US-based Kairos Power has finalised a contract with the US Department of Energy (DOE) to receive High-Assay Low-Enriched Uranium (HALEU), sourced from DOE material. This will be used for the start-up and operation of the Hermes Low-Power Demonstration Reactor (Hermes 1), currently under construction in Oak Ridge, Tennessee.
Kairos Power was one of five companies conditionally selected by DOE to receive HALEU in April 2025 under the agency’s HALEU Availability Program and has now completed negotiations to secure the HALEU required for the Hermes 1 programme. The company will use the material to produce HALEU TRISO (Tristructural-Isotropic) fuel pebbles for Hermes 1 in partnership with Los Alamos National Laboratory, using manufacturing processes developed and optimised in Kairos Power labs.
Kairos Power is developing Fluoride Salt-Cooled High-Temperature Reactors (KP-FHR) technology, following an iterative approach, moving from non-nuclear engineering test units (ETUs) to demonstration plants and finally a commercial fleet. First concrete for Hermes 1, a 35 MWt non-power reactor designed to demonstrate nuclear heat production, was poured in May 2025. The US Nuclear Regulatory Commission (NRC) issued a construction permit for Hermes 1 in 2023 – the first non-water-cooled reactor design to be approved for construction in the US in more than 50 years.
A construction permit was issued by NRC in November 2024 for Hermes 2, a two-unit plant (35 MWt each) designed to generate 50 MWe. Kairos plans deployment of a larger-scale version of the technology (188 MWt) starting in 2030.
Meanwhile, the ETUs are full-scale non-nuclear mock-ups used to test manufacturing and construction methods before applying them to nuclear projects. ETU 1.0 completed molten salt testing in Albuquerque, New Mexico; ETU 2.0, installed in 2025 was used to test modular equipment skids and fuel pebble handling; ETU 3.0, installed in Oak Ridge in July 2025, is the final testing and training platform for the Hermes reactor.
“We are pleased to secure the HALEU we need to demonstrate our technology with Hermes 1,” said Edward Blandford, Kairos Power Chief Technology Officer and co-founder. “The US Department of Energy has been a vital partner on the Hermes project, with its ongoing risk reduction investment through the Advanced Reactor Demonstration Program.”
Mike Laufer, Kairos Power CEO and co-founder, noted: “DOE’s support allows us to keep up our momentum, as we drive toward a shared goal of unlocking advanced nuclear energy’s potential and accelerating US reactor deployment. We appreciate DOE’s continued commitment to our iterative development process, helping us secure a reliable source of HALEU to meet our near-term fuel needs.”
The HALEU Availability Program was established in 2020 to secure a domestic supply of HALEU for civilian domestic research, development, demonstration, and commercial use. The programme acquires HALEU through purchase agreements with domestic industry partners and produces limited initial amounts of material from DOE-owned assets.
“The Department of Energy’s HALEU allocation programme is helping US nuclear reactor developers meet their near-term fuel needs,” said acting Deputy Assistant Secretary for Nuclear Fuel Cycle Florence Knauf. “We’re excited to see Kairos Power finalise their contract to receive HALEU and look forward to seeing them move forward with the fabrication of TRISO fuel for Hermes 1.”
DOE is investing up to $303m in the project through the Advanced Reactor Demonstration Program (ARDP) under a performance-based milestone contract. Kairos Power met two ARDP milestones in the last year, with the installation of reactor vessels for two non-nuclear hardware demonstrations that will test the integration of reactor systems, help establish the supply chain, and generate operating experience to inform the Hermes reactor series.
