Surface Engineering Technologies to Mitigate Chloride-Induced Stress-Corrosion Cracking in Stainless Steel Dry Cask Storage Containments for Used Nuclear Fuel

Jinwook Choi¹, Kumar Sridharan², Hwasung Yeom^1,*

Received 2024-06-18 ; Revised 2024-07-12 ; Approved 2024-08-14

Abstract

Interim dry cask storage systems comprising AISI 304 or 316 stainless steel canisters have become critical for the storage of spent nuclear fuel from light water reactors in the Republic of Korea. However, the combination of microstructural sensitization, residual tensile stress, and corrosive environments can induce chloride-induced stress corrosion cracking (CISCC) for stainless steel canisters. Suppressing one or more of these three variables can effectively mitigate CISCC initiation or propagation. Surface-modification technologies, such as surface peening and burnishing, focus on relieving residual tensile stress by introducing compressive stress to near-surface regions of materials. Overlay coating methods such as cold spray can serve as a barrier between the environment and the canister, while also inducing compressive stress similar to surface peening. This approach can both mitigate CISCC initiation and facilitate CISCC repair. Surface-painting methods can also be used to isolate materials from external corrosive environments. However, environmental variables, such as relative humidity, composition of surface deposits, and pH can affect the CISCC behavior. Therefore, in addition to research on surface modification and coating technologies, site-specific environmental investigations of various nuclear power plants are required.

Key Words : Dry cask storage system, Peening, Burnishing, Cold-spray coating