TerraPower
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TerraPower is an American advanced nuclear energy company chaired by Bill Gates, the co-founder of Microsoft, that is building Natrium, a 345 MWe sodium-cooled fast reactor paired with a molten salt energy storage system that can boost output to 500 MWe on demand, enough to power roughly 400,000 homes. [1][12] Headquartered in Bellevue, Washington, TerraPower traces its origins to a 2006-2007 effort inside Intellectual Ventures and was established as a company in 2008. [2][3] Its first commercial plant, Natrium Kemmerer Unit 1, is under construction near Kemmerer, Wyoming, and TerraPower describes it as the first commercial, utility-scale advanced nuclear power plant in the United States. [12][15] The company has become prominent in discussions of how to supply firm, carbon-free electricity to AI data centers, in part because Nvidia's venture arm led a 2025 investment and because TerraPower has signed an agreement to explore powering AI data centers with its reactors. [10][9]
TerraPower grew out of Intellectual Ventures, the invention and patent firm founded by former Microsoft chief technology officer Nathan Myhrvold. Gates and Myhrvold began the effort around 2006-2007 in Bellevue, Washington, to commercialize a new generation of nuclear reactors that the founders argued could be safer, cheaper, and better suited to displacing fossil fuels than conventional light-water plants; TerraPower itself describes its founding year as 2008, when it was spun out as the first company from Intellectual Ventures. [2][3] Gates serves as chairman of the board and Myhrvold as vice chairman, with nuclear physicist John Gilleland serving as the founding chief executive from 2008 to 2015. [2] Chris Levesque, a nuclear engineer who previously led new-reactor programs at Westinghouse and AREVA, joined TerraPower as president in 2015 and became president and chief executive officer in November 2018. [3]
Gates has tied much of his personal climate advocacy to the company. He has said he is investing more than $1 billion of his own money in TerraPower, and the firm has estimated that its first plant could be built for up to roughly $4 billion, which it argues is competitive with recent large U.S. nuclear projects. [3]
TerraPower's original concept was the Traveling Wave Reactor (TWR), a sodium-cooled fast reactor designed to run largely on depleted or natural uranium (uranium-238), breeding fissile material in place and stretching fuel resources. In September 2015 the company signed an agreement with the state-owned China National Nuclear Corporation to build a 600 MWe TWR prototype at Xiapu in China's Fujian province. In January 2019 TerraPower confirmed the project had been abandoned after the Trump administration tightened restrictions on nuclear technology transfer to China. [3]
After the China setback, TerraPower refocused on Natrium, a reactor and energy-storage system it developed jointly with GE Hitachi Nuclear Energy (now part of GE Vernova). Natrium blends elements of TerraPower's TWR work with GE Hitachi's PRISM sodium fast reactor lineage. The two companies introduced the commercial Natrium design in 2020. [4]
The Natrium reactor is a pool-type, sodium-cooled fast reactor rated at 345 MWe of baseload output and 840 MWth of thermal power. [1] Because liquid sodium boils at a much higher temperature than water, the primary loop runs at near-atmospheric pressure rather than the high pressures of a conventional water-cooled reactor, which TerraPower says reduces the need for heavy pressure containment and lowers cost. [1]
The distinctive feature of Natrium is that the nuclear island is decoupled from the power island by a gigawatt-hour-scale molten salt thermal energy storage system, using nitrate salts similar to those in concentrating solar plants. The reactor runs at a steady output and sends heat either directly to the steam generators or into the salt tanks. When grid demand spikes, stored heat is drawn down to lift the plant's output to as much as 500 MWe, equivalent to roughly 400,000 homes, for more than five and a half hours, without changing the reactor's power level. [1][12] This lets the plant follow daily load swings and complement variable wind and solar, a capability often cited as a reason advanced nuclear could pair well with AI energy consumption and other fast-growing loads. The Natrium design is one of the most prominent entries in the broader small modular reactor field, alongside competitors such as Oklo, X-energy, and Kairos Power.
| Parameter | Value |
|---|---|
| Reactor type | Pool-type sodium-cooled fast reactor (Natrium) |
| Base electrical output | 345 MWe |
| Thermal output | 840 MWth |
| Peak output with storage | up to 500 MWe (about 400,000 homes) |
| Storage system | Molten (nitrate) salt thermal energy storage, gigawatt-hour scale |
| Storage duration at peak | more than 5.5 hours |
| Coolant | Liquid sodium, near-atmospheric pressure |
| Fuel | HALEU (high-assay low-enriched uranium, enriched up to about 20% U-235) |
| Design partners | TerraPower and GE Hitachi Nuclear Energy |
| EPC contractor | Bechtel |
In June 2021 TerraPower announced a partnership with PacifiCorp, the Berkshire Hathaway Energy utility, to study siting a Natrium demonstration plant at a retiring coal facility in Wyoming. On November 16, 2021, the partners selected Kemmerer, a town of roughly 2,800 people in the state's southwest, as the site. Locating the plant beside a closing coal station lets it reuse existing transmission and a skilled workforce, a model often called coal-to-nuclear. [3]
TerraPower submitted its construction permit application for Kemmerer Power Station Unit 1 to the U.S. Nuclear Regulatory Commission (NRC) in March 2024, and the agency docketed it on May 14, 2024. [14] The company began non-nuclear construction in June 2024, building out the energy island, a Test and Fill Facility, and a training center while the safety review proceeded. [17] The NRC issued its final Environmental Impact Statement (NUREG-2268) in October 2025 and completed its final safety evaluation in December 2025, finishing the review in about 18 months rather than the 27 months originally planned. [13][17]
On March 4, 2026, the NRC approved the construction permit for Kemmerer Unit 1. [12] The agency described it as the first construction permit it had ever issued for a commercial non-light-water power reactor, and its first construction permit for any commercial power reactor in many years. [13][14] TerraPower and its engineering, procurement, and construction contractor, Bechtel, began full construction at the site on April 23, 2026. [15] The company expects to mobilize roughly 1,600 construction workers and to employ about 250 people once the plant is operating. [15][16] TerraPower will still need a separate Part 50 operating license before it can load fuel and run the reactor. [13]
TerraPower targets commercial operation in the 2030 to 2031 window. The project ownership entity, US SFR Owner LLC, has told the NRC it expects to finish construction by February 2031, after which it would apply for an operating license authorizing 40 years of operation. [17] PacifiCorp and TerraPower have also studied the feasibility of adding up to five additional Natrium units in PacifiCorp's territory by 2035. [20]
| Date | Milestone |
|---|---|
| 2006-2008 | TerraPower originates inside Intellectual Ventures (Bellevue, WA) and is established as a company in 2008 |
| September 2015 | TWR prototype agreement signed with China National Nuclear Corporation |
| January 2019 | China TWR project abandoned over U.S. technology-transfer limits |
| 2020 | Commercial Natrium design introduced with GE Hitachi Nuclear Energy |
| October 2020 | DOE selects Natrium for the Advanced Reactor Demonstration Program |
| June 2021 | Partnership with PacifiCorp to site a plant in Wyoming |
| November 16, 2021 | Kemmerer, Wyoming chosen as the demonstration site |
| December 2022 | HALEU supply disruption; minimum two-year delay announced |
| March 2024 | Construction permit application filed with the NRC |
| June 2024 | Non-nuclear construction begins at Kemmerer |
| October 2025 | NRC issues final Environmental Impact Statement |
| December 2025 | NRC completes final safety evaluation |
| March 4, 2026 | NRC approves the construction permit |
| April 23, 2026 | Full construction begins at Kemmerer Unit 1 |
| 2030 to 2031 | Targeted commercial operation |
Natrium, like most advanced reactors, requires high-assay low-enriched uranium (HALEU), enriched to between roughly 5% and 20% uranium-235, well above the 3% to 5% used in conventional reactors. When the project began, the only commercial-scale source of HALEU was the Russian state nuclear company Rosatom, through its trading arm Tenex, and TerraPower had expected an early fuel shipment from that supply. [6]
After Russia's invasion of Ukraine in February 2022, TerraPower cut ties with the Russian supply chain. On December 15, 2022, the company announced that the Natrium demonstration would slip by at least two years, from a planned 2028 in-service date to 2030 or later, because domestic and allied HALEU production would not reach commercial volumes in time. [6][7] Levesque said at the time that the company was "anticipating a minimum of a two-year delay" because of the fuel gap and the absence of new enrichment capacity. [6]
TerraPower has since assembled a domestic and allied HALEU strategy rather than relying on any single supplier. Reported partners include Centrus Energy, which is enriching HALEU at Piketon, Ohio and delivered its first material to the U.S. Department of Energy in 2023; Framatome, which is building a HALEU metallization pilot plant at Richland, Washington; Global Nuclear Fuel-Americas, for fuel fabrication; and ASP Isotopes, which plans to supply enriched material from South Africa later in the decade. [8] The U.S. Department of Energy has also begun allocating government-held HALEU to advanced reactor developers, including TerraPower, to bridge the gap until commercial supply matures. [8]
TerraPower's first plant is backed by a mix of federal cost-share funding and private capital. In October 2020 the Department of Energy selected Natrium as one of two flagship awards under its Advanced Reactor Demonstration Program (ARDP), providing $80 million in initial funding and committing to up to $2 billion in cost-shared federal support for the project on a roughly 50-50 basis, subject to congressional appropriations. The other flagship award went to X-energy. [5]
On the private side, TerraPower raised more than $830 million in 2022. [3] On June 18, 2025, it announced a $650 million private fundraise that added NVentures, the venture capital arm of Nvidia, as a new investor alongside returning backers including Gates and the South Korean shipbuilder HD Hyundai. [10] TerraPower said the round was NVentures' first nuclear investment and its largest single investment to that point. HD Hyundai Heavy Industries also entered a strategic partnership to manufacture the Natrium reactor vessel and help build out the supply chain. [10][11] Combining the 2025 round with the federal commitment, TerraPower said it had assembled more than $3.4 billion, including over $1.4 billion in private financing, to design and build the first commercial Natrium plant. [10][11]
| Date | Event | Amount | Backers |
|---|---|---|---|
| October 2020 | DOE ARDP flagship award | $80 million initial, up to $2 billion cost-share | U.S. Department of Energy |
| 2022 | Private fundraise | more than $830 million | Existing investors including Bill Gates |
| June 18, 2025 | Private equity round | $650 million | NVentures (Nvidia), Bill Gates, HD Hyundai |
| Ongoing | Founder commitment | more than $1 billion | Bill Gates (personal) |
TerraPower's profile has risen alongside surging electricity demand from AI computing. The 2025 NVentures investment directly links the company to Nvidia, whose chips power most AI data centers, and the firms framed the deal around the need for new firm generation to meet AI-driven load growth. Mohamed "Sid" Siddeek, the corporate vice president who heads NVentures, said that "as AI continues to transform industries, nuclear energy is going to become a more vital energy source to help power these capabilities." [10][11]
Earlier, on January 21, 2025, TerraPower and Sabey Data Centers signed a memorandum of understanding to develop a strategic collaboration for deploying Natrium plants to power AI data centers, naming the Rocky Mountain region and Texas as areas of interest. [9] The companies pointed to projections that AI and data centers could add hundreds of terawatt-hours to U.S. electricity demand by 2030. [9] Natrium's ability to dispatch up to 500 MWe on demand from its molten salt storage is central to this pitch, because data centers need steady, high-availability power. TerraPower is one of several advanced nuclear firms courting hyperscale buyers, a trend that also includes deals by Constellation Energy, Oklo, Kairos Power, and X-energy with large technology companies.
Separately from Natrium, TerraPower is developing a Molten Chloride Fast Reactor (MCFR), a Generation IV design that uses liquid chloride salt as both fuel and coolant and can run at high temperatures suited to industrial process heat. The work is led in partnership with Southern Company and is supported by the Department of Energy, with Idaho National Laboratory, Oak Ridge National Laboratory, the Electric Power Research Institute, and others contributing. [18] Under a DOE Advanced Reactor Demonstration Program risk-reduction award announced in 2020, with Southern Company as the prime, the team is preparing the Molten Chloride Reactor Experiment (MCRE), a sub-200-kilowatt test reactor to be built at Idaho National Laboratory and billed as the world's first fast-spectrum, salt-fueled fission reactor to go critical. [18] TerraPower built a roughly 1-megawatt nonnuclear Integrated Effects Test loop at its Everett, Washington laboratory to gather scaling data. A larger MCFR demonstration on the order of 180 MWe is targeted for the early 2030s, with commercial deployment envisioned around the middle of that decade.
TerraPower also runs a medical isotopes business, TerraPower Isotopes, focused on actinium-225 (Ac-225), a rare alpha-emitting isotope used in targeted alpha therapies for cancer. On March 17, 2026, the unit announced a $450 million investment in a roughly 250,000-square-foot Ac-225 manufacturing facility in the Bellwether District of Philadelphia, and it broke ground in May 2026. [19] TerraPower says the Philadelphia plant, together with expansion at its Everett, Washington site, will increase its Ac-225 production capacity roughly twentyfold and is expected to begin production around 2029, with the goal of making the company a leading global supplier of the isotope. [19]