First concrete marks start of safety-related construction for Hermes test reactor
Kairos Power announced this morning that safety-related nuclear construction has begun at the Oak Ridge, Tenn., site where the company is building its Hermes low-power test reactor. Hermes, a scaled demonstration of Kairos Power’s fluoride salt–cooled, high-temperature reactor technology, became the first non–light water reactor to receive a construction permit from the Nuclear Regulatory Commission in December 2023. The company broke ground at the site in July 2024.
A rebar cage is placed in the drilled shaft. (Photo: Kairos Power)
Concrete flows into the first drilled pier shaft for the Hermes foundation. (Photo: Kairos Power)
Foundational construction: Safety-related work on Hermes’s foundation began May 1. To ensure structural soundness, Hermes will have 51 six-foot-diameter drilled piers extending about 40 feet below grade to anchor the building to bedrock, Kairos said. After drilling and before concrete begins to pour, a rebar “cage” will be lowered into the pier shaft.
“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,” said Kairos Power CEO and cofounder Mike Laufer. “This achievement reflects the value of our iterative development process to meet the necessary nuclear quality standards and provide crucial real cost information that gives confidence to our customers.”
Tried and tested: Before drilling and filling the first pier for Hermes, Kairos and its contractors tested the process during two earlier projects.
Led by Barnard Construction Company, the construction team completed a test pier in November 2024 they called “Pier 52.” They then drilled 70 piers for Kairos Power’s nonnuclear Engineering Test Unit (ETU 3.0) facility over four months using quality control checklists like those required for Hermes. The team eventually was able to install as many as six piers in a single day, according to Kairos.
“The Hermes project team continues to lead the industry as we forge a new path in advanced reactor construction,” said Kairos Power chief technology officer and cofounder Edward Blandford. “Working with our partners and in close communication with the NRC, we are committed to maintaining the highest standards of quality and safety to ensure the success of this project.”
Part of a plan: As a 35-MWt fluoride salt–cooled, high-temperature reactor, Hermes is intended to demonstrate Kairos Power’s nuclear systems, manufacturing capabilities, supply chain, and licensing certainty. Both Hermes and Hermes 2, which got a construction permit in November 2024, will use TRISO fuel pebbles and FliBe molten fluoride salt coolant; both are part of Kairos’s “iterative pathway” to commercializing a 140-MWe fluoride salt–cooled, high-temperature reactor called KP-FHR.
In December 2020, Kairos received a Department of Energy Advanced Reactor Demonstration Program (ARDP) award for risk-reduction funding to support the development, construction, and commissioning of Hermes. The total award value was $629 million over seven years, with the DOE contributing $303 million. In February 2024, Kairos announced that it had reached an agreement with the DOE to use a performance-based, fixed-price milestone approach to implement the ARDP funding.
