[en] Nenadkevite samples from uranium bearing albitite and albitation zone of the samples containing the above-mentioned nenadkevite are investigated in detail. The samples are presented rather finely-dispersed products of hydrothermal-metasomatic and hypergeneous processes, therefore the methods of X-ray graphic electron microscopy and microdiffraction were applied for their investigation. Chemical composition and physical properties of the samples are described. The investigation results showed that nenadkevite formations present mainly finest mixtures of X-ray amorphic hydronasturane and urgite type, and more seldom, decrystallized uranium hydrooxides with uranium silicates having crystal structure of boltwoodite-kasolite. A relict uraninite is determined. These mixtures are considered to be formed at changing uranium-nasturane and uraninite oxides

[en] Studied has been post sedimentary uranium distribution in cenozoic sedimentary deposits of the Western Siberia by means of determination of uraniUm amounts in allochthonous leucoxene which initially did not contain uranium. The study of uranium distribUtion in selected minerals has been carried out with an aid of microradiographic analysis of sections. Investigation results and previously established experimental ability of titanium hydroxides to separation from solutions of uranium hydroxides permit to make a supposition that in nature Ti hydroxides are capable of uranium concentrating. Ti hydroxides are formed in the process of change of Ti-containing minerals. At infiltration of uranium-containing minerals with oxygen waters in grey-colour sediments uranium can be extracted by leucoxenes. The utmost U amounts are established in the intermediate zone on the boundary of oxidation-reduction conditions

No abstract available

[en] Electrodeposition of uranium, neptunium and thorium from isopropyl alcohol media was studied in some detail with a view to understanding the mechanism of electrodeposition of actinides from organic media. The deposits obtained by the electrodeposition of uranium, thorium and neptunium were examined by various techniques. The presence of a hydroxyl-rich layer at the cathode was detected using a phenolphathaline indicator. From the data gathered in this ivestigation it was concluded that these actinides are deposited as hydrolytic species from an organic medium as they are from an aqueous medium. (author)

[en] In oxidation zone of uranium deposit uranium hydroxides of the wolsendorfite group: calcuranoite, bauranoite, wolsendorfite and their varieties are studied. Chemical and microprobe analyses are carried out. It is established, that the minerals are encountered in the form of two generations. Early generation forms partial or complete pseudomorphosis over rich contrast pitchblende ores. The late one is encountered in the form of redeposited crystal aggregates in calcite-pitchblende streaks. Study in details of chemical composition of the group minerals permitted to establish the existence of a continuous isomorphous series with ultimate members calcuranoite and wolsendorfite with regular change in chemical and physical properties within the series. Existence of bauranoite-calcuranoite and bauranoite-wolsendorfite isomorphous series is assumed

[en] Hydrates or hydroxides have been confirmed primarily for the hexavalent uranium. Of the tetravalent uranium, the compound UO₂·xH₂O is known, the water content of which varies according to the conditions of preparation and drying. Studies of its formation, preparation, structure, magnetic susceptibility and chemical reactions are reviewed. Recent investigations have shown that a hydrate of U₃O₈ probably does not exist and the compound designated in the literature as U₃O₈xH₂O is a hydrate of composition UO_2.86nH₂O (where n = 0.5 and 1.5). Investigations of this compound's formation, preparation, optical properties, thermal stability and solubility are reviewed. The existence of four hydrates or hydroxides of uranium trioxide has been confirmed. They are UO₃nH₂O, where n = 0.5, 0.8, 1 and 2. They may be prepared by breaking down UO₄·xH₂O by hydrolysis of uranyl salts or hydrothermally from UO₃. Hydrothermal investigations in the range 25⁰C to 330⁰C, resulting in a phase diagram for the UO₂²⁺-UO₃-H₂O system, are reviewed. (UK)

[en] The thermodynamic model of uranium in situ leaching process at the stage of acidification was investigated. It was demonstrated that in the frontal zone of acid leaching solutions reduction of U(VI) up to U(IV) was possible due to the behavior of oxidation-reduction processes with the ferrous ions involved. At the same time uranium is precipitated as U(OH)₄. In order to eliminate the negative influence of ferrous iron ions, artificial oxidizers were proposed to be used not only at the stage of active leaching of cells but also at acidification stage of new process cells. (author)

[en] Ion exchange is performed by contacting a solution containing ions to be absorbed with a hydrous oxide of uranium in a suitable form. The hydrous oxide may be uranium dioxide or uranium hydroxide, and may be prepared by reducing a uranium species, precipitating the reduced species, and drying the precipitate to give the required hydrous oxide. (author)

[en] Experiments based on a modified MCC-3S test method were conducted to investigate the solubility of U(VI) hydroxide (the mineral schoepite) and Np(IV) hydrous oxide at ambient temperature. The solubility of U(VI) hydroxide was investigated in carbonate-free, oxidizing aqueous solutions in the pH range of 3 to 11. The measured concentrations of dissolved U confirm the amphoteric behavior of U(VI) hydroxide solid and the importance of anionic U(VI) hydroxyl complexes in accurately calculating the solubilities of U(VI) solids under basic pH conditions. the effect of fluoride complexation on the solubility of Np(IV) hydrous oxide was studied in carbonate-free, near-neutral to alkaline solutions that contained 100 ppM total F. For solutions in which sodium dithionite (Na₂S₂O₄) and metallic Fe were used as reducing agents, the addition of 100 ppM F had no measurable effect on the solubility of Np(IV) hydrous oxide

No abstract available