neutron-rich fission products were identified and their yields determined. In particular, we were able to observe Sn in all the runs and determine its yield. The data show that with our proposed radioactive device we will be able to produce more than 10{sup 12} {sup 132}Sn atoms per second in the target. Assuming an overall efficiency of 1 %, we will be able to deliver one particle nanoampere of {sup 132}Sn beam at a target location. Detailed analysis of the {gamma}-ray spectra is in progress.

  18. 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.

  19. Calculation of 1.25% 235U enriched UO2 solution safe slab, safe cylinder diameter, minimum safe mass, and ion exchange module for the CVDF

    SciTech Connect

    Roblyer, S.P.

    1997-06-26

    Support calculations were performed to establish safe parameters such as fissionable material slab thickness, diameter and safe mass. These calculations were performed by MCNP for the balance of plant equipment that contains homogeneous UO{sub 2} solutions with a maximum enrichment of 1.25 Wt% {sup 235}U . The calculations were performed with the most limiting concentration of moderator and reflection so that only the safety parameters identified in the problem description need to be controlled. These calculations represent the most limiting cases for all uranium enrichments and transuranic levels due to fuel exposure for balance of plant equipment used for handling of waste water containing fissionable materials from the MCO draining and drying activities.

  20. Determination of environmental radioactivity (238U, 232Th and 40K) and indoor natural background radiation level in Chennai city (Tamilnadu State), India.

    PubMed

    Babai, K S; Poongothai, S; Punniyakotti, J

    2013-01-01

    An extensive study on the determination of the natural radioactivity ((238)U, (232)Th and (40)K) levels in soil samples of Chennai city, India has been undertaken and the results of the same are compared with the levels reported in other Indian cities as well as other parts of the world. The radioactivity content in the soil samples, the absorbed dose rate, annual effective dose equivalent, radium equivalent activity, internal and external hazard indices were calculated and compared with UNSCEAR 2000 recommended values. In addition to the above, mapping of indoor natural background gamma radiation levels has been made using thermo luminescent dosemeters throughout Chennai city and the same are reported. PMID:22847868

  1. Measurement of Fragment Mass Yields in Neutron-Induced Fission of 232TH and 238U at 33, 45 and 60 Mev

    NASA Astrophysics Data System (ADS)

    Simutkin, V. D.; Pomp, S.; Blomgren, J.; Österlund, M.; Andersson, P.; Bevilacqua, R.; Ryzhov, I. V.; Tutin, G. A.; Khlopin, V. G.; Onegin, M. S.; Vaishnene, L. A.; Meulders, J. P.; Prieels, R.

    2011-10-01

    Over the past years, a significant effort has been devoted to measurements of neutron-induced fission cross-sections at intermediate energies but there is a lack of experimental data on fission yields. Here we describe recent measurements of pre-neutron emission fragment mass distributions from intermediate energy neutron-induced fission of 232Th and 238U. The measurements have been done at the quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE and neutron peak energies at 32.8, 45.3 and 59.9 MeV. A multi-section Frisch-gridded ionization chamber was used as a fission fragment detector. The measurement results are compared with available experimental data. Some TALYS code modifications done to describe the experimental results are discussed.

  2. Delayed neutron and delayed photon characteristics from photofission of 232Th, 235,238U, and 237Np with endpoint Bremsstrahlung photons in the giant dipole resonance region

    NASA Astrophysics Data System (ADS)

    Doré, D.; Dighe, P. M.; Berthoumieux, E.; Laborie, J.-M.; Ledoux, X.; Macary, V.; Panebianco, S.; Ridikas, D.

    2009-10-01

    A renewed interest in photonuclear reactions was stimulated by applications as radioactive ion beam production, irradiation stations by high energy photons, shielding of electron accelerators, etc. Today, a particular attention is paid to the non-destructive characterization of waste barrels and the detection of nuclear materials, both based on photofission process and the associated delayed neutron (DN) and delayed photon (DP) emissions. The need of accurate and complete data for DN and DP yields and time characteristics of actinides was the motivation for an experimental campaign, started in 2004. In this paper, the experimental setup and the data analysis method will be presented and the modeling work will be described. Experimental results for DN and DP characteristics will be compared to calculations in the case of photofission of 232Th, 235,238U, and 237Np.

  3. Physical characteristics of LWRs and SCLWRs loaded by ({sup 233}U-Th-{sup 238}U) oxide fuel with small additions of {sup 231}Pa

    SciTech Connect

    Kulikov, E.G.; Shmelev, A.N.; Apse, V.A.; Kulikov, G.G.

    2007-07-01

    The paper investigates the possibility and attractiveness of using (U-Th) fuel in light-water reactors (LWRs) and in light-water reactors with super-critical coolant parameters (SCLWRs). It is proposed to dilute {sup 233}U with {sup 238}U to enhance the proliferation resistance of this fissionable isotope. If is noteworthy that she idea was put forward for the first time by she well known American physicist and participant of the Manhattan Project Dr. T. Taylor. Various fuel compositions are analyzed and compared on fuel breeding, achievable values of fuel burn-up and cross-sections of parasitic neutron absorption. It is also demonstrated that small {sup 231}Pa additions (several percent) into the fuel allows: to increase fuel burn-up, to achieve more negative temperature reactivity coefficient of coolant and to enhance nonproliferation of the fuel. (authors)

  4. Production of new superheavy Z=108-114 nuclei with {sup 238}U, {sup 244}Pu, and {sup 248,250}Cm targets

    SciTech Connect

    Feng Zhaoqing; Jin Genming; Li Junqing

    2009-11-15

    Within the framework of the dinuclear system (DNS) model, production cross sections of new superheavy nuclei with charged numbers Z=108-114 are analyzed systematically. Possible combinations based on the actinide nuclides {sup 238}U, {sup 244}Pu, and {sup 248,250}Cm with the optimal excitation energies and evaporation channels are pointed out to synthesize new isotopes that lie between the nuclides produced in the cold fusion reactions and the {sup 48}Ca-induced fusion reactions experimentally, which are feasible to be constructed experimentally. It is found that the production cross sections of superheavy nuclei decrease drastically with the charged numbers of compound nuclei. Larger mass asymmetries of the entrance channels enhance the cross sections in 2n-5n channels.

  5. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  6. Estimating Reaction Cross Sections from Measured (Gamma)-Ray Yields: The 238U(n,2n) and 239Pu(n,2n) Cross Sections

    SciTech Connect

    Younes, W

    2002-11-18

    A procedure is presented to deduce the reaction-channel cross section from measured partial {gamma}-ray cross sections. In its simplest form, the procedure consists in adding complementary measured and calculated contributions to produce the channel cross section. A matrix formalism is introduced to provide a rigorous framework for this approach. The formalism is illustrated using a fictitious product nucleus with a simple level scheme, and a general algorithm is presented to process any level scheme. In order to circumvent the cumbersome algebra that can arise in the matrix formalism, a more intuitive graphical procedure is introduced to obtain the same reaction cross-section estimate. The features and limitations of the method are discussed, and the technique is applied to extract the {sup 235}U (n,2n) and {sup 239}Pu(n,2n) cross sections from experimental partial {gamma}-ray cross sections, coupled with (enhanced) Hauser-Feshbach calculations.

  7. Concentration and characteristics of depleted uranium in biological and water samples collected in Bosnia and Herzegovina.

    PubMed

    Jia, Guogang; Belli, Maria; Sansone, Umberto; Rosamilia, Silvia; Gaudino, Stefania

    2006-01-01

    During Balkan conflicts in 1994-1995, depleted uranium (DU) ordnance was employed and was left in the battlefield. Health concern is related to the risk arising from contamination of the environment with DU penetrators and dust. In order to evaluate the impact of DU on the environment and population in Bosnia and Herzegovina, radiological survey of DU in biological and water samples were carried out over the period 12-24 October 2002. The uranium isotopic concentrations in biological samples collected in Bosnia and Herzegovina, mainly lichens, mosses and barks, were found to be in the range of 0.27-35.7 Bq kg(-1) for (238)U, 0.24-16.8 Bq kg(-1) for (234)U, and 0.02-1.11 Bq kg(-1) for (235)U, showing uranium levels to be higher than in the samples collected at the control site. Moreover, the (236)U in some of the samples was detectable. The isotopic ratios of (234)U/(238)U showed DU to be detectable in many biological samples at most sites examined, but in very low levels. The presence of DU in the biological samples was as a result of DU contamination in air. The uranium concentrations in water samples collected in Bosnia and Herzegovina were found to be in the range of 0.27-16.2 m Bq l(-1) for (238)U, 0.41-15.6 m Bq l(-1) for (234)U and 0.012-0.695 m Bq l(-1) for (235)U, and two water samples were observed to be DU positive; these values are much lower than those in mineral water found in central Italy and below the WHO guideline for public drinking water. From radiotoxicological point of view, at this moment there is no significant radiological risk related to these investigated sites in terms of possible DU contamination of water and/or plants. PMID:16806612

  8. Separation and quantification of 238U, 232Th and rare earths in monazite samples by ion chromatography coupled with on-line flow scintillation detector.

    PubMed

    Borai, E H; Mady, A S

    2002-10-01

    An alternative procedure has been described for efficient separation and quantitative determination of uranium (U), thorium (Th) and rare earth elements (REEs) in monazite mineral by high performance ion chromatographic system (IC). Different variables affecting the distribution coefficient, the retention and hence separation efficiency such as eluent flow rate and concentrations of HCI and ammonium sulfate (NH4)2SO4 containing the mobile phase were studied. The developed separation protocol of U, Th and REEs was optimized using an Ion Pac CS5 separation column followed by post-column derivatization reaction with Arsenaso III and UV-VIS spectrophotometric detection. Comparative evaluation of U, Th and REEs concentration in monazite mineral was demonstrated using two different on-line detection modes including flow through cell scintillation detector (FSD) and UV-VIS spectrophotometer. Response of the FSD was found to be linear over the full range of activities investigated (4-100 Bq). The lower limits of detection (LLD) for the investigated radionuclides were 3.0+0.1 Bq for 238U and 6.0 +/- 0.1 Bq for 232Th. The detection of 238U and 232Th by FSD shows good agreement with the corresponding determination by UV-VIS spectrophotometer. The content of ThO2 and U3O8 in monazite sample were found to be 4.7 +/- 0.1% and 0.42 +/- 0.04% using UV-VIS detector and 4.3 +/- 0.1% and 0.45 +/- 0.1% using FSD, respectively. PMID:12361323

  9. Influence of a Decaying Cyclonic Eddy on Biogenic Silica and Particulate Organic Carbon in the Tropical South China Sea Based on 234Th-238U Disequilibrium.

    PubMed

    Yang, Weifeng; Chen, Min; Zheng, Minfang; He, Zhigang; Zhang, Xinxing; Qiu, Yusheng; Xu, Wangbin; Ma, Lili; Lin, Zhiyu; Hu, Wangjiang; Zeng, Jian

    2015-01-01

    Eddies play a critical role in regulating the biological pump by pumping new nutrients to the euphotic zone. However, the effects of cyclonic eddies on particle export are not well understood. Here, biogenic silica (BSi) and particulate organic carbon (POC) exports were examined inside and outside a decaying cyclonic eddy using 234Th-238U disequilibria in the tropical South China Sea. For the eddy and outside stations, the average concentrations of BSi in the euphotic zone were 0.17±0.09 μmol L-1 (mean±sd, n = 20) and 0.21±0.06 μmol L-1 (n = 34). The POC concentrations were 1.42±0.56 μmol L-1 (n = 34) and 1.30±0.46 μmol L-1 (n = 51). Both BSi and POC abundances did not show change at the 95% confidence level. Based on the 234Th-238U model, BSi export fluxes in the eddy averaged 0.18±0.15 mmol Si m-2 d-1, which was comparable with the 0.40±0.20 mmol Si m-2 d-1 outside the eddy. Similarly, the average POC export fluxes were 1.5±1.4 mmol C m-2 d-1 and 1.9±1.3 mmol C m-2 d-1 for the eddy and outside stations. From these results we concluded that cyclonic eddies in their decaying phase have little effect on the abundance and export of biogenic particles. PMID:26317555

  10. The cumulative effect of three decades of phosphogypsum amendments in reclaimed marsh soils from SW Spain: (226)Ra, (238)U and Cd contents in soils and tomato fruit.

    PubMed

    Abril, José-María; García-Tenorio, Rafael; Enamorado, Santiago M; Hurtado, M Dolores; Andreu, Luis; Delgado, Antonio

    2008-09-15

    Phosphogypsum (PG), a by-product of the phosphate fertiliser industries, has been applied as soil amendment to reduce Na saturation in soils, as in the reclaimed marsh area from SW Spain, where available PG has a typical fingerprint of 710+/-40 Bq kg(-1) of (226)Ra, 165+/-15 Bq kg(-1) of (238)U and 2.8+/-0.4 mg kg(-1) of Cd. This work was focussed on the cumulative effects of PG amendments on the enrichment of these pollutants in cultivated soils and plants (Lycopersicum esculentum Mill L.) from the area studied, where PG has been applied since 1978 at recommended rates of 20-25 Mg ha(-1) every 2-3 years. A field experiment was conducted over three years to compare activity concentrations of (226)Ra ((214)Pb) and (238)U ((234)Th) in non-reclaimed soils, reclaimed soils with no additional PG application, and reclaimed soils with two additional PG applications. A non-significant effect of two PG amendments (in three years) was observed when compared with non-amended reclaimed plots. Nevertheless, a significant (p<0.05) enrichment of (226)Ra was observed in the surface horizon (0-30 cm) of reclaimed plots relative to deeper horizons and also when compared with the surface horizon of non-reclaimed soil (p<0.05), thereby revealing the cumulative effect of three decades of PG applications. Furthermore, the effect of a continuous application of PG was studied by analysing soils and tomato fruits from six commercial farms with different cumulative rates of PG applied. Cadmium concentrations in tomatoes, which were one order of magnitude higher than those found in tomatoes from other areas in South Spain, were positively correlated (r = 0.917) with (226)Ra-concentration in soils, which can be considered an accurate index of the cumulative PG rate of each farm. PMID:18602676

  11. Influence of a Decaying Cyclonic Eddy on Biogenic Silica and Particulate Organic Carbon in the Tropical South China Sea Based on 234Th-238U Disequilibrium

    PubMed Central

    Yang, Weifeng; Chen, Min; Zheng, Minfang; He, Zhigang; Zhang, Xinxing; Qiu, Yusheng; Xu, Wangbin; Ma, Lili; Lin, Zhiyu; Hu, Wangjiang; Zeng, Jian

    2015-01-01

    Eddies play a critical role in regulating the biological pump by pumping new nutrients to the euphotic zone. However, the effects of cyclonic eddies on particle export are not well understood. Here, biogenic silica (BSi) and particulate organic carbon (POC) exports were examined inside and outside a decaying cyclonic eddy using 234Th-238U disequilibria in the tropical South China Sea. For the eddy and outside stations, the average concentrations of BSi in the euphotic zone were 0.17±0.09 μmol L-1 (mean±sd, n = 20) and 0.21±0.06 μmol L-1 (n = 34). The POC concentrations were 1.42±0.56 μmol L-1 (n = 34) and 1.30±0.46 μmol L-1 (n = 51). Both BSi and POC abundances did not show change at the 95% confidence level. Based on the 234Th-238U model, BSi export fluxes in the eddy averaged 0.18±0.15 mmol Si m-2 d-1, which was comparable with the 0.40±0.20 mmol Si m-2 d-1 outside the eddy. Similarly, the average POC export fluxes were 1.5±1.4 mmol C m-2 d-1 and 1.9±1.3 mmol C m-2 d-1 for the eddy and outside stations. From these results we concluded that cyclonic eddies in their decaying phase have little effect on the abundance and export of biogenic particles. PMID:26317555

  12. Feasibility of Colliding-beam fast-fission reactor via 238U80++238 U80+ --> 4 FF + 5n + 430 MeV beam with suppressed plutonium and direct conversion of fission fragment (FF) energy into electricity and/or Rocket propellant with high specific impulse

    NASA Astrophysics Data System (ADS)

    Maglich, Bogdan; Hester, Tim; Calsec Collaboration

    2015-10-01

    Uranium-uranium colliding beam experiment1, used fully ionized 238U92+ at energy 100GeV --> <-- 100 GeV, has measured total σ = 487 b. Reaction rate of colliding beams is proportional to neutron flux-squared. First functional Auto-Collider3-6, a compact Migma IV, 1 m in diameter, had self-colliding deuterons, D+, of 725 KeV --> <-- 725 KeV, resulting in copious production of T and 3He. U +U Autocollider``EXYDER'' will use strong-focusing magnet7, which would increase reaction rate by 104. 80 times ionized U ions accelerated through 3 MV accelerator, will collide beam 240 MeV --> <-- 240 MeV. Reaction is: 238U80+ +238 U80+ --> 4 FF + 5n + 430 MeV. Using a simple model1 fission σf ~ 100 b. Suppression of Pu by a factor of 106 will be achieved because NO thermal neutron fission can take place; only fast, 1-3 MeV, where σabs is negligible. Direct conversion of 95% of 430 MeV produced is carried by electrically charged FFs which are magnetically funneled for direct conversion of energy of FFs via electrostatic decelerators4,11. 90% of 930 MeV is electrically recoverable. Depending on the assumptions, we project electric _ power density production of 20 to 200 MWe m-3, equivalent to Thermal 1.3 - 13 GWthm-3. If one-half of unburned U is used for propulsion while rest powers system, heavy FF ion mass provides specific impulse Isp = 106 sec., 103 times higher than current rocket engines.

  13. 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

  14. Neutron-Induced Fission Cross Sections Measurements at n_TOF

    SciTech Connect

    Audouin, L.; Tassan-Got, L.; Isaev, S.; Koehler, Paul Edward; Collaboration, n_TOF

    2008-01-01

    The neutron-induced fission cross sections of {sup 233}U, {sup 234}U, {sup 235}U, {sup 238}U, {sup 232}Th, {sup 237}Np, {sup 209}Bi, {sup nat}Pb have been measured at the n{_}TOF facility at CERN over 9 orders of magnitude in neutron energy using {sup 235}U as a reference. Parallel Plate Avalanche Counters were used to detect both fission fragments in coincidence, thus efficiently discriminating fissions from other reactions. Data benefit from the remarkable energy resolution of the n{_}TOF facility. They are found in overall good agreement with databases and previous measurements, but some clear discrepancies can be put in evidence. These data are the first full coverage of the high-energy region (up to 1 GeV).

  15. Uranium, plutonium, and thorium isotopes in the atmosphere and the lithosphere

    SciTech Connect

    Essien, I.O.

    1983-01-01

    Concentration of /sup 238/U in rain and snow collected at Fayetteville (36/sup 0/N, 94/sup 0/W), Arkansas, showed a marked increase during the summer months of 1980, while Mount St. Helens remained active. This observed increase of /sup 238/U can be explained as due to the fallout of natural uranium from the eruption of Mount St. Helens. Large increases in the concentration of thorium isotopes detected in rain and snow samples during the last months of 1982 and early months of 1983 probably originated from the eruption of El Chichon volcano, which occurred on 28 March 1982. About 450 Ci of /sup 232/Th is estimated to have been injected into the atmosphere by this eruption. Isotopic anomalies were observed in atmospheric samples such as rain and snow. These anomalies can be attributed to various natural as well as man-made sources: nuclear weapon tests, nuclear accidents involving the burn-up of nuclear powered satellites, and volcanic eruptions. The variation of /sup 234/U//sup 238/U ratios in radioactive minerals when leached with nitric acid were also noticed and this variation, while /sup 235/U//sup 238/U remained fairly constant, can be explained in terms of the ..cap alpha..-recoil effect and changes in oxidation state of uranium. Difference found in /sup 239/Pu//sup 238/U ratios in terrestrial samples and uranium minerals can be explained as due to fallout contamination.

  16. Transfer Rates of 238U and 232Th for E. globulus, A. mearnsii, H. filipendula and Hazardous Effects of the Usage of Medicinal Plants From Around Gold Mine Dump Environs

    PubMed Central

    Tshivhase, Victor M.; Njinga, Raymond L.; Mathuthu, Manny; Dlamini, Thulani C.

    2015-01-01

    Medicinal plant consumption can be a source of human exposure to radioactive elements such as 238U and 232Th, which can lead to internal radiation doses. The uptake of 238U and 232Th from soils to the leaf samples of three different medicinal plant species (Eucalyptus globulus, Acacia mearnsii and Hyparrhenia filipendula) from the purlieu of the Princess gold mine dump, an abandoned contaminated tailings storage site (TSS), located at longitude 27°55′00″E and latitude 26°09′30″S in Davidsonville (Roodepoort, west of Johannesburg, South Africa) was measured. This was done using ICP-MS spectrometry and substantial differences were observed in the soil-plant transfer factor (TF) values between these radionuclides. The plant species E. globulus exhibited the highest uptake of 238U, with an average TF of 3.97, while that of H. filipendula was 0.01 and the lowest TF of 0.15 × 10−2 was measured for A. mearnsii. However, in the case of 232Th, the highest average TF was observed for A. mearnsii (0.29), followed by E. globulus (0.10) and lowest was measured for H. filipendula (0.27 × 10−2). The ratio of TF average value i.e., 238U to 232Th in the soil-plant leaves was 38.05 for E. globulus, 0.01 for A. mearnsii and 4.38 for H. filipendula. PMID:26690462

  17. U-Th-Pb and 230Th/ 238U disequilibrium isotope systematics: Precise accessory mineral chronology and melt evolution tracing in the Alpine Bergell intrusion

    NASA Astrophysics Data System (ADS)

    Oberli, Felix; Meier, Martin; Berger, Alfons; Rosenberg, Claudio L.; GierÉ, Reto

    2004-06-01

    In order to investigate the potential of combined Th-U-Pb isotope and 230Th/ 238U disequilibrium systematics for tracing magmatic crystallization and melt evolution, conventional high-resolution single-crystal TIMS techniques have been applied to zircon, titanite and fragments of geochemically characterized growth zones of allanite. These minerals were extracted from a single tonalite specimen collected from the feeder zone of the Tertiary Bergell pluton (Southern Steep Belt, S Switzerland/N Italy). The isotopic results document an extended history of crystallization and melt evolution of at least 5 Ma, with well-resolved zircon ages defining an early interval of 33.0 to 32.0 Ma, followed by crystallization of zoned allanite from 32.0 to 28.0 Ma and formation of magmatic epidote possibly as late as 26 Ma. Trace and major element patterns in zoned allanite closely mirror melt evolution, characterized by increase of U concentration and sharp decrease of Th and LREE, reflecting early crystallization of phases low in U and, in particular, the dominating control by allanite precipitation. Preservation of substantial quantities of excess 206Pb derived from initial excess 230Th in all analyzed allanite grains indicates that their isotopic systems have not been reset by loss of radiogenic Pb during prolonged residence at magmatic conditions and regional-metamorphic cooling, and that the measured sequence of 208Pb/ 232Th dates translates into a real age sequence. Major loss of radiogenic Pb from compositionally zoned allanite by volume diffusion would have resulted in a data pattern grossly different from the observed one, as demonstrated by numerical modeling of 232Th- 208Pb- 238U- 230Th- 206Pb isotopic evolution. The results therefore suggest closure temperatures ≥700°C for magmatic allanite. Quantification of 230Th/ 238U disequilibrium relationships reveals a smooth, initially steep decrease of Th/U in the magma from values of 2.9 at 32.0 Ma to < 0.1 at 28.0 Ma in

  18. Chemical fertilizers as a source of (238)U, (40)K, (226)Ra, (222)Rn, and trace metal pollutant of the environment in Saudi Arabia.

    PubMed

    Alshahri, Fatimh; Alqahtani, Muna

    2015-06-01

    The specific activities of (238)U, (226)Ra, (40)K, and (222)Rn in chemical fertilizers were measured using gamma ray spectrometer and Cr-39 detector. In this study, 21 chemical fertilizers were collected from Eastern Saudi Arabian markets. The specific activities of (238)U ranged from 23 ± 0.5 to 3900 ± 195 Bq kg(-1); (226)Ra ranged from 5.60 ± 2.80 to 392 ± 18 Bq kg(-1); and (40)K ranged from 18.4 ± 3 to 16,476 ± 820 Bq kg(-1). The radon concentrations and the radon exhalation rates were found to vary from 3.20 ± 1.20 to 1532 ± 160 Bq m(-3) and from 1.60 to 774 mBq m(-2) h(-1), respectively. Radium equivalent activities (Raeq) were calculated for the analyzed samples to assess the radiation hazards arising due to the use of these chemical fertilizers in the agriculture soil. The Raeq for six local samples (nitrogen, phosphorous, and potassium (NPK) and single superphosphate (SSP)) and one imported sample (Sulfate of Potash (SOP)) were greater than the acceptable value 370 Bq kg(-1). The total air absorbed doses rates in air 1 m above the ground (D) were calculated for all samples. All samples, except one imported granule sample diammonium phosphate (DAP), were higher than the estimated average global terrestrial radiation of 55 nGy h(-1). The highest annual effective dose was in triple super phosphate (TSP) fertilizers (2.1 mSv y(-1)). The results show that the local TSP, imported SOP, and local NPK (sample 13) fertilizers were unacceptable for use as fertilizers in agricultural soil. Furthermore, the toxic elements and trace metals (Pb, Cd, Cr, Co, Ni, Hg, and As) were determined using atomic absorption spectrometer. The concentrations of chromium in chemical fertilizers were higher than the global values. PMID:25532871

  19. Determination of long-lived actinides in soil leachates by inductively coupled plasma: Mass spectrometry

    SciTech Connect

    Crain, J.S.; Smith, L.L.; Yaeger, J.S.; Alvarado, J.A.

    1994-06-01

    Inductively coupled plasma -- mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t{sub 1/2} > 10{sup 4} y) actinide isotopes in soil samples. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L{sup {minus}1} ({sup 239}Pu) to 2 {mu}Bq L{sup {minus}1} ({sup 235}U) Hydride adducts of {sup 232}Th and {sup 238}U interfered with the determinations of {sup 233}U and {sup 239} Pu; thus, extraction chromatography was, used to eliminate the sample matrix, concentrate the analytes, and separate uranium from the other actinides. Alpha spectrometric determinations of {sup 230}Th, {sup 239}Pu, and the {sup 234}U/{sup 238}U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and a-spectrometric determinations of {sup 234}U and {sup 238}U activities.

  20. 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

  1. 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.

  2. Rotation of the compound nucleus 236U ∗ in the fission reaction 235U( n,f) induced by cold polarised neutrons

    NASA Astrophysics Data System (ADS)

    Goennenwein, F.; Mutterer, M.; Gagarski, A.; Guseva, I.; Petrov, G.; Sokolov, V.; Zavarukhina, T.; Gusev, Yu.; von Kalben, J.; Nesvizhevski, V.; Soldner, T.

    2007-08-01

    Surprisingly, for one of the best investigated nuclear reactions a new phenomenon was discovered. In an experiment performed at the High Flux Reactor of the Institut Laue Langevin in Grenoble, France, the reaction 235U(n , f) was studied. Fission was induced by cold polarised neutrons. Besides the two main fragments also ternary light charged particles were measured. The centres or the detector assemblies for fragments and light particles were positioned at right angles relative to each other in a plane perpendicular to the neutron beam. It is well known that the majority of ternary particles are emitted closely perpendicular to the fission axis. With the neutron spin pointing parallel or anti-parallel to the neutron beam it was observed that, upon flipping periodically the neutron spin, the distributions of angles between fragments and light particles are wobbling back and forth. The phenomenon is traced to the rotation of the scissioning nucleus while the light particles are ejected. This interpretation is corroborated by trajectory calculations for ternary α-particles being accelerated in a rotating Coulomb field provided by the two main fragments. The angle through which the fission axis and the trajectories of α-particles rotate is very small and barely exceeds 0.2°. This so far unreported feature of nuclear fission has been called the “ROT-effect”.

  3. Neutron induced fission of 238U at incident neutron energies from 1.2 to 5.8 MeV

    NASA Astrophysics Data System (ADS)

    Vivès, F.; Hambsch, F.-J.; Oberstedt, S.; Barreau, G.; Bax, H.

    1998-10-01

    The reaction 238U(n,f) has been studied at IRMM at different incident neutron energies ranging from En=1.2 to 5.8 MeV. The existence of vibrational resonances in the region of the threshold of the fission cross-section and the proton pairing effect should induce variations in the fission fragment properties. The fission fragment mass, mean total kinetic energy (TKE¯) and angular distributions have been investigated with a double Frisch-gridded ionization chamber. For each incident neutron energy, more than 105 events have been accumulated. The TKE¯ shows an increasing trend up to En=3.5 MeV with a sudden drop at roughly En=3.8 MeV which might be related to the onset of pair breaking. Above En=3.8 MeV TKE¯ is again continually increasing. The two-dimensional mass-TKE distributions have been compared by means of a fit with theoretical calculations performed recently in the frame of the multi-modal random neck-rupture model. Actually, two solutions are possible with assuming either two or three Gaussians for the asymmetric part of the mass distribution. However, both solutions lead to the same physical interpretation. The solution with three Gaussians is more in line with the theoretical predictions. In any case the super-long symmetric mode has to be included, in order to explain the dip in TKE¯ close to symmetry.

  4. Experimental Neutron-induced Fission Fragment Mass Yields of 232Th and 238U at Energies from 10 to 33 Me

    NASA Astrophysics Data System (ADS)

    Simutkin, V. D.; Pomp, S.; Blomgren, J.; Österlund, M.; Bevilacqua, R.; Andersson, P.; Ryzhov, I. V.; Tutin, G. A.; Yavshits, S. G.; Vaishnene, L. A.; Onegin, M. S.; Meulders, J. P.; Prieels, R.

    2014-05-01

    Development of nuclear energy applications requires data for neutron-induced reactions for actinides in a wide neutron energy range. Here we describe measurements of pre-neutron emission fission fragment mass yields of 232Th and 238U at incident neutron energies from 10 to 33 MeV. The measurements were done at the quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE; a multi-section twin Frisch-gridded ionization chamber was used to detect fission fragments. For the peak neutron energies at 33, 45 and 60 MeV, the details of the data analysis and the experimental results were published in Ref. [I.V. Ryzhov, S.G. Yavshits, G.A. Tutin et al., Phys. Rev. C 83, 054603 (2011)]. In this work we present data analysis in the low-energy tail of the neutron energy spectra. The preliminary measurement results are compared with available experimental data and theoretical predictions.

  5. High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims

    NASA Astrophysics Data System (ADS)

    Vazquez, Jorge A.; Lidzbarski, Marsha I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

  6. Fission-γ-Ray Coincidence Studies of ^238U Neutron-Induced Fission in the Range 1 < En < 200 MeV

    NASA Astrophysics Data System (ADS)

    Nelson, R. O.; Ethvignot, T.; Granier, T.; Casoli, P.; Fotiades, N.; Devlin, M.; Garrett, P. E.; Younes, W.; Becker, J. A.; Bernstein, L. A.

    2002-04-01

    Studies of prompt fission-γ-ray coincidences are being carried out using the high-resolution γ-ray detector array GEANIE at the WNR broad-spectrum neutron source at LANSCE. Thin Si solar cells with thin ^238U deposits are used to detect fission products in coincidence with their de-excitation γ rays. Low-energy γ rays and x-rays are detected with planar Ge detectors. Higher-energy γ rays are detected with coaxial Ge detectors. Incident neutron energies are determined by the time-of-flight technique. Recent measurements have recorded both x-rays and γ rays from fission products with a goal of extracting charge and mass distributions. The average total energy released as γ rays from the de-excitation of the fission products can be determined by deconvolution of the fission-γ-ray spectra. Examining the emitted-γ-ray energy as a function of incident-neutron energy provides insight into the evolution of the excitation of the fission products. Preliminary results of these studies and plans for further work will be presented.

  7. High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims

    USGS Publications Warehouse

    Vazquez, Jorge A.; Lidzbarski, Marsha I.

    2012-01-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

  8. Influence of different data tables on neutron induced reactions in quasi-infinite 238U and 232Th targets irradiated by protons with relativistic energy

    NASA Astrophysics Data System (ADS)

    Zhivkov, P.; Stoyanov, Ch; Tyutyunnikov, S.; Furman, W.

    2016-06-01

    The last decade saw the emergence of various theoretical analysis and developments of ADS (Accelerator Driving System). Different transport codes, nuclear models and nuclear cross sections have been used to predict and estimate the properties of ADS. The energy of the proton beam is supposed to range between 1 and 1.5 GeV, but some analyses suggest higher energy - up to 10 GeV. The recent papers examine the influence of the nuclear models on neutron induced reactions (n,f), (n,g), (n,xn), (n,el.) and (n,inel.). The experimental set-ups and the presumable ADS constructions consist of thousands of segments and details for example project Myrrha, Belgum [1]. The calculation of the above reactions depends on the neutron spectrum in each segment. There is a considerable difference in the size of these segments in ADS, which makes the estimation of the influence of the nuclear models and the cross sections on the integral number of neutron induced reactions more difficult. This article considers the influence of different cross section data tables on neutron induced reactions in 238U or 232Th targets. One nuclear model describing the high energy part of the nuclear interaction and various cross section data tagble (ENDF, ENDL, TENDL2014 and etc.) are used. All particles generated in the nuclear interaction process deposit their energy in the target volume. MCNP 6.1 transport code was used.

  9. Vertical and horizontal distribution of radionuclides (232Th, 238U and 40K) in sediment from Manjung coastal water area Perak, Malaysia

    NASA Astrophysics Data System (ADS)

    Abdullah, Anisa; Hamzah, Zaini; Saat, Ahmad; Wood, Ab. Khalik

    2016-01-01

    Distribution of radionuclides from anthropogenic activities has been widely studied in marine coastal area. Due to rapid population growth and socio-economic development in Manjung area such as coal fired power plant, iron foundries, port development, waste discharged from factories and agriculture runoff may contribute to increase in pollution rate. The radioactive materials from anthropogenic activities could deteriorate the quality of the marine ecosystem and thus lead to possible radiological health risk to the population. Radionuclides (232Th, 238U and 40K) content in surface and profile sediment from Manjung coastal area was determined in this study. Radionuclides in sediment from seven locations were collected using sediment core sampling and measurements were carried out using Energy Dispersive X-ray Fluorescence (EDXRF) spectroscopy. The results show that the concentration of radionuclides in surface sediment and distribution trend of depth vertical profile sediment generally varies depending on locations. Enrichment factors (EF), geo-accumulation index (Igeo) and pollution index (PI) were applied to determine level of pollution of this study area. The radiological risks related to human exposure were evaluated based on external hazard index (Hex).

  10. Synthesis of rutherfordium isotopes in the 238U(26Mg, xn)264-xRf reaction and study of their decay properties

    SciTech Connect

    Gates, Jacklyn M; Gates, J.M.; Garcia, M.A.; Gregorich, K.E.; Dullmann, Ch.E.; Dragojevic, I.; Dvorak, J.; Eichler, R.; Folden III, C.M.; Loveland, W.; Nelson, S.L.; Pang, G.K.; Stavsetra, L.; Sudowe, R.; Turler, A.; Nitsche, H.

    2008-01-15

    Isotopes of rutherfordium (258-261Rf) were produced in irradiations of 238U targets with 26Mg beams. Excitation functions were measured for the 4n, 5n and 6n exit channels. Production of 261Rf in the 3n exit channel with a cross section of 28+92-26 pb was observed. Alpha decay of 258Rf was observed for the first time with an alpha-particle energy of 9.05+-0.03 MeV and an alpha/total decay branching ratio of 0.31+-0.11. In 259Rf, the electron capture/total decay branching ratio was measured to be 0.15+-0.04. The measured half-lives for 258Rf, 259Rf and 260Rf were 14.7+1.2-1.0 ms, 2.5+0.4-0.3 s and 22.2+3.0-2.4 ms, respectively, in agreement with literature data. The systematics of the alpha decay Q values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the N = 152, Z = 100 deformed shell. The influence of the N = 152 shell on the alpha decay Q values for rutherfordium was observed to be similar to that of the lighter elements (96<_ Z<_ 102). However, the N = 152 shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements (96<_ Z<_102).

  11. Sources of alluvium in a coastal plain stream based on radionuclide signatures from the 238U and 232Th decay series

    NASA Astrophysics Data System (ADS)

    Yeager, Kevin M.; Santschi, Peter H.; Phillips, Jonathan D.; Herbert, Bruce E.

    2002-11-01

    Discerning alluvial sources and their change over time or distance is a fundamental question in hydrology and geology, often critical in identifying impacts of human and natural perturbations on fluvial systems. Surfaces of upland interfluves and subsoils, sources of alluvium in the lower Loco Bayou basin, Texas, were distinguished using the isotope ratios 226Ra/232Th, 226Ra/230Th, and 230Th/232Th. Channel alluvium indicates a transition from interfluve surface to subsoil sources during flood (subsoil ˜34% to ˜91%, over about 8 km) and bank-full stages (subsoil ˜9% to ˜74%, over about 12 km), with distance downstream. These results indicate strong coupling between hillslope and channel processes, reflecting land use change from forested to agricultural, concentrated in lower Loco Bayou. This methodology shows that sediment sources can be differentiated based upon landscape placement where lithologic contrast is absent. The geochemistry, long half-lives, and fractionation of 238U and 232Th decay series radionuclides during pedogenic and fluvial processes in humid climates suggest that these methods are applicable in a wide variety of fluvial systems.

  12. Real-time, in situ detection of {sup 90}Sr and {sup 238}U in soils via scintillating-fiber-sensor technology

    SciTech Connect

    Schilk, A.J.; Knopf, M.A.; Thompson, R.C.; Hubbard, C.W.; Abel, K.H.; Edwards, D.R.; Abraham, J.R.

    1994-05-01

    A revolutionary sensor has been developed for observing the highly energetic beta particles that originate from the decay daughters of {sup 238}U and {sup 9O}Sr. This is accomplished through (1) constructing flat ribbons that are each composed of numerous square scintillating fibers, (2) stacking these ribbons and coupling each bundled end to a photomultiplier tube, and (3) using custom-designed electronic circuitry to measure both interlayer and intralayer coincident events. By observing the relative penetration depths of incident particles, this sensor is able to discriminate between the highly energetic betas of interest and those of lower energy. After placing the sensor on the target surface and initiating data acquisition, one obtains in a few seconds to a few minutes an accurate indication of the contaminant activity per unit weight of material (in the uppermost millimeters) directly below the sensor. This combination of speed and efficiency allows rapid surface coverage in a relatively short period of time, thereby facilitating the timely removal of these contaminants. Laboratory evaluations of a prototype version of this sensor have indicated that contamination levels less than 5 pCi/g (1.8 x 10{sup 2} Bq/kg) can be determined within a few minutes.

  13. Uranium-series dating of corals in situ using laser-ablation MC-ICPMS

    NASA Astrophysics Data System (ADS)

    Potter, Emma-Kate; Stirling, Claudine H.; Wiechert, Uwe H.; Halliday, Alex N.; Spötl, Christoph

    2005-01-01

    The in situ U-series dating of corals has been achieved using laser-ablation multiple-collector inductively coupled plasma mass spectrometry (LA MC-ICPMS). Utilising a 193 nm excimer laser coupled to a Nu Instruments Nu Plasma equipped with multiple ion counters, percent-level analytical precision for 234U/238U and 230Th/238U is obtained. Approximately 70 [mu]g of carbonate is consumed during each analysis, containing approximately 0.2 ng of 238U, ~10 pg of 234U and less than 3 fg of 230Th. A two-cycle, fast magnet jumping procedure is adopted. In the first cycle 238U is measured in a Faraday collector while the low-abundance isotopes 234U, 232Th, and 230Th are measured simultaneously in ion counters. In the second cycle 235U is measured in an ion counter. All samples are bracketed with an isotopically characterised sample to correct for electron multiplier gain and variable elemental fractionation. U-series ages are then calculated from the measured 234U/238U and 230Th/238U. Here, we demonstrate the applicability of this technique by analysing a series of coral samples that have been previously characterised by conventional thermal ionisation mass spectrometry (TIMS) and solution-nebulisation multiple-collector ICP mass spectrometry. Excellent agreement is obtained with independent age estimates. The samples have varying degrees of preservation and ages ranging between <10 and 600 thousand years (ka). The age uncertainties achieved are +/-1 ka at 3 ka and +/-7 ka at 125 ka. Therefore the technique can be used to distinguish between major climatic sub-stages throughout the last 140,000 years spanning the last glacial-interglacial cycle, as recorded in coral reef terraces. The laser-ablation U-series results are independent of coral species. U-series age uncertainties are comparable to those attained using [alpha]-spectrometry but require ~104 times less sample and no chemical preparation.

  14. 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

  15. Evaluating the status of uranium isotope ratio measurements using an inter-laboratory comparison campaign

    NASA Astrophysics Data System (ADS)

    Richter, S.; Alonso, A.; Truyens, J.; Kühn, H.; Verbruggen, A.; Wellum, R.

    2007-07-01

    The REIMEP 18 (Regular European Inter-laboratory Measurement Evaluation Programme) campaign for the measurement isotopic ratios of uranium in nitric acid solution was completed in December 2006. The task for all participating laboratories was to measure the uranium isotopic composition of four uranium samples ranging from depleted to slightly enriched uranium. With 71 participating laboratories REIMEP 18 has become the largest nuclear isotopic measurement campaign organized by IRMM so far. Participation in this kind of measurement campaign is an integral part of the external quality control required for nuclear safeguards laboratories worldwide. For the first time also a significant number of academic laboratories, mainly from the geochemistry area was included. Certification measurements were carried out at IRMM using state-of-the-art mass spectrometric methodology. A MAT511 UF6-gas source mass spectrometer (GSMS) was used to determine the n(235U)/n(238U) ratios and a TRITON thermal-ionization mass-spectrometer (TIMS) for the minor isotope ratios n(234U)/n(238U) and n(236U)/n(238U). Verification measurements on ampouled samples were performed successfully prior to sample shipping and showed good agreement with the certified ratios. The results of the REIMEP 18 campaign confirm in general the excellent capability of nuclear safeguards and scientific laboratories in measuring isotopic abundances of uranium, although some problems were discovered for the measurements of the minor isotope ratios n(234U)/n(238U) and n(236U)/n(238U) and the calculation of measurement uncertainties for isotope ratios in general. This paper describes the outcome of the REIMEP 18 campaign. It includes a graphical evaluation and discussion of the results, an evaluation of the applied measurement and calibration techniques and a discussion of conclusions and actions to be taken.

  16. Investigations of the Space Parity Violation and Interference Effects in the Fragment Angular Distributions of 235U, 233U, and 239Pu Fission by Resonance Neutrons

    NASA Astrophysics Data System (ADS)

    Sokolov, V. E.; Gagarski, A. M.; Guseva, I. S.; Golosovskaya, S. P.; Krasnoshchokova, I. S.; Petrov, G. A.; Petrova, V. I.; Petukhov, A. K.; Pleva, Yu. S.; Alfimenkov, V. P.; Chernikov, A. N.; Lason, L.; Mareev, Yu. D.; Novitski, V. V.; Pikelner, L. B.; Pikelner, T. L.; Tsulaya, M. I.

    2005-05-01

    Investigations of the space parity nonconserving (PNC) asymmetry of 233U, 235U, and 239Pu fission fragment emission and parity conserving (PC) interference effects of left-right and forward-backward asymmetries were carried out on the neutron beams of the reactor IBR-30 (JINR, Dubna) over the range of neutron energies from 0.02 eV to about 100 eV. All experimental results obtained have been found to be in a good mutual accordance within the frames of modern theoretical conceptions about the mechanisms of PNC and PC effects forming in fission process induced by slow neutrons. In case of the P-even interference effects of asymmetry the evident mutual well-marked irregularities in their neutron energy dependencies up to about 100 eV were observed. It is connected with the interference of s, p-resonances at fission compound stage according to modern theory. As a remarkable result of the PNC effect measurements the resonance behavior of the PNC asymmetry coefficients in the low neutron energy region (En < 2 eV) was observed. Unfortunately, the statistical accuracy of the PNC effect measurements is not enough for observation of these resonance effects in other cases of more high energies. Results of simultaneous analysis of all three asymmetry effects for all three nuclei are presented. The satisfactory combined description of the experimental points is received. As a result of theoretical evaluation of these data main parameters and the estimates of nuclear matrix elements of the weak interaction for some p-resonances in the low energy range were extracted.

  17. TARGET FRAGMENT ENERGIES AND MOMENTA IN THE REACTION OF 4.8 GeV {sup 12}C AND 5.0 GeV {sup 20}Ne WITH {sup 238}U

    SciTech Connect

    Loveland, W.; Luo, Cheng; McGaughey, P. L.; Morrissey, D. J.; Seaborg, G. T.

    1980-10-01

    Target fragment recoil properties were measured using the thick target-thick catcher technique for the interaction of 4.8 GeV {sup 12}C and 5.0 GeV {sup 20}Ne with {sup 238}U. The target fragment energies and momenta are very similar for the reaction of 4.8 GeV (400 MeV/A) {sup 12}C and 5.0 GeV (250 MeV/A) {sup 20}Ne with {sup 238}U. In the complex variation of fragment momenta with their N/Z ratio, one finds evidence suggesting the existence of several mechanisms leading to the formation of the target fragments. Comparison of these results with the predictions of the intranuclear cascade model of Yariv and Fraenkel and the firestreak model shows that both model predictions grossly overestimate the target fragment momenta.

  18. Measurement of 238U and 232Th in Petrol, Gas-oil and Lubricant Samples by Using Nuclear Track Detectors and Resulting Radiation Doses to the Skin of Mechanic Workers.

    PubMed

    Misdaq, M A; Chaouqi, A; Ouguidi, J; Touti, R; Mortassim, A

    2015-10-01

    Workers in repair shops of vehicles (cars, buses, truck, etc.) clean carburetors, check fuel distribution, and perform oil changes and greasing. To explore the exposure pathway of (238)U and (232)Th and its decay products to the skin of mechanic workers, these radionuclides were measured inside petrol, gas-oil, and lubricant material samples by means of CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs), and corresponding annual committed equivalent doses to skin were determined. The maximum total equivalent effective dose to skin due to the (238)U and (232)Th series from the application of different petrol, gas-oil, and lubricant samples by mechanic workers was found equal to 1.2 mSv y(-1) cm(-2). PMID:26313584

  19. Investigation of the fission fragment properties of the reaction 238U(n,f) at incident neutron energies up to 5.8 MeV

    NASA Astrophysics Data System (ADS)

    Vivès, F.; Hambsch, F.-J.; Bax, H.; Oberstedt, S.

    2000-01-01

    The fission fragment properties of the reaction 238U(n,f) have been studied, at different incident neutron energies ranging from En=1.2 to 5.8 MeV. The pre-neutron emission mass, kinetic energy and fission fragment angular distributions have been investigated with a double Frisch-gridded ionization chamber. The influence of the subthreshold vibrational resonances and of the proton pairing effect on the fission fragment properties is clearly visible. The total kinetic energy averaged over all fission fragment masses ( overlineTKE) shows an increasing trend up to En=3.5 MeV with a sudden drop at roughly En=3.8 MeV which has been attributed to the onset of pair breaking at the barrier. Above En=3.8 MeV, the overlineTKE is again continuously increasing. The changes in the mass yield and overlineTKE( A) distributions have been studied as a function of the compound nuclear excitation energy and their contribution to the observed variations in the overlineTKE have been determined. The two-dimensional mass-TKE distributions have been described in terms of fission modes and compared with theoretical calculations performed recently in the frame of the multi-modal random neck-rupture model. Although theoretically six asymmetric fission modes are predicted which all surpass individual outer barriers, an interpretation in terms of only two asymmetric modes has physical meaning. This points to an influence of shell structure effects to the observed distributions. In any case, the super-long symmetric mode has to be included, in order to explain the dip in overlineTKE( A) distribution close to symmetry.

  20. Observation of new K isomers among neutron-rich rare earth nuclei produced by in-flight fission of 345 MeV/nucleon 238U

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Kubo, Toshiyuki; BigRIPS new isotope Collaboration

    2014-09-01

    We have performed search for new K isomers for a wide range of neutron-rich rare earth nuclei using the BigRIPS separator at RIKEN RIBF. The rare earth nuclei were produced by in-flight fission of a 238U beam at 345 MeV/nucleon, and isomeric gamma rays were detected using four clover-type germanium detectors. As a result, we have observed a total of 25 new microsecond isomers: 158 m , 159 m , 160 mNd, 158 m , 159 m , 161 mPm, 160 m , 161 m , 162 mSm, 163 m , 164 mEu, 162 m , 164 m , 165 m , 166 mGd, 164 m , 165 m , 166 m , 167 m , 168 mTb, 167 m , 168 m , 169 m , 170 mDy, and 171mHo, and obtained a wealth of spectroscopic information on these nuclei. The nuclei in this region are predicted to be well deformed with a prolate shape, and Kisomers are expected to appear due to the K hindrance. In the present measurement, as anticipated, many of the observed new isomers have been interpreted as a K isomer, because we could identify some gamma rays which belong to the grand-state rotational band being fed by isomeric transitions. The systematics of known K isomers, such as those in neighboring higher- Zisotones, also help and support the interpretation of isomerism. Here we will report on the details of the experimental results and discuss the possible configurations of deformed orbits for the observed new K isomers.

  1. Nuclear orientation in the reaction {sup 34}S+{sup 238}U and synthesis of the new isotope {sup 268}Hs

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nagame, Y.; Nishinaka, I.; Hofmann, S.; Hessberger, F. P.; Ackermann, D.; Duellmann, Ch. E.; Heinz, S.; Heredia, J. A.; Khuyagbaatar, J.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Schaedel, M.; Antalic, S.; Saro, S.; Aritomo, Y.

    2010-08-15

    The synthesis of isotopes of the element hassium was studied using the reaction {sup 34}S+{sup 238}U{yields}{sup 272}Hs{sup *}. At a kinetic energy of 163.0 MeV in the center-of-mass system we observed one {alpha}-decay chain starting at the isotope {sup 267}Hs. The cross section was 1.8{sub -1.5}{sup +4.2} pb. At 152.0 MeV one decay of the new isotope {sup 268}Hs was observed. It decays with a half-life of 0.38{sub -0.17}{sup +1.8} s by 9479{+-}16 keV {alpha}-particle emission. Spontaneous fission of the daughter nucleus {sup 264}Sg was confirmed. The measured cross section was 0.54{sub -0.45}{sup +1.3} pb. In-beam measurements of fission-fragment mass distributions were performed to obtain information on the fusion probability at various orientations of the deformed target nucleus. The distributions changed from symmetry to asymmetry when the beam energy was changed from above-barrier to sub-barrier values, indicating orientation effects on fusion and/or quasifission. It was found that the distribution of symmetric mass fragments originates not only from fusion-fission, but has a strong component from quasifission. The result was supported by a calculation based on a dynamical description using the Langevin equation, in which the mass distributions for fusion-fission and quasifission fragments were separately determined.

  2. Synthesis of rutherfordium isotopes in the {sup 238}U({sup 26}Mg, xn){sup 264-x}Rf reaction and study of their decay properties

    SciTech Connect

    Gates, J. M.; Garcia, M. A.; Dragojevic, I.; Folden, C. M. III; Nelson, S. L.; Nitsche, H.; Gregorich, K. E.; Stavsetra, L.; Sudowe, R.; Duellmann, Ch. E.; Dvorak, J.; Tuerler, A.; Eichler, R.; Loveland, W.; Pang, G. K.

    2008-03-15

    Isotopes of rutherfordium ({sup 258-261}Rf) were produced in irradiations of {sup 238}U targets with {sup 26}Mg beams. Excitation functions were measured for the 4n,5n, and 6n exit channels. Production of {sup 261}Rf in the 3n exit channel with a cross section of 28{sub -26}{sup +92} pb was observed. {alpha}-decay of {sup 258}Rf was observed for the first time with an {alpha}-particle energy of 9.05 {+-} 0.03 MeV and an {alpha}/total-decay branching ratio of 0.31 {+-} 0.11. In {sup 259}Rf, the electron capture/total-decay branching ratio was measured to be 0.15{+-}0.04. The measured half-lives for {sup 258}Rf, {sup 259}Rf, and {sup 260}Rf were 14.7{sub -1.0}{sup +1.2} ms, 2.5{sub -0.3}{sup +0.4} s, and 22.2{sub -2.4}{sup +3.0} ms, respectively, in agreement with literature data. The systematics of the {alpha}-decay Q-values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the N=152,Z=100 deformed shell. The influence of the N=152 shell on the {alpha}-decay Q-values for rutherfordium was observed to be similar to that of the lighter elements (96{<=}Z{<=}102). However, the N=152 shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements (96{<=}Z{<=}102)

  3. Equilibrium uranium isotope fractionation by nuclear volume and mass-dependent processes

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2006-12-01

    Uranium serves as a geochemical tracer of oxidation near the Earth's surface, and is also the basis for several isotopic geochronometers. It is thus important to understand possible non-radiogenic and non-radioactive isotopic fractionation of uranium in natural systems. This study presents theoretical estimates of equilibrium uranium isotope fractionations in U-bearing molecules and complexes, calculated using first-principles computational chemistry. Ion-exchange experiments (1,2) have indicated that mass-dependent mechanisms, alone, cannot explain 238U/234U and 238U/^{235}U fractionations, so nuclear volume (i.e., field shift) fractionation effects are also considered in theoretical calculations. The results indicate that equilibrium isotopic fractionation is likely when U4+ and U6+ species equilibrate. Nuclear volume fractionation leads to higher 238U/^{235}U in U4+-bearing species, overwhelming a smaller mass- dependent fractionation in the opposite direction. The calculated net fractionation between U(H2O)_94+ and UO2Cl3(H2O)_2^- is approximately 1 per mil at 20-150°C, in agreement with earlier experiments. These results also reproduce the apparent non mass-dependent signature observed in 238U/234U relative to 238U/^{235}U. In addition to redox reactions, significant fractionation is expected between different U6+-bearing uranyl complexes (e.g., UO2(H2O)_52+, UO2(NO3)_3^-, UO2(CO3)(H2O)3). These results suggest that U-isotope composition could be used as a proxy for the oxidation state and speciation of natural waters, and that U-isotope ratios are not constant in materials formed or equilibrated at low temperatures. More generally, nuclear volume fractionations are expected to partially cancel or reverse mass-dependent fractionations caused by redox transitions among the high oxidation states (≥+2) of lanthanides, actinides, and heavy transition elements. References: 1. Nomura, Higuchi and Fujii, 1996, J. Am. Chem. Soc., v. 118, p. 9127-9130. 2. Bigeleisen

  4. Mid-ocean ridge basalt generation along the slow-spreading, South Mid-Atlantic Ridge (5-11°S): Inferences from 238U-230Th-226Ra disequilibria

    NASA Astrophysics Data System (ADS)

    Turner, Simon; Kokfelt, Thomas; Hauff, Folkmar; Haase, Karsten; Lundstrom, Craig; Hoernle, Kaj; Yeo, Isobel; Devey, Colin

    2015-11-01

    U-series disequilibria have provided important constraints on the physical processes of partial melting that produce basaltic magma beneath mid-ocean ridges. Here we present the first 238U-230Th-226Ra isotope data for a suite of 83 basalts sampled between 5°S and 11°S along the South Mid-Atlantic Ridge. This section of the ridge can be divided into 5 segments (A0-A4) and the depths to the ridge axis span much of the global range, varying from 1429 to 4514 m. Previous work has also demonstrated that strong trace element and radiogenic isotope heterogeneity existed in the source regions of these basalts. Accordingly, this area provides an ideal location in which to investigate the effects of both inferred melt column length and recycled materials. 226Ra-230Th disequilibria indicate that the majority of the basalts are less than a few millennia old such that their 230Th values do not require any age correction. The U-Th isotope data span a significant range from secular equilibrium up to 32% 230Th excess, also similar to the global range, and vary from segment to segment. However, the (230Th/238U) ratios are not negatively correlated with axial depth and the samples with the largest 230Th excesses come from the deepest ridge segment (A1). Two sub-parallel and positively sloped arrays (for segments A0-2 and A3 and A4) between (230Th/238U) and Th/U ratios can be modelled in various ways as mixing between melts from peridotite and recycled mafic lithologies. Despite abundant evidence for source heterogeneity, there is no simple correlation between (230Th/238U) and radiogenic isotope ratios suggesting that at least some of the trace element and radiogenic isotope variability may have been imparted to the source regions >350 kyr prior to partial melting to produce the basalts. In our preferred model, the two (230Th/238U) versus Th/U arrays can be explained by mixing of melts from one or more recycled mafic lithologies with melts derived from chemically heterogeneous

  5. 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.

  6. 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. PMID:18514535

  7. Crystallisation ages in coeval silicic magma bodies: 238U-230Th disequilibrium evidence from the Rotoiti and earthquake flat eruption deposits, Taupo volcanic zone, New Zealand

    USGS Publications Warehouse

    Charlier, B.L.A.; Peate, D.W.; Wilson, C.J.N.; Lowenstern, J. B.; Storey, M.; Brown, S.J.A.

    2003-01-01

    The timescales over which moderate to large bodies of silicic magma are generated and stored are addressed here by studies of two geographically adjacent, successive eruption deposits in the Taupo Volcanic Zone, New Zealand. The earlier, caldera-forming Rotoiti eruption (>100 km3 magma) at Okataina volcano was followed, within months at most, by the Earthquake Flat eruption (??? 10 km3 magma) from nearby Kapenga volcano; both generated nonwelded ignimbrite and coeval widespread fall deposits. The Rotoiti and Earthquake Flat deposits are both crystal-rich high-silica rhyolites, with sparse glass-bearing granitoid fragments also occurring in Rotoiti lag breccias generated during caldera collapse. Here we report 238U-230Th disequilibrium data on whole rocks and mineral separates from representative Rotoiti and Earthquake Flat pumices and the co-eruptive Rotoiti granitoid fragments using TIMS and in situ zircon analyses by SIMS. Multiple-grain zircon-controlled crystallisation ages measured by TIMS from the Rotoiti pumice range from 69??3 ka ( 350 ka, with a pronounced peak at 70-90 ka. The weighted mean of isochrons is 83??14 ka, in accord with the TIMS data. One glass-bearing Rotoiti granitoid clast yielded an age of 57??8 ka by TIMS (controlled by Th-rich phases that, however, are not apparently present in the juvenile pumices). Another glass-bearing Rotoiti granitoid yielded SIMS zircon model ages peaking at 60-90 ka, having a similar age distribution to the pumice. Age data from pumices are consistent with a published 64??4 ka eruptive age (now modified to 62??2 ka), but chemical and/or mineralogical data imply that the granitoid lithics are not largely crystalline Rotoiti rhyolite, but instead represent contemporaneous partly molten intrusions reflecting different sources in their chemistries and mineralogies. Similarly, although the Earthquake Flat eruption immediately followed (and probably was triggered by) the Rotoiti event, age data from juvenile material

  8. Discriminating assimilants and decoupling deep- vs. shallow-level crystal records at Mount Adams using 238U-230Th disequilibria and Os isotopes

    USGS Publications Warehouse

    Jicha, B.R.; Johnson, C.M.; Hildreth, W.; Beard, B.L.; Hart, G.L.; Shirey, S.B.; Singer, B.S.

    2009-01-01

    A suite of 23 basaltic to dacitic lavas erupted over the last 350??kyr from the Mount Adams volcanic field has been analyzed for U-Th isotope compositions to evaluate the roles of mantle versus crustal components during magma genesis. All of the lavas have (230Th/238U) > 1 and span a large range in (230Th/232Th) ratios, and most basalts have higher (230Th/232Th) ratios than andesites and dacites. Several of the lavas contain antecrysts (crystals of pre-existing material), yet internal U-Th mineral isochrons from six of seven lavas are indistinguishable from their eruption ages. This indicates a relatively brief period of time between crystal growth and eruption for most of the phenocrysts (olivine, clinopyroxene, plagioclase, magnetite) prior to eruption. One isochron gave a crystallization age that is ~ 20-25??ka older than its corresponding eruptive age, and is interpreted to reflect mixing of older and juvenile crystals or a protracted period of magma storage in the crust. Much of the eruptive volume since 350??ka consists of lavas that have small to moderate 230Th excesses (2-16%), which are likely inherited from melting of a garnet-bearing intraplate ("OIB-like") mantle source. Following melt generation and subsequent migration through the upper mantle, most Mt. Adams magmas interacted with young, mafic lower crust, as indicated by 187Os/188Os ratios that are substantially more radiogenic than the mantle or those expected via mixing of subducted material and the mantle wedge. Moreover, Os-Th isotope variations suggest that unusually large 230Th excesses (25-48%) and high 187Os/188Os ratios in some peripheral lavas reflect assimilation of small degree partial melts of pre-Quaternary basement that had residual garnet or Al-rich clinopyroxene. Despite the isotopic evidence for lower crustal assimilation, these processes are not generally recorded in the erupted phenocrysts, indicating that the crystal record of the deep-level 'cryptic' processes has been

  9. 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

  10. 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

  11. 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

  12. Fragment-mass, kinetic energy, and angular distributions for 234U(n ,f ) at incident neutron energies from En=0.2 MeV to 5.0 MeV

    NASA Astrophysics Data System (ADS)

    Al-Adili, A.; Hambsch, F.-J.; Pomp, S.; Oberstedt, S.; Vidali, M.

    2016-03-01

    This work investigates the neutron-induced fission of 234U and the fission-fragment properties for neutron energies between En=0.2 and 5.0 MeV with a special highlight on the prominent vibrational resonance at En=0.77 MeV. Angular, energy, and mass distributions were determined based on the double-energy technique by means of a twin Frisch-grid ionization chamber. The experimental data are parametrized in terms of fission modes based on the multimodal random neck-rupture model. The main results are a verified strong angular anisotropy and fluctuations in the energy release as a function of incident-neutron energy.

  13. 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.

  14. The Effect of Redox Mechanisms on the Fractionation of Uranium `Stable' Isotopes

    NASA Astrophysics Data System (ADS)

    Kaltenbach, A.; Stirling, C. H.; Porcelli, D.; Hilton, D. R.; Kulongoski, J. T.

    2010-12-01

    Uranium is the heaviest naturally occurring element. It consists of three natural isotopes, 238U, 235U and 234U and has four oxidation states, U(III)-U(VI), of which only U(IV) and U(VI) are common. In the oxidized, hexavalent condition, U(VI) exists as uranyl ion (UO22+), which forms soluble, non-reactive complexes with carbonates. In the reduced condition, tetravalent U(IV) forms immobile minerals with hydroxides, fluorides and phosphates that are removed from the water column. In the recent years, isotopic fractionation between 235U and 238U has been detected in a range of terrestrial environments. Changes to U concentrations in natural waters occur due to biological uptake, adsorption/desorption to/from particulates and surfaces, diffusion into sediments, and chemically and biologically induced redox mechanisms (Swarzenski et al., 1999, Mar. Chem. 67, 181). The largest isotopic shifts evidently occur during the reduction of U(VI) to U(IV) in waters, during which precipitation changes the dissolved U concentration. However, the exact mechanisms controlling 235U/238U fractionation remain unclear. Some results implicate mass-dependent zero-point energy effects (preferential removal of 235U over 238U) (Rademacher et al., 2006, Environ. Sci. Technol. 40, 6943) as the main cause for the isotopic variations measured, while others suggest volume-dependent nuclear field shift effects (preferential removal of 238U over 235U) (Weyer et al., 2008, GCA 72, 345, Bopp et al., 2010, Environ. Sci. Technol. 44, 5927), which are predicted to be of the opposite sign and up to three times larger than mass-dependent effects. In this study, profiles of two different water masses were examined for their uranium concentration and their 235U/238U isotopic composition to determine the magnitude of the natural isotopic shifts as well as their origins. One set of samples was collected from a 160 m depth profile in the Framvaren Fjord, an anoxic basin. In this basin, the biogeochemical

  15. 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.

  16. 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.

  17. Determination of 40K, 232Th and 238U activity concentrations in ambient PM2.5 aerosols and the associated inhalation effective dose to the public in Jeddah City, Saudi Arabia.

    PubMed

    Zytoon, Mohamed A; Aburas, Hani M; Abdulsalam, Mohammed I

    2014-03-01

    Natural radioactivity of soil samples has been studied in many countries of the Arabian Peninsula, including Saudi Arabia. Radiological indices based on soil radioactivity have been widely used in these studies. However, there are no available data about natural radioactivity of fine aerosol particles in such countries. The objective of this study is to determine the activity concentrations of (40)K, (232)Th and (238)U in airborne PM2.5 and the associated internal inhalation radiation dose to the public in Jeddah City, Saudi Arabia. Twenty-four air samples in four locations throughout Jeddah were collected and analyzed for PM2.5 and the associated K, Th and U. The activity concentrations of the isotopes (40)K, (232)Th and (238)U were calculated. High atmospheric PM2.5 concentrations (mean: 50.81 ± 34.02 μg/m(3)) were found. The natural radioactivity associated with PM2.5 due to the isotopes (40)K, (232)Th and (238)U were 301.8 ± 76.1, 11.8 ± 4.2 and 10.8 ± 3.4 Bq/kg, respectively, and the Raeq was calculated as 44.9 ± 14.0 Bq/kg. The inhalation annual effective radiation dose to the public due to natural isotopes of the airborne PM2.5 was in the range 15.03-58.87 nSv/year, depending on the age group. Although these dose values were associated with the PM2.5 fraction only, they were higher than the world references values in air reported in the UNSCEAR, 2000 report. PMID:24462924

  18. Particle Leaking, Cross-Section Ratio 10B(n,{alpha})/238U(n,fission), and Excitation Function of the Reaction 10B(n,{alpha})7Li at MeV Energies

    SciTech Connect

    Giorginis, Georgios; Khryachkov, Vitali

    2005-05-24

    The 10B(n,{alpha})7Li reaction was studied in the energy range between 1.5 MeV and 5.6 MeV at the 7-MV Van de Graaff accelerator of IRMM by using a gridded ionisation chamber, signal digitisation, and an intrinsic 238U neutron monitor. The aim was to obtain accurate data for the IAEA Coordinated Research Project (CRP) on the improvement of standard cross sections for light elements. The effect of particle leaking was discovered and its implications investigated. The determination of the cross section {sigma}({alpha}0+{alpha}1) strongly benefits from it but measurements of angular distributions, individual cross sections {sigma}({alpha}0) and {sigma}({alpha}1), and the branching ratio {alpha}0/{alpha}1 are negatively affected. The correct number of reaction events was obtained by identification of unknown particle signatures in the energy spectra as 10B(n,{alpha})7Li events in the form of quasi 7Li+{alpha} particles created by particle leaking. The cross-section ratio 10B(n,{alpha})7Li/238U(n,fission) was measured and the excitation function of 10B(n,{alpha})7Li determined by simultaneously detecting the charged particles from the boron disintegration in the forward hemisphere and the 238U fission fragments in the backward hemisphere. The IRMM cross sections are compared to experimental data of other groups and to predictions of the ENDF/B-VI.8, JENDL-3.3, and JEF-2.2 evaluations.

  19. Angular distributions of target fragments from the reactions of 292 MeV - 25. 2 GeV /sup 12/C with /sup 197/Au and /sup 238/U

    SciTech Connect

    Morita, Y.

    1983-05-20

    Angular distributions of target fragments from the reactions of /sup 12/C with /sup 197/Au and /sup 238/U were measured at projectile energies of 292 MeV, 1.0 GeV, 3.0 GeV, 12.0 GeV and 25.2 GeV. The angular distributions of the /sup 197/Au target fragments were all forwardly peaked. Extensively forward peaked angular distributions were observed at the non-relativistic projectile energies (292 MeV, 1.0 GeV). No obvious differences were observed in the angular distributions at the different relativistic projectile energies of 3.0 GeV, 12.0 GeV and 25.2 GeV. The characteristic angular distribution pattern from the relativistic projectile energy experiments was also observed in the non-relativistic energy experiments. Maximum degree of forward-peaking in the angular distributions at each projectile energy was observed at the product mass number (A) around 190 from the 292 MeV projectile energy, at A=180 from 1.0 GeV and at A=175 from 3.0 GeV and 12.0 GeV. In general, two different types of angular distributions were observed in the relativistic projectile energy experiments with the /sup 238/U target. Isotropic angular distributions were observed for the fission product nuclides. The angular distributions of the fission products at the intermediate (292 MeV) energy showed slightly forward- peaked angular distributions. Because of the long projectile-target interaction time in the primary nuclear reaction, larger momentum was transferred from the projectile to the target nucleus. Steep forward-peaked angular distributions were also observed with the /sup 238/U target.

  20. Improved 206Pb/238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID-TIMS, ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards

    USGS Publications Warehouse

    Black, L.P.; Kamo, S.L.; Allen, C.M.; Davis, D.W.; Aleinikoff, J.N.; Valley, J.W.; Mundil, R.; Campbell, I.H.; Korsch, R.J.; Williams, I.S.; Foudoulis, C.

    2004-01-01

    Precise isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) documentation is given for two new Palaeozoic zircon standards (TEMORA 2 and R33). These data, in combination with results for previously documented standards (AS3, SL13, QGNG and TEMORA 1), provide the basis for a detailed investigation of inconsistencies in 206Pb/238U ages measured by microprobe. Although these ages are normally consistent between any two standards, their relative age offsets are often different from those established by ID-TIMS. This is true for both sensitive high-resolution ion-microprobe (SHRIMP) and excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) dating, although the age offsets are in the opposite sense for the two techniques. Various factors have been investigated for possible correlations with age bias, in an attempt to resolve why the accuracy of the method is worse than the indicated precision. Crystallographic orientation, position on the grain-mount and oxygen isotopic composition are unrelated to the bias. There are, however, striking correlations between the 206Pb/238U age offsets and P, Sm and, most particularly, Nd abundances in the zircons. Although these are not believed to be the primary cause of this apparent matrix effect, they indicate that ionisation of 206Pb/238U is influenced, at least in part, by a combination of trace elements. Nd is sufficiently representative of the controlling trace elements that it provides a quantitative means of correcting for the microprobe age bias. This approach has the potential to reduce age biases associated with different techniques, different instrumentation and different standards within and between laboratories. Crown Copyright ?? 2004 Published by Elsevier B.V. All rights reserved.

  1. Experimental study of the {sup 238}U({sup 36}S,3-5n){sup 269-271}Hs reaction leading to the observation of {sup 270}Hs

    SciTech Connect

    Graeger, R.; Gorshkov, A.; Tuerler, A.; Yakushev, A.; Ackermann, D.; Duellmann, Ch. E.; Hessberger, F. P.; Huebner, A.; Jaeger, E.; Khuyagbaatar, J.; Kindler, B.; Krier, J.; Lommel, B.; Schaedel, M.; Schausten, B.; Chelnokov, M.; Chepigin, V.; Kuznetsov, A.; Petrushkin, O.; Dvorak, J.

    2010-06-15

    The deformed doubly magic nucleus {sup 270}Hs has so far only been observed as the four-neutron (4n) evaporation residue of the reaction {sup 26}Mg+{sup 248}Cm, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of {sup 270}Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions {sup 48}Ca+{sup 226}Ra and {sup 36}S+{sup 238}U result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using hivap predict cross sections for the reaction {sup 36}S+{sup 238}U that are similar to those of the {sup 26}Mg+{sup 248}Cm reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction {sup 36}S+{sup 238}U and the observation of {sup 270}Hs, which is produced in the 4n evaporation channel, with a measured cross section of 0.8{sub -0.7}{sup +2.6} pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the {sup 26}Mg+{sup 248}Cm reaction at similar excitation energy.

  2. Theoretical investigation of shape parametrization’s effects on characteristics of fission fragments in 18O-induced fission of 154Sm, 197Au, 238U and 246Cm

    NASA Astrophysics Data System (ADS)

    Pahlavani, M. R.; Mirfathi, S. M.

    2015-06-01

    The multi-dimensional Langevin equations are employed to investigate mass and energy distributions of fission fragments. The calculations have been performed with two different shape classes of parametrization, namely Funny Hills and Cassinian Ovaloids. It was shown that inclusion of the Funny Hills parameterizations in the dynamical model produced considerable increase in neutron multiplicity as compared with available experimental data for 18O-induced fission of 154Sm, 197Au, 238U and 246Cm. The proposed shape-dependent multi-dimensional dynamical model reproduces well experimental data for mass distribution, neutron multiplicity and average kinetic energy of fission fragments over a wide range of mass-energy regions.

  3. Measurement of the 238U neutron-capture cross section and gamma-emission spectra from 10 eV to 100 keV using the DANCE detector at LANSCE

    SciTech Connect

    Ullmann, John L; Couture, A J; Keksis, A L; Vieira, D J; O' Donnell, J M; Jandel, M; Haight, R C; Rundberg, R S; Kawano, T; Chyzh, A; Baramsai, B; Wu, C Y; Mitchell, G E; Becker, J A; Krticka, M

    2010-01-01

    A careful new measurement of the {sup 238}U(n,{gamma}) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4{pi} calorimetric scintillator array consisting of 160 BaF{sub 2} crystals. Measurements were made on a 48 mg/cm{sup 2} depleted uranium target. The cross sections are in general good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.

  4. Radiogenic isotopic approaches for quantifying radionuclide transport (Invited)

    NASA Astrophysics Data System (ADS)

    Maher, K.; Depaolo, D. J.; Singleton, M. J.; Christensen, J. N.; Conrad, M. E.

    2009-12-01

    Naturally occurring variations in the isotopic compositions of U and Sr provide unique opportunities for assessing the fate and transport of radionuclides at field-scale conditions. When coupled with reactive transport models, U and Sr isotopes may also provide additional constraints on the rates of sediment-fluid or sediment-waste interactions. Such isotopic approaches can be useful for sites where subsurface characterization is complicated by a lack of accessibility or the presence of substantial heterogeneity. In addition, a variety of quantitative modeling approaches of different complexity can be used to evaluate experimentally determined parameters for radionuclide mobility at the field-scale. At the Hanford Site in eastern Washington, 87Sr/86Sr and 234U/238U ratios have been used to quantify the residence time of Sr and U in the unsaturated zone, the long-term background infiltration rate through the unsaturated zone, and to assess the influence of enhanced wastewater discharge on the regional unconfined aquifer. As a result of different processing techniques or due to interactions between caustic waste and the natural sediment, waste plumes may also inherit isotopic fingerprints (e.g. 234U/238U, 235U/238U, 236U/238U; δ15N & δ18O of nitrate) that can be used to resolve multiple sources of contamination. Finally, enriched isotopic tracers can be applied to experimental manipulations to assess the retardation of a variety of contaminants. Collectively this isotopic data contributes unique perspectives on both the hydrologic conditions across the site and the mobility of key radionuclides. Predicting the long-term fate and transport of radionuclides in the environment is often challenging due to natural heterogeneity and incomplete characterization of the subsurface, however detailed analysis of isotopic variations can provide one additional means of characterizing the subsurface.

  5. 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.

  6. Validation of MCNP with X6.XS cross-section set on the SUN Sparc Station 1+ computer for nominally 5 weight percent {sup 235}U enriched uranium systems

    SciTech Connect

    Lewis, K.D. |

    1994-09-01

    The national Atomic Vapor Laser Isotope Separation (AVLIS) project has conducted extensive nuclear criticality safety analyses both in the design of Uranium Demonstration System (UDS) equipment and in AVLIS plant design/plant deployment activities. Currently, the design limit of an AVLIS plant calls for uranium product enriched in {sup 235}U to 5 wt %. Since an objective of an AVLIS plant is to deliver its product in a form readily usable by customers, uranium enriched in {sup 235}U will appear in a variety of forms, including metallic; as oxides, e.g., UO{sub 2}, UO{sub 3}; as fluorides, e.g., UF{sub 6}, UF{sub 4}, UO{sub 2}F{sub 2}; as nitrates or nitrides, e.g., UO{sub 2} (NO{sub 3}){sub 2}; and perhaps as uranium salts mixed with hydrocarbons such as oil. A wide range of neutron moderation levels, ranging from zero to optimal, and beyond can also be anticipated in an AVLIS plant, because of decontamination and cleaning activities and other wet chemistry processes that may be required.

  7. 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

  8. IXth millenium B.C. ceramics from Niger: detection of a U-series disequilibrium and TL dating

    NASA Astrophysics Data System (ADS)

    Guibert, P.; Schvoerer, M.; Etcheverry, M. P.; Szepertyski, B.; Ney, C.

    A set of pottery sherds collected from two ancient neolithic sites in Niger (Tagalagal and Adrar Bous 10) has been dated by thermoluminescence. The natural radioactivity of these ceramics and of their surrounding sediments was measured using low background gamma spectrometry and atomic emission plasma spectrometry. With gamma spectrometry, the comparison between the activity of 238U (deduced from the 235U and 234Th gamma emissions) and that of 226Ra (deduced from 214Pb and 214Bi γ emissions in equilibrium with 222Rn) shows a significant disequilibrium of the U-series. The activity ratio {38U}/{226Ra}, which is greater than unity in this case, is interpreted as a result of either uranium enrichment ( 234U, 235U, 238U) or radium impoverishment that has been occurring since the burying of the archaeological artefacts. The effects of the changes in radiochemical composition on the annual dose are discussed and various determinations of the annual dose are analysed according to different hypotheses of disequilibrium (either permanent state or recent occurrence). The TL results: Tagalagal — 9820±780-10, 180±780 years/1993, Adrar Bous 10 — 9530±750-10,500±730 years/1993, are consistent with the radiocarbon dates obtained from charcoals collected at the same locations (the uncalibrated 14C dates belong to the 9100-9370 BP range). These results are of fundamental interest for the chronology of early neolithic cultures.

  9. Environmental characterization and radio-ecological impacts of non-nuclear industries on the Red Sea coast.

    PubMed

    El Mamoney, M H; Khater, Ashraf E M

    2004-01-01

    The Red Sea is a deep semi-enclosed and narrow basin connected to the Indian Ocean by a narrow sill in the south and to the Suez Canal in the north. Oil industries in the Gulf of Suez, phosphate ore mining activities in Safaga-Quseir region and intensified navigation activities are non-nuclear pollution sources that could have serious radiological impacts on the marine environment and the coastal ecosystems of the Red Sea. It is essential to establish the radiological base-line data, which does not exist yet, and to investigate the present radio-ecological impact of the non-nuclear industries to preserve and protect the coastal environment of the Red Sea. Some natural and man-made radionuclides have been measured in shore sediment samples collected from the Egyptian coast of the Red Sea. The specific activities of 226Ra and 210Pb (238U) series, 232Th series, 40K and 137Cs (Bq/kg dry weight) were measured using gamma ray spectrometers based on hyper-pure germanium detectors. The specific activities of 210Po (210Pb) and uranium isotopes (238U, 235U and 234U) (Bq/kg dry weight) were measured using alpha spectrometers based on surface barrier (PIPS) detectors after radiochemical separation. The absorbed radiation dose rates in air (nGy/h) due to natural radionuclides in shore sediment and radium equivalent activity index (Bq/kg) were calculated. The specific activity ratios of 228Ra/226Ra, 210Pb/226Ra, 226Ra/238U and 234U/238U were calculated for evaluation of the geo-chemical behaviour of these radionuclides. The average specific activity of 226Ra (238U) series, 232Th series, 40K and 210Pb were 24.7, 31.4, 427.5 and 25.6 Bq/kg, respectively. The concentration of 137Cs in the sediment samples was less than the lower limit of detection. The Red Sea coast is an arid region with very low rainfall and the sediment is mainly composed of sand. The specific activity of 238U, 235U and 234U were 25.3, 2.9 and 25.0 Bq/kg. The average specific activity ratios of 226Ra/228Ra, 210

  10. 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

  11. A new Certified Reference Material for radionuclides in Irish sea sediment (IAEA-385).

    PubMed

    Pham, M K; Sanchez-Cabeza, J A; Povinec, P P; Andor, K; Arnold, D; Benmansour, M; Bikit, I; Carvalho, F P; Dimitrova, K; Edrev, Z H; Engeler, C; Fouche, F J; Garcia-Orellana, J; Gascó, C; Gastaud, J; Gudelis, A; Hancock, G; Holm, E; Legarda, F; Ikäheimonen, T K; Ilchmann, C; Jenkinson, A V; Kanisch, G; Kis-Benedek, G; Kleinschmidt, R; Koukouliou, V; Kuhar, B; Larosa, J; Lee, S-H; Lepetit, G; Levy-Palomo, I; Liong Wee Kwong, L; Llauradó, M; Maringer, F J; Meyer, M; Michalik, B; Michel, H; Nies, H; Nour, S; Oh, J-S; Oregioni, B; Palomares, J; Pantelic, G; Pfitzner, J; Pilvio, R; Puskeiler, L; Satake, H; Schikowski, J; Vitorovic, G; Woodhead, D; Wyse, E

    2008-11-01

    A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra, (230)Th, (232)Th, (234)U, (238)U, (238)Pu, (239+240)Pu and (241)Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides ((90)Sr, (210)Pb((210)Po), (235)U, (239)Pu, (240)Pu and (241)Pu). Results for less frequently reported radionuclides ((60)Co, (99)Tc, (134)Cs, (155)Eu, (224)Ra and (239)Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes. PMID:18513984

  12. Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea).

    PubMed

    Pham, M K; Sanchez-Cabeza, J A; Povinec, P P; Arnold, D; Benmansour, M; Bojanowski, R; Carvalho, F P; Kim, C K; Esposito, M; Gastaud, J; Gascó, C L; Ham, G J; Hegde, A G; Holm, E; Jaskierowicz, D; Kanisch, G; Llaurado, M; La Rosa, J; Lee, S-H; Liong Wee Kwong, L; Le Petit, G; Maruo, Y; Nielsen, S P; Oh, J-S; Oregioni, B; Palomares, J; Pettersson, H B L; Rulik, P; Ryan, T P; Sato, K; Schikowski, J; Skwarzec, B; Smedley, P A; Tarján, S; Vajda, N; Wyse, E

    2006-01-01

    A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units. PMID:16549351

  13. 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.

  14. 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.

  15. 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

  16. Effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of 233U and 235U nuclei

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    The results of an experiment devoted to searches for effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of 233U nuclei are presented. The effects discovered in these angular distributions are opposite in sign to their counterparts in the polarized-neutron-induced fission of 235U nuclei. This is at odds with data on the relative signs of respective effects in the angular distribution of alpha particles from the ternary fission of the same nuclei and may be indicative of problems in the model currently used to describe the effect in question. The report on which this article is based was presented at the seminar held at the Institute of Theoretical and Experimental Physics and dedicated to the 90th anniversary of the birth of Yu.G. Abov, corresponding member of Russian Academy of Sciences, Editor in Chief of the journal Physics of Atomic Nuclei.

  17. NBL CRM 112-A: A new certified isotopic composition

    NASA Astrophysics Data System (ADS)

    Thomas, R. B.; Essex, R. M.; Mason, P.

    2007-12-01

    NBL CRM 112-A Uranium Metal Assay Standard is commonly used as a natural uranium isotopic reference material within the earth science mass spectrometry community. The metal is from the same parent material as NBS SRM 960, the uranyl nitrate solution, CRM 145, and the high-purity uranyl nitrate solution CRM 145-B. Because CRM 112-A has not yet been certified for isotopic composition, it has been assumed that this material has a natural 235U/238U (0.0072527), and the δ234U has been determined by measurement (e.g. -37.1‰; Cheng et al., 2000). These values have been widely used to calibrate the concentration of spikes and standards, and to correct measurements for instrument or mass bias. New, preliminary, isotopic measurements on CRM 145 and CRM 112-A performed at New Brunswick Laboratory suggest that these reference materials have a slightly lower 235U/238U and δ234U than have been commonly used. If this is the case, then data using the accepted values may be slightly biased. The significance of this bias will depend on the uncertainty of the measurement, how the CRM 112-A data is used to correct measurement data, the cited values that were used to correct the data, and the final certified values of the CRM. This fall, New Brunswick Laboratory is certifying the isotopic composition of the CRM 112-A metal using high precision thermal ionization mass spectrometry techniques. Upon completion of certification, the new CRM 112- A standard with certified isotopic ratios will provide the earth science community with a well characterized and traceable reference for calibrating and correcting their mass spectrometry measurement systems.

  18. 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.

  19. 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.

  20. Measurement of Absolute Fission Yields in the Fast Neutron-Induced Fission of Actinides: {sup 238}U, {sup 237}Np, {sup 238}Pu, {sup 240}Pu, {sup 243}Am, and {sup 244}Cm by Track-Etch-cum-Gamma Spectrometry

    SciTech Connect

    Iyer, R.H.; Naik, H.; Pandey, A.K.; Kalsi, P.C.; Singh, R.J.; Ramaswami, A.; Nair, A.G.C.

    2000-07-15

    The absolute fission yields of 46 fission products in {sup 238}U (99.9997 at.%), 46 fission products in {sup 237}Np, 27 fission products in {sup 238}Pu (99.21 at.%), 30 fission products in {sup 240}Pu (99.48 at.%), 30 fission products in {sup 243}Am (99.998 at.%), and 32 fission products in {sup 244}Cm (99.43 at.%) induced by fast neutrons were determined using a fission track-etch-cum-gamma spectrometric technique. In the case of highly alpha-active and sparingly available actinides - e.g., {sup 238}Pu, {sup 240}Pu, {sup 243}Am, and {sup 244}Cm - a novel recoil catcher technique to collect the fission products on a Lexan polycarbonate foil followed by gamma-ray spectrometry was developed during the course of this work. This completely removed interferences from (a) gamma rays of daughter products in secular equilibrium with the target nuclide (e.g., {sup 243}Am-{sup 239}Np), (b) activation products of the catcher foil [e.g., {sup 24}Na from Al(n,{alpha})], and (c) activation products of the target [e.g., {sup 238}Np from {sup 237}Np(n,{gamma}) and {sup 239}Np from {sup 238}U(n,{gamma})] reactions, making the gamma spectrometric analysis very simple and accurate. The high-yield asymmetric fission products were analyzed by direct gamma spectrometry, whereas the low-yield symmetric products (e.g., Ag, Cd, and Sb) as well as some of the asymmetric fission products (e.g., Br) and rare earths (in the case of {sup 238}U and {sup 237}Np) were radiochemically separated and then analyzed by gamma-ray spectrometry. The neutron spectra in the irradiation positions of the reactors were measured and delineated in the thermal to 10-MeV region using threshold activation detectors. The present data were compared with the ENDF/VI and UKFY2 evaluated data files. From the measured cumulative yields, the mass-chain yields have been deduced using charge distribution systematics. The mass yields, along with similar data for other fast neutron-induced fissioning systems, show several

  1. Use of Electrodeposition for Sample Preparation and Rejection Rate Prediction for Assay of Electroformed Ultra High Purity Copper for 232Th and 238U Prior to Inductively Coupled Plasma Mass Spectrometry (ICP/MS)

    SciTech Connect

    Hoppe, Eric W.; Aalseth, Craig E.; Brodzinski, Ronald L.; Day, Anthony R.; Farmer, Orville T.; Hossbach, Todd W.; McIntyre, Justin I.; Miley, Harry S.; Mintzer, Esther E.; Seifert, Allen; Smart, John E.; Warren, Glen A.

    2008-07-01

    The search for neutrinoless double beta decay in 76Ge has driven the need for ultra-low background Ge detectors shielded by electroformed copper of ultra-high radiopurity (<0.1µBq/kg). Although electrodeposition processes are almost sophisticated enough to produce copper of this purity, to date there are no methods sensitive enough to assay it. Inductively-coupled plasma mass spectrometry (ICP/MS) can detect thorium and uranium at femtogram levels, but in the past, this assay has been hindered by high copper concentrations in the sample. Electrodeposition of copper samples removes copper from the solution while selectively concentrating thorium and uranium contaminants to be assayed by ICP/MS. Spiking 232Th and 238U into the plating bath simulates low purity copper and allows for the calculation of the electrochemical rejection rate of thorium and uranium in the electroplating system. This rejection value will help to model plating bath chemistry.

  2. Attenuation of ambient dose equivalent from neutrons by thick concrete, cast iron and composite shields for high energy proton, 3He, 48Ca and 238U ions on Cu targets for shielding design

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yosuke; Ronningen, R. M.

    2011-02-01

    Data on neutron dose attenuation by thick concrete, cast iron, and cast iron plus concrete composite shields for heavy ions and protons having high energies (200-1000 MeV/u) are necessary for shielding designs of high-powered heavy ion accelerator facilities. Neutron production source terms, shield material attenuation lengths, and neutron dose rate reduction effectiveness of the bulk shielding in the angular range from 0° to 125° were determined by the Particle and Heavy Ion Transport Code (PHITS) for beams of 300 and 550 MeV/u 48Ca ions, 200 and 400 MeV/u 238U ions, 800 MeV/u 3He and 1 GeV protons. Calculated results of interaction lengths of concrete and cast iron were also compared with similar work performed by Agosteo et al., and to experimental and other calculated data on interaction lengths. The agreement can be regarded as acceptable.

  3. Uranium-series age determination of calcite veins, VC-1 drill core, Valles Caldera, New Mexico

    NASA Astrophysics Data System (ADS)

    Sturchio, Neil C.; Binz, Carl M.

    1988-06-01

    Uranium-series analysis (238U-234U-230Th) of 13 calcite veins from the hydrothermally altered Madera Limestone in the VC-1 drill core was performed to determine the ages of the veins and their relation to the Valles hydrothermal system. Thermal water from VC-1 and two hot springs in San Diego Canyon was analyzed for U and (234U/238U) to help evaluate the constancy of initial (234U/238U). The (230Th/234U) age of one of the veins is ˜95 kyr, and those of two other veins are ˜230 and ˜250 kyr. Five of the veins have near equilibrium (230Th/234U) and are probably older than ˜0.3 m.y. Uranium concentrations in the remaining veins are too low for analysis by the α-spectrometry techniques employed in this study. Of the five veins near (230Th/234U) equilibrium, four are also near (234U/238U) equilibrium, suggesting ages greater than ˜1.0 m.y., but one has (234U/238U) = 1.15, suggesting an age between ˜0.3 and ˜1.0 m.y. Calculated initial (234U/238U) of the veins yielding relatively young ages are neither equal to each other nor to (234U/238U) in thermal water from VC-1, indicating inconstancy of initial (234U/238U) that may be related to variations in groundwater mixing proportions. Three of the four veins that yield relatively young ages consist of coarse, sparry, vuggy calcite, suggesting that this may be the type of calcite vein which forms under conditions resembling those encountered presently in VC-1. The analytical data are consistent with closed-system behavior of U and Th in the VC-1 calcite veins.

  4. 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

  5. The mechanisms and timescales of rhyolite generation at Yellowstone caldera: New insights from 238U-230Th crystallization ages, trace-elements, and isotope compositions of zircon and sanidine

    NASA Astrophysics Data System (ADS)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Calvert, A. T.

    2013-12-01

    The Yellowstone Plateau hosts one of the largest Quaternary magmatic systems on Earth, with caldera forming eruptions at ~2.1 Ma, ~1.3 Ma, and ~0.64 Ma, as well as numerous intracaldera rhyolitic eruptions between caldera-forming events. The most recent post-caldera eruptive episode at Yellowstone produced the Central Plateau Member (CPM) of the Plateau Rhyolite, which erupted intermittently between ca. 170-70 ka with a cumulative volume ≥600 km3. Thus, the CPM rhyolites provide snapshots of a large silicic magmatic system though time. We examine five CPM rhyolites that erupted from ~125 ka to ~70 ka, and constrain the mechanisms and timescales of generating eruptible rhyolites at Yellowstone caldera by comparing (1) 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircons with (2) bulk 238U-230Th crystallization ages and in situ major-element, Ba, and Pb isotope data for sanidines hosted in each rhyolite. The zircon age and trace-element data show that zircons in CPM rhyolites record crystallization from their respective eruption age to >150 ka before eruption, with most zircon surfaces crystallizing close to eruption and many interiors crystallizing 10 kyr to 150 kyr before eruption. At any given age, zircon surfaces have homogeneous trace-element compositions relative to zircon interiors for most elements and element ratios. For example, when considering data from all five CPM rhyolites, the zircon surfaces and interiors show similar broad trends in Eu/Eu* and U/Th over time, but the surfaces display less scatter. These observations suggest that the zircon surfaces grew from a more homogeneous region of the magma reservoir relative to where the zircon interiors grew. Although the zircon surfaces and interiors are similar in some elements and element ratios (e.g., Eu/Eu*, U/Th) at a given age, zircon surfaces and interiors display distinct (Y, MREE, HREE)/(P, U) ratios at a given

  6. Influences of parameter uncertainties within the ICRP-66 respiratory tract model: regional tissue doses for 239PuO2 and 238UO2/238U3O8.

    PubMed

    Farfán, Eduardo B; Huston, Thomas E; Bolch, W Emmett; Vernetson, William G; Bolch, Wesley E

    2003-04-01

    This paper extends an examination of the influence of parameter uncertainties on regional doses to respiratory tract tissues for short-ranged alpha particles using the ICRP-66 respiratory tract model. Previous papers examined uncertainties in the deposition and clearance aspects of the model. The critical parameters examined in this study included target tissue depths, thicknesses, and masses, particularly within the thoracic or lung regions of the respiratory tract. Probability density functions were assigned for the parameters based on published data. The probabilistic computer code LUDUC (Lung Dose Uncertainty Code) was used to assess regional and total lung doses from inhaled aerosols of 239PuO2 and 238UO2/238U3O8. Dose uncertainty was noted to depend on the particle aerodynamic diameter. Additionally, dose distributions were found to follow a lognormal distribution pattern. For 239PuO2 and 238UO2/238U3O8, this study showed that the uncertainty in lung dose increases by factors of approximately 50 and approximately 70 for plutonium and uranium oxides, respectively, over the particle size range from 0.1 to 20 microm. For typical exposure scenarios involving both radionuclides, the ratio of the 95% dose fractile to the 5% dose fractile ranged from approximately 8-10 (corresponding to a geometric standard deviation, or GSD, of about 1.7-2) for particle diameters of 0.1 to 1 microm. This ratio increased to about 370 for plutonium oxide (GSD approximately 4.5) and to about 600 for uranium oxide (GSD approximately 5) as the particle diameter approached 20 microm. However, thoracic tissue doses were quite low at larger particle sizes because most of the deposition occurred in the extrathoracic airways. For 239PuO2, median doses from LUDUC were found be in general agreement with those for Reference Man (via deterministic LUDEP 2.0 calculations) in the particle range of 0.1 to 5 microm. However, median doses to the basal cell nuclei of the bronchial airways (BB

  7. 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.

  8. Ingestion dose from 238U, 232Th, 226Ra, 40K and 137Cs in cereals, pulses and drinking water to adult population in a high background radiation area, Odisha, India.

    PubMed

    Lenka, Pradyumna; Sahoo, S K; Mohapatra, S; Patra, A C; Dubey, J S; Vidyasagar, D; Tripathi, R M; Puranik, V D

    2013-03-01

    A natural high background radiation area is located in Chhatrapur, Odisha in the eastern part of India. The inhabitants of this area are exposed to external radiation levels higher than the global average background values, due to the presence of uranium, thorium and its decay products in the monazite sands bearing placer deposits in its beaches. The concentrations of (232)Th, (238)U, (226)Ra, (40)K and (137)Cs were determined in cereals (rice and wheat), pulses and drinking water consumed by the population residing around this region and the corresponding annual ingestion dose was calculated. The annual ingestion doses from cereals, pulses and drinking water varied in the range of 109.4-936.8, 10.2-307.5 and 0.5-2.8 µSv y(-1), respectively. The estimated total annual average effective dose due to the ingestion of these radionuclides in cereals, pulses and drinking water was 530 µSv y(-1). The ingestion dose from cereals was the highest mainly due to a high consumption rate. The highest contribution of dose was found to be from (226)Ra for cereals and drinking water and (40)K was the major dose contributor from the intake of pulses. The contribution of man-made radionuclide (137)Cs to the total dose was found to be minimum. (226)Ra was found to be the largest contributor to ingestion dose from all sources. PMID:22802517

  9. Neutron Resonance Parameters of 238U and the Calculated Cross Sections from the Reich-Moore Analysis of Experimental Data in the Neutron Energy Range from 0 keV to 20 keV

    SciTech Connect

    Derrien, H

    2005-12-05

    The neutron resonance parameters of {sup 238}U were obtained from a SAMMY analysis of high-resolution neutron transmission measurements and high-resolution capture cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) in the years 1970-1990, and from more recent transmission and capture cross section measurements performed at the Geel Linear Accelerator (GELINA). Compared with previous evaluations, the energy range for this resonance analysis was extended from 10 to 20 keV, taking advantage of the high resolution of the most recent ORELA transmission measurements. The experimental database and the method of analysis are described in this report. The neutron transmissions and the capture cross sections calculated with the resonance parameters are compared with the experimental data. A description is given of the statistical properties of the resonance parameters and of the recommended values of the average parameters. The new evaluation results in a slight decrease of the effective capture resonance integral and improves the prediction of integral thermal benchmarks by 70 pcm to 200 pcm.

  10. Measurements of fission product yield in the neutron-induced fission of 238U with average energies of 9.35 MeV and 12.52 MeV

    NASA Astrophysics Data System (ADS)

    Mukerji, Sadhana; Krishnani, Pritam Das; Shivashankar, Byrapura Siddaramaiah; Mulik, Vikas Kaluram; Suryanarayana, Saraswatula Venkat; Naik, Haladhara; Goswami, Ashok

    2014-07-01

    The yields of various fission products in the neutron-induced fission of 238U with the flux-weightedaveraged neutron energies of 9.35 MeV and 12.52 MeV were determined by using an off-line gammaray spectroscopic technique. The neutrons were generated using the 7Li(p, n) reaction at Bhabha Atomic Research Centre-Tata Institute of Fundamental Research Pelletron facility, Mumbai. The gamma- ray activities of the fission products were counted in a highly-shielded HPGe detector over a period of several weeks to identify the decaying fission products. At both the neutron energies, the fission-yield values are reported for twelve fission product. The results obtained from the present work have been compared with the similar data for mono-energetic neutrons of comparable energy from the literature and are found to be in good agreement. The peak-to-valley (P/V) ratios were calculated from the fission-yield data and were found to decreases for neutron energy from 9.35 to 12.52 MeV, which indicates the role of excitation energy. The effect of the nuclear structure on the fission product-yield is discussed.

  11. U and Th-series isotopes: a probe into time-dependent erosion processes in soils

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, Claude; Ghaleb, Bassam; Barbecot, Florent

    2010-05-01

    Disequilibria between 238U-234Th-234U-230Th-226Ra-210Pb-210Po, 235U-231Pa and 232Th-228Ra-228Th, offer probes into time dependent processes over time scales ranging 106 a to a few days, thus the means to document soil erosion rates over a large array of time scales and hydroclimatic forcings. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in carbonate-rich soils, with examples from cool-temperate (St Lawrence Lowlands, Canada) or arid settings (Palmyre area, Syria) but special attention to Mediterranean environments (SE France). In this later case, a >12 m thick unsaturated zone has been sampled, near Beziers, in the recharge zone of the "Astian carbonate sand Aquifer", firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes were complemented by 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements from soil surface, down to about 12 m below surface. Whereas the upper 7 m depict geochemical and isotopic features linked to dissolution/re-precipitation processes with highly variable radioactive disequilibria, the lower part of the sequence shows distinctive properties. In this deep horizon, strong excesses in 234U and 230Th over parent isotopes (i.e. 238U and 234U, respectively) are observed simultaneously whereas 226Ra and 230Th are in secular equilibrium. We interpret these features as an indication for a slow-process enrichment in 234Th(234U) and 230Th, linked to dissolved U-decay during groundwater recharge events. 210Pb deficits (vs. parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to 222Rn-diffusion. It is concluded from this example that beside the strong impact on U- and Th-series disequilibria of fast chemical process occurring in the upper soil horizons, slower processes still leave an imprint with longer

  12. 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

  13. Fallout of uranium and plutonium from recent volcanic eruptions

    SciTech Connect

    Sandoval, D.N.

    1984-01-01

    The concentrations of /sup 234/U, /sup 235/U, /sup 238/U in rain water were measured in a total of 102 individual samples which were collected at Fayetteville, Arkansas, from July 1980 through April 1983. A spectacular increase in the heavy isotope of uranium (/sup 238/U) was observed in the months of July, August (1980); January through April, November and December 1981. This large increase in /sup 238/U in rain appeared to have had its origin in the May 1980 eruption of Mount St. Helens. An increase in the concentration of /sup 238/U in rain, smaller than 1981, was observed, which seems to have originated from the El Chichon volcano eruption in March 1982, and the spring peak or so-called cycling effect. A striking increase in the average bimonthly concentration of /sup 239,240/Pu occurred during the months of September-October 1980 (15.6 fCi/l) and March-April 1981 (29.4 fCi/l). The excess deposition of /sup 239,240/Pu brought down by the rain at Fayetteville, Arkansas, from March 1980 through December 1982 was found to be 1.01 fCi/cm/sup 2/. The total amount of /sub 239,240/Pu deposited at Fayetteville, Arkansas, from March through December 1982, was found to be about 30 times higher than the total amount calculated from reported literature values. The excess /sup 239,240/Pu has been attributed to stratospheric /sub 239,240/Pu from nuclear weapons testing prior to the 25th Chinese nuclear test.

  14. 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.

  15. 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.

  16. Abundances of Natural Radionuclides (40K, 238U, 232Th) in Hanford and Rifle Integrated Field Research Challenge Site Sediments and the Application to the Estimation of Grain Size Distributions

    NASA Astrophysics Data System (ADS)

    Draper, K.; Ward, A. L.; Yabusaki, S.; Murray, C. J.; Greenwood, J.

    2009-12-01

    The distribution and geometry of lithofacies impact groundwater flow and solute spreading but are difficult to characterize at the scale controlling transport. We hypothesize that differences in γ-ray activity resulting from the natural distribution of 40K, 238U, and 232Th (K, U, T) are due to hydraulic separation and sorting and can be used to infer grain-size distributions at the scale of borehole γ-ray logs. The objective of this study was to investigate the feasibility of using γ-ray spectra to detect differences in grain size distributions as a means of characterizing small-scale variations in flow and reactive transport properties. The γ-ray spectra of whole and fractionated sediments from the Hanford and Old Rifle IFRC sites were characterized along with their grain size distributions. In the Hanford sediments, the abundance of K, U, and T was strongly correlated with the extent of weathering and with mean grain size. Hanford clay showed concentrations of 4%, 5.5 ppm, and 6.5 ppm for K, U, and T respectively. An increase in geometric mean diameter from 0.02 mm (clay) to 45.25 mm (very coarse gravel) showed increases in concentrations of 70% for K, 76% for U, and 83% for T. Old Rifle sediments showed no correlation between grain size and K, but there was an 81% increase in U and a 73 % increase in T. Cross plots of Th/U and Th/K also show strong correlations with grain size. The enrichment of natural isotopes with decreasing grain size is likely due to the increase in specific surface area. Thus, borehole γ-ray spectra could have a much wider application in characterizing grain separation and sorting and ultimately flow and reactive transport properties.

  17. Magma mixing and the generation of isotopically juvenile silicic magma at Yellowstone caldera inferred from coupling 238U-230Th ages with trace elements and Hf and O isotopes in zircon and Pb isotopes in sanidine

    NASA Astrophysics Data System (ADS)

    Stelten, Mark E.; Cooper, Kari M.; Vazquez, Jorge A.; Reid, Mary R.; Barfod, Gry H.; Wimpenny, Josh; Yin, Qing-zhu

    2013-08-01

    The nature of compositional heterogeneity within large silicic magma bodies has important implications for how silicic reservoirs are assembled and evolve through time. We examine compositional heterogeneity in the youngest (~170 to 70 ka) post-caldera volcanism at Yellowstone caldera, the Central Plateau Member (CPM) rhyolites, as a case study. We compare 238U-230Th age, trace-element, and Hf isotopic data from zircons, and major-element, Ba, and Pb isotopic data from sanidines hosted in two CPM rhyolites (Hayden Valley and Solfatara Plateau flows) and one extracaldera rhyolite (Gibbon River flow), all of which erupted near the caldera margin ca. 100 ka. The Hayden Valley flow hosts two zircon populations and one sanidine population that are consistent with residence in the CPM reservoir. The Gibbon River flow hosts one zircon population that is compositionally distinct from Hayden Valley flow zircons. The Solfatara Plateau flow contains multiple sanidine populations and all three zircon populations found in the Hayden Valley and Gibbon River flows, demonstrating that the Solfatara Plateau flow formed by mixing extracaldera magma with the margin of the CPM reservoir. This process highlights the dynamic nature of magmatic interactions at the margins of large silicic reservoirs. More generally, Hf isotopic data from the CPM zircons provide the first direct evidence for isotopically juvenile magmas contributing mass to the youngest post-caldera magmatic system and demonstrate that the sources contributing magma to the CPM reservoir were heterogeneous in 176Hf/177Hf at ca. 100 ka. Thus, the limited compositional variability of CPM glasses reflects homogenization occurring within the CPM reservoir, not a homogeneous source.

  18. Cogenetic late Pleistocene rhyolite and cumulate diorites from Augustine Volcano revealed by SIMS 238U-230Th dating of zircon, and implications for silicic magma generation by extraction from mush

    NASA Astrophysics Data System (ADS)

    Coombs, Michelle L.; Vazquez, Jorge A.

    2014-12-01

    Volcano, a frequently active andesitic island stratocone, erupted a late Pleistocene rhyolite pumice fall that is temporally linked through zircon geochronology to cumulate dioritic blocks brought to the surface in Augustine's 2006 eruption. Zircon from the rhyolite yield a 238U-230Th age of ˜25 ka for their unpolished rims, and their interiors yield a bimodal age populations at ˜26 ka and a minority at ˜41 ka. Zircon from dioritic blocks, ripped from Augustine's shallow magmatic plumbing system and ejected during the 2006 eruption, have interiors defining a ˜26 ka age population that is indistinguishable from that for the rhyolite; unpolished rims on the dioritic zircon are dominantly younger (≤12 ka) indicating subsequent crystallization. Zircon from rhyolite and diorite overlap in U, Hf, Ti, and REE concentrations although diorites also contain a second population of high-U, high temperature grains. Andesites that brought dioritic blocks to the surface in 2006 contain zircon with young (≤9 ka) rims and a scattering of older ages, but few zircon that crystallized during the 26 ka interval. Both the Pleistocene-age rhyolite and the 2006 dioritic inclusions plot along a whole-rock compositional trend distinct from mid-Holocene-present andesites and dacites, and the diorites, rhyolite, and two early Holocene dacites define linear unmixing trends often oblique to the main andesite array and consistent with melt (rhyolite) extraction from a mush (dacites), leaving behind a cumulate amphibole-bearing residue (diorites). Rare zircon antecrysts up to ˜300 ka from all rock types indicate that a Quaternary center has been present longer than preserved surficial deposits.

  19. Characterization of contaminant transport using naturally-occurring U-series disequilibria. 1998 annual progress report

    SciTech Connect

    Murrell, M.; Ku, T.L.

    1998-06-01

    'The goal of the research is to study the migratory behavior of contaminants in subsurface fractured systems using naturally occurring uranium- and thorium-series radionuclides as tracers under in-situ physico-chemical and hydrogeologic conditions. Naturally occurring U- and Th-series disequilibria can provide information on the rates of adsorption-desorption and transport of contaminants as well as on fluid transport and rock dissolution in a natural setting. The authors are developing a realistic model of contaminant migration in the Snake River Plain Aquifer beneath the INEEL by evaluating the retardation processes involved in the rock/water interaction. The major tasks are to: (1) determine the natural distribution of U, Th, Pa and Ra isotopes in the groundwater as well as in rock minerals and sorbed phases, and (2) study rock/water interaction processes using U/Th series disequilibria and a statistical analysis-based model code for the calculation of in-situ retardation factors of radionuclides and rock/water interaction time scales. This study will also provide an improved understanding of the hydrogeologic features of the site and their impact on the migration of contaminants. This report summarizes results after 20 months of a 36-month project. Studies performed at LANL include analysis of the long-lived nuclides {sup 238}U, {sup 235}U, {sup 234}U, {sup 230}Th, {sup 226}Ra, {sup 232}Th, and {sup 231}Pa by thermal ionization mass spectrometry (TIMS). Studies performed at the Univ. of Southern California include the measurement of short-lived naturally occurring radionuclides by decay-counting techniques and the development of models to predict the migration behavior of these radionuclides. Initial efforts began with analysis of 31, 0.5L water samples obtained through routine sampling by USGS and INEEL personnel. One significant observation from these data is that {sup 234}U/{sup 238}U activity ratios are highest in waters that emanate from local recharge

  20. 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

  1. Isotopes of uranium and plutonium in the atmosphere. [Cosmos-954 fall in Canada

    SciTech Connect

    Sakuragi, Y.

    1982-01-01

    The activities of /sup 234/U, /sup 235/U and /sup 238/U were measured in 24 individual rain samples and two composite rains collected at Fayetteville, Arkansas, during the months of March 1979 and March 1980 through May 1981. Uranium-234 and -235 were found to be highly enriched in several rain samples collected during the months of April and May 1980. Uranium-238 concentrations, on the other hand, were unusually high during the months of July, August and early September 1980. The concentrations of /sup 238/Pu and /sup 238/ /sup 240/Pu were measured in 76 individual rain samples and two composite rains which were collected at Fayetteville, Arkansas, during the period from February 1979 through December 1980. Plutonium-238 and plutonium-239,240 concentrations were found to be extremely high during the months of July, August and early September 1980. The anomalous uranium highly enriched in the light isotopes of uranium appears to have originated from the Soviet satellite Cosmos-954 which fell over Canada on 24 January 1978. The uranium fallout occurred just about the time Mount St. Helens erupted on 18 May 1980 and began to inject a large amount of natural uranium into the atmosphere. The pattern of variations of the concentrations of /sup 238/U in rain after the eruption of Mount St. Helens was found to be similar to that of plutonium isotopes.

  2. Natural radioactivity, dose assessment and uranium uptake by agricultural crops at Khan Al-Zabeeb, Jordan.

    PubMed

    Al-Kharouf, Samer J; Al-Hamarneh, Ibrahim F; Dababneh, Munir

    2008-07-01

    Khan Al-Zabeeb, an irrigated cultivated area lies above a superficial uranium deposits, is regularly used to produce vegetables and fruits consumed by the public. Both soil and plant samples collected from the study area were investigated for their natural radioactivity to determine the uranium uptake by crops and hence to estimate the effective dose equivalent to human consumption. Concentrations of (238)U, (235)U, (232)Th, (226)Ra, (222)Rn, (137)Cs and (40)K in nine soil profiles were measured by gamma-ray spectrometry whereas watermelon and zucchini crops were analyzed for their uranium content by means of alpha spectrometry after radiochemical separation. Correlations between measured radionuclides were made and their activity ratios were determined to evaluate their geochemical behavior in the soil profiles. Calculated soil-plant transfer factors indicate that the green parts (leaves, stems and roots) of the studied crops tend to accumulate uranium about two orders of magnitude higher than the fruits. The maximum dose from ingestion of 1 kg of watermelon pulp was estimated to be 3.1 and 4.7 nSv y(-1) for (238)U and (234)U, respectively. Estimations of the annual effective dose equivalent due to external exposure showed extremely low values. Radium equivalent activity and external hazard index were seen to exceed the permissible limits of 370 Bq kg(-1) and 1, respectively. PMID:18359539

  3. 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.

  4. Uranium isotope measurements by quadrupole ICP-MS for process monitoring of enrichment

    SciTech Connect

    Policke, T.A.; Bolin, R.N.; Harris, T.L.

    1998-12-31

    Historically, uranium isotopic ratio measurements in the nuclear industry have been performed using Thermal Ionization Mass Spectrometry (TIMS); primarily due to the high level of precision that can be achieved. TIMS analysis, however, requires sample purification and intricate sample loading. Quadrupole (low resolution, single detector) inductively coupled plasma--mass spectrometry, Q-ICP-MS, overcomes these disadvantages and is a cost-effective alternative, i.e., in terms of initial capital, maintenance, and operating costs. This paper presents a simple, single standard approach for measuring uranium isotope content in various solid and liquid nuclear materials along with some comparison data of Q-ICP-MS and TIMS. Intensity ratios of {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U to total U intensity are produced, providing the enrichment level or percent {sup 235}U. A detailed description of the instrument and data collection parameters are also provided. Optimal precision and accuracy are achieved through the use of a single standard which is closely matched to the enrichment and concentration of the samples. Depending upon the standard chosen, enrichments between depleted and 97% can be quantified. Standard deviations for the major uranium isotopes are typically within 0.02 absolute and at least an order of magnitude lower for the minor U isotope abundances.

  5. 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.

  6. 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

  7. High-Precision Isotope Analysis of Uranium and Thorium by TIMS

    NASA Astrophysics Data System (ADS)

    Neymark, L. A.; Paces, J. B.

    2006-12-01

    The U.S. Geological Survey (USGS) Yucca Mountain Project Branch laboratory in Denver, Colorado, conducts routine high-precision isotope analyses of uranium (U) and thorium (Th) using thermal ionization mass- spectrometry (TIMS). The measurements are conducted by a ThermoFinnigan Triton\\texttrademark equipped with a Faraday multi-collector system and an energy filter in front of an active-film-type secondary electron multiplier (SEM). The abundance sensitivity of the instrument (signal at mass 237 over 238U in natural U) with the energy filter is about 15 ppb and peak tails are reduced by a factor of about 100 relative to the Faraday cup measurements. Since instrument installation in April 2004, more than 500 rock and water samples have been analyzed in support of isotope-geochemical studies for the U.S. Department of Energy`s Yucca Mountain Project. Isotope ratios of sub-nanogram to microgram U and Th samples are measured on graphite-coated single- filament and double-filament assemblies using zone-refined rhenium filaments. Ion beams less than 5 mV are measured with the SEM, which is corrected for non-linearity on the basis of measurements of NIST U-500 and 4321B standards with ion beams ranging from 0.01 to 8 mV. Inter-calibration between the SEM and the Faraday multi-collector is performed for every mass cycle using a 5 mV beam switched between Faraday cup and SEM (bridging technique), because SEM-Faraday inter-calibrations prior to the measurement failed to produce acceptable results. Either natural (^{235}U) or artificial (^{236}U, ^{229}Th) isotopes were used for the bridging. Separate runs are conducted for minor isotopes using SEM only. These techniques result in high within-run precisions of less than 0.1 to 0.2 percent for 234U/238U and 0.2 to 0.5 percent for 230Th/238U. The performance of the instrument is monitored using several U and Th isotope standards. The mean measured 234U/238U in NIST SRM 4321B is (52.879±0.004)×10-6 (95 percent confidence, n

  8. Uranium and radium in groundwater and surface water samples in Morocco

    NASA Astrophysics Data System (ADS)

    Hakam, O. K.; Choukri, A.; Moutia, Z.; Chouak, A.; Cherkaoui, R.; Reyss, J.-L.; Lferde, M.

    2001-06-01

    Activities and activity ratios of uranium and radium isotopes ( 234U, 238U, 226Ra, 228Ra, 234U/ 238U, 226Ra/ 238U, 228Ra/ 226Ra) have been determined for 15 wells, 14 hot springs, 7 cold springs and 11 rivers. Activities of the radium isotopes were measured by ultra gamma spectrometry using a low background and high efficiency well type germanium detector whereas those of uranium were counted in an alpha spectrometer. The minimal, maximal and average values are reported here for each water source. The obtained results show that, unlike well waters, the thermal spring waters present relatively low 238U activities and elevated 226Ra activities and 234U/ 238U activity ratios. Uranium and radium activities are similar to those published for other non polluting regions of the world.

  9. 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.

  10. 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

  11. Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions 233,238 U , 242Pu , and 248Cm + 48Ca

    NASA Astrophysics Data System (ADS)

    Oganessian, Yu. Ts.; Utyonkov, V. K.; Lobanov, Yu. V.; Abdullin, F. Sh.; Polyakov, A. N.; Shirokovsky, I. V.; Tsyganov, Yu. S.; Gulbekian, G. G.; Bogomolov, S. L.; Gikal, B. N.; Mezentsev, A. N.; Iliev, S.; Subbotin, V. G.; Sukhov, A. M.; Voinov, A. A.; Buklanov, G. V.; Subotic, K.; Zagrebaev, V. I.; Itkis, M. G.; Patin, J. B.; Moody, K. J.; Wild, J. F.; Stoyer, M. A.; Stoyer, N. J.; Shaughnessy, D. A.; Kenneally, J. M.; Wilk, P. A.; Lougheed, R. W.; Il'Kaev, R. I.; Vesnovskii, S. P.

    2004-12-01

    We have studied the dependence of the production cross sections of the isotopes 282,283 112 and 286,287 114 on the excitation energy of the compound nuclei 286112 and 290114 . The maximum cross section values of the xn -evaporation channels for the reaction 238U ( 48Ca ,xn) 286-x 112 were measured to be σ3n = 2.5 +1.8 -1.1 pb and σ4n = 0.6 +1.6 -0.5 pb ; for the reaction 242Pu ( 48Ca ,xn) 290-x 114 : σ2n ˜0.5 pb , σ3n = 3.6 +3.4 -1.7 pb , and σ4n = 4.5 +3.6 -1.9 pb . In the reaction 233U ( 48Ca ,2 4n) 277 279 112 at E*=34.9±2.2 MeV we measured an upper cross section limit of σxn ⩽0.6 pb . The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section σER (E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of σER in the reactions of actinide targets with 48Ca is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N=184 . In the present work we detected 33 decay chains arising in the decay of the known nuclei 282112 , 283112 , 286114 , 287114 , and 288114 . In the decay of 287114 (α) → 283112 (α) → 279110 (SF) , in two cases out of 22, we observed decay chains of four and five sequential α transitions that end in spontaneous fission of 271Sg ( Tα/SF = 2.4 +4.3 -1.0 min) and 267Rf ( TSF ˜2.3 h) , longer decay chains than reported previously. We observed the new nuclide 292116 ( Tα = 18 +16 -6 ms, Eα =10.66±0.07 MeV) in the irradiation of the 248Cm target at a higher energy than in previous experiments. The observed nuclear decay properties of the nuclides with Z=104 118 are compared with theoretical nuclear mass calculations and the systematic trends of spontaneous fission properties. As a whole, they give a consistent pattern of decay of the 18 even- Z

  12. Plutonium age dating reloaded

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Although the age determination of plutonium is and has been a pillar of nuclear forensic investigations for many years, additional research in the field of plutonium age dating is still needed and leads to new insights as the present work shows: Plutonium is commonly dated with the help of the 241Pu/241Am chronometer using gamma spectrometry; in fewer cases the 240Pu/236U chronometer has been used. The age dating results of the 239Pu/235U chronometer and the 238Pu/234U chronometer are scarcely applied in addition to the 240Pu/236U chronometer, although their results can be obtained simultaneously from the same mass spectrometric experiments as the age dating result of latter. The reliability of the result can be tested when the results of different chronometers are compared. The 242Pu/238U chronometer is normally not evaluated at all due to its sensitivity to contamination with natural uranium. This apparent 'weakness' that renders the age dating results of the 242Pu/238U chronometer almost useless for nuclear forensic investigations, however turns out to be an advantage looked at from another perspective: the 242Pu/238U chronometer can be utilized as an indicator for uranium contamination of plutonium samples and even help to identify the nature of this contamination. To illustrate this the age dating results of all four Pu/U clocks mentioned above are discussed for one plutonium sample (NBS 946) that shows no signs of uranium contamination and for three additional plutonium samples. In case the 242Pu/238U chronometer results in an older 'age' than the other Pu/U chronometers, contamination with either a small amount of enriched or with natural or depleted uranium is for example possible. If the age dating result of the 239Pu/235U chronometer is also influenced the nature of the contamination can be identified; enriched uranium is in this latter case a likely cause for the missmatch of the age dating results of the Pu/U chronometers.

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

    SciTech Connect

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

    2004-03-30

    In the mid-1990s, a groundwater plume of uranium (U) was detected in monitoring wells in the B-BX-BY Waste Management Area (WMA) 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 (MC ICPMS) high precision uranium isotopic analyses were conducted of samples of vadose zone contamination and of groundwater. The ratios {sup 236}U/{sup 238}U, {sup 234}U/{sup 238}U and {sup 238}U/{sup 235}U are used to distinguish contaminant sources. Based on 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 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 {approx}0.7-0.8 m/day showing slight retardation relative to a ground water flow of {approx}1 m/day.

  14. 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. PMID:24621142

  15. 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.

  16. Disequilibrium of uranium isotopes in some Syrian groundwater.

    PubMed

    Abdul-Hadi, A; Alhassanieh, O; Ghafar, M

    2001-07-01

    Uranium concentration in groundwater samples from three areas of Syria was determined using alpha-spectrometry and INAA. It was in the range of 0-6.13 microg/l in the phosphate areas, and lower than 1 ppb in the volcanic areas. The activity ratio of 234U/238U was investigated, and disequilibrium of uranium isotopes was found to occur (234U/238U = 0.52-2.02). The excess of 234U was calculated. This excess can be interpreted by higher mobility of 234U, which more readily forms the soluble (UO2)2+ ion in comparison with 238U, most of which remains in the insoluble 4+ state. This excess increases with increase in uranium concentration. Thorium concentration was measured using INAA, it was found to be in the rang 0-1.15 microg/l. PMID:11339524

  17. 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

  18. Study of uranium and thorium isotopes in ground waters and solids of two uranium mines, south Texas

    SciTech Connect

    San Juan, F.C. Jr.

    1982-01-01

    Isotopic analysis was carried out on water and solid samples taken from both the ore zones and the general vicinity of two uranium mines in south Texas. The uranium deposits were of the roll-front type. The ore-bearing formations were the Catahoula Formation of Miocene age in Duval County and the Upper Jackson formation of Eocene age in Karnes County. Solid samples were analyzed for /sup 234/U, /sup 238/U and /sup 230/Th, water for /sup 234/U and /sup 239/U. In order to test several models which have been proposed to explain the fractionation of various nuclides in the vicinity of a reduction-oxidation front, plots incorporating uranium concentration and /sup 234/U//sup 238/U activity ratio (AR) of the water and /sup 234/U//sup 238/U and /sup 230/Th//sup 238/U - /sup 234/U//sup 238/U of the solid were used. The integration of data from each of these models, including contour maps of various isotopic parameters and statistical plots helped in predicting the presence, the stage of deposition (dispersing, stable or accumulating) and the degree of radioactive disequilibrium of the deposits under study. The isotopic data were also useful in determining the position of the redox boundary and the environment of a sample. These methods may be useful in prospecting studies of other possible uranium deposits, both in the oxidized and/or the reduced environment.

  19. Testing the Concept of Drift Shadow at Yucca Mountain, Nevada

    SciTech Connect

    J.B. Paces; L.A. Neymark; T. Ghezzehei; P.F. Dobson

    2006-03-10

    If proven, the concept of drift shadow, a zone of reduced water content and slower ground-water travel time beneath openings in fractured rock of the unsaturated zone, may increase performance of a proposed geologic repository for high-level radioactive waste at Yucca Mountain. To test this concept under natural-flow conditions present in the proposed repository horizon, isotopes within the uranium-series decay chain (uranium-238, uranium-234, and thorium-230, or {sup 238}U-{sup 234}U-{sup 230}Th) have been analyzed in samples of rock from beneath four naturally occurring lithophysal cavities. All samples show {sup 234}U depletion relative to parent {sup 238}U, indicating varying degrees of water-rock interaction over the past million years. Variations in {sup 234}U/{sup 238}U activity ratios indicate that depletion of {sup 234}U relative to {sup 238}U can be either smaller or greater in rock beneath cavity floors relative to rock near cavity margins. These results are consistent with the concept of drift shadow and with numerical simulations of meter-scale spherical cavities in fractured tuff. Differences in distribution patterns of {sup 234}U/{sup 238}U activity ratios in rock beneath the cavity floors are interpreted to reflect differences in the amount of past seepage into lithophysal cavities, as indicated by the abundance of secondary mineral deposits present on the cavity floors.

  20. Testing the concept of drift shadow at Yucca Mountain, Nevada

    USGS Publications Warehouse

    Paces, J.B.; Neymark, L.A.; Ghezzehei, T.; Dobson, P.F.

    2006-01-01

    If proven, the concept of drift shadow, a zone of reduced water content and slower ground-water travel time beneath openings in fractured rock of the unsaturated zone, may increase performance of a proposed geologic repository for high-level radioactive waste at Yucca Mountain, To test this concept under natural-flow conditions present in the proposed repository horizon, isotopes within the uranium-series decay chain (uranium-238, uranium-234, and thorium-230, or 238U-234U-230Th) have been analyzed in samples of rock from beneath four naturally occurring lithophysal cavities. All rock samples show 234U depletion relative to parent 238U indicating varying degrees of water-rock interaction over the past million years. Variations in 234U/238U activity ratios indicate that depletion of 234U relative to 238U can be either smaller or greater in rock beneath cavity floors relative to rock near cavity margins. These results are consistent with the concept of drift shadow and with numerical simulations of meter-scale spherical cavities in fractured tuff. Differences in distribution patterns of 234U/ 238U activity ratios in rock beneath the cavity floors are interpreted to reflect differences in the amount of past seepage into lithophysal cavities, as indicated by the abundance of secondary mineral deposits present on the cavity floors.

  1. Determination of uranium concentration in ground water samples of Northern Greece

    NASA Astrophysics Data System (ADS)

    Samaropoulos, I.; Efstathiou, M.; Pashalidis, I.; Ioannidou, A.

    2012-04-01

    The activity concentration of 238U and 234U has been determined in groundwater samples of hot springs and deep wells from the region of Northern Greece. The analysis was performed by alpha spectroscopy after pre-concentration and separation of uranium by cation exchange (Chelex 100 resin) and finally its electro-deposition on stainless steel discs. The uranium concentration in deep wells and springs varies strongly between 0.15 and 7.66 μg l-1. Generally the springs present higher uranium concentration than the deep wells, except of the Apol-lonia spring, which has shown the lowest value of 0.15 mg l-1. 238U and 234U activity concentration ranged between 1.8-95.3 mBq l-1 and 1.7-160.1 mBq l-1, respectively. The obtained isotopic ratio 234U/238U varies between 0.95 and 1.74 which means that the two isotopes are not in radioactive equilibrium. The highest 234U/238U activity ratio values correspond to the Langada springs, indicating most probably old-type waters. On the other hand, ground waters from wells with relatively low uranium activity concentration and low 234U/238U isotopic ratios, point to the presence of younger waters with a stronger contribution of a local recharge component to the groundwater.

  2. 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.

  3. 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 coupling these two isotopesystems it is possible to constrain both the long-term (ca. 100's to1000's of years) flow rate and bulk dissolution rate along the flow path.Previous estimates of the ratio of the dissolution rate to theinfiltration flux from Sr isotopes (87Sr/86Sr) are combined with a modelfor (234U/238U) to constrain the infiltration flux and dissolution ratefor a 70-m deep vadose zone core from Hanford, Washington. The coupledmodel for both (234U/238U) ratios and the 87Sr/86Sr data suggests aninfiltration flux of 5+-2 mm/yr, and bulk silicate dissolution ratesbetween 10-15.7 and 10-16.5 mol/m2/s. The process of alpha-recoilenrichment, while primarily responsible for the observed variation in(234U/238U) of natural systems, is difficult to quantify. However, therate of this process in natural systems affects the interpretation ofmost U-series data. Models for quantifying the alpha-recoil loss fractionbased on geometric predictions, surface area constraints, and chemicalmethods are also presented. The agreement between the chemical andtheoretical methods, such as direct measurement of (234U/238U) of thesmall grain size fraction and geometric calculations for that sizefraction, is quite good.

  4. Uranium and thorium isotopes and their state of equilibria in lungs from uranium miners.

    PubMed

    Wrenn, M E; Singh, N P; Saccomanno, G

    1983-01-01

    Radiochemical analysis of seven lungs obtained at autopsy show that concentrations ranged between 6 and 63 pCi/kg for 238U and 6-66 pCi/kg, for 234U. Similarly, 230Th ranged from 17 to 54 pCi/kg, two orders of magnitude higher than 230Th observed in the lungs of the general population from the Western mining region. For individual lungs, 238U and 234U were close to equilibrium with an average ratio of 238U/234U of 0.94 and a range of 0.80-1.02. Surprisingly, 230Th was close to equilibrium with 234U with a 230Th/234U ratio of 1.1 and a range from 0.54 to 2.6. Equilibrium between U and Th isotopes is in contrast to the disequilibrium reported in beagles which chronically inhaled carnotite, where the 230Th/234U ratio was observed to range from 5.4 to 7.4 with an average of 6.3. The average radiation dose rate to lung from each of the three radionuclides was calculated as follows: D = 18.7 CE where D = dose rate in mrad/year, C = activity concentration in tissue in pCi/g and E = energy absorbed per disintegration in MeV. The combined radiation dose rate (at death) due to three long-lived radionuclides 238U, 234U and 230Th varied from 2.5 to 14.2 mrad/yr with a mean of 9.6 mrad/yr. The concentration of 226Ra and daughters in the lung was not determined. An upper limit to the dose rate from the whole chain, calculated assuming 226Ra through 210Po are in equilibrium with 238U, 234U and 230Th, would be 30 mrad/yr. PMID:6862915

  5. 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.

  6. Ultratrace uranium fingerprinting with isotope selective laser ionization spectrometry.

    PubMed

    Ziegler, Summer L; Bushaw, Bruce A

    2008-08-01

    Uranium isotope ratios can provide source information for tracking uranium contamination in a variety of fields, ranging from occupational bioassay to monitoring aftereffects of nuclear accidents. We describe the development of isotope selective laser ionization spectrometry for ultratrace measurement of the minor isotopes (234)U, (235)U, and (236)U with respect to (238)U. The inherent isotopic selectivity of three-step excitation with single-mode continuous wave lasers results in measurement of the minor isotopes at relative abundances below 1 ppm and is not limited by isobaric interferences such as (235)UH(+) during measurement of (236)U. This relative abundance limit is attained without mass spectrometric analysis of the laser-created ions. Uranyl nitrate standards from an international blind comparison were used to test analytical performance for different isotopic compositions and with quantities ranging from 11 ng to 10 microg total uranium. Isotopic ratio determination was demonstrated over a linear dynamic range of 7 orders of magnitude with a few percent relative precision and detection limits below 500 fg for the minor isotopes. PMID:18613650

  7. 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

  8. High levels of natural radioactivity in biota from deep-sea hydrothermal vents: a preliminary communication.

    PubMed

    Charmasson, Sabine; Sarradin, Pierre-Marie; Le Faouder, Antoine; Agarande, Michèle; Loyen, Jeanne; Desbruyères, Daniel

    2009-06-01

    Hydrothermal deep-sea vent fauna is naturally exposed to a peculiar environment enriched in potentially toxic species such as sulphides, heavy metals and natural radionuclides. It is now well established that some of the organisms present in such an environment accumulate metals during their lifespan. Though only few radionuclide measurements are available, it seems likely that hydrothermal vent communities are exposed to high natural radiation doses. Various archived biological samples collected on the East Pacific Rise and the Mid-Atlantic Ridge in 1996, 2001 and 2002 were analysed by ICP-MS in order to determine their uranium contents ((238)U, (235)U and (234)U). In addition (210)Po-Pb were determined in 2 samples collected in 2002. Vent organisms are characterized by high U, and Po-Pb levels compared to what is generally encountered in organisms from outside hydrothermal vent ecosystems. Though the number of data is low, the results reveal various trends in relation to the site, the location within the mixing zone and/or the organisms' trophic regime. PMID:19362761

  9. 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

  10. 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.

  11. The ability of Helianthus annuus L. and Brassica juncea to uptake and translocate natural uranium and 226Ra under different milieu conditions.

    PubMed

    Vera Tomé, F; Blanco Rodríguez, P; Lozano, J C

    2009-01-01

    Seedlings of Helianthus annuus L. (HA) and Brassica juncea (BJ) were used to test the effect of the pH, the presence of phosphates, and the addition of ethylene-diamine-tetraacetic acid (EDTA) or citrate on the uptake and the translocation of uranium isotopes ((238)U, (235)U, and (234)U) and (226)Ra. The results indicated that the presence of phosphates generally reduces the uptake and transfer of uranium from the roots to the shoots of HA. In the case of BJ, while phosphate enhanced the retention of uranium by roots, the translocation was poorer. Likewise, for (226)Ra, the best translocation was in the absence of phosphates for both species. The addition of citrate increased the translocation of uranium for both species, but had no clear effect on the transfer of (226)Ra. The effect of EDTA was much more moderate both for uranium and for (226)Ra, and for both plant species. Only noticeable was a slightly better uptake of (226)Ra by BJ at neutral pH, although the translocation was lower. PMID:18848715

  12. Distribution of naturally occurring radionuclides (U, Th) in Timahdit black shale (Morocco).

    PubMed

    Galindo, C; Mougin, L; Fakhi, S; Nourreddine, A; Lamghari, A; Hannache, H

    2007-01-01

    Attention has been focused recently on the use of Moroccan black oil shale as the raw material for production of a new type of adsorbent and its application to U and Th removal from contaminated wastewaters. The purpose of the present work is to provide a better understanding of the composition and structure of this shale and to determine its natural content in uranium and thorium. A black shale collected from Timahdit (Morocco) was analyzed by powder X-ray diffraction and SEM techniques. It was found that calcite, dolomite, quartz and clays constitute the main composition of the inorganic matrix. Pyrite crystals are also present. A selective leaching procedure, followed by radiochemical purification and alpha-counting, was performed to assess the distribution of naturally occurring radionuclides. Leaching results indicate that 238U, 235U, 234U, 232Th, 230Th and 228Th have multiple modes of occurrence in the shale. U is interpreted to have been concentrated under anaerobic conditions. An integrated isotopic approach showed the preferential mobilization of uranium carried by humic acids to carbonate and apatite phases. Th is partitioned between silicate minerals and pyrite. PMID:17098337

  13. 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.

  14. Ultratrace Uranium Fingerprinting with Isotope Selective Laser Ionization Spectrometry

    SciTech Connect

    Ziegler, Summer L.; Bushaw, Bruce A.

    2008-08-01

    Uranium isotope ratios can provide source information for tracking uranium contamination in a variety of fields, ranging from occupational bioassay to monitoring aftereffects of nuclear accidents. We describe the development of Isotope Selective Laser Ionization Spectrometry (ISLIS) for ultratrace measurement of the minor isotopes 234U, 235U, and 236U with respect to 238U. Optical isotopic selectivity in three-step excitation with single-mode continuous wave lasers is capable of measuring the minor isotopes at relative abundances below 1 ppm, and is not limited by isobaric interferences such as 235UH+ during measurement of 236U. This relative abundance limit approaches the threshold for measurement of uranium minor isotopes with conventional mass spectrometry, typically 10-7, but without mass spectrometric analysis of the laser-created ions. Uranyl nitrate standards from an international blind comparison were used to test analytical performance for different isotopic compositions and with quantities ranging from 11 ng to 10 µg total uranium. Isotopic ratio determination was demonstrated over a linear dynamic range of 7 orders of magnitude with a few percent relative precision and detection limits below 500 fg for the minor isotopes.

  15. Spectroscopy of Actinide Nuclei - Perspectives with Position Sensitive HPGe Detectors

    NASA Astrophysics Data System (ADS)

    Reiter, P.; Birkenbach, B.; Kotthaus, T.

    Recent advances in in-beam gamma-ray spectroscopy of actinide nuclei are based on highly efficient arrays of escape-suppressed spectrometers. The sensitivity of these detector arrays is greatly enhanced by the combination with powerful mass separators or particle detector systems. This technique is demonstrated by an experiment to investigate excited states in 234U after the one-neutron-transfer reaction 235U(d,t). In coincidence with the outgoing tritons, γ-rays were detected with the highly efficient MINIBALL spectrometer. In the near future an even enhanced sensitivity will be achieved by utilizing position sensitive HPGe detectors which will exploit the novel detection method of gamma-ray energy tracking in electrically segmented germanium detectors. An example for this novel approach is the investigation neutron-rich actinide Th and U nuclei after multi nucleon transfer reactions employing the AGATA demonstrator and PRIS