World’s first fast-spectrum molten chloride reactor experiment nears critical testing

A nuclear experiment backed by the U.S. Department of Energy could deliver crucial operating data for next-generation reactors as early as 2027. The Molten Chloride Reactor Experiment (MCRE) aims to test a fast-spectrum molten chloride salt reactor under sustained fission conditions. Its results could help engineers move the technology closer to commercial use.

The DOE has approved additional cost-shared funding to accelerate the experiment’s final development stage. Southern Company, Idaho National Laboratory and CORE POWER are collaborating on the project through the department’s Advanced Reactor Demonstration Program.

Testing a different reactor design

Unlike conventional reactors, which typically use solid fuel, molten salt reactor designs can dissolve nuclear fuel in liquid salt. MCRE will investigate a chloride-based system that operates with a fast neutron spectrum.

Fast neutrons retain more energy than the thermal neutrons used in many conventional reactors. This difference influences how nuclear fuel behaves and how a reactor sustains fission. Engineers need experimental evidence to understand those effects and refine their designs.

MCRE aims to become the world’s first fast-spectrum molten chloride reactor experiment to achieve criticality. That milestone occurs when a reactor sustains a controlled nuclear chain reaction.

Idaho National Laboratory will help researchers gather direct measurements of the reactor’s behavior during operation. Associate Laboratory Director Jess Gehin said engineers currently rely on models to predict how this reactor design will perform.

“Enhancing those models with real-world operating evidence will reduce uncertainty for future reactor designers and regulators,” Gehin said.

The measurements could help developers validate simulation tools and assess engineering decisions. They could also inform future reactor licensing efforts, although regulators will still need project-specific safety evidence.

Reducing risks before deployment

Advanced reactor developers face significant technical challenges before they can bring new designs to market. Experimental results can help engineers identify uncertainties before committing to larger, more expensive demonstrations.

MCRE could provide data on fuel behavior and reactor performance during sustained fission. Those findings may help developers evaluate design choices and build stronger technical cases for future projects.

Southern Company sees the experiment as an example of how federal funding and private-sector expertise can advance nuclear research. Senior Vice President Mark S. Berry said collaboration could help reduce technical uncertainty as developers pursue reliable and affordable energy.

The research could also support applications beyond electricity generation. Fast-spectrum molten salt systems may eventually support industrial energy demands and medical isotope production. Developers are also exploring whether these reactors could extract additional value from used nuclear fuel.

Maritime nuclear power prospects

CORE POWER sees potential applications in commercial shipping, where nuclear propulsion could provide long-duration power without onboard carbon emissions during operation.

CEO Mikal Bøe said the company committed to building MCRE in 2020. The accelerated schedule now targets criticality as early as 2027.

Bøe said the experiment could help establish the engineering knowledge, licensing approaches, and supply chains needed for commercial deployment. CORE POWER also wants to connect advances in nuclear fuel technology with its maritime nuclear development efforts.

Nuclear-powered commercial vessels could eventually offer an alternative to conventional marine fuels. However, deployment would require substantial work on reactor safety, ship integration, regulation, and supporting infrastructure.

MCRE’s immediate goal remains scientific, not commercial. Its experimental results could help determine whether fast-spectrum molten chloride reactors can progress toward practical applications, including future maritime power systems.