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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%).
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]
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 ...
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 ...
Mixed oxide, or MOX fuel, is a blend of plutonium and natural or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to low enriched uranium (LEU) fuel used in the light water reactors which predominate nuclear power generation.
Its blend of oxides of plutonium and uranium constitutes an alternative to the low enriched uranium fuel predominantly used in light water reactors. Since uranium is present in mixed oxide, although plutonium will be burnt, second generation plutonium will be produced through the radiative capture of uranium-238 and the two subsequent beta ...
On the other hand, their fuel requires more highly enriched uranium, typically up to 20% U-235, [1] although some use 93% U-235; while 20% enrichment is not generally considered usable in nuclear weapons, 93% is commonly referred to as "weapons-grade". They also have a very high power density in the core, which requires special design features.
While heavy water is very expensive to isolate from ordinary water (often referred to as light water in contrast to heavy water), its low absorption of neutrons greatly increases the neutron economy of the reactor, avoiding the need for enriched fuel. The high cost of the heavy water is offset by the lowered cost of using natural uranium and/or ...