Quench Simulation of a DEMO TF Coil Using a Quasi-3D Coupling Tool

Abstract

In the framework of the EUROfusion DEMO project, design studies for the tokamak magnet systems are conducted across several European institutions. Superconducting magnets are required to generate the high magnetic fields needed for the plasma confinement and control. The reference conductor design is based on Cable-In-Conduit Conductors (CICC) cooled at cryogenic temperatures by forced circulation of supercritical helium. The proposed Toroidal Field (TF) coils Winding Pack (WP) design should satisfy the design/safety criteria during operation (e.g., minimal temperature margin) and in off-normal conditions (e.g., hotspot temperature). Quenches are studied to ensure that the proposed conductor design and associated quench protection system guarantee the integrity of the magnet; such events are a safety and investment protection issue, and as such deserve high levels of scrutiny. Quench propagation in a coil is a 3-dimensional (3D) problem. For this reason, a transient pseudo-3D modeling tool was developed for coupled thermal and thermo-hydraulic calculation in a tokamak superconducting coil. The coupling tool is based on a 1D model of the cable using the THEA code, considering current distribution, helium flow, thermal conduction in the strands and propagation of the quench along the conductor; the 2D transverse thermal diffusion across turns is modeled using the Cast3M code, considering the conductor jacket and insulation, on a selected set of cross-sections along the coil. The aim of the analysis is to assess the quench behavior of the CEA proposal for DEMO TF coil. The hotspot temperatures as well as the propagation of the normal zone along the conductor length are evaluated in a realistic quench scenario, taking into account the impact of transverse heat diffusion.