Background (Encyclopedia of Global Resources)
Plutonium (abbreviated Pu), element number 94 in the periodic table, is a silvery-white metal that oxidizes readily. Normally hard and brittle, it can be molded and machined if it is alloyed with gallium (0.9 percent by weight). Plutonium has fifteen known isotopes, ranging from plutonium 232 to plutonium 246; all of them are radioactive. Half-lives range from twenty-one minutes for plutonium 233 to eighty-one million years for plutonium 244. The most abundant isotope is plutonium 239, which has a half-life of 24,390 years. Minuscule amounts of plutonium 244 occur naturally in uranium ore, but the only way to obtain usable amounts is to make plutonium in a nuclear reactor.
Plutonium is radiotoxic: It harms by radiation. Plutonium primarily decays by emission of an alpha particle (a helium 4 nucleus, a grouping of two neutrons and two protons). Nonetheless, a grape-sized plutonium sample could be safely held in the hand, even though it would feel warm because of its radioactivity. Plutonium’s alpha particle radiation is easily blocked by the outermost layers of a person’s skin. Furthermore, plutonium is not easily absorbed by the body. If plutonium were ingested with food or water, almost all of it would be excreted. However, 4 parts per 10,000 might be absorbed and eventually settle in the liver or bones, where the plutonium might produce cancer tens of years later. The maximum long-term body burden of plutonium 239 believed...
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Plutonium as a Fuel (Encyclopedia of Global Resources)
A common type of nuclear power reactor contains natural uranium that has been enriched in the isotope uranium 235. When struck by a neutron, the rare uranium 235 may fission to produce two daughter nuclei, a few neutrons, and energy. Plutonium 239 is formed when the more common uranium 238 isotope absorbs a neutron. If left in the reactor, plutonium 239 may also absorb a neutron and either fission or become plutonium 240. Over half of the plutonium produced in a power reactor does fission, and this fission contributes about one-third of the total energy produced in the reactor.
It takes nearly 3 million metric tons of coal to produce the same amount of energy as 1 metric ton of plutonium 239. The world stock of civilian plutonium is approximately 1,000 metric tons. Eighty percent of it is tied up in used reactor fuel elements.
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Plutonium in Nuclear Weapons (Encyclopedia of Global Resources)
Thebomb dropped on Nagasaki, Japan, by the United States in World War II contained 6.1 kilograms of plutonium and had an explosive yield equal to almost 20,000 metric tons of dynamite. The much greater yield of a hydrogen bomb is triggered by detonating a small plutonium bomb.
The military organizations of the world possess about 250 metric tons of plutonium. With the ending of the Cold War, the U.S. Department of Energy and Department of Defense declared that 38 metric tons of weapons-grade plutonium (nearly one-half of its stockpile) was surplus plutonium. The two ways that this plutonium is most likely to be disposed of are to use it as fuel in nuclear reactors or to mix it with radioactive waste and molten glass in a vitrification process.
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Other Uses (Encyclopedia of Global Resources)
Radioisotope thermoelectric generators (RTGs) use plutonium 238 (with a half-life of 86 years) to heat silicon-germanium junctions which then produce electricity. Having no moving parts, RTGs can be made to be very sturdy and reliable. RTGs are used to provide electrical power for interplanetary spacecraft such as Galileo and the Voyagers, since solar panels are too inefficient beyond the orbit of Mars. RTGs may also be used to power navigational beacons, remote weather stations, and even cardiac pacemakers. Americium 241 formed by the decay of plutonium 241 is a vital constituent of household smoke detectors.
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Nuclear Terrorism (Encyclopedia of Global Resources)
It seems unlikely that terrorists would use plutonium as a radiological poison, because its toxicity is relatively low. Bernard L. Cohen has calculated that 0.45 kilogram of plutonium particles dispersed in a large city in the most effective way might produce twenty-seven fatalities ten to forty years later. Chemical or biological weapons are probably easier for terrorists to obtain. The nerve gas sarin, for example, was used by terrorists in the 1995 Tokyo subway attack in which thousands were immediately overcome; fifty-five hundred people were injured, and twelve died.
Following the breakup of the Soviet Union, there were several cases of smuggling small amounts of high-grade plutonium and uranium for sale in the West. After the terrorist attacks in the United States on September 11, 2001, fears of terrorists acquiring and using nuclear weapons were heightened. To lesson the chances of plutonium being diverted for weapons use, weapons-grade plutonium can be oxidized and mixed with uranium oxide to form mixed oxide fuel (MOX), which is suitable for use in some nuclear reactors. Terrorists might conceivably construct an inefficient bomb from MOX, but it would require hundreds to thousands of kilograms.
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Further Reading (Encyclopedia of Global Resources)
Bernstein, Jeremy. Nuclear Weapons: What You Need to Know. New York: Cambridge University Press, 2008.
_______. Plutonium: A History of the World’s Most Dangerous Element. Washington, D.C.: Joseph Henry Press, 2007.
Bodansky, David. Nuclear Energy: Principles, Practices, and Prospects. 2d ed. New York: Springer, 2004.
Greenwood, N. N., and A. Earnshaw. “The Actinide and Transactinide Elements.” In Chemistry of the Elements. 2d ed. Boston: Butterworth-Heinemann, 1997.
O’Very, David P., Christopher E. Paine, and Dan W. Reicher, eds. Controlling the Atom in the Twenty-first Century. Boulder, Colo.: Westview Press, 1994.
Patterson, Walter C. The Plutonium Business and the Spread of the Bomb. San Francisco: Sierra Club Books, 1984.
Rhodes, Richard. The Making of the Atomic Bomb. New York: Simon and Schuster, 1986.
Tsipis, Kosta. Arsenal: Understanding Weapons in the Nuclear Age. New York: Simon and Schuster, 1983.
Tucker, William. Terrestrial Energy: How Nuclear Power Will Lead the Green Revolution and End America’s Energy Odyssey. Savage, Md.: Bartleby Press, 2008.
U.S. Nuclear Regulatory Commission. Plutonium Fact Sheet. http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/plutonium.html
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Plutonium (Chemical Elements)
Plutonium is a synthetic (artificial) element. It exists naturally only in the smallest imaginable amounts. Plutonium was first prepared artificially by a team of researchers at the University of California at Berkeley (UCB) in 1941. News of this discovery was not released, however, until 1946. This delay was caused by the need for secrecy about scientific developments during World War II (1939-45).
Plutonium is a member of the actinide family. The actinides occur in Row 7 of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. The actinides get their name from element 89, actinium, which is sometimes considered the first member of the family. Plutonium is also called a transuranium element. The term transuranium means "beyond uranium." Elements with atomic numbers greater than that of uranium (92) are called transuranium elements.
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