Influence of changes of material properties on the operating conditions of welded reactor pressure components

The factors which may influence operating conditions of reactor pressure components in respect of probable changes in properties of structural materials can be characterized by: material toughness, loading rate, temperature, enveloping medium, components quality and components thickness, water chemistry and neutron irradiation. The paper pays special attention to the fracture toughness values of materials used, and discusses the significance of some requirements as stated in US 10 CFR 50. This discussion is referred to the information provided by reactor vessel surveillance programmes. The conclusion drawn is that if cracks are detected in components during operation, the major criterion should be the critical crack size and/or the fracture toughness against crack instability Ksub(IC). (author)