Design and feasibility of a pumping concept based on tritium direct recycling

In the DEMO Pre-Concept Design Phase, a novel fuel cycle architecture has been developed that aims at reducing the tritium inventory of the plant. In contrast to previous designs, the central role thereby is taken by an additional direct internal recycling loop. By already separating a significant proportion of the fuel at the pumping duct and providing this purified gas almost directly to the injection systems, the load on the tritium plant as well as the overall plant tritium inventory is reduced substantially. This paper summarizes the activities conducted in regard of integration and presents the results (aka the key design integration issues) for the design and feasibility of a pumping concept based on tritium direct recycling. The focus is on the aspects of integration of such a fuel separation function with the main technologies involved. In the functional position foreseen, these environment conditions mainly are space constraints, strong magnetic field, and the limited amount and restrictions in occupation of suitable ports. Two technical implementations for providing the fuel separation function have been identified: A metal foil pump relying on the physical phenomena of superpermeation of hydrogen through a metal membrane is able to provide continuous gas transfer. A multi-stage cryopump utilizing gas specific cryogenic trapping on several stages. Relying on gas binding, it only can operate intermittently. Within this activity, these variants are specifically reviewed for their suitability also to provide criteria for a future down selection.