Microstructural Characterization of Proton Irradiated 304L SS at 100°C and 360°C

摘要

Irradiation assisted stress corrosion cracking(IASCC) is a complex failure mechanism for whichmaterials exposed to neutron irradiation become moresusceptible to SCC with increasing fluence and is anactive degradation mechanism for stainless steels (SSs) inreactor cores. While proton irradiation has been used toemulate reactor core conditions at a fraction of the timeand cost, with reduced activity, it’s been limited inapplicability partly due to a shallow penetration depth.CNL has developed IASCC initiation testing capabilitiesfor proton irradiated specimens utilizing actively loaded,blunt-notch tensile specimens and in situ crack detectionvia direct current potential drop (DCPD). The goal is toextend the applicability of proton irradiated specimens toinclude such a technique to understand the mechanisms ofcrack initiation. To this end, Grade 304L SS wasirradiated with 3MeV protons using irradiationtemperatures of 360±10°C and 100±20°C to emulateneutron irradiation damage in a sink dominated/voidswelling regime for two cases: SS in the core of a boilingwater reactor or pressurized water reactor (288-330?C)and SS at the periphery of a CANDU reactor core(<150°C). Post-irradiation defect analysis has beenperformed using high resolution transmission electronmicroscopy (TEM) and atom probe tomography (APT) atthese two temperature regimes. TEM has been used tocharacterize the size and density distributions of cavities,loops, and assess radiation induced segregation at grainboundaries. APT is used to characterize clusterformation, and radiation induced segregation. This paperwill discuss the implications of the microstructure withrespect to IASCC susceptibility.