Thermodynamic Factors Affecting UC_1-xN_xIrradiation and Synthesis

摘要

There is interest in attempting to synthesize nearly pure uranium nitride (UN) kernels for high-temperature gas-cooled reactor (HTGR) fuel. Because the proposed process involves carbothermic conversion of a urania-carbon mixture in nitrogen and because there is a complete ideal solution of uranium carbide (UC) and UN, which is written as UC{sub 1-x}N{sub x}, the practical value of x for fuel irradiation needs to be determined. Insight is to be gained by relevant thermodynamic calculations of carbide-nitride equilibria for the fuel and fission product systems. The equilibria are readily compared on the nitrogen-based Ellingham diagram, which, in turn, provides guidance in interpreting past irradiations and in synthesis of the UC{sub 1-x}N{sub x} kernels.