TerraPower's Natrium plant in Wyoming gets the NRC's construction permit

March 2026 — The Nuclear Regulatory Commission issued construction permit CPAR-1 to US SFR Owner, a TerraPower subsidiary, for Kemmerer Power Station Unit 1 in Wyoming. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of March 16, 2026)

Outcome: an immediately effective construction permit, issued March 9, 2026. (Federal Register notice)
Plant: 345 MWe, with an energy storage system to temporarily boost output to as much as 500 MWe. (NRC release 26-028)
Review time: under 18 months of NRC staff technical review. (NRC release 26-028)
Cost: not stated in the NRC documents.
Status: authorized to build, not to operate. A separate operating licence is needed. (NRC release 26-028)

What the NRC found

The Commission voted on March 4, 2026 to authorize its staff to issue the permit, after a streamlined mandatory hearing, finding the staff's review adequate for the required safety and environmental findings. NRC Chairman Ho Nieh called it "a historic step forward for advanced nuclear energy in the United States." (NRC release 26-028)

The NRC said it was the first commercial reactor it had approved for construction in nearly a decade and the first approval for a non-light-water reactor in more than 40 years. (NRC release 26-028)

In the notice, the NRC found "reasonable assurance" that safety questions will be "satisfactorily resolved by the completion of construction," and that the plant can be built and run at the site "without undue risk to public health and safety," subject to the permit's conditions. It also found USO technically and financially qualified. (Federal Register notice)

The Commission's March 4 memorandum and order on the uncontested hearing serves as the record of decision. Staff issued the safety evaluation in December 2025 and the final environmental impact statement in October 2025. (Federal Register notice; NRC release 26-028)

The timeline

TerraPower filed the application in March 2024, for a site near an existing coal-fired power plant, and the NRC began formal review in May 2024. (NRC release 26-028) TerraPower says the NRC first set a 27-month schedule and that the review finished in 18 months, which it credits partly to its "complete application" and to federal support. (TerraPower release)

The permit was authorized by Commission Order CLI-26-5. (NRC notice)

The design, in TerraPower's words

TerraPower describes Natrium as a sodium-cooled fast reactor paired with a patented molten salt-based storage system, designed to keep base output steady and ramp up when demand peaks. It calls this "the only advanced reactor design with this unique feature," a claim we haven't checked. (TerraPower release)

TerraPower CEO Chris Levesque said the team had "worked relentlessly for over 4 years with the NRC staff," including extensive pre-application engagement, and filed the application almost two years before the vote. (TerraPower release)

The paperwork

The NRC also found that required notifications to other agencies had been made and that the environmental findings required under its National Environmental Policy Act rules were complete. The case sits under Docket No. 50-613 and docket ID NRC-2024-0078. (Federal Register notice)

What TerraPower says comes next

Chief executive Chris Levesque said the company planned "to start construction on the Natrium plant in the coming weeks." TerraPower says the plant is being developed through the Energy Department's Advanced Reactor Demonstration Program, a public-private partnership, and is expected to be completed in 2030. Those are company targets. (TerraPower release)

What went wrong

Not cleared to run. US SFR Owner still needs a separate operating licence approved by NRC staff before the plant can operate. (NRC release 26-028)
Vendor-dated finish. The 2030 completion date is TerraPower's expectation. (TerraPower release)
What we don't know yet: the plant's cost and the split between federal and private money. The NRC documents we read don't give either.

Our follow-up question for TerraPower

What is the current cost estimate for Kemmerer Unit 1, and how much of it does the Advanced Reactor Demonstration Program cover?

Sources

U.S. Nuclear Regulatory Commission, “NRC Issues First Commercial Reactor Construction Approval in 10 Years For TerraPower in Wyoming,” No. 26-028, March 4, 2026. nrc.gov
U.S. Nuclear Regulatory Commission, “NRC Issues Construction Permit to US SFR Owner,” March 9, 2026. nrc.gov
Federal Register, “US SFR Owner, LLC; Kemmerer Power Station, Unit 1; Construction Permit and Record of Decision,” 91 FR 12628, March 16, 2026. federalregister.gov
TerraPower, “NRC Approves the Natrium Reactor Construction Permit,” March 4, 2026. terrapower.com

Disclosure: [not in copy] Editor placeholder