Development of non-destructive evaluation methods for degradation of HTGR graphite components

炉内黒鉛構造物の劣化の非破壊的評価技術の開発

柴田 大受 ; 角田 淳弥 ; 多田 竜也; 沢 和弘

Shibata, Taiju; Sumita, Junya; Tada, Tatsuya; Sawa, Kazuhiro

高温ガス炉(HTGR)の黒鉛構造物の劣化を非破壊的に評価する手法を開発するため、マイクロインデンテーション法の残留応力測定への適用性を調べた。実験にはIG-110とIG-430黒鉛を用いた。(1)HTTR条件での黒鉛ブロックの残留応力を解析し、VHTR条件ではさらに過酷な条件で使用されると考えられるため、長寿命化が重要な課題であることを示した。(2)数種類の圧子について圧子押込み特性を調べ、試験片の表面状態を感度よく検出するため半径0.5mmの球状圧子で5及び10Nの押込み荷重条件を選定した。(3)押込み量の平均値と試験片の圧縮応力との関連を実験式で示し、押込み特性から圧縮応力を評価できる可能性を示した。今後、統計的手法によりデータのばらつきを評価する必要がある。

To develop the non-destructive evaluation methods for degradation of HTGR graphite components, the applicability of the micro-indentation method to detect the residual stress was studied. The IG-110 and IG-430 graphites were used. (1) The residual stress in a graphite block at the HTTR in-core condition was analyzed. For the components in the VHTR which would be used at much severer condition, the development of lifetime extension methods was suggested as an important subject. (2) Micro-indentation behavior at stress free condition was investigated with some indenters. The spherical indenter R0.5 mm with indentation load of 5 and 10 N was selected to detect the specimen surface condition sensitively. (3) The relationship between the average indentation depth and compressive stress of the specimen was expressed by an empirical formula. It would be possible to evaluate the residual stress by the indentation. It is necessary to assess the data with statistic method in the future study.