TerraPower is a private nuclear energy company founded in 2008 by Bill Gates and Nathan Myhrvold, the former Microsoft Chief Technology Officer, with the goal of developing advanced reactor technology that could operate on spent nuclear fuel and run for decades without refueling. The company was built around the traveling wave reactor (TWR), a sodium-cooled fast reactor concept in which a self-sustaining fission wave propagates slowly through a core loaded with depleted uranium, breeding and burning fuel in place. The TWR never reached construction. A 2015 partnership with China National Nuclear Corporation to prototype the design collapsed in 2019 when the Trump administration restricted nuclear technology transfers to China, forcing TerraPower to pivot its entire development program. The company redesigned around Natrium, a simpler sodium fast reactor paired with a molten salt thermal energy storage system, and won a $2 billion U.S. Department of Energy cost-share award in 2020. President and CEO Chris Levesque has led the company since 2017.
The Natrium design combines a 345-megawatt sodium-cooled fast reactor with a 1 gigawatt-hour molten salt thermal energy storage system, a combination that gives the plant a capability no conventional nuclear reactor offers: dispatchability. The reactor runs at full thermal output continuously, charging the molten salt storage when grid demand is low. When demand spikes — during summer afternoons, winter evenings, or whenever wind and solar generation drops — the stored heat supplements the reactor output, allowing the plant to deliver up to 500 megawatts of electric power for five and a half hours. The storage system effectively turns a baseload nuclear plant into a resource that can follow the grid in real time, making it compatible with a high-renewable system in a way that conventional nuclear plants are not.
TerraPower broke ground on non-nuclear site preparation at Kemmerer, Wyoming in June 2024, adjacent to PacifiCorp's retiring Naughton coal plant. The NRC completed its safety review in December 2025, ahead of schedule and under budget, and issued the first construction permit for a commercial non-light-water reactor in history. Official nuclear construction began April 23, 2026, with Bechtel as the engineering, procurement, and construction partner. The project targets commercial operation in 2030 to 2031. At peak, approximately 1,600 construction workers will be on site; the completed plant will employ about 250 people permanently, replacing much of the workforce from the coal plant it is transitioning.
Natrium is a sodium-cooled fast reactor (SFR) co-developed by TerraPower and GE Hitachi Nuclear Energy (GEH), whose PRISM and ARC SFR designs provide the engineering lineage. Sodium coolant operates at atmospheric pressure — a fundamental safety advantage over pressurized water reactors, which operate at 155 atmospheres. In a loss-of-coolant accident, a sodium-cooled reactor can shut itself down through passive physics: the fuel's geometry changes as it heats, reducing reactivity without operator action or pumped water. The reactor's fast neutron spectrum also enables it to consume long-lived actinides from spent nuclear fuel, addressing one of the primary waste concerns of the existing LWR fleet. The molten salt energy storage system uses nitrate salt as a heat transfer and storage medium, a technology with a commercial track record in concentrating solar plants. Storing reactor heat in salt and converting it to electricity on demand gives Natrium its dispatch capability. TerraPower has filed for multiple patents on the integrated reactor-storage system.
Kemmerer, a Wyoming coal town of about 2,700 people, was chosen partly for its existing nuclear-adjacent infrastructure (the Naughton coal plant has transmission connections and industrial water access) and partly for the political symbolism of siting an advanced nuclear facility in a Wyoming coal community. Rocky Mountain Power, a PacifiCorp subsidiary serving Wyoming, Utah, and Idaho, is the expected offtaker. The site received an environmental impact statement from the NRC — the first ever issued for a commercial advanced non-light-water reactor — and a construction permit in early 2026. Bechtel, which has more U.S. nuclear construction experience than any other contractor including the Vogtle Units 3 and 4 work, is the EPC partner. Total project cost is approximately $4 billion, with the DOE's ARDP cost-share covering roughly half. Construction is targeted for completion and first power by 2030 to 2031; the NRC license submission listed a construction completion date of February 2031.
In October 2020, the Department of Energy selected TerraPower's Natrium and X-energy's Xe-100 as the two demonstration projects for its Advanced Reactor Demonstration Program, committing approximately $2.5 billion in cost-share funding to each over seven years. ARDP was specifically designed to demonstrate that advanced reactors could be licensed and constructed in the United States on a compressed timeline after decades in which no new nuclear designs had moved through the NRC. TerraPower submitted its construction permit application to the NRC in March 2024, the first non-light-water reactor construction permit application in more than 40 years. The NRC accepted it in May 2024 and completed its safety review in December 2025 — ahead of the originally projected schedule and 11% under the agency's budgeted review cost, a noteworthy result given the NRC's historical reviews of novel reactor types. The construction permit was issued in early 2026, establishing the regulatory precedent that Natrium and future advanced reactors will rely on.
TerraPower was originally built around one of the most intellectually ambitious reactor concepts in modern nuclear history: the traveling wave reactor. The TWR's core insight was that a fast neutron chain reaction could be designed to breed fissile plutonium from fertile depleted uranium at the front of the reaction zone while burning previously bred fuel at the rear, with the reaction wave propagating slowly through the core over decades. A fully developed TWR would run on depleted uranium — the United States has approximately 700,000 metric tons of it stockpiled, a waste product of uranium enrichment — and produce power for 40 to 60 years without refueling or removing fuel for reprocessing. The spent fuel produced would contain significantly less long-lived transuranics than conventional LWR waste. Gates and Myhrvold believed the TWR was the reactor concept that could genuinely address nuclear power's cost, proliferation, and waste concerns simultaneously.
The TWR required proof-of-concept at scale, and building a prototype in the United States faced the same slow regulatory pathway that had made new nuclear construction economically unattractive for decades. In 2015, TerraPower signed an agreement with China National Nuclear Corporation (CNNC) to build a 600-megawatt TWR prototype at Xiapu in Fujian province, with construction planned for 2018 to 2025. The arrangement was practical: China was building nuclear capacity aggressively, had the construction infrastructure and regulatory willingness to move quickly, and was willing to fund a substantial share of the demonstration cost. The deal would give TerraPower the operational data needed to refine the TWR design for commercial deployment.
In 2018 and 2019, the Trump administration tightened restrictions on nuclear technology transfers to China amid broader trade tensions and nuclear nonproliferation concerns. TerraPower was required to terminate the CNNC partnership. The company lost four years of development time and the capital the Chinese partnership would have provided. Bill Gates was publicly critical of the decision, arguing that it prevented a valuable nuclear demonstration without meaningfully addressing proliferation risk. Regardless of the policy merits, the effect on TerraPower was concrete: the company had to find a new path to demonstrating its technology without a Chinese partner, in a U.S. nuclear regulatory environment that had not licensed a commercial non-light-water reactor since the 1970s.
The pivot to Natrium was a pragmatic response. The TWR's core physics, while theoretically elegant, required achieving very high fuel burnup levels and demonstrating novel fuel metallurgy that would take years to qualify. A sodium fast reactor without the traveling wave feature — operating more like established designs such as Russia's BN-800 or Idaho National Laboratory's EBR-II, which ran successfully for 30 years from 1964 to 1994 — could be built and licensed on the ARDP timeline. The molten salt thermal energy storage system was Natrium's genuine innovation: it reused salt storage technology proven in concentrating solar plants and applied it to nuclear to produce a dispatchable zero-carbon plant capable of competing with gas peakers for grid services. The DOE ARDP selection in October 2020 validated the design as fundable and buildable in the United States.
TerraPower has stated that the TWR concept is not abandoned. If Natrium demonstrates that a commercial sodium fast reactor can be built and operated in the United States, it establishes the platform — the regulatory precedent, the supply chain, the workforce, and the fuel cycle infrastructure — on which a TWR could be built as a second-generation design. Natrium is, in this framing, the proof-of-concept that the TWR needed China to provide but can now be supplied domestically.
TerraPower has raised approximately $1.4 billion in private equity. The most recent round, announced in June 2025, raised $650 million with NVentures (the venture capital arm of NVIDIA), Bill Gates through Cascade Investment, and HD Hyundai. Earlier investors include SK Group (which committed $250 million in 2022 through SK Inc and SK Innovation, a round co-led with Gates), Khosla Ventures, and Charles River Ventures. The DOE ARDP commitment of approximately $2 billion in cost-share brings total capital in the Kemmerer project to more than $3.4 billion, with additional private investment expected to close the gap to the approximately $4 billion total project cost.
The capital structure of the Kemmerer project matters for the replication case. At roughly $4 billion for a 345-megawatt plant, the overnight capital cost is approximately $11,600 per kilowatt — several times the cost of a combined-cycle gas plant but in line with recent conventional nuclear construction in the United States and lower than the final cost of Vogtle Units 3 and 4. TerraPower argues that the first plant is a demonstration project that will not reflect the economics of serial production, where factory-built modular components, a trained workforce, and an established supply chain would reduce costs substantially. Whether that argument holds depends on whether the first plant actually comes in at or near its $4 billion estimate, which is far from guaranteed given the track record of nuclear first-of-a-kind construction in the United States.
TerraPower's medium-term strategy is to complete Kemmerer Unit 1 on schedule and budget, establish the Natrium design as a licensed and demonstrated technology, and develop a pipeline of subsequent units. The company has said it expects to site additional Natrium plants adjacent to retiring coal facilities across the western United States, a deployment model that takes advantage of existing transmission infrastructure, experienced industrial workforces, and communities that need economic replacement for coal employment. Rocky Mountain Power and other PacifiCorp utilities are the most natural initial customers; broader deployment would require licensed designs and supply chains that only exist once Kemmerer operates.
Data center power demand has materially improved the commercial case for new nuclear in the period since TerraPower's ARDP award. Hyperscalers including Microsoft, Google, and Amazon have signed or announced agreements with nuclear operators for dedicated capacity, and several have expressed interest in advanced reactor projects including Natrium. NVIDIA's June 2025 investment through NVentures is an early signal of that alignment. A 345-megawatt sodium fast reactor operating at greater than 90% capacity factor, with the ability to burst to 500 megawatts on demand, is a strong match for a large data center campus that needs firm, carbon-free, around-the-clock power. The commercial structure of such an agreement — a long-term power purchase agreement at a fixed price — would provide the revenue certainty that makes subsequent Natrium units fundable without ARDP-style federal co-investment.
Nuclear first-of-a-kind construction in the United States has a poor cost and schedule track record. Vogtle Units 3 and 4, the most recent large nuclear project, took 15 years from license application to commercial operation, came in at roughly twice the projected cost, and required a federal loan guarantee and Georgia ratepayer support to survive. TerraPower's project has the advantage of Bechtel as a contractor with nuclear construction experience, a DOE cost-share that removes half the financial risk, and a simpler reactor design than Westinghouse's AP1000. But the Kemmerer project is still a first-of-a-kind sodium fast reactor built to a new NRC license basis in a country that has not built a commercial non-LWR in more than 50 years. The supply chain for sodium-compatible components — specialized pumps, heat exchangers, and instrumentation rated for liquid sodium service — is limited. The fuel qualification process for Natrium's sodium-compatible fuel is ongoing. Cost and schedule overruns are not a failure scenario; they are the historical base case for advanced nuclear construction.
Regulatory and policy continuity is a second consideration. The $2 billion DOE ARDP commitment is a multi-year cost-share that spans administrations. The political support for advanced nuclear in the United States has been bipartisan across the Biden and Trump administrations, and the Nuclear Energy Innovation and Modernization Act of 2018 specifically directed the NRC to develop a licensing pathway for non-LWR reactors. The construction permit issued in 2026 is a durable regulatory action that cannot easily be revoked. But future policy changes affecting DOE disbursements, uranium supply chains, or offtake agreements with regulated utilities would affect the project's economics.
The replication case is the most important long-run question. A single Natrium demonstration at $4 billion, even if it succeeds perfectly, does not by itself transform the economics of advanced nuclear. The path from one demonstration plant to 10 or 50 deployed units requires a supply chain, a trained workforce, standardized permitting, and commercial power purchase agreements at prices that reflect the cost of subsequent units rather than the cost of a demonstration. TerraPower is building all of those prerequisites simultaneously with the Kemmerer project. If Kemmerer completes on schedule and at or near cost, TerraPower will have accomplished something no advanced nuclear developer has done in the United States in half a century. That outcome is not certain, but the regulatory, financial, and engineering groundwork being laid between 2024 and 2026 is more credible than any advanced reactor project in recent U.S. history.
This profile was compiled from publicly available information including:
TerraPower corporate website — Natrium design specifications, Kemmerer project updates, Wyoming milestones, fundraising announcements.
DOE press release — NRC construction permit issuance for Natrium.
NRC Kemmerer application docket — Construction permit application, safety evaluation report, environmental impact statement.
TerraPower $650M fundraise announcement (June 2025); ANS Nuclear Newswire coverage of construction permit (December 2025) and construction start (April 2026); Power Magazine Kemmerer construction timeline; Geekwire NVIDIA NVentures investment report; Neutron Bytes coverage of China partnership cancellation (January 2019); EBR-II historical record, Idaho National Laboratory; DOE ARDP program announcement (October 2020).
This profile is for informational purposes only and does not constitute investment advice, a recommendation, or a solicitation to buy or sell any security.