Magnetohydrodynamic flows in liquid metal blankets for fusion reactors

Abstract

AbstractLiquid metal blankets will be tested in the experimental fusion reactor ITER. Three main concepts are currently under development. In the water‐cooled and in the helium‐cooled lead lithium blankets the PbLi alloy serves only as breeder material for producing the fuel component tritium used to generate the magnetically confined fusion plasma. The fusion heat is removed by a separated water or helium cooling system and therefore the liquid‐metal could be practically at rest. However, for tritium extraction and liquid metal purification a weak circulation (1 mm/s) is required. Instead in the dual coolant lead lithium blanket the liquid metal serves both to produce tritium and to remove the volumetric heat deposited in the breeding zone, while helium is employed to cool first wall and blanket structure. In this concept PbLi has to flow faster (10 cm/s) than in the separately cooled blanket designs to allow efficient cooling of the breeding zone.In all liquid metal blankets there are issues related to the specific characteristics of the liquid metal. The interaction of the electrically conducting fluid with the strong magnetic field induces electric currents and electromagnetic forces that influence velocity and pressure distribution in the blanket. Lorentz forces are balanced by pressure gradients and these additional magnetohydrodynamic (MHD) pressure losses are proportional to the electric current density induced in the fluid. The electrical coupling of adjacent fluid domains that results from the presence of leakage currents crossing common conducting walls, has also to be taken into account. Two examples of MHD flows typical in fusion blankets are discussed in this paper. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)