M. Baba

Neutron Capture Cross Section of 232Th

Abstract Consistent evaluation of the 232Th capture cross section is performed in the energy range from 4 keV to 5 MeV. The Hauser-Feshbach-Moldauer theory and coupled channel optical model are employed. Total, differential scattering, fission, and inelastic scattering data are consistently reproduced as a major constraint for the capture cross-section estimate. Average resonance parameters are obtained, which are consistent with the capture cross-section database.

231Pa and 233Pa Neutron‐Induced Fission Data Analysis

The 231Pa and 233Pa neutron‐induced fission cross‐section database is analyzed within the Hauser‐Feshbach approach. The consistency of neutron‐induced fission cross‐section data and data extracted from transfer reactions is investigated. The fission probabilities of Pa, fissioning in 231,233Pa(n,nf) reactions, are defined by fitting (3He,d) or (3He,t) transfer‐reaction data. The present estimate of the 233Pa(n,f) fission cross section above the emissive fission threshold is supported by smooth level‐density parameter systematics, validated in the case of the 231Pa(n,f) data description up to En =20 MeV.

U‐Th Fuel Cycle Neutron Data

Fission, capture, (n,xn), neutron elastic and inelastic scattering, and total data for the 232Th, 232,233,234U, and 231,233Pa, when available, are described within a Hauser‐Feshbach‐Moldauer theory and coupled‐channel optical model. For even targets direct excitation cross sections for quadrupole and octupole vibration band levels are calculated with a soft rotator model. Prompt fission neutron spectra are calculated with the model that takes into account contribution of the neutrons, emitted in the (n,xnf) reaction. Exclusive pre‐fission (n,xnf) neutron spectra are calculated using Hauser‐Feshbach theory. Local minima of the average prompt‐fission neutron‐spectra energies around (n,nf) and (n,2nf) thresholds are predicted. Evaluated data files are produced.

233U Neutron Data Evaluation

Fission, capture, neutron‐elastic‐scattering, and inelastic‐scattering data for the 233U are described within a Hauser‐Feshbach‐Moldauer theory. The rigid rotator optical model potential is obtained based on the total cross section, elastic‐, and inelastic‐angular distributions. Consistent estimates of capture and fission data are obtained up to En ∼1 MeV. Prompt‐fission neutron spectra are calculated with the model that takes into account the contribution of neutrons emitted in (n,xnf) reactions. Exclusive pre‐fission (n,xnf) neutron spectra are obtained by fitting of the fission cross section. Local minima of the average energies of prompt‐fission neutron spectra at En ∼7 MeV and En ∼12 MeV are predicted. A 233U evaluated data file is produced.