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Natrium
Under constructionTerraPower's sodium fast reactor with molten-salt thermal storage, holding a construction permit since 2026.
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 |