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TerraPower

TerraPower

🇺🇸 Bellevue, US · Founded 2006 · Active

TerraPower is a nuclear technology company in Bellevue, Washington, founded in 2006 by Bill Gates. Its main design is Natrium, a 345 MWe sodium-cooled fast reactor paired with molten-salt heat storage that lets the plant raise its output to 500 MWe for periods. The US Nuclear Regulatory Commission issued a construction permit for Kemmerer Unit 1 in Wyoming in March 2026, the first it has issued for a reactor not cooled by light water, and reactor construction began in April 2026. TerraPower earlier developed the travelling wave reactor, whose planned project in China was dropped in 2019, and in 2022 announced plans with Southern Company for a molten chloride fast reactor experiment at Idaho National Laboratory. Its subsidiary TerraPower Isotopes produces actinium-225 for cancer treatment.

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Sector
Fission
Technology
Sodium fast reactor
Fuel
High-assay low-enriched uranium
Role
Reactor developer

It is the operator of record for Kemmerer Power Station Unit 1 (under construction).

Its recorded equity, $1.5bn, is the 5th largest of the 25 organisations with a priced round here. Not every round is on record, so this is not its total raised.

4 regulatory milestones are tracked here, 3 of them anchored to a docket reference in the regulator's own record.

Terms

Sodium fast reactor
Liquid sodium coolant with a fast, unmoderated neutron spectrum. Sodium carries heat superbly at atmospheric pressure, but burns in air and reacts violently with water. Large sodium-cooled cores can have a positive sodium void effect that the core design must offset. Fuel is typically metal alloy or mixed-oxide.
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.

Funding

$1.5bn
equity in the 2 rounds recorded here
  1. 2025-06-18
    Equity round · Growth
    $650 million fundraise, announced as closed on 18 June 2025, with NVentures (NVIDIA), Bill Gates and HD Hyundai named. No round name is given. A later release (20 January 2026) says Korea Hydro & Nuclear Power invests through "SK's previously announced $250 million investment"; that SK commitment's date and relation to this round are not stated in any document opened, so it is not recorded.
    $650m
  2. 2022-08
    Equity round · Growth
    Equity raise first announced 15 August 2022 at a minimum of $750 million (co-led by SK Inc./SK Innovation and Bill Gates), then concluded at $830 million on 3 November 2022 after a further $80 million from ArcelorMittal, KSOE and others. One round: never record the $750 million announcement as a separate deal.
    $830m

Designs

Design Developer Approach Electrical output per unit Size class Licensing stage
Natrium TerraPower with GE Vernova Hitachi Nuclear Energy Sodium fast reactor 345 MWe planned Large reactor Construction permit issued for one plant: NRC construction permit CPAR-1 issued for Kemmerer Power Station Unit 1 (Natrium) · US Nuclear Regulatory Commission · 2026-03-09

Devices

Kemmerer Power Station Unit 1SFRUnder constructionNo figures yet

Licensing

  1. 2024-03-28achieved
    Application submitted
    Construction permit application submitted for Kemmerer Power Station Unit 1 (Natrium), Wyoming · US Nuclear Regulatory Commission
    Docket 50-613 · ADAMS ML24088A059 (application)
  2. 2024-05-21achieved
    Accepted for review
    Kemmerer Unit 1 construction permit application accepted for docketing · US Nuclear Regulatory Commission
    Docket 50-613 · ADAMS ML24135A109 (acceptance letter)
  3. 2026-03-09achieved
    Construction permit issued
    NRC construction permit CPAR-1 issued for Kemmerer Power Station Unit 1 (Natrium) · US Nuclear Regulatory Commission
    Construction Permit CPAR-1 · Docket 50-613 · ADAMS ML26034B247
  4. 2026-04-23claimed
    Construction start
    Kemmerer Unit 1: nuclear construction begins (reported)
    Aggregator source only. No regulator anchor: the construction permit (CPAR-1, 2026-03-09) is anchored separately; this start date is not. Non-nuclear site work began in June 2024.
    No public anchor for this stage

Related companies

Sources