Flow distribution systems for liquid metal cooled blankets

Previous conceptual design studies for liquid-metal (LM) cooled blankets of a fusion power plant often omit details of the complete flow distribution network required to bring coolant into and out of the blanket, and especially the manifolding required for the transition from a small number of feed pipes to the sometimes large number of parallel channels within the actively heated part of the power core. Manifolding can induce large 3D MHD currents and therefore dominate the pressure and flow distributions within the entire blanket, which is especially problematic for designs with electrically insulated channels. Within the ARIES-ACT1 power plant study a design concept for flow distribution networks has been developed that attempt to minimize 3-dimensional effects that can lead to large pressure gradients and large uncertainties in flow distribution. Desirable and undesirable design elements are described. Especially risky are those elements that require bends that redirect the flow from parallel to perpendicular to the magnetic field and vice versa, because in those cases the bulk of the liquid metal can act as a short circuit. Fully-developed flow in insulated ducts normally retains “well balanced” electric potentials, preventing large 3D currents; internal flows parallel to the magnetic field can easily disrupt this delicate balance. Additional to MHD effects also fabrication and maintenance issues were considered. Using SiC
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/SiC as structural material for blanket and manifolding and a complex structure for these parts with an inner and outer pipe separated by ribs required a more detailed consideration of manufacturing as well as joining and cutting possibilities. Available technologies have been taken into account for a possible solution. Trade-offs associated with vacuum vessel and structural ring penetrations as well as pipe connections required for maintenance are discussed. Results of both discussions concerning MHD and fabrication issues on the final design for ARIES-ACT1 are shown.