| Plutonium-238 | |
|---|---|
| General | |
| Name, symbol | Plutonium-238,238Pu |
| Neutrons | 142 |
| Protons | 94 |
| Nuclide data | |
| Half-life | 87.7 years |
| Parent isotopes | 242Cm (α) 238Np (β−) 238Am (β+) |
| Decay products | 234U |
| Spin | 0 |
Plutonium-238, is a radioactive isotope of plutonium with a half-life of 87.7 years. Because it is a very powerful alpha emitter, this isotope is used for radioisotope thermoelectric generators and radioisotope heater units. One gram of plutonium-238 generates approximately 0.5 watts of power.
Plutonium-238 was the first isotope of plutonium to be discovered. It was synthesized by Glenn Seaborg and 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-234 and then further along the radium series to lead-206.
Reactor-grade plutonium from spent nuclear fuel contains various isotopes of plutonium. Pu-238 makes up only a percent or two, but may be responsible for much of the short-term decay heat because of its short halflife. This is not useful for producing Pu-238 for RTGs because difficult isotopic separation would be needed.
Pure plutonium-238 is prepared by irradiation of neptunium-237, one of the minor actinides that can be recovered from spent nuclear fuel during reprocessing, or by the irradiation of americium[citation needed] in a reactor. In both cases, the targets are subjected to a chemical treatment, including dissolution in nitric acid to extract the plutonium-238. A 100 kg sample of light water reactor fuel 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.[1] Since 1993, all of the plutonium-238 the U.S. has used in space probes has been purchased from Russia. 16.5 kilograms in total have been purchased.[2] NASA is requesting funding to restart domestic production, but it is expected to take approximately 10 years to produce substantial amounts.[3]
| Lighter: Plutonium-237 |
Plutonium-238 is an isotope of Plutonium |
Heavier: Plutonium-239 |
| Decay product of: Curium-242 (α) Americium-238 (β+) Neptunium-238 (β-) Uranium-238 (β-β-) |
Decay chain of Plutonium-238 |
Decays to: Uranium-234 (α) |
See also
References
- ^ Borenstein, Seth (May 7, 2009). "Fuel for Deep Space Travel Running Low". Discovery News. Discovery Channel. http://dsc.discovery.com/news/2009/05/07/deep-space-fuel-02.html. Retrieved 2009-05-07.
- ^ http://nuclear.inl.gov/spacenuclear/docs/final72005faqs.pdf
- ^ http://www.npr.org/templates/story/story.php?storyId=113223613
External links
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