The processes occurring during accidental discharges of liquid uranium hexafluoride in the production rooms of the Chelnok-T section in the isotope separation plant at Siberian Chemical Combine are examined. The purification system, which uses KhP-MMD and KhP-MD chemical absorbers, permits localizing very quickly any accidental discharges of uranium hexafluoride and protect the atmosphere in the plant from harmful effects of fluorine-contained gases. The absorbers effectively catch HF (99.97%) and UF 6 (>99.9%) and have a high working capacity 30.5 mass% with respect to the fluorine ion. The system for catching and dispersing harmful contaminants provides the required sanitary standard with respect to atmospheric air on the territory of the plant and at the nearest populated points.

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The problem of the formation of uranium residue in spent sodium fluoride sorbent is studied. The mechanisms of the formation of un-desorbed uranium residue with thermal desorption of uranium hexafluoride from the surface sodium fluoride are examined. It is proved that hydrolysis of sorbed and gaseous uranium hexafluoride under the conditions of sublimate-separation production is impossible. The most likely mechanism of residue formation is partial reduction of hexavalent uranium, which is due to the chemical properties of the system UF 6 -NaF. A possible process of uranium reduction as a result of nuclear-chemical transformations requires study and experimental confirmation.Sorption technologies of catching, separation, decontamination, and salvaging of gaseous mixtures containing uranium hexafluoride, hydrogen fluoride, fluorine, and chlorine trifluoride as well as other volatile fluorides, using other fluoride adsorbents, for example, lithium fluoride, as the adsorbent granular sodium fluoride are finding increasing applications in industrial production and scientific research [1][2][3][4][5][6][7]. For this reason, some questions arising with the use sodium fluoride as the sorbent are general and require a scientific explanation and subsequent resolution.One problem is that the sorbent gradually loses capacity during multiple cycles of sorption-desorption of uranium hexafluoride. This problem is related with the accumulation in the sorbent of un-desorbed residues of uranium, which forms at the stage of desorption at elevated temperature with a strong complex compound of uranium and sodium fluorides being formed.The present work is devoted to a study and analysis of the formation and possible mechanisms of accumulation of un-desorbed uranium residue in the process of thermal desorption of uranium hexafluoride from sodium fluoride sorbent.The sorption of uranium hexafluoride on sodium fluoride occurs according to the reactions UF 6 + 2NaF = UF 6 ·2NaF;(1) UF 6 ·2NaF + UF 6 = 2(UF 6 ·NaF),and thermal desorption occurs according to the inverse reactions 2(UF 6 ·NaF) = UF 6 ·2NaF + UF 6 ;(3) UF 6 ·2NaF = UF 6 + 2NaF.

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