The Hermes Low-Power Demonstration Reactor in Oak Ridge, Tennessee, continues to advance through construction following the start of nuclear safety-related work in 2025. The project remains the first non-light-water reactor approved for construction in the United States in more than 50 years and serves as a critical demonstration of Kairos Power’s fluoride salt-cooled reactor technology. As of 2026, the project has moved beyond its initial site preparation phase while supporting broader efforts to commercialize next-generation nuclear energy across the country.
Hermes forms part of the U.S. Department of Energy’s Advanced Reactor Demonstration Program (ARDP), which aims to accelerate commercial deployment of advanced reactors. Since construction began in July 2024, Kairos Power has completed major site preparation activities and commenced nuclear safety-related concrete placement, marking a significant milestone toward reactor completion.
Hermes Low-Power Demonstration Reactor: Current project status (2026)
Construction remains active at the Hermes site, with nuclear safety-related structures progressing under NRC oversight. Kairos Power is also preparing its operating license application while advancing manufacturing capabilities for reactor components, molten salt production, and TRISO fuel deployment. Meanwhile, lessons learned from Hermes will directly support the larger Hermes 2 project and future commercial reactor deployments across the United States.
One of the project’s most significant developments in 2026 is the continued expansion of the Oak Ridge campus. In April 2026, Kairos Power broke ground on the adjacent Hermes 2 Demonstration Plant, the company’s first commercial-scale reactor and the first power-producing Generation IV reactor to receive a U.S. Nuclear Regulatory Commission construction permit. Hermes 2 will build on operational experience gained from Hermes while supplying electricity to the Tennessee Valley Authority grid under an agreement supporting Google data centers.
Another milestone came in January 2026 when the U.S. Department of Energy finalized an agreement to supply high-assay low-enriched uranium (HALEU) fuel for the Hermes reactor. The fuel supply supports future commissioning and strengthens the domestic advanced nuclear fuel supply chain.
The project also continues to demonstrate how advanced reactor construction is progressing nationwide. Similarly, the recently announced $15 Billion New Jersey Nuclear Project aims to deploy at least 1,100 MW of advanced nuclear generation through a competitive procurement process, highlighting growing state-level investment in next-generation nuclear infrastructure.
Technology innovation
The Hermes reactor derives from fluoride salt-cooled, high-temperature reactor (KP-HFR) instead of light-water reactors that dominate the United States’ reactor fleet. This new breed technology is expected to produce cheap nuclear heat in preparation for new breeds that will generate power. The Hermes reactor is not for power generation but is being used to communicate Kairos Power advanced reactor designs. NRC approval in December 2023 was vital for the further development of Kairos Power’s technology, as well as the various reviews and cooperation between the organization and the regulators. Pre-application interactions started in 2018 and comprised comprehensive assessments of the reactor’s safety and technical features to bolster the review process.
This successful regulatory approval occurs due to the safety design of the project while emphasizing its ability to progress the capability of nuclear energy in the U. S. Hermes is not just the project of a lifetime; it epitomizes the future of nuclear power in America. Through the proposed Hermes reactor, Kairos Power plans to make improvements in subsequent reactors in a bid to make the Hermes 2 plant and generate electricity. This stepwise approach is a part of the company’s approach to managing the technology, licensing, supply chain and construction risks in advanced reactor designs with the goal of achieving cost assurance as implemented in Kairos Power.
Completion date
Projected to be completed in 2027 l, The Hermes reactor construction will be a symbol of cooperation that involved the most important research facilities such as the Oak Ridge National Laboratory, Idaho National Laboratory, and the Electric Power Research Institute partners. These arrangements are crucial in assembling various forms of experience and support, which will only serve to strengthen the project and increase its possibilities for changing the face of nuclear power in the future. Thus far, the Hermes project by Kairos Power is not only about inventiveness in technology but also about people and the community’s responsibility to the planet.
The company has made a pledge to being a responsible corporate citizen in Oak Ridge and engaging with communities and other stakeholders making sure that the project has positive implications on different aspects of the society and not only in the technology realm. In a world transitioning towards seeking clean energy sources the HERMES reactor is a significant development within the nuclear field. It demonstrates that further development of the high technologies connected with nuclear energy is possible to ensure safe, affordable and reliable energy supplying which will contribute to the global efforts towards changeless future more effectively.
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Project fact sheet
Project name: Hermes Low-Power Demonstration Reactor
Location: Oak Ridge, Tennessee, USA
Project type: Advanced nuclear demonstration reactor
Reactor technology: Fluoride Salt-Cooled High-Temperature Reactor (KP-FHR)
Developer: Kairos Power
Thermal capacity: 35 MWth
Project status (2026): Under construction
Construction began: July 2024
Nuclear safety-related construction: Began May 2025
Current milestone: Site construction progressing; operating licence preparation underway
Fuel: TRISO pebble fuel using HALEU
Federal programme: U.S. DOE Advanced Reactor Demonstration Program (ARDP)
Key objective: Demonstrate advanced reactor technology before commercial deployment
Future expansion: Hermes 2 commercial-scale demonstration plant under construction
Expected operation: Targeted for 2027, subject to regulatory approvals.
Project team
Owner: Kairos Power
Developer: Kairos Power
Technology provider: Kairos Power
Federal partner: U.S. Department of Energy (DOE)
Regulator: U.S. Nuclear Regulatory Commission (NRC)
Construction contractor: Barnard Construction Company
Fuel partner: BWXT
Grid partner (Hermes 2): Tennessee Valley Authority (TVA)
Commercial offtake partner (Hermes 2): Google
Engineering and manufacturing: Kairos Power Manufacturing Development Campuses in Tennessee, California and New Mexico.
