Effect of Additional Chemical Assay Data on Actinide-Only Burnup Credit

摘要

Currently, the licensing basis used fro criticality analysis of spent fuel shipping casks assumes that the spent fuel is unburned. This assumption is very conservative for most of the spent fuel that is planned to be shipped so in recent years the NRC as approved guidance for burnup credit that utilizes the change in actinide isotopic concentration with burnup. As part of burnup credit analysis, it is required to demonstrate by use of experimental data that the isotopic concentrations are conservative. A great deal of documentation has been produced using 54 chemical assays of spent fuel. Recently, new data has been published based on chemical assays of fuel from the Takahama reactor. This new data represents 10 more points and covers a higher enrichment and burnup than most of the data in the original 54 chemical assays previously used. (The Takahama data also includes fission products. Previous chemical assays, which included fission products, was extremely limited.) This paper investigates the impact of the new Takahama data on the actinide-only analysis for spent fuel casks.