Chemical Fact Sheet
Plutonium
| Chemical Abstract Number (CAS #) | 7440-07-5 |
|---|---|
| Analytical Methods | 200.8 - 6020 |
| Molecular Formula | Pu |
|
Synopsis
|
Plutonium - (Planet pluto), Pu; at. wt. (244); at. no. 94; sp. gr. (alpha modification) 19.84 (25 deg C); m.p. 640 deg C; b.p. 3228 deg C; valence 3, 4, 5, or 6. 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,y)--->239U--B-->239Np--B-->239Pu Eighteen isotopes of plutonium are now known. Plutonium has assumed the position of dominant importance among the transuranium 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 with formation of the Pu+3 ion. The metal exhibits six allotropic modifications having various crystalline structures. The densities of these vary from 16.00 to 19.86 g/cu. cm. Plutonium also exhibits four ionic valence states in aqueous solutions: Pu+3 (blue lavender), Pul (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. Because of the high rate of emission of alpha particles and the element being specifically absorbed by bone marrow, 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 formation 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. Plutonium-238 is available to authorized users from the O.R.N.L. at a cost of about $7.50/mg (97%) plus packing costs of $1250 per package. |
| Apparent Color | Silver, white monoclinic (alpha) |
| Boiling Point | 3232 deg C |
| Melting Point | 641 deg C |
| Molecular Weight | 242.059 |
| Density | 19.84 @ 25 deg C |
|
Chemical and Physical Properties |
Plutonium exists as a number of isotopes. The common isotope (239)Pu is an alpha emitter (5 meV); (238)Pu is also an alpha emitter. Plutonium exhibits valences (3+) to (6+) in solutions, but in most common biological and physiological conditions it occurs as Pu(4+). Absolute entropy of alpha-plutonium @ 298 deg K= 56.15 J/(mol/deg K); heat capacity of liquid plutonium @ 913-4000 deg k)= 42.3 J/(mol deg K); entropy of vaporization @ 298 deg K= 121.8 kJ/mol The self heating of a (239)plutonium metal sphere: (1.923 + or - 0.019)X10-3 watts/g (1.82 + or - 0.18 Btu/(sec gram) /(239)Plutonium/ Atomic wt (most stable known isotopes) 242,244 Plutonium exhibits six allotropic forms and four valence states. |
|
Environmental Impact |
Contamination of food, water, hands, or careless handling are the main causes of radionuclide ingestion. In the USA, about 17,000 persons are estimated to have worked with plutonium since 1943-1944. In France, the number in 1986 was about 1000. Among the major effluents from the use and processing of nuclear fuel are plutonium. Of these, only tritium and plutonium can possibly enter water supplies. The predominant form of plutonium release from nuclear power and processing plants is as an aerosol that will have little or no impact on drinking water. Although a single incident has occurred in which as much as 18,750 Ci of plutonium were released from liquid storage on a local basis, none apparently reached off site water supplies. The usual rate of release from liquid storage at a controlled sites is about 1 mCi/yr. |
|
Environmental Fate |
Plutonium also exists in trace quantities in naturally occuring uranium ores. It is formed ... by iradiation of natural uranium with the neutrons which are present. Technologically, (239)plutonium is the most important isotope. It is characterized by a high fission reaction cross-section and is abundant in irradiated natural uranium. Occurrence in earth's crust: 10-22%. The levels of plutonium in food and in the environment are not significant as a radiation hazard, despite its being more toxic than radium as a potent carcinogen. Most of the plutonium found in field grown native plants & agricultural crops is due to surface contamination rather than soil plant transfer. Plutonium concn depends on plant species, on the type and age and status of vegetation; on the pH; cation exchange capacity; mineral and organic composition of the soil; and on the physical and chemical form of contamination; as well as its duration. The highest uptake of plutonium in cheat grass occurs, for example, when plutonium is present in the soil as the stable citrate complex or as a complex with macromulecules, like humic acid or fulvic acid. Absorption through the skin can occur through occupational exposure. Experiments show that the skin is an effective barrier and the percentage absorbed seldom exceeds 0.05% for intact skin. Since plutonium was produced in 1940 the adult human probably has about 2 pCi plutonium in his total body. |
|
Atmosphere |
On the basis of the measured and inferred plutonium concentration in the air of New York and a constant inhalation rate of 20 cu m/day, inhalation intake reflects the amt of radioactivity released by nuclear weapons tests. In 1960 the amt diminished & rose again in 1963 to a max of 450 mbecquerel following 1961-1962 nuclear weapons tests declined regularly after the Test Ban Treaty of 1963 to a value of about 7 mbecquerel/yr during the period from 1972-1974. At the end of 1973, it was estimated that 4.2 tons of (239)plutonium & (240) plutonium was dispersed in the atmosphere. This value should be compared to the est release of plutonium into the environment by the accident of the Chernobyl reactor. This release can be estimated to be in the maximum of 1 to 2% of the plutonium inside the reactor core, ie, 2.5-5 kg of (239)plutonium & (240)plutonium. |
 |
Alphabetical List of Compounds |
 |
List of Compounds by CAS Number |
 |
List of Services |
 |
Spectrum Laboratories Homepage |
