Search

Formulation of the forming paste for preparing unsupported granulated triuranium octoxide U3O8 was developed. The mixture contains U3O8 and (NH4)2U2O7 in a weight ratio from 1: 1 to 1: 1.5, and also water in an amount of 25–40 wt % relative to the sum of the dry components. Calcination of crude granules at 800–1100°С results in formation of strong ceramic granules with 57–45% open porosity, consisting of U3O8. Granulated U3O8 efficiently catalyzes the conversion of ammonium nitrate to nitrogen in an NH4NO3–H2O vapor–gas mixture with the addition of ammonium carbonate. The absence of support makes the catalyst composition more definite and simplifies its regeneration.

The complex Yb(BH3Me)3(THF) has been prepared and characterized by IR and 1H, 13C and 11B NMR spectroscopy. The crystal and molecular structures of the complex have been solved by single crystal XRD analysis. The vapor pressure as a function of temperature was measured in the batch mode.

It was demonstrated with an example of floodplain soil of the Yenisei River (Atamanovskii Isl.) that, in long-time percolation of the liquid phase through the soil, partial oxidation of the bioreduced iron with atmospheric oxygen strongly (by several times) increases the leaching of radiostrontium as compared to that under anaerobic conditions. The experiments were carried out on a laboratory setup allowing long-term controlled steady-state percolation of the liquid phase through a soil bed and collection of mobile soluble and colloid radiostrontium species at the outlet. Species coarser than 500 A were retained on a specially designed combined bilayer membrane operating in the contact ultrafiltration mode without applying external pressure. It was found that 92% of radiostrontium is leached from the soil with fine species (

Gleyzation-mediated leaching of radiostrontium from floodplain soils of the Krasnoyarsk Mining and Chemical Combine (MCC) activity zone [Atamanovskii Island (front part), Oseredysh Island (front part), and Berezovyi Island (rear part)] is studied with model systems. Leaching of radiostrontium from waterlogged soils is analyzed in terms of the model of anaerobic biosolubilization of gel films. The leaching of radiostrontium is found to correlate with that of iron, confirming the cosolubilization model. Addition of glucose (0.5%) as a stimulant for growth of iron-reducing microorganisms increases the dynamic coefficient of radiostrontium leaching, particularly in soils with lower organic matter content. The model experiments showed that the radiostrontium leaching rate from floodplain soil is higher by 2–3 orders of magnitude than that of radio-cesium, suggesting the possibility of escape of radiostrontium from the floodplain of the Yenisei River with the intrasoil runoff. This conclusion is supported by the experimental data on the 90Sr/137Cs ratio in the floodplain of the Yenisei River downstream of MCC (0.01–0.1).

Leaching of radiostrontium from soil under gleyzation is studied with a laboratory setup allowing controlled long-term percolation of the liquid phase through a soil sample and collection of mobile soluble and colloid species at the outlet. Introduction of a nutrient substrate for the growth of microorganisms promoting gleyzation enhances the leaching of radiostrontium from waterlogged soil. The results suggest joint solubilization of the macrocomponents of the clay-humus complex of the soil and associated radiostrontium under gleyzation. Data on the dynamic leaching and distribution coefficients show that, in the stagnant water regime, remobilization of strontium is less intensive than in the percolation mode. The gleyzation-mediated leaching of radiostrontium is suppressed after 2–2.5 months, which can be attributed to the inhibiting effect of Fe(II) accumulated in the system.

It is demonstrated in model experiments that in the presence of Ca ions (typomorphous cations of water of the Yenisei River) fulvic acids of floodplain soils and associated radionuclides (Am, Eu) form poorly soluble mixed Ca, Fe, Al(Am, Eu) fulvates. As a result, under the flooding conditions the migration of Am and Eu in the form of solubilized organomineral complexes is practically totally suppressed. With decreasing pH in the model system from 8 to 6 the mobility of the radionuclides noticeably increases.

The method was developed allowing quantitative extraction of fulvic acids from soil samples in the form close to native. Formation of gel-like and soluble forms of iron(III) fulvates in the systems containing equivalent amounts of iron(III) and fulvic acid was studied within pH range 1–9. The molecular structure of fulvates and the mechanism of transformation of gel to soluble forms was analyzed by IR spectroscopy. Distribution of microamounts of europium between gel-like iron fulvates and their solutions was studied. The correlation between phase distribution of europium and solubilization of iron(III) fulvates was analyzed.