TerraPower becomes first advanced reactor company to join INPO

TerraPower has been accepted into the Institute of Nuclear Power Operations, becoming the first advanced reactor company to join the U.S. industry's self-regulatory safety body. The July 21 announcement covers Kemmerer Unit 1 in Wyoming, the 345-MWe Natrium plant now under construction.

Key facts

• TerraPower joined the Institute of Nuclear Power Operations as an operating member on July 21, 2026, the first advanced reactor company admitted.
• The membership supports Kemmerer Unit 1, a 345-MWe sodium-cooled fast reactor with molten salt storage that can boost output to 500 MWe.
• The U.S. Nuclear Regulatory Commission issued the Kemmerer construction permit in March 2026, and construction began in April.
• INPO was created by U.S. utilities after the 1979 Three Mile Island-2 partial meltdown and today engages with plants in the U.S., Canada, China, Mexico, Romania, South Africa and the United Arab Emirates.
• TerraPower plans to submit a Part 50 operating license application for Kemmerer by March 2028, with the plant expected to be completed in 2030.

What happened

In a statement dated July 21, 2026, TerraPower President and CEO Chris Levesque said the company had been accepted into the Institute of Nuclear Power Operations (INPO) as an operating member in support of Kemmerer Unit 1, the first deployment of the Natrium power plant. INPO President and CEO Bob Willard confirmed the admission, saying: "As the first advanced reactor company accepted into INPO membership, TerraPower is demonstrating a commitment to the principles of operational excellence, safety, reliability and continuous learning that have defined commercial nuclear operations for decades."

The Natrium design pairs a 345-MWe sodium-cooled fast reactor with a patented molten salt energy storage system that can temporarily boost output to 500 MWe when demand peaks. Kemmerer Unit 1 is being built through the U.S. Department of Energy's Advanced Reactor Demonstration Program, a public-private cost-share. The NRC issued the construction permit in March 2026, the company broke ground in April, and earlier this week TerraPower told the NRC in a public meeting that it plans to file a Part 50 operating license application by March 2028. The project is expected to be completed in 2030 and would be the first utility-scale advanced nuclear plant in the United States.

Why it matters

INPO is not a regulator, but it is the closest thing the U.S. industry has to a gatekeeper of operating credibility. Utilities created it after Three Mile Island to run independent evaluations, set personnel qualification standards and accredit training programs, and its plant ratings carry real weight with insurers, investors and the NRC. Every operating U.S. commercial reactor sits inside its review regime. Until this week, no advanced reactor company did.

TerraPower joining while Kemmerer is still a construction site matters for two reasons. First, it means the company will build its operating organization — procedures, training, corrective-action culture — under INPO scrutiny from the start, rather than retrofitting it after first criticality. Second, it sets the template for the rest of the new-build cohort: Oklo, X-energy and the DOE Reactor Pilot Program companies now have a visible precedent that admission to the incumbent safety regime is part of the commercialization path, not an optional extra. NNN's coverage of the Oklo Groves startup authorization tracked the licensing side of that path; INPO membership is the operating-culture side. For a sector pitching utilities and hyperscalers on repeatability — TerraPower itself has an agreement with Meta for up to eight Natrium plants by 2035 — the credential is a sales asset as much as a safety one.

Background

INPO was founded in 1979, months after the Three Mile Island-2 partial meltdown, to address what the industry's own post-accident reviews called a central failure: the lack of qualified, competent people operating and managing plants. The Kemeny Commission, appointed by the Carter administration to investigate the accident, endorsed the institute as the right vehicle for setting standards and conducting independent evaluations. In the decades since, INPO has grown into a global operator-facing body, working with plants across North America, China, Romania, South Africa and the UAE, and alongside the World Association of Nuclear Operators. Its current work centers on four areas — industry performance, sustainability, teaching and learning, and data science — delivered through continuous monitoring, accreditation and courses.

TerraPower's path to this point is one NNN has tracked closely. The company began excavation at Kemmerer Unit 1 in 2024, making it one of the first Western advanced reactor projects to move from paper to heavy construction, and it anchors our tracker of U.S. nuclear plants under construction in 2026. The small modular reactor hub lays out the broader new-build landscape the Natrium design competes in, and our three-way comparison of the BWRX-300, AP300 and Natrium explains why the molten salt storage feature — the ability to flex between 345 and 500 MWe — is the design's commercial differentiator for grids absorbing intermittent renewables.

What's next

The concrete milestones to watch are all licensing and construction dated: TerraPower's Part 50 operating license application is due to the NRC by March 2028, construction at Kemmerer continues through the decade, and the company targets completion in 2030. On the INPO side, the practical test will be how the institute applies its evaluation and accreditation machinery to a sodium-cooled fast reactor with no U.S. operating precedent — and which advanced reactor company follows TerraPower through the door next.