ITER is the first fusion machine fully designed for operation with equimolar deuterium–tritium mixtures. The tokamak vessel will be fuelled through gas puffing and pellet injection, and the Neutral Beam heating system will introduce deuterium into the machine. Employing deuterium and tritium as fusion fuel will cause alpha heating of the plasma and will eventually provide energy. Due to the small burn-up fraction in the vacuum vessel a closed deuterium–tritium loop is required, along with all the auxiliary systems necessary for the safe handling of tritium. The ITER inner fuel cycle systems are designed to process considerable and unprecedented deuterium–tritium flow rates with high flexibility and reliability. High decontamination factors for effluent and release streams and low tritium inventories in all systems are needed to minimize chronic and accidental emissions. A multiple barrier concept assures the confinement of tritium within its respective processing components; atmosphere and vent detritiation systems are essential elements in this concept. Not only the interfaces between the primary fuel cycle systems – being procured through different Participant Teams – but also those to confinement systems such as Atmosphere Detritiation or those to fuelling and pumping – again procured through different Participant Teams – and interfaces to buildings are calling for definition and for detailed analysis to assure proper design integration. Considering the complexity of the ITER Tritium Plant configuration management and interface control will be a challenging task.

The ITER tritium systems

Publisher Summary This chapter discusses the synthesis, characterization, and applications of palladium membranes. The main role of the membrane film is to control the exchange of materials between two adjacent fluid phases. A membrane is able to act as a selective barrier, which separates different species either by sieving or by controlling their relative rate of transport through itself. Transport processes across the membrane are the result of a driving force associated with a gradient of concentration, pressure, temperature, and electric potential. The synthesis of stable microporous or dense inorganic materials for the preparation of membranes is the key factor for increasing the application of membrane-based reactive separations in the catalysis field. An important step before using a membrane in a separation or a reaction system is its characterization in terms of permeation as well as morphology.

Synthesis, characterization, and applications of palladium membranes

One of the design targets for the ITER Tokamak Exhaust Processing system is not to lose more than 10−5 g h−1 into the Normal Vent Detritiation System of the Tritium Plant. The plasma exhaust gas, therefore, needs to be processed in a way that an overall tritium removal efficiency of about 108 is reached. Such a high decontamination factor can only be achieved by multistage processes. The third step of the three step CAPER process developed at the TLK is based on a so-called permeator catalyst (PERMCAT) reactor, a direct combination of a Pd/Ag permeation membrane and a catalyst bed. The PERMCAT principle is based on isotopic swamping in a counter current mode. Previous tritium experiments employing laboratory scale PERMCAT reactors have revealed decontamination factors as high as 105 for the third CAPER step. First tritium tests with a technical scale PERMCAT reactor led to similar decontamination factors and clearly demonstrated that the required overall ITER decontamination factor can be reached with a technical PERMCAT as the final clean-up step of the CAPER process.

Tritium tests with a technical PERMCAT for final clean-up of ITER exhaust gases

Overview of R&D at TLK for process and analytical issues on tritium management in breeder blankets of ITER and DEMO

One of the design targets for the Tokamak Exhaust Processing (TEP) system of ITER is not to lose more than 10 -5 gh -1 into the Normal Vent Detritiation system of the Tritium Plant The plasma exhaust gas therefore needs to be processed in a way that a tritium removal efficiency of about 10 8 with respect to the flow rate is achieved Expressed in terms of tritium concentrations this corresponds to a decontamination from about 130 gm -3 down to about 10 -4 gm -3 (about 1 Cim -3 = 37*10 10 Bqm -3 ) The three step reference process for the TEP system of ITER is called CAPER and has been developed and realized at the Tritium Laboratory Karlsruhe (TLK) After the successful commissioning of the PERMCAT reactor as the key component of the third step detailed parametric tritium testing of the 3 steps involving the processing of more than 300 g tritium has been carried out and decontamination factors beyond the design requirements have been demonstrated for each process step and for the process as a whole Not only the decontamination factor of 10 8 as required by ITER, but also the operational mode of TEP as a waste dump for gases from diverse sources has been experimentally validated with the CAPER facility

R.-D. Penzhorn

Papers

A Permcat reactor for impurity processing in the JET Active Gas Handling System