Problematics due to tritium in materials in the nuclear field - some examples

After a presentation of the tritium sources in our environment, is evoked succinctly the different ways to produce it. Then, for each reactor type, are presented the main problematics due to tritium. In this part, the questions of tritium transfer are illustrated for fission reactors: pressurized water reactors, CANDU reactors and for fast neutrons reactors. The case of fusion tokamaks is described more particularly. Several aspects are presented successively: the requirement to produce it in-situ with fitted materials, the definition of a short fuel cycle allowing to recover important quantities of tritium having not react...In a last part, are presented the aspects directly induced by the behaviour of tritium in materials. The first point concerned is the control of the tritium inventory in a fusion tokamak, for safety reasons. Examples are given from experiment feedback on running fusion tokamaks. A projection at the ITER case is proposed. The mechanisms leading to tritium retention according to the materials considered at the present time are analyzed and synthesized. The second important point is the tritium management at the end of the tokamak running. The specific problematics of this management are presented. (O.M.)