Expression of Cytochrome c3 from Desulfovibrio vulgaris in Plant Leaves Enhances Uranium Uptake and Tolerance of Tobacco

Cytochrome c3 (uranyl reductase) from Desulfovibrio vulgaris can reduce uranium in bacterial cells and in cell-free systems. This gene was introduced in tobacco under control of the RbcS promoter, and the resulting transgenic plants accumulated uranium when grown on a uranyl ion containing medium. The uptaken uranium was detected by EM in chloroplasts. In the presence of uranyl ions in sublethal concentration, the transgenic plants grew phenotypically normal while the control plants’ development was impaired. The data on uranium oxidation state in the transgenic plants and the possible uses of uranium hyperaccumulation by plants for environmental cleanup are discussed.

CATALYTIC OXIDATION OF FERROUS IRON TO INCREASE THE EFFICIENCY OF URANIUM LEACHING

Currently, enterprises of the metallurgical complex in Kazakhstan are faced with the problem of raw materials quality and the impossibility of productive processing of a number of ores. In recent years, not a single significant mineral deposit has been discovered, and previously discovered deposits are not of industrial interest, due to the low content of mineral components. «Kazatomprom» enterprises producing uranium by in-situ leaching method (ISL) were no exception. Today, the metal content in productive solutions is steadily decreasing; to increase the concentration of uranium production, it is necessary to increase the amount of reagent consumption, which leads to significant costs. The cost of uranium in the world market has decreased, significant production costs lead to a decrease in the profitability of production. The mechanism of uranium oxidation by iron ions is catalytic in nature. To regenerate iron, air oxygen was supplied to the leaching solution along with the oxidizing agent. The paper presents the results of studies on the possibility of intensifying ISL of uranium by introducing sodium nitrite into the leaching solution with additional supply of compressed air or oxygen to the leaching solution to ensure the catalytic oxidation of iron (II) ions by dissolved oxygen. The positive effect of stirring is proven. Research works at the testing ground with simultaneous supply of sodium nitrite and pure oxygen to LS allowed reaching 1.0 and 1.2 g/l Fe (III) concentrations. Key words: uranium, in-situ leaching, leaching solution, sodium nitrite, oxidation.

Modeling of Nuclear Waste Forms: State-of-the-Art and Perspectives

ABSTRACTComputational modeling is an important aspect of the research on nuclear waste materials. In particular, atomistic simulations, when used complementary to experimental efforts, contribute to the scientific basis of safety case for nuclear waste repositories. Here we discuss the state-of-the-art and perspectives of atomistic modeling for nuclear waste management on a few cases of successful synergy of atomistic simulations and experiments. In particular, we discuss here: (1) the potential of atomistic simulations to investigate the uranium oxidation state in mixed-valence uranium oxides and (2) the ability of cementitious barrier materials to retain radionuclides such as 226Ra and 90Sr, and of studtite/metastudtite secondary peroxide phases to incorporate actinides such as Np and Am. The new contribution we make here is the computation of the incorporation of Sr by C-S-H (calcium silicate hydrate) phases.

Theoretical investigation of U(i) arene complexes: is the elusive monovalent oxidation state accessible?

With the goal to extend the uranium oxidation state, relativistic DFT unravels an energetically favored U(i) complex of a heterocalix[4]arene.

Quantifying small changes in uranium oxidation states using XPS of a shallow core level

Quantification of U(iv), U(v), and U(vi) in UO2+x using the 5d XPS.