NITE–Processed SiC/SiC Ceramic Composites in Liquid Sandwich Vacuum Vessel

Abstract

In 2022, the Biden-Harris Administration released their Bold Decadal Vision for Com-mercial Fusion Energy [1]. The plan called for the rapid development of robust and economical commercial fusion technology. This thesis focuses on the vacuum ves-sels (VVs) surrounding the plasma in an ARC-class fusion tokamak. VVs require significant development to go from their current state of the art in research-scale, non-breakeven fusion devices to the much larger, thinner, and robust VVs that com-mercial fusion tokamaks will require. Conventional research tokamaks have VVs made of thick-walled steel or superalloys so that the device can resist the large disruption forces that occur when the plasma quenches. Commercial-scale VVs need to let ther-mal energy and neutrons through to the tritium breeding blanket surrounding the plasma while maintaining a vacuum. Thick-walled VVs hinder efficient heat transfer and absorb neutrons. A new "liquid sandwich vacuum vessel" (LSVV) design proposes to use thin walls of silicon carbide ceramic composite (SiC/SiC) surrounding a layer of liquid lead. Because liquid lead is much more electrically conductive than SiC/SiC, the liquid lead absorbs disruption-induced currents and the resulting forces. This enables the use of a thin-walled VV to promote heat transfer while still resisting dis-ruption damage. The SiC/SiC ceramic composite that the LSVV development team is most interested in is made using the Nano-Infiltration Transient Eutectic (NITE) process, which allows for very low porosity composites to be achieved. NITE-type SiC/SiC samples were characterized experimentally. Then, COMSOL simulations were done using a combination of literature data and the novel property data ob-tained in this work to show how an LSVV compares to conventional VV designs. Simulations show that the LSVV design achieves a 32.5% increase in the modified Carnot efficiency and reduces the maximum Von Mises stress in the VV by an order of magnitude, while keeping a safety factor of 1.268, as compared to a conventional solid-walled VV made from EUROFER97.