The European DEMOnstration Fusion Power Plant (EU DEMO) is planned as an intermediate step between the ITER experimental reactor and the future prototype fusion power plant. The core of EU DEMO is a tokamak equipped with a fully superconducting magnet system, which includes six Poloidal Field (PF) coils. Two concepts of the PF winding packs (WP) are being developed by CEA IRFM (France) and EPFL-SPC (Switzerland) teams. Each of PF coils designed by CEA is double-pancake wound using a square NbTi Cable-in-Conduit Conductor with a central cooling channel. Our present work is focused on thermal-hydraulic analysis of the CEA design of the PF coils, based on the DEMO 2018 baseline. We performed simulations, using the THEA code by CryoSoft, of the behavior of each PF coil at normal operating conditions during the whole current scenario, which consists of Premagnetisation, Plasma Current Ramp-Up, burn and dwell phases. The aim of this study was to estimate the minimum temperature margin for each PF coil. We took into account the realistic magnetic field profiles along each conductor and heat loads due to the AC coupling and hysteresis losses. The obtained results serve as a verification of the proposed design with regard to the usual acceptance design criteria and provide information for further improvements and optimization of the PF winding packs design.

Figure caption:Location of the PF coils in the EU DEMO magnet system and schematic cross section of the PF conductor.

Keywords: EU DEMO, PF coils, thermal-hydraulic analysis, temperature margin