Tritium profiles in tiles from the first wall of fusion machines and techniques for their detritiation

Tritium profiles on a TFTR graphite tile exposed to D-D plasmas and a JET graphite tile from the first tritium campaigns were examined by full combustion, thermogravimetry and thermal desorption. Combustion measurements revealed that >98.9% of the tritium is trapped in a layer <50 mu m thick, the remainder being spread throughout the tile. The tritium distribution on the tile surface is not homogeneous. A significant fraction resides in the gaps between tiles. Graphite disks from the plasma-exposed side of JET tiles heated up to 1100 degrees C under a helium stream containing 0.1% hydrogen showed the highest tritium release rate at similar to 850 degrees C. The agreement between tritium measurements by full combustion and thermal release was reasonably good. Tritium on graphite tiles was released to >95% under a stream of moist air at about 400 degrees C. A large fraction of tritium can be removed from the tile surface with adhesive tape. (C) 2000 Elsevier Science B.V. All rights reserved.