Project Details
Developer
Location
Kemmerer, Wyoming, USA
Capacity
345 MW-electric, 853 MWh-electric
COD
Expected COD: 2030
About This Project
Executive Overview
The Natrium Demonstration Project is a 345 MW sodium-cooled fast reactor (SFR) with an integrated molten salt energy storage system, under construction at Kemmerer Power Station Unit 1 in Kemmerer, Wyoming, developed by TerraPower in partnership with GE Hitachi Nuclear Energy. On March 4, 2026, the NRC issued TerraPower's construction permit — the first for a commercial-scale advanced non-light-water reactor in U.S. history, and the first construction permit for any commercial reactor in nearly a decade. The review was completed in 18 months against an initial 27-month schedule. Nuclear construction is now underway, with first nuclear concrete targeted for 2027, fuel loading in 2030, and commercial operation in 2030. The DOE's Advanced Reactor Demonstration Program (ARDP) provides $2 billion of the project's approximately $4 billion total cost. PacifiCorp (Rocky Mountain Power) is the anticipated long-term power offtaker, with PacifiCorp's 2025 IRP modelling Natrium as available January 1, 2032.
How It Works & Differentiation
The Natrium reactor operates as a sodium-cooled fast reactor: liquid sodium circulates at near-atmospheric pressure through the reactor core, reaching outlet temperatures of approximately 500–550°C, driving a Brayton cycle power block. At 345 MW, the reactor can be boosted to 500 MW for approximately 5.5 hours by drawing on the integrated molten salt energy storage, which stores excess thermal energy during low-demand periods and dispatches it during peak demand — a hybrid dispatchable nuclear plus storage architecture with no commercial precedent. This capability is the technology's primary grid-integration differentiator: unlike conventional nuclear, Natrium can follow load and complement intermittent renewables. The reactor's SFR fast neutron spectrum also enables potential future fuel recycling and waste volume reduction. The fuel is HALEU (high-assay low-enriched uranium); a domestic HALEU supply chain is under active development in the United States.
Commercialization & Traction
The NRC construction permit arrived approximately eight months ahead of the original schedule, following accelerated review driven by executive orders in May 2025. The project is sited adjacent to the Naughton coal plant, which is scheduled to cease coal burning in 2026, creating a coal-to-nuclear transition with approximately 250 permanent operations staff. Construction peak employment is approximately 1,600 workers, with Bechtel as the EPC contractor. The nuclear island occupies approximately 16 acres of a 44-acre total site footprint. PacifiCorp has conducted feasibility studies on deploying up to five additional Natrium units co-located with retiring coal plants in its territory by 2035.
Scalability & Strategic Context
Natrium is the most advanced commercial advanced reactor project in the western hemisphere and the only sodium fast reactor to have received a construction permit from the NRC. TerraPower's 20 years of accumulated reactor design work and over 117,000 hours of NRC pre-application engagement gives the Kemmerer project a regulatory maturity advantage over competing advanced reactor platforms. The molten salt storage component represents a genuinely novel architecture for nuclear energy: if operational performance validates the peak dispatch capability, it repositions nuclear as a grid-balancing asset rather than a baseload-only resource — a potentially transformational commercial argument in electricity markets with high renewable penetration. Natrium is only the second Generation IV non-light-water reactor in commercial construction in the Western world (after China's HTR-PM 1), making it an internationally significant demonstration regardless of U.S. market context.
Project Timeline
NRC Formalizes Construction Exemption for Natrium Plant Energy Island
Further Reading
NRC Approves Natrium Reactor Construction Permit
The U.S. Nuclear Regulatory Commission has approved TerraPower's construction permit for the Natrium reactor, marking the first time a commercial-scale, advanced nuclear power plant has received such approval in the United States.
Natrium Project Receives First NRC-Issued Environmental Impact Statement for a Commercial Advanced Nuclear Power Plant
The article announces that TerraPower's Natrium project in Wyoming has become the first commercial advanced nuclear power plant to receive a favorable Environmental Impact Statement from the U.S. Nuclear Regulatory Commission, marking a major regulatory milestone for advanced nuclear technology.
More good news for TerraPower on Kemmerer construction permit
The article reports that the Nuclear Regulatory Commission has accelerated its review schedule for TerraPower’s construction permit application for the Kemmerer Power Station Unit 1 in Wyoming, aiming to complete the review by the end of 2025, eight months earlier than originally planned.
NRC Formalizes Construction Exemption for Natrium Plant Energy Island
The U.S. Nuclear Regulatory Commission has granted TerraPower an exemption allowing construction of the Natrium plant's energy island to begin before the full permit review is complete, supporting TerraPower's strategy to decouple the reactor from energy generation and accelerate deployment of its advanced nuclear technology.
OPUC 2-7-2025 with response
The document is a stakeholder feedback form from the Oregon Public Utility Commission to PacifiCorp regarding the draft 2025 Integrated Resource Plan, containing detailed questions and PacifiCorp's responses about emissions compliance, resource modeling, and planning assumptions under Oregon and federal policies.
TerraPower Awarded Pivotal State Permit for Natrium Plant
TerraPower has received a pivotal state permit from the Wyoming Industrial Siting Council, allowing it to begin construction of non-nuclear facilities for the first Natrium advanced nuclear plant, marking a major milestone for commercial advanced nuclear projects in the U.S..
TerraPower Begins Construction in Wyoming
TerraPower has begun construction in Wyoming on the Natrium reactor demonstration project, the world’s first advanced coal-to-nuclear power plant, which will provide carbon-free, dispatchable energy and is expected to create hundreds of jobs and support the clean energy transition.
TerraPower Submits Construction Permit Application to the NRC for the Natrium Reactor Demonstration Project
TerraPower has submitted a construction permit application to the U.S. Nuclear Regulatory Commission for its Natrium advanced reactor demonstration project, marking a significant step toward building a next-generation nuclear power plant near a retiring coal facility.
What TerraPower’s big milestone says about future nuclear projects
The article discusses TerraPower receiving a construction permit for its advanced nuclear reactor in Wyoming, highlighting what this milestone means for the future pace, challenges, and regulatory landscape of next-generation nuclear projects in the United States.
Natrium Reactor Demonstration Project, Wyoming, US
The Natrium Reactor Demonstration Project in Wyoming is a first-of-its-kind, 345MW sodium-cooled fast nuclear reactor with integrated molten salt energy storage, being developed by TerraPower and PacifiCorp to validate advanced reactor technology and support grid decarbonization, with completion expected in 2028.
Bill Gates’ nuclear venture plans reactor to complement wind and solar in Wyoming
Bill Gates and his company TerraPower have begun construction in Wyoming on a next-generation, sodium-cooled nuclear power plant aimed at providing safe, abundant, zero-carbon energy and revolutionizing power generation in the U.S..
WYOMING TRIBUNE EAGLE
The November 21, 2023 issue of the Kemmerer Gazette covers local news and events in Kemmerer, Wyoming, including city efforts to fund road repairs through a proposed sixth-penny tax, updates on the TerraPower nuclear plant project, local sports achievements, community happenings, and features on notable residents and regional issues.
Sodium Fast Reactor (SFR)
The Sodium Fast Reactor (SFR) is a Generation IV nuclear reactor that uses liquid sodium as a coolant and operates in the fast neutron spectrum, enabling efficient fuel use, reduced nuclear waste, and flexible operation modes, while drawing on extensive global experience but still facing challenges in sodium handling, safety, and cost competitiveness.
U.S. Department of Energy Announces $160 Million in First Awards under Advanced Reactor Demonstration Program
The article announces that the U.S. Department of Energy has awarded $160 million in initial funding to TerraPower and X-energy to demonstrate advanced nuclear reactors within 5 to 7 years as part of the Advanced Reactor Demonstration Program.
Natrium™ Reactor Technology
The TerraPower Natrium project is an advanced nuclear reactor and energy storage system designed to provide emissions-free, flexible, and cost-competitive power for the modern electric grid using innovative sodium fast reactor technology and molten salt energy storage.