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 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 iodine isotopes

Neutron nuclear data on six isotopes of iodine 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. Unresolved resonance parameters were obtained by fitting to the total and capture cross sections calculated from nuclear models, while resolved resonance parameters remain unchanged from JENDL-4.0. 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. Giant-dipole resonance parameters for γ-ray transition from iodine isotopes were determined so as to reproduce measured γ-ray spectrum for ¹²⁷I. The present results reproduce experimental data very well. The evaluated data are compiled into 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.     

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 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 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.     

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.     

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 equilibrium constants for deprotonation and lactonisation of α-D-isosaccharinic acid

A great deal of disagreement exists in the literature regarding the intrinsic deprotonation and lactonisation constants of α-D-isosaccharinic acid (ISA). Based on a combination of nuclear magnetic resonance and interpretations using the specific ion interaction theory (SIT) of extensive experimental Ca(ISA)₂(cr) solubility data involving α-D-isosaccharinic acid, the reliable value of log₁₀ K° for [HISA(aq) ISA^? + H⁺] is ?3.27 ± 0.01 and for [HISA(aq) ISL(α-D-isosaccharinate-1,4-lactone)(aq) + H₂O] is 0.49 ± 0.09. These data also provide log₁₀ K° of ?3.76 ± 0.09 for the reaction [ISL(aq) + H₂O ISA^? + H⁺] and ?3.88 ± 0.09 for the composite reaction [HISA(aq) + ISL(aq) ISA^? + H⁺]. Reinterpretation of extensive Ca(ISA)₂(cr) solubility data using the SIT activity coefficient model provides log₁₀ K° of ?6.40 ± 0.09 for [Ca(ISA)₂(cr) Ca²⁺ + 2(ISA)^?] and of 1.70 ± 0.09 for [Ca²⁺ + ISA^? CaISA⁺] which are consistent with all of the available values.     

A measurement of the U233, U235, Pu239 total cross sections. As well as the fission cross section of U235 for resonance neutrons

The measurement of the interaction cross sections between resonance neutrons and fissionable isotopes are of definite importance both for reactor calculations and for the construction of various nuclear models. In this work we present the results of measurements of the U²³³, U²³⁵, and Pu²³⁹ total cross sections, as well as the fission cross section of U²³⁵. The measurements were performed on a mechanical neutron spectrometer (neutron chopper) with a resolution of 0.1–0.2 sec/m in the neutron energy region from 3–5 to about 500 ev. The resonance parameters are calculated to energies of about 30–50 ev, for which the levels may still be considered resolved. For these resonances the neutron widths g_n are determined; the total widths are determined for sufficiently excited levels when the uncertainty in this determination is no greater than about 50%. For U²³⁵ resonance in the energy region from 2.5 to 20 ev, in addition to the above parameters, the ratio of the fission width _f to the total width is found.     

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 for Uranium-233

Neutron nuclear data of ²³³U have been evaluated in the energy range from 10-⁵ eV to 20 MeV. Evaluated quantities are the total, fission, capture, elastic and inelastic scattering, (n,2n) and (n,3n) reaction cross sections, and the average numbers of prompt and delayed neutrons emitted per fission. The thermal and resonance cross sections have been evaluated on the basis of the measured data. The resolved resonance parameters are given up to 100 eV and the unresolved resonance parameters between 100 eV and 30keV. The total and fission cross sections have been evaluated in the higher energy region on the basis of the recently measured data, while the theoretical calculation with the optical, statistical and evaporation models has been used for evaluation of the other cross sections. The presently adopted optical potential parameters have reproduced well the experimental total cross section in the entire energy range as well as the measured data of the s-wave strength function. The structure observed in the vp values below 1 MeV is reproduced by the semi-empirical formula based on the fission fragment kinematics. The presently evaluated fission cross section is considerably lower than that of ENDF/B-IV between 10 and 50keV. This low fission cross section is expected to resolve the ^Keff discrepancy pointed out from the benchmark tests in ²³³U critical assemblies.