Fusion nuclear technology issues studied on the JET facilities

The Joint European Torus (JET) machine was built from the beginning to perform DT studies and is for the next decade the only machine with DT capability. JET is thus the tokamak best suited for studies of various nuclear technology issues that will be of importance for future DT fuelled machines. The Active Gas Handling System (AGHS) built for the supply and reprocessing of tritium is still in operation to detritiate the exhaust gases and to provide the necessary ventilation during vessel openings because >1 g of tritium remain in the machine even 4 years after the DTE1 campaign. The tritium is bound in co-deposited layers and flakes formed mainly on the shadowed inner part of the divertor, and in the bulk of tiles. Areas of erosion and deposition are being identified and preliminary models for the material movement developed. Characterisation of the properties of tiles and flakes is very important to develop the best handling techniques. Due to the activation of the machine and the use of Be and T entry to the torus is limited by the need to minimise worker doses and is currently only possible in full pressurised suite. Work inside it is, therefore, performed with remote handling tools where practicable, e.g. the removal of the divertor septum and the collection of dust and flakes from areas below the divertor to achieve a more accurate tritium balance. Techniques need to be developed to reduce the tritium content in waste to permit disposal as low level waste (<12 kBq/g) and to recover tritium for re-use. Validation of activation models, understanding of the risks due to inhalation of tritiated particles and the local environmental impact of tritium are further important aspects. The paper presents various nuclear issues studied at JET due to activation and tritium.