Newly Evaluated Neutron Reaction Data on Chromium Isotopes

TL;DR

This paper reevaluates neutron reaction data for chromium isotopes from thermal energies up to 20 MeV, improving accuracy through resonance analysis and nuclear reaction models, and benchmarks the results with critical assembly simulations.

Contribution

It introduces updated neutron reaction data for chromium isotopes using advanced resonance analysis and statistical models, enhancing evaluation accuracy over previous data sets.

Findings

Improved thermal resonance parameters for $^{50,53}$Cr.

Enhanced reaction cross section evaluations up to 20 MeV.

Benchmarking shows significant performance improvements.

Abstract

Neutron reaction data for the set of major chromium isotopes were reevaluated from the thermal energy range up to 20 MeV. In the low energy region, updates to the thermal values together with an improved $R$-matrix analysis of the resonance parameters characterizing the cluster of large $s$-wave resonances for $^{50,53}$Cr isotopes were performed. In the intermediate and high energy range up to 20 MeV, the evaluation methodology used statistical nuclear reaction models implemented in the EMPIRE code within the Hauser-Feshbach framework to evaluate the reaction cross sections and angular distributions. Exceptionally, experimental data were used to evaluate relevant cross sections above the resonance region up to 5 MeV in the major $^{52}$Cr isotope. Evaluations were benchmarked with Monte Carlo simulations of a small suite of critical assemblies highly sensitive to Chromium data, and with the Oktavian shielding benchmark to judge deep penetration performance with a 14-MeV D-T neutron source. A significant improvement in performance is demonstrated compared to existing evaluations.