Large nuclear reactors
Gigawatt-class units such as AP1000, CANDU and Chinese Hualong designs. China accounts for most 2026 construction starts.
5 leading companies in large nuclear reactors, one segment of nuclear & small reactors — SMRs, reactor restarts, new large builds and the uranium/enrichment fuel chain behind them
new market segment · researched 2026-11-14
Small modular reactors (SMRs)Large nuclear reactorsReactor restarts & life extensionsUranium miningUranium enrichment & HALEUNuclear fuel & components
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Leading large nuclear reactors companies
5 companies, with the scale each source states. Scale is the whole company's unless the row says otherwise.
| Company | Where | What they do | Scale |
|---|---|---|---|
| Westinghouse Electric Company ↗ | Cranberry Township, PA, United States since 1999 | AP1000 large reactor and AP300 SMR designer, fuel and services; partner in the US$80B US government deployment deal | employees: 11,000 employees (">11,000") (2026) ↗ |
| Korea Hydro & Nuclear Power ↗ | Gyeongju, South Korea since 2001 | South Korean reactor operator and APR-1400 builder (Shin-Hanul 4 construction start May 2026) | employees: 12,551 employees (2020) ↗ |
| Rosatom ↗ | Moscow, RU since 2007 | Russian state nuclear group: reactor exports, the world's largest enrichment capacity, fuel, HALEU | enrichment capacity: 29,133 thousand SWU/yr (2025) ↗ |
| China National Nuclear Corporation (CNNC) ↗ | Beijing, China since 1955 | Chinese state nuclear group: reactor design and construction, enrichment, uranium | revenue: 39.6 USD billions (2023) ↗ |
| Ontario Power Generation ↗ | Oshawa, ON, Canada since 1999 | Owner/builder of Darlington New Nuclear (four BWRX-300 units); exploring large nuclear at Wesleyville | capital budget (4 SMR units): 20.9 CAD billions (2026) ↗ |
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The nuclear & small reactors market
The whole market this segment sits in.
installed capacity (operable reactors, net) · world405,667
↗MWe (443 reactors) · 2026
Growth, segments, risks and every company in nuclear & small reactors →
Quick answers
- What are large nuclear reactors?
- Gigawatt-class units such as AP1000, CANDU and Chinese Hualong designs. China accounts for most 2026 construction starts. They are one segment of the nuclear & small reactors market.
- Who are the leading large nuclear reactors companies?
- Westinghouse Electric Company (United States), Korea Hydro & Nuclear Power (South Korea), Rosatom (RU), China National Nuclear Corporation (CNNC) (China), Ontario Power Generation (Canada).
- Which Canadian companies are in large nuclear reactors?
- Ontario Power Generation, Oshawa, ON.
- How big is the nuclear & small reactors market?
- For the whole nuclear & small reactors market, not this segment alone: installed capacity (operable reactors, net) (world) 405,667 MWe (443 reactors), 2026 — World Nuclear Association.