RBMK

Also known as high power channel-type reactor

The RBMK (, РБМК; reaktor bolshoy moshchnosti kanalnyy, "high-power channel-type reactor") is a class of graphite-moderated nuclear power reactor designed and built by the Soviet Union. It is somewhat like a boiling water reactor as water boils in the pressure tubes. It is one of two power reactor types to enter serial production in the Soviet Union during the 1970s, the other being the VVER reactor. The name refers to its design where instead of a large steel pressure vessel surrounding the entire core, the core is surrounded by a cylindrical annular steel tank inside a concrete vault and eac

Key facts

Nuclear reactor.name: RBMK reactor class
Nuclear reactor.image: Smolensk Nuclear Power Plant.jpg
Nuclear reactor.image_size: 300px
Nuclear reactor.caption: View of the Smolensk Nuclear Power Plant site, with three operational RBMK-1000 reactors. A fourth reactor was cancelled before completion.
Nuclear reactor.concept: Graphite-moderated light water-cooled reactor
Nuclear reactor.generation: Generation II reactor
Nuclear reactor.reactor_line: RBMK
Nuclear reactor.type_label: Reactor types
Nuclear reactor.type: RBMK-1000RBMK-1500RBMKP-2400 (never built)
Nuclear reactor.status: 26 blocks: 7 operational 2 involved in accident 9 cancelled 9 decommissioned 4 small EGP-6 graphite moderated BWR shutdown at Bilibino Nuclear Power Plant (as of December 2025)
Nuclear reactor.fuel_type: NU_SEU_LEU
Nuclear reactor.fuel_state: Solid
Nuclear reactor.spectrum: Thermal
Nuclear reactor.control: Control rods
Nuclear reactor.coolant: Liquid (light water)
Nuclear reactor.moderator: Graphite
Nuclear reactor.electric: RBMK-1000: 1,000 MWeRBMK-1500: 1,500 MWeRBMKP-2400: 2,400 MWe
Nuclear reactor.thermal: RBMK-1000: 3,200 MWthRBMK-1500: 4,800 MWthRBMKP-2400: 6,500 MWth

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Wikidata facts

Image: RIAN archive 305011 Leningrad nuclear power plant.jpg

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Commons category: RBMK
native label: Реактор Большой Мощности Канальный
short name: RBMK

Sources (4)

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~64 min read

Article

29 sections

Contents

Lifespan
History
Reactor design and performance
Reactor vessel, moderator and shielding
Fuel channels
Fuel
Control rods
Gas circuit
Primary coolant circuit
ECCS
Reactor control/supervision systems
Containment
Other systems
Electrical systems
Turbogenerators
Design variants
RBMK-1500
RBMK-2000 and RBMK-3600
RBMKP-2400
Design flaws and safety issues
High positive void coefficient
Improvements since the Chernobyl accident
Deformed graphite moderator blocks
Further development
List of RBMK reactors
Other Graphite Moderated Reactors
Known incidents
References
Sources and external links

The RBMK is an early Generation II reactor and the oldest commercial reactor design still in wide operation. Certain aspects of the original RBMK reactor design had several shortcomings, such as the large positive void coefficient, the 'positive scram effect' of the control rods and instability at low power levels—which contributed to the 1986 Chernobyl disaster, in which an RBMK experienced an uncontrolled nuclear chain reaction, leading to a steam and hydrogen explosion, large fire, and subsequent core meltdown. Radioactive material was released over a large portion of northern and southern Europe—including Sweden, where evidence of the nuclear disaster was first registered outside of the Soviet Union, and before the Chernobyl accident was communicated by the Soviet Union to the rest of the world. The disaster prompted worldwide calls for the reactors to be completely decommissioned; however, there is still considerable reliance on RBMK facilities for power in Russia with the aggregate power of operational units at almost 7 GW of installed capacity. Most of the flaws in the design of RBMK-1000 reactors were corrected after the Chernobyl accident and a dozen reactors have since been operating without any serious incidents for over thirty years.