Reactor Surveillance Test and Fracture Mechanics Evaluation of Irradiation Embrittlement in Reactor Pressure Vessel Steels

With special reference to a nuclear reactor surveillance test, a new evaluation procedure for the fracture toughness from Charpy Vee-notch data is developed. This procedure utilizes a recrystallization-etch technique to determine the crack tip energy dissipation (W_p) within an intense strain region or the dissipation rate (dW_p/da). These two parameters serve to characterize the crack tip resistance to cleavage-controlled fracture initiation. The effects of specimen geometry, strain rate, temperature and notch acuity on the cleavage-controlled fracture toughness transition are explained using a critical value of W_p or dW_p/da and a modified rate parameter. A feasibility of the new surveillance test procedure for evaluating the irradiation embrittlement of reactor pressure vessel steel, such as SA533B-1, is here verified experimentally, utilizing the Charpy or small compact tension specimen irradiated in a test reactor.