Speaker
Ivan Alessio Maione
(Institute for Neutron Physics and Reactor Technology)
Description
Off-normal operations in Tokamak reactors result in the induction of eddy currents that, coupled with the large magnetic field, impose strong electromagnetic forces (Lorentz’s forces) to fusion reactor components. In addition the presence of ferromagnetic material induces Maxwell’s forces as interaction between the magnetized material and the external magnetic field that are thus present also during normal operation. Maxwell’s forces, due to its nature, differs from Lorentz’s one and can give a significant contribution to the related total loads as shown, for example, in the EM analysis of the ITER TBM. For this reason a particular attention is here given to these forces that were not evaluated in similar previous works.
The EM analysis of a DEMO reactor configuration, elaborated by EUROFusion in 2015, is here presented. The FEM model, developed with ANSYS-EMAG, represents a 20° sector of the DEMO machine including coils, VV and inboard (IB) and outboard (OB) segments. The segments radial segmentation is defined considering the HCPB concept. Due to the complex internal structure of each segment, simplifications in the design and material properties have been considered. The impact of the made assumptions on the final results is explained in detail.
The results, obtained considering a major central disruption, show that Lorentz’s forces mainly induce a poloidal moment on the segment components approximately directed towards the plasma center. On the other hand, the Maxwell’s forces are predominantly in the radial direction towards the center of the machine following the gradient of the toroidal magnetic field as predicted by Kelvin’s formula. In particular, due to their high value (around 6 MN for a whole segment), these forces have to be carefully considered during the evaluation of the structural integrity of the segments as well as for the design of the attachment system between segment and VV.
Co-author
Ivan Alessio Maione
(Institute for Neutron Physics and Reactor Technology , Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany)
