Magneto-Convective Analyses of the PbLi Flow for the EU-WCLL Fusion Breeding Blanket

Abstract

The Water Cooled Lithium Lead (WCLL) breeding blanket is one of the driver blanket concepts under development for the European Demonstration Reactor (DEMO). The majority of the blanket volume is occupied by flowing PbLi at eutectic composition. This liquid metal flow is subdued to high fluxes of particles coming from the plasma which are translated into a high non-homogeneous heat volumetric source inside the fluid. The heat is removed from the PbLi thanks to several water tubes immersed in the metal. The dynamics of the PbLi is heavily affected by the heat source and by the position of the tubes. Moreover, the conducting fluid is electrically coupled with the intense magnetic field used for the plasma confinement. As a result, the PbLi flow is strongly affected by the Magnetohydrodynamics (MHD) forces. In the WCLL, the MHD and convective interactions are expected to be comparable. Therefore, the PbLi dynamics and consequently the heat transfer between the liquid metal and the water coolant will be ruled by the magneto-convective phenomenon. This work presents 3D computational analyses of the PbLi flow in the frontal region of the WCLL design. The simulations include the combined effect of MHD forces caused by the magnetic field and the buoyancy interaction created by the temperature distribution. The latter is determined by the PbLi dynamics, the volumetric heat source and the position of the water tubes. Simulations have allowed computing the heat transfer between the PbLi and the water tubes. Nusselt and Grashof numbers have been obtained in the different regions of the system.

The DEMO Water-Cooled Lead–Lithium Breeding Blanket: Design Status at the End of the Pre-Conceptual Design Phase

“…The maximum temperature at the PbLi/EUROFER interface was found to be 580 °C (Figure 17), slightly above the temperature limit. The second group of analyses were dedicated to the frontal region of the BZ, close to the FW [31]. These needed to include buoyancy interactions since it is expected that they play a major role in this region.…”

“…This was done because it was found that, with the employed mesh, it was hard to preserve stability and charge conservation for Ha values higher than 3000. The second group of analyses were dedicated to the frontal region of the BZ, close to the FW [31]. These needed to include buoyancy interactions since it is expected that they play a major role in this region.…”

Design and Integration of the EU-DEMO Water-Cooled Lead Lithium Breeding Blanket

“…Dedicated CFD analyses have also been conducted to characterize the magnetoconvective regime in the OB equatorial elementary cell considering an idealized pipe layout (straight toroidal tubes) [27]. Compared to previous studies [28,29], the present model aimed to investigate the effect of a skewed magnetic field, more accurate FW thermal boundary conditions and higher magnetic field intensity (≈4 T, Ha = 9159).…”