Milestones
- Kemmerer selected as first Natrium siteNov 2021Complete.
- Non-nuclear construction beginsJun 2024Complete.
- NRC dockets construction permit applicationMay 2024Complete.
- NRC completes safety reviewDec 2025Complete.
- NRC construction permit issuedMar 2026Complete.
- Nuclear island constructionTarget Apr 2026Current milestone.
- Commercial operationTarget 2030+24 mo
originally 2028Not yet reached.
Most important updates
- 19d ago
- 31 Aug 2026
- Apr 2026
- 4 Mar 2026
- 10 Jun 2024
Upcoming
- Apr 2026Nuclear island construction (next)
- 2027Operating licence application to the NRC
- 2030Commercial operation+24 mo
originally 2028
Current obstacles
- HALEU for the first coreThe first fuel depends on new US enrichment and conversion plants that are still being built.
- First-of-a-kind cost and scheduleThe US hasn't built a commercial sodium fast reactor in decades, so costs, supply chains and schedule are uncertain.
Physics limits
- Sodium burns in air and reacts with waterLiquid sodium is an excellent coolant but ignites in air and reacts violently with water, so pipes need leak protection and the steam side must stay separate, here via a salt loop.
- Fast reactors need more enriched fuelWithout a moderator slowing neutrons, each neutron is less likely to cause fission, so the core needs HALEU enriched up to 19.75% uranium-235, versus about 5% in ordinary reactors.
- Stored heat is bounded by salt temperaturesMolten nitrate salt freezes near 220 °C and breaks down above ~600 °C. That window and tank size cap storage, so the boost to 500 MWe lasts about 5.5 hours, not days.
How it works
Core
Fast fission in metal fuel
Fast neutrons keep the chain reaction going in a compact metal-fuel core that sits in a pool of liquid sodium.
Heat transfer
Sodium heats molten salt
A second sodium loop carries heat out to warm nitrate salt, so the steam plant stays non-nuclear.
Storage
Hot and cold salt tanks
Hot salt is stored in tanks; drawing it faster than the reactor refills them lets the plant peak at 500 MWe.
Spec sheet
| Spec | Natrium (Kemmerer Unit 1) |
|---|---|
| Reactor electrical output | 345 MWeR (reported) |
| Peak output with storage | 500 MWeR (reported) |
| Boost duration | 5.5+ hoursR (reported) |
| Primary coolant | Liquid sodiumR (reported) |
| Fuel | Metallic HALEU (<20% U-235)R (reported) |
| Storage medium | Molten nitrate saltR (reported) |
R reported by the company
Papers & demos
- Mar 2024paperKemmerer Unit 1 construction permit application and preliminary safety analysis (opens nrc.gov)First commercial non-light-water reactor application the NRC accepted for review in over 40 years.
Update log
Mon 21 Sep
- Minor: PressCommercial
Mon 31 Aug
- Minor: PressCommercial
Apr 2026
- Major: PressManufacturing
Wed 4 Mar
- Major: RegulatorRegulatory
Tue 4 Nov 2025
- Minor: PressResearch
Mon 10 Jun 2024
- Major: PressManufacturing
Dec 2022
- Major: PressOther
Tue 16 Nov 2021
- Major: PressCommercial
About TerraPower
TerraPower
Natrium sodium fast reactor, molten salt storage
Nuclear company founded by Bill Gates. Its Natrium plant in Kemmerer, Wyoming pairs a 345 MWe sodium-cooled reactor with molten-salt heat storage that can boost output to 500 MWe. In March 2026 it won the first NRC construction permit for a commercial reactor not cooled by ordinary water.
- 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.
- Founded
- 200818 yrs
- Headquarters
- United States
- Status
- Private
- Valuation
- private
- Raised
- $1.4B2 rounds
- Last round
- Equity raise · $650MJun 2025
- Works in
- EnergyFission
- Coverage
- 2 programs · 14 updateslatest 19d agochecked 25 Sep
- Lead investors
- SK Inc.Bill Gates
- Customers
- Meta
- Partners
- U.S. Department of Energy (opens energy.gov)PacifiCorp (opens pacificorp.com)GE Vernova Hitachi Nuclear Energy (opens gevernova.com)
- Investors
- SK Inc. (opens sk-inc.com)NVIDIA
- People
- Chris Levesque (opens terrapower.com)President & CEOBill Gates (opens en.wikipedia.org)Founder & Chairman