How it Works

The IMSR® blends proven molten salt technology with innovative enhancements, including the integration of primary reactor components into a sealed, replaceable vessel

Rendering of the IMSR<span class="te-rtrademark">&reg;</span> Core-unit.
Rendering of the IMSR® Core-unit.
The IMSR® uses a fundamentally different reactor technology — a liquid fuel, a molten salt, rather than the solid fuel used exclusively in conventional reactors. This provides a fluid medium to carry a nuclear fuel, a uranium fluoride salt. Molten salts are thermally stable and are excellent heat-transfer fluids, ideal for capturing and dissipating heat from the fission process.

The IMSR® uses simple, safe and natural mechanisms to dissipate heat from the fission process, and this results in a far superior design to reactors that use conventional technology. The use of a molten salt is at the heart of many virtues of the IMSR® and directly leads to IMSR®’s key commercial advantages – a cost-competitive and “walk-away” safe nuclear power plant.

An IMSR® power plant generates 195 megawatts of electricity with a thermal-spectrum, graphite-moderated, molten-fluoride-salt reactor system. It uses standard-assay low-enriched uranium (less than 5 percent 235U) fuel. It incorporates many aspects of Molten Salt Reactor operation researched, demonstrated and proven by test reactors at the Oak Ridge National Laboratory.

The Replaceable IMSR® Core-unit

The Replaceable IMSR<span class="te-rtrademark">&reg;</span> Core-unit.
The Replaceable IMSR® Core-unit.
The IMSR® improves upon earlier Molten Salt Reactor designs by incorporating key innovations that create an industrial reactor ready for commercial deployment.The key challenge to MSR commercialization was graphite’s limited lifetime in a reactor core. Commercial power reactors require high energy densities in the reactor core to be economical, but such high-power densities significantly reduce the graphite moderator’s lifespan. Replacing the graphite moderator is difficult to do safely and economically.

The distinct IMSR® innovation is an elegant solution to this problem — integrating the primary reactor components, including the graphite moderator, into a sealed and replaceable reactor core. The IMSR® Core-unit, which has an operating lifetime of seven years, is simple and safe to replace. It 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 commercialization of MSRs.

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

The IMSR® power plant is the leading new clean energy alternative.