Effects of Radial Variation of the Magnetic Field on the Pressure Distribution in the European Liquid-Metal Blanket Concept

Liquid-metal flows in the European helium cooled lead lithium blanket are strongly affected by the intensity and the distribution of the externally applied magnetic field required for plasma confinement. An experimental campaign has been performed to investigate the pressure distribution of magnetohydrodynamic flows in a scaled model of a liquid-metal blanket module.

A variety of experiments has been carried out to asses the influence of flow rates and of the strength and non-uniformity of the magnetic field on the pressure distribution in the test-section. The magnetic field available in the laboratory is characterized by a large zone of uniform magnitude and gradients at the entrance and the exit. The mock-up has been located at various positions along the magnet axis to reproduce operating conditions in which the toroidal field varies in radial direction, i.e. it changes from the back plate to the first wall. Measurements show that the magnitude of the total pressure drop in the mock-up is significantly influenced by the strength of the local magnetic field at the manifolds, while gradients across the breeder units have minor effects. This study confirms the critical role of manifolds in determining the total pressure drop in the blanket.