Stability of oxide films on stainless steel during simulated PWR shutdown and start-up conditions

摘要

The results of this work show that the stability of the compact part of the oxide film formed on stainless steel in VVER conditions is not greatly influenced by the injection temperature of hydrogen peroxide during a cool-down period. The stability of the film is somewhat higher after injection at 50 and 130 than at 90°C, but these differences are no more observed after the following heat-up period. This suggests that the injection temperature of hydrogen peroxide does not change the steady state corrosion rate of the steel. Therefore, the long term effects of hydrogen peroxide injections may remain rather insignificant. The injection temperature was on the other hand found to have a marked influence on the deposited crystals in the outer part of the film. Injection at 130°C resulted in the disappearance and/or transformation of these crystals to smaller ones, while injections at other temperatures had no such influence. These changes were found to remain even after the next heat-up. This kind of changes in the deposited layer may have an impact on the rate of incorporation of radioactive species on and in the oxide films.