Construction has begun on the Hermes 2 Demonstration Plant in Oak Ridge, Tennessee, marking a step forward in advanced nuclear development in the United States.
The project is being developed by Kairos Power and represents the company’s first commercial-scale reactor. It is also the first power-producing Generation IV reactor to receive a construction permit from the Nuclear Regulatory Commission.
Hermes 2 will generate up to 50 megawatts of electricity for the Tennessee Valley Authority grid. The plant will support energy demand linked to data center operations associated with Google in Tennessee and Alabama.
The project builds on the earlier Hermes 1 low-power demonstration reactor, which entered the construction phase at the same Oak Ridge site in 2025. Hermes 1 remains the only Generation IV reactor currently under active nuclear construction in the United States.
Both reactors form part of a broader demonstration campus on land previously occupied by the Oak Ridge Gaseous Diffusion Plant. The U.S. Department of Energy led environmental cleanup at the site before redevelopment, and Kairos Power acquired the property in 2021.
Cooling
Hermes 2 will use fluoride-salt-cooled high-temperature reactor technology, incorporating TRISO fuel and molten fluoride salt coolant. The design is intended to improve safety characteristics while reducing construction complexity and costs.
Barnard Construction Company is the general contractor for the Hermes projects. Kairos Power will manufacture Hermes 2 reactor components at its facility in Albuquerque, New Mexico, and transport them to Tennessee for assembly.
The project will also apply modular construction methods, including precast concrete structures and a seismically isolated foundation. These approaches are aimed at shortening build timelines and enabling repeatable reactor designs.
Hermes 2 forms part of a broader agreement between Kairos Power and Google to develop a fleet of advanced nuclear reactors, with the demonstration plant serving as a precursor to future commercial deployments.
The Hermes 2 construction milestone follows other developments in the U.S. nuclear sector, including the EAGL-1 small modular reactor project, which has entered regulatory engagement with the Nuclear Regulatory Commission for a fast-spectrum lead-bismuth cooled design intended for utility-scale deployment.
Hermes 2 Demonstration Plant – Factsheet
- Project name: Hermes 2 Demonstration Plant
- Location: Oak Ridge, Tennessee, United States
- Project type: Advanced nuclear reactor (Generation IV)
- Status: Construction started
- Developer: Kairos Power
- Regulator: Nuclear Regulatory Commission
- Grid operator: Tennessee Valley Authority
- Commercial partner: Google
- General contractor: Barnard Construction Company
Capacity:
Up to 50 MW
- Reactor type: Fluoride-salt-cooled high-temperature reactor (KP-FHR)
- Fuel type: TRISO coated particle fuel
- Coolant: Flibe molten fluoride salt
- Construction approach: Modular construction with precast concrete and seismic isolation
- Manufacturing: Reactor modules fabricated in Albuquerque, New Mexico
- Site details: Built on former Oak Ridge Gaseous Diffusion Plant (K-33 site)
Related project:
Hermes 1 low-power demonstration reactor (under construction at same site)
- Purpose: Demonstration of commercial-scale advanced reactor technology and support for data center energy demand
- End use: Power supply to TVA grid, including support for Google operations in Tennessee and Alabama
