US firm advances next-gen nuclear with molten salt reactor construction milestone
American nuclear energy company Kairos Power has officially completed the first installation of its Hermes Low-Power Demonstration Reactor, in a bid to showcase its advanced molten salt reactor technology and pave the way for commercial deployment.
The major milestone marks the first time a non-light water reactor has entered nuclear construction in the country under a permit issued by the U.S. Nuclear Regulatory Commission (NRC).
To ensure structural integrity, the 35-megawatt thermal (MWt) reactor will rest on 51 six-foot-diameter drilled piers extending approximately 40 feet into bedrock, as part of the company’s broader effort to develop safer, cleaner next-generation nuclear systems in the U.S.
The system combines TRISO fuel pebbles with a molten fluoride salt coolant known as Flibe (a mixture of lithium and beryllium fluorides), offering a design with strong inherent safety features and low operating pressure.
Advanced reactor breakthrough
The NRC granted Kairos Power the construction permit for its Hermes reactor in December 2023, marking the first time a non–light water reactor has received such approval.
Following the regulatory green light, site work began with groundbreaking in July 2024, and excavation was completed by October, laying the groundwork for full-scale construction in Oak Ridge, Tennessee.
Now, following the recent pour of nuclear-grade concrete at the site, the reactor has officially entered its construction phase. As part of the foundation work, each drilled shaft is reinforced with steel rebar cages prior to the concrete placement, ensuring the structural soundness of the reactor.
“The first safety-related concrete pour for a U.S. advanced reactor under an NRC construction permit is a major milestone and a significant accomplishment for the Kairos Power team and our construction partners,” Mike Laufer, Kairos Power CEO and co-founder said.
Laufer emphasized that the achievement demonstrates the effectiveness of the company’s iterative development approach in meeting strict nuclear quality standards while delivering essential cost insights that build confidence among customers. Describing it as a testament to the team’s hard work and dedication, he said the project reflects significant learning and meaningful progress.
Extensive groundwork completed
The project comes after months of preparation, including two earlier efforts at the Oak Ridge site that allowed the construction team, led by Barnard Construction Company, to test the drilled pier installation process and improve their nuclear quality assurance program.
According to Kairos Power, the team completed a full-scale test pier, known as Pier 52, in November last year, before going on to install 70 piers for the non-nuclear Engineering Test Unit (ETU 3.0) over a four-month period. Improving efficiency over time over time, the team was able to install up to six piers in a single day, using quality control checklists similar to those intended for Hermes.
“The Hermes project team continues to lead the industry as we forge a new path in advanced reactor construction,” Edward Blandford, chief technology officer and co-founder of Kairos Power, concluded in a press release. Blandford stated that the company and its partners are under close coordination with the NRC, and are focused on upholding the highest standards of quality and safety to ensure the project’s successful execution.
Backed by USD 629 million in funding from the U.S. Department of Energy’s Advanced Reactor Demonstration Program, Hermes is designed to test Kairos Power’s reactor design, licensing approach, supply chain, and construction methods, marking a massive step in the company’s plan to launch its larger 140-MWe commercial reactor, KP-FHR.