Kairos Power

A company built around a different coolant

Kairos Power is an American nuclear energy company founded in 2016 and based in Alameda, California^[1]. Its co-founder and chief executive is Mike Laufer^[2]. The company's central project is not a scaled-up version of the light-water reactors that make up most of today's nuclear fleet, but a small modular reactor called KP-FHR — a fluoride salt-cooled high-temperature reactor^[1].

In a conventional reactor, water carries heat away from the fuel and is kept under pressure so that it does not boil at operating temperature. The KP-FHR changes two things at once. Its coolant is low-pressure molten fluoride salt rather than water, and its fuel is ceramic-coated TRISO pebbles rather than the familiar fuel rods^[1]. TRISO particles are small kernels of fuel wrapped in layers of ceramic; the coating is what gives the fuel its name and is meant to keep fission products inside the particle itself. A coolant that stays liquid at low pressure does not need the thick, highly pressurised vessel and high-pressure plumbing that a water-cooled plant requires, which changes what the surrounding systems have to withstand.

Kairos's stated goal is to deploy commercial plants built around 75-megawatt reactors, installed in pairs^[1]. Building two units together lets a site share turbines, controls and support facilities across both reactors.

Hermes, the demonstration reactor

In 2023 the Nuclear Regulatory Commission approved a construction permit for Hermes, a 35 MWth demonstration reactor built to test the design^[1]. The approval was the first granted for construction of a non-water-cooled reactor in the United States in more than 50 years^[1][2].

Kairos broke ground on the Hermes site at the East Tennessee Technology Park in Oak Ridge, Tennessee, in July 2024, and nuclear construction began in May 2025^[1].

Hermes 2 and the agreement with Google

Kairos applied in July 2023 for a construction permit for Hermes 2, a two-unit demonstration plant^[1]. After the company signed a power purchase agreement with Google, the design changed to a 50 MWe output integrated with the Tennessee Valley Authority grid, and the application was approved in November 2024^[1].

On 14 October 2024, Kairos Power and Google signed a Master Plant Development Agreement to deploy a fleet of advanced nuclear projects in the United States totalling 500 MW by 2035, with the first deployment by 2030^[2]. The companies said the deal was the first corporate agreement for multiple deployments of a single advanced reactor design in the United States^[2]. The arrangement links a reactor vendor directly to a large electricity buyer, rather than leaving the customer to shop among finished designs.

Licensing groundwork

As of January 2026, the NRC had approved 14 topical reports submitted by Kairos Power to support licensing of KP-FHR reactors^[1]. A topical report examines one technical subject in a reactor design — a method, a component, an analysis approach — and, once accepted by the regulator, can be cited in later licence applications instead of being argued again each time. Approving such reports in advance therefore settles some questions before a specific plant application arrives.

Where Kairos sits

The record of approvals is what distinguishes Kairos at this stage: a construction permit for a non-water-cooled reactor, the first in the United States in more than five decades^[1], a demonstration site under construction in Oak Ridge^[1], an approved two-unit follow-on plant^[1], and a corporate agreement for 500 MW of deployments by 2035^[2]. The design it is pursuing, salt-cooled with TRISO pebble fuel, is one of the routes being explored for reactors that operate at low pressure; whether the 75-megawatt paired commercial plants that are the company's goal get built will depend on how the demonstration units perform.