Safety management of remote handling and in-cell work for maintenance of spallation neutron production target components in J-PARC

Naoe, Takashi   ; Kinoshita, Hidetaka   ; Wakui, Takashi  ; Saruta, Koichi   

A mercury target vessel for a pulsed spallation neutron source in the MLF at J-PARC can be replaced by remote handling tools because it suffers radiation damage and cavitation erosion during the proton beam irradiation. Moreover, to study cavitation erosion quantitatively, we cut out remotely a specimen from the used target vessel inspect the surface of the specimen. These works are carried out in a hot cell of L40m W13m H12m. Before and after the remote maintenance, we entry the hot-cell for preparation and clean up works. For such works, we take safety measures for high-dose rate and residual contamination in the hot-cell as follows: install shielding to reduce dose rate in the hot-cell, make dose rate map and work plan based on the map, decide reasonable protective equipment depending on the tritium concentration in air, divide work area for contamination control. The result showed that external exposure of workers are lower than that the planned value and previous year although the dose rate in the hot-cell is increased by the ramp-up of beam power.