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Plutonium-238 (238 Pu or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years. Plutonium-238 is a very powerful alpha emitter ; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units .
U-232 hazards, a result of its highly radioactive decay products such as thallium-208, are significant even at 5 parts per million. Implosion nuclear weapons require U-232 levels below 50 PPM (above which the U-233 is considered "low grade"; cf. "Standard weapon grade plutonium requires a Pu-240 content of no more than 6.5
For instance, 3.6 kg of plutonium-238 undergoes the same number of radioactive decays per second as 1 tonne of plutonium-239. Since the morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly the same, [ 55 ] plutonium-238 is around 275 times more toxic by weight than plutonium-239.
The testing, completed by the Jefferson Parkway Public Highway Authority in preparation for road construction, observed one soil sample with a plutonium level of 264 picocuries per gram. For reference, the Rocky Flats remediation standard is 50 picocuries per gram. A second sample registered just 1.5 picocuries of plutonium per gram. [48]
Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion, and its decay products are naturally found in some concentrated ores of uranium, [52] such as the natural nuclear fission reactor in Oklo, Gabon. [53]
Plutonium–gallium alloy (Pu–Ga) is an alloy of plutonium and gallium, used in nuclear weapon pits, the component of a nuclear weapon where the fission chain reaction is started. This alloy was developed during the Manhattan Project .
The most stable are plutonium-244 with a half-life of 80.8 million years; plutonium-242 with a half-life of 373,300 years; and plutonium-239 with a half-life of 24,110 years; and plutonium-240 with a half-life of 6,560 years. This element also has eight meta states; all have half-lives of less than one second. The known isotopes of plutonium ...
The higher the burnup, the more plutonium is present in the spent fuel, but the available fissile plutonium is lower. Typically about one percent of the used fuel discharged from a reactor is plutonium, and some two thirds of this is fissile (c. 50% 239 Pu, 15% 241 Pu).