Recovery of tritium from different sources by the ITER Tokamak exhaust processing system

Plasma exhaust during D–D and D–T operation of ITER will certainly not be the only source for gaseous streams within the tritium plant from which deuterium and tritium need to be recovered. Besides the gases from other operational modes of the tokamak, such as deuterium or helium from glow discharge cleaning or the fluids from the retrieval of tritium from co-deposits, various other sources within ITER will generate tritiated waste gases which have to be processed. Since ITER does not have a dedicated system for the treatment of gaseous wastes, all the tritium needs to be recovered by the tokamak exhaust processing (TEP) system. Consequently the TEP system has many more duties than the name of this particular part of the ITER tritium plant may suggest. The TEP process is designed to be fully continuous and based on permeation of hydrogen isotopes through palladium/silver (first process step), heterogeneously catalyzed cracking or conversion reactions (second process step), and counter-current isotopic swamping (third process step). The overall decontamination factor of the three-stage TEP process for tritium removal from tokamak exhaust gas at a composition as specified for the DT phase of ITER is at least 108. Off-gases from this system can therefore be stacked via the normal vent detritiation system (N-VDS) of ITER after intermittent storage for decay of γ-active species in dedicated tanks.