Comparative analysis of the electromagnetic loads acting on the EU-DEMO divertor with alternative material options

This study is focused on the computation of the electromagnetic (EM) loads acting on the divertor of the EU- DEMO tokamak, related to the transients associated to plasma disruptions and to the ferromagnetic effects due to the use of materials with magnetic properties (EUROFER97). Specifically, plasma disruption events result in transient eddy and halo currents flowing into the divertor, which is then subjected to loads due to the interaction of the magnetic fields with these currents. This problem is here analyzed by using an Ansys- EMAG 3D magneto-quasi-static model simulating a toroidal sector of the tokamak that includes three divertors accurately detailed in their geometric features, and the main external components, such as blankets and vessel, described with a coarser definition. Equivalent current sources are used to impose the excitations associated to the considered conditions. The ferromagnetic effects are instead computed by using an Ansys- Maxwell magneto-static model, in which the EM loads are associated to the interaction between the magnetization of the ferromagnetic components and the known equilibrium magnetic field. The paper carries out a comparative analysis on the EM loads associated with different design options in terms of material choices for some components: (i) vertical targets support made of AISI 316 SS, EUROFER97 or CuCrZr; (ii) pipe manifolds and supports of the cooling system made of AISI 316 SS or EUROFER97; (iii) PFC tubes and manifolds insulated or not with respect to the vertical targets support; (iv) main tubes and supports insulated or not with respect to the cassette. The impact of these choices on the estimated value of the forces and moments acting on the divertor is discussed.