原子炉圧力容器鋼溶接熱影響部の監視試験片省略に関する検討,6; 非均質性と照射脆化を考慮した健全性評価

Investigation on surveillance specimen exclusion for heat affected zone (HAZ) materials of reactor pressure vessel (RPV) steels, 6; Structural integrity assessment based on inhomogeneity and irradiation embrittlement

勝山 仁哉  ; 眞崎 浩一; 鬼沢 邦雄 

Katsuyama, Jinya; Masaki, Koichi; Onizawa, Kunio

原子炉圧力容器鋼の溶接熱影響部(HAZ)に対する監視試験片の必要性判断に資するため、原子力機構にて開発してきた確率論的破壊力学解析コードPASCAL3に、多層盛溶接によるHAZの非均質性な材料特性分布や、HAZ組織ごとの破壊靱性のばらつき等を考慮可能な確率論的構造健全性評価手法を導入した。前報までに報告した母材及びHAZ組織ごとの中性子照射前後の材料特性試験結果をもとに、溶接入熱やPTS条件を変えて感度解析を行い、母材と同等か低靭性の組織が連続して存在する場合、その領域の破壊確率は母材と比べて同等か高い値を示す傾向がある等の知見が得られた。

In order to obtain the technical basis to judge the necessity of surveillance specimens from heat-affected zone (HAZ) materials, the evaluation method for the inhomogeneous properties of HAZ was improved. The structural integrity assessment procedure considering the inhomogeneity of HAZ in RPV welds was incorporated into probabilistic fracture mechanics analysis code PASCAL2 which has been developed at JAEA. Sensitivity analyses varying welding parameter and PTS condition were performed concerning initial fracture toughness properties and susceptibility for irradiation embrittlement of HAZ materials. Based on the comparison of results in crack propagation behavior between HAZ and base metal, it was shown that effectiveness of this procedure to evaluate the effect of inhomogeneity in HAZ on the structural integrity of RPV.