Key design integration issues addressed in the EU DEMO pre-concept design phase

Abstract The EU fusion roadmap defines the development of a DEMO plant that achieves a long operation time and demonstrates tritium self-sufficiency and net electricity output. The pre-conceptual design phase will be concluded with a gate review in 2020. Eight key design integration issues have been identified as critical, either because the corresponding solution found in ITER is not suitable in DEMO or because the issues are DEMO-specific and not present in ITER. All of these will affect in their resolution the design and possibly the technology of several tokamak and plant systems or even the DEMO architecture: (i) Feasibility of wall protection limiters during plasma transients, (ii) integrated design of breeding blanket and ancillary systems, (iii) power exhaust taking advantage of advanced divertor configurations, (iv) tokamak architecture based on vertical blanket segments, (v) direct or indirect power conversion concept, (vi) configuration of plant systems in the tokamak building, (vii) feasibility of hydrogen separation in the torus vacuum pump and direct internal fuel recycling, and (viii) development of a reliable plasma scenario. For each of these issues potential solutions have been identified. In some cases alternative solutions are recognized and are addressed for risk mitigation. The key design integration issues (KDIIs) will be introduced and discussed in this article including results achieved so far and future work yet to be carried out.