Scientists at the US Idaho National Laboratory (INL) have achieved a breakthrough by launching full-scale production of enriched fuel salt for the Molten Chloride Reactor Experiment (MCRE), a fast-spectrum, salt-fuelled reactor experiment scheduled to begin at INL in the 2030s. “This is the first time in history that chloride-based molten salt fuel has been produced for a fast reactor,” said Bill Phillips, technical lead for salt synthesis.
The MCRE project is a public-private collaboration between Southern Company, TerraPower, Core Power, and the Department of Energy (DOE) to demonstrate advanced nuclear technologies. It is the first planned reactor experiment to be hosted at the Laboratory for Operation and Testing (LOTUS) test bed, which DOE’s National Reactor Innovation Center (NRIC) is building at INL.
NRIC is developing two reactor demonstration test beds – DOME and LOTUS. The DOME test bed is repurposing the lab’s Experimental Breeder Reactor-II containment structure to lower the risk of developing microreactor designs capable of producing 20 MWt or less. LOTUS will be housed in INL’s former Zero Power Physics Reactor facility and is expected to support operations beginning in 2027/28.
Most molten salt reactors rely on liquid fuel, a mixture of salts containing fissile material, which allows for higher operating temperatures, better fuel efficiency, and enhanced safety. It also opens the door to new applications, including compact nuclear systems for remote and ships installations.
The fuel salt production process began in 2020. INL scientists set out to convert 90% of uranium metal into uranium chloride and produce 18 kilograms of fuel salt per batch – an ambitious target. Early attempts yielded less than the target amount with only an 80% conversion. However, in 2024, the team achieved a breakthrough: 95% conversion and full-batch production. They have since demonstrated they can produce a batch in as little as one day. The team delivered the first fuel salt production batch at the end of September and will produce four additional batches by March 2026.
MCRE will need 72 to 75 batches of fuel salt to enable it to go critical, giving INL its largest fuel production challenge in 30 years, according to the DOE Office of Nuclear Energy.
MCRE aims to evaluate the safety and physics of a molten chloride fast reactor (MCFR) that Southern Company and TerraPower plan to build. Conceptual designs of the MCFR expanded into testing in 2016 when DOE awarded a five-year, $40m cost-sharing award for continued research and development of the MCFR programme. The award initiated a public-private partnership that includes TerraPower, Southern Company, Oak Ridge National Laboratory, INL, the Electric Power Research Institute and Vanderbilt University.
In December 2020, DOE selected the MCRE proposal as a winner of the second Advanced Reactor Demonstration Program (ARDP) risk reduction pathway. Under the ARDP project, the team will construct the experimental system offsite and ship it to INL, where it will be fuelled. The MCRE experiment is scheduled to run for approximately six months at INL, after which it will be decommissioned. The aim is to provide data crucial to the development of the MCFR design.
“The Molten Chloride Fast Reactor represents a paradigm shift in the nuclear fuel cycle, and MCRE will directly inform the commercialisation of that reactor. Working with world-leading organisations such as INL to successfully synthesise this unique new fuel demonstrates how real progress in Gen IV nuclear is being made together,” said Jeff Latkowski, TerraPower Senior Vice President and MCFR Programme Director.
“The implications for the maritime industry are significant,” said Don Wood, MCRE senior technical advisor. “Molten salt reactors could provide ships with highly efficient, low-maintenance nuclear power, reducing emissions and enabling long-range, uninterrupted travel. The technology could spark the rise of a new nuclear sector—one that is mobile, scalable and globally transformative.”
Core Power CEO Mikal Boe noted: “With substantial private sector investments, including from the maritime industry, and with continued funding support from the DOE, this milestone accelerates completion of the MCRE, unlocking a new era of nuclear propulsion for a revitalised US merchant shipping fleet that can compete head-on with China.”
INL’s Associate Laboratory Director for Nuclear Science & Technology, Jess Gehin, said: “The administration implemented executive orders in May of this year to jumpstart America’s nuclear energy industrial base. These changes have had significant impact, enabling the acceleration of this technology and empowering INL in its efforts to spearhead global advancements in molten salt technology.”
James King, MCRE project director noted: “This milestone isn’t just about producing fuel – it’s about proving that the U.S. can lead in next-generation nuclear innovation,”. “We’re building the foundation for a more secure energy future, and MCRE is just the beginning.”
