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Krypton-85, with a half-life 10.76 years, is formed by the fission process with a fission yield of about 0.3%. Only 20% of the fission products of mass 85 become 85 Kr itself; the rest passes through a short-lived nuclear isomer and then to stable 85 Rb. If irradiated reactor fuel is reprocessed, this radioactive krypton may be released into ...
Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233. Plutonium-239 has a half-life of 24,110 years. [1]
Illustration of the concept of "critical mass" in respects to nuclear weapons design. The circles represent spheres of critical material (enriched uranium or plutonium), arrows represent neutron paths, and stars represent fission reactions. In the top frame, there is too little active material and so the fission reaction quickly ends.
Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion , and its decay products are naturally found in some concentrated ores of uranium, [ 54 ] such as the natural nuclear fission reactor in Oklo , Gabon . [ 55 ]
Weapons-grade plutonium is defined as being predominantly Pu-239, typically about 93% Pu-239. [24] Pu-240 is produced when Pu-239 absorbs an additional neutron and fails to fission. Pu-240 and Pu-239 are not separated by reprocessing. Pu-240 has a high rate of spontaneous fission, which can cause a
Plutonium-240 has a high rate of spontaneous fission, raising the background neutron radiation of plutonium. Plutonium is graded by proportion of 240 Pu: weapons grade (<7%), fuel grade (7–19%) and reactor grade (>19%). Lower grades are less suited for bombs and thermal reactors but can fuel fast reactors.
The odd numbered fissile plutonium isotopes present in spent nuclear fuel, such as Pu-239, decrease significantly as a percentage of the total composition of all plutonium isotopes (which was 1.11% in the first example above) as higher and higher burnups take place, while the even numbered non-fissile plutonium isotopes (e.g. Pu-238, Pu-240 and ...
Red: uranium-238, light green: plutonium-239, black: fission products. Intensity of blue color between the tiles indicates neutron density A traveling-wave reactor ( TWR ) is a proposed type of nuclear fission reactor that can convert fertile material into usable fuel through nuclear transmutation , in tandem with the burnup of fissile material.