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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 is the only naturally occurring fissile element in non-trace amounts, ... At 10 mg/m 3, uranium is immediately dangerous to life and health. [128]
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%).
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]
Enriching uranium means increasing the percentage of uranium-235, the isotope of uranium that can be used in nuclear fission. Show comments. Advertisement. Advertisement. Holiday Shopping Guides.
Uranium-235 makes up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a fission chain reaction. It is the only fissile isotope that is a primordial nuclide or found in significant quantity in nature. Uranium-235 has a half-life of 703.8 million years.
The term Strategic Special Nuclear Material (SSNM) refers to Uranium-235 contained in uranium enriched above 20 percent (Highly Enriched Uranium), as well as any concentration of Uranium-233 or Plutonium. [1] The distinction between SNM and SSNM is due to the fact that uranium-235 is typically found mixed with other isotopes such as Uranium-238.
Pu-239 decays to U-235 which is suitable for weapons and which has a very long half-life (roughly 10 9 years). Thus plutonium may decay and leave uranium-235. However, modern reactors are only moderately enriched with U-235 relative to U-238, so the U-238 continues to serve as a denaturation agent for any U-235 produced by plutonium decay.