Modeling of Changes in the Composition of Uranium–Zirconium Carbonitride with an Oxygen Impurity Depending on Temperature and Burnup

Thermodynamic modeling of changes in the chemical and phase composition of uranium–zirconium carbonitride nuclear fuel U0.9Zr0.1(C0.495N0.495O0.01)0.995 containing an oxygen impurity depending on the temperature (1600–2000 K) and burnup (1–10%) was performed. Under these conditions, accumulation of fission products in the fuel leads to the formation of a heterogeneous system consisting of a solid solution based on uranium–zirconium oxycarbonitride containing lanthanides and of separate condensed carbide, intermetallic, and oxide phases, of cesium and its iodide, of barium and its telluride, of strontium, and of technetium. The concentrations of these phases at the indicated temperatures and burnup levels were calculated.