Increase of fission gases above a certain limit can lead to fuel pin swelling and even puncture, so that fission gas measurement after discharging the fuel from the reactor is most important to make burn-up calculations, to study the nature of fuel inside the reactor, behaviour with pin materials, for effective utilization of fuel and also reactor safety. Despite the industrial applications of Krypton-85 and the relatively high prices of both Krypton and Xenon, they are not currently extracted from spent fuel to any appreciable extent even though Krypton and Xenon both become solid at the temperature of liquid nitrogen and could thus be captured in a cold trap if the flue gas of a voloxidation process were cooled by liquid nitrogen. Strictly speaking, the stage which is detected is the dissolution of used nuclear fuel in nitric acid, as it is at this stage that the krypton and other fission gases like the more abundant xenon are released. This krypton release can be detected and used as a means of detecting clandestine nuclear reprocessing. If irradiated reactor fuel is reprocessed, this radioactive krypton may be released into the air. Only 20% of the fission products of mass 85 become 85Kr itself the rest passes through a short-lived nuclear isomer and then to stable 85Rb. Krypton-85, with a half-life 10.76 years, is formed by the fission process withĪ fission yield of about 0.3%. Given that protons from this source are indistinguishable from protons from ternary fission or radiolysis of coolant water, their overall proportion is hard to quantify. Furthermore a tiny fraction of the free neutrons involved in the operation of a nuclear reactor decay to a proton and a beta particle before they can interact with anything else. If the first or only step of nuclear reprocessing is an aqueous solution (as is the case in PUREX) this poses a problem as tritium contamination cannot be removed from water other than by costly isotope separation. Lithium-6 produces tritium when hit by neutrons and is one of the main sources of commercially or militarily produced tritium. Another source of tritium is Helium-6 which immediately decays to (stable) Lithium-6. This is the main source of tritium from light water reactors. This ternary fission usually produces a very light nucleus such as helium (about 80% of ternary fissions produce an alpha particle) or hydrogen (most of the rest produce tritium or to a lesser extent deuterium and protium) as the third product. A small but non-negligible proportion of fission events produces not two, but three fission products (not counting neutrons or subatomic particles). ![]() These are found in used nuclear reactors and nuclear fallout. Neutron capture by materials of the nuclear reactor (shielding, cladding, etc.) or the environment (seawater, soil, etc.) produces activation products (not listed here). These are found mixed with fission products in spent nuclear fuel and nuclear fallout. ![]() Neutron capture by the nuclear fuel in nuclear reactors and atomic bombs also produces actinides and transuranium elements (not listed here). The isotopes are listed by element, in order by atomic number. 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. 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)
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