Novel Plating Process for Mitigating Stress Corrosion Cracking in Dry Storage Canister Welds

Spent Nuclear Fuel is currently stored in Dry Storage Canisters (DSCs) above-ground at Independent Spent Fuel Storage Installations, which are licensed for up to 40 years under Title 10 of the Code of Federal Regulations (CFR) 72.42. The NRC has identified Stress Corrosion Cracking (SCC) at the welds in stainless steel DSCs as a concern. SCC is a particularly difficult problem because it is hard to detect and failures could cause leakage from the canister. The work we propose will ensure that this does not happen. Corrdesa proposes to address this problem by selective non-drip electroplating of the welds with materials that will be corrosion-resistant and fully compatible galvanically with the stainless steel canister. The chosen material and its thickness will be determined by accurate computational modeling of the coating in the worst-case environment that any DSC will experience using methods validated and accredited by the Department of Defense. This modeling will ensure that the coated welds will not corrode, and therefore will not fail by SCC, well beyond their storage lifetime. Phase 1 will determine the materials to be used, their thickness, their corrosion performance, and the optimum methods for depositing them on the DSC welds. This will be done by carefully modeling the environment that the DSCs will experience over their storage period and beyond, as they cool, measuring the structure and corrosion chemistry of the DSC weld material and the applied coatings, using this data to accurately predict the protection performance of the coatings. Using this data we will design the optimum method for depositing these coatings on all of the DSC welds. We frequently use this method of accurate corrosion analysis combined with optimized protective coating to protect aircraft and other complex and expensive equipment. The coating method we propose is simple, clean, and environmentally benign. All of the coating electrolytes are contained within a closed-loop that prevents operator exposure and contamination of the environment. There are numerous applications of this technology beyond the nuclear power industry, including corrosion protection of storage tanks for fuels, chemicals and gases, and it has also been demonstrated for corrosion protection of welds on space rockets.