Off-gas processing system operations for mercury target vessel replacement at J-PARC

Kai, Tetsuya   ; Uchida, Toshitsugu; Kinoshita, Hidetaka   ; Seki, Masakazu; Oi, Motoki ; Wakui, Takashi  ; Haga, Katsuhiro  ; Kasugai, Yoshimi  ; Takada, Hiroshi   

At J-PARC an Off-gas processing system has been utilized to a purging process before the target vessel replacement and an air-flow control procedure to minimize radioactivity release during the replacement. In 2011 the first replacement was carried out after a 500 MWh operation, and the tritium release was measured. It was suggested that the tritium release must be less than that measured at the replacement in 2011 even at the nominal operation of 5,000 MWh. Some procedures of an air-flow control and a rubber plug insertion have been introduced from the replacements in 2013, resulting that the amount of tritium release could be reduced to less than that released in 2011 at the nominal operation.