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Dose Rate in the Reactor Room and Environment During Maintenance in Fusion Reactors

Koichi Maki, Satoshi Satoh, Hideyuki Takatsu, Yasushi Seki

Fusion Science and Technology

Volume 27 / Number 2 / March 1995 / Pages 176-182


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According to the International Thermonuclear Experimental Reactor (ITER) conceptual design activity, after reactor shutdown, damaged segments are pulled up from the reactor and hung from the reactor room ceiling by a remote handling device. The dose rate in the reactor room and the environment is estimated for this situation, and the following results are obtained: First, the dose rate in the room is >108 µSv/h. Since this dose rate is 107 times greater than the biological radiation shielding design limit of 25 µSv/h, workers cannot enter the room. Second, lenses and optical fiber composed of glass that is radiation resistant up to 106 Gy would be damaged after <100 h near the segment, and devices using semiconductors could not work after several hours or so in the aforementioned dose-rate conditions. Third, during suspension of one blanket segment from the ceiling, the dose rate in the site boundary can be reduced by one order by a 23-cm-thicker reactor building roof. To reduce dose rate in public exposure to a value that is less than one-tenth of the public exposure radiation shielding design limit of 100 µSv/yr, the distance of the site boundary from the reactor must be greater than 200 m for a reactor building with a 160-cm-thick concrete roof.

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