Skip to content
FusionBenchmark

Liquid-metal cooled

Reactors cooled by molten metal at near-atmospheric pressure. Most designs use no moderator, so the neutrons stay fast. A few do slow their neutrons: Aalo Atomics describes its sodium-cooled Aalo-1 as a thermal reactor, and the IAEA lists Idaho National Laboratory's MARVEL microreactor as liquid-metal-cooled with a thermal spectrum.

In the record: 13 companies, 3 laboratories and programmes, 9 reactors and 9 reactor designs. These counts include Sodium fast reactor and Lead fast reactor.

Related approaches

Broader: Fission

Narrower:

  • Sodium fast reactor Liquid sodium coolant with a fast, unmoderated neutron spectrum. Sodium carries heat superbly at atmospheric pressure, but burns in air and reacts violently with water. Large sodium-cooled cores can have a positive sodium void effect that the core design must offset. Fuel is typically metal alloy or mixed-oxide.
  • Lead fast reactor Molten lead or lead-bismuth coolant, fast and unmoderated. Does not burn in air or react violently with water, unlike sodium, at the cost of weight and corrosion engineering. Fuel is typically nitride or mixed-oxide.

Companies 13

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

Laboratories and programmes 3

Reactors 9

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

Reactor designs 9

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
4S Super-Safe, Small and Simple Toshiba Sodium fast reactor 10 MWe planned Microreactor No milestone recorded
Aalo-1 Aalo-1 Reactor Aalo Atomics Liquid-metal cooled 10 MWe planned Microreactor No milestone recorded
Aurora powerhouse Aurora Oklo Sodium fast reactor 15 to 75 MWe planned Small modular reactor Application denied for one plant: NRC denies Aurora combined licence application · US Nuclear Regulatory Commission · 2022-01-06
DF-1500 Dual Fluid Energy Liquid-metal cooled Output not stated Not classed No milestone recorded
DF-300 Dual Fluid Energy Liquid-metal cooled Output not stated Not classed No milestone recorded
LFR-AS-200 newcleo Lead fast reactor 200 MWe planned Small modular reactor No milestone recorded
Natrium TerraPower with GE Vernova Hitachi Nuclear Energy Sodium fast reactor 345 MWe planned Large reactor Construction permit issued for one plant: NRC construction permit CPAR-1 issued for Kemmerer Power Station Unit 1 (Natrium) · US Nuclear Regulatory Commission · 2026-03-09
SEALER-55 SEALER Blykalla Lead fast reactor 55 MWe planned Small modular reactor No milestone recorded
SVBR-100 Rosatom Lead fast reactor 100 MWe planned Small modular reactor No milestone recorded

Measurements

6 reactors using this approach carry 6 measurements: 4 claimed, 2 planned. The values, each with its status and source, are on the benchmark and on each device's page. Most measured: BOR-60 (1), China Experimental Fast Reactor (1), Fast Breeder Test Reactor (1), BREST-OD-300 (1), MYRRHA (1).

Guides

  • 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.

Liquid-metal cooled in the glossary · Fission overview · All approaches