Mitsubishi Heavy Industries Technical Review
    Vol. 53 No. 4 (2016)   New Products & Technologies
    Technical Papers

    Completion of "Joyo" Experimental Fast Reactor Upper Core Structure Replacement
    - Development of Fast Reactor Core Internal Equipment Replacement method -

    Masahide Hara,
    Junya Tanaka,
    Hiroyoshi Okazaki,
    Kenichiro Odani,
    Kazuya Tamura,
    Takuma Teramae

    In the "Joyo" experimental fast reactor of Japan Atomic Energy Agency, the upper core structure was damaged due to an accident with the experimental equipment in the reactor vessel. Under high radioactive atmosphere (with fuel loaded) and with the inert gas boundary of about maximum of 160°C, the old upper core structure was extracted through a gap of millimeters by remote control and was replaced with a new upper core structure. Such unprecedentedly difficult operation was successfully completed after a prior study of the risks, design validation using a full-scale mock-up and operational training. This replacement contributed to the development of the fast reactor core internal equipment replacement method.