ИСТИНА

Modern methods of SNF reprocessing based on solvent extraction technology with a primary use as extractant solutions of TBP in hydrocarbon diluents. The constantly increasing depth of burn-up of reprocessed SNF leads to increase in radiation load on extractant, which leads to formation and accumulation of more radiolysis products in it, which worsen the hydrodynamics and selectivity of extraction process, as well as characteristics of fire and explosion hazard. An important role in formation of radiolysis products of extraction mixture is played by products of diluents radiation decomposition, especially short-chain hydrocarbons. Their derivatives present an increased danger, both in relation to uncontrollable chemical exothermic reactions – thermal explosion, and in relation to formation of a vapor-gas phase capable of ignition, because the partial vapor pressure of combustible liquid increases with a decrease in length of hydrocarbon chain. The aim of investigation was to study different ways of regeneration of radiation – degraded system “30% TBP-Isopar – M”. The efficiency of regeneration methods was evaluated by such parameters as hydrodynamic characteristics, composition of degradation products and the lower temperature limit of flame propagation of samples before and after regeneration. Ionizing radiation of radionuclides was simulated by irradiation at linear electron accelerator. The extractant solution after contacting with 4.3 mol / l nitric acid solution was irradiated by accelerated electrons to doses of 0.5, 1 and 2 Mgy. Plates of copolymer with phenazine coloring agents were used for dosimetry. The composition of radiation degradation products before and after regeneration was determined by IR spectroscopy and gas chromatography. Regeneration of irradiated samples was carried out with solutions of sodium carbonate and bicarbonate, guanidine and methylamine carbonates, ammonium carbonate both by simple mixing in a separating funnel with a submersible stirrer, and by means of a separator with an upper separation chamber. In addition to regeneration solutions tried methods of bubbling in the separator and distillation. During the regeneration of the extractant irradiated in a cyclic mode, usual contact of the guanidine solution and methylamine carbonates equally remove impurities and quickly delaminate the organic and aqueous phases. During the regeneration of the irradiated extractant in continuous mode, all tested aqueous washing solutions with the use of a separator significantly reduce the concentration of low-boiling products. The lowest content of lowboiling products is observed after regeneration with sodium carbonate solutions. When bubbling, the total number of low-boiling products (with an exit time of up to 5 minutes), passing into the gas phase, is reduced by 10 times. Acknowledgments: The work was partially funded by the Ministry of Science and Higher Education of the Russian Federation (topic № AAA-A16-116110910010-3).