Neutron Data Evaluation of 243Am

TL;DR

This paper evaluates neutron data for 243Am using statistical methods, providing a consistent description of various cross sections and modeling the impact of pre-fission neutrons on fission spectra, with significant implications for nuclear data accuracy.

Contribution

It introduces a comprehensive evaluation of 243Am neutron data using statistical theories and least squares, addressing discrepancies and modeling pre-fission neutron effects.

Findings

Consistent description of total, capture, and fission data.

Identification of shape change in inelastic cross section at ~1.5 MeV.

Modeling of pre-fission neutron influence on fission spectra.

Abstract

The diverse measured data base of n+243Am was evaluated using a statistical theory and genera-lized least squares codes. Consistent description of total, capture and fission measured data provides an important constraint for the inelastic scattering cross section. Important constraints for the measured capture cross section in the 0.15-300 keV energy range come from the average radiative and neutron S0 and S1 strength functions. The evaluated inelastic cross sections of available evaluations are in severe disagreement, predicted change of the inelastic cross section shape at En ~1.5 MeV is attributed to the sharp increase of the level density of the residual odd-even nuclide 241Am due to the onset of three-quasi-particle excitations. The influence of exclusive (n, xnf) pre-fission neutrons on prompt fission neutron spectra (PFNS) and (n, xn) spectra is modelled. Contributions of emissive/non-emissive fission and exclusive spectra of (n, xnf) reactions are defined by a consistent description of the 241Am(n, F), 241Am(n, 2n). Data file is at https://www-nds.iaea.org/minskact/data/original/za095243