肉盛溶接による熱影響部の材質変化を考慮した原子炉圧力容器の溶接残留応力評価

Weld residual stress evaluation of reactor pressure vessel considering material property changes of heat-affected zone due to weld-overlay cladding

西川 弘之; 勝山 仁哉  ; 宇田川 誠; 中村 光行; 鬼沢 邦雄 

Nishikawa, Hiroyuki; Katsuyama, Jinya; Udagawa, Makoto; Nakamura, Mitsuyuki; Onizawa, Kunio

原子炉圧力容器の肉盛溶接及び溶接後熱処理による溶接残留応力を評価するため、熱影響部の材質変化を考慮した熱弾塑性クリープ解析を行った。熱影響部の材質変化を考慮することで、解析で得られた応力分布は平板型試験体から実測された応力分布によく一致した。この解析手法を用いて、原子炉圧力容器形状を模擬したモデルに対して、肉盛溶接,溶接後熱処理,耐圧試験,通常運転及び加圧熱衝撃時における応力分布を算出し、肉盛溶接が圧力容器の応力分布に及ぼす影響を評価した。得られた応力分布を用いて、PTS時におけるき裂を想定した際の応力拡大係数について検討を行った。

In order to evaluate residual stress distributions in the vessel wall of a reactor pressure vessel (RPV) due to weld-overlay cladding and post-weld heat-treatment (PWHT), thermal-elastic-plastic-creep analysis considering the changes of material properties in heat-affected zone (HAZ) has been performed. Analytical results of stress distributions considered the material property changes in HAZ agreed well with the ones measured experimentally from weld-overlay cladded plates. Applying the analysis method to a RPV model, through-wall residual stress distributions caused by weld-overlay cladding, PWHT, hydrostatic test, operational load and transient loads during pressurized thermal shock (PTS) events have been computed. Effects of the weld-overlay cladding on the stress distributions in the vessel wall of a RPV have been evaluated. Using the stress distributions, stress intensity factors for a postulated crack during PTS events have been studied.