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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 compounds are compounds formed by the element uranium (U). Although uranium is a radioactive actinide, its compounds are well studied due to its long half-life and its applications. It usually forms in the +4 and +6 oxidation states, although it can also form in other oxidation states.
They estimated a metallic sphere of uranium-235 with a radius of 2.1 centimetres (0.83 in) could suffice. This amount represented approximately 1 kilogram (2.2 lb) of uranium-235. [31] These results led to the Frisch–Peierls memorandum, which was the initial step in the development of the nuclear arms programme in Britain. This marked the ...
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%).
Many contemporary uses of uranium exploit its unique nuclear properties. Uranium is used in nuclear power plants and nuclear weapons because it is the only naturally occurring element with a fissile isotope – uranium-235 – present in non-trace amounts.
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]
For uranium, it uses a cold molecular beam with UF 6 in a carrier gas, in which the 235 UF 6 is selectively excited by an infrared laser near 16 μm. In contrast to the excited molecules, the nonexcited heavier isotopic molecules tends to form clusters with the carrier gas, and these clusters stay closer to the axis of the molecular beam, so ...
In fact, 235 U is the only naturally occurring fissile nucleus. [4] Because natural uranium is only about 0.72% 235 U by mass, it must be enriched to a concentration of 2–5% to be able to support a continuous nuclear chain reaction [5] when normal water is used as the moderator. The product of this enrichment process is called enriched uranium.