熟疲労荷重下における損傷許容設計法（熱疲労荷重下のき裂進展特性の検討）

摘要

Thermal fatigue is one of critical problems in nuclear power plants. To prevent crack initiation, JSME has issued a guideline for design. In this study, the feasibility of incorporating crack growth analysis into the design and integrity evaluation was investigated. It was shown that the steep stress gradient near the surface significantly reduced the stress intensity factor of deep cracks. It is concluded that, under thermal fatigue loading, the cracks that are detected in the in-service inspection have already been arrested if they do not penetrate the wall thickness. The crack arrest scenario is a reasonable method of assessing the integrity of cracked components.%プラント配管の合流?分岐部などにおける流体のrn温度変化に起因する疲労（以後，熱疲労）によってきrn裂が発生する事象が報告されている．そして，熱疲rn労による損傷を防止するための設計指針が2003年にrn日本機械学会より発行された．この指針では，熱疲rn労荷重による損傷を線形累積隕傷則に基づいて評価し，rnき裂の発生を防止する手順が示されている．