New Experimental Data on Partial Pressures of Gas Phase Components over Uranium-Zirconium Carbonitrides at High Temperatures and Its Comparative Analysis

Abstract

Data from the literature were analyzed and experimental data were obtained on the sublimation of uranium-zirconium carbonitrides with different contents of carbon, nitrogen and oxygen impurities in a wide temperature range (1773–2323 K). The composition of the gas phase was determined and the analytical dependences of the partial pressures of its components on temperature were calculated. It was shown that the sublimation of uranium-zirconium carbonitrides occurs incongruently with the predominant loss of nitrogen, which led to a shift in their compositions to the side richer in carbon. The chemical mechanism of sublimation was considered, according to which oxygen impurities in these materials contribute to the additional release of nitrogen and the appearance of oxide components UO, UO2 and CO in the gas phase. The introduction of zirconium carbonitrides and an increase in the carbon content led to a decrease in the partial pressures of uranium monoxide and nitrogen, thereby increasing the thermal stability of materials.