Electro dynamic model of eddy currents in EU DEMO TF coil casing during major plasma disruption

Abstract

The conceptual design of the EU DEMO reactor is currently ongoing within the EUROfusion consortium. Many different fault transients must be considered and carefully analyzed in the design phase; one of the most severe is the major plasma disruption (MPD), which causes several drawbacks on the magnet system. During a disruption, the plasma current decreases extremely fast, causing a fast variation of the magnetic field, which in turn induces an electric field. In presence of conductive materials, e.g., coil casing and vacuum vessel (VV), the electric field induces large eddy currents which deposit power by Joule effect. The conductive regions are tightly coupled on different timescales through the magnetic field induced by the eddy currents: the eddy currents in the VV influence the magnetic field evolution in the TF coil casing, thus affecting the power deposition in the latter. The aim of this work is the evaluation of the power deposited within the TF coil casing during a major plasma disruption due to eddy currents. The power deposition has been evaluated by means of the 3D-FOX, a finite element (FE) tool developed at Politecnico di Torino. The computed power deposition is used as input to the thermal-hydraulic (TH) simulation, performed with the 4C code, with the aim of assessing the erosion of the temperature margin given by MPD.