Enthalpy of formation of U3Si2: A high-temperature drop calorimetry study

Abstract

U3Si2 is presently receiving consideration as a high density light water reactor fuel. A reliable knowledge of the formation enthalpy of U3Si2 not only helps study the thermal stability but also facilitate the modeling efforts by serving as a benchmark parameter for thermodynamic calculations of phase equilibria at high temperatures. Previous high temperature thermal analysis on U3Si2 laid the basis for us to conduct two types of high-temperature drop calorimetric measurements to determine its enthalpy of formation: oxide-melt drop-solution calorimetry and transposed temperature drop calorimetry, from which the results obtained are consistent. The determined standard enthalpy of formation of U3Si2 per mole atom, −33.2 ± 3.1 kJ/mol⋅at.%, is in good agreement with previously reported values obtained by other techniques. Our drop calorimetry methods will be used for thermodynamic studies of other U-Si compounds whose enthalpies of formation are not available.