Structural integrity evaluation of reactor pressure vessels during PTS events using deterministic and probabilistic fracture mechanics analysis

決定論及び確率論的破壊力学解析によるPTS事象時における原子炉圧力容器の健全性評価

小坂部 和也*; 西川 弘之*; 眞崎 浩一*; 勝山 仁哉  ; 鬼沢 邦雄 

Osakabe, Kazuya*; Nishikawa, Hiroyuki*; Masaki, Koichi*; Katsuyama, Jinya; Onizawa, Kunio

日本電気協会規格(JEAC)の加圧熱衝撃(PTS)事象時の原子炉圧力容器(RPV)の健全性評価においては、決定論的に亀裂先端の応力拡大係数(SIF)と破壊靭性を計算し、PTS事象中にSIFが破壊靭性を超えなければRPVは健全と判断される。一方、確率論的破壊力学(PFM)解析手法は、さまざまなパラメータの不確かさを考慮して合理的に健全性を評価できる手法として、近年その有用性が着目されている。PFM解析では、亀裂進展確率や亀裂貫通確率を求めることができる。本研究では、PFM解析手法のJEACへの適用性を確認するため、決定論及び確率論的構造健全性評価を行い、初期亀裂等が亀裂進展確率等に及ぼす影響について解析的検討を行った。

To assess the structural integrity of reactor pressure vessels (RPV) during pressurized thermal shock (PTS) events, a deterministic fracture mechanics approach has been widely used. According to Japan Electric Association Code (JEAC), the stress intensity factors (SIF) at the crack tip and the fracture toughness are calculated. The structural integrity is judged to be maintained unless the SIF during PTS events is less than fracture toughness. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method has become attractive recently because uncertainties related to input parameters can be incorporated rationally. Probabilities of crack initiation and through-wall cracking can be obtained from PFM analyses. In this paper, in order to verify the applicability of a PFM method to JEAC, deterministic and probabilistic analyses have been performed and the effects of initial crack size on probability of crack initiation has been analyzed.