Stress Corrosion Cracking of Austenitic Stainless Steels in Environments Relevant to Spent Nuclear Fuel Storage

Abstract

Localized corrosion and stress corrosion cracking (SCC) are potential degradation mechanisms for stainless steels (SS) during exposure to corrosive environments. When localized corrosion features are subject to stresses (either external or residual), a crack can nucleate and grow. One potential scenario under which chloride-induced SCC may pose a risk is the interim storage of spent nuclear fuels (SNF) in SS canisters. In the U.S., these SS canisters are located at interim spent fuel storage installations across the country. As canisters cool over time, dust deposition can lead to the formation of corrosive brines, which form by various salt compositions. Initial studies have shown significant influences of environment on corrosion severity and morphology, which may in turn influence crack nucleation and growth. Recent, compositional analysis of salts on the surface of interim SNF SS storage canisters has been carried out with representative brine mixing formulations developed for laboratory exposures. This presentation evaluates the corrosivity, specifically in-situ crack growth rates influenced by the electrochemical environment of the prepared brines as compared to saturated salts and other seawater surrogate brines. The crack growth rates, in-situ electrochemical measurements, as well as fractography will be discussed in terms of testing methodologies and potential risks for canister degradation. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This document is SAND2023-02249A.