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Study for the Behavior of Tritiated Water Vapor on Organic Materials

Kazuhiro Kobayashi, Takumi Hayashi, Hirofumi Nakamura, Toshihiko Yamanishi, Yasuhisa Oya, Kenji Okuno

Fusion Science and Technology / Volume 52 / Number 3 / October 2007 / Pages 696-700

Technical Paper / The Technology of Fusion Energy - Tritium, Safety, and Environment /

In a fusion reactor of high safety and acceptability, safe confinement of tritium is one of key issues for the fusion reactor. Tritium should be well-controlled and not excessively released to the environment and to prevent workers from excess exposure. Especially, the hot cell and tritium facilities of ITER will use various construction materials such as the organic materials. The hot cell is maintained in the dry atmosphere very much, and the maintenance of the apparatus contaminated by high concentration tritium is assumed. Therefore, the hot cell may be contaminated by high concentration tritium. Since the epoxy paint which will be used as a paint on the wall of the hot cell was contaminated by tritium compared with metal material, it is very important to study the efficient decontamination of the epoxy paint from a viewpoint of the protection the excess exposure of the workers. For tritium decontamination processes, so-called 'soaking' effect is important. This effect is based on sorption of tritiated water vapor on the materials and subsequent desorption from them. Therefore, in order to develop for the optimal decontamination technique, the decontamination experiment was carried out as a function of water vapor concentration in the purge gas (N2) for epoxy paint, acrylic resin and butyl rubber. As the result, the desorption rate for the organic materials was evaluated by purging gas of N2, and then furthermore, the residual tritium on the organic materials was quickly removed by adding water vapor in purging gas. The effect of adding water vapor was found on the decontamination for the organic materials.

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