Dynamic analysis of the forces on the COMPASS-U tokamak foundations during vertical displacement events

Abstract

The COMPASS Upgrade tokamak (B = 5 T, IP = 2 MA, R = 0.894 m, a = 0.27 m) requires strengthening of the existing foundations due to larger electro-magnetic (EM) loads occurring during plasma disruption events. The focus is given to the VDE as they create the largest EM forces. Due to the fast rate of change of these forces, dynamic effects were considered. In order to find the time evolution of the electromagnetic forces during the VDE disruptions, a 2D electromagnetic model has been created. Current values in the central solenoid, poloidal field coils and the vacuum vessel were obtained from the FIESTA code and the plasma was modeled with finite number of filaments with prescribed currents to model the vertical motion. The time evolutions of the electromagnetic forces during 500 ms were imported to a 3D mechanical model built in Ansys Workbench. The transient analysis was solved with the mode superposition method based on 100, 400 and 1000 modes. The extremum reaction forces acting on the foundations were found to be -12.6 MN and +12.7 MN