OXIDATION OF A PROTON-IRRADIATED 316 STAINLESS STEEL IN SIMULATED BWR NWC ENVIRONMENT

摘要

A proton-irradiated SUS316 stainless steel was exposed to the simulated BWR NWC environment for 70 hours during a constant extension rate tensile test and the resulted oxide film was examined using transmission electron microscopy. The oxide film on both the unirradiated and irradiated parts of the sample consists of an outer layer of hematite particles and an inner layer of (Fe, Cr, Ni)_3O_4 spinel. Formation of hematite under BWR NWC condition is consistent with the predication by the potential-pH diagram. Both the outer layer and the inner layer of the oxide film show a strong dependence on grain orientation. Some grains exhibit an inner layer thickness of 40-100 nm while some others have barely any oxidation. Persistent damage induced by proton irradiation did not show a strong influence on the oxidation process as the thickness structure and compositions of the oxide film on both the unirradiated and irradiated parts of the sample were very similar.