Burnup credit validation of SCALE-4 using mixed-oxide critical experiments

Spent fuel contains many actinides and fission products that are not present in fresh fuel. From a criticality safety perspective, the most significant nuclides are the plutonium isotopes. In a previous study, the SCALE-4 modular code system 3 was validated for fresh light-water-reactor (LWR) fuel in various storage configurations. In addition, LWR core critical configurations have been modeled with SCALE-4 as part of the validation effort for the Burnup Credit Program sponsored by the US Department of Energy. However, criticality analyses performed to date with critical experiments containing low-enriched plutonium and uranium typical of LWR spent fuel have been limited to the single mixed-oxide case. Therefore, as part of the Burnup Credit Program, two sets of mixed-oxide critical experiments have been analyzed using KENO V.a and the 27-group burnup library in order to validate the SCALE-4 methodology for fuel containing PUO2 and UO2