EFFECT OF GAMMA-IRRADIATION ON STRESS-CORROSION BEHAVIOR OF AUSTENITIC STAINLESS-STEEL UNDER ITER-RELEVANT CONDITIONS

Stress corrosion crack growth tests were conducted on Type 316 SS and PCA sensitized to 5 C/cm2 at 100-degrees-C in deionized water with 10 ppm Cl-. A constant K test specimen was cyclically loaded at 1 Hz with an R of 0.5 and a DELTAK of 11 MPa square-root m in an autoclave immersed in a Co-60 source. Tests were conducted at 0, 2.3 X 10(2), and 6.5 X 10(5) rad/h. The average crack velocities were found to be 2.0 and 1.5 X 10(5) mm/cycle for the Type 316 SS and PCA, respectively, in the absence of gamma irradiation and 1.3 and 0.74 X 10(-5) MM/cycle, respectively, at both gamma fluxes. Gamma irradiation may have shifted the potential to more reducing rather than more oxidizing, as observed by others in high-temperature water with low 02 activity. This study suggests that there is no significant detrimental effect of gamma irradiation on the subcritical crack growth behavior of unirradiated Type 316 SS and PCA at ITER-relevant conditions.