Disruption induced mechanical loads calculated with a coupled 3-D eddy current/2-D MHD plasma model

For a more consistent determination of the disruption induced mechanical loads in tokamaks a 2-D magnetohydrodynamic plasma model was coupled to an existing 3-D eddy current code. Compared to previous publications of the author, where the plasma was assumed to be at rest, the main difference is that now the plasma movement in response to the induced eddy currents and magnetic fields is included. Because the plasma current and motion are treated as parts of the total dynamical system, the significance of the results could be improved considerably. The results of computations for three different tokamak geometries are presented. From these results it is concluded that the computational method describes the plasma behavior adequately and that the electrical design of the plasma facing components dominates the plasma current evolution and motion and thus the structural loads. Therefore presuming the same ‘design plasma disruptions’ for different structural designs, especially blanket designs, leads to considerable errors. Furthermore it is shown that for the present DEMO design the largest stresses will occur at the inboard blankets and that neglecting the poloidal halo currents the stresses generally do not exceed critical limits. The major advantage of the developed code lies in its applicability to structures with real 3-D character, which will have to be taken into account for future power reactors.