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Highlights: [•] A three-stage compound cryopump could be used in fusion reactors. [•] Helium “ash” is adsorbed at 4.5K, and deuterium and tritium are adsorbed at 15–22K. [•] We used a free Direct Simulation Monte Carlo code (DS2 and DS2V). [•] 90% of the deuterium and tritium are successfully trapped at 15K. [•] Fuel is returned directly to the plasma, without isotopic separation or storage. [ABSTRACT FROM AUTHOR]

To prepare the DEMO conceptual design phase a number of physics and engineering assessments were carried out in recent years in the frame of EFDA concluding in an initial design configuration of a DEMO tokamak. This paper gives an insight into the identified engineering requirements and constraints and describes their impact on the selection of the technologies and design principles of the main tokamak components. The EU DEMO program aims at making best use of the technologies developed for ITER (e.g., magnets, vessel, cryostat, and to some degree also the divertor). However, other systems in particular the breeding blanket require design solutions and advanced technologies that will only partially be tested in ITER. The main differences from ITER include the requirement to breed, to extract, to process and to recycle the tritium needed for plasma operation, the two orders of magnitude larger lifetime neutron fluence, the consequent radiation dose levels, which limit remote maintenance options, and the requirement to use low-activation steel for in-vessel components that also must operate at high temperature for efficient energy conversion. [ABSTRACT FROM AUTHOR]

High energy neutrons produced in future fusion reactors will cause significant transmutation reactions in the breeder blanket, including the important tritium breeding reactions. The reaction rate for a given reaction type depends on the neutron spectrum and material properties. The inventory consequences for tritium production of a solid-type breeder blanket are discussed in this paper. A DEMO fusion reactor with 19 homogeneous breeder blanket modules made of Eurofer, helium, Be 12 Ti and Li 4 SiO 4 , with enriched Li 6 content. Each blanket module was segmented radially in order to analyse the time-dependent reaction rate as a function of depth. The resolution of radial segmentation was varied and 5 radial divisions were found to be sufficient to accurately model the tritium inventory. Time-dependent tritium production was simulated with the use of the interface code, FATI, which couples radiation transport code MCNP 6 with the inventory code FISPACT-II. The simulated results show how the tritium production varies over the expected lifetime of the blanket. The overall tritium production of the solid-type blanket decreases as the Li 6 and Li 7 are burnt up. The effect of Li 6 burn-up in the breeder zones nearest to the plasma is identified as the main contributing factor to the decreasing tritium production of the whole breeder blanket. [ABSTRACT FROM AUTHOR]

In normal operation the JET neutral beam injectors have the operating gas supplied to the ion source and the neutraliser. For tritium operation the gas is supplied to both the ion source and neutraliser at a point close to the earth grid (“grid gas”) due to the difficulty in producing a gas line with a secondary containment and a ceramic break for high voltage standoff. In preparation for the next JET tritium campaign the JET EP2 PINIs have been characterised with grid gas flow. This paper reports measurements of arc efficiency, species and divergence in both normal and grid gas operation with hydrogen and deuterium. The data is used to predict the performance in tritium operation. [ABSTRACT FROM AUTHOR]