An Optimized Equation of the Irradiation Assisted Stress Corrosion Crack Growth Rates for Neutron-Irradiated Stainless Steels for Boiling Water Reactors

Abstract Irradiation assisted stress corrosion cracking (IASCC) growth rate equations based on the Hashimoto–Koshiishi model, a mechanistic model that is in turn based on the slip oxidation mechanism, have been revised and optimized from a theoretical standpoint. This optimization involved revising the strain rate equation at the crack tip for doses higher than 4 dpa. The Rice–Drugan–Sham (RDS) equation was used for the materials at doses higher than 4 dpa since these materials show little strain hardening. It was confirmed that the optimized crack growth rate (CGR) equation could predict experimental data of L-grade stainless steels (SSs) more accurately than the previously developed CGR equation. In addition, a comparison was made between the CGRs obtained with model calculations. Among the three models considered, the optimized equation could predict the CGRs of irradiated L-grade stainless steels with greater accuracy than the PLEDGE (Plant Life Extension Diagnosis by GE) model and the Eason and Pathania model adopted by the ASME (American Society of Mechanical Engineers). However, as there are not enough CGR data at present in regions such as K < 10 MPa√m, it is desirable in the future to expand the dataset and verify the predictive accuracy of each model.