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.

The IMSR® uses Generation IV molten salt technology. This is the heart of its competitive advantage. Molten salts are thermally very stable and superior to water as a coolant; water is the coolant in conventional reactor systems. The use of a molten salt coolant permits the IMSR® to operate at both high temperature and lower pressure, and benefit from the transformative advantages of both.

The IMSR® power plant’s 700°C high temperature operation achieves greater than 44 percent thermal efficiency for electric power generation, a game-changer. Conventional reactors use water and are forced to operate a much lower temperatures of no more than 300°C and are limited to 33 percent thermal efficiency; small conventional reactors are unable to reach 30 percent.  The 50 percent greater thermal efficiency of IMSR® power plants translates directly to 50 percent more electricity generated, and by extension, to 50 percent more revenues and lower costs per unit of electricity.

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

When a molten salt coolant and molten salt fuel are used in combination, as is the case with the IMSR® design, the reactor incorporates the powerful virtues of passive and inherent safety. Passive and inherent safety delivers a “walk-away” safe nuclear power plant with considerably reduced engineering complexity and cost.

At 195 megawatts, an IMSR® power plant is right sized for today’s market opportunity, and 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® power plant in four years, under half the time required for conventional nuclear power plants.

Selecting an IMSR® power plant means significantly lower construction and financing costs. Being smaller, an IMSR® power plant requires a much smaller upfront investment (less than U.S. $1 billion rather than $10 billion plus for conventional power plants). Consequently an IMSR® power plant is more affordable and easier to finance compared to conventional nuclear power 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, and modularity of the IMSR® power plant design that creates its transformative commercial potential. An IMSR® power plant is a clean and cost-competitive alternative to burning fossil fuels.

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

In industrial heat markets, IMSR® plants have the potential to be cost-competitive with natural gas and heating oil. They provide an in-furnace cost of heat of less than U.S. $6 per MMBtu, within U.S. $2.50 of North American in-furnace natural gas costs.

Simple, fast, modular plant construction

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

They use a modular design for ease and speed of construction, and each module is mass-manufactured in factory settings, easily transportable by truck or rail for on-site modular assembly.

This modular approach to manufacturing and assembly allows an IMSR® power plant to be built in four years, under half the time required for conventional reactor power plants. Selecting the IMSR® means lowering construction and financing costs very significantly.


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®).