Design of a compact type cryogenic accumulator to mitigate a pressure fluctuation caused by a sudden kW-order heat load

Tatsumoto, Hideki; Aso, Tomokazu ; Otsu, Kiichi; Uehara, Toshiaki; Sakurayama, Hisashi; Kawakami, Yoshihiko; Kato, Takashi; Futakawa, Masatoshi  

A cryogenic hydrogen system provides supercritical hydrogen to three moderators and removes a nuclear heating of 3.75 kW for a 1-MW proton beam power at the J-PARC. It was verified that the pressure fluctuation caused by the sudden heat load for a 120-kW proton beam operation was successfully mitigated by a control system that consisted of a heater and a cryogenic accumulator with a bellows. However, an internal leak was found at the bellows during a maintenance period, in February 2010. The cryogenic accumulator was too big to replace it easily and it took a long period. Therefore, a new compact type cryogenic accumulator has been designed to improve the replacement. And it has been installed six months later after the major failure. It has been confirmed through an on-beam commissioning that the performance satisfies the design requirements.