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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.
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]
Special nuclear materials have plutonium, uranium-233 or uranium with U 233 or U 235 that has a content found more than in nature. Source material is thorium or uranium that has a U 235 content equal to or less than what is in nature. Byproduct material is radioactive material that is not source or special nuclear material.
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 uranium-235 nucleus can split in many ways, provided the atomic numbers add up to 92 and the mass numbers add up to 236 (uranium-235 plus the neutron that caused the split). The following equation shows one possible split, namely into strontium-95 ( 95 Sr), xenon-139 ( 139 Xe), and two neutrons (n), plus energy: [ 7 ]
The prototype KRUSTY 1 kW e Kilopower reactor weighs 134 kg and contains 28 kg of 235 U. The space-rated 10 kW e Kilopower for Mars is expected to have a mass of 1500 kg in total (with a 226 kg core) and contain 43.7 kg of 235 U. [5] [11] Nuclear reaction control is provided by a single rod of boron carbide, which is a neutron absorber.
Yellowcake (also called urania) is a type of powdered uranium concentrate obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before fuel fabrication or uranium enrichment. Yellowcake concentrates are prepared by various extraction and ...
Uranium-235, the fissile isotope of uranium used in nuclear reactors, makes up about 0.7% of uranium from ore. It is the only naturally occurring isotope capable of directly generating nuclear power. While uranium-235 can be "bred" from 234 U, a natural decay product of 238