# Small modular reactors > Nuclear reactors up to 300 MWe per module, factory-built for speed; the United States, United Kingdom, and China are racing to commercial operation as AI data centres create demand. **Meta:** type: reference · date: 2026-07-03 · heads: · 3 takes · 2 lenses · 3 regions ## What it is Small modular reactors (SMRs) are nuclear reactors producing up to 300 megawatts electric (MWe) per module, factory-built and shipped to site rather than constructed on location. Designs below 10-20 MWe are called microreactors. The defining premise is that standardized, repeatable factory production compresses cost and schedule versus the decade-long, site-specific cycle of conventional gigawatt-scale plants. Technology families include pressurized water reactors (NuScale VOYGR; Rolls-Royce SMR at 470 MWe), boiling water reactors (GE Hitachi BWRX-300 at 300 MWe), sodium-cooled fast reactors (TerraPower Natrium at 345 MWe), and high-temperature gas-cooled reactors (China's HTR-PM). All modern commercial designs use passive safety systems, relying on gravity and natural convection rather than powered pumps, so reactors shut down safely without operator action or external power. ## History Reactors at SMR scale have existed since the 1950s in naval and research roles. Russia's KLT-40S, derived from icebreaker propulsion technology, became the first commercially operating modern SMR when the floating Akademik Lomonosov plant connected to the Russian Arctic grid at Pevek, Chukotka, in 2019. China commissioned HTR-PM, a pebble-bed high-temperature reactor (around 200 MWe electric), at Shidaowan in Shandong province in late 2023. The Western commercial wave gained momentum after the 2011 Fukushima disaster in Japan, when the case for smaller, inherently safer designs became politically compelling. The US Department of Energy backed NuScale's development from 2014; in January 2023, NuScale became the first company to receive a US Nuclear Regulatory Commission design certification for an SMR, covering its 50 MWe Power Module. The NRC issued a Standard Design Approval for the uprated 77 MWe variant in May 2025. More than 20 countries pledged to triple global nuclear capacity by 2050 at COP28 in Dubai in December 2023. ## Current state As of mid-2026, a small number of SMRs operate commercially; none of the new Western commercial designs is yet generating power. Russia's KLT-40S at Pevek delivers roughly 70 MWe to the Chukotka grid. China's HTR-PM at Shidaowan is in early commercial operation. China's ACP100 (Linglong One) at Changjiang in Hainan province targets commercial operation in 2026, which would make it the first land-based SMR of a new-generation design to reach that milestone. In North America, GE Hitachi's BWRX-300 is under Canadian Nuclear Safety Commission review at Ontario Power Generation's Darlington site, targeting 2030-31; the Tennessee Valley Authority submitted a US NRC construction permit application for a BWRX-300 at Clinch River in Tennessee. TerraPower's Natrium, backed by Bill Gates and partly funded by the US Department of Energy, broke ground at Kemmerer, Wyoming in 2024, targeting 2030. The [order book](/ar/n/smr-data-center-orders-2026) is large but pre-construction: Rolls-Royce is selected for three 470 MWe units in Sweden and up to eight at Wylfa, UK; Oklo holds a 12 GW master agreement with data-center developer Switch. The International Energy Agency projects 10-25 GWe of global SMR capacity by 2035. ## Relationships SMR deployment depends on [uranium supply](/ar/n/uranium-dossier) and [enrichment capacity](/ar/n/enrichment-dossier). TerraPower's Natrium and several Generation IV designs require high-assay low-enriched uranium (HALEU), enriched to 5-20% compared with the 3-5% standard used in most existing reactors; only the US Department of Energy's Centrus demonstration cascade and Russia's Rosatom currently produce HALEU at commercial scale. The [[us-enrichment-deRussification-2026|US enrichment buildout]] is partly motivated by eliminating dependence on Russian-origin fuel. [Uranium price cycles](/ar/n/uranium-price-plateau-2026) shape project economics; developers track long-term uranium contracts alongside enrichment pipeline availability. On the demand side, the linkage is increasingly to [AI data-centre load growth](/ar/n/data-centers-dossier): hyperscalers and data-centre operators are signing multi-decade SMR offtake agreements to secure firm, around-the-clock, low-carbon power at scale. ## What to watch - First-of-a-kind construction cost and schedule for any new Western commercial design: Canada's Darlington BWRX-300 is the nearest bellwether. - Whether China's ACP100 meets its 2026 commercial operation target; an on-schedule debut would accelerate Chinese SMR export outreach across South and Southeast Asia. - HALEU supply: US DOE funding for the Centrus enrichment cascade is the rate-limiting step for TerraPower and other Generation IV designs. - NRC and UK Office for Nuclear Regulation timelines for pending design certifications. - Conversion of data-centre offtake agreements into financed, sited projects with firm construction starts. ## Regional takes (batched by bias / lens) ### official record - **US Department of Energy** (north-america, en) — DOE announcement of the US Nuclear Regulatory Commission's January 2023 design certification for NuScale's 50 MWe Power Module, the first SMR design certified by the NRC and the seventh reactor design approved for use in the United States. Source: https://www.energy.gov/ne/articles/nrc-certifies-first-us-small-modular-reactor-design - **IAEA** (global, en) — IAEA topic hub covering SMR definitions, safety features, global development status across member states, and the agency's SMR Platform supporting countries preparing to deploy the technology. Source: https://www.iaea.org/topics/small-modular-reactors ### nuclear industry reference - **World Nuclear Association** (United Kingdom, en) — Continuously updated WNA reference on SMR definitions (up to 300 MWe per module; microreactors below 20 MWe), technology families, and the shift from government-led to private-sector development across more than 100 global designs. Source: https://world-nuclear.org/information-library/nuclear-power-reactors/small-modular-reactors/small-modular-reactors ## Across the graph - Related: [[smr-data-center-orders-2026]], [[uranium-dossier]], [[us-enrichment-deRussification-2026]], [[uranium-price-plateau-2026]], [[data-centers-dossier]], [[enrichment-dossier]] - Entities: Commodity:smr, Commodity:uranium, Commodity:enrichment, Commodity:rosatom, Data Centers --- Canonical: https://rbtfl.xyz/ar/n/smr-dossier