Stress Corrosion Cracking Behavior of 508Ⅲ LAS for RPV in High Temperature and High Pressure B/Li Water Environment

The stress corrosion crack growth curves of 508Ⅲ low alloy steel (LAS) for reactor pressure vessel (RPV) in a high temperature and high pressure boron-lithium water environment simulating pressurized water reactor (PWR) were measured online by direct current potential drop method. The stress corrosion cracking susceptibility of the LAS in an oxygen-containing and chloride-containing environment was evaluated. The results show that under relatively low constant load conditions, the crack growth rate of the 508Ⅲ LAS was lower than the predicted curve of BWRVIP-60 Line 1 in a 300 ℃ boron-lithium water environment whether it contained oxygen or not. And the 508Ⅲ LAS had a high stress corrosion cracking tolerance to oxidizing media and low concentration impurity ions, but the sudden change of corrosive medium or load resulted in a rapid increase in crack growth rate. The stress corrosion cracking of the LAS in oxygen-containing or de-oxygenated water environment was dominated by transcrystalline cracking, and there was violent metal dissolution and oxidation at the crack tip. The formation of a large amount of oxide was the main reason for being “blunt” of crack tip and the decrease of crack growth rate.