PROBABILISTIC FRACTURE-MECHANICS ANALYSES OF NUCLEAR PRESSURE-VESSELSUNDER PTS EVENTS

This paper describes some recent research activities on probabilistic fracture mechanics (PFM) for nuclear reactor pressure vessels (RPVs) p erformed by the RC111 research committee of the Japan Society of Mecha nical Engineers (JSME) under a subcontract of the Japan Atomic Energy Research Institute (JAERI). To establish standard procedures for evalu ating failure probabilities of nuclear RPVs, we have performed PFM ana lyses for aged RPV under pressurized thermal shock (PTS) events. The b asic problems are chosen from some of US benchmark problems such as EP RI (Electric Power Research Institute) and US NRC (Nuclear Regulatory Commission) joint PTS benchmark problems and H.B. Robinson problems. E mployed in this study are four PFM computer codes developed in Japan a nd in USA. Various sensitivity analyses are performed to quantitativel y evaluate the influences of the input data, i.e. (a) initial crack sh ape, (b) the probabilistic distribution of initial crack depth, (c) cl adding, (d) RTNDT shift, (e) impurity content, (f) the through-wall di stributions of material properties, (g) pre-service inspection (PST) a nd (h) warm prestressing. It is clearly shown that in most cases, thes e data affect failure probabilities significantly. Therefore, we shoul d use in the PFM analyses as reliable input data as possible. If any r eliable data are not available, the data resulting in most conservativ e results could be chosen, referring the analysis results presented in this paper. (C) 1997 Elsevier Science S.A.