Effect of proton irradiation on reactor internal material in PWR primary water

The cracking mechanism seems to be related with radiation assisted cracking under a high fluence, stress, and temperature environment. The effect of dissolved hydrogen (DH) concentration on the IASCC propagation has been studied. It was noted that DH of 0 to 50 cc/kg accelerated the SCC in PWR environments. SCC was observed at up to 100 cc/kg of dissolved hydrogen. The crack growth rate was not increased at high dissolved hydrogen level, but a significant decrease of the average crack growth rate was observed for the lowest dissolved hydrogen. Frutani and Arioka also showed the same trend of DH effect of the SCC growth of stainless steel in a PWR environment. Proton irradiation on reactor internal material (Type 316 stainless steel) was carried out by using Michigan Ion Beam Facility. Microchemistry change on the irradiated sample was measured; Cr depletion and Ni enrichment were clearly observed as usual. In addition that, faulted dislocation loop was dominant above 3 dpa irradiation. Stress corrosion cracks were initiated and propagated in intergranular mode for all samples