Irradiation Assisted Stress Corrosion Cracking of 304L and 347 Stainless Steel Alloys in Simulated PWR Primary Water

Abstract

The susceptibility of neutron-irradiated stainless steel of types 304L and 347 to irradiation- assisted stress corrosion cracking (IASCC) in a pressurized water reactor (PWR) primary water environment was examined using a miniature four-point bend testing method. Both alloys exhibited cracking in PWR PW condition at roughly the same minimum stress of 60% of the irradiated yield strength (YS). It was observed that dislocation channels (DC) played a prominent role in accelerating grain boundary (GB) oxidation and initiating cracks in SS304L, whereas deformation bands (DB) exhibited a similar role in SS347. In both cases, oxidation of GBs weakened their strength resulting in the early initiation of IASCC well below the YS. The cracking occurred through the oxide rather than the oxide-metal interface. Overall, the combined effect of GB oxidation and stress is believed to act as a precursor for IASCC initiation in both alloys.