Mass spectrometric study of the laser‐evaporated Fe–Zr–O system up to 3300 K

Abstract Material systems such as U–Zr–O, Fe–Zr–O, and Zr–O have been recognized as fundamental for the analysis of in‐vessel nuclear fuel debris behavior during a severe meltdown accident. In the present work, the evaporation behavior of ZrO 2 and Zr–Fe–O systems are investigated using heating with laser pulses of millisecond duration and time‐of‐flight mass spectrometry. The relative partial pressures of main species of vapor over ZrO 2 and ZrO 2 –FeO systems were measured at temperatures above 2750 K. The temperature dependence of O/Zr atomic ratio in vapor over zirconia was analyzed: it turned out that evaporation occurs in a noncongruent mode at temperatures above 3000 K. Evaporation of the Zr–Fe–O system was greatly affected by the fast evaporation of FeO, implying that the atomic Zr/Fe ratio, less than 0.1 below 3000 K, significantly increased with temperature. Moreover, the ratios of main vapor components were defined only by the surface temperature, independent of the zirconia sample origin.