Kairos Power
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Kairos Power is a United States advanced nuclear reactor developer founded in 2016 and headquartered in Alameda, California. The company is building the Kairos Power Fluoride salt-cooled High-temperature Reactor (KP-FHR), a Generation IV design that uses a molten fluoride salt coolant and ceramic-coated particle fuel in place of the pressurized water and metal-clad fuel rods of conventional light-water reactors. Kairos follows a hardware-driven, rapid-iteration development model, fabricating a series of full-scale non-nuclear test units before committing to nuclear construction. Its first reactor project, the Hermes low-power demonstration reactor in Oak Ridge, Tennessee, received a U.S. Nuclear Regulatory Commission (NRC) construction permit in December 2023, the first construction permit for a non-light-water reactor issued in the United States in more than 50 years. In October 2024 Kairos signed an agreement with Google to deploy up to 500 megawatts of advanced nuclear capacity by 2035, the first such agreement between a hyperscale technology company and an advanced reactor developer, which placed Kairos at the center of efforts to supply AI data centers with around-the-clock carbon-free power.
Kairos Power was founded in 2016 by Mike Laufer, Edward Blandford, and Per Peterson. Laufer serves as chief executive officer. Peterson is a nuclear engineering professor at the University of California, Berkeley, and the KP-FHR concept draws on academic fluoride salt-cooled, high-temperature reactor research carried out at Berkeley and partner universities, as well as on molten fluoride salt technology first developed at Oak Ridge National Laboratory during the Molten Salt Reactor Experiment of the 1960s. The company is singularly focused on commercializing the KP-FHR and describes its objective as delivering nuclear energy that is cost-competitive with natural gas.
The company is headquartered in Alameda, California, and operates manufacturing and testing campuses in Albuquerque, New Mexico, and Oak Ridge, Tennessee. Kairos has emphasized vertical integration, building in-house the specialized components that a fluoride salt reactor requires rather than depending on an immature external supply chain.
The KP-FHR is a molten salt coolant reactor. Unlike the molten salt reactors of the 1960s, which dissolved fissile material directly in the salt, the KP-FHR keeps the fuel solid and uses the salt only as a coolant. This combination of a salt coolant with solid coated-particle fuel is what distinguishes the fluoride salt-cooled high-temperature reactor class.
The reactor is cooled by Flibe, a chemically stable molten salt made of lithium fluoride and beryllium fluoride. Flibe remains liquid across a wide temperature band and operates at near-atmospheric (low) pressure, so the reactor does not need the thick, high-pressure vessel and containment that water-cooled plants require to keep their coolant from flashing to steam. The reactor outlet temperature is approximately 650 degrees Celsius, high enough to drive an efficient power-conversion cycle and to supply industrial process heat.
The fuel is TRISO (tristructural isotropic) coated particles. Thousands of poppy-seed-sized TRISO particles, each wrapped in a triple-layered ceramic shell, are packed into golf-ball-sized graphite pebbles that circulate through the core. The ceramic coatings act as a miniature containment around each fuel kernel and are designed to retain fission products at temperatures far above normal operation. The reactor uses HALEU (high-assay low-enriched uranium) enriched to roughly 19.75 percent, just below the 20 percent threshold that separates low-enriched from highly enriched uranium.
Kairos markets the KP-FHR on inherent and passive safety. Because the salt operates at low pressure and has a very high boiling point, there is no stored pressure energy to disperse radioactive material, and the coolant cannot boil away in an accident. The TRISO fuel cannot melt within the reactor's operating envelope. The design is engineered for automatic safe shutdown and passive decay-heat removal on a loss of power, so the core stays protected without operator action or external electricity.
The eventual commercial product is a KP-FHR power plant configured as a dual-unit module generating about 150 megawatts of electricity (two units of roughly 75 megawatts each), with the design intended to scale to larger sites of 450 megawatts or more. The Hermes reactors are demonstration steps toward that commercial plant rather than the final product.
| Parameter | Hermes 1 (demonstration) | Hermes 2 (demonstration) | KP-FHR commercial plant |
|---|---|---|---|
| Reactor type | KP-FHR test reactor | KP-FHR demonstration plant | KP-FHR power plant |
| Thermal power | 35 MWt (single reactor) | 2 x 35 MWt | commercial-scale units |
| Electric output | None (heat demonstration only) | About 28 MWe as permitted; up to 50 MWe per later agreements | About 150 MWe (2 x ~75 MWe), scalable to 450+ MWe |
| Coolant | Flibe, near-atmospheric pressure | Flibe | Flibe |
| Outlet temperature | About 650 C | About 650 C | About 650 C |
| Fuel | TRISO pebbles, HALEU (~19.75%) | TRISO pebbles, HALEU | TRISO pebbles, HALEU |
| Location | Oak Ridge, Tennessee | Oak Ridge, Tennessee | To be determined |
| NRC construction permit | December 2023 | November 2024 | Not yet filed |
Hermes is a 35-megawatt-thermal, single-reactor demonstration plant at the East Tennessee Technology Park (Heritage Center Industrial Park) in Oak Ridge, Tennessee. It is deliberately a heat-only machine: Hermes does not generate electricity, and its purpose is to demonstrate that Kairos can license, build, fuel, and operate a KP-FHR affordably and on schedule, proving out the salt systems, the pebble fuel handling, and the supply chain.
On December 12, 2023, the NRC voted to issue a construction permit for Hermes. The permit was a landmark in U.S. nuclear regulation: Hermes became the first Generation IV reactor approved for construction by the NRC and the first non-light-water reactor permitted in the United States in more than 50 years. Kairos credited the relatively fast review to extensive pre-application engagement with the NRC that began around 2018. Site excavation began on July 17, 2024, and Kairos poured its first nuclear safety-related concrete in May 2025, making Hermes the only Generation IV reactor under active nuclear construction in the country. The company initially targeted reactor operation around 2027. Project partners include Oak Ridge National Laboratory, Idaho National Laboratory, Los Alamos National Laboratory, the Electric Power Research Institute, Materion Corporation, and the Tennessee Valley Authority.
Hermes 2 is a larger demonstration plant at the same Oak Ridge site, designed to add a power-generation system so that Kairos can demonstrate electricity production. As filed and permitted, the plant comprises two 35-megawatt-thermal reactors. On November 20, 2024, the NRC voted to issue construction permits for Hermes 2, with the permits issued the following day. The review took roughly 16 months from the July 2023 application. Hermes 2 became the first electricity-producing Generation IV plant approved for construction in the United States. As permitted the plant was designed to generate about 28 megawatts of electricity; under its later supply agreements Kairos has described Hermes 2 as delivering up to 50 megawatts to the grid. Kairos broke ground on Hermes 2 in April 2026. It is the first deployment under the company's 2024 agreement with Google, and its output is contracted to the Tennessee Valley Authority to help power Google data centers in Tennessee and Alabama. Operations are scheduled to begin in 2030.
| Date | Milestone |
|---|---|
| 2016 | Kairos Power founded (Laufer, Blandford, Peterson) |
| December 16, 2020 | DOE ARDP Risk Reduction award selected (Hermes) |
| December 12, 2023 | NRC issues Hermes construction permit (first non-light-water permit in 50+ years) |
| February 2024 | DOE Technology Investment Agreement (up to $303M, milestone-based) |
| July 17, 2024 | Hermes site excavation begins |
| October 14, 2024 | Google 500 MW Master Plant Development Agreement signed |
| November 21, 2024 | NRC issues Hermes 2 construction permits (first electricity-producing Gen IV approved in U.S.) |
| May 2025 | First nuclear safety-related concrete poured at Hermes |
| August 18, 2025 | TVA, Google, and Kairos collaboration; TVA power purchase agreement for Hermes 2 |
| January 20, 2026 | DOE HALEU supply contract finalized for Hermes fuel |
| April 2026 | Hermes 2 groundbreaking |
On October 14, 2024, Kairos Power and Google signed a Master Plant Development Agreement creating a path to deploy a fleet of KP-FHR power plants totaling up to 500 megawatts of electricity in the United States by 2035, with the first plant targeted for around 2030. Under the structure, Kairos develops, builds, and operates the plants and sells Google the electricity, ancillary services, and environmental attributes through power purchase agreements, siting the reactors in grid service territories that serve Google data centers. Reporting at the time described the fleet as roughly six to seven reactors built across several plants. Google characterized it as the company's first nuclear energy deal and as the world's first corporate agreement for multiple advanced reactor deployments of the same design. For Kairos, the commitment provided an early demand signal that, in chief executive Mike Laufer's words, would let the company "quickly advance down the learning curve" toward cost and schedule certainty for its commercial product.
The arrangement was made concrete in 2025. On August 18, 2025, Kairos, Google, and the Tennessee Valley Authority announced a collaboration under which TVA agreed to buy up to 50 megawatts of around-the-clock power from Hermes 2, routing it to the grid that serves Google data centers in Tennessee and Alabama. Kairos and TVA described the arrangement as the first power purchase agreement ever signed for a U.S. advanced reactor. At the same time the targeted output of Hermes 2 was raised from about 28 megawatts to as much as 50 megawatts.
| Counterparty | Date | Key terms |
|---|---|---|
| U.S. Department of Energy (ARDP) | Dec 2020 / Feb 2024 | Up to $303M federal cost share within a $629M, seven-year Hermes risk-reduction project |
| October 14, 2024 | Master Plant Development Agreement; up to 500 MWe across multiple reactors by 2035, first around 2030 | |
| Tennessee Valley Authority / Google | August 18, 2025 | TVA power purchase agreement for up to 50 MW from Hermes 2 serving Google data centers (first PPA for a U.S. advanced reactor) |
| U.S. Department of Energy (HALEU) | January 20, 2026 | HALEU supply contract for Hermes TRISO fuel |
The Google deal sits within a broader 2024 to 2026 wave of agreements pairing hyperscale computing with new nuclear capacity, driven by surging AI energy demand. In the same period Microsoft contracted with Constellation Energy to restart a unit at Three Mile Island, and Amazon invested in X-energy, another TRISO-fueled developer. Kairos competes in the advanced reactor field with small modular reactor and microreactor developers including Oklo, TerraPower, and X-energy.
Kairos differentiates itself through an engineering culture of "design, build, test, repeat," constructing full-scale non-nuclear prototypes called Engineering Test Units (ETUs) to retire risk before nuclear hardware is committed. The ETUs run real Flibe salt and reactor-scale components without nuclear fuel, letting the company iterate quickly in a less restrictive environment.
The first unit, ETU 1.0, operated in 2023 at the company's Manufacturing Development Campus (KP Southwest) in Albuquerque, New Mexico, which Kairos established around 2020. ETU 1.0 transported 14 metric tons of Flibe from Ohio to New Mexico, loaded it at about 600 degrees Celsius, and logged more than 2,000 hours of pumped-salt operation, reportedly reaching the highest Flibe flow rate recorded at 3,000 gallons per minute; it was decommissioned in 2024. ETU 2.0, also in Albuquerque, is built from more than 30 modular, skid-mounted systems and produced the company's first internally fabricated ASME U-stamp reactor vessel. ETU 3.0, under construction in Oak Ridge, focuses on remote handling, operator training, civil construction methods, and advanced electron-beam welding, with completion targeted for the summer of 2026.
Supporting these units, Kairos has invested in in-house fabrication of stainless steel and graphite components, code-stamped pressure vessels, and surrogate (non-nuclear) TRISO pebbles. For coolant, the company commissioned a molten salt purification plant at the Materion campus in Elmore, Ohio, in 2022, and is standing up a dedicated salt production facility to make reactor-grade Flibe, planned to begin production in 2026. Fuel development for the Hermes reactors is being carried out in partnership with Los Alamos National Laboratory.
Kairos Power's financing leans heavily on federal cost-share and milestone-based contracts rather than disclosed venture rounds. On December 16, 2020, the U.S. Department of Energy selected Kairos's Hermes project as one of five awards under the Advanced Reactor Demonstration Program (ARDP) Risk Reduction pathway. The award covers a project valued at roughly $629 million over seven years, of which the DOE share is up to $303 million. In February 2024 the department and Kairos executed a Technology Investment Agreement implementing that award through a performance-based, fixed-price milestone structure, under which Kairos receives fixed payments as it meets defined design, construction, and commissioning milestones.
Federal support also extends to fuel. On January 20, 2026, Kairos finalized a contract with the DOE to receive high-assay low-enriched uranium for Hermes, following a conditional selection in 2025 under the department's HALEU Availability Program; that material will be fabricated into HALEU TRISO pebbles for the reactor in partnership with Los Alamos National Laboratory. Kairos has raised private capital in addition to these public commitments, but unlike many startups it has not published detailed venture financing rounds or a public valuation, relying instead on a mix of government agreements, customer offtake, and private investment.
Kairos Power matters as the first advanced reactor company to sign a multi-plant offtake with a hyperscale technology buyer, making the Google agreement a template for how AI-driven electricity demand might underwrite first-of-a-kind nuclear projects. Its Hermes reactors are the leading practical test of the fluoride salt-cooled, high-temperature reactor class in the United States, and Hermes was the first non-light-water reactor licensed for construction in the country in half a century. Whether Kairos can translate its rapid-iteration model and its government and corporate backing into a cost-competitive commercial plant remains the central open question, but as of 2026 it is among the most advanced of the new wave of developers attempting to do so.