Patent Number: 042016908
Section: summary

BACKGROUND TO THE INVENTION This invention relates to the processing of irradiated nuclear fuel and particularly to the dissolution of irradiated nuclear fuel in nitric acid prior to the reprocessing of the fuel. In one known process for the reprocessing of irradiated nuclear fuel the irradiated nuclear fuel material is first dissolved in nitric acid and the acid solution which contains uranium, plutonium and fission products is contacted with an organic solvent in a solvent extraction process which effects separation of the uranium and plutonium values from the fission products and from each other. During the dissolution of the irradiated fuel material gaseous fission products such as iodine 129, krypton and xenon are released. These gaseous fission products may present a hazard if released into the environment and they are preferably retained in the plant. SUMMARY OF THE INVENTION According to the present invention a process for the dissolution of irradiated nuclear fuel in nitric acid is operated under an atmosphere consisting essentially of carbon dioxide. The carbn dioxide may be circulated inside a plant in which the carbon dioxide is contained by alternatively condensing and evaporating at least a part of the atmosphere circulating in the plant in each of a pair of heat exchangers, one of said pair of heat exchangers being used to condense said part of the atmosphere whilst the other of said pair of heat exchangers is used to evaporate condensed carbon dioxide to provide a continuous driving force to effect circulation of the atmosphere around the plant. The carbon dioxide may be dried to remove moisture and cooled to remove condensible contaminants such as iodine before passing to the heat exchangers which may be purged to remove gases such as krypton and xenon which do not condense during the condensation of the carbon dioxide.