Spent Fuel Containment Corrosion Damage Mitigation

Schematic of dry cask storage used to contain spent nuclear fuel (NRC website)

Cold spray as a method to repair stress corrosion cracking in dry storage canisters

Dry cask storage is one of two types of storage used to contain spent nuclear fuel (SNF) in the United States. Dry casks are used as an interim storage option (about 20 years) while a more permanent solution is investigated. The SNF is contained in welded stainless steel canisters which are encased in a concrete shell. The dry casks are located outdoors, often in coastal environments. Due to residual stresses in the welds and the high chloride concentration of coastal environments, the welds are susceptible to stress corrosion cracking. Stress corrosion cracking in the canister welds could result in failure of the containment system and leak spent fuel into the environment.

Our work aims to use cold spray as a low heat input, low force solid state repair process for stress corrosion cracking. We hope to show that cold spray can be used to heal any stress corrosion cracks that may form in these welds.

To simulate stress corrosion cracking, thin EDM cuts were made on a 304L substrate. We have deposited 304L coatings under various conditions. Coating adhesion tests have also been conducted.

Future Work

Different 304L substrate types before and after deposition of 304L cold spray coating
  • Coating process optimization
  • Create samples with prototypical stress corrosion cracks
  • Fractography of adhesion test samples
  • Four-point bend tests to measure flexural strength
  • Salt spray corrosion tests
  • Helium leak tests
Mechanisms of SCC mitigation/ repair by cold spray: (i) compressive stresses, (ii) environmental barrier, (iii) powder extrusion into cracks.