Design features of the JET vacuum enclosure for safe operation with tritium

The JET (Joint European Torus) machine is intended for eventual operation with tritium-deuterium plasmas to produce very significant fusion reactions. Starting from the initial design concept, and then from its evolution resulting from operational experience and simultaneous theoretical studies, a consistent approach has been developed for the preparations needed for safer operations with D-T plasmas. The main machine vacuum components are inherently suitable as they were designed for tritium operation and are physically very strong, where necessary. Ongoing experience with certain components and appendages is indicating the detailed design changes necessary. Fundamental features of all-metal construction and double containment on weak points such as bellows create designs which have built-in primary safety. Work is in progress on detailed identification and rectification of weaknesses in the design. Tritium compatibility assessments of all subsystems are being undertaken as part of a safety approval program for the use of tritium in the JET