Spent Fuel Dry Storage Canister CISCC Prevention Technology Development

Approximately 76,000 fuel assemblies are currently in dry storage in the United States and the number of unique combinations of reactor sites, storage systems, and canisters could exceed 200 according to one Government estimate. None of these canisters have ever failed. Onsite dry storage of spent fuel was originally intended to be a temporary measure. However, not having a national spent fuel off-site storage, disposal (repository), or reprocessing options has resulted in projected dry storage times being extended from tens of years to possibly 100 years or more. This increases the concern that various hypothesized aging mechanisms including chloride-induced stress corrosion cracking (CISCC) for marine sites could lead to canister failures sometime down the road. NovaTech has developed a new technology called High-Pressure Vapor Blasting as a result of a previous DOE SBIR (DE-SC0017979) that when applied to the heat affected region of a weld, appears to be 100% effective at preventing subsequent CISCC during preliminary testing. NovaTech will revisit the limited 2020 laboratory results and explore the potential of this unique technology in depth. This will include determining how deeply the compressive stresses penetrate below the surface, how long the observed benefit is likely to persist, how the operating parameters of the process affects both outcomes, and how robust survivability of the treated specimens can best be achieved over the long term while minimizing process time and consumables. Depending on the outcome of that experimental program, NovaTech will then evaluate how best to implement such a preemptive remediation program on a DSC be it outside the storage overpack or transportation cask or in-situ if all of the weld heat affected zones are accessible.