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The nominal spherical critical mass for an untampered 235 U nuclear weapon is 56 kilograms (123 lb), [6] which would form a sphere 17.32 centimetres (6.82 in) in diameter. The material must be 85% or more of 235 U and is known as weapons grade uranium, though for a crude and inefficient weapon 20% enrichment is sufficient (called weapon(s)-usable).
Depleted uranium has an even higher concentration of the 238 U isotope, and even low-enriched uranium (LEU), while having a higher proportion of the uranium-235 isotope (in comparison to depleted uranium), is still mostly 238 U. Reprocessed uranium is also mainly 238 U, with about as much uranium-235 as natural uranium, a comparable proportion ...
Depleted uranium has an even higher concentration of 238 U, and even low-enriched uranium (LEU) is still mostly 238 U. Reprocessed uranium is also mainly 238 U, with about as much uranium-235 as natural uranium, a comparable proportion of uranium-236, and much smaller amounts of other isotopes of uranium such as uranium-234, uranium-233, and ...
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 only significant deviation from the 235 U to 238 U ratio in any known natural samples occurs in Oklo, Gabon, where natural nuclear fission reactors consumed some of the 235 U some two billion years ago when the ratio of 235 U to 238 U was more akin to that of low enriched uranium allowing regular ("light") water to act as a neutron ...
Of the 33 known radioactive primordial nuclides, two (235 U and 238 U) are isotopes of uranium. These two isotopes are similar in many ways, except that only 235 U is fissile (capable of sustaining a nuclear chain reaction of nuclear fission with thermal neutrons). In fact, 235 U is the only naturally occurring fissile nucleus. [4]
Unlike other isotopic dating methods, the "daughter" in fission track dating is an effect in the crystal rather than a daughter isotope.Uranium-238 undergoes spontaneous fission decay at a known rate, and it is the only isotope with a decay rate that is relevant to the significant production of natural fission tracks; other isotopes have fission decay rates too slow to be of consequence.
Both plutonium-239 and uranium-235 are obtained from Natural uranium, which primarily consists of uranium-238 but contains traces of other isotopes of uranium such as uranium-235. The process of enriching uranium , i.e. increasing the ratio of 235 U to 238 U to weapons grade, is generally a more lengthy and costly process than the production of ...