Physicochemical investigation and thermodynamics of oxide compounds of uranium and phase for immobilization of radionuclides

The present work presents the results of investigating oxide compounds of uranium obtained in thermodynamic field over the past few years. There is realized crystal chemistry systematization of studied compounds. The temperature dependences of heat capacities at constant pressure for 27 compounds in a temperature interval from 7 to 350 K and for 10 compounds between 80 and 350 K were studied in an adiabatic vacuum calorimeter. The standard enthalpies of formation at T = 298.15 K of 200 inorganic compounds were determined first by the method of reaction calorimetry. Several mathematical models having a predictive power and describing the behavior of compounds in “precipitate–solution”, “crystal–liquid” and “individual phase–solid solution” systems were suggested.

Research highlights▶ The developed techniques allowed obtaining in total more than 300 compounds. ▶ Crystal chemistry systematization of studied compounds is realized. ▶ The standard enthalpies of formation of 200 inorganic compounds were determined first. ▶ Several mathematical models describing the behavior of compounds were developed.