Tritium safety of fusion power plants

Tritium systems of a nuclear fusion plant, using the deuterium-tritium fuel cycle, has to ensure tritium safety during plant operation, and activated/tritiated materials management, during plant decommissioning. Accidents resulting in tritium releases to the environment may occur. It is important, therefore, to minimize the mobile tritium inventory by means of an adequate design and optimization of the plant tritium-bearing systems. Furthermore, the behaviour of tritium in the environment must be accurately studied, in order to take into account its oxidation and absorption by different materials. An experimental tritium-breeding module of DEMO fusion reactor is now under development in Russia. We plan to test it in the International Thermonuclear Experimental Reactor (ITER). The ceramic lithium orthosilicate will be used in it as tritium breeder. The Tritium Cycle System (TCS) will ensure tritium extracting and processing of gaseous mixtures containing tritium. The report contains the flow chart of the TCS using alloys producing hydrides. TCS assures highest possible autonomy and independence on ITER tritium plant at technological operations. The classification of the TCS modes of operation, adopted at the present stage of the module development, is described. The main initial events that may result in accidents are analysed. The maximum design accident and its consequences are considered. In particular, the maximum effective dose equivalent to the most exposed individual is calculated by means of the GEN II/FRAMES code. The flow sheet of technological operations at the maintenance and repair works and the System of Radiological Safety ensuring safety during these works is analyzed. Finally, some aspects of tritium decontamination from standpoint of waste handling are developed. In particular, material detritiation should be sufficient to allow clearance and recycling of less activated fusion materials.