Cost Advantage

IMSR® power plants are a clean and cost-competitive alternative to burning fossil fuels

small modular reactor innovation is found in the Reactor design, not its small size or it modular charateristics

Cutaway view of the IMSR® Core-unit.

Generation IV molten salt technology is essential to competitive advantage of IMSR® plants. Molten salts are thermally very stable and superior to water as reactor coolants; water is the coolant in conventional nuclear power plants. The use of a molten salt coolant permits IMSR® plants to operate with high safety at high temperature and lower pressure, benefiting from the transformative advantages of both.

IMSR® plants supply thermal energy at 585°C, and with this high temperature they achieve 44 percent thermal efficiency (net) when used for electric power generation, a near 50% improvement – this is game-changing. Conventional nuclear power plants use water and must operate at much lower temperatures of no more than 300°C. These factors limit them to just 33 percent thermal efficiency; small conventional power plants are unable to reach 30 percent. The 50 percent greater thermal efficiency of IMSR® plants translates into 50 percent more electricity generated, and that means 50 percent more revenues and lower costs per unit of electricity, better sustainability scores, and less waste too.

The IMSR® low-pressure operation avoids the considerable engineering complexity and costs of the high-pressure operation required for conventional reactors that all use as a water coolant.

When a molten salt coolant and molten salt fuel are used in combination, as is the case with the IMSR® plant, the reactor incorporates the powerful virtues of passive and inherent safety. That lowers engineering complexity and cost.

An IMSR® plant is right sized for today’s industrial needs. It is designed for fast modular construction using modules manufactured in factories and transported by truck or rail for on-site modular assembly. This modular approach to manufacturing and assembly allows for construction of an IMSR® plant in four years, under half the time required for conventional nuclear power plants.

Selecting an IMSR® plant means significantly lower construction and financing costs. Being smaller, an IMSR® plant requires a much smaller upfront investment (less than U.S. $3 per watt IOC), far less than the U.S. $10 billion plus capital requirement for conventional power plants. An IMSR® plant is more affordable and easier to finance compared to conventional nuclear plants, which today require government backing and financing support.

It is the combination of high-temperature and low-pressure operation, inherent and passive safety, smaller size, modularity and versatility that creates the transformative commercial potential of IMSR® plants. An IMSR® plant is a carbon-free and cost-competitive alternative to burning fossil fuels.

In industrial heat markets, IMSR® plants have the potential to be cost-competitive with thermal energy from natural gas and heating oil combustion. They provide heat at an in-furnace cost of less than U.S. $6 per MMBtu.

In electric power markets, IMSR® plants can dispatchable electricity at a levelized cost of under U.S. $50 per megawatt-hour. This is cost-competitive with natural gas and coal generation, and they never face the prospect of carbon penalties.


Simple, fast, modular plant construction

IMSR® plants are smaller and simpler to build than today’s conventional nuclear power plants.

They use a modular design for ease and speed of construction, and each module is mass-manufactured in factory settings using the latest advanced manufacturing methods. This approach makes them easily transportable by truck or rail for on-site modular assembly.

This modular approach allows an IMSR® plant to be built in four years, under half the time required for conventional nuclear power plants. Selecting an IMSR® plant means lower construction and financing costs.


1. Lazard: Natural gas fuel cost assumption as of October 2020. By August 2021, natural gas prices had risen by more than 50%.
2. IMSR® is Generation IV non-light water small modular reactor (SMR) design.
3. EIA: Based on Generation III light water reactor (LWR) SMR design.
4. Lazard: Generation III (LWR and PHWR) in large ~1 GWe design formats.
5. EIA: Technology is assumed to be photovoltaic (PV) with single-axis tracking. Lazard: The low represents a single-axis tracking system and high case represents a fixed-tilt system.
Levelized Cost Of Energy, Lazard, October 2020
Levelized Costs of New Generation Resources, Annual Energy Outlook 2021, Energy Information Administration
Assumptions to the Annual Energy Outlook 2021: Electricity Market Module, Annual Energy Outlook 2021, Energy Information Administration

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®).