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FusionBenchmark

Gas-cooled

Reactors cooled by gas, usually helium or carbon dioxide, allowing higher outlet temperatures than water.

In the record: 11 companies, 2 laboratories and programmes, 4 reactors and 14 reactor designs. These counts include High-temperature gas-cooled reactor.

Related approaches

Broader: Fission

Narrower:

  • High-temperature gas-cooled reactor Helium-cooled and graphite-moderated, running far hotter than a water reactor. Fuel is TRISO particles, typically formed into pebbles or prismatic blocks, at LEU or HALEU enrichment depending on the design. The high outlet temperature suits industrial process heat as well as electricity.

Companies 11

Includes companies recorded under a narrower approach, named beside each.

Laboratories and programmes 2

Reactors 4

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

  • HTR-10 Operating Tsinghua University · CN · High-temperature gas-cooled reactor · 1 measurement
  • HTR-PM demonstration plant, Shidao Bay Operating CN · High-temperature gas-cooled reactor · 1 measurement
  • HTTR Operating JAEA · JP · High-temperature gas-cooled reactor · 1 measurement
  • Long Mott Generating Station Planned US · High-temperature gas-cooled reactor · 1 measurement

Reactor designs 14

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 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
Energy Multiplier Module (EM2) EM2 General Atomics Gas-cooled 265 MWe planned Small modular reactor No milestone recorded
Fast Modular Reactor (FMR) FMR General Atomics Gas-cooled 44 MWe planned Small modular reactor No milestone recorded
GT-MHR Gas Turbine Modular Helium Reactor OKBM Afrikantov with Rosatom High-temperature gas-cooled reactor 288 MWe planned Small modular reactor No milestone recorded
GTHTR300 Gas Turbine High Temperature Reactor 300 JAEA High-temperature gas-cooled reactor 100 to 300 MWe planned Small modular reactor No milestone recorded
HTR50S JAEA High-temperature gas-cooled reactor 17.2 MWe planned Small modular reactor 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
LOKI MMR LOKI NANO Nuclear Energy High-temperature gas-cooled reactor 0.01 to 3 MWe planned Microreactor No milestone recorded
MHR-100 OKBM Afrikantov with Rosatom High-temperature gas-cooled reactor 25 to 87 MWe planned Small modular reactor No milestone recorded
MHR-T OKBM Afrikantov with Rosatom High-temperature gas-cooled reactor 205.5 MWe planned Small modular reactor No milestone recorded
SOLO SOLO Micro-Modular Reactor Terra Innovatum Gas-cooled 1 MWe planned Microreactor No milestone recorded
Xe-100 X-energy High-temperature gas-cooled reactor 80 MWe planned Small modular reactor Accepted for review for one plant: Long Mott construction permit application accepted for docketing · US Nuclear Regulatory Commission · 2025-05-12

Measurements

4 reactors using this approach carry 4 measurements: 3 claimed, 1 planned. The values, each with its status and source, are on the benchmark and on each device's page. Most measured: HTR-10 (1), HTR-PM demonstration plant, Shidao Bay (1), HTTR (1), Long Mott Generating Station (1).

Guides

Includes guides about the narrower approaches.

  • 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.
  • 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.

Gas-cooled in the glossary · Fission overview · All approaches