Optimization of the overall Toroidal Field Coil cryomagnetic system at the pre-conceptual design phase of the European DEMO fusion reactor

Abstract

Different superconducting conductor design options are considered for the Toroidal Field (TF) Coil magnets of the future European DEMO reactor. Four TF Winding Pack (WP) options have been proposed and consist of two layer-wound concepts and two pancake-wound concepts, each of them having specific conductor design. These TF WPs are cooled by supercritical helium forced flow driven by a cold circulator at about 4 K. At the pre-conceptual design stage, it is particularly relevant to also consider cryogenic system merits while designing the TF magnet system. Indeed, both cost drivers such as the superconductor amount and the refrigeration loads depend on the cooling parameters: temperature, pressure, mass flow/pressure drop across the conductor. Hence, these parameters shall be optimized in order to minimize the total cost for the cryomagnetic system. For the pancake-wound option designed by CEA, a new approach that combines the magnet design calculation and the refrigeration load calculation using CEA tools (an adapted version of MADMACS-TF code and the simulation library Simcryogenics) was implemented. An optimization problem that considers both magnet and cryogenic merits was assessed. This problem consists in optimizing the superconducting amount and the refrigeration loads while ensuring that the temperature margin of the superconductor remains at 1.5 K. This article presents the method for cost minimization and the information workflow between the different codes, as well as preliminary results. This method is relevant to optimize simultaneously the design of the magnets and the cryogenic system and to make comparisons between the different conductor designs during the next phase of EU DEMO, moving forwards to the conceptual design. With such a method, recommendations can be made to ensure that the combined investment and energetic consumption cost is kept as low as possible.