Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kasugai, Yoshimi
no journal, ,
In J-PARC, some of the e-learning materials on general and radiation safety have been produced and utilized so far. In this presentation, we will introduce one entitled "Five Safety Rules to Know at First in J-PARC." The material consists of the 5 quizzes, answers, and comments for tips and rules related to safety handling of overhead cranes, gas-cylinders, machine tools and radioactivity, also including explanations on "Stop Work Policy" and the ALALA principle.
Naoe, Takashi; Kinoshita, Hidetaka; Wakui, Takashi; Saruta, Koichi
no journal, ,
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.
Naoe, Takashi; Saruta, Koichi; Teshigawara, Makoto; Kinoshita, Hidetaka; Wakui, Takashi
no journal, ,
At the pulsed spallation neutron source J-PARC, a liquid mercury target, three types of cryogenic liquid hydrogen moderators and a reflector are placed with a shielding inside a helium-filled vessel. In October, 2023, we accessed on the top surface of the shielding in the helium vessel, where 3 mm upper from target, and replaced a target diagnostic system for monitoring the beam induced acoustic vibration. To accomplish the hands-on-work safely, we took following safety measures: installation of a greenhouse with a local exhaust upon the helium vessel, define the upper limit of suspend work for dose rate (100 
Sv/h) and tritium concentration in air (0.1 Bq/cm
) in green house, wear air-line aspirator and anorak to prevent internal exposure, place fall prevention rope in addition to wear safety belt to eliminate the risk of fall from shield of 5m in height. The result showed that the tritium concentration in air in the greenhouse was successfully reduced to the background level after 4 hours of ventilation, and dose rate of work area was 40 Sv/h. Therefore, the workers completed hands-on-maintenance without any detectable internal exposure.