Bechtel has begun mobilising teams and transitioning into field execution at the Natrium Kemmerer Unit 1 site in Kemmerer, Wyoming, marking the official start of construction on what is the first utility-scale advanced nuclear power plant to begin construction in the United States.
The announcement follows the U.S. Nuclear Regulatory Commission (NRC) issuing a construction permit for the project in March 2026, the NRC’s first approval to build a commercial reactor in nearly a decade and its first construction permit for a non-light-water reactor design in more than 40 years. Bechtel is serving as the EPC contractor for the project, with TerraPower as the developer and technology owner.
Natrium Kemmerer Unit 1 — Project Background
The Kemmerer Unit 1 project is located in Kemmerer, southwest Wyoming, adjacent to PacifiCorp’s retiring Naughton coal-fired power station. The site was selected in 2021, in part because of its location within an established energy community with an existing skilled workforce and grid infrastructure.
The project is supported by the U.S. Department of Energy’s Advanced Reactor Demonstration Program (ARDP), a public-private partnership designed to bring first-of-a-kind advanced reactors into commercial service on an accelerated schedule.
Non-nuclear site preparation work began in June 2024, when TerraPower broke ground on greenfield support facilities. Over the past year, Bechtel completed early works at the site including a Test and Fill Facility and the Kemmerer Training Center. The 23 April 2026 announcement marks the transition from early works into full field execution, triggering the mobilisation of the main construction workforce.
The Natrium Reactor — Technology and Design
The Natrium plant features a 345 MW sodium-cooled fast reactor paired with an integrated molten salt-based energy storage system. The storage system allows the plant to boost output temporarily to 500 MW during periods of peak grid demand, equivalent to powering approximately 400,000 homes. The technology was developed by TerraPower in partnership with GE Vernova Hitachi Nuclear Energy.
Key design features confirmed by TerraPower and Bechtel:
- Base reactor capacity: 345 MW (sodium-cooled fast reactor)
- Peak output with storage: 500 MW
- Coolant: Sodium (low-pressure, passive safety design)
- Energy storage: Integrated molten salt thermal storage system
- Fuel: High-assay low-enriched uranium (HALEU)
- Carbon output: Zero-carbon generation
The sodium-cooled design operates at low pressure and incorporates passive safety features designed to simplify construction and reduce cost compared to current-generation light-water reactors. The separation of the nuclear island from the energy island is a deliberate design choice intended to enable repeatable, scalable construction across future Natrium plants.
EPC Contract, Programme and Key Details
Key confirmed project details across Bechtel and TerraPower primary sources:
- EPC contractor: Bechtel (Nuclear, Security and Environmental business)
- Developer and technology owner: TerraPower
- Technology partner: GE Vernova Hitachi Nuclear Energy
- Government support: U.S. Department of Energy Advanced Reactor Demonstration Program (ARDP)
- NRC construction permit: Issued March 2026
- Construction start: 23 April 2026
- Peak construction workforce: Approximately 1,600 workers
- Permanent operational jobs: Approximately 250
- Target commercial operation: 2030-2031
- Location: Kemmerer, Wyoming, USA
Chris Levesque, President and CEO of TerraPower, said:
“This is the moment our industry has been working toward for a generation. We’re not just breaking new ground on a first-of-a-kind nuclear plant in Wyoming; we’re building the next generation of America’s energy infrastructure. The Natrium plant will deliver reliable and dispatchable power to the grid and Kemmerer Unit 1 will serve as a commercial blueprint to mobilise a fleet of Natrium plants across the country and around the world.”
Dena Volovar, President of Bechtel’s Nuclear, Security and Environmental business, said:
“By combining TerraPower’s reactor innovation with Bechtel’s processes, experience and execution model we will deliver these nuclear projects consistently, safely and at scale. By applying the latest digital tools and project delivery systems, Bechtel is uniquely positioned to deliver the nation’s first Natrium plant with efficiency and execution certainty.”
Natrium Delivery Profile — Construction Implications
The Kemmerer Unit 1 construction represents one of the most technically complex EPC assignments currently underway in the United States energy sector. As a first-of-a-kind non-light-water reactor, it carries all the delivery risks inherent to novel technology, including the absence of a domestic construction precedent for a sodium-cooled fast reactor at commercial scale, HALEU fuel supply chain constraints, and the need to demonstrate that the molten salt storage system can be integrated reliably with the nuclear island during construction and commissioning.
Bechtel has explicitly positioned its delivery model around repeatability: standardised work packages, digital execution tools, and early contractor involvement from the project’s inception — as the mechanism for managing first-of-a-kind risk.
Since 2020, Becthel has been working alongside TerraPower as its partner for plant design, licensing, procurement, and construction, in an approach similar to Early Contractor Involvement model used on major infrastructure programmes or Front-End Engineering Design in industrial projects, where the EPC or construction contractor is embedded into design and planning long before construction commences.
On a project of this novelty and complexity, the commercial consequences of schedule slippage are significant, touching liquidated damages provisions, ARDP milestone requirements, and the broader credibility of the advanced nuclear delivery model in the United State
The NRC’s technical review of the construction permit application — completed in approximately 18 months — was notably faster than initial estimates, a regulatory efficiency that Bechtel and TerraPower have cited as evidence that the licensing framework for advanced reactors is maturing. That matters for the pipeline of future Natrium plants: a faster, more predictable regulatory pathway is a precondition for the commercial repeatability that both companies are targeting.
Advanced Nuclear Market Outlook
The Kemmerer Unit 1 construction start is the most significant milestone in US advanced nuclear delivery since the completion of Vogtle Units 3 and 4 in Georgia — the last new large commercial reactors built in the United States. Bechtel is the only EPC contractor to have delivered new nuclear plants in the US in the 21st century, a track record that directly informs its appointment as EPC partner on Natrium.
Beyond Kemmerer, TerraPower has signed an agreement with Meta for up to eight Natrium plants by 2035, targeting data centre power demand, and is exploring a second commercial Natrium site in Utah. That commercial pipeline signals that Kemmerer is not being treated as a standalone demonstration — it is being designed from the outset as the first unit of a scalable fleet.
Recently, other significant nuclear projects have been reaching major milestones in North America, such as:
- Fluor securing FEL contract for Nuclear Project in Texas with X‑Energy,
- GE Vernova Hitachi’s BWRX-300 small modular reactor approved for construction for Darlington New Nuclear Project in Ontario,
- Oklo Selecting Kiewit as Lead Constructor for First Aurora Powerhouse at Idaho National Laboratory.
The broader US advanced nuclear sector is watching Kemmerer closely. If Bechtel and TerraPower can demonstrate that a sodium-cooled fast reactor can be delivered on programme and within budget at commercial scale, it will establish a construction and regulatory blueprint that could accelerate deployment of further advanced reactor designs currently in development, including small modular reactors being advanced by GE Vernova Hitachi at TVA’s Clinch River site and NuScale’s VOYGR design.
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