Partial Pressures of Gas Phase Components over Uranium-Zirconium Carbonitrides at High Temperatures

What is it about?

The high-temperature properties of uranium dioxide, a fuel currently used in various types of reactors, have been studied in much detail. Less studied among those used in practice were carbide fuels—uranium mono and dicarbide. Fuels based on uranium mononitride, as well as carbonitrides, although they were recognized as promising for use in certain types of nuclear power plants, for example, fast neutron reactors

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Photo by peter bucks on Unsplash

Photo by peter bucks on Unsplash

Why is it important?

An analysis of the experimental data obtained in this work and their comparison with the literature data on the sublimation of uranium-zirconium carbonitrides with different contents of carbon, nitrogen, and oxygen impurities at high temperatures showed that the sublimation of these materials occurs incongruently with a predominant loss of nitrogen, which led to a shift in their initial compositions in the direction of the phase that was richer in carbon. The gas phase in this case had a complex composition, which included: nitrogen, uranium, uranium monoxide, uranium dioxide, uranium mononitride and atomic zirconium. The considered chemical mechanism of sublimation of the studied materials indicated that oxygen impurities in them contributed to the additional release of nitrogen and the appearance of oxide components in the gas phase: UO, UO2 and CO. The introduction of zirconium carbonitrides and an increase in the carbon content (within the concentration regions U(0.9–1.0)Zr(0–0.1)(C(0.3–0.63)N(0.34–0.68)O(0.01–0.03)(0.92–0.97)) contributed to a decrease in the partial pressures of uranium monoxide and nitrogen, thereby increasing the thermal stability of this kind of nuclear fuel. So, this nuclear fuel has prospective applications in reactors with high burn-up rates.

Perspectives