High-temperature gas-cooled reactor
Also written HTGR
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.
In the record: 10 companies, 2 laboratories and programmes, 4 reactors and 11 reactor designs.
Related approaches
Broader: Gas-cooled
Companies 10
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 · 1 measurement
- HTR-PM demonstration plant, Shidao Bay Operating CN · 1 measurement
- HTTR Operating JAEA · JP · 1 measurement
- Long Mott Generating Station Planned US · 1 measurement
Reactor designs 11
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 |
|---|---|---|---|---|
| BWXT Advanced Nuclear Reactor (BANR) BANR | BWX Technologies | Output not stated | Not classed | No milestone recorded |
| GT-MHR Gas Turbine Modular Helium Reactor | OKBM Afrikantov with Rosatom | 288 MWe planned | Small modular reactor | No milestone recorded |
| GTHTR300 Gas Turbine High Temperature Reactor 300 | JAEA | 100 to 300 MWe planned | Small modular reactor | No milestone recorded |
| HTR50S | JAEA | 17.2 MWe planned | Small modular reactor | No milestone recorded |
| Jimmy | Jimmy | Output not stated | Not classed | No milestone recorded |
| Kaleidos | Radiant | Output not stated | Not classed | No milestone recorded |
| KRONOS MMR KRONOS, KRONOS MMR Energy System | NANO Nuclear Energy | 3.5 to 15 MWe planned | Stated range spans two size classes | No milestone recorded |
| LOKI MMR LOKI | NANO Nuclear Energy | 0.01 to 3 MWe planned | Microreactor | No milestone recorded |
| MHR-100 | OKBM Afrikantov with Rosatom | 25 to 87 MWe planned | Small modular reactor | No milestone recorded |
| MHR-T | OKBM Afrikantov with Rosatom | 205.5 MWe planned | Small modular reactor | No milestone recorded |
| Xe-100 | X-energy | 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
- 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.
High-temperature gas-cooled reactor in the glossary · Fission overview · All approaches