Stress Corrosion Cracking Growth Rates of Candidate Canister Materials for Spent Nuclear Fuel Storage in Chloride-Containing Atmosphere

Abstract

Chloride-induced stress corrosion crack growth rates were measured for candidate canister materials in a simulated marine atmospheric environment. Half-inch compact tension specimens were used to obtain stress corrosion crack growth rates by applying a direct-current potential-drop method to measure crack lengths. The crack growth rates of S31603 and S31260 stainless steels were 3×10⁻¹⁰ m·s⁻¹ and 4×10⁻¹³ m·s⁻¹ for an applied stress intensity factor of 30 MPa·m^0.5, respectively, at a test temperature of 353 K at a relative humidity of 35%. S31254 specimens did not show stress corrosion cracking susceptibility under the same conditions as above, suggesting their superior resistance to chloride-induced stress corrosion cracking. These data were consistent with the results that S31260 and S31254 stainless steels did not fail after up to 37700 h although S31603 failed after 533 h in constant-load tests under the same environmental conditions. Assuming active-path corrosion to be an anodic subprocess of stress corrosion crack growth, anodic polarization curves of the test materials were obtained in a synthetic seawater solution of pH 1 at 353 K. The maximum anodic current density of the active dissolution of S31603 stainless steel was ten times as large as that of S31260 stainless steel. This result qualitatively explains the difference in the crack growth behavior between S31603 and S31260 stainless steels.