WorldWideScience

Sample records for 238u funktsii vozbuzhdeniya

  1. On an investigation of the dynamics of ternary fission for the system 238U + 238U

    With the three center model we have studied the dynamics of ternary fission for the system 238U + 238U by solving the one-dimensional collective Schroedinger equation with the potential energy surface given by the liquid-drop model and the mass parameters given by the Werner-Wheeler method

  2. The Doppler effect measurement on 238U

    The UO2 sample was irradiated in the RB zero power reactor in order to determine the Doppler effect on the 238 U by measuring the change in the 238 capture cross section with temperature. The measurement was meant to verify the indigenous developed computer codes and nuclear data library

  3. 238U + n resolved resonance energies

    Neutron transmission measurements from 100 eV to 170 keV at 150 m through four 238U samples are reported. The energy calibration is described, and the resultant 233U resolved resonance energies are found to be intermediate between those from other workers. In addition, some energies for sharp resonances in 23Na, 27Al, 32S, and 206Pb are given

  4. Search for surviving actinides and superheavy nuclei in damped collisions of 238U with 238U and 248Cm

    In the present talk aspects of the reaction mechanism related to the survival probability of the heaviest fragments in 238U + 238U collisions are discussed first. This is followed by a description of the experiments that have been performed to search for surviving superheavy fragments in the 238U + 238U reaction and by a presentation of the results obtained so far. In a third section our recent first attempts with the 238U + 248Cm reaction are described and preliminary results are discussed. (orig.)

  5. Delayed neutron yield of 238U and 241Pu

    The total delayed neutron yield for 238U and 241Pu were observed as a function of the incident neutron energy. The measurements extend from 2.5 to 5 MeV for 238U and from 0.15 to 5 MeV for 241Pu. The average ratio of the 241Pu delayed neutron yield to that of 238U is 0.292 +- 0.022

  6. Study on the formation of the composite system of 238U+238U

    WU Xi-Zhen; TIAN Jun-Long; ZHAO Kai; ZHANG Ying-Xun; LI Zhu-Xia

    2009-01-01

    Strongly damped reactions of 238U+238U, at Ecm = 680-1880 MeV have been studied based on the improved quantum molecular dynamics model. We find that at a certain energy region the entrance channel potential is weakly repulsive and the dissipation is very strong after touching configuration, these two effects make the time delay of re-separation for colliding system. The single particle potential well of the transiently formed composite system has Coulomb barrier about 15-20 MeV high at the surface, which makes the excited unbound protons being still embedded in the potential well and moving in a common mono-single particle potential for a period of time and thus restrains from quick decay of the composite system.

  7. Dynamical Effects of Orientations on reaction 238U+238U near Coulomb Barrier

    The dynamical effects of three orientations (nose-nose, nose-side, and side-side) on reaction 238U+238U have been investigated by using Improved Quantum Molecular Dynamics(ImQMD) model. Due to Coulomb repulsive interaction, the change of the deformations or orientations of colliding nuclei is found even before touching configuration, especially for nose-nose. The average lifetime of the giant system and the probability producing super-heavy fragments (SHF) with Z>110 are found to be dependent on the orientations of two nuclei. At the time of 1000fm/c after re-separation of giant system, side-side orientation provide a larger probability of producing SHF than nose-nose case. And the maximum value of the probability locates a smaller incident energy for side-side orientation compared with nose-nose.

  8. Nuclear alignment: classical dynamic model for 238U- 238U system

    Dynamical properties of 238U- 238U system at the classical turning point, specifically the distance of closest approach, the relative orientations of the nuclei and deformations have been studied at sub-coulomb energy of Elab = 6.07 MeV/nucleon using a classical dynamical model with a variable moment of inertia. Probability of favorable alignment for anomalous positron-electron pair emission through vacuum decay is calculated. The calculated small favorable alignment probability value of 0.116 is found to be enhanced by about 16% in comparison with the results of a similar study using a fixed moment of inertia as well as the results from a semiquantal calculation reported earlier. (author)

  9. 238U issues resolved and unresolved

    The interaction of 1 eV to 20 MeV neutrons with 238U is discussed. In the region from 1.5 to 4 keV there are differences of the order of 15% between the values of the neutron widths of the main resonances reported by several experimenters or obtained by different evaluators. Above a 4 keV there are only sparse results of resonance analysis and most evaluations adopt a statistical treatment of the resonance structure. However, an inspection of good resolution data suggests that the energy and neutron width of the most prominent resonances could be determined with reasonable accuracy at least up to 10 keV. Some factors affecting the determination of the average properties of the resonance parameters are discussed. Above the inelastic-scattering threshold, energy-averaged neutron total, scattering, capture and fission cross sections are reviewed in a unified manner integrating measurement, calculation and evaluation. (n;n') and (n;2n') energy-transfer mechanisms are addressed. Particular attention is given to neutron capture, stressing precisions consistent with applied need. Fission properties are discussed including: prompt and delayed fission-neutron spectra and nubar, and fission-product yields. (Auth.)

  10. Mass distribution in 238U(32S, f) reaction

    Nuclear fission is a complex process involving large scale collective rearrangement of nuclear matter. Detailed fission fragment mass distribution studies are important to understand the interplay of the structure and dynamics in the fission process. Conventional methods to study fission fragment mass distribution (by measuring the energy and/or the time of flight of the correlated fission fragments) are limited to a mass resolution of 4-5 units. We have carried out fission fragment mass distribution studies for 238U(32S, f) and 238U(12C,f) systems. In this paper, we report the isotopic yield distribution and the fragment mass distribution for the 238U(32S,f) reaction at incident energies 220 MeV and 185 MeV

  11. Simultaneous evaluation for (n,f) cross section of 235U, 239Pu, 238U and (n,γ) cross sections of 238U

    The fission cross sections for 235U, 238U, 239Pu, the capture cross sections for 238U and the ratios for 239Pu(n,f)/235U(n,f), 238U(m,f)/235U(n,f), 238U(n,γ)/235U(n,f) were firstly evaluated respectively. The experimental data were collected, analysed, selected and corrected. The data were fitted with spline fit program

  12. Structure effects in 238U-induced dissipative collisions

    A high resolution kinematic coincidence set-up using position sensitive gas detectors was developed to study 238U - induced reactions on 110Pd and 124Sn targets between 5.70 and 6.02 MeV/u bombarding energies. Nuclear structure effects were observed in the distribution of binary reaction products possibly caused by enhanced multinucleon transfer matrix elements. (orig.)

  13. Precise measurement and calculation of 238U neutron transmissions

    The total neutron cross section of 238U has been measured above 0.5 eV in precise transmission experiments and results are compared with ENDF/B-IV. Emphasis has been on measuring transmissions through thick samples in order to obtain accurate total cross sections in the potential-resonance interference regions between resonances. 4 figures, 1 table

  14. Flux of 238U and 232Th in Changjiang estuary

    The study of fluxes of the U, Th of Changjiang River into the East China Sea and its adjacent waters is basic work to understanding of U, Th tracer theirselves and their corresponding biogeochemical cycles process in estuaries, coastal. By sampling in the Xuliujing (i.e. the interface between fresh water and sea water) every month, 200 L water was filtered through 0.45μm fabric cartridge to collect particle nuclides. The dissolved nuclides were co-precipitated using Fe(OH)3 and MnO2. The range of 238U activity in water is 2.30-10.32 Bq·m-3, with an average of 5.48±1.19 Bq·m-3; the activity of 232Th is 1.08-2.32 Bq·m-3, with an average of 1.75±0.29 Bq·m-3. Changjiang River conveyed 238U 4.06 x 1012Bq, 232Th 1.54 x 1012 Bq into the estuary every year. Further study of the seasonal variations 238U, 232Th input to the sea, indicating that: the activity of 238U and Changjiang River estuary water flux have a certain degree of negative correlation (R2=0.65, n=12); the main source of 232Th is the weathering of the river. The activity of 232Th is large on the spring and autumn because of strong weathering in Changjiang Basin comparison with other seasons. Compared with the other estuaries in the world, the flux of 238U and 232Th of the Changjiang River estuary is large because of its large fluxes of sediments and runoff in the world. (authors)

  15. Delayed fission of the 238U muonic atom

    The time distributions of fission and muon free decay events with respect to the moment of the muon-stop event have been measured for double and triple coincidences between these three events. The triple-coincidence time distributions give an indication of the o-curence of two new effects: the delayed fission of muonic 238U atom and conversion of muons from the fission fragments

  16. Radiochemical measurements of the formation cross sections of actinide isotopes in the reaction of 238U ions with 238U

    The method of high-pressure liquid chromatography was used to separate metal cations and anions. Thereby the influence of different parameters on the separation of lanthanides by cation exchange and extraction chromatography was systematically investigated. The results were used to optimize that separation cycle, in which the elements from Z = 26 to Z = 101 were separated taking into account especially the group of actinides. These separations and the subsequent spectroscopy of gamma radiation, alpha particles and spontaneous fission fragments were used to determine formation cross sections in heavy ion reactions as a function of the atomic charge and the mass number. The most important point was the investigation of the collision of 238U ions at different bombarding energies. On the basis of the measured formation cross sections conclusions can be drawn on the reaction mechanism and the excitation function of the formation of transplutonium elements. According to the results it seems to be reasonable to use transfer reactions between 238U and 238U or 248Cm to synthesize superheavy nuclei around Z = 114. Until now that has been tried only with the help of fusion reactions and the results were negative. (orig.)

  17. Phosphate fertilizer influence on 238 U content in vegetables

    Uranium is a naturally radioactive element, which is usually found in soils, superficial and ground water, vegetables and animals. After ingestion by human beings, most is excreted in few days by feces and urine, without reaching the bloodstream. However, a small part circulates through the body, being accumulated in the soft tissues, as kidneys. A minor fraction can remain in bones per some years, being able through the radioactive decay to irradiate adjacent tissues. Phosphate fertilizers used in conventional crop management can present variable amounts of uranium. In accordance with origin and use, the fertilizer can raise the content of this element in vegetables, and consequently to increase the human exposure for radiation due the consumption of vegetables. It is estimated that the use of phosphate fertilizer has at least doubled the prolonged exposure of humans from ingestion of food. This work aims to evaluate the contribution of organic and chemical fertilizer on the concentration of 238 U in vegetable samples. An experiment with black beans (a very important vegetable for Brazilian people) was conducted in a field which soil has never been fertilized with any sort of fertilizer, located near to the Rio de Janeiro city. On the organic management, bovine manure was used, while on conventional management urea, potassium chloride and superphosphate were used. Simultaneously, black bean samples from not fertilized management were collected. In addition, lettuce and carrot samples from organic and conventional managements were collected in Nova Friburgo farms (the most important vegetable supplier of Rio de Janeiro city market). The analyses of 238 U have been carried out by conventional fluorimetric method. The geometric mean of 238 U concentrations in the carrot and lettuce samples from conventional management were similar with those from organic management, while for beans the conventional samples had higher values than those ones found in organic management

  18. Phosphate fertilizer influence on {sup 238} U content in vegetables

    Lauria D, C.; Rodrigues S, J.I. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN), Av. Salvador Allende s/n, Rio de Janeiro-RJ (Brazil); Ribeiro, F.C.A. [Centro Regional de Ciencias Nucleares (CRCN/CNEN) Av. Prof. Luiz Freire 200 Cidade Universitaria Recife-PE (Brazil)]. e-mail: dejanira@ird.gov.br

    2006-07-01

    Uranium is a naturally radioactive element, which is usually found in soils, superficial and ground water, vegetables and animals. After ingestion by human beings, most is excreted in few days by feces and urine, without reaching the bloodstream. However, a small part circulates through the body, being accumulated in the soft tissues, as kidneys. A minor fraction can remain in bones per some years, being able through the radioactive decay to irradiate adjacent tissues. Phosphate fertilizers used in conventional crop management can present variable amounts of uranium. In accordance with origin and use, the fertilizer can raise the content of this element in vegetables, and consequently to increase the human exposure for radiation due the consumption of vegetables. It is estimated that the use of phosphate fertilizer has at least doubled the prolonged exposure of humans from ingestion of food. This work aims to evaluate the contribution of organic and chemical fertilizer on the concentration of {sup 238} U in vegetable samples. An experiment with black beans (a very important vegetable for Brazilian people) was conducted in a field which soil has never been fertilized with any sort of fertilizer, located near to the Rio de Janeiro city. On the organic management, bovine manure was used, while on conventional management urea, potassium chloride and superphosphate were used. Simultaneously, black bean samples from not fertilized management were collected. In addition, lettuce and carrot samples from organic and conventional managements were collected in Nova Friburgo farms (the most important vegetable supplier of Rio de Janeiro city market). The analyses of {sup 238} U have been carried out by conventional fluorimetric method. The geometric mean of {sup 238} U concentrations in the carrot and lettuce samples from conventional management were similar with those from organic management, while for beans the conventional samples had higher values than those ones found in

  19. Evaluation of the 238U neutron total cross section

    Experimental energy-averaged neutron total cross sections of 238U 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

  20. Neutron Induced Capture and Fission Processes on 238U

    Oprea Cristiana; Oprea Alexandru

    2016-01-01

    Nuclear data on Uranium isotopes are of crucial interest for new generation of nuclear reactors. Processes of interest are the nuclear reactions induced by neutrons and in this work mainly the capture and the fission process on 238U will be analyzed in a wide energy interval. For slow and resonant neutrons the many levels Breit – Wigner formalism is necessary. In the case of fast and very fast neutrons up to 200 MeV the nuclear reaction mechanism implemented in Talys will be used. The present...

  1. Charge-pickup of 238U at relativistic energies

    Cross sections for the charge-pickup of 238U projectiles were measured at E/A=600 and 1000 MeV for seven different targets (Be, C, Al, Cu, In, Au and U). Events with two fission fragments with a sum charge of 93 in the exit channel were selected. Due to the significant excitation energy, the dominant part of produced Np nuclei fission instead of decaying to the ground state by evaporation. The observed cross sections can be well reproduced by intranuclear-cascade-plus-evaporation calculations and, therefore, confirm recent results that no exotic processes are needed to explain charge-pickup processes. (orig.)

  2. Database for 238U inelastic scattering cross section evaluation

    There are discrepancies among evaluated neutron inelastic scattering cross sections for 238U in the evaluated nuclear data files, JENDL-3, ENDF/B-VI, JEF-2, BROND-2 and CENDL-2. Re-evaluating them is internationally being discussed to obtain the best outcome which can be accepted in common at the present by experts in the world. This report has been compiled to review the discrepancies among the evaluations in the present data files and to provide a common database for the re-evaluation work (author)

  3. Intermediate structure in the 238U neutron capture cross section

    Recent measurements of the 238U neutron capture cross section show large fluctuations in the unresolved resonance region. To test whether or not the observed long-range fluctuation of the neutron capture represent departures from the compound nuclear model, the Wald-Wolfowitz runs and correlation tests were applied to the 238U neutron capture data obtained at ORELA. The Wald-Wolfowitz runs test deals with the statistic, R, which is the number of unbroken sequences of data points above or below a given reference line. This statistic is to be compared with the expected value of runs E(R) +- sigma(R) arising from randomly distributed data. In the correlation test we have computed the first serial correlation coefficient of the data as well as its expected value and variance for a set of random data. In both tests one computes the probability, P, for the given statistical entity to depart from its expected value by more than epsilon standard deviations. Both tests confirm the presence of intermediate structure between 5 and 100 keV. The range of the structure far exceeds the width of the experimental resolution and level widths. 3 tables, 2 figures

  4. The production of unknown neutron-rich isotopes in $^{238}$U+$^{238}$U collisions at near-barrier energy

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

    2016-01-01

    The production cross sections for primary and residual fragments with charge number from $Z$=70 to 120 produced in the collision of $^{238}$U+$^{238}$U at 7.0 MeV/nucleon are calculated by the improved quantum molecular dynamics (ImQMD) model incorporated with the statistical evaporation model (HIVAP code). The calculation results predict that about sixty unknown neutron-rich isotopes from element Ra ($Z$=88) to Db ($Z$=105) can be produced with the production cross sections above the lower bound of $10^{-8}$ mb in this reaction. And almost all of unknown neutron-rich isotopes are emitted at the laboratory angles $\\theta_{lab}\\leq$ 60$^\\circ$. Two cases, i.e. the production of the unknown uranium isotopes with $A\\geq$ 244 and that of rutherfordium with $A\\geq$ 269 are investigated for understanding the production mechanism of unknown neutron-rich isotopes. It is found that for the former case the collision time between two uranium nuclei is shorter and the primary fragments producing the residues have smaller...

  5. Neutron Induced Capture and Fission Processes on 238U

    Oprea Cristiana

    2016-01-01

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

  6. Neutron Induced Capture and Fission Processes on 238U

    Oprea, Cristiana; Oprea, Alexandru

    2016-03-01

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

  7. Resonant upscattering effects on 238U absorption rates

    The new requirements of accuracy in reactor physics calculations justify a review of the current models, like that one adopted in the cross-section processing, for a better evaluation of the keff and the resonant absorption rates. In this context, the aim of this paper is to investigate the effects of the free gas kernel developed by Sanchez on the 238U absorption rates. Homogeneous medium tests point out the increase of the absorption rates in the left wing of the resonances due to the upscattering produced by the new kernel. Heterogeneous tests show that the absorption in the left wing of the resonances is mostly affected by the scattering anisotropy in the laboratory system. (author)

  8. New evaluation of 238U neutron resonance parameters

    The neutron resonance parameters of 238U were obtained in the energy range 1 keV to 20 keV from a SAMMY Reich-Moore analysis of high resolution transmission measurements performed at ORELA. In the energy range 1 keV to 10 keV, the analysis used as prior values the ENDF/B-VI resonance parameters. The analysis in the energy range 10 keV to 20 keV resulted in the creation of a set of resonance parameters for the representation of the cross section in this energy range. The results are compared to the ENDF/B-VI evaluation. Some statistical properties of the new resonance parameters are examined. (author)

  9. Precise measurement and analysis of neutron transmission through 238U

    The transmissions of 0.52- to 4000-eV neutrons through 3.62, 1.08-, 0.254-, 0.0762-, 0.0254-, and 0.0127-, and 0.0036-cm-thick samples of uranium, enriched in the 238U isotope, have been measured at 42 m with a 1.0-mm-thick 6Li glass detector using the Oak Ridge Electron Linear Accelerator pulsed neutron source. To obtain resonance parameters, the seven transmissions of neutrons having energies ranging from 0.52 to 1086.8 eV have been shape-fitted by least-squares analysis to a multilevel Breit-Wigner cross-section formalism with ''picket-fence'' terms to account for truncation effects. This simultaneous fit yielded a chi2 per degree of freedom near unity. Averaged over this energy range, an s-wave strength function of (0.968 +- 0.036) x 10-4 cm and an effective radius of (0.944 +- 0.005) x 10-12 cm were obtained. In addition, these transmission data yielded an average radiation width of 23.1 +- 1.0 meV for the 12 lowest energy s-wave resonances with radiation widths of 23.0 +- 0.8, 22.8 +- 0.8, and 22.9 +- 0.8 meV for the 6,67-, 20.9-, and 36.8-eV resonances, respectively. The derived radiation widths for these three resonances are shown to depend on the cross-section formalism employed. This work suggests that a multilevel formalism with truncation compensation is required to adequately represent the 238U total cross section

  10. Dose effect for South Serbians due to {sup 238}U in natural drinking water

    Sahoo, S.K.; Matsumoto, M.; Shiraishi, K.; Fujimoto, K. [Department of Radiation Dosimetry, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Cuknic, O.; Zunic, Z.S. [Institute of Nuclear Sciences, VINCA, PO Box 522, 11001 Belgrade (Serbia)

    2007-07-01

    The use of depleted uranium ammunition in South Serbia during the 1999 Kosovo conflict raised a great deal of public concern in the Balkans. Radioactivity levels of {sup 238}U in 20 wells and lake water samples were checked from the viewpoint of internal radiation exposure for South Serbian subjects. We have measured {sup 238}U concentration using inductively coupled plasma mass spectrometry, whereas thermal ionisation mass spectrometry has been used for the measurement of isotope ratios, e.g. {sup 234}U/{sup 238}U and {sup 235}U/{sup 238}U. The concentration of uranium in water samples varies in the range 1.37-63.18 mBq/L. {sup 234}U belongs to the {sup 238}U natural radioactive decay series, and at secular equilibrium, the abundance ratio, {sup 234}U/{sup 238}U, corresponds to the ratio of their half-lives. The {sup 234}U/{sup 238}U activity ratio varies in the range 0.88-2.2 and {sup 235}U/{sup 238}U isotope ratio varies from 0.00698 to 0.00745. These findings indicate that uranium in water was a mixture of natural and anthropogenic origin. The annual effective dose due to {sup 238}U was estimated to be in the range 9.2 x 10{sup -5} - 2.1 x 10{sup -3} mSv. (authors)

  11. Radioactive secular equilibrium in 238U and 232Th series in granitoids from Greece

    Granitoid rocks belonging to plutons of Greece, covering a wide range of compositions and rock-types, have been studied for their specific activity (Bq/kg) of 238U and 226Ra from 238U radioactive series and 228Ra and 228Th from 232Th radioactive series by using gamma-ray spectroscopy. Results on the radioactive secular equilibrium of both 238U and 232Th radioactive series are presented by studying the 226Ra/238U and 228Ra/228Th ratios. The majority of the samples are in radioactive secular equilibrium for 226Ra/238U±1σ. However, several samples exhibit 226Ra/238U ratios significantly different from 1. The distortion of the secular equilibrium in the 226Ra–238U isotopic system of those samples has occurred over the last 1 Ma, and can be associated with post-magmatic processes, mainly rock–water interactions. All studied samples have 228Ra/228Th ratios equal to unity ±1σ. Consequently, they can be considered to be in secular equilibrium for the last 40 a. - Highlights: ► Generally, a strong correlation between 238U and 226Ra is obvious. ► Post-magmatic processes caused radioactive disequilibrium in the 238U isotopic system. ► All samples are in radioactive secular equilibrium in the 232Τh isotopic system. ► There is no correlation between mineralogy, texture, colour, age and the isotopic ratios studied

  12. Studying nuclear level densities of 238U in the nuclear reactions within the macroscopic nuclear models

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

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

    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 234U/238U 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 234U/238U AR signature with depth which may be common to all U ore bodies. The 234U/238U 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 234U sites at the redox front due to preconditioning of the 234U sites by α recoil during the decay of 238U to 234U. Mass balance requires the solid material left behind the redox front to have a 234U/238U 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. -- Highlights: ► The 234U/238U AR data of the Koongaara U deposit was re-examined. ► The 234U/238U AR was depressed below 1 above the redox front. ► The 234U/238U AR was elevated above 1 at the redox front. ► The 234U/238U AR was decreased beyond the redox front. ► The data indicates that U ore bodies have a generic 234U/238U AR signature

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

    Capote R.

    2014-04-01

    Full Text Available 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.

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

    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. (author)

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

    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

  17. Measurement and calculation of 238U fission reaction rates induced by neutrons reflected by carbon material

    To check the data of carbon material reflecting neutrons, the distribution of 238U fission reaction rates induced by D-T fusion neutrons reflected by carbon material was measured by using the small depleted uranium fission chamber and the capturing detector. For comparison, 238U fission rates without carbon material was measured too. The combined standard uncertainty of 238U fission reaction rate is 5.1%-6.4%. The measured results are consistent with the calculated ones with MCNP/4A code and ENDF/B-IV library data in the range of the error

  18. Experimental Determination of the Antineutrino Spectrum of the Fission Products of $^{238}$U

    Haag, N; Hofmann, M; Oberauer, L; Potzel, W; Schreckenbach, K; Wagner, F M

    2013-01-01

    An experiment was performed at the scientific neutron source FRM II in Garching to determine the cumulative antineutrino spectrum of the fission products of $^{238}$U. This was achieved by irradiating target foils of natural uranium with a thermal and a fast neutron beam and recording the emitted $\\beta$-spectra with a gamma-suppressing electron-telescope. The obtained $\\beta$-spectrum of the fission products of $^{235}$U was normalized to the data of the magnetic spectrometer BILL of $^{235}$U. This method strongly reduces systematic errors in the $^{238}$U measurement. The $\\beta$-spectrum of $^{238}$U was converted into the corresponding antineutrino spectrum. The final $\\bar\

  19. Understanding of 234U/238U activity ratio in groundwater of agricultural ecosystem

    This study was carried out to clarify the natural variation of 234U/238U ratio in groundwater of an agricultural ecosystem. Water samples were collected from 21 locations from Bathinda and Mansa districts, of Punjab state and analysed for uranium concentration and activity ratio of its isotopes. The activity concentration ratio of 234U/238U in the groundwater samples varied between 0.39-0.98 with a mean value of 0.86. The lower isotopic ratio (less than 1) of 234U/238U indicates higher dissolution rate of parent 238U. The results suggest that, most of the dissolved uranium in groundwater is derived from the surrounding host soil or bed rock rather than from anthropogenic input. (author)

  20. Dissolution behaviour of 238U, 234U and 230Th deposited on filters from personal dosemeters

    Kinetics of dissolution of 238U, 234U and 230Th dust deposited on filters from personal alpha dosemeters was studied by means of a 26-d in vitro dissolution test with a serum ultra-filtrate simulant. Dosemeters had been used by miners at the uranium mine 'Dolni Rozinka' at Rozna, Czech Republic. The sampling flow-rate as declared by the producer is 4 l h-1 and the sampling period is typically 1 month. Studied filters contained 125 ± 6 mBq 238U in equilibrium with 234U and 230Th; no 232Th series nuclides were found. Half-time of rapid dissolution of 1.4 d for 238U and 234U and slow dissolution half-times of 173 and 116 d were found for 238U and 234U, respectively. No detectable dissolution of 230Th was found. (authors)

  1. Experimental determination of the antineutrino spectrum of the fission products of {sup 238}U

    Haag, Nils-Holger

    2013-10-09

    Fission of {sup 238}U contributes about 10 % to the antineutrino emission of a pressurized water reactor. In the present thesis, the beta spectrum of the fission products of {sup 238}U was determined in an experiment at the neutron source FRM II. This beta spectrum was subsequently converted into an antineutrino spectrum. This first measurement of the antineutrino spectrum supports all current and future reactor antineutrino experiments.

  2. Evaluation of neutron-induced reactions in 48Ti and 238U

    Preliminary results of the evaluation of neutron-induced reactions in 48Ti and 238U are presented. Calculated cross sections for the reactions (n,γ), (n,n'), (n, 2n) and (n,p) as well as for (n,f) in 238U are given. Comparisons with available experimental data are made and possible changes in the parameters are discussed. (Author)

  3. Experimental determination of the antineutrino spectrum of the fission products of 238U

    Fission of 238U contributes about 10 % to the antineutrino emission of a pressurized water reactor. In the present thesis, the beta spectrum of the fission products of 238U was determined in an experiment at the neutron source FRM II. This beta spectrum was subsequently converted into an antineutrino spectrum. This first measurement of the antineutrino spectrum supports all current and future reactor antineutrino experiments.

  4. 234U/238U signatures associated with uranium ore bodies: part 2 Manyingee

    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 234U/238U 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 234U/238U ARs are attributed to selective leaching of 234U sites by oxidising waters, with α recoil as a necessary precursor to produce activated 234U sites. Direct ejection into another phase following α recoil is considered to be a minor contributor to 234U –238U disequilibrium in this environment. The profile is considered to be typical of the 234U/238U AR profile at and down gradient of the redox front of a U ore body. -- Highlights: ► The 234U/238U AR of the ground water of a roll-front U deposit was determined. ► The ground water was sampled at and beyond the redox front. ► The 234U/238U AR was elevated to 1.8 at the redox front. ► The 234U/238U AR was decreased down gradient of the redox front. ► A generic 234U/238U AR signature is proposed for U ore bodies

  5. Analysis of transmission experiments for 238U in the unresolved resonance region

    From analysis of experimental data on transmission in the region of unresolved resonances, an evaluation of the mean resonance parameters for 238U is obtained. These parameters do not contradict the corresponding evaluations from the region of resolved resonances. On the basis of this evaluation, the group constants for 238U are determined, for the region of unresolved resonances. A comparison is made with data tables

  6. Coulomb fission of 238U in the interaction of 24.3 MeV/nucleon 238U with 197Au

    Coulomb fission of 238U has been studied in the interaction of a 24.3 MeV/nucleon U beam with an Au target. A novel experimental approach is followed, allowing to isolate the Coulomb fission from the nuclear fission on an event by event basis. The Z distribution of the fragments is studied for both fission processes. (author)

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

    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

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

    Lowson, Richard T

    2013-04-01

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

  9. Radiationless transition probabilities in muonic 208Pb, 232Th, and 238U

    The probabilities for non-radiative (n.r.) excitations Pn.r. in the muonic nuclides 208Pb, 232Th, and 238U have been determined for (μ-, γγ)-measurements by comparing the intensities of muonic X-ray transitions in single and coincidence spectra. The value of Pn.r. (3p→1s), measured for the first time, is about 90% for the actinides 232Th and 238U, but only about 8% for 208Pb. The value of Pn.r. (3d→1s) is found to be 10% for 233Th, 13% for 238U, and about 4% for 208Pb. For 208Pb a vanishing strength of the n.r. decay of the 2p-level is found, while for 232Th and for 238U n.r. strengths of about 20% and 26%, respectively, are observed. By regarding two subcomplexes of the 2p→1s transitions leading to different mean excitation energies the n.r. transition probabilities were found to be different for 238U only, 21.6% and 31.1%, respectively. (orig.)

  10. Fission fragment mass and angular distribution in 6,7Li+235,238U reactions

    Fission fragment (FF) angular distributions for 6,7Li+235,238U reactions and mass distributions for 6,7Li+ 238U reactions have been measured at energies near and above the Coulomb barrier. The angle integrated fission cross sections for 6Li induced reactions at sub-barrier energies are found to be higher than 7Li induced reactions possibly due to larger contribution of breakup induced fission in case of the former compared to the latter. The FF anisotropy for 6,7Li+235U was found to be smaller than 6,7Li+238U, manifesting the effect of target ground state spin. The statistical saddle point (SSP) model predictions were found to be consistent with the measured FF anisotropy for 6,7Li+235U, however they were under-estimated for 6,7Li+238U particularly at lower energies. Observation of larger FWHM of FF folding angle distribution and sharp increase in peak to valley ratio for FF mass distribution with the decrease in bombarding energy in 6,7Li+238U reactions confirms the presence of breakup induced fission. (authors)

  11. Fission fragment mass and angular distribution in 6,7Li+235,238U reactions

    Santra S.

    2013-12-01

    Full Text Available Fission fragment (FF angular distributions for 6,7Li+235,238U reactions and mass distributions for 6,7Li+238U reactions have been measured at energies near and above the Coulomb barrier. The angle integrated fission cross sections for 6Li induced reactions at sub-barrier energies are found to be higher than 7Li induced reactions possibly due to larger contribution of breakup induced fission in case of the former compared to the latter. The FF anisotropy for 6,7Li+235U was found to be smaller than 6,7Li+238U, manifesting the effect of target ground state spin. The statistical saddle point (SSP model predictions were found to be consistent with the measured FF anisotropy for 6,7Li+235U, however they were under-estimated for 6,7Li+238U particularly at lower energies. Observation of larger FWHM of FF folding angle distribution and sharp increase in peak to valley ratio for FF mass distribution with the decrease in bombarding energy in 6,7Li+238U reactions confirms the presence of breakup induced fission.

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

    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.

  13. 238U, 226Ra and 210Pb in some vent waters of the Galapagos spreading center

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

  14. Radiological impact from atmospheric releases of 238U and 226Ra from phosphate rock processing plants

    Phosphate rocks are used extensively, mainly as a source of phosphorus for fertilizers and secondly for phosphoric acid and gypsum (phosphogypsum). Phosphates are, therefore one of the sources of technologically enhanced exposure to man from natural radionuclides (TENR). Emissions from phosphate rocks processing plants in gaseous and particulate form contain radioisotopes, such as 238U and 226Ra, which are discharged into the environment causing radiation exposures to the population. About 10 MBq of 238U and 226Ra, respectively, are discharged to the environment each year from a phosphate rocks processing plant in Thessaloniki area, Northern Greece. The collective dose commitment to lung tissue resulting from atmospheric release was estimated to be ∼2x10-9 man Gy t-1 for 238U and ∼0.1x10-9 Plan Gy t-1 for 226Ra, i.e. about 2 times higher than that reported in UNSCEAR 1992 Report. (author)

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

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

    2016-01-01

    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 I...

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

    Vidic, Alfred; Ilić, Zorana; Benedik, Ljudmila

    2013-06-01

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

  17. Activity disequilibrium between 234U and 238U isotopes in natural environment

    The aim of this work was to calculate the values of the 234U/238U activity ratio in natural environment (water, sediments, Baltic organisms and marine birds from various regions of the southern Baltic Sea; river waters (the Vistula and the Oder River); plants and soils collected near phosphogypsum waste heap in Wislinka (Northern Poland) and deer-like animals from Northern Poland. On the basis of the studies it was found that the most important processes of uranium geochemical migration in the southern Baltic Sea ecosystem are the sedimentation of suspended material and the vertical diffusion from the sediments into the bottom water. Considerable values of the 234U/238U are characterized for the Vistula and Oder Rivers and its tributaries. The values of the 234U/238U activity ratio in different tissues and organs of the Baltic organisms, sea birds and wild deer are varied. Such a large variation value of obtained activity ratios indicates different behavior of uranium isotopes in the tissues and organisms of sea birds and wild animals. This value shows that uranium isotopes can be disposed at a slower or faster rate. The values of the 234U/238U activity ratio in the analyzed plants, soils and mosses collected in the vicinity of phosphogypsum dumps in Wislinka are close to one and indicate the phosphogypsum origin of the analyzed nuclides. Uranium isotopes 234U and 238U are not present in radioactive equilibrium in the aquatic environment, which indicates that their activities are not equal. The inverse relationship is observed in the terrestrial environment, where the value of the of the 234U/238U activity ratio really oscillates around unity. (author)

  18. Radionuclides of 210Po, 234U and 238U in drinking bottled mineral water in Poland

    A study of the radioactive content of drinking mineral bottled water in Poland was carried out. 210Po, 238U and 234U activity concentrations were determined by alpha-spectrometry with low-level-activity silicon detectors. The results revealed that the mean concentration of 210Po, 238U and 234U in analyzed water sample were 1.28, 0.80 and 0.80 mBq x dm-3, respectively. The effective doses due to the polonium and uranium emissions were calculated for bottled drinking water. (author)

  19. Effects of nuclear orientation on fusion and fission in the reaction using 238U target nucleus

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

    2011-01-01

    Fission fragment mass distributions in the reaction of 30Si+238U were measured around the Coulomb barrier. At the above-barrier energies, the mass distribution showed a Gaussian shape. At the subbarrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at AL/AH ≈ 90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections for 30Si+238U. Th...

  20. Measurement of resonance self-shielding factors of neutron capture cross section by 238U

    Resonance self-shielding factors fsub(c) of neutron capture cross section by 238U in the 20-100 keV energy range are measured. The method for determining the fsub(c) factor consists in measuring partial transmission and transmission in the total cross section at different 238U filter thickness. The fsub(c) factor values in the 46.5-100 and 21.5-46.5 keV energy ranges are equal to 0.89+-0.03 and 0.81+-0.04, respectively

  1. Determination of 238U nucleus number using grid ionization chamber method and small solid angle method

    Using the grid ionization chamber method and small solid angle method, the number of 238U nucleus in the highly pure U3O8 sample is determined. Although the ratio of efficiency for the two methods is as high as 484, the results are in good agreement

  2. 238U spontaneous fission half-life and a new probable radioactivity mode

    The 238U spontaneous fission half-life is reinvestigated using a special nuclear emulsion technique previously developed in our laboratory. A perfect visualisation of the fission fragments tracks in the absence of alpha particle tracks was obtained with the present method that also avoids the fading of the latent image. Under these conditions, two well defined peaks are observed experimentaly: one corresponding to the well-known range (approx 24 μm) of the 238U fission fragments tracks and the other showing evidence of short range tracks (approx 10 μm). For the 238U spontaneous fission half-life our result is (6.0+-0.4) x1015 y, in good agreement with the values obtained by some other workers using different experimental methods. A systematic theoretical analysis shows that the 238U spontaneous emission of nuclides with mass number between approx 20 e 70 is possible. The Kinetic energies calculated for these nuclides are found to fit the short range tracks observed in our experiment. From the experimental data, we attribute a (2 +- 1) x 1015 y half-life for all modes of emission involved in this process. (Author)

  3. Two types of adakites revealed by 238U-230Th disequilibrium from Daisen volcano, southwestern Japan

    Daisen volcano is located on the Quaternary volcanic front in southwestern Japan. The volcano is composed mainly of andesite and dacite, which chemically resemble adakites, with high Al2O3 and Sr/Y, steep REE patterns, and no negative Eu anomaly. (238U/230Th) disequilibrium (herein, a ratio in parentheses denotes the activity ratio) and trace element analyses of adakites from two volcanic domes, Karasugasen and Misen, indicate two adakite types. Adakite from Karasugasen is characterized by excess (230Th) over (238U), typical of most adakites, whereas adakite from Misen is characterized by excess (238U) over (230Th). The latter is consistent with enrichment in fluid-mobile elements relative to fluid immobile elements compared to rocks from Karasugasen. The values of (230Th/232Th) of adakites from Karasugasen and Misen are, respectively, around 0.75 and 0.81. These low (230Th/232Th) ratios result from the incorporation of subducted sedimentary material. The ratios, nevertheless, are higher than that for the estimate of lower crustal material suggesting significant incorporation of lower crust is unlikely. As adakites from Misen have (238U) excess over (230Th), adakite magma must have interacted with wedge mantle metasomatized by a slab-derived fluid, confirming the presence of a fluid-metasomatized mantle beneath Daisen volcano. (author)

  4. Energy dependence of 238U fission yields investigated in inverse kinematics

    Veselsky M.

    2010-03-01

    Full Text Available The production cross sections of neutron-rich fission residues produced in reactions induced by a 238U beam impinging onto Pb and Be targets were investigated at the Fragment Separator (FRS at GSI using the inverse kinematic technique. These data allowed us to discuss the optimum energies in fission for producing the most neutron-rich residues.

  5. Photo fission cross-section of 232Th, 238U and 237Np

    In the present work, photo fission cross-section of 232Th, 238U and 237Np evaluated with the help of fission fragment angular distribution measurements by using Bremsstrahlung radiation from 7.4 MeV to 9.0 MeV have been carried out by employing high efficiency SSNTD technique

  6. Radiochemical measurement of mass distribution in 16O+238U reaction at sub-barrier energy

    In the present, radiochemical study of the mass distribution in 16O+238U has been carried out at sub-barrier energy to investigate the nature of mass distribution in CFF and TF channels. In addition, cross sections of evaporation residues formed in one nucleon transfer/pick-up reactions have also been measured

  7. Some important aspects of fragment angular momentum in medium energy fission of 238U

    Independent isomeric yield ratios of 131Te, 133Te and 134I have been determined at five different energies in the range of 25-44 MeV alpha particle induced fission of 238U using radiochemical and gamma spectrometric techniques. From the independent isomeric yield ratios, fragment angular momenta (Jrms) have been deduced using a statistical model analysis. The Jrms were also calculated theoretically based on thermal equilibration of various collective modes after considering the occurrence of multichance fission. These data and the literature data for various fragments in the mass region 126-136 in 238U (α,f), 238U (p,f) and 238U (γ,f) show the following important features: (i) Both the entrance channel excitation energy and input angular momentum affect the fragment angular momentum in the exit channel. (ii) There are two groups of fission products from the point of view of change of fragment angular momentum with increase in excitation energy and input angular momentum. (iii) Fragment angular momentum depends on nuclear structure effect such as shell closure proximity and odd-even effect. (iv) The fragment angular momentum calculated theoretically based on statistical equilibration of various collective modes are in good agreement with the experimental values indicating the validity of such an assumption

  8. 238U(n,γ) cross section above the resonance region

    A number of measurements of the 238U(n,γ) cross section above the resonance region have been completed in the past few years. In the keV range, these measurements suggest a considerable amount of intermediate structure. Comparisons are made of pre-1970 and more recent evaluations with ENDF/B-IV results. Discrepancies and uncertainties are discussed

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

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

    2016-05-01

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

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

    LLNL Internal Dosimetry Program - The new procedure satisfies the requirement to determine 235U/238U ratio in bioassay urine samples. MDA - The LC and MDA95 for 235U are well below the required detection limit of 0.00035 μg/L. Turn around time - Analysis of 10 samples plus 2 QCs can be completed in one work day (8 hours).

  11. Uses of uranium isotopes 234U and 238U in hydrology and hydrogeology

    This work describes the application of the uranium isotopes 234U, 238U as a practically usuable indicator in hydrology and hydrogeology as well as its value in scientific research. The emphasis is laid on the methods of interpretation of U-data and the application of these methods to special hydrologic and hydrogeologic problems in the GDR. (author)

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

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

  13. Energy distribution of neutrons from the (n,2n) reaction in 238U

    Energy distribution of the first and second neutrons from (n,2n) scattering event in 238U was evaluated according to the consistent compound nucleus model recently proposed by Segev. The law for deriving the energy distribution of secondary neutrons from a (n,2n) scattering event, depends on whether the reaction is considered as a simultaneous emission of two neutrons from one compound nucleus, or a successive emission of neutrons from different compound nuclei. Segev has presented a means of calculating the energy distribution assuming the latter model. The laws presented in the ENDF/B data files suggest the former model. The evaluation was based on inelastic level excitation and evaporation data for 238U and 237U. Data was retrieved from ENDF/B files. The evaporation data for 237U was based on (γ,n) reaction 238U. The inelastic level excitation data for 237U was evaluated at the Soreq Nuclear Research Centre. It is concluded from the application of Segev's model to 238U, that the energetic spectrum of secondary neutrons, is harder in the high range of energy than the one predicted by the use of the distribution law presented in ENDF/B data files. The spectrum of secondary (n,2n) neutrons, resulting from the interaction of 14 MeV neutrons in 238U calculated with Segev's model, is compared with the corresponding spectrum of the LLL library, ENDF/B library and the recent evaluation of BNWL. It is found that the spectrum evaluated by LLL and BNWL is harder than that evaluated with Segev's model

  14. Experimental study of 238U Doppler reactivity worth in FCA XVI-1 and XVI-2 cores

    Doppler reactivity worths of natural uranium samples were measured in metallic fueled cores, FCA XVI-1 and XVI-2, using a sample heating technique. In a metallic fueled LMFBR, the neutron spectrum is generally harder than a similar size oxide fueled LMFBR owing to the luck of oxygen. The accuracy of Doppler effect calculation for a harder neutron spectrum was evaluated by comparing C/E values of Doppler reactivity worth in oxide fueled cores and in metallic fueled cores using FCA experiments. It was found that calculation using 70-group constant set JFS-3-J2 underestimates 238U Doppler reactivity worth in metallic fueled cores. An inadequate treatment of resonance parameters of 238U above 50 keV in JENDL-2 is one of the reasons for this underestimation. In JENDL-2 the resonance parameters of 238U above 50 keV are not included, and hence JFS-3-J2 which is processed from JENDL-2 does not have a self-shielding factor table above 40.9 keV of 238U. When the contribution of this energy region for Doppler reactivity worth was corrected using ENDF/B-VI, which includes resonance parameters of 238U up to 149 keV, the JFS-3-J2 based calculation gave 13% higher values for metallic sample experiments and 8% for oxide samples. Even after this correction, the calculation still gave smaller Doppler reactivity worths than the measurements, and the ratios of calculated value to experimental one vary widely from 0.6 to 1.0. (author)

  15. Studying nuclear level densities of {sup 238}U in the nuclear reactions within the macroscopic nuclear models

    Razavi, Rohallah; Aghajani, Maghsood; Khooy, Asghar [Imam Hossein Comprehensive Univ., Tehran (Iran, Islamic Republic of). Dept. of Physics; Rahmatinejad, Azam; Taheri, Fariba [Univ. of Zanjan (Iran, Islamic Republic of). Dept. of Physics; Kakavand, Tayeb [Imam Khomeini International Univ., Qazvin (Iran, Islamic Republic of). Dept. of Physics

    2016-05-01

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

  16. 238U, and its decay products, in grasses from an abandoned uranium mine

    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. Exploring the multi-humped fission barrier of 238U via sub-barrier photofission

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

    2013-01-01

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

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

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

    2013-04-01

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

  19. 238U self-indication ratio measurement in the resonance region

    An accurate representation of the 238U cross-section structures in the resonance region is required to compute the resonance self-shielded effective cross sections used in the calculation of thermal and fast-reactor performance parameters. Several authors have demonstrated the usefulness of self-indication and average transmission measurements to investigate the resonance structure of the 238U cross sections. This paper compares measured self-indication ratios with calculations based on ENDF/B-V, in the resolved energy range from 100 eV to 4 keV. In that energy range the ENDF/B-V evaluation is chiefly based on high resolution transmission measurements. The immediate purpose of the comparison presented is not to generate a new set of improved resonance parameters but to provide an additional test of the adequacy of the ENDF/B-V representation for the calculation of resonance self-shielding

  20. Effects of nuclear orientation on fusion and fission in the reaction using 238U target nucleus

    Hirose K.

    2010-03-01

    Full Text Available Fission fragment mass distributions in the reaction of 30Si+238U were measured around the Coulomb barrier. At the above-barrier energies, the mass distribution showed a Gaussian shape. At the subbarrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at AL/AH ≈ 90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER cross-sections for 30Si+238U. The cross-section for 263Sg at the abovebarrier energy agree with the statistical model calculation which assumes that the measured fission cross-section originates from fusion-fission, whereas the one for 264 Sg measured at the sub-barrier energy is smaller than the calculation, which suggests the presence of quasifission.

  1. Neutron and fragment yields in proton-induced fission of 238U at intermediate energies

    The primary fission fragment mass and kinetic energy distributions, and neutron multiplicities as function of fragment mass have been measured in the proton-induced fission of 238U at energies Ep=20, 35, 50 and 60 MeV using time-of-flight technique. Pre-scission and post-scission neutron multiplicities have been extracted from double differential distributions. The fragment mass dependence of the post-scission neutron multiplicities reveals the gross nuclear shell structure effect even at the higher proton energies we measured. The yields of neutron-rich fission products in the fission of 238U by 25 MeV protons were measured using an ion guide-based isotope separator technique. The results indicate enhancement for superasymmetric mass division at intermediate excitation energy of the fissioning nucleus. The experimental results have been analysed in the framework of a time-dependent statistical model with inclusion of nuclear friction effects in the fission process

  2. Comparison of Yields of neutron rich nuclei in Proton and Photon induced $^{238}$U fission

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

    2016-01-01

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

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

    Duke, Dana; TKE Team

    2014-09-01

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

  4. Measurement and resonance analysis of neutron transmissions through four samples of 238U

    Accurate total and partial cross sections for 238U are important for nuclear reactor design. In the resolved resonance region, energies below 4.0 keV, these cross sections are described in terms of individual resonance parameters of which the neutron widths in the 1.5 to 4.0 keV region from various workers appear discrepant. In order to determine these widths, (0.880 to 100.0 keV) neutron transmissions through 0.076, 0.254, 1.080, and 3.620 cm thick enriched 238U samples were measured, and (0.880 to 100.0 keV) range transmissions were analyzed

  5. Spatiotemporal variation of dissolved 238U in the Gironde fluvial-estuarine system (France)

    Dissolved uranium (238UD) was measured within the Gironde fluvial-estuarine system (France), which is well known for its heavy metal pollution and its subsequent environmental effects. Dissolved 238U activities exhibit the highest levels and variability in the small watersheds of the Isle and Riou-Mort rivers, ascribed to low discharges and the occurrence of peculiar features (local U ore deposits; Permian layers). The major tributaries of the Gironde Estuary: Garonne, Lot and Dordogne, show rather stable 238UD, higher than the global mean riverine uranium activity. In the Gironde Estuary 238UD behaves conservatively along the river-estuary-ocean transect. Dissolved 238U distribution in the Gironde fluvial-estuarine system can be explained by the characteristics of considered drainage basins. There is no evidence of anthropogenic pollution

  6. Measurement of neutron inelastic scattering cross section of {sup 238}U

    Miura, Takako; Baba, Mamoru; Ibaraki, Masanobu; Sanami, Toshiya; Win, Than; Hirasawa, Yoshitaka; Matsuyama, Shigeo; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan)

    1998-03-01

    Neutron scattering from the 0{sup +}, 2{sup +} (1-st) and 4{sup +} (2nd) levels of {sup 238}U was measured for incident energies between 0.4 and 0.85 MeV at the Tohoku University 4.5 MV Dynamitron facility, using the time-of-flight (TOF) method with monoenergetic pulsed neutrons by the {sup 7}Li(p,n) reaction. The results are presented in comparison with other experimental data and evaluated data. (author)

  7. Photofission cross section of 238U in the quasi-deuteron region

    The photofission cross section of 238U induced by monochromatic and polarized photons has been measured using LADON facility at the Frascati National Laboratory. The experiment has been performed at six different energies in the range 46-72 Mev by detecting the fission fragments either in uranium-loaded nuclear-track emulsion plates or in uranium-mica sandwiches. Results are consistent with existing data, however they suggest the opportunity of further investigation in this energy range. (author)

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

    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).

  9. Spontaneous 238U fission half-life measurements based on fission-track techniques

    In the last recommendation of the International Union of Pure and Applied Chemistry (I.U.P.A.C.) on spontaneous fission half-lives for ground-state nuclides, a number of measurements of 238U based on fission-track techniques were discarded. The arguments given by the authors are not clear. A more detailed discussion of these determinations is given, considering the possible systematical errors inherent in fission-track approaches. (author)

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

    Srncik, M.; P. Steier; 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 ...

  11. Sensitivity coefficients for the 238U neutron-capture shielded-group cross sections

    In the unresolved resonance region cross sections are represented with statistical resonance parameters. The average values of these parameters are chosen in order to fit evaluated infinitely dilute group cross sections. The sensitivity of the shielded group cross sections to the choice of mean resonance data has recently been investigated for the case of 235U and 239Pu by Ganesan and by Antsipov et al; similar sensitivity studies for 238U are reported

  12. Microscopic approach of fission dynamics applied to fragment kinetic energy and mass distributions in 238U

    Goutte, H.; Berger, J.F.; Casoli, P.; Gogny, D.

    2005-01-01

    The collective dynamics of low energy fission in 238U is described within a time-dependent formalism based on the Gaussian Overlap Approximation of the time-dependent Generator Coordinate Method. The intrinsic deformed configurations of the nucleus are determined from the self-consistent Hartree-Fock-Bogoliubov procedure employing the effective force D1S with constraints on the quadrupole and octupole moments. Fragment kinetic energy and mass distributions are calculated and compared with exp...

  13. Capture width of the 6.67 eV level in 238U

    In a comparison between a Monte Carlo calculation and a measurement of the capture probability in a thick sample of 238U it has been suggested that the width of the 6.67 eV level might be appreciably smaller than the value 25.6 MeV, evaluated in Version III and IV of ENDF/B. A few comments are made on this topic. (SDF)

  14. Proton-induced fission on 241Am, 238U and 237Np at intermediate energies

    Deppman, A.; Andrade-II, E.; Guimaraes, V; Karapetyan, G. S.; Balabekyan, A. R.; Demekhina, N. A.

    2013-01-01

    Intermediate energy data of proton-induced fission on 241Am, 238U and 237Np targets were analysed and investigated using the computational simulation code CRISP. Inelastic interactions of protons on heavy nuclei and both symmetric and asymmetric fission are regarded. The fission probabilities are obtained from the CRISP code calculations by means of the Bohr-Wheeler model. The fission cross sections, the fissility and the number of nucleons evaporated by the nuclei, before and after fission, ...

  15. The inflow of 234U and 238U from the River Odra drainage basin to the Baltic Sea

    Bogdan Skwarzec

    2010-12-01

    Full Text Available In this study the activity of uranium isotopes 234U and 238U in Odra river water samples, collected from October 2003 to July2004, was measured using alpha spectrometry. The uranium concentrations were different in each of the seasons analysed; the lowest values were recorded in summer. In all seasons, uranium concentrations were the highest in Bystrzyca river waters (from 27.81 ± 0.29Bq m-3 of 234U and 17.82 ± 0.23 Bq m-3 of 238U in spring to 194.76 ± 3.43 Bq m-3 of 234U and 134.88 ± 2.85 Bq m-3 of 238U in summer. The lowest concentrations were noted in the Mała Panew (from 1.33 ± 0.02 Bq m-3 of 234U and 1.06 ± 0.02 Bq m-3 of 238U in spring to 3.52 ± 0.05 Bq m-3 of 234U and 2.59± 0.04 Bq m-3 of 238U in autumn. The uranium radionuclides 234U and 238U in the water samples were not in radioactive equilibrium. The 234U / 238U activity ratios were the highest in Odra water samples collected at Głogów (1.84 in autumn, and the lowest in water from the Noteć (1.03 in winter and spring. The 234U / 238U activity ratio decreases along the main stream of the Odra, owing to changes in the salinity of the river's waters. Annually, 8.19 tons of uranium (126.29 G Bq of 234U and 100.80 G Bq of 238U flow into the Szczecin Lagoon with Odra river waters.

  16. Distribution of 137Cs, 40K, 238U and 232Th in soils from Northern Venezuela

    More than one hundred undisturbed soil samples form Northern Venezuela and the islands of Margarita and Los Roques have been analyzed for 137Cs, 40K, 238U and 232Th by γ-ray spectroscopy. The specimens were taken from between 5-10 cm below the earth's surface. Thus, they are valid not only for the 137Cs deposition studies but also for the estimation of the natural γ-ray dose from primordial radionuclides that form the terrestrial component. The concentrations of 40K was directly determined from its 1461 keV γ-ray, while those of 137Cs, 238U and 232Th were performed using a γ-ray from one of their daughter radionuclides: the 661 keV γ-ray of 137mBa for 137Cs, the 1760 keV γ-ray of 214Bi for 238U and the 2620 keV γ-ray of 208Tl for 232Th. Finally, the concentration values were compared with those of global estimates. (author) 15 refs.; 4 figs.; 2 tabs

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

    Ahmad, I.; Back, B.B.; Betts, R.R. [and others

    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.

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

    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 (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 variable α values are found. These results may suggest that microbes adept at inducing U(VI) reduction play a crucial role in facilitating significant 238U/235U isotope fractionation in nature.

  19. 232Th and 238U neutron emission cross section calculations and analysis of experimental data

    In this study, pre-equilibrium neutron-emission spectra produced by (n,xn) reactions on nuclei 232Th and 238U have been calculated. Angle-integrated cross sections in neutron induced reactions on targets 232Th and 238U have been calculated at the bombarding energies up to 18 MeV. We have investigated multiple pre-equilibrium matrix element constant from internal transition for 232Th (n,xn) neutron emission spectra. In the calculations, the geometry dependent hybrid model and the cascade exciton model including the effects of pre-equilibrium have been used. In addition, we have described how multiple pre-equilibrium emissions can be included in the Feshbach-Kerman-Koonin (FKK) fully quantum-mechanical theory. By analyzing (n,xn) reaction on 232Th and 238U, with the incident energy from 2 Me V to 18 Me V, the importance of multiple pre-equilibrium emission can be seen cleady. All calculated results have been compared with experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other

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

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

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

  1. Uranium content and 235U/238U isotopic ratio in dental porcelain powders determined by neutron activation analysis

    The uranium contents and 235U/238U isotopic ratios in 48 dental porcelain powders of 8 brands marketed in Japan were determined by non-destructive neutron activation analysis. The photopeak counts of 277.6 keV of 239Np formed by the 238U(n,γ)239U (yield to)239Np + β- reaction and at 1.595.2 keV of 140La produced by 235U fission were measured with a Ge(Li) semiconductor detector system to determine the uranium content and 235U/238U isotopic ratio. The results of the analysis are tabulated and their significance discussed. (author)

  2. Preparation of 237U in photonuclear reaction 238U(γ,n) in electron accelerator - microtron MT-25

    237U are obtained in 238U(γ,n) reaction in electron accelerator - microtron MT-25 FLYaR. Radiation yield of 237U is 1 kBq/(mcA h mg 238U). Purification of 237U from fission products is carried out using extraction and ion exchange. Preparation of 237U with specific radioactivity 49500 kBq/mg 238U is prepared. Content of radioactive impurities in preparation does not exceed 10-5. Chemical yield of 237U is 70 %

  3. Spins of resonances in reactions of neutrons with (238)U and (113)Cd. Doctoral thesis; Spins van resonanties in reacties van neutronen met (238)u en (113)cd

    Gunsing, F.

    1994-12-31

    In this thesis experiments are described that have lead to the assignments of spins to a large number of resonances in reactions of epithermal neutrons with the nuclei (238)U and (113)Cd. When a neutron is captured by an atomic nucleus, a compound nucleus is formed which is in a highly excited state with an energy of the order of the neutron binding energy. If the kinetic neutron energy is varied around a state of the compound nucleus, one observes a peak in the cross section. This is called a resonance in the reaction. Dependent on the amount or orbital momentum l that the neutron adds to the system, the resonances are indicated with spectroscopic notations as s- and p-waves for l = 0 and 1 respectively. The purpose of this thesis is to determine the spins of such resonances.

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

    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

  5. 238U removal and accumulation in Concepción bay sediments, Chile

    Laura Farías

    2000-12-01

    Full Text Available Activity profiles of 234U, 238U and 210Pb, as well as the 234U/238U ratio, and 210Pb xs radiochemical parameters and macrobenthic abundance in sediments were measured and calculated at different times during a year (1991, along a transect between the head and the mouth of Concepción Bay, Chile. This bay is a semi-enclosed shallow embayment with a strong seasonality in its hydrographic and biological characteristics due to wind driven upwelling. Upwelling of oxygen-poor and nutrient-rich water occurs and organic detritus reaches the seabed, creating a sub-oxic and anoxic environment during, at least, 57% of the year. 238U and 234U activities in the sediments show a gradual increase from 1.57 to 6.07 dpm g-1 from the surface to 15 cm depth in the sediments. Under suboxic-anoxic conditions, this pattern is consistent with a reduction of U(VI to U(IV and its subsequent removal from pore-water. A 234U/238U ratio of 1.10 ±0.08 indicates an authigenic origen. The 238U accumulation rate and inventory show a significant increase from Station 1 (head of the bay to Station 3 (mouth of the bay from 348 to 794 dpm cm-2 kyr-1 and of 14 to 32 dpm cm-2, respectively. The organic-rich and highly reducing sediments also show an increase in sulphate-reduction rates, sulfur speciation and bioturbation activities of macrobenthos. These patterns suggest that the extent of U enrichment in these sediments is regulated by bacterial sulphate reduction rate and bioturbation and bioirrigation activities. The estimated 238U accumulation rates are higher than those reported for other anoxic environments, representing an important U sink in marine sediments. The geochemical behaviour of U seems to be very sensitive to the redox condition and this characteristic could become an important paleoceanographic tool to identify changes in oceanographic conditions during the last millenniumRemoción y acumulación de 328U en los sedimentos de la bahía de Concepción, Chile. Las

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

    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.

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

    Privas E.

    2016-01-01

    Full Text Available 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.

  8. The inflow of uranium 234U and 238U from the Vistula River catchment area to the Baltic Sea

    In the study, the activities of uranium 234U and 238U in the Vistula River water samples which were collected from November 2002 to October 2003, were measured using alpha spectrometry. In winter, the highest concentration of uranium isotopes and total uranium was in the Vistula River water from Malbork (13.13 ± 0.22 Bq m-3 for 234U, 12.45 ± 0.21 Bq m-3 for 238U and 1.02 ± 0.30 mg m-3 for total uranium), and the lowest was in water from Deblin (1.73 ± 0.07 Bq m-3 for 234U, 1.55 ± 0.07 Bq m-3 for 238U and 0.13 ± 0.09 mg m-3 for total uranium). In analyzed river samples uranium isotopes 234U and 238U are not in the radioactive equilibrium state. The values of 234U/238U activity ratio lie between 1.05-1.70. During spring, the highest concentration of uranium isotopes and total uranium was found in the Vistula River water from Malbork (12.36 ± 0.19 Bq m-3 for 234U, 10.77 ± 0.17 Bq m-3 for 238U and 0.88 ± 0.25 mg m-3 for total uranium), and the lowest was in water taken from Sandomierz (5.77 ± 0.14 Bq m-3 for 234U) and Krakow (4.08 ± 0.11 Bq m-3 for 238U and 0.33 ± 0.18 mg m-3 for total uranium). The values of 234U/238U activity ratio lie between 1.15-1.64. In summer, the highest concentration of uranium isotopes and total uranium was found in the Vistula River water samples taken from Malbork (8.22 ± 0.21 Bq m-3 for 234U, 7.60 ± 0.21 Bq m-3 for 238U and 0.62 ± 0.29 mg m-3 for total uranium), and the lowest was in water from Sandomierz (6.37 ± 0.12 Bq m-3 for 234U) and Krakow (3.56 ± 0.19 Bq m-3 for 238U and 0.29 ± 0.33 mg m-3 for total uranium). The values of 234U/238U activity ratio lie between 1.08-1.95. In autumn the highest concentration of uranium isotopes and total uranium was in the Vistula River water from Malbork (17.80 ± 0.25 Bq m-3 for 234U, 15.12 ± 0.23 Bq m-3 for 238U and 1.23 ± 0.34 mg m-3 for total uranium) and the lowest was in water from Torun (8.15 ± 0.49 Bq m-3 for 234U) and Krakow (6.34 ± 0.47 Bq m-3 for 238U and 0.52 ± 0

  9. Absolute fission rate measurement of 238U induced by 14 MeV neutrons penetrated composite material

    In order to prove the model calculation method and parameter, the 238U absolute fission rate in the case of 14 MeV neutrons penetrating through the special composite material was measured by minitype slab uranium fission chambers. The measuring spots are distributed in the surface of iron ball hull along the different position of equator. The calculated results are compared with the experiment results. The total error of measured 238U absolute fission rate is 6.1%. (author)

  10. Neutron inelastic-scattering cross sections of 232Th, 233U, 235U, 238U, 239Pu and 240Pu

    Differential-neutron-emission cross sections of 232Th, 233U, 235U, 238U, 239Pu and 240Pu 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. 232Th, 233U, 235U and 238U inelastic-scattering values, poor agreement is observed for 240Pu, and a serious discrepancy exists in the case of 239Pu

  11. Transition from asymmetric to symmetric fission in 45-69 MeV proton induced fission of 238U

    H. Noshad

    2007-01-01

    Thin targets of 238U were bombarded with 45, 55, 65 and 69 MeV protons at the Cyclotron and Radioisotope Center (CYRIC) of Tohoku University in Japan. Gamma rays emitted from the fission products were recorded and analyzed by using gamma spectroscopy. Then, the cross sections for the formation of fission products, fragment mass distributions, and total fission cross sections were measured. Special care was taken to make this measurement precisely. The experimental results show that for 238U(p...

  12. Studies on 232Th and 238U levels in marine algae collected from the coast of Niigata Prefecture

    To evaluate the properties of algae to concentrate radioactive elements, 14 species of algae like Sargassum were collected in the Prefecture and analyzed for their 232Th and 238U levels with Yokogawa HP4500 ICP-MS apparatus. The places of collection included those near the water discharge of an atomic power station. Mean 232Th and 238U levels were found to be 120 and 260 ng/g dry wt, respectively, and Phaeophyta showed more than several times higher 238U level than Chlorophyta and Rhodophyta. There was no clear difference in 232Th levels. No difference between places of collection was observed in Sargassum 232Th or 238U level. Adsorption of 232Th particle to and incorporation of soluble 238U into algae body were suggested. Mean 232Th and 238U radioactivities were found 73 and 510 μBq/g wet wt, respectively, and the respective annual committed effective doses, 0.2 and 0.3 μSv, calculated from those values were confirmed to be enough lower than the annual public dose limit, 1 mSv. (K.H.)

  13. 238U-series radionuclides in Finnish groundwater-based drinking water and effective doses

    The thesis deals with the occurrence of 238U-series radionuclides and particle-bound 210Pb and 210Po in Finnish groundwater-based drinking water, methods used for removing 234U, 238U, 210Pb and 210Po, and the annual effective doses caused by 238U-series radionuclides in drinking water. In order to reduce radiation exposure and avoid high doses, it is important to examine the activity levels of natural radionuclides in groundwater. In this work, the activity concentrations of radon (222Rn), radium (226Ra), uranium (238U and 234U), lead (210Pb) and polonium (210Po) were determined from 472 private wells, which were selected randomly from across Finland. On the basis of the results, the activity concentrations in groundwater and the radiation exposure from drinking water of people living outside the public water supply in Finland was specified. The efficiency of 238U, 234U, 210Pb and 210Po removal from drinking water was examined at ten private homes. In order to obtain accurate results and correct estimates of effective doses, attention was paid to the sampling of 222Rn and 210Pb, and the determination of 210Pb. The results revealed that the median activity concentrations of natural radionuclides were as much as ten times higher in drilled wells than in wells dug in soil. The average activity concentration of 222Rn in drilled wells was 460 Bq/l and in dug wells 50 Bq/l. The highest activity concentrations were found in Southern Finland. In addition, occasional high activity concentrations were found all over Finland. The average activity concentrations of 234U and 238U in drilled wells were 0.35 and 0.26 Bq/l and in dug wells 0.020 and 0.015 Bq/l, respectively. The spatial distribution of 234U, 238U, 210Pb and 210Po was essentially similar to that of 222Rn. In contrast to other natural radionuclides, the highest 226Ra activity concentrations were found in coastal areas, since drilled well water near the sea has a higher salinity than water in drilled wells inland

  14. Multifragmentation for 36Ar+238U treated as statistical dynamic interaction processes

    The exclusive multifragment multiplicities for the system 36Ar+238U at 35 MeV/nucleon incident energy are calculated using the Boltzmann master equation for the fast cascade, and the Weisskopf-Ewing evaporation model for successive binary decay of the equilibrated residues. These calculated results are consistent with the experimental results of Kim et al. We show that the multiplicity distribution in such a model has a sensitivity to the equilibrated excitation, so that multiplicity could be an observable characteristic of excitation. This in turn may be used to infer time delay for fragment emission (in a model dependent way)

  15. Photo-fission of 232Th and 238U at intermediate energies

    Deppman, A.(Universidade de São Paulo (USP), São Paulo, Brazil); Andrade-II, E.; Guimaraes, V.; Demekhina, N. A.; Karapetyan, G. S.

    2013-01-01

    In this work we present an analysis of the yields of fission fragments induced by bremsstrahlung photons with endpoint energies of 50 and 3500 MeV on 232Th and 238U targets using the simulation code CRISP. A multimodal fission option was added to this code and an extension of the calculation to the properties of the fission products is presented. By dividing the fissioning nuclei according to their fissionability, an approach is introduced which accounts for the contribution of symmetric and ...

  16. The evaluation of the mass distribution data for 238U, 239Pu and 242Pu fission

    The mass distribution data for 238U at En=1.5, 5.5, 8.3, 11.3, 14.9, 22.0, 27.5, 50.0, 99.5, 160.0 MeV, Ep=20.0, 60.0 MeV 239Pu at En=0.17, 7.9, 14.5 MeV and 242Pu at En=15.1 MeV were evaluated and recommended based on the main available experimental data up to now. The experimental data were make necessary corrections and their errors were also made necessary adjustments. The problems concerned were discussed

  17. Evaluation of resonance self-shielding factors for 238U in the unresolved resonance region

    On the basis of a theoretical model of identical equidistant resonances for the energy dependence of cross-sections in the unresolved resonance region, the authors have parametrized the values of the resonance self-shielding factors and their Doppler increments for 238U. They have proposed a method by which the Doppler increments of the self-shielding factors can be calculated from simple analytical formulae by redetermination of the model parameters. Analysing the experimental data on direct and capture transmissions in the unresolved resonance region, they demonstrate the possibility of describing those data as a whole and of deriving from them the cross-section group functionals. (author)

  18. Fission product yields from 19.1 MeV neutron induced fission of 238U

    36 chain yields were determined for the fission of 238U induced by 19.1 MeV neutrons for the first time. Absolute fission rate was monitored with a double-fission chamber. Fission product activities were measured by HPGe γ-ray spectrometry. Threshold detector method was used to measure the neutron spectrum in order to estimate the fission events induced by break-up neutrons and scattering neutrons. A mass distribution curve was obtained and the dependence of fission yield on neutron energy was discussed

  19. Angular distribution of photofission fragments in 238U at 5.43 MeV

    The angular distribution of photofission fragments of 238U, produced by 5.43 MeV monochromatic photons from the η,γ reaction in sulphur, has been measured using glass plates as detectors. In the analysis of the results only the contributions from the (Jπ, K) 1= (1-,0), (1-,1) and (2+,0) terms were considered. The coefficients of the angular distributions of the fission fragments were obtained. An analysis of the data available in the literature on the angular distribution near the photofission threshold is also presented. (author)

  20. Effect of energy self-shielding methods on 238U for criticality safety problems

    Multigroup cross sections are obtained by weighting point-wise nuclear data with a flux spectrum. For nuclides having a resonance structure, energy self-shielding calculations are performed to calculate a more detailed flux spectrum. Subsequently, self-shielded multigroup cross sections are generated. Different methods exist for energy self-shielding calculations. Among them are the Bondarenko method, the NJOY flux calculator, and the CENTRM method. The CENTRM method is a more advanced technique that utilizes both multigroup and point-wise cross sections in a one-dimensional transport calculation to solve for a point-wise flux distribution. The method of energy self-shielding is one of the elements in a multigroup cross-section generation that may have a significant impact on the multiplication factor in criticality safety calculations. This paper compares the three aforementioned self-shielding methods applied to 238U. A criticality problem having 23 cases is considered. This system includes water-moderated, low-enriched UO2 fuel rods in square-pitched array, with a thermal flux spectrum. Multiplication factors obtained from transport calculations that use multigroup and continuous energy data are compared. It is observed that multiplication factors calculated with multigroup data containing different self-shielding methods for 238U have less than 500 pcm difference with continuous energy results. (authors)

  1. The dependence of cumulative 238U(n,f) fission yield on incident-neutron energy

    ZHENG Na; ZHONG Chunlai; MA Liyong; CHEN Zhongjing; LI Xiangqing; LIU Tingjin; CHEN Jinxiang; FAN Tieshuan

    2009-01-01

    This work is aim at studying the dependence of fission yields on incident neutron energy,so as to produce evaluated yield sets of the energy dependence.Experimental data at different neutron energies for gas fission products 85m,87,88Kr and 138Xe resulting from the 238U(n,f) reaction are processed using codes AVERAGE for weighed average and ZOTT for simultaneous evaluation.Energy dependence of the cumulative fission product yields on the incident neutron is presented.The evaluated curve of product yield is compared with the results calculated by the TALYS-0.64 code.The present evaluation is consistent with other main libraries in error permission.The fit curve of 87,88Kr can be recommended to predict the unmeasured fission yields.Comparisons of the evaluated energy dependence curves with theoretical calculated results show that the predictions using purely theoretical model for the fission process are not sufficiently accurate and reliable for the calculations of the cumulative fission yields for the 238U(n,f).

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

    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 230Th was preferentially retained over either 234U or 238U 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 234U and 238U 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 230Th. 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 230Th in ore dust is questioned

  3. Total kinetic energy distribution of fission fragments in 6,7Li + 238U reactions

    The shape and width of fission-fragment (FF) mass and kinetic energy distribution provides a lot of information on the fission reaction mechanism and the structure of the compound nucleus (CN), the fragments as well as the interacting nuclei. The shape of the mass distribution of the fission fragments for the actinides induced by the proton or neutron is known to change with the incident energy. At low energies, it shows a double humped distribution which changes slowly to a single humped distribution as energy increases. However, for a reaction involving a weakly bound projectile (i.e., 6Li + 232Th), a sharp change in the shape of the mass distribution with energy was observed. The sharp increase in the peak to valley ratio (P:V) in the fission-fragment mass distribution in 6Li + 232Th reaction by Itkis et al. and in 6,7Li + 238U reactions by Santra et al. was concluded to be due to the reduced energy transfer to the composite system caused by incomplete fusion (ICF) of alpha or deuteron/triton followed by fissions. Total Kinetic Energy (TKE) distribution of fission fragments is another important observable on which the effect of projectile breakup is not explored yet. In this contribution, the study of breakup/transfer effect on average TKE distribution for 6,7Li + 238U reactions is presented

  4. Determination of specific concentrations of 40K, 238U and 232Th in mineral fertilizer samples

    The use of fertilizer is an established practice worldwide to promote agricultural productivity increased without increasing the planted area, resulting in native forests protection and increase of the food availability. Some kinds of fertilizer have in their chemical composition some radionuclides due the origin of its feedstock, such as 238U, the 232Th, and their descendants, beyond 40K. Knowledge of the radioactivity levels in the environment is great importance to know the gamma radiation dose that the human being is exposed. For identification and quantitation of radionuclides, it was used gamma spectrometry where HPGe detector was used to obtain the spectra, and LabSOCS software for calculating the detection efficiency for each energy. The values of 232Th specific concentrations ranged from 4.1 to 368.1 Bq.Kg-1, the values of 238U specific concentrations ranged from 16.0 to 647.7 Bq.Kg-1 and 40K specific concentrations ranged from 19.1 to 12713 Bq.Kg-1. Concentrations of values are consistent with those found in literature. (author)

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

    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.

  6. Natural activities of 238U, 232Th and 40K in building materials

    Seven kinds of building materials were analysed for 238U, 232Th and 40K using a direct γ-counting method. The activity concentrations measured for 238U (30-448 Bq kg-1) and 40K (328-7541 Bq kg-1) were greater than the world average activity for soil (25 and 370 Bq kg-1, respectively) for all building materials analysed, while the activity concentrations of 232Th were found to exceed the average of 25 Bq kg-1 (soil) for red-clay brick (51 Bq kg-1) and ceiling asbestos sheet materials (162 Bq kg-1). The calculated Ra equivalent activities (Raeq) for all materials are higher than the world average value for soil (89 Bq kg-1). For red-clay brick and ceiling asbestos, the Raeq values are found to exceed the limit of 370 Bq kg-1, equivalent to a γ-dose of 1.5 mSv yr-1. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  7. Measurement of radiative capture cross section on 238U at the nTOF CERN facility

    The need of sources of energy different from fossil fuels is nowadays a crucial point. As the EU-SET Plan points out, it is necessary to investigate new concepts for nuclear systems to improve the sustainability of nuclear energy. These concepts cover from energy production, through both advanced light water reactors and fast reactors foreseen in generation IV, to minimization and discharge of nuclear waste through subcritical fast systems (ADS). Despite many previous measurements and recent efforts, the present knowledge of basic nuclear data is still inadequate to fulfill the precision and accuracy required for the design and development of these new technologies. In this context the Nuclear Energy Agency addresses the most relevant isotopes, decay data, nuclear reaction channels and energy ranges that have to be investigated in more detail in the NEA High Priority Request List. The measurement of 238U(n,g) reaction cross section falls within this list because of its importance for the security of operating light water reactors and the design of generation IV reactors. Even if the number of measurements present in the EXFOR database is large, inconsistencies are still present for the 238U capture cross section both in the low energy and in the unresolved resonance region. This uncertainty influences both fast and thermal reactor systems, and contributes to the uncertainty on Pu isotope density at the end of fuel cycles. As such, there is a proposal of three independent measurement of the 238U(n,g) cross section in order to reach the required precision of 2% within an energy range from few eV to hundreds of keV. One measurement was performed at the EC-JRC-IRMM facility GELINA, while the other two at the nTOF facility at CERN. Combined together they should lead to the desired accuracy. Here the preliminary results of the 238U(n,g) cross section measurement are presented, which was performed at nTOF with C6D6 scintillation detectors on April 2012 and covers an

  8. State of disequilibrium between 238U, 234U, 226Ra and 222Rn in groundwater from bedrock

    Approximately one thousand drilled wells were investigated for their natural radioactivity. The determinations of 238U, 234U, 226Ra and 222Rn from 310 samples showed a high state of radioactive disequilibrium between the members of the uranium series present in water. The 238U/226Ra activity ratio usually fell in the range 1 to 20 and the 238U/222Rn activity ratio in the range 1 to 20 x 10-4, the highest activity ratios being from samples with an elevated uranium content. The 234U/238U activity ratio varied between 0.76 and 4.67, the most frequent values showing a 60% excess of 234U in the samples. Most of the 234U/238U activity ratios near unity were found in samples with a high uranium content. Several drilled wells with anomalously high uranium contents were found in southern Finland. The average 226Ra and 222Rn contents of these wells were not exceptionally high, which suggests high mobility of uranium in groundwater from the areas involved. (author)

  9. High-precision determination of 234U/238U activity ratios in natural waters and carbonates by ICPMS

    A method has been developed for precise measurement of 234U/238U activity ratios in natural waters and carbonates using quadrupole inductively coupled plasma mass spectrometry. A recovery of 80--85% of seawater U is achieved by Fe(III) coprecipitation followed by extraction chromatography with a supported dipentyl pentane phosphonate material; 90--95% of U is recovered from carbonates, which are dissolved in HNO3 and subjected to the same extraction chromatographic preparation. Isotopic measurements are made via recirculating pneumatic nebulization of small volumes of solutions containing 0.5--5 mg/L U. 234U/235U is measured as a proxy for determination of 234U/238U; iridium is added to sample solutions and the ion ratio 191Ir40Ar+/193Ir40Ar+ is measured for internal mass discrimination correction 234U/238U activity ratios in the range 1.143--1.154 are observed for 13 seawater and contemporary corals, in agreement with the established marine 234U/238U activity ratio. For samples sizes of 5--25 microg U, ICPMS uncertainties of ± 0.2--0.5% relative, 2θ standard error, approach those obtained for 234U/238U activity ratios in bottled waters, Lake Erie surface waters, mollusk fossils, and fertilizers are also demonstrated

  10. Analysis of 209 Bi and 238 U photofission cross section in the quasi-deuteron region of photonuclear absorption

    An analysis of the photofission reactions in the quasi-deuteron energy range of photonuclear absorption (∼ 30-140 MeV) has been performed for 209 Bi and 238 U nuclei. Experimental cross section data available in the literature have been compared with calculated values obtained from a model in which the incoming photon is assumed to be absorbed by a neutron-proton pair (Levinger's quasi-deuteron photoabsorption), followed by a mechanism of evaporation-fission competition for the excited residual nuclei. The model has been shown to reproduce the main experimental features of 209 Bi and 238 U photofission cross section, although unexplained differences still remain in the case of 238 U-fission by 30-50 MeV incident photons. (author). 49 refs, 10 figs, 2 tabs

  11. Production of $^{237}$U in the $^{238}$U ($\\gamma, n$) photonuclear reaction at the electron accelerator MT-25 microtron

    Sabelnikov, A V; Gustova, M V; Belov, A G; Dmitriev, S N

    2004-01-01

    $^{237}$U was obtained in the $^{238}$U($\\gamma, n$) reaction at the electron accelerator MT-25 microtron of the FLNR of the JINR. The $^{237}$U radiation yield under experimental conditions amounted to 1 kBq/$\\mu $A$\\cdot $h$\\cdot$mg $^{238}$U. Capture of recoil atoms in a solid-solid system was used for isolation of $^{237}$U from the target material. Fluorides of chemical elements from I-III series of the Periodic Table of the Elements were used as $^{237}$U acceptors. The $^{237}$U isolation from radioactive impurities was realized by means of extraction and ion exchange. Specific activity of the $^{237}$U preparation was equal to 49500 kBq/mg $^{238}$U. The radioactive impurity content did not exceed 10$^{-6}$ Bq/Bq. The $^{237}$U chemical yield amounted to 70{\\%}.

  12. 238U-230Th-226Ra radioactive disequilibria in the products from 1707 eruption of Fuji volcano, Japan

    Time scale of magmatic processes in the 1707 eruptive activity of Fuji volcano, Japan, was estimated by the 238U-230Th-226Ra disequilibria observed in the 1707 volcanic products. The activity ratios of 226Ra/230Th in the products were larger than unity, being enriched in 226Ra relative to 230Th. The decay-corrected 226Ra/230Th activity ratio to the time of the eruption versus 238U/230Th activity ratio diagram for the 1707 volcanic products showed a positive correlation, suggesting that the 238U/230Th-226Ra disequilibria occurred during the magma genesis of Fuji volcano. The 230Th-226Ra disequilibria in the 1707 volcanic products suggested that the time scale from the magma genesis to the eruption, including the melting of the mantle wedge, magma storage and magmatic differentiation from basalt to andesite, was less than 8000 years. (author)

  13. 238U, 234U, 226Ra, 210Po concentrations of bottled mineral waters in Italy and their dose contribution

    Due to the importance of bottled mineral water in human diet with special regard to children in lactation period, a monitoring of natural radioactivity in some bottled mineral waters produced in Italy was performed. Gross alpha and beta activities and 226Ra, 238U, 234U, and 210Po concentrations were measured. Gross alpha and beta activities were determined by standards ISO 9696 and ISO 9697; for 226Ra determination liquid scintillation was used. The 238U and 234U concentrations were determined by alpha spectrometry after their separation from matrix by extraction chromatography and electroplating. 210Po was measured by alpha spectrometry. The results revealed that the concentrations (mBq L-1) of 226Ra, 238U, 234U, and 210Po ranged from -1; for infants (-1

  14. Verification tests on nondestructive assay for 238U content in uranium-contaminated waste drums using gamma method

    We have proposed a new theory on gamma assay for 238U determination of uranium-contaminated waste drums. According to this theory, regardless of the inhomogeneity of waste matrix density or uranium source distribution, we can accurately determine the amount of 238U contained in drums nondestructively using count rates of gamma rays of two energies(1001keV and 766keV) emitted from 238U progeny nuclide 234mPa. In this paper, we have verified the theory by tests under various waste conditions made by simulated waste drums. We have estimated the relative error to be less than 20%, and the detection limit to be 1.2Bq/g when the specific activity of uranium is 25000Bq/g, in these cases. We have confirmed that this new assay system is efficient for the rational classification of uranium wastes to be disposed of. (author)

  15. Performance evaluation of indigenous thermal ionization mass spectrometer for determination of 235U/238U atom ratios

    A magnetic sector based Thermal Ionization Mass Spectrometer (TIMS) designed and developed at Technical Physics Division, B.A.R.C., was evaluated for its performance for the determination of 235U/238U atom ratios in uranium samples. This consisted of evaluating the precision and accuracy on the 235U/238U atom ratios in various isotopic reference materials as well as indigenously generated uranium samples. The results obtained by the indigenous TIMS were also compared with those obtained using a commercially available TIMS system. The internal and external precision were found to be around 0.1% for determining 235U/238U atom ratios close to those of natural uranium ( i.e. 0.00730). (author)

  16. Precise measurements of 234U/238U and U concentrations in profiles of Pacific and Atlantic waters

    High precision measurement of 234U/238U ratios and U concentrations in profiles of Atlantic and Pacific waters have been made in order to determine the degree of heterogeneity of these parameters in the open ocean. The measurements were made possible by the development of mass spectrometric techniques to measure 234U/238U to +/- ∼ 5 per thousand (2σ) and U concentrations to +/- 2 per thousand with 2-5 x 109 atoms of 234U. A 233U-236U double spike is used to correct for instrumental mass fractionation. The average 234U/238U for 4 samples from the Pacific profile is 144 +/- 4 per thousand higher than the equilibrium atomic 234U/238U ratio (5.47 x 10-5). The average for 5 samples in the Atlantic profile is identical (144 +/- 4 per thousand). A comparison of 234U/238U values for samples above and below the thermocline shows similar homogeneity. U concentrations normalized to 35 per thousand salinity are the same within ∼ 1% (3.215 +/- 6 to 3.257 +/- 6 ppb) but clearly show variation greater than the +/- 2 per thousand error. The reason for this fine scale variation requires further investigation. The authors data suggest that 234U/238U in the open ocean is homogeneous to within 8 per thousand. This is consistent with the long residence time of U and the long 234U half life compared to the residence time of water in the deep ocean. Similar measurements on marine pore fluids which can easily be done using the authors technique should provide constraints on the U flux across the sediment-water interface

  17. Charge-stripping system for 238U ion beam with recirculating He gas

    Recent developments in a charge-stripping system employing high-flow rate He gas circulation (∼200 L/min) for 238U35+ beams injected at 10.8 MeV/u are reported. He gas is confined in a target section and is separated from a vacuum duct using five-stage differentially-pumped sections. To minimize the gas leakage rate via beam apertures, a high-performance differential pumping was required. To avoid huge gas consumption, a clean gas recycling with high-flow rate was simultaneously required. To realize these, we developed multi-stage mechanical booster pump array. The recycling rate of He gas was achieved as more than 99 %. The system performance has been checked with the present maximum beam current up to 13 eμA (∼1 kW beam power). (author)

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

    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. (authors)

  19. Dielectric constant/ loss behaviour of high energy 238U ion irradiated polymer liquid crystal

    Dielectric constant/loss behaviour in high energy 238U (11.6 MeV/n) ion irradiated poly (P-hydroxy benzoic acid-co-ethylene terephthalate) PET/ x.PHB (x is the molar concentration) has been investigated. The observations were made at temperature ranging from 20 to 250 degC at the frequencies 120Hz, 1kHz, 10kHz and 100kHz by using Keithley precession LCZ meter. PET rich phase has been affected drastically by high energy heavy ion irradiation as the dielectric constant is suppressed in contrast to sharp increase in dielectric constant between 40 to 100 degC in pristine PET. The appearance of few kinks in the low temperature region due to decomposition of carboxyl group is evident in high energy heavy ion irradiated 0.7 PHB. (author)

  20. Nuclear model calculation on neutron induced fission fragment mass yields of 238U

    The fission fragment mass yield is one of the most important characteristics of the fission process in both applications and basic nuclear physics. In nuclear energy applications, the configuration of fission products must be known because they are accumulated during the operation of a nuclear reactor. In theoretical physics, the ability to describe and predict fission yields is required for an effective nuclear fission model. Since the nuclear fission process is described by a great number of parameters, and the existing theoretical models fail to describe the fission process completely, the fission yields are amongst the most important consequences to benchmark the validity of fission models. In the present study, two different approaches to predict the neutron-induced fission fragment mass distribution of 238U has been applied. The first approach is temperature dependent Brosa model, and the other based on GEF model. The model-based predicted results are in good agreement with the experimental data

  1. Tests of the 238U+n evaluation for JEF-2 in the unresolved resonance region

    During the JEF-2 test phase the new evaluation for 238U+n in the unresolved resonance region (adopted for JEF-2 up to 200 keV, for ENDF/B-VI up to 149 keV) has been checked against recent capture cross section measurements and against thick-sample transmission data and capture self-indication ratios. Effects of the unresolved resonance structure on self-shielding and multiple scattering were treated by Monte Carlo techniques based on resonance statistics and average resonance parameters. It was found that the average cross sections and the average resonance parameters given in the new evaluation permit very satisfactory reproduction of all the test data. The resonance-averaged capture cross sections below 200 keV appear now to be known with roughly 2% uncertainty. (orig.)

  2. Measurement of capture cross sections of 238U on the filtered keV-neutron beams

    Capture cross sections for the 238U(n,γ) reaction were measured related to that of the 197Au(n,γ) reaction on the filtered keV-neutron beams at the Dalat reactor using the activation method. Radioactivities of samples after irradiation were measured with HPGe detectors (50 mm2 sensitive area, FWHM = 150 eV for 55Fe and 70 cc volume, FWHM = 2.5 keV at 1332 keV γ-transition of 60Co). The data obtained by the authors were compared with the evaluations in ENDF/B-VI and JEF-2 and also with the results from recent experimental works. (author). 12 refs, 1 fig., 4 tabs

  3. Two-phonon giant resonances in 136Xe, 208Pb, and 238U

    The excitation of the double-phonon giant dipole resonance was observed in heavy projectile nuclei impinging on targets of high nuclear charge with energies of 500-700 MeV/nucleon. New experimental data are presented for 136Xe and 238U together with further analysis of earlier data on 208Pb. Differential cross sections dσ/dE* and dσ/dθ for electromagnetic excitations were deduced. Depending on the isotope, cross sections appear to be enhanced in comparison to those expected from a purely harmonic nuclear dipole response. The cumulative effect of excitations of two-phonon states composed of one dipole and one quadrupole phonon, of predicted anharmoniticies in the double-phonon dipole response, and of damping of the dipole resonance during the collision may account for the discrepancy. In addition, decay properties of two-phonon resonances were studied and compared to that of a statistical decay. (orig.)

  4. 238U/235U determinations of some commonly used reference materials and U-bearing accessory minerals (Invited)

    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

  5. Transition from asymmetric to symmetric fission in 45-69 MeV proton induced fission of 238U

    H. Noshad

    2007-03-01

    Full Text Available Thin targets of 238U were bombarded with 45, 55, 65 and 69 MeV protons at the Cyclotron and Radioisotope Center (CYRIC of Tohoku University in Japan. Gamma rays emitted from the fission products were recorded and analyzed by using gamma spectroscopy. Then, the cross sections for the formation of fission products, fragment mass distributions, and total fission cross sections were measured. Special care was taken to make this measurement precisely. The experimental results show that for 238U(p, f reaction at Ep > 65 MeV, the asymmetry component in the mass distribution is eliminated, and the symmetric fission remains the dominant fission mode.

  6. Radioactivity of Natural Nuclides (40K, 238U, 232Th, 226Ra) in Coals from Eastern Yunnan, China

    Xin Wang; Qiyan Feng; Ruoyu Sun; Guijian Liu

    2015-01-01

    The naturally occurring primordial radionuclides in coals might exhibit high radioactivity, and can be exported to the surrounding environment during coal combustion. In this study, nine coal samples were collected from eastern Yunnan coal deposits, China, aiming at characterizing the overall radioactivity of some typical nuclides (i.e., 40K, 238U, 232Th, 226Ra) and assessing their ecological impact. The mean activity concentrations of 238U, 232Th, 40K and 226Ra are 63.86 (17.70–92.30 Bq· kg-...

  7. Assessment of environmental radioactivity (238U, 232Th and 40K) and radiological mapping of Tata Nagar city (Jharkhand), India

    Study on the natural radioactivity concentration levels (238U, 232Th and 40K) in soil samples of Tata Nagar city obtained from seven locations at Tata Nagar city, India was undertaken and the results of the same are reported. In addition, radiological mapping of natural background gamma radiation levels was carried out throughout Tata Nagar city using vehicle based Mobile monitoring technique and the same is presented here. The activity concentrations were assayed and estimated for 238U, 232Th and 40K isotopes in Bq/Kg, using gamma ray spectrometry and the radiation dose rates were estimated. (author)

  8. Measurement of nuclide cross-sections of spallation residues in 1 A GeV 238U + proton collisions

    The production of heavy nuclides from the spallation-evaporation reaction of 238U induced by 1 GeV protons was studied in inverse kinematics. The evaporation residues from tungsten to uranium were identified in-flight in mass and atomic number. Their production cross-sections and their momentum distributions were determined. The data are compared with empirical systematics. A comparison with previous results from the spallation of 208Pb and 197Au reveals the strong influence of fission in the spallation of 238U. (orig.)

  9. 234Th/238U disequilibrium and particulate organic carbon export in the northern South China Sea

    We utilized 234Th, a naturally occurring radionuclide, to quantify the particulate organic carbon (POC) export rates in the northern South China Sea (SCS) based on data collected in July 2000 (summer), May 2001 (spring) and November 2002 (autumn). Th-234 deficit was enhanced with depth in the euphotic zone, reaching a sub-surface maximum at the Chl-a maximum in most cases, as commonly observed in many oceanic regimes. Th-234 was in general in equilibrium with 238U at a depth of ∼100 m, the bottom of the euphotic zone. In this study the 234Th deficit appeared to be less significant in November than in July and May. A surface excess of 234Th relative to 238U was found in the summer over the shelf of the northern SCS, most likely due to the accumulation of suspended particles entrapped by a salinity front. Comparison of the 234Th fluxes from the upper 10 m water column between 2-D and traditional 1-D models revealed agreement within the errors of estimation, suggesting the applicability of the 1-D model to this particular shelf region. 1-D model-based 234Th fluxes were converted to POC export rates using the ratios of bottle POC to 234Th. The values ranged from 5.3 to 26.6 mmol C m-2d-1 and were slightly higher than those in the southern SCS and other oligotrophic areas. POC export overall showed larger values in spring and summer than in autumn, the seasonality of which was, however, not significant. The highest POC export rate (26.6 mmol C m-2d-1) appeared at the shelf break in spring (May), when Chl-a increased and the community structure changed from pico-phytoplankton (<2 μm) dominated to nano-phytoplankton (2-20 μm) and micro-phytoplankton (20-200 μm) dominated. (author)

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

    Ahmad, I.; Back, B.B.; Betts, R.R. [and others

    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.

  11. 238 U, 232 Th and 40 K in wheat flour samples of Iraq markets

    Ali Abid Abojassim

    2015-05-01

    Full Text Available Introduction. Wheat flour is a nutritious type of food that is widely consumed by various age groups in Iraq. This study investigates the presence of long-lived gamma emitters in different type of wheat flour in Iraqi market. Materials and methods. Uranium (238 U, Thorium (232 Th and Potassium (40 K specific activity in (Bq/kg were measured in (12 different types of wheat flours that are available in Iraqi markets. The gamma spectrometry method with a NaI(Tl detector has been used for radiometric measurements. Also in this study we have calculated the internal hazard index, radium equivalent and absorbed dose rate in all samples. Results and discussion. It is found that the specific activity in wheat flour samples were varied from (1.086±0.0866 Bq/kg to (12.532±2.026 Bq/kg with an average (6.6025 Bq/kg for 238 U, For 232 Th From (0.126±0.066 Bq/kg to (4.298±0.388 Bq/kg with an average (1.9465Bq/kg and for 40 K from (41.842±5.875 Bq/kg to (264.729±3.843 Bq/kg with an average (133.097 Bq/kg. Also, it is found that the radium equivalent and the internal hazard index in wheat flour samples ranged from (3.4031 Bq/kg to (35.1523 Bq/kg with an average (19.6346 Bq/kg and from (0.0091 to (0.1219 with an average (0.0708 respectively. Conclusion. This study prove that the natural radioactivity and radiation hazard indices were lower than the safe.

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

    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.

  13. 238 U, 232 Th and 40 K in wheat flour samples of Iraq markets

    A. A.

    2014-09-01

    Full Text Available Introduction. Wheat flour is a nutritious type of food that is widely consumed by various age groups in Iraq. This study investigates the presence of long-lived gamma emitters in different type of wheat flour in Iraqi market. Materials and methods. Uranium ( 238 U, Thorium ( 232 Th and Potassium ( 40 K specific activity in (Bq/kg were measured in (12 different types of wheat flours that are available in Iraqi markets. The gamma spectrometry method with a NaI(Tl detector has been used for radiometric measurements. Also in this study we have calculated the internal hazard index, radium equivalent and absorbed dose rate in all samples. Results and discussion. It is found that the specific activity in wheat flour samples were varied from (1.086±0.0866 Bq/kg to (12.532±2.026 Bq/kg with an average (6.6025 Bq/kg for 238 U, For 232 Th From (0.126±0.066 Bq/kg to (4.298±0.388 Bq/kg with an average (1.9465Bq/kg and for 40 K from (41.842±5.875 Bq/kg to (264.729±3.843 Bq/kg with an average (133.097 Bq/kg. Also, it is found that the radium equivalent and the internal hazard index in wheat flour samples ranged from (3.4031 Bq/kg to (35.1523 Bq/kg with an average (19.6346 Bq/kg and from (0.0091 to (0.1219 with an average (0.0708 respectively. Conclusion. This study prove that the natural radioactivity and radiation hazard indices were lower than the safe.

  14. Application of Energy Window Concept in Doppler Broadening of 238U Cross Section

    Currently, the NJOY code is used for construction and Doppler broadening of microscopic cross sections. There exist several methods or formalisms to produce microscopic cross sections and there are also different methods of Doppler broadening. In this paper, Multi-Level Breit-Wigner (MLBW) formalism and the Psi method are used for generation and Doppler broadening of the resonance cross section. Accuracy of the energy window concept applied MLBW (EW MLBW) Doppler broadened cross section was compared with that of the cross section generated by conventional MLBW (Con MLBW) formalism for 238U isotope using MATLAB. The conventional method requires Doppler broadening of all resonances, including resonances far from the target energy point, which do not change much with respect to the temperature change. The energy window concept makes Doppler broadening possible with a smaller number of resonances neighboring to the energy point we are interested in, and just adds up 0 K temperature cross sections of other resonances. Multi-level Breit-Wigner formalism and the Doppler broadening method were used to construct microscopic cross sections of 238U at different temperatures. The energy window concept was applied only for the 1st resonance energy region (4.5∼11.2 eV). The energy window concept demonstrates high competitiveness because the relative differences were less than 0.0016% for all types of cross sections. The advantage of the energy window concept is that the number of resonances broadened for every energy point is significantly reduced, which allows a reduction of computation time by almost 45 % of Doppler broadening time of the cross section generation at temperatures higher than 0 K

  15. Measurement of Fragment Mass Distributions in Neutron-induced Fission of 238U and 232Th at Intermediate Energies

    Conceptual analysis of accelerator-driven systems assumes extensive use of nuclear data on neutron-induced reactions at intermediate energies. In particular, information about the fission fragment yields from the 238U(n,f) and 232Th(n,f) reactions is of particular interest at neutron energies from 10 to 200 MeV. However, there is a lack of such data for both 238U and 232Th. Up to now, the intermediate energy measurements have been performed for 238U only, and there are no data for the 232Th(n,f) reaction. The aim of the work is to provide such data. Fission fragment mass distributions for the 232Th(n,f) and 238U(n,f) reactions have been measured for the incident neutron energies 32.8 MeV, 45.3 MeV and 59.9 MeV. The experiments have been performed at the neutron beam facility of the Universite Catholique de Louvain, Belgium. A multi-section Frisch-gridded ionization chamber has been used as a fission fragment detector. The data obtained have been interpreted in terms of the multimodal random neck-rupture model (MMRNRM). (authors)

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

    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.

  17. The effect of the 238U neutron strength function uncertainty on resonance structure calculations in unresolved regions

    The effects of the neutron strength function uncertainties on the calculated values of the self-shielding factors and energy dependence of the total and capture 238U cross-sections in the unresolved resonance region are investigated. (author). 26 refs, 5 figs

  18. Concentration of 238U and 232Th among constituent minerals of two igneous plutonic rocks exhibiting elevated natural radioactivity levels

    The concentrations of 238U and 232Th of the constituent minerals in two plutonic rock samples, from N. Greece, exhibiting elevated levels of bulk rock natural radioactivity were determined by using LA-ICP-MS. The available data of whole rock 238U and 232Th concentrations were also used. The minerals were separated using a combination of heavy liquids of various densities, shaking table and magnetic separation techniques. The great variation in the concentrations of 238U and 232Th is probably indicative of the different distribution of U and Th within the same rock, as well as to secondary post-magmatic processes that were responsible for the redistribution of U and Th. An estimation of the contribution of each mineral constituent to the natural radioactivity levels of the bulk rock is attempted. Thorite and zircon contribute the most to the whole rock 238U and 232Th content, while the contribution of apatite is moderate. The contribution of the rest of the minerals examined (fluorite, quartz, plagioclase, K-feldspar, amphibole, pyroxene, magnetite and biotite) is not important. (author)

  19. Cross sections of barium isotopes in the interaction of 60 MeV/nucleon 18O with 238U

    Barium isotopes were produced by 60 MeV/u 18O ion bombardment of natural uranium via 238U (18O, X) reactions. Ba sources were prepared by radiochemical separation, and measured by a HPGe detector. The cumulative cross sections were obtained by analysis of measured time sequence γ-ray spectra. A double peak phenomenon in Ba isotope distribution was observed. (author)

  20. Feasibility study of measuring the 238U fission rates by neutrons of 14 MeV in specifical experiment condition

    Using uranium fission chambers of minitype slab in the case of 14 MeV neutrons penetrating through the special experiment model, the pure 238U absolute fission rates are measured. Comparing the measurement results with and without reflect shell, the reflect coefficient of shell is gained. The calculate results are compared with experiment results, to prove the model calculate method and parameter. (author)

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

    The radioactivities of 238U and 226Ra 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 238U and 226Ra 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. - Highlights: • A portable HPGe was used in the field to quantify 238U and 226Ra in mill tailings. • 238U and 226Ra quantification was performed on samples with strong radioactive disequilibrium. • HPGe measurements are compared with results obtained on the same samples by ICP-AES and emanometry. • We show the vertical distributions of U and 226Ra measured in two ∼30 m mill tailings piles. • Portable HPGe can be used directly in the field to observe slight variations of content

  2. Determination of the isotopic ratio 235U/238U in UF6 using quadrupole mass spectrometry

    In this work measurements of isotope ratios 235U / 23'8U in uranium hexafluoride are carried out using a quadrupole mass spectrometer. The operational parameters, which affect the final precision of the results, are standardized. Optimized procedures for the preparation of uranium hexafluoride samples by fluorination of uranium oxides using cobalt trifluoride method are established. Careful attention is given to the process of purification of uranium hexafluoride samples by fractional distillation. Adequate statistical methods for analysing the results obtained for single ratio measurements as well as the ratio ' of isotopic ratios of sample and standard ar.e developed. A precision of about 10-4 for single ratio measurements and accuracy of about 0,3% for the ratio of sample and standard ratios are obtained. These results agree with the values which have been obtained using magnetic mass spectrometers. The procedures and methods established in this work can be employed in the systematic uranium isotope analysis in UF6 form. (author)

  3. Evaluation of correlating factors between 238U concentration measured in fine and course atmospheric particles

    Air quality is ever more important in function of the enormous proportion of human actions that have affected the environment over the last two centuries. Particulate material is one among many pollutants that can cause great risk to human health and the environment. It can be classified as: Total Suspended Particles (TSP), defined simply as particles with less than 50 μm aerodynamic diameter (one group of these particles can be inhaled and may cause health problems, while others may unfavorably affect the population's quality of life, interfering in environmental conditions and impairing normal community activities); and Inhalable Particles (PM10), defined as those particles with less than 10 μm aerodynamic diameter. These particles penetrate the respiratory system and can reach pulmonary alveoli due to their small size, causing serious health damage. The Nuclear Technology Development Center (CDTN) has monitored air quality around its installations since 2000. CDTN's Environmental Monitoring Program (EMP) includes monitoring radioactivity levels contained in atmospheric TSP. In order to optimize its program, CDTN is carrying out a study to estimate the correlation between concentrations of particulate material measured in TSP and those measured in PM10, PI2.5 and PI1, as well as determination of activity concentration for each controlled radionuclide in all parts. The objective of this study is to present preliminary results and report 238U activity concentration results. (author)

  4. Effect of 222Rn emanation from crystals on their 206Pb/238U age dating

    The escape of radon from certain minerals with high uranium is of particular interest to those concerned with the determination of ages of rocks, minerals and tectonic events. To the extent that radon escapes, these minerals are not closed systems from the thermodynamic point of view and, more particularly, from the geochronological point of view. This investigation aimed to determine the radon escape from zircon crystals and how this fit into the severe isotopic constraints of the concordia dating model. To evaluate the consequences of radon loss on 238U/ 206Pb age dating methods, 20 zircon concentrates were analyzed. The observed range of relative percentage of radon loss was of 0.2-12 % and correlations with weathering of the crystals with natural alpha dose and with U-Pb age discordances were found. These correlations indicate relationships between the amount of lattice damage by radiation, the radon leakage out of the crystal and Pb mobility. Some of the stochastic complexities in specific age determinations are also discussed. (author)

  5. Structure of 4He and 4Li and decay of the giant resonances in 238U

    With the p(α, 3He p)n reaction it has been succeeded for the first time to produce 4Li really. The total cross section of this reaction could be described consistently regarding the sequential decay of states in the α particle, in 4Li, and the p-n final-state interaction for all measured spectra. For the excitation of the low-lying L=1 1- and 2- states in the α(p, p')α and the α(p, n)4Li reaction cross sections were extracted. These values are consistent with predictions from DWBA calculations for a one-particle transition from the s into the p shell. The found values for the resonance energies and the widths for the 2- ground state and the first excited 1- state of 4Li amount to Er = 3.4 MeV, γ2 = 1.0 MeV respectively Er = 5.7 MeV, γ2=1.5 MeV. With the coincident measurement of the 238U(α, α'f) reaction the decay of the giant quadrupole resonance was detected in the fission channel. (orig./HSI)

  6. High resolution photofission measurements in 238U and 232Th. Final report

    A novel technique for measuring the photofission cross section with very high photon energy resolution has been developed. The photons are obtained from selected resonances in the (p,γ) reaction on various light nuclei. The photon energy resolution approaches 200 eV in favorable cases. The photon energy spread at each (p,γ) resonance is approx.20 keV on the average. Measurements of the photo-fission cross sections of 232Th and 238U have been carried out in the energy range from 5.8 to 12 MeV. Intermediate structure has been found in both nuclei at excitation energies around 6 MeV. Various properties of this structure, such as average areas of resonances, their spacing, width, and the underlying bakground, as well as the experimental fission probability averaged over the intermediate structure have been found to agree with theoretical predictions based on a double-humped fission barrier. In the case of 232Th, the feature of this barrier, a rather high first hump and a deep secondary well, are quite different from those predicted by current theoretial barrier calculations. 13 refs., 4 figs., 3 tabs

  7. Evaluation of correlating factors between {sup 238}U concentration measured in fine and course atmospheric particles

    Peixoto, Claudia Marques; Jacomino, Vanusa Maria Feliciano; Barreto, Alberto Avelar; Dias, Vagner Silva, E-mail: cmp@cdtn.b, E-mail: vmfj@cdtn.b, E-mail: aab@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Dias, Fabiana Ferrari, E-mail: fdias@cnen.gov.b [Brazilian Nuclear Energy Commission (CNEN-/MG), Pocos de Caldas, MG (Brazil). Lab. de Pocos de Caldas (LAPOC)

    2009-07-01

    Air quality is ever more important in function of the enormous proportion of human actions that have affected the environment over the last two centuries. Particulate material is one among many pollutants that can cause great risk to human health and the environment. It can be classified as: Total Suspended Particles (TSP), defined simply as particles with less than 50 mum aerodynamic diameter (one group of these particles can be inhaled and may cause health problems, while others may unfavorably affect the population's quality of life, interfering in environmental conditions and impairing normal community activities); and Inhalable Particles (PM{sub 10}), defined as those particles with less than 10 mum aerodynamic diameter. These particles penetrate the respiratory system and can reach pulmonary alveoli due to their small size, causing serious health damage. The Nuclear Technology Development Center (CDTN) has monitored air quality around its installations since 2000. CDTN's Environmental Monitoring Program (EMP) includes monitoring radioactivity levels contained in atmospheric TSP. In order to optimize its program, CDTN is carrying out a study to estimate the correlation between concentrations of particulate material measured in TSP and those measured in PM{sub 10}, PI{sub 2.5} and PI{sub 1}, as well as determination of activity concentration for each controlled radionuclide in all parts. The objective of this study is to present preliminary results and report {sup 238}U activity concentration results. (author)

  8. Emission of light and energetic medium masses in multiparticle exit channels in the reactions 238U+sup(nat)U and 238U+Au at 16.7 MeV/N energy

    Employing the 2π-geometry technique, two Solid State Nuclear Track Detectors (SSNTD) of different registration threshold have been used for studying the interaction of 16.7 MeV/N 238U with sup(nat)U and Au targets. The abundant production of five-pronged fission events, together with other experimental results show the emission of considerable amount of light (40 with respect to the beam direction

  9. Natural activities of 40K, 238U and 232Th in elephant grass (Pennisetum purpureum) in Ibadan metropolis, Nigeria

    Samples of elephant grass collected at some pasturing farmlands across different locations in Ibadan metropolis were analyzed for their natural radioactivity concentrations due to 40K, 238U and 232Th radionuclides. Radioactivity measurements were carried out using γ-ray spectroscopy. The average radioactivity concentration of 40K was found to be 64.5±8.1 Bq kg-1, 25.7±5.5 Bq kg-1 for 238U and 33.4±3.9 Bq kg-1 for 232Th. The radiological health implication to the population that may result from these values is found to be very low and almost insignificant. No artificial radionuclide, however, was detected in any of the samples, hence, measurements have been taken as representing baseline values of these radionuclides in the grass in the metropolis

  10. Comparison of measured and calculated 238U capture self-indication ratios from 4 to 10 keV

    From 4 keV to 149 keV the 238U cross sections are represented in ENDF/B-V by unresolved-resonance parameters (URP). The purpose of this representation is to enable the calculation of resonance self-protection as a function of temperature and dilution. Since the URPs are not defined unambiguously by the cross-section data, it is important that the unresolved representation be tested with appropriate experiments, such as capture self-indication ratio (SIR) measurements. In this paper we compare 238U capture SIR measurements in the 4- to 10-keV energy range with calculations done with ENDF/B-V and with recently published resolved resonance parameters

  11. Measurement and analysis of the 238U (n, 2n) reaction rate in depleted uranium/polyethylene shells

    In order to check the conceptual design of the subcritical blanket in a fusion-fission hybrid reactor, a depleted uranium/polyethylene simulation device with alternate shells has been established. The measurement of the 238U (n, 2n) reaction rate was carried out using an activation technique, by measuring the 208 keV γ rays emitted from 237U. The self-absorption of depleted uranium foils with different thicknesses was experimentally corrected. The distribution of the 238U (n, 2n) reaction rate at 90° to the incident D+ beam was obtained, with uncertainty between 5.3% and 6.0%. The experiment was analyzed using MCNP5 code with the ENDF/BVI library, and the calculated results are all about 5% higher than the measured results. (authors)

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

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

    2011-10-01

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

  13. Measurement of the fast neutron capture cross section of 238U relative to 235U(n,f)

    The capture cross section of 238U was measured using the activation technique and 235U(n,f) as a reference cross section. Capture events were measured by detection of two prominent γ-transitions in the decay of the 239U daughter nuclide, 239Np, employing a high resolution Ge(Li) detector. The system was calibrated with samples activated in a thermal neutron flux relative to the capture cross section of gold, and with an absolutely calibrated α-emitter, 243Am, which decays to 239Np. Cross section measurements were carried out in the neutron energy range from 30 keV to 3 MeV. Emphasis was on absolute values between 150 keV and 1 MeV where the 238U(n,γ) cross section and its cross section is small. Background from fission products was found to restrict the accuracy of the measured data at energies > 1.5 MeV

  14. Time-dependent Hartree-Fock calculations for multinucleon transfer and quasifission processes in $^{64}$Ni+$^{238}$U reaction

    Sekizawa, Kazuyuki

    2016-01-01

    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 TDHF calculations and measurements for $^{64}$Ni+$^{238}$U 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 $^{64}$Ni+$^{238}$U reaction. They show reasonable agreements with measurements. At small impact parameters, collision dynamics depends sensitively on th...

  15. Report to the 238U discrepancy task force on SIOB fits to the ORNL, CBNM, and JAERI transmission data

    The computer code SIOB has been used to obtain least-squares simultaneous-sample shape fits to the recent 238U transmission data of ORNL, CBNM, and JAERI over the energy regions 1460 to 1820 eV, 2470 to 2740 eV, and 3820 to 4000 eV. The fits indicate that much of the systematic discrepancy in the published neutron widths from these data arose in the data analysis procedure. Except for the 3820- to 4000-eV JAERI data, the systematic differences in the resulting neutron widths from the present widths are larger than those contained in any existing evaluation. These fits were performed as part of the work for the NEANDC ad hoc 238U Discrepancy Task Force. 20 references

  16. Measurement and analysis of the 238U(n, 2n) reaction rate in depleted uranium/polyethylene shells

    YAN Xiao-Song; LIU Rong; LU Xin-Xin; JIANG Li; WEN Zhong-Wei; HAN Zi-Jie

    2012-01-01

    In order to check the conceptual design of the subcritical blanket in a fnsion-fission hybrid reactor,a depleted uranium/polyethylene simulation device with alternate shells has been established.The measurement of the 238U(n,2n) reaction rate was carried out using an activation technique,by measuring the 208 keV γ rays emitted from 237 U.The self-absorption of depleted uranium foils with different thicknesses was experimentally corrected.The distribution of the 238U(n,2n) reaction rate at 90° to the incident D+ beam was obtained,with uncertainty between 5.3% and 6.0%.The experiment was analyzed using MCNP5 code with the ENDF/BVI library,and the calculated results are all about 5% higher than the measured results.

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

    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

  18. Tectonic and radioactivity impacts of 238U on groundwater-based drinking water at Gosa and Lugbe areas of Abuja, North Central Nigeria

    Tectonic contribution of activity level of 238U in groundwater-based drinking water in Gosa and Lugbe areas of Abuja was measured using inductively coupled plasma mass spectrometry (ICP-MS). The highest activity level of 2736 µBq L-1 reported in Lugbe borehole, whereas the lowest value of 443 µBq L-1 reported at Gosa borehole. The inhabitants permanently used water from the boreholes for daily consumption. The group receives 5.55 × 10-5 mSv of the annual collective effective dose due to 238U in drinking water. The radiological risks of 238U in the water samples were found to be low, typically in magnitude of 10-7 with cancer mortality value of 1.03 × 10-7 and morbidity value of 1.57 × 10-7. The chemical toxicity risk of 238U in drinking water over a lifetime consumption has a mean value of 4.0 × 10-3 μg kg-1 day-1. It could be that the human risk due to 238U content in groundwater supplies from ingestion may likely be the chemical toxicity of 238U as a heavy metal rather than radiological risk. Significantly, Lugbe subsurface may have developed some fractions of granitic strata that contributed to the distribution of radioactive of 238U in tectonically weak zones. (author)

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

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

    2016-08-01

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

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

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

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

    Leal-Cidoncha E.

    2016-01-01

    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.

  2. Measurement of 238U, 232Th and 40K in boreholes at Gosa and Lugbe, Abuja, north central Nigeria

    The purpose of this project is to evaluate the suitability of different sites as locations for obtaining underground water for consumption. The analysis of 238U, 232Th and 40K from rock samples from each layer of borehole at a depth of ∼50 m at Site A borehole, S3L1-S3L6 in Gosa and 40 m at Site B borehole, S4L1-S4L5 in Lugbe, Abuja, north central Nigeria is presented. The gamma-ray spectrometry was carried out using a high-purity germanium detector coupled to a computer-based high-resolution multichannel analyzer. The activity concentrations at Site A borehole for 238U have a mean value of 26±3, ranging from 23±2 to 30±3 Bq kg-1, 232Th a mean value of 63±5, ranging from 48±4 to 76±6 Bq kg-1 and 40K a mean value of 573±72, ranging from 437±56 to 821±60 Bq kg-1. The activity concentrations at Site B borehole for 238U have a mean value of 20±2, ranging from 16±2 to 23±2 Bq kg-1, 232Th a mean value of 46±4, ranging from 43±4 to 49±4 Bq kg-1, 40K a mean value of 915±116 and ranging from 817±103 Bq kg-1 to 1011±128 Bq kg-1. It is noted that the higher activity concentrations of 232Th and 238U are found in Site A at Gosa. Site B has lower radioactivity, and it is recommended that both sites are suitable for underground water consumption. (authors)

  3. Determination of Photofission Fragment Characteristics of 234,238U and 232Th in the Barrier Region

    GÖÖK Alf

    2012-01-01

    The photofission of 232Th, 234U and 238U at excitation energies in the barrier region has been studied. The goal has been to extract information on the mass, total kinetic energy (TKE) and angular distributions of the fission fragments. The experiments were performed using bremsstrahlung, produced by an electron beam in a copper radiator at the injector of the Superconducting Darmstadt linear accelerator (S-DALINAC). Mass and TKE distributions were determined by means of the double kinet...

  4. Binary fission studies in 24 MeV/u 238U induced reactions on C, Si, Ni and Au

    Fission is often used to analyse intermediate energy heavy ion reactions or probe the properties of formed nuclei. In our work, the neutron multiplicity is used to measure the violence of a 238U beam on 12C, 28Si, 58Ni or 197Au targets. We present preliminary results concerning the events in which two charged fragments (in addition to neutrons) were detected in coincidence. (D.L.). 5 refs., 5 figs

  5. Fission-Residues Produced in the Spallation Reaction 238U+p at 1 A GeV

    Bernas, M.; Armbruster, P.; Benlliure, J.; Boudard, A.; Casarejos, E.; Czajkowski, S.; Enqvist, T.; Legrain, R.; Leray, S.; Mustapha, B.; Napolitani, P.; Pereira, J; Rejmund, F.; Ricciardi, M.-V.; Schmidt, K. -H.

    2003-01-01

    Fission fragments from 1 A GeV 238U projectiles irradiating a hydrogen target were investigated by using the fragment separator FRS for magnetic selection of reaction products including ray-tracing and DE-ToF techniques. The momentum spectra of 733 identified fragments were analysed to provide isotopic production cross sections, fission-fragment velocities and recoil momenta of the fissioning parent nuclei. Besides their general relevance, these quantities are also demanded for applications. ...

  6. Estimation of uncertainties in resonance parameters of {sup 56}Fe, {sup 239}Pu, {sup 240}Pu and {sup 238}U

    Nakagawa, Tsuneo; Shibata, Keiichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-05-01

    Uncertainties have been estimated for the resonance parameters of {sup 56}Fe, {sup 239}Pu, {sup 240}Pu and {sup 238}U contained in JENDL-3.2. Errors of the parameters were determined from the measurements which the evaluation was based on. The estimated errors have been compiled in the MF32 of the ENDF format. The numerical results are given in tables. (author)

  7. Speciation of 226Ra, 238U and 228Ra in an upland organic soil overlying a uraniferous granite

    A sequential chemical extraction procedure was implemented in order to ascertain the chemical speciation of 226Ra, 238U and 228Ra within fractions of an upland organic soil. A number of samples and depth cores were taken from a region where the soil contains elevated levels of these radionuclides. Sequential chemical extractions were employed to identify within which of the three soil phases, namely exchangeable cations, easily oxidisable organic matter or iron oxides, the radionuclides were incorporated. The primary analytical technique was high-resolution gamma ray spectrometry. A number of other chemical parameters likely to affect the mode of occurrence of the radionuclides were also analysed. These included humic acid content, iron and manganese content and cation exchange capacity. Results indicate that the average amount of radionuclides bound as exchangeable cations, expressed as a percentage of the specific activities of each radionuclide, are: 226Ra - 2.13% (S.D. 2.15), 238U - 5.2% (S.D. 4.6) and 228Ra - 12.2% (S.D. 7.0). For easily oxidisable organic matter, the average percentages are: 236Ra - 3.2% (S.D. 3.2), 238U - 21.9% (S.D. 18.4), and 228Ra - 8.5% (S.D. 8.7). Percentages for iron oxides are 226Ra - 8.7% (S.D. 7.5), 238U - 54.8% (S.D. 22.2) and 228Ra - 19.7% (S.D. 12.9). N equals 17 in all cases. The results indicate that the primary factor controlling U238 accumulation, and to a lesser extent 226Ra and 228Ra, is the redox condition of the peat. Release of radionuclides from the peat could possibly occur via changes in the redox status as a result of activities such as forestry or drainage of the peat. (orig.)

  8. Alpha Spectrometry for Determination of 238U, 235U, 234U, 232Th and 230Th in Soil Sample

    Monitoring of radioactivity in soil around the nuclear power plant is important. In this study, the radioactivity of uranium and thorium isotopes in soil (NIST SRM 2709a) is analyzed by alpha spectrometry. Alpha spectrometry is a powerful analytical tool for the identification and assay of the alpha-emitting sources primarily due to its high counting efficiency, high sensitivity and low price. Another aim of this study is to present the extent of disequilibrium of 238U/234U and 238U/230Th. The soil sample was decomposed by a fusion technique, and the source for the alpha spectrometry was prepared by electrodeposition of an alpha-emitting nuclides onto a metallic substrate. In this work, uranium and thorium isotopes were chemically separated from a soil sample (NIST SRM 2709a) using chromatographic columns, and electrodeposited on a stainless steel disc to measure the radioactivity concentration of the isotopes with an alpha spectrometer. The ratio of 238U/234U for the soil sample was ca. 1 which is considered to be in secular equilibrium

  9. Theoretical modeling of traveling wave reactor fed with non-irradiated and pre-irradiated 238U fuels

    This paper deals with a traveling wave reactor theoretically. The breeding/burning wave is generated by a continuous radial fuel shuffling. Two-dimensional cylindrical core geometry is considered and the fuel is assumed to drift in the radial direction, which corresponds to a continuous radial fuel shuffling in practice. A one-group diffusion equation coupled with a burn-up solution is set up. The burn-up solution is obtained numerically, where the actinide inventories are simplified as functions of neutron fluence only. The uranium-plutonium (U-Pu) conversion cycle with pure 238U or 238U with its irradiation descendants as fresh fuel is considered under conditions of a typical sodium cooled fast reactor with uranium metallic fuel loaded. The asymptotic problems are solved by a time-stepping iteration scheme and the radial stationary wave solution is obtained together with certain eigenvalue keff. As a particular feature of this paper, the 238U pre-irradiated fuel is distributed with different irradiation doses along the axial axis. The purpose of this treatment is to remedy the power shape deformation in the uniform fresh fuel case. The results of both non-irradiated and pre-irradiated fuel, as examples for the inward fuel drifting motion, are compared and discussed. (author)

  10. 238U/235U variations in meteorites: extant 247Cm and implications for Pb-Pb dating.

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

    2010-01-22

    The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAIs) of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409 +/- 0.039 and 137.885 +/- 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAIs, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of 238U/235U in CAIs were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial 247Cm/235U ratio of approximately 1.1 x 10(-4) to 2.4 x 10(-4). PMID:20044543

  11. A dispersive optical model potential for nucleon induced reactions on 238U nucleus with 15 coupled levels

    A new dispersive coupled-channel optical model potential (OMP) for 238U nucleus is presented. The derived OMP couples almost all 238U excited levels below 1 MeV of excitation energy, including the ground state, octupole, beta, gamma, and non-axial bands. The coupled-channel potential is based on a vibrational-rotational description of the target nucleus structure, where dynamic vibrations are considered as perturbations of the rigid rotor underlying structure. OMP parameters that show a smooth energy dependence and energy independent geometry were determined from fits to the available experimental database (including strength functions and scattering radius) for neutron and proton scattering. The energy range 0.001-200 MeV is covered. Derived high-quality OMP is used to calculate the reaction cross section and corresponding theoretical uncertainties in nucleon-induced reactions on U-238. Theoretical calculations are compared with available results derived from existing experimental data on total cross-sections and angular distributions measurements based on the Wick's limit. Reduction of the uncertainty of the calculated reaction cross-section for neutron-induced reactions on 238U is discussed. (author)

  12. Investigation of fission properties and evaporation residue measurement in the reactions using 238U target nucleus

    Saro S.

    2011-10-01

    Full Text Available Fragment mass distributions for fission after full momentum transfer were measured in the reactions of 30Si,34,36 S,31P,40Ar + 238U at bombarding energies around the Coulomb barrier. Mass distributions change significantly as a function of incident beam energy. The asymmetric fission probability increases at sub-barrier energy. The phenomenon is interpreted as an enhanced quasifission probability owing to orientation effects on fusion and/or quasifission. The evaporation residue (ER cross sections were measured in the reactions of 30Si + 238U and 34S + 238U to obtain information on fusion. In the latter reaction, significant suppression of fusion was implied. This suggests that fission events different from compound nucleus are included in the masssymmetric fragments. The results are supported by a model calculation based on a dynamical calculation using Langevin equation, in which the mass distribution for fusion-fission and quasifission fragments are separately determined.

  13. Uranium separation by solvent extraction and determination of 234U/238U isotopic ratios using liquid scintillation spectrometry

    Liquid Scintillation Spectrometer (LSS) coupled with Pulse Shape Analysis has proved to be useful tool for determination of alpha emitting radionuclide, providing high counting efficiency, low background but only moderate energy resolution. Application of solvent extraction significantly reduces the extensive chemical separation needed for alpha spectroscopy technique using surface barrier detectors which allows many simple and effective nuclide separations as a part of sample preparation. LSS provides a nearly total rejection of β-γ emissions by means of pulse shape discrimination combined with counting efficiency higher than 99%. Liquid scintillation coupled with solvent extraction is a reliable, specific, very attractive and quick technique for the determination of U. In the present study, radiochemical separation method was used for the analysis of total uranium concentration as well as determination of 234U/238U isotopic ratios in standard U-ores by LSS. Measurements were carried out using Ultra Low Level LKB Wallac Quantulus 1220 LSS which has built-in Pulse Shape Discriminator and external standard 152Eu which allows the measurement of External Quench Parameter (SQP(E)). For determination of Uranium content in the ores, the direct extraction method by extractive cocktail was used. Liquid scintillation technique was successfully tested on the standard ores with total digestion of the samples to assess the possibility of faster analysis. Results was achieved as an effect of total digestion of the ores followed by extraction of Uranium by Toluene scintillator. Peak fitting procedure available in spectroscopy software was utilized for resolving the α peaks due to 4.17 MeV and 4.77MeV of 238U and 234U. It is seen that the 238U and 234U peaks are well resolved, allowing assessment of their ratio. The Uranium activity determined in the reference U ores is exemplified. The activity concentrations and isotopic Uranium activity ratios derived from LSS indicates

  14. The metrological activity determination of 238 U and 230 Th by gamma spectrometry to industrial fuel-cycle application

    This work describes the difficulty for determining the activity of 238 U and 230 Th using gamma spectrometry due to the low gamma-ray emission probabilities of 92 and 67 keV, and, mainly, the associated high uncertainties about 13 and 11%, respectively. 230 Th is a 238 U daughter and it is product from uranium mills and refineries. 230 Th decays to 226 Ra and this decay has to be measured because these radionuclides are not in secular equilibrium with their daughter products, besides the gamma-energies have high uncertainties in the emission probabilities. These radionuclides, mostly 238 U, are important in the nuclear fuel-cycle, since the mining of uranium ore, where the nominal isotopic content of natural uranium is 99.27% of 238 U, until the irradiated fuel reprocessing, where this isotope, a fertile material, is recovered to be used again. The uranium and thorium are considered safeguarded nuclear materials and the metrology tries to calibrate and standardize these materials to improve the activity determination techniques applied in different fuel-cycle scopes. The essential characteristics of the safeguarded materials are low gamma energies (less than 100 keV) and emission probabilities but with high uncertainties. In this way, the metrology can contribute to homeland security defense against illicit nuclear trafficking with the identification and quantification of the safeguarded radionuclides such as uranium and thorium, using specific gamma window energy and high resolution planar or coaxial germanium detector. The efficiency curve is obtained from the reference source spectrum considering the photopeak areas corresponding the standard activities. This curve depends on radiation energy, sample geometry, photon attenuation (sample absorption and material absorption between sample-detector), dead time and sample-detector position. The metrological activity determinations of 238 U solid sources, and of 230 Th, in solution (5 ml flask), were performed using

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

    Zhang Guohui, E-mail: guohuizhang@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China); Liu Xiang; Gao Zhiqi; Wu Hao; Liu Jiaming [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China)

    2012-05-15

    Using two {sup 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 {sup 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. - Highlights: Black-Right-Pointing-Pointer Fluences of monoenergetic fast neutrons were determined in four runs. Black-Right-Pointing-Pointer One {sup 238}U sample was placed in a gridded ionization chamber. Black-Right-Pointing-Pointer Another {sup 238}U sample was placed in a parallel-plate fission chamber. Black-Right-Pointing-Pointer Results are in agreement for different runs and different detectors.

  16. High energy resolution measurement of the 238U neutron capture yield in the energy region between 1 and 100 keV

    A measurement of the 238U neutron capture yield was performed at the 150 meter flight-path of the ORELA facility on two 238U samples (0.01224 and 0.0031 atomsbarn). The capture yeild data were normalized by Moxon's small resonance method. The energy resolution achieved in this measurement frequently resulted in doublet and triplet splittings of what appeared to be single resonance in previous measurements. This resolution should allow extension of the resolved resonance energy region in 238U from the present 4-keV limit up to 15 or 20 keV incident neutron energy. Some 200 small resonances of the (238U /plus/ n) compound nucleus have been observed which had not been detected in transmission measurement, in the energy range from 250 eV to 10 keV

  17. High energy resolution measurement of the 238U neutron capture yield in the energy region between 1 and 100 keV

    A measurement of the 238U neutron capture yield was performed at the 150 meter flight-path of the ORELA facility on two 238U samples (0.0124 and 0.0031 atoms/barn). The capture yield data were normalized by Moxon's small resonance method. The energy resolution achieved in this measurement frequently resulted in doublet and triplet splittings of what appeared to be single resonances in previous measurements. This resolution should allow extension of the resolved resonance energy region in 238U from the present 4-keV limit up to 15 or 20 keV incident neutron energy. Some 200 small resonances of the (238U + n) compound nucleus have been observed which had not been detected in transmission measurements, in the energy range from 250 eV to 10 keV. (author)

  18. Dietary 232Th and 238U intakes for Japanese as obtained in a market basket study and contributions of imported foods to internal doses

    Thorium-232 and 238U contents in four food groups were measured by inductively coupled plasma mass spectrometry (ICP-MS). Daily intakes of 232Th and 238U for Japanese were estimated to 2.22 mBq and 15.5 mBq per person, respectively. Furthermore, preliminary estimations were made for the effects of imported foods on internal exposures for Japanese. (author). 16 refs., 1 fig., 3 tabs

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

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

    2012-05-01

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

  20. Effects on elevating cancer risk in population exposed to natural radionuclide 226Ra if parent radionuclide 238U is entered the body by inhalation or ingestion

    People have always been exposed to ionizing radiation originating from natural radionuclides including 238U, 40K, 232Th that exist in earths crust. Although received doses are small, due to the fact that threshold does not exist, there is a certain risk of developing cancer. Purpose of this study was to measure 238U concentrations in soil of Bela Crkva territory. Based on these measurements, risks of developing cancers are calculated using Monte Carlo method.(author)

  1. Estimation of radiation doses to member of the public in northern corridor of India from intake of naturally occurring radionuclide (238U) in drinking water

    In the present paper radiological quality in drinking water collected from northern corridor of India has been evaluated on the basis of 238U activity. Places considered under present study are distinctive for their geological point of view. Adsorptive stripping voltammetric (AdSV) technique has been used to estimate the total uranium content of water samples and then converted to 238U activity concentration using specific activity of 238U (12.356 mBq μg-1 of 238U) and used accordingly. The uranium concentration in water samples varies in a wide range from 0.15-251 μg L-1. These values are compared with safe limit values recommended for drinking water by WHO and USEPA. Most of the water samples are found to have uranium concentration below the safe limit of 30 μg L-1 (USEPA, 2003). Annual committed effective doses due to 238U was evaluated for the adult member of the public through the ingestion of the drinking water samples studied and compared with the reference level of the committed effective dose (100 μSv yr-1 recommended by the WHO. The dose due to 238U for all analysed samples of drinking water are in the range of 0.06-18.74 μSv yr-1 and found to be well below the reference level recommended by the WHO. (author)

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

    The study of the reactions between heavy ions and 208Pb, 209Bi, 238U, and 248 Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the 238U(18O,xn)256-xFm, 238U(22Ne,xn)260-xNo, and 248Cm(15N,xn)263-xLr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The 208Pb(48Ca,xn)256-xNo, 208Pb(50Ti,xn)258-xRf, 208Pb(51V,xn)259-xDb, 209Bi(50Ti,xn)259-xDb, and 209Bi(51V,xn)260-xSg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics

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

    Patin, Joshua B.

    2002-05-24

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

  4. A study on physical characteristics of supercritical light - water reactor loaded with (232U-238Th-238U) oxide fuel

    The attractiveness of using (U-Th)-fuel in supercritical light water reactor is considered. The dilution of 233U in 238U is proposed with the purpose of increasing non-proliferation of this fissile isotope. Comparison of different fuel compositions is accomplished from the point of view of fissile isotope breeding and achieved burn-up; parasitic neutron absorption cross-sections are also compared. It is analyzed the impact for neutron balance of both cladding materials: zirconium alloy and stainless steel

  5. Production of medium-weight isotopes by fragmentation in 750 A MeV 238U on 208Pb collisions

    Projectile fragmentation of 238U in a lead target was investigated at a bombarding energy of 750 A MeV. Isotopic production cross sections of about 250 different projectile fragments in the element range Z=30-53 were measured with the fragment separator (FRS). The magnetic selection and the kinematical analysis of the measured isotopes allowed to disentangle fission and fragmentation residues. The mass loss of these residues indicates a violent collision where a large amount of energy is dissipated. The position of the fragmentation corridor defined by the measured residues was used to determine an effective proton-evaporation barrier. (orig.)

  6. Evaluation of covariances for resolved resonance parameters of 235U, 238U, and 239Pu in JENDL-3.2

    Evaluation of covariances for resolved resonance parameters of 235U, 238U, and 239Pu was carried out. Although a large number of resolved resonances are observed for major actinides, uncertainties in averaged cross sections are more important than those in resonance parameters in reactor calculations. We developed a simple method which derives a covariance matrix for the resolved resonance parameters from uncertainties in the averaged cross sections. The method was adopted to evaluate the covariance data for some important actinides, and the results were compiled in the JENDL-3.2 covariance file. (author)

  7. Fragment properties from fission of 234,238U induced by 6 -10 MeV bremsstrahlung

    Experiments to investigate the photon-induced fission of actinide nuclei at excitation energies in the vicinity of the fission barrier are carried out at the super conducting Darmstadt linear electron accelerator S-DALINAC. A twin Frisch grid ionization chamber is used to deduce mass, total kinetic energy, and angular distributions of the fission fragments. In this contribution results on fission fragment mass and total kinetic energy distributions from 234,238U are presented along with the currently on-going investigation of 234U and 232Th fragment angular distributions.

  8. Most probable charge of fission products in 24 MeV proton induced fission of 238U

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

  9. Determination of photofission fragment characteristics of {sup 234,238}U and {sup 232}Th in the barrier region

    Goeoek, Alf

    2012-11-05

    The photofission of {sup 232}Th, {sup 234}U and {sup 238}U at excitation energies in the barrier region has been studied. The goal has been to extract information on the mass, total kinetic energy (TKE) and angular distributions of the fission fragments. The experiments were performed using bremsstrahlung, produced by an electron beam in a copper radiator at the injector of the Superconducting Darmstadt linear accelerator (S-DALINAC). Mass and TKE distributions were determined by means of the double kinetic energy technique using a twin Frisch grid ionization chamber. The angular distributions were derived simultaneously by measuring the drift time of ionization electrons. Results show that this drift-time method is comparable in accuracy to other more commonly used methods, but with a simplified procedure for setting up the experiment. Mass, TKE and angular distributions have been obtained from bremsstrahlung-induced fission of {sup 232}Th at average excitation energies left angle E{sub x} right angle =6.68 MeV and 7.26 MeV, for {sup 234}U at left angle E{sub x} right angle =5.80 MeV, 6.49 MeV and 7.23 MeV, and for {sup 238}U at left angle E{sub x} right angle =5.90 MeV, 6.11 MeV and 6.93 MeV. Results on fission fragment characteristics from {sup 238}U({gamma},f) show good agreement with literature data, which verifies the experimental procedure. The correlated mass and TKE data have been analyzed in terms of fission modes within the multi-modal random-neck-rupture model. The result exhibits a dominant yield of the mass asymmetric standard-2 mode in all the investigated fissioning nuclei, with a relative yield of {proportional_to}77 % in {sup 232}Th, {proportional_to}75 % in {sup 234}U and {proportional_to}67 % in {sup 238}U. No strong fluctuation of the mode yields were found as a function of the excitation energy. Correlations between mass, TKE and angular distributions have been investigated in {sup 232}Th and {sup 234}U. The correlation takes the form of an

  10. Constraints on mantle melting at mid-ocean ridges from global 238U-230Th disequilibrium data

    The extent of radioactive disequilibrium between 238U and its daughter product 230Th in mid-ocean-ridge basalts from around the world is negatively correlated with axial ridge depth; local positive correlations with inferred mantle source composition are also observed. The larger 230Th excesses seen in samples from shallow ridges reflect a larger melt contribution from a garnet-bearing source which may be explained by a deepening of the solidus in hotter mantle regions. These observations provide important constraints for modelling melt generation at mid-ocean ridges. (author)

  11. 238U, 232TH, AND 222RN concentration measured in various traditional medicinal plant preparation using nuclear track detectors

    Full text: 238U, 232Th, 222Rn concentrations were measured inside traditional medicinal plants preparations widely used by patients in classic and modern phyto therapy by using a technique based on the use of solid state nuclear track detectors. The intakes of these radionuclides have been determined for adult patients from the ingestion of the studied medical preparations. The influence of mass intake as well as pollution on the contents of the considered radionuclides was investigated. The resulting radiation doses to adult patients from the ingestion of the traditional medical preparations were evaluated.

  12. Evaluation of the 238U neutron cross-sections for incident neutron energies up to 4 keV

    An evaluation is described of the 238U cross-sections below 4 keV. Recent measurements and re-analyses of older data are discussed. Evaluated resonance parameters are obtained for 164 s-wave levels. The capture widths of the first three s-wave levels are significantly lower than in the ENDF/B-1V evaluation. The s-wave strength function above 1.5 keV is systematically larger than in ENDF/B-1V. Statistical and systematic uncertainties are evaluated for the resonance parameters and for the smooth backgrounds. The statistical distributions of the resonance parameters are compared with theoretically expected distributions. (author)

  13. Quantitative determination of 235U and 238U by measuring the gamma radiation from short-lived fission products

    On the basis of two successive activations of the sample by neutrons of different energy distribution and of measuring the gamma radiation from the resulting short-lived fission products the masses of uranium 235 and 238, the enrichment and the uranium concentration have been determined. The procedure can only be used for unirradiated uranium. The analysis takes 50 min. The method has been tested with samples of 10 g and up to 90% enrichment. The minimum detectable amounts were 1 mg 235U and 1 g 238U, respectively, with the random error of measurement being 4%. (author)

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

    The uranium content and 235U/238U 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 235U/238U ratio of topsoils showed great variability and were inversely correlated. The highest uranium levels (up to 31.47 mg kg-1) and lowest 235U/238U 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 235U/238U 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 uranium concentrations

  15. Transfer of 210Po, 210Pb and 238U from some medicinal plants to their essential oils

    Essential oils were extracted from 35 medicinal plants used by Syrians, organic compounds were determined in these oils and concentrations of 210Po 210Pb and 238U were determined in the original plants and in the essential oils. The results showed that the highest activity concentrations of 210Po and 210Pb were found in leaves with large surfaces and in Sage were as high as 73.5 Bq kg−1 and 73.2 Bq kg−1, respectively. The activity concentration of 238U was as high as 4.26 Bq kg−1 in Aloe. On the other hand, activity concentrations of 210Po ranged between 0.2 and 71.1 Bq kg−1 in extracted essential oils for Rosemary and False yellowhead, respectively. The activity concentration of 210Pb reached 63.7 Bq kg−1 in Aloe oil. The activity concentrations of 238U were very low in all extracted oils; the highest value was 0.31 Bq kg−1 in peel of Orange oil. The transfer of 210Po and 210Pb from plant to its oil was the highest for Eugenia; 7.1% and 5.5% for 210Po and 210Pb, respectively. A linear relationship was found between the transfer factor of radionuclides from plant to its essential oil and the chemical content of this oil. - Highlights: • Natural radionuclides 210Po, 210Pb and 238U were determined in 35 medicinal plants and their essential oils. • The highest activity concentration of 210Po and 210Pb were 73.5 Bq kg−1 and 73.2 Bq kg−1 in Sage, respectively. • The transfer of 210Po and 210Pb from Eugenia plant to its oil was the highest amongst other plants. • The data obtained in this study can be considered the first reported data for medicinal plants and their oils in Syria

  16. Uranium isotopic ratio measurements (235U/238U) by laser ablation high resolution inductively coupled plasma mass spectrometry for environmental radioactivity monitoring - 235U/238U isotope ratio analysis by LA-ICP-MS-HR for environmental radioactivity monitoring

    The protection of the aquatic and terrestrial environments from a broad range of contaminants spread by nuclear activities (nuclear plants, weapon tests or mining) require continuous monitoring of long-lives radionuclides that were released into the environment. The precise determination of uranium isotope ratios in both natural and potential contaminated samples is of primary concern for the nuclear safeguards and the control of environmental contamination. As an example, analysis of environmental samples around nuclear plants are carried out to detect the traces in the environment originating from nuclear technology activities. This study deals with the direct analysis of 235U/238U isotope ratios in real environmental solid samples performed with laser ablation (LA)-HR-ICP-MS. A similar technique has already been reported for the analysis of biological samples or uranium oxide particles [1,2] but to our knowledge, this was never applied on real environmental samples. The high sensitivity, rapid acquisition time and low detection limits are the main advantages of high resolution ICP-MS for accurate and precise isotope ratio measurements of uranium at trace and ultra-trace levels. In addition, the use of laser ablation allows the analysis of solid samples with minimal preparation. A a consequence, this technique is very attractive for conducting rapid direct 235U/238U isotope ratio analysis on a large set of various matrix samples likely to be encountered in environmental monitoring such as corals, soils, sands, sediments, terrestrial and marine bio-indicators. For the present study, LA-ICP-MS-HR analyses are performed using a New Wave UP213 nano-second Nd:YAG laser coupled to a Thermo Element-XR high resolution mass spectrometer. Powdered samples are compacted with an hydraulic press (5 tons) in order to obtain disk-shaped pellet (10-13 mm in diameter and 2 mm in thickness). The NIST612 reference glass is used for LA-ICP-MS-HR tuning and as standard control during

  17. 238U, 232Th and 40K radioactivity level of soil and concrete floor in Zhuhai, Guangdong province, China

    In-situ gamma-ray spectrometer survey is carried out in Zhuhai, Guangdong province from 2002 to 2003 in order to estimate the radiation level of natural radionuclides. Measured area is more than 100 km2 and 970 sites with NaI(Tl) (φ75 mm x 75 mm) gamma-ray spectrometer. The specific activity of 40K, 238U and 232Th are 654.2 ± 338.0, 85.7 ± 31.6, and 159.9 ± 49.0 Bq·kg-1 in weathered granite, and 632.3 ± 75.1, 35.2 ± 14.6 and 70.2 ± 18.6 Bq·kg-1 in the sediments, respectively. Biotite Granite is the source of 40K, 238U and 232Th in the medium on ground in Zhuhai. The specific activity of natural radionuclides have significant dependence relation with geological background, such as lithology. (authors)

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

    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.

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

    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.

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

    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.

  1. Behaviour of 238U family radionuclides in continental environment: case of the U mining area near Limoges (France)

    The objectives of this work are to study the behaviour of 238U and its daughters in the continental environment and to determine the radiological impact of U mining past activities in the Haute-Vienne French department. The distribution of radionuclides among different size fraction was investigated upstream and downstream mines to better understand the transport of radionuclides in the Vienne river basin. Particulate (>0,45 ), colloidal (0,45μ-10 kD) and dissolved (238U, 234Th, 226Ra, 210Pb, 228Ra, 228Th, 7Be, 137Cs and 40 K activities. A preconcentration step by evaporation was elaborated and validated for liquid samples. Results indicate that radiological impact of U mines are the enhancement of radionuclides activities and a change of their distribution between particulate, colloidal and dissolved fraction. While activity levels depend on the input intensity, the distribution is controlled by the mine water treatment witch reduces drastically the contribution of mine radionuclides in streams. Analysis of particles from traps and sediments confirms that the distribution of mine radionuclides promote their accumulation in lacustrine sediments. Therefore, sediments have recorded the U mining history. Nevertheless, the impact of the past activities decreases over time and is very limited in space. Indeed, it becomes weak at 10 km downstream the inputs and it is no more detectable at 30 km downstream. (author)

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

    Badhan, K; Mehra, R

    2012-11-01

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

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

    The aim of the present work was to study the activity concentration and absorbed gamma dose rates due to primordial radionuclides (238U, 232Th and 40K) 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 238U, 232Th and 40K 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 Dept.. The calculated value of external health hazard index is lower than unity. (authors)

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

    Chiba Satoshi

    2013-03-01

    Full Text Available 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.

  5. Measurement of the fast neutron capture cross section of /sup 238/U relative to /sup 235/U(n,f)

    Fawcett, L.R. Jr.; Poenitz, W.P.; Smith, D.L.

    1979-01-01

    The capture cross section of /sup 238/U was measured using the activation technique and /sup 235/U(n,f) as a reference cross section. Capture events were measured by detection of two prominent ..gamma..-transitions in the decay of the /sup 239/U daughter nuclide, /sup 239/Np, employing a high resolution Ge(Li) detector. The system was calibrated with samples activated in a thermal neutron flux relative to the capture cross section of gold, and with an absolutely calibrated ..cap alpha..-emitter, /sup 243/Am, which decays to /sup 239/Np. Cross section measurements were carried out in the neutron energy range from 30 keV to 3 MeV. Emphasis was on absolute values between 150 keV and 1 MeV where the /sup 238/U(n,..gamma..) cross section and its cross section is small. Background from fission products was found to restrict the accuracy of the measured data at energies > 1.5 MeV.

  6. Resolved-resonance neutron widths from a consistent reanalysis of the most recent 238U transmission data

    The 238U neutron differential capture cross sections are one of the most important nuclear data for reactor physics calculations. Nevertheless, differential data have persistently over-predicted the ratio of the 238U capture rate relative to the 239Pu fission rate in fast-reactor spectra as measured by integral experiments. One of the possible ways of perhaps reducing this discrepancy is to extend the theoretically sound resolved-resonance range upwards in energy from the present 4 to 10 keV. One of the major obstacles to such an extension is the published discrepancies among the resolved-resonance region neutron widths from 1 to 4 keV from the three most recent transmission measurements and analysis: the 1978 results of Olsen from Oak Ridge National Laboratory (ORNL); the 1975 results of Poortmans from the Central Bureau of Nuclear Measurements (CBNM) in Belgium; and the 1975 results of Nakajima from the Japan Atomic Energy Research Institute (JAERI). In this paper, the results of a detailed reanalysis of the three recent transmission measurements over three narrow energy regions are reported: region 1, 3820 to 4000 eV, six large resonances; region 2, 2470 to 2740 eV, ten large resonances; and region 3, 1460 to 1820 eV, twelve large resonances

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

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

    2011-12-01

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

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

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

  9. Determination of specific concentrations of {sup 40}K, {sup 238}U and {sup 232}Th in mineral fertilizer samples

    Garcez, Ricardo W.D.; Lopes, Jose M.; Silva, Ademir X., E-mail: r.w.o.g@fisica.if.uff.br, E-mail: ademir@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Domingues, Alessandro M.; Lima, Marco F. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil)

    2015-07-01

    The use of fertilizer is an established practice worldwide to promote agricultural productivity increased without increasing the planted area, resulting in native forests protection and increase of the food availability. Some kinds of fertilizer have in their chemical composition some radionuclides due the origin of its feedstock, such as {sup 238}U, the {sup 232}Th, and their descendants, beyond {sup 40}K. Knowledge of the radioactivity levels in the environment is great importance to know the gamma radiation dose that the human being is exposed. For identification and quantitation of radionuclides, it was used gamma spectrometry where HPGe detector was used to obtain the spectra, and LabSOCS software for calculating the detection efficiency for each energy. The values of {sup 232}Th specific concentrations ranged from 4.1 to 368.1 Bq.Kg{sup -1}, the values of {sup 238}U specific concentrations ranged from 16.0 to 647.7 Bq.Kg{sup -1} and {sup 40}K specific concentrations ranged from 19.1 to 12713 Bq.Kg{sup -1}. Concentrations of values are consistent with those found in literature. (author)

  10. Environmental geochemistry of 238U, 232Th, 40K and some heavy metals in River Nile sediments

    Environmental geochemistry is concerned with the abundance, distribution, and mobility of chemical elements in surface materials at the surface of earth crust. This study aimed at better understanding of geochemical behavior of 238U,23'2Th and 40K in river sediments and some heavy elements with emphasis on Mg, Ca, Mn, Fe, Ni, Cu, Zn and Pb. The analysis was conducted for a total of 33 bulk sediment samples from White Nile, Blue Nile and River Nile within Khartoum, the samples were fractionated into seven grain sizes each (2000-1000, 1000-500, 500-250, 250-200, 200-125, 125-100 and > 100 μm), using high resolution gamma spectrometer for radionuclides measurements, whereas Particle Induced X-ray Emission (PIXE) was used for heavy metals analysis. On the average, the activity concentration of 238U, 232Th and 40K were 17.90±5.23, 16.38±5.34 and 379.82±107.76 Bq -1Kg in White Nile, 19.56±5.04, 17.72±4.69, and 494.36±105.79 Bq -1Kg in Blue Nile and 19.27±2.88, 17.48±2.78, 359.50±83.15 Bq -1Kg in the River Nile sediments. Results revealed inverse relationship between activity concentration and grain size in White and Blue Nile, while the trend is not clear in the River Nile. In general, the variation of the measured values within single grain size was smaller in White Nile compare to Blue and River Nile sediments, and it was observed that the data are highly scattered in grain size (200-125μm). The ratio between 238U/232Th is grater than unity in the three rivers indicating that there is relative enrichment of 238U in the surface sediments. The activity concentration of the fallout radionuclide 137Cs is one order of magnitude lower in the White Nile sediments (0.89±0.96) Bq -1Kg compared to values in the Blue Nile sediments (3.60±1.55) Bq -1Kg. Comparison of the values obtained for natural radionuclides and the fallout radionuclide (137Cs in the three sites with the global data reflect low and /or insignificant difference. For heavy metal concentrations

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

    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

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

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

    2006-09-01

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

  13. 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

    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.

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

    Feng, Zhao-Qing; Li, Jun-Qing

    2009-01-01

    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 $^{238}$U, $^{244}$Pu and $^{248,250}$Cm with the optimal excitation energies and evaporation channels are pointed out to synthesize new isotopes which lie between the nuclides produced in the cold fusion and the $^{48}$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.

  15. Most probable charge of fission products in proton-induced fission of 238U and 232Th

    The charge distributions of fission products in proton-induced fission of 238U and 232Th were measured in a wide mass range. The most probable charges lay on the proton-rich side in the light fragment region and on the proton-deficient side in the heavy one compared with the unchanged charge distribution hypothesis. This result implies that the charge polarization occurs in the fission process. The charge polarization was examined with respect to the ground-state Q values. The estimations by the Q values fairly well reproduced the experimental most probable charges. These results suggest that the fission path to the most favorable charge division may go through the most energetically favorable path at scission point. (author)

  16. Polonium 210Po, uranium (234U, 238U and plutonium (238Pu, 239+240Pu bioaccumulation in marine birds

    Strumińska-Parulska D. I.

    2013-04-01

    Full Text Available The aim of this work was the determination of 210Po, 234U, 238U, 238Pu and 239+240Pu concentration in marine birds which permanently or temporally live in the southern Baltic Sea coast. We chose 11 species of seabirds: three species permanently residing at southern Baltic Sea, four species of wintering birds and three species of migrating birds. The results show that analyzed radionuclides are non-uniformly distributed in the marine birds. The highest activities of 210Po were observed in feathers, muscles and liver. The highest uranium content was found in liver, rest of viscera and feathers, while plutonium in the digestion organs and feathers. Omnivore seabirds accumulated more polonium, plutonium than species that feed on fish, while herbivore seabirds accumulated more uranium than carnivore.

  17. ENDF/B-IV representation of the 238U total neutron cross section in the resolved resonance energy region

    The ENDF/B-IV prescription fails to represent correctly the 238U total (and scattering) cross section between the levels of the resolved range. It is shown how this representation can be improved by properly accounting for the contribution of levels outside the resolved region to the cross section at energies inside the resolved region, and by substituting the more precise multilevel Breit-Wigner formula for the presently used single-level formula. The importance of computing accurately the minima in the total cross section is illustrated by comparing values of the self-shielded capture resonance integral computed with ENDF/B-IV and with a more accurate cross section model

  18. Finite Range Effects on Fusion and/or Breakup of 6He+238U and 11Li+208Pb Systems

    Sukhvinder S. Duhan; Manjeet Singh; Rajesh Kharab; H.C. Sharma

    2011-01-01

    We have studied the effects of the finite range of the interaction between the fragments of the projectile on the fusion and/or breakup of 6He+238U and 11 Li+208 Pb systems at near barrier energies within the framework of dynamic polarization potential approach.It has been found that at near barrier energies the maximum flux is lost to the breakup channel and at energies well above the Coulomb barrier the fusion coupled with the breakup channel opens up, initially with sharp rise and later becoming saturated at energy nearly twice of the Coulomb barrier.Further, it is found that the breakup cross section increases with the increasing range of the interaction between the fragments of the projectile while the fusion coupled with the breakup channel cross section decreases with the increasing range.

  19. Radioactivity of 238U, 232Th, 40K, and 137Cs and assessment of depleted uranium in soil of the Musandam Peninsula, Sultanate of Oman

    SALEH, Ibrahim Hindawy

    2012-01-01

    238U, 232Th, 40K, and 137Cs radioactivities were determined in soil samples collected from the Musandam Peninsula, Sultanate of Oman, using a high resolution gamma-ray spectroscopy system. In addition, total uranium was measured in selected soil samples by inductively coupled plasma optical emission spectroscopy (ICP-OES). The averages of radioactivity levels in the soil for 238U, 232Th, and 40K were 14.42 Bq kg-1, 9.95 Bq kg-1, 158.21 Bq kg-1, and 2770 Bq m-2 for 137Cs, respectively...

  20. The transfer of uranium isotopes 234U and 238U to the waters interacting with carbonates from Mendip Hills area (England)

    Laboratory time-scale experiments were conducted on limestone and dolomite gravels from the Mendip Hills area, England, with the purpose of evaluating the release of 238U and 234U to different aqueous solutions. The 234U/238U activity ratio (AR) lab data were reliable to interpret the field data. The obtained values do not indicate a reduction in the amount of dissolved U and an increase in the AR of the remaining dissolved U as commonly observed for groundwater systems close to redox boundaries

  1. Resonance parameters of the 6.67-, 20.9-, and 36.8-eV levels in 238U

    The ENDF/B-IV 238U cross sections (MAT-1262) yield an effective capture resonance integral in strongly self-shielded situations which is too high. This situation suggests that the ENDF/B capture widths for the first few s-wave levels may be too large. Recent ORELA measurements of transmission through 238U have been analyzed with a multilevel formula to determine the parameters of the 6.67-, 20.9-, and 36.6-eV levels. These three levels provide 86 percent of the infinitely dilute capture resonance integral

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

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

    2016-08-01

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

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

    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.

  4. Measurement of Fragment Mass Distributions in Neutron-induced Fission of {sup 238}U and {sup 232}Th at Intermediate Energies

    Simutkin, V.D. [Uppsala University, P.O Box 525, SE-751 20 Uppsala (Sweden)

    2008-07-01

    Conceptual analysis of accelerator-driven systems assumes extensive use of nuclear data on neutron-induced reactions at intermediate energies. In particular, information about the fission fragment yields from the {sup 238}U(n,f) and {sup 232}Th(n,f) reactions is of particular interest at neutron energies from 10 to 200 MeV. However, there is a lack of such data for both {sup 238}U and {sup 232}Th. Up to now, the intermediate energy measurements have been performed for {sup 238}U only, and there are no data for the {sup 232}Th(n,f) reaction. The aim of the work is to provide such data. Fission fragment mass distributions for the {sup 232}Th(n,f) and {sup 238}U(n,f) reactions have been measured for the incident neutron energies 32.8 MeV, 45.3 MeV and 59.9 MeV. The experiments have been performed at the neutron beam facility of the Universite Catholique de Louvain, Belgium. A multi-section Frisch-gridded ionization chamber has been used as a fission fragment detector. The data obtained have been interpreted in terms of the multimodal random neck-rupture model (MMRNRM). (authors)

  5. 234U/238U isotope data from groundwater and solid-phase leachate samples near Tuba City Open Dump, Tuba City, Arizona

    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.

  6. Target residues from the reaction of 3.65A GeV 12C with 232Th and 238U

    The cross sections for the production of about a hundred different radionuclides of 24Na - 237U range from the reaction of 3.65A GeV 12C with 232Th and 238U were measured by off-line gamma-ray spectroscopy. 5 refs.; 1 tab

  7. The activity concentrations of 40K, 226Ra, 232Th, 238U and 7Be in moss from spas in eastern Serbia in the period 2000-2012

    Čučulović Ana

    2014-01-01

    Full Text Available In this work we present the activity concentrations of natural radionuclides 40K, 226Ra, 232Th, 238U and 7Be in mosses. One hundred and sixty-seven moss samples were collected between 2001 and 2012 from the territory of the Sokobanja, Banja Jošanica and Gamzigradska Banja spas. They were classified into 23 species. The activity concentrations (Bq/kg in moss from Sokobanja spa were: 40K 25-427; 226Ra 0.3-36; 232Th 1.0-37; 238U 0.4-28 and 7Be 29-210; from Banja Jošanica spa they were: 40K 90-242; 226Ra 2.4-11.7; 232Th 2.0-12.7; 238U 1.6-11.3 and 7Be 142-212; Gamzigradska Banja spa: 40K 95-351; 226Ra 8.0-21; 232Th 5.1-19; 238U 6.7-18 and 7Be 20-144. The activity concentrations of dominant natural radionuclides (potassium, radium, thorium and uranium in the moss samples were within the usual ranges for the territory of Serbia. [Projekat Ministarstva nauke Republike Srbije, br. III 43009

  8. Transfer of {sup 40}K, {sup 238}U, {sup 210}Pb, and {sup 210}Po from soil to plant in various locations in south of Syria

    Al-Masri, M.S. [Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic)], E-mail: scientific1@aec.org.sy; Al-Akel, B.; Nashawani, A.; Amin, Y.; Khalifa, K.H.; Al-Ain, F. [Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic)

    2008-02-15

    Transfer factors of {sup 40}K, {sup 238}U, {sup 210}Pb, and {sup 210}Po from soil to some agriculture crops in various locations in south of Syria (Dara'a and Assuwaydaa districts) have been determined. Soil and vegetable crops (green pepper, cucumber, tomato, and eggplant), legumes crops (lentil, chickpea, and broad bean), fruit trees (apple, grape, and olives) and cereals (barley and wheat) were collected and analyzed for {sup 238}U, {sup 210}Pb, and {sup 210}Po. The results have shown that higher transfer factors (calculated as Bq kg{sup -1} dry wt. plant material per Bq kg{sup -1} dry wt. soil) for {sup 210}Po, {sup 210}Pb and {sup 238}U were observed in vegetable leaves than fruits and cereals leaves; the highest values of transfer factor (TF) for {sup 238}U were found to be 0.1 for straw of chickpea. Transfer factors for {sup 210}Po varied between 2.8 x 10{sup -2} and 2 in fruits of eggplant and grain of barley, respectively. In addition, several parameters affecting transfer factors of the radionuclides were evaluated. The results can be considered as base values for TF of natural radionuclides in the region.

  9. High-resolution measurement of the 238U neutron capture yield for incident neutron energies between 1 and 100 keV

    The capture cross section of 238U in the energy range up to 100 keV is one of the important nuclear parameters in reactor design. Nevertheless, the uncertainties in this parameter are still above reactor design requirements. These uncertainties, which were discussed at the Antwerp Conference on Nuclear Data (Sept. 1982), led to the formation of the 238U task force of the Nuclear Energy Agency Nuclear Data Committee (NEANDC). Among the most relevant conclusions arrived at by the NEANDC task force were that, since most of the capture cross-section measurements were old and disagreed among themselves by more than expected from their respective error assignment, a new high-resolution measurement was needed and the resolved resonance energy region should be extended above its present 4-keV limit. In response to these requests, a measurement of the 238U capture yield was performed at the 150-m flight-path station of the Oak Ridge Electron Linear Accelerator (ORELA) facility. The energy resolution achieved in this measurement frequently resulted in spectacular doublet and triplet splittings of what appeared to be single resonances in previous measurements. The present 238U capture yield measurements has provided a wealth of data that, when combined with recent transmission results, will have a significant impact in both reactor design and neutron spectroscopy studies

  10. Fission Cross Sections of {209}Bi, {232}Th, {235}U, {238}U and {237}Np for Intermediate Energy Protons and Deuterons

    Yurevich, V I; Yakovlev, R M; Sosnin, A N

    2001-01-01

    Fission cross sections of {209}Bi, {232}Th, {235}U, {238}U and {237}Np have been measured with 1.0-3.7 GeV protons and 1.0 GeV deuterons. The results are compared with other experimental data, available evaluations and predictions of the theoretical model.