D. A. Malikov

New approaches to reprocessing of oxide nuclear fuel

Dissolution of UO2, U3O8, and solid solutions of actinides in UO2, including those containing Cs, Sr, and Tc, in weakly acidic (pH 0.9–1.4) aqueous solutions of Fe(III) nitrate or chloride was studied. Complete dissolution of the oxides is attained at a molar ratio of Fe(III) nitrate or chloride to uranium of 1.6 or 2.0, respectively. In the process, actinides pass into the solution in the form of U(VI), Np(V), Pu(III), and Am(III). At 60°C, actinide oxides dissolve in these media faster than at room temperature. In the solutions obtained, U(VI) and Pu(III) are stable both at room temperature and at elevated temperatures (60°C), and also at high U concentrations (up to 300 mg ml−1) typical of process solutions (6–8 M HNO3, ∼60–80°C). After the oxide fuel dissolution, U and Pu are recovered from the solution by peroxide precipitation. In so doing, the content of Fe, Tc, Cs, and Sr in the precipitate does not exceed ∼0.05 wt %. From the solution after the U and Pu separation, the fission lanthanides, Tc, Cs, and Sr can be recovered by precipitation of Fe hydroxides in the presence of ferrocyanide ions and can be immobilized in appropriate matrices suitable for long-term and environmentally safe storage.

Sorption of Np(V) on montmorillonite from solutions of MgCl2 and CaCl2

AbstractThe Np(V) distribution coefficients between montmorillonite and solutions of MgCl2 and CaCl2 were determined experimentally. The Np sorption decreases with increasing concentration of the supporting electrolyte. The sorption is very fast within the first several hours after the start of the experiment and then decelerates, reaching the equilibrium in approximately two weeks. The constants of binary ion exchange NpO2+-Mg2+ and NpO2+-Ca2+ on montmorillonite determined by fitting the experimental results are

Behavior of fission products in the course of dissolution of simulated spent nuclear fuel in iron nitrate solutions and of recovery of uranium and plutonium from the resulting solutions

\log K_{NpO_2^ + - Mg^{2 + } } = 0.083 \pm 0.03

Preparation of uranium oxides in nitric acid solutions by the reaction of uranyl nitrate with hydrazine hydrate

and

Sorption of plutonium in various oxidation states from aqueous solutions on Taunit carbon nanomaterial

\log K_{NpO_2^ + - Ca^{2 + } } = 0.106 \pm 0.014

Carbon nanotubes: Potential uses in radionuclide concentration

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