Recovery of damaged components in reactor vessel of the experimental fast reactor Joyo

高速実験炉「常陽」の原子炉容器内で変形した照射装置の回収

青山 卓史 ; 芦田 貴志 ; 伊東 秀明; 北村 了一

Aoyama, Takafumi; Ashida, Takashi; Ito, Hideaki; Kitamura, Ryoichi

高速実験炉「常陽」で、平成19年に発生した計測線付実験装置(MARICO-2)との干渉による燃料交換機能の一部阻害が発生している。この復旧のため、回転プラグに据え付けられ、MARICO-2との干渉により損傷した炉心上部機構を引き抜き、その孔から変形したMARICO-2を取り出す方法と装置を考案し、炉内での把持試験を経て、その手法が有効であることを確認した。

The experimental fast reactor Joyo is the first sodium cooled fast reactor in Japan. When the R/P was jacked down during the 15th periodical inspection, measured load of the hold-down shaft revealed an abnormal decrease. This indicated that anomaly occurred in the upper part of the in-reactor vessel storage rack. In order to investigate the cause of this, in reactor vessel observation was conducted. As a result of the MARICO-2 lift-up test, the basic function, mechanism and the procedure to retrieve bent subassembly stayed in the in-vessel storage pot is confirmed and it will be used to design and fabricate the retrieval device with the shielding cask as the next step. The experience obtained through the restoration work in Joyo will provided valuable prospect for further improvements of in-reactor vessel inspection and repair techniques in sodium-cooled fast reactors.