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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 (0.7% U235) in light-water reactor: 443,000: 35%: Ta-180m isomer: 41,340: 689,964: Metallic hydrogen (recombination energy) 216 [2] Specific orbital energy of Low Earth orbit (approximate) 33.0: Beryllium + Oxygen: 23.9 [3] Lithium + Fluorine: 23.75 [citation needed] Octaazacubane potential explosive: 22.9 [4] Hydrogen + Oxygen ...
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]
2 ion represents the uranium(VI) state and is known to form compounds such as uranyl carbonate, uranyl chloride and uranyl sulfate. UO 2+ 2 also forms complexes with various organic chelating agents, the most commonly encountered of which is uranyl acetate .
The increased percentage of 234 U in enriched natural uranium is acceptable in current nuclear reactors, but (re-enriched) reprocessed uranium might contain even higher fractions of 234 U, which is undesirable. [30] This is because 234 U is not fissile, and tends to absorb slow neutrons in a nuclear reactor—becoming 235 U. [29] [30]
However, because of the low abundance of uranium-235 in natural uranium (which is overwhelmingly uranium-238), uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons and is fertile , meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor .
In this process, the uranium oxides are combined with fluorine to form uranium hexafluoride gas (UF 6). Next, the gas undergoes isotope separation through the process of gaseous diffusion, or in a gas centrifuge. This can produce low-enriched uranium containing up to 20% U-235 that is suitable for use in most large civilian electric-power reactors.
Separative work – the amount of separation done by a Uranium enrichment process – is a function of the concentrations of the feedstock, the enriched output, and the depleted tailings; and is expressed in units which are so calculated as to be proportional to the total input (energy / machine operation time) and to the mass processed.