High-temperature and high-pressure SCC device for synchrotron radiation diffraction experiments and application using an austenitic stainless steel

放射光を用いた高温高圧水中下におけるオーステナイト系ステンレス鋼の応力その場観察測定

山本 厚之*; 中東 重雄*; 寺澤 倫孝*; 三田村 徹*; 秋庭 義明*; 山田 孝幸*; Liu, L.*; 菖蒲 敬久  ; 椿野 晴繁*

Yamamoto, Atsushi*; Nakahigashi, Shigeo*; Terasawa, Michitaka*; Mitamura, Toru*; Akiniwa, Yoshiaki*; Yamada, Takayuki*; Liu, L.*; Shobu, Takahisa; Tsubakino, Harushige*

原子炉内シュラウドや再循環系配管で発生する応力腐食割れの機構解明を行うために、沸騰水中型原子炉と同じ環境である高温高圧水中下におけるオーステナイト系ステンレス鋼SUS316Lを用いた応力その場観察測定のための技術開発を行った。独自に開発したオートクレーブ内に鍵状に作成した試験片を固定し、沸騰水を流すことで高温高圧環境を模擬させた。このオートクレーブには10mm厚のサファイア窓があり、ここから高エネルギー放射光X線を入射、及び出射できる。このようにして、試料に内在する応力をsin法で観測することに成功した

Suppressing the stress corrosion cracking (SCC) by reducing the carbon content in austenitic stainless steels is apparently not effective on core shrouds used in boiling water reactors in Japan: trans-granular cracking was found in the shrouds. To clarify the mechanism of the cracking, in situ stress measurements on specimens under stretched conditions in hot water have been attempted in the present study. In situ experiments have been carried out at SPring-8. The SUS316L steel specimen was placed in the in situ device. Sapphire windows were used for the light path in the device. A sufficient diffracted beam intensity was obtained through two sapphire windows and water. The side-inclination method was used for measuring the stress exerted on the specimen. A 2 sin plot showed that a tensile stress was induced. The measured stress value is considered to be the summation of stresses owing to pre-straining, in situ loading and residual stress owing to surface grinding.