Supply will be used for Hermes 1 advanced reactor demonstration programme
US-based advanced nuclear reactor developer 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, for the startup and operation of the company’s Low-Power Demonstration Reactor, Hermes 1, currently under construction in Oak Ridge, Tennessee.
Kairos Power was conditionally selected by the DOE to receive Haleu earlier this year under the agency’s Haleu Availability Program and has successfully completed negotiations to secure the Haleu required for the Hermes 1 programme.
The company will use the material to produce Haleu Triso fuel pebbles for Hermes 1 in partnership with Los Alamos National Laboratory, using manufacturing processes developed and optimised in Kairos Power labs.
Hermes 1 is a scaled demonstration of Kairos’ KP-FHR fluoride salt-cooled high-temperature reactor technology and the first non-light-water reactor to be approved for construction by the US Nuclear Regulatory Commission. Kairos Power broke ground at the Hermes 1 site in Oak Ridge in July 2024 and began nuclear safety-related construction in May 2025.
Kairos Power sad the Hermes 1 reactor and fuel fabrication programme will provide crucial learning to enable the success of Kairos Power’s future commercial fleet.
Hermes 1 will use Triso pebble fuel with a mixture of lithium fluoride and beryllium fluoride salts known as Flibe as its coolant. It will have thermal power output of 35 MWth and no electric capacity.
Background: Advantages And Project Pipeline
Salt-cooled reactors, also known as molten salt reactors, are said to have advantages over more traditional water-cooled plants, including improved safety and higher efficiency. Molten salts have excellent chemical stability and tremendous capacity for transferring heat at high temperature and retaining fission products.
Triso – or “tristructural-isotropic” – fuel particles contain a spherical kernel of enriched uranium oxycarbide surrounded by layers of carbon and silicon carbide, which contains fission products.
According to the DOE, Triso is essentially a “robust, microencapsulated fuel form” developed originally in the 1950s.
Hermes is one of several projects being supported through the US DOE’s advanced reactor demonstration programme, which is designed to help the domestic nuclear industry demonstrate its advanced reactor designs and ultimately help the US build a competitive portfolio of new US reactors that offer significant improvements over today’s technology.
In October tech company Google announced it would back the construction of seven SMRs from Kairos Power, becoming the first tech company to commission new nuclear power plants to provide low-carbon electricity for its energy-hungry data centres.
Kairos is one of four companies chosen by Texas A&M University System to explore developing advanced nuclear power reactors on its Rellis research campus.
It is also one of eight companies chosen to potentially demonstrate their ability to deliver nuclear power for defence installations in the US.
