Evaluation of expected behavior of LWR stainless steel-clad fuel in long-term dry storage. Final report

The commercial light-water reactor (LWR) nuclear power industry in the United States has used two basic fuel types in its reactors: UO{sub 2} clad with Zircaloy or UO{sub 2} clad with stainless steel alloys. An assessment was conducted to provide a summary of the current technical basis for the long-term dry storage of LWR stainless steel-clad SNF, to describe potential issues associated with the continued safe long-term storage of LWR stainless steel-clad SNF during wet and/or dry storage, and to provide guidance for possible activities needed to resolve the potential issues. The potential failure modes that might be active in the expected storage modes were assessed and prioritized, and bounding conditions were identified. The bounding conditions for the potential degradation phenomena and failure modes were found to include the bounds identified in the technical basis for storing Zircaloy-clad SNF; it was thus concluded that storage systems now employed for Zircaloy-clad SNF could safely accommodate the colder stainless steel-clad SNF inventory with similar integrity.