goingcritical:natrium-kemmererUnited States · Power reactor

Kemmerer Unit 1 (Natrium)

Status: Under construction target criticality 2030 (confidence: medium) ? Reactor status full glossary → Announced Publicly announced — a site and design are proposed, but construction has not begun. Site preparation Early site and civil works are under way; the first safety-related ("nuclear") concrete has not yet been poured. Under construction Formal construction has begun, marked by the first nuclear concrete. Fuel loaded Nuclear fuel has been loaded into the core. The reactor is fuelled but has not yet gone critical. Critical Has reached first criticality — a self-sustaining chain reaction, usually at low power — but is not yet connected to the grid. Grid connected Synchronised to the electrical grid and exporting power for the first time, but still in commissioning and power-ascension testing — not yet in commercial service. Operating In commercial operation — the operator has formally declared the unit in regular commercial service. Shut down Permanently shut down and no longer generating; may be defuelled, undergoing decommissioning, or preserved in place. Canceled Abandoned before completion.

Developer: TerraPower

Site: Kemmerer, Wyoming

OaklandKansas CityLas VegasPortlandSeattleDenverTulsa

TerraPower says the project is expected to be completed in 2030; construction_start is the start of NRC-permitted nuclear construction (non-nuclear sitework began June 2024)

Details

Design	Natrium sodium-cooled fast reactor with molten salt thermal storage (345 MWe, boostable to 500 MWe)
Electrical output	345 MWe

Milestone history

1. Announced November 2021
2. Construction start April 23, 2026
3. Fuel load —
4. First criticality target 2030
5. Grid connection —
6. Commercial operation —