DEMO double null architectural study

Highlights: • Results of a focused design study to investigate a double null DEMO architecture featuring split breeding blankets. • Several possible configurations were developed exploring some new design features, including a vertical lower port. • Initial studies enabled an evaluation of the different configurations and highlighted feasibility and main risks. DEMO is a key part of the EU fusion roadmap, and the programme reaches the end of the pre-conceptual phase with a gate review in 2020. As part of the work to complete this phase, eight Key Design Integration Issues (KDII's) have been identified as critical to the programme. Two of these KDII's identified a requirement for a more detailed architectural study. Within KDII#3 (advanced divertor configurations) a double null configuration has been developed; in parallel KDII#4 (vertical segment architecture) identified a need to evaluate a split breeding blanket architecture. These two requirements were combined into a single study that assesses the in-vessel architecture for a double null DEMO featuring split breeding blankets. This paper presents the configurations developed and an evaluation of their feasibility with respect to integration of key in-vessel components (breeding blankets, divertors), port hardware (service pipes, shielding, vacuum pumping), and maintenance strategy. Furthermore, wider considerations such as the impact of the port orientation on the building architecture are also included. Finally, this paper will identify the risks and further work required to advance the double null configuration.