A Revised Formulation of the Irradiation Assisted Stress Corrosion Crack Growth Rates for Neutron-Irradiated Stainless Steels for a Boiling Water Reactor

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 proposed and studied. This study optimized the crack growth rate (CGR) equation by revising the strain rate equation at the crack tip according to the irradiation dose. The Gao-Hwang equation was used for the crack tip strain rate when strain hardening occurred, and the Rice-Drugan-Sham (RDS) equation was used when strain hardening was small. It was confirmed that the proposed equation could predict experimental data of L-grade stainless steels more accurately than the previously developed CGR equation. In addition, a comparison was made between the CGRs with some model calculations. Among the three models, the proposed equation was the best and the PLEDGE (Plant Life Extension Diagnosis by GE) model was second in accuracy. The Eason and Pathania model adopted by the ASME (American Society of Mechanical Engineers) was third. It was thought that one of the reasons why the calculation results using the Eason and Pathania model were less in agreement with the experimental data was that the K dependence of the CGR was treated as constant regardless of the irradiation fluence.