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X-energy

X-energy

🇺🇸 Rockville, US · Founded 2009 · Active

X-energy is a US reactor and fuel company in Rockville, Maryland, founded in 2009 by Kam Ghaffarian. Its Xe-100 is a pebble-bed small modular reactor: helium gas cools a core of fuel pebbles packed with TRISO particles, and each module is rated at 200 MW of heat, about 80 MW of electricity. With Dow it applied in 2025 for a US Nuclear Regulatory Commission construction permit for the Long Mott Generating Station at a Dow site on the Texas Gulf Coast, and with Energy Northwest and Amazon it is planning the Cascade Advanced Energy Facility in Washington State, expected to operate in the mid-2030s. Its subsidiary TRISO-X is building a fuel plant, TX-1, which received an NRC licence in February 2026.

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Sector
Fission, Fuel cycle
Technology
High-temperature gas-cooled reactor
Fuel
TRISO particle fuel, High-assay low-enriched uranium
Role
Reactor developer, Supplier

Its recorded equity, $2.5bn, is the 4th largest of the 25 organisations with a priced round here. Not every round is on record, so this is not its total raised.

2 regulatory milestones are tracked here, all anchored to a docket reference in the regulator's own record.

Terms

High-temperature gas-cooled reactor
Helium-cooled and graphite-moderated, running far hotter than a water reactor. Fuel is TRISO particles, typically formed into pebbles or prismatic blocks, at LEU or HALEU enrichment depending on the design. The high outlet temperature suits industrial process heat as well as electricity.
TRISO particle fuel
Fuel kernels about the size of a poppy seed, each wrapped in layers of carbon and silicon carbide, so every particle acts as a tiny containment for its own fission products. The US Department of Energy reports that irradiated particles came through more than 300 hours of testing at temperatures up to 1,800 °C with no to minimal damage. That record covers the particle designs, temperatures and burnups actually tested; a claim outside that envelope is not covered by it.
High-assay low-enriched uranium
High-assay low-enriched uranium: uranium enriched to between 5% and just under 20% uranium-235, as the US Department of Energy defines it. It is still formally low-enriched, because the international line for highly enriched uranium is 20%, which is why many designs specify 19.75%. The binding supply constraint for many advanced reactor designs. The 5 to 10% part, which carries lighter US physical-security requirements than material from 10% up, is also tagged as LEU+. A developer calling fuel in that band 'LEU' is making a labelling choice, not describing a different enrichment.
TRISO fuel
Tri-structural isotropic fuel: fissile kernels in ceramic coatings that retain fission products at high temperature. The safety case for several advanced designs rests on it.

Funding

$2.5bn
equity in the 3 rounds recorded here
$438m
Grant
  1. 2026-04-23
    IPO
    Initial public offering on Nasdaq (XE): prospectus dated 23 April 2026, IPO closed 27 April 2026. 50,892,857 Class A shares at $23.00 including the over-allotment. Recorded at $1,089,764 thousand, the proceeds net of all issuance costs reported in the 10-Q equity statement; the 10-Q cash-flow line net of underwriting only is $1,103,235 thousand, and the gross at $23.00 a share is about $1.17 billion.
    $1.1bn
  2. 2025-11
    Equity round · Series D
    Series D Preferred Units: $700.0 million gross, closed 21 November 2025 (48,154,955 units). The prospectus reports $22.4 million of issuance costs against it. Investors are not named in the filing text used here.
    $700m
  3. 2024-10
    Equity round · Series C
    Series C-1, announced 16 October 2024 at about $500 million anchored by Amazon's Climate Pledge Fund, closed upsized at $700 million on 6 February 2025. One round: never record the October $500 million as a separate deal.
    $700m
  4. 2021-02
    Grant
    DOE Advanced Reactor Demonstration Program cooperative agreement (Award DE-NE0009040), effective 2 February 2021: a 50/50 cost share of $2.4 billion of eligible costs, i.e. up to $1.2 billion of DOE reimbursement through 2027. The amount recorded is what X-energy reports as actually reimbursed, about $438 million by 31 December 2025, not the $1.2 billion ceiling. Reimbursement continues: the 10-Q for Q1 2026 reports a further $28.8 million received in that quarter, not included here.
    $438m

Designs

Design Developer Approach Electrical output per unit Size class Licensing stage
Xe-100 X-energy High-temperature gas-cooled reactor 80 MWe planned Small modular reactor Accepted for review for one plant: Long Mott construction permit application accepted for docketing · US Nuclear Regulatory Commission · 2025-05-12

Licensing

  1. 2025-03-31achieved
    Application submitted
    Construction permit application submitted for Long Mott (Dow Seadrift) · US Nuclear Regulatory Commission
    Docket 50-614 · ADAMS ML25090A057 (application package)
  2. 2025-05-12achieved
    Accepted for review
    Long Mott construction permit application accepted for docketing · US Nuclear Regulatory Commission
    Docket 50-614 · ADAMS ML25115A247 (acceptance letter)

People

  • Dr. Kam GhaffarianFounder & Chairman · founder
  • J. Clay SellChief Executive Officer
  • Joel DulingPresident, TRISO-X
  • Steve MillerExecutive Vice President, Chief Legal and Administration Officer
  • Daniel GrossChief Financial Officer
  • Dragan PopovicExecutive Vice President, Chief of Global Operations
  • Dinkar S. BhatiaExecutive Vice President, Chief Commercial Officer
  • Laura GarciaSenior Vice President, Chief Accounting Officer
  • Carol LaneSenior Vice President, Government Affairs
  • Sam LevenbackSenior Vice President, Chief Growth & Strategy Officer
  • David BannisterChief Nuclear Officer; ARDP Project Deputy Director
  • Rachel Lappin ScheinmanChief Human Capital Officer
  • Jesse B. WalkerChief Supply Chain Officer
  • Matt WelshVice President & Chief Information Officer

Related companies

Sources