Plutonium is a transuranic 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, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, and silicon. When exposed to moist air, it forms oxides and hydrides that expand the sample up to 70% in volume, which in turn flake off as a powder that can spontaneously ignite. It is also radioactive and can accumulate in the bones. These properties make the handling of plutonium dangerous.

Plutonium is the heaviest primordial element by virtue of its most stable isotope, plutonium-244, whose half-life of about 80 million years is just long enough for the element to be found in trace quantities in nature. Plutonium is mostly a byproduct of nuclear fission in reactors where some of the neutrons released by the fission process convert uranium-238 nuclei into plutonium.

One utilized isotope of plutonium is plutonium-239, which has a half-life of 24,100 years. Plutonium-239 and plutonium-241 are both fissile, meaning the nuclei of their atoms can split when bombarded by thermal neutrons, releasing energy, gamma radiation and more neutrons. These neutrons can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors.

Plutonium-238 has a half-life of 88 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium-240 has a high rate of spontaneous fission, raising the neutron flux of any sample it is in. The presence of plutonium-240 limits a sample's usability for weapons or reactor fuel, and determines its grade. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors.

Plutonium was first synthesized in 1940 by a team led by Glenn T. Seaborg and Edwin McMillan at the University of California, Berkeley laboratory by bombarding uranium-238 with deuterons. Trace amounts of plutonium were subsequently discovered in nature. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II, which developed the first atomic bombs. The first nuclear test, "Trinity" (July 1945), and the second atomic bomb used to destroy a city (Nagasaki, Japan, in August 1945), "Fat Man", both had cores of plutonium-239. Human radiation experiments studying plutonium were conducted without informed consent, and a number of criticality accidents, some lethal, occurred during and after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern. Other sources of plutonium in the environment are fallout from numerous above-ground nuclear tests (now banned).

Other articles related to "plutonium":

Plutonium(III) Fluoride
... Plutonium(III) fluoride or plutonium trifluoride is the chemical compound composed of plutonium and fluorine with the formula PuF3 ... Plutonium(III) fluoride has the LaF3 structure where the coordination around the plutonium atoms is complex and usually described as tri-capped ...
Leo Brewer - Manhattan Project
... task of predicting the possible high-temperature properties of the newly discovered element plutonium, then available only in trace amounts developing refractory materials ... Brewer's crucibles were ready when the plutonium became available ...
Mononuclidic Element - Contamination By Unstable Trace Isotopes
... Almost all of the plutonium found in nature is the single radioactive primordial nuclide 244Pu ... This makes the plutonium mononuclidic by this definition, but in practice, the very large contamination from artificial plutonium isotopes (such as 239Pu) from reactors and nuclear ... Plutonium is therefore not usually listed as a mononuclidic, due to its lack of utility as a mononuclidic ...
List Of Crimes Involving Radioactive Substances - Murder/attempted Murder - The Karlsruhe Plutonium Affair
... man was convicted of attempting to poison his ex-wife in 2001 with plutonium stolen from WAK (Wiederaufbereitungsanlage Karlsruhe), a small scale reprocessing plant where he worked ... He did not steal a large amount of plutonium, only rags used for wiping surfaces and a small amount of liquid waste ... At least two people (besides the criminal) were contaminated by the plutonium ...
Plutonium - Transportation - Air
... Government air transport regulations permit the transport of plutonium by air, subject to restrictions on other dangerous materials carried on the same flight, packaging requirements ... In 2012 media revealed that plutonium has been flown out of Norway on commercial passenger airlines—around every other year—including one time in 2011 ... Such plutonium transportation is without problems, according to a Senior Advisor (seniorrådgiver) at Statens strålevern ...