MEKKA

MEKKA is an experimental research facility for investigation of magnetohydrodynamic (MHD) phenomena in liquid metal blankets for future fusion reactors using the surrogate alloy sodium potassium (NaK). The facility is designed for fundamental investigations of MHD duct flows and for applied experiments in larger complex geometries such as entire mock-ups of breeder blankets for fusion-relevant parameters.

Where magnetic fields govern liquid metal flows

Technical description

MEKKA consists of a liquid metal loop containing 200 liters of sodium-potassium alloy (NaK) with a bypass into a purification circuit containing a cold trap. The loop is kept permanently under an inert argon atmosphere and is continuously monitored for safety reasons. Although experiments in MEKKA are performed at ambient temperature due to the low melting point of NaK, it is possible to operate the loop even at temperatures above 300°C. This is required to establish perfect wetting at the wall of new test sections by removing any contact resistance. The liquid metal flow is driven by a flat channel linear induction pump (0.5 bar, 3000 kg/h, up to 350 °C) and a canned motor centrifugal pump (9.5 bar, 25 m³/h, up to 150 °C). The loop is equipped with a thermostat to control and maintain a constant temperature. Magnetohydrodynamic effects are investigated in the gap of a 20-ton, water-cooled resistive electromagnet (1500 A, 2.1 T), which offers a large experimental volume within a uniform magnetic field.

Representative Projects

1. Mock-up experiments in support of the ITER test blanket program, pressure drop in manifolds and flow distribution in breeder units.
2. Studies of fundamental MHD flows and methods for pressure drop reduction in channels.
3. Generation of benchmark data for validation of predictive numerical tools.

Representative publications

L. Bühler, C. Courtessole, B. Lyu, and C. Mistrangelo. Electric potential on a WCLL TBM mock-up in MHD experiments as indication for flow distribution in breeder units. Fusion Engineering and Design, 212:114846,

2025.

C. Courtessole, H-J. Brinkmann, L. Bühler, and J. Roth. Characterization of MHD pressure losses in a mock-up of the WCLL test blanket module. Fusion Engineering and Design, 2019:115216, 2025.

C. Courtessole, H-J. Brinkmann, L. Bühler, and J. Roth. Experimental investigation of MHD flows in a WCLL TBM mock-up. Fusion Engineering and Design, 202:114306, 2024.

C. Courtessole, H-J. Brinkmann, and L. Bühler. Experimental investigation of magneto-convective flows around two differentially heated cylinders. Journal of Fluid Mechanics, 993:A6–1 – A6–22, 2024.

C. Mistrangelo, L. Bühler, and C. Courtessole. Numerical and experimental analysis of magneto-convective flows around pipes. Fusion Engineering and Design, 202:113425, 2024.

C. Koehly, L. Bühler, and C. Courtessole. Design of a scaled mock-up of the WCLL TBM for MHD experiments in liquid metal manifolds and breeder units. Fusion Engineering and Design, 192:113753, 2023.

L. Bühler, B. Lyu, H.-J. Brinkmann, and C. Mistrangelo. Reconstruction of 3D MHD liquid metal velocity from measurements of electric potential on the external surface of a thick-walled pipe. Fusion Engineering and

Design, 168:112590, 2021.

L. Bühler, C. Mistrangelo, and H.-J. Brinkmann. Experimental investigation of liquid metal MHD flow entering a flow channel insert. Fusion Engineering and Design, 154:111484, 2020