Liquid metal MHD research at KIT: Fundamental phenomena and flows in complex blanket geometries

The present paper gives an overview of liquid metal research activities performed in recent years at the Karlsruhe Institute of Technology (KIT). The work is motivated by applications in liquid metal blankets for a DEMO fusion reactor where lead lithium (PbLi), which serves as a neutron multiplier and tritium breeder, interacts with the plasma-confining magnetic field as it flows in the blanket covering the inner walls of the reactor. Liquid metal magnetohydrodynamic (MHD) research at KIT supports blanket design activities through theoretical and experimental investigations. Predictive computational tools are developed and validated by empirical data obtained for fundamental problems, such as flows in non-uniform magnetic fields or magnetoconvective heat transfer from submerged obstacles. In addition, technological developments like pressure drop reduction by insulating flow channel inserts are pursued both theoretically and experimentally. Two complementary experimental facilities (MEKKA and MaPLE) provide a unique and versatile platform for MHD investigations at fusion relevant parameters. Using NaK as a model fluid in MEKKA allows experiments to be conducted at high Hartmann numbers in large complex geometries, such as scaled blanket mock-ups of ITER test blanket modules. For magneto-convection and heat transfer studies, MaPLE is well suited since it enables experiments with the prototypical fluid PbLi in test sections inclined at various orientations with respect to gravity. Some recent results have been selected to illustrate the broad spectrum of MHD activities at KIT.