Gas-cooled reactor

A gas-cooled reactor (GCR) is a nuclear reactor that uses graphite as a neutron moderator and carbon dioxide as coolant. Although there are many other types of reactor cooled by gas, the terms GCR and to a lesser extent gas cooled reactor are particularly used to refer to this type of reactor.

The GCR was able to use natural uranium as fuel, enabling the countries that developed them to fabricate their own fuel without relying on other countries for supplies of enriched uranium, which was at the time of their development in the 1950s only available from the United States or the Soviet Union.

Generation I GCR

There were two main types of generation I GCR:

• The Magnox reactors developed by the United Kingdom.
• The UNGG reactors developed by France.

The main difference between these two types is in the fuel cladding material. Both types were mainly constructed in their countries of origin, with a few export sales: two Magnox plants to Italy and Japan, and one UNGG to Spain. More recently, GCRs based on the declassified drawings of the early Magnox reactors have been constructed by North Korea at the Yongbyon Nuclear Scientific Research Center.

Both types used fuel cladding materials that were unsuitable for medium term storage under water, making reprocessing an essential part of the nuclear fuel cycle. Both types were, in their countries of origin, also designed and used to produce weapons-grade plutonium, but at the cost of major interruption to their use for power generation despite the provision of online refuelling.

Generation II GCR

In the UK, the Magnox was replaced by the advanced gas-cooled reactor (AGR), an improved Generation II gas cooled reactor. In France, the UNGG was replaced by the pressurized water reactor (PWR).

Types

Gas-cooled reactor types include:

• Gas-cooled reactor (graphite moderated, CO₂ cooled)
  • Magnox (British design, 28 built, 1956-2015)
  • UNGG reactor (French design, 10 built, 1956-1994)
  • Advanced Gas-cooled Reactor (Magnox successor, 15 built, 1962-today)
• Heavy water gas cooled reactor (heavy water moderated, CO₂ cooled)
  • Brennilis Nuclear Power Plant (1967-1985)
  • KS 150 (1972-1979)
• High & Very-high temperature reactor (graphite moderated, He cooled)
  • Prismatic block reactor
    • Dragon reactor (1964-1975)
    • Peach Bottom Atomic Power Station (1967-1974)
    • Fort Saint Vrain Generating Station (1979-1989)
    • High-temperature engineering test reactor (1999-today)
    • Gas Turbine Modular Helium Reactor (General Atomics design)
    • Steam Cycle High-Temperature Gas-Cooled Reactor (Areva SMR design)
  • Pebble bed reactor
    • AVR reactor (1966-1988)
    • THTR-300 (1983-1989)
    • HTR-10 (2003-today)
    • HTR-PM (under construction)
    • Pebble bed modular reactor (design)
• Gas-cooled fast reactor (No moderator, He cooled)
  • Energy Multiplier Module (General Atomics design)

See also

• UHTREX