Ricerc@Sapienza

The blanket in a magnetic confinement fusion reactor is a critical component that provides, among other functions, the cooling for the plasma-facing first wall and breeds the tritium required to fuel the reactor operation. The most promising concepts involve the use of a liquid metal as working fluid, i.e. lithium-lead eutectic alloy, thanks to excellent thermal properties and the possibility to double the coolant role as tritium breeder. The interaction between the liquid metal and the plasma-confining magnetic field defines many, if not all, of the relevant thermal-hydraulic features of these components and are not yet completely understood. In the framework of the development of the prototype reactor DEMO, the EUROfusion consortium is funding the study of three liquid metal blanket conceptual designs: Helium-Cooled (HCLL), Dual-Cooled (DCLL) and Water-Cooled (WCLL). This proposal aims to study a key phenomenon for the blanket design: the mixed convective MHD flows. The non-uniform volumetric heating of the liquid metal due to the fusion high energy neutrons creates sharp temperature gradients in the blanket which, in turn, promote significant buoyancy forces. These are expected to at least affect the main pressure-driven flow, i.e. causing local flow reversal in long vertical ducts. Blanket concepts (e.g. WCLL) that rely on the minimization of the molten metal velocity to less than 1 mm/s to reduce the MHD pressure drop to manageable levels are expected to exhibit a buoyancy-dominated flow. Preliminary hydrodynamic CFD studies have found a considerable deviation in the blanket temperature distribution compared with the pure forced convection case. The main purpose of this work is to support these results performing a MHD CFD analysis with ANSYS CFX. The work would be divided in two phases: a validation against numerical data in the literature for flows in 2D and 3D geometries and, finally, the simulation in realistic blanket conditions.