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In a fission nuclear reactor, uranium-238 can be used to generate plutonium-239, which itself can be used in a nuclear weapon or as a nuclear-reactor fuel supply. In a typical nuclear reactor, up to one-third of the generated power comes from the fission of 239 Pu, which is not supplied as a fuel to the reactor, but rather, produced from 238 U. [5] A certain amount of production of 239
The uranium in yellowcake is almost exclusively (>99%) U-238, with very low radioactivity. U-238 has a half-life of 4.468 billion years and emits radiation at a slow rate. This stage of processing is before the more radioactive U-235 is concentrated, so by definition, this stage of uranium has the same radioactivity as it did in nature when it ...
The breakthrough with plutonium was by Bretscher and Norman Feather at the Cavendish Laboratory. They realised that a slow neutron reactor fuelled with uranium would theoretically produce substantial amounts of plutonium-239 as a by-product. This is because uranium-238 absorbs slow neutrons and forms a short-lived new isotope, uranium-239.
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%).
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.
It became popular in the U.S. and uranium was widely used to color glassware until 1943, when the government started regulating its use so that they could save uranium to build atom bombs.
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]
234 U occurs in natural uranium as an indirect decay product of uranium-238, but makes up only 55 parts per million of the uranium because its half-life of 245,500 years is only about 1/18,000 that of 238 U. The path of production of 234 U is this: 238 U alpha decays to thorium-234. Next, with a short half-life, 234 Th beta decays to ...