Investigation of burnup credit allowance in the criticality safety evaluation of spent fuel casks

The payloads of present generation spent fuel casks are constrained by a criticality design basis that assumes loading with unirradiated fuel. This presentation discusses work in progress on criticality analysis verification for designs which take into account burn up and aging in the transported fuel. The work includes verification of cross section data, correlation with experiments, proper extension of the methods into regimes not covered by experiments, establishing adequate reactivity margins, and complete documentation of the project. Recommendations for safe operational procedures are included, as well as a discussion of the economic and safety benefits of such designs.