European DEMO design strategy and consequences for materials

TLDR

Fusion power exploitation hinges on demonstrating net electricity and closed fuel‑cycle operation, and realistic performance targets and conservative technology choices are essential for selecting the technical features of the forthcoming DEMO reactor. The paper outlines the aims of a post‑ITER DEMO reactor and reviews European design options considered in current conceptual studies under the Horizon 2020 Roadmap. The study analyzes materials nuclear design requirements and radiation‑damage effects for a pulsed low‑extrapolation DEMO system, using mature technologies extrapolated from ITER and materials suited to the expected neutron fluence, within the European conceptual design framework. The paper critically discusses the main technical issues from plasma and nuclear loads, especially radiation‑damage impacts on vessel structural and heat‑sink materials.

Abstract

Demonstrating the production of net electricity and operating with a closed fuel-cycle remain unarguably the crucial steps towards the exploitation of fusion power. These are the aims of a demonstration fusion reactor (DEMO) proposed to be built after ITER. This paper briefly describes the DEMO design options that are being considered in Europe for the current conceptual design studies as part of the Roadmap to Fusion Electricity Horizon 2020. These are not intended to represent fixed and exclusive design choices but rather 'proxies' of possible plant design options to be used to identify generic design/material issues that need to be resolved in future fusion reactor systems. The materials nuclear design requirements and the effects of radiation damage are briefly analysed with emphasis on a pulsed 'low extrapolation' system, which is being used for the initial design integration studies, based as far as possible on mature technologies and reliable regimes of operation (to be extrapolated from the ITER experience), and on the use of materials suitable for the expected level of neutron fluence. The main technical issues arising from the plasma and nuclear loads and the effects of radiation damage particularly on the structural and heat sink materials of the vessel and in-vessel components are critically discussed. The need to establish realistic target performance and a development schedule for near-term electricity production tends to favour more conservative technology choices. The readiness of the technical (physics and technology) assumptions that are being made is expected to be an important factor for the selection of the technical features of the device.