Plutonium
Introduction
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flares spontaneously in air at room temperature.
Discovery and Production
Plutonium was first produced and isolated on December 14, 1940, by a team led by Glenn Seaborg and Edwin McMillan at the University of California, Berkeley. They bombarded uranium-238 with deuterons to produce neptunium-238, which then beta-decayed to form this new element. Plutonium-239, the isotope found in most nuclear reactors, is made from uranium-238. When a neutron strikes the nucleus of a uranium-238 atom, the uranium atom captures the neutron to become uranium-239. This unstable isotope undergoes beta decay to become neptunium-239, which further undergoes beta decay to form plutonium-239.
Characteristics
Plutonium is a heavy, radioactive, metallic element. The most important isotope of plutonium is plutonium-239, which can undergo fission with slow neutrons in a similar manner to uranium-235. Plutonium-239 is the isotope most useful for nuclear weapons. Plutonium-238 and 242 are also used in industry and research. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors.
Applications
Plutonium has been used in several applications. The most well-known of these is in nuclear weapons, where it is used as a fissile material. Plutonium-239, in particular, is suitable for this purpose due to its ease of fission and availability. Plutonium is also used in nuclear reactors, where it can be used both as a fuel and as a means of disposing of excess plutonium from dismantled weapons. Other uses of plutonium include the production of radioisotope thermoelectric generators (RTGs) for spacecraft and the use of plutonium-238 in pacemakers.
Health and Environmental Effects
Plutonium is a hazardous material with both chemical and radiological hazards. The most significant health effect of plutonium is the potential for it to contribute to the development of cancer. This is primarily due to the fact that plutonium emits alpha particles, which can cause damage to DNA and lead to the development of cancer. Plutonium can also have environmental effects, particularly if it is released into the environment as a result of a nuclear accident or the improper disposal of nuclear waste.