UCLA

The liquid-metal fusion blanket constitutes a pivotal element in the infrastructure of magnetic field confined fusion nuclear power plants, undertaking a multifaceted role crucial to their operation. Its responsibilities span from breeding tritium, essential fuel for fusion reactions, to converting the energy from high-energy neutrons and plasma into electricity, while also shielding structural components from the impact of high-energy species produced during fusion processes. Specifically engineered for this purpose, a liquid metal fusion blanket employs materials such as lithium or lithium alloys, serving as coolants and breeding materials simultaneously. Within the domain of liquid-metal (LM) blankets, mixed-convection presents a significant challenge, emerging as the dominant flow phenomenon in most fusion LM blanket designs. The magnetohydrodynamics (MHD) flows of liquid breeders, like PbLi, within blanket conduits experience notable buoyancy forces due to heightened temperature gradients resulting from intense heat loads. The intricate interplay of MHD effects and buoyant forces gives rise to strongly coupled phenomena. Understanding and predicting the complex flow behaviors arising from the interaction of these multiple effects necessitate both experimental data and numerical investigations of three-dimensional mixed-convection MHD flows for advancing LM blanket designs.Chapter two of this thesis outlines the establishment of the MaPLE-U facility, dedicated to high-temperature liquid metal experiments under intense magnetic fields and various flow orientations with respect to gravity. Subsequently, the first experimental dataset is presented, focusing on PbLi, a prominent blanket breeding candidate, to elucidate mixed-convection MHD flow behaviors and heat transfer phenomena. The findings challenge the assumption of complete flow laminarization under strong MHD effects, widely adopted in LM MHD R&D strategy, emphasizing the need for simultaneous consideration of multiple effects. Chapter three delves into numerical investigations employing COMSOL Multiphysics, where flow predictions are validated against analytical solutions, benchmarked experimental data, and results from other MHD codes. A novel MHD-heat transfer flow model is developed to address the lack of numerical simulation tools for wall-bounded fully developed flows concurrently coupling MHD flow and heat transfer equations under harsh nuclear fusion reactor conditions (Ha ~ 10^4,Gr ~ 10^11). Building upon this groundwork, chapter four provides further insights into mixed-convection MHD flows within complex LM blanket geometries under fusion-relevant conditions, showcasing the versatility and computational accuracy of the COMSOL Multiphysics platform, particularly in scenarios surpassing existing experimental and numerical studies.