Estimation of fracture toughness transition curves of RPV steels from Charpy impact test data

Abstract

The major concern for reactor pressure vessels (RPVs) in terms of integrity is the reduction in fracture toughness of materials due to radiation embrittlement. In order to ensure the structural integrity of RPVs, a very conservative approach has been employed since the first commercial operation of a nuclear power plant (NPP). RT NDT has been used as a principal parameter to indicate the degree of irradiated degradation in RPV material, which is determined using Charpy impact and drop weight tests based on the ASME code requirements. Charpy test is very practical and easy, but it does not provide the fracture toughness itself. Therefore, the Master Curve method, as a direct method to determine the fracture toughness of RPV, was investigated by a number of researchers during the last decade. An alternative approach is proposed in this paper to estimate the reference transition temperature, T 0, in the Master Curve method using Charpy impact test data, which are abundant for old NPPs. Two well-known correlations between Charpy absorbed energy and K Ic were used to estimate the fracture toughness transition curves.