Decontamination assessment for ITER blanket remote handling system

Saito, Makiko; Maruyama, Takahito; Ueno, Kenichi; Takeda, Nobukazu; Kakudate, Satoshi

In ITER, after plasma operation, The Blanket Remote Handling System (BRHS) will be installed in the vacuum vessel and it will remove and install the shield blanket module. BRHS will undergo hands-on maintenance in the maintenance area after the exchange of the shield blanket module. Since BRHS will be contaminated the radioactive dust in the vacuum vessel, the workers will be exposed by radioactive dust. In this study, potential contaminated areas and their respective dose rates from the BRHS using MCNP5 code to assess the exposure of maintenance workers. The assessment was performed using 3 types of equipment, vehicle manipulator, combination of cable handling and rail support, and sliding beam, which are installed in vacuum vessel or port. The dose calculations used the nuclides Ta-182 and W-181 and the dose was calculated from each of the 20 points spaced evenly around the equipment. As a result, there are some local points with high dose rates, which are exceed the target of acceptable dose limit for hands-on work in ITER (5 Sv/h) in vehicle manipulator and combination of cable handling and rail support. To decrease the dose rate, lead blocks were used for shielding and as a result, the dose rate decreased to around 2.5 Sv/h using 5 mm and 10 mm lead shielding.