Radiation Embrittlement of a PWR Vessel Steel: Effects of Impurities and Nickel Content

Nickel-manganese-molybdenum low-alloy steels are employed today for the beltline regions of French pressurized water reactor vessels subject to radiation embrittlement. Brittle ductile transition temperature shifts observed in Charpy V-notch tests were used to evaluate the effects of some elements on embrittlement. The role of residuals such as phosphorus, copper, and tin was carefully studied with special laboratory heats. The detrimental effects of phosphorus and copper were quantitatively determined, particularly for low copper content heats. Tin also appears to be undesirable. Silicon and nickel contents may be modified in the future. Their effects were examined. It was not possible to establish the role played by silicon. The detrimental effects of nickel additions were, however, clearly demonstrated. The effects of certain other oligoelements were also studied.