PRODUCTION AND RESEARCH OF TABLETS OF MIXED URANIUM, PLUTONIUM, AMERICIUM AND NEPTUNIUM NITRIDES

The method of carbothermic synthesis produced 260 g tablets of mixed nitrides of uranium, plutonium, americium and neptunium with a mass fraction of americium 0.61%. For the production of tablets were used uranium oxide manufactured by the water method, as well as plutonium dioxide containing impurities of uranium and americium oxides with a mass of 0.9 g americium, obtained by volumetric crystallization method in a NaCl — 2CsCl melt. Neptunium dioxide and americium oxide were added to the mixture of uranium and plutonium oxides before carbothermic synthesis. The resulting tablets had a density of 11.6-11.9 g / cm3. By methods of gamma-spectrometry, scanning electron microscopy and x-ray microanalysis is showed that the heat treatment of the mixture of the source chemicals - oxides of uranium, plutonium, americium, neptunium with carbon black at a temperature 1600-1500 °C for 72 h (24 h in nitrogen and 48 h in nitrogen-hydrogen atmospheres), and also the subsequent sintering synthesized by the press powders for 48 h at a temperature of 1800°C in nitrogen-hydrogen atmosphere doesn't leads in average to the significant losses of americium.

Thermodynamic analysis of the interaction of components in the Si–C–O system in the carbothermic synthesis of silicon carbide

Phase equilibria in the Si–C–O system at temperatures of 1400–1700°C were modeled to theoretically determine the optimal conditions for implementing our proposed method of carbothermic synthesis of silicon carbide in reactors with an autonomous protective atmosphere. It was found that, depending on the ratio between the initial components and the synthesis temperature, the equilibrium products of the synthesis can be various combinations of silicon carbide, a gas phase, residual amounts of silicon oxide and carbon, andan oxide melt formed at high temperatures.