Barnard Construction Co. Inc., Bozeman, Mont., is building the facility construction in Oak Ridge, Tenn., at a former U.S. Energy Dept. site that is set to complete by 2027 as a “critical step” to commercialize the technology, said Kairos Power. It anticipates a commercial reactor could operate "in the early 2030s."  

The Tennessee Valley Authority has been working with the developer to provide engineering, operations and licensing support.

The Hermes project received in 2020 a seven-year funding award of $629 million under the U.S. Energy Dept.'s Advanced Reactor Demonstration Program, with the agency to directly invest about $303 million. Payments are based on milestones such as construction progress and application for a future federal operating license, it said.

"This investment ... will complement Kairos Power’s substantial private investment in the Hermes project and supporting infrastructure," the developer said, although it not disclose its own investment total or names of other supporting private investors.

Barnard and Kairos Power also are building a third engineering test unit in Oak Ridge, what the developer said is a “non-nuclear” facility “that will generate supply chain, construction and operational experience to inform the Hermes project.” Two other test units have been built at a research location operated by Kairos Power in Albuquerque, N.M.

The reactor will be built using modular construction techniques, with reactor modules fabricated at the Albuquerque site and shipped to Oak Ridge for assembly—“demonstrating the potential of a factory-built small modular reactor design to transform conventional nuclear construction,” Kairos Power said. It seeks to reduce technical risk “through a novel approach to test iteration that often is lacking in the nuclear space.” 

The facility is designed to operate at high temperatures and near‐atmospheric pressure, using a special particle fuel coupled with a molten fluoride salt coolant, the company told the nuclear commission in a 2023 filing. “The combination of extremely high‐temperature‐tolerant fuel and low‐pressure, single‐phase, chemically stable reactor coolant removes entire classes of potential fuel‐damage scenarios, greatly simplifying the design and reducing the number of safety systems," said Peter Hastings, Kairos Power vice president of regulatory affairs and quality in the filing.

"This historic initiative presents a critical opportunity to transform the way we generate power in the U.S., as well as an opportunity to expand economic and employment opportunities for the greater Tennessee area,” said Quincy Anderson, Barnard vice president and operating manager.

Kairos Power also plans to develop a successor project, Hermes 2, at Oak Ridge, which will comprise two 35-MWh test reactors. It will use the same fuel but is set to produce a combined electrical output of 20 MWe via an integrated steam-powered conversion system, the developer said, adding that the project will “further de-risk technology, construction, supply chain and licensing for a multi-reactor plant.” In July, the commission completed its final safety evaluation for Hermes 2.