World's Nuclear Reactors

Some info about where the nuclear reactors are. Find one near you!

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Pressurised water reactors (PWRs) This is the most common type worldwide. Enriched uranium oxide is formed into rods and water is used both as a coolant, flowing through the reactor core to transfer heat away, and as a moderator, slowing down neutrons released by fission so that they promote further nuclear reactions. The main cooling circuit transfers heat via a steam generator to a second circuit, which drives the electricity-generating turbine.

Boiling water reactors This is the next most common type, used in countries including the US, Sweden and Japan – the reactors at Fukushima Daiichi are ageing examples. The fuel is enriched uranium oxide, and water is used both as a coolant and as a moderator. However, these reactors differ from PWRs in that there is only one cooling loop, flowing between turbine and reactor.

Heavy water-moderated reactors These all use heavy water as a moderator. Most reactors of this type are known as pressurised heavy water reactors, favoured especially in Canada. PHWRs are similar to PWRs, but use raw uranium rather than enriched uranium oxide as fuel, and deploy heavy water – in which hydrogen is replaced by deuterium – as both moderator and coolant.

Gas-cooled reactors Developed in the UK, these reactors use graphite to moderate neutrons and carbon dioxide to cool the core. Older versions, known as Magnox reactors, use uranium metal as fuel, while newer ones use enriched uranium oxide.

Fast breeder reactors These reactors are cooled by liquid sodium, which is not an efficient moderator. In addition to driving fission reactions, 'fast' neutrons are readily captured by uranium-238, which is then converted to plutonium-239. These reactors therefore 'breed' plutonium, which can be used to make more fuel or nuclear weapons.

Light water-cooled graphite-moderated reactors Fuelled by low-enriched uranium oxide, these reactors use graphite as a moderator and water to cool the core. The most common variant of this type, known as RBMK, was responsible for the 1986 Chernobyl disaster. The design is considered inherently hazardous because graphite can react explosively with metal pipes, yet some reactors of the type continue to be operated in the former Soviet Bloc.

Map showing the population size living within 75 kilometres of each of the world's nuclear power plants. Population increases with circle size and with colour, from green (< 0.5 million) to red (> 20 million). You need to download the Google Earth plug-in to view this graphic. See 'How population sizes were estimated' for an explanation of how the analysis was carried out.