原子炉圧力容器鋼の高照射量領域の照射脆化予測,6; 確率論的破壊力学に基づく健全性評価法の検討

Prediction of radiation embrittlement for highly irradiated reactor vessel steels, 6; Study on integrity assessment method based on probabilistic fracture mechanics

鬼沢 邦雄 ; 松澤 寛*

Onizawa, Kunio; Matsuzawa, Hiroshi*

高経年化した原子炉圧力容器の加圧熱衝撃時における構造健全性評価手法に関して、確率論的評価手法の検討を進めている。国内脆化予測式の改定や米国における規則改定案等の最新の知見をもとに、確率論的破壊力学解析コードPASCAL2を用いて、原子炉圧力容器の破壊確率解析を行った。初期き裂分布,照射脆化予測式や破壊靱性評価式等が破壊確率に及ぼす影響に関する知見を得た。また、決定論的評価と確率論的評価の結果を比較し、過渡事象によらず、破損確率と決定論的な安全裕度には良い相関があることが示された。

Concerning the structural integrity analysis method for aged reactor pressure vessel (RPV) during pressurized thermal shok (PTS) event, a probabilistic analysis approach has been investigated. Based on the survey on the proposed revision of the PTS rule in USA and the revision of radiation embrittlement prediction equation in Japan, probabilistic analyses of RPV integrity were performed using probabilistic fracture mechanics (PFM) analysis code PASCAL2. The effects of major factors affecting the integrity such as crack existing probability, radiation embrittlement prediction equation, fracture toughness equation have been studied. From the comparison of analysis results by deterministic and probabilistic methods, it was shown that the transient loading had little effect on the correlation between deterministic safety margin and corresponding probabilistic fracture probability.