Effect of Nanostructure Changes on Stress Corrosion Cracking of Proton Irradiated Nuclear Energy Structural Materials

Austenitic stainless alloys are used extensively as structural materials in the internal components of light water reactor (LWR) pressure vessels because of their relatively high strength, ductility, and fracture toughness. Irradiation-assisted stress corrosion cracking (IASCC) is main degradation process that affects LWR internal components exposed to radiation. The existing data on proton irradiated austenitic alloys were reviewed to evaluate the effects of key parameters such as material composition, irradiation dose on IASCC susceptibility of these materials in LWR environments. The significance of deformation nanostructure and stacking fault energy (SFE) changes in the material on IASCC susceptibility is also discussed. Results show that the IASCC susceptibility of the alloys increases with increasing irradiation dose and decreasing stacking fault energy. IASCC tends to initiate at locations where slip dislocation channels intersect grain boundaries. Localized deformation in the form of grain boundary sliding due to the interaction of slip channels and grain boundaries is likely the primary cause of the observed cracking initiation. It may play a key role in the underlying mechanism of IASCC in light water reactor core components.