Search results
Results From The WOW.Com Content Network
The fissile isotope uranium-235 fuels most nuclear reactors.When 235 U absorbs a thermal neutron, one of two processes can occur.About 85.5% of the time, it will fission; about 14.5% of the time, it will not fission, instead emitting gamma radiation and yielding 236 U. [1] [2] Thus, the yield of 236 U per 235 U+n reaction is about 14.5%, and the yield of fission products is about 85.5%.
uranium-236: 23.42 739 10 15 seconds (petaseconds) isotope half-life 10 6 years 10 15 seconds niobium-92: 34.7 1.10 plutonium-244: 80 2.5 samarium-146: 103 3.3 ...
Uranium-236 has a half-life of about 23 million years; and is neither fissile with thermal neutrons, nor very good fertile material, but is generally considered a nuisance and long-lived radioactive waste. It is found in spent nuclear fuel and in the reprocessed uranium made from spent nuclear fuel.
Uranium-236 occurs in spent nuclear fuel when neutron capture on 235 U does not induce fission, or as a decay product of plutonium-240. Uranium-236 is not fertile, as three more neutron captures are required to produce fissile 239 Pu, and is not itself fissile; as such, it is considered long-lived radioactive waste. [115]
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.
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%).
Fission product yields by mass for thermal neutron fission of U-235 and Pu-239 (the two typical of current nuclear power reactors) and U-233 (used in the thorium cycle). This page discusses each of the main elements in the mixture of fission products produced by nuclear fission of the common nuclear fuels uranium and plutonium.
96% of the mass is the remaining uranium: most of the original 238 U and a little 235 U. Usually 235 U would be less than 0.8% of the mass along with 0.4% 236 U. Reprocessed uranium will contain 236 U , which is not found in nature; this is one isotope that can be used as a fingerprint for spent reactor fuel.