Choice of evaporation regimes and sample area influence are the most important factors during high-temperature tests of uranium mononitride. It is shown that as the sample area increases, the rate of mass loss is also rises. Significant increase in the rate of mass loss is observed with test regime change: study sample on the substrate at the top of the crucible instead at the bottom of the crucible. These experiments are
in agreement with the theoretical concepts of uranium nitride evaporation kinetics. Thus, it is necessary to make amendment for the surface area of the samples, as well as take into account evaporation regimes of the experiments to compare different results of thermal stability.