What is plutonium used for?
In nature, small amounts of plutonium are formed by the capture of free neutrons by uranium in the same way as in a nuclear reactor.
Small amounts of plutonium are found in nature, formed by the capture of free neutrons by uranium in the same way as in a nuclear reactor. Nature also contains traces of plutonium-244, (with a half-life of 82.6 million years) which was formed when all the other elements on Earth were formed.
Pure plutonium is a metallic element. In its metallic form, plutonium reacts with air to form oxides. This reaction occurs spontaneously at room temperature and therefore any handling of plutonium metal must take place in enclosed spaces with an oxygen-free atmosphere.
Uses of plutonium
Plutonium has three major uses: in nuclear fuel, in nuclear explosives and in special purpose batteries.
Nuclear fuel
The capture of neutrons in uranium-238 in ordinary nuclear fuel produces plutonium. Some of the plutonium formed is burned (by nuclear fission) while the fuel remains in the reactor, thus contributing to energy production.
In a modern light water reactor with enriched uranium fuel, on average about one third of the energy output comes from nuclear fission of plutonium. Spent LWR fuel contains less than ten kilograms of plutonium per ton of uranium. The remaining plutonium can be recovered by reprocessing and reused in reactors as mixed oxide fuel (MOX), which is a mixture of plutonium and uranium oxides.
Nuclear explosives
To make nuclear warheads, you need a special grade of plutonium with a high proportion of plutonium-239, known as weapons plutonium. A few kilograms are needed to make a nuclear device. Weapons plutonium contains at least 93% plutonium-239. Lower levels require larger quantities and probably more advanced technology.
Batteries
The plutonium in batteries is mainly plutonium-238, a strong alpha emitter and therefore a long-lived heat source. Such batteries have been used as an energy source in satellites, to power instruments on the moon, in lighthouses and other types of devices in isolated locations, but also in so-called 'pace-makers'.
Health effects of plutonium
Plutonium can only harm a human being if it enters the body because it is essentially an alpha emitter. Plutonium is most dangerous if it enters the lungs as dust via inhalation.
Cancerous tumours caused by plutonium in the body have not been found in humans (this is true of most substances considered to be carcinogenic). Since the dangers of plutonium were already known when it was first handled (it was discovered in 1941), overexposure of those working with it has been avoided.