Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel Used for Dry Storage of Spent Nuclear Fuel

Abstract

Some dry cask storage system (DCSS) designs utilize austenitic stainless steel canisters surrounded by concrete shielding structures to store spent nuclear fuel (SNF) at Independent Spent Fuel Storage Installations (ISFSIs). ISFSIs that are located where chlorides can be deposited on the canisters may have the potential for initiating chloride-induced stress corrosion cracking (SCC). Susceptibility to chloride-induced SCC depends on the environmental conditions at the canister surface, including the following key parameters: temperature; relative humidity (RH); areal density, composition and aqueous concentration of deposited salts; and the stress state of the canister, particularly in the weld and the weld heat affected zone (HAZ). National and international literature was reviewed to understand threshold values and uncertainties associated with these key parameters. Current models have uncertainties associated with salt deposition rate, local humidity and aqueous chemistry on the canister surface, salt composition and water volume, gamma radiolysis, and laboratory test methods.