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The fissile isotope uranium-235 fuels most nuclear reactors.When 235 U absorbs a thermal neutron, one of two processes can occur.About 85.5% of the time, it will fission; about 14.5% of the time, it will not fission, instead emitting gamma radiation and yielding 236 U. [1] [2] Thus, the yield of 236 U per 235 U+n reaction is about 14.5%, and the yield of fission products is about 85.5%.
uranium-236: 23.42 739 10 15 seconds (petaseconds) isotope half-life 10 6 years 10 15 seconds niobium-92: 34.7 1.10 plutonium-244: 80 2.5 samarium-146: 103 3.3 ...
28 Mg 233 U: 92 141 233.0396343(24) ... Uranium-236 has a half-life of about 23 million years; ... but is generally considered a nuisance and long-lived radioactive ...
The long half-life of uranium-238 ... Uranium-236 occurs in spent ... has set the permissible exposure limit for uranium exposure in the workplace as 0.25 mg/m 3 ...
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 three long-lived nuclides are uranium-238 (half-life 4.5 billion years), uranium-235 (half-life 700 million years) and thorium-232 (half-life 14 billion years). The fourth chain has no such long-lasting bottleneck nuclide near the top, so almost all of the nuclides in that chain have long since decayed down to just before the end: bismuth-209.
Natural uranium is made weapons-grade through isotopic enrichment. Initially only about 0.7% of it is fissile U-235, with the rest being almost entirely uranium-238 (U-238). They are separated by their differing masses. Highly enriched uranium is considered weapons-grade when it has been enriched to about 90% U-235. [citation needed]
A chart or table of nuclides maps the nuclear, or radioactive, behavior of nuclides, as it distinguishes the isotopes of an element.It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides that are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen.