Magnetostructural assessment of DEMO TF coils with ENEA Winding Pack configuration

The present paper deals with a multiphysics study of the DEMO Toroidal Field (TF) coils with Winding Pack (WP) layout proposed by the Italian agency ENEA. The latest WP configuration, so far designed adopting the Wind&React technique, is composed of 202 Nb3Sn rectangular conductors, with steel jacket thickness progressively increased from the plasma-facing side, arranged in 6 double layers. Each conductor is designed to carry an operative current of 73.4 kA (14.8 MAt for one TF coil) and to ensure the requirement of 12 T of magnetic peak field. The electromagnetic (EM) Lorentz forces have been preliminary evaluated with a magnetostatic 3D analysis at different instants of plasma scenario and then used to perform the 3D structural assessment of the TF coil. For both models (i.e., electromagnetic and mechanical), the WP has been represented as a homogenized material with the cyclic symmetry boundary conditions, allowing to reduce the computational effort. In the structural model, a preliminary design of outer inter-coil structures and gravity support have been included allowing them to identify critical locations in a reliable way. In addition to the EM loads at different plasma scenario instants also the cooling down has been considered as loading condition. The stress assessment on the steel Casing was performed, exploiting the stress linearization along several paths chosen in the most critical locations.