THE RECYCLING AND HANDLING OF TRITIUM AND BERYLLIUM AT JET

The D-T phase of the JET Project (DTE1) planned for early 1997 has a 1 4 MeV neutron production limit of 2 x 10(20) and requires more than 10 g of tritium. As well as maximising fusion power and investigating al pha particle behaviour, the series of experiments include the assessme nt of tritium retention and clean-up. An active gas handling system (A GHS) has been constructed and commissioned to supply tritium to the ma chine and to recover and analyse the process exhaust gases. In this fa shion, the majority of tritium can be recycled, discharges to the envi ronment minimised and tritium accountancy performed. As well as the se paration of hydrogen isotopes, the AGHS, which has a design throughput of > 10 g/day and an inventory limit of 90 g, can recover tritium fro m impurities such as methane. Recovered tritium and deuterium can be s upplied in both neutral beam and torus injection systems with up to ap proximately 1 g/pulse. The range of experiments during the DTE1 phase includes a number with low concentration of tritium in deuterium (simi lar to 1%) and D-D shots. The exhaust gas from the latter will contain significant tritium from wall interactions and the quantities of deut erium used may be significantly greater than the storage capacity of t he AGHS. Accordingly, the AGHS must be capable of detritiating excess deuterium to discharge levels. In addition, there is an exhaust detrit iation system which acts as a safety system for the torus in the event of major air or water leaks. Components removed from the JET machine, as well as being contaminated with tritium, may be contaminated with beryllium which is used for some in-vessel components and as an evapor ated layer during certain experiments. In-vessel Be components may als o require to be modified on site. JET has a number of waste handling a nd access facilities to enable operations on radioactive and beryllium contaminated items to be carried out safely and waste to be minimised . The results of the use of the AGHS are presented, with particular em phasis on the efficiency of tritium recovery for recycling and the env ironmental impact. The paper also describes the waste management and h andling arrangements for tritiated and beryllium contaminated material s. (C) 1998 Published by Elsevier Science S.A. All rights reserved.