Corrosion behavior of ion-irradiated stainless steel in simulated PWR primary water

Radiation effects on corrosion behavior were investigated by using Fe ion-irradiated cold-worked 316 stainless steel specimens immersed in a simulated PWR primary water of 320degC for 1000 h to clarify the IASCC mechanism from the viewpoint of corrosion. The oxide film was confirmed to be double-layered, the outer layer was Fe-rich spinel and the inner layer was Fe- and Cr-rich spinel, and the microstructure and microchemistry of the oxide film were the same as those known in unirradiated condition. At the surface, corroded grains and non-corroded grains were observed. Area fraction of corroded grains increased as the dose increased, suggesting that ion irradiation would promote corrosion. The increase of area fraction of corroded grains correlated with the product of average diameter and number density of dislocation loops, indicating that the formation of dislocation loop might relate to the irradiation accelerated corrosion of stainless steel. Preferential corrosion along grain boundaries was also found. (author)