Molten salt–fueled reactor experiment approved for DOE cost-shared funding

Yesterday, Southern Company and Core Power announced that the Department of Energy approved cost-shared funding through the Advanced Reactor Demonstration Program (ARDP) for an accelerated final stage of the Molten Chloride Reactor Experiment (MCRE), which the companies are conducting in collaboration with Idaho National Laboratory.

According to the announcement, MCRE could achieve criticality as early as 2027, which could be a world-first: To date, no fast-spectrum molten chloride salt reactor has reached criticality.

If it achieves this milestone, MCRE is expected to generate data on fuel behavior, reactor operations, and system performance. The experiment is planned to be DOE-authorized and located at the Zero Power Physics Reactor cell (repurposed as LOTUS-Laboratory for Operations and Testing in the United States) in INL's Materials and Fuels Complex.

The journey: MCRE is designed to be a 150-kWt reactor, and its fuel will be dissolved in liquid chloride salt, which avoids the need for a solid fuel assembly. The relatively simple system is intended to be used for experiments that can help inform future reactor designs, licensing pathways, and potential commercial applications.

It originally was selected as an ARDP project led by Southern Company in 2020. The fuel salt production process began that year, and in 2025, INL announced that it had perfected the fuel-making process and created the first batch of fuel salt for MCRE. Roughly 75 batches will be required for the reactor to go critical, and INL has demonstrated it can produce a batch in as little as one day.

"The purpose of the experiment is to obtain direct measurements of reactor behavior during sustained fission and generate operational data that can improve analytical models and reduce technical uncertainty for future reactor designers and regulators," said Lauren Lathem, Southern Company's advanced nuclear R&D manager.

The said it: "MCRE will be the world's first fast-spectrum molten chloride reactor to achieve criticality. It will provide direct measurements of how this novel reactor behaves during sustained fission, data that until now, has come from models alone. Enhancing those models with real-world operating evidence will reduce uncertainty for future reactor designers and regulators," said Jess Gehin, associate laboratory director for nuclear science and technology at INL.

"Public-private partnerships play an essential role in advancing energy technologies from concept to demonstration. Through collaboration among DOE, Idaho National Laboratory and industry partners, MCRE will help expand knowledge of molten salt reactor technology and help reduce technical uncertainty for future developers," said Mark S. Berry, Southern Company senior vice president of research, environment, and sustainability.

"The data generated by this unique experiment will help determine how we develop engineering, licensing, and an entirely new supply chain to practical commercial deployment of fast-spectrum molten salt reactors. Core Power's role in this partnership is to help translate advanced reactor technology into deployable industrial systems and unique delivery mechanisms needed to realize the potential of this technology," said Mikal Bøe, CEO of Core Power.