Tritium depth profiles in 2D and 4D CFC tiles from JET and TFTR

Carbon fibre composite (CFC) is currently the candidate material for the vertical target tiles in the International Thermonuclear Experimental Reactor (ITER) divertor because of its superior thermomechanical properties. However, its affinity for hydrogen isotopes and their co-deposition with eroded carbon may severely limit ITER plasma operations. Recently tritium depth profiles in divertor tiles retrieved from the Joint European Torus have been obtained by the coring/full combustion technique. The results revealed that a surprisingly large fraction (up to 61%) of the retained tritium had diffused deep into the bulk of the tile, most probably between the woven sheets of the CFC. Additionally, the coring/full combustion technique has shown that only the surface tritium (few ten μm) is efficiently released by air baking while the bulk tritium is almost not affected. Baking the tile under air even at 500 °C does not detritiate the bulk.