Heat transfer and computational fluid dynamics for molten salt reactor technologies

Molten salt reactors (MSRs) are characterized by the use of a fluoride or chloride salt as coolant. Two major design variants are being considered, characterized by solid or liquid fuel. The solid fuel option (often referred to as fluoride-cooled high-temperature reactors or FHRs) is more similar to other nuclear reactor concepts: salt is used to transfer heat from solid fuel to a secondary loop; fuel is typically made of small particles (i.e., TRISO) dispersed in a graphite matrix to form blocks, pebbles, or plates. In the liquid fuel design, instead, actinides are directly dispersed in the salt that, kept at high temperature (above 500°C), flows in and out of the reactor core. In the core, the salt is heated up by the fission reactions and heat is then transferred to a secondary loop when the fuel salt itself flows through the heat exchangers. Compared to light-water reactors, MSRs are expected be more economical because of higher power conversion efficiency, low-pressure containment, and absence of active safety systems [1].