Crack Prevention and Mitigation for New and In-Service Dry Storage Canisters

C56-41b-273026Welded stainless steel canisters at near-marine sites that contain spent nuclear fuel (SNF) have been found with salts on their outer surface that can produce an aggressive chemical environment. These conditions could lead to pitting, stress corrosion cracking (SCC), and potential release of radioactive materials. We propose to develop an innovative process and device for mitigating potential SCC in dry storage canisters for SNF. The process will eliminate high residual tensile stresses in the heat-affected zones of the welds using a safe and benign process that will not affect the mechanical strength of the canister. The process will be administered as a part of typical canister maintenance via minor modifications to existing service equipment and procedures. In Phase I, we will conduct accelerated corrosion tests to demonstrate our technology’s effectiveness on realistic canister weld samples over a broad range of environmental and canister conditions. As a part of these tests, we plan to use advanced imaging techniques to gain further insight into formation of crack networks in untreated samples and show how these processes are prevented or interrupted by our SCC mitigation process. We also plan to develop an approach for conducting these tests on full-scale mockups in the next phase of the project. Full-scale mockups will allow us to demonstrate our technology at temperatures and backfill gas pressures representative of actual storage canisters in the field. Creare’s system will ensure safe long-term storage of SNF. The process can treat canisters that are already loaded and deployed in the field or be used during manufacture of new canisters before loading. Creare will sell systems to managers of spent fuel storage facilities, manufacturers of SNF storage canisters and systems, and vendors of other large, welded structures to mitigate crack growth.