background = #7F7
mass_number = 238
symbol = Pu
num_neutrons = 142
num_protons = 94
halflife = 87.7 years
parent = Curium-242
parent_mass = 242
parent3_symbol = Am
Plutonium 238, is a
radioactiveisotope of plutoniumwith a half-life of 87.7 years and is a very powerful alpha emitter. Because of its high level of alpha activity, it is used for radioisotope thermoelectric generators and radioisotope heater units. The use of plutonium-238 in American and Russian (and old Soviet Union) spacecraft is somewhat controversial.
Plutonium-238 was the first
isotopeof plutonium to be discovered. It was synthesized by Glenn Seaborgand associates in 1941 by bombarding uranium-238 with deuterons. Neptunium-238 is made as an intermediate product, which then decays to form plutonium-238. Plutonium-238 decays to Uranium-234and then further along the radium series to Lead-206.
Today, Plutonium 238 is usually prepared by the irradiation of
neptunium 237, a minor actinide produced in nuclear reactors, that can be recovered from spent nuclear fuelduring reprocessing, or by the irradiation of americiumin a reactor. In both cases, the targets are subjected to a chemical treatment, including dissolution in nitric acidto extract the plutonium-238. A 100kg sample of light water reactorfuel that has been irradiated for three years contains only about 700 grams of neptunium 237, and the neptunium must be extracted selectively.
The United States currently has limited facilities to produce plutonium-238. Since 1993, the U.S. has purchased all of the plutonium-238 it has used in space probes from Russia. 16.5 kilograms total have been purchased. [http://nuclear.inl.gov/spacenuclear/docs/final72005faqs.pdf]
* [http://sciencereview.berkeley.edu/articles/issue1/elementary.pdf Story of Seaborg's discovery of Pu-238, especially page 34-35.]
* [http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+plutonium,+radioactive NLM Hazardous Substances Databank – Plutonium, Radioactive]
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