Evaluation of neutron nuclear data on tantalum isotopes

Neutron nuclear data on four isotopes of tantalum have been evaluated for the next version of Japanese Evaluated Nuclear Data Library general-purpose file in the energy region from 10^?5 eV to 20 MeV. Unresolved resonance parameters were obtained by fitting to the total and capture cross sections calculated from nuclear models, while resolved resonance parameters were selected from experimental data. A statistical model code was applied to evaluate cross sections above the resolved resonance region. Compound, pre-equilibrium and direct-reaction processes were considered for cross-section calculation. Coupled-channel optical-model parameters were employed for the interaction between neutrons and nuclei. Giant-dipole and pygmy resonance parameters for E1 γ-ray transition from tantalum isotopes were determined so as to reproduce measured γ-ray spectrum for ¹⁸¹Ta. The present results reproduce experimental data very well. The evaluated data are compiled into Evaluated Nuclear Data File (ENDF) formatted data files.     

Evaluation of neutron nuclear data on platinum isotopes

Neutron nuclear data on 10 isotopes of platinum have been evaluated for the next version of Japanese Evaluated Nuclear Data Library general-purpose file in the energy region from 10^?5 eV to 20 MeV. Resolved resonance parameters of naturally occurring isotopes were taken from a compilation work, while unresolved resonance parameters were obtained by fitting to the total and capture cross sections calculated from nuclear models. A statistical model code was applied to evaluate cross sections above the resolved resonance region. Compound, pre-equilibrium and direct-reaction processes were considered for cross-section calculation. Coupled-channel optical model parameters were employed for the interaction between neutrons and nuclei. Giant-dipole and pygmy resonance parameters for E1 γ-ray transition from platinum isotopes were determined so as to reproduce measured γ-ray spectrum. The present results reproduce experimental data very well. The evaluated data are compiled into Evaluated Nuclear Data File formatted data files.     

Evaluation of Neutron Nuclear Data on Bromine and Krypton Isotopes for JENDL-4.0

Neutron nuclear data on ^79,81Br and ^{78,80,82,83,84,85,86}Kr have been evaluated for the evaluated nuclear data library JENDL-4.0 in the energy region from 10^?5 eV to 20 MeV. The resolved resonance parameters were adjusted so as to reproduce recommended or measured thermal capture cross sections for some isotopes. The statistical model was applied to calculate the cross sections above the resolved resonance region. In the calculations, coupled-channel optical model parameters were used for neutrons. Preequilibrium and direct-reaction processes were taken into account in addition to the compound process. The present evaluation is consistent with available experimental data. The evaluated results were compiled into JENDL-4.0.     

Evaluation of neutron nuclear data on mercury isotopes

Neutron nuclear data on 10 isotopes of mercury have been evaluated for the next version of Japanese evaluated nuclear data library (JENDL) general-purpose file in the energy region from 10^?5 eV to 20 MeV. Resolved resonance parameters (RRPs) for ^{200, 202}Hg were supplemented with the data which had not been considered in the previous library. Unresolved resonance parameters (URPs) were obtained by fitting to the total and capture cross sections calculated from nuclear models. A statistical model code was applied to evaluate cross sections above the resolved resonance region. Coupled-channel optical model parameters were employed for the interaction between neutrons and nuclei except ²⁰³Hg. Compound, pre-equilibrium, and direct-reaction processes were considered for cross-section calculation in the high energy region. The present results reproduce experimental data very well. The evaluated data are compiled into evaluated nuclear data file (ENDF) formatted data files.     

Evaluation of neutron nuclear data on tellurium isotopes

Neutron nuclear data on 13 Te isotopes have been evaluated for the next release of Japanese Evaluated Nuclear Data Library (JENDL) general purpose file in the energy region from 10^{? 5} eV to 20 MeV. Thermal capture cross sections of ^{120, 121m, 127m, 129m, 131m, 132}Te were determined from the latest measurements or from a simplified formula, although the resolved resonance parameters, which describe the low-energy behavior of cross sections, remain unchanged from JENDL-4.0 for ^{122, 123, 124, 125, 126, 128, 130}Te. A statistical model code was applied to evaluate the cross sections above the resolved resonance region. Coupled-channel optical model parameters were employed for the interaction between neutrons and nuclei. Compound, pre-equilibrium, and direct-reaction processes were considered for cross-section calculation in high-energy region. The present results reproduce experimental data very well, and are found to be much better than the JENDL-4.0 data. The evaluated data are compiled into evaluated nuclear data file (ENDF)-formatted data files.     

Evaluation of neutron nuclear data on ruthenium isotopes

Neutron nuclear data on ^{96,98,99,100,101,102,103,104,105,106}Ru have been evaluated for the next version of JENDL general-purpose file in the energy region from 10^{? 5} eV to 20 MeV. The thermal capture cross sections of ^96,102Ru were modified so as to reproduce the latest measured data. The statistical model was applied to calculate the cross sections above the resolved resonance region. In the calculations, coupled-channel optical-model parameters were used for neutrons. Preequilibrium and direct-reaction processes were taken into account in addition to the compound process. The present evaluation is consistent with available experimental data. The evaluated data are compiled into an ENDF-formatted data file.     

Measurement of the 77Se(γ, n) cross section and uncertainty evaluation of the 79Se(n, γ) cross section

The ⁷⁷Se (γ, n) cross section was measured for the energy range from 7.6 to 13.8 MeV by using quasi-monochromatic laser-Compton scattering γ-rays. The advanced method to deduce γ-ray strength functions from (γ, n) cross section was developed. By utilizing the method, the γ-ray strength functions of ^{77, 78, 80}Se were deduced so as to reproduce the ^{77, 78, 80}Se (γ, n) cross sections measured in this work and previous systematic measurements. The inverse (n, γ) cross sections for ^{76, 77, 79}Se isotopes were calculated using the statistical model calculation code CCONE with the deduced γ-ray strength functions. The uncertainty of the calculated ⁷⁹Se(n, γ)⁸⁰Se cross section was evaluated by comparing the calculations and the experimental data on ^{76, 77}Se (n, γ) cross sections.     

Evaluation of neutron nuclear data for gallium

Neutron nuclear data on ^69,71Ga have been evaluated for the next version of the Japanese Evaluated Nuclear Data Library (JENDL) general purpose file in the energy region from eV to 20 MeV. The resolved resonance parameters at negative energies were adjusted so as to reproduce measured thermal capture cross sections. The statistical model was applied to calculate the cross sections above the resolved resonance region. In the calculations, coupled-channel optical model parameters were used for neutrons. Pre-equilibrium and direct-reaction processes were taken into account in addition to the compound process. The present evaluation is consistent with available experimental data. The evaluated data are compiled into an ENDF-formatted data file.     

New Evaluation of Neutron Nuclear Data for Zinc Isotopes

New evaluation of neutron-induced nuclear data for five stable isotopes of zinc (mass numbers A = 64, 66, 67, 68, and 70) was consistently carried out in the incident neutron energy range from 10^?5 eV up to 20MeV. In the low energy region up to about 100keV, the resonance parameters were evaluated by taking account of the available measured data. In the fast neutron region, the comprehensive calculations with nuclear reaction models, in which compound, preequilibrium, and direct processes are taken into account, were performed to estimate cross sections for various reactions and double differential cross sections of emitted neutrons and γ-rays. The comparisons of the evaluated cross sections with the experimental data and existing evaluated nuclear data libraries are made and show a good agreement with the measurements.     

Evaluation of neutron nuclear data on xenon isotopes

Neutron nuclear data of Xe isotopes have been evaluated in the energy region, including the resolved resonance one, from 1 keV to 20 MeV by using the theoretical nuclear reaction models. The phenomenological optical model potential was employed to calculate the total cross section for natural Xe with the coupled-channels method. The cross sections for channels of capture, (n, 2n), (n, p) and (n, α) reactions were calculated and compared with available experimental results including recently measured data. The elastic scattering angular distributions and particle emission spectra were calculated, although there is no experimental information available. Reaction cross sections of evaluated libraries were considered for comparison with the calculated results. The presently calculated cross sections reproduce better the available experimental data.     

Evaluation of neutron nuclear data for erbium

Neutron nuclear data on ^{162,164,166,167,168.170}Er have been evaluated for the next version of JENDL general purpose file in the energy region from 10^?5 eV to 20 MeV. The resolved resonance parameters remain unchanged from JENDL-4.0, while the unresolved resonance parameters were revised. The statistical model was applied to calculate the cross sections above the resolved resonance region. In the calculations, coupled-channel optical model parameters were used for neutrons. Pre-equilibrium and direct-reaction processes were taken into account in addition to the compound process. A modified Lorentzian was employed for E1 gamma-ray strength functions. The present evaluation is consistent with available experimental data. The evaluated data are compiled into an ENDF-formatted data file.     

Evaluation of neutron cross sections for a complete set of Dy isotopes

Neutron cross sections for a complete set of Dy isotopes, ^{156,158,160,161,162,163,164}Dy, were evaluated in the incident energy range from 10⁻⁵ eV to 20 MeV. In the low energy region, including thermal and resolved resonances, our evaluations are based on the latest data published in the Atlas of Neutron Resonances. In the unresolved resonance region we performed additional evaluation by using the averages of the resolved resonances and adjusting them to the experimental data. In the fast neutron region, we used the nuclear reaction model code EMPIRE-2.19 with the model parameters adjusted to the experimental data. The results are compared with the available experimental data and with the existing nuclear data libraries, including ENDF/B-VI.8 and JEFF-3.1. The new evaluations are suitable for neutron transport calculations and they were adopted by the new US evaluated nuclear data library, ENDF/B-VII.0, released in December 2006.     

Evaluation of neutron nuclear data of praseodymium-141 and -143

For the next version of JENDL general purpose file, neutron nuclear data on ^141,143Pr are evaluated considering cross sections and spectra provided from experiments in the fast neutron energy region up to 20 MeV. Total and elastic cross sections are derived from optical model. Pre-equilibrium and direct-reaction processes are taken into account in addition to the compound process. The statistical model is applied to calculate the cross sections above the resolved resonance region. For unstable ¹⁴³Pr nuclide having less experimental data, we use the same parameters as ¹⁴¹Pr for mass-dependent and -independent terms in the optical potential. The resolved resonance parameter remains unchanged from JENDL-4.0. The present evaluations give consistent results with experimental data, reflecting newly measured one. The evaluated data are compiled in ENDF-6 format for the next version of JENDL.     

Neutron Nuclear Data Evaluation for Thorium-232

An evaluation was made on the neutron cross sections, resonance parameters and average neutron yield in fission for ²³²Th in the energy range from thermal energy to 20 MeV. The fission and capture cross sections were evaluated on the basis of the experimental data by converting the relative ratio data into cross section values by making use of recent evaluations for reference cross sections. The total cross section was determined from experimental data in the region from 24 keV to 15 MeV and then extrapolated to lower and higher energies by using the optical model whose parameters had been adjusted as so to reproduce the measured data. The elastic and inelastic scattering, (n, 2n) and (n, 3n) reaction cross sections were calculated by means of the statistical model combined with the optical model. A set of resonance parameters were recommended in the energy range below 3.5 keV and average resonance parameters were deduced in the unresolved resonance region. A value of 7.40 b was chosen for the capture cross section at 0.025 eV, and the picket-fence negative-energy levels were introduced so as to reproduce the non-l/v behavior of the capture cross section in the epithermal region.

The results were incorporated in the Japanese Evaluated Nuclear Data Library, Version 2 (JENDL-2). Comparison was made between the present and other evaluations such as ENDF/B-V and possible reasons for the discrepancy were discussed.     

Evaluation of Neutron Nuclear Data of Natural Silver and Its Isotopes

Neutron nuclear data of natural silver and its isotopes (¹⁰⁷Ag and ¹⁰⁹Ag) have been evaluated in the energy range of 10^?5eV–20 MeV. Evaluated quantities are the total, elastic and inelastic scattering, capture, (n, Zn), (n, 3n), (n, p), (n, α), (n, np), (n, nα) reaction and γ-ray production cross sections, the resonance parameters and the angular and energy distributions of emitted neutrons and γ-rays. The evaluation is based on available experimental data and theoretical calculations. Multi-step Hauser-Feshbach calculation played an important role in the determination of the reaction cross sections. In the calculation, the precompound process was taken into account above 5MeV, in addition to the compound one. The evaluated data have been compiled into JENDL-3 in the ENDF-5 format.     

Neutron Nuclear Data Evaluation of Cesium Isotopes for JENDL-4.0

For the development of JENDL-4.0, neutron nuclear data for fission product nuclides, ^{133,134,135,136,137}Cs, were revised in the incident neutron energy range from 1 eV to 20MeV by using a coupled-channels optical model (OM), and nuclear reaction models. The OM potential parameters were determined for stable ¹³³Cs to reproduce the experimental data of total and elastic scattering cross sections and angular distributions of elastically scattered neutrons. The present results reasonably reproduce measured data for (n; 2n), (n; p), (n; α), and capture reactions on ¹³³Cs. Important differences between the present results and JENDL-3.3 are found for the capture cross sections of ^134,137Cs. The cross section obtained for ¹³⁷Cs was smaller than that in JENDL-3.3. This result makes the transmutation of medium-lived ¹³⁷Cs increasingly difficult. The production probabilities of metastable states for ^134,138Cs via capture reactions on ^133,137Cs are compared with experimental values. The present result for ^134m Cs production is marginally consistent with measured data. However, a large discrepancy is recognized for ^138m Cs production. The γ-ray emission data were evaluated with available measurements, and newly compiled in JENDL-4.0. Maxwellian-averaged capture cross sections were calculated in the energy range from 1 to 103 keV, and are compared with other derived data.     

Evaluation of Neutron Nuclear Data for Mercury

Neutron nuclear data of stable mercury isotopes (¹⁹⁶Hg, ¹⁹⁸Hg, ¹⁹⁹Hg, ²⁰⁰Hg, ²⁰¹Hg, ²⁰²Hg and ²⁰⁴Hg) have been evaluated in the energy range of 10^?5eV–20MeV. Evaluated quantities are the total, elastic and inelastic scattering, capture, (n, 2n), (n, 3n), (n, p), (n, d), (n, α), (n, np), (n, nα) reaction and γ-ray production cross sections, the resonance parameters, and the angular and energy distributions of emitted neutrons and γ-rays. The evaluation is mainly based on nuclear reaction model calculations. Statistical-model calculation played a significant role in the determination of the reaction cross sections. The evaluated data have been compiled in the ENDF-6 format, and are used for the design study of a mercury target system proposed at the Neutron Science Research Center, Japan Atomic Energy Research Institute.     

Evaluation of Neutron Nuclear Data for Sodium-23

Neutron nuclear data of ²³Na have been evaluated in the neutron energy region up to 20 MeV. Evaluated are the elastic and inelastic scattering, capture, (n, 2n), (n, p), (n, α), (n, np), (n, nα) reaction and γ-ray production cross sections, and the angular and energy distributions of neutrons and γ-rays. The evaluation is mainly based on nuclear model calculations. The pre-equilibrium and direct-reaction processes were taken into account in addition to the compound process. The evaluated data have been compiled into the latest version of JENDL, JENDL-3.3.     

Evaluation of neutron-induced and γ-ray-production cross sections for elemental sulfur

A new evaluation for natural S is described, this was a completely new evaluation done for ENDF/B-V. The secondary neutron cross sections and angular distributions as well as the secondary neutron energy distribution for the continuum inelastically scattered neutrons have been included. In addition, the isotopic cross sections for the various (n, particle) reactions were evaluated with the help of experimental data and model-calculated results to construct the corresponding natural S files. Precompound effects were included. The least abundant isotope ³⁶S was not considered in the evaluation. The resolved resonance region for natural S extends from 1.0 × 10^?5 eV to 1091.0 keV, and the resonance parameters for the three S isotopes ³²S, ³³S and ³⁴S have been evaluated from experimentally determined resonance parameters. The Karlsruhe total S cross-section data extending up to 20 MeV were used to construct a smooth cross-section file. Measurements due to other investigators were also used in the evaluation.     

Reaction-yield dependence of the (γ, γ′) reaction of 238U on the target thickness

The dependence of the nuclear resonance fluorescence (NRF) yield on the target thickness was studied. To this end, an NRF experiment was performed on ²³⁸U using a laser Compton back-scattering (LCS) γ-ray beam at the High Intensity γ-ray Source facility at Duke University. Various thicknesses of depleted uranium targets were irradiated by an LCS γ-ray beam with an incident beam energy of ～2.475 MeV. The scattering NRF γ-rays were measured using an High-purity Germanium (HPGe) detector array positioned at scattering angles of 90° relative to the incident γ-beam. An analytical model for the NRF reaction yield (NRF RY model) is introduced to interpret the experimental data. Additionally, a Monte Carlo simulation using GEANT4 was performed to simulate the NRF interaction for a wide range of target thicknesses of the ²³⁸U. The measured NRF yield shows the saturation behavior. The results of both of the simulation and the analytical model can reproduce the saturation curve of the scattering NRF yield of ²³⁸U against the target thickness. In addition, we propose a method to deduce the precise integral cross section of the NRF reaction by fitting the NRF yield dependency on the target thickness without any absolute measurements.