Above -PPPL physicist Andrei Khodak next to diagrams showing his concept for a porous fusion facility wall (Collage by Elle Starkman / PPPL Office of Communications)
New computer simulations show that placing the holes — porous, sponge-like covers that cap off reservoirs of liquid lithium — around the inner walls of doughnut-shaped tokamak(link is external) fusion facilities can absorb damaging excess heat inside the facilities. The heat can then be moved to generators to help produce electricity.
Khodak and Maingi are now exploring whether 3D printing can create the porous wall more easily and precisely. “There is a program in the Department of Energy’s Fusion Energy Sciences division that is devoted to liquid metal concepts,” Khodak said. “After we finish optimizing, the next step will be to build a prototype and do some testing.”
Flowing liquid lithium can, in principle, create a renewable surface interacting with the plasma, providing protection for the underlying solid substrate. Recent experiments  showed that liquid lithium supplied through a porous medium can limit the plasma facing surface temperature, even at high heat flux values in excess of 10 MW/m2. The use of new 3D printing techniques allows creation of plasma facing components that supply liquid lithium through capillary channels. Numerical analysis can be used to develop and optimize porous plasma facing component using virtual prototyping. The present contribution introduces a numerical model of liquid metal flow in a porous structure, interacting with the plasma. The model uses computational fluid dynamics (CFD) to model a flow through a complex 3D geometry including magneto-hydrodynamics (MHD) effects. The CFD set-up covers the liquid metal, plasma and solid structures, simultaneously, connected by realistic interfaces. Small scale interface structures are modeled separately to obtain a self-consistent interface functions. Customized version of the general-purpose CFD is used to handle complex 3D geometries, and efficient pre- and post-processing. MHD is introduced using the magnetic vector potential approach, allowing precise fluid–solid interface treatment. Special stabilization procedures were derived and applied to improve convergence of the momentum balance equations with source terms due to Lorentz force and surface tension. Conjugate heat transfer analysis was performed in the plasma, liquid metal and solid components. The customized code was validated using analytical results for high Hartmann number flow. Results of the validation and numerical analysis of liquid lithium plasma facing components using porous walls will be presented.
SOURCES- Princeton Plasma Physics Laboratory (PPPL), Nuclear Materials and Energy
Written By Brian Wang, Nextbigfuture.com
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