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TerraPower

Natrium sodium fast reactor, molten salt storage

USprivateest. 2008terrapower.com (opens terrapower.com)Checked 25 Sep

The brief

Analyst view
  • Won its NRC construction permit in March 2026 and started nuclear construction in April 2026.
  • Molten-salt tanks sit between reactor and turbine, so a 345 MWe reactor can peak at 500 MWe.
  • Operation targeted for 2030, slipped from 2028 mainly by a shortage of HALEU fuel.

Technical approach

As reported
Reactor

Sodium-cooled fast reactor

Liquid sodium cools the core at normal pressure. It boils at 883 °C, far above operating heat, so there is no high-pressure coolant to leak.

Fuel

Metal HALEU fuel

Uranium-zirconium metal fuel enriched to under 20% (HALEU), based on decades of EBR-II experience. It burns more of its fuel than water reactors.

Storage

A molten-salt heat battery

Reactor heat is stored in tanks of hot salt, as at solar plants. Drawing on them lets output surge to 500 MWe for 5+ hours.

Safety

Cooling without pumps

Air flowing naturally around the reactor vessel removes leftover heat, with no pumps or operators needed.

Programs

TerraPower, two programs

Updated 19d ago
Natrium (Kemmerer Unit 1)First Natrium plant, near Kemmerer, Wyoming, replacing a retiring coal plant. A sodium-cooled reactor heats molten salt, which drives an ordinary steam turbine.PilotNextNuclear island construction · Apr 2026Updated 19d agoView program →Molten Chloride Fast ReactorA fast reactor whose fuel is dissolved in molten chloride salt, developed with Southern Company and DOE. A small experiment (MCRE) at INL will test the physics.ResearchNextMCRE test reactor starts its chain reaction at INLUpdated 1 Sep 2025View program →
Research · Proto · Pilot · Deploy · Scaling

Research & demos

1 item

Open technical problems

Open · Active · Partial
  • HALEU fuel supplyActive research

    The US has almost no commercial HALEU enrichment since Russian supply was cut off, pushing Natrium from 2028 to 2030.

  • Handling sodium at scalePartially solved

    Sodium reacts violently with water and burns in air, so leaks must be prevented for decades.

Upcoming catalysts

Company-wide
  • 2027Operating licence application to the NRCNatrium (Kemmerer Unit 1)by ~15 mo
  • 2028Molten Chloride Reactor Experiment expected to run at INL for about six monthsMolten Chloride Fast Reactorby ~27 mo
  • 2030Natrium commercial operationNatrium (Kemmerer Unit 1)by ~51 mo

Peers

Fission · 4

Company & funding

2 rounds · as reported
Raised
$1.4Bdisclosed private rounds
Last round
Equity raiseJun 2025
HQ
US
Founded
2008
DateRoundAmountPost-moneyLead
Jun 2025Equity raise$650M——
Aug 2022Equity raise$750M—SK Inc., Bill Gates

Partners & customers

3 partners · 2 investors · 1 customer

People

Key people
Primer