Tolerance assessment and crack growth of chloride-induced stress corrosion cracking for Chinshan dry storage system

Abstract

Evaluating the susceptibility of canister used in Chinshan Independent Spent Fuel Storage Installation (CSISFSI) to chloride-induced stress corrosion cracking (CISCC) has been an aging management plan in an initial license period of 20 years. The presence of concentrated chlorides, temperature and relative humidity, and sufficient weld residual stress are the three key environmental conditions for atmospheric CISCC. A single 2-D model was used to simulate natural exposure of austenitic stainless steel (SS) of SS304 and SS304L dry storage system (DSS) for transportable storage canister (TSC). This model will calculate the temperature on the TSC surface based on CFD method. This study estimated RH and DRH on the TSC surface by the realistic environmental conditions (e.g., ambient RH, ambient temperature, and the temperature on the TSC surface) after 1st, 10th, and 20th years, respectively. The flaw tolerance to part-depth (PD) and through-wall (TW) critical flaw were evaluated, and the two-phase CGR induced by CaCl2 or MgCl2 of the TSC surface under 0.18 m height were predicted. The results show that the fastest CISCC CGR was on the bottom induced by CaCl2 in the 20th year, and the slowest CGR was at the 0.18 m of TSC induced by MgCl2 in the 10th year. The two-phase CGR trends were very close if the deliquescence threshold had been considered under different environmental conditions.