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Sample records for 238u 232th 237np

  1. Distinguishing fissions of 232Th, 237Np and 238U with beta-delayed gamma rays

    NASA Astrophysics Data System (ADS)

    Iyengar, A.; Norman, E. B.; Howard, C.; Angell, C.; Kaplan, A.; Ressler, J. J.; Chodash, P.; Swanberg, E.; Czeszumska, A.; Wang, B.; Yee, R.; Shugart, H. A.

    2013-06-01

    Measurements of beta-delayed gamma-ray spectra following 14-MeV neutron-induced fissions of 232Th, 238U, and 237Np were conducted at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Spectra were collected for times ranging from 1 min to 14 h after irradiation. Intensity ratios of gamma-ray lines were extracted from the data that allow identification of the fissioning isotope.

  2. Nondestructive Determination of 235U Enrichment of Uranium Samples in the Presence of Actinides (232Th, 236U, 237Np)

    NASA Astrophysics Data System (ADS)

    Stogov, Yu V.

    2017-01-01

    The measurements were performed using a planar Ge detector. The multi-group analysis (MGA) for the determination isotopic abundances in low enriched uranium samples is applied in this study. In order to perform the analysis of complex gamma-spectrums, were taken a number of gamma-spectrums of single reference samples, containing 235U, 238U, 232Th, 236U, 237Np with declared isotopic abundance. The gamma-ray spectrums in the range of low energy X-ray and gamma-ray peaks of these samples were obtained and analyzed.

  3. The applicability of MGA method for depleted and natural uranium isotopic analysis in the presence of actinides (232Th, 237Np, 233Pa and 241Am).

    PubMed

    Yücel, Haluk

    2007-11-01

    The multi-group analysis (MGA) method for the determination of uranium isotopic abundances in depleted uranium (DU) and natural uranium (NU) samples is applied in this study. A set of non-destructive gamma-ray measurements of DU and NU samples were performed using a planar Ge detector. The relative abundances of 235U and 238U isotopes were compared with the declared values of the standards. The relative abundance for 235U obtained by MGA for a "clean" DU or NU sample with a content of uranium>1wt% is determined with an accuracy of about +/-5%. However, when several actinides such as 232Th, 237Np, 233Pa and 241Am are present along with uranium isotopes simulating "dirty" DU or NU, it has been observed that MGA method gives erroneous results. The 235U abundance results for the samples were 6-25 times higher than the declared values in the presence of above-mentioned actinides, since MGA is utilized the X-ray and gamma-ray peaks in the 80-130 keV energy region, covering XKalpha and XKbeta regions. After the least-squares fitting of the spectra, it is found that the increases in the intensities of the X-ray and gamma-ray peaks of uranium are remarkably larger in the complex 80-130 keV region. On the other hand, it is observed that the interferences of the actinide peaks are relatively less dominant in the higher gamma-ray region of 130-300 keV. The results imply the need for dirty DU and NU samples that the MGA method should utilize the higher energy gamma-rays (up to 1001 keV of (234m)Pa) combined with lower energies of the spectra, which may be collected in a two detector mode (a planar Ge and a high efficient coaxial Ge).

  4. 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.

  5. The low-energy dipole structure of 232Th , 236U and 238U actinide nuclei

    NASA Astrophysics Data System (ADS)

    Kuliev, A. A.; Guliyev, E.; Ertugral, F.; Özkan, S.

    2010-03-01

    In this study, ensuremath I^{π} = 1+ and ensuremath I^{π} = 1- dipole mode excitations are systematically investigated within the rotational and translational + Galilean invariant quasiparticle random-phase approximation for 232Th , 236U , and 238U actinide nuclei. It is shown that the investigated nuclei reach a B( M1) strength structure, which corresponds to the scissors mode. The calculated mean excitation energies as well as the summed B( M1) value of the scissors mode excitations are consistent with the available experimental data. The results of calculations indicate large differences to the rare-earth nuclei as is the case for the experiment: a doubling of the observed dipole strengths and a shift of the energy centroid to the lower energies by about 800keV. The calculations indicate the presence of a few prominent negative-parity ensuremath K^{π} = 1- states in the 2.0-4.0MeV energy interval. The occurrence of the negative-parity dipole states with the rather high B( E1) value less than 4MeV shows the necessity of explicit parity measurements for the correct determination of the scissors mode strength in 232Th , 236U , and 238U isotopes.

  6. 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.

  7. 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.

  8. Absolute and relative cross section measurements of 237Np(n,f) and 238U(n,f) at the National Physical Laboratory

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, Paula; Hambsch, Franz-Josef; Göök, Alf; Vidali, Marzio; Hawkes, Nigel P.; Roberts, Neil J.; Taylor, Graeme C.; Thomas, David J.

    2017-09-01

    Cross section measurements in the fast energy region are being demanded as one of the key ingredients for modelling Generation-IV nuclear power plants. However, in facilities where there are no time-of-flight possibilities or it is not convenient to use them, using the 235U(n,f) cross section as a benchmark would require a careful knowledge of the room scatter in the experimental area. In this paper we present measurements of two threshold reactions, 238U(n,f) and 237Np(n,f), that could become a standard between their fission threshold and 2.5 MeV, if the discrepancies shown in the evaluations and in some experimental data can be solved. The preliminary results are in agreement with the present ENDF/B-VII.1 evaluation.

  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.

  10. A dispersive optical model potential for nucleon induced reactions on 238U and 232Th nuclei with full coupling

    NASA Astrophysics Data System (ADS)

    Quesada, José Manuel; Soukhovitskiĩ, EfremS.; Capote, Roberto; Chiba, Satoshi

    2013-03-01

    A dispersive coupled-channel optical model potential (DCCOMP) that couples the ground-state rotational and low-lying vibrational bands of 238U and 232Th nuclei is studied. The derived DCCOMP couples almost all excited levels below 1 MeV of excitation energy of the corresponding even-even actinides. The ground state, octupole, beta, gamma, and non-axial bands are coupled. The first two isobar analogue states (IAS) populated in the quasi-elastic (p,n) reaction are also coupled in the proton induced calculation, making the potential approximately Lane consistent. The coupled-channel potential is based on a soft-rotor description of the target nucleus structure, where dynamic vibrations are considered as perturbations of the rigid rotor underlying structure. Matrix elements required to use the proposed structure model in Tamura coupled-channel scheme are derived. Calculated ratio R(U238/Th232) of the total cross-section difference to the averaged σT for 238U and 232Th nuclei is shown to be in excellent agreement with measured data.

  11. Atmospheric aerosol measurements of 238U and 232Th at Fernald, Ohio, and implications on inhalation dose calculations.

    PubMed

    Leifer, Robert Z; Jacob, Ethel M; Marschke, Stephen F; Praniti, David M

    2002-12-01

    Measurements of the aerosol size distribution of 238U and 232Th at the U.S. Department of Energy's Fernald Environmental Management Project site were made to improve the inhalation dose calculations to off-site individuals. For approximately 1 y an 8-stage cascade impactor was co-located with a high volume sampler and operated at the Fernald Environmental Management Project site to collect aerosol samples. During most of the year, the site was dominated by giant particles with more than 70% of the mass of 238U above 15 microm. The seasonal average of the activity median aerodynamic diameter, based on the impactor samples, which excluded particles >15 microm, for both uranium and thorium was approximately 6.5 microm. These numbers reflect the activities at the site and the domination of the resuspension processes. During most sampling periods the size distribution was bimodal. Thorium concentrations were comparable to the uranium concentrations during the late spring and summer period and decreased to approximately 25% of the 238U concentration in the late summer. Fernald Environmental Management Project is required to calculate the maximum allowable dose from airborne emissions, excluding radon, to meet NESHAP compliance. These calculations assume an AMAD of 1 microm. We found that if you combine size distribution information with the latest ICRP 66 lung model you reduce the estimated dose by a factor of 7. Inclusion of the size distribution of radionuclides at any sampling site would substantially improve the dose estimates to the population.

  12. Theoretical analyses of (n,xn) reactions on sup 235 U, sup 238 U, sup 237 Np, and sup 239 Pu for ENDF/B-VI

    SciTech Connect

    Young, P.G.; Arthur, E.D.

    1991-01-01

    Theoretical analyses were performed of neutron-induced reactions on {sup 235}U, {sup 238}U, {sup 237}Np, and {sup 239}Pu between 0.01 and 20 MeV in order to calculate neutron emission cross sections and spectra for ENDF/B-VI evaluations. Coupled-channel optical model potentials were obtained for each target nucleus by fitting total, elastic, and inelastic scattering cross section data, as well as low-energy average resonance data. The resulting deformed optical model potentials were used to calculate direct (n,n{prime}) cross sections and transmission coefficients for use in Hauser-Feshbach statistical theory analyses. A fission model with multiple barrier representation, width fluctuation corrections, and preequilibrium corrections were included in the analyses. Direct cross sections for higher-lying vibrational states were calculated using DWBA theory, normalized using B(E{ell}) values determined from (d,d{prime}) and Coulomb excitation data, where available, and from systematics otherwise. Initial fission barrier parameters and transition state density enhancements appropriate to the compound systems involved were obtained from previous analyses, especially fits to charged-particle fission probability data. The parameters for the fission model were adjusted for each target system to obtain optimum agreement with direct (n,f) cross section measurements, taking account of the various multichance fission channels, that is, the different compound systems involved. The results from these analyses were used to calculate most of the neutron (n,n), (n,n{prime}), and (n,xn) cross section data in the ENDF/B/VI evaluations for the above nuclei, and all of the energy-angle correlated spectra. The deformed optical model and fission model parameterizations are described. Comparisons are given between the results of these analyses and the previous ENDF/B-V evaluations as well as with the available experimental data. 14 refs., 3 figs., 1 tab.

  13. 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

  14. A beta-alpha coincidence counting system for measurement of trace quantities of 238U and 232Th in aqueous samples at the Sudbury Neutrino Observatory.

    NASA Astrophysics Data System (ADS)

    Dawson, M.; Doucas, G.; Fergani, H.; Jelley, N. A.; Majerus, S.; O'Keeffe, H. M.; Peeters, S. J. M.; Perry, C.

    2016-08-01

    The Sudbury Neutrino Observatory experiment was built to measure the total flux of 8B solar neutrinos via the neutral current disintegration deuterium nuclei. This process can be mimiced by daughter isotopes of 232Th and 238U which can photodisintegrate the deuterium nucleus. Measurement of the concentration of such radioisotopes in the heavy water was critical to the success of the experiment. A radium assay technique using Hydrous Titanium Oxide coated filters was developed for this purpose and it was used in conjunction with a delayed beta-alpha coincidence counting system. The design, calibration and operation of this counting system are described in this paper. The counting efficiency for 232Th (224Ra) and 238U (226Ra) were measured to be 50 ± 5% and 62 ± 7%

  15. Resonance Region Covariance Analysis Method and New Covariance Data for {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, and {sup 239}Pu

    SciTech Connect

    Leal, L.C. Arbanas, G.; Wiarda, D.; Derrien, H.

    2008-12-15

    Resonance-parameter covariance matrix (RPCM) evaluations in the resolved resonance region were done for {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, and {sup 239}Pu using the computer code SAMMY. The retroactive approach of the code SAMMY was used to generate the RPCMs for {sup 233}U and {sup 235}U. RPCMs for {sup 232}Th, {sup 238}U and {sup 239}Pu were generated together with the resonance parameter evaluations. The RPCMs were then converted in the ENDF format using the File32 representation. Alternatively, for computer storage reasons, the File32 was converted in the File33 cross section covariance matrix (CSCM). Both representations were processed using the computer code PUFF-IV. This paper describes the procedures used to generate the RPCM with SAMMY.

  16. Comparison of activity concentration of 238U, 232Th and 40K in different Layers of subsurface Structures in Dei-Dei and Kubwa, Abuja, northcentral Nigeria

    NASA Astrophysics Data System (ADS)

    Maxwell, Omeje; Wagiran, Husin; Ibrahim, Noorddin; Lee, Siak Kuan; Sabri, Soheil

    2013-10-01

    The study of activity concentration of 232Th, 238U and 40K of rock samples from site one (S1L1-S1L11, 70 m) and site two (S2L1-S2L9, 60 m) boreholes in Dei-Dei and Kubwa was presented and the first time in the region to be compared. Activity concentrations were analysed using a high resolution co-axial HPGe gamma ray spectrometer system. The activity concentration ranges in site one borehole were from 45±1 to 98±6 Bq kg-1 for 232Th, from 18±2 to 37±4 Bq kg-1 for 238U and from 254 ±32 Bq kg-1 to 1195 ±151 Bq kg-1 for 40K. The activity concentration ranges in site two borehole were from 32±3 to 84±7 Bq kg-1 for 232Th, from 15±2 to 52±5 Bq kg-1 for 238U and from 119±15 to 705±94 for 40K Bq kg-1. Significantly higher concentration of 232Th and 238U occurs in samples collected from S1L7, S1L11 and S2L1 layers. These zones experienced granitic intrusions produced by denudation and tectonism. 40K in rock samples of S1L4 and S2L4 activity concentrations is close; it could be that biotite granitic intrusion that is inferred as the formation in that layer reflects the same activity of potassium in rock's radioactivity measurement. The area requires further investigation of soil geochemistry and activity concentration of radionuclides in groundwater.

  17. Assay Methods for 238U, 232Th, and 210Pb in Lead and Calibration of 210Bi Bremsstrahlung Emission from Lead

    SciTech Connect

    Orrell, John L.; Aalseth, Craig E.; Arnquist, Isaac J.; Eggemeyer, Tere A.; Glasgow, Brian D.; Hoppe, Eric W.; Keillor, Martin E.; Morley, Shannon M.; Myers, Allan W.; Overman, Cory T.; Shaff, Sarah M.; Thommasson, Kimbrelle S.

    2016-02-13

    Assay methods for measuring 238U, 232Th, and 210Pb concentrations in refined lead are presented. The 238U and 232Th concentrations are assayed via inductively coupled plasma mass spectrometry (ICP-MS) after anion exchange column separation on dissolved lead samples. The 210Pb concentration is inferred through α-spectroscopy of a daughter isotope, 210Po, after chemical precipitation separation on dissolved lead samples. Subsequent to the 210Po α-spectroscopy assay, a method for evaluating 210Pb concentrations in solid lead samples was developed via measurement of bremsstrahlung radiation from β-decay of a daughter isotope, 210Bi, by employing a 14-crystal array of high purity germanium (HPGe) detectors. Ten sources of refined lead were assayed. The 238U concentrations were <34 microBq/kg and the 232Th concentrations ranged <0.6 – 15 microBq/kg, as determined by the ICP-MS assay method. The 210Pb concentrations ranged from ~0.1 – 75 Bq/kg, as inferred by the 210Po α-spectroscopy assay method.

  18. 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.

  19. 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.

  20. Quantification of transfer of (238)U, (226)Ra, (232)Th, (40)K and (137)Cs in mosses of a semi-natural ecosystem.

    PubMed

    Dragović, S; Mihailović, N; Gajić, B

    2010-02-01

    There is a lack of appropriate data on transfer of some radionuclides on many terrestrial biota groups. To expand the available data concentration ratios of (238)U, (226)Ra, (232)Th, (40)K and (137)Cs in mosses are presented in this paper. The relationship between concentration ratios of radionuclides and physicochemical characteristics of the underlying soil was also investigated. The data on concentration ratios obtained here will provide a useful addition to the currently used database of transfer parameters, particularly for natural radionuclides.

  1. 238U and 232Th series nuclides in groundwater from the J-13 well at the Nevada Test Site: Implications for ion retardation

    NASA Astrophysics Data System (ADS)

    Copenhaver, Sally A.; Krishnaswami, S.; Turekian, Karl K.; Shaw, Henry

    1992-07-01

    The activities of members of the 238U and 232Th decay chains have been determined in water from well J-13 at the Nevada Test Site near Yucca Mountain. Using 222Rn as a measure of recoil flux, adsorption (k1) and desorption (k2) rate constants for Ra and Pb have been determined. The ratio (k1/k2), defined as the dimensionless distribution coefficient, K, is 1.3 × 104 for Ra and 2.7 × 104 for Pb and is estimated to be about 104 for Th.

  2. Neutron inelastic-scattering cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu. [LMFBR

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1982-01-01

    Differential-neutron-emission cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu are measured between approx. = 1.0 and 3.5 MeV with the angle and magnitude detail needed to provide angle-integrated emission cross sections to approx. < 3% accuracies. Emitted-neutron resolutions are quantitatively defined and vary from approx. = 0.1 to 0.35 MeV. The experimental results are corrected for fisson-neutron contributions to obtain pseudo-elastic-neutron-scattering cross sections which, together with the neutron total cross sections, define the non-elastic cross sections to within well specified energy resolutions. These results imply inelastic-neutron-scattering cross sections which are compared with comparable quantities derived from ENDF/B-V. Good general agreement is noted for /sup 232/Th, /sup 233/U, /sup 235/U and /sup 238/U inelastic-scattering values, poor agreement is observed for /sup 240/Pu, and a serious discrepancy exists in the case of /sup 239/Pu.

  3. 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.

  4. 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.

  5. 238U series isotopes and 232Th in carbonates and black shales from the Lesser Himalaya: implications to dissolved uranium abundances in Ganga-Indus source waters.

    PubMed

    Singh, S K; Dalai, Tarun K; Krishnaswami, S

    2003-01-01

    238U and (232)Th concentrations and the extent of (238)U-(234)U-(230)Th radioactive equilibrium have been measured in a suite of Precambrian carbonates and black shales from the Lesser Himalaya. These measurements were made to determine their abundances in these deposits, their contributions to dissolved uranium budget of the headwaters of the Ganga and the Indus in the Himalaya and to assess the impact of weathering on (238)U-(234)U-(230)Th radioactive equilibrium in them. (238)U concentrations in Precambrian carbonates range from 0.06 to 2.07 microg g(-1). The 'mean' U/Ca in these carbonates is 2.9 ng U mg(-1) Ca. This ratio, coupled with the assumption that all Ca in the Ganga-Indus headwaters is of carbonate origin and that U and Ca behave conservatively in rivers after their release from carbonates, provides an upper limit on the U contribution from these carbonates, to be a few percent of dissolved uranium in rivers. There are, however, a few streams with low uranium concentrations, for which the carbonate contribution could be much higher. These results suggest that Precambrian carbonates make only minor contributions to the uranium budget of the Ganga-Indus headwaters in the Himalaya on a basin wide scale, however, they could be important for particular streams. Similar estimates of silicate contribution to uranium budget of these rivers using U/Na in silicates and Na* (Na corrected for cyclic and halite contributions) in river waters show that silicates can contribute significantly (approximately 40% on average) to their U balance. If, however, much of the uranium in these silicates is associated with weathering resistant minerals, then the estimated silicate uranium component would be upper limits. Uranium concentration in black shales averages about 37 microg g(-1). Based on this concentration, supply of U from at least approximately 50 mg of black shales per liter of river water is needed to balance the average river water U concentration, 1.7 microg L

  6. Charge distribution of light mass fission products in the fast neutron induced fission of (232)Th, (238)U, (240)Pu and (244)Cm.

    PubMed

    Naik, Haladhara; Singh, Ram Janam; Dange, Shrikant Pandurang

    2017-09-01

    Fractional cumulative yields (FCY) of various light mass fission products in the fast neutron induced fission of (232)Th, (238)U, (240)Pu and (244)Cm have been determined by using the off-line γ-ray spectrometric technique. From present and literature data, width of isobaric charge distribution (σZ), the most probable charge (ZP) and the experimental charge polarization (∆ΖEXPT) as a function of fragment mass were deduced. The ∆ΖEXPT values from the present work for light mass chains and earlier work for heavy mass chains show oscillating nature due to nuclear structure effect. The ∆ΖMPE values based on minimum potential energy surface were theoretically calculated, which shows a systematic decrease trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. 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

  8. Radionuclides (40K, 232Th and 238U) and Heavy Metals (Cr, Ni, Cu, Zn, As and Pb) Distribution Assessment at Renggam Landfill, Simpang Renggam, Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Zaidi, E.; FahrulRazi, MJ; Azhar, ATS; Hazreek, ZAM; Shakila, A.; Norshuhaila, MS; Omeje, M.

    2017-08-01

    The assessment of radioactivity levels and the distribution of heavy metals in soil samples at CEP Farm landfill, Renggam in Johor State was to determine the activity concentrations of naturally occurring radionuclides and heavy metal concentrations of this landfill. The background radiation was monitored to estimate the exposure level. The activity concentrations of radionuclides in soil samples were determined using HPGe gamma ray spectroscopy whereas the heavy metal concentration was measured using X-RF analysis. The mean exposure rate at the landfill site was 36.2±2.4 μR hr-1 and the annual effective dose rate at the landfill site was 3.19 ± 0.22 mSv yr-1. However, residential area has lower mean exposure dose rate of about 16.33±0.72 μR hr-1 and has an annual effective dose rate of 1.43±0.06 mSv yr-1 compared to landfill sites. The mean activity concentration of 40K, 238U and 232Th at landfill site were 239.95±15.89 Bq kg-1, 20.90±2.49 Bq kg-1 and 40.61±4.59 Bq kg-1, respectively. For heavy metal compositions, Cr, Ni and Cu have mean concentration of 232±10 ppm, 23±2 ppm, and 46±19 ppm, respectively. Whereas, Zn has concentration of 64±9 ppm and concentration of 12±1 ppm and 71±2 ppm was estimated for As and Pb respectively. The higher activity concentration of 40K down the slope through leaching process whereas the higher activity level of 238U content at the landfill site may be attributed to the soil disruption to local equilibrium.

  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. High precision 230Th/232Th and 234U/238U measurements using energyfiltered ICP magnetic sector multiple collector mass spectrometry

    NASA Astrophysics Data System (ADS)

    Luo, Xiaozhong; Rehkamper, Mark; Lee, Der-Chuen; Halliday, Alex N.

    1997-12-01

    We have developed new chemical and mass spectrometric techniques for the precise determination of 234U/238U and 230Th/232Th ratios in geological materials. The isotope ratio measurements were performed using an inductively coupled plasma double focusing magnetic sector multiple-collector mass spectrometer (MC-ICPMS) equipped with an additional energy filter. Following sample dissolution, U and Th are first separated from the rock matrix by a new and highly efficient column chromatographic procedure utilizing TRU-Spec resin. The strong affinity of U and Th for this material allows the use of extremely small ( < 0.5 ml resin) columns, even for the processing of silicate samples as large as ~5 g. Our new mass-spectrometric techniques permit precise corrections for mass discrimination and gain variation during analysis. As a consequence, the precision and external reproducibility of uranium and thorium isotopic analysis is improved by a factor of ~3-5 compared with previous results by conventional thermal ionization mass spectrometry (TIMS). A sensitivity of ~0.04% is routinely achieved for Th and this is comparable to the best values achieved by TIMS for large sample sizes. Recent instrumental improvements, however, have further increased our sensitivity by about a factor of five. Our Th and U isotope data for standard reference materials and other geological samples are in excellent agreement with previously published values from other laboratories, further highlighting the reliability and analytical capabilities of our new techniques.

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

    SciTech Connect

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

    2016-01-22

    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 ({sup 232}Th, {sup 238}U and {sup 40}K) 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 (I{sub geo}) 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 (H{sub ex})

  12. 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).

  13. Characterization of bauxite residue (red mud) for (235)U, (238)U, (232)Th and (40)K using neutron activation analysis and the radiation dose levels as modeled by MCNP.

    PubMed

    Landsberger, S; Sharp, A; Wang, S; Pontikes, Y; Tkaczyk, A H

    2017-07-01

    This study employs thermal and epithermal neutron activation analysis (NAA) to quantitatively and specifically determine absorption dose rates to various body parts from uranium, thorium and potassium. Specifically, a case study of bauxite residue (red mud) from an industrial facility was used to demonstrate the feasibility of the NAA approach for radiological safety assessment, using small sample sizes to ascertain the activities of (235)U, (238)U, (232)Th and (40)K. This proof-of-concept was shown to produce reliable results and a similar approach could be used for quantitative assessment of other samples with possible radiological significance. (238)U and (232)Th were determined by epithermal and thermal neutron activation analysis, respectively. (235)U was determined based on the known isotopic ratio of (238)U/(235)U. (40)K was also determined using epithermal neutron activation analysis to measure total potassium content and then subtracting its isotopic contribution. Furthermore, the work demonstrates the application of Monte Carlo Neutral-Particle (MCNP) simulations to estimate the radiation dose from large quantities of red mud, to assure the safety of humans and the surrounding environment. Phantoms were employed to observe the dose distribution throughout the human body demonstrating radiation effects on each individual organ. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. 187Re - 232Th - 238U nuclear geochronometry: constraining magmatism in East-Antarctica and the break-up of Gondwana

    NASA Astrophysics Data System (ADS)

    Roller, Goetz

    2017-04-01

    187Re - 232Th - 238U nuclear geochronometry is a new dating method for astronomy, earth and planetary sciences [1-4]. Nucleogeochronometric Rhenium-Osmium two-point-isochron (TPI) ages are calculated using a nuclear geochronometer as one data point in a two-point-isochron diagram [5-7]. The IVREA chronometer, for example, is one of five terrestrial nuclear geochronometers identified so far [8]. Here, it is used to constrain the magmatism of the Ferrar flood basalt province, which has been related to continental rifting and the break-up of Gondwana in the Jurassic.TPI ages for seven (basaltic) andesite whole rock samples from the Prince Albert Mountains (Victoria Land, Antarctica) are calculated. An isochron age of 172 ± 5 Ma (187Os/188Osi = 0.194 ± 0.023) has previously been published for these rocks [9]. Initial TPI 187Os/188Osi ratios show only minor scatter between 187Os/188Osi = 0.2149 ± 0.0064 and 187Os/188Osi = 0.22231 ± 0.00080, in agreement with the enigmatic, suprachondritic 187Os/188Osi = 0.194 ± 0.023 from the isochron [9]. TPI ages for the Mount Joyce samples range from 125.4 ± 9.9 Ma to 139 ± 17 Ma and thus constrain the youngest magmatic event(s) in the Transantarctic Mountains. For the Thumb Point basalt, a TPI age of 219 ± 81 Ma is calculated. Despite of its large uncertainty, the age itself is in agreement with the Triassic 224 Ma and 240 Ma events reported from North Patagonia [10]. The TPI age of 186.1 ± 8.1 Ma from the Ricker Hill basalt can be clearly distinguished from the Mount Murray TPI age of 158 ± 14 Ma, while at Brimstone Peak two TPI age groups of 155 ± 14 Ma and 175.3 ± 3.1 Ma are observed. From this it may be concluded that the seven TPI ages indicate episodic magmatic activity in East-Antarctica between 125 Ma and 219 Ma, leading to the break-up of Gondwana. This picture is consistent with the geochronology of the Antarctic Peninsula, Patagonia, the Karoo and the Ferrar mafic rocks [10]. Thus, besides constraining

  15. 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Plant uptake of (238)U, (235)U, (232)Th, (226)Ra, (210)Pb and (40)K from a coal ash and slag disposal site and control soil under field conditions: A preliminary study.

    PubMed

    Skoko, Božena; Marović, Gordana; Babić, Dinko; Šoštarić, Marko; Jukić, Mirela

    2017-06-01

    The aim of this study was to investigate the uptake of (238)U, (235)U, (232)Th, (226)Ra, (210)Pb and (40)K by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of (238)U, (235)U, (226)Ra and (210)Pb in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for (226)Ra. On the contrary, a significantly smaller activity concentration of (40)K in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of (238)U, (235)U, (226)Ra and (210)Pb is significantly smaller in comparison with the uptake at the control site, while it is vice versa for (40)K. No significant difference was observed between the disposal site and the control site's plant uptake of (232)Th. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Assessment of (226)Ra, (238)U, (232)Th, (137)Cs and (40)K activities from the northern coastline of Oman Sea (water and sediments).

    PubMed

    Darabi-Golestan, F; Hezarkhani, A; Zare, M R

    2017-02-27

    Water and sediment samples were collected from northern coast of Oman Sea covering from Goatr to Hormoz canyon seaport. Water and sediment quality assessment for naturally or anthropogenic radionuclides at Oman Sea as a main strategic golf for trade and transit, is an important issue. Correspondence analysis (CA) by R-mode analysis represents that sigma(T)-temperature-conductivity-O2 parameters are well-correlated with (226)Ra, (232)Th and (40)K. Accordingly Q-mode analysis revealed an indicator samples of ST13W for different radionuclides, ST03W for O2, and simultaneously ST34W-ST21W-ST08W-ST04W for sigma(T) parameters. The CA results overlapped with factor and cluster analysis results that explained 85.8% of total variance of water samples. Descriptive analysis of sediments indicates more significant variation than water samples. The (232)Th and (226)Ra generally showing that ST13D to ST25D sediments that restricted to Pi Bashk coastline are concentrated from (137)Cs and (40)K. By comparison with reference-values from Iran and other parts of the world, they are acceptable with respect to environmental and radioisotope hazards.

  18. 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.

  19. Neutron scattering cross sections for /sup 232/Th and /sup 238/U inferred from proton scattering and charge exchange measurements. [7 MeV, 26 and 27 MeV

    SciTech Connect

    Hansen, L.F.; Grimes, S.M.; Pohl, B.A.; Poppe, C.H.; Wong, C.

    1980-01-01

    Differential cross sections for the (p,n) reactions to the isobaric analog states (IAS) of /sup 232/Th and /sup 238/U targets were measured at 26 and 27 MeV. The analysis of the data was done in conjunction with the proton elastic and inelastic (2/sup +/, 4/sup +/, 6/sup +/) differential cross sections measured at 26 MeV. Because collective effects are important in this mass region, deformed coupled-channels calculations were carried out for the simultaneous analysis of the proton and neutron outgoing channels. The sensitivity of the calculations was studied with respect to the optical model parameters used in the calculations, the shape of the nuclear charge distribution, the type of coupling scheme assumed among the levels, the magnitude of the deformation parameters, and the magnitude of the isovector potentials, V/sub 1/ and W/sub 1/. A Lane model-consistent analysis of the data was used to infer optical potential parameters for 6- to 7-MeV neutrons. The neutron elastic differential cross sections obtained from these calculations are compared with measurements available in the literature, and with results obtained using neutron parameters from global sets reported at these energies. 7 figures, 3 tables.

  20. The 237Np(n,f) cross section at the CERN n-TOF facility

    NASA Astrophysics Data System (ADS)

    Karadimos, D.; Vlastou, R.; Vlachoudis, V.; Pavlopoulos, P.; Konovalov, V.; Diakaki, M.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Becvár, F.; Benlliure, J.; Berthoumieux, E.; Calviño, F.; Cano-Ott, D.; Capote, R.; de Albornoz, A. Carrillo; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Cortina, D.; Couture, A.; Cox, J.; David, S.; Dolfini, R.; Domingo-Pardo, C.; Dorochenko, A.; Dridi, W.; Duran, I.; Eleftheriadis, Ch.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Goncalves, I.; Gallino, R.; Cennini, P.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Kolokolov, D.; Kossionides, E.; Krticka, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Perrot, L.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Savvidis, I.; Sedysheva, M.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Voss, F.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2011-10-01

    The 237Np(n,f) cross sections have been measured at the n-TOF facility relative to the 235U and 238U fission cross sections. The n-TOF spallation neutron source at CERN is characterized by a high intensity flux, an excellent time resolution and an extensive neutron energy range (from eV to GeV). A fast ionization chamber was used as a fission fragment detector with efficiency better than 97%. Preliminary 237Np(n,f) cross sections have been deduced in the energy range from 20 keV to 10 MeV and are found in good agreement with data from literature.

  1. Criticality of a {sup 237}Np Sphere

    SciTech Connect

    Sanchez, Rene G.; Hayes, David K.; Cappiello, Charlene C.; Myers, William L.; Jaegers, Peter J.; Clement, Steven D.; Butterfield, Kenneth B.

    2003-07-22

    A critical mass experiment using a 6-kg {sup 237}Np sphere has been performed. The purpose of the experiment is to get a better estimate of the critical mass of {sup 237}Np. To attain criticality, the {sup 237}Np sphere was surrounded with 93 wt % {sup 235}U shells. A 1/M as a function of uranium mass was performed. An MCNP neutron transport code was used to model the experiment. The MCNP code yielded a k{sub eff} of 0.99089 {+-} 0.0003 compared with a k{sub eff} 1.0026 for the experiment. Based on these results, it is estimated that the critical mass of {sup 237}Np ranges from kilogram weights in the high fifties to low sixties.

  2. Nuclear resonance fluorescence of {sup 237}Np

    SciTech Connect

    Angell, C. T.; Yee, R.; Joshi, T. H.; Swanberg, E.; Norman, E. B.; Hicks, C. L. Jr.; Klimenko, A.; Korbly, S.; Wilson, C.; Kulp, W. D.; Warren, G. A.; Bray, T. H.; Copping, R.; Glans, P. A.; Tyliszczak, T.; Shuh, D. K.

    2010-11-15

    Measurements of states excited by nuclear resonance fluorescence in {sup 237}Np were performed using a bremsstrahlung beam. Fifteen new states were observed in the region of 1.7 to 2.5 MeV. They can be used to detect or assay {sup 237}Np nondestructively for applications in security and safeguards. The states are populated with similar strength as those states found previously in {sup 235}U and {sup 239}Pu but are spread out more in energy.

  3. Perturbed angular distribution of 237Np gamma rays from the 237U parent

    NASA Astrophysics Data System (ADS)

    Ansaldo, Eduardo J.

    1980-09-01

    The anisotropy was measured for the 208.0-59.54 keV gamma cascade in 237Np, corresponding to a positive sign for the M1-E2 mixing ratio of the 208.0 keV transition. The sources were prepared by means of the 238U(e, n) reaction. A discussion on the implications of the present results for the study of hyperfine interactions in neptunium compounds and alloys is included.

  4. The {sup 237}Np(n,f) cross section at the CERN n-TOF facility

    SciTech Connect

    Karadimos, D.; Vlastou, R.; Diakaki, M.; Papadopoulos, C.; Vlachoudis, V.; Chiaveri, E.; Ferrari, A.; Fitzpatrick, L.; Cennini, P.; Herrera-Martinez, A.; Kadi, Y.; Mengoni, A.; Sarchiapone, L.; Wendler, H.; Pavlopoulos, P.; Konovalov, V.; Furman, W.; Sedysheva, M.; Abbondanno, U.; Milazzo, P. M.

    2011-10-28

    The {sup 237}Np(n,f) cross sections have been measured at the n-TOF facility relative to the {sup 235}U and {sup 238}U fission cross sections. The n-TOF spallation neutron source at CERN is characterized by a high intensity flux, an excellent time resolution and an extensive neutron energy range (from eV to GeV). A fast ionization chamber was used as a fission fragment detector with efficiency better than 97%. Preliminary {sup 237}Np(n,f) cross sections have been deduced in the energy range from 20 keV to 10 MeV and are found in good agreement with data from literature.

  5. 237Np absolute delayed neutron yield measurements

    NASA Astrophysics Data System (ADS)

    Doré, D.; Ledoux, X.; Nolte, R.; Gagnon-Moisan, F.; Thulliez, L.; Litaize, O.; Roettger, S.; Serot, O.

    2017-09-01

    237Np absolute delayed neutron yields have been measured at different incident neutron energies from 1.5 to 16 MeV. The experiment was performed at the Physikalisch-Technische Bundesanstalt (PTB) facility where the Van de Graaff accelerator and the cyclotron CV28 delivered 9 different neutron energy beams using p+T, d+D and d+T reactions. The detection system is made up of twelve 3He tubes inserted into a polyethylene cylinder. In this paper, the experimental setup and the data analysis method are described. The evolution of the absolute DN yields as a function of the neutron incident beam energies are presented and compared to experimental data found in the literature and data from the libraries.

  6. Determination of 237Np and Pu isotopes in large soil samples by inductively coupled plasma mass spectrometry.

    PubMed

    Maxwell, Sherrod L; Culligan, Brian K; Jones, Vernon D; Nichols, Sheldon T; Bernard, Maureen A; Noyes, Gary W

    2010-12-03

    A new method for the determination of (237)Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of (237)Np and Pu isotopes by ICP-MS. (238)U can interfere with (239)Pu measurement by ICP-MS as (238)UH(+) mass overlap and (237)Np via (238)U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1×10(6). Alpha spectrometry can also be applied so that the shorter-lived (238)Pu isotope can be measured successfully. (239) Pu, (242)Pu and (237)Np were measured by ICP-MS, while (236)Pu and (238)Pu were measured by alpha spectrometry. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. DETERMINATION OF 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

    SciTech Connect

    Maxwell, S.

    2010-07-26

    A new method for the determination of {sup 237}Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of {sup 237}Np and Pu isotopes by ICP-MS. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via {sup 238}U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1 x 10{sup 6}. Alpha spectrometry can also be applied so that the shorter-lived {sup 238}Pu isotope can be measured successfully. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu and {sup 238}Pu were measured by alpha spectrometry.

  8. Determination of traces of 237Np in environmental samples by ICP-MS after separation using TOA extraction chromatography.

    PubMed

    Ji, Y Q; Li, J Y; Luo, S G; Wu, T; Liu, J L

    2001-09-01

    A simple, rapid, cost-efficient, and robust method for separation of 237Np with an extraction chromatographic column (TOA: tri-n-octylamine on Teflon powder) is outlined in detail and further improved for direct ICP-MS analysis. The column efficiently retained 237Np in 2 mol L(-1) HNO3 medium and all of the 237Np was easily eluted with 0.02 mol L(-1) oxalic acid in 0.16 mol L(-1) HNO3 at 95 degrees C. The separated solutions were free from most matrix elements and were aspirated into the ICP-MS directly. The decontamination factor for 238U is more than 10(4). The instrumental detection limit for 237Np was 0.46 pg mL(-1), which corresponds to 1.2 x 10(-5) Bq mL(-1). The method is more rapid than traditional radiometric techniques. It is also considered to be more suitable for environmental monitoring than existing methods based on TOA.

  9. RAPID DETERMINATION OF 237 NP AND PU ISOTOPES IN WATER BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY

    SciTech Connect

    Maxwell, S.; Jones, V.; Culligan, B.; Nichols, S.; Noyes, G.

    2010-06-23

    A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of {sup 237}Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry; a hybrid approach. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4 to 6 hours, and can also be used for emergency response. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu, {sup 238}Pu, and {sup 239}Pu were measured by alpha spectrometry.

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

    PubMed

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

    2013-11-19

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

  11. Updated and revised neutron reaction data for 237Np

    NASA Astrophysics Data System (ADS)

    Chen, Guochang; Wang, Jimin; Cao, Wentian; Tang, Guoyou; Yu, Baosheng

    2017-09-01

    Nuclear data with high accuracy for minor actinides play an important role in nuclear technology applications, including reactor design and operation, fuel cycle, estimation of the amount of minor actinides in high burn-up reactors and the minor actinides transmutation. Based on the evaluated experimental data, the updated and revised evaluation of a full set of n+237Np nuclear data from 10-5 eV ˜ 20 MeV are carried out and recommended. Mainly revised quantities are neutron multiplicities from fission reaction, inelastic, fission, (n, 2n) and (n, γ) reaction cross sections as well as angular distribution and so on. The promising results are obtained when the renewal evaluated data of 237Np will be used to instead of the evaluated data in CENDL-3.1 database.

  12. Global distribution of Pu isotopes and 237Np.

    PubMed

    Kelley, J M; Bond, L A; Beasley, T M

    1999-09-30

    Inventories and compositions of Pu isotopes and 237Np in archived soil samples collected in the 1970s from 54 locations around the world were determined to provide regional baselines for recognizing possible future environmental inputs of non-fallout Pu and Np. As sample sizes used in this work were small (typically 1 g), inhomogeneities in Pu and Np concentrations were easily recognizable and, as a result, we were able to determine that atypical debris in South America, from French testing in the South Pacific, is more widely and uniformly distributed than previously supposed. From our results we conclude that fallout 237Np/239Pu atom ratios are generally lower in the Southern Hemisphere (approximately 0.35) than in the Northern Hemisphere (approximately 0.47.) Moreover, 237Np/239Pu atom ratios are more device-dependent, hence more variable, than counterpart 240Pu/239Pu atom ratios. Given predictable trends caused by sample inhomogeneities, with only two exceptions, the Pu results of this work are entirely consistent with (and in several instances improve on) results previously reported for these same samples. However, unlike earlier interpretations used to explain these results, we recommend that fallout isotopic signatures be represented by mixing lines, rather than averages, to better reflect regional variations of stratospheric fallout inventories relative to tropospheric fallout inventories, and provide the theoretical basis for doing so. Finally, the Np results of this work constitute one of the largest single compilations of such data reported to date.

  13. 237 Np Mössbauer isomer shifts in neptunium chalcogenides

    NASA Astrophysics Data System (ADS)

    Thévenin, T.; Jové, J.; Pagès, M.

    1984-10-01

    We report237Np Mössbauer spectrometry measurements on some Np polychalcogenides: NpS3, β-NpS2, Np3Se5, NpTe3, α-Np2S3 and γ-Np2Se3. The experiments have been performed at 4.2 K and 77 K. From the isomeric shift values, the oxidation state of the Np ion can easily be assigned in these kinds of compounds: Np(IV) in NpS3, β-NpS2 and Np(III) in NpTe3, α-Np2S3 and γ-Np2 Se3. A mixture of Np(III) and Np(IV) ions has been observed in Np3Se5. Comparisons of the IS values have pointed out the influence of the electronegativity of the chalcogen atom and of the bond length Np- X(X≡ S, Se, Te).

  14. {sup 237}Np in Hemp-palm leaves of Bontenchiku for fishing gear used by the Fifth Fukuryu-Maru: 40 year after {open_quotes}Bravo{close_quotes}

    SciTech Connect

    Yamamoto, Masayoshi; Komura, Kazuhisa; Ueno, Kaoru

    1996-05-01

    The alpha radioactive components in the Hemp-palm leaves of Bontenchiku were determined with emphasis on the measurement of low-level {sup 237}Np by alpha-ray spectrometry after chemical separation. Bontenchiku is a kind of fishing gear for long-line fishing used by the Fifth Fukuryu-Maru (Lucky Dragon). This gear was exposed to fallout from the second thermonuclear test explosion (Bravo) at Bikini Atoll in March 1954. The {sup 237}Np content in the Bontenchiku sample was determined to be 11.5 {plus_minus}0.8 mBq g{sup {minus}1} with an activity ratio of {sup 237}Np: {sup 239,240}Pu and an atom ratio of {sup 237}Np: {sup 239}Pu estimated to be (2.2 {plus_minus}0.2) x 10{sup {minus}3} and 0.42 {plus_minus}0.04, respectively. The data showed the existence of a chain reaction of {sup 238}U and its ratio to be {sup 237}Np: {sup 239}Pu, as well as the presence of {sup 237}U at the time of fallout from Bravo event in March 1954. 12 refs., 5 figs., 1 tab.

  15. Multinucleon transfer in central collisions of 238U+238U

    NASA Astrophysics Data System (ADS)

    Ayik, S.; Yilmaz, B.; Yilmaz, O.; Umar, A. S.; Turan, G.

    2017-08-01

    Quantal diffusion mechanism of nucleon exchange is studied in the central collisions of 238U+238U in the framework of the stochastic mean-field (SMF) approach. For bombarding energies considered in this work, the dinuclear structure is maintained during the collision. Hence, it is possible to describe nucleon exchange as a diffusion process for mass and charge asymmetry. Quantal neutron and proton diffusion coefficients, including memory effects, are extracted from the SMF approach and the primary fragment distributions are calculated.

  16. {sup 237}Np: Oxidation state in vivo and chelation by multidentate catecholat and hydroxypyridinonate ligands

    SciTech Connect

    Durbin, P.W.; Kullgren, B.; Allen, P.G.; Bucher, J.J.; Edelstein, N.M.; Shuh, D.K.; Xu, J.; Raymond, K.N. |

    1998-07-01

    Chemically, {sup 237}Np(V) is as toxic as U(VI), and radiologically, about as toxic as {sup 239}Pu. Depending on redox conditions in vivo, {sup 237}Np exists as weakly complexing Np(V) (NpO{sub 2}{sup +}) or as Np(IV), which forms complexes as stable as those of Pu(IV). Ten multidentate catecholate (CAM) and hydroxypyridinonate (HOPO) ligands with great affinity for Pu(IV) were compared with CaNa{sub 3}-DTPA for in vivo chelation of {sup 237}Np. Mice were injected intravenously with {sup 237}NpO{sub 2}Cl: those in a kinetic study were killed 1 to 2,880 min; in ligand studies, fed mice were injected intraperitoneally with a ligand 5, 60, or 1,440 min after {sup 237}Np(V), mice fasted for 16 h were gastrically intubated with a ligand 3 min after {sup 237}Np(V), and all were killed 24 h after ligand administration; tissues and excreta were radioanalyzed. Rapid plasma clearance and urinary excretion of {sup 237}Np(V) resemble U(VI); deposition and early retention in skeleton and liver resemble Pu(IV). The x-ray absorption near edge structure spectroscopy (XANES) spectra of femora of {sup 237}Np(V)-injected mice, compared with spectra of Np(V) and Np(IV) from reference solids, showed predominantly Np(IV). Significant in vivo {sup 237}Np chelation was obtained with all of the HOPO and CAM ligands injected at molar ratio 22; the HOPO ligands reduced {sup 237}Np in skeleton, liver, and other soft tissue, on average, to 72, 25, and 25% of control, respectively, while CaNa{sub 3}-DTPA was ineffective.

  17. Study on migration behaviour of 237Np and 241Am in near-surface environments.

    PubMed

    Tanaka, Tadao; Ya-Anant, Nanthavan

    2011-07-01

    Laboratory-scale experiments were performed to investigate migration behaviour of (237)Np and (241)Am, which were deposited onto the ground surface from spent fuel reprocessing facilities. Migration experiments by column method were conducted for a sandy soil and a reddish soil by varying the volume of eluting solution. There seemed to be two chemical species of (237)Np in the sandy soil column: one is cationic and the other is particulate form. The particulates moved without significant interaction with the sandy soil. The sorption of cationic (237)Np was controlled by both a reversible ion-exchange reaction and irreversible reactions. Most of (241)Am was formed into rather large particulates and trapped in the sandy soil column. The (237)Np and (241)Am loaded into the reddish soil column moved deeper with increasing eluting volume. The sorption was mainly controlled by ion-exchange reaction. The migration behaviour might be evaluated by the distribution coefficient.

  18. (237)Np analytical method using (239)Np tracers and application to a contaminated nuclear disposal facility.

    PubMed

    Snow, Mathew S; Morrison, Samuel S; Clark, Sue B; Olson, John E; Watrous, Matthew G

    2017-06-01

    Environmental (237)Np analyses are challenged by low (237)Np concentrations and lack of an available yield tracer; we report a rapid, inexpensive (237)Np analytical approach employing the short lived (239)Np (t1/2 = 2.3 days) as a chemical yield tracer followed by (237)Np quantification using inductively coupled plasma-mass spectrometry. (239)Np tracer is obtained via separation from a (243)Am stock solution and standardized using gamma spectrometry immediately prior to sample processing. Rapid digestions using a commercial, 900 W "Walmart" microwave and Parr microwave vessels result in 99.8 ± 0.1% digestion yields, while chromatographic separations enable Np/U separation factors on the order of 10(6) and total Np yields of 95 ± 4% (2σ). Application of this method to legacy soil samples surrounding a radioactive disposal facility (the Subsurface Disposal Area at Idaho National Laboratory) reveal the presence of low level (237)Np contamination within 600 m of this site, with maximum (237)Np concentrations on the order of 10(3) times greater than nuclear weapons testing fallout levels. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 237Np analytical method using 239Np tracers and application to a contaminated nuclear disposal facility

    DOE PAGES

    Snow, Mathew S.; Morrison, Samuel S.; Clark, Sue B.; ...

    2017-03-21

    In this study, environmental 237Np analyses are challenged by low 237Np concentrations and lack of an available yield tracer; we report a rapid, inexpensive 237Np analytical approach employing the short lived 239Np (t1/2 = 2.3 days) as a chemical yield tracer followed by 237Np quantification using inductively coupled plasma-mass spectrometry. 239Np tracer is obtained via separation from a 243Am stock solution and standardized using gamma spectrometry immediately prior to sample processing. Rapid digestions using a commercial, 900 W "Walmart" microwave and Parr microwave vessels result in 99.8 ± 0.1% digestion yields, while chromatographic separations enable Np/U separation factors on themore » order of 106 and total Np yields of 95 ± 4% (2σ). Application of this method to legacy soil samples surrounding a radioactive disposal facility (the Subsurface Disposal Area at Idaho National Laboratory) reveal the presence of low level 237Np contamination within 600 m of this site, with maximum 237Np concentrations on the order of 103 times greater than nuclear weapons testing fallout levels.« less

  20. Neutron-induced fission cross section of 237Np in the keV to MeV range at the CERN n_TOF facility

    NASA Astrophysics Data System (ADS)

    Diakaki, M.; Karadimos, D.; Vlastou, R.; Kokkoris, M.; Demetriou, P.; Skordis, E.; Tsinganis, A.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Bečvář, F.; Berthoumieux, E.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; David, S.; Dolfini, R.; Domingo-Pardo, C.; Dorochenko, A.; Dridi, W.; Duran, I.; Eleftheriadis, Ch.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fuji, K.; Furman, W.; Goncalves, I.; Gallino, R.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Ioannidis, K.; Isaev, S.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Kolokolov, D.; Konovalov, V.; Krtička, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Savvidis, I.; Sedysheva, M.; Stamoulis, K.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Voss, F.; Wendler, H.; Wiescher, M.; Wisshak, K.; n TOF Collaboration

    2016-03-01

    The neutron-induced fission cross section of 237Np was experimentally determined at the high-resolution and high-intensity facility n_TOF, at CERN, in the energy range 100 keV to 9 MeV, using the 235U(n ,f ) and 238U(n ,f ) cross section standards below and above 2 MeV, respectively. A fast ionization chamber was used in order to detect the fission fragments from the reactions and the targets were characterized as far as their mass and homogeneity are concerned by means of α spectroscopy and Rutherford backscattering spectroscopy respectively. Theoretical calculations within the Hauser-Feshbach formalism have been performed, employing the empire code, and the model parameters were tuned in order to successfully reproduce the experimental fission cross-sectional data and simultaneously all the competing reaction channels.

  1. Status of the Neutron Capture Measurement on 237Np with the DANCE Array at LANSCE

    SciTech Connect

    Esch, E.-I.; Bond, E.M.; Bredeweg, T. A.; Glover, S. E.; Haight, R. C.; Kronenberg, A.; O'Donnell, J. M.; Pitcher, E. J.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wender, S. A.; Wouters, J. M.; Alpizar-Vicente, A.; Greife, U.; Hatarik, R.

    2005-05-24

    Neptunium-237 is a major constituent of spent nuclear fuel. Estimates place the amount of 237Np bound for the Yucca Mountain high-level waste repository at 40 metric tons. The Department of Energy's Advanced Fuel Cycle Initiative program is evaluating methods for transmuting the actinide waste that will be generated by future operation of commercial nuclear power plants. The critical parameter that defines the transmutation efficiency of actinide isotopes is the neutron fission-to-capture ratio for the particular isotope in a given neutron spectrum. The calculation of transmutation efficiency therefore requires accurate fission and capture cross sections. Current 237Np evaluations available for transmuter system studies show significant discrepancies in both the fission and capture cross sections in the energy regions of interest. Herein we report on 237Np (n,{gamma}) measurements using the recently commissioned DANCE array.

  2. 237Np and 57Fe Mössbauer study of NpFeGa5

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Nakada, M.; Nakamura, A.; Nasu, S.; Aoki, D.; Sakai, H.; Ikeda, S.; Yamamoto, E.; Haga, Y.; Ōnuki, Y.; Shiokawa, Y.

    2006-02-01

    57Fe and 237Np Mössbauer Ōmeasurements have been performed for NpFeGa5, which is one of the so-called neptunium 1-1-5 compounds. The 57Fe Mössbauer spectra below T N = 118 K show the magnetically ordered state. The magnitude of the hyperfine magnetic field at the 57Fe nucleus is determined to be 1.98 ± 0.05 T at 10 K. From the 237Np Mössbauer spectrum at 10 K, the hyperfine magnetic field at the 237Np nucleus is 203 T and the hyperfine coupling constant is determined to be 237 T/μB using the Np atomic magnetic moment of 0.86 μB determined by the neutron diffraction study.

  3. 237Np and 57Fe Mdssbauer study of NpFeGa5

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Nakada, M.; Nakamura, A.; Nasu, S.; Aoki, D.; Sakai, H.; Ikeda, S.; Yamamoto, E.; Haga, Y.; Onuki, Y.; Shiokawa, Y.

    57Fe and 237Np Mössbauer Omeasurements have been performed for NpFeGa5, which is one of the so-called neptunium 1-1-5 compounds. The 57Fe Mössbauer spectra below T N=118 K show the magnetically ordered state. The magnitude of the hyperfine magnetic field at the 57Fe nucleus is determined to be 1.98 ± 0.05 T at 10K. From the 237Np Mössbauer spectrum at 10 K, the hyperfine magnetic field at the 237Np nucleus is 203 T and the hyperfine coupling constant is determined to be 237 T/μB using the Np atomic magnetic moment of 0.86 μB determined by the neutron diffraction study.

  4. Status of the Neutron Capture Measurement on 237Np with the DANCE Array at LANSCE

    NASA Astrophysics Data System (ADS)

    Esch, E.-I.; Alpizar-Vicente, A.; Bond, E. M.; Bredeweg, T. A.; Glover, S. E.; Greife, U.; Haight, R. C.; Hatarik, R.; Kronenberg, A.; O'Donnell, J. M.; Pitcher, E. J.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wender, S. A.; Wouters, J. M.

    2005-05-01

    Neptunium-237 is a major constituent of spent nuclear fuel. Estimates place the amount of 237Np bound for the Yucca Mountain high-level waste repository at 40 metric tons. The Department of Energy's Advanced Fuel Cycle Initiative program is evaluating methods for transmuting the actinide waste that will be generated by future operation of commercial nuclear power plants. The critical parameter that defines the transmutation efficiency of actinide isotopes is the neutron fission-to-capture ratio for the particular isotope in a given neutron spectrum. The calculation of transmutation efficiency therefore requires accurate fission and capture cross sections. Current 237Np evaluations available for transmuter system studies show significant discrepancies in both the fission and capture cross sections in the energy regions of interest. Herein we report on 237Np (n,γ) measurements using the recently commissioned DANCE array.

  5. Reliable determination of 237Np in environmental solid samples using 242Pu as a potential tracer.

    PubMed

    Qiao, Jixin; Hou, Xiaolin; Roos, Per; Miró, Manuel

    2011-04-15

    This paper reports an analytical method for rapid determination of neptunium ((237)Np) in environmental solid samples exploiting automated sequential injection (SI)-based anion exchange separation. Pivotal issues on analytical method performance were investigated including sorption behavior of (237)Np onto various AG 1-type anion exchangers; suitability of (242)Pu as a tracer for (237)Np determination in environmental solid samples; and long-term chemical stability of tetravalent Np. Experimental results revealed that the degree of resin cross-linking has a significant influence on the separation efficiency in terms of chemical yields of (237)Np and removal of interfering nuclides. Although ca. 30% of sorbed Np onto AG 1- × 4 was stripped out during HCl rinsing step for the removal of Th, chemical yield ratios of (237)Np to (242)Pu were proven steady with an average value of 0.67 ± 0.04 (n=15) under selected experimental conditions. Disulfite-8M HNO(3) was selected as a redox pair for valence adjustment to Np(IV) and the tetravalent Np in the sample solution was demonstrated to be stabilized for up to 5 days under 3°C. The analytical results for reference materials showed a good agreement with the expected values, thereby demonstrating the usefulness of (242)Pu as a non-isotopic tracer for (237)Np chemical yield monitoring. The on-column separation procedure fosters rapid analysis as required in emergency situations since each individual sample can be handled within 2.5h, and leads to a significant decrease in labor intensity compared to conventional batch-wise protocols.

  6. Analysis of the 237Np-233Pa photon spectrum using the full response function method.

    PubMed

    Shchukin, G; Iakovlev, K; Morel, J

    2004-01-01

    A study has been made of X- and gamma-ray emission from 237Np in equilibrium with 233Pa using the full response function method. This analysis process is characterised by photon spectrometry in which the entire spectrum is modelled in a pseudo-empirical way by means of elementary functions describing the total absorption and escape peaks, the Compton diffusion internal and external to the detector and the peaks resulting from detection of internal conversion electrons. This method has been applied to determine the L X-, K X- and gamma-rays emission probabilities in 237Np and 233Pa decay studies.

  7. Radiochemical determination of 237NP in soil samples contaminated with weapon grade plutonium

    NASA Astrophysics Data System (ADS)

    Antón, M. P.; Espinosa, A.; Aragón, A.

    2006-01-01

    The Palomares terrestrial ecosystem (Spain) constitutes a natural laboratory to study transuranics. This scenario is partially contaminated with weapon-grade plutonium since the burnout and fragmentation of two thermonuclear bombs accidentally dropped in 1966. While performing radiometric measurements in the field, the possible presence of 237Np was observed through its 29 keV gamma emission. To accomplish a detailed characterization of the source term in the contaminated area using the isotopic ratios Pu-Am-Np, the radiochemical isolation and quantification by alpha spectrometry of 237Np was initiated. The selected radiochemical procedure involves separation of Np from Am, U and Pu with ionic resins, given that in soil samples from Palomares 239+240Pu levels are several orders of magnitude higher than 237Np. Then neptunium is isolated using TEVA organic resins. After electrodeposition, quantification is performed by alpha spectrometry. Different tests were done with blank solutions spiked with 236Pu and 237Np, solutions resulting from the total dissolution of radioactive particles and soil samples. Results indicate that the optimal sequential radionuclide separation order is Pu-Np, with decontamination percentages obtained with the ionic resins ranging from 98% to 100%. Also, the addition of NaNO2 has proved to be necessary, acting as a stabilizer of Pu-Np valences.

  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. Spectral interference corrections for the measurement of (238)U in materials rich in thorium by a high resolution gamma-ray spectrometry.

    PubMed

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

    2009-11-01

    In this study, the spectral interferences are investigated for the analytical peaks at 63.3 keV of (234)Th and 1001.0 keV of (234m)Pa, which are often used in the measurement of (238)U activity by the gamma-ray spectrometry. The correction methods are suggested to estimate the net peak areas of the gamma-rays overlapping the analytical peaks, due to the contribution of (232)Th that may not be negligible in materials rich in natural thorium. The activity results for the certified reference materials (CRMs) containing U and Th were measured with a well type Ge detector. The self-absorption and true coincidence-summing (TCS) effects were also taken into account in the measurements. It is found that ignoring the contributions of the interference gamma-rays of (232)Th and (235)U to the mixed peak at 63.3 keV of (234)Th ((238)U) leads to the remarkably large systematic influence of 0.8-122% in the measured (238)U activity, but in case of ignoring the contribution of (232)Th via the interference gamma-ray at 1000.7 keV of (228)Ac to the mixed peak at 1001 keV of (234m)Pa ((238)U) results in relatively smaller systematic influence of 0.05-3%, depending on thorium contents in the samples. The present results showed that the necessary correction for the spectral interferences besides self-absorption and TCS effects is also very important to obtain more accurate (238)U activity results. Additionally, if one ignores the contribution of (232)Th to both (238)U and (40)K activities in materials, the maximum systematic influence on the effective radiation dose is estimated to be ~6% and ~1% via the analytical peaks at 63.3 and 1001 keV for measurement of the (238)U activity, respectively.

  10. Why are so many arc magmas close to 238U- 230Th radioactive equilibrium?

    NASA Astrophysics Data System (ADS)

    Condomines, Michel; Sigmarsson, Olgeir

    1993-09-01

    New analyses of 238U- 230Th disequilibria are reported for four active volcanoes: Merapi and Krakatoa in the Sunda arc (Indonesia), Masaya in Central America (Nicaragua), and Ambrym in the New Hebrides island arc. Despite a large range in ( 230Th /232Th ) ratios (from 0.65 in Merapi andesites to 2.5 in Masaya basalts), 238U and 230Th are close to radioactive equilibrium, as in many other arc magmas. In several mantle sources, Th/U ratios have clearly been modified by metasomatic processes associated with subduction. This is demonstrated in Central America by the correlation between ( 230Th /232Th ) and 10Be /9Be ratios for several active volcanoes along the arc. It is proposed that the 238U- 230Th radioactive equilibrium found in many arc magmas is the result of disequilibrium melting involving an easily melted, slab-derived, metasomatic component which dominates the uranium and thorium budget of the mantle sources. The departure from equilibrium may be either due to mixing with 230Th enriched melts derived from unmetasomatized mantle sources or to a late stage uranium addition by fluids. This latter process, producing uranium enriched magmas, has a greater influence in uranium and thorium poor magmas.

  11. Measurement of delayed-neutron yield from {sup 237}Np fission induced by thermal neutrons

    SciTech Connect

    Gundorin, N. A.; Zhdanova, K. V.; Zhuchko, V. E.; Pikelner, L. B. Rebrova, N. V.; Salamatin, I. M.; Smirnov, V. I.; Furman, V. I.

    2007-06-15

    The delayed-neutron yield from thermal-neutron-induced fission of the {sup 237}Np nucleus was measured using a sample periodically exposed to a pulsed neutron beam with subsequent detection of neutrons during the time intervals between pulses. The experiment was realized on an Isomer-M setup mounted in the IBR-2 pulsed reactor channel equipped with a mirror neutron guide. The setup and the experimental procedure are described, the background sources are thoroughly analyzed, and the experimental data are presented. The total delayed-neutron yield from {sup 237}Np fission induced by thermal neutrons is {nu}{sub d} = 0.0110 {+-} 0.0009. This study was performed at the Frank Laboratory of Neutron Physics (JINR, Dubna)

  12. 237Np Mössbauer studies on actinide superconductors and related materials

    NASA Astrophysics Data System (ADS)

    Colineau, Eric; Gaczyński, Piotr; Griveau, Jean-Christophe; Eloirdi, Rachel; Caciuffo, Roberto

    2012-03-01

    Actinide materials play a special role in condensed matter physics, spanning behaviours of itinerant d-electron and localized 4f-electron materials. This duality of the 5f electrons confer to actinide-based intermetallic compounds a broad variety of physical properties such as magnetic or multipolar ordering, heavy fermion behaviour, quantum criticality, unconventional superconductivity... 237Np Mössbauer spectroscopy is a unique microscopic tool for gaining information on the electronic and magnetic properties of Np systems.

  13. Standardization and photon emission probabilities in the decay of 237Np/233Pa

    PubMed

    Schotzig; Schonfeld; Janszen

    2000-04-01

    The activity concentration of a 237Np solution was determined by 4pialpha counting, by alpha particle spectroscopy with defined solid angle and by liquid scintillation counting (LSC). These methods yielded results which differ by less than 0.1% from the mean, the relative standard uncertainties being 0.23% (4pialpha), 0.27% (LSC) and 0.5% (solid angle). X-ray and gamma-ray emission probabilities of several transitions were measured using semiconductor detectors.

  14. Nuclear Resonance Fluorescence Measurements on ^237Np for Security and Safeguards Applications

    NASA Astrophysics Data System (ADS)

    Angell, C. T.; Joshi, T.; Yee, Ryan; Norman, E. B.; Kulp, W. D.; Warren, G. A.; Korbly, S.; Klimenko, A.; Wilson, C.; Copping, R.; Shuh, D. K.

    2009-10-01

    The smuggling of nuclear material and the diversion of fissile material for covert weapon programs both present grave risks to world security. Methods are needed to detect nuclear material smuggled in cargo, and for proper material accountability in civilian fuel re-processing facilities. Nuclear resonance fluorescence (NRF) is a technique that can address both needs. It is a non-destructive active interrogation method that provides isotope-specific information. It works by using a γ-ray beam to resonantly excite levels in a nucleus and observing the γ-rays emitted whose energy and intensity are characteristic of that isotope. ^237Np presents significant safeguard challenges; it is fissile yet currently has fewer safeguard restrictions. NRF measurements on ^237Np will expand the nuclear database and will permit designing interrogation and assay systems. Measurements were made using the bremsstrahlung beam at the HVRL at MIT on a 7 g target of ^237Np with two incident electron energies of 2.8 and 3.1 MeV. Results will be presented with discussion of the relevant nuclear structure necessary to predict levels in other actinides.

  15. Preparation of Microvolume Anion-Exchange Cartridge for Inductively Coupled Plasma Mass Spectrometry-Based Determination of (237)Np Content in Spent Nuclear Fuel.

    PubMed

    Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo; Saito, Kyoichi; Yamada, Shinsuke; Hirota, Hideyuki

    2016-03-15

    Microvolume anion-exchange porous polymer disk-packed cartridges were prepared for Am/Np separation, which is required prior to the measurement of Neptunium-237 ((237)Np) with inductively coupled plasma mass spectrometry (ICPMS). Disks with a volume of 0.08 cm(3) were cut out from porous sheets having anion-exchange-group-containing polymer chains densely attached on the pore surface. Four different amine-based groups, N,N-dimethylaminoethyl methacrylate, trimethylammonium, diethylamine, and triethylenediamine (TEDA), were selected as the anion-exchange groups to be introduced into the porous sheets. The separation performances of Am/Np were evaluated using a standard solution of (243)Am, which had the same activity as its daughter nuclide (239)Np in secular equilibrium. (239)Np recovery of close to 100% with practically no contamination of (243)Am was achieved using the TEDA-introduced disk-packed cartridge. The time to elute (239)Np from the cartridge was approximately 40 s. The TEDA-introduced disk-packed cartridge was applied to the separation of Np from a spent nuclear fuel sample to confirm its separation performance. A known amount of (243)Am ((239)Np) was added to the spent nuclear fuel sample solution to monitor the chemical yield of Np. The chemical yield of Np calculated from a measured concentration of (239)Np was 90.4%. Am leakage in the Np-eluted solution was less than 1 ppt, corresponding to 0.001% of the original Am concentration in the sample. This indicates that no additional (239)Np was produced by the decay of the (243)Am remaining in the Np-eluted solution, thus providing a reliable chemical yield. U, which can cause a serious spectral interference involving the peak tail from the mass spectrum of (238)U, was thoroughly removed with the TEDA cartridge, providing interference-free measurement of (237)Np. The concentration of (237)Np obtained by ICPMS was 718 ± 12 ng/mg-U, which agrees well with the theoretically calculated value. Compared with

  16. Pygmy dipole response in 238U nucleus

    NASA Astrophysics Data System (ADS)

    Guliyev, Ekber; Kuliev, Ali Akbar; Quliyev, Huseynqulu

    2017-02-01

    The presence of the El pygmy dipole resonance (PDR) in the actinide nucleus 238U was shown via QRPA. Below the particle threshold energy, 24 excitation states were calculated. The calculations, is demonstrating the presence of a PDR with evidence for K splitting. The calculations further suggest that the PDR in 238U is predominantly K=0. The obtained results show universality of the PDR in atomic nuclei.

  17. RAPID SEPARATION METHOD FOR 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES

    SciTech Connect

    Maxwell, S.; Culligan, B.; Noyes, G.

    2010-07-26

    A new rapid method for the determination of {sup 237}Np and Pu isotopes in soil and sediment samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for large soil samples. The new soil method utilizes an acid leaching method, iron/titanium hydroxide precipitation, a lanthanum fluoride soil matrix removal step, and a rapid column separation process with TEVA Resin. The large soil matrix is removed easily and rapidly using this two simple precipitations with high chemical recoveries and effective removal of interferences. Vacuum box technology and rapid flow rates are used to reduce analytical time.

  18. (237)Np(n,f) Cross Section: New Data and Present Status

    SciTech Connect

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

    2011-01-01

    In this document, we present the final result obtained at the n-TOF experiment for the neutron-induced fission cross section of the {sup 237}Np, from the fission threshold up to 1 GeV. The method applied to get this result is briefly discussed. n-TOF data are compared to the last experimental measurements using other TOF facilities or the surrogate method, reported experiments performed with monoenergetic sources and the FISCAL systematic, including a discussion about the existing discrepancies.

  19. Fission Product Yields from 232Th, 238U, and 235U Using 14 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Pierson, B. D.; Greenwood, L. R.; Flaska, M.; Pozzi, S. A.

    2017-01-01

    Neutron-induced fission yield studies using deuterium-tritium fusion-produced 14 MeV neutrons have not yet directly measured fission yields from fission products with half-lives on the order of seconds (far from the line of nuclear stability). Fundamental data of this nature are important for improving and validating the current models of the nuclear fission process. Cyclic neutron activation analysis (CNAA) was performed on three actinide targets-thorium-oxide, depleted uranium metal, and highly enriched uranium metal-at the University of Michigan's Neutron Science Laboratory (UM-NSL) using a pneumatic system and Thermo-Scientific D711 accelerator-based fusion neutron generator. This was done to measure the fission yields of short-lived fission products and to examine the differences between the delayed fission product signatures of the three actinides. The measured data were compared against previously published results for 89Kr, -90, and -92 and 138Xe, -139, and -140. The average percent deviation of the measured values from the Evaluated Nuclear Data Files VII.1 (ENDF/B-VII.1) for thorium, depleted-uranium, and highly-enriched uranium were -10.2%, 4.5%, and -12.9%, respectively. In addition to the measurements of the six known fission products, 23 new fission yield measurements from 84As to 146La are presented.

  20. 238U, 232Th profiling and U-series isotope analysis of fossil teeth by laser ablation-ICPMS

    NASA Astrophysics Data System (ADS)

    Eggins, Stephen; Grün, Rainer; Pike, Alistair W. G.; Shelley, Michael; Taylor, Lois

    2003-05-01

    U and Th concentration profiles in fossil hominid and faunal teeth have been measured by laser ablation ICPMS. These profiles record diverse modes of U and Th uptake, particularly within enamel, that can be broadly related to the state of sample preservation. Observed U profiles are in general inconsistent with existing diffusion-adsorption models developed for U-uptake in bone and teeth. Where the models appear applicable, calculated diffusion rates are several orders of magnitude smaller than previous estimates. Laser ablation ICPMS offers a means of rapidly characterizing U and Th distributions in the enamel and dentine components of teeth as a precursor to ESR and U-series dating. In particular, it should allow the identification of teeth (and also bone) samples that have simple U-uptake histories and are amenable to precise dating by time-consuming and expensive Th-U and Pa-U TIMS techniques. We also demonstrated the use of laser ablation ICPMS to measure U-series isotopes in dentine and enamel samples with relatively high U concentrations (>20 ppm). These results, obtained using a quadrupole ICPMS, illustrate significant promise for in situ U-series isotope analysis, particularly when combined with the greater sensitivity and multi-collection capabilities of new sector ICPMS instrumentation. The latter may permit precise isotope ratio measurements on samples containing only a few ppm of U.

  1. (237)Np Mössbauer effect study on NpFeAsO.

    PubMed

    Gaczyński, P; Klimczuk, T; Walker, H; Springell, R; Colineau, E; Eloirdi, R; Griveau, J-C; Caciuffo, R

    2014-04-16

    We report (237)Np Mössbauer measurements on NpFeAsO. The Np atoms were found to occupy only one crystallographic site. The value of the isomer shift (δ ∼ 9.1 mm s(-1) versus NpAl2) indicates a 5f(4) electronic configuration (Np(3+) ions). The magnetic ordering of the Np sublattice below 60 K is established and the saturated ordered magnetic moment is determined to be 1.73μB at 3.6 K. The unique set of hyperfine parameters exclude a modulated magnetic structure or spin waves on the Np site. The neptunium magnetic moments μNp are found to lie along the tetragonal c-axis.

  2. 237Np Mössbauer spectroscopy on neptunium doped borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Bogé, M.; Blaise, A.; Bonnisseau, D.; Fournier, J. M.; Thérond, P. G.; Poirot, I.; Beauvy, M.

    1986-02-01

    Mössbauer and magnetization measurements have been carried out on borosilicate glasses containing neptunium. Different melting and annealing times, in various crucibles have been investigated. Using the 59.5 keV Mössbauer resonance in237Np we have characterized valency states of neptunium ions in glasses and studied hyperfine interactions. Roughly, absorption spectra show two sites easily differenciated above 50 K by two lines. Isomer shifts (relative to NpAl2) are respectively: - 10.0 (1.0) and + 32.5(.5) mm/s. These resonance lines can be assigned, the first at Np4+, the second at Np3+ species. The intensity ratio Np4+/Np3+ varies with elaboration conditions. At 4.2 K, Np4+ ions exhibit a hyperfine splitting arising from relaxation phenomenon. Magnetization measurements do not show any magnetic ordering.

  3. Role of transitional levels in {sup 237}Np ({gamma},f): Perspectives for studying highly deformed systems

    SciTech Connect

    Arruda-Neto, J. D. T.; Garcia, F.; Rodriguez, O.; Geraldo, L. P.; Rodrigues, T. E.; Shtejer, K.; Semmler, R.

    2006-09-15

    The transition levels at the top of the two {sup 237}Np fission barriers were obtained for the first time by means of the so-called semimicroscopic combined method, which we have developed and implemented. To overcome the difficulties in dealing with large nuclear deformations, we used our developed BARRIER code, which calculates single-particle spectra in a deformed Woods-Saxon potential using a coordinate system based on Cassini ovaloids as nuclear shape parametrization. The results enabled us to describe the experimentally observed near-barrier photofission cross-section structures for {sup 237}Np, as well as a subbarrier shelf, the latter being consistently interpreted in terms of the accumulation of levels at the top of the inner and outer double fission barrier of {sup 237}Np.

  4. Coulomb excitation of states in 232Th

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1993-09-01

    Twenty-five states in 232Th have been observed with 18 MeV 4He ions on a thick target. Eleven 2 + states between 774 and 1554 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and/or populated by the decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.024 to 3.5 W.u. (222 W.u. for the first 2 + state). For the 3 - states, the B(E3,0 → 3 -) values are 1.7, 11, and 24 W.u. A possible two-phonon state at 1554 keV, which is nearly harmonic, decays to four members of the one-phonon states, to the ground-state band, and to the K = 0 - octupole band. The B(E2) value for excitation of this state is 0.66 ± 0.05 W.u. and the B(E1) values for decay of this state are (2 and 6)×10 -4 W.u. The B(E2) values between two- and one-phonon vibrational states range between 16 and 53 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if this 2 + state is considered to be a collective two-phonon excitation. The 2 + states at 1477 and 1387 keV, which are also nearly harmonic, are possible candidates with two-phonon structure. The agreement between the experimental results and the microscopic calculations by Neergård and Vogel of the B(E3,0 → 3) for the 3 - members of the one-phonon octupole quadruplet is satisfactory when the Coriolis coupling between the states with K and K ± 1 is included. The B(E1) branching ratios for transitions from the 3 - and 1 - states to the ground-state band have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the octupole quadruplet in deformed nuclei.

  5. Lung carcinogenesis in rats after inhalation exposure to (237)NpO2.

    PubMed

    Dudoignon, N; Guézingar-Liébard, F; Guillet, K; L'Hullier, I; Rateau, G; Monchaux, G; Fritsch, P

    1999-12-01

    The results of several studies of experimental carcinogenesis suggest that, after inhalation of alpha-particle emitters, lung tumor incidence varies depending on the exposure rate and dose distribution in the tissue. In the case of transuranics, the main influencing factor would be the specific alpha-particle activity of the inhaled actinide. To confirm these results, long-term studies were performed using male Sprague-Dawley rats exposed to (237)NpO(2) by inhalation. The initial lung burdens of the animals ranged from 0. 1 to about 7 kBq. The rats were followed during their life span and weighed regularly, and their lung burdens were determined in vivo and at death to estimate the lung dose. At death, the incidence of lung tumors and their malignancy and histological types were analyzed. The analysis revealed a typically linear-quadratic dose response for incidence of malignant lung neoplasm and a differential dose response for various types of tumors. Although these results confirm the influence of the activity of the inhaled actinide oxide, further experiments are needed to be able to compare a more homogeneous population of animals.

  6. Measurement and resonance analysis of the 237Np neutron capture cross section

    NASA Astrophysics Data System (ADS)

    Guerrero, C.; Cano-Ott, D.; Mendoza, E.; Abbondanno, U.; Aerts, G.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Becvár, F.; Belloni, F.; Berthoumieux, E.; Calviño, F.; Calviani, M.; Capote, R.; Carrapiço, C.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Dolfini, R.; Domingo-Pardo, C.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Goncalves, I.; González-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Ketlerov, V.; Kerveno, M.; Koehler, P.; Konovalov, V.; Kossionides, E.; Krtička, M.; Lampoudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lossito, R.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Martínez, T.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vicente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2012-04-01

    The neutron capture cross section of 237Np was measured between 0.7 and 500 eV at the CERN n_TOF facility using the 4π BaF2 Total Absorption Calorimeter. The experimental capture yield was extracted minimizing all the systematic uncertainties and was analyzed together with the most reliable transmission data available using the sammy code. The result is a complete set of individual as well as average resonance parameters [D0=0.56(2) eV, <Γγ>=40.9(18) meV, 104S0=0.98(6), R'=9.8(6) fm]. The capture cross section obtained in this work is in overall agreement with the evaluations and the data of Weston and Todd [Nucl. Sci. Eng. 79, 184 (1981)], thus showing sizable differences with respect to previous data from Scherbakov [J. Nucl. Sci. Technol. 42, 135 (2005)] and large discrepancies with data Kobayashi [J. Nucl. Sci. Technol.JNSTAX0022-313110.3327/jnst.39.111 39, 111 (2002)]. The results indicate that a new evaluation combining the present capture data with reliable transmission data would allow reaching an accuracy better than 4%, in line with the uncertainty requirements of the nuclear data community for the design and operation of current and future nuclear devices.

  7. Radium-226, 232Th, and 40K distribution in the environment of Kaiga of south west coast of India.

    PubMed

    Karunakara, N; Somashekarappa, H M; Avadhani, D N; Mahesh, H M; Narayana, Y; Siddappa, K

    2001-05-01

    Systematic studies on gamma radiation level and the distribution of natural radionuclides were carried out under a pre-operational survey for the establishment of baseline data on background radiation level and the distribution of radio-nuclides in the environment of Kaiga, in the south west coast of India, where a nuclear power reactor of 235 MWe has just been commissioned. The external gamma absorbed dose rates prevailing in the region were measured using a portable plastic scintillometer. Soil samples from 18 stations were collected from depth intervals of 0-5, 5-10, and 10-25 cm and analyzed for their 226Ra, 232Th, and 40K activity concentrations by gamma spectrometry employing a 90 cc PGT HpGe detector coupled to an EG&G ORTEC 8K multichannel analyzer. The activity of 226Ra was found to vary between 15.5-61.2 Bq kg(-1) with a mean value of 31.3 Bq kg(-1), that of 232Th varies between 11.4-41.9 Bq kg(-1) with a mean value of 27.5 Bq kg(-1) and of 40K between 78.3-254.8 Bq kg(-1) with a mean value of 159.9 Bq kg(-1) in 0-5 cm soil profiles of the region. The contributions of 238U, 232Th, and 40K to the total gamma absorbed dose rate were 39.9%, 40.7%, and 16.0%, respectively. The gamma absorbed dose rate in air estimated using the results of activity concentration of 226Ra, 232Th, and 40K are found to compare well with that of the direct measurement. The results of the study were compared with the literature values reported for other environs of the country as well as the world, and conclusions are drawn.

  8. Effect of DTPA on concentration ratios of /sup 237/Np and /sup 244/Cm in vegetative parts of bush bean and barley

    SciTech Connect

    Romney, E.M.; Wallace, A.; Mueller, R.T.; Cha, J.W.; Wood, R.A.

    1981-07-01

    We grew bush beans, barley, and rice in two different soils in a glasshouse with /sup 237/Np or /sup 244/Cm mixed into separate containers of the soil. The chelating agent DTPA at 100 ..mu..g/g soil was added to half of the containers. The concentration ratio (CR) for /sup 237/Np without DTPA was two orders of magnitude higher than for /sup 244/Cm without DTPA for all three plant species. The DTPA increased the CR of /sup 244/Cm by two to three orders of magnitude, but had no influence on that for /sup 237/Np. In bush beans, both /sup 237/Np and /sup 244/Cm CRs were higher in primary leaves than in trifoliate leaves, which were higher than for stems. The CRs for bush beans were generally higher for both /sup 237/Np and /sup 244/Cm than for either barley or rice, especially without DTPA.

  9. 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.

  10. Measurement of 226Ra, 232Th, 137Cs and 40K activities of Wheat and Corn Products in Ilam Province – Iran and Resultant Annual Ingestion Radiation Dose

    PubMed Central

    CHANGIZI, Vahid; SHAFIEI, Elham; ZAREH, Mohammad Reza

    2013-01-01

    Background: Background: Natural background radiation is the main source of human exposure to radioactive material. Soils naturally have radioactive mineral contents. The aim of this study is to determine natural (238 U, 232 Th, 40 K) and artificial (137 Cs) radioactivity levels in wheat and corn fields of Eilam province. Methods: HPGe detector was used to measure the concentration activity of 238 U and 232 Th series, 40 K and 137 Cs in wheat and corn samples taken from different regions of Eilam province, in Iran. Results: In wheat and corn samples, the average activity concentrations of 226 Ra, 232 Th, 40 K and 137 Cs were found to be 1, 67, 0.5, 91.73, 0.01 and 0.81, 0.85, 101.52, 0.07 Bq/kg (dry weight), respectively. H ex and H in in the present work are lower than 1. The average value of H ex was found to be 0.02 and 0.025 and average value of H in to be found 0.025 and 0.027 in wheat fields samples and corn samples in Eilam provinces, respectively. The obtained values of AGDE are 30.49 mSv/yr for wheat filed samples and 37.89 mSv/yr for corn samples; the AEDE rate values are 5.28 mSv/yr in wheat filed samples and this average value was found to be 6.13 mSv/yr in corn samples in Eilam. Transfer factors (TFs) of long lived radionuclide such as 137 Cs, 226 Ra, 232 Th and 40 K from soils to corn and wheat plants have been studied by radiotracer experiments. Conclusion: The natural radioactivity levels in Eilam province are not at the range of high risk of morbidity and are under international standards. PMID:26056646

  11. Natural radioactivity (226Ra, 232Th and 40K) and assessment of radiological hazards in the Kestanbol granitoid, Turkey.

    PubMed

    Canbaz, Buket; Cam, N Füsun; Yaprak, Günseli; Candan, Osman

    2010-09-01

    The surveys of natural gamma-emitting radionuclides in rocks and soils from the Ezine plutonic area were conducted during 2007. Direct dose measurement using a survey meter was carried out simultaneously. The present study, which is part of the survey, analysed the activity concentrations of (238)U, (232)Th and (40)K in granitoid samples from all over the region by HPGe gamma spectrometry. The activity concentrations of (226)Ra ranged from 94 to 637 Bq kg(-1), those of (232)Th ranged from 120 to 601 Bq kg(-1)and those of (40)K ranged from 1074 to 1527 Bq kg(-1) in the analysed rock samples from different parts of the pluton. To evaluate the radiological hazard of the natural radioactivity in the samples, the absorbed dose rate (D), the annual effective dose rate, the radium equivalent activity (Ra(eq)) and the external (H(ex)) hazard index were calculated according to the UNSCEAR 2000 report. The thorium-to-uranium concentration ratios were also estimated.

  12. Actinides produced by /sup 12/C + /sup 242/Pu and /sup 16/O + /sup 238/U reactions

    SciTech Connect

    Shinohara, N.; Usuda, S.; Ichikawa, S.; Suzuki, T.; Magara, M.; Okashita, H.; Yoshikawa, H.; Horiguchi, T.; Iwata, Y.; Shibata, S.; and others

    1986-09-01

    The cross sections for /sup 250/Fm, /sup 244-246/Cf, /sup 242-244/Cm, and /sup 242/Am/sup g-italic/ produced by the /sup 12/C+ /sup 242/Pu and the /sup 16/O+ /sup 238/U reactions leading to the same compound nucleus of /sup 254/Fm have been measured by using radiochemical methods. The excitation functions show that the difference between the /sup 12/C+ /sup 242/Pu and the /sup 16/O+ /sup 238/U reactions can be attributed mainly to the Coulomb barriers. Our results were compared with others reported previously for /sup 22/Ne+ /sup 232/Th, /sup 12/C+ /sup 238/U, /sup 12/C+ /sup 240,241/Pu, /sup 13/C+ /sup 241/Pu, /sup 16/O+ /sup 233/U, and /sup 16/O+ /sup 242/Pu reaction systems, and support a mechanism involving transfer of ..cap alpha..-particle clusters (C,Be,He) from projectile to target for the production of Cf and Cm isotopes.

  13. High-Resolution Study of 237Np Fission Cross Section from 5 eV to 1 MeV

    NASA Astrophysics Data System (ADS)

    Furman, W.; Cennini, P.; Ketlerov, V.; Goverdovski, A.; Konovalov, V.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Bec̆vár̆, F.; Benlliure, J.; Berthoumieux, E.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrillo de Albornoz, A.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Cortina, D.; Couture, A.; Cox, J.; David, S.; Dolfini, R.; Domingo-Pardo, C.; Dorochenko, A.; Dridi, W.; Duran, I.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Guerrero, C.; Goncalves, I.; Gallino, R.; Gonzalez-Romero, E.; Gramegna, F.; Griesmayer, E.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karamanis, D.; Karadimos, D.; Kerveno, M.; Koehler, P.; Kolokolov, D.; Kossionides, E.; Krtička, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Sedysheva, M.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Wendler, H.; Wiescher, M.; N Tof Collaboration

    2005-05-01

    A series of measurements of 237Np fission cross section have been performed at the CERN spallation neutron facility n_TOF which covers a wide energy range from 1 eV up to 250 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with registration efficiency of not less than 97 %. Particular attention was paid to correct the fission cross section with use of 235U standard. Total experimental uncertainties are determined to be at the level of 3%. Analysis of the experimental data in the restricted neutron energy from 5 eV up to 1 MeV showed a systematic deviation from evaluated data (ENDF/B-VI). This discrepancy amounts to up to a factor 3 for resolved resonances in the neutron energy range of 5 eV - 2 KeV, and is in good agreement with some previous experiments. A similar disagreement at the level of 6-7% was found for higher energies around the threshold (En = 300 keV-1 MeV). This energy range is essential for the transmutation of neptunium in ADS or fast reactors. It is concluded that an updated evaluation of nuclear data for 237Np is required.

  14. Dating open systems by the 238U- 234U- 230Th method: application to Quaternary reef terraces

    NASA Astrophysics Data System (ADS)

    Villemant, B.; Feuillet, N.

    2003-05-01

    The sedimentation conditions and diagenetic processes of biogenic and inorganic carbonates are such that the assumptions of a closed system evolution and the absence of initial Th invoked in classical 238U- 234U- 230Th dating methods are very often not fulfilled for such material. This problem is of interest for all studies requiring accurate dating of corals or aragonite-rich sediments as in palaeoclimatology or neotectonics. Extending the approach of Henderson and Slowey [Nature 404 (2000) 61-66], we propose a consistent model that takes into account possible initial 230Th excess and where continuous selective redistribution (gain or loss) of 234U, 234Th and 230Th is controlled by recoil processes. This model applied to Quaternary marine terraces in Barbados, Marie Galante (Lesser Antilles arc) and Pacific islands, is able to explain the large scatter in isotopic compositions observed in the series of cogenetic corals or sediments. We show that recoil processes generally tend to increase the ( 234U/ 238U) and ( 230Th/ 234U) ratios with time, leading to an overestimation of the apparent ages calculated using classical methods. On the basis of simple assumptions (identical 'marine' initial ( 234U/ 238U) 0 and ( 230Th/ 232Th) 0 ratios), we propose a method for calculating a best estimate of the age of cogenetic series. Our model offers an alternative way to date old reef terraces where corals are almost systematically altered and where classical dating methods do not apply. It may also explain the apparent variations of the ( 234U/ 238U) seawater initial ratio estimated from corals formed in the last 300 ka and the apparent uncoupling between sea-level highstands and high-latitude Northern Hemisphere summer insolation. Our set of equations can be applied to all weathering processes where the mobility of U-series isotopes is controlled by recoil.

  15. Coulomb excitation of states in 238U

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1994-05-01

    Twenty-two states in 238U have been observed with 18 MeV 4He ions on a thick target. Eight 2 + states between 966 and 1782 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and /or populated by the γ-ray decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.10 to 3.0 W.u. (281 W.u. for the first 2 + state). For the 3 states, the B(E3, 0 → 3 -) values are 7.1, 7.8, and 24.2 W.u. Several of the 2 + states have decay branches to the one-phonon states with B(E2) values between 27 and 56 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if these 2 + states are considered to be collective two-phonon excitations. However, the excitation energies of these 2 + states with respect to the one-phonon states are only 1.3 to 1.6. The B(E1) values for 17 transitions between the positive- and negative-parity states range between 10 -3 and 10 -7 W.u. The B(E1) branching ratios for many of these transitions have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the one-phonon octupole quadruplet in deformed nuclei. The general features of the experimental results for the B(E3) values are reproduced by the microscopic calculations of Neergård and Vogel when the Coriolis coupling between the states of the octupole quadruplet is included.

  16. Coulomb Excitation and Few Nucleon Transfer Reactions with ^209Bi Beams on ^237Np and ^241Am Targets

    NASA Astrophysics Data System (ADS)

    Abu Saleem, K.; Janssens, R. V. F.; Carpenter, M. P.; Kondev, F. G.; Ahmad, I.; Greene, J. P.; Caggiano, J.; Heinz, A.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Seweryniak, D.; Sonzogni, A.; Wiedenhoever, I.; Hackman, G.; Chowdhury, P.; Cline, D.; Wu, C.; Machiavelli, A. O.; Devlin, M.; Fotiades, N.; Seabury, E. H.

    2002-10-01

    Two separate Coloumb excitation measurements have been performed at ATLAS using Pb beams, at bombarding energies ˜ 15% above the Coulomb barrier, incident upon ^237Np and ^241Am targets. Using these reactions, γ-ray coincidence data were collected with the Gammasphere array. In both measurements, rotational bands built on a πi_13/2 configuration were observed to high-spin in the target nuclei. From these new data and those available for even- and odd-A U and Pu isotopes, we have concluded that the i_13/2 quasiprotons dominate the observed alignments in this mass region and that there is little contribution from aligning j_15/2 neutron pairs. This is unexpected based on Cranked Shell Model predictions which indicate that both quasiparticle pairs should be involved in the observed alignment processes.

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

    SciTech Connect

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

    1998-03-01

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

  18. Rapid determination of (237)Np in soil samples by multi-collector inductively-coupled plasma mass spectrometry and gamma spectrometry.

    PubMed

    Yi, Xiaowei; Shi, Yanmei; Xu, Jiang; He, Xiaobing; Zhang, Haitao; Lin, Jianfeng

    A radiochemical procedure is developed for the determination of (237)Np in soil with multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) and gamma-spectrometry. (239)Np (milked from (243)Am) was used as an isotopic tracer for chemical yield determination. The neptunium in the soil is separated by thenoyl-trifluoracetone extraction from 1 M HNO3 solution after reducing Np to Np(IV) with ferrous sulfamate, and then purified with Dowex 1 × 2 anion exchange resin. (239)Np in the resulting solution is measured with gamma-spectrometry for chemical yield determination while the (237)Np is measured with MC-ICP-MS. Measurement results for soil samples are presented together with those for two reference samples. By comparing the determined value with the reference value of the (237)Np activity concentration, the feasibility of the procedure was validated.

  19. 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.

  20. Geochronology and petrogenesis of MORB from the Juan de Fuca and Gorda ridges by 238U230Th disequilibrium

    USGS Publications Warehouse

    Goldstein, S.J.; Murrell, M.T.; Janecky, D.R.; Delaney, J.R.; Clague, D.A.

    1991-01-01

    A highly precise mass spectrometric method of analysis was used to determine 238U234U230Th232Th in axial and off-axis basalt glasses from Juan de Fuca (JDF) and Gorda ridges. Initial 230Th activity excesses in the axial samples range from 3 to 38%, but generally lie within a narrow range of 12 to 15%. Secondary alteration effects were evaluated using ??234U and appear to be negligible; hence the 230Th excesses are magmatic in origin. Direct dating of MORB was accomplished by measuring the decrease in excess 230Th in off-axis samples. 238U230Th ages progressively increase with distance from axis. Uncertainties in age range from 10 to 25 ka for UTh ages of 50 to 200 ka. The full spreading rate based on UTh ages for Endeavour segment of JDF is 5.9 ?? 1/2 cm/yr, with asymmetry in spreading between the Pacific (4.0 ?? 0.6 cm/yr) and JDF (1.9 ?? 0.6 cm/yr) plates. For northern Gorda ridge, the half spreading rate for the JDF plate is found to be 3.0 ?? 0.4 cm/yr. These rates are in agreement with paleomagnetic spreading rates and topographic constraints. This suggests that assumptions used to determine ages, including constancy of initial 230Th 232Th ratio over time, are generally valid for the areas studied. Samples located near the axis of spreading are typically younger than predicted by these spreading rates, which most likely reflects recent volcanism within a 1-3 km wide zone of crustal accretion. Initial 230Th/232Th ratios and 230Th activity were also used to examine the recent Th/U evolution and extent of melting of mantle sources beneath these ridges. A negative anomaly in 230Th 232Th for Axial seamount lavas provides the first geochemical evidence of a mantle plume source for Axial seamount and the Cobb-Eickelberg seamount chain and indicates recent depletion of other JDF segment sources. Large 230Th activity excesses for lavas from northern Gorda ridge and Endeavour segment indicate formation from a lower degree of partial melting than other segments. An

  1. Correction methodology for the spectral interfering γ-rays overlapping to the analytical peaks used in the analysis of 232Th.

    PubMed

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

    2011-06-01

    In the γ-ray spectrometric analysis of the radionuclides, a correction factor is generally required for the spectral interfering γ-rays in determining the net areas of the analytical peaks because some interfering γ-rays often might contribute to the analytical peaks of interest. In present study, a correction methodology for the spectral interfering γ-rays (CSI) is described. In particular, in the analysis of (232)Th contained in samples, the interfering γ-rays due to (226)Ra, (235)U, (238)U and their decay products often overlap to the peaks of interest from (232)Th decay products, and vise versa. For the validation of the proposed CSI method, several certified reference materials (CRM) containing U and Th were measured by using a 76.5% efficient n-type Ge detector. The required correction factors were quantified for spectral interference, self-absorption and true coincidence summing (TCS) effects for the relevant γ-rays. The measured results indicate that if one ignores the contributions of the interfering γ-rays to the analytical peaks at 583.2 keV of (208)Tl and 727.3 keV of (212)Bi, this leads to a significantly systematic influence on the resulted activities of (232)Th. The correction factors required for spectral interference and TCS effects are estimated to be ∼13.6% and ∼15.4% for 583.2 keV peak. For the 727.3 keV peak, the correction factor is estimated to be ∼15% for spectral interference, and ∼5% for the TCS effects at the presently used detection geometry. On the other hand, the measured results also indicate that ignoring the contribution of the interfering γ-rays to the areas of the analytical peaks at 860.6 keV of (208)Tl, 338.3 and 911.2 keV of (228)Ac does not lead to any significant systematic influence on the (232)Th analysis. Because these factors are remained generally less than ∼5%, i.e., within overall uncertainty limits. The present study also showed that in view of both the spectral interference and TCS effects, the

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

    PubMed

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

    2013-01-01

    Uranium and thorium isotopes from sludge samples taken from an area of influence of a dicalcium phosphate factory, located close to the Ebro River reservoir in Flix, and from mineral raw materials (coal and phosphate) which were deposited in Tarragona Harbour (Catalonia) have been measured. To do that, several procedures to determine these isotopes have been applied and compared in terms of accuracy, precision and total analysis time. In particular, digestion procedures, such as one based on conventional acidic digestion or another based on the use of microwave digestion, have been tested. Moreover, different radiochemical separation procedures have been applied. In this regard, one method based on liquid-liquid extraction using TBP/Xylene and another based on the use of extraction chromatography using UTEVA resins have been compared. Firstly, the different proposed methods were tested by analyzing a phosphogypsum sediment and a moss-soil sample from two different intercomparison exercises. The microwave digestion - UTEVA method provided the best results (recoveries higher than 82% for uranium and thorium isotopes) and was then applied to the NORM samples. The obtained results showed that the higher uranium and thorium activities values were found in phosphate raw material and in the more superficial samples located in sludge sediments next to the dicalcium phosphate factory. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Concurrent determination of 237Np and Pu isotopes using ICP-MS: analysis of NIST environmental matrix standard reference materials 4357, 1646a, and 2702.

    PubMed

    Matteson, Brent S; Hanson, Susan K; Miller, Jeffrey L; Oldham, Warren J

    2015-04-01

    An optimized method was developed to analyze environmental soil and sediment samples for (237)Np, (239)Pu, and (240)Pu by ICP-MS using a (242)Pu isotope dilution standard. The high yield, short time frame required for analysis, and the commercial availability of the (242)Pu tracer are significant advantages of the method. Control experiments designed to assess method uncertainty, including variation in inter-element fractionation that occurs during the purification protocol, suggest that the overall precision for measurements of (237)Np is typically on the order of ± 5%. Measurements of the (237)Np concentration in a Peruvian Soil blank (NIST SRM 4355) spiked with a known concentration of (237)Np tracer confirmed the accuracy of the method, agreeing well with the expected value. The method has been used to determine neptunium and plutonium concentrations in several environmental matrix standard reference materials available from NIST: SRM 4357 (Radioactivity Standard), SRM 1646a (Estuarine Sediment) and SRM 2702 (Inorganics in Marine Sediment). Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. 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)..

  5. Neutron-induced transmutation reactions in 237Np, 238Pu, and 239Pu at the massive natural uranium spallation target

    NASA Astrophysics Data System (ADS)

    Zavorka, L.; Adam, J.; Baldin, A. A.; Caloun, P.; Chilap, V. V.; Furman, W. I.; Kadykov, M. G.; Khushvaktov, J.; Pronskikh, V. S.; Solnyshkin, A. A.; Sotnikov, V.; Stegailov, V. I.; Suchopar, M.; Tsoupko-Sitnikov, V. M.; Tyutyunnikov, S. I.; Voronko, V.; Vrzalova, J.

    2015-04-01

    Transmutation reactions in the 237Np, 238Pu, and 239Pu samples were investigated in the neutron field generated inside a massive (m = 512 kg) natural uranium spallation target. The uranium target assembly QUINTA was irradiated with the deuteron beams of kinetic energy 2, 4, and 8 GeV provided by the Nuclotron accelerator at the Joint Institute for Nuclear Research (JINR) in Dubna. The neutron-induced transmutation of the actinide samples was measured off-line by implementing methods of gamma-ray spectrometry with HPGe detectors. Results of measurement are expressed in the form of both the individual reaction rates and average fission transmutation rates. For the purpose of validation of radiation transport programs, the experimental results were compared with simulations of neutron production and distribution performed by the MCNPX 2.7 and MARS15 codes employing the INCL4-ABLA physics models and LAQGSM event generator, respectively. In general, a good agreement between the experimental and calculated reaction rates was found in the whole interval of provided beam energies.

  6. Measurement of 232Th(n,5n γ) cross sections from 29 MeV to 42 MeV

    NASA Astrophysics Data System (ADS)

    Kerveno, M.; Nolte, R.; Baumann, P.; Dessagne, Ph.; Jericha, E.; Jokic, S.; Koning, A. J.; Lukic, S.; Meulders, J. P.; Nachab, A.; Pavlik, A.; Reginatto, M.; Rudolf, G.

    2014-10-01

    The excitation function of the reaction 232 Th( n, 5 nγ)228 Th from 29 to 42 MeV has been measured for the first time at the quasi-monoenergetic neutron beam of the UCL cyclotron CYCLONE employing the 7Li(p,n) source reaction. Taking advantage of the good energy resolution of the planar High-Purity Germanium (HPGe) detectors, prompt γ-ray spectroscopy was used to detect the γ-rays resulting from the decay of excited states of nuclei created by the (n, xn) reactions. The neutron beam was characterized by a combination of time of flight measurements carried out using a liquid scintillation detector and a 238U fission ionization chamber. Fluence measurements were performed using a proton recoil telescope. The results are compared with TALYS-1.4 code calculations.

  7. Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the 18O + 232Th reaction

    NASA Astrophysics Data System (ADS)

    Léguillon, R.; Nishio, K.; Hirose, K.; Makii, H.; Nishinaka, I.; Orlandi, R.; Tsukada, K.; Smallcombe, J.; Chiba, S.; Aritomo, Y.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.; Tamura, N.; Goto, S.; Tsekhanovich, I.; Petrache, C. M.; Andreyev, A. N.

    2016-10-01

    It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O + 232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.

  8. Proton induced fission of 232Th at intermediate energies

    NASA Astrophysics Data System (ADS)

    Gikal, K. B.; Kozulin, E. M.; Bogachev, A. A.; Burtebaev, N. T.; Edomskiy, A. V.; Itkis, I. M.; Itkis, M. G.; Knyazhev, G. N.; Kovalchuk, K. V.; Kvochkina, T. N.; Piasecki, E.; Rubchenya, V. A.; Sahiev, S. K.; Trzaska, W. H.; Vardaci, E.

    2016-12-01

    The mass-energy distributions and cross sections of proton-induced fission of 232Th have been measured at the proton energies of 7, 10, 13, 20, 40, and 55 MeV. Experiments were carried out at the proton beam of the K-130 cyclotron of the JYFL Accelerator Laboratory of the University of Jyväskylä and U-150m cyclotron of the Institute of Nuclear Physics, Ministry of Energy of the Republic of Kazakhstan. The yields of fission fragments in the mass range A = 60-170 a.m.u. have been measured up to the level of 10-4%. The three humped shape of the mass distribution up has been observed at higher proton energies. The contribution of the symmetric component grows up with increasing proton incident energy; although even at 55 MeV of proton energy the shoulders in the mass energy distribution clearly indicate the asymmetric fission peaks. Evolution of shell structure was observed in the fission fragment mass distributions even at high excitation energy.

  9. Proton induced fission of {sup 232}Th at intermediate energies

    SciTech Connect

    Gikal, K. B. Kozulin, E. M.; Bogachev, A. A.; Burtebaev, N. T.; Edomskiy, A. V.; Itkis, I. M.; Itkis, M. G.; Knyazhev, G. N.; Kovalchuk, K. V.; Kvochkina, T. N.; Piasecki, E.; Rubchenya, V. A.; Sahiev, S. K.; Trzaska, W. H.; Vardaci, E.

    2016-12-15

    The mass-energy distributions and cross sections of proton-induced fission of {sup 232}Th have been measured at the proton energies of 7, 10, 13, 20, 40, and 55 MeV. Experiments were carried out at the proton beam of the K-130 cyclotron of the JYFL Accelerator Laboratory of the University of Jyväskylä and U-150m cyclotron of the Institute of Nuclear Physics, Ministry of Energy of the Republic of Kazakhstan. The yields of fission fragments in the mass range A = 60–170 a.m.u. have been measured up to the level of 10−4%. The three humped shape of the mass distribution up has been observed at higher proton energies. The contribution of the symmetric component grows up with increasing proton incident energy; although even at 55 MeV of proton energy the shoulders in the mass energy distribution clearly indicate the asymmetric fission peaks. Evolution of shell structure was observed in the fission fragment mass distributions even at high excitation energy.

  10. 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.

  11. 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)

  12. 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

  13. Rapid determination of (237)Np and plutonium isotopes in urine by inductively-coupled plasma mass spectrometry and alpha spectrometry.

    PubMed

    Maxwell, Sherrod L; Culligan, Brian K; Jones, Vernon D; Nichols, Sheldon T; Noyes, Gary W; Bernard, Maureen A

    2011-08-01

    A new rapid separation method was developed for the measurement of plutonium and neptunium in urine samples by inductively-coupled plasma mass spectrometry (ICP-MS) and/or alpha spectrometry with enhanced uranium removal. This method allows separation and preconcentration of plutonium and neptunium in urine samples using stacked extraction chromatography cartridges and vacuum box flow rates to facilitate rapid separations. There is an increasing need to develop faster analytical methods for emergency response samples. There is also enormous benefit to having rapid bioassay methods in the event that a nuclear worker has an uptake (puncture wound, etc.) to assess the magnitude of the uptake and guide efforts to mitigate dose (e.g., tissue excision and chelation therapy). This new method focuses only on the rapid separation of plutonium and neptunium with enhanced removal of uranium. For ICP-MS, purified solutions must have low salt content and low concentration of uranium due to spectral interference of (238)U(1)H(+) on m/z 239. Uranium removal using this method is enhanced by loading plutonium and neptunium initially onto TEVA resin, then moving plutonium to DGA resin where additional purification from uranium is performed with a decontamination factor of almost 1×10(5). If UTEVA resin is added to the separation scheme, a decontamination factor of ~3 × 10(6) can be achieved.

  14. Determination of 232Th in seawater by ICP-MS after preconcentration and separation using a chelating resin.

    PubMed

    Takata, Hyoe; Zheng, Jian; Tagami, Keiko; Aono, Tatsuo; Uchida, Shigeo

    2011-09-30

    This article describes an analytical method for the separation, preconcentration and determination of (232)Th in seawater samples at sub-ng/L levels using a NOBIAS CHELATE PA1 resin and a sector field (SF) inductively coupled plasma mass spectrometer (ICP-MS). The resin showed excellent adsorption of (232)Th at a low pH of 2.4 ± 0.4 in a relatively small volume (200 mL) of seawater. (232)Th adsorbed on the resin was easily eluted using 5 mL of 0.8M HNO(3). An enrichment factor of 40 was achieved for (232)Th analysis. Ethylenediamine-tetraacetic acid disodium salt dehydrate (EDTA) was used to investigate the effect of (232)Th-binding organic ligand on the retention of (232)Th on the chelating resin. Results obtained using acidified samples (pH of 2.4 ± 0.4) showed EDTA had no significant effect on (232)Th recovery, indicating that at this low pH, (232)Th was dissociated from the (232)Th-binding organic ligand and quantitatively retained on the NOBIAS CHELATE PA1 resin. The developed analytical method was characterized by a separation and preconcentration taking approximately 4h and a low detection limit of 0.0038 ng/L for (232)Th, and was successfully applied to the determination of (232)Th in seawater samples collected from coastal areas, Japan. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Temporal evolution of (137)Cs, (237)Np, and (239+240)Pu and estimated vertical (239+240)Pu export in the northwestern Mediterranean Sea.

    PubMed

    Bressac, M; Levy, I; Chamizo, E; La Rosa, J J; Povinec, P P; Gastaud, J; Oregioni, B

    2017-10-01

    The evolution of (137)Cs, (237)Np and (239+240)Pu at the DYFAMED station (NW Mediterranean) is discussed in relation to physical processes, downward fluxes of particles, and changes in the main input sources. The data set presented in this study represents the first complete (237)Np vertical profiles (0.12-0.27μBqL(-1)), and constitutes a baseline measurement to assess future changes. A similar behavior of Cs and Np has been evidenced, confirming that Np behaves conservatively. While the (137)Cs decrease has been driven by its radioactive decay, the vertical distribution of (237)Np has not substantially changed over the last decade. In the absence of recent major inputs, a homogenization of their vertical distribution occurred, partly due to deep convection events that became more intense during the last decade. In contrast, (239+240)Pu surface levels in the NW Mediterranean waters have fallen in the past four decades by a factor of 5. This decrease in surface has been balanced by higher concentrations in the deep-water layers. A first estimate of the downward (239+240)Pu fluxes in the NW Mediterranean Sea is proposed over more than two decades. This estimation, based on the DYFAMED sediment trap time-series data and published (239+240)Pu flux measurements, suggests that sinking particles have accounted for 60-90% of the upper layer (0-200m) Pu inventory loss over the period 1989-2013. The upper layer residence time of Pu is estimated to be ~28years, twice as long as the residence time estimated for the whole western Mediterranean (~15years). This difference highlights the slow removal of Pu in the open waters of the NW Mediterranean and confirms that most of the Pu removal occurs along the coastal margin where sedimentation rates are high. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. 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.

  17. Measurement of the temporal characteristics of delayed neutrons from neutron induced fission of 237Np in the energy range from 14.2 to 18 MeV

    NASA Astrophysics Data System (ADS)

    Gremyachkin, Dmitrii E.; Piksaikin, Vladimir M.; Egorov, Andrey S.; Mitrofanov, Konstantin V.

    2017-09-01

    Analysis of existing database on the relative abundances of delayed neutrons and half-lives of their precursors measured for neutron induced fission of heavy nuclei in the energy range above 14 MeV shows that such data are not available for many nuclides, which are important for nuclear fuel cycle. In the present work for the first time the time dependence of delayed neutron activity for the neutron-induced fission of 237Np in the energy range above 14 MeV was obtained using T(d,n)4He.

  18. On the sequential separation and quantification of (237)Np, (241)Am, thorium, plutonium, and uranium isotopes in environmental and urine samples.

    PubMed

    Vasile, M; Jacobs, K; Bruggeman, M; Van Hoecke, K; Dobney, A; Verrezen, F

    2017-07-13

    The implementation of the one-pass-through separation technique using two stacked chromatography columns of TEVA - TRU resins for the separation of (237)Np, (241)Am, thorium, plutonium and uranium from environmental and urine samples was investigated. The sequential separation technique proved to be successful and gave similar results to those obtained when using individual separations. The analysis time was considerably improved. The amount of chemical waste was also reduced by 50% and the use of HClO4 was avoided. The technique of ICP-MS was also investigated as a complementary technique to alpha-spectrometry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 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.

  20. Relationship between 237Np Mössbauer parameters and bond distances in nitrogen coordinated [NpO2(acac)2py

    NASA Astrophysics Data System (ADS)

    Kawasaki, Takeshi; Kitazawa, Takafumi; Nishimura, Tatsuru; Nakada, Masami; Saeki, Masakatsu

    2005-11-01

    We now report the 237Np Mössbauer spectra for [NpO2(acac)2py] I. The neptunium(VI) ion in I is coordinated by six oxygen atoms and the one nitrogen atom of pyridine. The isomer shift value obtained for I is -40 mm/s, which falls in the range for the Np(VI) oxidation state. The relationship between the isomer shift and Np O bond distance of the neptunyl group for oxygen coordination compounds is in good agreement with the reported structure of I. It is well known that the mean Np O bond distance of the neptunium compounds is shorter by 0.01 Å than that of analogous uranium compounds. The good agreement in the 237Np Mössbauer parameters and the Np O distance has indicated that the reported analogous [UO2(acac)2py] structure may have some inaccuracies. Therefore, we have re-determined the crystal structure of [UO2(acac)2py]. The U O bond distance we have obtained is reasonable.

  1. Concentrations of (226)Ra, (232)Th and (4)(0)K in industrial kaolinized granite.

    PubMed

    Todorović, Nataša; Hansman, Jan; Mrđa, Dušan; Nikolov, Jovana; Kardos, Richárd; Krmar, Miodrag

    2017-03-01

    Activity concentrations of (226)Ra, (232)Th and (4)(0)K in 120 kaolinized granite samples imported in Serbia from the Motajica mine, Bosnia and Herzegovina, were measured. The (226)Ra concentration ranged from 61 to 319 Bq kg(-1), the (232)Th from 44 to 272 Bq kg(-1), and the (4)(0)K from 590 to 1470 Bq kg(-1). The frequency distribution of (4)(0)K concentrations was near-Gaussian, where those of (226)Ra and (232)Th were right-skewed. In 6 samples, the gamma index, I, was higher than 2, which exceeds the exemption dose criterion (0.3 mSv y(-1)). The absorbed dose rate and annual effective doses for workers in the ceramic industries in Serbia who worked with kaolinized granite were below levels of concern.

  2. 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.

  3. Feasibility of 238U NRF Detection in Shipping Containers

    NASA Astrophysics Data System (ADS)

    Ryan, Ben

    2010-11-01

    Sophisticated detection methods are required to efficiently screen the immense volume of containers imported into the United States for the presence of special nuclear materials. The likelihood of detection of characteristic nuclear resonance fluorescence (NRF) lines for the 238U isotope inside a shipping container is examined. Similarly to atoms, nuclei fluoresce when they are excited by incident photons of particular energies unique to each isotope. Detection of the resulting gamma transitions induced by a γ-source allows for nonintrusive interrogation of materials. The Geant4 Monte Carlo simulation toolkit was modified to support detection of NRF. Simulations of a number of typical cargo container geometries containing natural uranium irradiated by a realistic nearly monoenergetic tunable gamma source were developed. The existence of NRF lines in the resulting spectra of exterior detectors will be described.

  4. Reaction rate calibration techniques at ZPPR for /sup 239/Pu fission, /sup 235/U fission, /sup 238/U fission, and /sup 238/U capture

    SciTech Connect

    Brumbach, S.B.; Maddison, D.W.

    1982-06-10

    Reaction-rate calibration techniques used at ZPPR are described for /sup 239/Pu fission, /sup 235/U fission, /sup 238/U fission and /sup 238/U capture. In addition to these absolute reaction rates, calibration techniques are described for fission-rate ratios and the ratio of /sup 238/U capture to /sup 239/U capture to /sup 239/Pu fission. Uncertainty estimates are presented for all calibrations. Intercomparison measurements are reported which support the validity of the calibration techniques and their estimated uncertainties.

  5. 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)

  6. Transmutation of 129I and 237Np using spallation neutrons produced by 1.5, 3.7 and 7.4 GeV protons

    NASA Astrophysics Data System (ADS)

    Wan, J.-S.; Schmidt, Th.; Langrock, E.-J.; Vater, P.; Brandt, R.; Adam, J.; Bradnova, V.; Bamblevski, V. P.; Gelovani, L.; Gridnev, T. D.; Kalinnikov, V. G.; Krivopustov, M. I.; Kulakov, B. A.; Sosnin, A. N.; Perelygin, V. P.; Pronskikh, V. S.; Stegailov, V. I.; Tsoupko-Sitnikov, V. M.; Modolo, G.; Odoj, R.; Phlippen, P.-W.; Zamani-Valassiadou, M.; Adloff, J. C.; Debeauvais, M.; Hashemi-Nezhad, S. R.; Guo, S.-L.; Li, L.; Wang, Y.-L.; Dwivedi, K. K.; Zhuk, I. V.; Boulyga, S. F.; Lomonossova, E. M.; Kievitskaja, A. F.; Rakhno, I. L.; Chigrinov, S. E.; Wilson, W. B.

    2001-05-01

    Small samples of 129I and 237Np, two long-lived radwaste nuclides, were exposed to spallation neutron fluences from relatively small metal targets of lead and uranium, that were surrounded with a 6 cm thick paraffin moderator, and irradiated with 1.5, 3.7 and 7.4 GeV protons. The (n,γ) transmutation rates were determined for these nuclides. Conventional radiochemical La- and U-sensors and a variety of solid-state nuclear track detectors were irradiated simultaneously with secondary neutrons. Compared with results from calculations with well-known cascade codes (LAHET from Los Alamos and DCM/CEM from Dubna), the observed secondary neutron fluences are larger.

  7. Transmutation of 129I, 237Np, 238Pu, 239Pu, and 241Am using neutrons produced in target-blanket system 'Energy plus Transmutation' by relativistic protons

    NASA Astrophysics Data System (ADS)

    Adam, J.; Katovsky, K.; Balabekyan, A.; Kalinnikov, V. G.; Krivopustov, M. I.; Kumawat, H.; Solnyshkin, A. A.; Stegailov, V. I.; Stetsenko, S. G.; Tsoupko-Sitnikov, V. M.; Westmeier, W.

    2007-02-01

    Target-blanket facility `Energy + Transmutation' was irradiated by proton beam extracted from the Nuclotron Accelerator in Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction yields (residual nuclei production yields) have been determined using g-spectroscopy. Neutron field's energy distribution has also been studied using a set of threshold detectors. Results of transmutation studies of 129I, 237Np, 238Pu, 239Pu and 241Am are presented.

  8. Dating ivory by determination of 14C, 90Sr and 228/232Th.

    PubMed

    Schmied, Stefanie A K; Brunnermeier, Matthias J; Schupfner, Robert; Wolfbeis, Otto S

    2012-09-10

    A method is described to determine the time of death of elephants. This is accomplished by analysis of the radionuclides 14C, 90Sr and 228/232Th in known samples of ivory, and in samples of unknown age. The reliability of this method is considerably increased by multi nuclide analysis.

  9. Elastic and inelastic scattering of neutrons on 238U nucleus

    NASA Astrophysics Data System (ADS)

    Capote, R.; Trkov, A.; Sin, M.; Herman, M. W.; Soukhovitskiĩ, E. Sh.

    2014-04-01

    Advanced modelling of neutron induced reactions on the 238U nucleus is aimed at improving our knowledge of neutron scattering. Capture and fission channels are well constrained by available experimental data and neutron standard evaluation. A focus of this contribution is on elastic and inelastic scattering cross sections. The employed nuclear reaction model includes - a new rotational-vibrational dispersive optical model potential coupling the low-lying collective bands of vibrational character observed in even-even actinides; - the Engelbrecht-Weidenmüller transformation allowing for inclusion of compound-direct interference effects; - and a multi-humped fission barrier with absorption in the secondary well described within the optical model for fission. Impact of the advanced modelling on elastic and inelastic scattering cross sections including angular distributions and emission spectra is assessed both by comparison with selected microscopic experimental data and integral criticality benchmarks including measured reaction rates (e.g. JEMIMA, FLAPTOP and BIG TEN). Benchmark calculations provided feedback to improve the reaction modelling. Improvement of existing libraries will be discussed.

  10. [The action of 232Th separately and in combination with heavy and alkaline metal salts on Tradescantia (clone 02)].

    PubMed

    Evseeva, T I; Geras'kin, S A

    2000-01-01

    The action of 232Th-nitrate in concentration 0.09, 0.18 and 0.36 mg/l (counting on 232Th ion) on water cultures of Tradescantia (clone 02) was investigated. It was found that all investigated concentrations of 232Th showed statistically significant genotoxic effect and increased level of morphological abnormal cells in the stamen hairs of Tradescantia in the absence of modifying action of other metal ions. Synergistic toxic interaction was found between the 232Th in concentration 0.18 mg/l and metal ions for all samples of thawed water. Synergistic genotoxic effect of the combined action of these factors was revealed only at the low total contents of ions of heavy and alkaline metals in thawed water samples. The observed synergistic effects of the combined action of 232Th and metal ions should be taken into account when controlling the radionuclide level in the environment.

  11. 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

  12. Reliability of using 238U/235U and 234U/238U ratios from alpha spectrometry as qualitative indicators of enriched uranium contamination.

    PubMed

    Minteer, Mark; Winkler, Paul; Wyatt, Bill; Moreland, Scott; Johnson, Jamie; Winters, Tim

    2007-05-01

    Alpha spectrometry is a commonly used technique for the measurement of uranium isotopes in environmental samples because it is widely available at a relatively low cost. For natural uranium the (234)U to (238)U activity ratio should be 1 and the (238)U to (235)U activity ratio should be 21.7. However, a lower (238)U to (235)U ratio is usually observed in alpha spectrometric analysis of environmental soil samples. This observation has led to the conclusion that soils from nuclear weapons facilities were contaminated with highly enriched uranium. This study was undertaken to test the reliability of using activity ratios from alpha spectrometry to infer the presence of highly enriched uranium in soil samples. The results of these experiments indicate that the (238)U to (235)U activity ratio is not a reliable indicator, but that the (234)U to (238)U activity ratio can be used to qualitatively indicate the presence of highly enriched uranium at concentrations near 10 ng g(-1) and above.

  13. Prospects of heavy and superheavy element production via inelastic nucleus-nucleus collisions - from 238U+238U to18O+254Es

    NASA Astrophysics Data System (ADS)

    Schädel, Matthias

    2016-12-01

    Multi-nucleon transfer reactions, frequently termed deep-inelastic, between heavy-ion projectiles and actinide targets provide prospects to synthesize unknown isotopes of heavy actinides and superheavy elements with neutron numbers beyond present limits. The 238U on 238U reaction, which revealed essential aspects of those nuclear reactions leading to surviving heavy nuclides, mainly produced in 3n and 4n evaporation channels, is discussed in detail. Positions and widths of isotope distributions are compared. It is shown, as a general rule, that cross sections peak at irradiation energies about 10% above the Coulomb barrier. Heavy target nuclei are essential for maximizing cross sections. Experimental results from the 238U on 248Cm reaction, including empirical extrapolations, are compared with theoretical model calculations predicting relatively high cross sections for neutron-rich nuclei. Experiments to test the validity of such predictions are proposed. Comparisons between rather symmetric heavy-ion reactions like 238U on 248Cm (or heavier targets up to 254Es) with very asymmetric ones like 18O on 254Es reveal that the ones with 238U as a projectile have the highest potential in the superheavy element region while the latter ones can be advantageous for the synthesis of heavy actinide isotopes. Concepts for highly efficient recoil separators designed for transfer products are presented.

  14. Study of contents of 226Ra, 232Th and 40K in fertilisers.

    PubMed

    Tahir, S N A; Alaamer, A S; Omer, R M

    2009-02-01

    In this study concentrations of naturally occurring radionuclides (226)Ra, (232)Th and (40)K were measured in the fertiliser samples in Pakistan using a high-resolution and high-purity germanium detector. Samples were collected from main fertiliser depots located in 10 big cities in the Punjab province. Gamma spectrometric analysis revealed that concentrations of (226)Ra, (232)Th and (40)K existed in the ranges from 232 to 511 Bq kg(-1), 21 to 58 Bq kg(-1) and 556 to 1302 Bq kg(-1) with average values of 386 +/- 92, 38 +/- 14 and 885 +/- 220 Bq kg(-1), respectively. Average values of the three natural radionuclides measured in this study were within the range of reported values from some of the other countries of the world. Correlations drawn between measured concentrations were not significant.

  15. [Cytogenetic effects of separate and combined action of 232Th and Cd nitrates on Allum cepa root meristem cells].

    PubMed

    Evseeva, T I; Geras'kin, S A; Khramova, E S

    2001-01-01

    Effects of separate and combined action of 232Th and Cd on Allium cepa root tip cells were investigated. It has been shown that cytogenetic effects of 232Th results mainly from its ability to induce genome damages. Cadmium in the examined concentration does not induce chromosomal vagrants, and this effect is not intensified by the combined action of 232Th and Cd (with 232Th). Cd induced increased aberrations of chromosome type frequency (1.5 times more than in control group), and fragment frequence, while mitotic index was significantly decreased. While taking into consideration the frequency of anaphase--telophase damages, and the number of aberrations per cell, the combined effects of 232Th and Cd may be considered as synergic. The aberration type ratio, frequencies of bridges and fragments, and also the level of proliferative activity of 232Th and Cd in the presence of both ions were similar with the corresponding parameters obtained when Cd acted alone. Possible mechanisms of formation of 232Th and Cd synergic effects are discussed.

  16. Ultra Sensitive Neutron Activation Measurements of {sup 232}Th in Copper

    SciTech Connect

    Clemenza, M.; Previtali, E.; Borio di Tigliole, A.; Salvini, A.

    2011-04-27

    Copper, thanks to its low content in radioactive contaminations, is a material widely used for shielding, holders and other objects close to the sensitive parts of the detectors in many experiments in rare event physics. This implies that tools able to reach sensitivity of the order of <10{sup -12} gram of contaminants per gram of copper are of crucial importance. A methodology based in Neutron Activation Analysis (NAA) has been developed to obtain an extremely high sensitivity in the analysis of {sup 232}Th in copper samples. A detection limit of 5x10{sup -13} g {sup 232}Th/g Cu has been achieved through the irradiation of 200 g of copper sample which subsequently was radio-chemically concentrated using nitric acid and then actinide resin from Eichrom Inc. Several elutions were performed with various inorganic acids to concentrate the {sup 232}Th activation product ({sup 233}Pa) from the copper matrix and to also eliminate the radioactive background induced by the neutron bombardment to reach higher sensitivity.

  17. 232Th, 233Pa, and 234U capture cross-section measurements in moderated neutron flux

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

  18. Feasibility of 99Mo production by proton-induced fission of 232Th

    NASA Astrophysics Data System (ADS)

    Abbas, Kamel; Holzwarth, Uwe; Simonelli, Federica; Kozempel, Jan; Cydzik, Izabela; Bulgheroni, Antonio; Cotogno, Giulio; Apostolidis, Christos; Bruchertseifer, Frank; Morgenstern, Alfred

    2012-05-01

    The current global crisis in supply of the medical isotope generator 99Mo/99mTc has triggered much research into alternative non-reactor based production methods for 99Mo including innovative radionuclide production techniques using ion accelerators. A novel method is presented here that has thus far not been considered: 232Th is used as target material to produce carrier-free 99Mo for 99Mo/99mTc generators by proton-induced fission (232Th (p, f) 99Mo). The thick target yields of 99Mo are estimated as 3.6 MBq/μA·h and 21 MBq/μA·h for proton energies of 22 MeV and 40 MeV, respectively, energies that are available from many cyclotrons. With respect to 99Mo reactor based methods using uranium targets, the presented concept using 232Th does not pose proliferation concerns, transport of highly radioactive target materials can be reduced and unused cyclotron capacities could be exploited. Radiochemical target processing could be based on existing technologies of extraction of 99Mo from reactor irradiated 235U. The presented method could be used for co-production of other radioisotopes of medical interest such as 131I.

  19. Structural investigation of Na3NpO4 and Na3PuO4 using X-ray diffraction and (237)Np Mössbauer spectroscopy.

    PubMed

    Smith, A L; Raison, P E; Hen, A; Bykov, D; Colineau, E; Sanchez, J-P; Konings, R J M; Cheetham, A K

    2015-11-14

    α-Na3NpO4 and α-Na3PuO4 exhibit an orthorhombic structure (Z = 8), in space group Fmmm, with lattice parameters a = 13.352(2) Å, b = 9.629(2) Å, and c = 6.673(2) Å for the neptunium compound, and a = 13.302(2) Å, b = 9.634(2) Å, and c = 6.651(2) Å for the plutonium analogue. The corresponding structure has been solved ab initio as no structural analogue could be found in the literature. The pentavalent state of neptunium has moreover been confirmed by (237)Np Mössbauer spectroscopy, and the local structural properties inferred from the X-ray Rietveld refinement have been related to the fitted quadrupole coupling constant and asymmetry parameters. The existence of a low temperature metastable m phase of Na3NpO4 and Na3PuO4, of the NaCl type, has also been suggested.

  20. Dissolved and Particulate 230Th - 232Th systematics in the Central Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Lopez, G. I.; Marcantonio, F.

    2013-12-01

    To complement our work in the eastern Equatorial Pacific, we have measured total and dissolved 230Th and 232Th in the central Equatorial Pacific at two sites, one at 8°N and the other at the equator (ML1208-03CTD; 00° 13.166' S, 155° 57.668' W and ML1208-12CTD; 8° 19.989' N, 159° 18.000' W). The two seawater casts were collected in May 2012 during an NSF-funded "Line Islands" cruise to test for the extent of advection or diffusion of dissolved 230Th from the oligotrophic North Pacific gyre (low particle flux) to the more productive equatorial region (high particle flux). Our thorium results are similar to previous data published for the western and central North Pacific Ocean. Dissolved 230Th concentrations range from 1.1 fg/kg at 100 m to 30.8 fg/kg at 4400 m, while dissolved 232Th concentrations span from 8.1 pg/kg at 900 m to 19.7 pg/kg at 4400 m. The pattern of the dissolved 230Th profile at 8°N is essentially linear from the surface to 2000 m. From 2000 m to 3000 m, the dissolved 230Th concentrations are constant, and then from 3000 m to the bottom, the profile is linear again. At the same site, the particulate fraction of the total seawater 230Th increases exponentially from about 0% at the surface to 38% at 4400 m. From 0 to 3000 m at 8°N, dissolved 232Th concentrations display a relatively constant pattern (variability of about 20%). From 3000 m to 4400 m, dissolved 232Th contents are more variable, but generally increase toward greater depths. The proportion of 232Th in the particulate fraction of the total seawater sample increases exponentially with depth to a value of 58% in the bottommost sample. We will present additional data from the equator and assess the particulate dynamics that control the distribution of thorium isotopes in central equatorial Pacific seawater.

  1. [Mechanisms of 232Th effects on Chlorella vulgaris Beljer and modifications of it's toxic effect with caffeine and buthionine sulfoximine].

    PubMed

    Evseeva, T I; Maĭstrenko, T A; Geras'kin, S A; Belykh, E S

    2006-01-01

    232Th effects and its modifications with caffeine and D, L-buthionine-(S, R)-sulphoximine in Chlorella vulgaris Beijer cells was studied with use an optical density measure after 24 hours growth. Was shown relationship between concentration and toxic effect that is nonlinear and characterized with three parts different in induced damages level. In the first concentration range (0.001-1.551 micromol/l) chlorella growth parameters don't significantly differ from control ones. In the second one (1.724-3.017 micromol/1) statistically significant increase of optical density is but the effect does not dependent on 232Th concentration. The 232Th concentration (>3.448 micromol/l) increase the monotonous decrease in optical density was observed. The main role in 232Th toxic effect decrease make processes of DNA reparation, but not free radical scavenging with glutathione.

  2. (234)U/(238)U signatures associated with uranium ore bodies: part 1 Ranger 3.

    PubMed

    Lowson, Richard T; McIntyre, Mark G

    2013-04-01

    The Ranger 3 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 between 30 and 50 m below the surface. The ground water U concentration and (234)U/(238)U AR signature in the top 10 m of the weathered zone are reported for 357 samples collected over 4 wet seasons, at 5 depths, along a transect in-line with the hydraulic gradient and along the centre line of the ore body and its associated dispersion halo. The results show that the weathered zone displays a general U isotope feature for this type of ore body with the (234)U/(238)U AR for the ground water and amorphous phase of the solid matrix being less than 1. The ground water (234)U/(238)U AR is independent of the annual monsoonal climate and depth within the range surface to 10 m. In the vicinity of the U ore body the ground water (234)U/(238)U AR is 0.75 and is very similar to the (234)U/(238)U AR of the amorphous phase of the solid (0.76). The (234)U/(238)U ARs of the amorphous phase and ground water rise and separate to values of 0.88 and 1.02 at the end of the transect. The rise and separation in (234)U/(238)U AR are interpreted as evidence that the source of the U in the ground water is from the water-soluble sub-phase of the amorphous phase and that the ground water flow is too fast to allow the processes occurring across the solid-water interface to reach chemical equilibrium. The data set is a robust characterisation of the coarse and fine detail of the (234)U/(238)U AR signature in the weathered zone of U ore bodies.

  3. 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.

  4. 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.

  5. 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

  6. 450,000 years of groundwater (234U/238U)0 variations in SW Nevada, USA

    NASA Astrophysics Data System (ADS)

    Wendt, Kathleen A.; Moseley, Gina E.; Pythoud, Mathieu; Dublyansky, Yuri; Edwards, R. Lawrence; Spötl, Christoph

    2017-04-01

    Subaqueous speleothems represent a unique archive for geochemical variations in regional groundwater systems. Devils Hole 2 cave, located in SW Nevada, USA, is an open fault zone intersecting the Ash Meadows groundwater flow system. Speleothem layers that coat the submerged walls of Devils Hole 2 cave record the isotopic composition of groundwater uranium at the time of precipitation. Past variations of 234U/238U initial activity ratios in groundwater may provide insight into paleohydrological conditions, such as changes to groundwater flow rates or source inputs. We aim to reconstruct 450 ka of groundwater (234U/238U)0 variations at Devils Hole 2 cave. To do so, an 80 cm-long core was drilled from the cave wall. Over 100 (234U/238U) and U-Th ages were measured in order to calculate initial activity ratios. Despite relatively constant uranium concentrations and growth rates throughout the core, preliminary results show a range in values (2.851 -2.616) deviating from modern day groundwater (234U/238U)0 which we measured to 2.762 (±0.002). (234U/238U)0 variations appear to follow interglacial-glacial cycles from 450 ka to present day, such that maximum (234U/238U)0 ratios identified at roughly 43, 185, 289, 374, and 449 ka correspond to glacial periods, while minimum (234U/238U)0 ratios at roughly 5, 121, 239, 336 and 422 ka correspond to interglacial periods. Focusing on the last 200 ka, we observe increasing (234U/238U)0 ratios coupled with depleted Devils Hole 2 δ18O values and water table high-stands (Moseley et al. 2016, Science 2016). We suggest that (234U/238U)0 variations are positively correlated to precipitation amount, contrary to dripstone speleothem records in the Great Basin region. Mechanisms driving the fluctuation in (234U/238U)0 values are still uncertain, but may be due to increased inputs of additional minor groundwater sources to the Ash Meadows flow system during pluvial periods.

  7. Measurement of the {sup 237}Np(n,{gamma}) cross section from 20 meV to 500 keV with a high efficiency, highly segmented 4{pi} BaF{sub 2} detector

    SciTech Connect

    Esch, E.-I.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Glover, S. E.; Haight, R. C.; Jandel, M.; Kawano, T.; Mertz, A.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Reifarth, R.; Greife, U.; Hatarik, A. M.; Hatarik, R.

    2008-03-15

    The {sup 237}Np(n,{gamma}){sup 238}Np cross section has been measured in the neutron energy range from 20 meV to 500 keV using the DANCE array at the Los Alamos National Laboratory. This new facility allows experiments with submilligram samples and is therefore well suited to investigate isotopes with half-lives as low as a few hundred days. In this benchmark measurement, only 0.42 mg of {sup 237}Np was sufficient to determine differential cross sections relative to the well-known resonance at 0.5 eV. The thermal cross section was measured to {sigma}{sub 2200m/s}=177{+-}5 barn, {sigma}{sub kT=25.3meV}=167{+-}4 barn and the resonance integral to RI=693{+-}6 barn.

  8. 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

  9. Internal dose assessment of 238U contaminated soils based on in-vitro gastrointestinal protocol

    NASA Astrophysics Data System (ADS)

    Perama, Yasmin Mohd Idris; Rashid, Nur Shahidah Abdul; Majid, Amran Ab.; Siong, Khoo Kok

    2017-01-01

    Human exposure to natural radioactive uranium has been a great interest as more industrial rapidly growing contributes to radiation risks. The aim of this case study was to determine the internal dose in humans incorporated with ingestion of 238U contaminated soils. A gastrointestinal analogue test was employed to simulate the human digestive tract. In-vitro approach via German DIN 19738 model was developed in order to estimate the internal exposure of 238U due to ingestion of different types of soils. Synthetic gastrointestinal fluids assay via in-vitro method were produced to determine the concentration of 238U in various soils using ICP-MS. Based on the results, concentration of 238U in BRIS, laterite, peat and alluvium soils were in ranged between (0.0061 ± 0.0057 - 0.0488 ± 0.0148) ppm and (0.0005 ± 0.0004 - 0.0046 ± 0.0007) ppm in gastric and gastrointestinal phase respectively. Types of soil compositions and pH medium were some of the factors that influence mobilization and solubility of 238U contaminanted soil into the digestive juices that resembles human gastrointestinal tract. For the purpose of internal dose assessment, the committed efective dose from 238U intake in soils ranged between 1.237 × 10-11 - 9.8993 × 10-11 Sv y-1 for gastric phase and 1.0184 × 10-12 - 9.3294 × 10-12 Sv y-1 for gastric-intestinal phase. The internal dose measurements from this study were much lower from the recommended values. Hence, ingestion of 238U contaminated soils would not be expected to pose major health risk to humans.

  10. 238U, 232Th, 222Rn, AND 220Rn concentrations measured in various bottled mineral waters and resulting radiation doses to the members of the European population living in the city of Marrakech (Morocco).

    PubMed

    Misdaq, M A; Chaouqi, A

    2008-03-01

    U, Th, Rn, and Rn concentrations were measured in thirteen bottled mineral water samples from Morocco, France, and Italy widely consumed by the European population living in the city of Marrakech (Morocco) by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). K contents were also evaluated in the same mineral water samples. The measured concentrations of U, Th, Rn, Rn, and K ranged from (4.2 +/- 0.2) mBq L to (8.6 +/- 0.6) mBq L, (0.90 +/- 0.05) mBq L to (3.4 +/- 0.3) mBq L, (4.2 +/- 0.2) Bq L to (8.6 +/- 0.6) Bq L, (0.91 +/- 0.06) Bq L to (3.4 +/- 0.2) Bq L and 15 mBq L to 1,082 mBq L, respectively. Alpha activities due to the annual intakes of U, Th, and Rn were assessed in the tissues and organs of the human body of the considered consumers. Committed equivalent doses due to annual intakes of U, Th, and Rn were evaluated in the human body compartments of adult members of the European population living in Marrakech. The influence of the target tissue mass and activities due to U, Th, and Rn on the annual committed equivalent doses in the compartments of the human body was investigated.

  11. Determination of 232Th in urine by ICP-MS for individual monitoring purposes.

    PubMed

    Baglan, N; Cossonnet, C; Ritt, J

    2001-07-01

    Thorium is naturally occurring in various ores used for industrial purposes and has numerous applications. This paper sets out to investigate urine analysis as a suitable monitoring approach for workers potentially exposed to thorium. Due to its biokinetic behavior and its low solubility, urinary concentrations are generally very low, requiring therefore high sensitivity analytical methods. An analytical procedure has been developed for detecting 232Th concentrations of below 1 mBq L(-1) quickly and easily. Due to the long half-life (1.41 x 10(10) y) of 232Th, the potential of a procedure based on urine sample dilution and ICP-MS (inductively coupled plasma-mass spectrometry) measurement was investigated first. Two dilution factors were chosen: 100, which is more suitable for long-term measurement trials, and 20, which increases sensitivity. It has been shown that a 100-fold dilution can be used to measure concentrations of below 1 mBq L(-1), whereas a 20-fold one can be used to reach concentrations of below 0.06 mBq L(-1). Then, on the basis of the limitation of the procedure based on urine dilution, the suitable field of application for the different procedures (100-fold and 20-fold dilution and also a chemical purification followed by an ICP-MS measurement) was determined in relation to monitoring objectives.

  12. 232Th-228Ra-228Th Recording of Estuarine and Coastal Sedimentological Events

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, C.; Ghaleb, B.; Ruiz-Fernandez, A.

    2011-12-01

    Climatic events (e.g., storminess, floods) and river/coastal management activities (e.g., dredging) may result in the removal and re-suspension of contaminated sediments in shallow coastal areas and estuaries, thus leading to long-term contamination of such environments. Short-lived daughter isotopes of 232Th (228Ra-228Th) in sediments may then provide some quantitative assessment of the amount of material removed/re-deposited as well as some indications on the chronology of causal events. Examples from the Gulf of St. Lawrence (GSL) and the Pacific coastal rea of Mexico (PcM) are used to illustrate such isotopic responses to natural or anthropogenic disturbances. In the GSL relatively steady accumulation processes are usually observed, although sedimentary sequences show variable benthic mixing patterns over a large array of sedimentation rates (from mm/a to cm/a). In undisturbed sequences, 232Th-daughter isotopes in particulate matter show strong disequilibria due i) to 228Ra-diffusion/228Th adsorption in source-soils and during particulate transport, ii) 228Ra-behavior at the water column/sea-floor interface. Core-top sediments thus depict a strong excess in 228Th vs. 232Th. Below, a fast return (within ~ 10 a) of 228Th to equilibrium with its parent 228Ra leads to a 228Th deficit vs 232Th, in response to 228Ra-losses and diffusion towards the water column. Deeper, a return to full equilibrium conditions is observed (~ 30 a), but for "non-local mixing" events. Few disturbances are observed in the area. They include nearly cyclic pulses in 210Pb at the head of the Laurentian Trough, which we attribute to dredging operations of the St. Lawrence Sea-Way, and in the sealing of Hg-contaminated sediments in the Saguenay Fjord, by flood layers. Comparatively most sequences cored in estuarine settings of the PcM illustrate more critical situations with respect to the re-suspension of sediments, which are often contaminated due to land management and industrial practices

  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.

  14. Proton-induced fission of actinides at energies 26.5 and 62.9 MeV—Theoretical interpretation

    NASA Astrophysics Data System (ADS)

    Demetriou, P.; Keutgen, Th.; Prieels, R.; El Masri, Y.

    2011-10-01

    Fission properties of proton-induced fission on 232Th, 237Np, 238U, 239Pu and 241Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code TALYS. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed.

  15. FFTF (FAST FLUX TEST FACILITY) REACTOR CHARACTERIZATION PROGRAM ABSOLUTE FISSION RATE MEASUREMENTS

    SciTech Connect

    FULLER JL; GILLIAM DM; GRUNDL JA; RAWLINS JA; DAUGHTRY JW

    1981-05-01

    Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

  16. FFTF (Fast Flux Test Facility) Reactor Characterization Program: Absolute Fission-rate Measurements

    SciTech Connect

    Fuller, J.L.; Gilliam, D.M.; Grundl, J.A.; Rawlins, J.A.; Daughtry, J.W.

    1981-05-01

    Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

  17. Transmission Nuclear Resonance Fluorescence Measurements of 238U in Thick Targets

    SciTech Connect

    Quiter, Brian J.; Ludewigt, Bernhard A.; Mozin, Vladimir V.; Wilson, Cody; Korbly, Steve

    2010-08-31

    Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86 g/cm2. The 238U content n the targets varied from 0 to 8.5percent (atom fraction). The experiment demonstrates the capability of using transmission measurements as a non-destructive technique to identify and quantify the presence of an isotope in samples with thicknesses comparable to he average thickness of a nuclear fuel assembly. The experimental data also appear to demonstrate the process of notch refilling with a predictable intensity. Comparison of measured spectra to previous backscatter 238U measurements indicates general agreement in observed excited states. Two new 238U excited states and possibly a third state have also been observed.

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

    USGS Publications Warehouse

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

    1992-01-01

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

  19. Ocean mixing and ice-sheet control of seawater 234U/238U during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Chen, Tianyu; Robinson, Laura F.; Beasley, Matthew P.; Claxton, Louis M.; Andersen, Morten B.; Gregoire, Lauren J.; Wadham, Jemma; Fornari, Daniel J.; Harpp, Karen S.

    2016-11-01

    Seawater 234U/238U provides global-scale information about continental weathering and is vital for marine uranium-series geochronology. Existing evidence supports an increase in 234U/238U since the last glacial period, but the timing and amplitude of its variability has been poorly constrained. Here we report two seawater 234U/238U records based on well-preserved deep-sea corals from the low-latitude Atlantic and Pacific Oceans. The Atlantic 234U/238U started to increase before major sea-level rise and overshot the modern value by 3 per mil during the early deglaciation. Deglacial 234U/238U in the Pacific converged with that in the Atlantic after the abrupt resumption of Atlantic meridional overturning. We suggest that ocean mixing and early deglacial release of excess 234U from enhanced subglacial melting of the Northern Hemisphere ice sheets have driven the observed 234U/238U evolution.

  20. Transfer factor of 226Ra, 232Th and 40K from soil to Alpinia Galangal plant grown in northern Thailand

    NASA Astrophysics Data System (ADS)

    Kritsananuwat, R.; Chanyotha, S.; Kranrod, C.; Pengvanich, P.

    2017-06-01

    This paper reports the activity concentration of three natural radionuclides, 226Ra, 232Th and 40K, found in Alpinia Galangal plants which are widely used in various Asian cuisines and traditional medicine. The galangal plants and their relevant soils were collected from four provinces in the north of Thailand under natural field conditions. The activity concentration of radionuclides was determined using gamma-ray spectrometry. Soil-to-plant transfer factors (TFs) for 226Ra, 232Th and 40K were investigated in rhizome and aerial parts of the galangal plants. The activity concentration in the soils ranged from 22 to 88 Bq kg-1 for 226Ra, 27 to 157 Bq kg-1 for 232Th and 58 to 1157 Bq kg-1 for 40K. In Alpinia Galangal, the concentration ranged from < 0.2 to 2.0 Bq kg-1 for 226Ra, < 0.1 to 2.9 Bq kg-1 for 232Th and 205 to 2247 Bq kg-1 for 40K. The TF ranged from < 0.002 to 0.073 for 226Ra, < 0.001 to 0.061 for 232Th and 0.26 to 7.9 for 40K. The TFs in the aerial parts were higher than those for the rhizomes. The obtained values can be considered as a baseline data for activity concentrations of natural radionuclides and their TFs in Thailand for future environmental radiation monitoring. The Annual effective ingestion dose due to ingestion of 226Ra, 232Th and 40K in galangals is significantly below the worldwide value reported by UNSCEAR 2000.

  1. 232Th(n,γ)233Th Thermal Reaction Cross-Section Measurement

    NASA Astrophysics Data System (ADS)

    Maidana, Nora L.; Vanin, Vito R.; Castro, Ruy M.; Pascholati, Paulo R.; Helene, Otaviano; Dias, Mauro S.; Koskinas, Marina F.

    2005-05-01

    The 232Th(n,γ)233Th thermal neutron-capture reaction cross section was measured using targets of ˜ 1.5 mg of high-purity metallic thorium irradiated in the IPEN IEA-R1m 5 MW pool research reactor. The 197Au(n,γ)198Au reaction was used to monitor the thermal and epithermal neutron fluxes in the irradiation position, which was found using the Westcott formalism. The residual gamma-ray activity was followed with an HPGe detector. The detector efficiency curve was fitted by the least-squares method applying covariance analysis to all uncertainties involved. The experimental result is σ0 =7.20±0.20 b, in agreement with previous published values.

  2. 232Th(n,{gamma})233Th Thermal Reaction Cross-Section Measurement

    SciTech Connect

    Maidana, Nora L.; Vanin, Vito R.; Pascholati, Paulo R.; Helene, Otaviano; Castro, Ruy M.; Dias, Mauro S.; Koskinas, Marina F.

    2005-05-24

    The 232Th(n,{gamma})233Th thermal neutron-capture reaction cross section was measured using targets of {approx} 1.5 mg of high-purity metallic thorium irradiated in the IPEN IEA-R1m 5 MW pool research reactor. The 197Au(n,{gamma})198Au reaction was used to monitor the thermal and epithermal neutron fluxes in the irradiation position, which was found using the Westcott formalism. The residual gamma-ray activity was followed with an HPGe detector. The detector efficiency curve was fitted by the least-squares method applying covariance analysis to all uncertainties involved. The experimental result is {sigma}0 =7.20{+-}0.20 b, in agreement with previous published values.

  3. Systematics of the mean energy and the mean multiplicity of prompt neutrons originating from {sup 232}Th fission

    SciTech Connect

    Svirin, M. I.

    2012-12-15

    The cross section for the neutron-induced fission of {sup 232}Th target nuclei, {sigma}{sub f} (E{sub n}), was described within statistical theory. The spectra of the mean multiplicity, v-bar (E{sub n}), and the mean energy, E-bar(E{sub n}), of secondary neutrons accompanying {sup 232}Th fission induced by neutrons of energy extending up to E{sub n} = 20 MeV were analyzed on the basis of the chance structure of the cross section.

  4. Size-fractionated thorium isotopes (228Th, 230Th, 232Th) in surface waters in the Jiulong River estuary, China.

    PubMed

    Zhang, Lei; Chen, Min; Yang, Weifeng; Xing, Na; Li, Yanping; Qiu, Yusheng; Huang, Yipu

    2005-01-01

    Thorium isotopes (228Th, 230Th, 232Th and 234Th) are useful tracers for studying particle dynamics and trace element scavenging in marine environments. In this study, surface waters were collected along a salinity gradient from the Jiulong River estuary, China, for determination of activity concentrations of 228Th, 230Th and 232Th in different size fractions, namely, the >53 microm, 10-53 microm, 2-10 microm, 0.4-2 microm, 10 kDa-0.4 microm and the <10 kDa fractions. Our results indicated that the activity concentrations of 228Th, 230Th and 232Th in the Jiulong River estuarine waters were significantly higher than most of the previously reported values in coastal and oceanic seawaters, suggesting a higher lithogenic U and Th contribution from the Jiulong River Basin. When normalized to the particulate mass concentration, the activity concentrations of the three thorium isotopes decreased with increasing particle size, demonstrating the important role of surface areas of particles in controlling the scavenging of thorium from the water column. The partitioning of three thorium isotopes showed a common characteristic, i.e., the >53 microm fraction had the least share (0-1%), while the 10-53 microm fraction had the largest share of Th isotopes. The average value of the 230Th/232Th activity ratio (230Th/232Th)(A.R.) increased from 0.8 in the >53 microm fraction to 3.7 in the 10 kDa-0.4 microm fraction, indicating that the radiogenic Th isotopes are preferentially scavenged by the small size particles. (230Th/232Th)(A.R.) in the <10 kDa and 10 kDa-0.4 microm fractions were similar, however, suggesting a similar chemical composition and/or equilibrium partitioning between the low molecular weight and colloidal Th. It was very interesting to note that the geochemical behaviors of the three Th isotopes were different from each other. Dissolved 228Th had the highest concentration in the mid-salinity region, showing a non-conservative behavior with additional input. In

  5. 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

  6. Investigating the use of 232Th/230Th as a dust proxy using co-located seawater and sediment samples from the low-latitude North Atlantic

    NASA Astrophysics Data System (ADS)

    Rowland, George H.; Ng, Hong Chin; Robinson, Laura F.; McManus, Jerry F.; Mohamed, Kais J.; McGee, David

    2017-10-01

    The thorium isotope ratio 232Th/230Th can be measured in seawater and sediment samples, and has been used as a proxy to reconstruct lithogenic fluxes to the oceans for the modern day and the Pleistocene. There has not yet been a systematic study testing the proxy using the 232Th/230Th ratio in seawater and the ratio recorded in the underlying sediment. In this study we use co-located core-top sediments and seawater samples from five seamount sites spanning the tropical North Atlantic to investigate the link between seawater and sediment 232Th/230Th ratios across a range of water depths. Our results indicate that a broad correlation exists between seawater and sedimentary 232Th/230Th ratios. Both seawater and sedimentary 232Th/230Th ratios record a signal consistent with decreasing lithogenic input east to west, from Africa to South America. However, calculated 232Th fluxes for the core-top sediment samples indicate a strong dependence on depth, with up to a factor of ∼4 difference from shallow (<600 m) to deep sites (>2900 m). This depth dependence is likely caused by either a deficit of 230Th burial at depth compared to the production in the overlying water column, through addition of 232Th, or by a combination of the two. By comparing seawater and sedimentary 232Th/230Th ratios we derive an apparent fractional solubility of 232Th of 29 ± 3%, in reasonable agreement with the upper end of existing estimates.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  8. Production of neutron-rich transcalifornium nuclei in 238U-induced transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2016-11-01

    In order to produce more unknown neutron-rich transcalifornium nuclei, the collisions of 238U with the targets 248Cm, 249Cf, and 250Cm are investigated within the framework of the dinuclear system model. The production cross sections of unknown neutron-rich nuclei with Z =99 -104 in these reactions are predicted. The influences of N /Z ratios and charge numbers of the targets on the production cross sections are studied. It is found that high N /Z ratios of 248Cm and 250Cm targets enhance the production cross sections of neutron-rich transcalifornium nuclei. However, due to high charge number of the target 249Cf the predicted production cross sections of unknown neutron-rich nuclei with Z =104 in the reaction 238U+249Cf are higher than those in 238U+248Cm . We also have studied the entrance angular momentum effects on production probabilities of transfer products in the reaction 238U+248Cm . It is found that the formation probabilities of the final neutron-rich products increase first and then decrease with the increasing J .

  9. (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.

  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. 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.

  12. Sorption of {sup 60}Co, {sup 85}Sr, {sup 137}Cs, {sup 237}Np and {sup 241}Am on soil under coexistence of humic acid: Effects of molecular size of humic acid

    SciTech Connect

    Tanaka, Tadao; Senoo, Muneaki

    1995-12-31

    Sorption experiments have been performed by a batch method, to study the effects of humic acid of different molecular size on the complexing stability with {sup 60}Co, {sup 85}Sr, {sup 137}Cs, {sup 237}Np and {sup 241}Am, and on the sorption behavior of these radionuclides on a sandy soil. Equilibrium constants K in the sorption of {sup 137}Cs and {sup 237}Np onto the soil were not changed at different concentrations of humic acid since {sup 137}Cs and {sup 237}Np do not interact with humic acid, while those of {sup 60}Co and {sup 241}Am decreased with increasing humic acid concentration due to forming humic complexes. However, the K of {sup 85}Sr was not changed at different humic acid concentrations, despite {sup 85}Sr interacts with humic acid. This contradiction was probably caused from that a main binding of {sup 85}Sr with humic acid is not based on coordination bond but electrostatic force, due to relatively high concentration of non-radioactive strontium. The theoretical sorption model taking account of the interaction of {sup 60}Co and {sup 241}Am with humic acid could well reproduce the values of K for each radionuclide at different concentrations of humic acid. Concentration profiles of the radionuclides in each size fraction of the solution before and after the sorption experiments were examined by ultrafiltration technique. The reduction of concentration of {sup 60}Co in the fraction less than 300,000 of cutoff molecular weight (MW) and that of concentration of {sup 241}Am in the fraction larger than 100,000MW, respectively, by the sorption onto the soil decreased with increasing humic acid concentration. This decrease resulted in the decrease in the K of {sup 60}Co and {sup 241}Am with increasing humic acid concentration.

  13. High precision {sup 230}Th and {sup 232}Th in the Norwegian Sea and Denmark by thermal ionization mass spectrometry

    SciTech Connect

    Moran, S.B.; Hoff, J.A.; Edwards, R.L.

    1995-10-01

    Seawater samples (1-2 liters) were collected from the Norwegian Sea and Denmark Strait and analyzed for {sup 230}Th and {sup 232}Th using highly sensitive thermal ionization mass spectrometry (TIMS). Depth profiles of dissolved {sup 230}Th and {sup 232}Th are characterized by surface water minima (<1 fg/kg, <5 pg/kg), subsurface maxima (12 fg/kg, 134 pg/kg), and intermediate concentrations that progressively decrease toward the bottom ({approximately}5 fg/kg, {approximately}17 pg/kg), respectively. The lack of an increase in {sup 230}Th with depth is suggested to result from the short ventilation age of Norwegian Sea Deep Water combined with enhanced scavenging near the basin margins. The {sup 230}Th maximum is attributed to advection of high {sup 230}Th in the Arctic Intermediate Water, whereas the {sup 232}Th maximum may he related to a particulate source. The low dissolved {sup 230}Th and {sup 232}Th concentrations observed in the NADW formation regions implies a minor advective export of these long-lived Th tracers to the North Atlantic. 24 refs., 1 fig., 1 tab.

  14. Measurement of fission products yields in the quasi-mono-energetic neutron-induced fission of 232Th

    NASA Astrophysics Data System (ADS)

    Naik, H.; Mukherji, Sadhana; Suryanarayana, S. V.; Jagadeesan, K. C.; Thakare, S. V.; Sharma, S. C.

    2016-08-01

    The cumulative yields of various fission products in the 232Th(n, f) reaction at average neutron energies of 5.42, 7.75, 9.35 and 12.53 MeV have been determined by using an off-line γ-ray spectrometric technique. The neutron beam was produced from the 7Li(p, n) reaction by using the proton energies of 7.8, 12, 16 and 20 MeV. The mass chain yields were obtained from the cumulative fission yields by using the charge distribution correction of medium energy fission. The fine structure in the mass yield distribution was interpreted from the point of nuclear structure effect. On the other hand, the higher yield around mass number 133-134 and 143-144 as well as their complementary products were explained based on the standard I and standard II asymmetric mode of fission. From the mass yield data, the average value of light mass (), heavy mass (), the average number of neutrons (< ν >) and the peak-to-valley (P / V) ratios at different neutron energies of present work and literature data were obtained in the 232Th(n, f) reaction. The different parameters of the mass yield distribution in the 232Th(n, f) reaction were compared with the similar data in the 232Th(γ, f) reaction at comparable excitation energy and a surprising difference was observed.

  15. Projectile-breakup-induced fission-fragment angular distributions in the 6Li+232Th reaction

    NASA Astrophysics Data System (ADS)

    Pal, A.; Santra, S.; Chattopadhyay, D.; Kundu, A.; Ramachandran, K.; Tripathi, R.; Roy, B. J.; Nag, T. N.; Sawant, Y.; Sarkar, D.; Nayak, B. K.; Saxena, A.; Kailas, S.

    2017-08-01

    Background: Experimental anisotropy in fission-fragment (FF) angular distribution in reactions involving weakly bound stable projectiles with actinide targets are enhanced compared to statistical saddle-point model (SSPM) predictions. Contributions from breakup- or transfer-induced fission to total fission are cited as possible reasons for such enhancement. Purpose: To identify the breakup- or transfer-induced fission channels in 6Li+232Th reaction and to investigate their effects on FF angular anisotropy. Methods: The FF angular distributions have been measured exclusively at three beam energies (28, 32, and 36 MeV) around the Coulomb barrier in coincidence with projectile breakup fragments like α , d , and p using Si strip detectors. The angular anisotropy obtained for different exclusive breakup- or transfer-induced fission channels are compared with that for total fission. SSPM and pre-equilibrium fission models have been employed to obtain theoretical FF angular anisotropy. Results: Angular anisotropy of the fission fragments produced by different transfer- or breakup-induced fission reactions have been obtained separately in the rest frame of respective recoiling nuclei. Some of these anisotropies were found to be stronger than those of the inclusive fission. Overall angular distributions of transfer or breakup fission, integrated over all possible recoil angles with weight factor proportional to differential cross section of the complementary breakup fragment emitted in coincidence in all possible directions, were obtained. It was observed that the overall FF angular anisotropy for each of these fission channels is less than or equal to the anisotropy of total fission at all the measured energies. Assuming isotropic out-of-plane correlations between the fission fragments and light-charged particles, the overall breakup- or transfer-induced fission fragment angular distributions do not explain the observed enhancement in FF anisotropy of total fission. Pre

  16. 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

  17. Mass distribution and mass resolved angular distribution of fission products in 28Si+232Th

    NASA Astrophysics Data System (ADS)

    Sodaye, Suparna; Tripathi, R.; John, B. V.; Ramachandran, K.; Pujari, P. K.

    2017-01-01

    Background: Fission process with heavier projectiles and actinide targets has contributions from processes, such as compound nucleus fission, transfer-induced fission, and noncompound nucleus fission. Mass distribution and mass-dependent anisotropy can be used to identify and delineate the contributions due to these different processes. Purpose: Mass distribution in 28Si+232Th has been studied at beam energies of 180 and 158 MeV to investigate the nature of mass distribution arising from complete and incomplete momentum-transfer fission events. Mass-dependent angular anisotropy has been measured at 166 MeV to investigate the dominant noncompound nucleus process contributing to the fission. Method: Mass distribution and mass resolved angular distribution of fission products were measured by the recoil catcher method followed by off-line γ -ray spectrometry. Results: Mass distributions for full momentum-transfer fission processes were found to be symmetric, and those for transfer-induced fission were found to be asymmetric at both beam energies. The relative contribution from transfer-induced fission was found to be higher at lower beam energy. The anisotropy of the fission product angular distribution was found to increase with decreasing mass asymmetry. Conclusions: The mass distribution indicates that, apart from the full momentum-transfer fission process, there is a significant contribution due to transfer-induced fission. The mass dependence of angular anisotropy indicated that preequilibrium fission is the dominant noncompound nucleus process in the present reaction system at near barrier energy (Ec .m ./VC=1.06 ) .

  18. New evaluation of the{sup 232}Th resonance parameters in the energy range

    SciTech Connect

    Derrien, H.; Leal, L. C.; Larson, N. M.

    2006-07-01

    Neutron resonance parameters of {sup 232}Th were obtained from a Reich-Moore SAMMY analysis of high-resolution neutron transmission measurements performed at the Oak Ridge Linear Accelerator (ORELA) by Olsen et al. in 1981 and of high-resolution neutron capture measurements performed recently at the Geel Linear Accelerator (GELINA (Belgium)) by Schillebeeckx et al. and at n-TOF (CERN (Switzerland)) by Aerts et al. The ORELA data were analyzed previously by Olsen using the Breit-Wigner multilevel code SIOB, and their results were used for the ENDF/B-VI evaluation. In our new analysis of the Olsen neutron transmissions using the modern computer code SAMMY, better accuracy is obtained for the resonance parameters by including recent experimental neutron capture data in the experimental data base. The experimental data base and the method of analysis are described in the report. Neutron transmissions and capture cross sections calculated with the resonance parameters are compared to the experimental values. A description is given of the statistical properties of the resonance parameters. The new evaluation produces a decrease in the capture resonance integral, and improves the prediction of integral thermal benchmarks. (authors)

  19. Evidence of complete fusion in the subbarrier {sup 16}O+{sup 238}U reaction

    SciTech Connect

    Nishio, K. Ikezoe, H.; Asai, M.; Tsukada, K.; Mitsuoka, S.; Tsuruta, K.; Satou, K.; Lin, C. J.; Ohsawa, T.

    2006-08-15

    Evaporation residue cross sections in the {sup 16}O+{sup 238}U reaction were measured for the energy range from above-to extreme subbarrier. We used a He-gas-jet system to transport the fusion products, and the {alpha} decay of the evaporation residues was measured by using a rotating wheel system. The measured cross sections for {sup 248,249,250}Fm are reproduced by a statistical model calculation, for which partial cross sections are calculated by a coupled-channel model taking into account the prolate deformation of {sup 238}U. We conclude that complete fusion is the main process in the subbarrier energy region, and quasifission is not an important channel.

  20. 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

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

    SciTech Connect

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

    2011-10-19

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

  2. Origin and transport of (238)U and (226)Ra in riverine, estuarine and marine sediments of the Krka River, Croatia.

    PubMed

    Cukrov, Neven; Mlakar, Marina; Cuculić, Vlado; Barisić, Delko

    2009-06-01

    Spatial distribution of (238)U and (226)Ra activities in sediment columns along the Krka River and estuary, were studied using gamma spectrometry. Markedly different (238)U and (226)Ra activities between riverine, estuarine and marine sediments were observed. Distribution of these radionuclides, as well as their anthropogenic and natural origin, was evaluated by activity measurements, taking into account sedimentation rates estimated by (137)Cs distribution in sediment columns. Naturally present (238)U and (226)Ra activities were highest in riverine and lowest in marine sediments. (238)U and (226)Ra activities in historic riverine sediments revealed anthropogenic influence from town of Knin, which diminished for 15-20% in 1990s due to warfare that caused stop of industrial, agricultural and transport activities. Drainage of the flysch material naturally elevates (238)U and (226)Ra activities in the vicinity of its inflow in the upper part of estuary. (238)U and (226)Ra from the phosphate ore discharge in the port of Sibenik did not spread further in estuary, which was also confirmed by (238)U and (226)Ra activities detected in Mytilus sp. mussels' tissue.

  3. 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.

  4. Study of 232Th(n, γ) and 232Th(n,f) reaction rates in a graphite moderated spallation neutron field produced by 1.6 GeV deuterons on lead target

    NASA Astrophysics Data System (ADS)

    Asquith, N. L.; Hashemi-Nezhad, S. R.; Westmeier, W.; Zhuk, I.; Tyutyunnikov, S.; Adam, J.

    2015-02-01

    The Gamma-3 assembly of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is designed to emulate the neutron spectrum of a thermal Accelerator Driven System (ADS). It consists of a lead spallation target surrounded by reactor grade graphite. The target was irradiated with 1.6 GeV deuterons from the Nuclotron accelerator and the neutron capture and fission rate of 232Th in several locations within the assembly were experimentally measured. 232Th is a proposed fuel for envisaged Accelerator Driven Systems and these two reactions are fundamental to the performance and feasibility of 232Th in an ADS. The irradiation of the Gamma-3 assembly was also simulated using MCNPX 2.7 with the INCL4 intra-nuclear cascade and ABLA fission/evaporation models. Good agreement between the experimentally measured and calculated reaction rates was found. This serves as a good validation for the computational models and cross section data used to simulate neutron production and transport of spallation neutrons within a thermal ADS.

  5. 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

  6. The Concentrations of {sup 40}K, {sup 226}Ra and {sup 232}Th in Soil Sample in Osmaniye (Turkey)

    SciTech Connect

    Akkurt, I.; Guenoglu, K.; Kara, A.; Mavi, B.; Karaboerklue, S.

    2011-12-26

    The {sup 40}K, {sup 226}Ra and {sup 232}Th concentration is due to the magmatic structure of the earth and it can be varied from place to place. Osmaniye is located in the Eastern side of Mediteranean Region. It holds the climatic characteristics of the same region and arises with Middle Taurus Mountains from west to North and with Amonos Mounations in East and West-east parts and is situated between 35 deg. .52'-36 deg. .42' east longitudes and 36 deg. .57'-37 deg. .45' north latitudes. In this study, the natural radioactivity concentrations {sup 40}K, {sup 226}Ra and {sup 232}Th in some soil samples collected in Osmaniye have been investigated. The measurements have been performed using 3x3{sup ''} NaI(Tl) detector system.

  7. Quasi-elastic scattering and transfer angular distribution for B,1110+232Th systems at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Dubey, Shradha; Biswas, D. C.; Mukherjee, S.; Patel, D.; Gupta, Y. K.; Prajapati, G. K.; Joshi, B. N.; Danu, L. S.; Mukhopadhyay, S.; John, B. V.; Suryanarayana, S. V.; Vind, R. P.

    2016-12-01

    Quasi-elastic scattering and transfer angular distributions for B,1110+232Th reactions have been measured simultaneously in a wide range of bombarding energies around the Coulomb barrier. The quasi-elastic angular distribution data are analyzed using the optical model code ecis with phenomenological Woods-Saxon potentials. The obtained potential parameters suggest the presence of usual threshold anomaly, confirming tightly bound characteristics for both the projectiles. The reaction cross sections are obtained from the fitting of quasi-elastic angular distribution data. The reduced cross sections at sub-barrier energies compared with Li,76+232Th systems show a systematic dependence on projectile breakup energy. The angular distribution of the transfer products show similar behavior for both the systems.

  8. Covariance data for{sup 232}Th in the resolved resonance region from 0 to 4 keV

    SciTech Connect

    Leal, L. C.; Derrien, H.; Arbanas, G.; Larson, N. M.; Wiarda, D.

    2006-07-01

    This paper reports on the generation and testing of the covariance matrix associated with the resonance parameter evaluation for {sup 232}Th up to 4 keV. [1] Covariance data are required to correctly assess uncertainties in design parameters in nuclear applications. The error estimation of calculated quantities relies on the nuclear data uncertainty information available in the basic nuclear data libraries, such as the US Evaluated Nuclear Data Library, ENDF/B. Uncertainty files in the ENDF/B library are obtained from analysis of experimental data and are stored as variance and covariance data. In this paper, we address the generation of covariance data in the resonance region via the computer code SAMMY, which is used in the evaluation of experimental data in the resolved and unresolved resonance energy regions. The resolved resonance parameter covariance matrix for {sup 232}Th, obtained using the retroactive approach, is also presented here. (authors)

  9. Development of a method for activity measurements of 232Th daughters with a multidetector gamma-ray coincidence spectrometer.

    PubMed

    Antovic, N; Svrkota, N

    2009-06-01

    The method for activity measurements of the (232)Th daughters, developed at the six-crystal gamma-ray coincidence spectrometer PRIPYAT-2M and based on coincidence counting of the 583 and 2615 keV photons from cascade transitions which follow beta(-)-decay of (208)Tl, as well as on counting the 911 keV photons which follow beta(-)-decay of (228)Ac in the integral and non-coincidence mode of counting, is presented.

  10. [About the contents of 40K, 226Ra and 232Th in forest soils of the Republic of Belarus].

    PubMed

    Perevolotskiĭ, A N; Perevolotskaia, T V

    2014-01-01

    The specific activity of 40K, 232Th and 226Ra in forest soil ecotopes (A2-B2-C2-D2) has been investigated. When the fertility of the soil increases from A2 to D2, then the specific activity of 40K increases in the rooting zone of the soil from 275 ± 6.9 up to 499 ± 11 Bq/kg, 232Th--from 11.8 ± 0.5 to 17.1 ± 1.1 Bq/kg, 226Ra- from 19.2 γ 0.8 to 27.9 ± 1.5 Bq/kg. The calculated capacity of the absorbed dose of γ-radiation conditioned by 40K, 232Th and 226Ra increases from A2 to D2 from 27.5 ± 0.5 to 44.1 ± 1.1 nGy / h at the height of 1 m.

  11. Solubility assessment of 232Th from various types of soil in Malaysia using USP and DIN In Vitro digestion method

    NASA Astrophysics Data System (ADS)

    Rashid, Nur Shahidah Abdul; Perama, Yasmin Mohd Idris; Salih, Fitri Hakeem Mohd; Sarmani, Sukiman; Majid, Amran Ab.; Siong, Khoo Kok

    2016-11-01

    The overall results of the study showed that the concentrations of 232Th radionuclide using DIN digestion method during gastric phase are 0.0015 mg/kg - 0.0554 mg/kg and 0.0015 mg/kg - 0.0139 mg/kg during intestinal phase, respectively. As for USP digestion method during gastric phase are between 0.0877 mg/kg - 0.4964 mg/kg and 0.0207 mg/kg - 0.2291 mg/kg. The results from the measurements in various types of soils indicates some elevation of 232Th concentration in some types of soil compared to UNSCEAR reference values, in which may be a result from the impact of previous mining activity in the surrounding area and considered to be safe. In general, the results of 232Th concentrations from in vitro extraction technique is considered to be safe. By natural processes, thorium ingestion is getting transferred to living beings through different pathways and need to be monitored in order to assess possible hazards. Environmental studies are generally carried out to trace the pathway of radionuclides/radiotoxic elements to reach living organism. Environmental monitoring and meaningful interpretation of data from man-made pollution are more complicated without adequate knowledge about the natural abundance of radioactive elements in the environment.

  12. (226)Ra, (232)Th and (40)K contents in soil samples from Garhwal Himalaya, India, and its radiological implications.

    PubMed

    Ramola, R C; Gusain, G S; Badoni, Manjari; Prasad, Yogesh; Prasad, Ganesh; Ramachandran, T V

    2008-09-01

    The exposure of human beings to ionising radiation from natural sources is a continuing and inescapable feature of life on earth. Natural radionuclides are widely distributed in various geological formations and ecosystems such as rocks, soil groundwater and foodstuffs. In the present study, the distribution of (226)Ra, (232)Th and (40)K was measured in soil samples collected from different lithological units of the Thauldhar and Budhakedar regions of Garhwal Himalaya, India. The collected soil samples were analysed using gamma ray spectrometry. The activity concentrations of the naturally occurring radionuclides (226)Ra, (232)Th and (40)K in these soil samples were found to vary from below detection level (BDL) to 131 +/- 18 Bq kg(-1), 9 +/- 6 to 384 +/- 53 Bq kg(-1) and 471 +/- 96 to 1406 +/- 175 Bq kg(-1), respectively. The distribution of radionuclides depends upon the rock formation and chemical properties within the earth. The activity concentrations vary widely depending on the sample origin. The external absorbed gamma dose rates due to (226)Ra, (232)Th and (40)K were found to vary from 49 to 306 nGy h(-1). The average radium equivalent activity from these soil samples was 300 Bq kg(-1).

  13. Monte Carlo and deterministic simulations of activation ratio experiments for 238U(n,f), 238U(n,g) and 238U(n,2n) in the Big Ten benchmark critical assembly

    SciTech Connect

    Descalle, M; Clouse, C; Pruet, J

    2009-07-28

    The authors have compared calculations of critical assembly activation ratios using 3 different Monte Carlo codes and one deterministic code. There is excellent agreement. Discrepancies between the different Monte Carlo codes are the 1-2% level. Notably, the deterministic calculations with 87 groups are also in good agreement with the continuous energy Monte Carlo results. The three codes underestimate the {sup 238}U(n,f) reaction, suggesting that there is room for improvement in the evaluation, or in the evaluations of other reactions influencing the spectrum in BigTen. Until statistical uncertainties are implemented in Mercury, they strongly advise long runs to guarantee sufficient convergence of the flux at high energies, and they strongly encourage comparing Mercury results to a well-developed and documented code such as MCNP5 and/or COG. It may be that ENDL2008 will be available for use in COG within a year. Finally, it may be worthwhile to add a 'standard' reaction rate tally similar to those implemented in COG and MCNP5, if the goal is to expand the central fission and activation ratios simulations to include isotopes that are not part of the specifications for the assembly material composition.

  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 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

  16. Measurement of fission cross section for 232Th (n,f) 131 ZX ( Z = 50 , 51, 52, 53) reaction induced by neutrons around 14 MeV

    NASA Astrophysics Data System (ADS)

    Lan, Chang-lin; Qiu, Yi-jia; Wang, Qiang; Zhang, Zheng-wei; Zhang, Qian; Tan, Jun-cai; Lai, Cai-feng; Fang, Kai-hong

    2017-06-01

    The fission cross sections of 232Th (n,f) 131m, gSn , 232Th (n,f) 131Sb , 232Th (n,f) 131m, gTe , 232Th (n,f) 131I fission reactions induced by 14MeV neutrons were measured precisely with the neutron activation technique. The neutron flux was monitored by accompanying α particle in the irradiation and the neutron energies were determined by the cross section ratio of 90Zr (n,2n) 89Zr to 93Nb (n,2n) 92mNb reaction. The values of the cross sections of 232Th (n,f) 131m, gSn were analyzed, and the cross sections of 232Th (n,f) 131Sb were deduced to be 6.5± 0.7 , 6.3± 0.6 , 6.1± 0.6 mb at 14.1± 0.3 , 14.5± 0.3 and 14.8± 0.3 MeV, respectively. The values of the cross sections of 232Th (n,f) 131gTe were deduced to be 1.8± 0.1 , 1.5± 0.1 and 1.4± 0.1 mb at 14.1± 0.3 , 14.5± 0.3 and 14.8± 0.3 MeV, respectively. The values of the cross sections of 232Th (n,f) 131I were given as 1.8± 0.2 , 1.6± 0.2 , 1.5± 0.1 mb at 14.1± 0.3 , 14.5± 0.3 and 14.8± 0.3 MeV, respectively.

  17. (238)U and total radioactivity in drinking waters in Van province, Turkey.

    PubMed

    Selçuk Zorer, Özlem; Dağ, Beşir

    2014-06-01

    As part of the national survey to evaluate natural radioactivity in the environment, concentration levels of total radioactivity and natural uranium have been analysed in drinking water samples. A survey to study natural radioactivity in drinking waters was carried out in the Van province, East Turkey. Twenty-three samples of drinking water were collected in the Van province and analysed for total α, total β and (238)U activity. The total α and total β activities were counted by using the α/β counter of the multi-detector low background system (PIC MPC-9604), and the (238)U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2). The samples were categorised according to origin: tap, spring or mineral supply. The activity concentrations for total α were found to range from 0.002 to 0.030 Bq L(-1) and for total β from 0.023 to 1.351 Bq L(-1). Uranium concentrations ranging from 0.562 to 14.710 μg L(-1) were observed in drinking waters. Following the World Health Organisation rules, all investigated waters can be used as drinking water.

  18. 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

  19. 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.

  20. 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)

  1. Oceanic stratified euphotic zone as elucidated by /sup 234/Th:/sup 238/U disequilibria

    SciTech Connect

    Coale, K.H.; Bruland, K.W.

    1987-01-01

    Profiles of dissolved and particulate /sup 234/Th were determined at the VERTEX 2 and 3 stations off Manzanillo, Mexico, and at the VERTEX 4 station about 900 km north of Hawaii. By modeling the disequilibria between /sup 234/Th and /sup 238/U in the dissolved and particulate form, estimates of scavenging rates for Th from the dissolved to particulate phases, particle residence times, and the flux of Th via particle removal can be obtained. /sup 234/Th:/sup 238/U activity ratio profiles indicate that the euphotic zone can be separated into two layers: an upper oligotrophic layer characterized by low new production values, low net scavenging, and long dissolved /sup 234/Th residence times; and a subsurface eutrophic layer with higher new production values, more intense scavenging, and shorter dissolved /sup 234/Th residence times. New production, rather than total primary production may determine net scavenging rates of reactive elements from oceanic surface waters. These results contribute to the emerging descriptions of the layered structure of oligotrophic euphotic zones and support the notion that this may be a general and ubiquitous feature of global stratified oligotrophic regimes.

  2. Photon-induced Fission Product Yield Measurements on 235U, 238U, and 239Pu

    NASA Astrophysics Data System (ADS)

    Krishichayan, Fnu; Bhike, M.; Tonchev, A. P.; Tornow, W.

    2015-10-01

    During the past three years, a TUNL-LANL-LLNL collaboration has provided data on the fission product yields (FPYs) from quasi-monoenergetic neutron-induced fission of 235U, 238U, and 239Pu at TUNL in the 0.5 to 15 MeV energy range. Recently, we have extended these experiments to photo-fission. We measured the yields of fission fragments ranging from 85Kr to 147Nd from the photo-fission of 235U, 238U, and 239Pu using 13-MeV mono-energetic photon beams at the HIGS facility at TUNL. First of its kind, this measurement will provide a unique platform to explore the effect of the incoming probe on the FPYs, i.e., photons vs. neutrons. A dual-fission ionization chamber was used to determine the number of fissions in the targets and these samples (along with Au monitor foils) were gamma-ray counted in the low-background counting facility at TUNL. Details of the experimental set-up and results will be presented and compared to the FPYs obtained from neutron-induced fission at the same excitation energy of the compound nucleus. Work supported in part by the NNSA-SSAA Grant No. DE-NA0001838.

  3. 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.

  4. 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

  5. Radionuclide ((226)Ra, (232)Th, (40)K) accumulation among plant species in mangrove ecosystems of Pattani Bay, Thailand.

    PubMed

    Kaewtubtim, Pungtip; Meeinkuirt, Weeradej; Seepom, Sumalee; Pichtel, John

    2017-02-15

    Little is known regarding phytoremediation of radionuclides from soil; even less is known about radionuclide contamination and removal in tropical ecosystems such as mangrove forests. In mangrove forests in Pattani Bay, Thailand, 18 plant species from 17 genera were evaluated for radionuclide concentrations within selected plant parts. Two shrub species, Avicennia marina and Pluchea indica, accumulated the highest (232)Th (24.6Bqkg(-1)) and (40)K (220.7Bqkg(-1)) activity concentrations in roots, respectively. Furthermore, the aquatic species Typha angustifolia accumulated highest (232)Th, (40)K and (226)Ra activity concentrations (85.2, 363.5, 16.6Bqkg(-1), respectively) with the highest transfer factors (TFs) (3.0, 2.0, 5.9, respectively) in leaves. Leaves of T. angustifolia had an absorbed dose rate in air (D) over the recommended value (74.8nGyh(-1)) that was considered sufficiently high to be of concern for human consumption. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Soil-to-root vegetable transfer factors for (226)Ra, (232)Th, (40)K, and (88)Y in Malaysia.

    PubMed

    Asaduzzaman, Kh; Khandaker, Mayeen Uddin; Amin, Y M; Bradley, D A; Mahat, R H; Nor, R M

    2014-09-01

    Soil-to-plant transfer factors (TFs) are of fundamental importance in assessing the environmental impact due to the presence of radioactivity in soil and agricultural crops. Tapioca and sweet potato, both root crops, are popular foodstuffs for a significant fraction of the Malaysian population, and result in intake of radionuclides. For the natural field conditions experienced in production of these foodstuffs, TFs and the annual effective dose were evaluated for the natural radionuclides (226)Ra, (232)Th, (40)K, and for the anthropogenic radionuclide (88)Y, the latter being a component of fallout. An experimental tapioca field was developed for study of the time dependence of plant uptake. For soil samples from all study locations other than the experimental field, it has been shown that these contain the artificial radionuclide (88)Y, although the uptake of (88)Y has only been observed in the roots of the plant Manihot esculenta (from which tapioca is derived) grown in mining soil. The estimated TFs for (226)Ra and (232)Th for tapioca and sweet potato are very much higher than that reported by the IAEA. For all study areas, the annual effective dose from ingestion of tapioca and sweet potato are estimated to be lower than the world average (290 μSv y(-1)). Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Covariances of Evaluated Nuclear Cross Section Data for (232)Th, (180,182,183,184,186)W and (55)Mn

    SciTech Connect

    Trkov, A.; Capote, R.; Soukhovitskii, E; Leal, Luiz C; Sin, M; Kodeli, I.; Muir, D W

    2011-01-01

    The EMPIRE code system is a versatile package for nuclear model calculations that is often used for nuclear data evaluation. Its capabilities include random sampling of model parameters, which can be utilized to generate a full covariance matrix of all scattering cross sections, including cross-reaction correlations. The EMPIRE system was used to prepare the prior covariance matrices of reaction cross sections of (232)Th, (180,182,183,184,186)W and (55)Mn nuclei for incident neutron energies up to 60 MeV. The obtained modeling prior was fed to the GANDR system, which is a package for a global assessment of nuclear data, based on the Generalized Least-Squares method. By introducing experimental data from the EXFOR database into GANDR, the constrained covariance matrices and cross section adjustment functions were obtained. Applying the correction functions on the cross sections and formatting the covariance matrices, the final evaluations in ENDF-6 format including covariances were derived. In the resonance energy range, separate analyses were performed to determine the resonance parameters with their respective covariances. The data files thus obtained were then subjected to detailed testing and validation. Described evaluations with covariances of (232)Th, (180,182,183,184,186)W and (55)Mn nuclei are included into the ENDF/B-VII.1 library release.

  8. Covariances of Evaluated Nuclear Cross Section Data for 232Th, 180,182,183,184,186W and 55Mn

    NASA Astrophysics Data System (ADS)

    Trkov, A.; Capote, R.; Soukhovitskii, E. Sh.; Leal, L. C.; Sin, M.; Kodeli, I.; Muir, D. W.

    2011-12-01

    The EMPIRE code system is a versatile package for nuclear model calculations that is often used for nuclear data evaluation. Its capabilities include random sampling of model parameters, which can be utilised to generate a full covariance matrix of all scattering cross sections, including cross-reaction correlations. The EMPIRE system was used to prepare the prior covariance matrices of reaction cross sections of 232Th, 180,182,183,184,186W and 55Mn nuclei for incident neutron energies up to 60 MeV. The obtained modelling prior was fed to the GANDR system, which is a package for a global assessment of nuclear data, based on the Generalised Least-Squares method. By introducing experimental data from the EXFOR database into GANDR, the constrained covariance matrices and cross section adjustment functions were obtained. Applying the correction functions on the cross sections and formatting the covariance matrices, the final evaluations in ENDF-6 format including covariances were derived. In the resonance energy range, separate analyses were performed to determine the resonance parameters with their respective covariances. The data files thus obtained were then subjected to detailed testing and validation. Described evaluations with covariances of 232Th, 180,182,183,184,186W and 55Mn nuclei are included into the ENDF/B-VII.1 library release.

  9. 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.

  10. /sup 234/Th: /sup 238/U disequilibria within the California Current

    SciTech Connect

    Coale, K.H.; Bruland, K.W.

    1985-01-01

    Profiles of dissolved and particulate /sup 234/Th were determined at several stations within the California Current. Modeling of the disequilibria between the /sup 234/Th and /sup 238/U within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging, the particle residence time, and the particulate /sup 234/Th flux exiting the surface layer. The model-derived, first-order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production. Particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present. Model-derived particulate /sup 234/Th fluxes are in good agreement with direct measurements by sediment traps.

  11. 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.

  12. Symmetric splitting for the system 32S+238U at energies near and below the barrier

    NASA Astrophysics Data System (ADS)

    Freifelder, R.; Braun-Munzinger, P.; Deyoung, P.; Schicker, R.; Sen, S.; Stachel, J.

    1987-06-01

    The total capture cross section for the system 32S+238U has been measured at energies from 0.93 to 1.08 times the s-wave interaction barrier by detecting coincident fission fragments following full momentum transfer reactions. The subbarrier cross section cannot be reproduced by a one-dimensional barrier penetration model. Using a quantum mechanical coupled channels model, good agreement is obtained. The measured angular distributions of fission fragments were compared to the predictions of saddle and scission point transition state theory. Saddle point transition state model calculations fail to reproduce the data, while scission point transition state calculations are in agreement with their qualitative trend. Evidence for nonequilibrium processes is presented.

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

    DOE PAGES

    Sadhukhan, J.; Mazurek, K.; Dobaczewski, J.; ...

    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.

  14. 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.

  15. 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 .

  16. Isotopic resolution of fission fragments from 238U+12C transfer and fusion reactions

    NASA Astrophysics Data System (ADS)

    Caamaño, M.; Rejmund, F.; Derkx, X.; Schmidt, K.-H.; Andouin, L.; Bacri, C.-O.; Barreau, G.; Benlliure, J.; Casarejos, E.; Fernández-Domínguez, B.; Gaudefroy, L.; Golabek, C.; Jurado, B.; Lemasson, A.; Navin, A.; Rejmund, M.; Roger, T.; Shrivastava, A.; Schmitt, C.; Taieb, J.

    2009-10-01

    Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238U beam and a 12C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments.

  17. 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.

  18. Fluxes of 238U decay series radionuclides in a dicalcium phosphate industrial plant.

    PubMed

    Casacuberta, N; Masqué, P; Garcia-Orellana, J

    2011-06-15

    The production of dicalcium phosphate (DCP) is part of the phosphate industry, which has been recently included in the positive list of the NORM industries defined in the revised version of the EU-BSS (Euratom 29/96). The objective of the present work is to study specific concentrations and fluxes of (238,234)U, (230)Th, (226)Ra, (210)Pb and (210)Po at the different stages of the DCP production. Results showed highest activities of (238)U and (210)Pb were found in DCP (1500-2000 Bq kg(-1)); (230)Th and (210)Po were released together with the sludges (1600-2000 Bq kg(-1)) and (226)Ra presented particularly high activities in water (48 × 10(3) Bq m(-3)) and in the reactor scales (115 × 10(3) Bq kg(-1)). Fluxes of radionuclides showed that (238)U outflows were equally distributed between sludges (16 × 10(3) kBq h(-1)) and dicalcium phosphate (20 × 10(3) kBq h(-1)); (230)Th and (210)Po were almost entirely released in the sludges (30 × 10(3)kBq h(-1)) and the greatest (210)Pb outflow was the DCP current (25 × 10(3) kBq h(-1)). (226)Ra was mainly discharged through the water effluent (12 × 10(3) kBq h(-1)). This work highlights the importance of studying the industrial processes involving NORM, as minor changes in the production steps lead to different radionuclide distribution in the process.

  19. Influence of soil structure on the "Fv approach" applied to (238)U and (226)Ra.

    PubMed

    Blanco Rodríguez, P; Vera Tomé, F; Lozano, J C

    2017-02-01

    The soil-to-plant transfer factors were determined in a granitic area for the two long-lived uranium series radionuclides (238)U and (226)Ra. With the aim to identify a physical fraction of soil whose concentration correlates linearly with the plant concentration, the soil compartment was analyzed in various stages. An initial study identified the soil compartments as being either bulk soil or its labile fraction. The bulk soil was subsequently divided into three granulometric fractions consisting of: coarse sand, fine sand, and silt and clay. The soil-to-plant transfer of radionuclides for each of these three texture fractions was analyzed. Lastly, the labile fraction was extracted from each textural part, and the activity concentration of the radionuclides (238)U and (226)Ra was measured. In order to assess the influence of soil texture on the soil-to-plant transfer process, we sought to identify possible correlations between the activity concentration in the plant compartment and those found in the different fractions within each soil compartment. The results showed that the soil-to-plant transfer process for uranium and radium depends on soil grain size, where the results for uranium showed a linear relationship between the activity concentration of uranium in the plant and the fine soil fraction. In contrast, a linear relation between the activity concentration of radium in the plant and the soil coarse-sand fraction was observed. Additionally, the presence of phosphate and calcium in the soil of all of the compartments studied affected the soil-to-plant transfer of uranium and radium, respectively.

  20. 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.

  1. 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.

  2. 238U and 235U isotope fractionation upon oxidation of uranium-bearing rocks by fracture waters

    NASA Astrophysics Data System (ADS)

    Chernyshev, I. V.; Golubev, V. N.; Chugaev, A. V.; Mandzhieva, G. V.

    2016-10-01

    The variations in 238U/235U values accompanying mobilization of U by fracture waters from uranium-bearing rocks, in which U occurs as a fine impregnation of oxides and silicates, were studied by the high-precision (±0.07‰) MC-ICP-MS method. Transition of U into the aqueous phase in the oxidized state U(VI) is accompanied by its isotope fractionation with enrichment of dissolved U(VI) in the heavy isotope 238U up to 0.32‰ in relation to the composition of the solid phases. According to the sign, this effect is consistent with the tendency of the behavior of 238U and 235U upon interaction of river waters with rocks of the catchment areas [11] and with the effect observed during oxidation of uraninite by the oxygen-bearing NaHCO3 solution [12].

  3. 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

  4. Neutron Capture Cross Sections and Gamma Emission Spectra from Neutron Capture on 234,236,238U Measured with DANCE

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    A new measurement of the 238U(n, γ) cross section using a thin 48 mg/cm2 target was made using the DANCE detector at LANSCE over the energy range from 10 eV to 500 keV. The results confirm earlier measurements. Measurements of the gamma-ray emission spectra were also made for 238U(n, γ) as well as 234,236U(n, γ). These measurements help to constrain the radiative strength function used in the cross-section calculations.

  5. Evaluation of the 232Th Neutron Cross Sections between 4 keV and 140 keV

    SciTech Connect

    Volev, K.; Koyumdjieva, N.; Brusegan, A.; Borella, A.; Siegler, P.; Schillebeeckx, P.; Janeva, N.; Lukyanov, A.; Leal, L.

    2005-05-24

    An evaluation of the 232Th neutron total and capture cross sections has been performed in the energy region between 4 keV and 140 keV. The evaluation results from a simultaneous analysis of capture, transmission, and self-indication measurement data, including the most recent capture cross-section data obtained at the GELINA facility of the Institute for Reference Materials and Measurements at Geel (B) and at the n-TOF facility at CERN (CH). The experimental data have been analysed in terms of average resonance parameters exploiting two independent theoretical approaches -- the Characteristic Function model and the Hauser-Feshbach-Moldauer theory. The resulting parameters are consistent with the resolved resonance parameters deduced from the transmission measurements of Olsen et al. at the ORELA facility.

  6. Measurement of resolved resonances of 232Th(n,γ) at the n_TOF facility at CERN

    NASA Astrophysics Data System (ADS)

    Gunsing, F.; Berthoumieux, E.; Aerts, G.; Abbondanno, U.; Álvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Bečvář, F.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillman, I.; Dolfini, R.; Domingo-Pardo, C.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Goncalves, I.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Konovalov, V.; Kossionides, E.; Krtička, M.; Lampoudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2012-06-01

    The yield of the neutron capture reaction 232Th(n,γ) has been measured at the neutron time-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The reduction of the acquired data to the capture yield for resolved resonances from 1 eV to 4 keV is described and compared to a recent evaluated data set. The resonance parameters were used to assign an orbital momentum to each resonance. A missing level estimator was used to extract the s-wave level spacing of D0=17.2±0.9 eV.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  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. 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

  11. Uranium stable isotope fractionation in the Black Sea: Modern calibration of the 238U/235U paleo-redox proxy

    NASA Astrophysics Data System (ADS)

    Rolison, John M.; Stirling, Claudine H.; Middag, Rob; Rijkenberg, Micha J. A.

    2017-04-01

    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. Reliable interpretation of sedimentary isotopic information requires a thorough understanding 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 world's largest anoxic basin. Paired measurements of 238U/235U and U concentration, supported by other redox parameters, were obtained for water column and sediment samples collected during the 2013 GA04N GEOTRACES expedition to the Black Sea. Removal of U from the water column occurs during the redox transition of soluble U(VI) to relatively insoluble U(IV), resulting in up to 43% of U being removed from solution in euxinic bottom waters. Uranium reduction and removal is accompanied by a progressive shift in 238U/235U towards isotopically light values in the water column as heavier 238U is preferentially exported to sediments over lighter 235U. This gives rise to apparent isotope enrichment factors of ε = -0.63 ± 0.09‰ and ε = -0.84 ± 0.11‰ when U removal is modelled by Rayleigh and closed system equilibrium isotope fractionation, respectively. These ε values fall within the range determined for bacterial U reduction experiments, and together with a striking correlation between the distributions of U and H2S, implicate microbially-mediated U(VI)-U(IV) reduction as the primary mechanism controlling U isotopic shifts in the Black Sea. The 238U/235U of underlying sediments is related to the the 238U/235U of Black Sea bottom waters through the isotope enrichment factor of the U reduction reaction but the relationship between sedimentary and water column 238U/235U is complicated

  12. Mass yield distributions of fission products from photo-fission of 238U induced by 11.5-17.3 MeV bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Naik, H.; Carrel, Frédérick; Kim, G. N.; Laine, Frédéric; Sari, Adrien; Normand, S.; Goswami, A.

    2013-07-01

    The yields of various fission products in the 11.5, 13.4, 15.0 and 17.3 MeV bremsstrahlung-induced fission of 238U have been determined by recoil catcher and an off-line γ-ray spectrometric technique using the electron linac, SAPHIR at CEA, Saclay, France. The mass yield distributions were obtained from the fission product yields using charge-distribution corrections. The peak-to-valley ( P/ V ratio, average light mass (< A L>) and heavy mass (< A H>) and average number of neutrons (< v>) in the bremsstrahlung-induced fission of 238U at different excitation energies were obtained from the mass yield data. From the present and literature data in the 238U ( γ, f ) and 238U ( n, f ) reactions at various energies, the following observations were obtained: i) The mass yield distributions in the 238U ( γ, f ) reaction at various energies of the present work are double-humped, similar to those of the 238U ( n, f ) reaction of comparable excitation energy. ii) The yields of fission products for A = 133-134, A = 138-140, and A = 143-144 and their complementary products in the 238U ( γ, f) reaction are higher than other fission products due to the nuclear structure effect. iii) The yields of fission products for A = 133-134 and their complementary products are slightly higher in the 238U ( γ, f ) than in the 238U ( n, f ) , whereas for A = 138-140 and 143-144 and their complementary products are comparable. iv) With excitation energy, the increase of yields of symmetric products and the decrease of the peak-to-valley ( P/ V ratio in the 238U ( γ, f) reaction is similar to the 238U ( n, f) reaction. v) The increase of < v> with excitation energy is also similar between the 238U ( γ, f ) and 238U ( n, f) reactions. However, it is surprising to see that the < A L> and < A H> values with excitation energy behave entirely differently from the 238U ( γ, f ) and 238U ( n, f ) reactions.

  13. Neutron Productions from thin Be target irradiated by 50 MeV/u 238U beam

    NASA Astrophysics Data System (ADS)

    Lee, Hee-Seock; Oh, Joo-Hee; Jung, Nam-Suk; Oranj, Leila Mokhtari; Nakao, Noriaki; Uwamino, Yoshitomo

    2017-09-01

    Neutrons generated from thin beryllium target by 50 MeV/u 238U beam were measured using activation analysis at 15, 30, 45, and 90 degrees from the beam direction. A 0.085 mm-thick Be stripper of RIBF was used as the neutron generating target. Activation detectors of bismuth, cobalt, and aluminum were placed out of the stripper chamber. The threshold reactions of 209Bi(n, xn)210-xBi(x=4 8), 59Co(n, xn)60-xCO(x=2 5), 59Co(n, 2nα)54Mn, 27Al(n, α)24Na, and 27Al(n,2nα)22Na were applied to measure the production rates of radionuclides. The neutron spectra were obtained using an unfolding method with the SAND-II code. All of production rates and neutron spectra were compared with the calculated results using Monte Carlo codes, the PHITS and the FLUKA. The FLUKA results showed better agreement with the measurements than the PHITS. The discrepancy between the measurements and the calculations were discussed.

  14. 230Th/238U dating of hydrothermal sulfides from Duanqiao hydrothermal field, Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Yang, Weifang; Tao, Chunhui; Li, Huaiming; Liang, Jin; Liao, Shili; Long, Jiangping; Ma, Zhibang; Wang, Lisheng

    2017-06-01

    Duanqiao hydrothermal field is located between the Indomed and Gallieni fracture zones at the central volcano, at 50°28'E in the ultraslow-spreading Southwest Indian Ridge (SWIR). Twenty-eight subsamples from a relict chimney and massive sulfides were dated using the 230Th/238U method. Four main episodes of hydrothermal activity were determined according to the restricted results: 68.9-84.3, 43.9-48.4, 25.3-34.8, and 0.7-17.3 kyrs. Hydrothermal activity of Duanqiao probably started about 84.3 (±0.5) kyrs ago and ceased about 0.737 (±0.023) kyrs ago. The periodic character of hydrothermal activity may be related to the heat source provided by the interaction of local magmatism and tectonism. The estimated mean growth rate of the sulfide chimney is <0.02 mm/yr. This study is the first to estimate the growth rate of chimneys in the SWIR. The maximum age of the relict chimney in Duanqiao hydrothermal filed is close to that of the chimneys from Mt. Jourdanne (70 kyrs). The hydrothermal activity in Dragon Flag field is much more recent than that of Duanqiao or Mt. Jourdanne fields. The massive sulfides are younger than the sulfides from other hydrothermal fields such as Rainbow, Sonne and Ashadze-2. The preliminarily estimated reserves of sulfide ores of Duanqiao are approximately 0.5-2.9 million tons.

  15. Anomalies in the Charge Yields of Fission Fragments from the ^{238}U(n,f) Reaction.

    PubMed

    Wilson, J N; Lebois, M; Qi, L; Amador-Celdran, P; Bleuel, D; Briz, J A; Carroll, R; Catford, W; De Witte, H; Doherty, D T; Eloirdi, R; Georgiev, G; Gottardo, A; Goasduff, A; Hadyńska-Klęk, K; Hauschild, K; Hess, H; Ingeberg, V; Konstantinopoulos, T; Ljungvall, J; Lopez-Martens, A; Lorusso, G; Lozeva, R; Lutter, R; Marini, P; Matea, I; Materna, T; Mathieu, L; Oberstedt, A; Oberstedt, S; Panebianco, S; Podolyák, Zs; Porta, A; Regan, P H; Reiter, P; Rezynkina, K; Rose, S J; Sahin, E; Seidlitz, M; Serot, O; Shearman, R; Siebeck, B; Siem, S; Smith, A G; Tveten, G M; Verney, D; Warr, N; Zeiser, F; Zielinska, M

    2017-06-02

    Fast-neutron-induced fission of ^{238}U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ-γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly.

  16. Anomalies in the Charge Yields of Fission Fragments from the 238U (n ,f ) Reaction

    NASA Astrophysics Data System (ADS)

    Wilson, J. N.; Lebois, M.; Qi, L.; Amador-Celdran, P.; Bleuel, D.; Briz, J. A.; Carroll, R.; Catford, W.; De Witte, H.; Doherty, D. T.; Eloirdi, R.; Georgiev, G.; Gottardo, A.; Goasduff, A.; Hadyńska-Klek, K.; Hauschild, K.; Hess, H.; Ingeberg, V.; Konstantinopoulos, T.; Ljungvall, J.; Lopez-Martens, A.; Lorusso, G.; Lozeva, R.; Lutter, R.; Marini, P.; Matea, I.; Materna, T.; Mathieu, L.; Oberstedt, A.; Oberstedt, S.; Panebianco, S.; Podolyák, Zs.; Porta, A.; Regan, P. H.; Reiter, P.; Rezynkina, K.; Rose, S. J.; Sahin, E.; Seidlitz, M.; Serot, O.; Shearman, R.; Siebeck, B.; Siem, S.; Smith, A. G.; Tveten, G. M.; Verney, D.; Warr, N.; Zeiser, F.; Zielinska, M.

    2017-06-01

    Fast-neutron-induced fission of 238U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ -ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ -γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly.

  17. 230Th/238U dating of hydrothermal sulfides from Duanqiao hydrothermal field, Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Yang, Weifang; Tao, Chunhui; Li, Huaiming; Liang, Jin; Liao, Shili; Long, Jiangping; Ma, Zhibang; Wang, Lisheng

    2016-11-01

    Duanqiao hydrothermal field is located between the Indomed and Gallieni fracture zones at the central volcano, at 50°28'E in the ultraslow-spreading Southwest Indian Ridge (SWIR). Twenty-eight subsamples from a relict chimney and massive sulfides were dated using the 230Th/238U method. Four main episodes of hydrothermal activity were determined according to the restricted results: 68.9-84.3, 43.9-48.4, 25.3-34.8, and 0.7-17.3 kyrs. Hydrothermal activity of Duanqiao probably started about 84.3 (±0.5) kyrs ago and ceased about 0.737 (±0.023) kyrs ago. The periodic character of hydrothermal activity may be related to the heat source provided by the interaction of local magmatism and tectonism. The estimated mean growth rate of the sulfide chimney is <0.02 mm/yr. This study is the first to estimate the growth rate of chimneys in the SWIR. The maximum age of the relict chimney in Duanqiao hydrothermal filed is close to that of the chimneys from Mt. Jourdanne (70 kyrs). The hydrothermal activity in Dragon Flag field is much more recent than that of Duanqiao or Mt. Jourdanne fields. The massive sulfides are younger than the sulfides from other hydrothermal fields such as Rainbow, Sonne and Ashadze-2. The preliminarily estimated reserves of sulfide ores of Duanqiao are approximately 0.5-2.9 million tons.

  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. Cross-sections of the reaction 232Th(p,3n)230Pa for production of 230U for targeted alpha therapy.

    PubMed

    Morgenstern, Alfred; Apostolidis, Christos; Bruchertseifer, Frank; Capote, Roberto; Gouder, Thomas; Simonelli, Federica; Sin, Mihaela; Abbas, Kamel

    2008-10-01

    (230)U/(226)Th is a promising novel alpha-emitter system for application in targeted alpha therapy of cancer. The therapeutic nuclides can be produced by proton irradiation of natural (232)Th according to the reaction (232)Th(p,3n)(230)Pa, followed by subsequent beta decay of (230)Pa to (230)U. In this study, the experimental excitation function for the (232)Th(p,3n)(230)Pa reaction up to 34 MeV proton energy has been measured using the stacked-foil technique. The proton energies in the various foils were calculated with the SRIM 2003 code and gamma-ray spectrometry was used to measure the activities of the various radioisotopes produced. The measured cross-sections are in good agreement with selected literature values and with model calculations using the EMPIRE II code. The reaction (232)Th(p,3n)(230)Pa allows the production of carrier-free (230)U in clinically relevant levels.

  20. 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

  1. Light and heavy transfer products in 136Xe+238U multinucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Vogt, A.; Birkenbach, B.; Reiter, P.; Corradi, L.; Mijatović, T.; Montanari, D.; Szilner, S.; Bazzacco, D.; Bowry, M.; Bracco, A.; Bruyneel, B.; Crespi, F. C. L.; de Angelis, G.; Désesquelles, P.; Eberth, J.; Farnea, E.; Fioretto, E.; Gadea, A.; Geibel, K.; Gengelbach, A.; Giaz, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hess, H.; John, P. R.; Jolie, J.; Judson, D. S.; Jungclaus, A.; Korten, W.; Leoni, S.; Lunardi, S.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Montagnoli, G.; Napoli, D.; Pellegri, L.; Pollarolo, G.; Pullia, A.; Quintana, B.; Radeck, F.; Recchia, F.; Rosso, D.; Şahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Steinbach, T.; Stezowski, O.; Szpak, B.; Theisen, Ch.; Ur, C.; Valiente-Dobón, J. J.; Vandone, V.; Wiens, A.

    2015-08-01

    Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in +238U 136Xe have been measured in a high-resolution γ -ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the grazing model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z =93 is found to perform nuclear structure investigations. In-beam γ -ray spectroscopy is feasible for few-neutron transfer channels in U and the -2 p channel populating Th isotopes.

  2. 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.

  3. High precision measurement of the radiative capture cross section of 238U at the n_TOF CERN facility

    NASA Astrophysics Data System (ADS)

    Mingrone, F.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Barbagallo, M.; Bečvář, F.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calviño, F.; Calviani, M.; 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.; Durán, I.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Furman, V.; Göbel, K.; Gómez-Hornillos, M. B.; Ganesan, S.; García, A. R.; Giubrone, G.; Gonçalves, I. F.; González, E.; Goverdovski, A.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Heftrich, T.; Hernández-Prieto, A.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Katabuchi, T.; Ketlerov, V.; Khryachkov, V.; Kivel, N.; Koehler, P.; Kokkoris, M.; Kroll, J.; Krtička, M.; Lampoudis, C.; Langer, C.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Leong, L. S.; Lerendegui-Marco, J.; Losito, R.; Mallick, A.; Manousos, A.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mirea, M.; Mondelaers, W.; Paradela, C.; Pavlik, A.; Perkowski, J.; Plompen, A. J. M.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Robles, M.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiss, C.; Wright, T.; Žugec, P.

    2017-09-01

    The importance of improving the accuracy on the capture cross-section of 238U has been addressed by the Nuclear Energy Agency, since its uncertainty significantly affects the uncertainties of key design parameters for both fast and thermal nuclear reactors. Within the 7th framework programme ANDES of the European Commission three different measurements have been carried out with the aim of providing the 238U(n,γ) cross-section with an accuracy which varies from 1 to 5%, depending on the energy range. Hereby the final results of the measurement performed at the n_TOF CERN facility in a wide energy range from 1 eV to 700 keV will be presented.

  4. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Counting neutrons from the spontaneous fission of {sup 238}U using scintillation detectors and mixed field analysers

    SciTech Connect

    Parker, Helen M. O'D.; Joyce, Malcolm J.; Jones, Ashley

    2015-07-01

    It is well documented that {sup 238}U decays by spontaneous fission, and that it is the main component of most nuclear fuels. As nuclear fuels are largely classed as Special Nuclear Material (SNM), they have to be fully accounted for by owners and processing facilities. One possible method for verifying declared amounts of SNM is to count the spontaneous neutrons produced from {sup 238}U. Using four EJ-309 liquid scintillation detectors and a mixed field analyser, spontaneous neutrons from 16.4 g of depleted uranium (0.3% enrichment) have been assayed. The assay method shows promising results and this proof of principle will be researched further in order for it to be applied in an industrial setting. (authors)

  6. 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.

  7. Comparison of yields of neutron-rich nuclei in proton- and photon-induced 238U fission

    NASA Astrophysics Data System (ADS)

    Khan, F. A.; Bhowmick, Debasis; Basu, D. N.; Farooq, M.; Chakrabarti, Alok

    2016-11-01

    A comparative study of fission of actinides, especially 238U, by proton and bremsstrahlung photon is performed. The relative mass distribution of 238U fission fragments has been explored theoretically for both proton- and photon-induced fission. The integrated yield along with charge distribution of the products are calculated to find the neutron richness in comparison with the nuclei produced by the r process in nucleosynthesis. Some r -process nuclei in the intermediate-mass range for symmetric fission mode are found to be produced almost two orders of magnitude more for proton-induced fission than for photofission, although the rest of the neutron-rich nuclei in the asymmetric mode are produced in comparable proportion for both processes.

  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. Separation of actinides using capillary extraction chromatography-inductively coupled plasma mass spectrometry.

    PubMed

    Peterson, Dominic S; Montoya, Velma M

    2009-08-01

    Trace levels of actinides have been separated on capillary extraction chromatography columns. Detection of the actinides was achieved using an inductively coupled plasma mass spectrometer, which was coupled with the extraction chromatography system. In this study, we compare 30-cm long, 4.6 mm i.d. columns to capillary columns (750 microm i.d.) with lengths from 30 cm up to 150 cm. The columns that were tested were packed with TRU resin. We were able to separate a mixture of five actinides ((232)Th, (238)U, (237)Np, (239)Pu, and (241)Am). This work has application to rapid bioassay as well as automated separations of actinide materials.

  10. /sup 238/U, /sup 226/Ra and /sup 210/Pb in some vent waters of the Galapagos spreading center

    SciTech Connect

    Krishnaswami, S.; Turekian, K.K.

    1982-08-01

    The concentrations of /sup 226/Ra, /sup 238/U and /sup 210/Pb have been measured in waters from the Mussel Bed and the Rose Garden thermal fields at the Galapagos spreading center over a temperature range of approx.2.5--16 /sup 0/C. The /sup 226/Ra-T plots yield slopes of 0.112 and 0.036 dpm/kg /sup 0/C for the Mussel Bed and the Rose Garden respectively yielding a global hydrothermal /sup 226/Ra flux less than 5% of that required to sustain the oceanic inventory. /sup 238/U concentration in waters <9 /sup 0/C is the same as that in ambient sea water whereas water hotter than approx.9 /sup 0/C shows a decreasing trend with temperature to zero /sup 238/U at approx.29 /sup 0/C. /sup 210/Pb concentration in Mussel Bed increases with temperature, and extrapolated to approx.350 /sup 0/C yields a /sup 210/Pb concentration considerably less than that expected from /sup 222/Rn decay and basalt alteration.

  11. Investigation of the 238U(d ,p ) surrogate reaction via the simultaneous measurement of γ -decay and fission probabilities

    NASA Astrophysics Data System (ADS)

    Ducasse, Q.; Jurado, B.; Aïche, M.; Marini, P.; Mathieu, L.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Tornyi, T.; Wilson, J. N.; Barreau, G.; Boutoux, G.; Czajkowski, S.; Giacoppo, F.; Gunsing, F.; Hagen, T. W.; Lebois, M.; Lei, J.; Méot, V.; Morillon, B.; Moro, A. M.; Renstrøm, T.; Roig, O.; Rose, S. J.; Sérot, O.; Siem, S.; Tsekhanovich, I.; Tveten, G. M.; Wiedeking, M.

    2016-08-01

    We investigated the 238U(d ,p ) reaction as a surrogate for the n +238U reaction. For this purpose we measured for the first time the γ -decay and fission probabilities of *239U simultaneously and compared them to the corresponding neutron-induced data. We present the details of the procedure to infer the decay probabilities, as well as a thorough uncertainty analysis, including parameter correlations. Calculations based on the continuum-discretized coupled-channels method and the distorted-wave Born approximation (DWBA) were used to correct our data from detected protons originating from elastic and inelastic deuteron breakup. In the region where fission and γ emission compete, the corrected fission probability is in agreement with neutron-induced data, whereas the γ -decay probability is much higher than the neutron-induced data. We have performed calculations of the decay probabilities with the statistical model and of the average angular momentum populated in the 238U(d ,p ) reaction with the DWBA to interpret these results.

  12. 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.

  13. 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.

  14. Testing the 234U/238U weathering tracer in a tropical granitoid watershed, Luquillo, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Pett-Ridge, J. C.; Derry, L. A.

    2006-12-01

    Recent studies have employed U-series disequilibria as a tracer of both weathering profile development and of timescale of erosion for whole watersheds. We have undertaken a detailed analysis of the behavior of the U- series isotopes in a previously well-characterized watershed in order to test this approach. In the Rio Icacos watershed in the Luquillo Mountains of Puerto Rico, previous studies have determined both the rate of propagation of the chemical weathering front by regolith mass balance analysis, and the surface denudation rate using the cosmogenic 10Be tracer. Our study aims to determine whether the U-series approach provides regolith development and erosion rates in agreement with those previously determined. In order to better constrain interpretations based on U-series data, we have coupled the U-series analysis with analyses of trace element concentrations, δ^{30}Si, Ge/Si, and 87Sr/86Sr ratios. Used together, these geochemical tracers provide a powerful tool for understanding weathering reactions, chemical transfers within and out of the weathering profile, and the timing of these chemical transfers. Analyses of soil, saprolite and pore water samples reveal a complex history of U and Th transformations including mobilization of both U and Th in the soil followed by re-adsorption deeper in the profile. 234U/238U activity ratios in soil and saprolite show significant variability both with depth, and also among individual mineral phases at any particular depth. This variation among mineral phases, combined with the likely physical sorting of these phases during erosional transport, results in an additional isotopic fractionation unrelated to that imparted by the weathering process. This implies that suspended sediment samples taken from streamwater are unlikely to accurately reflect the average disequilibria carried by the secondary minerals phases in the soil and saprolite. Our analyses also reveal a significant contribution of atmospheric mineral

  15. Using 238U/235U ratios to understand the formation and oxidation of reduced uranium solids in naturally reduced zones

    NASA Astrophysics Data System (ADS)

    Jemison, N.; Johnson, T. M.; Druhan, J. L.; Davis, J. A.

    2016-12-01

    Uranium occurs in groundwater primarily as soluble and mobile U(VI), which can be reduced to immobile U(IV), often observed in sediments as uraninite. Numerous U(VI)-contaminated sites, such as the DOE field site in Rifle, CO, contain naturally reduced zones (NRZ's) that have relatively high concentrations of organic matter. Reduction of heavy metals occurs within NRZ's, producing elevated concentrations of iron sulfides and U(IV). Slow, natural oxidation of U(IV) from NRZ's may prolong U(VI) contamination of groundwater. The reduction of U(VI) produces U(IV) with a higher 238U/235U ratio. Samples from two NRZ sediment cores recovered from the Rifle site revealed that the outer fringes of the NRZ contain U(IV) with a high 238U/235U ratio, while lower values are observed in the center . We suggest that as aqueous U(VI) was reduced in the NRZ, it was driven to lower 238U/235U values, such that U(IV) formed in the core of the NRZ reflects a lower 238U/235U. Two oxidation experiments were conducted by injecting groundwater containing between 14.9 and 21.2 mg/L dissolved O2 as an oxidant into the NRZ. The oxidation of U(IV) from this NRZ increased aqueous U(VI) concentrations and caused a shift to higher 238U/235U in groundwater as U(IV) was oxidized primarily on the outer fringes of the NRZ. In total these observations suggest that the stability of solid phase uranium is governed by coupled reaction and transport processes. To better understand various reactive transport scenarios we developed a model for the formation and oxidation of NRZ's utilizing the reactive transport software CrunchTope. These simulations suggest that the development of isotopically heterogeneous U(IV) within NRZ's is largely controlled by permeability of the NRZ and the U(VI) reduction rate. Oxidation of U(IV) from the NRZ's is constrained by the oxidation rate of U(IV) as well as iron sulfides, which can prevent oxidation of U(IV) by scavenging dissolved oxygen.

  16. 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

  17. Determination of neutron capture cross sections of 232Th at 14.1 MeV and 14.8 MeV using the neutron activation method

    NASA Astrophysics Data System (ADS)

    Lan, Chang-Lin; Zhang, Yi; Lv, Tao; Xie, Bao-Lin; Peng, Meng; Yao, Ze-En; Chen, Jin-Gen; Kong, Xiang-Zhong

    2017-04-01

    The 232Th(n, γ)233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method. The neutron flux was determined using the monitor reaction 27Al(n,α)24Na. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VII.1, JENDL-4.0u+, and CENDL-3.1. The excitation functions of the 232Th(n,γ)233Th reaction were also calculated theoretically using the TALYS1.6 computer code. Supported by Chinese TMSR Strategic Pioneer Science and Technology Project-The Th-U Fuel Physics Term (XDA02010100) and National Natural Science Foundation of China (11205076, 21327801)

  18. 226Ra, 232Th and 40K contents in water samples in part of central deserts in Iran and their potential radiological risk to human population

    PubMed Central

    2014-01-01

    Background The radiological quality of 226Ra, 232Th and 40K in some samples of water resources collected in Anarak-Khour a desertic area, Iran has been measured by direct gamma ray spectroscopy using high purity germanium detector in this paper. Result The concentration ranged from ≤0.5 to 9701 mBq/L for 226Ra; ≤0.2 to 28215 mBq/L for 232Th and < MDA to 10332 mBq/L for 40K. The radium equivalent activity was well below the defined limit of 370Bq/L. The calculated external hazard indices were found to be less than 1 which shows a low dose. Conclusion These results can be contributed to the database of this area because it may be used as disposal sites of nuclear waste in future. PMID:24883192

  19. Fission cross section of the 232Th(n,f)131Sb reaction induced by neutrons around 14 MeV

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Lv, Tao; Pan, Xiao-dong; Wang, Qiang; Fang, Kai-hong; Lan, Chang-lin

    2017-06-01

    In order to make a more detailed study on the 232Th fission process, the cross section of 232Th(n,f)131Sb fission reaction induced by 14 MeV neutrons was measured precisely with the neutron activation method and off-line gamma ray spectrometric technique. Neutron flux was monitored on line using the accompanying α particle from T(d,n)4He reaction in the irradiation and neutron energies were given by the cross section ratio of 90Zr(n,2 n)89Zr reaction to 93Nb(n,2 n)92 mNb reaction. The experimentally determined cross sections were deduced to be 6.27±0.47, 6.19±0.54, 6.00±0.51 mb at 14.1±0.3, 14.5±0.3 and 14.8±0.3 MeV, respectively.

  20. Uranium ((238)U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi.

    PubMed

    Annamalai, Sathesh Kumar; Arunachalam, Kantha Deivi

    2017-03-02

    The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of (238)U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC50 doses of waterborne (238)U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods-0h, 24h, 48h, 72h, 96h, 7, days 14days and 21 days-using ICP-MS to determine the toxic effects of uranium and the accumulation of (238)U concentrations. The bioaccumulation of (238)U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills>liver>brain>tissue, with the highest accumulation in the gills. It was observed that exposure to (238)U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term (238)U exposure studies in fish showed increasing micronucleus frequencies in erythrocytes with greater exposure time. The higher the concentration of (238)U is, the greater is the effect observed, suggesting a close relationship between accumulation and toxicity. A possible ROS-mediated (238)U toxicity mechanism and antioxidant responses have been proposed.

  1. 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.

  2. STUDY OF NATURAL RADIOACTIVITY (226Ra, 232Th AND 40K) IN SOIL SAMPLES FOR THE ASSESSMENT OF AVERAGE EFFECTIVE DOSE AND RADIATION HAZARDS.

    PubMed

    Bangotra, Pargin; Mehra, Rohit; Kaur, Kirandeep; Jakhu, Rajan

    2016-10-01

    The activity concentration of (226)Ra (radium), (232)Th (thorium) and (40)K (potassium) has been measured in the soil samples collected from Mansa and Muktsar districts of Punjab (India) using NaI (Tikl) gamma detector. The concentration of three radionuclides ((226)Ra, (232)Th and (40)K) in the studied area has been varied from 18±4 to 46±5, 53±7 to 98±8 and 248±54 to 756±110 Bq kg(-1), respectively. Radium equivalent activities (Raeq) have been calculated in soil samples for the assessment of the radiation hazards arising due to the use of these soil samples. The absorbed dose rate of (226)Ra, (232)Th and (40)K in studied area has been varied from 8 to 21, 33 to 61 and 9 to 25 nGy h(-1), respectively. The corresponding indoor and outdoor annual effective dose in studied area was 0.38 and 0.09 mSv, respectively. The external and internal hazard has been also calculated for the assessment of radiation hazards in the studied area.

  3. Measurement of cross sections for the {sup 232}Th(P,4n){sup 229}Pa reaction at low proton energies

    SciTech Connect

    Jost, C. U.; Griswold, J. R.; Bruffey, S. H.; Mirzadeh, S.; Stracener, D. W.; Williams, C. L.

    2013-04-19

    The alpha-emitters {sup 225}Ac and {sup 213}Bi are of great interest for alpha-radioimmunotherapy which uses radioisotopes attached to cancer-seeking antibodies to efficiently treat various types of cancers. Both radioisotopes are daughters of the long-lived {sup 229}Th(t{sub 1/2} = 7880y). {sup 229}Th can be produced by proton irradiation of {sup 232}Th and {sup 230}Th, either directly or through production of isobars that beta-decay into {sup 229}Th. To obtain excitation functions, {sup 232}Th and {sup 230}Th have been irradiated at the On-Line Test Facility at the Holifield Radioactive Ion Beam Facility at ORNL. Benchmark tests conducted with Cu and Ni foils show very good agreement with literature results. The experiments with thorium targets were focused on the production of {sup 229}Pa and its daughter {sup 225}Ac from both {sup 232}Th and {sup 230}Th. Differential cross-sections for production of {sup 229}Pa and other Pa isotopes have been obtained.

  4. TECHNICAL EQUIVALENCE BETWEEN PERKIN-ELMER DRCe AND ELAN 6000 FOR THE ANALYSIS OF 238U IN URINE BIOASSAY SAMPLES

    SciTech Connect

    Wong, C T; Collins, L J

    2007-09-05

    The LLNL Bioassay Laboratory recently purchased a Perkin-Elmer DRCe ICP-MS (DRCe) to replace the existing Perkin-Elmer Elan 6000 ICP-MS (Elan 6000) used for the analysis of {sup 238}U in urine bioassay samples. In accordance with section 5.7.2 of DOE-STD-1112-98, 'The Department of Energy Laboratory Accreditation Program for Radiobioassay', this document demonstrates that the DRCe is technically equivalent to the Elan 6000. This paper documents: (1) Minor changes made in the procedure to improve the sensitivity; (2) Detection limits for the Elan 6000 and the DRCe; (3) Determination of the measurement uncertainty for the DRCe; and (4) Comparison of results from the DRCe versus the Elan 6000. A 1 mL aliquot of the sample is transferred to an auto sampler tube. Nitric acid and {sup 233}U (used as an internal standard) are added to the samples and the samples are digested in a microwave oven. The digested samples are diluted to 10 mL with deionized water and the {sup 238}U concentration is determined by ICP-MS. The ICP-MS is calibrated with a series of {sup 238}U standards. {sup 233}U is used as an internal standard to correct for suppression of the signal due to the sample matrix. The Elan 6000 is run in the peakhopping mode with 100 ms dwell times and 50 sweeps. The total integration time is 5,000 ms. The average of two measurements is used for the determination.

  5. 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.

  6. 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.

  7. Probing the role of Skyrme interactions on the fission dynamics of the 6Li + 238U reaction

    NASA Astrophysics Data System (ADS)

    Sharma, Ishita; Kumar, Raj; Sharma, Manoj K.

    2017-06-01

    The performance of selected five Skyrme forces (out of a set of 240), tested by Dutra et al., is analyzed in view of fusion-fission dynamics. These forces are assumed to perform better for neutron-rich systems, so the choice of the reaction is accordingly made by opting for a neutron-rich target in 6Li + 238U reaction. This reaction is diagnosed further in reference to fusion hindrance within the dynamical approach of the cluster-decay model (DCM). In order to reduce the computational time, three Skyrme forces are figured out with the criteria that these forces cover the barrier characteristics of the remaining two forces as well. The fission cross-sections are successfully addressed at low energies for the 6Li + 238U reaction. However, at relatively higher energies, the excitation functions show theoretical suppression with respect to experimental data, which may be associated with the possible existence of incomplete fusion (ICF). For ICF, we have considered that the 6Li broke into 4He + 2H, as mentioned in the experimental work. The calculations of ICF are carried out for the 4He + 238U reaction with the selected Skyrme forces at E_{c.m.} = 26.20 and 27.51 MeV. These forces address the data nicely for the compound nucleus (CN) as well as ICF processes. Here, the NRAPR force seems to require lesser barrier modification as compared to the other forces, therefore it can be used as an alternate choice for calculating the interaction potential. Additionally, the prediction of cross-sections at lower energies has been done with DCM using the NRAPR force. The ℓ-dependent % barrier modification of the Skyrme forces undertaken is also worked out in reference to fusion hindrance at below barrier energies.

  8. Neutron multiplicity in the fission of 238U and 235U with neutrons up to 200 MeV.

    PubMed

    Ethvignot, T; Devlin, M; Duarte, H; Granier, T; Haight, R C; Morillon, B; Nelson, R O; O'Donnell, J M; Rochman, D

    2005-02-11

    Prompt-fission-neutron multiplicities were measured for 238U(n,f) and 235U(n,f) from 0.4 to 200 MeV. The data are of great importance in connection with accelerator-coupled nuclear reactor systems incinerating actinides. We report that fission induced by 200 MeV neutrons produces approximately 10 more prompt neutrons than fission induced by reactor neutrons. Most neutrons are evaporated from the fission fragments and the prefission compound nucleus, as the preequilibrium emission of energetic neutrons accounts for a maximum of 15% of the prompt neutrons at 200 MeV.

  9. 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.

  10. Spectroscopy of neutron-rich Fe isotopes populated in the {sup 64}Ni+{sup 238}U reaction

    SciTech Connect

    Lunardi, S.; Lenzi, S. M.; Farnea, E.; Bazzacco, D.; Beghini, S.; Mason, P.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Scarlassara, F.; Ur, C. A.; Vedova, F. Della; Gadea, A.; Corradi, L.; Angelis, G. de; Fioretto, E.; Napoli, D. R.; Orlandi, R.; Stefanini, A. M.; Valiente-Dobon, J. J.

    2007-09-15

    The neutron-rich Fe isotopes from A=61 to 66 were studied through multinucleon transfer reactions by bombarding a {sup 238}U target with a 400 MeV {sup 64}Ni beam. Unambiguous identification of prompt {gamma} rays belonging to each nucleus was achieved using coincidence relationships with the ions detected in a high-acceptance magnetic spectrometer. The new data extend our knowledge of the level structure of Fe isotopes, which is discussed in terms of the systematics of the region and compared with large-scale shell-model calculations.

  11. 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

  12. Uranium contents and (235)U/(238)U atom ratios in soil and earthworms in western Kosovo after the 1999 war.

    PubMed

    Di Lella, L A; Nannoni, F; Protano, G; Riccobono, F

    2005-01-20

    The uranium content and (235)U/(238)U atom ratio were determined in soils and earthworms of an area of Kosovo (Djakovica garrison), heavily shelled with depleted uranium (DU) ammunition during the 1999 war. The aim of the study was to reconstruct the small-scale distribution of uranium and assess the influence of the DU added to the surface environment. The total uranium concentration and the (235)U/(238)U ratio of topsoils showed great variability and were inversely correlated. The highest uranium levels (up to 31.47 mg kg(-1)) and lowest (235)U/(238)U ratios (minimum 0.002147) were measured in topsoils collected inside, or very close to, the clusters of DU penetrator holes. Regarding the fractionation of uranium in the surface soils, the uranium concentrations in the soluble and exchangeable fractions increased as the total uranium concentration of the topsoils increased. High and rather uniform percentage contents of uranium (24-36%) were associated with the poorly crystalline iron oxide phases of soils. In the U-enriched soils the elevated levels of the element were probably due to the presence of very small, unevenly distributed oxidized DU particles. The total uranium concentration in earthworms was in the range 0.142-0.656 mg kg(-1), with the highest concentrations in Lumbricus terrestris. The juveniles of all three studied species seemed to accumulate uranium more than adults, probably due to age-related differences in metabolism. The (235)U/(238)U ratio in the earthworms was variable (0.005241-0.007266) and independent of both the total uranium contents in soils and the absolute uranium levels in the animals. Bioconcentration was greater at lower U concentrations in soil, probably due to an increasing rate of elimination of uranium by the earthworms as the soil contents of the element increase. The results of this study clearly indicate that DU was added to the soil of the study area. Nevertheless, the phenomenon was very limited spatially and the total

  13. Activity concentration, transfer factors and resultant radiological risk of 226Ra, 232Th, and 40K in soil and some vegetables consumed in Selangor, Malaysia

    NASA Astrophysics Data System (ADS)

    Solehah, A. R.; Yasir, M. S.; Samat, S. B.

    2016-11-01

    The activity concentrations of the natural radionuclides 226Ra, 232Th, and 40K were determined in vegetable crops consumed by Malaysian people in Sungai Besar, Selangor. Sample of vegetables and the soil where the crops were cultivated and collected at five different location. The activity concentrations in Bq/kg of 226Ra, 232Th, and 40K were measured by the gamma-ray spectroscopy using the high purity germanium detector. The range activity concentration in soil is between 51.81 and 71.84 Bq/kg, 64.18 and 78.00 Bq/kg, and 210.49 and 244.29 Bq/kg for 226Ra, 232Th, and 40K, respectively. The activity concentration of 226Ra, 232Th, and 40K in vegetables were found to be in the range of 2.06 to 5.44 Bq/kg, Not Detectable to 0.61 Bq/kg, and 101.00 to 1223.09 Bq/kg, respectively. The activity concentration in both soil and vegetables were all less than lower limit stated by UNSCEAR. The Transfer Factors range value for 226Ra, 232Th, and 40K varied from 0.02 to 0.06, 0.003 to 0.008, and 1.79 to 5.19 respectively. Radium equivalent for soil range from 165.57 to 194.84 Bq/kg. It was within the international accepted value (370 Bq/kg). Absorb dose rate for soil range between 73.5 to 86.40 nGyh-1, in safe range from limit of international accepted value (55nGyh-1). Effective dose rate is found to be in range of 0.09 to 0.11 mSvy-1 for soil which is less than 2.4 mSv/y. External and Internal Hazard indices of soil was all below 1, within agreement of other researcher and UNSCEAR. The estimation of the consequent radiological risk due to the presence of those radionuclides is significantly low.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Finkel, R. C.

    In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and 234U/238U 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. 234U/238U 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.

  19. 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

  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. 238U-Series in Fe Oxy/Hydroxides by LA-MC-ICP-MS, New Insights Into Weathering Geochronology

    NASA Astrophysics Data System (ADS)

    Bernal, J.; McCulloch, M.; Eggins, S.; Grun, R.; Eggleton, R.

    2003-12-01

    The establishment of a geochronological framework for weathering processes is essential for an understanding of the evolution of the regolith and its dynamics. However, there are few robust answers regarding the absolute age of weathering and its rates. Nowadays, 40Ar/39Ar analysis of Mn-Oxides (cryptomelane) and K-bearing secondary sulphates have provided one of the few generally reliable chronometers (e.g. 1), but is restricted to high-K secondary phases. This work presents a different approach to obtain geochronological information from weathering minerals, namely measurement of 238U-series disequilibria in authigenic Fe oxy/hydroxides. These may be potentially useful recorders of weathering processes as they commonly occur as weathering products and have high affinity towards dissolved uranyl complexes. Furthermore, U-Th fractionation during weathering has been extensively reported [2], effectively resetting the U/230Th geochronometer. LA-MC-ICP-MS facilitates in situ measurement of 238U-series disequilibria in authigenic microcrystalline iron oxy/hydroxides (precipitated between cracks and veins in partially and heavily weathered chlorite-muscovite schist) and pisoliths (ferruginous concretions). Contrary to previous studies [e.g. 3], in situ measurement of 238U-nuclides enables selective analysis or iron oxy/hydroxides phases, minimizes contributions from allogenic phases and, reduces the need of mathematical corrections to obtain the activity ratios for the authigenic phase [4, 5]. The results suggest that supergene iron oxy/hydroxides are good recorders of weathering processes; they precipitate during the early stages of weathering, reflect the U-isotopic composition of the groundwater, appear to act as closed-systems in weathering conservative environments, and behave in a predictable fashion when subjected to intense weathering and leaching conditions. The 230Th-ages of the iron oxy/hydroxides indicate that the timing and intensity of weathering appears

  2. Measurement of the Total Kinetic Energy Release (TKE) in 232 Th(n,f) with En = 2.59 - 87.31 MeV

    NASA Astrophysics Data System (ADS)

    King, Jonathan; Yanez, Ricardo; Barrett, Jonathan; Loveland, Walter; Tovesson, Fredrik; Fotiades, Nick; Lee, Hye Young

    2015-04-01

    Experimental results for the Total Kinetic Energy Release (TKE) of 232 Th(n,f) with En = 2.59 - 87.31 MeV will be presented. The experiment was performed at the 15R beamline at the Weapons Neutron Research(WNR) facility at LANL-LANSCE. WNR provides a white spectrum of neutrons peaking at 2 MeV and reaching up to 800 MeV, with neutron energies being deduced from measurements of the neutron time of flight (TOF). A thin-backed 232 ThF4 target of 2 cm diameter with a thorium areal density of 178.9 μg/cm2 was placed between two arrays of Hammamatsu PIN diodes (active area 4 cm2 each). The beam was collimated to 1 cm diameter. The target was placed 45 degrees off of the beam axis, with the detectors at 60 degrees and 120 degrees from the beam axis. Over 25,000 fission fragment coincidence events were recorded, allowing for sixteen energy bins between 2.59 and 87.31 MeV. We believe that this will be the most comprehensive published measurement of the TKE for 232 Th(n,f) with En = 2.59 - 87.31 MeV. This work was supported in part by the Director, Office of Energy Research, Division of Nuclear Physics of the Office of High Energy and Nuclear Physics of the USDoE under Grant DE-FG06-97ER41026. This work has benefited from the use of the Los Alamos Neutron Science Center at the Los Alamos National Laboratory. This facility is funded by the USDoE under DOE Contract No. DE-AC52-06NA25396.

  3. Cost-based optimizations of power density and target-blanket modularity for {sup 232}Th/{sup 233}U-based ADEP

    SciTech Connect

    Krakowski, R.A.

    1995-07-01

    A cost-based parametric systems model is developed for an Accelerator-Driven Energy Production (ADEP) system based on a {sup 232}Th/{sup 233}U fuel cycle and a molten-salt (LiF/BeF{sub 2}/ThF{sub 3}) fluid-fuel primary system. Simplified neutron-balance, accelerator, reactor-core, chemical-processing, and balance-of-plant models are combined parametrically with a simplified costing model. The main focus of this model is to examine trade offs related to fission power density, reactor-core modularity, {sup 233}U breeding rate, and fission product transmutation capacity.

  4. Activity measurements of a suite of radionuclides (241Am, 239,240Pu, 238Pu, 238U, 234U, 235U, 232Th, 230Th, 228Th, 228Ra, 137Cs, 210Pb, 90Sr and 40K) in biota reference material (Ocean Shellfish): CCRI(II)-S3

    NASA Astrophysics Data System (ADS)

    Nour, S.; Karam, L. R.; Inn, K. G. W.

    2012-01-01

    In 2005, the CCRI decided that a comparison undertaken from 2002 to 2008 by the NIST (under the auspices of the Inter-America Metrology System [SIM]) in the development of a new biota (Ocean Shellfish) standard reference material (SRM) was sufficiently well constructed that it could be converted into a supplementary comparison under CCRI(II), with comparison identifier CCRI(II)-S3. This would enable the comparison to be used to support calibration and measurement capability (CMC) claims for radionuclide measurements in reference materials (specifically, animal-based organic materials). Previous comparisons of radionuclides have been of single or multiple nuclides in non-complex matrices and results of such could not be extended to support capabilities to measure the same nuclides in reference materials. The results of this comparison have been used to determine the certified reference value of the SRM. The key comparison working group (KCWG) of the CCRI(II) has approved this approach as a mechanism to link all the results to certified 'reference values' in lieu of the key comparison reference value (KCRV) of these specified radionuclides in this type of matrix (shellfish) so as to support CMCs of similar materials submitted by the present participants. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  5. SUPPLEMENTARY COMPARISON: Activity measurements of a suite of radionuclides (40K, 137Cs, 210Pb, 210Po, 228Ra, 232Th, 234U, 235U, 238U, 238Pu, 239Pu, 239+240Pu, 241Am) in vegetal reference material (seaweed)

    NASA Astrophysics Data System (ADS)

    Outola, I.; Inn, K. G. W.; Karam, L. R.

    2008-01-01

    In 2005, the CCRI decided that a comparison undertaken from 2002 to 2005 by the NIST (SIM) in the development of a new seaweed standard reference material (SRM) was sufficiently well constructed that it could be converted into a supplementary comparison under CCRI(II), with comparison identifier CCRI(II)-S1, so as to support calibration and measurement capability (CMC) claims for radionuclide measurements in reference material (specifically, plant material). Previous comparisons of radionuclides have been of single or multiple nuclides in non-complex matrices and results of such could not be extended to support capabilities to measure the same nuclides in reference materials. The results of this comparison have been reported to the participants, and were also used to determine the certified reference values of the SRM. The key comparison working group (KCWG) of the CCRI(II) has approved this approach as a mechanism to link all the results to the certified 'reference values' in lieu of the key comparison reference value (KCRV) of these specified radionuclides in this type of matrix (vegetative) so as to support CMCs of similar materials. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Swarzenski, Peter; Campbell, Pamela; Porcelli, Don; McKee, Brent

    2004-12-01

    Natural concentrations of 238U and δ234U 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 δ234U 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 δ234U 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 δ234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface

  8. Decay Measurement of 283Cn Produced in the 238U(48Ca,3n) Reaction Using GARIS-II

    NASA Astrophysics Data System (ADS)

    Kaji, Daiya; Morimoto, Kouji; Haba, Hiromitsu; Wakabayashi, Yasuo; Takeyama, Mirei; Yamaki, Sayaka; Komori, Yukiko; Yanou, Shinya; Goto, Shin-ichi; Morita, Kosuke

    2017-08-01

    The production of 283Cn in the hot fusion reaction of 238U(48Ca,3n) was confirmed using a new gas-filled recoil ion separator GARIS-II. At the excitation energies of the compound nucleus E* = 34.5 MeV, two decay events from 283Cn were observed, resulting in the cross section of σ 3n = 2.0 - 1.3 + 2.7 pb. One is the spontaneous fission with decay time τ = 14.4 s. The other is the 9.45 MeV α-decay with τ = 5.4 s, followed by the spontaneous fission of 279Ds (154 ms).

  9. γ-ray studies of the fission of 238U induced by 12C, spectroscopy and fission dynamics

    NASA Astrophysics Data System (ADS)

    Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Theisen, Ch.; Barreau, G.; Doan, T. P.; Aiche, M.; Aleonard, M. M.; Chemin, J. F.; Scheurer, J. N.; Belier, G.; Meot, V.; Ethvignot, Th.; Durell, J.; Grimwood, D.; Phillips, W. R.; Roach, A.; Smith, A. G.; Varley, B. J.; Deloncle, I.; Porquet, M. G.; Astier, A.; Perries, S.; Redon, N.

    1998-10-01

    Fission studies have been known for a long time to provide neutron-rich nuclei in various states of excitation energy, spin and deformation. Although many studies have been performed concerning fission fragments from spontaneous fission and neutron induced fission, a renewed interest in fission-fragment spectroscopy has occurred with the elaboration of large Ge detector arrays such as EUROBALL. We have recently performed an experiment with EUROBALL III using SAPhIR; a fission-fragment detector made from photovoltaic cells. The compact and versatile geometry of SAPhIR allows it to be installed inside the γ-ray detector, and to obtain additional information from the fission process as well as a timing reference. Neutron-rich nuclei have been populated in the fusion-fission reaction 238U+12C leading to the compound nucleus 250Cf. First results of this experiment are presented.

  10. Measurement of activation of helium gas by 238U beam irradiation at about 11 A MeV

    NASA Astrophysics Data System (ADS)

    Akashio, A.; Tanaka, K.; Imao, H.; Uwamino, Y.

    2017-09-01

    A new helium-gas stripper system has been applied at the 11 A MeV uranium beam of the Radioactive Isotope Beam Factory of the RIKEN accelerator facility. Although the gas stripper is important for the heavy-ion accelerator facility, the residual radiation that is generated is a serious problem for maintenance work. The residual dose was evaluated by using three-layered activation samples of aluminium and bismuth. The γ-rays from produced radionuclides with in-flight fission of the 238U beam and from the material of the chamber activated by neutrons were observed by using a Ge detector and compared with the values calculated by using the Monte-Carlo simulation code PHITS.

  11. New neutron-rich microsecond isomers observed among fission products of {sup 238}U at 80 MeV/nucleon

    SciTech Connect

    Folden, C. M. III; Ginter, T. N.; Hausmann, M.; Portillo, M.; Nettleton, A. S.; Amthor, A. M.; Sherrill, B. M.; Kubo, T.; Takeda, H.; Loveland, W.; Manikonda, S. L.; Morrissey, D. J.; Nakao, T.; Souliotis, G. A.; Strong, B. F.; Tarasov, O. B.

    2009-06-15

    Eight new isomeric states in neutron-rich nuclides have been discovered in fission fragments produced by the reaction of an 80 MeV/nucleon {sup 238}U beam with a {sup 9}Be target and separated in-flight using the A1900 fragment separator. The experiment was conducted at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. Gamma rays were detected in a high-purity germanium detector located at the focal plane within a time window of 20 {mu}s following ion implantation. In some cases the isomers were observed to decay into previously reported states, allowing us to assign the initial decay from the isomeric state. Among the outcomes, the results suggest that many studies on the nuclear structure of medium-mass neutron-rich nuclei are feasible at projectile fragmentation facilities using induced fission.

  12. 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.

  13. 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.

    2008-11-14

    Abstract–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 photons in the MeV energy range. 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 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.

  14. The dissolved uranium concentration and (234)U/(238)U activity ratio in groundwaters from spas of southeastern Brazil.

    PubMed

    Bonotto, Daniel Marcos

    2017-01-01

    This paper describes the natural radioactivity due to (238)U and (234)U in 75 water sources from spas located in 14 municipalities in São Paulo and Minas Gerais states, Brazil. These waters are extensively utilized for drinking in public places, bottling and bathing purposes, among other uses. The water samples were taken from springs and pumped tubular wells drilled into different aquifer systems in the Paraná and Southeastern Shield hydrogeological provinces. The measurements of alpha-emitting radionuclides were also accompanied by the monitoring of temperature, pH, Eh, electrical conductivity, dissolved gases (O2, CO2, H2S, radon, thoron) and major constituents. The dissolved U concentration data were lognormally distributed. The median and mean values corresponded to 0.02 and 0.09 μg/L, respectively. Significant relationships were found among the (234)U/(238)U activity ratio (AR) of dissolved uranium, the total dissolved solids (TDS) and dissolved bicarbonate contents, and also between the AR and dissolution rate in the monitored sites. The logU versus AR diagram used for the hydrogeochemical prospecting of concealed U deposits indicated that the water sources were mainly from reduced environments. The possibility of using the reciprocal of the dissolved U concentration and AR data to determine mixing volumes of different groundwater masses was demonstrated. The highest dissolved U concentration (4.82 μg/L) was well below the maximum allowed by WHO. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. 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.

  16. 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.

  17. Mapping radon hazard areas using (238)U measurements and geological units: a study in a high background radiation city of China.

    PubMed

    Liu, Hongtao; Wang, Nanping; Chu, Xingming; Li, Ting; Zheng, Ling; Yan, Shouliang; Li, Shijun

    In order to identify radon-prone areas and evaluate radon risk level, a soil gas radon survey combined with gamma-ray spectrometry measurements was carried out in Shenzhen City, south China. Meanwhile, the statistical analysis was applied to evaluate the distribution of measured results. This paper presents the methodology of the radon risk assessment. A radon risk map was accomplished based on a combination of soil gas radon concentration (RC), soil air permeability (Perm.) and uranium ((238)U) concentration. The results showed that the distribution of soil gas RC and radon-prone areas were closely related to geologic distribution of uranium ((238)U) and local lithology.

  18. Assessment of environmental (226)Ra, (232)Th and (40)K concentrations in the region of elevated radiation background in Segamat District, Johor, Malaysia.

    PubMed

    Saleh, Muneer Aziz; Ramli, Ahmad Termizi; Alajerami, Yasser; Aliyu, Abubakar Sadiq

    2013-10-01

    Extensive environmental survey and measurements of gamma radioactivity in the soil samples collected from Segamat District were conducted. Two gamma detectors were used for the measurements of background radiation in the area and the results were used in the computation of the mean external radiation dose rate and mean weighted dose rate, which are 276 nGy h(-1) and 1.169 mSv y(-1), respectively. A high purity germanium (HPGe) detector was used in the assessment of activity concentrations of (232)Th, (226)Ra and (40)K. The results of the gamma spectrometry range from 11 ± 1 to 1210 ± 41 Bq kg(-1) for (232)Th, 12 ± 1 to 968 ± 27 Bq kg(-1) for (226)Ra, and 12 ± 2 to 2450 ± 86 Bq kg(-1) for (40)K. Gross alpha and gross beta activity concentrations range from 170 ± 50 to 4360 ± 170 Bq kg(-1) and 70 ± 20 to 4690 ± 90 Bq kg(-1), respectively. These results were used in the plotting of digital maps (using ARCGIS 9.3) for isodose. The results are compared with values giving in UNSCEAR 2000.

  19. Vertical Profiles Of {sup 226}Ra, {sup 232}Th And {sup 40}K Activities In Rocks From The Irati Formation Of The Parana Sedimentary Basin, Southern Brazil

    SciTech Connect

    Ferreira, Ademar de O.; Bastos, Rodrigo O.; Appoloni, Carlos R.

    2008-08-07

    Naturally occurring radioisotopes are present in different concentrations in sedimentary rocks, reflecting the origin of the sediments, the depositional environment, and more recent events such as weathering and erosion. Using a high-resolution {gamma}-ray spectrometry methodology, sedimentary rocks were measured to assess the concentration activities of the natural radioisotopes. The surveyed rocks are from the Irati formation in the Parana sedimentary basin, which are exposed by an abandoned, open-pit limestone mine, in the city of Sapopema, southern Brazil. The exposed vertical profile is 5 m, and its stratigraphy is represented by an alternation of limestone and bituminous shale (layers being a few decimeters thick), and some millimeter rhythm layers with limestone and bituminous shale laminas. Eleven samples were collected along this profile, each of them dried in the open air during 48 hours, sieved through 4 mm mesh and sealed in cylindrical recipients. Measurements were accomplished using a 66% relative efficiency HPGE detector connected to a standard gamma ray spectrometry electronic chain. The detector efficiency in the range of 60 to 1800 keV was carried out with the certified IAEA-385 sediment sample. The Lower Limit of Detection (LLD) to the system is 2.40 Bq{center_dot}kg{sup -1} for {sup 226}Ra, 1.84 Bq{center_dot}kg{sup -1} for {sup 232}Th and 4.20 Bq{center_dot}kg{sup -1} for {sup 40}K. Activity concentrations were determined for {sup 226}Ra (from 16.22 to 151.55 Bq{center_dot}kg{sup -1}), {sup 232}Th (from 2.93 to 56.12 Bq{center_dot}kg{sup -1}) and {sup 40}K (from 38.45 to 644.63 Bq{center_dot}kg{sup -1}). The layers enriched with organic matter presented the higher values of activity. The measured concentrations of the natural radioisotopes were lower for limestone samples (average values and respective deviations were 22.81{+-}0.22 Bq{center_dot}kg{sup -1} for {sup 226}Ra, 4.21{+-}0.07 Bq{center_dot}kg{sup -1} for {sup 232}Th, and 50

  20. Internal tides and sediment dynamics in the deep sea—Evidence from radioactive 234Th/ 238U disequilibria

    NASA Astrophysics Data System (ADS)

    Turnewitsch, Robert; Reyss, Jean-Louis; Nycander, Jonas; Waniek, Joanna J.; Lampitt, Richard S.

    2008-12-01

    Residual flow, barotropic tides and internal (baroclinic) tides interact in a number of ways with kilometer-scale seafloor topography such as abyssal hills and seamounts. Because of their likely impact on vertical mixing such interactions are potentially important for ocean circulation and the mechanisms and the geometry of these interactions are a matter of ongoing studies. In addition, very little is known about how these interactions are reflected in the sedimentary record. This multi-year study investigates if flow/topography interactions are reflected in distributional patterns of the natural short-lived (half-life: 24.1 d) particulate-matter tracer 234Th relative to its conservative (non-particle-reactive) and very long-lived parent nuclide 238U. The sampling sites were downstream of, or surrounded by, fields of short seamounts and, therefore, very likely to be influenced by nearby flow/topography interactions. At the sampling sites between about 200 and 1000 m above the seafloor recurrent 'fossil' disequilibria were detected. 'Fossil' disequilibria are defined by clearly detectable 234Th/ 238U disequilibria (total 234Th radioactivity < 238U radioactivity, indicating a history of intense particulate 234Th scavenging and particulate-matter settling from the sampled parcel of water) and conspicuously low particle-associated 234Th activities. 'Fossil' disequilibria were centered at levels in the water column that correspond to the average height of the short seamounts near the sampling sites. This suggests the 'fossil' disequilibria are formed on the seamount slopes. Moreover, the magnitude of the 'fossil' disequilibria suggests that the slopes of the short seamounts in the study region are characterized by particularly vigorous fluid dynamics. Since 'fossil' disequilibria already occurred at ˜ O(1-10 km) away from the seamount slopes it is likely that these vigorous fluid dynamics rapidly decay away from the slopes on scales of O(1-10 km). These conclusions

  1. Low export flux of particulate organic carbon in the central Arctic Ocean as revealed by 234Th:238U disequilibrium

    NASA Astrophysics Data System (ADS)

    Cai, P.; Rutgers van der Loeff, M.; Stimac, I.; NöThig, E.-M.; Lepore, K.; Moran, S. B.

    2010-10-01

    The loss of Arctic sea ice has accelerated in recent years. With the decline in sea ice cover, the Arctic Ocean biogeochemistry is undergoing unprecedented change. A key question about the changing Arctic Ocean biogeochemistry is concerning the impact of the shrinking sea ice cover on the particulate organic carbon (POC) export from the upper Arctic Ocean. Thus far, there are still very few direct measurements of POC export in the permanently ice-covered central Arctic Ocean. A further issue is that the magnitude of the POC export so far documented in this region remains controversial. During the ARK-XXII/2 expedition to the Arctic Ocean from 28 July to 7 October in 2007, we conducted a high-resolution study of POC export using 234Th/238U disequilibrium. Depth profiles of total 234Th in the upper 200 m were collected at 36 stations in the central Arctic Ocean and its adjacent seas, i.e., the Barents Sea, the Kara Sea and the Laptev Sea. Samples were processed using a small-volume MnO2 coprecipitation method with addition of a yield tracer, which resulted in one of the most precise 234Th data sets ever collected. Thorium-234 deficit with respect to 238U was found to be evident throughout the upper 100 m over the Arctic shelves. In comparison, 234Th deficit was confined to the upper 25 m in the central Arctic Ocean. Below 25 m, secular equilibrium was approached between 234Th and 238U. The observed 234Th deficit was generally associated with enhanced total chlorophyll concentrations, indicating that in situ production and export of biogenic particles are the main mechanism for 234Th removal in the Arctic Ocean. Thorium-234-derived POC fluxes were determined with a steady state model and pump-normalized POC/234Th ratios on total suspended particles collected at 100 m. Results showed enhanced POC export over the Arctic shelves. On average, POC export fluxes over the various Arctic shelves were 2.7 ± 1.7 mmol m-2 d-1 (the Barents Sea), 0.5 ± 0.8 mmol m-2 d-1 (the Kara

  2. 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.

  3. 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.

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

    PubMed

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

    2010-08-01

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

  5. 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

  6. Effect of projectile breakup on fission-fragment mass distributions in the Li,76 + 238U reactions

    NASA Astrophysics Data System (ADS)

    Santra, S.; Pal, A.; Rath, P. K.; Nayak, B. K.; Singh, N. L.; Chattopadhyay, D.; Behera, B. R.; Singh, Varinderjit; Jhingan, A.; Sugathan, P.; Golda, K. S.; Sodaye, S.; Appannababu, S.; Prasad, E.; Kailas, S.

    2014-12-01

    Background: Detailed studies on the effect of the breakup of weakly bound projectile on fission are scarce. Distinguishing the events of compound nuclear (CN) fission from the breakup or transfer induced fission to understand the properties of measured fission fragments is difficult but desirable. Purpose: To investigate the effect of projectile breakup and its breakup threshold energy on fission-fragment (FF) mass distributions and folding angle distributions for Li,76 + 238U reactions and find out the differences in the properties of the fission events produced by complete fusion (CF) from the total fusion (TF). Methods: The FF mass and folding angle distributions have been measured at energies around the Coulomb barrier using gas detectors by time-of-flight technique. The results are compared with the ones involving tightly bound projectiles as well as predictions from systematics to bring out the effect of the breakup. Results: A sharp increase in the peak to valley (P:V) ratio of FF mass distribution with the decrease in bombarding energy for Li,76 + 238U reactions is observed when all events are assumed to be CN fission. As the beam energy falls through the fusion barrier, the full width half maximum (FWHM) of the FF folding angle distribution is found to increase at sub-barrier energies, unlike the reactions involving tightly bound projectiles where a linear decrease in FWHM is expected. By selecting pure CN events from the scatter plot of the velocity components of the composite nuclei, the energy dependence of the deduced FWHM is found to be consistent with the ones involving tightly bound projectiles. Similarly, the P:V ratio obtained for the selected CN events is consistent with the theoretical calculations as well as the experimental data for the proton induced reaction forming similar CN. Conclusions: The presence of projectile breakup induced fission and a relatively low breakup threshold for 6Li compared to 7Li explains the observed differences in

  7. Measurement of activity concentrations of 40K, 226Ra and 232Th for assessment of radiation hazards from soils of the southwestern region of Nigeria.

    PubMed

    Ajayi, Oladele Samuel

    2009-08-01

    Activity concentrations of the selected radionuclides (40)K, (226)Ra and (232)Th were measured in surface soil samples collected from 38 cities in the southwest region of Nigeria by means of gamma spectroscopy with a high-purity germanium detector. Measured activity concentration values of (40)K varied from 34.9 +/- 4.4 to 1,358.6 +/- 28.5 Bq kg(-1) (given on a dry mass (DM) basis) with a mean value of 286.5 +/- 308.5 Bq kg(-1); that of (226)Ra varied from 9.3 +/- 3.7 to 198.1 +/- 13.8 Bq kg(-1) with a mean value of 54.5 Bq kg(-1) and a standard deviation of 38.7 Bq kg(-1), while that of (232)Th varied from 5.4 +/- 1.1 to 502.0 +/- 16.5 Bq kg(-1) with a mean value of 91.1 Bq kg(-1) and standard deviation of 100.9 Bq kg(-1). The mean activity concentration values obtained for (226)Ra and (232)Th are greater than the world average values reported by the United Nations Scientific Committee on Effects of Atomic Radiation for areas of normal background radiation. Radiological indices were estimated for the radiation/health hazards of the natural radioactivity of all soil samples. Estimated absorbed dose rates in air varied from 12.42 +/- 2.25 to 451.33 +/- 19.06 nGy h(-1), annual outdoor effective dose rates from 0.015 +/- 0.003 to 0.554 +/- 0.023 mSv year(-1), internal hazard index from 0.10 +/- 0.03 to 3.02 +/- 0.16, external hazard index from 0.07 +/- 0.01 to 2.60 +/- 0.11, representative level index from 0.19 +/- 0.03 to 6.84 +/- 0.29, activity index from 0.09 +/- 0.02 to 3.42 +/- 0.15, and radium equivalent activity from 26.95 +/- 5.04 to 963.15 +/- 41.87 Bq kg(-1). Only the mean value of the representative level index exceeds the limit for areas of normal background radiation. All other indices show mean values that are lower than the recommended limits.

  8. Determination of extremely low (236)U/(238)U isotope ratios in environmental samples by sector-field inductively coupled plasma mass spectrometry using high-efficiency sample introduction.

    PubMed

    Boulyga, Sergei F; Heumann, Klaus G

    2006-01-01

    A method by inductively coupled plasma mass spectrometry (ICP-MS) was developed which allows the measurement of (236)U at concentration ranges down to 3 x 10(-14)g g(-1) and extremely low (236)U/(238)U isotope ratios in soil samples of 10(-7). By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5,000 counts fg(-1) uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH(+)/U(+) down to a level of 10(-6). An abundance sensitivity of 3 x 10(-7) was observed for (236)U/(238)U isotope ratio measurements at mass resolution 4000. The detection limit for (236)U and the lowest detectable (236)U/(238)U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the (236)U/(238)U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the (235)U/(238)U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP (Mogilev region). The concentration of (236)U in the upper 0-10 cm soil layers varied from 2 x 10(-9)g g(-1) within radioactive spots close to the Chernobyl NPP to 3 x 10(-13)g g(-1) on a sampling site located by >200 km from Chernobyl.

  9. 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).

  10. 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.

  11. Fission-fragment properties in 238U(n ,f ) between 1 and 30 MeV

    NASA Astrophysics Data System (ADS)

    Duke, D. L.; Tovesson, F.; Laptev, A. B.; Mosby, S.; Hambsch, F.-J.; Bryś, T.; Vidali, M.

    2016-11-01

    The fragment mass and kinetic energy in neutron-induced fission of 238U has been measured for incident energies from 1 to 30 MeV at the Los Alamos Neutron Science Center. The change in mass distributions over this energy range were studied, and the transition from highly asymmetric to more symmetric mass distributions is observed. A decrease in average total kinetic energy (TKE ¯) with increasing excitation energy is observed, consistent with previous experimental work. Additional structure at multichance fission thresholds is present in the TKE ¯ data. The correlations between fragment masses and total kinetic energy and how that changes with excitation energy of the fissioning compound nucleus were also measured. The fission mass yields and average total kinetic energy are important for fission-based technologies such as nuclear reactors to understand nuclear waste generation and energy output when developing new and advanced concepts. The correlations between fragment mass and kinetic energy are needed both as input for theoretical calculations of the deexcitation process in fission fragments by prompt radiation emission and for validating advanced theoretical fission models describing the formation of the primordial fragments.

  12. 234Th: 238U disequilibrium as an indicator of sediment resuspension in Thermaikos Gulf, northwestern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Muir, G. K. P.; Pates, J. M.; Karageorgis, A. P.; Kaberi, H.

    2005-12-01

    234Th: 238U disequilibria have been used extensively as tracers of particle dynamics in marine environments. 234Th ( t1/2=24.1 days) can be used as "proxy" for particle reactive pollutants, due to their similar rapid rate of scavenging onto particles and subsequent removal from the water column, to the sediments. Radioactive disequilibrium can be exploited to determine the rates and time-scales of processes occurring over days to months; in this instance the residence times of dissolved and particulate species with the benthic nepheloid layer (BNL). Three sampling cruises were undertaken in Thermaikos Gulf (NW Aegean Sea) during contrasting periods, to examine the impact of natural and anthropogenic activity on sediment resuspension. September and October 2001 represented background and trawling periods, respectively; January 2002 represented a mixed period, of trawling and storms. Dissolved 234Th is scavenged actively at the BNL, in the presence of suspended particulate material (SPM), with a mean residence time of 16 days. There is a weak inverse correlation between dissolved 234Th residence time and SPM concentration in the BNL, with the shortest residence times occurring during October 2001. No relationship was observed between particulate 234Th activities and SPM concentrations, indicating that particles are rapidly removed from the system, either by sinking or advection. The mean particulate 234Th residence time is 5 days.

  13. Yield and recoil properties of iodine isotopes from the interaction of 240 MeV 12C with 238U

    NASA Astrophysics Data System (ADS)

    Yu, Y. W.; Lee, C. H.; Moody, K. J.; Kudo, H.; Lee, D.; Seaborg, G. T.

    1987-12-01

    The independent yields, recoil properties, and forward-to-backward ratios (F/B) of iodine isotopes from the interaction of 240 MeV 12C with 238U have been measured radiochemically by the thick-target/thick-catcher method. The isotopic yield distribution curve has been constructed and is found to consist of two overlapping Gaussians, peaking at A=126.5 and 133.8 with width parameters of 2.29 and 2.04 mass units, respectively. All the measured iodine isotopes had ranges of 7.7+/-0.4 mg/cm2. The neutron-deficient products have F/B of 1.76+/-0.14, but the neutron-excessive products have F/B of only 1.09+/-0.06. The yield curve was analyzed with the liquid drop model and the recoil curve was analyzed by the standard two-step vector model; the results show that the neutron-deficient products are formed from nonequilibrium processes and the neutron-excessive products are formed from the normal low-energy fission process.

  14. 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.

  15. The Use of the Photofission of 238U for a Neutron-Rich Radioactive Ion Beams Generation

    NASA Astrophysics Data System (ADS)

    Szöllős, O.; Kliman, J.

    2003-10-01

    The fission fragments yield for photofission of 238U, induced by bremsstrahlung photons with endpoint energies of 25 and 50MeV was evaluated to estimate the possibility of producing the neutron-rich nuclei. The systematics coming from A.C. Wahl's Zp model 1 for charge distribution of fission fragments were used. Results for xenon and krypton isotopes are compared with experimental data 2 obtained on the DRIBs 3 (Dubna Radioactive Ion Beams) facility for neutron-rich nuclei production in Flerov Laboratory. The fission rate and fission density in production target for metallic uranium and UCx compounds were simulated with Geant4 4 simulation toolkit to design the target geometry, The fission rate dependence on material of the electron stopping target was examined, At nominal beam values on microtron MT-25 (Ie = 20μA, Ee = 25MeV) up to 2.1011 fissions/s could be achieved. Then the production rate of neutron-rich isotopes reaching order of 109s-1. The induced activity in the production target depending on an irradiation time was calculated for radiation protection purposes and target safety estimation. The cumulation of actinide nuclei was also calculated.

  16. Photo-fission Product Yield Measurements at Eγ=13 MeV on 235U, 238U, and 239Pu

    NASA Astrophysics Data System (ADS)

    Tornow, W.; Bhike, M.; Finch, S. W.; Krishichayan, Fnu; Tonchev, A. P.

    2016-09-01

    We have measured Fission Product Yields (FPYs) in photo-fission of 235U, 238U, and 239Pu at TUNL's High-Intensity Gamma-ray Source (HI γS) using mono-energetic photons of Eγ = 13 MeV. Details of the experimental setup and analysis procedures will be discussed. Yields for approximately 20 fission products were determined. They are compared to neutron-induced FPYs of the same actinides at the equivalent excitation energies of the compound nuclear systems. In the future photo-fission data will be taken at Eγ = 8 . 0 and 10.5 MeV to find out whether photo-fission exhibits the same so far unexplained dependence of certain FPYs on the energy of the incident probe, as recently observed in neutron-induced fission, for example, for the important fission product 147Nd. Work supported by the U. S. Dept. of Energy, under Grant No. DE-FG02-97ER41033, and by the NNSA, Stewardship Science Academic Alliances Program, Grant No. DE-NA0001838 and the Lawrence Livermore, National Security, LLC under Contract No. DE-AC52-07NA27344.

  17. 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.

  18. Precise measurement and analysis of neutron transmission through /sup 232/Th. [6. 0 MeV to 0. 1 MeV

    SciTech Connect

    Olsen, D.K.; Ingle, R.W.; Portney, J.L.

    1980-01-01

    Three sets of transmission time spectra through up to eight samples of /sup 232/Th have been measured for neutron energies from 6.0 MeV to 0.1 MeV by use of a flight-time technique over 22- and 40-m path lengths, the ORELA pulsed neutron source, and a 1-mm-thick lithium glass detector. The resulting total cross section from 0.1 to 20.0 eV seems to be smaller than that contained in the ENDF/B-V evaluation. Least-squares analysis of the transmissions from 9 to 440 eV using a multilevel Breit-Wigner formalism results in neutron widths consistent with those previously reported. An average radiation width of 25.2 MeV is obtained for 19 low-energy s-wave resonances. 3 figures, 5 tables.

  19. Particulate organic carbon export from the North and South Atlantic gyres: The 234Th/ 238U disequilibrium approach

    NASA Astrophysics Data System (ADS)

    Thomalla, Sandy; Turnewitsch, Robert; Lucas, Mike; Poulton, Alex

    2006-07-01

    Subtropical ocean gyres are believed to be characterized by low carbon export from the surface into the deep ocean. However, due to their large areas, even relatively small average export could be of significance for the global carbon cycle. To better constrain carbon export from the surface ocean in such regions, radioactive disequilibria between the particle-reactive, short-lived radionuclide 234Th (half-life 24.1 d) and its parent 238U were used to estimate fluxes of 234Th and particulate organic carbon (POC) from surface waters of the North and South Atlantic subtropical gyres and their fringes. Samples were collected between ˜50°S and ˜50°N as part of the Atlantic Meridional Transect (AMT) programme during April/May 2004 (AMT14). Application of a steady-state model to the 234Th data revealed particle export from the surface ( 234Th deficit) and, in one instance, some evidence for shallow particle remineralisation at depth ( 234Th excess). Export fluxes of POC were calculated from water column 234Th / 238U disequilibria and the POC to 234Th ratios on large rapidly sinking particles (>50 μm). Based on latitudinal distributions of selected hydrographic and biological parameters within the topmost 300 m of the water column, the transect was divided into six regions: 'temperate' (35°-50°N and 35°-50°S), 'oligotrophic' (20°-35°N and 5°-35°S), 'equatorial' (5°S-5°N), and 'upwelling' (5°-20°N). The lowest 234Th-derived POC export fluxes were found in the oligotrophic gyres and ranged from 0 in the northern to 6 mmol C m -2 d -1 in the southern oligotrophic, indicating a tightly coupled food web. Enhanced POC export was associated with the equatorial region (25 mmol C m -2 d -1) and the upwelling region north of the equator (15 mmol C m -2 d -1). POC export in the temperate regions ranged from 7 mmol C m -2 d -1 to a maximum of 41 mmol C m -2 d -1. High fluxes at the poleward edges of the oligotrophic gyres probably result from episodic nutrient

  20. 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.

  1. 238U-230Th disequilibrium in hydrothermally altered material: a tool for dating volcano flank-collapse events

    NASA Astrophysics Data System (ADS)

    Salaun, A.; Villemant, B.; Gérard, M.; Komorowski, J. C.; Louvat, P.; Manhès, G.; Michel, A.; Moureau, J.

    2009-12-01

    Flank instability has been recognized as a very common and often recurrent process in the evolution of volcanoes. Prolonged and extensive hydrothermal system activity is a major cause of volcano instability in promoting conditions of mechanical weakness in the edifice that can lead to partial edifice-collapse with emplacement of debris avalanche deposits (DAD). We report results from U-series disequilibrium analysis of altered material collected in active hydrothermal systems and in DADs that have sampled different regions of the paleo-hydrothermal systems developed prior to collapse on La Soufrière of Guadeloupe and Soufriere Hills (Montserrat) volcanoes. Significant redistribution of chemical elements occurs during hydrothermal alteration with a large fractionation between elements of the U-decay series. Indeed, samples of active hydrothermal systems show large variations in U/Th ratio at generally constant (230Th/232Th). This chemical fractionation between U and Th offers the opportunity to date hydrothermal alteration and to constrain the age of the active hydrothermal system involved in edifice collapses. The evolution of trace element compositions (REE, U, Th) are documented throughout the successive stages of andesite-dacite alteration and discussed in terms of relative element mobility and associated mineralogical assemblages. A progressive HREE depletion occurs together with significant U enrichment at low alteration degrees, followed by a final U depletion. Alteration of glass into smectite is accompanied by large U depletions relative to Th. On the contrary, U enrichment is associated with silica polymorphs. All these processes are discussed in terms of relative U behaviours during leaching, incorporation and adsorption processes. U and Th isotope contents have been determined in hydrothermally altered material contained in two distinct DADs of La Soufrière of Guadeloupe (14C ages: 7 700 yrs BP and 45 000 yrs BP) and one DAD from Soufrière Hills

  2. 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.

  3. 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.

  4. Intermediate mass fragment emission in 32S + 51V, 109Ag, and 238U collisions at E = 31.6 MeV A

    NASA Astrophysics Data System (ADS)

    Machner, H.; Nolte, M.; Palarczyk, M.; Kutsarova, T.

    2015-11-01

    Intermediate mass fragment emission for reactions of 32S + 51V, 109Ag, and 238U has been studied. Double differential cross sections were analysed in terms of the generalised moving source model yielding charge distributions. Isotope ratios show strong fragment mass dependencies. The data were successfully reproduced by the coalescence model as well as by statistical multifragmentation model calculations. Quantum molecular dynamics model calculations were not so successful.

  5. 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)}.

  6. Double beta decay of Uranium-238: Proton reactions of {sup 238}U in 5--12 MeV range. Final report, April 15, 1987--March 31, 1992

    SciTech Connect

    Turkevich, A.; Economou, T.E.

    1993-06-01

    This report is in two parts. The first part reports on the experimental work determining the half-life for double beta decay of {sup 238}U to {sup 238}PU to be (2.0 {plus_minus} 0.6) {times} 10{sup 21} years. This is the first evidence for a third mode of decay of this heaviest naturally occurring nucleus. This rate is about 10{sup 6} times slower than spontaneous fission, which itself is about 10{sup 6} times slower than alpha decay. The implication of this double beta decay to neutrino masses depends on uncertain theoretical calculations of the rate for such a heavy nucleus. The second part reports on yields of principal fission products from 5.6, 7.3, 9.4, and 11.5 MeV proton interactions with {sup 238}U. The yields at 11.5 MeV are similar to those from 14 MeV neutron fission of {sup 238}U. At the same time, the production cross sections of {sup 238}Np at the same energies are determined. This nuclide is produced as often as fission at the lowest energy but only 3.8% as often at the highest energy.

  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.

  8. 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. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  9. 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.

  10. Distribution of long-lived radionuclides of the 238U series in the sediments of a small river in a uranium mineralized region of Spain.

    PubMed

    Lozano, J C; Blanco Rodríguez, P; Tomé, F Vera

    2002-01-01

    A study is presented on the distribution and mobilization of the natural U isotopes (238U and 234U), 230Th, and 226Ra in the sediments of a small river crossing an uranium mineralized zone where a disused uranium mine is located. Due to the preferential directions for surface run-off waters and to the mine's situation, one sampling point along the river bed was identified as a point of accumulation of radionuclides. The average values of the activity concentrations (Bq/kg) in this sediment sample were 5,025, 5,055, 5,915 and 1,694 for 238U, 234U, 230Th and 226Ra, respectively, while the respective average values of the activity concentrations (Bq/kg) for the sediment sample considered to give the background level were 125, 124, 131 and 370. Isotopic ratios between the descendants of 238U served to clarify some paths of distribution, involving the soils nearest to the sampling points and the location of these points with respect to the disused mine. The differences in behaviour found between the uranium, thorium and radium isotopes were associated to the mobility of these radionuclides in the fluvial system studied. Correlations between the radionuclide activity concentration ratios and stable element concentrations in the sediment samples were also investigated.

  11. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Determination of specific activity of (226)Ra, (232)Th and (40)K for assessment of radiation hazards from Turkish pumice samples.

    PubMed

    Turhan, Seref; Gündüz, Lüfullah

    2008-02-01

    The specific activity of (226)Ra, (232)Th and (40)K in 52 Turkish pumice samples collected from 11 geographical areas located in Central Anatolia, Eastern Anatolia, Mediterranean and Aegean regions was determined by gamma-ray spectrometry with a high-purity germanium (HPGe) detector. The specific activity of (226)Ra, (232)Th and (40)K ranged from 12.7+/-0.5 to 256.2+/-9.1Bqkg(-1) with a mean of 89.1+/-65.2Bqkg(-1), 12.3+/-1.0 to 237.9+/-12.2Bqkg(-1) with a mean of 87.0+/-61.4Bqkg(-1) and 300.1+/-5.5 to 1899.0+/-30.8Bqkg(-1) with a mean of 1211.9+/-419.8Bqkg(-1), respectively. Elemental concentrations were determined for U (from 1.0 to 20.7ppm with a mean of 7.2+/-5.3ppm), Th (from 3.0 to 58.6ppm with a mean of 21.4+/-15.1ppm) and K (from 1.0 to 6.1% with a mean of 3.9+/-1.3%). The radium equivalent activity (Ra(eq)), the activity index, the emanation coefficient, the (222)Rn mass exhalation rate, the indoor absorbed dose rate and the effective dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated mean Ra(eq) value was 306.6+/-177.7Bqkg(-1) (54.6+/-5.5 to 737.6+/-49.0Bqkg(-1)) for all pumice samples. This value is lower than the recommended limit value of 370Bqkg(-1) for building raws and products. The emanation coefficient and the (222)Rn mass exhalation rate of all samples ranged from 29.4 to 42.9% with a mean of 36.2% and from 11.0 to 196.4microBqkg(-1)s(-1) with a mean of 73.5microBqkg(-1)s(-1), respectively. The mean indoor absorbed dose rate and the corresponding mean effective dose rate were 274.6+/-153.6nGyh(-1) (50.4-644.6nGyh(-1)) and 1.35+/-0.75mSvy(-1) (0.24-3.16mSvy(-1)), respectively. For all pumice samples the mean indoor absorbed dose rate is about three times higher than the population-weighted average of 84nGyh(-1), while the mean effective dose rate values except for PUM 05, PUM 06, PUM 10 and PUM 15 exceed the dose criterion of 1mSvy(-1).

  13. Equilibrium and Disequilibrium of 230Th-238U in Zircon from the Minoan Eruption, Santorini, Aegean Sea, Greece

    NASA Astrophysics Data System (ADS)

    Schmitt, A. K.; Stockli, D. F.; Song, E. J.; Storm, S.

    2016-12-01

    The Minoan eruption (ca. 1600 BCE; 40-80 km3 dense rock equivalent) occurred after a ca. 18 ka period of dormancy followed by rapid reinvigoration through arrival of new magma from deep reservoirs colliding with evolved magmas in shallow storage. Although zoned phenocrysts indicate brief timescales ranging between years to decades for final pre-eruptive magma recharge and mixing, it remains unclear how magma accumulation vs. crystallization were balanced in the subvolcanic reservoir during the preceding inter-eruptive cycle. To directly probe magma presence over the repose interval prior to the Minoan eruption and further back in time, we reconnoitered the potential of U-Th zircon geochronology to date the crystallization of individual zircon crystals from pumice from the Minoan eruption. Zircon crystals were extracted from composite pumice samples (several kg each) from basal fall out deposits using gravity and magnetic separation. Etching in cold HF removed adherent glass and revealed the shape of crystals, which were pressed into indium metal to expose unpolished rims to the ion beam of a CAMECA IMS 1270 secondary ionization mass spectrometer. Adherent glass was ubiquitous, indicating that crystals were in contact with melt at the time of eruption. Six of 18 crystals were in 230Th/238U secular equilibrium, two crystals yielded ages of ca. 160 ka, and the remaining rims dated between eruption age and ca. 20 ka. Low Th/U of some secular equilibrium zircon suggests recycling of metamorphic basement zircon, which is also indicated by the presence of rutile in heavy mineral separates. U-Th dates also reveal recycling of zircon from Pleistocene intrusions that likely represent left-over magma from antecedent eruption cycles. We tentatively interpret the dominant zircon population with near-eruption to ca. 20 ka ages to indicate continuous melt presence underneath Santorini during the last repose interval. Distinguishing a hiatus in zircon crystallization between 20 ka

  14. Detection of inherited monazite in the Manaslu leucogranite by 208Pb/(232Th) ion microprobe dating: Crystallization age and tectonic implications

    NASA Astrophysics Data System (ADS)

    Harrison, T. Mark; McKeegan, K. D.; LeFort, P.

    1995-07-01

    Although leucogranites are among the least petrologically variable of all igneous rocks, ironically they are among the most difficult to reliably date. The High Himalayan leucogranites have been the subject of numerous geochronological investigations because of their interrelationship with the most significant tectonic features of that mountain belt. For a variety of reasons linked to the minimum melt composition of these leucogranites, these dating studies have not been entirely successful. We report results of a new ion microprobe dating method based on the decay of 232Th to 208Pb in monazite that has directly revealed the presence of inherited Pb in monazite from the Manalsu granite, casting doubt on its previously accepted age. Monazite ages obtained from this leucogranite yield two distinct populations, a large number of ages with a normal distribution and mean age of 22.4 ± 0.5 Ma (±2 S.E.) that we interpret to be the crystallization age, and a smaller inherited fraction with an age of ca. 600 Ma. Because formation of the granite is thought to be related to slip on the Main Central Thrust, both this date and a second less precise result from a structurally similar pluton near Mt. Everest indicate that the Main Central Thrust was active in the interval 24-22 Ma, but do not constrain its initiation. Together with crosscutting relationships, these data require that movement on the North Himalayan Fault occurred prior to 22 Ma at both locations.

  15. Calibration factors for determination of relativistic particle induced fission rates in natU, 235U, 232Th, natPb and 197Au foils

    NASA Astrophysics Data System (ADS)

    Hashemi-Nezhad, S. R.; Zhuk, Igor; Potapenko, A.; Kievets, M.; Krivopustov, M. I.

    2012-02-01

    Calibration factors w, for determination of fission rate in metallic foils of natU, 235U, 232Th, natPb and 197Au were determined for foils in contact with synthetic mica track detectors. Proton-induced fission at proton energies of 0.7 GeV and 1.5 GeV were used. Using our experimental results as well as those of the other authors, w for different foil-mica systems were determined. Two methods were used to calculate w, relative to the calibration factor for uranium-mica system, which has been obtained in a standard neutron field of energy 14.7 MeV. One of these methods requires the knowledge of the mean range of the fission fragments in the foils of interest and other method needs information on the values of the fission cross-sections at the required energies as well as the density of the tracks recorded in the track detectors in contact with the foil surfaces. The obtained w-values were compared with Monte Carlo calculations and good agreements were found. It is shown that a calibration factor obtained at low energy neutron induced fissions in uranium isotopes deviates only by less than 10% from those obtained at relativistic proton induced fissions.

  16. Large scale accelerator production of (225)Ac: Effective cross sections for 78-192MeV protons incident on (232)Th targets.

    PubMed

    Griswold, J R; Medvedev, D G; Engle, J W; Copping, R; Fitzsimmons, J M; Radchenko, V; Cooley, J C; Fassbender, M E; Denton, D L; Murphy, K E; Owens, A C; Birnbaum, E R; John, K D; Nortier, F M; Stracener, D W; Heilbronn, L H; Mausner, L F; Mirzadeh, S

    2016-12-01

    Actinium-225 and (213)Bi have been used successfully in targeted alpha therapy (TAT) in preclinical and clinical research. This paper is a continuation of research activities aiming to expand the availability of (225)Ac. The high-energy proton spallation reaction on natural thorium metal targets has been utilized to produce millicurie quantities of (225)Ac. The results of sixteen irradiation experiments of thorium metal at beam energies between 78 and 192MeV are summarized in this work. Irradiations have been conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing was carried out at Oak Ridge National Laboratory (ORNL). Excitation functions for actinium and thorium isotopes, as well as for some of the fission products, are presented. The cross sections for production of (225)Ac range from 3.6 to 16.7mb in the incident proton energy range of 78-192MeV. Based on these data, production of curie quantities of (225)Ac is possible by irradiating a 5.0gcm(-2 232)Th target for 10 days in either BNL or LANL proton irradiation facilities.

  17. R-MATRIX ANALYSIS of 232Th NEUTRON TRANSMISSIONS and CAPTURE CROSS SECTIONS in the ENERGY RANGE THERMAL to 4 keV

    SciTech Connect

    Derrien, Herve; Leal, Luiz C; Larson, Nancy M

    2008-01-01

    Neutron resonance parameters of 232Th were obtained from the Reich-Moore SAMMY analysis of high-resolution neutron transmission measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) by Olsen in 1981, along with the high-resolution neutron capture measurements performed in 2005 at the Geel Linear Accelerator (GELINA, Belgium) by Schillebeeckx and at the n-TOF facility (CERN, Switzerland) by Aerts. The ORELA data were analyzed previously by Olsen with the Breit-Wigner multilevel code SIOB, and the results were used in the ENDF/B-VI evaluation. In the new analysis of the Olsen neutron transmissions by the modern computer code SAMMY, better accuracy is obtained for the resonance parameters by including in the experimental data base the recent experimental neutron capture data. The experimental data base and the method of analysis are described in the report. The neutron transmissions and the capture cross sections calculated with the resonance parameters are compared to the experimental values. A description is given of the statistical properties of the resonance parameters. The new evaluation results in a decrease in the capture resonance integral and improves the prediction of integral thermal benchmarks.

  18. Measurements of isomeric yield ratios of fission products from proton-induced fission on natU and 232Th via direct ion counting

    NASA Astrophysics Data System (ADS)

    Rakopoulos, Vasileios; Lantz, Mattias; Al-Adili, Ali; Gorelov, Dmitry; Jokinen, Ari; Kolhinen, Veli; Mattera, Andrea; Moore, Iain D.; Penttilä, Heikki; Prokofiev, Alexander V.; Solders, Andreas; Pomp, Stephan

    2017-09-01

    Independent isomeric yield ratios (IYR) of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyväskylä. A direct ion counting measurement of the isomeric fission yield ratios was accomplished for the first time, registering the fission products in less than a second after their production. In addition, the IYRs of natU were measured by means of γ-spectroscopy in order to verify the consistency of the recently upgraded experimental setup. From the obtained results, indications of a dependence of the production rate on the fissioning system can be noticed. These data were compared with data available in the literature, whenever possible. Using the TALYS code and the experimentally obtained IYRs, we also deduced the average angular momentum of the fission fragments after scission.

  19. Activity concentrations of 226Ra, 232Th, 40K and 137Cs radionuclides in Turkish medicinal herbs, their ingestion doses and cancer risks

    NASA Astrophysics Data System (ADS)

    Parmaksız, Aydın; Ağuş, Yusuf

    2014-11-01

    Twenty-two medicinal herb samples, each representing a distinct species, were collected from Turkish markets and measured by the gamma spectrometric method. The activity concentration of 226Ra in medicinal herbs was found in the range of minimum detectable activity (MDA) and 15.1 ± 2.2 Bqkg-1. The activity concentration of 232Th ranged from MDA values to 3.5 ± 0.8 Bqkg-1. The activity concentration of 40K varied between 50.0 ± 16.8 and 1311.5 ± 57.3 Bqkg-1. All 137Cs activity concentrations of medicinal herbs were found to have lower than MDA values. The bone surface dose, lower large intestine and colon doses were found to be 182.9, 18.8 and 18.7 µSvy-1, respectively. The highest committed effective dose originated from the annual ingestion of 1 kg medicinal herb was calculated notably low as 9.0 µSv. The cancer risk of ingestion of medicinal herbs was found to be small enough to be neglected. The selected Turkish medicinal herbs are considered safe for human consumption.

  20. 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

  1. 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

  2. Reconstruction of the 236U input function for the Northeast Atlantic Ocean: Implications for 129I/236U and 236U/238U-based tracer ages

    NASA Astrophysics Data System (ADS)

    Christl, Marcus; Casacuberta, Núria; Vockenhuber, Christof; Elsässer, Christoph; Bailly du Bois, Pascal; Herrmann, Jürgen; Synal, Hans-Arno

    2015-11-01

    A reconstruction of historical discharges of 236U into the Northeast Atlantic Ocean by nuclear installations is presented. The nuclear reprocessing facilities Sellafield (SF), Great Britain (GB) and La Hague (LH), France and potentially also the nuclear fuel processing installation Springfields (SP), GB represent the main contributors of 236U in the Northeast Atlantic Ocean. Because data on 236U releases is lacking, 236U discharges from SP and SF are estimated based on the U-isotopic systematics found in the discharges from LH. The resulting reconstruction of 236U releases indicates that, until 2013, a total of (95 ± 32) kg of 236U was discharged from SF, SP, and LH. In a second step, the reconstructed 236U releases are combined with 129I data from literature and oceanic and atmospheric box models are used to derive the 129I/236U and 236U/238U input functions that, for example, can be used to calculate tracer ages of Atlantic Waters in the Arctic Ocean. Our conceptual results show that the combination of 129I/236U and 236U/238U generally allows the estimation of tracer ages over the past approximately 25 years if contributions of 236U from global fallout are considered. Finally, as a proof of concept, the new method is applied to calculate tracer ages of Arctic Ocean surface samples (collected in 2011/2012) and the results are in good agreement with literature data. We conclude that the combination of 129I/236U with 236U/238U in a dual tracer approach provides a sensitive tool for the calculation of tracer ages and ventilation rates in the North Atlantic region.

  3. 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. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Yields of neutron-rich isotopes around Z = 28 produced in 30 MeV proton-induced fission of 238U

    NASA Astrophysics Data System (ADS)

    Kruglov, K.; Andreyev, A.; Bruyneel, B.; Dean, S.; Franchoo, S.; Górska, M.; Helariutta, K.; Huyse, M.; Kudryavtsev, Yu.; Mueller, W. F.; Prasad, N. V. S. V.; Raabe, R.; Schmidt, K.-H.; Van Duppen, P.; Van Roosbroeck, J.; Van de Vel, K.; Weissman, L.

    Heavy 65-70Co, 68-74Ni, 70-76Cu and 74-81Ga isotopes were produced at the LISOL facility by means of 30 MeV proton-induced fission of 238U. Production rates were deduced and compared to two types of cross-section calculations: the empirical model (V. Rubchenya, private communication) and the PROFI code. Comparison with experimental data favors the latter model. Yields using different beam-target combinations and different energies are calculated and discussed.

  5. Investigations on the activity concentrations of 238U, 226RA, 228RA, 210PB and 40K in Jordan phosphogypsum and fertilizers.

    PubMed

    Al-Jundi, J; Al-Ahmad, N; Shehadeh, H; Afaneh, F; Maghrabi, M; Gerstmann, U; Höllriegl, V; Oeh, U

    2008-01-01

    The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)Pb and (40)K) in Jordanian phosphate ore, fertilizer material and phosphogypsum piles were investigated. The results show the partitioning of radionuclides in fertilizer products and phosphogypsum piles. The outcome of this study will enrich the Jordanian radiological map database, and will be useful for an estimation of the radiological impact of this industrial complex on the immediate environment. The activity concentration of (210)Pb was found to vary from 95 +/- 8 to 129 +/- 8 Bq kg(-1) with a mean value of 111 +/- 14 Bq kg(-1) in fertilizer samples, and from 364 +/- 8 to 428 +/- 10 Bq kg(-1) with a mean value of 391 +/- 30 Bq kg(-1) in phosphogypsum samples; while in phosphate wet rock samples, it was found to vary between 621 +/- 9 and 637 +/- 10 Bq kg(-1), with a mean value of 628 +/- 7 Bq kg(-1). The activity concentration of (226)Ra in fertilizer samples (between 31 +/- 4 and 42 +/- 5 Bq kg(-1) with a mean value of 37 +/- 6 Bq kg(-1)) was found to be much smaller than the activity concentration of (226)Ra in phosphogypsum samples (between 302 +/- 8 and 442 +/- 8 Bq kg(-1) with a mean value of 376 +/- 62 Bq kg(-1)). In contrast, the activity concentration of (238)U in fertilizer samples (between 1011 +/- 13 and 1061 +/- 14 Bq kg(-1) with a mean value of 1033 +/- 22 Bq kg(-1)) was found to be much higher than the activity concentration of (238)U in phosphogypsum samples (between 14 +/- 5 and 37 +/- 7 Bq kg(-1) with a mean value of 22 +/- 11 Bq kg(-1)). This indicates that (210)Pb and (226)Ra show similar behaviour, and are concentrated in phosphogypsum piles. In addition, both isotopes enhanced the activity concentration in phosphogypsum piles, while (238)U enhanced the activity concentration in the fertilizer. Due to the radioactivity released from the phosphate rock processing plants into the environment, the highest collective dose commitment for the lungs

  6. EXCALIBUR-at-CALIBAN: a neutron transmission experiment for {sup 238}U(n,n'{sub continuum}γ) nuclear data validation

    SciTech Connect

    Bernard, David; Leconte, Pierre; Destouches, Christophe; Casoli, Pierre; Chambru, Laurent; Chanussot, Didier; Chateauvieux, Herve; Gevrey, Gaetan; Guilbert, Frederique; Lereuil, Hugues; Rousseau, Guillaume; Schaub, Muriel; Heusch, Murielle; Meplan, Olivier; Ramdhane, Mourad

    2015-07-01

    Two recent papers justified a new experimental program to give a new basis for the validation of {sup 238}U nuclear data, namely neutron induced inelastic scattering and transport codes at neutron fission energies. The general idea is to perform a neutron transmission experiment through natural uranium material. As shown by Hans Bethe, neutron transmissions measured by dosimetric responses are linked to inelastic cross sections. This paper describes the principle and the results of such an experience called EXCALIBUR performed recently (January and October 2014) at the CALIBAN reactor facility. (authors)

  7. 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.

  8. 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.

  9. Predictions of characteristics of prompt-fission γ -ray spectra from the n +238U reaction up to En=20 MeV

    NASA Astrophysics Data System (ADS)

    Oberstedt, A.; Billnert, R.; Oberstedt, S.

    2017-09-01

    Systematics from 2001, describing prompt-fission γ -ray spectra (PFGS) characteristics as a function of mass and atomic number of the fissioning system, was revisited and parameters were revised, based on recent experimental results. Although originally expressed for spontaneous and thermal-neutron induced fission, validity for fast neutrons was assumed and applied to predict PFGS characteristics for the reaction n +238U up to incident neutron energies of En=20 MeV . The results from this work are in good agreement with corresponding results from both model calculations and experiments.

  10. A study on possible use of Urtica dioica (common nettle) plants as uranium ((234)U, (238)U) contamination bioindicator near phosphogypsum stockpile.

    PubMed

    Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

    The aim of this study was to determine uranium concentrations in common nettle (Urtica dioica) plants and corresponding soils samples which were collected from the area of phosphogypsum stockpile in Wiślinka (northern Poland). The uranium concentrations in roots depended on its concentrations in soils. Calculated BCF and TF values showed that soils characteristics and air deposition affect uranium absorption and that different uranium species have different affinities to U. dioica plants. The values of (234)U/(238)U activity ratio indicate natural origin of these radioisotopes in analyzed plants. Uranium concentration in plants roots is negatively weakly correlated with distance from phosphogypsum stockpile.

  11. Study of secondary neutron interactions with 232Th, 129I, and 127I nuclei with the uranium assembly “QUINTA” at 2, 4, and 8GeV deuteron beams of the JINR Nuclotron accelerator

    DOE PAGES

    Adam, J.; Chilap, V. V.; Furman, V. I.; ...

    2015-11-04

    The natural uranium assembly, “QUINTA”, was irradiated with 2, 4, and 8 GeV deuterons. The 232Th, 127I, and 129I samples have been exposed to secondary neutrons produced in the assembly at a 20-cm radial distance from the deuteron beam axis. The spectra of gamma rays emitted by the activated 232Th, 127I, and 129I samples have been analyzed and several tens of product nuclei have been identified. For each of those products, neutron-induced reaction rates have been determined. The transmutation power for the 129I samples is estimated. Furthermore, experimental results were compared to those calculated with well-known stochastic and deterministic codes.

  12. Investigation of heavy-ion fusion with deformed surface diffuseness: Actinide and lanthanide targets

    NASA Astrophysics Data System (ADS)

    Alavi, S. A.; Dehghani, V.

    2017-05-01

    By using a deformed Broglia-Winther nuclear interaction potential in the framework of the WKB method, the near- and above-barrier heavy-ion-fusion cross sections of 16O with some lanthanides and actinides have been calculated. The effect of deformed surface diffuseness on the nuclear interaction potential, the effective interaction potential at distinct angle, barrier position, barrier height, cross section at each angles, and fusion cross sections of 16O+147Sm,150Nd,154Sm , and 166Er and 16O+232Th,238U,237Np , and 248Cm have been studied. The differences between the results obtained by using deformed surface diffuseness and those obtained by using constant surface diffuseness were noticeable. Good agreement between experimental data and theoretical calculation with deformed surface diffuseness were observed for 16O+147Sm,154Sm,166Er,238U,237Np , and 248Cm reactions. It has been observed that deformed surface diffuseness plays a significant role in heavy-ion-fusion studies.

  13. Allanite from the El Muerto Pegmatite, Oaxaca, Mexico: A Potential New Standard for 232Th-208Pb Dating by LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Price, J.; Crowley, J. L.; Solari, L.; Prol-Ledesma, R.

    2012-12-01

    Allanite dating may be important to studies addressing tectonomagmatic evolution, provenance of monocyclic sediment, and mineral weathering. Obtaining accurate allanite ages by SIMS has been challenging and time-consuming due to the mineral's extreme chemical variability which often prevents finding adequately matrix-matched standards. Isotopic measurements by LA-ICP-MS minimize the need for standards of nearly identical composition to the unknown allanite being analyzed, and it is done relatively rapidly. Dating by LA-ICP-MS requires high quality standards for isotopic fractionation corrections. However, readily accessible and well characterized allanite standards are scarce. We investigated gemstone allanite from the El Muerto pegmatite, Oaxaca, Mexico, as a potential new geochronology standard for 232Th-208Pb allanite dating by LA-ICP-MS. Compositional homogeneity was thoroughly investigated by scanning and backscatter electron microscopy, cathodoluminescence, quantitative and qualitative energy dispersive x-ray spectroscopy, electron microprobe, and LA-ICP-MS. The possibility of metamictization was investigated by extensive X-ray diffraction analyses. The El Muerto allanite was U-Pb dated by ID-TIMS, with common Pb ratios determined from cogenetic K-feldspar by ID-TIMS and LA-MC-ICP-MS. Future work includes Th-Pb dating by ID-TIMS. The samples investigated are homogeneous with respect to major and trace elements. Major element compositional results are generally in agreement with published values, and no metamictization was identified despite the allanite being nearly 1 Ga. The only limitation of the El Muerto allanite is that it contains small, generally <100 μm, scarce inclusions of quartz, calciothorite, albite, calcite, and biotite. However, these grains are easily recognized and avoided during LA-ICP-MS analyses. Based on these results, the El Muerto allanite has the potential to serve as a standard for LA-ICP-MS dating.

  14. A precise 232Th-208Pb chronology of fine-grained monazite: Age of the Bayan Obo REE-Fe-Nb ore deposit, China

    USGS Publications Warehouse

    Wang, Jingyuan; Tatsumoto, M.; Li, X.; Premo, W.R.; Chao, E.C.T.

    1994-01-01

    We have obtained precise Th-Pb internal isochron ages on monazite and bastnaesite for the world's largest known rare earth elements (REE)-Fe-Nb ore deposit, the Bayan Obo of Inner Mongolia, China. The monazite samples, collected from the carbonate-hosted ore zone, contain extremely small amounts of uranium (less than 10 ppm) but up to 0.7% ThO2. Previous estimates of the age of mineralization ranged from 1.8 to 0.255 Ga. Magnetic fractions of monazite and bastnaesite samples (<60-??m size) showed large ranges in 232Th 204Pb values (900-400,000) and provided precise Th-Pb internal isochron ages for paragenetic monazite mineralization ranging from 555 to 398 Ma within a few percent error (0.8% for two samples). These results are the first indication that REE mineralization within the giant Bayan Obo ore deposit occurred over a long period of time. The initial lead isotopic compositions (low 206Pb 204Pb and high 208Pb 204Pb) and large negative ??{lunate}Nd values for Bayan Obo ore minerals indicate that the main source(s) for the ores was the lower crust which was depleted in uranium, but enriched in thorium and light rare earth elements for a long period of time. Zircon from a quartz monzonite, located 50 km south of the ore complex and thought to be related to Caledonian subduction, gave an age of 451 Ma, within the range of monazite ages. Textural relations together with the mineral ages favor an epigenetic rather than a syngenetic origin for the orebodies. REE mineralization started around 555 Ma (disseminated monazite in the West, the Main, and south of the East Orebody), but the main mineralization (banded ores) was related to the Caledonian subduction event ca. 474-400 Ma. ?? 1994.

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

    PubMed

    Shizuma, Kiyoshi; Endo, Satoru; Fujikawa, Yoko

    2012-02-01

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

  16. 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.

  17. 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).

  18. 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.

  19. 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.

  20. Identification of new neutron-rich isotopes produced by in-flight fission of ^238U at 345 MeV/u

    NASA Astrophysics Data System (ADS)

    Ohnishi, Tetsuya; Kubo, Toshiyuki; Takeda, Hiroyuki; Fukuda, Naoki; Kameda, Daisuke; Kusaka, Kensuke; Yoshida, Atsushi; Yoshida, Koichi; Ohtake, Masao; Inabe, Naohito; Yanagisawa, Yoshiyuki; Tanaka, Kanenobu

    2009-10-01

    At RI Beam Factory (RIBF) at RIKEN Nishina Center, an in-flight radioactive isotope beam separator BigRIPS[1] was commissioned in 2007. Then we made a search for new isotopes using in-flight fission of a ^238U beam at 345 MeV/u, and observed two new palladium isotopes ^125Pd and ^126Pd.[2] In November 2008, we revisited this experiment with improved experimental conditions and better tuning of BigRIPS. The intensity of the ^238U beam was 1.6x10^9 particle/sec on average, which was about 40 times higher than in 2007. The search was performed for three Bρ settings that targeted different isotope regions. The achieved resolution of particle identification was good enough to well identify fission fragments even if some of them were not fully stripped. We observed more than 20 new isotopes with Z = 26 to 53, including ^128Pd, which demonstrated the RI-beam production power of BigRIPS at RIBF. The details of the experiment will be reported. [1]T. Kubo, Nucl. Instr. and Meth. B204, 97(2003). [2]T. Ohnishi et al, J. Phys. Soci. Jpn. 77, 083201(2008).

  1. 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.

  2. 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.

  3. AN INTEGRAL REACTOR PHYSICS EXPERIMENT TO INFER ACTINIDE CAPTURE CROSS-SECTIONS FROM THORIUM TO CALIFORNIUM WITH ACCELERATOR MASS SPECTROMETRY

    SciTech Connect

    G. Youinou; M. Salvatores; M. Paul; R. Pardo; G. Palmiotti; F. Kondev; G. Imel

    2010-04-01

    The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor (ATR) at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectroscopy (AMS) technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am and 248Cm.

  4. MANTRA: An Integral Reactor Physics Experiment to Infer Actinide Capture Cross-sections from Thorium to Californium with Accelerator Mass Spectrometry

    SciTech Connect

    G. Youinou; C. McGrath; G. Imel; M. Paul; R. Pardo; F. Kondev; M. Salvatores; G. Palmiotti

    2011-08-01

    The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectrometry technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm and 248Cm.

  5. Cross sections and barriers for nuclear fission induced by high-energy nucleons

    SciTech Connect

    Grudzevich, O. T.; Yavshits, S. G.

    2013-03-15

    The cross sections for the fission of {sup 232}Th, {sup 235,238}U, {sup 237}Np, and {sup 239}Pu target nuclei that was induced by 20- to 1000-MeV neutrons and protons were calculated. The respective calculations were based on the multiconfiguration-fission (MCFx) model, which was used to describe three basic stages of the interaction of high-energy nucleons with nuclei: direct processes (intranuclear cascade), equilibration of the emerging compound system, and the decay of the compound nucleus (statistical model). Fission barriers were calculated within the microscopic approach for isotopic chains formed by 15 to 20 nuclei of the required elements. The calculated fission cross sections were compared with available experimental data. It was shown that the input data set and the theoretical model used made it possible to predict satisfactorily cross section for nuclear fission induced by 20- to 1000-MeV nucleons.

  6. Separation of actinides using capillary extraction chromatography-inductively coupled plasma mass spectrometry

    SciTech Connect

    Peterson, Dominic S

    2008-01-01

    Trace levels of actinides have been separated on extraction chromatography columns. Detection of the actinides was achieved using an inductively coupled plasma mass spectrometer (ICP-MS), which was coupled with the extraction chromatography system. In this study we compare 30 cm long, 4.6 mm ID columns to capillary columns (750 {micro}m ID) with lengths from 30 cm up to 150 cm. The columns that were tested were packed with TRU resin. We were able to separate a mixture of five actinides ({sup 232}Th, {sup 238}U, {sup 237}Np, {sup 239}pU, {sup 241}Am). This work has application to rapid bioassay as well as for automated separations of actinide materials.

  7. Actinide integral measurements in the CFRMF and integral tests for ENDF/B-V

    SciTech Connect

    Anderl, R.A.

    1982-01-01

    Integral capture and/or fission rates have been reported earlier for several actinides irradiated in the fast neutron field of the Coupled Fast Reactivity Measurements Facility (CFRMF). These nuclides include /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 237/Np, /sup 239/Pu, /sup 240/Pu, /sup 242/Pu, /sup 241/Am and /sup 243/Am. This paper forucses on the utilization of these integral data for testing the respective cross sections on ENDF/B-V. Integral cross sections derived from the measured reaction rates are tabulated. Results are presented for cross-section data testing which includes integral testing based on a comparison of calculated and measured integral cross sections and testing based on least-squares-adjustment analyses.

  8. 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.

  9. 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)

  10. 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.

  11. (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

  12. 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

  13. Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Tetsuya Ohnishi,; Toshiyuki Kubo,; Kensuke Kusaka,; Atsushi Yoshida,; Koichi Yoshida,; Masao Ohtake,; Naoki Fukuda,; Hiroyuki Takeda,; Daisuke Kameda,; Kanenobu Tanaka,; Naohito Inabe,; Yoshiyuki Yanagisawa,; Yasuyuki Gono,; Hiroshi Watanabe,; Hideaki Otsu,; Hidetada Baba,; Takashi Ichihara,; Yoshitaka Yamaguchi,; Maya Takechi,; Shunji Nishimura,; Hideki Ueno,; Akihiro Yoshimi,; Hiroyoshi Sakurai,; Tohru Motobayashi,; Taro Nakao,; Yutaka Mizoi,; Masafumi Matsushita,; Kazuo Ieki,; Nobuyuki Kobayashi,; Kana Tanaka,; Yosuke Kawada,; Naoki Tanaka,; Shigeki Deguchi,; Yoshiteru Satou,; Yosuke Kondo,; Takashi Nakamura,; Kenta Yoshinaga,; Chihiro Ishii,; Hideakira Yoshii,; Yuki Miyashita,; Nobuya Uematsu,; Yasutsugu Shiraki,; Toshiyuki Sumikama,; Junsei Chiba,; Eiji Ideguchi,; Akito Saito,; Takayuki Yamaguchi,; Isao Hachiuma,; Takeshi Suzuki,; Tetsuaki Moriguchi,; Akira Ozawa,; Takashi Ohtsubo,; Michael A. Famiano,; Hans Geissel,; Anthony S. Nettleton,; Oleg B. Tarasov,; Daniel P. Bazin,; Bradley M. Sherrill,; Shashikant L. Manikonda,; Jerry A. Nolen,

    2010-07-01

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: 71Mn, 73,74Fe, 76Co, 79Ni, 81,82Cu, 84,85Zn, 87Ga, 90Ge, 95Se, 98Br, 101Kr, 103Rb, 106,107Sr, 108,109Y, 111,112Zr, 114,115Nb, 115,116,117Mo, 119,120Tc, 121,122,123,124Ru, 123,124,125,126Rh, 127,128Pd, 133Cd, 138Sn, 140Sb, 143Te, 145I, 148Xe, and 152Ba.

  14. Quantification of Uncertainties due to 235,238U, 239,240,241Pu and Fission Products Nuclear Data Uncertainties for a PWR Fuel Assembly

    NASA Astrophysics Data System (ADS)

    da Cruz, D. F.; Rochman, D.; Koning, A. J.

    2014-04-01

    Uncertainty analysis on reactivity and discharged inventory for a typical PWR fuel element as a result of uncertainties in 235,238U, 239,240,241Pu, and fission products nuclear data was performed. The Total Monte-Carlo (TMC) method was applied using the deterministic transport code DRAGON. The nuclear data used in this study is from the JEFF-3.1 evaluations, with the exception of the nuclear data files for U, Pu and fission products isotopes, which are taken from the nuclear data library TENDL-2012. Results show that the calculated total uncertainty in keff (as result of uncertainties in nuclear data of the considered isotopes) is virtually independent on fuel burnp and amounts to 700 pcm. The uncertainties in inventory of the discharged fuel is dependent on the element considered and lies in the range 1-15% for most fission products, and is below 5% for the most important actinides.

  15. High-accuracy determination of the 238U/235U fission cross section ratio up to ≈1 GeV at n_TOF at CERN

    NASA Astrophysics Data System (ADS)

    Paradela, C.; Calviani, M.; Tarrío, D.; Leal-Cidoncha, E.; Leong, L. S.; Tassan-Got, L.; Le Naour, C.; Duran, I.; Colonna, N.; Audouin, L.; Mastromarco, M.; Lo Meo, S.; Ventura, A.; Aerts, G.; Altstadt, S.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Badurek, G.; Barbagallo, M.; Baumann, P.; Bécares, V.; Bečvář, F.; Belloni, F.; Berthier, B.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Cennini, P.; Cerutti, F.; Chiaveri, E.; Chin, M.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Couture, A.; Cox, J.; David, S.; Diakaki, M.; 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.; García, A. R.; Giubrone, G.; Gómez-Hornillos, M. B.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Gurusamy, P.; Haight, R.; Heil, M.; Heinitz, S.; Igashira, M.; Isaev, S.; Jenkins, D. G.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Kivel, N.; Kokkoris, M.; Konovalov, V.; Krtička, M.; Kroll, J.; Lampoudis, C.; Langer, C.; Lederer, C.; Leeb, H.; Losito, R.; Lozano, M.; Manousos, A.; Marganiec, J.; Martínez, 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.; 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.; Žugec, P.; n TOF Collaboration

    2015-02-01

    The 238U to 235U fission cross section ratio has been determined at n_TOF up to ≈1 GeV, with two different detection systems, in different geometrical configurations. A total of four datasets has been collected and compared. They are all consistent to each other within the relative systematic uncertainty of 3-4%. The data collected at n_TOF have been suitably combined to yield a unique fission cross section ratio as a function of neutron energy. The result confirms current evaluations up to 200 MeV. Good agreement is also observed with theoretical calculations based on the INCL ++/ Gemini++ combination up to the highest measured energy. The n_TOF results may help solve a long-standing discrepancy between the two most important experimental datasets available so far above 20 MeV, while extending the neutron energy range for the first time up to ≈1 GeV.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 238U-230Th-226Ra disequilibria in plagioclase from recent mixed magmas at Mount Hood: constraints on crystal storage timescales and eruption triggering processes

    NASA Astrophysics Data System (ADS)

    Eppich, G. R.; Cooper, K. M.; Kent, A. J.; Koleszar, A. M.

    2010-12-01

    Uranium-series crystal ages, interpreted within a textural and geochemical framework, can provide insight into crystal storage timescales and eruption triggering processes. Mount Hood is a mixing-driven volcano that consistently erupts magmas of intermediate composition. Mixed magmas incorporate plagioclase derived from mafic and silicic end-member magmas (Kent AJR; Darr C; Koleszar AM; Salisbury MJ; Cooper KM. 2010. Preferential eruption of andesitic magmas through recharge filtering. Nature Geosci.). We measured 238U-230Th-226Ra disequilibria for four plagioclase size fractions, groundmass separates, and mafic inclusions from the Timberline (1500 a) and Old Maid (215 a) eruptive sequences. Measured (230Th)/(238U) was 1.126-1.143 for Timberline plagioclase and 1.127-1.143 for Old Maid plagioclase. Measured (226Ra)/(230Th) was 1.22-1.62 for Timberline plagioclase and 1.27-1.43 for Old Maid plagioclase. Corrections were performed for the presence of groundmass in the >500 µm plagioclase separates, and large plagioclase + groundmass in the <500 µm plagioclase separates. Small (<500 µm) plagioclase, derived from mafic magma, records enriched present-day (226Ra)/Ba relative to equilibrium with liquid proxies (groundmass and mafic inclusions), leading to undefined Ra-Th model ages. However, the measured disequilibria require that the majority of plagioclase in the separate is young (<<10 ka). Large (>500 µm) plagioclase, derived from the silicic mixing end-member, records (238U)/(230Th) disequilibrium and minor (226Ra)/(230Th) disequilibrium. Ra-Th model ages are 5-10 ka. Rims of large plagioclase crystallized within weeks of eruption (Kent et al., 2010), suggesting that the 5-10 ka Ra-Th model ages are averages of young rim growth and old cores, which could be >10 ka. Crystallization timescales of large plagioclase cores are longer than timescales of repose between eruptions, suggesting that the crystals must have been present yet remained untapped during older

  2. 238U-230Th-226Ra disequilibria in dacite and plagioclase from the 2004-2005 eruption of Mount St. Helens: Chapter 36 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    USGS Publications Warehouse

    Cooper, Kari M.; Donnelly, Carrie T.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    2008-01-01

    230Th)/(232Th) measured for the 1980s reference suite. However, (230Th)/(232Th) for plagioclase separates for dome samples erupted during October and November 2004 are significantly different from corresponding whole-rock values, which suggests that a large fraction (>30 percent) of crystals in each sample are foreign to the host liquid. Furthermore, plagioclase in the two 2004 samples have U-series characteristics distinct from each other and from plagioclase in dacite erupted in 1982, indicating that (1) the current eruption must include a component of crystals (and potentially associated magma) that were not sampled by the 1980-86 eruption, and (2) dacite magmas erupted only a month apart in 2004 contain different populations of crystals, indicating that this foreign component is highly heterogeneous within the 2004-5 magma reservoir.

  3. 234U/238U Disequilibrium along stylolitic discontinuities in deep Mesozoic limestone formations of the Eastern Paris basin: evidence for discrete uranium mobility over the last 1-2 million years

    NASA Astrophysics Data System (ADS)

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

    The (234U/238) equilibrium state of borehole core samples from the deep, low-permeability limestone formations surrounding the target argilite layer of the Meuse/Haute-Marne experimental site of the French agency for nuclear waste management -ANDRA- (Agence nationale pour la gestion des déchets radioactifs) was examined to improve understanding of naturally occurring radionuclide behaviour in such geological settings. Highly precise, accurate MC-ICP-MS measurements of the (234U/238U) activity ratio show that limestone samples characterised by pressure dissolution structures (stylolites or dissolution seams) display systematic (234U/238U) disequilibria, while the pristine carbonate samples remain in the secular equilibrium state. The systematic feature is observed throughout the zones marked by pressure dissolution structures: (i) the material within the seams shows a deficit of 234U over 238U ((234U/238U) down to 0.80) and (ii) the surrounding carbonate matrix is characterised by an activity ratio greater than unity (up to 1.05). These results highlight a centimetric-scale uranium remobilisation in the limestone formations along these sub-horizontal seams. Although their nature and modalities are not fully understood, the driving processes responsible for these disequilibria were active during the last 1-2 Ma.

  4. 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.

  5. Distinct 238U/235U ratios and REE patterns in plutonic and volcanic angrites: Geochronologic implications and evidence for U isotope fractionation during magmatic processes

    NASA Astrophysics Data System (ADS)

    Tissot, François L. H.; Dauphas, Nicolas; Grove, Timothy L.

    2017-09-01

    Angrites are differentiated meteorites that formed between 4 and 11 Myr after Solar System formation, when several short-lived nuclides (e.g., 26Al-26Mg, 53Mn-53Cr, 182Hf-182W) were still alive. As such, angrites are prime anchors to tie the relative chronology inferred from these short-lived radionuclides to the absolute Pb-Pb clock. The discovery of variable U isotopic composition (at the sub-permil level) calls for a revision of Pb-Pb ages calculated using an ;assumed; constant 238U/235U ratio (i.e., Pb-Pb ages published before 2009-2010). In this paper, we report high-precision U isotope measurement for six angrite samples (NWA 4590, NWA 4801, NWA 6291, Angra dos Reis, D'Orbigny, and Sahara 99555) using multi-collector inductively coupled plasma mass-spectrometry and the IRMM-3636 U double-spike. The age corrections range from -0.17 to -1.20 Myr depending on the samples. After correction, concordance between the revised Pb-Pb and Hf-W and Mn-Cr ages of plutonic and quenched angrites is good, and the initial (53Mn/55Mn)0 ratio in the Early Solar System (ESS) is recalculated as being (7 ± 1) × 10-6 at the formation of the Solar System (the error bar incorporates uncertainty in the absolute age of Calcium, Aluminum-rich inclusions - CAIs). An uncertainty remains as to whether the Al-Mg and Pb-Pb systems agree in large part due to uncertainties in the Pb-Pb age of CAIs. A systematic difference is found in the U isotopic compositions of quenched and plutonic angrites of +0.17‰. A difference is also found between the rare earth element (REE) patterns of these two angrite subgroups. The δ238U values are consistent with fractionation during magmatic evolution of the angrite parent melt. Stable U isotope fractionation due to a change in the coordination environment of U during incorporation into pyroxene could be responsible for such a fractionation. In this context, Pb-Pb ages derived from pyroxenes fraction should be corrected using the U isotope composition

  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. 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. New prompt fission neutron spectra measurements in the 238U(n,f) reaction with a dedicated setup at LANSCE/WNR

    NASA Astrophysics Data System (ADS)

    Laurent, Benoit; Marini, Paola; Bélier, Gilbert; Bonnet, Thomas; Chatillon, Audrey; Taieb, Julien; Etasse, David; Devlin, Matthew; Haight, Robert

    2017-09-01

    A new prompt fission neutron spectra (PFNS) measurement in the 238U(n,f) reaction was performed at LANSCE/WNR facility. Evaluated data show discrepancies on the low (below 1 MeV) and high (above 5 MeV) energy parts in the PFNS for different major and minor actinides. The goal is to improve these measurements in a wide range of incident energy. The energy of the incoming neutron, inducing the fission, and the prompt neutron energies, are measured by time-of-flight method. A dedicated fission chamber was developed, in order to improve alpha-fission discrimination, timing resolution, actinide mass, and to reduce the amount of neutron scattering. To detect prompt neutrons, the 54 Chi-Nu scintillator cells array were surrounding the fission chamber. High statistics were recorded during this experiment, allowing a precise study of PFNS behavior as a function of incident neutron energy, from 1 MeV to 200 MeV. This experiment also showed that all the new tools developed to improve PFNS measurements are performing. Therefore, measurements of PFNS with others actinides such as 239Pu are planned.

  9. Spatial variations of particle export in the South China Sea and the Luzon Strait based on 234Th-238U disequilibrium

    NASA Astrophysics Data System (ADS)

    Chen, W.

    2016-12-01

    We examined the spatial variations of particulate organic carbon (POC) export derived from 234Th/238U disequilibria based on the summer cruise in 2014, covering the South China Sea (SCS) and Luzon Strait. Thorium-234 was sampled using a small-volume MnO2 co-precipitation technique, which maximized the spatial resolution of 234Th distribution. A stratified structure of 234Th activities was observed with a subsurface maximum of the 234Th deficit, as seen in many other oligotrophic regimes. The high resolution sampling and the site and depth-specific POC/234Th ratio on suspended particles allowed us to estimate the 234Th fluxes and POC export. POC fluxes were higher in the basin of the northern SCS, with an average of 3.2 mmolC m-2 d-1 as compared to the lower value of 1.7mmolC m-2 d-1 for the southern SCS and 1.2 mmolC m-2 d-1 for the Luzon Strait. Such pattern might be related to variation of nutrient supply and the primary production. Combined with the historical data the interannual variation of POC fluxes in the northern SCS will be examined and presented.

  10. Identification of 45 new neutron-rich isotopes produced by in-flight fission of a {sup 238}U beam at 345 MeV/nucleon.

    SciTech Connect

    Ohnishi, T.; Kubo, T.; Kusaka, K.; Yoshida, A.; Yoshida, K.; Manikonda, S.; Nolen, J.

    2010-07-12

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon {sup 238}U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: {sup 71}Mn, {sup 73,74}Fe, {sup 76}Co, {sup 79}Ni, {sup 81,82}Cu, {sup 84,85}Zn, {sup 87}Ga, {sup 90}Ge, {sup 95}Se, {sup 98}Br, {sup 101}Kr, {sup 103}Rb, {sup 106,107}Sr, {sup 108,109}Y, {sup 111,112}Zr, {sup 114,115}Nb, {sup 115,116,117}Mo, {sup 119,120}Tc, {sup 121,122,123,124}Ru, {sup 123,124,125,126}Rh, {sup 127,128}Pd, {sup 133}Cd, {sup 138}Sn, {sup 140}Sb, {sup 143}Te, {sup 145}I, {sup 148}Xe, and {sup 152}Ba.

  11. R-Matrix Analysis of 238U High Resolution Neutron Transmissions and Capture Cross Sections in the Energy Range 0 keV to 20 keV

    SciTech Connect

    Derrien, Herve; Leal, Luiz C; Larson, Nancy M

    2009-01-01

    The neutron resonance parameters of 238U 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 to 200 pcm.

  12. 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).

  13. Observation of new neutron-rich micro-second isomers among fission products of ^238U at 345 MeV/u

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Nakao, Taro; Kubo, Toshiyuki; Ohnishi, Tetsuya; Takeda, Hiroyuki; Fukuda, Naoki; Kusaka, Kensuke; Yoshida, Atsushi; Yoshida, Koichi; Ohtake, Masao; Inabe, Naohito; Yanagisawa, Yoshiyuki; Tanaka, Kanenobu; Gono, Yasuyuki

    2009-10-01

    In the production of the radioactive isotope (RI) beam using projectile fragment separators, γ rays emitted from metastable states, isomers, of the reaction products can be used as a fingerprint of the isotope that is analyzed in the separator. In the operation of the superconducting in-flight RI beam separator BigRIPS [1] at RIKEN RI Beam Factory, the detection of such γ rays plays important roles not only in the identification of the RI beam [2] but also in searching for new isomers, providing valuable spectroscopic information on the isotopes. In the recent new-isotope production experiment with BigRIPS using in-flight fission of 345 MeV/nucleon ^238U at the beam intensity around 0.3 pnA, we have observed a number of short-lived isomeric decays which include unknown decays from more than 10 isotopes, using three clover-type Ge detectors with a beam stopper of aluminum. The primal result of the observations will be reported. [1] T. Kubo: Nucl. Instr. and Meth. B 204 (2003) 97. [2] T. Ohnishi et al.: J. Phys. Soc. Japan, 77 (2008) 083201.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  16. Decay of {sup 246}Bk* formed in similar entrance channel reactions of {sup 11}B+{sup 235}U and {sup 14}N+{sup 232}Th at low energies using the dynamical cluster-decay model

    SciTech Connect

    Singh, BirBikram; Sharma, Manoj K.; Gupta, Raj K.

    2008-05-15

    The decay of the {sup 246}Bk* nucleus, formed in entrance channel reactions {sup 11}B+{sup 235}U and {sup 14}N+{sup 232}Th at different incident energies, is studied by using the dynamical cluster-decay model (DCM) extended to include the deformations and orientations of nuclei. The main decay mode here is fission. The other (weaker) decay channels are the light particles evaporation (A{<=}4) and intermediate mass fragments (5{<=}A{<=}20). All decay products are calculated as emissions of preformed clusters through the interaction barriers. The calculated fission cross sections {sigma}{sub fiss}, taken as a sum of the energetically favored symmetric and near symmetric fragments (A{sub CN}/2{+-}7 and A=106-110 plus complementary fragments) show an excellent agreement with experimental data at all experimental incident c.m. energies for both reactions, except for the top three energies in the case of the {sup 11}B+{sup 235}U reaction. The disagreement between the DCM calculations and data at higher incident c.m. energies for the {sup 11}B+{sup 235}U entrance channel is associated with the presence of additional effects of noncompound, quasifission (qf) components, in contradiction with the measured anisotropy effects which indicate the other entrance channel {sup 14}N+{sup 232}Th to contain the noncompound nucleus contribution. The prediction of two fission windows, the symmetric fission (SF) and near symmetric or heavy mass fragments (HMFs), suggests the presence of a fine structure of fission fragments, which also need an experimental verification. The only parameter of the model is the neck length parameter {delta}R whose value is shown to depend strongly on limiting angular momentum, which in turn depends on the use of sticking or nonsticking moment of inertia for angular momentum effects.

  17. Energy dependence of fission product yields from 235U, 238U, and 239Pu with monoenergetic neutrons between thermal and 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Gooden, Matthew; Arnold, Charles; Bhike, Megha; Bredeweg, Todd; Fowler, Malcolm; Krishichayan; Tonchev, Anton; Tornow, Werner; Stoyer, Mark; Vieira, David; Wilhelmy, Jerry

    2017-09-01

    Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and γ-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of two months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from thermal irradiations at the MIT research reactor will also be presented and compared to present data and evaluations. 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, Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and by Duke University and Triangle Universities Nuclear Laboratory through NNSA Stewardship Science Academic Alliance grant No. DE-FG52-09NA29465, DE-FG52-09NA29448 and Office of Nuclear Physics Grant No. DE-FG02-97ER41033.

  18. Extensive radioactive characterization of a phosphogypsum stack in SW Spain: 226Ra, 238U, 210Po concentrations and 222Rn exhalation rate.

    PubMed

    Abril, José-María; García-Tenorio, Rafael; Manjón, Guillermo

    2009-05-30

    Phosphogypsum (PG) is a by-product of the phosphate fertilizer industries that contains relatively high concentrations of uranium series radionuclides. The US-EPA regulates the agriculture use of PG, attending to its (226)Ra content and to the (222)Rn exhalation rate from inactive stacks. Measurements of (222)Rn exhalation rates in PG stacks typically show a large and still poorly understood spatial and temporal variability, and the published data are scarce. This work studies an inactive PG stack in SW Spain of about 0.5 km(2) from where PG can be extracted for agriculture uses, and an agriculture soil 75 km apart, being representative of the farms to be amended with PG. Activity concentrations of (226)Ra, (238)U and (210)Po have been measured in 30 PG samples (0-90 cm horizon) allowing for the construction of maps with spatial distributions in the PG stack and for the characterization of the associated PG inputs to agriculture soils. Averaged (226)Ra concentrations for the stack were 730+/-60 Bq kg(-1) (d.w.), over the US-EPA limit of 370 Bq kg(-1). (222)Rn exhalation rate has been measured by the charcoal canister method in 49 sampling points with 3 canisters per sampling point. Values in PG stack were under the US-EPA limit of 2600 Bq m(-2)h(-1), but they were one order of magnitude higher than those found in the agriculture soil. Variability in radon emissions has been studied at different spatial scales. Radon exhalation rates were correlated with (226)Ra concentrations and daily potential evapotranspiration (ETo). They increased with ETo in agriculture soils, but showed an opposite behaviour in the PG stack.

  19. 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).

  20. Implications for Seawater 234U/238U Composition and Weathering on Glacial-Interglacial Timescales Based on Modern and Fossil Corals

    NASA Astrophysics Data System (ADS)

    Chutcharavan, P. M.; Dutton, A.; Ellwood, M. J.

    2016-12-01

    U-Th dating of fossil corals provides absolute age constraints on records of ancient sea level and climate change and is also used to calibrate the radiocarbon timescale. Unfortunately, coralline aragonite is susceptible to diagenesis, requiring screening procedures to identify altered samples. One commonly employed screening method assesses the initial δ234U value, which represents seawater 234U/238U composition at the time of coral skeleton formation. Seawater δ234U is typically assumed to have remained constant during recent glacial-interglacial cycles; hence corals with initial δ234U­ values that are significantly different than that of modern seawater are typically rejected as being diagenetically altered. However, this approach is complicated by (1) uncertainty in the appropriate value to use for modern seawater, arising from discrepancies between different measurements of modern seawater and/or corals, and (2) the possibility that seawater δ234U has varied on glacial-interglacial timescales. To address these two issues, we present and analyze a compilation of over 2,000 individual U-series coral measurements from 60,000 years ago to present. By normalizing for the 234U decay constant used and correcting for inter-lab variability, including offsets introduced by different types of standards and variability between different aliquots of the same standard, this study reconciles multiple independent measurements of δ234U in modern corals and seawater over several decades, causing nearly all measurements to converge on a value of 145‰. Additionally, the fossil coral record demonstrates a salient increase in δ234U of 7‰ in-step with the last deglaciation. The coupling of δ234U variability with changes Pb-isotope compositions of Fe-Mn crusts suggest that physical weathering of high U and Pb-bearing mineral phases in glaciated regions may be responsible for the observed changes in seawater chemistry that are critical to interpreting U-Th dates of fossil

  1. 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.

  2. 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.

  3. Beta and gamma decay heat measurements between 0.1s--50,000s for neutron fission of {sup 235}U, {sup 238}U and {sup 239}Pu. Final report, June 1, 1992--December 31, 1996

    SciTech Connect

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

    1996-01-01

    This is a final reporting on the composition of separate beta and gamma decay heat measurements following neutron fission of {sup 235}U and {sup 238}U and {sup 239}Pu and on cumulative and independent yield measurements of fission products of {sup 235}U and {sup 238}U. What made these studies unique was the very short time of 0.1 s after fission that could be achieved by incorporating the helium jet and tape transport system as the technique for transporting fission fragments from the neutron environment of the fission chamber to the low-background environment of the counting area. This capability allowed for the first time decay heat measurements to extend nearly two decades lower on the logarithmic delay time scale, a region where no comprehensive aggregate decay heat measurements had extended to. This short delay time capability also allowed the measurement of individual fission products with half lives as short as 0.2s. The purpose of such studies was to provide tests both at the aggregate level and at the individual nuclide level of the nation`s evaluated nuclear data file associated with fission, ENDF/B-VI. The results of these tests are in general quite encouraging indicating this data base generally predicts correctly the aggregate beta and aggregate gamma decay heat as a function of delay time for {sup 235}U, {sup 238}U and {sup 239}Pu. Agreement with the measured individual nuclide cumulative and independent yields for fission products of {sup 235}U and {sup 238}U was also quite good although the present measurements suggest needed improvements in several individual cases.

  4. 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

  5. Eruption and magma crystallization ages of Las Tres Vírgenes (Baja California) constrained by combined 230Th/ 238U and (U-Th)/He dating of zircon

    NASA Astrophysics Data System (ADS)

    Schmitt, Axel K.; Stockli, Daniel F.; Hausback, Brian P.

    2006-11-01

    Las Tres Vírgenes volcano is a calc-alkaline composite cone located near the main Gulf of California escarpment on the E coast of the Baja California peninsula. High-sensitivity ion microprobe U-series ( 230Th/ 238U) ages for zircon from La Vírgen tephra average 121 - 10 + 12 ka (1σ; MSWD = 2.7), with discrete age peaks at ˜ 100 and 160 ka. The noble gas mass spectrometric (U-Th)/He zircon age, corrected for disequilibrium and pre-eruptive storage, is 36 ± 3 ka. This result for the eruption age of La Vírgen tephra is significantly older than previously postulated historic or Holocene ages that were based on an 18th century map reference and 14C dating of accidental charcoal, respectively. The new (U-Th)/He zircon age is consistent with a > 26 ± 4 ka age derived from cosmogenic He exposure dating of an overlying basaltic lava flow [Hausback, B.P. and Abrams, M.J., 1996. Plinian eruption of La Virgen Tephra, Volcán Las Tres Virgenes, Baja California Sur, Mexico. Eos, Transactions, American Geophysical Union, 77(46, Suppl.): 813-814.]. U-Pb zircon analysis of ignimbrites erupted from the adjacent Early Pleistocene La Reforma and El Aguajito calderas yielded ages of 1.38 ± 0.03 Ma ( n = 12; MSWD = 1.0) and 1.17 ± 0.07 Ma ( n = 23; MSWD = 1.3), respectively. No evidence for these ages is found among La Vírgen zircons, whereas pre-Quaternary zircon xenocrysts are common. The La Vírgen magma, therefore, evolved unrelated to Early Pleistocene magmatism in adjacent calderas, but assimilated local basement rocks. A gap between average Th-U and (U-Th)/He zircon ages suggests that zircon crystallization was discontinuous in the La Vírgen magma chamber. In addition, partial resorption of zircon suggests episodic thermal rejuvenation, most likely by basaltic recharge. Based on the zircon record, the > 100 ka lifetime of the thermal anomaly that sustained repeated intrusive pulses significantly exceeds the age of the last eruption. This strengthens the view that Tres

  6. 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

  7. Neutron capture cross section measurement of 238U at the CERN n_TOF facility in the energy region from 1 eV to 700 keV

    NASA Astrophysics Data System (ADS)

    Mingrone, F.; Massimi, C.; Vannini, G.; Colonna, N.; Gunsing, F.; Žugec, P.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Barbagallo, M.; Bécares, V.; Bečvář, F.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Duran, I.; Dressler, R.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Ganesan, S.; García, A. R.; Giubrone, G.; Gonçalves, I. F.; González-Romero, E.; Griesmayer, E.; Guerrero, C.; 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.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Leong, L. S.; Lo Meo, S.; Losito, R.; Mallick, A.; Manousos, A.; Marganiec, J.; Martínez, T.; Mastinu, P. F.; Mastromarco, M.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mirea, M.; Mondalaers, W.; Paradela, C.; Pavlik, A.; Perkowski, J.; Plompen, A.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego, A.; Robles, M. S.; Rubbia, C.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Tagliente, G.; Tain, J. L.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Variale, V.; Vaz, P.; Ventura, A.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiß, C.; Wright, T.; n TOF Collaboration

    2017-03-01

    The aim of this work is to provide a precise and accurate measurement of the 238U(n ,γ ) reaction cross section in the energy region from 1 eV to 700 keV. This reaction is of fundamental importance for the design calculations of nuclear reactors, governing the behavior of the reactor core. In particular, fast reactors, which are experiencing a growing interest for their ability to burn radioactive waste, operate in the high energy region of the neutron spectrum. In this energy region most recent evaluations disagree due to inconsistencies in the existing measurements of up to 15%. In addition, the assessment of nuclear data uncertainty performed for innovative reactor systems shows that the uncertainty in the radiative capture cross section of 238U should be further reduced to 1-3% in the energy region from 20 eV to 25 keV. To this purpose, addressed by the Nuclear Energy Agency as a priority nuclear data need, complementary experiments, one at the GELINA and two at the n_TOF facility, were proposed and carried out within the 7th Framework Project ANDES of the European Commission. The results of one of these 238U(n ,γ ) measurements performed at the n_TOF CERN facility are presented in this work. The γ -ray cascade following the radiative neutron capture has been detected exploiting a setup of two C6D6 liquid scintillators. Resonance parameters obtained from this work are on average in excellent agreement with the ones reported in evaluated libraries. In the unresolved resonance region, this work yields a cross section in agreement with evaluated libraries up to 80 keV, while for higher energies our results are significantly higher.

  8. 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.

  9. 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.

  10. 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.

  11. Photofission cross-section ratio measurement of 235 U/ 238 U using monoenergetic photons in the energy range of 9.0–16.6 MeV

    DOE PAGES

    Krishichayan,; Bhike, Megha; Finch, S. W.; ...

    2017-05-01

    Photofission cross-section ratios of 235U and 238U have been measured using monoenergetic photon beams from the High Intensity Gamma-ray Source facility at the Triangle Universities Nuclear Laboratory. These measurements have been performed in small energy steps between 9.0 and 16.6 MeV using a dual-fission ionization chamber. The measured cross-section ratios are compared with the previous experimental data as well as with the recent evaluated nuclear data library ENDF.

  12. 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.

  13. 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.

  14. Fission-fragment total kinetic energy and mass yields for neutron-induced fission of 235U and 238U with En =200 keV - 30 MeV

    NASA Astrophysics Data System (ADS)

    Duke, D. L.; Tovesson, F.; Brys, T.; Geppert-Kleinrath, V.; Hambsch, F.-J.; Laptev, A.; Meharchand, R.; Manning, B.; Mayorov, D.; Meierbachtol, K.; Mosby, S.; Perdue, B.; Richman, D.; Shields, D.; Vidali, M.

    2017-09-01

    The average Total Kinetic Energy (TKE) release and fission-fragment yields in neutron-induced fission of 235U and 238U was measured using a Frisch-gridded ionization chamber. These observables are important nuclear data quantites that are relevant to applications and for informing the next generation of fission models. The measurements were performed a the Los Alamos Neutron Science Center and cover En = 200 keV - 30 MeV. The double-energy (2E) method was used to determine the fission-fragment yields and two methods of correcting for prompt-neutron emission were explored. The results of this study are correlated mass and TKE data.

  15. Spin-alignment and g-factor measurement of the I^{π} = 12+ isomer in 192Pb produced in the relativistic-energy fragmentation of a 238U beam

    NASA Astrophysics Data System (ADS)

    Kmiecik, M.; Maj, A.; Gerl, J.; Neyens, G.; Atanasova, L.; Balabanski, D. L.; Becker, F.; Bednarczyk, P.; Benzoni, G.; Blasi, N.; Bracco, A.; Brambilla, S.; Caceres, L.; Camera, F.; Ciemała, M.; Crespi, F. C. L.; Chamoli, S. K.; Chmel, S.; Daugas, J. M.; Detistov, P.; Doornenbal, P.; Georgiev, G.; Gladnishki, K.; Górska, M.; Grawe, H.; Grȩbosz, J.; Hass, M.; Hoischen, R.; Ilie, G.; Ionescu-Bujor, M.; Jolie, J.; Kojuharov, I.; Krasznahorkay, A.; Kulessa, R.; Lach, M.; Lakshmi, S.; Leoni, S.; Lo Bianco, G.; Lozeva, R.; Maier, K. H.; Mallion, S.; Mazurek, K.; Mȩczyński, W.; Million, B.; Montanari, D.; Myalski, S.; Petrache, C.; Pfützner, M.; Pietri, S.; Podolyák, Zs.; Prokopowicz, W.; Rudolph, D.; Saito, N.; Saito, T. R.; Saltarelli, A.; Simpson, G. S.; Styczeń, J.; Vermeulen, N.; Werner-Malento, E.; Wieland, O.; Wollersheim, H. J.; Ziȩbliński, M.

    2010-08-01

    The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV ensuremath I^{π}=12^+ isomer in 192Pb with tau = 1.57 μs has been produced using the fragmentation of a 1 A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, tau = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.

  16. Use of radiometric ((234/238)U and (228/226)Ra) and mass spectrometry ((87/86)Sr) methods for studies of the stability of groundwater reservoirs in Central Poland.

    PubMed

    Grabowski, P; Bem, H; Romer, R L

    The uranium ((234)U/(238)U) and radium ((228)Ra/(226)Ra) activity ratios and (87)Sr/(86)Sr isotopic ratio in thermal groundwater, subsurface water (groundwater) and river water from Poddebice and Uniejow were determined. The uranium and radium activity ratios and strontium isotopic ratio varied from 0.629 to 1.471, from 0.396 to 4.961 and from 0.708438 to 0.710344, respectively. The results for the thermal groundwater samples showed that the radiometric method together with mass spectrometry stable strontium isotope ratio measurements can be used for underground water transport studies. On the basis of the uranium and radium activity and the strontium isotopic ratio differences in subsurface water (groundwater) and in river water, any possible water influx between these adjacent reservoirs can be observed. The obtained results exclude any water transport from surface and subsurface water to thermal ground water reservoirs in this region of Poland.

  17. Time-dependent mean-field determination of the excitation energy in transfer reactions: Application to the reaction 238U on 12C at 6.14 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Scamps, G.; Rodríguez-Tajes, C.; Lacroix, D.; Farget, F.

    2017-02-01

    The internal excitation of nuclei after multinucleon transfer is estimated by using the time-dependent mean-field theory. Transfer probabilities for each channel as well as the energy loss after reseparation are calculated. By combining these two pieces of information, we show that the excitation energy distribution of the transfer fragments can be obtained separately for the different transfer channels. The method is applied to the reaction involving a 238U beam on a 12C target, which has recently been measured at GANIL. It is shown that the excitation energy calculated with the microscopic theory compares well with the experimental observation, provided that the competition with fusion is properly taken into account. The reliability of the excitation energy is further confirmed by the comparison with the phenomenological heavy-ion phase-space model at higher center-of-mass energies.

  18. 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

    2014-06-25

    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.

  19. Carbon export fluxes and export efficiency in the central Arctic during the record sea-ice minimum in 2012: a joint 234Th/238U and 210Po/210Pb study

    NASA Astrophysics Data System (ADS)

    Roca-Martí, Montserrat; Puigcorbé, Viena; Rutgers van der Loeff, Michiel M.; Katlein, Christian; Fernández-Méndez, Mar; Peeken, Ilka; Masqué, Pere

    2016-07-01

    The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234Th/238U and 210Po/210Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234Th/238U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m-2 d-1) in late summer. Relationships obtained between the 234Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of 210Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210Po fluxes and 210Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice-covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.

  20. 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

  1. 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

  2. Measurements of plutonium, 237Np, and 137Cs in the BCR 482 lichen reference material

    DOE PAGES

    Lavelle, Kevin B.; Miller, Jeffrey L.; Hanson, Susan K.; ...

    2015-10-01

    Select anthropogenic radionuclides were measured in lichen reference material, BCR 482. This material was originally collected in Axalp, Switzerland in 1991 and is composed of the epiphytic lichen Pseudevernia furfuracea. Samples from three separate bottles of BCR 482 were analyzed for uranium, neptunium, and plutonium isotopes by inductively coupled plasma mass spectrometry (ICP-MS) and analyzed for cesium-137 by gamma-ray spectrometry. The isotopic composition of the radionuclides measured in BCR 482 suggests contributions from both global fallout resulting from historical nuclear weapons testing and more volatile materials released following the Chernobyl accident.

  3. Mössbauer effect studies on organometallic237Np-compounds

    NASA Astrophysics Data System (ADS)

    Adrian, G.; Appel, H.; Bohlander, R.; Haffner, H.; Kanellakopulos, B.

    1988-02-01

    A series of organometallic compounds of tetravalent Neptunium was studied by Moessbauer methods. Three of them will be presented here. Their molecular structure is close to C3v symmetry. The data were parameterised on the basis of an anisotropic paramagnetic relaxation model and will be interpreted for each individual compound. In general it can be stated that distortions from axially symmetric hyperfine parameters were observed, no magnetic ordering occured at all temperatures above 1.5 K and anisotropic relaxation frequencies had to be introduced to fit the spectra.

  4. Post-Irradiation Examination of 237Np Targets for 238Pu Production

    SciTech Connect

    Morris, Robert Noel; Baldwin, Charles A; Hobbs, Randy W; Schmidlin, Joshua E

    2015-01-01

    Oak Ridge National Laboratory is recovering the US 238Pu production capability and the first step in the process has been to evaluate the performance of a 237Np target cermet pellet encased in an aluminum clad. The process proceeded in 3 steps; the first step was to irradiate capsules of single pellets composed of NpO2 and aluminum power to examine their shrinkage and gas release. These pellets were formed by compressing sintered NpO2 and aluminum powder in a die at high pressure followed by sintering in a vacuum furnace. Three temperatures were chosen for sintering the solution precipitated NpO2 power used for pellet fabrication. The second step was to irradiate partial targets composed of 8 pellets in a semi-prototypical arrangement at the two best performing sintering temperatures to determine which temperature gave a pellet that performed the best under the actual planned irradiation conditions. The third step was to irradiate ~50 pellets in an actual target configuration at design irradiation conditions to assess pellet shrinkage and gas release, target heat transfer, and dimensional stability. The higher sintering temperature appeared to offer the best performance after one cycle of irradiation by having the least shrinkage, thus keeping the heat transfer gap between the pellets and clad small minimizing the pellet operating temperature. The final result of the testing was a target that can meet the initial production goals, satisfy the reactor safety requirements, and can be fabricated in production quantities. The current focus of the program is to verify that the target can be remotely dissembled, the pellets dissolved, and the 238Pu recovered. Tests are being conducted to examine these concerns and to compare results to code predictions. Once the performance of the full length targets has been quantified, the pellet 237Np loading will be revisited to determine if it can be increased to increase 238Pu production.

  5. MOX and MOX with 237Np/241Am Inert Fission Gas Generation Comparison in ATR

    SciTech Connect

    G. S. Chang; M. Robel; W. J. Carmack; D. J. Utterbeck

    2006-06-01

    The treatment of spent fuel produced in nuclear power generation is one of the most important issues to both the nuclear community and the general public. One of the viable options to long-term geological disposal of spent fuel is to extract plutonium, minor actinides (MA), and potentially long-lived fission products from the spent fuel and transmute them into short-lived or stable radionuclides in currently operating light-water reactors (LWR), thus reducing the radiological toxicity of the nuclear waste stream. One of the challenges is to demonstrate that the burnup-dependent characteristic differences between Reactor-Grade Mixed Oxide (RG-MOX) fuel and RG-MOX fuel with MA Np-237 and Am 241 are minimal, particularly, the inert gas generation rate, such that the commercial MOX fuel experience base is applicable. Under the Advanced Fuel Cycle Initiative (AFCI), developmental fuel specimens in experimental assembly LWR-2 are being tested in the northwest (NW) I-24 irradiation position of the Advanced Test Reactor (ATR). The experiment uses MOX fuel test hardware, and contains capsules with MOX fuel consisting of mixed oxide manufactured fuel using reactor grade plutonium (RG-Pu) and mixed oxide manufactured fuel using RG-Pu with added Np/Am. This study will compare the fuel neutronics depletion characteristics of Case-1 RG-MOX and Case-2 RG-MOX with Np/Am.

  6. Neutron spectral and angular distribution measurements for 113 and 256 MeV protons on range-thick Al and sup 238 U targets using the foil activation techniques

    SciTech Connect

    Greenwood, L.R.; Intasorn, A.

    1989-07-01

    Second neutron yields, energy spectra, and angular distributions have been measured at seven angles from 0 to 150{degree} for 113 and 256 MeV protons stopped in range-thick targets of aluminum and depleted uranium ({sup 238}U). Thin foil stacks of ten different materials were activated by secondary neutrons at distances of 20--30 cm from the targets. Following each irradiation, 30--40 different activation products were measured by gamma-ray spectroscopy. These activation rates were then used to adjust neutron energy spectra calculated by the HETC computer code. Activation cross sections were taken from ENDF/BV below 20 MeV, from literature values tested in Be(d,n) fields up to 50 MeV, and from proton spallation data and calculations from 50--250 MeV. Spectral adjustments were made with the STAY'SL computer code using a least-squares technique to minimize {chi}{sup 2} for a covariance matrix determined from uncertainties in the measured activities, cross sections, and calculated flux spectra. Neutron scattering effects were estimated from foil packets irradiated at different distances from the target. Proton effects were measured with (p,n) reactions. Systematic differences were found between the adjusted and calculated neutron spectra, namely, that HETC underpredicts the neutron flux at back angles by a factor of 2--3 and slightly overpredicts the flux at forward angles. 19 refs., 23 figs., 13 tabs.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  9. POC and particulate 234 Th export fluxes estimated using 234 Th/ 238 U disequilibrium in an enclosed Eastern Mediterranean region (Saronikos Gulf and Elefsis Bay, Greece) in seasonal scale

    NASA Astrophysics Data System (ADS)

    Evangeliou, Nikolaos; Florou, Heleny; Scoullos, Michael

    2011-10-01

    Activity concentrations of the naturally occurring, short-lived and highly particle-reactive radionuclide tracer 234Th in the dissolved and particulate phase were determined at 7 shallow-water stations (maximum depths: 30 (S.1 and S.2), 65 (S.3), 97 (S.5), 105 (S.6) and 220 m (S.4 and S.7) in Saronikos Gulf and Elefsis Bay (central Aegean Sea, Greece) during 3 seasonal cruises (summer 2008, autumn 2008 and winter 2009) to assess the time scales of the dynamics and the depositional fate of particulate matter (POC, particulate 234Th). For that reason, in situ filtrating systems were deployed in several depths of the water column consisting of GF/A disc prefilters to scavenge particulate fraction of 234Th and organic carbon and impregnated cartridges to adsorb dissolved 234Th. The obtained data showed average particulate 234Th activity concentrations of 3.7 ± 0.4 Bq m -3 in summer, 2.1 ± 0.2 Bq m -3 in autumn and 2.4 ± 0.2 Bq m -3 in winter. The respective average dissolved 234Th activity concentrations were 30.1 ± 2.8 Bq m -3 in summer, 30.2 ± 2.9 Bq m -3 in autumn and 27.4 ± 3.0 Bq m -3 in winter. The activity ratios of total 234Th and its long-lived conservative parent 238U were below unity in most of the stations indicating radioactive disequilibrium throughout the water column, thus very dynamic trace-metal scavenging and particle export from the water column. These profiles ( 234Th and 238U) were used to estimate the export fluxes and scavenging rates of 234Th, as well as their residence times in the water column. The average cumulative export fluxes of particulate 234Th were estimated to be 33 ± 4 Bq m -2 d -1 in summer, 35 ± 5 Bq m -2 d -1 in autumn and 45 ± 6 Bq m -2 d -1 in winter, whereas the respective average cumulative scavenging rates of dissolved 234Th were 39 ± 5, 33 ± 5 and 50 ± 7 Bq m -2 d -1. Moreover, the cumulative average residence times of 234Th were 25 ± 4 d in summer, 45 ± 6 d in autumn and 64 ± 7 d in winter 2009 for the

  10. 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.

  11. 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.

  12. 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.

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

    USGS Publications Warehouse

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

    1997-01-01

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

  14. Review and Assessment of Neutron Cross Section and Nubar Covariances for Advanced Reactor Systems

    SciTech Connect

    Maslov,V.M.; Oblozinsky, P.; Herman, M.

    2008-12-01

    In January 2007, the National Nuclear Data Center (NNDC) produced a set of preliminary neutron covariance data for the international project 'Nuclear Data Needs for Advanced Reactor Systems'. The project was sponsored by the OECD Nuclear Energy Agency (NEA), Paris, under the Subgroup 26 of the International Working Party on Evaluation Cooperation (WPEC). These preliminary covariances are described in two recent BNL reports. The NNDC used a simplified version of the method developed by BNL and LANL that combines the recent Atlas of Neutron Resonances, the nuclear reaction model code EMPIRE and the Bayesian code KALMAN with the experimental data used as guidance. There are numerous issues involved in these estimates of covariances and it was decided to perform an independent review and assessment of these results so that better covariances can be produced for the revised version in future. Reviewed and assessed are uncertainties for fission, capture, elastic scattering, inelastic scattering and (n,2n) cross sections as well as prompt nubars for 15 minor actinides ({sup 233,234,236}U, {sup 237}Np, {sup 238,240,241,242}Pu, {sup 241,242m,243}Am and {sup 242,243,244,245}Cm) and 4 major actinides ({sup 232}Th, {sup 235,238}U and {sup 239}Pu). We examined available evaluations, performed comparison with experimental data, taken into account uncertainties in model parameterization and made use state-of-the-art nuclear reaction theory to produce the uncertainty assessment.

  15. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    NASA Astrophysics Data System (ADS)

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Davila, Jesus; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio

    2015-07-01

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e'n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides 232Th, 238U and 237Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  16. Prompt and Delayed Inelastic Scattering Reactions from Fission Neutron PGAA - First Results of FaNGaS

    SciTech Connect

    Rossbach, M.; Randriamalala, T.; Revay, Zs.; Kudejova, P.; Soelradel, S.; Wagner, F.

    2015-07-01

    The new instrument Fast Neutron Gamma Spectroscopy (FaNGaS) has been installed at the SR10 beam line of the FRM II Research Reactor in Garching and tested successfully. Complimentary to cold neutron PGAA, with FaNGaS inelastic scattering reactions induced by fission neutrons can be studied. Gamma lines from (n,n'γ) reactions up to now have been rarely studied and no adequate compilation of the emitted gamma energies exist. In developing nondestructive analytical techniques using neutron generator based PGAA such data are badly needed for quantification of heavy metals and actinides in e.g. nuclear waste or safeguards samples. A number of elements and relevant actinides have been irradiated in the fast neutron beam SR10 at the FRM II reactor in Garching, Germany. A heavily shielded 50% eff. HPGe detector perpendicular to the beam is looking at the samples exposed to 2.3 E8 cm{sup -2}s{sup -1} fission neutrons. Prompt gamma spectra have been taken and evaluated using the available data in scattered sources. Additional gamma lines have been detected and are being compiled to create a data base for (n,n') reactions. Particular emphasis is given on actinides including {sup 238}U, {sup 232}Th, {sup 237}Np, {sup 242}Pu and {sup 241}Am. Some examples will be given and first results will be discussed in this contribution. (authors)

  17. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    SciTech Connect

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio; Davila, Jesus

    2015-07-23

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides {sup 232}Th, {sup 238}U and {sup 237}Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  18. Characterization of actinide physics specimens for the US/UK joint experiment in the Dounreay Prototype Fast Reactor

    SciTech Connect

    Walker, R.L.; Botts, J.L.; Cooper, J.H.; Adair, H.L.; Bigelow, J.E.; Raman, S.

    1983-10-01

    The United States and the United Kingdom are engaged in a joint research program in which samples of the higher actinides are irradiated in the Dounreay Prototype Fast Reactor in Scotland. The purpose of the porogram is (1) to study the materials behavior of selected higher actinide fuels and (2) to determine the integral cross sections of a wide variety of the higher actinide isotopes. Samples of the actinides are incorporated in fuel pins inserted in the core. For the fuel study, the actinides selected are /sup 241/Am and /sup 244/Cm in the form of Am/sub 2/O/sub 3/, Cm/sub 2/O/sub 3/, and Am/sub 6/Cm(RE)/sub 7/O/sub 21/, where (RE) represents a mixture of lanthanides. For the cross-section determinations, the samples are milligram quantities of actinide oxides of /sup 248/Cm, /sup 246/Cm, /sup 244/Cm, /sup 243/Cm, /sup 243/Am, /sup 241/Am, /sup 244/Pu, /sup 242/Pu, /sup 241/Pu, /sup 240/Pu, /sup 239/Pu, /sup 238/Pu, /sup 237/Np, /sup 238/U, /sup 236/U, /sup 235/U, /sup 234/U, /sup 233/U, /sup 232/Th, /sup 230/Th, and /sup 231/Pa encapsulated in vanadium. Coincident with the irradiations, neutron flux and energy spectral measurements are made with vanadium-encapsulated dosimeter materials located within the same fuel pins.

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

    SciTech Connect

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

    1982-05-01

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

  20. Dose coefficients and derived guidance and clinical decision levels for contaminated wounds

    SciTech Connect

    Bertelli, Luiz; Toohey, Richard E

    2009-01-01

    The NCRP Wound Model describing the retention of selected radionuclides at the site of a contaminated wound and their uptake into the transfer compartment has been combined with the ICRP element-specific systemic models for those radionuclides to derive dose coefficients for intakes via contaminated wounds. Those coefficients have been used to generate derived guidance levels (i.e., the activity in a wound that would result in an effective dose of 20 or 50 mSv, or in some cases, a committed organ equivalent dose of 500 mSv), and clinical decision levels (i.e., activity levels that would indicate the need for consideration of medical intervention to remove activity from the wound site or administration of decorporation therapy or both), typically set at 5 times the derived guidance levels. Data are provided for the radionuclides commonly encountered at nuclear power plants and nuclear weapons, fuel fabrication or recycling, waste disposal, medical and research facilities. These include: {sup 60}Co, {sup 90}Sr, {sup 99m}Tc, {sup 131}I, {sup 137}Cs, {sup 192}Ir, {sup 210}Po, {sup 226,228}Ra, {sup 228,232}Th, {sup 235,238}U, {sup 237}Np, {sup 238,239}Pu, {sup 241}Am, {sup 242,244}Cm, and {sup 252}Cf.

  1. Update of the α - n Yields for Reactor Fuel Materials for the Interest of Nuclear Safeguards

    NASA Astrophysics Data System (ADS)

    Simakov, S. P.; van den Berg, Q. Y.

    2017-01-01

    The neutron yields caused by spontaneous α-decay of actinides and subsequent (α,xn) reactions were re-evaluated for the reactor fuel materials UO2, UF6, PuO2 and PuF4. For this purpose, the most recent reference data for decay parameters, α-particle stopping powers and (α,xn) cross sections were collected, analysed and used in calculations. The input data and elaborated code were validated against available thick target neutron yields in pure and compound materials measured at accelerators or with radioactive sources. This paper provides the specific neutron yields and their uncertainties resultant from α-decay of actinides 241Am, 249Bk, 252Cf, 242,244Cm, 237Np, 238-242Pu, 232Th and 232-236,238U in oxide and fluoride compounds. The obtained results are an update of previous reference tables issued by the Los Alamos National Laboratory in 1991 which were used for the safeguarding of radioactive materials by passive non-destructive techniques. The comparison of the updated values with previous ones shows an agreement within one estimated uncertainty (≈ 10%) for oxides, and deviations of up to 50% for fluorides.

  2. Rapid determination of actinides and (90)Sr in river water.

    PubMed

    Habibi, A; Boulet, B; Gleizes, M; Larivière, D; Cote, G

    2015-07-09

    Nuclear accidents occurred in latest years highlighted the difficulty to achieve, in a short time, the quantification of alpha and beta emitters. Indeed, most of the existing methods, though displaying excellent performances, can be very long, taking up to several weeks for some radioisotopes, such as (90)Sr. This study focuses on alpha and beta radioisotopes which could be accidentally released from nuclear installations and which could be measured by inductively coupled plasma mass spectrometer (ICP-MS). Indeed, a new and rapid separation method was developed for (234,235,236,238)U, (230,232)Th, (239,240)Pu, (237)Np, (241)Am and (90)Sr. The main objective was to minimize the duration of the separation protocol by the development of a unique radiochemical procedure with elution media compatible with ICP-MS measurements. Excellent performances were obtained with spiked river water samples. These performances are characterized by total yields exceeding 80% for all monitored radionuclides, as well as good reproducibility (RSD≤10%, n=12). The proposed radiochemical separation (including counting time) required less than 7h for a batch of 8 samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Study of calculated and measured time dependent delayed neutron yields. [TX, for calculating delayed neutron yields; MATINV, for matrix inversion; in FORTRAN for LSI-II minicomputer

    SciTech Connect

    Waldo, R.W.

    1980-05-01

    Time-dependent delayed neutron emission is of interest in reactor design, reactor dynamics, and nuclear physics studies. The delayed neutrons from neutron-induced fission of /sup 232/U, /sup 237/Np, /sup 238/Pu, /sup 241/Am, /sup 242m/Am, /sup 245/Cm, and /sup 249/Cf were studied for the first time. The delayed neutron emission from /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu, /sup 241/Pu, and /sup 242/Pu were measured as well. The data were used to develop an empirical expression for the total delayed neutron yield. The expression gives accurate results for a large variety of nuclides from /sup 232/Th to /sup 252/Cf. The data measuring the decay of delayed neutrons with time were used to derive another empirical expression predicting the delayed neutron emission with time. It was found that nuclides with similar mass-to-charge ratios have similar decay patterns. Thus the relative decay pattern of one nuclide can be established by any measured nuclide with a similar mass-to-charge ratio. A simple fission product yield model was developed and applied to delayed neutron precursors. It accurately predicts observed yield and decay characteristics. In conclusion, it is possible to not only estimate the total delayed neutron yield for a given nuclide but the time-dependent nature of the delayed neutrons as well. Reactors utilizing recycled fuel or burning actinides are likely to have inventories of fissioning nuclides that have not been studied until now. The delayed neutrons from these nuclides can now be incorporated so that their influence on the stability and control of reactors can be delineated. 8 figures, 39 tables.

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

    DOE PAGES

    Gooden, M. E.; Arnold, C. W.; Becker, J. A.; ...

    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

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

    SciTech Connect

    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.; and others

    2016-01-15

    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 {sup 235}U, {sup 238}U and {sup 239}Pu. 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

  6. 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

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

    SciTech Connect

    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.

    2004-12-01

    We have studied the dependence of the production cross sections of the isotopes {sup 282,283}112 and {sup 286,287}114 on the excitation energy of the compound nuclei {sup 286}112 and {sup 290}114. The maximum cross section values of the xn-evaporation channels for the reaction {sup 238}U({sup 48}Ca,xn){sup 286-x}112 were measured to be {sigma}{sub 3n}=2.5{sub -1.1}{sup +1.8} pb and {sigma}{sub 4n}=0.6{sub -0.5}{sup +1.6} pb; for the reaction {sup 242}Pu({sup 48}Ca,xn){sup 290-x}114: {sigma}{sub 2n}{approx}0.5 pb, {sigma}{sub 3n}=3.6{sub -1.7}{sup +3.4} pb, and {sigma}{sub 4n}=4.5{sub -1.9}{sup +3.6} pb. In the reaction {sup 233}U({sup 48}Ca,2-4n){sup 277-279}112 at E*=34.9=2.2 MeV we measured an upper cross section limit of {sigma}{sub xn}{<=}0.6 pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section {sigma}{sub ER}(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 {sigma}{sub ER} in the reactions of actinide targets with {sup 48}Ca 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 {sup 282}112, {sup 283}112, {sup 286}114, {sup 287}114, and {sup 288}114. In the decay of {sup 287}114({alpha}){yields}{sup 283}112({alpha}){yields}{sup 279}110(SF), in two cases out of 22, we observed decay chains of four and five sequential {alpha} transitions that end in spontaneous fission of {sup 271}Sg (T{sub {alpha}}{sub /SF}=2.4{sub -1.0}{sup +4.3} min) and {sup 267}Rf (T{sub SF}{approx}2.3 h), longer decay chains than reported previously. We observed the new nuclide {sup 292}116 (T{sub {alpha}}=18{sub -6}{sup +16} ms,E{sub {alpha}}=10.66{+-}0.07 MeV) in the irradiation of the

  8. Neptunium separations

    SciTech Connect

    Wild, J.F.

    1983-05-09

    Two procedures for the separation of Np are presented; the first involves separation of /sup 239/Np from irradiated /sup 238/U, and the second involves separation of /sup 237/Np from a solution representing that from a dissolved fuel element.

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

    SciTech Connect

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

    2007-08-28

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

  10. Solar r-process-constrained actinide production in neutrino-driven winds of supernovae

    NASA Astrophysics Data System (ADS)

    Goriely, S.; Janka, H.-Th.

    2016-07-01

    Long-lived radioactive nuclei play an important role as nucleo-cosmochronometers and as cosmic tracers of nucleosynthetic source activity. In particular, nuclei in the actinide region like thorium, uranium, and plutonium can testify to the enrichment of an environment by the still enigmatic astrophysical sources that are responsible for the production of neutron-rich nuclei by the rapid neutron-capture process (r-process). Supernovae and merging neutron-star (NS) or NS-black hole binaries are considered as most likely sources of the r-nuclei. But arguments in favour of one or the other or both are indirect and make use of assumptions; they are based on theoretical models with remaining simplifications and shortcomings. An unambiguous observational determination of a production event is still missing. In order to facilitate searches in this direction, e.g. by looking for radioactive tracers in stellar envelopes, the interstellar medium or terrestrial reservoirs, we provide improved theoretical estimates and corresponding uncertainty ranges for the actinide production (232Th, 235, 236, 238U, 237Np, 244Pu, and 247Cm) in neutrino-driven winds of core-collapse supernovae. Since state-of-the-art supernova models do not yield r-process viable conditions - but still lack, for example, the effects of strong magnetic fields - we base our investigation on a simple analytical, Newtonian, adiabatic and steady-state wind model and consider the superposition of a large number of contributing components, whose nucleosynthesis-relevant parameters (mass weight, entropy, expansion time-scale, and neutron excess) are constrained by the assumption that the integrated wind nucleosynthesis closely reproduces the Solar system distribution of r-process elements. We also test the influence of uncertain nuclear physics.

  11. PRELIMINARY CROSS SECTION AND NU-BAR COVARIANCES FOR WPEC SUBGROUP 26

    SciTech Connect

    ROCHMAN,D.

    2007-01-31

    We report preliminary cross section covariances developed for the WPEC Subgroup 26 for 45 out of 52 requested materials. The covariances were produced in 15- and 187-group representations as follows: (1) 36 isotopes ({sup 16}O, {sup 19}F, {sup 23}Na, {sup 27}Al, {sup 28}Si, {sup 52}Cr, {sup 56,56}Fe, {sup 58}Ni, {sup 90,91,92,94}Zr, {sup 166,167,168,170}Er, {sup 206,207,208}Pb, {sup 209}Bi, {sup 233,234,236}U, {sup 237}Np, {sup 238,240,241,242}Pu, {sup 241,242m,243}Am, {sup 242,243,244,245}Cm) were evaluated using the BNL-LANL methodology. For the thermal region and the resolved and unresolved resonance regions, the methodology has been based on the Atlas-Kalman approach, in the fast neutron region the Empire-Kalman method has been used; (2) 6 isotopes ({sup 155,156,157,158,160}Gd and {sup 232}Th) were taken from ENDF/B-VII.0; and (3) 3 isotopes ({sup 1}H, {sup 238}U and {sup 239}Pu) were taken from JENDL-3.3. For 6 light nuclei ({sup 4}He, {sup 6,7}Li, {sup 9}Be, {sup 10}B, {sup 12}C), only partial cross section covariance results were obtained, additional work is needed and they do not report the results here. Likewise, the cross section covariances for {sup 235}U, which they recommend to take from JENDL-3.3, will be included once the multigroup processing is successfully completed. Covariances for the average number of neutrons per fission, total {nu}-bar, are provided for 10 actinides identified as priority by SG26. Further work is needed to resolve some of the issues and to produce covariances for the full set of 52 materials.

  12. Measurement and calculation of high-actinide burnup in the prototype fast reactor

    SciTech Connect

    Broadhead, B.L.; Raman, S.; Dickens, J.K. )

    1991-01-01

    An agreement was signed in May 1979 as a part of a long-term cooperative program between the United Kingdom and the US under the liquid-metal fast breeder reactor agreement of 1976. This agreement included an experiment to carry out irradiations of physics specimens of fissile and fertile actinides to improve our knowledge of basic nuclear physics phenomena. Three fuel pins were prepared by the US to contain the actinide physics samples; two of these pins were irradiated at the Dounreay prototype fast reactor (PFR) for a total irradiation of 63 full-power days. The third pin has only recently been removed from the PFT, following an irradiation of > 500 full-power days. Each pin houses 35 capsules containing milligram quantities of actinide oxides of {sup 231}Pa, {sup 230}Th, {sup 232}Th, {sup 233}U, {sup 234}U, {sup 235}U, {sup 236}U, {sup 238}U, {sup 237}Np, {sup 238}Pu, {sup 239}Pu, {sup 240}Pu, {sup 241}Pu, {sup 242}Pu, {sup 244}Pu, {sup 241}Am, {sup 243}Am, {sup 243}Cm, {sup 244}Cm, {sup 246}Cm, and {sup 248}Cm. Following the return of the first fuel pin (FP-1) to the United States in May 1984, the actinide samples were prepared for studies of fission product yields, isotopics, and material concentrations. The measurements were repeated for the second fuel pin (FP-2) to remedy several problems encountered in the processing of the FP-1 pin. A brief description of the measured and calculated {sup 137}Cs yields for both FP-1 and FP-2 are included in this paper.

  13. Enumeration of Microbial Populations in Radioactive Environments by Epifluorescence Microscopy

    SciTech Connect

    Pansoy-Hjelvik, M.E.A.; Strietelmeierr, B.A.; Paffett, M.T.; Kitten, S.M.; Leonard, P.A.; Dunn, M.; Gillow, J.B.; Dodge, C.J.; Villarreal, R.; Triay, I.; Francis, A.J.

    1996-12-02

    Epifluorescence microscopy was utilized to enumerate halophilic bacterial populations in two studies involving inoculated, actual radioactive waste/brine mixtures and pure brine solutions. The studies include an initial set of experiments designed to elucidate potential transformations of actinide-containing wastes under salt-repository conditions, including microbially mediated changes. The first study included periodic enumeration of bacterial populations of a mixed inoculum initially added to a collection of test containers. The contents of the test containers are the different types of actual radioactive waste that could potentially be stored in nuclear waste repositories in a salt environment. The transuranic waste was generated from materials used in actinide laboratory research. The results show that cell numbers decreased with time. Sorption of the bacteria to solid surfaces in the test system is discussed as a possible mechanism for the decrease in cell numbers. The second study was designed to determine radiological and/or chemical effects of {sup 239}Pu, {sup 243}Am, {sup 237}Np, {sup 232}Th and {sup 238}U on the growth of pure and mixed anaerobic, denitrifying bacterial cultures in brine media. Pu, Am, and Np isotopes at concentrations of <=1 x 10{sup {minus}5}M, <=5 x 10{sup {minus}6}M and <=5 x 10{sup {minus}4}M respectively, and Th and U isotopes <=4 x 10{sup {minus}3}M were tested in these media. The results indicate that high actinide concentration affected both the bacterial growth rate and morphology. However, relatively minor effects from Am were observed at all tested concentrations with the pure culture.

  14. Enumeration of microbial populations in radioactive environments by epifluorescence microscopy

    SciTech Connect

    Pansoy-Hjelvik, M.E.; Strietelmeier, B.A.; Paffett, M.T.

    1997-01-01

    Epifluorescence microscopy was utilized to enumerate halophilic bacterial populations in two studies involving inoculated, actual waste/brine mixtures and pure brine solutions. The studies include an initial set of experiments designed to elucidate potential transformations of actinide-containing wastes under salt-repository conditions, including microbially mediated changes. The first study included periodic enumeration of bacterial populations of a mixed inoculum initially added to a collection of test containers. The contents of the test containers are the different types of actual radioactive waste that could potentially be stored in nuclear waste repositories in a salt environment. The transuranic waste was generated from materials used in actinide laboratory research. The results show that cell numbers decreased with time. Sorption of the bacteria to solid surfaces in the test system is discussed as a possible mechanism for the decrease in cell numbers. The second study was designed to determine radiological and/or chemical effects of {sup 239}Pu, {sup 243}Am, {sup 237}Np, {sup 232}Th and {sup 238}U on the growth of pure and mixed anaerobic, denitrifying bacterial cultures in brine media. Pu, Am, and Np isotopes at concentrations of {le}1x10{sup -6} M , {le}5x10{sup -6} M and {le}5x10{sup -4}M respectively, and Th and U isotopes {le}4x10{sup -3}M were tested in these media. The results indicate that high concentrations of certain actinides affected both the bacterial growth rate and morphology. However, relatively minor effects from Am were observed at all tested concentrations with the pure culture.

  15. Natural radioactivity measurements in the granite rock of quarry sites, Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Alnour, I. A.; Wagiran, H.; Ibrahim, N.; Laili, Z.; Omar, M.; Hamzah, S.; Idi, Bello. Y.

    2012-12-01

    This study was conducted to determine the concentration of natural radionuclides in the granite rocks of selected quarry sites in Johor state, Malaysia and their possible radiological effects. The activity concentrations of 238U, 232Th and 40K in the areas of study indicated varying values of 238U, 232Th and 40K. The highest values of 238U and 232Th concentrations (67±1 and 85±2 Bq kg-1, respectively) were observed at Kamad Quarry (IJM), whereas the highest value of 40K concentration (722±18 Bq kg-1) was detected in Kim Seng Quarry, while the values of activity concentration are lower in Hanson Quarry Products (Kulai) (25±0.5 for 238U, 24±0.5 for 232Th and 429±11 for 40K). Overall, 40K has the highest concentration in the granite rocks of the quarry sites, followed by 232Th and the least for 238U. The radium equivalent activity concentration was found in the range between 94 and 239 Bq kg-1, the absorbed dose rate was found to be in the range between 47 and 112 nGy h-1, and effective dose ranged from 58 to 137 μSv h-1. Moreover, the internal and external hazard index values were given in results lower than unity.

  16. 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.

  17. Alpha-induced reaction cross-section for Sm, U, Np targets: influence of hexadecapole deformation and deformed surface diffuseness

    NASA Astrophysics Data System (ADS)

    Alavi, S. A.; Dehghani, V.

    2017-06-01

    Alpha-induced reactions on 154Sm, 233,235,236,238U, and 237Np deformed nuclei are studied theoretically. The effects of hexadecapole deformation, deformed surface diffuseness parameter, and orientation on barrier height and position, fusion cross-section at any angle, and fusion cross-section have been investigated. Both hexadecapole deformation and deformed surface diffuseness can affect barrier characteristics and enhance fusion cross-section. Good agreement between experimental data and theoretical calculations with quadrupole and hexadecapole deformation and deformed surface diffuseness were observed for the 4He+154Sm, 235U, 237Np reactions.

  18. A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

    NASA Astrophysics Data System (ADS)

    Quesada, José Manuel; Capote, Roberto; Soukhovitski, Efrem S.; Chiba, Satoshi

    2016-03-01

    An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238U and 232Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232Th, 233,235,238U and 239Pu nuclei. Quasi-elastic (p,n) scattering data on 232Th and 238U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.

  19. Natural activity concentrations in bottled drinking water and consequent doses.

    PubMed

    Kabadayi, Önder; Gümüs, Hasan

    2012-07-01

    The radioactivity concentrations of nuclides (238)U, (232)Th and (40)K in bottled drinking water from six different manufacturers from Turkey were measured using high-resolution gamma-ray spectrometry. The measurement was done using a coaxial high-purity germanium detector system coupled to Ortec-Dspect jr digital MCA system. The average measured activity concentrations of the nuclides (238)U, (232)Th and (40)K are found to be 0.781, 1.05 and 2.19 Bq l(-1), respectively. The measured activity concentrations have been compared with similar studies from different locations. The annual effective doses for ingestion of radionuclides in the water are found to be 0.0246 mSv for (238)U and 0.169 mSv for (232)Th.

  20. Monte Carlo simulation of indoor external exposure due to gamma-emitting radionuclides in building materials

    NASA Astrophysics Data System (ADS)

    Deng, Jun; Cao, Lei; Su, Xu

    2014-10-01

    The use of building materials containing naturally occurring radionuclides, such as 40K, 238U, 232Th and their progeny, could lead to external exposures to the residents of such buildings. In this paper, a set of models are constructed to calculate the specific effective dose rates (the effective dose rate per Bq/kg of 40K, the 238U series, and the 232Th series) imposed on residents by building materials with the MCNPX code. The effect of chemical composition, position concerned in the room and thickness as well as density of material is analyzed. In order to facilitate more precise assessment of indoor external dose due to gamma-emitting radionuclides in building materials, three regressive expressions are proposed and validated by measured data to calculate specific effective rates for 40K. the 238U series and the 232Th series, respectively.

  1. Natural radioactivity and evaluation of effective dose equivalent of granites in Turkey.

    PubMed

    Osmanlioglu, Ahmet Erdal

    2006-01-01

    Annual effective dose equivalent due to natural gamma radiation from (238)U, (232)Th and (40)K have been evaluated from granites in Turkey. Forty samples were taken for spectrometric analysis. Specific concentrations of (238)U, (232)Th and (40)K in granite samples were determined. Spectroscopy system was used with 1.8 keV (FWHM) coaxial high purity germanium (HPGe) detector. Average values of concentrations of (238)U, (232)Th and (40)K were detected at 15.85, 33.76 and 359 Bq kg(-1), respectively. The average value of radon varies from 0.073 to 0.185 Bq m(-2) h(-1) exhalation depends on the specific concentration of uranium. The dose rate due to this highest activity which have been evaluated by a Monte Carlo transport calculations does not exceed 0.4 mSv a(-1).

  2. Estimation of internal radiation dose to the adult Asian population from the dietary intakes of two long-lived radionuclides.

    PubMed

    Iyengar, G V; Kawamura, H; Dang, H S; Parr, R M; Wang, J W; Akhter, Perveen; Cho, S Y; Natera, E; Miah, F K; Nguyen, M S

    2004-01-01

    Daily dietary intakes of two naturally occurring long-lived radionuclides, 232Th and 238U, were estimated for the adult population living in a number of Asian countries, using highly sensitive analytical methods such as instrumental and radiochemical neutron activation analysis (INAA and RNAA), and inductively coupled plasma mass spectrometry (ICP-MS). The Asian countries that participated in the study were Bangladesh (BGD), China (CPR), India (IND), Japan (JPN), Pakistan (PAK), Philippines (PHI), Republic of Korea (ROK) and Vietnam (VIE). Altogether, these countries represent more than 50% of the world population. The median daily intakes of 232Th ranged between 0.6 and 14.4 mBq, the lowest being for Philippines and the highest for Bangladesh, and daily intakes of 238U ranged between 6.7 and 62.5 mBq, lowest and the highest being for India and China, respectively. The Asian median intakes were obtained as 4.2 mBq for 232Th and 12.7 mBq for 238U. Although the Asian intakes were lower than intakes of 12.3 mBq (3.0 ug) 232Th and 23.6 mBq (1.9 ug) 238U proposed by the International Commission on Radiological Protection (ICRP) for the ICRP Reference Man, they were comparable to the global intake values of 4.6 mBq 232Th and 15.6 mBq 238U proposed by the United Nation Scientific Commission on Effects of Radiation (UNSCEAR). The annual committed effective doses to Asian population from the dietary intake of 232Th and 238U were calculated to be 0.34 and 0.20 microSv, respectively, which are three orders of magnitude lower than the global average annual radiation dose of 2400 microSv to man from the natural radiation sources as proposed by UNSCEAR.

  3. Solubility of uranium and thorium from a healing earth in synthetic gut fluids: a case study for use in dose assessments.

    PubMed

    Höllriegl, Vera; Li, Wei Bo; Leopold, Karsten; Gerstmann, Udo; Oeh, Uwe

    2010-11-01

    The aim of this case study was to estimate the bioaccessibility of uranium ((238)U) and thorium ((232)Th) from a healing earth by analysing the solubility of these radionuclides in synthetic gastric and intestinal fluids. An easy applicable in vitro test system was used to investigate the fractional mobilization of the soil contaminants being potentially available for absorption under human in vivo conditions. These findings provided the basis for a prospective dose assessment. The solubility experiments were performed using two different in vitro digestion methods. The concentrations of (238)U and (232)Th in the solutions extracted from the soil were measured by inductively coupled plasma mass spectrometry (ICP-MS). The dissolved fractions in the synthetic gastrointestinal fluid ranged in average from 10.3% to 13.8% for (238)U and from 0.3% to 1.6% for (232)Th, respectively, depending on the digestion method. Subsequently, the committed effective doses from intake of (238)U and (232)Th after ingestion of the healing earth during 1 year were evaluated for adult persons. Thereby ingestion dose coefficients calculated as a function of bioaccessibility were used. The dose assessments ranged between 4.3 × 10(-7)-1.9 × 10(-6) Sv y(-1) for (238)U and 5.6 × 10(-7)-3.3 × 10(-6) Sv y(-1) for (232)Th, respectively. On the basis of the assumptions and estimations made, the present work indicates a relatively low radiation risk due to (238)U and (232)Th after internal exposure of the healing earth.

  4. Measurement of natural and 137Cs radioactivity concentrations at Izmit Bay (Marmara Sea), Turkey

    NASA Astrophysics Data System (ADS)

    Öksüz, I.; Güray, R. T.; Özkan, N.; Yalçin, C.; Ergül, H. A.; Aksan, S.

    2016-03-01

    In order to determine the radioactivity level at Izmit Bay Marmara Sea, marine sediment samples were collected from five different locations. The radioactivity concentrations of naturally occurring 238U, 232Th and 40K isotopes and also that of an artificial isotope 137Cs were measured by using gamma-ray spectroscopy. Preliminary results show that the radioactivity concentrations of 238U and 232Th isotopes are lower than the average worldwide values while the radioactivity concentrations of the 40K are higher than the average worldwide value. A small amount of 137Cs contamination, which might be caused by the Chernobyl accident, was also detected.

  5. Informal progress report on neutron-scattering studies in the actinide region, August 1, 1982-July 31, 1983

    SciTech Connect

    Beghian, L.E.; Kegel, G.H.R.

    1983-01-01

    This informational techical progress report summarizes the principal results of the research performed during the period August 1, 1982 to July 31, 1983. The report covers two areas of neutron cross section measurements: (1) the excited states (E/sub x/ > 650 keV) of /sup 232/Th and /sup 238/U; and (2) the ground state rotational band (0/sup +/, 2/sup +/, 4/sup +/ states) of /sup 232/Th and /sup 238/U from 520 to 940-keV bombarding energy.

  6. Criticality of a Neptunium-237 sphere surrounded with highly enriched uranium shells and an iron reflector

    SciTech Connect

    Sanchez, R. G.; Loaiza, D. J.; Hayes, D. K.; Kimpland, R. H.

    2004-01-01

    An additional experiment has been performed using the recently cast 6-kg {sup 237}Np sphere. The experiment consisted of surrounding the neptunium sphere with highly enriched uranium and an iron reflector. The purpose of the critical experiment is to provide additional criticality data that can be used to validate criticality safety evaluations involving the deposition of neptunium. It is well known that {sup 237}Np is primarily produced by successive neutron capture events in {sup 235}U or through the (n, 2n) reaction in {sup 238}U. These nuclear reactions lead to the production of {sup 237}U, which decays by beta emission into {sup 237}Np. In addition, in the spent fuel, {sup 241}Am decays by alpha emission into {sup 237}Np. Because {sup 237}Np is a threshold fissioner, the best reflectors for critical systems containing neptunium are those materials that exhibit good neutron scattering properties such as low carbon steel (99 wt % Fe). In this experiment, the iron reflector reduced the amount of uranium used in the critical experiment and increased the importance of the neptunium sphere.

  7. Environmental evolution records reflected by radionuclides in the sediment of coastal wetlands: A case study in the Yellow River Estuary wetland.

    PubMed

    Wang, Qidong; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Cao, Lei

    2016-10-01

    Vertical profiles of environmental radionuclides ((210)Pb, (137)Cs, (238)U, (232)Th, (226)Ra and (4)(0)K) in a sediment core (Y1) of the Yellow River Estuary wetland were investigated to assess whether environmental evolutions in the coastal wetland could be recorded by the distributions of radionuclides. Based on (210)Pb and (137)Cs dating, the average sedimentation rate of core Y1 was estimated to be 1.0 cm y(-1). Vertical distributions of natural radionuclides ((238)U, (232)Th, (226)Ra and (40)K) changed dramatically, reflecting great changes in sediment input. Concentrations of (238)U, (232)Th, (226)Ra and (40)K all had significant positive relationships with organic matter and clay content, but their distributions were determined by different factors. Factor analysis showed that (238)U was determined by the river sediment input while (226)Ra was mainly affected by the seawater erosion. Environmental changes such as river channel migrations and sediment discharge variations could always cause changes in the concentrations of radionuclides. High concentrations of (238)U and (226)Ra were consistent with high accretion rate. Frequent seawater intrusion decreased the concentration of (226)Ra significantly. The value of (238)U/(226)Ra tended to be higher when the sedimentation rate was low and tide intrusion was frequent. In summary, environmental evolutions in the estuary coastal wetland could be recorded by the vertical profiles of natural radionuclides.

  8. Tracing the metasomatic and magmatic evolution of continental mantle roots with Sr, Nd, Hf and and Pb isotopes: A case study of Middle Atlas (Morocco) peridotite xenoliths

    NASA Astrophysics Data System (ADS)

    Wittig, Nadine; Pearson, D. Graham; Duggen, Svend; Baker, Joel A.; Hoernle, Kaj

    2010-02-01

    We studied clinopyroxenes from spinel-facies peridotite xenoliths sampled by the Quaternary intra-plate volcanism of the Middle Atlas (Morocco) and present new trace element and Sr-Nd-Hf isotope data. However, we focus in particular on Pb isotope data and 238U/ 204Pb and 232Th/ 204Pb ratios of these clinopyroxenes. This data allows us to investigate: (a) the timing of metasomatic events, (b) the prevalence and persistence of elevated 238U/ 204Pb, 232Th/ 238U and 232Th/ 204Pb in continental mantle roots and (c) the 238U/ 204Pb and 232Th/ 204Pb composition of putative basaltic melts generated from such metasomatised sub-continental lithospheric mantle (SCLM). Incompatible trace element concentrations in these clinopyroxenes are elevated, marked by high-field strength element depletion and fractionated elemental ratios (e.g., U/Nb, Zr/Hf) most consistent with enrichment due to carbonatitic liquids. Sr, Nd and Hf isotopes have an affinity to HIMU. U, Th and Pb abundances in the clinopyroxenes generally exceed estimates of primitive mantle clinopyroxene. Pb isotope compositions of these clinopyroxenes are radiogenic and vary between 206Pb/ 204Pb = 19.93-20.25, 207Pb/ 204Pb = 15.63-15.66 and 208Pb/ 204Pb = 39.72-40.23. These Pb isotope systematics result in generally negative Δ7/4 but positive Δ8/4; setting these samples distinctly apart from typical HIMU. These Pb isotope compositions are also distinct from the associated host volcanic rocks. 238U/ 204Pb and 232Th/ 204Pb of these clinopyroxenes, which range from 26 to 81 and 136 to 399, respectively, are elevated and more extreme than estimates of MORB- and HIMU-source mantle. The Pb isotope evolution of the clinopyroxenes suggests that the metasomatic enrichment is younger than 200 Ma, which discounts the volcanic activity due to the opening of the Atlantic and the onset of the collision of the African and Eurasian plates as processes generating the lithophile element and isotope composition of this continental

  9. Distribution, enrichment and principal component analysis for possible sources of naturally occurring and anthropogenic radionuclides in the agricultural soil of Punjab state, India.

    PubMed

    Kumar, Ajay; Joshi, Vikram M; Mishra, Manish K; Karpe, Rupali; Rout, Sabyasachi; Narayanan, Usha; Tripathi, Raj M; Singh, Jaspal; Kumar, Sanjeev; Hegde, Ashok G; Kushwaha, Hari S

    2012-06-01

    Enrichment factor (EF) of elements including geo-accumulation indices for soil quality and principal component analysis (PCA) were used to identify the contributions of the origin of sources in the studied area. Results of (40)K, (137)Cs, (238)U and (232)Th including their decay series isotopes in the agricultural soil of Mansa and Bathinda districts in the state of Punjab were presented and discussed. The measured mean radioactivity concentrations for (238)U, (232)Th and (40)K in the agricultural soil of the studied area differed from nationwide average crustal abundances by 51, 17 and 43 %, respectively. The sequence of the EFs of radionuclides in soil from the greatest to the least was found to be (238)U > (40)K > (226)Ra > (137)Cs > (232)Th > (228)Ra. Even though the enrichment of naturally occurring radionuclides was found to be higher, they remained to be in I(geo) class of '0', indicating that the soil is uncontaminated with respect to these radionuclides. Among non-metals, N showed the highest EF and belonged to I(geo) class of '2', indicating that soil is moderately contaminated due to intrusion of fertiliser. The resulting data set of elemental contents in soil was also interpreted by PCA, which facilitates identification of the different groups of correlated elements. The levels of the (40)K, (238)U and (232)Th radionuclides showed a significant positive correlation with each other, suggesting a similar origin of their geochemical sources and identical behaviour during transport in the soil system.

  10. Gis predictive mapping of terrestrial gamma radiation in the Northern State, Sudan.

    PubMed

    Hamed Bashier, E; Salih, I; Khatir Sam, A

    2012-09-01

    This study presents the evaluation of absorbed dose in air due to gamma-emitting nuclides from (238)U and (232)Th series, (40)K and (137)Cs and the corresponding geographical information system (GIS) predictive mapping for the Northern State. Activity concentration of (238)U, (232)Th , (40)K and (137)Cs in soil samples collected from different locations have been measured using high-resolution gamma spectrometry. On  average, activity concentrations were 19±4 ((238)U), 47±11 ((<