Determination of tritium profiles in tiles from first wall of fusion machines and development of techniques for their detritiation

The tritium profiles in a TFTR graphite tile exposed to D-D plasmas and in a JET graphite tile employed during the first tritium campaigns in 1991 were examined in detail by full combustion, thermogravimetry, and thermal desorption. The combustion measurements showed that most of the tritium, i.e. > 98.9%, is trapped in a co-deposited and an implanted layer of less than 50 #mu#m thickness. The remainder of the tritium, i.e. < 1.1%, was found to be distributed homogeneously throughout the whole tile. The tritium distribution on the surface of the tiles is not homogeneous; measurements indicate that the concentration varies by a factor of up to 10. A significant fraction of the tritium was found in the gaps between the tiles. The concentrations of tritium on the upper edge of the lateral side of a tile were as high as 30% of those at the plasma-exposed side. However, the total tritium on the lateral sides of the tiles is only 5% of the tritium on the tile surface. A fraction of the co-deposited layer was found to be easily removable with adhesive tape from the tile surface. Graphite disks from the plasma-exposed side of JET tiles heated up to 1100 deg. C under a helium carrier gas containing 0.1% hydrogen showed the highest tritium release rate at about 850 deg. C. The agreement between tritium measurements by full combustion and thermal release was reasonably good. More than 95% of the tritium in the co-deposited layer of graphite tiles can be released by prolonged heating at about 400 deg. C under a stream of moist synthetic air. The implications of the observations and measurements carried out in this work on the development of detritiation methods for contaminated tiles are discussed. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:4672.262((99)53) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Communication and its Development in Autism Spectrum Disorders

Communication deficits are one of the core symptoms of Autism Spectrum Disorders (ASD)