Reactivity Effects of Differences Between JEFF-3.1 and ENDF/B-VI.8 in Analysis of Six MASURCA Cores of the R-Z Program

摘要

Reactivity contributions of differences between JEFF-3.1 and ENDF/B-VI.8 were analyzed for six early MASURCA cores of the R-Z program using ERANOS 2.1. These cores were designed such that their neutron spectra would emulate that of an oxide-fueled sodium-cooled fast reactor, some containing enriched uranium and others containing depleted uranium and plutonium. Effects of modeling assumptions and solution methods both in ECCO lattice calculations and in BISTRO S_n flux solutions were first evaluated using JEFF-3.1 cross-section libraries. Comparisons were made between calculated and measured values for reactivity and several spectral indices. Reactivity effects of differences between JEFF-3.1 and ENDF/B-VI.8 were also quantified using perturbation theory analysis. The most important nuclide with respect to reactivity differences between cross-section libraries was ~(23)Na, primarily a result of differences in the angular dependence of elastic scattering, which is more forward peaked in ENDF/B-VI.8 than in JEFF-3.1. Differences in ~(23)Na inelastic scattering cross sections between libraries also generated significant differences in reactivity, more due to the differences in magnitude of the cross sections than to the angular dependence. The nuclide ~(238)U was also found to be important with regard to reactivity differences between the two libraries mostly due to a large effect of inelastic scattering differences and two smaller effects of elastic scattering and fission cross sections. In the cores that contained plutonium, ~(239)Pu fission cross-section differences contributed significantly to the reactivity differences between libraries.