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For nuclear batteries.
(Planet pluto) Plutonium was the second transuranium element of the actinide series to
be discovered. The isotope 238Pu was produced in 1940 by Seaborg,
McMillan, Kennedy, and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at
Berkeley, California. Plutonium also exists in trace quantities in naturally occurring
uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural
uranium with the neutrons which are present.
By far of greatest importance is the isotope Pu239, with a
half-life of 24,100 years, produced in extensive quantities in nuclear reactors from
natural uranium: 238U(n, gamma) --> 239U--(beta)
--> 239Np--(beta) --> 239Pu. Fifteen
isotopes of plutonium are known.
Plutonium also exhibits four ionic valence states in aqueous solutions: Pu+3
(blue lavender), Pu+4 (yellow brown), PuO+
(pink?), and PuO+2(pink-orange). The ion PuO+
is unstable in aqueous solutions, disproportionating into Pu+4 and
PuO+2. The Pu+4 thus formed, however, oxidizes
the PuO+ into PuO+2, itself being reduced to
Pu+3, giving finally Pu+3 and PuO+2.
Plutonium forms binary compounds with oxygen: PuO, PuO2, and intermediate
oxides of variable composition; with the halides: PuF3, PuF4, PuCl3,
PuBr3, PuI3; with carbon, nitrogen, and silicon: PuC, PuN, PuSi2.
Oxyhalides are also well known: PuOCl, PuOBr, PuOI.
Plutonium has assumed the position of dominant importance among the trasuranium
elements because of its successful use as an explosive ingredient in nuclear weapons and
the place which it holds as a key material in the development of industrial use of nuclear
power. One kilogram is equivalent to about 22 million kilowatt hours of heat energy. The
complete detonation of a kilogram of plutonium produces an explosion equal to about 20,000
tons of chemical explosive. Its importance depends on the nuclear property of being
readily fissionable with neutrons and its availability in quantity. The world's
nuclear-power reactors are now producing about 20,000 kg of plutonium/yr. By 1982 it was
estimated that about 300,000 kg had accumulated. The various nuclear applications of
plutonium are well known. 238Pu has been used in the Apollo lunar missions to power
seismic and other equipment on the lunar surface. As with neptunium and uranium, plutonium
metal can be prepared by reduction of the trifluoride with alkaline-earth metals.
The metal has a silvery appearance and takes on a yellow tarnish when slightly
oxidized. It is chemically reactive. A relatively large piece of plutonium is warm to the
touch because of the energy given off in alpha decay. Larger pieces will produce enough
heat to boil water. The metal readily dissolves in concentrated hydrochloric acid,
hydroiodic acid, or perchloric acid. The metal exhibits six allotropic modifications
having various crystalline structures. The densities of these vary from 16.00 to 19.86
Because of the high rate of emission of alpha particles and the element being
specifically absorbed on bone the surface and collected in the liver, plutonium, as well
as all of the other transuranium elements except neptunium, are radiological poisons and
must be handled with very special equipment and precautions. Plutonium is a very dangerous
radiological hazard. Precautions must also be taken to prevent the unintentional
formulation of a critical mass. Plutonium in liquid solution is more likely to become
critical than solid plutonium. The shape of the mass must also be considered where
criticality is concerned.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.
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