Fracture Safety Analysis Concepts for Nuclear Pressure Vessels, Considering the Effects of Irradiation

One of the most important aspects of the growth of nuclear power has been the development and use of quantitative methods of analysis for insuring the reliability of plant components and for protecting the public health and safety. Nuclear pressure vessels have always received close attention with regard to their structural strength and reliability. This paper summarizes some of the fracture mechanics concepts now being considered for application to the safety analysis of nuclear pressure vessels. The effects of thickness, temperature, strain rate, and irradiation on fracture toughness are discussed in terms of their relevance to a safety analysis. The amount of neutron irradiation likely to be received by a light water reactor pressure vessel is examined in terms of reactor type and the thermal power level. The ranges of temperature and fluence that are of most importance with regard to irradiation effects data on pressure vessel steels are identified. An example safety analysis problem is included to illustrate the application of the concepts discussed.