Summary

Kairos Power is an Alameda, California Gen IV nuclear developer founded in 2016. Its KP-FHR (Kairos Power Fluoride salt-cooled High-temperature Reactor) uses TRISO fuel pebbles suspended in a liquid fluoride salt coolant — a fundamentally different approach from light water reactors and sodium fast reactors. The Hermes Low-Power Demonstration Reactor at Oak Ridge, Tennessee began nuclear safety-related construction in May 2025 — the first non-water-cooled reactor approved for construction in the United States in over 50 years, and the first Gen IV reactor to break ground in the US. In August 2025, Google, TVA, and Kairos announced a three-way PPA for Hermes 2 (the commercial follow-on, 50 MW) to power Google’s Tennessee Valley datacenters starting in 2030 — the first US utility PPA for Gen IV nuclear power. Kairos’s deal with Google calls for 500 MW of advanced nuclear capacity online by 2035.

Key Facts

  • Founded: 2016
  • HQ: Alameda, CA
  • Type: Private
  • Key investors / grants: ~$650M raised; DOE Advanced Reactor Demonstration Program (ARDP) award; private investors include Alphabet (Google), Breakthrough Energy Ventures
  • Reactor design: KP-FHR — Fluoride salt-cooled High-temperature Reactor
  • Fuel type: TRISO (Tri-structural ISOtropic) fuel pebbles — ceramic-coated uranium fuel particles embedded in graphite pebbles; manufactured by BWXT
  • Coolant: Liquid fluoride salt (flibe — lithium-beryllium fluoride); not water; operates at atmospheric pressure
  • Temperature: Outlet temperature ~600°C (higher than LWR at ~330°C); enables higher thermal efficiency and potential industrial process heat applications
  • Hermes (demonstration reactor): Low-power demonstration reactor, <35 MWth; at East Tennessee Technology Park, Oak Ridge TN; nuclear safety-related construction commenced May 8, 2025; NRC construction permit granted November 2023
  • Hermes 2 (first commercial unit): 50 MW electric (upgraded from original 28 MW); at Oak Ridge; commercial operation targeted 2030
  • Google PPA: 500 MW of advanced nuclear capacity by 2035; supplied to TVA grid powering Google datacenters in Tennessee and Alabama; first US utility PPA for a Gen IV reactor (announced August 2025)
  • TVA role: Purchases Hermes 2 power under PPA; distributes to Google loads; first utility to sign a Gen IV nuclear PPA in the US

What It Is / How It Works

Fluoride salt-cooled reactor physics: In a conventional LWR, pressurized water both cools the reactor and moderates neutrons (slowing them to the thermal range needed for chain reactions). In the KP-FHR, these functions are separated: liquid fluoride salt cools the reactor core and carries heat away, while graphite in the TRISO fuel pebbles and surrounding structure moderates the neutrons. The fluoride salt coolant operates at near-atmospheric pressure (unlike LWR pressurized water at ~155 bar) — which eliminates the risk of a pressure-driven loss-of-coolant accident and simplifies the reactor vessel design.

TRISO fuel: Each TRISO particle is a uranium fuel kernel surrounded by multiple ceramic layers (carbon buffer, inner PyC, SiC, outer PyC). The SiC layer is the primary fission product barrier — it is extremely hard and retains fission products up to ~1800°C, well above the maximum temperature the reactor can reach. TRISO is often described as “walk-away safe” fuel because even in a complete loss-of-cooling scenario, the fuel itself retains fission products. The pebbles are baseball-sized graphite spheres containing thousands of TRISO particles; they circulate through the core and can be replaced while the reactor operates.

Atmospheric pressure operation: Because fluoride salt doesn’t boil until ~1400°C and operates at atmospheric pressure, the reactor building does not need the massive pressure containment structures required for LWRs. Kairos designs the containment around retaining fluoride salt (a different engineering challenge) rather than resisting pressure. This is a source of potential cost reduction vs. LWR construction.

Heat conversion: Hermes 2 uses a steam cycle (conventional turbine-generator) to convert the high-temperature heat to electricity, with a plant efficiency advantage over LWRs because of the higher coolant outlet temperature.

The demonstration strategy: Kairos is using a “fly-many, fail-fast” approach borrowed from aerospace. Hermes (low-power) is intentionally designed to validate the reactor technology and NRC licensing process at low capital cost before Hermes 2 (commercial power). This sequenced demonstration model is different from TerraPower and NuScale’s direct-to-commercial-scale approach, and is arguably lower-risk: Hermes failure modes are containable, and lessons learned feed directly into Hermes 2 design.

Notable Developments

  • 2025-08: Google, TVA, and Kairos announce three-way PPA — TVA to purchase Hermes 2 output (50 MW) for Google datacenters; first US utility PPA for Gen IV nuclear; targeted operation 2030. (Kairos Press Release; Google Blog)
  • 2025-05-08: First nuclear safety-related concrete poured for Hermes reactor at Oak Ridge — formal start of nuclear construction; first non-water-cooled reactor to begin nuclear construction in the US in over 50 years. (Kairos Press Release)
  • 2023-11: NRC issues construction permit for Hermes — the first construction permit issued for a non-LWR advanced reactor in the US.
  • 2016: Founded by Edward Blandford, Raluca Scarlat, and Mike Laufer.

Key People

Edward Blandford — Co-Founder and Chief Nuclear Officer

  • LinkedIn: Search “Edward Blandford Kairos Power”
  • Background: Nuclear engineering professor at UC Berkeley; research focus on fluoride salt reactor thermal hydraulics; co-developed the KP-FHR concept in the Berkeley nuclear engineering department

Raluca Scarlat — Co-Founder

  • LinkedIn: Search “Raluca Scarlat Kairos Power”
  • Background: Nuclear engineering faculty at UC Berkeley; expertise in fluoride salt chemistry and materials compatibility — the key technical challenge for liquid salt-cooled systems

Mike Laufer — Co-Founder and CEO

  • LinkedIn: Search “Mike Laufer Kairos Power”
  • Background: Nuclear engineering background; CEO of Kairos since founding; leads regulatory strategy and commercialization

People — Last Reviewed: 2026-03-25

Supply Chain Position

Layer Detail
TRISO fuel BWXT — only current US TRISO manufacturer; Kairos has a TRISO supply agreement; BWXT’s capacity is a potential constraint as multiple TRISO-dependent programs (Kairos, X-energy) scale up
Fluoride salt coolant Flibe (Li-7 enriched lithium fluoride + beryllium fluoride); Li-7 enrichment is a specialized process; limited global suppliers
Reactor vessel and components Custom fluoride-salt-compatible alloys (Hastelloy N or similar); limited qualified fabricators
Turbine-generator Conventional steam turbine (Hermes 2); GE Vernova, Siemens, or Mitsubishi Power
Construction NRC-licensed nuclear construction contractor (not named for Hermes)
Power offtake TVA (utility) → Google (datacenter end user) via PPA

⚑ TRISO supply concentration: BWXT is the only US manufacturer of TRISO fuel. Both Kairos and X-energy depend on TRISO (X-energy’s Xe-100 also uses TRISO fuel). As both programs scale, BWXT’s TRISO production capacity becomes a shared constraint. BWXT is expanding TRISO capacity at its Lynchburg, VA facility but the expansion timeline must keep pace with reactor deployment schedules.

⚑ Li-7 enrichment: Fluoride salt coolant requires Li-7 enriched to >99.99% (to avoid tritium production from Li-6 neutron capture). The US currently has no commercial Li-7 enrichment capability — the historical US producer (Y-12) stopped production in the 1960s. Russia (TENEX) was the primary Western supplier; the Ukraine war has disrupted this. ORNL and DOE are developing a domestic Li-7 enrichment capability, but this is an unresolved supply chain dependency for Kairos.

Claim Verification

Claim: “First non-water-cooled reactor approved for construction in the US in over 50 years”

Status: Verified — NRC issued Hermes construction permit November 2023; nuclear safety construction commenced May 2025

Supporting: NRC public docket confirms the construction permit; no other non-LWR construction permit has been issued in the US since the 1970s

Summary: Accurate and verified.

Claim: 500 MW by 2035 (Google PPA)

Status: Contractually committed under the Google/TVA PPA; technically aspirational at this stage

Supporting: PPA is a binding commercial agreement; Hermes 2 (50 MW, 2030) is the first tranche; the remaining ~450 MW requires additional reactors whose siting, permitting, and construction haven’t yet started

Refuting / questioning: 2035 is 10 years from the Hermes 2 2025 construction start — aggressive but not impossible for a standardized design with an established licensing pathway; depends on Hermes 2 performing as expected and subsequent units receiving expedited NRC review

Summary: The Hermes 2 / 50 MW / 2030 component is on a credible path. The full 500 MW / 2035 is dependent on execution performance and regulatory velocity on subsequent units. Track Hermes 2 construction progress as the bellwether.

Sources