Kairos Power has started installing nuclear safety-related concrete for the Hermes Low-Power Demonstration Reactor project in Oak Ridge, Tennessee.

The project, which broke ground for the scaled demonstration of its KP-FHR fluoride salt-cooled high-temperature reactor technology, began on May 1 with safety-related construction activities under oversight from the US Nuclear Regulatory Commission (NRC), reported World Nuclear News.

The project will have 51 6-ft-diameter piers, anchoring the building to bedrock. About 70 piers have been drilled for Kairos Power's ETU 3.0 non-nuclear engineering test unit.

The Hermes reactor will use tri-structural isotropic (TRISO) uranium fuel and a mixture of lithium fluoride and beryllium fluoride salts known as Flibe as its coolant, ensuring robust inherent safety while simplifying the reactor's design.

The reactor is the first non-light-water reactor to be permitted in the US in more than 50 years and will not produce electricity. The commercial deployment of the reactor is supported by a master plant development agreement signed with Google in October 2024, for power from a fleet of up to 500 MW of capacity by 2035.