SENSITIVITY STUDY ON THE EFFECTS OF NONDESTRUCTIVE EXAMINATIONS ON FAILURE PROBABILITIES OF REACTOR PRESSURE VESSELS

摘要

Reactor pressure vessels (RPVs) in nuclear power plants are important components that prevent non-ductile fracture considering neutron irradiation embrittlement as aging degradation and several types of transients. An analysis code called PASCAL for assessing failure frequencies of RPVs based on probabilistic fracture mechanics has been developed by the Japan Atomic Energy Agency. In failure frequency analyses, flaw size distribution in RPVs is one of the most important parameters, and it is determined by considering possible flaws generated during fabrication and the flaw-detection capabilities of nondestructive examinations (NDEs). Flaw-detection capabilities of NDEs are represented as probability of detection (POD) curves related to flaw sizes. In this study, the effects of NDEs on failure frequencies of RPVs are evaluated using PASCAL considering simplified POD curves in terms of minimum detectable flaw size, the smallest probability of non-detection (PND), and flaw size where POD value reaches the smallest PND.