page_title: Plutonium
section_title: Occurrence
hierarchical_section_title: Plutonium / Characteristics / Occurrence
caption_attribution_description: English: Radioactive Plutonium sample at Questacon museum, Canberra, Australia Radioactive Plutonium sample at Questacon museum, Canberra, Australia depicts: plutonium location: Questacon (Questacon)
context_page_description: 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 flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.
  Plutonium was first produced and isolated on December 14, 1940, by a deuteron bombardment of uranium-238 in the 1.5 metre cyclotron at the University of California, Berkeley. First, neptunium-238 was synthesized, which subsequently beta-decayed to form the new element with atomic number 94 and atomic weight 238. Since uranium had been named after the planet Uranus and neptunium after the planet Neptune, element 94 was named after Pluto, which at the time was considered to be a planet as well.
context_section_description: Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion, and its decay products are naturally found in some concentrated ores of uranium, such as the natural nuclear fission reactor in Oklo, Gabon. The ratio of plutonium-239 to uranium at the Cigar Lake Mine uranium deposit ranges from 2.4×10⁻¹² to 44×10⁻¹². These trace amounts of ²³⁹Pu originate in the following fashion: on rare occasions, ²³⁸U undergoes spontaneous fission, and in the process, the nucleus emits one or two free neutrons with some kinetic energy. When one of these neutrons strikes the nucleus of another ²³⁸U atom, it is absorbed by the atom, which becomes ²³⁹U. With a relatively short half-life, ²³⁹U decays to ²³⁹Np, which decays into ²³⁹Pu. Finally, exceedingly small amounts of plutonium-238, attributed to the extremely rare double beta decay of uranium-238, have been found in natural uranium samples.
  Due to its relatively long half-life of about 80 million years, it was suggested that plutonium-244 occurs naturally as a primordial nuclide, but early reports of its detection could not be confirmed. However, its long half-life ensured its circulation across the solar system before its extinction, and indeed, evidence of the spontaneous fission of extinct ²⁴⁴Pu has been found in meteorites. The former presence of ²⁴⁴Pu in the early Solar System has been confirmed, since it manifests itself today as an excess of its daughters, either ²³²Th (from the alpha decay pathway) or xenon isotopes (from its spontaneous fission). The latter are generally more useful, because the chemistries of thorium and plutonium are rather similar (both are predominantly tetravalent) and hence an excess of thorium would not be strong evidence that some of it was formed as a plutonium daughter. ²⁴⁴Pu has the longest half-life of all transuranic nuclides and is produced only in the r-process in supernovae and colliding neutron stars; when nuclei are ejected from these events at high speed to reach Earth, ²⁴⁴Pu alone among transuranic nuclides has a long enough half-life to survive the journey, and hence tiny traces of live interstellar ²⁴⁴Pu have been found in the deep sea floor. Because ²⁴⁰Pu also occurs in the decay chain of ²⁴⁴Pu, it must thus also be present in secular equilibrium, albeit in even tinier quantities.
  Minute traces of plutonium are usually found in the human body due to the 550 atmospheric and underwater nuclear tests that have been carried out, and to a small number of major nuclear accidents. Most atmospheric and underwater nuclear testing was stopped by the Limited Test Ban Treaty in 1963, which was signed and ratified by the United States, the United Kingdom, the Soviet Union, and other nations. Continued atmospheric nuclear weapons testing since 1963 by non-treaty nations included those by China (atomic bomb test above the Gobi Desert in 1964, hydrogen bomb test in 1967, and follow-on tests), and France (tests as recently as the 1990s). Because it is deliberately manufactured for nuclear weapons and nuclear reactors, plutonium-239 is the most abundant isotope of plutonium by far.
caption: Sample of plutonium metal displayed at the Questacon museum
exif: {"Image Make": "samsung", "Image Model": "SM-G955F", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "G955FXXS5DSI1", "Image DateTime": "2019:11:22 15:09:37", "Image YCbCrSubSampling": "[2, 1]", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "226", "GPS GPSVersionID": "[2, 2, 0, 0]", "GPS GPSLatitudeRef": "S", "GPS GPSLatitude": "[35, 17, 54]", "GPS GPSLongitudeRef": "E", "GPS GPSLongitude": "[149, 7, 53]", "GPS GPSAltitudeRef": "0", "GPS GPSAltitude": "585", "GPS GPSTimeStamp": "[4, 9, 32]", "GPS GPSDate": "2019:11:22", "Image GPSInfo": "826", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1156", "Thumbnail JPEGInterchangeFormatLength": "5321", "EXIF ExposureTime": "1/101", "EXIF FNumber": "17/10", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "40", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2019:11:22 15:09:37", "EXIF DateTimeDigitized": "2019:11:22 15:09:37", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "333/50", "EXIF ApertureValue": "153/100", "EXIF BrightnessValue": "443/100", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "153/100", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "21/5", "EXIF SubSecTime": "0367", "EXIF SubSecTimeOriginal": "0367", "EXIF SubSecTimeDigitized": "0367", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2990", "EXIF ExifImageLength": "2650", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "1032", "EXIF SceneType": "Directly Photographed000", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0/0", "EXIF FocalLengthIn35mmFilm": "26", "EXIF SceneCaptureType": "Standard", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF ImageUniqueID": "1acb888c78b5d20d0000000000000000"}