DL-EPR Study of Neutron Irradiation in Type 304 Stainless Steel

Double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests and modified Strauss tests of neutron irradiated type 304 stainless steel (SS) were conducted to evaluate fluence dependence of degree of sensitization (DOS). DL-EPR tests of thermally sensitized type 304 SS were also performed. As for unirradiated SS, reactivation was not observed; however, it was observed for irradiated SS. The reactivation ratio of type 304 SS in DL-EPR tests increased with the increase of neutron fluence. This fluence dependence of intergranular corrosion susceptibility or DOS was also observed in the modified Strauss tests. These results suggested that Cr depletion may occur due to neutron irradiation, with the degree of Cr depletion or DOS increasing with increasing fluence. Finally, the relation between EPR test results and irradiation-assisted stress corrosion cracking (IASCC) susceptibility was considered. The Cr depletion at the grain boundary was seen as one of the dominant factors for IASCC.