ENDF/B-VIII.0-based fast neutron removal cross sections database in Z = 1 to 92 generated via multi-layered spherical geometry

Abstract

A fast neutron mass removal cross sections (ΣR/ρ) database covering the elemental range of Z = 1 to 92 is generated for source neutron energy distributions based on 241Am–Be, 252Cf, and 235U. Monte Carlo simulations using ENDF/B-VIII.0 nuclear data were performed with the fast neutron removal theory's ideal spherical representation. The ENDF/B-VIII.0-based ΣR/ρ′s derived were compared with values from the Oak Ridge National Laboratory's Lid Tank Shielding Facility (LTSF) experiments, values from software Phy-X/PSD and MRCsC, values obtained by an empirical model in Zoller, and values derived using the older ENDF/B-VII.0 nuclear data library. Subsequently, the generated ΣR/ρ′s were evaluated for convergence under varying moderator thickness. Results indicate that the ΣR/ρ quantity for fission and (alpha, n) spectra is universal, with slight deviations for low Z elements. The ΣR/ρ values generated from ENDF/B-VIII.0 agreed with LTSF experiments with an average relative deviation of 8.58%. Moreover, using ENDF/B-VIII.0-based ΣR/ρ′s, the derived fast neutron effective removal cross sections (ΣR's) for several light compounds and dry concrete have better agreement on average with LTSF experiments compared with values derived from the available ΣR/ρ′s in the literature. Significant differences were found for ΣR/ρ′s that were generated with ENDF/B-VIII.0 as compared with the superseded ENDF/B-VII.0. Furthermore, ENDF/B-generated ΣR/ρ′s through spherical model showed the expected convergence towards singular values at moderator thicknesses practical for fast neutron removal theory applications. Owing to the relatively high unavoidable uncertainties of the LTSF experimental ΣR/ρ′s, the ENDF/B-VIII.0-based ΣR/ρ′s present a new and potentially favorable database in ΣR general calculations for homogeneous multi-element materials for point-kernel shielding applications.