Comparison between fracture mechanics evaluation methods in ASME Boiler & Pressure Vessel Code, section XI and those in JSME leak-before-break evaluation guidelines for sodium-cooled fast reactors

ASME Boiler&Pressure Vessel Code Section XIとJSMEナトリウム冷却型高速炉破断前漏えい評価ガイドラインにおける破壊評価法の比較

矢田 浩基 ; 高屋 茂  ; 町田 秀夫*

Yada, Hiroki; Takaya, Shigeru; Machida, Hideo*

ASME Boiler and Pressure Vessel code (BPVC), Section XI, Division 2をナトリウム冷却高速炉に適用するために必要となる追加規定の検討が進められている。ナトリウム冷却炉用の追加規定案では、ASME Code Case N-875を基にナトリウム内包機器に対して連続漏えい監視が試験要求として採用されており、連続漏えい監視を有効なものとするために破断前漏えい(LBB)評価が求められる。しかし、ASME BPVCにはナトリウム炉に適用可能なLBB評価法が無いため、JSMEで開発されたLBB評価ガイドラインの採用が提案されている。本研究では、亀裂を有する構造物の不安定破壊評価法に着目し、ASMEにおける既存評価法とLBB評価ガイドラインの手法の違いを分析した。

ASME Boiler and Pressure Vessel code (BPVC), Section XI, Division 2 provides requirements for protecting passive components that affect reliability of the plant. It generally consists of technology-neutral common requirements, and additional ones for individual reactor types. Currently, an Appendix for sodium-cooled fast reactors (SFRs) is being developed based on Code Case N-875. In the Code Case, continuous leakage monitoring was employed as inspection method for components retaining liquid sodium. It is also important to introduce leak-before-break (LBB) assessment procedures in the Appendix because demonstration of LBB is necessary to show the adequacy of applying continuous leakage monitoring to the component of interest. However, LBB assessment method is not provided in ASME BPVCs. On the other hand, recently, LBB assessment guidelines for SFRs has been developed by the Japan Society of Mechanical Engineers (JSME). It could be used to prepare LBB assessment procedures for the Appendix, but it needs to confirm the consistency with ASME BPVC Sec. XI. In this study, fracture evaluation methods for pipes with through-wall crack are compared between JSME LBB assessment guidelines and applicable evaluation method in ASME BPVC Sec. XI, Div. 1.