SCC growth behavior of BWR core shroud materials

Recent studies suggest that material hardening should cause enhancement in stress corrosion cracking (SCC) growth rate of stainless steels (SS). In this study, SCC growth rates of SS irradiated up to 1.2×1025 n/m2 and of un-irradiated SS were measured in order to obtain the reasonable estimation for SCC growth behavior in the core shrouds, using 0.5, 0.7, 1.0T-CT specimens prepared from the actual BWR components (a core shroud made of 304SS and a top guide made of 316SS) as well as 0.5T-CT specimens prepared from H3 and H4 shroud weld mock-ups made of 316L. In irradiated SS, SCC growth rate in actual core shroud of high fluence was estimated later to be 10−10 m/s. In un-irradiated SS, all SCC growth rates were below the K-da/dt disposition curve of the JSME NA1-2002 standard, and this fact suggests that the degree of hardening assumed in the actual shrouds’ heat-affected zone (HAZ) should bring little enhancement effect in SCC growth rates.