Ricerc@Sapienza

The magnetohydrodynamic flow and heat transfer of a liquid metal in a channel past a circular cylinder with walls of non-uniform conductivity were investigated. The applied magnetic field was transversal to the forced flow (x-direction) and coplanar with the obstacle, featuring non-null components in both the z- and y-directions. Moreover, the cylinder was displaced by the duct centreline toward the bottom wall and its surface was at uniform temperature, so that a ΔT was present between the obstacle and the fluid at the inlet.

In the Water-Cooled Lithium Lead (WCLL) blanket, a critical problem faced by the design is to ensure that the breeding zone (BZ) is properly cooled by the refrigeration system to keep the structural materials under the maximum allowed temperature by the design criteria. CFD simulations are performed using ANSYS CFX to assess the cooling system performances accounting for the magnetic field effect in the sub-channel closest to the first wall (FW). Here, intense buoyancy forces (Gr = 10^10) interact with the pressure-driven flow (Re = 10^3) in a MHD mixed convection regime.

The Breeding Blanket is a fundamental component of a nuclear fusion reactor and the Water-Cooled Lead Lithium (WCLL) blanket is one of the possible solutions proposed. In this concept, liquid lithium-lead eutectic alloy (PbLi) serves as tritium breeder, tritium carrier and neutron multiplier. The liquid metal is distributed within the breeding zone by two co-axial rectangular channels and, interacting with the reactor magnetic field, leads to the arising of MagnetoHydroDynamic (MHD) effects.

In the Water-Cooled Lithium Lead (WCLL) blanket, the eutectic alloy lithium-lead (PbLi) is used as tritium breeder and carrier, neutron multiplier, and heat transfer medium. The PbLi hydraulic loop section in the range of the reactor field coils, which includes the blanket and a non-negligible length of the connection pipes, is affected by intense magnetic fields which cause the transition to a MHD regime. Lorentz forces oppose the fluid motion and cause pressure losses several orders of magnitude higher than for the ordinary hydrodynamic regime.

The Water-Cooled Lithium-Lead Breeding Blanket is a key component of a fusion power plant, in charge of ensure Tritium production, shield Vacuum Vessel and magnets and remove the heat power deposited by radiation and particles arising from plasma. The last function is fulfilled by First Wall and Breeding Zone independent cooling systems.

The Water-Cooled Lithium-Lead (WCLL) Breeding Blanket (BB) is a key component in charge of ensuring Tritium production, shield the Vacuum Vessel and remove the heat generated by plasma thermal radiation and nuclear reactions. It relies on PbLi eutectic alloy adopted as breeder and neutron multiplier and refrigerate by subcooled pressurized water. The last function is fulfilled by two independent cooling systems: First Wall (FW) that faces the plasma heat flux and the Breeding Zone (BZ) that removes the deposited power of neutron and photon interaction.