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 14 MeV neutron production limit of 2×1020 and requires more than 10 g of tritium. As well as maximising fusion power and investigating alpha particle behaviour, the series of experiments include the assessment of tritium retention and clean-up. An active gas handling system (AGHS) has been constructed and commissioned to supply tritium to the machine and to recover and analyse the process exhaust gases. In this fashion, the majority of tritium can be recycled, discharges to the environment minimised and tritium accountancy performed. As well as the separation of hydrogen isotopes, the AGHS, which has a design throughput of >l0 g/day and an inventory limit of 90 g, can recover tritium from impurities such as methane. Recovered tritium and deuterium can be supplied in both neutral beam and torus injection systems with up to approximately l g/pulse. The range of experiments during the DTE1 phase includes a number with low concentration of tritium in deuterium (∼1%) and D–D shots. The exhaust gas from the latter will contain significant tritium from wall interactions and the quantities of deuterium used may be significantly greater than the storage capacity of the AGHS. Accordingly, the AGHS must be capable of detritiating excess deuterium to discharge levels. In addition, there is an exhaust detritiation 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 evaporated layer during certain experiments. In-vessel Be components may also require to be modified on site. JET has a number of waste handling and 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 emphasis on the efficiency of tritium recovery for recycling and the environmental impact. The paper also describes the waste management and handling arrangements for tritiated and beryllium contaminated materials.