Small modular reactors for AI data centres: designs and timelines

A small modular reactor, or SMR, is a nuclear unit of roughly 300 megawatts electric or less, built from factory made modules. Google, Amazon and Meta have signed agreements with several SMR developers to supply AI data centres, but as of 19 October 2026 none of the US designs in those deals is producing power. The earliest company targets for first power cluster around 2030.

This post explains what SMRs are, compares the designs that data centre buyers have backed, and sets out what regulators, company filings and trade press say about permits, fuel, cost and schedule. Each figure carries its source and date. Company targets are company targets, not forecasts, and figures from private companies are unaudited. This is not investment advice.

Key numbers at a glance

• SMR size: generally 300 MWe or less per unit, with some definitions extending to 600 MWe (World Nuclear Association, page updated 1 October 2026).
• Microreactors: most designs would produce 1 to 20 megawatts thermal (US Department of Energy, 26 February 2021).
• Russia's floating plant Akademik Lomonosov: two KLT-40S reactors of 35 MWe each, in commercial operation since May 2020 (World Nuclear News, 16 January 2025).
• China's Linglong One (ACP100): 125 MWe, hot functional tests under way, fuel loading aimed for within 2026 (World Nuclear News, 14 October 2026).
• Google and Kairos Power: up to 500 MW of new carbon free power, first reactor targeted by 2030 and more through 2035 (Google, 14 October 2024).
• Kairos Hermes 2: TVA to buy up to 50 MW, operations scheduled to begin in 2030 (World Nuclear News, 18 August 2025).
• Amazon and X-energy: up to 5 GW of Xe-100 reactors in the US by 2039; first project four reactors totalling 320 MWe, expandable to 960 MWe (World Nuclear News, 16 October 2024).
• TerraPower Natrium at Kemmerer, Wyoming: 345 MWe, able to reach 500 MW using storage; NRC construction permit voted 4 March 2026 (TerraPower, 4 March 2026; DOE, 9 March 2026).
• Meta and TerraPower: up to eight Natrium plants, up to 2.8 GW of baseload power, first units as early as 2032 (TerraPower, 9 January 2026).
• TVA Clinch River: one 300 MWe GE Vernova Hitachi BWRX-300; construction permit announced 29 September 2026 (GE Vernova, 29 September 2026).
• NuScale US460: six 77 MWe modules, 462 MWe per plant; NRC standard design approval announced 29 May 2025 (Utility Dive, 2 June 2025; DOE, 30 May 2025).
• NuScale US600 design certification: final rule published 19 January 2023, effective 21 February 2023 (Federal Register).
• Data centre demand: 4.4 percent of US electricity in 2023, projected 6.7 to 12 percent by 2028 (US Department of Energy, 20 December 2024).

What "small" and "modular" actually mean

Traditional reactors are large, often producing 1,000 megawatts or more from one unit, and are mostly built on site. An SMR is smaller, and the idea is to make large pieces in a factory and ship them, so that the site job becomes assembly rather than construction from raw materials.

The size limit is a convention, not a law of physics. The World Nuclear Association describes SMRs as "generally 300 MWe equivalent or less, designed with modular technology", and notes that some definitions stretch to 600 MWe. Below SMRs sit microreactors. The Department of Energy says most microreactor designs would produce 1 to 20 megawatts of thermal energy, which can be used as heat or turned into electricity. The Department's own SMR page simply says advanced SMRs are envisioned to range from tens of megawatts to hundreds of megawatts.

Two units matter for reading the deals. Megawatts electric (MWe) measure the power sent to the grid. Megawatts thermal (MWt) measure the heat the reactor produces, which is roughly two to three times larger for the same plant because turning heat into electricity loses energy. X-energy's Xe-100, for example, is described by World Nuclear News as a 200 MWt reactor that drives an 80 MWe generator.

Scale explains why buyers sign for many units at once. The Department of Energy reported on 20 December 2024 that US data centres used about 176 terawatt hours in 2023, around 4.4 percent of national electricity, and could use 325 to 580 terawatt hours by 2028. A single SMR of 50 to 300 MWe covers only part of a large AI campus, so data centre agreements are written in gigawatts and unit counts rather than single reactors.

Where SMRs already run

Only a handful of SMRs operate anywhere, and none in North America. NuScale's annual report filed on 26 February 2026 states that China and Russia currently operate SMRs, and X-energy's prospectus amendment of 8 April 2026 says competitors based in Russia and China operate commercial or near commercial SMRs at home.

Russia's Akademik Lomonosov is a floating plant moored in the Arctic. World Nuclear News reported on 16 January 2025 that it carries two KLT-40S reactors of 35 MWe each, entered commercial operation in May 2020, and supplies about 60 percent of the energy for western Chukotka and Chersky in Yakutia. The reactor type descends from those used in nuclear icebreakers.

China's HTR-PM at Shidaowan in Shandong is a high temperature gas cooled plant with two reactors of 250 MWt each feeding a single 210 MWe turbine. It was connected to the grid in December 2021, and China's National Energy Administration announced its commercial operation in December 2023, according to World Nuclear News on 6 December 2023.

China's Linglong One, the 125 MWe ACP100 pressurised water reactor on Hainan island, is close but not yet running. First concrete was poured on 13 July 2021. World Nuclear News reported on 14 October 2026 that hot functional tests were under way, with the aim of loading fuel within the year. It has not yet loaded fuel, so it does not count as operating.

The designs buyers have backed

SMRs differ mainly in how they remove heat from the core. Four families appear in the data centre deals.

Light water designs. These use ordinary water as coolant, like most reactors operating today. TVA's Clinch River project near Oak Ridge, Tennessee, plans one GE Vernova Hitachi BWRX-300, a boiling water design that the Department of Energy describes as a 300 megawatt electric advanced light water system. The same design is under construction at Ontario Power Generation's Darlington site in Canada, where the Canadian regulator issued a licence to construct in April 2025 and OPG applied for a licence to operate in March 2026, per GE Vernova's 29 September 2026 release. NuScale is the other light water design. Its 10-K filed in February 2026 describes a 77 MWe power module that uses passive safety features and conventional low enriched uranium fuel.

High temperature gas cooled designs. X-energy's Xe-100 uses helium as coolant and graphite as moderator. X-energy's prospectus gives a helium outlet temperature of 750 degrees Celsius and 565 degrees Celsius steam, compared with roughly 300 degrees Celsius for light water reactors, which is why the design is also pitched for industrial heat. The fuel is TRISO, short for tri-structural isotropic: small uranium kernels coated in carbon and silicon carbide layers and packed into graphite pebbles. The standard plant groups four 80 MWe reactors into a 320 MWe block.

Molten salt cooled designs. Kairos Power's reactor uses molten fluoride salt as coolant with TRISO pebble fuel. Hermes, the first low power test reactor in Oak Ridge, received its construction permit in December 2023. Kairos said on 20 January 2026 that groundbreaking was in July 2024 and nuclear safety related construction began in May 2025. Hermes 2 is the demonstration plant meant to sell power. World Nuclear News reported on 18 August 2025 that Kairos planned to raise Hermes 2 from 28 MWe to 50 MWe from a single reactor.

Sodium cooled designs. TerraPower's Natrium and Oklo's Aurora both use liquid sodium as coolant and fast neutrons. Natrium pairs a 345 MWe reactor with a molten salt energy store. TerraPower says each unit can ramp to 500 MW for more than five hours, which lets the plant follow demand. Oklo's 10-Q filed on 7 August 2026 says the Aurora product line is designed to produce 15 to 75 MWe, with potential to go to 100 MWe and higher, on fresh, recycled or down blended fuel.

The chemistry matters less than the consequence. Each family has its own supply chain, its own fuel form and its own regulatory history, so the risk of delay differs from one design to the next.

The data centre deals, one by one

Google, Kairos Power and TVA. On 14 October 2024 Google called its agreement with Kairos "the world's first corporate agreement to purchase nuclear energy from multiple small modular reactors", covering up to 500 MW with a first reactor targeted by 2030 and more through 2035. The first concrete step followed on 18 August 2025: TVA agreed to buy up to 50 MW from Hermes 2 for its grid, which serves Google data centres in Tennessee and Alabama. World Nuclear News described it as the first agreement by a US utility to buy electricity from an advanced Gen IV reactor.

Amazon, X-energy and Energy Northwest. Amazon announced on 16 October 2024 a goal of deploying up to 5 GW of Xe-100 reactors in the US by 2039. The first project, the Cascade Advanced Energy Facility with Energy Northwest at the Columbia Generating Station site in Washington State, starts with four reactors totalling 320 MWe and could grow to 960 MWe. X-energy's 8 April 2026 prospectus describes the 5 GW figure as a target that assumes Amazon exercises all of its options, so it is not firm capacity. The same filing says X-energy plans its first commercial delivery in the early 2030s and has not yet reached a final investment decision on any reactor.

Meta and TerraPower. On 9 January 2026 TerraPower announced an agreement with Meta for up to eight Natrium plants, worth up to 2.8 GW of baseload power and up to 4 GW with storage. Meta supports early development of two units and holds rights to energy from up to six more. TerraPower said the first units could be delivered as early as 2032. A dual unit plant would provide 690 MW of firm power and up to 1 GW of dispatchable electricity, per the same announcement.

Meta and Oklo. Oklo's 10-Q says that on 5 January 2026 it signed a prepayment agreement with Meta to advance a planned 1.2 GW power campus in Pike County, Ohio, for Meta's data centres, with Meta's funding to be used to secure nuclear fuel for the project. The same filing lists a 12 GW master power agreement signed with data centre operator Switch in December 2024. Oklo also states that it is uncertain when, if at all, it will obtain NRC approvals for the design, construction and operation of its powerhouses.

TVA, ENTRA1 and NuScale. NuScale's annual report says TVA and ENTRA1 signed a non binding agreement on 2 September 2025 to develop up to 6 GW of new nuclear generation for TVA, with ENTRA1 planning to use NuScale equipment. The same report states plainly that NuScale has not yet entered into a binding contract with a customer to deliver its modules.

Where each project stands

Permits are the clearest milestones, so the short version is below. A related post, Nuclear for AI data centres: regulatory steps, timelines, risks, explains the licensing steps and review times in detail. A construction permit lets an owner build. A separate operating licence is still needed before fuel can be loaded and power produced.

• TerraPower Kemmerer Unit 1: application filed March 2024 and docketed May 2024; the NRC Commission voted to issue the construction permit on 4 March 2026. TerraPower calls Kemmerer Unit 1 the first commercial scale advanced nuclear plant to receive this permit, and DOE said the project is expected to be completed in 2030.
• Kairos: Hermes construction permit in December 2023; Hermes 2 permits approved by the NRC on 20 November 2024, per Kairos. Hermes 1 fuel is covered by a Department of Energy HALEU contract finalised on 20 January 2026.
• TVA Clinch River: TVA applied in May 2025, and the permit was announced on 29 September 2026. World Nuclear News reported that the review took 14 months, four months ahead of schedule. TVA has not announced a construction start and is still negotiating cost sharing with industry partners.
• X-energy with Dow at Seadrift, Texas: construction permit application filed March 2025 and docketed May 2025, with the permit expected in the first quarter of 2027 and commercial operation in the early 2030s, per X-energy's prospectus. The prospectus also discloses that, as of 22 January 2026, an NRC licensing board had admitted two contentions on financial qualifications from an intervenor, with the hearing ongoing.
• X-energy with Energy Northwest: no construction permit application yet in the sources cited here.
• Oklo: a Department of Energy site use permit at Idaho National Laboratory and a fuel award of five metric tons of HALEU recovered from EBR-II material, per its 10-Q; no NRC licence yet.

The NuScale certification date, resolved. Secondary summaries give 2020, 2022 or 2023 for NuScale's first approval. The primary record separates three steps. NuScale's 10-Q filed 5 August 2026 says the NRC issued the final safety evaluation and standard design approval for the 50 MWe, 12 module design in August 2020. The certification itself is a rule: the Federal Register published the final rule certifying the NuScale design on 19 January 2023, effective 21 February 2023. Separately, the uprated six module 77 MWe design, called US460, received a standard design approval announced by the NRC on 29 May 2025. A standard design approval can be referenced in a licence application, but it is not a licence to build.

What it costs, and why the evidence is thin

SMR costs are the weakest part of the evidence, because almost no comparable plants have been finished. The announcements cited in this post for Kairos, X-energy, TerraPower, TVA and Oklo do not include firm construction budgets, and TVA has said it wants partners to share first of a kind cost so that ratepayers do not carry it, per World Nuclear News on 30 September 2026.

The best documented cautionary case is NuScale's Carbon Free Power Project. The Utah Associated Municipal Power Systems had planned a 462 MWe plant using NuScale modules. NuScale's 10-K filed on 15 March 2024 records a settlement and release agreement dated 7 November 2023 ending that project, payments of 49.8 million dollars to the project company, and a plan announced on 8 January 2024 to cut 154 full time staff, or 28 percent of the workforce. The filing does not restate the project's cost estimates, so they are not repeated here.

Company filings are frank about the risk. X-energy's prospectus warns that "the nuclear industry has historically experienced significant cost overruns, schedule delays and cancellations on first-of-a-kind and follow-on projects", and that if cost reductions from building many units are "lower or slower than expected", its products may not be cost competitive. It also notes that the Dow project timeline runs beyond the Department of Energy's demonstration programme funding period, which could leave Dow to fund remaining costs.

For context on what buyers pay for other new capacity, a related post, How much does an AI data centre cost per megawatt and per gigawatt?, covers the data centre side of the bill.

Fuel: the quiet bottleneck

Several advanced designs need HALEU, short for high assay low enriched uranium. The Department of Energy defines it as uranium enriched between 5 and 20 percent in uranium 235, compared with up to 5 percent for the existing US fleet. DOE says HALEU is required for most US advanced reactors to reach smaller designs with more power per unit of volume, that it is not yet available at commercial scale, and that domestic demand could reach 50 metric tons a year by 2035 (article updated 3 December 2024).

Light water SMRs largely sidestep this problem. NuScale's annual report says its module uses the conventional low enriched uranium fuel supply that has served light water reactors for decades. The Xe-100, Kairos and Natrium designs rely on HALEU instead.

The supply picture is still being built. X-energy's prospectus says the Energy Act of 2020 created DOE's HALEU Availability Program, that Centrus is producing about 1 metric ton of HALEU a year at a pilot cascade in Piketon, Ohio, and that Centrus has stated an objective of up to 6 metric tons a year by the first quarter of 2029. It adds that DOE's stated goal is for commercial enrichment plants to come online as early as 2027, and that early reactors may rely on government material, including highly enriched uranium down blended to HALEU. If supply outside Russia and China fails to materialise, the filing says, that would materially harm the business. On the demand side, Kairos finalised its DOE contract for Hermes 1 fuel in January 2026, and Oklo holds its EBR-II material award.

What is firm and what is uncertain

Firm:

• The NRC has approved construction for TerraPower at Kemmerer (March 2026), Kairos Hermes and Hermes 2 (December 2023 and November 2024) and TVA Clinch River (September 2026).
• NuScale's 50 MWe design is certified by rule, and its 77 MWe design holds a standard design approval.
• Google, Amazon and Meta have signed agreements naming specific developers, sizes and target years.
• SMRs operate in Russia and China, and Linglong One is in hot testing.

Uncertain:

• Whether any US SMR delivers power to a data centre before 2030. Company targets for Hermes 2 and Kemmerer are 2030.
• Final costs. No US data centre linked project has published a firm budget in the sources cited here.
• HALEU supply for the designs that need it.
• How much of the headline capacity becomes binding. Amazon's 5 GW is option based, Meta holds rights to six of eight Natrium units, and the TVA and ENTRA1 agreement is non binding.
• Contested licensing, such as the open hearing on the Dow application.

What to watch next

• An NRC decision on the X-energy and Dow construction permit, expected in the first quarter of 2027 per X-energy.
• Operating licence applications and decisions for Hermes 1 and Kemmerer.
• A construction start date and cost sharing deal for TVA Clinch River.
• Fuel loading and grid connection at Linglong One.
• A site announcement for Meta's first two Natrium units.
• Any firm NuScale customer order.
• Progress on the Darlington licence to operate in Canada, the first BWRX-300.

For how restarts compare with new builds, see How a US nuclear plant restart works, from licence to grid. For the wider menu of nuclear options, see Nuclear power for AI data centres: restarts, uprates, new reactors.

Quick check

If your team tracks the software behind its own infrastructure projects, Safeguard offers SBOM and dependency scanning, with a free scan at https://gold.safeguard.sh/scan.

Sources

• Small Nuclear Power Reactors, World Nuclear Association, updated 1 October 2026, accessed 19 October 2026.
• What is a Nuclear Microreactor?, US Department of Energy, 26 February 2021, accessed 19 October 2026.
• Advanced Small Modular Reactors (SMRs), US Department of Energy, accessed 19 October 2026.
• What is High-Assay Low-Enriched Uranium (HALEU)?, US Department of Energy, updated 3 December 2024, accessed 19 October 2026.
• DOE releases new report evaluating increase in electricity demand from data centers, US Department of Energy, 20 December 2024.
• Russia's floating nuclear power plant passes one billion kWh, World Nuclear News, 16 January 2025.
• China's demonstration HTR-PM enters commercial operation, World Nuclear News, 6 December 2023.
• Hot testing of Chinese SMR under way, World Nuclear News, 14 October 2026.
• Google, Kairos Power nuclear energy agreement, Google, 14 October 2024.
• Google, Kairos Power, TVA announce collaboration, World Nuclear News, 18 August 2025.
• Nuclear Regulatory Commission approves construction permits for Hermes 2 demonstration plant, Kairos Power, 20 November 2024.
• U.S. Department of Energy to provide HALEU for Hermes demonstration reactor, Kairos Power, 20 January 2026.
• Amazon invests in X-energy, unveils SMR project plans, World Nuclear News, 16 October 2024.
• X-Energy, Inc. Form S-1/A, Amendment No. 2, US Securities and Exchange Commission, filed 8 April 2026.
• NRC approves the Natrium reactor construction permit, TerraPower, 4 March 2026.
• NRC issues construction permit for TerraPower's Natrium advanced reactor, US Department of Energy, 9 March 2026.
• TerraPower and Meta enter agreement for 8 Natrium advanced nuclear plants, TerraPower, 9 January 2026.
• NRC issues first US construction permit for BWRX-300 small modular reactor at TVA Clinch River, GE Vernova, 29 September 2026.
• First construction permit issued for BWRX-300 SMR in US, World Nuclear News, 30 September 2026.
• NRC dockets construction permit application for TVA small modular reactor, US Department of Energy, 10 July 2025.
• NuScale small modular reactor design certification, final rule, Federal Register via GovInfo, 19 January 2023.
• NRC certifies first US small modular reactor design, US Department of Energy, 20 January 2023.
• NRC approves NuScale Power's uprated small modular reactor design, US Department of Energy, 30 May 2025.
• NRC approves NuScale small modular reactor design, Utility Dive, 2 June 2025.
• NuScale Power Corporation Form 10-K for 2023, US Securities and Exchange Commission, filed 15 March 2024.
• NuScale Power Corporation Form 10-K for 2025, US Securities and Exchange Commission, filed 26 February 2026.
• NuScale Power Corporation Form 10-Q for the quarter ended 30 June 2026, US Securities and Exchange Commission, filed 5 August 2026.
• Oklo Inc. Form 10-Q for the quarter ended 30 June 2026, US Securities and Exchange Commission, filed 7 August 2026.

Last reviewed: 19 October 2026.