Lists of nuclear reactors

Lists of nuclear reactors comprise comprehensive catalogs documenting nuclear fission reactors globally, including commercial electricity-generating units, research and test facilities, and prototype designs, with entries detailing specifications such as location, capacity, fuel type, coolant system, and operational history.^[1][2] These lists primarily focus on the roughly 440 operable commercial power reactors distributed across more than 30 countries, which as of late 2024 provided approximately 9% of worldwide electricity production through a total installed capacity of about 398 gigawatts electric (GWe), operating at an average capacity factor of 83% that exceeds other major energy sources.^[3][4] They also encompass around 70 reactors under construction, hundreds of research reactors (many smaller-scale and non-power producing), and decommissioned units, enabling tracking of technological evolution from early graphite-moderated designs to dominant pressurized water reactors (PWRs, comprising over 65% of the fleet) and boiling water reactors (BWRs).^[4][5][2] Such compilations facilitate empirical assessment of nuclear energy's contributions to baseload power and low-carbon generation, while highlighting challenges like the stagnation in new builds following major incidents—Chernobyl in 1986 and Fukushima in 2011—that prompted enhanced safety protocols and influenced deployment patterns, with recent upticks driven by energy security demands and decarbonization imperatives.^[4][3] Lists are often segmented by national inventories, reactor generations (e.g., Generation II dominating current operations, with emerging Generation III+ and advanced designs), or status categories, drawing from authoritative databases maintained by bodies like the International Atomic Energy Agency (IAEA) to support proliferation safeguards, performance benchmarking, and policy analysis amid debates over waste disposal and capital-intensive construction.^[2][4]

Global Overview

Worldwide Operational Statistics

As of October 2025, approximately 440 commercial nuclear power reactors are operable worldwide, distributed across 32 countries plus Taiwan, with a total net installed capacity of about 400 gigawatts electric (GWe).^[4] These reactors primarily serve electricity generation, operating with a global average capacity factor of 83% in 2024, reflecting high reliability compared to intermittent renewables and enabling consistent baseload power output.^[6] Nuclear power contributed roughly 9-10% of global electricity generation in 2024, producing a record 2,667 terawatt-hours (TWh), surpassing previous highs due to improved operational performance and restarts in regions like Japan.^[7][8] The United States operates the largest fleet with 94 reactors totaling 97 GWe, accounting for about 20% of the global total and generating over 800 TWh annually.^[9] France relies on nuclear for approximately 70% of its electricity, with 57 reactors providing 63 GWe, while China maintains 57 reactors amid rapid expansion, contributing to Asia's growing share.^[9] Empirical safety data underscores nuclear's low risk profile: lifecycle deaths per TWh stand at about 0.04, far below coal's 24.6 or oil's 18.4, based on comprehensive analyses including accidents like Chernobyl and Fukushima alongside routine operations and air pollution avoidance from displaced fossil fuels.^[10] This metric, derived from peer-reviewed studies aggregating global incident data, highlights nuclear's superior safety when normalized by energy output, despite public perceptions influenced by high-profile events.61253-7/fulltext)

Construction and Expansion Trends

As of late 2025, approximately 70 nuclear reactors are under construction worldwide, with the majority located in Asia, where rapid deployment addresses surging energy needs and supports industrialization.^[11] China leads this expansion, having approved 10 new units in April 2025 alone, contributing to its operational fleet nearing 60 gigawatts while under-construction capacity adds further gigawatts annually amid targets for 110 gigawatts by 2030.^[12][13] These builds persist despite regulatory delays in some regions, driven by proven construction efficiencies in standardized designs. Over 110 additional reactors are planned globally, emphasizing scalable technologies such as small modular reactors (SMRs) and Generation IV systems to mitigate financing risks and site constraints associated with large-scale projects.^[11] In the United States, restarts like the Palisades plant and pursuits of microreactors exemplify efforts to leverage existing infrastructure for quicker capacity gains, countering historical permitting bottlenecks.^[14] This pipeline reflects a shift toward modular approaches that enable factory fabrication and phased deployment, potentially accelerating timelines compared to traditional builds. Key drivers include the empirical requirement for reliable baseload power to meet rising electricity demand, projected to grow substantially due to electrification, data centers, and AI compute needs—such as U.S. data center loads expected to double or triple by 2028—while offsetting the variability of wind and solar intermittency.^[15][16] Energy security imperatives, including reduced reliance on imported fuels amid geopolitical tensions, further propel investment, as nuclear provides dense, low-carbon dispatchable generation essential for grid stability and decarbonization without compromising reliability.^[17][18] Technological advancements in safety and fuel efficiency, alongside policy support in nations prioritizing long-term security over short-term opposition, sustain momentum despite entrenched regulatory and public perception challenges.^[14]

Decommissioning and Historical Totals

Since the first commercial nuclear power reactor began operation in 1954 at Obninsk in the Soviet Union, approximately 658 commercial nuclear power reactors have been constructed and connected to grids worldwide, encompassing a range of designs primarily for electricity generation.^[19][20] Of these, around 440 remain operable as of late 2025, generating about 10% of global electricity, while 218 have been permanently shut down, predominantly due to economic factors, license expirations, or policy decisions rather than safety incidents.^[4][21] Decommissioning refers to the administrative and technical processes following permanent shutdown, aimed at ensuring site safety, removing radioactive materials, and enabling potential reuse or unrestricted release. Common strategies include immediate dismantlement (DECON), which facilitates prompt site restoration within about seven years, and deferred dismantling (SAFSTOR or ENTOMB), involving safe storage for decades before full cleanup to allow radioactive decay.^[22][23] Globally, full decommissioning—defined as complete dismantlement and regulatory release—has been achieved for only about 11 commercial reactors larger than 100 MW(e), reflecting the lengthy timelines (often 20–50 years) and costs, which typically range from 9–15% of a plant's lifetime generation revenue when funded via dedicated trusts.^[24][23] These processes underscore operational longevity, with average shutdown ages around 29 years, though many plants have exceeded 40–60 years of service without design-basis accidents prompting closures beyond the atypical 1986 Chernobyl event, attributable to inherent flaws in the RBMK graphite-moderated design such as positive void coefficients and inadequate containment.^[19] Nuclear decommissioning generates relatively low volumes of radioactive waste compared to the reactor's overall footprint, with high-level waste (spent fuel and reprocessing byproducts) comprising less than 1% of total waste volume and fitting into a few dozen cubic meters per reactor after vitrification or encapsulation.^[25][26] Low- and intermediate-level wastes, which form the bulk by volume (about 95%), are managed through compaction, incineration, or shallow disposal, enabling cost-effective handling; for context, the entire U.S. commercial spent fuel inventory to date occupies a volume equivalent to a football field at 10 yards deep. End-of-life management advances include deep geological repositories, such as Finland's Onkalo facility at Olkiluoto, which commenced trial operations with non-spent fuel in 2024 and is slated for spent fuel emplacement by mid-decade pending final licensing, marking the first such permanent disposal site globally.^[27][28] This approach demonstrates feasible isolation for millennia-scale hazards, contrasting with interim storage practices elsewhere where retrieval remains an option for future recycling technologies.^[29]

By Primary Use

Electricity Generation Reactors

Electricity generation reactors, also known as power reactors, dominate the operational nuclear fleet, accounting for over 90% of large-scale nuclear installations worldwide and providing dispatchable, low-emission baseload power to electrical grids. As of October 2025, 416 such reactors operate across 31 countries with a total net capacity of 376 GW.^[30] These units generated a record 2,667 TWh of electricity in 2024, surpassing the prior peak from 2006 and equivalent to about 10% of global electricity demand while displacing an estimated 2.1 billion tonnes of CO2 emissions relative to coal-fired alternatives.^[7] Their high capacity factors, often above 80% annually, enable consistent output that supports grid stability, contrasting with variable renewables like wind and solar, which rely on storage or backups for reliability.^[31] Major national fleets exemplify this dominance. France operates 56 reactors with 61.4 GWe capacity, supplying over 65% of its electricity and exemplifying nuclear's role in energy independence.^[32] The United States leads in total capacity with 94 reactors at 97 GW, powering about 20% of domestic needs through a diverse set of plants.^[9] China follows with rapid expansion, operating over 50 reactors contributing to its grid amid coal phase-down efforts. Lists of these reactors often prioritize scale and output. The largest by installed capacity is Japan's Kashiwazaki-Kariwa plant, with seven boiling water reactors totaling 8,212 MW gross, though restarts post-Fukushima have limited full operation to select units. Other top producers include South Korea's Kori complex (7,489 MW across multiple units) and Canada's Bruce station (6,430 MW), both emphasizing multi-unit designs for economies of scale. Comprehensive inventories, such as those from the IAEA's PRIS database, track individual units by operator, start date, and performance metrics, facilitating analysis of fleet reliability and upgrades.^[33] This table highlights facilities with the highest design capacities, though actual output varies with maintenance and regulatory factors; for instance, Zaporizhzhia has faced disruptions since 2022.^[34] Such lists inform policy on extending plant lifespans beyond 40-60 years, as many units achieve load factors over 90% post-refueling.^[31]

Research and Materials Testing Reactors

Research and materials testing reactors encompass a class of nuclear facilities distinct from power-generating units, optimized for high neutron flux in compact designs to support scientific experimentation, structural integrity assessments under irradiation, and radioisotope generation for industrial and medical applications. As of 2024, approximately 230 such reactors operate globally across more than 50 countries, with most rated below 100 MWth thermal power to prioritize flux density over energy output.^[35] These reactors enable precise control of neutron spectra, including thermal, epithermal, and fast neutrons, facilitating studies unattainable in larger power reactors due to operational constraints.^[36] Key applications include materials irradiation to simulate decades of neutron damage in hours or days, critical for validating fuel cladding, control rods, and structural alloys against swelling, embrittlement, and fission product accumulation. The U.S. Department of Energy's Advanced Test Reactor (ATR) at Idaho National Laboratory, operating at 250 MWth since 1967, exemplifies this with its adjustable flux up to 1×10^15 n/cm²·s, supporting qualification of advanced fuels for both current light-water reactors and emerging designs.^[37] Similarly, the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, at 85 MWth, delivers one of the highest steady-state fluxes globally (∼5×10^15 n/cm²·s thermal), used for severe irradiation testing and neutron activation analysis.^[38] These capabilities underpin verifiable progress in reactor longevity and safety margins, grounded in empirical dosimetry and post-irradiation examinations rather than speculative modeling alone. Isotope production represents another cornerstone, with research reactors supplying over 95% of the world's molybdenum-99 (Mo-99), the precursor to technetium-99m essential for ∼80% of diagnostic nuclear medicine procedures like cardiac and oncology imaging.^[39] Facilities such as the University of Missouri Research Reactor (MURR), a 10 MWth pool-type reactor, contribute significantly by irradiating low-enriched uranium targets, yielding diverse isotopes including Mo-99, iodine-131, and lutetium-177 for targeted therapies.^[37] The Belgian Reactor-2 (BR2) at Mol, rated at 100 MWth, similarly produces a broad spectrum of medical and industrial isotopes while doubling for materials testing under high-burnup conditions.^[40] This production chain relies on fission-based extraction from uranium targets, with yields optimized via target geometry and irradiation cycles, ensuring supply chain resilience absent from alternative non-reactor methods still in development.^[41] For advanced reactor prototyping, particularly Generation IV concepts requiring tolerance to higher temperatures and radiation doses, materials testing reactors provide indispensable data on corrosion, creep, and transmutation effects. The ATR, for instance, has irradiated fuels for sodium-cooled fast reactors and molten salt systems, generating empirical datasets on metallic and oxide fuels under prototypical fast spectra.^[42] Despite an aging fleet—many commissioned in the 1950s–1970s—these reactors persist due to their unique causal role in derisking innovations, contrasting with delays in unproven alternatives like fusion where empirical validation lags.^[35] Operational sustainability involves periodic refurbishments, such as core redesigns and flux trap replacements, to maintain safety and output amid declining numbers from retirements without equivalents.^[40] Notable examples include: These facilities, tracked via international databases, underscore the sector's focus on targeted R&D outputs over commercial scaling.^[37][40]

Propulsion and Specialized Military Reactors

Propulsion reactors, predominantly pressurized water reactors (PWRs), enable nuclear-powered naval vessels to achieve extended operational endurance without frequent refueling, supporting strategic mobility such as sustained carrier strike groups and submerged submarine patrols.^[43] These compact designs prioritize high power density, safety through redundant systems, and minimal radiological risk, contrasting with less reliable fossil fuel alternatives in contested environments.^[44] Military applications emphasize non-disclosed specifics for operational security, with aggregate operational data demonstrating reliability: the U.S. Navy alone has accrued over 6,200 reactor-years of experience across hundreds of cores without reactor accidents or significant radioactivity releases.^[44] In the United States, naval reactors power 11 aircraft carriers—each equipped with two PWRs—and approximately 68 submarines, totaling around 99 reactors across 79 warships as of 2023.^[45] These S6G and S9G series reactors, developed under the Naval Reactors program, support carrier operations exceeding 50 years with a single mid-life refueling and submarine cores lasting up to 33 years in Virginia-class vessels without refueling.^[46] This design yields empirical advantages in logistics independence, with fleets logging over 177 million miles steamed safely by 2025, underscoring causal reliability from rigorous engineering and quality controls rather than inherent vulnerability.^[46] Russia employs KLT-40 series reactors, compact PWR variants, in its nuclear icebreaker fleet to maintain Arctic shipping routes, with vessels like the Taymyr-class featuring two 135 MWth units per ship for ice-breaking propulsion up to 171 MW total power.^[47] Operational since the 1980s, these reactors power active icebreakers such as Yamal and 50 Let Pobedy, enabling year-round navigation with refueling intervals supporting multi-year deployments.^[48] The fleet's proven durability in harsh conditions highlights propulsion efficiency, though details remain limited due to state secrecy. The United Kingdom's Astute-class attack submarines utilize Rolls-Royce PWR2 reactors, providing 25-year fuel cycles for unlimited range at speeds over 30 knots, enhancing stealth and strike capabilities without surface dependency.^[49] Seven boats are planned or in service, replacing Trafalgar-class units with improved core life and safety margins derived from iterative PWR evolution.^[50] Similar PWR adaptations appear in other navies, such as France's Triomphant-class, prioritizing endurance over disclosed counts to preserve tactical edges.

By Technological Type

Pressurized Water Reactors (PWR)

Pressurized water reactors (PWRs) represent the dominant technology in commercial nuclear power, comprising approximately 65% of the world's operable reactors. As of August 2025, there are about 290 operational PWR units globally, with a combined electrical capacity exceeding 250 GW(e), primarily due to their proven reliability, scalability, and adaptability to grid demands.^[51][52] These reactors maintain primary coolant water at high pressure (typically 15.5 MPa) to suppress boiling in the core, transferring heat via steam generators to a secondary loop that produces steam for turbines, thereby isolating non-radioactive secondary systems from potential fission product release and reducing operational contamination risks compared to direct-cycle designs.^[1] PWRs exhibit inherent safety features, such as a negative void coefficient that stabilizes reactivity during coolant loss, and advanced variants incorporate passive cooling systems capable of 72-hour operation without external power. Fuel assemblies achieve high burnup levels—empirically validated up to 60 GWd/t in licensed operations—through optimized uranium enrichment and cladding materials like ZIRLO, which extend cycle lengths to 18-24 months and improve economic dispatchability by minimizing refueling outages.^[53][54] This technology underpins over 80% of new reactor constructions since 2010, driven by standardized designs that facilitate serial production and regulatory pre-approval.^[55] Major PWR deployments cluster around evolutionary designs from key vendors. The U.S.-origin Westinghouse AP1000, a two-loop Generation III+ unit rated at 1,117 MWe, operates at Vogtle Units 3 and 4 in Georgia (commercial since July 2023 and April 2024) and four sites in China (Sanmen 1-2, Haiyang 1-2, with 12 more approved or under construction as of August 2024).^[56][57] France's Framatome EPR, a 1,650 MWe four-loop design with enhanced containment and core catcher, entered service at Olkiluoto 3 in Finland (April 2023) and Flamanville 3 (2024), with six units under construction including Hinkley Point C in the UK.^[55] China operates over 50 PWRs, predominantly CPR-1000 variants (900-1,000 MWe, three-loop based on French M310), with at least 34 units from early series and evolutions like ACPR-1000 deployed across sites such as Daya Bay and Ling Ao; these form 90% of China's 58 operable reactors as of 2025.^[58][59] Indigenous HPR1000 (Hualong One) follows, with Fuqing 5 operational since 2021.^[60] Russia's Rosatom VVER series, evolutionary PWRs with horizontal steam generators, includes over 30 VVER-1000/1200 units domestically (e.g., Novovoronezh) and exports like Akkuyu in Turkey (four units under construction since 2018).^[55]

Boiling Water Reactors (BWR)

Boiling water reactors (BWRs) are a type of light-water nuclear reactor in which the coolant water boils directly in the reactor core under controlled pressure, producing steam that drives turbines for electricity generation without an intermediate heat exchanger, unlike pressurized water reactors (PWRs). This direct cycle design simplifies the system by eliminating steam generators and a separate secondary loop, reducing the number of components and potentially lowering construction complexity. However, it introduces operational traits such as steam void fractions of 12-15% in the core, which affect neutron moderation and require precise control to maintain stability.^[1] As of October 23, 2025, 43 BWRs are operational worldwide, providing a total net electrical capacity of 44,720 MW(e), with an additional 17 units in suspended operation totaling 16,274 MW(e). These reactors are concentrated primarily in the United States and Japan, where early commercial development by General Electric (now GE Hitachi) and Toshiba led to widespread deployment starting in the 1960s. In the U.S., BWRs achieve average annual capacity factors exceeding 90%, comparable to the broader light-water reactor fleet, reflecting high reliability after post-1970s safety upgrades including enhanced containment and emergency core cooling systems.^[61][62] The BWR's simpler architecture contributes to estimated capital costs 10-20% lower than equivalent PWRs in some analyses, due to fewer pressure vessels and piping, though empirical data from completed projects show variability influenced by site-specific factors and regulatory requirements. Safety records indicate comparable performance to PWRs following upgrades, with no core damage incidents in Western BWRs since initial deployments, though the 2011 Fukushima Daiichi accident—involving six BWR units—highlighted direct-cycle vulnerabilities, including rapid steam release to the turbine hall during loss-of-coolant events, complicating containment and increasing radiological release risks without secondary isolation.^[63][64] Advanced BWR variants, such as the GE Hitachi ABWR (Generation III+ design), incorporate passive safety features like gravity-driven core cooling and fine-motion control rods, with six units operational in Japan and Taiwan as of 2023, demonstrating evolved reliability amid declining overall BWR market share due to PWR dominance in new builds.^[65]

Heavy Water Reactors (PHWR and CANDU)

Heavy water reactors, specifically pressurized heavy water reactors (PHWRs), utilize deuterium oxide (D₂O) as both moderator and coolant, enabling the use of unenriched natural uranium fuel due to the lower neutron absorption of heavy water compared to light water. This design achieves a higher neutron economy, allowing for greater fuel efficiency without reliance on foreign enrichment services, which benefits nations with limited uranium enrichment infrastructure or abundant natural uranium reserves. The pressure tube architecture, common in PHWRs, facilitates online refueling, minimizing downtime and enhancing capacity factors, with typical thermal efficiencies around 30-35%.^[1] The CANDU (CANada Deuterium Uranium) variant, originating from Canadian development in the 1950s, represents the archetype of commercial PHWRs, with the first prototype (NPD) achieving criticality in 1962 and full-scale units operational by 1971. As of 2025, approximately 27 CANDU reactors operate across seven countries, including 19 in Canada, primarily at Bruce (8 units), Darlington (4), and Pickering (phased operations totaling 7 before recent shutdowns offset by refurbishments). Exports include units in Argentina (Embalse and Atucha adaptations), Romania (Cernavoda 2 units), China (Qinshan Phase III, 2 units), and South Korea (Wolsong 4 units), demonstrating adaptability for international deployment despite geopolitical sensitivities around technology transfer.^[66][1] India operates 22 indigenous PHWRs, totaling over 10 GW capacity, which form the backbone of its nuclear fleet and draw partial inspiration from early CANDU collaborations, though evolved independently for self-reliance. These include multi-unit stations like Rajasthan (6 units, 220-700 MWe each) and Madras (2 units), with high availability factors exceeding 80% in recent years due to standardized designs and domestic fuel supply. Globally, PHWRs number 46 operational units with 24,430 MWe net capacity, concentrated in Canada and India, which account for over 80% of the type, underscoring their role in resource-constrained yet uranium-rich contexts.^[67][1] PHWRs exhibit potential for plutonium production from uranium-238 via neutron capture, yielding fissile Pu-239, but empirical evidence shows low proliferation risk in operational fleets under IAEA safeguards, with no verified diversions for weapons programs from commercial CANDU or Indian PHWR spent fuel—unlike historical research reactor cases elsewhere. The design's continuous refueling and dispersed fuel channels complicate material diversion, and international inspections have maintained accountability since the 1970s. Additionally, PHWRs support advanced fuel cycles, notably India's pursuit of thorium utilization through the Advanced Heavy Water Reactor (AHWR), a 300 MWe prototype integrating thorium-plutonium fuels to leverage India's vast thorium reserves for long-term sustainability.^[55][1]

Gas-Cooled Reactors (GCR, AGR, Magnox)

Gas-cooled reactors utilize inert gases, primarily carbon dioxide, as coolant to achieve higher operating temperatures than water-cooled designs, enabling thermal efficiencies exceeding 40% and suitability for both electricity generation and process heat applications. These reactors employ graphite as a neutron moderator and have been predominantly developed in the United Kingdom, where early designs prioritized dual-use for plutonium production and power. The two principal subtypes are Magnox reactors, which use natural uranium fuel clad in magnesium-aluminum alloy, and Advanced Gas-cooled Reactors (AGR), which incorporate slightly enriched uranium dioxide fuel in stainless steel cladding for improved performance.^[68] Magnox reactors, the UK's first commercial nuclear power design, operated from 1956 to 2015 across 26 reactor units at 11 sites, with a total capacity of approximately 3 GW. All Magnox units have been permanently shut down, with decommissioning ongoing under the Nuclear Decommissioning Authority; the final unit at Wylfa ceased operation in December 2015 after 44 years of service. Key stations included Berkeley (two reactors, 276 MWe total, shut 1989), Bradwell (two, 246 MWe, shut 2002), and Oldbury A (two, 434 MWe, shut 2012). The design's graphite moderation stability was enhanced post the 1957 Windscale fire in air-cooled graphite piles, which released radionuclides due to Wigner energy buildup and prompted mandatory annealing procedures and fire suppression systems in subsequent CO2-cooled graphite-moderated reactors.^[69][70] Data aggregated from UK government records; capacities are approximate net electrical output.^[69] AGR designs superseded Magnox to attain higher coolant outlet temperatures around 640°C, yielding thermal-to-electric efficiencies of about 41%, compared to Magnox's roughly 32%. Fourteen AGR units, totaling over 7 GW capacity, were constructed at seven stations from the 1970s onward, with CO2 coolant at elevated pressures for enhanced heat transfer. As of mid-2025, eight AGR reactors remain operational at five sites, including extensions for Heysham 1 and Hartlepool beyond original 40-year designs, though most are slated for retirement by 2030 amid graphite core inspections and corrosion management. EDF Energy reports daily generation statuses, confirming active output from units at Torness, Heysham 2, and Hinkley Point B.^[71][72][73] Capacities reflect gross design values adjusted for net; shutdowns verified against regulatory extensions.^[74][75] Gas-cooled designs offer empirical advantages in graphite's neutron economy and gas's low neutron absorption, supporting potential revival in Generation IV high-temperature gas reactors using helium coolant for temperatures over 900°C, enabling hydrogen production or advanced power cycles beyond current AGR limits. No commercial helium-cooled GCRs operate today, but prototypes like the UK's Dragon reactor (1960s) demonstrated feasibility.

Fast Neutron Reactors (including Breeders)

Fast neutron reactors utilize unmoderated, high-energy neutrons to sustain fission, primarily in uranium-plutonium oxide fuel cycles, allowing direct fission of U-238 and higher neutron yields per fission (approximately 2.9 fast neutrons versus 2.4 in thermal spectra).^[76] This spectrum enables breeding ratios greater than 1 in optimized designs, where fertile U-238 captures neutrons to form Pu-239 faster than fissile consumption, theoretically multiplying fuel availability by exploiting over 99% of mined uranium otherwise unused in light-water reactors.^[76] Such efficiency counters resource depletion concerns, as empirical fuel cycle analyses indicate potential extensions of supply from decades (U-235 limited) to thousands of years with closed cycles incorporating reprocessing.^[77] Most operational and historical fast reactors employ liquid sodium coolant for its low neutron absorption, high thermal conductivity, and boiling point above 800°C, supporting compact cores with power densities up to 500 kW/liter—far exceeding thermal reactors.^[76] Breeding variants, like pool-type sodium-cooled designs, have demonstrated ratios of 1.1-1.3 in prototypes, validated through isotopic assays and burnup tracking.^[76] Waste transmutation benefits arise from fast-spectrum fission of minor actinides (e.g., Am-241, Cm-244), reducing long-lived radiotoxicity by factors of 10-100 over open cycles, as confirmed in irradiation tests.^[77] Sodium coolant's reactivity with air and water poses risks of leaks or fires, mitigated empirically through inert argon blanketing, double-walled piping, and leak-detection systems; Russia's BN-600 has logged over 40 years of operation with only managed incidents via rapid sodium draining and nitrogen purging.^[79] High operating temperatures (500-550°C) enhance thermodynamic efficiency (up to 40%) but demand robust materials like stainless steels resistant to swelling under fast fluence, addressed via empirical surveillance from long-running units.^[80] Despite these, economic viability hinges on reprocessing integration, as standalone operation yields breeding ratios near unity without it.^[76]

Advanced and Emerging Types (Gen IV, SMRs)

Small modular reactors (SMRs) are advanced nuclear designs with capacities typically under 300 MWe, emphasizing factory fabrication, modular assembly, and passive safety features to enhance scalability and reduce construction risks compared to traditional large-scale plants.^[81] These systems aim to lower capital costs through serial production, targeting overnight costs around $3,000/kW, versus historical averages exceeding $6,000/kW for gigawatt-scale reactors plagued by overruns.^[82] However, early projects like NuScale's VOYGR have seen projected levelized costs rise to $89/MWh due to detailed engineering refinements, underscoring persistent challenges in achieving economies despite modular promises.^[83] Prominent SMR designs include GE Hitachi's BWRX-300, a 300 MWe boiling water reactor under U.S. Nuclear Regulatory Commission pre-application review as of 2025, with deployments eyed for coal replacements in Poland and Romania via 24-36 month modular builds.^[84][85] NuScale's technology, meanwhile, advances through partnerships like the 6 GW program with TVA and ENTRA1 Energy for carbon-free baseload in the U.S. Southeast.^[86] In the U.S., microreactors—SMR subsets under 10 MWe—progress via Department of Energy initiatives, including the Demonstration of Microreactor Experiments (DOME) launched in July 2025 to test fuels and components, and Project Pele's 1.5 MWe mobile prototype core manufacturing started in 2025 for Department of Defense applications by 2028.^[87][88] Generation IV (Gen IV) reactors represent longer-term innovations selected by the Generation IV International Forum for superior sustainability, safety, and proliferation resistance, including molten salt reactors (MSRs), lead-cooled fast reactors (LFRs), and very high-temperature reactors (VHTRs).^[89] China's HTR-PM, a 210 MWe VHTR pebble-bed demonstration with two 250 MWth modules, achieved commercial operation in December 2023 after grid connection in 2021, validating inherent safety through loss-of-cooling tests and multi-module coordination at full power.^[90][91] MSRs, using liquid fuel for online reprocessing and thorium compatibility, advance with China's planned 2 MWth prototype by 2029, while LFRs—cooled by lead or lead-bismuth for fast-spectrum breeding—remain in R&D without commercial prototypes, though designs target 50-150 MWe "battery" units for extended fuel cycles.^[92][93] These designs prioritize passive cooling and reduced waste via closed fuel cycles, positioning them for decarbonization roles, though deployment hinges on resolving material corrosion and licensing hurdles evidenced in ongoing GIF collaborations.^[94]

By Geographical Location

Asia-Pacific Region

The Asia-Pacific region encompasses a diverse array of nuclear power programs, with China, India, Japan, and South Korea operating the majority of the world's reactors in this area, driven by imperatives for energy security, economic industrialization, and decarbonization amid surging electricity demand. As of October 2025, the region hosts approximately 129 operational nuclear reactors, representing about 30% of the global total, alongside more than 40 under construction—accounting for over 50% of worldwide new nuclear builds.^[30][95] This expansion reflects state-directed strategies that prioritize indigenous technology development and supply chain localization, yielding construction timelines often under 7 years per unit, contrasting with overruns in Western projects.^[95] China dominates the region's fleet with 57 operational reactors totaling over 55 GW capacity, supplemented by 29 under construction as of early 2025, including advanced Generation III+ designs like the Hualong One and AP1000 derivatives.^[9][96] These efforts support Beijing's target of 200 GW nuclear capacity by 2035, with recent approvals for 10 additional reactors in 2025 emphasizing grid stability for coal phase-down and export-oriented manufacturing.^[97] India maintains 22 operational reactors, predominantly pressurized heavy-water types integral to its thorium-based three-stage fuel cycle, with 6-8 more under construction to reach 15 GW by 2030, leveraging domestic uranium resources and Russian VVER collaborations.^[95] Japan, following the 2011 Fukushima Daiichi accident, has progressively restarted reactors under stringent safety regulations, achieving 12-14 operational units from its original 33-reactor fleet by mid-2025, primarily boiling-water types, to offset fossil fuel imports amid energy shortages. South Korea operates 26 reactors efficiently, with a capacity factor exceeding 90%, and three under construction; its APR-1400 design has demonstrated export viability, powering plants in the UAE since 2020.^[95] Smaller programs include Pakistan's six CANDU-derived reactors, Taiwan's two operational units facing political restart debates, and emerging builds like Bangladesh's Rooppur-1 (Russian VVER, grid connection expected 2025).^[98] State-led initiatives in these nations have enabled high on-time delivery rates, with China's program achieving over 90% adherence to schedules through centralized planning and domestic fabrication, mitigating risks from international supply disruptions.^[95] This contrasts with regulatory delays elsewhere, positioning Asia-Pacific as the epicenter of nuclear capacity growth, projected to add 70 GW by 2035.^[14]

Europe and Russia

Europe and Russia collectively operate approximately 180 commercial nuclear power reactors, accounting for a significant portion of the region's electricity generation, though national policies diverge sharply. France relies heavily on nuclear energy, with its 57 pressurized water reactors (PWRs) supplying around 70% of the country's electricity as of 2025.^[99] In contrast, Germany completed its nuclear phase-out in April 2023 by shutting down its last three reactors, prioritizing renewables and fossil fuels despite warnings from the International Energy Agency about potential carbon emission increases from the decision.^[100] Russia maintains 38 operational units, primarily VVER types managed by Rosatom, supporting domestic needs and exports to allies.^[101] Ukraine, inheriting a Soviet-era fleet of VVER reactors, operates 9 units across Rivne (4), South Ukraine (3), and Khmelnytskyi (2) nuclear power plants as of 2025, with the six reactors at the Russian-occupied Zaporizhzhia plant remaining in long-term shutdown since September 2022 for safety reasons amid the ongoing conflict.^[102] Despite military disruptions, including power line damages and occupation, Ukraine's operational reactors have demonstrated resilience, avoiding unplanned shutdowns through IAEA-monitored safeguards and backup systems, underscoring the robustness of VVER designs under stress.^[103] Post-2022 safety enhancements to these reactors have included fuel diversification efforts and upgraded cooling systems to mitigate blackout risks, as analyzed in station blackout scenarios.^[104] Russia's VVER technology features inherent safety improvements over earlier Soviet designs, such as passive cooling and containment structures capable of withstanding extreme events like magnitude-9 earthquakes, enabling exports and expansions in Eastern Europe.^[105] Hungary is expanding its Paks plant with two Russian-supplied VVER-1200 units under construction, approved in 2014 to boost capacity.^[106] Slovakia operates four VVER-440 reactors at Bohunice and Jaslovske Bohunice, with Mochovce units 3 and 4 nearing completion using similar technology, while pursuing diversification through a 2025 U.S. deal for potential new builds.^[107] These developments reflect Eastern Europe's continued dependence on Russian reactor expertise amid EU efforts to phase out such imports, though implementation faces technical and political hurdles.^[108]

North America

North America operates the world's largest fleet of commercial nuclear reactors, with the United States accounting for 94 units generating nearly 18% of the nation's electricity as of October 2025.^[109][110] These reactors predominantly consist of pressurized water reactors (PWRs) and boiling water reactors (BWRs), distributed across 28 states and managed by about 30 utilities.^[111] The fleet demonstrates exceptional longevity, with average capacity factors consistently above 90% since 2001, reflecting low unplanned outage rates and robust empirical performance under regulatory oversight.^[111] Major U.S. operators include Constellation Energy, which manages 21 reactors at 12 sites, producing carbon-free baseload power.^[112] Other key players encompass Entergy (operating units at plants like Arkansas Nuclear One and Waterford), Duke Energy (e.g., Oconee and McGuire), and Southern Nuclear (Vogtle and Farley), collectively ensuring diversified ownership and geographic spread.^[113] License extensions via the Nuclear Regulatory Commission's subsequent license renewal process have approved operations up to 80 years for multiple plants, including Oconee in April 2025, based on aging management programs validated by operational data rather than theoretical limits.^[114][115] Canada maintains 17 operational CANDU heavy-water reactors, all using natural uranium fuel, with 16 in Ontario (at Bruce, Darlington, and Pickering sites) and one at Point Lepreau in New Brunswick.^[116] These units, totaling about 13.5 GWe capacity, undergo major refurbishments—such as at Bruce (eight units) and Darlington (four units)—extending service lives by 30 years through component replacements and safety upgrades, sustaining high availability.^[66] The CANDU design, indigenous to Canada, underpins exports to countries like Romania and Argentina, but domestically emphasizes reliable, heavy-water-moderated operation with refueling flexibility during runtime.^[117] Mexico operates two BWR units at the Laguna Verde plant in Veracruz state, contributing 4-5% of national electricity with a combined capacity of about 1.6 GWe.^[118] Unit 1's license extends to 2050, and Unit 2 to 2055, following safety reviews and upgrades that affirm continued viability based on performance records.^[118]

Other Regions (Africa, South America, Middle East)

In Africa, nuclear power infrastructure is minimal, with only two commercial reactors operational at the Koeberg Nuclear Power Station in South Africa, each a 900 MWe pressurized water reactor (PWR) commissioned in 1984 and 1985, respectively, contributing approximately 5% of the country's electricity generation.^[119] These units, supplied by Framatome (formerly Framaotome), have undergone life extensions, with Koeberg 1 licensed until 2044 following refurbishment completed in August 2024.^[119] Koeberg exemplifies early adoption in the region, driven by energy diversification needs amid coal dependency, though operational challenges like transmission constraints have limited output reliability. Egypt's El Dabaa project marks the continent's primary construction effort, featuring four Russian VVER-1200 PWRs totaling 4.8 GWe, with ground broken in 2022 and the first unit slated for grid connection in 2028, financed via a $25 billion Rosatom loan amid geopolitical ties with Russia.^[120][121] No other African nations host commercial power reactors, though exploratory programs in Ghana and Rwanda emphasize research reactors and small modular reactor (SMR) pilots for eventual baseload diversification from hydropower and fossils.^[120] South America's nuclear sector centers on Argentina and Brazil, with five operational reactors providing about 6% of regional electricity, underscoring tech transfer from heavy-water designs inherited from 1970s programs. Argentina operates three pressurized heavy-water reactors (PHWRs): Atucha I (362 MWe, online 1974), Embalse (648 MWe, refurbished and restarted 2010s), and Atucha II (745 MWe, online 2014), all managed by Nucleoeléctrica Argentina with Canadian and German origins, supporting industrial self-sufficiency amid natural gas abundance.^[122] Brazil's Angra facility includes two PWRs—Angra 1 (640 MWe, Westinghouse design, online 1985) and Angra 2 (1,350 MWe, online 2001)—delivering reliable output despite delays in Angra 3 (1,405 MWe PWR, construction resumed 2010s, expected 2029), motivated by hydropower variability and fossil import risks.^[123] These programs demonstrate causal successes in local operator training and fuel fabrication, reducing foreign reliance, though economic hurdles have stalled expansion elsewhere like Peru or Chile.^[124] In the Middle East, the United Arab Emirates leads with four operational APR-1400 PWRs at Barakah (each 1,400 MWe), constructed by a South Korean consortium under Emirates Nuclear Energy Corporation (ENEC); Unit 1 entered commercial operation in April 2021, followed by Units 2–4 by September 2024, supplying up to 25% of UAE electricity and enabling fossil fuel displacement with demonstrated 99%+ capacity factors.^[125][126] Turkey's Akkuyu plant, four Russian VVER-1200 units (4.8 GWe total), advances under construction since 2018, with the first reactor targeting 2025 commissioning as part of energy independence from imports, though reliant on Rosatom's build-own-operate model raising sovereignty concerns.^[11] Regional drivers include oil exporters like UAE seeking post-carbon revenue preservation via tech localization—evidenced by ENEC's 6,000+ Emirati workforce—and broader diversification, with projections for capacity tripling to 19 GWe by 2035 amid grid stability gains over intermittent renewables.^[127] These nascent efforts, totaling under 20 units, highlight geopolitical vectors like Russian and Korean vendor dominance, yielding empirical baseload successes but exposing vulnerabilities to supply-chain dependencies.^[128]

By Operational Status

Currently Operational Reactors

As of October 23, 2025, 415 commercial nuclear power reactors are in operation across 31 countries, providing a total net electrical capacity of 374,791 MWe according to IAEA data.^[129] These units demonstrate varying performance, with South Korea's fleet of 26 reactors achieving among the highest global capacity factors at up to 96.5% in recent years, reflecting efficient operations and minimal outages.^[130] In China, operational reactors reached 57 units by late 2025, bolstered by the grid connection and commercial startup of the Zhangzhou-1 Hualong One reactor (1,126 MWe) on January 1, 2025.^[129][131] The distribution of operational reactors by country is as follows: This tally excludes reactors under long-term suspension or shutdown, focusing solely on those actively contributing to the grid.^[129]

Reactors Under Construction

As of October 2025, 64 commercial nuclear power reactors are under construction worldwide, with a combined net electrical capacity of 72,190 MWe.^[132] These projects, if completed on schedule, would significantly expand global nuclear capacity, particularly in Asia, where over 40 units are advancing amid rapid industrialization and energy security priorities. Construction progress varies, with Asian nations achieving faster timelines through standardized designs and serial production, while Western projects often encounter extended delays from regulatory scrutiny, supply chain bottlenecks, and novel engineering adaptations.^[11] Asia dominates ongoing builds, accounting for the majority of units and capacity. China leads with 29 reactors totaling 30,847 MWe, including advanced pressurized water reactors like the Hualong One and CAP1000 models, many of which began construction in the 2010s and target grid connection within 5-7 years.^[132] India has 6 units under construction, encompassing 700 MWe pressurized heavy water reactors (PHWRs) at sites such as Kakrapar and Gorakhpur, designed for indigenous fuel cycles and expected to add over 4,700 MWe by the late 2020s.^[132][133] Russia contributes 5 reactors, including the VVER-1200 at Kursk II-1, with construction started in 2021 and projected completion in 2025, leveraging proven VVER technology for export-oriented builds.^[11] Outside Asia, activity is more limited but includes notable firsts, such as Egypt's four VVER-1200 units at El Dabaa (totaling 4,800 MWe, started 2022-2023) and Türkiye's Akkuyu plant with four VVER-1200s (also 4,800 MWe, initiated 2018 onward), both under Russian engineering with initial units nearing fuel loading.^[132] In Europe, the UK advances two EPR reactors at Hinkley Point C (3,200 MWe total, construction since 2016), though plagued by delays from supply chain issues and concrete defects, pushing full operation beyond 2027.^[11] Delays in reactor construction stem empirically from multifaceted causes, including protracted regulatory approvals in democracies, where iterative design reviews and public consultations extend timelines by years, contrasted with streamlined processes in state-directed programs. Supply chain disruptions—exacerbated by global events like the COVID-19 pandemic and geopolitical tensions affecting steel and forgings—have added 1-3 years to many projects, as seen in Western AP1000 builds. First-of-a-kind implementations, such as novel safety features post-Fukushima, introduce unforeseen engineering hurdles, evidenced by the U.S. Vogtle AP1000 units, which incurred over $20 billion in overruns and 7-year delays due to incomplete designs at construction start and workforce inexperience, before Unit 4 entered commercial operation in 2024.^[134] In contrast, serial construction in China mitigates these, achieving on-time delivery for dozens of units through modular prefabrication and experienced labor pools. These factors underscore that while regulatory rigor enhances safety, it correlates with higher costs and slower progress absent economies of repetition.^[135]

Planned and Proposed Reactors

Approximately 110 nuclear power reactors, with a combined gross capacity of about 110 GWe, are planned worldwide as of late 2025, according to assessments by the World Nuclear Association (WNA).^[11] These plans predominantly feature large-scale light-water reactors and emerging small modular reactor (SMR) designs, with deployment timelines extending into the 2030s and beyond, contingent on regulatory approvals and financing. The International Atomic Energy Agency (IAEA) corroborates this scale in its projections, noting that while under-construction units number around 70, planned additions could contribute to global capacity growth exceeding 100% by mid-century in high-growth scenarios.^[136] In the United States, emphasis falls on SMR pilots and advanced reactors, with the U.S. Army targeting microreactor deployment at military bases by the end of 2028 to support national security needs.^[137] Private sector initiatives, such as Amazon's updated plans for up to 12 SMRs at a Washington state facility, aim for operational readiness in the late 2020s, leveraging modular construction to address rising electricity demand from data centers and electrification.^[138] Similarly, Constellation Energy intends to restart the 835 MW Three Mile Island Unit 1 by 2028 under a power purchase agreement with Microsoft, though this involves refurbishment rather than new build.^[139] Globally, SMR deployments are advancing in over 30 countries, with designs like NuScale and GE Hitachi targeting commercial pilots post-2028, driven by scalability and reduced upfront capital risks compared to traditional gigawatt-scale plants.^[140] The United Kingdom has committed to expanding nuclear capacity to up to 24 GWe by 2050, supporting 25% of electricity needs through a mix of large reactors and SMRs, as outlined in government policy.^[141] This includes site selections for new stations and selection of Rolls-Royce SMR as a preferred vendor for a £2.5 billion program managed by Great British Nuclear.^[142] In Saudi Arabia, proposals center on an initial two-reactor program with 2.9 GWe capacity, alongside ambitions for up to 16 additional units, backed by U.S. cooperation agreements on civil nuclear technology and uranium enrichment plans.^[143][144] Financing remains a primary hurdle, with high capital costs and long lead times deterring investment absent government guarantees or streamlined licensing; WNA notes that many plans hinge on memoranda of understanding rather than firm contracts.^[11] Nonetheless, IAEA forecasts indicate potential for the global fleet to surpass 500 operational reactors by 2030 under accelerated deployment, fueled by energy security imperatives and decarbonization goals, though realization depends on overcoming supply chain and geopolitical constraints.^[136] Over 300 further proposals exist, including in Asia-Pacific nations like India and Turkey, but these lack binding commitments and face similar barriers.^[11]

Decommissioned Reactors

Over 200 commercial nuclear reactors worldwide have been permanently shut down as of 2023, with the majority reaching the end of their licensed operational lives of 40 to 60 years or facing economic pressures from competition with low-cost natural gas and intermittent renewables in deregulated markets, particularly in the United States during the 2010s.^[145][146] Decommissioning processes have commenced on most of these units, though full radiological release to unrestricted use has been achieved for only about 25 globally, reflecting the lengthy timelines involved—often 10 to 50 years depending on the strategy employed.^[23] Safety-related incidents have prompted fewer than 5% of shutdowns, underscoring the rarity of forced closures due to operational failures; major events like Three Mile Island (1979 partial core melt) and Fukushima (2011 tsunami-induced losses) affected a handful of units, while the overwhelming majority retired for commercial reasons without compromising public health or environmental standards during operation.^[147] Post-shutdown, low incident rates persist, with no verified cases of significant off-site radiological releases from decommissioning activities at commercial sites.^[148] Notable examples include the United Kingdom's Magnox reactors, an early graphite-moderated design series of 26 units operational from the 1950s to the 1980s, all now in decommissioning due to age and graphite degradation concerns; these pioneered deferred dismantling, with sites progressively released for reuse after fuel removal and waste management.^[23] In the United States, Yankee Rowe, a 180 MWe pressurized water reactor in Massachusetts, operated from 1961 to 1991 before shutdown for economic and embrittlement issues, then underwent prompt decontamination and dismantlement (DECON method), achieving full site release by 2007 with costs covered by prepaid trust funds and no adverse environmental impacts.^[149] Similar successes mark other U.S. "Yankee" plants and early units like Shippingport (1957–1982), where DECON or safe storage (SAFSTOR) strategies—entailing entombment of waste in place followed by delayed dismantling—facilitated site repurposing for industrial, recreational, or solar energy uses in over a dozen cases.^[22] Decommissioning costs, estimated at 9–15% of a plant's lifetime generation expenses (typically $300–500 million per reactor), are largely funded via operator-accumulated trusts or government-backed mechanisms, enabling orderly transitions without taxpayer burdens in most jurisdictions.^[148] SAFSTOR, used for about 70% of U.S. cases, allows natural decay of short-lived isotopes before full DECON, reducing worker exposure and aligning with empirical data showing dose rates below regulatory limits (e.g., <1 mSv/year average).^[22] These methods have proven effective, with U.S. regulators releasing over 10 sites to unrestricted access by 2017 and ongoing projects demonstrating radiological cleanup to background levels.^[22]