Over decades of experimentation, molten-salt nuclear reactors have been shown to deliver high-temperature heat and extremely efficient electricity at reduced pressures. However, these reactors have yet to make the leap into widespread industrial adoption. Terrestrial Energy Inc. (Charlotte, N.C.; www.terrestrialenergy.com) has built upon previous molten-salt research to establish a modular nuclear-plant concept designed to meet the heating and power demands of industrial processes. “Terrestrial Energy is developing the Integral Molten Salt Reactor (IMSR), which uses a molten-fluoride salt mixture to both fuel and cool the reactor. Categorized as a Generation IV Small Modular Reactor, the IMSR will be deployed as a plant consisting of two operating reactors, a central control room and a non-nuclear thermal and electric-power conversion facility, which is separate from the regulated nuclear facility,” explains Simon Irish, chief executive officer of Terrestrial Energy.
This separation allows integration of natural gas or other energy sources into the plant’s power-generation and heat-delivery systems, providing an extra layer of flexibility and reliability, and also serving to reduce regulatory complexity and associated costs. Low-pressure operation further decreases complexity (and therefore manufacturing and construction costs) when compared to other nuclear technologies. IMSR plants are designed to deliver 390 MW of electricity, or 822 MW of thermal power, or a combination therein, depending on user needs.
Within the core unit of the IMSR is a molten-salt reservoir containing low-enriched uranium, and the main reaction systems, comprising heat exchangers, pumps and a graphite moderator. “As the IMSR is a thermal spectrum reactor, the uranium in the molten-salt fuel undergoes fission as it passes through the graphite moderator within the core unit. A heat exchanger near the top of the core unit transfers the fission heat to an external secondary heat exchanger operating a non-nuclear molten salt loop. This non-nuclear loop connects to the thermal and electric-power conversion facility. There, this very high-temperature heat (585ºC) can be used to produce electricity nearly 50% more efficiently than from traditional nuclear reactors or produce high-temperature steam for industrial processes such as chemical production,” says Irish.
Terrestrial Energy is actively developing 10 commercial deployment projects for its IMSR plants, and is also participating in the U.S. Dept. of Energy’s Advanced Reactor and Fuel Line Pilot programs. “The data collected and experience gained from these pilot programs will directly support our licensing applications for commercial IMSR plant operation with the Nuclear Regulatory Commission. We see industrial processes and chemical production as key parts of our customer base and currently are working with several prospective customers in the petrochemical industry,” notes Irish.