There are small amounts of plutonium that can be found in nature and which are formed when free neutrons are captured by uranium in the same way as in a nuclear reactor. Traces of plutonium-244 (with a half-life of 82.6 million years) that were formed at the same time as all of the earth's other elements can also be found in nature.
Pure plutonium is a metallic element. Plutonium reacts with air and forms oxides in its metallic form. This reaction occurs spontaneously at room temperature. Because of this, all handling of plutonium metal must take place in confined spaces that are oxygen-free.
Uses of plutonium
Plutonium has three important fields of application: in nuclear fuel, in nuclear charges and in batteries used for special purposes.
Plutonium is formed when neutrons are captured by uranium-238 in standard nuclear fuel. Part of the plutonium that is formed is consumed (through nuclear fission) while the nuclear fuel remains in the reactor and thus contributes to the production of energy.
In a modern light-water reactor with enriched uranium fuel about a third of the energy output, on average, comes from the nuclear fission of plutonium. Spent light-water reactor fuel contains barely ten kilograms plutonium per ton of uranium. The plutonium that remains can be recycled by reprocessing and reusing it in reactors as mixed oxide (MOX) fuel, which is a mixture of plutonium and uranium oxides.
In order to produce nuclear charges you need to have plutonium of a certain quality with a high fraction of plutonium-239, called weapon-grade plutonium. Only a few kilograms of this are required to produce a nuclear charge. Weapon-grade plutonium contains at least 93 per cent of plutonium-239. If you have a lower percentage, then larger quantities and most likely more advanced technology are required.
The plutonium that is found in batteries is mainly constituted of plutonium-238, a strong alpha beam and is by that a long-lived source of heat. Such batteries have been used as energy sources in satellites, to operate instruments on the moon, in beacons and other types of devices in isolated places, and also in pace-makers.
Health effects of plutonium
Plutonium can only harm a person if it enters the body, due to the fact that it is mainly an alpha beam. Plutonium is most dangerous if it enters the lungs as dust through inhalation.
Cancer tumours in humans caused by plutonium in the body have not been possible to prove. (This incidentally applies to most substances that are considered to be carcinogenic). Because the danger of plutonium has been known since handling of plutonium began (plutonium was discovered in 1941), overexposure for people working with plutonium has been avoided.