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Around 99.284% of natural uranium's mass is uranium-238, which has a half-life of 1.41 × 10 17 seconds (4.468 × 10 9 years, or 4.468 billion years). [1] Due to its natural abundance and half-life relative to other radioactive elements , 238 U produces ~40% of the radioactive heat produced within the Earth. [ 2 ]
All three isotopes are radioactive (i.e., they are radioisotopes), and the most abundant and stable is uranium-238, with a half-life of 4.4683 × 10 9 years (about the age of the Earth). Uranium-238 is an alpha emitter, decaying through the 18-member uranium series into lead-206.
uranium-238: 4.468 141.0 thorium-232: 14.05 443 10 18 seconds ... Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 ...
Uranium-235 has a half-life of about 7.04 × 10 8 years; it is the next most stable uranium isotope after 238 U and is also predominantly an alpha emitter, decaying to thorium-231. [7] Uranium-235 is important for both nuclear reactors and nuclear weapons , because it is the only uranium isotope existing in nature on Earth in significant ...
96% of the mass is the remaining uranium: most of the original 238 U and a little 235 U. Usually 235 U would be less than 0.8% of the mass along with 0.4% 236 U. Reprocessed uranium will contain 236 U, which is not found in nature; this is one isotope that can be used as a fingerprint for spent reactor fuel.
The method relies on two separate decay chains, the uranium series from 238 U to 206 Pb, with a half-life of 4.47 billion years and the actinium series from 235 U to 207 Pb, with a half-life of 710 million years.
On rare occasions, earlier in geologic history when uranium-235 was more abundant, uranium ore was found to have naturally engaged in fission, forming natural nuclear fission reactors. Uranium-235 decays at a faster rate (half-life of 700 million years) compared to uranium-238, which decays extremely slowly (half-life of 4.5 billion years ...
Enriched uranium produced at LLNL plant was collected as nuggets the size and thickness of several quarters. The HEU feedstock can contain unwanted uranium isotopes: 234 U is a minor isotope contained in natural uranium (primarily as a product of alpha decay of 238 U —because the half-life of 238 U is much larger than that of 234