Plutonium-238
Plutonium-238 oxide pellet glowing from its own heat
Plutonium-238 (also known as Pu-238 or 238Pu) is a radioactive isotope of plutonium that has a half-life of 87.7 years.
Plutonium-238 is a very powerful alpha emitter. This makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units – one gram of plutonium-238 generates approximately 0.5 W of thermal power.
Plutonium-238 was the first isotope of plutonium to be discovered. It was synthesized by Glenn Seaborg and associates in December, 1940 by bombarding uranium-238 with deuterons, creating neptunium-238, which then decays to form plutonium-238. Plutonium-238 decays to uranium-234 and then further along the radium series to lead-206. Plutonium-238 was produced by irradiating Neptunium-237 (half life 2.144M years), which is a by-product of the production of Plutonium-239 weapons-grade material. As produced by Savannah River in their weapons reactor, shut down in 1988, Plutonium-238 was mixed with about 16% Plutonium-239.
The first application was its use in a weapons component made at Mound for the Weapons Design Agency Lawrence Livermore Laboratory (LLL). Mound was chosen for this work because of its experience in producing the Polonium-210 fueled Urchin initiator and its work with several heavy elements in a Reactor Fuels program. Two Mound scientists spent 1959 at LLL in joint development while the Special Metallurgical Building was constructed at Mound to house the project. Meanwhile the first sample of Plutonium-238 came to Mound in 1959.
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