Surveillance test program and assessment of structural integrity of reactor pressure vessels

Tobita, Toru

To maintain the structural integrity of reactor pressure vessels (RPVs) difficult to replace is one of the key safety issues in a nuclear plant operation. RPVs are operated in the ductile regime to prevent the non-ductile fracture of RPV that may lead to a catastrophic accident. Since RPV steel is subjected to neutron from the reactor core which causes a shift in ductile-to-brittle transition temperature, a surveillance test is performed to monitor the fracture toughness decrease due to neutron irradiation. The present paper gives an overview on how to perform the surveillance test and assess the structural integrity of RPVs in a long-term operation.