Balance of plant challenges for a near-term EU demonstration power plant

Balance of plant issues for the current baseline EU near-term demonstration power plant design (DEMO) have been assessed for the first time by exploratory power cycle modeling considering both Rankine (water/steam-based) and Brayton (helium-based) cycles, together with examination of the technology readiness, precedence and risk for components within each power cycle option. Fixed primary circuit designs were considered for DEMO with the assumption of near-term, ITER-like components with operational temperatures dictated by material performance. Cycle simulations indicate Rankine cycles are able to meet the required net plant efficiency target of 25% via incorporation of the divertor heat in the cycle with reheat and feed heating. By contrast, for the operational temperatures proposed, Brayton cycles offer very low plant efficiencies and cannot meet the electrical output target. A technology assessment demonstrates that the required water/steam-based plant for the Rankine cycle offers substantial operational precedence and low levels of technical risk for key components. Helium-based plant instead presents increased risk and limited component precedence, at these powers, for both the primary blanket circuit and any secondary Brayton cycle applications.

I. Introduction

Under the European Fusion Development Agreement (EFDA) Power Plant Physics and Technology (PPPT) work programme, the EU is undertaking a range of pre-conceptual research and development activities towards the realization of a demonstration power plant (EU DEMO) design that will be capable of construction in the 2030s. The top-level requirements of this near-term DEMO device include the demonstration of significant net electricity production (~several hundred MWs) with self-sufficient tritium fuel supply and the achievement of realistic availability targets.