WorldWideScience

Sample records for 238u photofission issledovanie

  1. 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.

  2. 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)

  3. 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.

  4. 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.

  5. 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)

  6. 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

  7. 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

  8. 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...

  9. 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.

  10. 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

  11. 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 ...

  12. Cross section of the 238 U photofission in the quasi-deuteron region

    The U-238 photofission cross section was measured ranging six different energies in the quasi-deuteron region using nearly photo chromatic photons. Fission fragments tracks detection in nuclear emulsion K O-Ilford and mica foils were used. In the first case a loading was made resulting in a very thin film containing 8 x 1018 uranium atoms per cm2. In the second case, very thin uranium oxide layers were deposited on the mica foils resulting in effective densities of 15 x 1018 uranium atoms per cm2 for each sample. (L.C.J.A.)

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

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

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

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

    2009-10-01

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

  15. Yields of neutron-rich nuclei by actinide photofission in giant dipole resonance region

    Bhowmick, Debasis; Basu, D N; Chakrabarti, Alok

    2015-01-01

    Photofission of actinides is studied in the region of nuclear excitation energies that covers the entire giant dipole resonance (GDR) region. A comparative analysis of the behavior of the symmetric and asymmetric modes of photon induced fission as a function of the average excitation energy of the fissioning nucleus is performed. The mass distributions of $^{238}$U photofission fragments are obtained at the endpoint bremsstrahlung energy of 29.1 MeV which corresponds to mean photon energy of 13.7$\\pm$0.3 MeV that coincides with GDR peak for $^{238}$U photofission. The integrated yield of $^{238}$U photofission as well as charge distribution of photofission products are calculated and its role in the production of neutron-rich nuclei and their exoticity is explored.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. The fission fragment yields at the photofission of actinide nuclei

    The fission fragment yields of isotopes 101Mo, 135I, 135mCs were measured at the photo-fission of actinide nuclei 232Th, 238U, 237Np. These fission fragments have some peculiarities in nuclear structure or in practical using. The measurements were performed on the microtron bremsstrahlung at the Flerov Laboratory of Nuclear Reactions, JINR, at the electron energy 22 MeV. The activation method with an HPGe detector was used in these measurements of the yields

  1. 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.)

  2. 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

  3. 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.

  4. 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.

  5. 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)

  6. 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.)

  7. Production of photofission fragments and study of their nuclear structure

    The fission fragments of heavy nuclei (Z > 90) are neutron-rich isotopes of the elements from Zn (Z = 30) to Nd (Z = 60) with a neutron number of 45 - 90. The large neutron excess in the fission fragments under study could lead to the essential change in their structure and radioactive decay characteristics. This change will manifest itself in the appearance of new magic numbers of protons or neutrons, new regions of deformation, of new islands of isomerism. The high energy of β-decay can result in the new, much rarer, modes of radioactive decay (for example, β2n or βα). Study of the nuclear structure of fission fragments is one of the main directions of the DRIBs project, being developed in the Flerov Laboratory of Nuclear Reactions, JINR. The aim of this project is the production of the intense beams of accelerated radioactive nuclei in a wide range of Z and A and the study of their properties. The neutron-rich nuclei of medium mass numbers will be produced in the photofission reactions on the electron accelerator microtron MT-25. The parameters of this microtron allow to produce the high yield of photofission fragments (up to 1011s-1 at the irradiation of thick uranium target by Bremsstrahlung. The first experiments using photofission fragments were performed. The independent yields of Kr (A = 87 - 93) and Xe (A = 137 - 143) fragments at the photofission of different heavy nuclei 232 Th, 238 U, 237 Np, 244 Pu were measured. These data allows to refer about yields of the most neutron-rich isotopes. The rare mode decay, emission of delayed neutron pair (β2n), was observed at the photofission of 238 U. It is, probably, 136 Sb, the intensity of β 2n branch is about 10-3. Other experiments using neutron, gamma and laser spectroscopy methods are planned. (authors)

  8. 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

  9. 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

  10. Photofission Analysis for Fissile Dosimeters Dedicated to Reactor Pressure Vessel Surveillance

    Bourganel Stéphane

    2016-01-01

    Full Text Available Fissile dosimeters are commonly used in reactor pressure vessel surveillance programs. In this paper, the photofission contribution is analyzed for in-vessel 237Np and 238U fissile dosimeters in French PWR. The aim is to reassess this contribution using recent tools (the TRIPOLI-4 Monte Carlo code and latest nuclear data (JEFF3.1.1 and ENDF/B-VII nuclear libraries. To be as exhaustive as possible, this study is carried out for different configurations of fissile dosimeters, irradiated inside different kinds of PWR: 900 MWe, 1300 MWe, and 1450 MWe. Calculation of photofission rate in dosimeters does not present a major problem using the TRIPOLI-4® Monte Carlo code and the coupled neutron-photon simulation mode. However, preliminary studies were necessary to identify the origin of photons responsible of photofissions in dosimeters in relation to the photofission threshold reaction (around 5 MeV. It appears that the main contribution of high enough energy photons generating photofissions is the neutron inelastic scattering in stainless steel reactor structures. By contrast, 137Cs activity calculation is not an easy task since photofission yield data are known with high uncertainty.

  11. Photofission Analysis for Fissile Dosimeters Dedicated to Reactor Pressure Vessel Surveillance

    Bourganel, Stéphane; Faucher, Margaux; Thiollay, Nicolas

    2016-02-01

    Fissile dosimeters are commonly used in reactor pressure vessel surveillance programs. In this paper, the photofission contribution is analyzed for in-vessel 237Np and 238U fissile dosimeters in French PWR. The aim is to reassess this contribution using recent tools (the TRIPOLI-4 Monte Carlo code) and latest nuclear data (JEFF3.1.1 and ENDF/B-VII nuclear libraries). To be as exhaustive as possible, this study is carried out for different configurations of fissile dosimeters, irradiated inside different kinds of PWR: 900 MWe, 1300 MWe, and 1450 MWe. Calculation of photofission rate in dosimeters does not present a major problem using the TRIPOLI-4® Monte Carlo code and the coupled neutron-photon simulation mode. However, preliminary studies were necessary to identify the origin of photons responsible of photofissions in dosimeters in relation to the photofission threshold reaction (around 5 MeV). It appears that the main contribution of high enough energy photons generating photofissions is the neutron inelastic scattering in stainless steel reactor structures. By contrast, 137Cs activity calculation is not an easy task since photofission yield data are known with high uncertainty.

  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. Isoscaling and fission modes in the yields of the Kr and Xe isotopes from photofission of actinides

    Drnoyan, J.; Zhemenik, V. I.; Mishinsky, G. V.

    2016-05-01

    Yields of Kr and Xe isotopes in photofission of 232Th, 238U, 237Np, 244Pu, 243Am, and 248Cm were tested for isoscaling dependence. Isoscaling for Kr is revealed. For Xe, isoscaling is found to be affected by the STI and STII fission modes governed by the N = 82 and N = 88 neutron shells. The work was performed at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (JINR).

  17. 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.)

  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. 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

  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. 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

  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. 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.)

  4. Characterization of detector systems for photofission studies

    Thirolf, P.G.; Habs, D.; Tajima, T. [LMU Muenchen, Garching (Germany); Csatlos, M.; Csige, L.; Gulyas, J.; Krasznahorkay, A. [Inst. Nucl. Res. of the Hungarian Acad. of Sciences, Debrecen (Hungary); Fujiwara, M. [Res. Center f. Nucl. Phys., Osaka University (Japan); Pietralla, N.; Savran, D. [IKP, TU Darmstadt (Germany)

    2009-07-01

    A brilliant source of photon beams in the X-ray-MeV range can be realized by (coherent) Compton backscattering of laser photons off a dense relativistic electron mirror generated from thin (few nm) diamond-like carbon foils. Highly monochromatic photon beams can be expected with unprecedented photon flux intensities of up to 10{sup 12} photons/pulse at 8 MeV photon energy, operated at a laser repetition rate of 10 Hz. Such photon beams will offer new perspectives for photon-induced nuclear structure studies, e.g. in the second and third minima of actinides. Preparing for photofission studies in actinides, Parallel Plate Avalanche gas detector (PPAC) arrays have been commissioned, each equipped with a stack of 15-25 large area fissile actinide targets ({sup 235,238}U, {sup 232}Th), where the actinide targets simultaneously act as detector electrodes. Properties of the detector systems will be presented, which will be included in first experiments at the Darmstadt NEPTUN tagger facility or the NEW SUBARU facility in Osaka.

  5. 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

  6. 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...

  7. 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.

  8. 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.

  9. 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)

  10. 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)

  11. 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

  12. 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)

  13. 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

  14. 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.

  15. 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.

  16. 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)

  17. 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

  18. 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

  19. 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

  20. 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\

  1. Tests of a novel method to assay SNM using polarized photofission and its sensitivity in the presence of shielding

    A novel method to identify Special Nuclear Material was recently developed (Mueller et al., 2014) [1]. This method relies upon using a linearly polarized γ-ray beam to induce photofission of a sample and then comparing the prompt fission neutron yields in and out of the plane of beam polarization. The present paper will describe experimental tests of this new technique and assess its sensitivity in the presence of shielding. The capability of this technique to measure the enrichment of uranium was tested by using combinations of thin 235U and 238U foils of known enrichments. The sensitivity of this assay to shielding by lead, steel, and polyethylene was experimentally measured and simulated using GEANT4. These tests show that the measured asymmetry can indeed be used to determine the enrichment of materials composed of an admixture of 235U and 238U, and this asymmetry is relatively insensitive to moderate amounts of shielding

  2. 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)

  3. 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)

  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. 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.

  6. 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

  7. 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.

  8. 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)

  9. 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)

  10. 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

  11. 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.)

  12. 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)

  13. 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.

  14. (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

  15. 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

  16. 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.

  17. 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)

  18. 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...

  19. 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

  20. 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)

  1. 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...

  2. 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)

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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)

  9. 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)

  10. 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)

  11. 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).

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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)

  17. 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

  18. 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.

  19. Exploratory analysis of a neutron-rich nuclei source based on photo-fission

    A source of neutron rich ions can be conceived through the photo-fission process. An exploratory study of such a source is realized. A survey of the radiative electron energy loss theory is reported in order to estimate numerically the bremsstrahlung production of thick targets. The resulted bremsstrahlung angular and energy theoretical distributions delivered from W and UCx thick converters are presented and compared with previous results. Some quantities as the number of fission events produced in the fissionable source and the energy loss in the converters are also reported as function of the geometry of the combination and the incident electron energy. An attempt of comparison with experimental data shows a quantitative agreement. This study is focussed on initial kinetic energies of the electron beam included in the range 30-60 MeV, suitable for the production of large radiative γ-ray yields able to induce the 238U fission through the giant dipole resonance. A confrontation with the number of fission events produced in the frame of the fast neutron induced fission method indicates that the photo-fission can be a competitive concept

  20. Exploratory analysis of a neutron-rich nuclei source based on photo-fission

    A source of neutron reach ions can be conceived through the photo-fission process. An exploratory study of such a source is realized. A survey of the radiative electron energy loss theory is reported in order to estimate numerically the Bremsstrahlung production of thick target. The resulted Bremsstrahlung angular and energy theoretical distribution delivered from W and UCx thick converters are presented and compared with previous result. Some quantities as the number of fission events produce in the fissionable source and the energy loss in the converters are also reported as a function of the geometry of the combination and the incident electron energy. An attempt of comparison with experimental data shows a quantitative agreement. This study is focused on initial kinetic energies of the electron beam included in the range 30-60 MeV, suitable for the production of large radiative γ-ray yields able to induce the 238U fission through the giant dipole resonance. A confrontation with the number of fission events produced in the frame of the fast neutron induced fission method indicates that the photo-fission can be a competitive concept. (authors)

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. 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...

  10. 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).

  11. 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)

  12. 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 ...

  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. 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)

  16. 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.

  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. 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

  20. 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

  1. 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 %

  2. 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.

  3. 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)

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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)

  11. 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

  12. 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...

  13. 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.)

  14. 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

  15. 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

  16. 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)

  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. 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

  20. 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).

  1. 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.)

  2. 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)

  3. 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)

  4. 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

  5. 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

  6. 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)

  7. 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

  8. 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)

  9. 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

  10. 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{\\%}.

  11. 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)

  12. 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)

  13. 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

  14. 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)

  15. 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)

  16. 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

  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. 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

  19. 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.)

  20. 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.)

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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)

  6. 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

  7. 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

  8. 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.

  9. 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-...

  10. 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.)

  11. 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)

  12. Resource Note on Photofission of Nuclei

    Nieto, M M

    2003-01-01

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

  13. 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.

  14. 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

  15. 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)

  16. 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)

  17. 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)

  18. 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

  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. Exploratory analysis of a neutron-rich nuclei source based on photo-fission

    Mirea, M; Clapier, F; Essabaa, S; Groza, L; Ibrahim, F; Kandri-Rody, S; Müller, A C; Pauwels, N; Proust, J

    2003-01-01

    A source of neutron rich ions can be conceived through the photo-fission process. An exploratory study of such a source is realized. A survey of the radiative electron energy loss theory is reported in order to estimate numerically the bremsstrahlung production of thick targets. The resulted bremsstrahlung angular and energy theoretical distributions delivered from W and UCx thick converters are presented and compared with previous results. Some quantities as the number of fission events produced in the fissionable source and the energy loss in the converters are also reported as function of the geometry of the combination and the incident electron energy. An attempt of comparison with experimental data shows a quantitative agreement. This study is focussed on initial kinetic energies of the electron beam included in the range 30-60 MeV, suitable for the production of large radiative gamma-ray yields able to induce the $^{238}$U fission through the giant dipole resonance. A confrontation with the number of fi...

  1. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio [Universidad Simón Bolívar, Nuclear Physics Laboratory, Apdo 89000, Caracas 1080A (Venezuela, Bolivarian Republic of); Davila, Jesus [Física Médica C. A. and Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of)

    2015-07-23

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides {sup 232}Th, {sup 238}U and {sup 237}Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  2. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides 232Th, 238U and 237Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program

  3. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Davila, Jesus; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio

    2015-07-01

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e'n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides 232Th, 238U and 237Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  4. 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)

  5. 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)

  6. 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)

  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. 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)

  9. Multipole components of 235U photofission

    The absolute electrofission cross section for 235U has been experimentally obtained in the energy range 5.8 - 18.0 MeV, using the electron beam of the Linear Accelerator of Institute of Physics of the University of Sao Paulo. From a combined analysis of this cross section and a previously measured photofission cross section, using virtual photon spectra calculated in the Distorted Wave Born Approximation (DWBA), the '' non electric dipole photofission'' cross section σNDEγ,f (ω) has been obtained, which contains all multipolarities allowed by the reaction Kinematics, except El. This cross section presents a resonant shape, probably associated with the Giant Quadrupole Resonance (GQR). Once the fission channel exhausts a great amount of the Energy Weighted Sum Rule (EWSR), it is therefore the major decay mode of the GQR. All these aspects agree with the ones verified for the other Uranium isotopes previously analysed in this Laboratory. (author)

  10. 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

  11. 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

  12. 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)

  13. 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

  14. 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

  15. 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.

  16. 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

  17. 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...

  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. 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

  20. 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°.

  1. 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

  2. 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

  3. 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. ...

  4. 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.

  5. 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)

  6. 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.)

  7. 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)

  8. 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)

  9. 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

  10. 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

  11. 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.

  12. 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)

  13. 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

  14. 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

  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. 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

  19. 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

  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. Simulation of photofission experiments at the ELI-NP facility

    Constantin, P.; Balabanski, D. L.; Cuong, P. V.

    2016-04-01

    An extensive experimental program for the study of photofission will take place at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility, where different actinide targets will be exposed to a brilliant gamma beam to produce fission fragments. We report on the implementation within the Geant4 simulation toolkit of the photofission process, of related background processes, and of extended ionic charge parameterization. These developments are used to evaluate the production rates of photofission fragments and their release efficiency from the actinide targets.

  2. 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)

  3. 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

  4. 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.

  5. 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)

  6. 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.

  7. 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

  8. 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)

  9. 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

  10. 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.)

  11. 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

  12. 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)

  13. 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

  14. 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.

  15. 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)

  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. Heavy Nuclei Photofission at Intermediate Energies

    Deppman, A; Guimaraes, V; Demekhina, N A; Karapetyan, G S

    2013-01-01

    In the present work the yields of fission fragments, from Bremsstrahlung induced fission of 232Th, 238U targets, were reproduced by CRISP model calculations, to which a multimodal fission option had been added. An extension of the calculation to the properties of the fission products is presented. Dividing the fissioning nuclei according to their fissionability, an approach which accounts for the contribution of symmetric and asymmetric fission is introduced. It allows to calculate the main parameters of the fission fragment charge distribution: the most probable charge for a given fission product mass chain and the width parameter. Furthermore, it reproduces the features of fragment mass distribution, and evaluates the fissility of fissioning nuclei in photon-induced fission. A comparison between the results of this calculation and experimental data is accomplished.

  18. 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)

  19. 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

  20. 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)

  1. 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.

  2. 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.

  3. 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)

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. 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.

  11. 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

  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. 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

  14. 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.

  15. 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.

  16. 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)

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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...

  4. 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

  5. Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification

    John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

    2012-11-01

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

  6. 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

  7. 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.

  8. 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)

  9. 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.

  10. 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

  11. Self-absorption correction in determining the 238U activity of soil samples via 63.3 keV gamma ray using MCNP5 code

    The essential issue in analyzing the activity of 238U in an HPGe detector based gamma spectrometer via 63.3 keV line is relating to the strong self-absorption of this weak gamma ray in sample material. The present work suggests a method of the self-absorption corrections for 63.3 keV gamma rays by a combination of experimental measurements and Monte Carlo MCNP5 calculations. The effects of sample chemical composition, density and geometry were calculated in terms of self-attenuation factors. The method, developed for a cylindrical sample geometry, accounted for variable sample heights and densities. The analysis of 238U activity was applied for three main soil types in Vietnam, which are grey, alluvial and red soils. The results obtained with the above outlined method were in good agreement with those derived by other methods. - Highlights: ► Determination of the 238U activity via 63.3 keV gamma rays. ► Self-attenuation factors of 63.3 keV gamma rays for cylindrical sample container. ► The density, chemical composition and geometry effects are taken into account. ► Determination of the 238U activity in three soil types: grey, alluvial and red soils.

  12. 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.

  13. 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

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

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

    2016-04-01

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

  15. Intake of 238U and 232Th through the consumption of foodstuffs by tribal populations practicing slash and burn agriculture in an extremely high rainfall area

    The concentration of naturally occurring radionuclides 232Th, 238U was determined using Instrumental Neutron Activation Analysis (INAA) in different food groups namely cereals, vegetables, leafy vegetables, roots and tubers cultivated and consumed by tribal population residing around the proposed uranium mine. The study area is a part of rural area K. P. Mawthabah (Domiasiat) in the west Khasi Hills District of Meghalaya, India located in the tropical region of high rainfall that remains steeped in tribal tradition without much outside influence. Agriculture by Jhum (slash and burn) cultivation and animal husbandry are the main occupation of the tribal populations. A total of 89 samples from locally grown food products were analyzed. The concentration of 238U and 232Th in the soil of the study area was found to vary 1.6–15.5 and 2.0–5.0 times respectively to the average mean value observed in India. The estimated daily dietary intake of 238U and 232Th were 2.0 μg d−1 (25 mBq d−1) and 3.4 μg d−1 (14 mBq d−1) is comparable with reported range 0.5–5.0 μg d−1 and 0.15–3.5 μg d−1 respectively for the Asian population. - Highlights: ► 232Th, 238U were determined using Instrumental Neutron Activation Analysis (INAA). ► Study area located in the tropical region of high rainfall that remains steeped in tribal tradition. ► Agriculture by Jhum (slash and burn) cultivation and animal husbandry are the main occupation of the tribal populations. ► The estimated daily intake of 232Th and 238U in high rainfall area was found to be 3.4 and 2.0 μg respectively.

  16. Photofission tomography of nuclear waste packages

    Quantifying the mass of actinides in large concrete waste packages using non-destructive methods is a major challenge for the management and the storage of packages in appropriate facilities. Since the beginning of 1990s, our team in CEA has been working on the development of a method based on interrogation with high-energy photons to assay actinides in large concrete waste package. The method consists in using photons of high energy (bremsstrahlung radiation) in order to induce photofission reactions on the fissile nuclei present in the wastes. The measurement of the delayed neutrons emitted by fission products allows us to quantify the actinides present in the wastes. The accuracy of the method can be deeply improved by carrying out a tomography, i.e. computing the three-dimensional spatial distribution of the actinide mass inside the nuclear waste package. This paper presents the first experimental results of a tomography carried out on a 1.2 t real concrete waste package. Measurements associated with reconstruction algorithms and Monte Carlo simulations have allowed to locate an equivalent mass of 690 mg of uranium 238 centered in a disc of 20-25 cm of diameter at 75 cm height. These measurements have been performed in the SAPHIR irradiation facility at CEA/Saclay. This facility houses a pulsed linear electron accelerator (energy range from 15 to 30 MeV, pulse duration of 2.5 μs, peak current of 130 mA). The located mass has been subsequently confirmed by a destructive analysis of the package

  17. Observation of an isomeric level in 239U by means of the 238U(n,γ)239U reaction

    Low-energy-capture gamma-ray spectra (238U up to a neutron energy of 350 eV. The data were obtained using a 25-cm3 Ge(Li) detector at the Harwell 45 MeV Electron Linac. Capture events were recorded as functions of gamma-ray energy and neutron time-of-flight, and by suitable analysis of the data time-of-flight spectra have been obtained for individual gamma-rays. The strongest low-energy gamma-ray, at 134 keV, depopulates a level in 239U at the same energy by an E2-transition to the ground state. The time-of-flight spectrum for this transition indicates that the 134-keV level is isomeric with a half-life of approximately 1 microsecond. This is evident from the long tails on the low-energy side of each resonance, which are not present for other regions of the gamma-ray spectrum. The possibility of using low-energy gamma-rays as a measure of the total capture cross-section is investigated by comparing the time-of-flight spectrum for the 134-keV transition with that for a Moxon-Rae detector under the same experimental conditions. (author)

  18. A Study of the Resonance Interaction Effect between 238U and 239Pu in Lower Energy Region

    An investigation has been made of the statistical frequency function for the distances between the 238U and the 239Pu resonances in the region 4-244 eV. It is concluded that the frequency function is probably constant but that the distances diverge appreciably from a constant function in the actual case, and that the divergence is such that the interaction effect on the resonance integral is smaller than would be expected from statistical considerations. This is also confirmed by calculations on the interaction effect. These have been performed using three different methods, namely: a) considering the actual positions and widths of the resonances, b) assuming a constant frequency function for the resonance. spacing and applying a theory developed by Rowlands and E A Fischer. c) applying a simplified, approximate method for calculations based on the statistical theory. The calculations are made for two temperatures and two values of the plutonium enrichment. It is shown that the average cross sections are considerably larger than the statistical calculations indicate

  19. Neutron capture cross section measurements of $^{238}$U, $^{241}$Am and $^{243}$Am at n_TOF

    Koehler, P E; Plag, R

    The increase of the world energy demand and the need of low carbon energy sources have triggered the renaissance and/or enhancement of nuclear energy in many countries. Fundamental nuclear physics can contribute in a practical way to the sustainability and safety of the nuclear energy production and the management of the nuclear waste. There exists a series of recent studies which address the most relevant isotopes, decay data, nuclear reaction channels and energy ranges which have to be investigated in more detail for improving the design of different advanced nuclear systems [1] and nuclear fuel cycles [2]. In this proposal, we aim at the measurement of the neutron capture cross sections of $^{238}$U, $^{241}$Am and $^{243}$Am. All three isotopes are listed in the NEA High Priority Request List [37], are recommended for measurements [1] and play an important role in the nuclear energy production and fuel cycle scenarios. The measurements will provide as well valuable nuclear structure data necessary for the...

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

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

    2005-01-01

    Lichens are widely used to assess the atmospheric pollution by heavy metals and radionuclides. However, few studies are available in publications on using lichens to qualitatively assess the atmospheric pollution levels. The paper presents research results applying epiphytic lichens as bio-monitors of quantitative atmospheric contamination with uranium. The observations were conducted during 2.5 years in the natural environment. Two experimental sites were used: one in the vicinity of a uranium contamination source, the other one - at a sufficient distance away to represent the background conditions. Air and lichens were sampled at both sites monthly. Epiphytic lichens Hypogimnia physodes were used as bio-indicators. Lichen samples were taken from various trees at about 1.5m from the ground. Air was sampled with filters at sampling stations. The uranium content in lichen and air samples as well as isotopic mass ratios (235)U/(238)U were measured by mass-spectrometer technique after uranium pre-extraction. Measured content of uranium were 1.45 mgkg(-1) in lichen at 2.09 E-04 microgm(-3) in air and 0.106 mgkg(-1) in lichen at 1.13 E-05 microgm(-3) in air. The relationship of the uranium content in atmosphere and that in lichens was determined, C(AIR)=exp(1.1 x C(LICHEN)-12). The possibility of separate identification of natural and man-made uranium in lichens was demonstrated in principle. PMID:16083999

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

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

    2015-09-01

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

  2. Origin and geochemical behavior of uranium in marine sediments. Utilization of the 234U/238U ratio in marine geochemistry

    The first part of this thesis presents the current situation of knowledge of uranium in marine environment. The second part describes the methods of analysis as well as the material support of the study, i.e., the sediments and marine deposits investigated. The third part is dedicated to the study of uranium mobility in marine sediments characterized by detrital terrigenous composition (pelagic clays). This approach allowed quantifying the entering and leaving flux of uranium after the sediment settling and, to discuss, on this basis, the consequences on the uranium oceanic balance. In the third part the origin and behavior of uranium in zones of high surface productivity is studied. The uranium enrichments observed in the hemi-pelagic sediments of the EUMELI (J.G.O.F.S.-France) programme will constitute a material of study adequate for measuring the variations in the 234U/238U ratio in solid phase, in response to the oxido-reducing characteristics of the sediment. Thus establishing the origin of the trapped uranium has been possible. Also, the nature of the sedimentary phases related to uranium in bio-genetic sediments in the Austral Ocean was determined. Thus a relationship between the variations in the 234U/238 and the diagenetic transformations was possible to establish. Finally in the fifth part a study of the behavior of uranium in a polymetallic shell characteristic for deposits of hydrogenized origin

  3. 230Th, 232Th and 238U determinations in phosphoric acid fertilizer and process products by ICP-MS

    Through processing of Santa Quiteria-CE mine phosphate rock, Brazil has established a project for production of phosphoric acid fertilizer and uranium as a by-product. Under leaching conditions of phosphate rock with sulfuric acid, which is the common route for preparing phosphoric acid fertilizer, a large part of uranium, thorium and their decay products naturally present in the rock are solubilized. In order to assess the contamination potential in phosphoric acid and others process products, this paper describes a previous precipitation and direct methods for routine analysis of thorium and uranium isotopes by ICP-MS. In all samples, 230Th, 232Th and 238U were directly determined after dilution, except 230Th in phosphoric acid loaded with uranium sample, which to overcome equipment contamination effect, was determined after its separation by oxalate precipitation using lanthanum as a carrier. The results obtained by the proposed method by ICP-MS, were in good agreement when compared to alpha spectrometry for 230Th, and ICP-OES and spectrophotometry with arsenazo III for elementary uranium and thorium determinations. (author)

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

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

    2015-10-01

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

  5. Magmatic evolution of a volcano studied by 230Th-238U disequilibrium and trace elements systematics: the Etna case

    Age determinations of several lava flows from Etna through 230Th-238U disequilibrium (internal isochrons) yield a precise chronology of the volcano's history for the last 200,000 years, and emphasize the main episodes in the formation of this huge complex strato-volcano. Study of (230Th/232Th)0 initial ratios of lavas together with their trace-element compositions yields a consistent model of magmatic evolution implying the existence, for 200,000 years, of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity. These short periods of mixing appear to be related to the formation of the large calderas of Etna. In addition to these processes affecting the deep reservoir, fractional crystallization also occurred in more superficial levels of the volcanic edifice, thereby yielding several series of differentiation of relatively short duration. As for its geochemistry, Etna's volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context, at the edge of the African Plate. (author)

  6. Determination of 234U and 238U activity concentrations in groundwaters from three deep wells drilled in Itu Intrusive Suite (SP)

    Activity concentrations of (234U) and (238U) were determined in groundwaters drawn from three deep wells drilled in rocks from Itu Intrusive Suite (SP), two located in Salto town (S and SY wells) and the other one in Itu (I well). Sampling was done from September, 2004 to December, 2005, and twelve samples of each well were collected monthly. For those determinations alpha spectrometry technique was used, providing high precision results, as shown by the very good agreement of the data obtained in the analyses of 23 duplicates. The waters from the three wells presented a considerable enrichment of 234U in relation to 238U, indicating an important radioactive disequilibrium of these isotopes. In well I, the activity concentrations of (238U) varied from (1,06 +- 0,03) to (2,1+- 0,2) mBq/L and those of (234U) spanned from (3,1 +- 0,2) to (6,0 +- 0,4) mBq/L, whereas (234U/238U) activity ratios did not present significant variation, during the sampling time interval, presenting an average of 2,8 +- 0,1. The S waters showed the lowest uranium concentrations and the largest diversity of (238U) and (234U) activity concentrations, which varied from (0,26 +- 0,02) to (1,07+- 0,08) mBq/L and from (1,8 +- 0,1) to (7,0 +- 0,5) mBq/L, respectively, and also presented variable (234U/238U) activity ratios, spanning from (2,79 +- 0,07) to (8,1+- 0,3). In SY well, (238U) activities varied between (0,8 +- 0,1) and (4,2 +- 0,3) mBq/L and those ones of (234U) from (14 +- 1) to (53 +- 4) mBq/L, whereas (234U/238U) ratios fell in the interval from 12,6 +- 0,3 to 18,3 +- 0,4, with the highest activities of both radioisotopes registered during the dry season and the lowest ones in the rainy time period. The (234U/238U) activity ratios, which were invariable during sampling period of well I, indicated the contribution of rainfall to recharge the aquifer. The observed correlation between those ratios and uranium concentrations, for S and SY wells, showed complex and distinct recharging

  7. Bioaccumulation of polonium ({sup 210}Po) and uranium ({sup 234}U, {sup 238}U) in plants around phosphogypsum waste heap in Wislinka (northern Poland)

    Borylo, A.; Skwarzec, B. [Gdansk Univ. (Poland). Faculty of Chemistry

    2011-07-01

    In the study the activities of polonium {sup 210}Po and uranium {sup 234}U, {sup 238}U in plants, collected near phosphogypsum waste heap in Wis'linka (northern Poland), were determined by using the alpha spectrometry. The obtained results revealed that the concentrations of {sup 210}Po, {sup 234}U, and {sup 238}U in the analyzed plants were differentiated. In the analyzed flora organisms the highest amounts of polonium and uranium were found in ruderal plant samples as well as willow samples (Salix viminalis) from protection zone of phosphogypsum waste heap. The concentrations of {sup 210}Po, {sup 234}U and {sup 238}U in the analyzed plants were higher in roots than in green parts of plants. The higher concentrations of {sup 210}Po and {sup 238}U radionuclides were estimated for hydrophyte (common sedge Carex nigra Reichard), the favourite habitat of which is particularly wet meadow and for plants collected in the vicinity of phosphogypsum waste heap. The major source of polonium and uranium in analyzed plants is root system. The values of {sup 234}U/ {sup 238}U activity ratio in all analyzed plants are closed to one, what indicated that source of uranium in analyzed plants is phosphogypsum. The highest uranium and polonium concentrations were characterized for plants, which are covered with tomentose. The comparability polonium and uranium contents were confirmed in edible plants, but higher accumulation was determined in ripe species than immature species of vegetables. The higher polonium and uranium concentrations were noticed in green parts of plant, the lower in roots. Polonium concentration in cultivated plants samples was not species diverse. Therefore, the significant source of polonium and uranium in analyzed plants is wet and dry atmospheric falls gathering the soil and air dust from phosphogypsum waste dump. The maximum {sup 210}Po and {sup 238}U radionuclides concentrations were found in green parts of red beet (Beta vulgaris esculenta), the

  8. Activity concentrations of {sup 238}U and {sup 226}Ra in scales formed on pipes of industrial boilers in the state of Pernambuco, Brazil

    Poggi, Claudia M.B.; Farias, Emerson E.G. de, E-mail: claudiapoggi04@gmail.com, E-mail: emersonemiliano@yahoo.com.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Franca, Elvis J.; Hazin, Clovis A., E-mail: chazin@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Gazineu, Maria H.P., E-mail: helena@unicap.br [Universidade Catolica de Pernambuco (UNICAP), Recife, PE (Brazil). Centro de Ciencias e Tecnologia

    2015-07-01

    The procedures employed in the industry can generate significant amounts of solid, liquid and gaseous wastes that usually contain toxic or materials of difficulty degradation. One of the facts that contribute to the formation of such wastes is the generation of steam used in operating processes and industry segments. Currently, steam supplied by boilers is the most economical and practical mode of heat transfer in industrial processes. Due to the high temperature of water used in these processes, compounds which were previously soluble become insoluble, generating residues called scales. This material, which contains stable ions, can also present naturally occurring radionuclides such as {sup 238}U and {sup 226}Ra, which concentrate over time in piping and equipment surfaces. If not disposed correctly, this material also can contaminate the environment. The main origin of these radionuclides is the use of groundwater in industrial processes. Thus, in regions of naturally enriched in radionuclides such as the Region of Pernambuco, including the municipalities of Paulista and Goiana, there is a greater possibility of radioactive scale formation. Therefore, this study aimed to determine the activity concentrations of {sup 238}U and {sup 226}Ra present in the solid wastes generated by industries situated in Paulista and Goiana, in order to assess radionuclide disequilibrium. For the sake of comparison, scale samples collected from industries located in the municipality of Caruaru, far from the previous municipalities, were also analyzed. The determination of the activity concentrations for {sup 238}U and {sup 226}Ra was performed by High Resolution Gamma-Ray Spectrometry. Samples were collected, prepared, packed in plastic containers and set aside for a minimum time of 21 days, for the secular equilibrium to occur between {sup 226}Ra and its short lived descendants. The counting time was 80,000 seconds. Gamma energies used for determination of activity concentrations

  9. Activity concentrations of 238U and 226Ra in scales formed on pipes of industrial boilers in the state of Pernambuco, Brazil

    The procedures employed in the industry can generate significant amounts of solid, liquid and gaseous wastes that usually contain toxic or materials of difficulty degradation. One of the facts that contribute to the formation of such wastes is the generation of steam used in operating processes and industry segments. Currently, steam supplied by boilers is the most economical and practical mode of heat transfer in industrial processes. Due to the high temperature of water used in these processes, compounds which were previously soluble become insoluble, generating residues called scales. This material, which contains stable ions, can also present naturally occurring radionuclides such as 238U and 226Ra, which concentrate over time in piping and equipment surfaces. If not disposed correctly, this material also can contaminate the environment. The main origin of these radionuclides is the use of groundwater in industrial processes. Thus, in regions of naturally enriched in radionuclides such as the Region of Pernambuco, including the municipalities of Paulista and Goiana, there is a greater possibility of radioactive scale formation. Therefore, this study aimed to determine the activity concentrations of 238U and 226Ra present in the solid wastes generated by industries situated in Paulista and Goiana, in order to assess radionuclide disequilibrium. For the sake of comparison, scale samples collected from industries located in the municipality of Caruaru, far from the previous municipalities, were also analyzed. The determination of the activity concentrations for 238U and 226Ra was performed by High Resolution Gamma-Ray Spectrometry. Samples were collected, prepared, packed in plastic containers and set aside for a minimum time of 21 days, for the secular equilibrium to occur between 226Ra and its short lived descendants. The counting time was 80,000 seconds. Gamma energies used for determination of activity concentrations were 1001 keV for 238U, and 352 keV, 609 ke

  10. A statistical study of 238U and 234U/238U distributions in coral samples from the Egyptian shoreline of the north-western Red sea and in fossil mollusk shells from the Atlantic coast of High Atlas in Morocco: implications for 230Th/234U dating

    In this work, radiochemical analysis results of 126 uncrystallized coral samples from the Egyptian shoreline of northwestern Red Sea and 120 fossil mollusk shell samples from the Atlantic coast of Moroccan High Atlas at the North of Agadir City in Morocco are presented and discussed. The coral samples were collected in Egypt from the emerged coral reef terraces over 500 km from The Ras Gharib-Ras Shukeir depression (28 10') in the north to Wadi Lahami (north of Ras Banas, 24 10') in the south. The fossil mollusk shells were collected in Morocco from Agadir-Harbour in the south to Tamri village in the north extending over about 50 km. The statistical distributions of results (238U content, 234U/238U activity ratio and ages) obtained on the dated materials in the two different regions were compared for three fossil sea levels corresponding to three different climatic stages (Holocene, 5e, 7 and/or 9) in the aim to establish methodological criteria for judging validity of the measured ages. For corals, 238U content varies in narrow interval around the same average value of 3 ppm for the three sea levels, the calculated initial 234U/238U values are in agreement with the actual sea water ratio (1.15) with some values slightly higher than for the older sea levels. The obtained ages are in good agreement with the ages reported previously for the three emerged fossil sea levels on unrecrystallized corals by alpha spectrometry and by mass spectrometry. For mollusk shells, except for Holocene sea level, 238U and initial 234U/238U activity ratios vary for the older levels in wide intervals, independent of species and calcite contents of samples. The high 238U contents and 234U/238U activity ratio are due eventually to a post-incorporation of secondary uranium from sea water or from continental waters drained away rivers. This incorporation leads to a rejuvenation of mollusk shell ages and is responsible for the wide dispersion of their apparent ages according to the mode and

  11. Understanding and modeling of the vertical downward migration of 238U within the soil profile of south-western (SW) Punjab, India

    The vertical downward migration of 238U in soils collected from south-western Punjab was studied from the depth distributions using the diffusion-convection model. The time-dependent convective rates (ν) of 238U were found to be in the order of 10-7-10-4 cm year-1, whereas under the assumption of steady state (time-independent), values were in the order of 10-5-10-4 cm year-1. However, the diffusion rates (D) were in the order of 10-6-10-3 cm2 year-1 and under the steady state, values obtained to be relatively higher as 0.002-0.70 cm2 year-1. These values were within the range of reported literature values. (author)

  12. Bioaccumulation of polonium (210Po, uranium (234U, 238U isotopes and trace metals in mosses from Sobieszewo Island, northern Poland

    Boryło A.

    2013-04-01

    Full Text Available The objective of this study was determination of the polonium (210Po, uranium (234U and 238U radionuclides and trace metals (Pb, Fe, Zn, Cu, Ni, Cd, Hg concentrations in mosses samples from Sobieszewo Island near the phosphogypsum waste dump in Wiślinka (northern Poland. The obtained results revealed that the concentrations of 210Po, 234U, and 238U in the two analyzed kinds of mosses: Pleurozium schreberi and Dicranum scoparium were similar. Among the analyzed trace metals the highest concentration in mosses was recorded for iron, while the lowest for nickel, cadmium and mercury. The obtained studies showed that the sources of polonium and uranium isotopes, as well as trace metals in analyzed mosses are air city contaminations transported from Gdańsk and from existing in the vicinity the phosphogypsum waste heap in Wiślinka (near Gdańsk.

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

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

    2011-02-01

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

  14. Distribution of radioactive pollution of 238U, 232Th, 40K and 137Cs in northwestern coasts of Persian Gulf, Iran

    A reconnaissance study has been made of the distribution of 238U, 232Th, 40K and 137Cs and geochemical features in soils and sediments samples at various locations in the northwestern coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 30 soil and sediment samples collected from this region. From the measured spectra, activity concentrations were determined for 40K (range from 146 to 500 Bq kg-1), 137Cs (from 5 to 20 Bq kg-1), 238U (from 21 to 65 Bq kg-1) and 232Th (from 15 to 45 Bq kg-1) with lowest limit detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq kg-1, respectively. The dose rate from ambient air at the soil ranges was between 19 and 58 nGy h-1 with an average of 37.41 ± 9.66 nGy h-1

  15. Study of the 238U(d,p) surrogate reaction via the simultaneous measurement of gamma-decay and fission probabilities

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

    2015-01-01

    We investigated the 238U(d,p) reaction as a surrogate for the n + 238U reaction. For this purpose we measured for the first time the gamma-decay and fission probabilities of 239U* simultaneously and compared them to the corresponding neutron-induced data. We present the details of the procedure to infer the decay probabilities, as well as a thorough uncertainty analysis, including parameter correlations. Calculations based on the continuum-discretized coupled-channels and distorted-wave Born approximations were used to correct our data from detected protons originating from elastic and inelastic deuteron breakup. The corrected fission probability is in agreement with neutron-induced data, whereas the gamma-decay probability is much higher than the neutron-induced data. The performed statistical-model calculations are not able to explain these results.

  16. Desequilibri 234Th/238U per a l'estudi del cicle de partícules al Mediterrani nord-occidental

    Bermejo Cisneros, Mercè; Masqué Barri, Pere

    2010-01-01

    El desequilibri 238U/234Th s'utilitza per traçar el cicle de les partícules a la part més superficial dels oceans. Això és possible degut a les diferències entre els seus períodes de semidesintegració (T1/2 (234Th)=24,1 d; T1/2 (238U)=4,5 10 9 anys) i a les seves característiques biogeoquímiques: el Th presenta una gran afinitat per les partícules mentre que l'U és conservatiu en aigua de mar. En absència de partícules s'esperaria tenir equilibri secular entre ambdós radionúclids, però com qu...

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

    Aerosols of depleted uranium oxides, formed upon high-energy impact of shells on hard targets during military operations, are able to disperse, reach the alveolar region of the lungs and be absorbed and distributed throughout various parts of the body. The absorbed particles are subjected to clearance in the upper respiratory tract, distribution to other body districts, dissolution and excretion. While the soluble forms of uranium are known to deliver a small dose of radiation to the body due to their homogeneous distribution and the low specific activity of 238U, ceramic particles exhibit a low dissolution rate and irradiate a limited volume of tissue for a long time with alpha particles with an energy of 4.267 MeV. The extent of the irradiated tissues depends on the radius of the particles and the total intake of uranium oxides. For the measured intake of U3O8 of a war veteran (15.51 μg) the number of particles ranges from 5.56x104 to 6.95x106 for sizes of 0.4-2.0 μm. Modelling the distribution of the particles between two compartments of the body, the averaged dose absorbed in 20 y by tissues surrounding the particles and within the range of the alpha particles varies from 6.8 mGy to 0.85 Gy for lungs and 8.1 mGy to 1.0 Gy for the lymph nodes, respectively. Correspondingly, due to the clearance and redistribution, the mass irradiated by 2.0-mm particles falls in 20 y from 6.06 mg to 0.94 μg in the lungs and grows from 0 to 1.0 mg in the lymph nodes. The estimated rate of formation of hydroxyl radicals upon radiolysis of water in the lungs and lymph nodes is 5.17x104 d-1 per cell after 1 y. (authors)

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

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

    2010-02-01

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

  19. Evaluation of the extractive procedure for determination of 238U and 234U in groundwater and comparison with traditional α-spectrometry technique

    Photon/Electron Rejecting Alpha Liquid Scintillation (PERALS) spectrometry has been used for the determination of uranium radionuclides in the ground water samples. The technique utilizes a commercially available extractive scintillant URAEX, which is selective for uranium. The cocktail extracted uranium from aqueous medium quantitatively and the efficiency of extraction was nearly 100% with no self-absorption or geometry problems. This method applies to pulse-shape discrimination of PERALS counting spectrometry and completely separates the alpha activity from the beta/gamma background. The resolutions of the 238U, 234U and 232U obtained in this method were good enough to for measurement of uranium isotopes in a quantitative way. The lower limit of detection was found to be 2.0 mBq l-1 for 2 hours counting time for a sample volume of 200 ml. The levels of 238U and 234U concentrations in groundwater samples of several locations were found to range from 12.8 ± 1.0 to 148.3 ± 10.8 mBq l-1 and 16.1 ± 1.2 to 106.7 ± 8.2 mBq l-1, respectively. For the bottled drinking water samples collected from markets, the 238U and 234U concentrations were found to range from below detectable level (BDL) to 38.7 ± 2.4 mBq l-1 and 47.3 ± 2.8 mBq l-1, respectively. The results of uranium radionuclides (238U and 234U) in groundwater and bottled water samples measured by PERALS method were compared with that obtained by alpha spectrometric method. (author)

  20. Improving the Neutron Cross-section Standards 238U(n,f) and 6Li(n,a) : Measurements and Simulations

    Jansson, Kaj

    2015-01-01

    Improving or extending the range of cross-section standards, which in general are believed to be well known, require good control of the experimental conditions and the uncertainties involved. Two experiments that aspire to improve two different neutron cross-section standards, 238U(n,f) and 6Li(n,a, are presented in this thesis. Both standards have previously been extensively measured, but outside certain energy ranges discrepancies exist. In this thesis, a future precision measurement of th...

  1. Measurement of the energy deposition profile for 238U ions with specific energy 500 and 950 MeV/u in stainless steel and copper targets

    The paper presents the results of precision measurements of the total stopping range and energy deposition function of 238U ions with specific energies E = 500 and 950 MeV/u in stainless steel and copper targets. The experiment was performed at the SIS-18 facility (GSI Darmstadt) in the experimental area Cave A in September 2004-May 2005. The measured energy deposition profiles are compared with calculations using the codes ATIMA, PHITS, SHIELD and SRIM

  2. Measurement of the 238U to 235U fission cross-section ratio for neutron energies between 0.1 and 25 MeV

    The 238U to 235U fission cross-section ratio was measured for incident neutrons from 0.1 to 25.0 MeV. A ratio shape measurement was normalized by the threshold cross-section method. A fission cross-section ratio of 0.436 +- 0.004 was found averaged over neutron energies from 2.35 to 2.95 MeV. 8 figures, 12 tables

  3. Study of The Total Reaction Cross Section of 17.0 MeV=N 132 Xe + 238 U Heavy Ion Interactions

    BALUCH, J.J.; Khan, E. U.

    1998-01-01

    We have studied heavy ion nuclear interactions of 17.0 MeV/N 132Xe+238U using muscovite mica as Solid State Nuclear Track Detector (SSNTD). Experimental reaction cross section has been determined by two independent methods. Theoretical reaction cross section has been calculated by a classical formula taking into account the energy dependence of the nuclear radius parameter. The cross section determined in the present work has been compared with those at two other energies for the same reaction.

  4. On the energy balance and on dynamical aspects of proton induced fission of 235,236,238U by coincident spectroscopy of neutrons and fragments

    An improved experimental set up has been developed and applied to the measurement of neutrons in coincidence with fragments originating in proton induced fission of heavy nuclei. The reaction systems studied were p+235,236,238U for Ep = 12.84 MeV and Ep = 20.4 MeV. Data interpretation focuses on the following aspects: 1. Neutron multiplicities and average kinetic energies were studied as a function of fragment mass and total kinetic energies of these fragments. 2. The isotropic (i.e. the prefission plus scission) neutrons reveal a dependence of their multiplicities on the primary excitation energy E*CN that indicates a preference of the neutron over the fission exit channel with increasing E*CN not found in statistical model calculations. 3. A consistent analysis of all existing data for p+235,236,238U covering the interval 18 MeV ≤ E*CN ≤ 30 MeV in terms of neutron multiplicities and nuclear temperatures yields that pre- and postfission neutrons carry away comparable fractions of the additional energy ΔE*CN. 4. The total energy released in neutron and fragment emission is shown for p+238U (Ep = 20.4 MeV) to compare with the energy expected from mass tables for the fragmentations selected to within 2-3%. (orig.)

  5. Determination of the 238U capture to total fission ratio in alternate depleted uranium/polyethylene shells with D-T neutrons

    Aiming at checking the conceptual design of the subcritical blanket in the fusion–fission hybrid reactor, an integral experiment was carried out on an alternate depleted uranium/polyethylene-shell setup with D-T neutrons using activation technique. 18 depleted uranium foils were placed at 90° direction to the incident D beam, and the distribution of the 238U capture to total fission ratio was determined by measuring the 277.6 keV γ ray generated by neutron capture of 238U and the 293.3 keV γ ray generated by fission of 235U and 238U. The ratios were generally between 1 and 2 in the depleted uranium shells, with relative uncertainties between 3.0% and 5.5%. The ratios were calculated by the MCNP4B code employing ENDF/B-VI nuclear data library, the discrepancies between calculations and experiments were all within 6%, and the average calculation to experiment(C/E) ratio was 0.998.

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

    This report is in two parts. The first part reports on the experimental work determining the half-life for double beta decay of 238U to 238PU to be (2.0 ± 0.6) x 1021 years. This is the first evidence for a third mode of decay of this heaviest naturally occurring nucleus. This rate is about 106 times slower than spontaneous fission, which itself is about 106 times slower than alpha decay. The implication of this double beta decay to neutrino masses depends on uncertain theoretical calculations of the rate for such a heavy nucleus. The second part reports on yields of principal fission products from 5.6, 7.3, 9.4, and 11.5 MeV proton interactions with 238U. The yields at 11.5 MeV are similar to those from 14 MeV neutron fission of 238U. At the same time, the production cross sections of 238Np at the same energies are determined. This nuclide is produced as often as fission at the lowest energy but only 3.8% as often at the highest energy

  7. Uncertainty analysis on reactivity and discharged inventory for a pressurized water reactor fuel assembly due to 235,238U nuclear data uncertainties

    This paper discusses the uncertainty analysis on reactivity and inventory for a typical PWR fuel element as a result of uncertainties in 235,238U nuclear data. A typical Westinghouse 3-loop fuel assembly fuelled with UO2 fuel with 4.8% enrichment has been selected. The Total Monte-Carlo method has been applied using the deterministic transport code DRAGON. This code allows the generation of the few-groups nuclear data libraries by directly using data contained in the nuclear data evaluation files. The nuclear data used in this study is from the JEFF3.1 evaluation, and the nuclear data files for 238U and 235U (randomized for the generation of the various DRAGON libraries) are taken from the nuclear data library TENDL. The total uncertainty (obtained by randomizing all 238U and 235U nuclear data in the ENDF files) on the reactor parameters has been split into different components (different nuclear reaction channels). Results show that the TMC method in combination with a deterministic transport code constitutes a powerful tool for performing uncertainty and sensitivity analysis of reactor physics parameters. (authors)

  8. Assessment of annual effective dose from 238U and 226Ra due to consumption of foodstuffs by inhabitants of Tehran city (IR)

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

  9. Concentrations of uranium and 235U/238U ratios in soil and plant samples collected around the uranium conversion building in the JCO campus

    In order to assess possible contamination by U in the JCO campus following the criticality accident, 10 soil samples and 15 plant samples were collected around the uranium conversion building. Uranium concentrations and isotopic compositions (235U/238U ratio) were determined by ICP-MS. Concentrations of Th in soil were also determined for comparison. Concentrations of U in soils were comparable to the U values for common Japanese soils. However, the U/Th ratios for these soil samples were markedly higher than the control value, suggesting possible contamination by U. The 235U/238U atom ratios in soil and plant samples were notably higher than the natural ratio, 0.00725. The highest values, 0.0162 for soil and 0.0193 for plant, were found in samples collected near the conversion building. However, a relatively high ratio was observed at a site more than 50 m from the building, indicating that enriched U may have been released not only from the conversion building but also from other unknown sources. 235U/238U atom ratios were in general higher in plants than in soils collected at the same points

  10. 238U series isotopes and 232Th in carbonates and black shales from the Lesser Himalaya: implications to dissolved uranium abundances in Ganga-Indus source waters

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

  11. Production of exotic nuclei by photofission. ALTO Project: First results

    This PhD thesis has been carried out in the framework of ALTO Project (Accelerateur Lineaire Aupres du Tandem d'Orsay). a project exploiting photofission mode of neutron-rich nuclei for ISOL facilities. Our work deals with adaptation modes of the production environment represented by the target-ion source unit. We undertook an exhaustive radioprotection study in order to design and define the kinds of shielding necessary to face intense flux of photons and neutrons generated in the production target. Monte Carlo simulation with FLUKA code allowed to calculate the simultaneous transport of photons and neutrons with an entire modelling of very complicated geometrical structures. For the target-source unit and the critical points of beam loss, we propose an optimized shielding based mainly on the segmented structure. We have studied the adequacy of a thick carbide uranium target to produce neutron-rich nuclei by photofission. In particular, comparing the results of simulation with the experimental data, we have benchmarked FLUKA code for photofission with a 50 MeV electron beam. Finally, we present our works on the design and development of a FEBIAD-type-ion-source prototype: IRENA ion source, designed for next generation facilities. This work shows how important radioprotection considerations are also involved in the design of the ion source. (author)

  12. Uranium, thorium and bismuth photofission cross sections at high energies

    The U238, Th232 and Bi209 photofission using nuclear emulsion technique for fission fragments detection is presented. The photofission cross sections were measured using Bremsstrahlung photon which were produced irradiating thin tungsten radiators with electrons accelerated at the energy range from 1,0 to 5,5 GeV in the ''Deutsches Elektronen Synchrotron'' (Hamburg), and aluminium radiator with electrons accelarated at 16,0 GeV in Stanford Linear Accelerator Center. A special revelation technique for nuclear emulsion pellicles loaded with uranium and thorium, allowed the discrimination between alpha particles tracks and fission fragments tracks. The results show a decrease in the cross sections, which is in good agreement, within experimental errors, with the conclusions of other authors. The estimations from the two-step mechanism for high energy nuclear reactions (intranuclear cascade followed by fission-evaporation competition) show that, the primary interaction according to the photomesonic model and the quasi-deuteron photon interaction are sufficient to explain the general behavior exhibited by photofission cross sections for investigated nuclei. The calculations show a resonant structure around 300 MeV, with a width at half maximum of 200 MeV, and another not so pronounced, near to 700 MeV. (Author)

  13. 230Th/ 234U/ 238U and 231Pa/ 235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry

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

    2005-02-01

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

  14. {sup 238}U and {sup 232}Th concentrations in various foodstuffs in Morocco and resulting radiation doses to the members of the public; Concentrations en {sup 238}U et {sup 232}Th dans differents aliments au Maroc et doses de radiations en resultant pour les membres du public

    Misdaq, M.A.; Elamyn, H.; Erramli, H. [Cadi Ayyad Univ., Nuclear Physics and Techniques Lab., Faculty of Sciences Semlalia, Marrakech (Morocco)

    2008-04-15

    Uranium ({sup 238}U) and thorium ({sup 232}Th) concentrations were measured in different foods widely consumed in Morocco by using C.R.-39 and L.R.-115 type II solid state nuclear track detectors (S.S.N.T.D.). Data obtained were compared to those obtained by using isotope dilution mass spectrometry (I.D.M.S.). Total daily intakes of {sup 238}U and {sup 232}Th for a typical food basket were estimated to be 1.3 {+-} 0.1 mBq d{sup -1} and 0.98 {+-} 0.08 mBq d{sup -1}, 1.4 {+-} 0.1 mBq d{sup -1} and 1.06 {+-} 0.08 mBq d{sup -1}, 1.7 {+-} 0.1 mBq d{sup -1} and 1.26 {+-} 0.08 mBq d{sup -1} and 2.0 {+-} 0.1 mBq d{sup -1} and 1.5 {+-} 0.1 Bq d{sup -1} for the 2-7 years, 7-12 years, 12-17 years and adult's age groups, respectively. Alpha-activities due to annual {sup 238}U and {sup 232}Th intakes from the ingestion of the studied foodstuffs were determined in different organs and tissues of the human body of members of the public by using the ICRP gastrointestinal tract and systemic part models for these radionuclides. Committed equivalent doses due to annual intakes of {sup 238}U and {sup 232}Th were evaluated in the human body organs and tissues for different age groups of the Moroccan population by exploiting data obtained for alpha-doses deposited by 1 Bq of {sup 238}U and 1 Bq of {sup 232}Th in the considered human organs and tissues. The influence of the mass of the target tissue and activities due to {sup 238}U and {sup 232}Th on the committed equivalent doses due to annual intakes of these radionuclides in the organs and tissues of the human body was studied. (authors)

  15. 90Sr, 238U, 234U, 137Cs, 40K and 239/240Pu in Emmental type cheese produced in different regions of Western Europe

    A method is presented for the determination of 90Sr and uranium in Emmental type cheese collected in dairy plants from different European countries. Results display a significant correlation (r=0.708, Student t-test=6.02) between the 90Sr content of the cheese and the altitude of grazing. The highest 90Sr activity is 1.13 Bq kg-1 of cheese and the lowest is 0.29 Bq kg-1. Uranium activity is very low with a highest 238U value of 27 mBq kg-1. In addition, 234U/238U ratio shows a large enrichment in 234U for every location. Without any significant indication of the geographic origin of the cheese, this enrichment is believed to be due to the geological features of the pasture, soil and underground water. These results tend to prove that the contamination of milk by uranium originates principally from the water that the cows drink instead of the forage. This finding may have a great importance in models dealing with dairy food contamination by radionuclides following a nuclear accident. Also, the 90Sr content and to a lesser extent the 234U/238U ratio could be used to trace the authenticity of the origin of the cheese. 137Cs activity is lower than the detection limit of 0.1 Bq kg-1 in all the samples collected (n=20). Based on natural 40K activity in cheese (15-21 Bq kg-1), the decontamination factor for the alkaline cations from milk to cheese is about 20. Plutonium activity stays below the detection limit of 0.3 mBq kg-1

  16. Contribution of 238U-234U-230Th to the mineralogical and geochemical study of alteration profiles. The case of two African lateritic profiles

    In weathering profiles, water-rock interactions generate chemical fluxes from continents to oceans, as dissolved elements or particles. Laterites cover one third of the continents' surface and their formation processes are discussed. It is proposed to study such profiles to decipher their formation and evolution and to recognize the active weathering processes affecting them. Whole rock samples were analysed as well as fine clay fractions (238U-234U-230Th disequilibria in characterising recent mobilities were particularly considered. Two laterites were studied: a ferri-crete from Burkina Faso, and a latosol from Cameroon. The superposed petrographical horizons of lateritic profiles derive from different weathering conditions of the bedrock, and not from a continuous and progressive weathering process. The autochthonous formation of the ferruginous caps is evidenced by mineralogical and geochemical arguments. Remobilization and redistribution of chemical elements occur during the evolution of the profiles, as shown by the lanthanide distribution, which also modifies the signature of long period isotopic systems. Recent, or present, chemical mobilities affect the whole profiles, as evidenced by the 238U-234U-230Th disequilibria. The characteristics of U mobilization processes can be evaluated by use of radioactive decay equations for simple systems affected by a single U mobilization process and then evolving as closed systems. In the case of open systems affected by both U leaching and U input, an appropriate modelling allow to estimate the characteristics of U mobilities (flux, variations). The 238U-234U-230Th disequilibria are useful to detect and characterise the recent chemical mobilities affecting the weathering profiles. It appears that several processes presently affect each horizon of the lateritic profiles, and thus participate to the exported chemical fluxes. (author)

  17. The radiochemical contamination (210Po and 238U of zone around phosphogypsum waste heap in Wiślinka (northern Poland

    Boryło A.

    2013-04-01

    Full Text Available The aim of this work was the determination of the impact of phosphogypsum waste heap in Wiślinka (northern Poland for radiological protection of zone around waste heap. The activity of 210Po, 234U, and 238U were measured using an alpha spectrometer. The values of uranium and polonium concentration in water with immediate area of waste heap are considerably higher than in the waters of the Martwa Wisła river. The values of activity ratio 234U/238U are approximately about one in the phosphogypsum (0.97±0.05 and in the water of retention reservoir and pumping station (0.92±0.01 and 0.99±0.08, while in the water from the Martwa Wisła river they are slightly higher than one (1.03±0.07 and 1.17±0.06. In the analyzed plants species the highest amounts of polonium and uranium were found in ruderal plants samples as well as hygrophilous plant samples. The more amounts of 210Po and 238U radionuclides were accumulated mainly in the roots of the analyzed plant species. The significant source of polonium and uranium in the natural environment is dry and wet atmospheric fallout in the immediate vicinity of phosphogypsum waste heap and the transfer via root for distant areas. The general conclusion of realized study is higher influence of phosphogypsum on radioactive contamination of environmental zone around heap waste in Wiślinka (northern Poland.

  18. Temporal evolution of natural radionuclides distributions 238U, 234Th, 226Ra, 228Ra, 210Pb and 210Po in the Bransfield strait, Antarctica peninsula

    Research on the distribution of natural radionuclides in Antarctica is rare and thus, there is great interest in to know their occurrence and factors related to its mobilization, transference and accumulation in this extremely fragile environment. Natural radionuclides have been used intensively as tracers in the ocean, helping to better understand processes as sinking and particle resuspension, water masses mixture and oceanic circulation. 234Th (t½ = 24.1 days) is a particle-reactive radionuclide produced continuously in seawater by the decay of its soluble precursor conservative with salinity 238U (t½ = 4.5 109 years). Since 234Th presents relatively short half-life, it is used to quantify processes that occur in temporal scale varying from days to weeks. The disequilibrium 234Th/238U in the surface ocean has been applied to estimate carbon fluxes exported via sinking material. The flux of particles biologically productive out of the euphotic zone in the Southern Ocean has special attention due to its importance in the control of CO2 atmospheric concentrations. The radionuclides 210Pb (t½ = 22.3 years) and 210Po (t½ = 138 days) are also particle-reactive. The disequilibrium 210Po/210Pb has been used to estimate fluxes of particles exported in the ocean in the time scale of weeks. The long-lived Ra isotopes, 226Ra (t½ = 1,600 years) and 228Ra (t½ = 5.75 years) are soluble in seawater, presenting unique properties that make them excellent tracers of water masses. This research work had the aim to study the distributions of natural radionuclides 238U, 234Th, 22'6Ra, 22'8Ra, 210Pb and 210Po in the Bransfield Strait during 2 samplings carried out in the 2011 Austral Summer (OPERANTAR XXIX and XXX). (author)

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

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

    2011-09-01

    To assess the quality of the environment in southern Iraq after the Gulf War II, a geochemical survey was carried out. The survey provided data on the chemistry of Euphrates waters, as well as the trace element contents, U and Pb isotopic composition, and PAH levels in soil and tree bark samples. The trace element concentrations and the (235)U/(238)U ratio values in the Euphrates waters were within the usual natural range, except for the high contents of Sr due to a widespread presence of gypsum in soils of this area. The trace element contents in soils agreed with the common geochemistry of soils from floodplain sediments. Some exceptions were the high contents of Co, Cr and Ni, which had a natural origin related to ophiolitic outcrops in the upper sector of the Euphrates basin. The high concentrations of S and Sr were linked to the abundance of gypsum in soils. A marked geochemical homogeneity of soil samples was suggested by the similar distribution pattern of rare earth elements, while the (235)U/(238)U ratio was also fairly homogeneous and within the natural range. The chemistry of the tree bark samples closely reflected that of the soils, with some notable exceptions. Unlike the soils, some tree bark samples had anomalous values of the (235)U/(238)U ratio due to mixing of depleted uranium (DU) with the natural uranium pool. Moreover, the distribution of some trace elements (such as REEs, Th and Zr) and the isotopic composition of Pb in barks clearly differed from those of the nearby soils. The overall results suggested that significant external inputs occurred implying that once formed the DU-enriched particles could travel over long distances. The polycyclic aromatic hydrocarbon concentrations in tree bark samples showed that phenanthrene, fluoranthene and pyrene were the most abundant components, indicating an important role of automotive traffic. PMID:21774965

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

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

    2015-06-01

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

  1. Determination of radioactivity level of 238U, 232Th and 40K in surface medium in Zhuhai city by in-situ gamma-ray spectrometry

    A gamma-ray spectrometry survey with NaI(Tl) (φ75mm x 75mm) has been performed on a large scale to determine the distribution of 40K, 238U and 232Th in soil and rocks in Zhuhai, a southern Chinese city located in Guangdong Province. The survey sampled 970 sites which covered an area of more than 100 km2. The average activities of 40K. 238U and 222Th were found 655±338, 85.8±31.6, and 159.8±49.0 Bq·kg-1 in soil or cement of pavement in the urban area; 832±455, 87.3±41.6, and 179.3±40.7 Bq·kg-1 in weathered granite; 634±76.8, 35.2±14.6 and 70.2±18.6Bq·kg-1 in the Quaternary sediments in Doumen District. The average 232Th activity (159.8±49.0 Bq·kg-1) is above the average in both China (49 Bq·kg-1) and the world (30 Bq·kg-1). Terrestrial air-absorbed dose rates calculated from the above activities are 85.08±15.63, 183.33±40.80 nGy·h-1 respectively over the Quaternary sediments and weathered granite, and 163.49±30.15 nGy·h-1 in the urban area. The average calculated air-absorbed dose rate is about 12.63% larger than the value measured by a portable plastic scintillator dosemeter. The 40K, 238U and 232Th activities in surface medium are mainly originated from biotite granites, as indicated by a strong correlation between the radioactivity level and geological lithology in the surveyed area. (author)

  2. A comparison of measured and calculated neutron inelastic scattering cross sections for vibrational states from 680 to 1060 keV in 238U

    Measured and calculated data are presented on neutron inelastic scattering cross sections for vibrational states from 680 to 1060 keV in 238U. Time-of-flight measurements were made at the University of Lowell, Massachusettes, (U.S.A.) using incident neutrons up to 2.2 MeV, and are compared with theoretical calculations carried out at the Los Alamos National Laboratory (U.S.A.). The paper was given at the International Conference on 'Nuclear data for basic and applied science', Santa Fe, (U.S.A.) 1985. (UK)

  3. Experimental Neutron-Induced Fission Fragment Mass Yields of 232Th and 238U at Energies from 10 to 33 MeV

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

    2013-01-01

    Development of nuclear energy applications requires data for neutron-induced reactions for actinides in a wide neutron energy range. Here we describe measurements of pre-neutron emission fission fragment mass yields of 232Th and 238U at incident neutron energies from 10 to 33 MeV. The measurements were done at the quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE; a multi-section twin Frisch-gridded ionization chamber was used to detect fission fragments. For...

  4. Daily intake of /sup 234,235,238/U, /sup 228,230,232/Th and /sup 226,228/Ra by New York City residents

    The daily intake of long-lived alpha-emitting members of the U, Th and Ac series by New York City residents has been estimated from measurements of diet, water and air samples. The total daily intakes from inhalation, food and water consumption in mBq are 18 (234U), 0.7 (235U), 16 (238U), 6 (230Th), 4 (232Th) and 52 (226Ra). From this, we infer that the total daily intakes of 228Th and 228Ra are 4 and 35 mBq, respectively

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

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

    2016-03-01

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

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

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

    2016-08-01

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

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

    Riccobono, Francesco; Perra, Guido; Pisani, Anastasia; Protano, Giuseppe, E-mail: protano@unisi.it

    2011-09-01

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

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

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

  9. Evaluation of fission cross sections and covariances for {sup 233}U, {sup 235}U, {sup 238}U, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu

    Kawano, Toshihiko [Kyushu Univ., Fukuoka (Japan); Matsunobu, Hiroyuki [Data Engineering, Inc. (Japan); Murata, Toru [AITEL Corporation, Tokyo (JP)] [and others

    2000-02-01

    A simultaneous evaluation code SOK (Simultaneous evaluation on KALMAN) has been developed, which is a least-squares fitting program to absolute and relative measurements. The SOK code was employed to evaluate the fission cross sections of {sup 233}U, {sup 235}U, {sup 238}U, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu for the evaluated nuclear data library JENDL-3.3. Procedures of the simultaneous evaluation and the experimental database of the fission cross sections are described. The fission cross sections obtained were compared with evaluated values given in JENDL-3.2 and ENDF/B-VI. (author)

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

    Gates, J. M.

    2008-01-01

    Isotopes of rutherfordium (258-261Rf) were produced in irradiations of 238U targets with 26Mg beams. Excitation functions were measured for the 4n, 5n and 6n exit channels. Production of 261Rf in the 3n exit channel with a cross section of 28+92-26 pb was observed. Alpha decay of 258Rf was observed for the first time with an alpha-particle energy of 9.05+-0.03 MeV and an alpha/total decay branching ratio of 0.31+-0.11. In 259Rf, the electron capture/total decay branching ratio was measured t...

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

    Chatillon A.

    2016-01-01

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

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

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

  13. Neutron induced 238U subthreshold fission cross section for neutron energies between 5 eV and 3.5 MeV

    A measurement of the 238U fission cross section between 5 eV and 3.5 MeV was performed. Included is the identification of 85 resonances or clusters of resonances below 200 keV. Also the fission widths for the 27 resolved class I levels were computed from their fission areas, and a neutron width of 0.005 MeV was estimated for the quasi-class II level in the 721 eV fission cluster. The fission level spacing and cross sections are discussed. 9 references

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

    Di Lella, L.A.; Nannoni, F.; Protano, G.; Riccobono, F. [Dipartimento di Scienze Ambientali ' G. Sarfatti' -Sezione di Geochimica Ambientale, University of Siena, Via del Laterino 8, I-53100, Siena (Italy)

    2005-01-20

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

  15. Sub-barrier resonance fission and its effects on fission fragment properties, exemplified on 234,238U(n,f)

    Oberstedt S.; Hambsch F.-J.; Tudora A.

    2013-01-01

    The correlation between the sub-barrier resonant behaviour of fission crosssection of non-fissile actinides (pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron data (post-scission stage) around the incident energies of sub-barrier resonances is outlined and supported by quantitative results for two fissioning systems 234,238U(n,f). These quantitative results refer to both stages of the fission process: a) The pre-scission stage including the calculat...

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

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

  17. Quantification of transfer of {sup 238}U, {sup 226}Ra, {sup 232}Th, {sup 40}K and {sup 137}Cs in mosses of a semi-natural ecosystem

    Dragovic, S., E-mail: sdragovic@inep.co.r [Institute for the Application of Nuclear Energy - INEP, University of Belgrade, Banatska 31b, 11080 Belgrade (Serbia); Mihailovic, N. [Institute for the Application of Nuclear Energy - INEP, University of Belgrade, Banatska 31b, 11080 Belgrade (Serbia); Gajic, B. [Faculty of Agriculture, Institute of Land Management, Laboratory of Soil Physics, University of Belgrade, Nemanjina 6, 11081 Belgrade (Serbia)

    2010-02-15

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

  18. Origin of the {sup 238}U-{sup 230}Th disequilibrium in magmas from subduction zones: the Arenal example; Origine du desequilibre {sup 238}U-{sup 230}TH dans les magmas des zones de subduction: exemple de l`Arenal

    Villemant, B. [Paris-6 Univ., 75 (France)

    1996-12-31

    The existence in some volcanic products of strong excess of {sup 238}U with respect to {sup 230}Th is one of the characteristics of volcanic arc magmas. These excesses are generally attributed to fluid additions inside mantellic sources before magma segregation, differentiation and eruption. These fluids should be linked to the dehydration of the subducted rocks. These hypotheses are essentially based on correlations between {sup 10}Be, {sup 87}Sr anomalies, Ba/La ratios and on the distribution of volcanic centers with respect to the subduction zone. Recent studies suggest an evolution of the composition of volcanic sources in Central America from a depleted mantle type (MORB) in the North (Nicaragua) to a less transformed enriched type (OIB) in the South (Costa Rica). The Arenal volcano belongs to a transition zone between these two types. The preliminary study of trace elements and {sup 238}U-{sup 230}Th disequilibria in recent volcanic products (1968-1993) indicates a more complex situation. At least two different mantle sources were successively involved characterized by different Th/La and La/Yb ratios and very different to the OIB type. Also most lavas are in equilibrium with {sup 238}U/{sup 232}Th ratios of about 1.2 to 1.3. However, in eruptive cycle, some lavas are characterized by a strong {sup 238}U excess with respect to {sup 230}Th with cannot be linked to the sources, even when modified by fluids in depth. These results are interpreted in terms of heterogeneities of mantle sources and low depths late interactions with hydrothermal fluids during eruptions. Abstract only. (J.S.). 2 refs.

  19. Photofission experiments at the ELI-NP facility

    Dimiter L Balabanski; ELI-NP Science Team

    2015-09-01

    At ELI-NP, high-power lasers together with a very brilliant beam are the main research tools. The high-power laser system (HPLS) and the beam system (GBS) of ELI-NP are presented. The expected performance of the electron accelerator and production lasers of the GBS, and the targeted operational parameters of the beam are described. Possible laser-induced fission and beam photofission experiments which are under preparation at ELI-NP, and the different set-ups and instrumentation, are designed for these experiments, are presented.

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

    Pruet, J; Hagmann, C

    2007-01-26

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

  1. Use of LabSOCS for determination of specific concentrations of 40K, 238U and 232Th in fertilizer samples

    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)

  2. Distribution of 238U, 232Th, 40K, and 137Cs concentrations in soil samples nearby a nuclear laboratory, Capao Island, Brazil

    Oliveira Luciano S.R.

    2015-01-01

    Full Text Available Absolute soil concentrations of 238U, 232Th, 40K, and 137Cs samples were measured using high-resolution gamma spectrometry. The area of interest encompasses an embankment in a mangrove swamp in Guaratiba, Rio de Janeiro, called Capao Island, where nuclear, chemical and biological defense laboratories of the Brazilian Army Technology Center are in operation for more than 30 years. In order to ensure that no significant environmental impact has resulted from neutron physics experiments performed in a graphite exponential pile in addition to the operation of two cesium-driven irradiating facilities, radiation monitoring of the isotopes was carried out. A total of eight 250 ml soil samples were extracted within an area of 300 m x 300 m. No trace of 137Cs was detected and the measured levels of 238U were found to be close to the global mean. However, some data that slightly exceeded the expected normal range for 232Th (60 % of samples and 40K (20 % of samples should be attributed to the construction debris (cement, rocks, and sand used in the embankment at the site. Since there is no handling of those isotopes at that site or adjacent facilities that could affect their presence, it was concluded that no detectable contamination has occurred.

  3. Seasonal variations of total 234Th and dissolved 238U concentration activities in surface water of Bransfield Strait, Antarctica, from March to October 2011

    In this study the naturally occurring radionuclides 234Th and 238U were used to investigate the magnitude of upper ocean particulate organic carbon export in Bransfield Strait, Southern Ocean. This region is the largest oceanic high-nitrate low-chlorophyll (HNLC) area in the world and is known to contribute to regulate of the atmospheric CO2 via the biological pump. Due to its different geochemical behavior in seawater, the resulting U/Th disequilibria can be easily used to constrain the transport rates of particles and reaction processes between solution and particulate phases. Sampling occurred during the summer (March and November) 2011. Total 234Th activities in surface seawater samples ranged from 1.3 to 3.7 dpm L-1 (station EB 011) during March/11 campaign, while in October/11 total 234Th activity concentrations varied from 1.4 to 2.9 dpm L-1. Highest total 234Th activities were found late in the austral summer season. Activity concentrations of dissolved 238U in surface seawater varied from 2.1 to 2.4 dpm L-1. Taking into account all sampling stations established in March and October/11 the relative variability of total 234Th distribution was 22%. (author)

  4. Seasonal variations of total {sup 234}Th and dissolved {sup 238}U concentration activities in surface water of Bransfield Strait, Antarctica, from March to October 2011

    Lapa, Flavia V.; Oliveira, Joselene de; Costa, Alice M.R., E-mail: fvlapa@ipen.br, E-mail: jolivei@ipen.br, E-mail: lice_mrc@hotmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Laboratorio de Radiometria Ambiental; Braga, Elisabete S., E-mail: edsbraga@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Inst. Oceanografico. Lab. de Nutrientes, Micronutrientes e Tracos nos Oceanos

    2013-07-01

    In this study the naturally occurring radionuclides {sup 234}Th and {sup 238}U were used to investigate the magnitude of upper ocean particulate organic carbon export in Bransfield Strait, Southern Ocean. This region is the largest oceanic high-nitrate low-chlorophyll (HNLC) area in the world and is known to contribute to regulate of the atmospheric CO{sub 2} via the biological pump. Due to its different geochemical behavior in seawater, the resulting U/Th disequilibria can be easily used to constrain the transport rates of particles and reaction processes between solution and particulate phases. Sampling occurred during the summer (March and November) 2011. Total {sup 234}Th activities in surface seawater samples ranged from 1.3 to 3.7 dpm L{sup -1} (station EB 011) during March/11 campaign, while in October/11 total {sup 234}Th activity concentrations varied from 1.4 to 2.9 dpm L{sup -1}. Highest total {sup 234}Th activities were found late in the austral summer season. Activity concentrations of dissolved {sup 238}U in surface seawater varied from 2.1 to 2.4 dpm L{sup -1}. Taking into account all sampling stations established in March and October/11 the relative variability of total {sup 234}Th distribution was 22%. (author)

  5. Measurement of double-differential neutron emission cross sections of 238U, 232Th and 12C for 18 MeV neutrons

    Double-differential neutron emission cross sections of 238U, 232Th and 12C have been measured for 18-MeV incident neutrons using the neutron time-of-flight technique and Tohoku University 4.5MV Dynamitron accelerator as a pulsed neutron generator. In the experiment, energy resolution of the spectrometer was improved by employing a newly developed post-acceleration beam-chopper and by adjustment of timing property of the neutron detector. Measurements were made at laboratory angles between 30- and 145- deg., and data were obtained for secondary neutrons between 0.8 and 18 MeV. In the data processing, a care was taken for the data correction for the effects of parasitic neutrons associated with primary neutrons; the correction proved to be of special importance in the present measurement. We compared the data obtained in the present experiment with the evaluated data, JENDL-3 and ENDF/B-IV (B-V for 12C), and discussed the origin of the discrepancies. The anisotropy observed for secondary neutrons from 238U and 232Th was found to be reproduced by Kalbach-Mann systematics on the assumption of isotropy of fission neutrons. The experimental results for 12C showed marked discrepancies concerning the scattering cross sections and neutron spectrum in the continuum region. (author)

  6. Transfer of {sup 238}U, {sup 230}Th, {sup 226}Ra, and {sup 210}Pb from soils to tree and shrub species in a Mediterranean area

    Blanco Rodriguez, P. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Vera Tome, F. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain)], E-mail: fvt@unex.es; Lozano, J.C. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Laboratorio de Radiaciones Ionizantes, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca (Spain); Perez Fernandez, M.A. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Area de Ecologia, Universidad Pablo Olavide, Carretera de Utrera km. 1, 41013 Sevilla (Spain)

    2010-06-15

    The soil-to-plant transfer factors of natural uranium isotopes ({sup 238}U and {sup 234}U), {sup 230}Th, {sup 226}Ra, and {sup 210}Pb were studied in a disused uranium mine located in the Extremadura region in the south-west of Spain. The plant samples included trees (Quercus ilex, Quercus suber, and Eucalyptus cameldulensis) and one shrub (Cytisus multiflorus). All of them are characteristic of Mediterranean environments. The activity concentrations in leaves and fruit were determined for the tree species at different stages of growth. For the shrub, the total above-ground fraction was considered in three seasons. For old leaves and fruit, the highest activity concentrations were found in Eucalyptus cameldulensis for all the radionuclides studied, except in the case of {sup 230}Th that presented similar activity concentrations in all of the tree species studied. In every case, the transfer to fruit was less than the transfer to leaves. In the shrub, the results depended on the season of sampling, with the highest value obtained in spring and the lowest in autumn. Important correlations were obtained for {sup 238}U and {sup 226}Ra between the activity ratio in soils with that in leaves or fruit.

  7. Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

    The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 228Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 μg), 2.0 mBq of 238U (0.17 μg), 19 mBq of 226Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 μSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 μSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation

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

    The activity concentrations of 238U, 232Th and 40K in riverbank soil along the Chao Phraya river basin was determined through gamma-ray spectrometry measurements made using a hyper-pure germanium detector in a low background configuration. The ranges of activity concentrations of 238U, 232Th and 40K were found to be 13.9 ↔ 76.8, 12.9 ↔ 142.9 and 178.4 ↔ 810.7 Bq kg−1, respectively. The anthropogenic radionuclide, 137Cs, was not observed in statistically significant amounts above the background level in the current study. The absorbed gamma dose rate in air at 1 m above the ground surface, the outdoor annual effective dose equivalent, the values of the radium equivalent activity and the external hazard index associated with all the soil samples in the present work were evaluated. The results indicate that the radiation hazard from primordial radionuclides in all soil samples from the area studied in this current work is not significant. - Highlights: • Radioactivity in surface soils from the Chao Phraya river basin in Thailand is evaluated. • Gamma-ray spectrometric analysis is to identify decays associated with 226Ra, 232Th and 40K. • The results provide baseline measurements for any changes in future radioactivity levels

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

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

    2001-02-01

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

  10. Measurement of the intrinsic radiopurity of {sup 137}Cs/{sup 235}U/{sup 238}U/{sup 232}Th in CsI(Tl) crystal scintillators

    Zhu, Y.F. [Department of Engineering Physics, Tsing Hua University, Beijing (China); Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Lin, S.T. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Department of Physics, National Taiwan University, Taipei, Taiwan (China); Singh, V. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Department of Physics, Banaras Hindu University, Varanasi (India); Chang, W.C. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Deniz, M. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Department of Physics, Middle East Technical University, Ankara (Turkey); Lai, W.P. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Li, H.B. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Li, J. [Department of Engineering Physics, Tsing Hua University, Beijing (China); Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Institute of High Energy Physics, Chinese Academy of Science, Beijing (China); Li, Y.L. [Department of Engineering Physics, Tsing Hua University, Beijing (China); Liao, H.Y. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Department of Physics, National Taiwan University, Taipei, Taiwan (China); Lee, F.S. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Wong, H.T. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China)]. E-mail: htwong@phys.sinica.edu.tw; Wu, S.C. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Yue, Q. [Department of Engineering Physics, Tsing Hua University, Beijing (China); Zhou, Z.Y. [Department of Nuclear Physics, Institute of Atomic Energy, Beijing (China)

    2006-02-15

    The inorganic crystal scintillator CsI(Tl) has been used for low energy neutrino and Dark Matter experiments, where the intrinsic radiopurity is an issue of major importance. Low-background data were taken with a CsI(Tl) crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape discrimination capabilities of the crystal, as well as the temporal and spatial correlations of the events, provide powerful means of measuring the intrinsic radiopurity of {sup 137}Cs as well as the {sup 235}U, {sup 238}U and {sup 232}Th series. The event selection algorithms are described, with which the decay half-lives of {sup 218}Po, {sup 214}Po, {sup 22}Rn, {sup 216}Po and {sup 212}Po were derived. The measurements of the contamination levels, their concentration gradients with the crystal growth axis, and the uniformity among different crystal samples, are reported. The radiopurity in the {sup 238}U and {sup 232}Th series are comparable to those of the best reported in other crystal scintillators. Significant improvements in measurement sensitivities were achieved, similar to those from dedicated massive liquid scintillator detector. This analysis also provides in situ measurements of the detector performance parameters, such as spatial resolution, quenching factors, and data acquisition dead time.

  11. Nuclear charge distribution of fission products originated from fission of 238U nuclei induced by45-69 MeV protons

    Houshyar Noshad

    2007-12-01

    Full Text Available  Fission of 238U nuclei was performed by 45-69 MeV protons at the Cyclotron and Radioisotope Center of Tohoku University in Japan. The fission products originated in the reaction were identified by using gamma spectroscopy. The experimental data show that the charge distribution of isobar fission products follows a Gaussian distribution with a standard deviation independent of the selected mass number. The standard deviations were measured for the reaction 238U(p, f with 45, 55, 65 and 69 MeV protons. For Ep = 45 MeV, the standard deviation obtained from the experiment is in agreement with the existing data and satisfies the prediction of the Hauser-Feshbach statistical model. For other proton energies, measurement of this quantity has not been reported in the literature. The experimental results show that the value of standard deviation increases, when the excitation energy of the fissioning nucleus increases. Furthermore, the most probable charge was determined for the isobar fission products detected in the experiment. The results are consistent with the prediction of the minimum potential energy (MPE model. Moreover, the experimental data show that nuclear charge polarization occurs in the fission process.

  12. Experiments to improve uncertainty of the 1st delayed neutron group abundance in fast fissions of 238U and sensitivity studies of the relative parameters

    The delayed neutron nuclear data are limited by its short lifetime, limited yield fraction, difficulty to obtain a well-defined sample, an inefficient (uncharacterized) experimental system, and numerical instabilities of fitting methods. The uncertainties on the relative abundances of the longer-lived delayed neutron groups are up to 13% for thermal fissions of 235U and 16% for fast fissions of 238U. To evaluate more accurate delayed neutron nuclear data, a novel approach to experimentally measure the relative uncertainties on the delayed neutron group abundances has been proposed by Jordan and Perret. This approach combines delayed gamma and delayed neutron fission rate measurement techniques; with two independent estimates of the same fission rate, higher uncertainty delayed neutron parameters can be linked to lower uncertainty delayed gamma parameters. The present authors have designed, optimized, and built an experimental apparatus capable of producing high accuracy measurements for delayed gamma-rays and neutrons, with the goal of implementing the above approach. Finally, sensitivity studies of the parameters that have non-negligible contributions to the overall uncertainty were carried out. With regards to the designed setup and the combined technique, the relative uncertainty of the longest-lived delayed neutron group is calculated. The calculation shows that the uncertainty of the longest-lived delayed neutron group of 238U can be reduced by a factor of two to 8.81%. (author)

  13. Fast evaluation of 235U/238U ratio in nuclear spent fuel safe guard by thermal ionization mass spectrometry by using refractory metal oxides

    A direct simple and fast method was established, to overcome the influence of low and high level impurities on the measurement of 235U/238U isotopic ratio in nuclear spent fuel safeguard by thermal ionization mass spectrometry (TIMS), by using refractory metal oxide. The addition of refractory metal oxides forming solution (RMOFS), in certain proportions alongside with the spent fuel solution on the sample filaments were found to be useful during the analysis of uranium isotopic ratio by TIMS. RMOFS (with oxide melting point exceeding 2,000 deg C), and particularly that of magnesium, were found to be very effective in improving the quality of the ion signal of 235U and 238U, when added without the need for prior purification. Solutions of chromium, cerium, thorium, and magnesium were investigated, to select the more convenient one, and it was found that magnesium was very useful to start with. The method was very simple, improve both the accuracy and precision of the collected data, reduce the time required to achieve steady uranium pilot signal, and hence the over all time of the analysis, regardless of the level of impurities present. (author)

  14. Cryogenic stopping cell for photofission fragments at the ELI-NP facility

    Constantin, P., E-mail: paul.constantin@eli-np.ro; Balabanski, D. L. [ELI-NP, IFIN-HH, Str. Reactorului 30, 077125 Bucharest Magurele (Romania); Cuong, P. V. [Centre of Nuclear Physics, Institute of Physics, No. 10, Daotan, Thu le, Badinh, Hanoi (Viet Nam)

    2015-10-15

    The brilliant gamma beam at the future Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility will be used to generate a beam of exotic neutron-rich isotopes via photofission of actinide targets. We present simulations with the Geant4 toolkit of the photofission process for the design and optimization of the expected performance parameters of the Cryogenic Stopping Cell (CSC). The CSC will be used to extract the photofission fragments into the secondary beam of about 10{sup 6} ions/s. We propose an experimental program to study refractory neutron-rich isotopes.

  15. Nuclear photofission studies with monochromatic γ ray beams

    Csige, L.; Gulyás, J.; Habs, D.; Krasznahorkay, A.; Thirolf, P. G.; Tornyi, T. G.

    2012-07-01

    Two new research facilities will be ready for operation very soon (MEGa-Ray at Liver-more National Laboratory) or start construction (ELI-Nuclear Physics in Bucharest), both providing highly brilliant γ beams with so far unprecedented properties via Compton backscattering of laser photons from a high-quality, relativistic electron beam. With these intense, monochromatic γ beams, a new era of photonuclear physics will be enabled. A new research campaign is proposed to exploit the unprecedented properties of these highly-brilliant, novel γ beams on highly-selective studies of extremely deformed nuclei in the multiple-humped potential energy landscape of the actinides via photofission. With the unique γ beam bandwidth of ΔE/E = 10-3, we can aim at resolving individual resonances which could never be achieved so far due to the limited γ bandwidth of bremsstrahlung beams. Exploratory, non-bremsstrahlung photofission experiments are going to be performed very soon at the HIγS facility (Duke University, USA) to investigate the fine structure of the sub-barrier transmission resonances of the actinides.

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

    Nolen, J.A.; Ahmad, I.; Back, B.B. [and others

    1995-08-01

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

  17. Contents and daily intakes of gamma-ray emitting nuclides, 90Sr, and 238U using market-basket studies in japan

    To investigate the contents of radionuclides in foods marketed in Japan and their daily intakes and exposure doses in adults, we performed market-basket studies concerning radionuclide intakes. The study period was 2003-2005, and the studies were performed in 13 cities in Japan. Foods including drinking water were divided into 14 food groups, and samples were prepared by common cooking procedures. γ-ray emitting nuclides (an artificial radionuclide, radioactive Cs, and natural radionuclides, 40K and U series such as 214Bi, and 212Pb, and Th series) were measured in each food group, and artificial radionuclides, 90Sr and 238U, were measured in a mixed sample of 13 food groups excluding drinking water. The daily intakes in adults were calculated from the concentrations of the radionuclides and mean daily consumption of foods and drinking water. The daily 137Cs and 40K intakes (mBq/person · day) in the 13 cities were 12.5-90Sr intake from the food groups excluding drinking water was 20.8-53.6, with a mean of 39.2 (mBq/person · day) (deviation of the mean: 23%). Similarly, the daily 238U intake was 5.9-31.1, with a mean of 12.6 (mBq/person · day) (deviation: 60%), showing a more than 5-fold difference between the minimum and maximum values, and there were regional differences. Since the contents of the U series, such as 214Bi and 212Pb, and Th series were lower than the lower detection limits in many samples, their daily intakes were not calculated. Regarding the daily intake of 137Cs from each food group, the intakes from fish and shellfish, milk, meat/eggs, and mushrooms/seaweed tended to be higher. The daily 40K intake from each food group varied among the areas, but the total intake from the 14 food groups was similar in all 13 cities. 40K from these foods accounted for most of the annual effective dose (μSv/person · year) of γ-ray emitting nuclides, and the doses of 40K, 90Sr, and 238U were 130-217, 0.21-0.55, and 0.10-0.51, respectively. (author)

  18. Determination of committed effective doses from annual intakes of 238U and 232Th from the ingestion of cereals, fruits and vegetables by using CR-39 and LR-115 II SSNTD

    Uranium (238U) and thorium (232Th) concentrations were evaluated in different cereal, fruit and vegetable samples by using a method based on the calculation of the detection efficiencies of the emitted α-particles by CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) and measuring the resulting track densities. The influence of the soils on which the plants grow, and the fertilizers used was investigated. Total daily intakes of 238U and 232Th for a typical food basket were estimated to be 1.16 Bq x d-1 and 0.94 Bq x d-1, respectively, corresponding to a total committed effective dose of 0.27 x 10-7 Sv x d-1. Annual committed effective doses due to 238U and 232Th originated from the ingestion of different foodstuffs were evaluated for the adult members of the population by using the ICRP ingestion dose coefficients. (author)

  19. Photo-fission at the S-DALINAC

    Göök, Alf; Barday, Roman; Chernykh, Maksym; Eckardt, Christian; Eichhorn, Ralf; Enders, Joachim; Hambsch, Franz-Josef; von Neumann-Cosef, Peter; Oberstedt, Andreas; Oberstedt, Stephan; Poltoratska, Yuliya; Richter, Achim; Wagner, Markus

    2009-10-01

    Experiments on photo-induced fission of 238U and 234U using bremsstrahlung with endpoint energies between 6 MeV and 9 MeV have been carried out at the superconducting Darmstadt electron linear accelerator S-DALINAC. A twin Frisch grid ionization chamber has been used to determine energy and mass distributions via the 2E-technique. The fission fragment emission angle, which is used to correct for energy loss in the target and backing material for a correct determination of fragment energy and mass, is deduced from the time difference between cathode and anode signals. The research program including the foreseen search for parity violation in photo-induced fission and first experimental results will be presented.

  20. The dietary intake of 238U, 234U, 230Th, 232Th, 228Th and 226Ra from food and drinking water by inhabitants of the Walbrzych region

    Intake with food and water of the natural radionuclides of the uranium and thorium series was determined for adult population of the south-western region in Poland, where in the 1950-ies an exploration of uranium ore was conducted. Concentration of the radionuclides was determined in food products and drinking water and their annual intake was estimated on the basis of the average annual consumption. The intake of 238U, 234U and 230Th occurred mainly with water (33% to 68%), whereas the intake of 232Th, 228Th and 226Ra was mainly with vegetables, potatoes, milk and flour. From the intake and dose coefficients the annual effective doses from the ingested radionuclides were calculated. The total dose was 5.6μSv, of which 74% originated from 226Ra. (author)

  1. Daily intakes of 238U, 234U, 232Th, 230Th, 228Th and 226Ra in the adult population of central Poland

    Activity concentration of the uranium and thorium series radionuclides was determined in foodstuffs and drinking water in central Poland. Annual and daily intake for the adult population was estimated from the concentrations determined and average annual consumption of food and water. The daily intakes (in mBq) were 22.1 (238U), 26.5 (234U), 2.38 (232Th), 4.06 (230Th), 11.2 (228Th) and 42.2 (226Ra). The intake of uranium isotopes occurred mainly with water; the main intake of thorium isotopes was with animal products, vegetables, cereals and potatoes, whereas 226Ra entered mainly with animal products, cereals and vegetables. From the intake and dose coefficients, the annual effective doses for the ingested radionuclides were calculated. The annual effective dose was 5.95 μSv, of which 72.4% originated from 226Ra

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

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

    2013-01-01

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

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

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

    2011-10-01

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

  4. MEASUREMENT OF PROMPT NEUTRON SPECTRA OF 238U FISSION INDUCED BY 10.17 AND 12.12 MeV NEUTRONS

    李安利; 白希祥; 等

    1994-01-01

    Experimental method to measure the prompt neutron spectra of 238U fission induced by fast neutrons has been developed at HI-13 Tandem Van de Graaff Accelerator Laboratory of CIAE.These techniques employ a multi-segment fission chamber and two liquid scintillator neutron detectors.TOF(time of flight)techniques are used for primary neutrons to select the fission events induced by monoenergetic neutron from 2H(d,n) reactions instead of breakup neutrons from 2H(d,np) reactions.The fission neutron TOF spectra are measured in coincidence with the fission fragments to distinguish fission neutrons from other secondary neutrons.The method permits measurements to a fairly good accuracy under large neutron and gamma ray background.The techniques are described and experimental spectra are presented.

  5. High accuracy determination of the $^{238}$U/$^{235}$U fission cross section ratio up to $\\sim$1 GeV at n_TOF (CERN)

    Paradela, C; Tarrío, D; Leal-Cidoncha, E; Leong, L S; Tassan-Got, L; Naour, C Le; Duran, I; Colonna, N; Audouin, L; Mastromarco, M; Meo, S Lo; Ventura, A; Altstadt, S; Andrzejewski, J; Barbagallo, M; Bécares, V; Bečvář, F; Belloni, F; Berthoumieux, E; Billowes, J; Boccone, V; Bosnar, D; Brugger, M; Calviño, F; Cano-Ott, D; Carrapiço, C; Cerutti, F; Chiaveri, E; Chin, M; Cortés, G; Cortés-Giraldo, M A; Cosentino, L; Diakaki, M; Domingo-Pardo, C; Dressler, R; Eleftheriadis, C; Ferrari, A; Finocchiaro, P; 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; Heinitz, S; Jenkins, D G; Jericha, E; Käppeler, F; Karadimos, D; Kivel, N; Kokkoris, M; Krtička, M; Kroll, J; Langer, C; Lederer, C; Leeb, H; Losito, R; Manousos, A; Marganiec, J; Martínez, T; Massimi, C; Mastinu, P; Mendoza, E; Mengoni, A; Milazzo, P M; Mingrone, F; Mirea, M; Mondalaers, W; Musumarra, A; Pavlik, A; Perkowski, J; Plompen, A; Praena, J; Quesada, J; Rauscher, T; Reifarth, R; Riego, A; Roman, F; Rubbia, C; 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; Versaci, R; Vermeulen, M J; Vlachoudis, V; Vlastou, R; Wallner, A; Ware, T; Weigand, M; Weiß, C; Wright, T; Žugec, P

    2015-01-01

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

  6. Experimental Neutron-Induced Fission Fragment Mass Yields of 232Th and 238U at Energies from 10 to 33 MeV

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

    2013-01-01

    Development of nuclear energy applications requires data for neutron-induced reactions for actinides in a wide neutron energy range. Here we describe measurements of pre-neutron emission fission fragment mass yields of 232Th and 238U at incident neutron energies from 10 to 33 MeV. The measurements were done at the quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE; a multi-section twin Frisch-gridded ionization chamber was used to detect fission fragments. For the peak neutron energies at 33, 45 and 60 MeV, the details of the data analysis and the experimental results have been published before and in this work we present data analysis in the low-energy tail of the neutron energy spectra. The preliminary measurement results are compared with available experimental data and theoretical predictions.

  7. Daily intakes of 238U, 234U, 232Th, 230Th, 228Th and 226Ra in the adult population of central Poland

    Pietrzak-Flis, Z.; Rosiak, L.; Suplinska, M.M.; Chrzanowski, E.; Dembinska, S. [Central Laboratory for Radiological Protection, Konwaliowa 7, 03-194 Warsaw (Poland)

    2001-06-12

    Activity concentration of the uranium and thorium series radionuclides was determined in foodstuffs and drinking water in central Poland. Annual and daily intake for the adult population was estimated from the concentrations determined and average annual consumption of food and water. The daily intakes (in mBq) were 22.1 (238U), 26.5 (234U), 2.38 (232Th), 4.06 (230Th), 11.2 (228Th) and 42.2 (226Ra). The intake of uranium isotopes occurred mainly with water; the main intake of thorium isotopes was with animal products, vegetables, cereals and potatoes, whereas 226Ra entered mainly with animal products, cereals and vegetables. From the intake and dose coefficients, the annual effective doses for the ingested radionuclides were calculated. The annual effective dose was 5.95 {mu}Sv, of which 72.4% originated from 226Ra.

  8. A four phases model to simulate the dispersion of 226Ra, 238U and 232Th in an estuary affected by phosphate rock processing

    A numerical model to simulate the dispersion of non conservative radionuclides in tidal waters has been developed. The model includes four phases: water, suspended matter and two grain size sediment fractions. Ionic exchanges between water and the solid phases have been formulated in terms of kinetic transfer coefficients instead of distribution coefficients, because the model was developed for nonequilibrium conditions. The model simultaneously solves the shallow water hydrodynamic equations, the suspended matter dispersion equation and the four equations which give the time evolution of specific activity in each phase. The model has been applied to the Odiel river (southwest Spain), where a phosphate complex releases its wastes. It gives good results in predicting concentrations of 226Ra, 238U and 232Th in water, suspended matter, distribution coefficients and Th/U mass rations. (author)

  9. Natural Isotopes 238U I40k Content In Rigosol From The Area Of School Estate Good „Radmilovac” Of Faculty Of Agriculture, Zemun

    Distribution of natural gamma-emitting radionuclides 238U and 40K were determined in the soil profiles from the peach-trees field on experimental farm Radmilovac, southeast Belgrade. Internal soil morphology has been changed in 1992 when soil rigosol type with deep Ap-horizon (0-80 cm) has been formed by special treatment of parent soil, chernozem type. Gamma-spectrometry method is applied in measurement of radionuclide activities in soil samples by using hyperpure coaxial gamma-ray detector, Canberra type. Investigation results has been shown that the natural activity contents obtained in the experiment are within the range of normal backround activity according to UNSCEAR (2000) and that radionuclide activity decreased in the plant root zone

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

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

    2016-01-01

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

  11. Neutron induced fission cross section ratios for 232Th, /sup 235,238/U, 237Np, and 239Pu from 1 to 400 MeV

    Time-of-flight measurements of neutron induced fission cross section ratios for 232Th, /sup 235,238/U, 237Np, and 239Pu, were performed using the WNR high intensity spallation neutron source located at Los Alamos National Laboratory. A multiple-plate gas ionization chamber located at a 20-m flight path was used to simultaneously measure the fission rate for all samples over the energy range from 1 to 400 MeV. Because the measurements were made with nearly identical neutron fluxes, we were able to cancel many systematic uncertainties present in previous measurements. This allows us to resolve discrepancies among different data sets. In addition, these are the first neutron-induced fission cross section values for most of the nuclei at energies above 30 MeV. 8 refs., 3 figs

  12. Rare-gas yields in 238U and 232Th fission by 14MeV neutrons, measured by an emanating method

    A direct method, using emanation of rare gases by uranyle stearate and thorium stearate, has been applied to the measurement of cumulative fractional yields of certain isotopes of krypton and xenon, in the fissions of 238U and 232Th by 14MeV-neutrons. The independent yields of the same isotopes were measured previously by means of isotopic on-line separation. From these results, the widths of the mass and charge distributions, the relative chain yields, the fractional cumulative yields of certain bromine and iodine isotopes, the values of Zsub(p) the most probable charge, in the isobaric chains 87-93 and 137-142, and the elemental yields of krypton and xenon were calculated

  13. A Method To Directly Analyze The Activity Of 238U Nuclide In An HPGe Detector Based GAMMA Spectrometer Using MCNP5 Code

    One of the direct analysis methods of the activity of 238U nuclide in an HPGe detector based gamma spectrometer is to measure the 63.3 keV gamma ray emitted from 234Th nuclide. The advantage of this method is to overcome the difficulty of sample sealing in the analysis of 226Ra nuclide. However for the samples of low activity as environmental ones, they must have large masses and volumes. Then another difficulty appears relating with the significant self-absorption effect of this low energy gamma ray in the sample. This effect depends on the sample geometry, density and chemical composition. The present work suggests a method to correct the self-absorption effect by applying the Monte Carlo MCNP5 code. The sample containers used in this study have cylindrical and Marinelli forms with the sample masses of hundreds grams and sample volumes of hundreds cm3. (author)

  14. Rapid uranium preconcentration and separation method from fresh water samples for total U and 235U/238U isotope ratio measurements by ICP-MS

    A simple and rapid method using TRU resin cartridges (Eichrom Technologies, Inc., USA) and quadrupole ICP-MS for total uranium (U) and 235U/238U isotope ratio measurements in fresh water samples was investigated. After U extraction on the resin by sample solution loading, three alkaline reagents, tetramethyl ammonium hydroxide (TMAH), NaOH and NH4OH were studied for U elution behavior from the resin cartridges and applicability of these eluates was evaluated with respect to direct introduction to ICP-MS. Among the studied eluants, TMAH showed the best results with high U recovery and no counting interferences with internal standard elements such as thallium and bismuth. Moreover, U in water samples was separated from many major and minor elements with the TRU cartridges. Almost all U was concentrated in 10 mL of 0.014 M TMAH in 2 h using 200 mL of water sample

  15. Rapid uranium preconcentration and separation method from fresh water samples for total U and {sup 235}U/{sup 238}U isotope ratio measurements by ICP-MS

    Tagami, K. [Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan)]. E-mail: k_tagami@nirs.go.jp; Uchida, S. [Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan)

    2007-05-29

    A simple and rapid method using TRU resin cartridges (Eichrom Technologies, Inc., USA) and quadrupole ICP-MS for total uranium (U) and {sup 235}U/{sup 238}U isotope ratio measurements in fresh water samples was investigated. After U extraction on the resin by sample solution loading, three alkaline reagents, tetramethyl ammonium hydroxide (TMAH), NaOH and NH{sub 4}OH were studied for U elution behavior from the resin cartridges and applicability of these eluates was evaluated with respect to direct introduction to ICP-MS. Among the studied eluants, TMAH showed the best results with high U recovery and no counting interferences with internal standard elements such as thallium and bismuth. Moreover, U in water samples was separated from many major and minor elements with the TRU cartridges. Almost all U was concentrated in 10 mL of 0.014 M TMAH in 2 h using 200 mL of water sample.

  16. Measurement of neutron transmissions from 0.52 eV to 4.0 keV through seven samples of 238U at 40 m

    Neutron transmissions through 1.5-, 5-, 10-, 30-, 100-, 425-, and 1425-mil samples of depleted 238U were measured from 0.52 eV to 4.0 keV using the ORELA pulsed electron linac neutron source and time-of-flight technique with a 1-mm 6Li-glass detector with a flight path of 40 m. The measurements are tabulated and compared with transmissions calculated from the ENDF/B-IV total cross section. In addition, the 1425-mil transmission from 50 to 300 eV is compared with transmissions calculated by using multilevel formalisms, and some neutron widths are extracted with area analysis and compared with those from previous measurements. 14 figures, 10 tables

  17. The learning of the evolution and temporary characteristics of the decay nuclei 14C, 238U, 232Th, 40K, 87Rb

    Quantum-mechanical method, which was proposing earlier for the theoretical description of the resonance scattering of the γ-quantum, was generalizing with Doppler effect using. New algorithm for the definition of the characteristic functions for the energy distribution, decay probability and decay functions elaborated. It gives possibility more precise estimate temporary characteristics of the nuclei chronometers and to define a number of the steps of the γ-absorption γ-emission in the decay process. It is give the quantum- mechanical ground of the necessity of revision of the temporary characteristics of the nuclei-chronometers. The calculations have been doing for the concrete case decay of exited nuclei 14C, 238U, 232Th, 40K, 87Rb under room temperature taking into account Doppler effect and without it. 4 refs., 1 tab., 6 figs

  18. Search for quasifission in 12C + 238U and 18O + 232Th reactions at near and sub-barrier energies

    The main motivation of this present work is to study the onset of quasifission process in the fissility region > 0.8. It was observed that angular distribution of fission fragments produced in reaction in this fissility region showed anomalously large anisotropies at subbarrier energies as compared to SSPM, implying presence of pre-equilibrium fission. Here, mass-angle correlation studies of 12C + 238U and 18O + 232Th reactions has been reported, forming same compound nucleus 250Cf (Fissility = 0.86), at similar excitation energy and angular momentum. The measurements were carried out in the energy range Ecm /Vb ∼ 0.88 - 1.1, where Ecm is the energy in centre of mass frame and Vb is the Coulomb barrier

  19. Tracing uranium mobility if mesozoic formations on the site of Bure based of radioactive disequilibria (234U/238U): survey/modelling

    Within the frame of investigations performed by the French national agency for the management of radioactive wastes (ANDRA, Agence nationale pour la gestion des dechets radioactifs) in the Eastern part of the Parisian Basin in order to assess the feasibility of a radioactive waste storage in deep geological formations, the authors characterized the mobility of natural radionuclides in the target clayey formation and in its surrounding carbonated formations. The original aims were to determine the radioactive equilibrium or disequilibrium state 234U/238U in the deep formations where the experimental laboratory has been located, to characterize the processes responsible of the observed radioactive disequilibria, and then to determine the chronological implications regarding the chemical stability of these formations

  20. Application of 234U/238U activity ratios to investigations of subterranean groundwater discharge in the Cádiz coastal area (SW Spain)

    The activity ratios of 234U/238U were used to investigate processes of subterranean groundwater discharge into coastal marine waters in a study location at Bay of Cádiz (southwest Spain). Marine waters in the bay and surrounding open ocean exhibited U concentrations of 3.4 ± 0.1 μg/L and activity ratios of 1.15 ± 0.01, in agreement with the expected composition of seawater (234U/238U activity ratio = 1.148 ± 0.002). Three water samples obtained from the discharge zone of the Guadalete River exhibited activity ratios of 1.17–1.22 along with slightly lower U concentrations compared to seawater, which is likely due to mixing between seawater and a groundwater end-member. One possible source of groundwater was characterized by sampling and analyzing a well water sample collected in the neighboring village of El Puerto de Santa María; this water sample exhibited an activity ratio of 1.34 ± 0.03 and a U concentration of 1.22 μg/L. Water from the Guadelete River estuarine zone can be explained to result from a two-component mixture of seawater and groundwater from the El Puerto de Santa María well; however, if there are several groundwater reservoirs with different U activity ratios that discharge to the coastal water, then, it may be difficult and more studies are being conducted to address this issue. - Highlights: • The U concentrations are very similar to those expected for average seawater, though in wells closest to the coast are evident lower. • There is some evidence of the existence of submarine groundwater discharge (SGD) based on the obtained values of U concentrations and U ratios. • This methodology could be applied to others study areas within the region and obtain an overview of the movements of water masses in the zone as a hole

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

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

  2. 234U/238U isotope ratios in groundwater from Southern Nevada: a comparison of alpha counting and magnetic sector ICP-MS.

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

    2005-11-01

    The 234U/238U activity ratio (AR) is extensively used as a geochemical tool to investigate movement and flow relationships in major hydrological units, information that is particularly important when considering nuclear waste disposal. It is usually determined by radiochemical separation and concentration of U, followed by energy-specific alpha particle counting. Alternatively, sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) can be used to measure U isotopic signatures directly in groundwater samples. Here, we compare the two methods for samples of spring and groundwater from southern Nevada. Results for samples stripped from stainless steel disks, previously used for alpha counting, and for splits of groundwater samples show good agreement between the methods. However, SF-ICP-MS is faster, requires much less sample, and produces essentially no waste. We demonstrate applicability of the SF-ICP-MS method for groundwater collected from over 25 wells on and near the Nevada Test Site during 2003. Uranium concentrations ranged from 0.17 to 9.87 ppb with a mean of 2.9 ppb, while 234U/238U AR values ranged from 1.9 to 11.5 with a mean of 4.3. Groundwater collected from deep wells in the northern part of the study area tended to have moderate to high U concentrations and AR values, possibly representative of older volcanic-type waters, whereas groundwater from wells in the Fortymile Wash area had relatively low AR and U concentrations, suggesting younger waters with a possible local recharge component. PMID:16227084

  3. The influence of the nature of soil and plant and pollution on the 238U, 232Th, 222Rn and 220Rn concentrations in various natural honey samples using nuclear track detectors: Impact on the adult consumers

    M A Misdaq; A Mortassim

    2009-11-01

    238U and 232Th concentrations as well as 222Rn and 220Rn -activities per unit volume were measured in various natural honey samples collected from different regions in Morocco using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). These radionuclides were also measured in soils, plant flowers and nectar solutions corresponding to the honey samples studied. In addition, these radionuclides were measured in different imported honey samples. The measured 238U, 232Th, 222Rn and 220Rn concentrations ranged from (1.5 ± 0.1) mBq kg-1 to (10.6 ± 0.6) mBq kg-1, (1.1 ± 0.1) mBq kg-1 to (4.2 ± 0.2) mBq kg-1 , (1.5 ± 0.1) Bq kg-1 to (10.6 ± 0.6) Bq kg-1 and (1.1 ± 0.1) Bq kg-1 to (4.2 ± 0.2) Bq kg-1 for the honey samples studied, respectively. Annual 238U, 232Th and 222Rn intakes by Moroccan adults from the consumption of honey were assessed. The influence of the nature of soil and plant on the 238U and 232Th contents of the studied honey samples was investigated. These measurements were completed by an investigation of the 238U and 232 Th transfer between soils and plant flowers and that between plant flowers and honey, and also by the investigation of the influence of pollution due to different material dusts on 238U, 232Th and 222Rn in the honey samples studied. Committed equivalent doses due to the annual intake of 238U, 232Th and 222Rn were evaluated in the organs of adult members of the Moroccan rural population from the ingestion of the honey samples. The maximum total committed effective dose due to 238U, 232Th and 222Rn from the ingestion of natural honey by the Moroccan rural population was found to be equal to 0.64 Sv y-1 .

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

    Victor M. Tshivhase

    2015-12-01

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

  5. Use of LabSOCS for determination of specific concentrations of {sup 40}K, {sup 238}U and {sup 232}Th in fertilizer samples; Uso de LabSOCS no calculo da eficiencia de detecao para determinacao da concentracao especifica de {sup 40}K, {sup 238}U e {sup 232}Th em amostras de fertilizantes

    Garcez, Ricardo Washington Dutra; Lopes, Jose Marques; Silva, Ademir Xavier da, E-mail: rgarcez@con.ufrj.br, E-mail: marqueslopez@yahoo.com.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Domingues, Alessandro Mariano; Lima, Marco Frota, E-mail: slessandrodomingues@fisica.if.uff.br, E-mail: marcofrotalima@yahoo.com.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Biologia

    2015-07-01

    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)

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

    David, K.; Mokili, M.B.; Rousseau, G.; Deniau, I.; Landesman, C. [SUBATECH, Ecole des Mines de Nantes, Universite de Nantes, CNRS/IN2P3, 4 rue Alfred Kastler, 44307 Nantes cedex 3 (France)

    2014-07-01

    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 {sup 235}U/{sup 238}U 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 {sup 235}U/{sup 238}U 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

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

    Alshahri, Fatimh; Alqahtani, Muna

    2015-06-01

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

  8. Simulation smuggling study for shielded sources of 235U, 238U, 232Th, 137Cs and 60Co by using gamma detection

    In the present time, smuggling and illicit trafficking of nuclear and radioactive materials are targeted by international groups and networks. Hundreds of smuggled nuclear and radioactive materials have been seized and currently recorded in the Illicit Trafficking Database (ITDB) of the International Atomic Energy Agency (IAEA). As a matter of fact, these materials can be used for manufacturing of dirty or Radiological Dispersal Device (RDD) or for sabotage and malicious purposes. This work deals with gamma detection of shielded sources containing natural 235U , 238U , standard 232Th and mixed 137Cs and 60Co sources by using HpGe and NaI detectors. The detection was carried out through the main characteristic γ- energies ; 185.7 KeV for 235U ,(63.3 ,1001 KeV) for 238U , (583 and 911.2 KeV) for 232Th, 661.6 KeV for 137Cs and (1173.2 and 1332.5 keV) for 60Co. The radioactive sources used are 30nCi of 232Th , 1.99 μCi of mixed 137Cs and 60Co source and uranyl nitrate crystals. These radioactive sources were separately hid (placed) in containers of different materials; aluminum (Al) , cupper (Cu) and iron (Fe) of different wall thickness; 3, 6, 9, 12, 15, 18 mm. The sources were also measured together by NaI and HpGe detector. Overlapping of different gamma transitions leads to some difficulties to identify and discriminate between the investigated γ-energies particularly with using the low resolution NaI detector. The attenuation factors (I/Io), ratio of radiation intensity with and without shield (containers), were calculated for all the investigated energies. The relationship between the attenuation factor of γ-energies and the studied thickness was depicted and discussed. It was observed, as expected, that the studied gamma transitions were attenuated by the used different thickness of Fe, Cu and Al and hardly detected especially for low energy and at 18mm thickness. Generally, it can concluded that radioactive materials of small activity can easily be smuggled

  9. Determination of natural radionuclides from 238U and 232Th series, trace and major elements in sediment cores from baixada Santista and evaluation of impacted areas

    Baixada Santista is the region of higher population of the coast of Sao Paulo State, where it is located the largest port in Latin America, in the city of Santos, and the most important industrial complex of Latin America, in the city of Cubatao. This region has received in recent years a considerable load of industrial and domestic effluents in its water bodies, as a direct result of the industrial and port activities and the large population growth in recent decades, and is considered nowadays highly impacted. In the present study sediment cores were collected in the estuary of Santos-Cubatao, in the estuary of Sao Vicente, in the channel of Bertioga and Santos Bay, in order to determine the concentration of trace and major elements and natural radionuclides from the 238U and 232Th series. The techniques used were neutron activation analysis, X-ray fluorescence and gamma spectrometry, respectively. The obtained values for the elements Cr, Sb, Ta and Zn in some cores, are higher than data from literature, and can indicate a possible anthropic contribution. Comparing the obtained values of Cr and Zn elements determined in the sediment cores with the values of TEL and PEL index for sediment quality, it was verified that the studied region presents Cr levels higher than TEL in Santos-Cubatao estuary and Bertioga channel and Zn element presented values higher than TEL for some core slices of Santos-Cubatao estuary, for one core of Sao Vicente estuary, one core in Bertioga channel and Santos Bay. For the other elements, the values obtained in this study can be considered as reference values for the region. Although the element As presented higher values than the TEL in all the studied environments, the concentrations obtained are of the same order of magnitude as literature data and, therefore, can be considered also as reference values for the region. No enrichment was found for the major elements in all the ecosystems studied, with the exception for the element P

  10. Assessment of natural radionuclides concentration from 238U and 232Th series in Virginia and Burley varieties of Nicotiana tabacum L

    Brazil is the largest exporter and second largest producer of tobacco worldwide, according to the crop production of 2013/2014. The tobacco plant (Nicotiana tabacum L.) is used to manufacture all derivatives and the chemical composition of the resulting tobacco products varies with the type of tobacco leaves, how they are grown, the region where they are cultivated, the characteristics of preparation (compression, filter and paper) and the temperature variations resulting from the incomplete combustion of tobacco. Tobacco products are extensively used throughout the world, and the most consumed are cigarettes, cigars and narghile. The damaging effects that these products cause to human health are discussed globally, and many surveys are performed with the aim of relating the use of these products with various illnesses. There is a lack of information about the radiological characterization of the tobacco plant both in international and Brazilian literature. The objective of this study was to determine the concentration of radionuclides 238U, 234U, 230Th, 22'6Ra, 210Pb and 210Po, members from the 238U decay series, and the radionuclides 232Th and 228Ra members of the 232Th decay series in the varieties Burley and Virginia, which are the most cultivated in Brazil. Plants from these varieties were cultivated in pots with organic substrate and fertilizer and also acquired from the producers and analyzed by alpha spectrometry for U and Th isotopes and 210Po determination, and gross alpha and beta counting, 228Ra, 226Ra and 210Pb determination. The whole plant, from both places, was analyzed; root, stem, leaves, as well as the organic substrate, the fertilizers, and the soil. The results for U and Th isotopes presented values below the detection limits of the methods to the leaves and stems of all plants analyzed, with measurable results only in roots, soil, and substrate. The radionuclides 226Ra, 228Ra, 210Pb, and 210Po, were determined in most parts of the plants

  11. Sub-barrier resonance fission and its effects on fission fragment properties, exemplified on 234,238U(n,f)

    The correlation between the sub-barrier resonant behaviour of fission cross-section of non-fissile actinides (pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron data (post-scission stage) around the incident energies of sub-barrier resonances is outlined and supported by quantitative results for two fissioning systems 234,238U(n,f). These quantitative results refer to both stages of the fission process: a) the pre-scission stage including the calculation of neutron induced cross-sections with focus on fission. Calculations are done in the frame of the refined statistical model for fission with sub-barrier effects also extended to take into account the multi-modal fission; b) the post-scission stage including the prompt neutron emission treated in the frame of the Point-by-Point model. Total quantities characterizing the fission fragments and the prompt neutrons obtained by averaging the Point-by-Point results as a function of fragment over the fission fragment distributions reveal variations around the energies of sub-barrier resonances in the fission cross-section. (authors)

  12. Correlation of the activity of the 238 U in soil and 222 Rn in domiciles, with the rocks of cities of the Estado de Chihuahua

    The state of Chihuahua has numerous locations of uranium, being Pena Blanca the great and more important location of the country. Diverse rock types with important quantities of uranium are distributed by the whole state. The igneous extrusive acid rocks are those that have bigger quantity of uranium, like they are the rhyolites and dacites and these rocks are located in enough proportion by the whole state. Some of the main cities of the state are near to locations or uraniferous rocks, as Aldama, Nuevo Casas Grandes, Chihuahua, Jimenez and Bocoyna, other important cities are not near important locations. It was determined specific activity by gamma spectroscopy of the series of the 238 U in soils and determination of the radon concentration in domiciles of the main cities of the state. They were found high specific activity values in soil in eight of the thirteen analyzed cities and important radon concentrations in three cities. It was found relationship among the specific activity in soil in near cities to uraniferous locations. (Author)

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

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

    2014-05-01

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

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

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

    1998-10-01

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

  15. Sub-barrier resonance fission and its effects on fission fragment properties, exemplified on 234,238U(n,f

    Oberstedt S.

    2013-03-01

    Full Text Available The correlation between the sub-barrier resonant behaviour of fission crosssection of non-fissile actinides (pre-scission stage and the visible fluctuations of their fission fragment and prompt neutron data (post-scission stage around the incident energies of sub-barrier resonances is outlined and supported by quantitative results for two fissioning systems 234,238U(n,f. These quantitative results refer to both stages of the fission process: a The pre-scission stage including the calculation of neutron induced cross-sections with focus on fission. Calculations are done in the frame of the refined statistical model for fission with sub-barrier effects also extended to take into account the multi-modal fission. b The post-scission stage including the prompt neutron emission treated in the frame of the Point-by-Point model. Total quantities characterizing the fission fragments and the prompt neutrons obtained by averaging the Point-by-Point results as a function of fragment over the fission fragment distributions reveal variations around the energies of sub-barrier resonances in the fission crosssection.

  16. Estimation of multi-group cross section covariances for 235,238U, 239Pu, 241Am, 56Fe, 23Na and 27Al

    This paper presents the methodology used to estimate multi-group covariances for some major isotopes used in reactor physics. The starting point of this evaluation is the modelling of the neutron induced reactions based on nuclear reaction models with parameters. These latest are the vectors of uncertainties as they are absorbing uncertainties and correlation arising from the confrontation of nuclear reaction model to microscopic experiment. These uncertainties are then propagated towards multi-group cross sections. As major breakthroughs were then asked by nuclear reactor physicists to assess proper uncertainties to be used in applications, a solution is proposed by the use of integral experiment information at two different stages in the covariance estimation. In this paper, we will explain briefly the treatment of all type of uncertainties, including experimental ones (statistical and systematic) as well as those coming from validation of nuclear data on dedicated integral experiment (nuclear data oriented). We will illustrate the use of this methodology with various isotopes such as 235,238U, 239Pu, 241Am, 56Fe, 23Na and 27Al. (authors)

  17. Speciation analysis of 129I, 137Cs, 232Th, 238U, 239Pu and 240Pu in environmental soil and sediment

    The environmental mobility and bioavailability of radionuclides are related to their physicochemical forms, namely species. We here present a speciation analysis of important radionuclides including 129I (also 127I), 137Cs, 232Th, 238U and plutonium isotopes (239Pu and 240Pu) in soil (IAEA-375) and sediment (NIST-4354) standard reference materials and two fresh sediment samples from Øvre Heimdalsvatnet Lake, Norway. A modified sequential extraction protocol was used for the speciation analysis of these samples to obtain fractionation information of target radionuclides. Analytical results reveal that the partitioning behaviour, and thus the potential mobility and bioavailability, are exclusively featured for the individual radionuclide. Iodine is relatively mobile and readily binds to organic matter, while plutonium is mainly bound to both organic matter and nitric acid leachable fractions. Thorium is predominated in nitric acid leachable fraction and caesium is primarily observed in nitric acid and aqua regia leachable fractions and residue. Our analytical results reveal that around 50% of uranium might still remain in the residue which could not be extracted with aggressive acid, namely, aqua regia.

  18. Options for the deduction of target and intervention values for radon precursors of the 238U- and 232Th-series in soils

    Radiation protection policy in the Netherlands applies to human activities in which ionizing radiation presents a hazard, not to naturally occurring sources of radiation. The risk levels (maximum permissible risk and negligible risk) apply to sources of radiation that cause an additional risk. Translation of these levels into practical environmental quality objectives therefore implies that both the extent and the origin of the risk are determined. The distinction between the natural and the additional radiation dose is of particular interest. In this report various possibilities are described for measuring, explaining and predicting the naturally occurring concentrations of the precursors of the element radon in the two radioactive decay series starting with 238U and 232Th. Several methods are given that may be used to derive environmental quality objectives for the soil with respect to these radionuclides. These environmental quality objectives are an important basis for among other things the soil sanitation policy. The nature of the radionuclides considered may have consequences for the choice of sanitation techniques. Because possible sources and cases of soil pollution may have important consequences for the Dutch policy on soil sanitation, a short overview is given of data published on these subjects. The foundation and the control of intervention levels requires insight in the relative importance of pollution pathways. As a result, pathways have been given ample attention. 9 figs., 17 tabs., 66 refs

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

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

  20. Investigations of the mass and charge distribution of fission products from the 238U(n14,f) reaction by direct Ge(Li) method

    The fission yields can be measured by the well-known activation method if it is taken into account that the fission process results in 5-6 nuclides in an isobaric chain. The method which is based only on the gamma-spectrometric measurement of the irradiated fissioning sample is referred to as the direct Ge(Li) method for fission yield measurement. The thesis contains detailed description of the direct Ge(Li) method. The method was tested by the measurement of cumulative yields of 47 fission products and independent yields of 7 products in the reaction of 238U(n14,f). These are the members of 37 mass chains in the A=83-149 mass number region. The half-lives of the studied products are in the range of Tsub(1/2)=102-109 s; the gamma spectrometric method was improved by extending its applicability to the measurement of short-lived products. Applying short irradiation time (5 min) the yields of 16 fission products with half-lives shorter than 1 hour could be measured. The lowest measured partial fission cross sections (yields) are in the order of 1 mb (0.1%). The accuracy of the yield measured by the direct Ge(Li) method is as high as or higher than that obtained radiochemically, especially for the products measured by many intensive gamma lines. (author)

  1. Simulation smuggling study for shielded sources of 235U, 238U, 232Th, 137Cs and 60Co by using γ-detection

    This work deals with gamma detection of shielded sources of 235U, 238U, 232Th, 137Cs and 60Co by using HpGe and NaI detectors through their main characteristic energies; 185.7 keV, (63, 1001), (583 and 911), 661.6 and (1173 and 1332) KeV respectively. These radioactive sources were individually hidden in containers of aluminum (Al), iron (Fe) and cupper (Cu) of different thicknesses; 3, 6, 9, 12, 15, 18 mm. Thin containers of lead (Pb) were also used with the same sources. The attenuation factor (I/I0), the ratio of radiation intensity with and without container or shield, was calculated for all the investigated γ-energies. The relationship between the attenuation factor and the studied thicknesses of the containers was given, depicted and discussed. Detection of the mixed sources shielded by different materials of different thicknesses was also carried out by using PDR-77 survey meter. The radiation levels were found to be within the natural background at 65cm distance from the shielded sources. Telescopic arm carrying 2x2 NaI and radiometer was also used. Generally, It can be concluded that smuggling of radioactive materials of low radioactivity can be done without detection by hiding them in containers or within scrap of Cu, Fe or even Al rather than using the conventional heavy lead shield. (author)

  2. {sup 230}Th, {sup 232}Th and {sup 238}U determinations in phosphoric acid fertilizer and process products by ICP-MS

    Nascimento, Marcos R.L. do; Guerreiro, Luisa M.R.; Bonifacio, Rodrigo L.; Taddei, Maria H.T., E-mail: pmarcos@cnen.gov.br [Comissao Nacional de Energia Nuclear (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas

    2015-07-01

    Through processing of Santa Quiteria-CE mine phosphate rock, Brazil has established a project for production of phosphoric acid fertilizer and uranium as a by-product. Under leaching conditions of phosphate rock with sulfuric acid, which is the common route for preparing phosphoric acid fertilizer, a large part of uranium, thorium and their decay products naturally present in the rock are solubilized. In order to assess the contamination potential in phosphoric acid and others process products, this paper describes a previous precipitation and direct methods for routine analysis of thorium and uranium isotopes by ICP-MS. In all samples, {sup 230}Th, {sup 232}Th and {sup 238}U were directly determined after dilution, except {sup 230}Th in phosphoric acid loaded with uranium sample, which to overcome equipment contamination effect, was determined after its separation by oxalate precipitation using lanthanum as a carrier. The results obtained by the proposed method by ICP-MS, were in good agreement when compared to alpha spectrometry for {sup 230}Th, and ICP-OES and spectrophotometry with arsenazo III for elementary uranium and thorium determinations. (author)

  3. Charge distributions from reactions of 58Ni and 64Ni with 238U at 8.7 MeV/nucleon

    One of the basic questions which remains under discussion in deep inelastic reactions is the nature of the driving force which determines product charge and mass distributions. In order to further investigate this problem, reactions of 58Ni and 64Ni with 238U have been studied at the LBL SuperHILAC. The two projectiles have very different N/Z ratios of 1.07 and 1.28, respectively. Since the target N/Z ratio is 1.59, the projectile-like products should show significantly different charge drifts for the different projectiles. The energy and charge of the projectile-like fragments were determined by a ΔE-E detection system which consisted of a two segment gas ionization chamber backed by a new large-area Si detector. The anodes of the two gas sections were rotated by 900 providing X-Y position sensitivity using the two drift times. This allowed position correction to the time-of-flight, which is essential to obtain optimum mass resolution. There is a significant yield of products with masses greater than the projectile value of A=58, especially in the quasielastic region, where corrections due to evaporation deexcitation are small. 4 references, 3 figures

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

    Vazquez, Jorge A.; Lidzbarski, Marsha I.

    2012-12-01

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

  5. Systematic experimental survey on projectile fragmentation and fission induced in collisions of 238U at 1 A GeV with lead

    Projectile fragmentation and fission, induced in collisions of 238U at 1 A GeV with lead, have systematically been studied. A complete survey on the isotopic production cross sections of all elements between vanadium (Z = 23) and rhenium (Z = 75) down to a cross section of 0.1 mb is given. About 600 isotopes produced in fragmentation and about 600 isotopes produced in fission were identified in the GSI fragment separator FRS from magnetic rigidities, time-of-flight values, and the energy loss in an ionisation chamber. In addition, the velocity distributions of all these reaction products have been mapped, and the products are unambiguously attributed to the different reaction mechanisms due to their kinematical properties. The results are compared with empirical systematics and previous data. The velocity of the fragments obtained in the fission process by the Coulomb repulsion allows to reconstruct the TKE-value of the break-up and to identify the atomic number of the fissioning nucleus in hot fission. The mean velocities of light projectile fragments were found to be higher than the beam velocity. (orig.)

  6. EC comparison on the determination of {sup 226}Ra, {sup 228}Ra, {sup 234}U and {sup 238}U in water among European monitoring laboratories

    Waetjen, U., E-mail: uwe.waetjen@ec.europa.e [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium); Benedik, L.; Spasova, Y.; Vasile, M.; Altzitzoglou, T. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium); Beyermann, M. [Bundesamt fuer Strahlenschutz (BfS), Koepenicker Allee 120-130, D-10318 Berlin (Germany)

    2010-07-15

    In anticipation of new European requirements for monitoring radioactivity concentration in drinking water, IRMM organized an interlaboratory comparison on the determination of low levels of activity concentrations (about 10-100 mBq L{sup -1}) of the naturally occurring radionuclides {sup 226}Ra, {sup 228}Ra, {sup 234}U and {sup 238}U in three commercially available mineral waters. Using two or three different methods with traceability to the International System of Reference (SIR), the reference values of the water samples were determined prior to the proficiency test within combined standard uncertainties of the order of 3%-10%. An overview of radiochemical separation and measurement methods used by the 45 participating laboratories are given. The results of the participants are evaluated versus the reference values. Several of the participants' results deviate by more than a factor of two from the reference values, in particular for the radium isotopes. Such erroneous analysis results may lead to a crucial omission of remedial actions on drinking water supplies or to economic loss by an unjustified action.

  7. Seasonal cycles of particle and solute transport processes in nearshore sediments: 222Rn/226Ra and 234Th/238U disequilibrium at a site in Buzzards Bay, MA

    Particle mixing rates and irrigation rates in the sediments of a site in Buzzards Bay, Massachusetts, have been estimated over two nearly full seasonal cycles. Seasonal variability is consistent with biologically driven transport mechanisms. 234Th/238U disequilibrium measurements were used to estimate particle mixing rates, a cold-season average rate of 5.6 cm2/yr and a warm-season average rate of 17 cm2/yr were found. Excess 234Th inventories in the upper 5 cm of the sediments also varied seasonally, with a cold-season average value of 1.8 dmp/cm2, and a warm-season value of 3.4 dpm/cm2. 222Rn/226Ra disequilibrium in sediment pore waters was used to estimate sediment irrigation. Three seasonal groupings of results were made: (1) December through March, when 222Rn deficits could be explained by vertical molecular diffusion alone, (2) early summer (June), when irrigation was important to at least 20 cm, (3) early fall, when irrigation was important to about 10 cm. A nonlocal exchange/vertical molecular diffusion model (Emerson et al., 1984) was used to obtain quantitative estimates of irrigation rates; model Rn deficit profiles could be fitted to measured profiles quite well. (author)

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

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

    2016-01-01

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

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

    Abdullah, Anisa, E-mail: coppering@ymail.com; Hamzah, Zaini; Wood, Ab. Khalik [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor (Malaysia); Saat, Ahmad [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450, Shah Alam, Selangor (Malaysia); Institute of Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)

    2016-01-22

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

  10. Systematic experimental survey on projectile fragmentation and fission induced in collisions of {sup 238}U at 1 A GeV with lead

    Enquist, T.; Benlliure, J.; Farget, F.; Schmidt, K.H.; Armbruster, P. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Bernas, M.; Tassan-Got, L. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Boudard, A.; Legrain, R.; Volant, C. [CEA Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de Physique des Particules, de Physique Nucleaire et de l`Instrumentation Associee (DAPNIA); Boeckstiegel, C.; Jong, M. de [Technische Univ. Darmstadt (Germany); Dufour, J.P. [CEA Centre d`Etudes Nucleaires de Bordeaux-Gradignan, 33 - Gradignan (France)

    1999-03-01

    Projectile fragmentation and fission, induced in collisions of {sup 238}U at 1 A GeV with lead, have systematically been studied. A complete survey on the isotopic production cross sections of all elements between vanadium (Z = 23) and rhenium (Z = 75) down to a cross section of 0.1 mb is given. About 600 isotopes produced in fragmentation and about 600 isotopes produced in fission were identified in the GSI fragment separator FRS from magnetic rigidities, time-of-flight values, and the energy loss in an ionisation chamber. In addition, the velocity distributions of all these reaction products have been mapped, and the products are unambiguously attributed to the different reaction mechanisms due to their kinematical properties. The results are compared with empirical systematics and previous data. The velocity of the fragments obtained in the fission process by the Coulomb repulsion allows to reconstruct the TKE-value of the break-up and to identify the atomic number of the fissioning nucleus in hot fission. The mean velocities of light projectile fragments were found to be higher than the beam velocity. (orig.) 41 refs.

  11. Capture and Fission rate of 232-Th, 238-U, 237-Np and 239-Pu from spallation neutrons in a huge block of lead.

    Vlachoudis, Vasilis

    2000-01-01

    The study is centered on the research of the incineration possibility of nuclear waste, by the association of a particle accelerator with a multiplying medium of neutrons, in the project "Energy Amplifier" of C. Rubbia. It consists of the experimental determination of the rates of capture and fission of certain elements (232-Th, 238-U, 237-Np and 239-Pu) subjected to a fluence of fast spallation neutrons. These neutrons are produced by the interaction of high kinetic energy protons (several GeV) provided by the CERN-PS accelerator, on a large lead solid volume. The measurement techniques used in this work, are based on the activation of elements in the lead volume and the subsequent gamma spectroscopy of the activated elements, and also by the detection of fission fragment traces. The development, of a Monte Carlo code makes it possible, on one hand, to better understand the relevant processes, and on the other hand, to validate the code, by comparison with measurements, for the design and the construction of...

  12. Temporal evolution of natural radionuclides distributions {sup 238}U, {sup 234}Th, {sup 226}Ra, {sup 228}Ra, {sup 210}Pb and {sup 210}Po in the Bransfield strait, Antarctica peninsula; Evolucao temporal das distribuicoes dos radionuclideos naturais {sup 238}U, {sup 234}Th, {sup 226}Ra, {sup 228}Ra, {sup 210}Pb and {sup 210}Po no estreito de Bransfiel, peninsula Antartica

    Lapa, Flavia Valverde

    2013-07-01

    Research on the distribution of natural radionuclides in Antarctica is rare and thus, there is great interest in to know their occurrence and factors related to its mobilization, transference and accumulation in this extremely fragile environment. Natural radionuclides have been used intensively as tracers in the ocean, helping to better understand processes as sinking and particle resuspension, water masses mixture and oceanic circulation. {sup 234}Th (t½ = 24.1 days) is a particle-reactive radionuclide produced continuously in seawater by the decay of its soluble precursor conservative with salinity {sup 238}U (t½ = 4.5 10{sup 9} years). Since {sup 234}Th presents relatively short half-life, it is used to quantify processes that occur in temporal scale varying from days to weeks. The disequilibrium {sup 234}Th/{sup 238}U in the surface ocean has been applied to estimate carbon fluxes exported via sinking material. The flux of particles biologically productive out of the euphotic zone in the Southern Ocean has special attention due to its importance in the control of CO{sub 2} atmospheric concentrations. The radionuclides {sup 210}Pb (t½ = 22.3 years) and {sup 210}Po (t½ = 138 days) are also particle-reactive. The disequilibrium {sup 210}Po/{sup 210}Pb has been used to estimate fluxes of particles exported in the ocean in the time scale of weeks. The long-lived Ra isotopes, {sup 226}Ra (t½ = 1,600 years) and {sup 228}Ra (t½ = 5.75 years) are soluble in seawater, presenting unique properties that make them excellent tracers of water masses. This research work had the aim to study the distributions of natural radionuclides {sup 238}U, {sup 234}Th, {sup 22}'6Ra, {sup 22}'8Ra, {sup 210}Pb and {sup 210}Po in the Bransfield Strait during 2 samplings carried out in the 2011 Austral Summer (OPERANTAR XXIX and XXX). (author)

  13. Photo-fission for the production of radioactive beams ALTO project

    In order to probe neutron rich radioactive noble gases produced by photo-fission, a PARRNe-1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) has been carried out at CERN. The incident electron beam of 50 MeV was delivered by the LIL machine: LEP Injector Linac. The experiment allowed us to compare under the same conditions two production methods of radioactive noble gases: fission induced by fast neutrons and photo-fission. The obtained results show that the use of the electrons is a promising mode to get intense neutron rich ion beams. After the success of this photo-fission experiment, a conceptual design for the installation at IPN Orsay of a 50 MeV electron accelerator close to the PARRNe-2 device has been worked out: ALTO Project. This work has started within a collaboration between IPNO, LAL (Laboratoire de l'Accelerateur Lineaire) and CERN groups

  14. Tomography of actinides by photofission in bulky radioactive waste packages

    Quantifying actinides using non-destructive methods, in radioactive waste packages, is a great stake to turn packages towards appropriate storage facility. But the nature of radiations emitted by actinides (alpha radiations) makes the detection of those very difficult for large volume packages characterization. Indeed, the emitted radiation is too weak, either to be detected by emission tomography or to reach required sensitivities. Therefore, it is necessary to turn to an external probing source. Tomography based on detection of delayed neutrons induced by photofission, allows to probe bulky packages. We demonstrate the suitability of this method to an industrial stage. Firstly, we determine and qualify projection matrix which connects measures at reconstructed activity of tomographic picture. Thus, during measurements on a model and a real package, we carry out convincing tomographic reconstructions with real acquisition conditions. More, we prove that it is possible to take all disruptive chemical element into account, for tomographic reconstructions, in order to obtain the best image of activity. So, we propose a finalised tomographic device, integrating a shielding cell, and checking all the activity and distribution activity criterions fixed for acceptance of radioactive waste packages in superficial storage facility. (author)

  15. Simulation Of A Photofission-Based Cargo Interrogation System

    King, Michael; Gozani, Tsahi; Stevenson, John; Shaw, Timothy

    2011-06-01

    A comprehensive model has been developed to characterize and optimize the detection of Bremsstrahlung x-ray induced fission signatures from nuclear materials hidden in cargo containers. An effective active interrogation system should not only induce a large number of fission events but also efficiently detect their signatures. The proposed scanning system utilizes a 9-MV commercially available linear accelerator and the detection of strong fission signals i.e. delayed gamma rays and prompt neutrons. Because the scanning system is complex and the cargo containers are large and often highly attenuating, the simulation method segments the model into several physical steps, representing each change of radiation particle. Each approximation is carried-out separately, resulting in a major reduction in computational time and a significant improvement in tally statistics. The model investigates the effect on the fission rate and detection rate by various cargo types, densities and distributions. Hydrogenous and metallic cargos, homogeneous and heterogeneous, as well as various locations of the nuclear material inside the cargo container were studied. We will show that for the photofission-based interrogation system simulation, the final results are not only in good agreement with a full, single-step simulation but also with experimental results, further validating the full-system simulation.

  16. Simulation Of A Photofission-Based Cargo Interrogation System

    A comprehensive model has been developed to characterize and optimize the detection of Bremsstrahlung x-ray induced fission signatures from nuclear materials hidden in cargo containers. An effective active interrogation system should not only induce a large number of fission events but also efficiently detect their signatures. The proposed scanning system utilizes a 9-MV commercially available linear accelerator and the detection of strong fission signals i.e. delayed gamma rays and prompt neutrons. Because the scanning system is complex and the cargo containers are large and often highly attenuating, the simulation method segments the model into several physical steps, representing each change of radiation particle. Each approximation is carried-out separately, resulting in a major reduction in computational time and a significant improvement in tally statistics. The model investigates the effect on the fission rate and detection rate by various cargo types, densities and distributions. Hydrogenous and metallic cargos, homogeneous and heterogeneous, as well as various locations of the nuclear material inside the cargo container were studied. We will show that for the photofission-based interrogation system simulation, the final results are not only in good agreement with a full, single-step simulation but also with experimental results, further validating the full-system simulation.

  17. Standard practice for the determination of 237Np, 232Th, 235U and 238U in urine by inductively coupled plasma-Mass spectrometry (ICP-MS) and gamma ray spectrometry.

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This practice covers the separation and preconcentration of neptunium-237 (237Np), thorium-232 (232Th), uranium-235 (235U) and uranium-238 (238U) from urine followed by quantitation using ICP-MS. 1.2 This practice can be used to support routine bioassay programs. The minimum detectable concentrations (MDC) for this method, taking the preconcentration factor into account, are approximately 1E-2Bq for 237Np (0.38ng), 2E-6Bq for 232Th (0.50ng), 4E-5Bq for 235U (0.50ng) and 6E-6Bq for 238U (0.48ng). 1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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

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

    2015-10-01

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

  19. Non-destructive determination of 235U, 238U, 232Th and 40K concentrations in various consumed nuts and their implication on radiation dose levels to the human body

    The naturally occurring radionuclides of 238,235,234U,232Th and 40K and their daughter products are a potential source of radiation found in food. We have determined these five radiation sources in five popular consumed nuts. We used the following neutron activation analysis reactions of 238U(n,γ)239U, 232Th(n,γ)233Th and 41K(n,γ)42K to determine 238U and 232Th and 40K, respectively. Using known activity ratios of uranium stable isotopes we determined the activity of 234,235U, while 40K was found by the determined concentrations of 41K in the nuts. While the radiation doses are small we have established a reliable methodology to determine these radionuclides in typical edible nuts. (author)

  20. Fission reactions of 469-MeV 56Fe+238U: Detection of 4He/1H emission from pre- and post-fission sources

    The emission of 4He and 1H has been measured in coincidence with fission for reactions of 469-MeV 56Fe+238U. By using a gas-ionization telescope in kinematic coincidence with a position-sensitive avalanche detector, the folding angle between two fission fragments was determined in order to distinguish fusion reactions from fission following smaller-momentum-transfer collisions. In both fusion fission and sequential fission reactions, the 4He/1H energy spectra are relatively narrow with relatively flat angular distributions at backward angles and become broader in energy with enhanced cross-sections at forward angles. The extent of forward peaking is significantly greater for peripheral collisions than for central collisions. The light-charged-particle multiplicities are quite similar for 4He and 1H, being much larger for fusion fission than for sequential fission. Detailed comparisons of the spectral shapes with Monte Carlo simulations of reaction kinematics impose strong constraints on the participation of different emission sources. We find important contributions to the observed 4He/1H emission both from accelerated fragments (FE) and from the composite system prior to fission (CE). For 4He emission, the multiplicity of CE is much larger for fusion fission than for sequential fission, possibly as a consequence of the higher spins and shorter reaction times associated with deeply inelastic and quasi-elastic processes. For 1H emission, a corresponding but somewhat smaller difference is observed for the CE multiplicities. An excess of 4He/1H particles, found at forward angles in both fusion and sequential fission processes, cannot be attributed to evaporative emission from any fragments and therefore must originate in pre-thermalization emission. (orig.)

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

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

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

    Abril, Jose-Maria, E-mail: jmabril@us.es [Dpto. Fisica Aplicada I, Universidad de Sevilla, EUITA, Ctra Utrera Km 1, 41013 Seville (Spain); Garcia-Tenorio, Rafael, E-mail: gtenorio@us.es [Dpto. Fisica Aplicada II, Universidad de Sevilla, ETSA, Avda. Reina Mercedes s/n, 41012 Seville (Spain); Manjon, Guillermo, E-mail: manjon@us.es [Dpto. Fisica Aplicada II, Universidad de Sevilla, ETSA, Avda. Reina Mercedes s/n, 41012 Seville (Spain)

    2009-05-30

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

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

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

    2000-01-01

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

  4. Fusion and fission properties of rapidly rotating nuclei 40Ar + 238U → 278110 at E/sub cm/ = 291 MeV

    Coincident fission fragments were detected to study the complete capture reaction, 40Ar + 238U → 278110 → f, at E/sub cm/ = 291 MeV (E/sub lab/ = 340 MeV). The detection system had a high efficiency to detect and subsequently veto events showing evidence of incomplete momentum transfer. The angular distribution of fission fragments was obtained between the center-of-mass angles of 1190 and 1640. The mass distributions of the fission fragments were also obtained for these angles. One non-coincident measurement made at theta/sub cm/ = 43.70 confirmed the symmetry of the angular distribution about 900. This study is distinguished from other recent studies by the use of a novel veto technique. This is the first measurement which has not been compromised by contamination with incomplete momentum-transfer reactions due to either pre-equilibrium emission or fission following deeply inelastic scattering. This is also the first investigation which reports detailed angular distributions with a majority (approx. 90%) of the capture cross section leading to nuclei having vanishing fission barriers. The rotating liquid-drop-model parameters were extracted from the data. The RLDM shapes along with statistical fission models, when applied to all partial waves, fail to reproduce the angular distributions. We interpret the angular distributions by applying statistical-equilibrium models and RLDM shapes for the nonvanishing fission-barrier partial waves and by assuming that the vanishing fission-barrier partial-wave contribution is given by l/sin theta. A l/sin theta distribution is expected for a system which has not reached complete statistical equilibrium and maintains a memory of its entrance channel, with the fission fragments being emitted in the reaction plane defined by the initial contact

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

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

  6. Application of 234U/238U isotope ratio data for the study of geochemical problems associated with local water sources from Aguas da Prata (SP, Brazil)

    The uranium-238, uranium-234 and radon content of spring waters of Aguas da Prata (SP) - Platina, Paiol, Villela, Sao Bento, Prata-Radioativa, Prata-Nova, Boi, Vitoria and Prata-Antiga - was found; the activity ratio AR (234U/238U) was applied to the geochemistry of local water sources. The uranium analysis procedure consisted of the following steps: adition of 232U-228Th spike to the samples, coprecipitation with iron, iron extraction with organic solvent, separation on anion-exchange resin, extraction with TTA, deposition on stainless steel disc and determination of uranium content by alpha spectrometry. The uranium-238 content changed from 0,10 to 11,56 ppb (average value = 2,3 ppb). The higher values were observed for the waters circulating through sandstones and the lower through volcanic rocks. The inverse correlation (r sub(s) =-0,76) between pH and uranium-238 content confirmed the contribution of this factor on its solubility. The significative correlation r sub(s) = 0,76 between dissolved oxygen and uranium-238 content also confirmed the higher uranium on the more oxidizing zones. The AR changed from 2,84 to 11,68 (average value = 6). These values defined the regional aquifer systems as mineralized in uranium. The higher AR were observed for the deep groundwaters and the lower for the shallow one. Because the 238U→234Th decay, the 234Th ejection to the solution was confirmed as the most important factor responsible for the extreme observed isotopic fractionation. (Author)

  7. 234U/238U and δ87Sr in peat as tracers of paleosalinity in the Sacramento-San Joaquin Delta of California, USA

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

    2013-01-01

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

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

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

  9. Development of sequential analytical method for the determination of U-238, U-234, Th-232, Th-230, Th-228, Ra-226 and Ra-228 and its application in mineral waters

    A sequential analytical method for the determination of U-238, U-234, Th-232, Th-230, Th-228, Ra-226 and Ra-228 in environmental samples and applied to the analysis of mineral waters is studied. Thorium isotopes are coprecipitated with lanthanium fluoride before counting in alpha spectrometer, the uranium isotopes are determined by alpha spectrometry following extraction with TOPO onto a polymenic membrane. Radium-226 is determined with the radom emanation technique. (M.J.C.)

  10. Use of electrodeposition for sample preparation and rejection rate prediction for assay of electroformed ultra high purity copper for 232Th and 238U prior to inductively coupled plasma mass spectrometry (ICP/MS)

    The search for neutrinoless double beta decay in 76Ge has driven the need for ultra-low background Ge detectors shielded by electroformed copper of ultra-high radiopurity (232Th and 238U into the plating bath simulates low purity copper and allows for the calculation of the electrochemical rejection rate of thorium and uranium in the electroplating system. This rejection value will help to model plating bath chemistry. (author)

  11. Linac based photofission inspection system employing novel detection concepts

    Stevenson, John, E-mail: jstevenson@rapiscansystems.com [Rapiscan Laboratories, Inc., 520 Almanor Avenue, Sunnyvale, CA 94085 (United States); Gozani, Tsahi, E-mail: tgozani@rapiscansystems.com [Rapiscan Laboratories, Inc., 520 Almanor Avenue, Sunnyvale, CA 94085 (United States); Elsalim, Mashal; Condron, Cathie; Brown, Craig [Rapiscan Laboratories, Inc., 520 Almanor Avenue, Sunnyvale, CA 94085 (United States)

    2011-10-01

    Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO{sub 4}) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10{sup 8} cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9

  12. Linac based photofission inspection system employing novel detection concepts

    Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

    2011-10-01

    Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV

  13. Linac based photofission inspection system employing novel detection concepts

    Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 108 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV

  14. Neutron Energy Spectra from Neutron Induced Fission of 235U at 0.95 MeV a of 238U at 1.35 and 2.02 MeV

    The shapes of fission neutron spectra are of interest for power reactor calculations. Recently it has been suggested that the neutron induced fission spectrum of 235U may be harder than was earlier assumed. For this reason measurements of the neutron spectra of some fissile isotopes are in progress at our laboratory. This report will present results from studies of the energy spectra of the neutrons emitted in the neutron induced fission of 235U and 238U. The measurements were performed at an incident neutron energy of 0.95 MeV for 235U and at energies of 1.35 and 2.02 MeV for 238U using time-of-flight techniques. The time-of-flight spectra were only analysed at energies higher than those of the incident neutrons and up to about 10 MeV. Corrections for neutron attenuation in the uranium samples were calculated using a Monte Carlo program. The corrected fission neutron spectra were fitted to Maxwellian temperature distributions. For 235U a temperature of 1.27 ± 0.01 MeV gives the best fit to the experimental data and for 238U the corresponding values are 1.29 ± 0.03 MeV at 1.35 MeV and 1.29 ± 0.02 MeV at 2.02 MeV

  15. Active Interrogation using Photofission Technique for Nuclear Materials Control and Accountability

    Yang, Haori [Oregon State Univ., Corvallis, OR (United States)

    2016-03-31

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. In addition to thermal or high-energy neutrons, high-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. Electron linear accelerators (linac) are widely used as the interrogating photon sources for inspection methods involving photofission technique. After photofission reactions, prompt signals are much stronger than the delayed signals, but it is difficult to quantify them in practical measurements. Delayed signals are easily distinguishable from the interrogating radiation. linac-based, advanced inspection techniques utilizing the delayed signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope.

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

    Natural radioactivity of soil samples has been studied in many countries of the Arabian Peninsula, including Saudi Arabia. Radiological indices based on soil radioactivity have been widely used in these studies. However, there are no available data about natural radioactivity of fine aerosol particles in such countries. The objective of this study is to determine the activity concentrations of 40K, 232Th and 238U in airborne PM2.5 and the associated internal inhalation radiation dose to the public in Jeddah City, Saudi Arabia. Twenty-four air samples in four locations throughout Jeddah were collected and analyzed for PM2.5 and the associated K, Th and U. The activity concentrations of the isotopes 40K, 232Th and 238U were calculated. High atmospheric PM2.5 concentrations (mean: 50.81 ± 34.02 μg/m3) were found. The natural radioactivity associated with PM2.5 due to the isotopes 40K, 232Th and 238U were 301.8 ± 76.1, 11.8 ± 4.2 and 10.8 ± 3.4 Bq/kg, respectively, and the Raeq was calculated as 44.9 ± 14.0 Bq/kg. The inhalation annual effective radiation dose to the public due to natural isotopes of the airborne PM2.5 was in the range 15.03–58.87 nSv/year, depending on the age group. Although these dose values were associated with the PM2.5 fraction only, they were higher than the world references values in air reported in the UNSCEAR, 2000 report. - Highlights: • High airborne PM2.5 concentrations over 4 months (24 samples) were found in Jeddah. • The mean activity concentrations of 40K, 232Th and 238U were assessed in PM2.5. • Effective inhalation dose due to 40K, 232Th and 238U was 59 nSv/year for adults. • Effective inhalation dose was higher than the world reference values in air. • Studying the inhalation dose due to other radioisotopes in PM2.5 is recommended

  17. Assessment of natural radionuclides concentration from {sup 238}U and {sup 232}Th series in Virginia and Burley varieties of Nicotiana tabacum L; Avaliacao da concentracao dos radionuclideos naturais das series do {sup 238}U e {sup 232}Th nas variedades Burley e Virginia da Nicotiana tabacum L.

    Silva, Carolina Fernanda da

    2015-07-01

    Brazil is the largest exporter and second largest producer of tobacco worldwide, according to the crop production of 2013/2014. The tobacco plant (Nicotiana tabacum L.) is used to manufacture all derivatives and the chemical composition of the resulting tobacco products varies with the type of tobacco leaves, how they are grown, the region where they are cultivated, the characteristics of preparation (compression, filter and paper) and the temperature variations resulting from the incomplete combustion of tobacco. Tobacco products are extensively used throughout the world, and the most consumed are cigarettes, cigars and narghile. The damaging effects that these products cause to human health are discussed globally, and many surveys are performed with the aim of relating the use of these products with various illnesses. There is a lack of information about the radiological characterization of the tobacco plant both in international and Brazilian literature. The objective of this study was to determine the concentration of radionuclides {sup 238}U, {sup 234}U, {sup 230}Th, {sup 22}'6Ra, {sup 210}Pb and {sup 210}Po, members from the {sup 238}U decay series, and the radionuclides {sup 232}Th and {sup 228}Ra members of the {sup 232}Th decay series in the varieties Burley and Virginia, which are the most cultivated in Brazil. Plants from these varieties were cultivated in pots with organic substrate and fertilizer and also acquired from the producers and analyzed by alpha spectrometry for U and Th isotopes and {sup 210}Po determination, and gross alpha and beta counting, {sup 228}Ra, {sup 226}Ra and {sup 210}Pb determination. The whole plant, from both places, was analyzed; root, stem, leaves, as well as the organic substrate, the fertilizers, and the soil. The results for U and Th isotopes presented values below the detection limits of the methods to the leaves and stems of all plants analyzed, with measurable results only in roots, soil, and substrate. The

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

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

    2009-01-01

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

  19. Fission barrier determinations and fragment angular correlations for the 244Pu, 242Pu, 240U, 238U, 234Th, and 232Th compound nuclei from (t, pf) reactions

    Fission probabilities and the angular distribution of the fission fragments have been measured for six even-even compound nuclear systems using the (t, pf) reaction. Angular correlations of fission fragments obtained in these experiments provide information about the low-lying collective excitations or transition states at the fission barrier. The (t, p) reaction in particular leads to neutron-rich residual nuclei unobtainable by other methods. The absence of spin coupling for (t, p) reactions on even-even targets provides angular distributions with well defined structure in the region of the fission barrier. The experimental data were obtained using an 18-MeV triton beam on targets of 242Pu, 240Pu, 238U, 236U, 232Th and 230Th at Los Alamos Van-de-Graaff accelerator facility. Outgoing protons were detected at 140 deg relative to the incident triton beam. Excitation energies ranging from 3.0 to 9.0 MeV were obtained in these experiments. Fission fragment angular distributions were measured at 24 angles from 0 deg to 140 deg relative to the kinematic recoil angle. The data were fitted to a series of even Legendre polynomials W(θ) = A0 [1 + ΣL gL PL (cos θ)] and the coefficients g2 through g12 and A0 were determined as a function of excitation energy. The fission probability Pf was obtained from the ratio of A0 to the (t, p) cross-section for the target nucleus. The results exhibit well defined structure in the angular coefficients which correlates with structure in the fission probability for most of the nuclei studied. In an attempt to interpret this observed structure the experimentally determined fitting parameters Pf and g are compared with calculated results of a microscopic model. This model takes into consideration the penetrability and angular dependence of fission through each member of the various transition bands at the saddle point and appropriately sums the results for comparison with the data. The effects of barrier penetration through a two

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

    Maglich, Bogdan; Hester, Tim; Calsec Collaboration

    2015-10-01

    Uranium-uranium colliding beam experiment1, used fully ionized 238U92+ at energy 100GeV --> 4 FF + 5n + 430 MeV. Using a simple model1 fission σf ~ 100 b. Suppression of Pu by a factor of 106 will be achieved because NO thermal neutron fission can take place; only fast, 1-3 MeV, where σabs is negligible. Direct conversion of 95% of 430 MeV produced is carried by electrically charged FFs which are magnetically funneled for direct conversion of energy of FFs via electrostatic decelerators4,11. 90% of 930 MeV is electrically recoverable. Depending on the assumptions, we project electric _ power density production of 20 to 200 MWe m-3, equivalent to Thermal 1.3 - 13 GWthm-3. If one-half of unburned U is used for propulsion while rest powers system, heavy FF ion mass provides specific impulse Isp = 106 sec., 103 times higher than current rocket engines.

  1. Correlation of the activity of the {sup 238} U in soil and {sup 222} Rn in domiciles, with the rocks of cities of the Estado de Chihuahua; Correlacion de la actividad del {sup 238} U en suelo y {sup 222} Rn en domicilios, con las rocas de ciudades del Estado de Chihuahua

    Colmenero S, L.; Villalba, L.; Montero C, M.E. [Centro de Investigacion en Materiales Avanzados (CIMAV), Av. Miguel de Cervantes 120 C.P. 31109 Chihuahua (Mexico)]. e-mail: luis.colmenero@cimav.edu.mx

    2004-07-01

    The state of Chihuahua has numerous locations of uranium, being Pena Blanca the great and more important location of the country. Diverse rock types with important quantities of uranium are distributed by the whole state. The igneous extrusive acid rocks are those that have bigger quantity of uranium, like they are the rhyolites and dacites and these rocks are located in enough proportion by the whole state. Some of the main cities of the state are near to locations or uraniferous rocks, as Aldama, Nuevo Casas Grandes, Chihuahua, Jimenez and Bocoyna, other important cities are not near important locations. It was determined specific activity by gamma spectroscopy of the series of the {sup 238} U in soils and determination of the radon concentration in domiciles of the main cities of the state. They were found high specific activity values in soil in eight of the thirteen analyzed cities and important radon concentrations in three cities. It was found relationship among the specific activity in soil in near cities to uraniferous locations. (Author)

  2. CREATING THE KULTUK POLYGON FOR EARTHQUAKE PREDICTION: VARIATIONS OF (234U/238U AND 87SR/86SR IN GROUNDWATER FROM ACTIVE FAULTS AT THE WESTERN SHORE OF LAKE BAIKAL

    S. V. Rasskazov

    2015-12-01

    Full Text Available Introduction. Determinations of (234U/238U in groundwater samples are used for monitoring current deformations in active faults (parentheses denote activity ratio units. The cyclic equilibrium of activity ratio 234U/238U≈≈(234U/238U≈γ≈1 corresponds to the atomic ratio ≈5.47×10–5. This parameter may vary due to higher contents of 234U nuclide in groundwater as a result of rock deformation. This effect discovered by P.I. Chalov and V.V. Cherdyntsev was described in [Cherdyntsev, 1969, 1973; Chalov, 1975; Chalov et al., 1990; Faure, 1989]. In 1970s and 1980s, only quite laborious methods were available for measuring uranium isotopic ratios. Today it is possible to determine concentrations and isotopic ration of uranium by express analytical techniques using inductively coupled plasma mass spectrometry (ICP‐MS [Halicz et al., 2000; Shen et al., 2002; Cizdziel et al., 2005; Chebykin et al., 2007]. Sets of samples canbe efficiently analysed by ICP‐MS, and regularly collected uranium isotope values can be systematized at a new quality level for the purposes of earthquake prediction. In this study of (234U/238U in groundwater at the Kultuk polygon, we selected stations of the highest sensitivity, which can ensure proper monitoring of the tectonic activity of the Obruchev and Main Sayan faults. These two faults that limit the Sharyzhalgai block of the crystalline basement of the Siberian craton in the south are conjugated in the territory of the Kultuk polygon (Fig 1. Forty sets of samples taken from 27 June 2012 to 28 January 2014 were analysed, and data on 170 samples are discussed in this paper.Methods. Isotope compositions of uranium and strontium were determined by methods described in [Chebykin et al., 2007; Pin et al., 1992] with modifications. Analyses of uranium by ISP‐MS technique were performed using an Agilent 7500ce quadrapole mass spectrometer of the Ultramicroanalysis Collective Use Centre; analyses of

  3. {sup 90}Sr, {sup 238}U, {sup 234}U, {sup 137}Cs, {sup 40}K and {sup 239/240}Pu in Emmental type cheese produced in different regions of Western Europe

    Froidevaux, P. E-mail: pascal.froidevaux@inst.hospvd.ch; Geering, J.-J.; Pillonel, L.; Bosset, J.-O.; Valley, J.-F

    2004-07-01

    A method is presented for the determination of {sup 90}Sr and uranium in Emmental type cheese collected in dairy plants from different European countries. Results display a significant correlation (r=0.708, Student t-test=6.02) between the {sup 90}Sr content of the cheese and the altitude of grazing. The highest {sup 90}Sr activity is 1.13 Bq kg{sup -1} of cheese and the lowest is 0.29 Bq kg{sup -1}. Uranium activity is very low with a highest {sup 238}U value of 27 mBq kg{sup -1}. In addition, {sup 234}U/{sup 238}U ratio shows a large enrichment in {sup 234}U for every location. Without any significant indication of the geographic origin of the cheese, this enrichment is believed to be due to the geological features of the pasture, soil and underground water. These results tend to prove that the contamination of milk by uranium originates principally from the water that the cows drink instead of the forage. This finding may have a great importance in models dealing with dairy food contamination by radionuclides following a nuclear accident. Also, the {sup 90}Sr content and to a lesser extent the {sup 234}U/{sup 238}U ratio could be used to trace the authenticity of the origin of the cheese. {sup 137}Cs activity is lower than the detection limit of 0.1 Bq kg{sup -1} in all the samples collected (n=20). Based on natural {sup 40}K activity in cheese (15-21 Bq kg{sup -1}), the decontamination factor for the alkaline cations from milk to cheese is about 20. Plutonium activity stays below the detection limit of 0.3 mBq kg{sup -1}.

  4. Evaluations of the 253U/238U Isotope Ratio through Thick-Walled Containers using the 185.7 keV and 1001.0 keV Gamma Rays

    Lanier, R G; Hayden, C F; Clark, D; Parker, W E

    2001-04-13

    The non-destructive determination of isotope ratios (NDA) present in plutonium- and uranium-bearing materials is best accomplished with a MultiGroup Analysis methodology on spectral data obtained with high-resolution germanium detector systems. This methodology is currently employed in codes such as MGA, MGAU or U235. The MGA code, for example, works well on Pu samples and employs a number of isolated spectral lines in the analysis. The algorithm uses Gaussian and Lorentzian peak shapes that are empirically modified to account for various physical and instrumental effects. Additional effects due to external absorbers, sample self-attenuation and detector relative efficiency are also included. Uranium samples are analyzed with MGAU and U235 using a simpler but similar algorithm in the narrow energy range between 85- and 100-keV. Although the details can be complex, the problem described above is ultimately reduced to evaluating a simple ratio. Applied to uranium, for example, one evaluates where the subscripts A and B refer to quantities associated with {sup 235}U and {sup 238}U, respectively. Specifically, N{sub 235U}/N{sub 238U} is the isotope ratio {sup 235}U/{sup 238}U, I is the measured gamma-ray peak intensity, and E is the counting efficiency, BR is the appropriate branching ratio, t is the appropriate half-life, {alpha}{sup Ab} is an external absorber correction (such as cadmium, iron, etc.) and {beta}{sup U} is a correction for sample self absorption. Indications of other isotopes can, of course, be determined from different ratios evaluated with data from other characteristic gamma rays that may be present in the spectrum.

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

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

    2004-01-01

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

  6. Measurement of neutron-induced fission cross-sections of Th232, U238, U233 and Np237 relative to U235 from 1 MeV to 200 MeV

    Shcherbakov, O.A.; Laptev, A.B.; Petrov, G.A. [Petersburg Nuclear Physics Inst., Gatchina, Leningrad district (Russian Federation); Fomichev, A.V.; Donets, A.Y.; Osetrov, O.I.

    1998-11-01

    The measurements of neutron-induced cross-section ratios for Th232, U238, U233 and Np237 relative to U235 have been carried out in the energy range from 1 MeV up to 200 MeV using the neutron time-of-flight spectrometer GNEIS based on 1 GeV proton synchrocyclotron. Below 20 MeV, the results of present measurements are roughly in agreement with evaluated data though there are some discrepances to be resolved. (author)

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

    A careful new measurement of the 238U(n,γ) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4π calorimetric scintillator array consisting of 160 BaF2 crystals. Measurements were made on a 48 mg/cm2 depleted uranium target. The cross sections are in general good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.

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

    Ullmann, John L [Los Alamos National Laboratory; Couture, A J [Los Alamos National Laboratory; Keksis, A L [Los Alamos National Laboratory; Vieira, D J [Los Alamos National Laboratory; O' Donnell, J M [Los Alamos National Laboratory; Jandel, M [Los Alamos National Laboratory; Haight, R C [Los Alamos National Laboratory; Rundberg, R S [Los Alamos National Laboratory; Kawano, T [Los Alamos National Laboratory; Chyzh, A [NORTH CAROLINA STATE UNIV; Baramsai, B [NORTH CAROLINA STATE UNIV; Wu, C Y [LLNL; Mitchell, G E [NORTH CAROLINA STATE UNIV; Becker, J A [LLNL; Krticka, M [CHARLES UNIV

    2010-01-01

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

  9. Photofission for the production of radioactive beams: Experimental data from an on-line measurement

    A PARRNe 1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) aimed at the production of neutron-rich radioactive noble gases produced by photofission has been performed at CERN. The LEP Pre-Injector (LPI) has been used to deliver a 50 MeV electron beam. The results obtained show clearly that the use of an electron beam to produce neutron-rich fission fragments for futur RNB facilities is an option that should not be neglected. (orig.)

  10. Development of an analytical method for the determination of U-238, U-234, Th-232, Th-230, Th-228, Ra-228, Ra-226, Pb-210 and Po-210 and its application on environmental samples

    A comparison between the environmental impact by nuclear facilities with the burden suffered from natural radioactivity calls for studying the long-lived radionuclides of the U-238 and Th-232 decay series U-238, U-234, Th-232, Th-230, Th-228, Ra-228, Ra-226, Pb-210 and Po-210. This work describes the development of a fast isotope dilution analysis method allowing to separate with one sample solution U, Th, Ra, Pb and Po both from each other and, at the same time, from the matrix. To test its applicability, the method was used with samples consisting of soil, sediments, plants, water, carbon and air dust filter. The detection limit for the chemical yield attained of approx. 70% was 0.27 mBq per sample for Th-232, Th-230, Th-228, U-238, U-234 and Po-210. The detection limit for Pb-210 was 10 mBq per sample. On account of the influence by Ra-226 in the Ra-228 measurement and vice versa the detection limit is a function of the Ra-226 and Ra-228 concentrations, respectively, in the sample. The detection limits for the pure nuclides are 0.9 mBq per sample and 10 mBq per sample, respectively, for Ra-226 and Ra-228. (orig./HP)

  11. Determination of 234U/238U ratio: Comparison of multi-collector ICPMS and ICP-QMS for water, hair and nails samples, and comparison with alpha-spectrometry for water samples

    The 234U/238U ratio in water, hair and nails samples was determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and by alpha-spectrometry for the water samples only. A correlation of 0.99 was found between the two ICPMS methods and of 0.98 with alpha-spectrometry. The range of activity ratios was between 0.9 and 2.6 according to the MC-ICPMS measurements. The reproducibility of both ICPMS techniques was better than 4% for water samples containing 1μg l-1 of uranium and a 234U/238U atom ratio of 54.9 x 10-6. Sample preparation for the ICPMS consisted of dilution of water samples containing >10 μg l-1 of uranium and measurement time was ∼1 min, while alpha-spectrometry involved pre-concentration and separation of the uranium and counting times of 1000 min. (authors)

  12. A year-by-year record of 236-U/238-U in coral as a step towards establishing 236-U from nuclear weapons testing fall-out as oceanic tracer

    Since uranium is known to behave conservatively in ocean waters, 236-U has great potential in application as oceanic tracer. 236-U (t1/2=23.4 Ma) was introduced into the oceans by atmospheric nuclear weapon testing with amount estimates ranging from 700 kg to 1500 kg. Thus a resulting initial average 236-U/238-U ratio of at least 5e-9 is expected for an oceanic mixed layer depth of 100 m. This ratio is already higher than the natural pre-nuclear background, which is expected to be at 10e-14 levels. Even the elevated ratios of global stratospheric fall-out are beyond the capabilities of ICPMS and TIMS methods. However, the exceptional sensitivity and ultra-low background for 236-U of the Vienna Environmental Research Accelerator's Accelerator Mass Spectrometry system allows us to measure down to 10-13 detection limits. We present a year-by-year record of 236-U/238-U for a Caribbean coral core covering years 1944 to 2006, thus allowing to us put constraints on the oceanic input of 236-U by atmospheric testing. Moreover modeling of the results also demonstrates the capabilities of 236-U as oceanic tracer.

  13. 234U/238U - δ7Li - δ11B isotope systematics on aquifer groundwaters from deep scientific boreholes from the Meuse-Haute Marne site. Preliminary results

    direction more or less parallel to the groundwater flow, i.e. on a NWSE axis. The lowest activity ratios (0.54) are measured in the North (MSE 101 borehole), whereas sampling points located in the South (EST 322 borehole) display higher activity ratios, one of them being even slightly higher than the equilibrium (1.18). These U activities may still result from water-rock interaction processes, but may also indicate different flow rates of groundwaters characterized by U activity ratios largely lower than the equilibrium value at the recharge areas. In this case, the flow rate would be much higher in the North (234U/238U < 0.6) than in the South. Such a hypothesis is compatible with the presence of karstification at the recharge areas (Doc. Agence de l'Eau Rhin-Meuse). δ7Li and δ11B, measured in Oxfordian groundwaters range from 11.6 to 18.6 0/00 (with one exception) and from 0.75 to 19.9 0/00, respectively. Dogger groundwaters display lithium isotopic compositions that are comparable though more homogeneous (between 14.7 and 18 0/00), whereas boron isotopic compositions are much 'heavier', from 17.5 to 28.4 0/00. Hence waters derived from the two aquifers may be clearly distinguished when reported on a δ7Li vs. d11B diagram. It is noticeable that, in this diagram, Oxfordian groundwaters from boreholes EST 342 (this water may have been contaminated during sampling by contact to argillites which have been partly drilled before sampling of Oxfordian groundwater) and EST 421, as well as Dogger waters from boreholes EST 342 and EST 432 display isotopic signatures that are very comparable (δ11B ∼ 19 0/00; δ7Li ∼ 15.5 0/00). It is remarkable that these data are from the boreholes that are located on the Joinville - Commercy line (see above). Additional samples that have been recovered in the framework of the BULiTh research project are at present being analyzed. It is expected that the next results will help to propose a more comprehensive scheme for

  14. Determination of the concentration of {sup 238}U, {sup 234}U, {sup 232}Th, {sup 228}Th, {sup 228}Ra, {sup 226}Ra and {sup 210}Pb in the feces of workers from a mining company of niobium and their families; Determinacao da concentracao de {sup 238}U, {sup 234}U, {sup 232}Th, {sup 228}Th, {sup 228}Ra, {sup 226}Ra e {sup 210}Pb na excrecao fecal de trabalhadores de uma mineradora de niobio e de seus familiares

    Oliveira, Roges de; Lopes, Ricardo T. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (LIN/COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Nuclear. Lab. de Intrumentacao Nuclear; Melo, Dunstana R.; Juliao, Ligia M.Q.C. [Instituto de Radioprotecao e Dosimetria (SEMINIRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Servico de Monitoracao Individual Interna

    2005-07-01

    The object of this study consists of an open mine from which Niobium ore (pyrochlore) is extracted and a metallurgy company, where Fe-Nb alloys are produced for export. For geological reasons, the main ore is associated to natural radionuclides U and Th, and its decay products. The concentration of {sup 234}U, {sup 238}U, {sup 232}Th, {sup 226}Ra and {sup 228}Ra, {sup 228}Th, including {sup 210}Pb in fecal excretion of 12:0 am, 29 workers and 13 family members were determined. The technique employed for the determination of the elements was the sequential method of radiochemical separation, followed by alpha spectrometry and counting {alpha} and {beta} in proportional detector. Statistically significant difference was observed in the concentration of {sup 234}U and {sup 238}U, in feces samples, among the group of mining workers and family members; as well as for {sup 232}Th in the feces of workers of crushing and metallurgy groups when compared with the Family Group. No statistically significant difference was detected at a concentration of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb, in feces of any group of workers of the installation in relation to the family group.

  15. Production of exotic fragments by photofission process combined with stopping gas cell at ELI-NP facility

    Extreme Light Infrastructure Nuclear Physics (ELI-NP) facility is being built at Bucharest-Magurele, which then allow to do research about nuclear physics using new set of research tools: high power laser system and high brilliance gamma beams. One of day-one experiments proposed at this facility is to study the photofission of actinide by the high-intensity gamma beam through measurement of mass and beta decay. In addition, ternary fission will be also studied. In particular, the measurements of exotic neutron-rich nuclei produced by photofission, especially isotopes of refractory elements, is of great interest and requires the development of an IGISOL-type. In this report, we will present benchmark simulation of photofission rate and rates of related background processes. (author)

  16. Study of the continuum production between 2.1 and 2.7 GeV/c2 and J/Ψ in the 32S+238U → μ μ +X collisions at 200 GeV per nucleon

    Quantum chromodynamics predicts a phase transition of nuclear matter at high energy density, or high temperature, to a quark gluon plasma (QGP). One of the possible signal of the QGP is the J/Ψ suppression. Since transverse energy is proportional to energy density, transverse energy and transverse momentum cross section distributions give an accurate study of the J/Ψ suppression. Experimentally we compare the J/Ψ production to the continuum production versus transverse energy produced in 32S-238U collisions. Our results are compared to the predictions of the quark gluon plasma and absorption models. Nuclear absorption cannot explain the 50% suppression of J/Ψ that we obtain. Dense pion gas and gluon multiscattering in the initial state explain the suppression and its transverse momentum dependence; however the accuracy of our results does not allow us to discriminate between models

  17. Sorption behavior of U(VI), 234U(VI) and 238U(VI) onto fracture-filling clays in Beishan granite, Gansu: Application to selecting the site of high-level radwaste repository in China

    MIN; Maozhong; LUO; Xingzhang; WANG; Ju; JIN; Yuanxin; WAN

    2005-01-01

    The first results of sorption experiments of U(VI), 234U(VI) and 238U(VI) onto original (unpurified) fracture-filling clays from No.1 monzonitic granite intrusion, Beishan area, Gansu Province, China are reported. The monzonitic granite intrusion is a potential location for a high-level radwaste (HLW) repository in China. The present experimental results show that the maximum U(VI) sorption reached 92% at near-neutral Ph and the distribution coefficient (Kd) was 1226 Ml/g. A high sorption capacity of the fracture-filling clays in host rock on radioactive elements is necessary for HLW deep geological disposal repository. No preferential sorption of 234U onto the clays was found. Finally, the sorption of U(VI) onto the clays was also modeled using a surface complexation model.

  18. The fission cross sections of 230Th, 232Th, 233U, 234U, 236U, 238U, 237Np, 239Pu and 242Pu relative 235U at 14.74 MeV neutron energy

    The measurement of the fission cross section ratios of nine isotopes relative to 235U at an average neutron energy of 14.74 MeV is described with particular attention to the determination of corrections and to sources of error. The results are compared to ENDF/B-V and to other measurements of the past decade. The ratio of the neutron induced fission cross section for these isotopes to the fission cross section for 235U are: 230Th - 0.290 +- 1.9%; 232Th - 0.191 +- 1.9%; 233U - 1.132 +- 0.7%; 234U - 0.998 +- 1.0%; 236U - 0.791 +- 1.1%; 238U - 0.587 +- 1.1%; 237Np - 1.060 +- 1.4%; 239Pu - 1.152 +- 1.1%; 242Pu - 0.967 +- 1.0%. 40 refs., 11 tabs., 9 figs

  19. Determination of 234U and 238U in seawater samples by alpha spectrometry after concentration of U(VI) onto hydrotalcite and co-precipitation with LaF3

    This paper presents a simple and accurate method for determination of uranium isotopes (234U and 238U) in seawater samples using alpha spectrometry. Uranium is pre-concentrated from seawater samples via adsorption on hydrotalcite at pH 6.5. The absorbent is dissolved into 50 ml of 8M HNO3; then filtered through a Dowex-1 column. U(VI) in the elution solution is reduced to U(IV) using zinc metal in 4M solution of HCl and then co-precipitated with LaF3. The chemical separation efficiency is found to be 97.12 ± 2.68%, eliminating the need of using 232U tracer in other published methods. This method is validated via comparison with results obtained using inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis (NAA) for three seawater samples. (orig.)

  20. Statistical tests for the detection of intermediate structure: Application to the structure of the 238U neutron capture cross section between 5 keV and 0.1 MeV

    Recent measurements of the 238U neutron capture cross section show a considerable amount of fluctuation between 5 and 100 keV. Statistical tests performed on the measured cross section suggest that the fluctuations are not compatible with the statistical model of nuclear reactions and imply the existence of intermediate structure, which is interpreted in terms of doorway states. The validity of the statistical tests used here is confirmed by numerical experiments with simulated cross sections generated by the Monte Carlo method, in accordance with the statistical method. The behavior of the capture cross section is compared to those of the subthreshold fission cross section and of the inelastic scattering cross section. The threshold anomaly at the opening of the inelastic channel at 45 keV is seen in the form of a rounded step

  1. Isotope ratio analysis of 235U and 238U nuclide using a microwave digestion associated with ICP-MS and the large areal soil survey related to Fukushima Daiichi nuclear disaster

    Isotope ratio analysis for 235U and 238U in soil samples using a microwave digestion procedure associated with ICP-MS was proposed and demonstrated. In the microwave digestion procedure, the dissolution of natural uranium in silicate (in rocks) was reduced by using a mixture of nitric acid and hydrogen peroxide (to measure the radioactive uranium from a disaster). Upon ICP-MS, the isotope ratio of the certificated geochemical reference material was realized to precisely correct the isotope ratio in real soil samples. In addition, cell-pass voltage can be available to make calibrations and/or to correct the mass bias in the mass-spectrometer. By these effects, the isotope ration of uranium can be measured with an accuracy of 0.37% without using a radioactive standard source. 235U and 238U were quantitatively determined, and those detection limits were both 0.010 μg/kg. In the case of an emergency, like a nuclear hazard, the proposed method is useful to immediately gather a large amount of information in large area as compared with a common method such as a complete dissolution process associated with an α-ray spectrometer or ICP-MS. In addition, the survey of how radioactive uranium spreads was conducted from 7 to 80 km around the Fukushima Daiichi Nuclear Power Plant (Fukushima-DNPP) (115 points in Fukushima prefecture). As a result, the values of the uranium isotope ratio for those soils were similar to the natural abundance, although the various concentrations of uranium were detected from sampling points. (author)

  2. Pre-neutron-emission Mass Distributions for Neutron-induced 238U Fission at Low and Intermediate Energies%中低能中子诱发238U裂变的碎片质量分布

    孙小军; 余呈刚; 王宁

    2012-01-01

    乏燃料中238U含量最多(高达95%),研究中子诱发238U裂变产物的分布特性对乏燃料的循环后处理具有非常重要的意义.本文基于微观和唯象方法的裂变势模型理论,研究入射能量从0.9 MeV-60.0 MeV能区的中子诱发238U裂变反应的发射中子前碎片质量分布,结果表明:在中能区,理论计算结果能很好地重现实验数据,甚至比国际著名的TALYS理论计算的结果要好;在低能区,理论计算结果也较为合理,并分析了与实验数据有所偏差的原因.%238Utof which abundance is almost 95% ,is one of the most important isotopes of the spent nuclear fuel. The study of neutron-induced 238U fission is in favor of the cycle processing of the spent fuel. Based on the microscopic and phenomenological approach,the pre-neutron-emission mass distributions of neutron-induced 238U fission at incident energies from 0. 9 to 60 MeV have been studied with the fission potential theory proposed in previous paper. The calculated results could well reproduce the experimental data,and are even better than that of the famous TALYS code at intermediate energies.The results can also reasonably predict the distributions at the vibrational resonances,and the deviation between the experimental and the theoretical data is also analyzed.

  3. Tracing of natural radionuclides mobility in deep sedimentary environment using radioactive (234U/238U) disequilibria: application to the Mesozoic formations of the Eastern part of the Paris Basin

    This thesis forms part of the geological investigations undertaken by the French agency for nuclear waste management, ANDRA, around the Meuse/Haute-Marne Underground Research Laboratory (URL) located in the Eastern part of the Paris Basin in order to evaluate the feasibility of high-level radioactive waste repository in deep argilite formations. The aim of the study is to examine the radionuclide migration in the deep Callovo-Oxfordian target argilite layer and its surrounding low- permeability Bathonian and Oxfordian limestone formations in order to assess the long term confining capacities of the sedimentary series. This study is based on measurement of radioactive disequilibria within U-series by Multiple- Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). The high precision and accuracy achieved allowed to demonstrate the 234U/238U radioactive equilibrium in the Callovo-Oxfordian argilites. This result shows the uranium immobility in the target formation and provides a strong evidence for the current chemical stability and closure of the system for uranium and most probably for the other actinides. This is a fundamental result with respect to the problematic of disposal of high level radioactive waste in deep geological formation since it provides a in situ indication of the confining capacities of the clayey target formation in the current settings. Conversely, (234U/238U) disequilibria are systematically observed within zones, located in the surrounding carbonate formations, that are characterized by pressure dissolution structures (stylolites or dissolution seams). These disequilibria provide evidence for a discrete uranium relocation during the last two million years in the vicinity of stylolitic structures. This is a surprising result since it is generally supposed that these deep, low permeability, compact formations behave as closed system at the time scale of the U-series. (author)

  4. Tracing of natural radionuclides mobility in deep sedimentary environment using radioactive ({sup 234}U/{sup 238}U) disequilibria: application to the Mesozoic formations of the Eastern part of the Paris Basin; Tracage de la mobilite des radionucleides naturels en milieu sedimentaire profond a l'aide des desequilibres radioactifs ({sup 234}U/{sup 238}U): application aux formations mesozoiques de l'est du Bassin de Paris

    Deschamps, P

    2003-11-01

    This thesis forms part of the geological investigations undertaken by the French agency for nuclear waste management, ANDRA, around the Meuse/Haute-Marne Underground Research Laboratory (URL) located in the Eastern part of the Paris Basin in order to evaluate the feasibility of high-level radioactive waste repository in deep argilite formations. The aim of the study is to examine the radionuclide migration in the deep Callovo-Oxfordian target argilite layer and its surrounding low- permeability Bathonian and Oxfordian limestone formations in order to assess the long term confining capacities of the sedimentary series. This study is based on measurement of radioactive disequilibria within U-series by Multiple- Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). The high precision and accuracy achieved allowed to demonstrate the {sup 234}U/{sup 238}U radioactive equilibrium in the Callovo-Oxfordian argilites. This result shows the uranium immobility in the target formation and provides a strong evidence for the current chemical stability and closure of the system for uranium and most probably for the other actinides. This is a fundamental result with respect to the problematic of disposal of high level radioactive waste in deep geological formation since it provides a in situ indication of the confining capacities of the clayey target formation in the current settings. Conversely, ({sup 234}U/{sup 238}U) disequilibria are systematically observed within zones, located in the surrounding carbonate formations, that are characterized by pressure dissolution structures (stylolites or dissolution seams). These disequilibria provide evidence for a discrete uranium relocation during the last two million years in the vicinity of stylolitic structures. This is a surprising result since it is generally supposed that these deep, low permeability, compact formations behave as closed system at the time scale of the U-series. (author)

  5. Experimental study of delayed neutron emission from photo-fission of actinides

    Recently there has been a strong interest in a number of applications using the detection of delayed neutrons. Some ongoing projects, as non-destructive characterization of nuclear waste, have shown an urgent need of associated nuclear data. In this context, an experimental program has been launched to measure the delayed neutron yields and their time spectra from photo-fission of actinides. The very first measurements had been performed earlier in our laboratory with the uranium-238 and thorium-232 targets. In this thesis work the follow-up experiments, data analysis and results are reported for uranium-235 and neptunium-237. The high efficiency delayed neutron detector was designed, optimised, constructed and employed for these experiments with the endpoint Bremsstrahlung photons from 15 to 18 MeV. The photo-fission delayed neutron group parameters (ai, λi) were obtained and compared both with earlier work found in the literature and our own modelling results. The energy dependence of the total delayed neutron yield (νd) was also experimentally studied with the endpoint Bremsstrahlung photons in the energy range from 12 to 18 MeV for the uranium-235, 238, thorium-232, and neptunium-237 targets. Finally, some feasibility experiments were successfully performed with mixed samples in order to quantify the different actinide presence in the target. In parallel, the energy dependence of the total delayed neutron yield (νd) was also experimentally studied for thorium-232 but from neutron induced fission. (author)

  6. The cumulative effect of three decades of phosphogypsum amendments in reclaimed marsh soils from SW Spain: {sup 226}Ra, {sup 238}U and Cd contents in soils and tomato fruit

    Abril, Jose-Maria [Dpto. Fisica Aplicada I, Universidad de Sevilla, EUITA, Ctra Utrera Km 1, 41013 Seville (Spain); Garcia-Tenorio, Rafael [Dpto. Fisica Aplicada II, Universidad de Sevilla, ETSA, Avda. Reina Mercedes s/n, 41012 Seville (Spain); Enamorado, Santiago M. [Dpto. Fisica Aplicada I, Universidad de Sevilla, EUITA, Ctra Utrera Km 1, 41013 Seville (Spain); Hurtado, M. Dolores; Andreu, Luis; Delgado, Antonio [Dpto. Ciencias Agroforestales, Universidad de Sevilla, EUITA, Ctra Utrera Km 1, 41013, Seville (Spain)

    2008-09-15

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

  7. Measurement and Analysis of Specific Activities of 238U, 232Th,226Ra, 40K and 137Cs in Soil Samples from Phatthalung Province (Thailand) using Gamma Ray Spectrometry

    Full text: Specific activity of natural (238U, 232Th, 226Ra and 40K ) and anthropogenic radionuclide (137Cs) in 109 soil samples collected from 11 districts in Phathalung province have been measured and analyzed. Experimental results were obtained by using a high purity germanium (HPGe) detector and gamma spectrometry analysis system at Nuclear and Material Physics laboratory in Department of Physics Faculty of Science Thaksin University Songkhla Campus. Gamma ray radioactive standard sources 60Co, 137Cs and 133Ba were used to calibrate the measurement system. The KCl and two reference materials (RGU-1 and RGTh-1) obtained from the International Atomic Energy Agency were also used to analyze and compute the 40K, 238U (or 226Ra) and 232Th specific activity in all soil samples. The IAEA/SL-2 was also used to evaluate the specific activity of 137Cs in all soil samples. The measuring time of each sample was 10,800 seconds. It was found that specific activity ranged from 148.17 to 11276.78 Bq/kg for 40K, 58.29 to 518.45 Bq/kg for 226Ra, 8.40 to 236.19 Bq/kg for 232Th and 0.00 tp 12.39 Bq/kg for 137Cs with mean values of 3573.35 ± 203.89 Bq/kg, 135.89 ± 6.71 Bq/kg, 76.34 ± 5.32 Bq/kg and 1.05 ± 0.70 Bq/kg respectively. Furthermore, absorbed dose rate in air (D), radium equivalent activity (Raeq), external hazard index (Hex), and annual effective dose rate (AEDout) of this area were also evaluated by using the mean values of specific activities of the 40K, 226Ra and 232Th. Moreover, the experimental results were also compared with Office of Atoms for Peace (OAP) research data, Thailand and global radioactivity measurement and evaluations. The radioactive contour maps of specific activities of natural and anthropogenic radionuclides from this study were created by using the program ArcGis Version 9.2

  8. 1.4MeV-5MeV中子诱发238U裂变产额测量%Fission Product Yield Measurement of 238 U Induced by 1.4-5 MeV Neutrons

    李映映; 肖军; 王攀; 李子越; 汪超; 罗小兵

    2016-01-01

    238 U fission yield measurement has a significant meaning in nuclear data measurement .This thesis a-dopts1.4 MeV-5 MeV mono -energetic neutrons generated by 2.5 MeV proton electrostatic accelerator to stimulate 238U fission, and then measures the yield of fission product nuclide 135I、133I、105Ru and 91Sr through measuring fission product radioactivity .Neutron flux during irradiation process is determined by activation meth-od .Subsequently , this thesis analyzes multiple components influencing experiment measurement , including cor-rection on neutron′s multiple scattering and self -shielding effect in target head and sample on the basis of MC-NPX program as well as correction on sample′s self-absorption of γ-ray.Typical deviation of yield data is concluded as 3.5%.Finally, this thesis compares measurement consequences with existing fission yield data .%238 U裂变产额测量工作在核数据测量中有着重要意义,本工作利用2.5MeV质子静电加速器产生的1.4MeV-5MeV单能中子诱发238 U裂变,通过对裂变产物放射性的测量对裂变产物核素135 I、133 I、105 Ru和91 Sr的产额进行了测定。照射过程中中子通量用活化法确定。分析了影响实验测量的多个因素,包括用MCNPX程序对中子在靶头及样品中的多次散射和自屏蔽效应进行了修正,对γ射线在样品中的自吸收进行修正等。得到产额数据典型误差为3.5%,最后把测量结果与已有的裂变产额数据进行比对。

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

    Mayra Y. Luna-Porres

    2014-06-01

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

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

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

    2014-01-01

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

  11. U-series radioactive disequilibria {sup 238}U-{sup 230}Th-{sup 226}Ra: discussions on sources and processes responsible for volcanism of the Andean cordillera and on the deglaciation in Iceland; Les desequilibres radioactifs {sup 238}U-{sup 230}Th-{sup 226}Ra: discussions sur les sources et processus responsables du volcanisme de la Cordillere des Andes et sur la deglaciation en Islande

    Chmeleff, J

    2005-10-15

    Thanks to precise analyses of uranium series radioactive disequilibria, permitted by improvements of mass spectrometry data acquisition and optimization of chemistry, two questions were tackled and answers about the periods of glaciation in Iceland and the petrogenesis of Andean lavas were proposed. Two methods were used to date lava flows from the Reykjanes peninsula and the island of Heimaey, in Iceland, directly linked to the periods of deglaciation or reheating around the last ice age. An original method based on the use of segregation veins present in the lava flows has been developed. Thanks to the formation of this particular geological object this methods permits to be freed from xeno-crystals when using the internal isochron method in the {sup 238}U-{sup 230}Th system. Using this method some constraints are brought both on the quaternary geology of the area of Reykjavik and on the age of the end of the Wurm glaciation on Heirnaey. In parallel, due to the homogeneity of the historical and Holocene lavas of the Reykjanes peninsula, regarding the ({sup 230}Th/{sup 232}Th) and Th/U ratios, it is possible to derive the ({sup 230}Th/{sup 232}Th) ratio in time to determine the age of lava flows installed during the ice age. Thus we confirmed that the magnetic excursion recorded in the Skalamaelifell lava flow is most probably the same one as that of Laschamp-Olby and that at this time (approximately 48.000 years) the Reykjanes peninsula was entirely covered with a glacier. Thanks to this method the extent of the glacier was also constrained by dating of a picritic shield around 22.000 years, thus the peninsula has to be free of any ice cap despite the fact that glaciation is the most intense around this time.Then Andean arc magmas petrogenesis was constrained in time and space. Almost systematic excesses of {sup 226}Ra compared to {sup 230}Th in lavas of austral, southern and northern volcanic zones of the Andes (AVZ, SVZ and NVZ) constrain the ascending time

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

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

  13. Accumulation of polonium 210Po, uranium (234U and 238U and plutonium (238Pu and 239+240Pu in tissues and organs of deer Carvidae from northern Poland

    Strumińska-Parulska D. I.

    2013-04-01

    Full Text Available Livers, kidneys and muscles of large herbivorous animals: roe deer (Capreolus capreolus, red deer (Cervus elaphus and fallow deer (Dama dama, collected in northern Poland, were the subject of the investigation. Polonium, uranium and plutonium activities were measured using alpha spectrometry along with relevant radiochemical procedures. The average concentrations of 210Po ranged between 0.02±0.01 Bq kg−1 ww in muscles and 7.15±0.12 Bq kg−1 ww in kidneys. The concentration of 238U ranged widely between 2.49±0.18 and 69.37±5.45 mBq kg−1 ww. The average concentrations of 239+240Pu ranged between 0.18±0.04 mBq kg−1 ww in muscle and 2.77±0.60 mBq kg−1 ww in kidneys. Statistical analysis showed that the sampling location, sex, age and species did not influence on the radioisotope activities in the analyzed samples.

  14. Measurements of Cross Sections and Decay Properties of the Isotopes of Elements 112, 114 and 116 Produced in the Fusion Reactions $^{233,238}$U, $^{242}$Pu, and $^{248}$Cm + $^{48}$Ca

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

    2004-01-01

    We have studied the dependence of the production cross-sections of the isotopes $^{282,283}$112 and $^{286,287}$114 on the excitation energy of the compound nuclei $^{286}$112 and $^{290}$114. The maximum cross-section values of the \\textit{xn}-evaporation channels for the reaction $^{238}$U($^{48}$Ca, \\textit{xn})$^{286 - x}$112 were measured to be: $\\sigma _{3n}=2.5_{-1.1}^{ + 1.8} $pb and $\\sigma _{4n}=0.6_{ - 0.5}^{ + 1.6} $ pb; for the reaction $^{242}$Pu($^{48}$Ca, \\textit{xn})$^{290 - x}$114: $\\sigma _{2n}\\sim 0.5$ pb, $\\sigma _{3n}=3.6_{- 1.7}^{ + 3.4} $ pb and $\\sigma _{4n}=4.5_{ - 1.9}^{ + 3.6} $ pb. In the reaction $^{233}$U($^{48}$Ca, 2--4$n$)$^{277 - 279}$112 at $E^*=34.9\\pm $2.2 MeV we measured an upper cross-section limit of $\\sigma _{xn} \\leqslant 0.6$ pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section $\\sigma _{\\rm {ER}}(E^*)$ to values significantly higher than that associated with the calculated Coulomb barrier can be caused by ...

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

    Derrien, H

    2005-12-05

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

  16. Neutrons production in thick targets of Be and 238U bombarded by 100 MeV/u deuterons and in a thick target of C bombarded by 95 MeV/u 36Ar. Attenuation in concrete and dose equivalent rate of the activated uranium

    Neutrons production in thick targets of Be and 238U bombarded by 100 MeV/u deuterons and in a thick target of C bombarded by 95 MeV/u 36Ar. Attenuation in concrete and dose equivalent rate of the activated uranium. The yields of secondary neutrons produced by the interaction of a beam with thick target were determined with activation detectors. Three projectile-target couples have been studied: deuterons (100 MeV/u)+238U, deuterons (100 MeV/u)+9Be and 36Ar (95 MeV/u)+12C. At 0 deg.. the yields were also measured after a piece of concrete and the corresponding attenuation length evaluated. The dose rate of the uranium target was monitored during several days after the end of the irradiation. (author)

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

    Coombs, Michelle L.; Vazquez, Jorge A.

    2014-12-01

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

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

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

    2016-01-01

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

  19. Fluxes of 238U Series Radionuclides in the Industrial Production of Dicalcium Phosphate and the Biokinetic Analysis of 210Pb and 210Po in Poultry Tissue Due to its Ingestion

    NORM derived from the wet acid digestion of phosphate rock might represent a serious problem facing the phosphate industry. The aim of this work is to discuss both: (a) the fluxes of the 238U series radionuclides (U and Th isotopes, 226Ra, 210Pb and 210Po) during the DCP production process and, (b) the accumulation of 210Pb and 210Po in chicken tissues due to the ingestion of DCP. Industrial samples were collected from different production steps at a factory in Spain that uses phosphate rock from Morocco. The results showed that whereas uranium is equally distributed within products and by-products, thorium and 210Po are mainly eliminated through the sludges and 210Pb is mostly found in the final product (DCP). The 210Pb and 210Po results in chicken tissues and faeces after animals were bred with different amounts of DCP for 42 days have shown that about 95% of the ingested 210Pb and 210Po was immediately excreted. From the amount accumulated in tissues it was observed that whereas 210Pb is mostly found in bones, 210Po accumulates in the liver and kidneys. A one compartment non-linear kinetic model has been developed in order to determine the variation of the total activity of 210Pb and 210Po accumulated in the chicken body throughout its 6 weeks life. This model correctly reproduces experimental results and also allows calculating of transfer rates for 210Pb and 210Po, useful for first order models, that is, under stationary metabolic conditions. (author)

  20. Use of electron beams for the production of radioactive nuclei through photo-fission

    The IPN (institute of nuclear physics) of Orsay decided to build a linear accelerator in order to produce an electron beam of 50 MeV energy and of 10 μA average intensity. It is the ALTO project (Linear Accelerator near the Tandem of Orsay). This project will be dedicated to the production of the radioactive ions using the photo-fission process. The central topic of this thesis is the study of the beam dynamics of the ALTO facility. The first part presents studies concerning the injector. The simulations made with the simulation code PARMELA allowed the optimization of the characteristics of pre-buncher (dephasing HF, accelerating field peak...) to obtain a good bunching factor at the entrance of the buncher and at the entrance of the accelerating section according to the distance separating the two systems. The second part of this thesis is related to measurements of transverse emittance of the beam at the buncher exit. The three gradients method has been selected and the optical system used is a solenoid. The results obtained are in good agreement with former measurements. Finally a calculation of the beam line was carried out to optimize the transport of the beam to the PARRNe target without degrading its characteristics. The calculation codes that have been used are BETA and TRACE-WIN. (author)

  1. Perspectives for photofission studies with highly brilliant, monochromatic γ-ray beams

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

    2012-12-01

    New research facilities like MEGa-Ray (Livermore) or ELI-NP (Bucharest) will provide within the next years (2013-2016) photon beams of unprecedented quality with respect to both photon intensity (total flux ~ 1013 γ/s) and spectral intensity (~ (104-106)/eVs), thus exceeding the performance of existing facilities by severalorders of magnitude. This tremendous progress will be enabled by Compton-backscattering of an intense laser off a high-quality electron beam, in conjunction with novel refractive bremsstrahlung beams focusing γ optics and efficient monochromatization techniques. We envisage to employ these γ beams for photofission studies on extremely deformed nuclear states of actinides, investigating their multiple-humped potential energy landscape in a highly selective way. Transmission resonances in the prompt fission cross section from the (superdeformed) second and (hyperdeformed) third potential minimum will be studied, where the fission decay channel can be expressed as a tunnelling process of these gateway states through the multiple-humped fission barrier.

  2. Use of electrons beams for the production of radioactive nuclei by photofission

    The IPN of Orsay decided to build a linear accelerator in order to produce an electron beam of 50 MeV energy and of 10 mA average intensity. It is the ALTO project (Linear Accelerator near the Tandem of Orsay). This project will be dedicated to the production of the radioactive ions using the photo-fission process. The central topic of this thesis is the study of the beam dynamics of the ALTO facility. The first part presents studies concerning the injector. The simulations made with the simulation code PARMELA allowed the optimization of the characteristics of pre-buncher (dephasing HF, accelerating field peak...) to obtain a good bunching factor at the entrance of the buncher and at the entrance of the accelerating section according to the distance separating the two systems. The second part of this thesis is related to measurements of transverse emittance of the beam at the buncher exit. The three gradients method has been selected and the optical system used is a solenoid. The results obtained are in good agreement with former measurements. Finally a calculation of the beam line was carried out to optimize the transport of the beam to the PARRNe target without degrading its characteristics. The calculation codes that have been used are BETA and TRACE-WIN. (author)

  3. Photofission of actinide and pre-actinide nuclei in the quasideuteron and delta energy regions

    Berman, B L; Cole, P L; Dodge, W R; Feldman, G; Sanabria, J C; Kolb, N; Pywell, R E; Vogt, J; Nedorezov, V; Sudov, A; Kezerashvili, G Ya

    1999-01-01

    The photofission cross sections for the actinide nuclei sup 2 sup 3 sup 2 Th, sup 2 sup 3 sup 3 sup , sup 2 sup 3 sup 5 sup , sup 2 sup 3 sup 8 U, and sup 2 sup 3 sup 7 Np have been measured from 68 to 264 MeV and those for the pre-actinide nuclei sup 1 sup 9 sup 7 Au and sup N sup A sup T Pb from 122 to 222 MeV at the Saskatchewan Accelerator Laboratory, using monoenergetic tagged photons and novel parallel-plate avalanche detectors for the fission fragments. The aim of the experiment was to obtain a comprehensive and self-consistent data set and to investigate previous anomalous results in this energy region. The fission probability for transuranic nuclei is expected to be close to unity here. However, important discrepancies have been confirmed for sup 2 sup 3 sup 7 Np and sup 2 sup 3 sup 2 Th, compared with sup 2 sup 3 sup 8 U, which have serious implications for the inferred total photoabsorption strengths, and hence call into question the 'Universal Curve' for photon absorption at these energies. High-s...

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

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

    2016-01-01

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

  5. Specific Activities and Radioactive Contour Maps of Natural (238U, 232Th, 226Ra and 40K ) and Anthropogenic (137Cs) Radionuclides in Beach Sand Samples Collected from Nai Yang Beach of Phuket Province After Tsunai Disaster

    Full text: Specific activities of natural (238U, 232Th, 226Ra and 40K) and artificial anthropogenic (137Cs) radionuclides in 50 beach sand samples collected from Nai Yang beach in Phuket province which was effected from 2004 tsunami disaster, have been studied and measured. Experimental results were obtained by using a high-purity germanium (HPGe) detector and gamma spectrometry analysis system and also evaluated by using the standard reference materials IAEA/RGU-1, IAEA/RGTh-1, KCL and SL-2 which were obtained from Department of Physics, Faculty of Science, Prince of Songkhla University Hat Yai Campus. Experimental set-up and measurements were operated and carried out at Nuclear and Material Physics Laboratory in Department of Physics, Faculty of Science, Thaksin University Songkhla Campus. It was found that, the beach sand specific activity ranges from 862.50 to 3,356.35 Bq/kg for 40K, 3.51- 28.58 Bq/kg for 226Ra, 10.15 to 30.22 Bq/kg for 232Th and 0.00 to 2.39 Bq/kg for 137Cs with mean values of 1,843.03 ± 152.49 Bq/kg, 14.88 ± 3.30 Bq/kg, 19.19 ± 2.80 Bq/kg and 0.14 ± 0.11 Bq/kg, respectively. Furthermore, the results were also used to evaluate the absorbed dose rates in air (D), the radium equivalent (Raeq), the external hazard index (Hex) and the annual effective dose rate (AED) in all beach area. Moreover, experimental results were also compared to the Office of Atoms for Peace (OAP) research data, Thailand and global radioactivity measurements and evaluation, the recommended values which were proposed by the Organization for Economic Cooperation and Development (OECD, 1979) and United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 1988, 1993, 2000). Specific activities of natural and artificial anthropogenic radionuclides in all of Nai Yang beach sand samples could be also used to create the radioactive contour maps

  6. Photofission cross sections of U-233 and Pu-239 near threshold induced by gamma-rays from thermal neutron capture

    The photofission cross sections of U-233 and PU-239 have been studied using monochromatic photons produced by thermal neutron capture in several materials placed in a radial beam hole of the IEA-R1, 2 MW pool type research reactor, in the energy interval from 5.43 MeV to 9.72 MeV. The gamma flux incident on the samples were measured using a (3X3) inch. NaI(Tl) crystal. The photofission fragments were detected in MAKROFOL-KG (solid state nuclear track detector) etched 30 min. in a KOH (35%wt) solution at 600C. The efficiency of the detector was obtained using a Californium-252 calibrated source and its value was (0.4323 ± 3%). The tracks were counted by means of an automatic spark counting. Analyzing the photofission data we have observed similarities between the cross sections obtained for the two samples in comparison with other authors. A structure was also observed in the U-233 cross section near the energy of 7.23 MeW. Acoording to the liquid drop model the height of the simple fission barrier were determined: (5.6 ± 0.2) MeV and (5.7 ± 0.2) MeV for U-233 and Pu-239 respectively. The relative fissionability of the samples to U-238 were also determined in each excitation energy and showed to be energy independent: (2.12 +-0.25) for U-233, and (3.32+-0.41) for Pu-239. (author)

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

    We have studied the dependence of the production cross sections of the isotopes 282,283112 and 286,287114 on the excitation energy of the compound nuclei 286112 and 290114. The maximum cross section values of the xn-evaporation channels for the reaction 238U(48Ca,xn)286-x112 were measured to be σ3n=2.5-1.1+1.8 pb and σ4n=0.6-0.5+1.6 pb; for the reaction 242Pu(48Ca,xn)290-x114: σ2n∼0.5 pb, σ3n=3.6-1.7+3.4 pb, and σ4n=4.5-1.9+3.6 pb. In the reaction 233U(48Ca,2-4n)277-279112 at E*=34.9=2.2 MeV we measured an upper cross section limit of σxn≤0.6 pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section σER(E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of σER in the reactions of actinide targets with 48Ca is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N=184. In the present work we detected 33 decay chains arising in the decay of the known nuclei 282112, 283112, 286114, 287114, and 288114. In the decay of 287114(α)→283112(α)→279110(SF), in two cases out of 22, we observed decay chains of four and five sequential α transitions that end in spontaneous fission of 271Sg (Tα/SF=2.4-1.0+4.3 min) and 267Rf (TSF∼2.3 h), longer decay chains than reported previously. We observed the new nuclide 292116 (Tα=18-6+16 ms,Eα=10.66±0.07 MeV) in the irradiation of the 248Cm target at a higher energy than in previous experiments. The observed nuclear decay properties of the nuclides with Z=104-118 are compared with theoretical nuclear mass calculations and the systematic trends of spontaneous fission properties. As a whole, they give a consistent pattern of decay of the 18 even-Z neutron-rich nuclides with Z=104-118 and N=163-177. The experiments were

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

    We have studied the dependence of the production cross sections of the isotopes 282,283112 and 286,287114 on the excitation energy of the compound nuclei 286112 and 290114. The maximum cross-section values of the xn-evaporation channels for the reaction 238U(48Ca, xn)286-x112 were measured to be: σ3n = 2.5-1.1+1.8 pb and σ4n = 0.6-0.5+1.6 pb; for the reaction 242Pu(48Ca, xn)290-x114: σ2n ∼ 0.5 pb, σ3n 3.6-1.7+3.4 pb and σ4n = 4.5-1.9+3.6 pb. In the reaction 233U(48Ca, 2-4n)277-279112 at E* = 34.9±2.2 MeV we measured an upper cross-section limit of σxn ≤ 0.6 pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section σER(E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of σER in the reactions of actinide targets with 48Ca is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N = 184. In the present work we detected 33 decay chains arising in the decay of the known nuclei: 282112, 283112, 286114, and 288114. In the decay of 287114(α) → 283112(α) → 279110(SF), in two cases out of 22, we observed decay chains of four and five sequential α transitions that end in spontaneous fission of 271Sg(Tα/SF = 2.4 -1.0+4.3 min) and 267Rf(TSF ∼ 2.3 h), longer decay chains than reported previously. We observed the new nuclide 292116(Tα = 18-6+16 ms, Eα = 10.66 ± 0.07 MeV in the irradiation of 248Cm target at a higher energy than in previous experiments. The observed nuclear decay properties of the nuclides with Z = 104-118 are compared with theoretical nuclear mass calculations and the systematic trends of spontaneous fission properties. As a whole, they give a consistent pattern of decay of the 18 even-Z neutron-rich nuclides with Z = 104-118 and N = 163

  9. Competing C-Br and O-NO Photofission upon Excitation of BrCH2CH2ONO at 193 nm.

    Wang, Lei; Scrape, Preston G; Roberts, Trevor D; Joshi, Prakriti P; Butler, Laurie J

    2015-12-17

    This study characterizes two of the primary photodissociation channels of 2-bromoethyl nitrite, BrCH2CH2ONO, at 193 nm and the subsequent unimolecular dissociation channels of the nascent vibrationally excited BrCH2CH2O radicals produced from the O-NO bond photofission. We use a crossed laser-molecular beam scattering apparatus with electron bombardment detection. Upon photodissociation of BrCH2CH2ONO at 193 nm, the measured branching ratio between primary O-NO photofission and C-Br photofission is 3.9:1 (O-NO/C-Br). The measured O-NO photofission recoil kinetic energy distribution (P(ET)) peaks near 30 kcal/mol and extends from 20 to 50 kcal/mol. We use the O-NO photofission P(ET) to characterize the internal energy distribution in the nascent ground-electronic-state BrCH2CH2O radicals. At 193 nm, all of the BrCH2CH2O radicals are formed with enough internal energy to unimolecularly dissociate to CH2Br + H2CO or to BrCH2CHO + H. We also investigated the possibility of the BrCH2CH2O → CH2CHO + HBr reaction arising from the vibrationally excited BrCH2CH2O radicals produced from O-NO primary photodissociation. Signal strengths at HBr(+), however, demonstrate that the vinoxy product does not have HBr as a cofragment, so the BrCH2CH2O → HBr + vinoxy channel is negligible compared to the CH2Br + H2CO channel. We also report our computational prediction of the unimolecular dissociation channels of the vibrational excited CH2CH2ONO radical resulting from C-Br bond photofission. Our theoretical calculations on the ground-state CH2CH2ONO potential energy surface at the G4//B3LYP/6-311++G(3df,2p) level of theory give the energetics of the zero-point corrected minima and transition states. The lowest accessible barrier height for the unimolecular dissociation of CH2CH2ONO is a 12.7 kcal/mol barrier from the cis-ONO conformer, yielding NO2 + ethene. Our measured internal energy distribution of the nascent CH2CH2ONO radicals together with this computational result suggests

  10. V-bar in Neutron-Induced Fission of U235 and Th232, and in Photofission of U238

    The average number of prompt neutrons (v) emitted in the neutron-induced fission of U235 and Th232 and in the photofission of U238 has been measured with a large liquid scintillator as the fission neutron detector. The measurements were made relative to v for the spontaneous fission of Cf252. The v-values of U235 were measured at some different incident energies between 30 keV and 15 MeV, and the results are in agreement with measurements by Moat et al., and Hopkins and Diven. The measurements of Th232 were made for several incident neutron energies from the fission threshold at about 1.4 MeV to 15 MeV. Special interest was concentrated on the energy region near the fission threshold where the fission cross-section and the fragment angular distribution show strong variations with neutron energy. The measurements indicate that the energy dependence of b in this region may be non-linear. A measurement of v in the photofission of U238 at a gamma-ray energy of 7 MeV has been made. The result is not in agreement with measurements by Prokohorova et al. arid Lazareva et al. The spontaneous fission of Pu245 and the thermal-neutron-induced fission of Pu239 give a difference in v corresponding to 0.10 n/MeV. The result of the present investigation combined with the D-value for the spontaneous fission of U238 gives 0.10 ± 0.02 in agreement with the data obtained for the compound nucleus of Pu240. (author)

  11. Bayesian methods to restore and re build images: application to gamma-graphy and to photofission tomography; Methodes bayesiennes pour la restauration et la reconstruction d`images application a la gammagraphie et a la tomographie par photofissions

    Stawinski, G

    1998-10-26

    Bayesian algorithms are developed to solve inverse problems in gamma imaging and photofission tomography. The first part of this work is devoted to the modeling of our measurement systems. Two models have been found for both applications: the first one is a simple conventional model and the second one is a cascaded point process model. EM and MCMC Bayesian algorithms for image restoration and image reconstruction have been developed for these models and compared. The cascaded point process model does not improve significantly the results previously obtained by the classical model. To original approaches have been proposed, which increase the results previously obtained. The first approach uses an inhomogeneous Markov Random Field as a prior law, and makes the regularization parameter spatially vary. However, the problem of the estimation of hyper-parameters has not been solved. In the case of the deconvolution of point sources, a second approach has been proposed, which introduces a high level prior model. The picture is modeled as a list of objects, whose parameters and number are unknown. The results obtained with this method are more accurate than those obtained with the conventional Markov Random Field prior model and require less computational costs. (author)

  12. Use of electron beams for the production of radioactive nuclei through photo-fission; Utilisation de faisceaux d'electrons pour la production des noyaux radioactifs par photo-fission

    M' garrech, Slah

    2004-09-01

    The IPN (institute of nuclear physics) of Orsay decided to build a linear accelerator in order to produce an electron beam of 50 MeV energy and of 10 {mu}A average intensity. It is the ALTO project (Linear Accelerator near the Tandem of Orsay). This project will be dedicated to the production of the radioactive ions using the photo-fission process. The central topic of this thesis is the study of the beam dynamics of the ALTO facility. The first part presents studies concerning the injector. The simulations made with the simulation code PARMELA allowed the optimization of the characteristics of pre-buncher (dephasing HF, accelerating field peak...) to obtain a good bunching factor at the entrance of the buncher and at the entrance of the accelerating section according to the distance separating the two systems. The second part of this thesis is related to measurements of transverse emittance of the beam at the buncher exit. The three gradients method has been selected and the optical system used is a solenoid. The results obtained are in good agreement with former measurements. Finally a calculation of the beam line was carried out to optimize the transport of the beam to the PARRNe target without degrading its characteristics. The calculation codes that have been used are BETA and TRACE-WIN. (author)

  13. Bayesian methods to restore and re build images: application to gamma-graphy and to photofission tomography

    Bayesian algorithms are developed to solve inverse problems in gamma imaging and photofission tomography. The first part of this work is devoted to the modeling of our measurement systems. Two models have been found for both applications: the first one is a simple conventional model and the second one is a cascaded point process model. EM and MCMC Bayesian algorithms for image restoration and image reconstruction have been developed for these models and compared. The cascaded point process model does not improve significantly the results previously obtained by the classical model. To original approaches have been proposed, which increase the results previously obtained. The first approach uses an inhomogeneous Markov Random Field as a prior law, and makes the regularization parameter spatially vary. However, the problem of the estimation of hyper-parameters has not been solved. In the case of the deconvolution of point sources, a second approach has been proposed, which introduces a high level prior model. The picture is modeled as a list of objects, whose parameters and number are unknown. The results obtained with this method are more accurate than those obtained with the conventional Markov Random Field prior model and require less computational costs. (author)

  14. Issledovanie solnecnogo vetra v experimente GELION proekta INTERGELIOZOND.

    Verigin, M.; Remizov, A.; Kotova, G.; Bezrukikh, V.; Truhlík, Vladimír; Hruška, František; Auster, U.; Hilchenbach, M.

    Moscow : IZMIRAN, 2012, s. 132-138. ISSN 2075-6836. [Proekt INTERGELIOZOND. Tarusa (RU), 11.05.2011-23.05.2011] R&D Projects: GA MŠk(CZ) LH11123 Institutional support: RVO:68378289 Keywords : Solar wind * plasma parameters * INTERHELIOSOND Subject RIV: BL - Plasma and Gas Discharge Physics

  15. Detecting fissionable materials in a variety of shielding matrices via delayed gamma and neutron photofission signatures—Part 2: Experimental results

    Proctor, Alan; Gabriel, Tony A.; Hunt, Alan W.; Manges, JoAnn; Handler, Thomas

    2012-01-01

    Successful detection of fissionable material contained in a variety of matrices was demonstrated by photon active interrogation of fissionable and inert target materials. Samples were irradiated with pulsed 15 MeV photons generated by a LINAC and tungsten electron/photon converter, operating at 15 Hz. Matrix materials included air (no matrix), wood, water, and lead. A unique dual mode gamma/neutron detector was used to acquire data from both fission product gamma and fission product neutron emission. Neutron emission was recorded by detecting the 478 keV capture gamma from the 10B (n,α) 7Li reaction, generating a photopeak in the recorded gamma spectrum. Two signatures were found to correctly differentiate between the fissionable target ( 238U) and inert targets (lead, steel, air, and beryllium), with substantial differences in delayed gamma and neutron signatures for fissionable and inert materials in all cases. The signatures are simple to compute and are not significantly affected by system variations or interferences expected during cargo scanning.

  16. On the role of energy separated in fission process, excitation energy and reaction channels effects in the isomeric ratios of fission product 135Xe in photofission of actinide elements

    Thiep, Tran Duc; An, Truong Thi; Cuong, Phan Viet; Vinh, Nguyen The; Mishinski, G. V.; Zhemenik, V. I.

    2016-07-01

    In this work we present the isomeric ratio of fission product 135Xe in the photo-fission of actinide elements 232Th, 233U and 237Np induced by end-point bremsstrahlung energies of 13.5, 23.5 and 25.0 MeV which were determined by the method of inert gaseous flow. The data were analyzed, discussed and compared with the similar data from literature to examine the role of energy separated in fission process, excitation energy and reaction channels effects.

  17. Photonuclear measurements on fissionable isotopes using monoenergetic photons

    The LLL linac monochromatic photon facility is used for measurements, which to date have included at least some data on the eight isotopes: 232Th, 233U, 234U, 235U, 236U, 237Np, 238U, and 239Pu. Photofission events are determined from an analysis of the emitted neutron multiplicity distributions as determined with the LLL 4π neutron detector. A sampling of data taken to date is included and is organized as follows: low-energy photofission cross sections, neutrino and fission neutron multiplicity distribution width parameter data, ring-ratio multiplicity coincidence data, delayed-neutron fraction data, and photonuclear and photofission cross sections. 2 refs., 32 figs

  18. Investigation and realization at the Saclay linear accelerator of a line from a tagged photon beam bremsstrahlung in a wide energy range: Application to the measurement of the total cross section of the photofission (γ, f) of uranium 238

    A monochromatic tagged photon facility is described. The source is produced by tagging the photons from a continuous bremsstrahlung spectrum resulting from a monoenergetic electron beam traversing a thin target. A magnetic spectrometer is used to detect and measure the energy of the tagged electrons associated with the tagged photons. Tagging system characteristics include: 16 adjacent paths; a tagged energy range equal to 20% to 80% of the energy of the electrons of the incident beam; a constant relative resolution of the tagged energy bands equal to ±4%. The acquisition system is described and an example of the use of the system (measurement of the total cross section of photofission of U238 between 20 and 120 MeV) is shown. Tests show that the system can cover a range of monochromatic photon energy from 12 to 176 MeV, divided into 32 energy bands, with only two adjustements to the accelerator

  19. Issledovanie mezostructury kompositov na osnove cellulosy s nanocasticami serebra metodom MURR

    Ezdakova, K. V.; Kopitsa, G. P.; Smislov, R. Y.; Nekrasova, T. N.; Hripunov, A. K.; Tkachenko, A. A.; Angelov, Borislav

    Gatchina: National Research Centre "Kurchatov Institute", Petersburg Nuclear Physics Institute B. P. Konstantinov, 2014. s. 85. [PNPI School on condensed state physics /48./ - CSP-2014. 10.03.2014-15.03.2014, St. Petersburg] R&D Projects: GA ČR GAP208/10/1600 Institutional support: RVO:61389013 Keywords : cellulose * silver nanoparticles * small-angle X-ray scattering Subject RIV: CF - Physical ; Theoretical Chemistry

  20. 238U And 232Th Concentration In Rock Samples using Alpha Autoradiography and Gamma Spectroscopy Techniques

    The activity concentrations of uranium and thorium were measured for some rock samples selected from Dahab region in the south tip of Sinai. In order to detect any harmful radiation that would affect on the tourists and is becoming economic resource because Dahab have open fields of tourism in Egypt. The activity concentration of uranium and thorium in rocks samples was measured using two techniques. The first is .-autoradiography technique with LR-115 and CR-39 detectors and the second is gamma spectroscopic technique with NaI(Tl) detector. It was found that the average activity concentrations of uranium and thorium using .-autoradiography technique ranged from 6.41-49.31 Bqkg-1, 4.86- 40.87 Bqkg-1 respectively and by gamma detector are ranged from 6.70- 49.50 Bqkg-1, 4.47- 42.33 Bqkg-1 respectively. From the obtained data we can conclude that there is no radioactive healthy hazard for human and living beings in the area under investigation. It was found that there are no big differences between the calculated thorium to uranium ratios in both techniques