9/24/2023 0 Comments Nuclear fission productsAt the age of 5 years, the short-lived fission products contribute about 90% of the heat release and the minor actinides (americium and curium) for only 11%. They still emit excessive heat caused mainly by the decay of fission products contained therein. This highly mobile and volatile element was the main radioactive hazard immediately after the accident, since it is estimated that around 10% of fission products present in the reactor have been dispersed in the atmosphere.Ĭontainers of vitrified waste from the nuclear industry are too recent to have had time to age. Iodine-131 is one of the fresh fission products that were released during the Chernobyl accident. The accumulation of xenon-135 after a reactor shutdown becomes a poison for fission reactions and prevents its immediate restart. On the contrary, if the half-life is of a few years, the radioactive nuclei will accumulate because they do not have had time generally to disappear.Įxamples of very short-lived fission products are xenon-135 (period 8 hours) and iodine-131 (period of 8 days). Will be present at a given time only freshly produced such nuclei. When the period is very short – for example a few days – much of the radioactive nuclei have reached stability when the fuel is discharged from the core. These radioactive life times are to be compared with the residence time of the nuclear fuel in the reactors which is usually three years. Strontium-90 is one of the major radioactive fission products found in reactors. It will take about 10 times that long for the fragment radioactivity to disappear. The light fragment of 90 nucleons evolves rapidly at the beginning, but the cascade remains stranded with the fourth element, the strontium-90 whose period is around 30 years. Here, a heavy fragment of 143 nucleons passes through 3 intermediate nuclei, whose period ranges from 14 minutes to 33 days, to reach the stable nucleus terminal of the chain (neodymium-143). The products found in reactor spent fuels are no longer the fresh fragments of an Uranium-235 fission.
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