How it Works

The IMSR® incorporates proven molten salt reactor technology with patented enhancements for a reactor that has high industrial value.

Molten Salt Reactor Rendering – the IMSR Core-unit.
Molten Salt Reactor Rendering – the IMSR® Core-unit.
The IMSR® uses a Generation IV reactor technology. It uses a molten salt as coolant and fuel.  This is in contrast to water circulating through a highly pressurized cooling system and solid fuel, both of which are the signature features of Generation I, II and III conventional reactors.

Molten salts are thermally very stable, making them superior coolants compared to water. This permits lower pressure and high temperature operation. Both are crucial to reducing cost and substantially improving efficiency of electric power generation.

When a molten salt coolant and molten salt fuel are used in combination, the reactor has the potential to incorporate the virtues of passive and inherent reactor safety as well. As a result, using molten salt technology in the IMSR® design leads to a nuclear power plant that is “walk-away” safe and has transformative commercial advantages.

Operating at greater than 44 percent thermal efficiency, an IMSR® power plant generates 195 megawatts of electricity with a thermal-spectrum, graphite-moderated, molten-fluoride-salt reactor system. It uses today’s standard nuclear fuel – comprising standard-assay low-enriched uranium (less than 5 percent 235U) – critical for near-term commercial deployment. The IMSR® power plant design incorporates many aspects of Molten Salt Reactor operation that were researched, demonstrated and proven by test reactors at the Oak Ridge National Laboratory.

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The Replaceable IMSR® Core-unit

The Replaceable IMSR Core-unit.
The Replaceable IMSR® Core-unit.

The IMSR® improves upon earlier Molten Salt Reactor designs by incorporating key innovations that create a reactor suitable for industrial use and ready for commercial deployment. The key challenge to MSR commercialisation has been graphite’s limited lifetime in a reactor core.

Commercial power reactors require high energy densities in the reactor core to be economic, but such high-power densities significantly reduce the graphite moderator’s lifespan. Replacing the graphite moderator is difficult to do safely and economically in a commercial setting.

The IMSR® patented innovation is an elegant solution to this problem: integrating the primary reactor components, including the graphite moderator, into a sealed and replaceable reactor core – called the “IMSR® Core-unit.” This has an operating lifetime of seven years, and it is simple and safe to replace.

The Core-unit supports high capacity factors of IMSR® power plants and hence high capital efficiency. It also ensures that the materials’ lifetime requirements of other reactor core components are met, a challenge often cited as an impediment to immediate commercialisation of MSRs.

The result is a small modular reactor that delivers a combination of safety, high energy output, simplicity of operation, and cost-competitiveness necessary to drive broad commercial deployment.

For all these reasons, the IMSR® power plant is the leading new clean-energy alternative.


Learn More About Terrestrial Energy

Terrestrial Energy is an industry-leading technology company committed to delivering reliable, emission-free, and cost-competitive nuclear energy with a truly innovative advanced reactor design, the Integral Molten Salt Reactor (IMSR®).