Advanced Nuclear Facility Plant Rendering
The efficiency of the machines in our modern world is defined by the amount of thermal energy that can be captured as mechanical energy for production commercial use. It is mechanical energy that spins an electric generator to make electricity or propels cars, or planes or ships. It is mechanical energy used for commercial purposes. The more mechanical energy a machine captures, the more efficient and commercially attractive it is. That efficiency is called the thermal efficiency of a machine and its financial analogue is called “Return-on-Capital.

The problem with conventional power

Thermal efficiency varies with the temperatures of thermal energy, high temperature equals high efficiency, low temperature equals low efficiency. Thermal efficiency translates directly to financial efficiency and commercial performance reflected in measures such as return-on-capital.

Coal, oil and natural gas fired power plants operate at high efficiency because coal, oil and natural gas combustion creates heat at high temperature (585°C steam). They have a thermal efficiency that exceeds 45% and generate inexpensive electricity. But burning fossil fuels creates air pollution that contributes to pulmonary diseases and climate change.

Conventional nuclear power plants are carbon-free but inefficient machines, because conventional nuclear technology generates heat at low temperature (290°C steam). They have a thermal efficiency that is low; 30% for small plants, 33% for large plants.

The IMSR difference

IMSR cogeneration plants are efficient machines. The IMSR generates heat at high temperature (585 degree C steam). They have a thermal efficiency of 44%, a near 50% efficiency improvement. Conventional nuclear power plants use water as the reactor coolant and must operate at low temperatures.

In addition to cost and Return-on-Capital, thermal efficiency impacts all aspects of plant operation including the efficiency of land-use, material use, and waste production.

Advanced Nuclear Facility Plant Rendering
In industrial heat markets, IMSR plants can be cost-competitive with thermal energy (heat) from burning natural gas and heating oil. They provide heat at an in-furnace cost of less than U.S. $6.60 per MMBtu.

Cost-competitive power

In electric power markets, IMSR plants generate dispatchable electricity at a levelized cost of under U.S. $54 per megawatt-hour. This is cost-competitive with natural gas and coal generation, and they never face the prospect of carbon penalties.

The IMSR low-pressure operation avoids the considerable engineering complexity and costs of the high-pressure operation required for water-cooled conventional reactors.

Total System Cost of New Plant Graph
IMSR cogeneration plants are smaller and simpler to build than today’s conventional nuclear power plants. They are are right sized for today’s industrial needs.
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.

Under four years lead time

This modular approach allows for building an IMSR plant in under four years, less than half the time for conventional nuclear plants. Selecting an IMSR plant means lower construction and financing costs.

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 cogeneration plants. IMSR plants are a carbon-free and cost-competitive alternative to burning fossil fuels.


  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