An Economic Evaluation of a Storage System for Casks with Burnup Credit

It is generally recognized that casks designed with burnup credit are more economical than those without burnup credit. The higher the initial uranium enrichment, the larger the fuel assembly separation is necessary in the cask to satisfy criticality safety criteria when the fresh fuel assumption is adopted. On the other band, the consideration of burnup credit in the cask design gives smaller basket channel pitch necessary for sub-criticality requirement. Accordingly larger number of fuel assemblies can be loaded in a limited size of cask, especially for highly enriched fuels, and considered more economical. To estimate how much more economical they are, conceptual designs of storage/transport (S/1') casks were made with and without burnup credit for PWR and BWR fuels of various uranium enrichment and total costs were evaluated of cask storage systems incorporating casks with and without burnup credit. The costs were estimated for the assumed typical BWR cask storage systems in Japan with the capacity of 700 MTU and for the PWR cask storage systems with the capacity of 500 MTU, respectively, assuming that 125ton casks were installed at the storage site.