US-based Kairos Power has broken ground on the Hermes 2 Demonstration Plant in Oak Ridge, Tennessee. Hermes 2 is Kairos Power’s first deployment under its deal with Google to develop an advanced reactor fleet. The plant will supply up to 50 MWe to the Tennessee Valley Authority (TVA) grid, helping to decarbonise Google data centres in Tennessee and Alabama.
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 the Hermes Low-Power Demonstration Reactor (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). 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.
Through Kairos Power’s iterative development approach, Hermes 2 will build on lessons learned from Hermes 1, which began nuclear construction at the same site in 2025. The Hermes series will be the first fluoride salt-cooled high-temperature reactors (KP-FHRs) ever built, incorporating proven nuclear technologies that originated in Oak Ridge. These include TRISO coated particle fuel and Flibe molten fluoride salt coolant, which simplify the reactor’s design, lower capital costs, and yield robust inherent safety. As the immediate precursor to Kairos Power’s full-scale commercial plants, Hermes 2 will further advance technology, licensing, supply chain, and construction certainty for the company’s future deployments.
The Hermes 2 groundbreaking event was a recognition of the cumulative progress Kairos Power has made to date at its Oak Ridge reactor demonstration campus. Key stakeholders, including elected officials, community members, and commercial partners attended the event. They observed foundation work now in progress for Hermes 1 and saw the supporting infrastructure Kairos Power has built to enable testing and construction activities that will help drive down costs for the fleet. Barnard Construction Company, Inc. (Barnard) is serving as the general contractor for both Hermes reactor projects.
Kairos Power will fabricate Hermes 2 reactor equipment modules at its Manufacturing Development Campus in Albuquerque, New Mexico, and ship them to Oak Ridge for assembly, pioneering a factory-built small modular reactor (SMR) concept with the potential to transform nuclear project delivery.
The Hermes 2 civil structure will leverage modular construction methods, incorporating precast concrete and a seismically isolated foundation. The construction methods piloted with the Hermes series are expected to shrink project timelines, lower nuclear construction costs, and enable a standardised, repeatable design. Hermes 2 will be built on the footprint of the former Oak Ridge Gaseous Diffusion Plant at the K-33 site, which the Department of Energy (DOE) reclaimed through a cleanup effort and returned to the community for economic development. Kairos Power acquired the land in 2021, along with the adjacent K-31 site, for its reactor demonstration campus.
“For nuclear projects to be successful, we need more than just the right technology. We need to understand every aspect of project delivery. Hermes 2 is where that all comes together,” said Kairos Power CEO and co-founder Mike Laufer, “Oak Ridge, Tennessee, is our hub for nuclear construction and operations. We’re training a real workforce to do nuclear construction, learning from the Hermes 1 experience, and translating that knowledge to the Hermes 2 project next door.”
Edward Blandford, Kairos Power Chief Technology Officer and co-founder. “Hermes 2 culminates all of the lessons learned from Kairos Power’s iterative hardware demonstration program. It’s our first power-producing plant, the first delivery under our master plant development agreement with Google, and a long-term commitment to the Oak Ridge community.”
Matt Rasmussen, TVA Senior Vice President, and Chief Nuclear Officer noted that Kairos Power’s disciplined approach to next‑generation reactor design, paired with TVA’s first‑of‑its‑kind power purchase agreement, underscores how American innovation can set the pace for global nuclear advancement. “This project shows what’s achievable when industry and technology leaders align to expand US nuclear capability and secure a stronger, more resilient energy future for our country.”
Amanda Peterson Corio, Global Head of Data Centre Energy at Google said that, by pioneering a standardised, repeatable design, Kairos Power is addressing the historical challenges of nuclear construction costs. “This shift toward a more efficient, factory-based manufacturing approach is a proven path toward lower-cost, cleaner power for our operations and the communities we serve.”
