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Pressurised water reactor

Also written PWR

Ordinary (light) water kept under high pressure so it heats without boiling, transferring heat to a separate steam loop; the water is both coolant and moderator. Fuel is low-enriched uranium oxide pellets in zirconium-alloy rods. The most common reactor type in service worldwide.

In the record: 26 companies, 3 laboratories and programmes, 5 reactors and 21 reactor designs.

Related approaches

Broader: Water-cooled

Companies 26

Laboratories and programmes 3

Reactors 5

Operating reactors first, then those being built or planned, then those shut down, suspended or cancelled.

Reactor designs 21

Size class is worked out from the electrical output of one unit: up to 10 MWe is a microreactor, up to 300 MWe a small modular reactor. A design with no stated output is not classed.

Design Developer Electrical output per unit Size class Licensing stage
ABV-6E OKBM Afrikantov with Rosatom 6 to 9 MWe planned Microreactor No milestone recorded
ACP100 Linglong One CNNC 125 MWe planned Small modular reactor No milestone recorded
ACP100S CNNC 125 MWe planned Small modular reactor No milestone recorded
AP1000 Westinghouse Electric Company 1,110 MWe claimed Large reactor No milestone recorded
AP300 Westinghouse Electric Company 330 MWe planned Large reactor No milestone recorded
CAREM CAREM25 CNEA 30 MWe planned Small modular reactor No milestone recorded
EPR European Pressurised Reactor, Evolutionary Power Reactor Framatome Output not stated Not classed No milestone recorded
Gravity Nuclear Reactor Gravity reactor, Deep Fission Borehole Reactor Deep Fission 15 MWe planned Small modular reactor No milestone recorded
Hualong One HPR1000 CNNC with CGN Output not stated Not classed No milestone recorded
i-SMR innovative SMR Korea Hydro & Nuclear Power with KAERI 170 MWe planned Small modular reactor No milestone recorded
KLT-40S OKBM Afrikantov with Rosatom 35 MWe claimed Small modular reactor No milestone recorded
NuScale Power Module (US460) US460, NPM, VOYGR NuScale Power 77 MWe planned Small modular reactor Design approval or certification for the design · US Nuclear Regulatory Commission · 2025-05-29
PWR-20 Last Energy 20 MWe planned Small modular reactor No milestone recorded
RITM-200M OKBM Afrikantov with Rosatom 50 MWe planned Small modular reactor No milestone recorded
RITM-200N OKBM Afrikantov with Rosatom 55 MWe planned Small modular reactor No milestone recorded
Rolls-Royce SMR Rolls-Royce SMR 470 MWe planned Large reactor Accepted for review for the design · Office for Nuclear Regulation · 2022-04
SHELF-M NIKIET with Rosatom 10 MWe planned Microreactor No milestone recorded
SMART System-integrated Modular Advanced Reactor, SMART100 KAERI 107 MWe planned Small modular reactor No milestone recorded
SMR-300 Holtec International 320 MWe planned Large reactor Accepted for review for one plant: Pioneer Units 1 and 2: Part 1 of phased construction permit application accepted for docketing · US Nuclear Regulatory Commission · 2026-02-13
UNITHERM NIKIET with Rosatom 6.6 MWe planned Microreactor No milestone recorded
VBER-300 OKBM Afrikantov with Rosatom 325 MWe planned Large reactor No milestone recorded

Measurements

2 reactors using this approach carry 2 measurements: 1 claimed, 1 planned. The values, each with its status and source, are on the benchmark and on each device's page. Most measured: Akademik Lomonosov (1), Linglong One demonstration unit, Changjiang (1).

Guides

  • How fission reactors work How a fission reactor sustains a chain reaction, what the moderator, coolant and control rods do, why delayed neutrons make control possible, where decay heat comes from, and what passive safety does and does not mean.
  • 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.
  • Reactor types explained The three questions that classify any fission reactor, and how pressurised water, boiling water, heavy water, gas-cooled, salt-cooled, molten-salt, sodium, lead and heat-pipe reactors each answer them.

Pressurised water reactor in the glossary · Fission overview · All approaches