Engineering challenges for accelerated fusion demonstrators

There are several programmes within the fusion community that are engaged in the design of fusion devices to follow the International Thermonuclear Experimental Reactor (ITER), referred to as 'demonstrators'. These programmes have identified many issues over the past decade, and research now concentrates on optimizing the combination of systems against a set of Key Performance Indicators (KPI) which may vary between programmes. While the return on investment in and experience from ITER is seen as an important factor in this research there are significant differences in the operational conditions and KPI of demonstrators that generate additional problems requiring different solutions. Among these problems are the necessary use of uncommon materials for structural and functional purposes, the impact of the availability KPI on basic machine design, configuration and component lifetime and the integration of the tritium fuel and thermodynamic cycles. These raise issues of component manufacture and standards and of resource availability in the required quantities and quality that are independent of device size and design. Interpreting 'accelerating fusion' in a wider sense, the impact of these issues, analysed in respect of developmental timescales, shows that a strategy of early engagement with the industrial supply chain and the development of computational engineering testing and verification will be essential to prevent prolonged timescales to fusion progress. This article is part of a discussion meeting issue 'Fusion energy using tokamaks: can development be accelerated?'