Validation of MPACT cross section library with shift using VERA-CS

Cross section libraries are essential for accurately simulating iieutronics behavior in numerical simulations of nuclear reactors. Our objective in this research is to validate the 51-group microscopic cross section library used by MPACT by comparing with the microscopic cross sections tallied by Shift when running VERA-CS. This study intends to replicate and extend the reaction rate comparison previously performed with MCNP. In this investigation, absorption and v-fission microscopic cross sections for both ²³⁸U and ²³⁵U arc compared. In total, this study investigated 450 cases for four different reactor pinccll geometries and one assembly geometry (where the enrichment and temperatures were varied). For the pinccll case reported in the previous CASL report, the reaction rates from Shift showed very good agreement with MPACT and MCNP. All reaction rales were within 5% compared to both MCNP and MPACT. Over all pincell cases, the maximum, minimum and average absolute differences in the reaction rate are 8.80%, -4.71%, and 1.06% respectively. With the exception of the outside corner pincell, the assembly cases also showed good agreement between Shift and MPACT. Ignoring the corner pin, the maximum, minimum and average absolute value of the relative differences in the reaction rate are 8.84%, -6.46%, and 1.13% respectively. Overall, the results of this investigation showed the reaction rates and cross sections calculated by Shift through VERA-CS showed excellent agreement with MPACT in all cases as well as previous results from MCNP. Therefore, the 51-group cross section library used in MPACT accurately depicts the ncutronics behavior for the cases investigated.