Tritium related studies at the JET facilities

JET is a unique facility in the preparation of ITER in that it is the largest operating fusion device and provides the closest plasma parameters to ITER. Furthermore, it offers the largest variety of heating possibilities, it has Be handling capability, and was built from the beginning to perform DT experiments and will be the only magnetic fusion device for the next decade able to study tritium related issues. Various research activities of importance for JET and ITER are performed within the EFDA JET Fusion Technology Task Force (FT-TF) involving the JET Operator (UKAEA) and several EU Laboratories. Some of the tritium related issues studied are reported here: Tritium in flakes and tiles: During the 1997 Deuterium-Tritium Experiment (DTE1) tritium accountancy performed within the Active Gas Handling System (AGHS) revealed clearly that a large fraction (up to 40%) of the tritium injected into the tokamak was trapped in the machine. At the end of the tritium clean-up campaign the tritium release rates were very small, but there were still 6 g tritium (17%) remaining in the machine. Inspection of the machine revealed the presence of flaking co-deposited carbon-hydrogen layers mainly at the inner water-cooled louvres. These flakes have a very high specific tritium activity and represent the main trap for tritium, as the tritium content measured in tiles was small in comparison. During the 2001 shutdown flakes from the sub-divertor region of the tokamak were collected remotely to help reconcile the tritium balance at JET. Detritiation of tritium contaminated materials: Due to the injection of 36 g tritium into the tokamak during DTE1 and the multiple reprocessing of 20 g tritium available in AGHS, components which were in contact with tritium are now contaminated. Special detritiation techniques are developed for components replaced during operations to allow waste disposal under economically sound and environmentally safe conditions. Development of water detritiation: Two batches of tritiated water collected at JET have been sent to Canada for reprocessing. As this route might not be available in the future, design studies of a water detritiation plant at JET are very important. Laboratory size plants with liquid phase catalytic exchange (LPCE) column have been built to test the performance of various packing materials and catalysts and to determine mass transfer for D and T between water and gas. Use of AGHS as a test bed for ITER: Special ITER components such as a PERMCAT reactor which is one of the main components of the ITER Tritium Exhaust Processing System, and cryo-panels of the same design as those to be used in the ITER cryo-pumps will be tested in the AGHS at JET under ITER-like conditions.