Understanding the Risk of Chloride Induced Stress Corrosion Cracking of Interim Storage Containers for the Dry Storage of Spent Nuclear Fuel: Residual Stresses in Typical Welded Containers

摘要

The majority of current dry storage systems used for spent nuclear fuel consist of a welded 304 stainless steel container placed within a passively-ventilated concrete or steel overpack. In service, atmospheric salts, a portion of which will be chloride bearing, will be deposited on the surface of these containers. As the canister surface cools over time, these salts will deliquesce to form potentially corrosive chloride-rich brines. Because austenitic stainless steels are prone to chloride-induced stress corrosion cracking (CISCC), the concern has been raised that SCC may significantly impact long-term canister performance. While the susceptibility of austenitic stainless steels to CISCC is well known, uncertainties exist in terms of the residual stress states that will exist at the container welds. A full-scale cylindrical mock-up was produced, and the residual stresses associated with the weldments in that structure characterized. Results to date indicate that residual stresses will be large and tensile in both the axial and hoop directions, extending through the thickness of the container wall.