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Uranium-235 (235 U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nature as a primordial nuclide. Uranium-235 has a half-life of 703.8 million years.
uranium-235: 703.8 22.21 10 9 years 10 15 seconds potassium-40: 1.251 39.5 uranium-238: 4.468 141.0 thorium-232: 14.05 443 10 18 seconds (exaseconds) isotope half-life
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.
Uranium (92 U) is a naturally occurring radioactive element (radioelement) with no stable isotopes.It has two primordial isotopes, uranium-238 and uranium-235, that have long half-lives and are found in appreciable quantity in Earth's crust.
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235 U) has been increased through the process of isotope separation.Naturally occurring uranium is composed of three major isotopes: uranium-238 (238 U with 99.2732–99.2752% natural abundance), uranium-235 (235 U, 0.7198–0.7210%), and uranium-234 (234 U, 0.0049–0.0059%).
The long half-life of uranium-238 ... Uranium-235 is important for both nuclear reactors and nuclear weapons, because it is the only uranium isotope existing in ...
Uranium mining companies such as Cameco, ... with $235 million in cash and a burn rate of only $26 million. That gives the stock a nine-year lifespan so long as it's careful with its cash ...
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]