Irradiation-assisted stress corrosion cracking of austenitic alloys in supercritical water

Four commercial austenitic alloys, 316L, D9, 690 and 800H were irradiated with 2.0 MeV protons to doses of up to 7 dpa at temperatures of 400 and 500 °C to study the role of irradiation and temperature on stress corrosion cracking in supercritical water. Constant extension rate tensile (CERT) tests were performed on the irradiated specimens in deaerated supercritical water at the same temperature as the irradiation. The results showed that irradiation significantly increased the severity of intergranular stress corrosion cracking in all four alloys. Cracking severity increased with dose and temperature. The severity of cracking correlated with both the hardness and the grain boundary chromium concentration, making attribution to a single irradiation feature difficult. However, a very significant increase in cracking of alloy 690 at 500 °C is likely due primarily to RIS rather than to hardening. Cracking of the irradiated alloys in supercritical water follows the same behavior as in subcritical water, implying that a common mechanism may be controlling.