Urania Vapor Composition at Very High Temperatures

Due to the chemically unstable nature of uranium dioxide its vapor composition at very high temperatures is, presently, not sufficiently studied though more experimental knowledge is needed for risk assessment of nuclear reactors. We used laser vaporization coupled to mass spectrometry of the produced vapor to study urania vapor composition at temperatures in the vicinity of its melting point and higher. The very good agreement between measured melting and freezing temperatures and between partial pressures measured on the temperature increase and decrease indicated that the change of stoichiometry during laser heating was very limited. The evolutions with temperature (in the range 2800-3400 K) of the partial pressures of the main vaporspecies (UO2, UO3 and UO2 +) were compared with theoretically predicted evolutions for equilibrium non-congruent gas-liquid and gas-solid phase coexistence and showed very good agreement. The measured main relative partial pressure ratios around 3300 K all agree withcalculated values for total equilibrium between condensed and vapor phase. It is the first time the three main partial pressure ratios above stoichiometric liquid urania are measured at the same temperature under conditions close to equilibrium non-congruent gas-liquid phase coexistence.

PFLIEGER Rachel;  COLLE Jean-Yves;  IOSILEVSKIY Igor;  SHEINDLIN Michael; 

2011-10-26

AMER INST PHYSICS

JRC61838

0021-8979,   

http://dx.doi.org/10.1063/1.3533439,    https://publications.jrc.ec.europa.eu/repository/handle/JRC61838,   

10.1063/1.3533439,