Effects of irradiation on crack propagation during creep

In-reactor stress to rupture results in excess of 11,000 hours are reported. Stress rupture properties during in-reactor testing of AISI 316 CW were demonstrated to be greater than or equal to the unirradiated material properties. Failure strains of the pressurized tube specimens were found to be stress dependent with a minimum in failure strain occurring at 200 Mpa for unirradiated tests. Higher failure strains at lower stresses resulted from a transition in crack propagation mechanisms from triple point wedge cracking to grain boundary cavitation. Irradiation was found to shift to lower stresses the triple point cracking to cavitation transition. 18 figs., 20 refs