Small modular reactors and microreactors
A small modular reactor produces up to 300 megawatts of electricity (MWe) per unit, and is meant to be built largely in a factory. A microreactor is the smallest kind, up to about 10 MWe. Both lines are the International Atomic Energy Agency's, which describes SMRs as "typically up to 300 MW(e) per unit" and microreactors as "typically up to 10 MW(e)". The US Department of Energy describes microreactors by heat output instead, as 1 to 20 megawatts thermal.
This page classes each design from the output of one unit as recorded, not from how its developer describes it. A design with no stated output is listed, but not classed. Size says nothing about reactor type, which is shown beside each design; the types themselves are described on fission.
Small modular reactors 31
Above 10 MWe and up to 300 MWe per unit.
| Design | Developer | Approach | Electrical output per unit | Licensing stage |
|---|---|---|---|---|
| ACP100 Linglong One | CNNC | Pressurised water reactor | 125 MWe planned | No milestone recorded |
| ACP100S | CNNC | Pressurised water reactor | 125 MWe planned | No milestone recorded |
| Aurora powerhouse Aurora | Oklo | Sodium fast reactor | 15 to 75 MWe planned | Application denied for one plant: NRC denies Aurora combined licence application · US Nuclear Regulatory Commission · 2022-01-06 |
| BWRX-300 | GE Vernova Hitachi Nuclear Energy | Boiling water reactor | 300 MWe planned | Construction permit issued for one plant: CNSC licence to construct one BWRX-300 at the Darlington New Nuclear Project · Canadian Nuclear Safety Commission · 2025-04-04 |
| CAREM CAREM25 | CNEA | Pressurised water reactor | 30 MWe planned | No milestone recorded |
| Compact Molten Salt Reactor (CMSR) CMSR | Saltfoss Energy | Molten salt reactor | 110 MWe planned | No milestone recorded |
| Energy Multiplier Module (EM2) EM2 | General Atomics | Gas-cooled | 265 MWe planned | No milestone recorded |
| Fast Modular Reactor (FMR) FMR | General Atomics | Gas-cooled | 44 MWe planned | No milestone recorded |
| Gravity Nuclear Reactor Gravity reactor, Deep Fission Borehole Reactor | Deep Fission | Pressurised water reactor | 15 MWe planned | No milestone recorded |
| GT-MHR Gas Turbine Modular Helium Reactor | OKBM Afrikantov with Rosatom | High-temperature gas-cooled reactor | 288 MWe planned | No milestone recorded |
| GTHTR300 Gas Turbine High Temperature Reactor 300 | JAEA | High-temperature gas-cooled reactor | 100 to 300 MWe planned | No milestone recorded |
| HTR50S | JAEA | High-temperature gas-cooled reactor | 17.2 MWe planned | No milestone recorded |
| i-SMR innovative SMR | Korea Hydro & Nuclear Power with KAERI | Pressurised water reactor | 170 MWe planned | No milestone recorded |
| Integral Molten Salt Reactor (IMSR) IMSR, IMSR400 | Terrestrial Energy | Molten salt reactor | 195 MWe planned | No milestone recorded |
| KLT-40S | OKBM Afrikantov with Rosatom | Pressurised water reactor | 35 MWe claimed | No milestone recorded |
| KP-FHR Kairos Power Fluoride Salt-Cooled High-Temperature Reactor, KP-X | Kairos Power | Fluoride salt-cooled high-temperature reactor | 75 MWe planned | No milestone recorded |
| LFR-AS-200 | newcleo | Lead fast reactor | 200 MWe planned | No milestone recorded |
| MHR-100 | OKBM Afrikantov with Rosatom | High-temperature gas-cooled reactor | 25 to 87 MWe planned | No milestone recorded |
| MHR-T | OKBM Afrikantov with Rosatom | High-temperature gas-cooled reactor | 205.5 MWe planned | No milestone recorded |
| NuScale Power Module (US460) US460, NPM, VOYGR | NuScale Power | Pressurised water reactor | 77 MWe planned | Design approval or certification for the design · US Nuclear Regulatory Commission · 2025-05-29 |
| PWR-20 | Last Energy | Pressurised water reactor | 20 MWe planned | No milestone recorded |
| RITM-200M | OKBM Afrikantov with Rosatom | Pressurised water reactor | 50 MWe planned | No milestone recorded |
| RITM-200N | OKBM Afrikantov with Rosatom | Pressurised water reactor | 55 MWe planned | No milestone recorded |
| SEALER-55 SEALER | Blykalla | Lead fast reactor | 55 MWe planned | No milestone recorded |
| SMART System-integrated Modular Advanced Reactor, SMART100 | KAERI | Pressurised water reactor | 107 MWe planned | No milestone recorded |
| Stable Salt Reactor - Wasteburner (SSR-W) SSR-W, SSR-W300 | Moltex Energy | Molten salt reactor | 300 MWe planned | No milestone recorded |
| Stellarium | Stellaria | Molten salt reactor | 110 MWe planned | No milestone recorded |
| SVBR-100 | Rosatom | Lead fast reactor | 100 MWe planned | No milestone recorded |
| ThorCon ThorCon 500, TMSR-500 | ThorCon International | Molten salt reactor | 250 MWe planned | No milestone recorded |
| Thorizon One Thorizon | Thorizon | Molten salt reactor | 100 MWe planned | No milestone recorded |
| Xe-100 | X-energy | High-temperature gas-cooled reactor | 80 MWe planned | Accepted for review for one plant: Long Mott construction permit application accepted for docketing · US Nuclear Regulatory Commission · 2025-05-12 |
Microreactors 10
Up to 10 MWe per unit.
| Design | Developer | Approach | Electrical output per unit | Licensing stage |
|---|---|---|---|---|
| 4S Super-Safe, Small and Simple | Toshiba | Sodium fast reactor | 10 MWe planned | No milestone recorded |
| Aalo-1 Aalo-1 Reactor | Aalo Atomics | Liquid-metal cooled | 10 MWe planned | No milestone recorded |
| ABV-6E | OKBM Afrikantov with Rosatom | Pressurised water reactor | 6 to 9 MWe planned | No milestone recorded |
| eVinci | Westinghouse Electric Company | Heat-pipe microreactor | 5 MWe planned | No milestone recorded |
| LOKI MMR LOKI | NANO Nuclear Energy | High-temperature gas-cooled reactor | 0.01 to 3 MWe planned | No milestone recorded |
| MoveluX | Toshiba | Heat-pipe microreactor | 3 to 4 MWe planned | No milestone recorded |
| R1 Microreactor Antares R1 | Antares Nuclear | Heat-pipe microreactor | 0.1 to 1 MWe planned | No milestone recorded |
| SHELF-M | NIKIET with Rosatom | Pressurised water reactor | 10 MWe planned | No milestone recorded |
| SOLO SOLO Micro-Modular Reactor | Terra Innovatum | Gas-cooled | 1 MWe planned | No milestone recorded |
| UNITHERM | NIKIET with Rosatom | Pressurised water reactor | 6.6 MWe planned | No milestone recorded |
Output not stated 12
Fission designs with no per-unit electrical rating in the record. They may be small or large; the record does not say.
| Design | Developer | Approach | Electrical output per unit | Size class | Licensing stage |
|---|---|---|---|---|---|
| BWXT Advanced Nuclear Reactor (BANR) BANR | BWX Technologies | High-temperature gas-cooled reactor | Output not stated | Not classed | No milestone recorded |
| Copenhagen Atomics Waste Burner CA Waste Burner, Onion Core | Copenhagen Atomics | Molten salt reactor | Output not stated | Not classed | No milestone recorded |
| DF-1500 | Dual Fluid Energy | Liquid-metal cooled | Output not stated | Not classed | No milestone recorded |
| DF-300 | Dual Fluid Energy | Liquid-metal cooled | Output not stated | Not classed | No milestone recorded |
| EPR European Pressurised Reactor, Evolutionary Power Reactor | Framatome | Pressurised water reactor | Output not stated | Not classed | No milestone recorded |
| Hualong One HPR1000 | CNNC with CGN | Pressurised water reactor | Output not stated | Not classed | No milestone recorded |
| Jimmy | Jimmy | High-temperature gas-cooled reactor | Output not stated | Not classed | No milestone recorded |
| Kaleidos | Radiant | High-temperature gas-cooled reactor | Output not stated | Not classed | No milestone recorded |
| KRONOS MMR KRONOS, KRONOS MMR Energy System | NANO Nuclear Energy | High-temperature gas-cooled reactor | 3.5 to 15 MWe planned | Stated range spans two size classes | No milestone recorded |
| LDR-50 | Steady Energy | Water-cooled | Output not stated | Not classed | No milestone recorded |
| MSR-100 | Natura Resources | Molten salt reactor | Output not stated | Not classed | No milestone recorded |
| ZEUS | NANO Nuclear Energy | Fission | Output not stated | Not classed | No milestone recorded |
9 designs are rated above 300 MWe per unit and listed on fission.
Guides
- Small modular reactors What makes a reactor a small modular reactor, where the IAEA draws the size lines, why size is judged per unit rather than per plant, which ones actually operate, and why their cost claims are not yet proven.
- Microreactors What microreactors are, how heat-pipe, gas-cooled and sodium-cooled designs work, what they are meant for, why most need HALEU or TRISO fuel, and where the leading projects actually stand.