[en] For more than a decade CEA Bruyeres-le-Chatel and LANL theoretical division have been cooperating on the development of nuclear theories and their application to the nuclear data. Dr. Eric Bauge of CEA had vigorously participated in the collaborative efforts to promote ideas in fundamental theoretical physics to the basis of scientific and/or technological achievements in the applied area. Our joint efforts include incorporation of theoretical nuclear structure models into reaction theories, implementation of advanced nuclear reaction theories into computer codes that are widely used in nuclear data production, quantifying nuclear data uncertainties by considering nuclear reaction models, exchanging ideas for improvement of evaluated nuclear data, and so on. This talk summarizes the CEA-LANL collaborative activities on the development of nuclear theory and data, and demonstrates how the efforts have been expanded into the wider nuclear science community.

[en] Published in summary form only

[en] Although independent and cumulative fission product yields have been a part of evaluated libraries for decades, there have been few updates over the years. The fission product yield sub-library in the ENDF/B-VIII.0 library is still largely based on the evaluation of England and Rider from the mid-90’s [1], with only more recent updates to the energy dependence of Pu below 2 MeV [2] and fixes to isomeric states and missing fission products [3]. This previous evaluation depends strongly on phenomenological parameter variations and can include robust incident-energy dependence only where enough experimental data are available. However, over the past several years, there have been a wealth of new measurements of independent and cumulative fission product yields, particularly those with short half-lives, and there have been significant improvements in the modeling of prompt and delayed fission observables. In this talk, we describe recent progress in the improvement of fission product yield calculations, using the BeoH code and the underlying Hauser Feshbach Fission Fragment Decay (HF D) model, developed at Los Alamos National Laboratory [4,5]. BeoH is a deterministic fission fragment decay code that uses the Hauser-Feshbach statistical model to follow the de-excitation of initial fission fragments through the emission of prompt neutrons and gamma rays, starting from phenomenologically parametrized fission fragment initial conditions. After this emission, a time-independent method, combined with decay data (branching ratios, half-lives, etc.) is used to calculate the cumulative fission product yields. This model, while still relying on phenomenologically parametrized inputs, models the multi-chance fission process without approximations, and therefore, energy-dependent calculations can be performed, even where experimental data are scarce. We will describe our recent calculations for consistent prompt and delayed fission observables for major and minor actinides, including new work investigating isomeric ratios. We will detail the ongoing evaluation process for energy-dependent fission product yields from thermal up to 20 MeV incident energy and some validation work that has been performed for these new fission product yield calculations. Additionally, we will discuss future perspectives of this work, including highlighting the need for additional data. LA-UR-24-22531 [1] T.R. England and B.F. Rider, LA-UR-94-3106 (1994) [2] M.B. Chadwick, T. Kawano, et al., NDS 111, 2923 (2010) [3] A. Mattera and A. Sonzogni, BNL-220804-2021-INRE (2021) [4] S. Okumura, et al., JNST 55, 1009 (2018) [5] A.E. Lovell, et al., PRC 103, 014615 (2021)

[en] We derive the fully self-consistent quasiparticle random-phase approximation (QRPA) equations with noniterative finite amplitude methods and calculate the transition strengths of giant resonances. Then, we apply the QRPA results to both neutron radiative capture calculations based on the statistical Hauser-Feshbach theory and inelastic scattering calculations based on distorted-wave Born approximation (DWBA). We compare the calculated results with available experimental data and demonstrate how our approach can reproduce giant resonances and various nuclear reactions.

[en] The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 resulted in the release of large amounts of radioactive cesium-137 (137Cs) into the environment. It is important to characterize the Cs-137 dynamics throughout the river from the headwaters to the downstream. Previous studies have suggested the importance of dissolved forms of Cs-137 in organic matter in small watersheds and dissolved forms in suspended solids in large watersheds. Since the concentration of suspended-form Cs has been shown to decrease significantly after decontamination in evacuated areas (Feng et al. 2022), this rapid decrease in suspended-form Cs-137 concentration can be used to determine the cause of dissolved-form Cs. Therefore, we attempted to evaluate whether the dissolved Cs-137 was derived from organic matter or suspended solids by comparing data before and after decontamination. The objective of this study is to compare the decreasing trends of Cs-137 concentrations in decontaminated and undecontaminated areas based on long-term monitoring of suspended solids, dissolved solids, and coarse organic matter Cs-137 concentrations since 2011. The study area includes four headwater basins and four river basins (eight sites in total) in the Kuchibuto River watershed in the Yamakiya district of Fukushima Prefecture, located approximately 35 km northwest of the FDNPP. In the Kuchibuto River watershed, a large inflow of decontaminated soil with low Cs-137 concentrations due to an increase in the amount of bare land caused by decontamination resulted in a rapid decrease in the concentration of suspended-form 137Cs in the decontaminated area in the headwaters and in the upper reaches of the river. However, no clear effect of decontamination was observed in the concentrations of dissolved Cs-137 and Cs-137 in coarse organic matter. Comparison of the slopes of Cs-137 concentrations in the suspended, dissolved, and coarse organic matter showed that the slope of the dissolved form was similar to that of the coarse organic matter in the source watersheds, and similar to that of the SS in the downstream watersheds. These results suggest that the contribution of dissolved Cs-137 from organic matter in small watersheds and that from suspended solids in large watersheds is significant.

[en] Ultrastructural studies of Biomphalaria glabrata embryos (MOllusca: Gastropoda), and important snail vector of schistosomiasis has not been explored. In the present work it was evaluated a suitable electron microscopical technique for embryos processing. Promising results was obtained with double fixation in 1% glutaraldehyde plus 1% osmium tetroxide in 0.05 M cacodylate buffer (pH 7.4), preliminary staining overnight in 1% uranyl acetate and embedding in EPON or Polylite under vacuum. It was used embryos at young trochophore stage wich is characterized by active organogenesis. Some ultrastructural aspects of B. glabrata embryos cells are presented. (author)

[en] In previous studies, a conceptual tritium cleanup system was developed to remove tritium in various chemical forms from exhaust gases. This cleanup system differs from conventional ones employed at many facilities where tritium is handled in that tritium is removed as tritiated hydrogen molecules. In conventional systems, the tritium is removed in the form of water vapor. The present system consists of five main components: hydrogen separator, decomposition-processing vessel, hydrogen-absorbing vessel, circular pump, and buffer tank. The decomposition-processing vessel of the five main components was developed for this system in our laboratory. For the present study, it was assumed that the gas for processing was composed of hydrogen, methane, and helium. Some of the hydrogen and methane molecules were assumed to be tritiated, and helium was added to maintain a steady flow of gas through the stages of processing in the cleanup system. The performance of the tritium cleanup system was examined by computer-based simulation with simulated exhaust gas. To monitor removal of tritium from the exhaust gas, the partial pressures of hydrogen and methane were examined in a series of performance tests by computer simulation. Results indicate that the partial pressure of hydrogen underwent a characteristic change with two bend points, even though the partial pressure of methane continued to decrease steadily. The time positions of the bends and time interval between the two bend points on the curve of hydrogen partial pressure were investigated under various conditions in relation to component fraction and gas volume. The first bend appears to correspond to the completion of one cycle of processing and the second bend may correspond to the period where helium becomes the dominant determinant of pump speed. Both bends were observed at longer times, and the time interval between both bends increased as the amount of gas to be processed increased. Similarly, the second bend was observed at longer times, and the time interval between both bends increased with methane percentage. The results suggest that some features of exhaust gas can be estimated by inspecting both bend points, because the positions of the bend points and the time interval between them provided information about exhaust gas components and volume. (orig.)

[en] Compound nuclear reactions play a crucial role in nuclear physics, reactor physics and astrophysics. However, even though the concept of the compound nucleus is rather old, further research is still necessary in order to establish a comprehensive, quantitative picture of the processes involved in the formation and decay of the compound nucleus. This requires a deep understanding of the fundamental aspects in nuclear physics such as reaction mechanisms and nuclear structure. CNR*15 will assess the status of knowledge of compound-nuclear reactions, review current theoretical and experimental efforts aimed at understanding compound-nuclear reactions, identify areas in need of development, and outline possible strategies for addressing these needs. The presentations have been gathered around 7 global topics: the nuclear fission, the shell model, fission experiments, particle emission from fission, cluster models, nuclear structure and neutron-induced reactions

[en] McGNASH is a modern statitistical/preequilibrium nuclear reaction code, being developed at Los Alamos, which can simulate neutron-, proton- and photon-induced reactions in the energy range from a few-keV to about 150 MeV. It is written in modern Fortran 95 scientific language, offering new capabilities both for the developer and the user. McGNASH is still in a development stage, and a first public release is planned for later in 2005. The statisticaUpre-equilibrium nuclear reaction code GNASH has been used successfully over the years to compute neutron-, proton- and photon-induced reactions cross sections on a variety of nuclei targets, and for incident particle energies from tens of keV up to 150-200 MeV. This code has been instrumental in producing numerous nuclear data evaluation files for various ENDF libraries around the World, and in particular the ENDFB-VI and pre-ENDFB-VII libraries in the US. More recently, GNASH was used extensively for the creation of the LA1501ibrary, including data on neutron- and proton-induced reactions up to 150 MeV incident energy. We are now developing a modern version of the code, called McGNASH.

[en] Some experiments have been carried out, dealing with the interations of caffeine and gamma radiation in the embryonic development of Biomphalaria glabrata. Gamma radiation was used in a dosis of 1000r (exposure time of 1/2 hour) and caffeine concentration was 0.1% (Exposure time of 24 hours). Experiment I. The embryos were irradiated before treatment with caffeine. In this experiment we have observed a synergistic effect between caffeine and gamma radiation. Experiment II. The embryos in the caffeine solution were irradiated 8 hours after the beginning of the experiment. The synergistic effect observed in this experiment was reduced when compared with the first one. Experiment III. In this experiment we made the pre-treatment with caffeine. We have not observed any synergistic effect between the drug and gamma radiation. Experiment IV. Embryos were irradiated, and after 24 hours treated with caffeine during another 24 hours. As in the previous experiment, we have not observed any synergism between the radiation and the drug. According to the above results, we conclude that the synergistic effect between caffeine and gamma radiation in the embryos was more effective when the embryos have been treated with caffeine after irradiation. (Author)