Search results
Results From The WOW.Com Content Network
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 ...
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 ...
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 ...
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 three long-lived nuclides are uranium-238 (half-life 4.5 billion years), uranium-235 (half-life 700 million years) and thorium-232 (half-life 14 billion years). The fourth chain has no such long-lasting bottleneck nuclide near the top, so almost all of the nuclides in that chain have long since decayed down to just before the end: bismuth-209.
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]
Pu-239 is produced artificially in nuclear reactors when a neutron is absorbed by U-238, forming U-239, which then decays in a rapid two-step process into Pu-239. [22] It can then be separated from the uranium in a nuclear reprocessing plant. [23] Weapons-grade plutonium is defined as being predominantly Pu-239, typically about 93% Pu-239. [24]