- Plutonium-244
Plutonium -244 has ahalflife of 80 million years. This is longer than any of the otherisotopes of plutonium . In fact, it is longer than anyactinide except for the three naturally abundant onesU-235 (700my),U-238 , andThorium-232 , longer than any otherisotope s exceptsamarium -146 (103my),potassium -40 (1.25by), and a number of nearly stable isotopes with halflives much longer than theage of the universe .Some studies have claimed to detect a few atoms of
primordial Pu-244. As theage of the Earth is about 50 half-lives, the amount of Pu-244 left would be very small. However, since Pu-244 cannot be easily produced by natural neutron capure in low neutron activity environment of uranium ores (see below), its presence is difficult to explain by any other means than creation byR process nucleosynthesis in supernovae.Unlike
Pu-238 ,Pu-239 ,Pu-240 ,Pu-241 , andPu-242 , 244Pu is not produced in quantity by thenuclear fuel cycle , because furtherneutron capture on 242Pu produces 243Pu which has a short halflife (5 hours) and quicklybeta decay s toamericium -243 before having much opportunity to further capture neutrons in any but very high neutron flux environments.
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