|
| |
238
|
| |
Pu
|
| |
142
|
| |
94
|
| |
877 years
|
| |
Uranium-234
|
| |
234
|
| |
U
|
| |
Curium-242
|
| |
242
|
| |
Cm
|
| |
a
|
| |
Neptunium-238
|
| |
238
|
| |
Np
|
| |
b-
|
| |
Americium-238
|
| |
238
|
| |
Am
|
| |
b+
|
| |
0
|
, is a
Radioactive isotope of
Plutonium with 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 Generator s and
Radioisotope Heater Unit s. The use of plutonium-238 in American and Soviet spacecraft is somewhat controversial.
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 .
Today, Plutonium 238 is usually prepared by the irradiation of
Neptunium 237 , a minor actinide produced in
Nuclear Reactor s, that can be recovered from
Spent Nuclear Fuel during
Reprocessing , or by the irradiation of
Americium 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 100kg 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. 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
