Small modular reactors
What counts as a small modular reactor, why factory fabrication matters, the one floating plant in operation, the use cases, and the named designs with their status and dates.
What counts as small
The IAEA defines small modular reactors as advanced reactors that produce up to 300 MW(e) per module, deployable as single or multi-module plants and designed to be built in factories and shipped to utilities for installation as demand arises; it tracks more than 80 SMR designs and concepts globally. The World Nuclear Association uses "small" for reactors of generally 300 MWe equivalent or less, designed with modular technology using module factory fabrication, pursuing economies of series production and short construction times.
Sources: IAEA - Small modular reactors (topic page), 9 Oct 2026 (smr_iaea_definition) · WNA - Small Nuclear Power Reactors, 1 Oct 2026 (smr_wna_definition)Below that, the IAEA describes microreactors as producing up to 10 MW(e): small enough for the whole plant to be built in a factory and transported by truck, and able to operate independently of the grid for remote communities, mining sites or as backup power for hospitals. The US Department of Energy draws its line in thermal output instead: most microreactors would produce 1 to 20 megawatts of thermal energy (MWt), be fully assembled in a factory and shipped to site, and operate for up to 10 years without refuelling. The two definitions use different units, electric and thermal, so a microreactor figure should say which one it quotes.
Sources: IAEA Bulletin - Small reactors, great potential (Irena Chatzis), 9 Oct 2026 (smr_microreactor_iaea) · US DOE Office of Nuclear Energy - What is a Nuclear Microreactor?, 26 Feb 2021 (smr_microreactor_doe)The case made for them
As the World Nuclear Association states it, the case for SMRs rests on factory fabrication of modules under controlled conditions, series production, a significantly lower capital outlay per unit (lower financial risk), deployment on grids too small for large reactors or at industrial sites and potentially nearer urban areas, and passive safety features that may allow smaller emergency planning zones. That is the association's statement of the case; the status of each named design is further down this page.
Source: WNA - Small Nuclear Power Reactors, 1 Oct 2026 (smr_rationale)Inside an integral pressurised water SMR
NuScale's US460 design has 77 MWe per nuclear power module and six modules per plant (462 MWe); the NRC issued its standard design approval in May 2025 on an application dated 31 December 2022, building on the 50 MWe design certified in 2023.
Source: US NRC - NuScale US460 (applicant project page), 16 Sep 2026 (sd_nuscale_us460)RoPower's six-module NuScale plant at the former Doicesti coal site in Romania (462 MWe) took its final investment decision in February 2026. The cost was put at USD 6 to 7 billion, first module commercial operation is targeted for 2033, and the US DFC and EXIM issued letters of interest for up to USD 1 billion and USD 3 billion.
Source: WNN - Final investment decision taken for Romania's SMRs, 13 Feb 2026 (sd_nuscale_ropower)"Integral" means that the reactor core, the pressuriser and the steam generators sit in one common reactor pressure vessel. In NuScale's certified power module, a natural circulation light water reactor, the two steam generators are helical coils and the vessel is housed in a compact cylindrical steel containment; each certified module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules, and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the building. The US460 is the uprate of this module to 77 MWe.
Source: Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 (sd_nuscale_module_configuration)The cross-section below names the parts; each numbered part opens a note with the verified facts behind it.
Integral pressurised water SMR (NuScale US460), schematic cross-section. Drawn from scratch in the site's style; parts are placed for reading, not to scale. Hotspots: Tab to a numbered part, Enter or Space opens its note, Escape closes it. Every note is a verified fact with its source.
Core
The core is the bundle of fuel assemblies at the bottom of the reactor vessel, where fission heats the primary water.
Nuclear fission occurs when a uranium-235 nucleus absorbs a neutron and splits into two lighter fragments, releasing about 200 MeV of energy and, on average, 2.45 further neutrons that can sustain a chain reaction.
WNA - Physics of Nuclear Energy, 30 Mar 2026 · U-235 thermal fission· reputable secondaryControl rods
The control rods are rods of neutron-absorbing material, driven from mechanisms on the vessel head, that are inserted into or withdrawn from the core to control the chain reaction.
Control rods or blades made of neutron-absorbing material such as cadmium, hafnium or boron are inserted into or withdrawn from the core to control or halt the chain reaction.
WNA - Nuclear Power Reactors, 5 Aug 2026· reputable secondaryReactor pressure vessel
The reactor pressure vessel is the steel vessel that holds the core, the riser, the pressuriser and the two steam generators together: an integral vessel.
The certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceHelical-coil steam generators
The steam generators are helical tube coils in the annulus between the riser and the vessel wall: primary water flows over the outside of the tubes while feedwater inside them boils to steam.
NuScale's helical-coil steam generators differ from those of operating pressurised water reactors in that the primary reactor coolant is on the outside of the steam generator tubes and the steam is on the inside.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design· primary sourceThe certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceIntegral pressuriser
The pressuriser is the space at the top of the reactor vessel that sets the pressure of the primary water so that it does not boil in the core.
The certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceIn a PWR the water in the core reaches about 325 C and is kept under about 150 times atmospheric pressure so that it does not boil; steam is raised in separate steam generators.
WNA - Nuclear Power Reactors, 5 Aug 2026 · typical PWR· reputable secondaryNatural-circulation riser
The riser is the open tube above the core: water heated in the core rises through it, turns over at the top and sinks through the annulus past the steam generator coils, so the primary water circulates by natural circulation.
The certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceContainment vessel
The containment is the cylindrical steel vessel that encloses the reactor vessel and its steam and feedwater connections and stands partly submerged in the pool.
The certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceThe certified NuScale design needs no Class 1E safety-related power (no emergency diesel generators) and no pumps to inject water into the core after an accident; its emergency core cooling relies on natural circulation, venting steam from the top of the reactor pressure vessel through three reactor vent valves into the containment vessel and returning the condensed water through two reactor recirculation valves.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design· primary sourceReactor pool
The reactor pool is the body of water in the below-grade part of the reactor building in which the modules stand partly submerged; it is the plant’s ultimate heat sink.
The certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceTurbine and generator
The turbine is driven by steam from the module’s steam generators and turns the generator; the exhaust steam is condensed and pumped back to the steam generators as feedwater.
In a PWR the steam line directs the steam to the main turbine, which turns the turbine generator that produces electricity; the unused steam is exhausted to the condenser, condensed into water, pumped out of the condenser by a series of pumps, reheated and pumped back to the steam generator.
US NRC - Pressurized Water Reactors, 14 Sep 2026 · US NRC description of a PWR· primary sourceIn a PWR the secondary circuit is under less pressure than the primary circuit and its water boils in the heat exchangers, which are thus steam generators; the steam drives the turbine to produce electricity, and is then condensed and returned to the heat exchangers in contact with the primary circuit.
WNA - Nuclear Power Reactors, 5 Aug 2026· reputable secondarySix modules per plant
A module is one reactor vessel in its own containment, and a plant places several modules side by side in a common pool, as the plan view shows.
NuScale's US460 design has 77 MWe per nuclear power module and six modules per plant (462 MWe); the NRC issued its standard design approval in May 2025 on an application dated 31 December 2022, building on the 50 MWe design certified in 2023.
US NRC - NuScale US460 (applicant project page), 16 Sep 2026 · NRC applicant page updated 16 Sep 2026· primary sourceThe certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceThe one floating plant in operation
Russia's Akademik Lomonosov at Pevek, Chukotka, is the only operating floating nuclear power plant. It carries two 35 MWe (32 MWe net) KLT-40S reactors on a 21,500-tonne, 144 m long hull; both units were connected to the grid on 19 December 2019 and entered commercial operation in May 2020. The other floating and barge-mounted designs on record are in the project table below, with their status as recorded.
Source: WNA - Nuclear Power in Russia (country profile), 22 Jul 2026 (smr_lomonosov)Use cases
Use cases cited by the IAEA, and the two that vendors add:
- power for hard-to-reach places and small grids
- remote communities and mining sites
- backup supply for hospitals
- seawater desalination, as at Akademik Lomonosov
- industrial heat and data centres, which SMR vendors target; the fact base's data-centre examples are Kairos Hermes 2 for Google via TVA and Natrium for PacifiCorp
Named designs and where they stand
Grouped by family: water-cooled, high-temperature gas-cooled, fast neutron, salt-cooled, then the US test-reactor scheme. Each block states the latest verified step with its date; the table that follows lists every project in the dataset.
GE Vernova Hitachi BWRX-300 (boiling water)
For the 300 MWe BWRX-300, the Canadian regulator granted OPG a licence to construct the first unit at Darlington in April 2025; nuclear construction is under way, and OPG's licence-to-operate application of March 2026 is under CNSC review. On 29 September 2026 the NRC issued TVA a construction permit for a BWRX-300 at the Clinch River site in Tennessee, the first US construction permit for the design, on an application submitted in April 2025 according to GE Vernova (the NRC docketed it in May 2025, the date the table records); Blue Energy filed part one of a construction permit application for a BWRX-300 in Texas in September 2026.
Source: GE Vernova press release - NRC issues first US construction permit for BWRX-300 SMR (TVA Clinch River), 29 Sep 2026 (sd_bwrx300_darlington, sd_bwrx300_clinch_river)Rolls-Royce SMR (pressurised water)
The Rolls-Royce SMR is a 470 MWe (1,358 MWt) factory-built plant. It entered the UK Generic Design Assessment in March 2022 and reached Step 3, the final step, in July 2024; Great British Energy - Nuclear named it preferred bidder on 10 June 2025 within a programme funded with over GBP 2.5 billion and aiming at grid connection in the mid-2030s, and Wylfa on Anglesey was selected on 13 November 2025 as the site for three units.
Source: GOV.UK press release - Rolls-Royce SMR selected to build small modular nuclear reactors, 10 Jun 2025 (sd_rolls_royce_smr)ACP100 Linglong One (pressurised water)
China's 125 MW ACP100 "Linglong One" at Changjiang, Hainan, has been under construction since July 2021. It completed cold functional testing in October 2025 and was reported (unconfirmed local media, 7 October 2026) to be in hot functional testing, with fuel loading and grid connection targeted before the end of 2026; it could be the world's first onshore commercial SMR to operate.
Source: NucNet - Hot testing begins at China's Linglong-1 small modular reactor, 7 Oct 2026 (sd_linglong_one)Holtec SMR-300 (pressurised water)
Holtec plans two SMR-300 pressurised-water SMRs at its Palisades site in Michigan; the NRC accepted the first part of the construction permit application for review in February 2026, with the final safety evaluation and environmental impact statement expected in March 2027.
Source: NucNet - US nuclear regulator accepts partial construction permit application for Palisades SMRs, 25 Feb 2026 (sd_holtec_smr300)Westinghouse AP300 (pressurised water)
Westinghouse's AP300 SMR is rated 330 MWe (990 MWt) and is based on the licensed AP1000 technology; Westinghouse says it is designed to reach and maintain safe shutdown without operator action, back-up power or pumps, has a four-year refuelling cycle and targets an 80-year life. It is in NRC pre-application engagement with no design approval application filed. The project table below lists the AP300 at 300 MWe, the dataset's figure; Westinghouse's own page says 330 MWe.
Source: Westinghouse - AP300 SMR, 9 Oct 2026 (sd_westinghouse_ap300)Last Energy PWR-5 and PWR-20 (pressurised water)
Last Energy's PWR-5 pilot reactor at the Texas A&M-RELLIS campus received DOE approval of its preliminary documented safety analysis in late May 2026 and planned an initial criticality test in summer 2026 pending DOE authorisation; criticality had not been confirmed when the dataset was read in October 2026. The company's commercial product is the 20 MWe PWR-20, proposed for sites including the former Llynfi power station in Wales.
Source: ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026 (sd_last_energy)HTR-PM (high-temperature gas-cooled, operating)
High-temperature gas-cooled reactors use helium coolant, a graphite moderator and TRISO coated-particle fuel, reaching about 750 to 950 °C. China's HTR-PM at Shidao Bay, Shandong, two 250 MWt pebble-bed HTGR modules feeding one 210 MWe turbine with TRISO fuel enriched to 8.5%, was declared in commercial operation on 6 December 2023 and is the world's only operating commercial HTGR.
Sources: WNA - Nuclear Power Reactors, 5 Aug 2026 (rf_htgr) · WNN - Chinese HTR-PM Demo begins commercial operation (via data/smr_projects.csv), 6 Dec 2023 (sd_htr_pm)X-energy Xe-100 (high-temperature gas-cooled)
X-energy's Xe-100 is an 80 MWe high-temperature gas reactor using TRISO fuel. Four units are planned at Dow's Seadrift site (Long Mott Generating Station, Texas), where the NRC docketed the construction permit application in May 2025, issued an environmental assessment in May 2026 and held the mandatory hearing on 22 September 2026, with the permit decision pending.
Source: US NRC - mandatory hearing notice, Long Mott Generating Station (via data/smr_projects.csv), 22 Sep 2026 (sd_xe100)TerraPower Natrium (sodium-cooled fast)
Fast neutron reactors have no moderator and use a liquid-metal coolant, normally sodium, at around 500 to 550 °C and near-atmospheric pressure; they can breed plutonium from U-238 or burn long-lived actinides. TerraPower's Natrium plant (Kemmerer Unit 1, Wyoming) pairs a 345 MW sodium-cooled fast reactor with molten-salt energy storage that can raise output to 500 MW; on 4 March 2026 the NRC Commissioners voted to issue its construction permit, the first for a commercial-scale advanced reactor, 18 months after the March 2024 application.
Sources: WNA - Fast Neutron Reactors, 31 Mar 2026 (rf_fast_reactors) · TerraPower - NRC Approves Natrium Reactor Construction Permit, 4 Mar 2026 (sd_natrium)Oklo Aurora (liquid-metal-cooled fast)
Oklo's Aurora-INL is a 75 MWe liquid-metal-cooled, metal-fuelled fast reactor at Idaho National Laboratory. Oklo broke ground in September 2025 and secured DOE approval of its preliminary documented safety analysis on 11 June 2026 under the Reactor Pilot Program, with no criticality timeline given.
Source: ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026 (sd_oklo_aurora)newcleo LFR (lead-cooled fast)
newcleo submitted the safety options dossier for its lead-cooled fast reactor to France's ASNR (reported 15 January 2026). It plans construction-authorisation applications before the end of 2027, a final investment decision around 2029 and first operation in France as early as 2032, with a MOX fuel pilot line planned at Nogent-sur-Seine and a non-nuclear precursor prototype due in 2026 at ENEA Brasimone, Italy.
Sources: WNN - Licensing of newcleo's SMR progresses in France, 15 Jan 2026 (sd_newcleo) · WNA - Fast Neutron Reactors, 31 Mar 2026 (rf_fast_reactors)Kairos Hermes (fluoride-salt-cooled)
Molten salt reactors use molten fluoride (or chloride) salts as coolant and usually as the fuel carrier, at low pressure and about 700 °C. Kairos Power's fluoride-salt-cooled Hermes 1 low-power demonstration reactor is under nuclear construction at Oak Ridge, Tennessee, currently the only Gen IV reactor under active nuclear construction in the US; the company broke ground on 17 April 2026 for Hermes 2, its first power-producing plant, which will supply up to 50 MW to the TVA grid for Google data centres.
Sources: WNA - Molten Salt Reactors, 21 Nov 2025 (rf_msr) · Kairos Power - Kairos Power breaks ground on Hermes 2 demonstration plant, 17 Apr 2026 (sd_kairos_hermes)US Reactor Pilot Program (test reactors)
Executive Order 14301 set a goal of three reactors achieving criticality by 4 July 2026 under DOE's Reactor Pilot Program; by 2 July 2026 three companies, Antares Nuclear, Valar Atomics and Deployable Energy, had achieved DOE-authorised (zero-power) criticality. The dataset records a fourth, Aalo-X, on 4 July 2026; these rows carry the status "operating" in the table below because the dataset counts fuelled criticality for test reactors.
Source: ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026 (sd_reactor_pilot_program)| Design | Developer | Country | MWe per module × modules = total | Status | Regulator stage | Key milestone | Target year | Source | Confidence |
|---|---|---|---|---|---|---|---|---|---|
| KLT-40S floating NPP (Akademik Lomonosov)Pevek, Chukotka | Rosatom / OKBM Afrikantov | Russia | 35 × 2 = 70 | Operating | Grid connection 19 Dec 2019; commercial operation May 2020 | 22 May 2020 | 2020 | WNA Russia profile (updated 22 Jul 2026) | high |
| HTR-PM (2x250 MWt pebble-bed HTGR)Shidao Bay (Shidaowan), Rongcheng, Shandong | China Huaneng / CNEC / Tsinghua INET | China | 210 × 1 = 210 | Operating | Operating permit Aug 2021; grid connection Dec 2021; commercial operation declared 6 Dec 2023 | 6 Dec 2023 | 2023 | WNN 6 Dec 2023 | high |
| Aalo-X (sodium-cooled, 10 MWe design)Idaho National Laboratory, Idaho | Aalo Atomics | United States | 10 × 1 = 10 | Operating | DSA approved Apr 2026; zero-power fuelled criticality early 4 Jul 2026; fourth RPP criticality, meeting the July 4 goal | 4 Jul 2026 | 2026 | DOE 6 Jul 2026 + Neutron Bytes 8 Jul 2026 | medium |
| Antares Mark-0 (zero-power test reactor)Idaho National Laboratory, Idaho | Antares Nuclear | United States | 0 × 1 = 0 | Operating | Zero-power fuelled criticality achieved 4 Jun 2026; first DOE Reactor Pilot Program criticality | 4 Jun 2026 | 2026 | ANS Nuclear News 2 Jul 2026 (RPP status) + DOE releases | medium |
| Deployable Energy Unity (water-moderated, gas-cooled microreactor, 1 MWe)National Reactor Innovation Center, Idaho National Laboratory, Idaho | Deployable Energy | United States | 1 × 1 = 1 | Operating | Zero-power fuelled criticality announced 1 Jul 2026 (third RPP criticality) | 1 Jul 2026 | 2026 | WNN 2 Jul 2026 | medium |
| Valar Atomics Ward 250 (helium-cooled, graphite-moderated HTGR)Utah San Rafael Energy Lab, Emery County, Utah | Valar Atomics | United States | n/a × 1 = n/a | Operating | Zero-power fuelled criticality 18 Jun 2026 (second RPP criticality); 10 kWt output converted to electricity 22 Jun 2026 | 18 Jun 2026 | 2026 | WNN 22 Jun 2026 + ANS 2 Jul 2026 | medium |
| ACP100 (Linglong One)Changjiang NPP, Hainan | CNNC | China | 125 × 1 = 125 | Under construction | Construction since Jul 2021; cold tests completed Oct 2025; hot functional testing reported underway Oct 2026; fuel loading and grid connection targeted before end-2026 | 7 Oct 2026 | 2026 | NucNet 7 Oct 2026 | medium |
| Last Energy PWR-5 pilot (scaled PWR-20)Texas A&M-RELLIS campus, Bryan, Texas | Last Energy | United States | 5 × 1 = 5 | Under construction | PDSA approved by DOE late May 2026; final DSA submitted; building complete, critical components installed; criticality targeted summer 2026 pending DOE authorisation (not confirmed achieved as of 9 Oct 2026) | 29 May 2026 | 2026 | NucNet 29 May 2026 | medium |
| Radiant Kaleidos (helium-cooled microreactor, ~1 MWe / 3 MWt)NRIC DOME test bed, Idaho National Laboratory, Idaho | Radiant Industries | United States | 1 × 1 = 1 | Under construction | PDSA approved Feb 2026; first fuel tranche received 1 Jul 2026; five-phase test campaign (zero-power criticality then full power) planned summer 2026; criticality not confirmed in sources reviewed | 1 Jul 2026 | 2026 | ANS Nuclear News 2 Jul 2026 (RPP status) + DOE releases | medium |
| Deep Fission Gravity (borehole PWR, 15 MWe)Parsons, Kansas (underground borehole ~1 mile deep) | Deep Fission | United States | 15 × 1 = 15 | Under construction | Groundbreaking Dec 2025; 6,000-ft test well drilled; DOE safety approvals not reported as of 2 Jul 2026 | 1 Dec 2025 | 2027 | ANS Nuclear News 2 Jul 2026 (RPP status) + DOE releases | low |
| Kairos Hermes (35 MWt FHR test reactor)Heritage Center (ETTP), Oak Ridge, Tennessee | Kairos Power | United States | 0 × 1 = 0 | Under construction | Construction permit Dec 2023; safety-related construction began 1 May 2025; NRC extended latest construction completion date from 31 Dec 2026 to 30 Apr 2029 (Apr 2026) | 22 Apr 2026 | 2028 | WNN 22 Apr 2026 | high |
| GE Vernova Hitachi BWRX-300Darlington New Nuclear Project, Clarington, Ontario | GE Vernova Hitachi Nuclear Energy | Canada | 300 × 1 = 300 | Under construction | Licence to Construct issued Apr 2025; Licence to Operate application submitted Mar 2026 (under review, hearing date TBA); hold point 1 (reactor building foundation) lifted 30 Mar 2026 | 30 Mar 2026 | 2030 | WNN 2 Apr 2026 | high |
| Kairos Hermes 2 (KP-FHR demonstration, ~50 MWe)Heritage Center (ETTP), Oak Ridge, Tennessee | Kairos Power | United States | 50 × 1 = 50 | Under construction | Construction permit Nov 2024; groundbreaking 17 Apr 2026 | 17 Apr 2026 | 2030 | Kairos Power 17 Apr 2026 | high |
| TerraPower Natrium (SFR + molten-salt storage)Kemmerer Power Station Unit 1, near Naughton plant, Kemmerer, Wyoming | TerraPower | United States | 345 × 1 = 345 | Under construction | NRC Commission approved construction permit 4 Mar 2026 (first US commercial advanced-reactor CP); ground broken on nuclear plant spring 2026 | 4 Mar 2026 | 2031 | TerraPower press release 4 Mar 2026 | high |
| Oklo Aurora Powerhouse (liquid-metal fast reactor, 75 MWe)Idaho National Laboratory (DOE site-use permit area), Idaho | Oklo Inc. | United States | 75 × 1 = 75 | Under construction | Groundbreaking Sep 2025; DOE PDSA approved 11 Jun 2026 under Reactor Pilot Program; NRC pre-application docket 99902095 (COLA phase-1 readiness assessment 2025; pre-phase-2 audit under review); no COLA docketed | 11 Jun 2026 | n/a | ANS Nuclear News 2 Jul 2026 (RPP status) | medium |
| RITM-200S floating power units (PEB-106)Cape Nagloynyn, Chaun Bay, Chukotka | Rosatom (Atomenergomash / Baltic Shipyard; hulls Wison Nantong) | Russia | 106 × 4 = 424 | Under construction | Units 1-2 under construction since 31 Aug 2022 (WNA); first RITM-200S reactor shipped from ZiO-Podolsk May 2026 | 27 May 2026 | n/a | NucNet 27 May 2026 | low |
| Groves Isotope Test Reactor (15 MWt pool-type, ex-Atomic Alchemy)Lockhart, Texas | Oklo Isotopes (formerly Atomic Alchemy) | United States | 0 × 1 = 0 | Licensed | DOE DSA secured week of 2 Jul 2026; criticality planned July 2026 (achievement not confirmed in sources reviewed) | 2 Jul 2026 | 2026 | ANS Nuclear News 2 Jul 2026 (RPP status) + DOE releases | low |
| RITM-200N land-based SMRUst-Kuyga, Ust-Yansky District, Yakutia | Rosatom | Russia | 55 × 2 = 110 | Licensed | Construction licence granted Apr 2023; site preparation (camps, access road) 2025; first concrete not confirmed in sources reviewed | 1 Apr 2023 | 2030 | WNA Russia profile (updated 22 Jul 2026) | low |
| GE Vernova Hitachi BWRX-300Darlington New Nuclear Project, Clarington, Ontario | GE Vernova Hitachi Nuclear Energy | Canada | 300 × 3 = 900 | Licensed | Covered by the Darlington site licence framework; the April 2025 Licence to Construct covered unit 1 only (construction licence for units 2-4 pending) | 4 Apr 2025 | n/a | CNSC Darlington New Nuclear Project page | medium |
| GE Vernova Hitachi BWRX-300Clinch River Nuclear Site, Oak Ridge, Tennessee | GE Vernova Hitachi Nuclear Energy | United States | 300 × 1 = 300 | Licensed | NRC construction permit issued 29 Sep 2026 (first US BWRX-300 CP; CPA submitted May 2025, review 14 months); early site permit held since 2019 | 29 Sep 2026 | n/a | GE Vernova press release 29 Sep 2026 | high |
| Natura Resources MSR-1 (1 MWt molten salt research reactor)Abilene Christian University (NEXT Lab/SERC), Abilene, Texas | Natura Resources | United States | 0 × 1 = 0 | Licensed | NRC construction permit issued Sep 2024 to ACU; DOE Reactor Pilot Program OTA announced Dec 2025; operating licence not yet applied for per sources reviewed | 1 Dec 2025 | n/a | ANS Nuclear News 2 Jul 2026 (RPP status) + DOE releases | medium |
| ARC-100 (sodium fast reactor)Point Lepreau, New Brunswick | ARC Clean Technology | Canada | 100 × 1 = 100 | Licence application | Licence to Prepare Site application submitted 30 Jun 2023; CNSC 'awaiting additional submissions from NB Power' (page updated 26 Jan 2026); CNSC VDR Phase 2 completed July 2025 ('no fundamental barriers') | 11 Jul 2025 | n/a | CNSC NB Power ARC-100 page (updated 26 Jan 2026) | medium |
| Blykalla SEALER-55 (lead-cooled fast reactor) x6Norrsundet, Gävle municipality | Blykalla | Sweden | 55 × 6 = 330 | Licence application | Application to the Swedish government for a six-reactor park submitted 18 May 2026 (announced); SSM and court processes to follow; second park application (up to 440 MW) reported Aug 2026 | 18 May 2026 | n/a | ANS 20 May 2026 | medium |
| GE Vernova Hitachi BWRX-300Blue Energy Center, Port of Victoria, Texas | GE Vernova Hitachi Nuclear Energy / Blue Energy | United States | 300 × 1 = 300 | Licence application | Part 1 of phased construction permit application (with limited work authorization request) submitted 16 Sep 2026; part 2 expected 2027 after one year of site data collection | 16 Sep 2026 | n/a | GE Vernova press release 16 Sep 2026 | medium |
| Holtec SMR-300 (Pioneer Units 1 and 2)Palisades site, Covert Township, Michigan | Holtec International (Hyundai E&C EPC partner) | United States | 300 × 2 = 600 | Licence application | Phase-1 construction permit application with limited work authorization submitted Jan 2026 (Federal Register 22 Jan 2026); NRC accepted part 1 for review Feb 2026; final SER/EIS expected Mar 2027 | 25 Feb 2026 | n/a | NucNet 25 Feb 2026 | medium |
| i-SMR (170 MWe x 4) | KHNP / KAERI (i-SMR Technology Development Project Group) | South Korea | 170 × 4 = 680 | Licence application | Standard design approval application received by NSSC 27 Feb 2026; approval targeted 2028 | 27 Feb 2026 | n/a | WNN 4 Mar 2026 | medium |
| NANO Nuclear KRONOS MMR (ex-USNC MMR, HTGR)University of Illinois Urbana-Champaign, Illinois | NANO Nuclear Energy (acquired USNC MMR/Pylon assets in Jan 2025 bankruptcy sale) | United States | n/a × 1 = n/a | Licence application | Construction permit application submitted by UIUC 31 Mar 2026; NRC accepted for review (announced 20 May 2026); review expected complete 2027; construction planned H2 2027 | 20 May 2026 | n/a | NANO Nuclear press release 20 May 2026 | medium |
| X-energy Xe-100 (HTGR)Long Mott Generating Station, Dow Seadrift Operations, Calhoun County, Texas | X-energy | United States | 80 × 4 = 320 | Licence application | CPA docketed May 2025; environmental assessment with FONSI issued May 2026 (Federal Register 20 May 2026); mandatory hearing held 22 Sep 2026; CP decision pending (safety review due later 2026) | 22 Sep 2026 | n/a | NRC mandatory hearing notice (22 Sep 2026 hearing) | high |
| Copenhagen Atomics thorium molten-salt critical experiment ('Onion Core')Paul Scherrer Institute, Villigen, Aargau | Copenhagen Atomics | Switzerland | 0 × 1 = 0 | Pre-licensing | Collaboration agreement with PSI signed July 2024 targeting a critical experiment in 2026; Swiss licensing status and 2026 execution not confirmed in sources reviewed | 3 Jul 2024 | 2026 | NEI 3 Jul 2024 | low |
| GE Vernova Hitachi BWRX-300Włocławek (Anwil site), Kuyavian-Pomeranian | GE Vernova Hitachi Nuclear Energy / OSGE | Poland | 300 × n/a = n/a | Pre-licensing | Decisions-in-principle for six sites (2023); pre-licensing regulatory opinion requests filed 22 Jun 2026 (fuel, software); CfD/state-aid application for 14 units filed Jul 2026; no construction licence application yet | 1 Jul 2026 | 2032 | NucNet 1 Jul 2026 | medium |
| newcleo LFR-AS-30 demonstrator / LFR-AS-200 | newcleo | France | 30 × 1 = 30 | Pre-licensing | Safety options dossier submitted to ASNR (reported 15 Jan 2026); construction authorisation applications for reactor and MOX fuel line planned before end-2027; public debate 2026 | 15 Jan 2026 | 2032 | WNN 15 Jan 2026 | medium |
| NuScale US460 (VOYGR-6)Doicești (former coal plant), Dâmbovița County | NuScale Power | Romania | 77 × 6 = 462 | Pre-licensing | Licensing process ongoing after FID; no construction licence yet (WNN 13 Feb 2026) | 13 Feb 2026 | 2033 | WNN 13 Feb 2026 | medium |
| GE Vernova Hitachi BWRX-300Candidate sites: Kunda (Viru-Nigula) and Aa (Lüganuse); Madala property near Kunda port under conditional agreement | GE Vernova Hitachi Nuclear Energy / Fermi Energia | Estonia | 300 × 2 = 600 | Pre-licensing | Nuclear Energy and Safety Act (TEOS) passed by Riigikogu Jun 2026, in force Jan 2027; national spatial plan/SEA started May 2025; construction permit application planned 2029 | 30 Jun 2026 | 2035 | WNA Estonia profile (updated 4 Aug 2026) | medium |
| GE Vernova Hitachi BWRX-300Rafferty Reservoir site near Estevan, Saskatchewan | GE Vernova Hitachi Nuclear Energy | Canada | 300 × 2 = 600 | Pre-licensing | Site selected for further study 29 Sep 2026; no licence application filed | 29 Sep 2026 | n/a | Government of Saskatchewan release 29 Sep 2026 | medium |
| Last Energy PWR-20 (4 units)Former Llynfi power station, Maesteg, Bridgend, Wales | Last Energy | United Kingdom | 20 × 4 = 80 | Pre-licensing | 'Key regulatory review' completed July 2025 (NucNet headline); no nuclear site licence application confirmed | 1 Jul 2025 | n/a | NucNet related-story index (July 2025 review) | low |
| Rolls-Royce SMR (470 MWe PWR)Wylfa / Gwyndod, Ynys Môn (Anglesey), Wales | Rolls-Royce SMR Ltd | United Kingdom | 470 × 3 = 1,410 | Pre-licensing | GDA Step 3 (final step) since 30 Jul 2024, originally due to complete Aug 2026 (completion not confirmed as of 9 Oct 2026); Wylfa selected as first site 13 Nov 2025; nuclear site licence application not yet reported | 13 Nov 2025 | n/a | ONR 13 Nov 2025 | medium |
| Rolls-Royce SMR (470 MWe PWR)Temelín nuclear site, South Bohemia | Rolls-Royce SMR Ltd | Czechia | 470 × n/a = n/a | Pre-licensing | Early Works Contract (design, permitting preparation, site application development) signed Apr 2026 and Temelín EWC reported Sept 2026; no siting permit application confirmed | 27 Apr 2026 | n/a | ANS Nuclear Newswire 27 Apr 2026 | medium |
| Rolls-Royce SMR (470 MWe PWR)Värö peninsula near Ringhals, Halland | Rolls-Royce SMR Ltd | Sweden | 470 × 3 = 1,410 | Pre-licensing | Technology selected 15 Jun 2026 over BWRX-300; state-aid application lodged with Swedish government Dec 2025 (act in force 1 Aug 2025); no SSM licence application yet | 15 Jun 2026 | n/a | WNN 15 Jun 2026 | medium |
| Steady Energy LDR-50 (50 MWt district-heating reactor)Pilot plant inside a decommissioned coal plant, Helsinki (exact plant not named in source) | Steady Energy | Finland | 0 × 1 = 0 | Pre-licensing | STUK-led international joint early review closure report published 6 Jul 2026 (SSM, PAA, SÚJB, SNRIU participated); not a licensing decision; documentation 'not yet sufficiently detailed' to launch formal licensing | 6 Jul 2026 | n/a | NucNet SMR 6 Jul 2026 | medium |
| Terrestrial Energy IMSR (Project TETRA)Texas A&M-RELLIS Energy Proving Ground, Bryan, Texas (77-acre lease) | Terrestrial Energy | United States | 392 × 1 = 392 | Pre-licensing | DOE RPP OTA signed Jan 2026; ground lease and research agreements with TAMUS signed Jun 2026; NRC safety evaluation approving IMSR principal design criteria (late 2025); CPA not yet filed | 17 Jun 2026 | n/a | ANS 23 Jun 2026 | medium |
| ThorCon TMSR-500 (shipyard-built molten salt plant)Kelasa Island, Bangka Belitung | ThorCon International | Indonesia | 250 × 2 = 500 | Pre-licensing | BAPETEN approved site evaluation plan and site evaluation management system plan (reported 6 Aug 2025); first licensing step; no construction licence | 6 Aug 2025 | n/a | ANS 6 Aug 2025 | low |
| Thorizon One (250 MWt / 100 MWe MSR)Borssele site, Zeeland (pre-feasibility validated) | Thorizon | Netherlands | 100 × 1 = 100 | Pre-licensing | MoU (Thorizon, EPZ, NRG-Pallas, provinces, Invest-NL) signed 17 Apr 2026 setting construction target 2034; no licence application | 17 Apr 2026 | n/a | WNN 17 Apr 2026 | medium |
| Thorizon Pioneer (non-power MSR demonstrator)NRG-Pallas Energy & Health Campus, Petten, North Holland | Thorizon | Netherlands | 0 × 1 = 0 | Pre-licensing | MoU 17 Apr 2026 targets construction by 2028; NRG-Pallas to be owner, licensee and operator; no licence application | 17 Apr 2026 | n/a | WNN 17 Apr 2026 | medium |
| X-energy Xe-100 (HTGR)Cascade Advanced Energy Facility, DOE Hanford Reservation adjacent to Columbia Generating Station, Benton County, Washington | X-energy | United States | 80 × 12 = 960 | Pre-licensing | NRC pre-application activities since Aug 2024 (docket 99902130) for a future Part 50 construction permit application; no CPA submitted as of 8 Sep 2026 page update | 1 Aug 2024 | n/a | NRC pre-application page (updated 8 Sep 2026) | medium |
| Saltfoss (ex-Seaborg) Compact Molten Salt Reactor power barge | Saltfoss Energy (renamed from Seaborg Technologies, April 2025) | South Korea | 100 × n/a = n/a | Concept | No licence application; first power barge hoped for H1 2030 | 1 Apr 2025 | 2030 | Wikipedia (Saltfoss Energy), tertiary | low |
| Undetermined US SMR design (USTDA-funded review) | Meralco PowerGen (MGEN) with US vendors TBD | Philippines | n/a × n/a = n/a | Concept | USTDA USD 2.7m technical assistance to MGEN for SMR design review and roadmap announced 16 Feb 2026; DOE circular grants first NPP priority dispatch | 16 Feb 2026 | 2032 | WNN 17 Feb 2026 | low |
| Undetermined (100-300 MW SMR options under study) | Nuclear Power and Energy Agency (Kenya) | Kenya | n/a × n/a = n/a | Concept | No licence application; groundbreaking for first NPP targeted by March 2027, commissioning 2034 (CNNC MoU March 2025) | 1 Mar 2025 | 2034 | Energy for Growth Hub 17 Sep 2026 | low |
| EDF Nuward (redesigned; 2x170 MWe reference) | Nuward (EDF subsidiary) | France | 170 × 2 = 340 | Concept | Design relaunched with proven technologies after 2024 pause; conceptual design due mid-2026, detailed design 2031; no licensing application | 21 Apr 2026 | n/a | NucNet 21 Apr 2026 | medium |
| NuScale US460 (VOYGR-6, 77 MWe modules) | NuScale Power / ENTRA1 Energy | United States | 77 × n/a = 6,000 | Concept | NRC standard design approval for uprated 77 MWe module (US460) announced 29 May 2025 and 30 May 2025; no site-specific CP/COL application filed | 4 Sep 2025 | n/a | WNN 4 Sep 2025 | medium |
| NuScale VOYGR-12 | NuScale Power / Regnum Technology Group | Ghana | 77 × 12 = 924 | Concept | No licence application; Ghana in IAEA Milestones Phase 2 (Feb 2026 update) | 3 Sep 2024 | n/a | NEI 3 Sep 2024 | low |
| Westinghouse AP300 | Westinghouse Electric Company | United States | 300 × n/a = n/a | Concept | NRC pre-application (docket 99902111); regulatory engagement plan updated 11 Jun 2026; 11 white papers with NRC feedback; no DC/SDA application date published | 11 Jun 2026 | n/a | NRC AP300 pre-application page (updated 8 Sep 2026) | medium |
| CAREM-25 prototypeAtucha site, Lima, Zárate Partido, Buenos Aires Province | CNEA | Argentina | 25 × 1 = 25 | On hold | Construction licence held since 2014 (first concrete Feb 2014); construction halted 2024 amid layoffs; CNEA 'engineering revision stage'; no restart date | 17 Sep 2024 | n/a | NEI 17 Sep 2024 | low |
| Moltex SSR-W (Stable Salt Reactor-Wasteburner) + WATSSPoint Lepreau, New Brunswick (prospective) | Moltex Energy (in UK administration; assets being acquired by Nuclea Energy) | Canada | 300 × 1 = 300 | On hold | No licence application; vendor in UK administration; Nuclea Energy Canada signed definitive asset purchase agreement 13 Aug 2026 (closing subject to UK NSI review) | 13 Aug 2026 | n/a | Nuclea Energy press release via Yahoo Finance 13 Aug 2026 | medium |
Source: data/smr_projects.json, read 9 Oct 2026, 53 projects, status as recorded per row; each row links its own source and carries the dataset's confidence class. The regulator stage is the dataset's free text, printed in full. Capacity 0 = no electrical output (a test reactor or a heat-only plant, per the row's notes in the dataset); n/a = no figure in the dataset; a total shown without a module count is the developer's own figure. Country is the country of the site, or the intended market where no site is named, from the dataset's ISO code. Status definitions, from the dataset:
- Operating
- Grid-connected commercial operation, or for DOE Reactor Pilot Program test reactors: fuelled criticality achieved (zero-power unless stated).
- Under construction
- Safety-related/nuclear construction or on-site commissioning underway (includes test reactors awaiting fuel load).
- Licensed
- Construction permit/licence (or DOE DSA authorisation) granted but safety-related construction not confirmed started.
- Licence application
- A site-specific licence application (construction permit, licence to prepare site, standard design approval for i-SMR) is docketed/under review.
- Pre-licensing
- Named site; pre-application/vendor design review/early works or siting studies, but no licence application filed for the site.
- Concept
- No named site and/or no regulatory filing; may include design-level regulatory engagement (e.g. NRC pre-application) and non-binding agreements.
- On hold
- Construction or development suspended / vendor in administration.
"Operating" therefore includes DOE Reactor Pilot Program test reactors at fuelled criticality, as the Reactor Pilot Program block above explains.
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Facts on this page
34 verified facts from the explainer fact base (docs/explainers/FACTS.md); each id links to the page that was read. Nothing from the "could not verify" list appears on this page.
The IAEA defines small modular reactors as advanced reactors that produce up to 300 MW(e) per module, deployable as single or multi-module plants and designed to be built in factories and shipped to utilities for installation as demand arises; it tracks more than 80 SMR designs and concepts globally.
IAEA - Small modular reactors (topic page), 9 Oct 2026 · IAEA topic page (no date printed)· primary sourceWNA uses 'small' for reactors of generally 300 MWe equivalent or less, designed with modular technology using module factory fabrication, pursuing economies of series production and short construction times.
WNA - Small Nuclear Power Reactors, 1 Oct 2026· reputable secondaryThe IAEA describes microreactors as producing up to 10 MW(e), small enough for the whole plant to be built in a factory and transported by truck, and able to operate independently of the grid for remote communities, mining sites or as backup power for hospitals.
IAEA Bulletin - Small reactors, great potential (Irena Chatzis), 9 Oct 2026 · IAEA Bulletin· primary sourceDisagreement between sources: US DOE describes microreactors as producing 1-20 megawatts of thermal energy (MWt), transportable by truck, ship, airplane or railcar, and running up to 10 years without refuelling. The brief's '<~10-20 MWe' mixes the two definitions; cite electric (IAEA) or thermal (DOE) explicitly.DOE: most microreactors would produce 1-20 megawatts of thermal energy, be fully assembled in a factory and shipped to site, and operate for up to 10 years without refuelling.
US DOE Office of Nuclear Energy - What is a Nuclear Microreactor?, 26 Feb 2021 · DOE Office of Nuclear Energy· primary sourceThe case for SMRs rests on factory fabrication of modules under controlled conditions, series production, a significantly lower capital outlay per unit (lower financial risk), deployment on grids too small for large reactors or at industrial sites and potentially nearer urban areas, and passive safety features that may allow smaller emergency planning zones.
WNA - Small Nuclear Power Reactors, 1 Oct 2026· reputable secondaryNuScale's US460 design has 77 MWe per nuclear power module and six modules per plant (462 MWe); the NRC issued its standard design approval in May 2025 on an application dated 31 December 2022, building on the 50 MWe design certified in 2023.
US NRC - NuScale US460 (applicant project page), 16 Sep 2026 · NRC applicant page updated 16 Sep 2026· primary sourceRoPower's six-module NuScale plant at the former Doicesti coal site in Romania (462 MWe) took its final investment decision in February 2026; the cost was put at USD 6-7 billion, first module commercial operation is targeted for 2033, and US DFC and EXIM issued letters of interest for up to USD 1 billion and USD 3 billion.
WNN - Final investment decision taken for Romania's SMRs, 13 Feb 2026· reputable secondaryThe certified NuScale power module is a natural circulation light water reactor whose reactor core, pressuriser and two helical-coil steam generators sit in one common reactor pressure vessel housed in a compact cylindrical steel containment; each module is rated 160 MWt and 50 MWe, a reactor building holds up to 12 modules (600 MWe), and all the modules are partially submerged in a common safety-related pool, the ultimate heat sink, in the below-grade part of the reactor building.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design (final rule effective 21 February 2023); the US460 is the uprate of this module to 77 MWe (DOE)· primary sourceNuclear fission occurs when a uranium-235 nucleus absorbs a neutron and splits into two lighter fragments, releasing about 200 MeV of energy and, on average, 2.45 further neutrons that can sustain a chain reaction.
WNA - Physics of Nuclear Energy, 30 Mar 2026 · U-235 thermal fission· reputable secondaryControl rods or blades made of neutron-absorbing material such as cadmium, hafnium or boron are inserted into or withdrawn from the core to control or halt the chain reaction.
WNA - Nuclear Power Reactors, 5 Aug 2026· reputable secondaryNuScale's helical-coil steam generators differ from those of operating pressurised water reactors in that the primary reactor coolant is on the outside of the steam generator tubes and the steam is on the inside.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design· primary sourceIn a PWR the water in the core reaches about 325 C and is kept under about 150 times atmospheric pressure so that it does not boil; steam is raised in separate steam generators.
WNA - Nuclear Power Reactors, 5 Aug 2026 · typical PWR· reputable secondaryThe certified NuScale design needs no Class 1E safety-related power (no emergency diesel generators) and no pumps to inject water into the core after an accident; its emergency core cooling relies on natural circulation, venting steam from the top of the reactor pressure vessel through three reactor vent valves into the containment vessel and returning the condensed water through two reactor recirculation valves.
Federal Register - NuScale Small Modular Reactor Design Certification, final rule (88 FR 3287), 19 Jan 2023 · certified design· primary sourceIn a PWR the steam line directs the steam to the main turbine, which turns the turbine generator that produces electricity; the unused steam is exhausted to the condenser, condensed into water, pumped out of the condenser by a series of pumps, reheated and pumped back to the steam generator.
US NRC - Pressurized Water Reactors, 14 Sep 2026 · US NRC description of a PWR· primary sourceIn a PWR the secondary circuit is under less pressure than the primary circuit and its water boils in the heat exchangers, which are thus steam generators; the steam drives the turbine to produce electricity, and is then condensed and returned to the heat exchangers in contact with the primary circuit.
WNA - Nuclear Power Reactors, 5 Aug 2026· reputable secondaryRussia's Akademik Lomonosov at Pevek, Chukotka - the only operating floating nuclear power plant - has two 35 MWe (32 MWe net) KLT-40S reactors on a 21,500-tonne, 144 m long hull; both units were connected to the grid on 19 December 2019 and entered commercial operation in May 2020.
WNA - Nuclear Power in Russia (country profile), 22 Jul 2026· reputable secondaryUse cases cited by the IAEA include power for hard-to-reach places and small grids, remote communities and mining sites, backup supply for hospitals and seawater desalination (as at Akademik Lomonosov); SMR vendors also target industrial heat and data centres.
IAEA Bulletin - Small reactors, great potential (Irena Chatzis), 9 Oct 2026· reputable secondaryFor the 300 MWe GE Vernova Hitachi BWRX-300, the Canadian regulator granted OPG a licence to construct the first unit at Darlington in April 2025, nuclear construction is under way, and OPG's licence-to-operate application (March 2026) is under CNSC review.
GE Vernova press release - NRC issues first US construction permit for BWRX-300 SMR (TVA Clinch River), 29 Sep 2026· reputable secondaryOn 29 September 2026 the NRC issued TVA a construction permit for a BWRX-300 at the Clinch River site, Tennessee - the first US construction permit for the design - on an application submitted in April 2025; Blue Energy filed part one of a construction permit application for a BWRX-300 in Texas in September 2026.
GE Vernova press release - NRC issues first US construction permit for BWRX-300 SMR (TVA Clinch River), 29 Sep 2026· reputable secondaryDisagreement between sources: data/smr_projects.csv says the Clinch River CPA was submitted in May 2025 (NRC docketing); GE Vernova says TVA submitted it in April 2025 - submission vs docketing date.The Rolls-Royce SMR is a 470 MWe (1,358 MWt) factory-built plant; it entered the UK Generic Design Assessment in March 2022 and reached Step 3 (the final step) in July 2024, was named preferred bidder by Great British Energy - Nuclear on 10 June 2025 within a programme funded with over GBP 2.5 billion for grid connection in the mid-2030s, and Wylfa (Anglesey) was selected on 13 November 2025 as the site for three units.
GOV.UK press release - Rolls-Royce SMR selected to build small modular nuclear reactors, 10 Jun 2025· primary sourceChina's 125 MW ACP100 'Linglong One' at Changjiang, Hainan, under construction since July 2021, completed cold functional testing in October 2025 and was reported (unconfirmed local media, 7 October 2026) to be in hot functional testing, with fuel loading and grid connection targeted before the end of 2026; it could be the world's first onshore commercial SMR to operate.
NucNet - Hot testing begins at China's Linglong-1 small modular reactor, 7 Oct 2026· reputable secondaryHoltec plans two SMR-300 pressurised-water SMRs at its Palisades site in Michigan; the NRC accepted the first part of the construction permit application for review in February 2026, with the final safety evaluation and environmental impact statement expected in March 2027.
NucNet - US nuclear regulator accepts partial construction permit application for Palisades SMRs, 25 Feb 2026· reputable secondaryWestinghouse's AP300 SMR is rated 330 MWe (990 MWt), is based on the licensed AP1000 technology, is designed to reach and maintain safe shutdown without operator action, back-up power or pumps, has a four-year refuelling cycle and targets an 80-year life; it is in NRC pre-application engagement with no design approval application filed.
Westinghouse - AP300 SMR, 9 Oct 2026 · Westinghouse product page (brochure dated April 2023)· primary sourceDisagreement between sources: The project brief and data/smr_projects.csv list the AP300 at 300 MWe; Westinghouse's own page says 330 MWe (990 MWth). Use 330 MWe and flag the dataset for correction.Last Energy's PWR-5 pilot reactor at the Texas A&M-RELLIS campus received DOE approval of its preliminary documented safety analysis in late May 2026 and planned an initial criticality test in summer 2026 pending DOE authorisation; the company's commercial product is the 20 MWe PWR-20, proposed for sites including the former Llynfi power station in Wales.
ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026· reputable secondaryHigh-temperature gas-cooled reactors (HTGRs) use helium coolant, a graphite moderator and TRISO coated-particle fuel, reaching about 750-950 C; the only commercial unit is China's HTR-PM (two 250 MWt pebble-bed modules on one 210 MWe turbine, commercial operation declared 6 December 2023).
WNA - Nuclear Power Reactors, 5 Aug 2026· reputable secondaryChina's HTR-PM at Shidao Bay, Shandong - two 250 MWt pebble-bed HTGR modules feeding one 210 MWe turbine, with TRISO fuel enriched to 8.5% - was declared in commercial operation on 6 December 2023 and is the world's only operating commercial HTGR.
WNN - Chinese HTR-PM Demo begins commercial operation (via data/smr_projects.csv), 6 Dec 2023 · per data/smr_projects.csv (WNN 6 Dec 2023, verified 9 Oct 2026)· reputable secondaryX-energy's Xe-100 is an 80 MWe high-temperature gas reactor using TRISO fuel; four units are planned at Dow's Seadrift site (Long Mott Generating Station, Texas), where the NRC docketed the construction permit application in May 2025, issued an environmental assessment in May 2026 and held the mandatory hearing on 22 September 2026, with the permit decision pending.
US NRC - mandatory hearing notice, Long Mott Generating Station (via data/smr_projects.csv), 22 Sep 2026 · status per data/smr_projects.csv (sources NRC hearing notice, WNN 19 May 2026, verified 9 Oct 2026)· reputable secondaryFast neutron reactors have no moderator and use a liquid-metal coolant (normally sodium) at around 500-550 C and near-atmospheric pressure; they can breed plutonium from U-238 or burn long-lived actinides, extracting about 60 times more energy from uranium than a conventional reactor.
WNA - Fast Neutron Reactors, 31 Mar 2026· reputable secondaryTerraPower's Natrium plant (Kemmerer Unit 1, Wyoming) pairs a 345 MW sodium-cooled fast reactor with molten-salt energy storage that can raise output to 500 MW; on 4 March 2026 the NRC Commissioners voted to issue its construction permit - the first for a commercial-scale advanced reactor - 18 months after the March 2024 application.
TerraPower - NRC Approves Natrium Reactor Construction Permit, 4 Mar 2026· primary sourceOklo's Aurora-INL is a 75 MWe liquid-metal-cooled, metal-fuelled fast reactor at Idaho National Laboratory; Oklo broke ground in September 2025 and secured DOE approval of its preliminary documented safety analysis on 11 June 2026 under the Reactor Pilot Program, with no criticality timeline given.
ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026· reputable secondarynewcleo submitted the safety options dossier for its lead-cooled fast reactor to France's ASNR (reported 15 January 2026), plans construction-authorisation applications before the end of 2027, a final investment decision around 2029 and first operation in France as early as 2032, with a MOX fuel pilot line planned at Nogent-sur-Seine and a non-nuclear precursor prototype due in 2026 at ENEA Brasimone, Italy.
WNN - Licensing of newcleo's SMR progresses in France, 15 Jan 2026· reputable secondaryMolten salt reactors use molten fluoride (or chloride) salts as coolant and usually as the fuel carrier, at low pressure and about 700 C; freeze plugs can drain the salt into dump tanks on overheating.
WNA - Molten Salt Reactors, 21 Nov 2025· reputable secondaryKairos Power's fluoride-salt-cooled Hermes 1 low-power demonstration reactor is under nuclear construction at Oak Ridge, Tennessee (currently the only Gen IV reactor under active nuclear construction in the US), and the company broke ground on 17 April 2026 for Hermes 2, its first power-producing plant, which will supply up to 50 MW to the TVA grid for Google data centres.
Kairos Power - Kairos Power breaks ground on Hermes 2 demonstration plant, 17 Apr 2026· primary sourceExecutive Order 14301 set a goal of three reactors achieving criticality by 4 July 2026 under DOE's Reactor Pilot Program; by 2 July 2026 three companies - Antares Nuclear, Valar Atomics and Deployable Energy - had achieved DOE-authorised (zero-power) criticality.
ANS Nuclear Newswire - The deadline arrives: checking in on the Reactor Pilot Program, 2 Jul 2026· reputable secondary