Electric potential on a WCLL TBM mock-up in MHD experiments as indication for flow distribution in breeder units

The distribution of electric potential on the surface of a scaled mock-up of the water-cooled lead lithium test blanket module for ITER has been measured in magnetohydrodynamic experiments using the MEKKA facility at the Karlsruhe Institute of Technology (KIT). The electric potential is a physical quantity that can be recorded with high accuracy. For strong magnetic fields, i.e. for high Hartmann numbers, the potential may be considered as approximate hydrodynamic stream-function of the liquid metal flow, from which the core velocity is obtained by differentiation. Moreover, experimental potential data may be directly compared with numerical simulations for both validation of computational tools and interpretation of measurements. Experimental and numerical data of potential confirm anticipations from measured pressure values that the major fraction of the flow in breeder units occurs near both ends of the module, while in a larger central domain the flow is almost negligible.