The pre-concept design of the DEMO tritium, matter injection and vacuum systems

In the Pre-Concept Design Phase of EU-DEMO, the work package TFV (Tritium – Matter Injection – Vacuum) has developed a tritium self-sufficient three-loop fuel cycle architecture. Driven by the need to reduce the tritium inventory in the systems to an absolute minimum, this requires the continual recirculation of gases in loops without storage, avoiding hold-ups of tritium in each process stage by giving preference to continuous over batch technologies, and immediate use of tritium extracted from tritium breeding blankets. In order to achieve this goal, a number of novel concepts and technologies had to be found and their principal feasibility to be shown. This paper starts from a functional analysis of the fuel cycle and introduces the results of a technology survey and ranking exercise which provided the prime technology candidates for all system blocks. The main boundary conditions for the TFV systems are described based on which the fuel cycle architecture was developed and the required operational windows of all subsystems were defined. To validate this, various R&D lines were established, selected results of which are reported, together with the key technology developments. Finally, an outlook towards the Concept Design Phase is given.