M. Glugla

The inner deuterium/tritium fuel cycle of ITER

Abstract Beyond the initial hydrogen phase of the International Thermonuclear Experimental Reactor (ITER) the Tritium Plant is essential for the operation of the machine as tritium will be produced from D –D reactions. The inner deuterium/tritium fuel cycle of the Tritium Plant comprises the Tokamak Exhaust Processing (TEP) system, the Storage and Delivery System (SDS) including the Long Term Storage (LTS), the Isotope Separation System (ISS) and the Analytical System (ANS) as major subsystems. Besides the supply of the deuterium and tritium fuel and other gases to the tokamak and the recovery of tritium from all off-gases of the machine the inner fuel cycle has quite a number of additional duties. Incoming and outgoing tritium shipments need to be handled, tritium accountancy is an essential requirement and tritiated streams from sources other than the tokamak need to be processed. Not only in view of the control of effluents and releases, but also for economic incentives as much tritium as possible needs to be recovered for reuse from all off-gases and waste streams within the Tritium Plant of ITER.

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

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.

The tritium fuel cycle of ITER-FEAT

The Tritium Plant of ITER-FEAT is essential for the operation of the machine after the initial hydrogen phase, as tritium will be produced from DD fusion reactions. Within the fuel cycle of the Tokamak deuterium and later also tritium will be provided to the Fuelling Systems, and the unburned DT fraction recovered from the exhaust gases. The design of the tritium fuel cycle has to be based upon well proven technology to assure the safe handling of tritium along with credible accountancy, low tritium inventory, low generation of wastes and a high reliability of all components throughout the lifetime of ITER-FEAT.

Design of the ITER tritium plant, confinement and detritiation facilities

Abstract This paper describes the design of the ITER tritium plant subsystems, layout in the tritium building and the construction plan. The tritium plant comprises tokamak fuel cycle processing systems, as well as tritium confinement and detritation systems. The plant processes tritiated gases received from the tokamak and other sources to produce the D, T gas streams for fuelling, and detritiates various waste streams including tritiated water before discharge to the environment. The plant has been designed to meet not only all anticipated plasma operation scenarios in the DD and DT phases with a wide range of burn pulse durations from short pulse (450 s) and long pulse (3000 s), but also safety requirements (minimization of equipment tritium inventory and environmental tritium release from different accidental events in tokamak and tritium processing subsystems, and reduction of workers’ tritium exposure, etc).

Successful experimental verification of the Tokamak exhaust processing concept of iter with the caper facility

One of the design targets for the Tokamak Exhaust Processing (TEP) system of ITER is not to lose more than 10-5gh-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 108 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 = 3.7*1010 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 108 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.

ITER DESIGN REVIEW : TRITIUM ISSUES

Abstract One of the key activities on ITER during 2007 is a Design Review covering selected high priority areas of the project in which a significant number of features of the design with the potential to compromise the achievement of some objectives of ITER have been identified. These issues are being addressed by a number of focussed working groups to develop solutions for these issues which will enhance operating margins, reliability and availability, and ensure compliance with the French licensing framework. One of the working groups has been set up to investigate tritium-related issues. The principal design features which are being addressed by this group and the proposed resolutions of these issues are described in the paper.One of the key activities on ITER during 2007 is a Design Review covering selected high priority areas of the project in which a significant number of features of the design with the potential to compromise the achievement of some objectives of ITER have been identified. These issues are being addressed by a number offocussed working groups to develop solutions for these issues which will enhance operating margins, reliability and availability, and ensure compliance with the French licensing framework. One of the working groups has been set up to investigate tritium-related issues. The principal design features which are being addressed by this group and the proposed resolutions of these issues are described in the paper.

Experience gained during the modification of the Caprice system to Caper

Abstract The experimental facility Caprice was designed to comply with the requirements for clean-up of tokamak exhaust gases. In the last 3 years simulated fusion exhaust gases containing 7 g of tritium have been processed with this facility achieving detritiation factors of up to 106. New requirements specifying detritiation factors of about 108 triggered the addition of a further tritium recovery step to the two already existing process loops. The main component of the third step is the so-called Permcat, a permeator–catalyst combination designed for isotopic swamping in a counter current mode. The upgrade of Caprice to the new system is now called Caper and involved the replacement of highly contaminated pipe work and the installation of an additional glove box, which houses the new components for the third loop as well as further equipment needed for the continuous operation of Caper.

TRENTA Facility for Trade-Off Studies Between Combined Electrolysis Catalytic Exchange and Cryogenic Distillation Processes

One of the most used methods for tritium recovery from different sources of tritiated water is based on the combination between Combined Electrolysis Catalytic Exchange (CECE) and Cryogenic Distillation (CD) processes. The development, i.e. configuration, design and performance testing of critical components, of a tritium recovery system based on the combination CECE-CD is essential for both JET and ITER. For JET, a Water Detritiation System (WDS) is not only needed to process tritiated water which has already been accumulated from operation, but also for the tritiated water which will be generated during decommissioning. For ITER, the WDS is one of the key systems to control the tritium content in the effluents streams, to recover as much tritium as possible and consequently to minimize the impact on the environment. A cryogenic distillation facility with the aim to investigate the trade-off between CECE-CD, to validate different components and mathematical modelling software is current under development at Tritium Laboratory Karlsruhe (TLK) as an extension of the existing CECE facility.

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

Abstract 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 10 8 . 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.

A Decade of Tritium Technology Development and Operation at the Tritium Laboratory Karlsruhe

Abstract The Tritium Laboratory Karlsruhe (TLK) has been designed to handle relevant amounts of tritium for the development of tritium technology for fusion reactors. This paper describes the tritium technology development and experience gained during the upgrade of facilities, interventions, replacement of failed components and operation of the TLK since its commissioning with tritium in 1994.