Application of the master curve to assessment of nuclear reactor pressure vessels

摘要

In the early 1970s, ASME adopted an approach to estimate the lower-bound fracture toughness values used to assess the integrity of pressure vessels, including nuclear reactor pressure vessels (RPVs). This approach involves establishing an index temperature, RT_(NDT), which positions the K_(IC) and K_(IR) curves on the temperature axis. RT_(NDT) is determined through a combination of Charpy V-notch and NDT testing. Also, nuclear RPV surveillance programs currently rely on shifts of CVN trasnition temperature to estimate the effect of neutron irradiation on RT_(NDT) (see ASTM Standard E185-94 and U.S. NRC Regulatory Guide 1.99, Revision 2). All of these approaches use correlations to fracture toughness, rather than direct measurements of fracture toughness, due to the large specimen size required to measure "valid" linearelastic fracture toughness values.