Low-Temperature Annealing: A Process to Mitigate Irradiation-Assisted Stress Corrosion Cracking

Abstract

Low-temperature (400°C to 500°C) annealing (LTA) treatments were conducted on type 304 (UNS S30400) stainless steel (SS) that had been irradiated to fast neutron fluences from 1.74 x 1021 n/cm2 to 2.95 x 1021 n/cm2 (E [energy] > 1 MeV). The purpose of these treatments was to restore the stress corrosion cracking (SCC) resistance of the unirradiated material. Certain treatments that were conducted at sufficiently high temperatures and for sufficient times were successful in restoring part or all of the preirradiation SCC and hardness properties. Complete restoration of the SCC properties was observed before restoration of the preirradiation hardness. SCC resistance was measured in constant extension rate tensile (CERT) and constant-deflection tests. The effectiveness of a given LTA treatment was found to depend upon the type of SCC test.