Exploration of ARC-class reactor vessel and divertor cooling system

ARC (Affordable, Robust, and Compact) is a compact tokamak design proposed by Commonwealth Fusion Systems and the Plasma Science and Fusion Center at the Massachusetts Institute of Technology. ARC features REBCO (Rare Earth Barium Copper Oxide) high temperature superconducting magnets, demountable coils, a replaceable vacuum vessel and a liquid immersion blanket (LIB). The LIB is a Li2BeF4 (FLiBe) molten that provides cooling, tritium breeding, and neutron shielding. The compact dimensions of ARC result in very high heat fluxes on the first wall ( ) and the divertor ( ). These heat fluxes mandate a high heat transfer coefficient in the cooling channels that cannot be achieved without adopting heat transfer enhancement techniques. The scope of this work is to analyze the FLiBe flows through the vacuum vessel channels, and the exploration of different passive heat transfer enhancement techniques to provide adequate cooling to the vessel, which must withstand considerable heat flux and volumetric power generation. Minimum cooling requirements for vessel and divertor are evaluated, and the performance of different turbulence promoters is compared to find the most advantageous design. In particular, wire coil inserts decrease pressure drops by 39% with respect to twisted tapes inserts while providing the same cooling performance.