Natrium
TerraPower's sodium fast reactor with molten-salt thermal storage, holding a construction permit since 2026.
An 840 MWt sodium fast reactor providing 345 MWe continuously, coupled to thermal storage that can raise system output to 500 MWe. ARIS 2024 classified it as conceptual design; in March 2026 the NRC authorized construction of Kemmerer 1, which still requires a separate operating licence.
- Stated output
- 840 MWt · 345 MWe net/gross basis not stated · per unit
- Maturity
- Conceptual design
- Developer
- TerraPower / GE Vernova Hitachi Nuclear Energy
- Origin
- United States
Energy and applications
Published magnitudes; this is not an engineering diagram.
Three different states
Maturity, licensing and deployment are not equivalent.
Maturity
Conceptual designHow far the published engineering has progressed.
Licensing and review
1 regulatory readingWhat a regulator decided, where and on what date.
Linked deployment
1 geolocated unitWhich projects or units are linked to the design.
Linked deployment
| Plant | Unit | Country | Dataset status |
|---|---|---|---|
| Kemmerer | 1 | United States | planned |
Licensing and review
What a regulator decided, where and on what date.
| Jurisdiction | Reading | Method | Date |
|---|---|---|---|
| United States · Kemmerer | Site construction authorized | Construction permit CPAR-1 for Kemmerer Power Station Unit 1; a separate operating licence is required | 2026-03-09 |
Technical sources
- IAEA ARIS · SMR Catalogue 2024IAEA · 2024
- U.S. NRC · Kemmerer Power Station Unit 1 applicationRegulator · 2026-03-09
- U.S. NRC · Construction permit CPAR-1 issued to US SFR OwnerRegulator · 2026-03-09
- TerraPower · Natrium technology by the numbersDeveloper · 2024
How it works and why it matters
Natrium pairs a 345 MWe sodium-cooled fast reactor with a molten-salt tank that stores heat and lets output rise to 500 MWe for hours, to complement renewables. It uses metallic HALEU fuel.
It is being built at Kemmerer, Wyoming, on the site of a retiring coal plant. Non-nuclear construction began in 2024 and the NRC granted the construction permit in March 2026, the first for a commercial fast reactor in decades.
Quick facts
| Power | 345 MWe, up to 500 MWe with storage |
|---|---|
| Type | sodium fast reactor, pool type |
| Fuel | metallic HALEU |
| Status 2026 | under construction |