Thermal Expansion of 〈UN〉, 〈UO2〉, 〈UO2·ThO2〉, and 〈ThO2〉

Abstract

The thermal expansion characteristics of polycrystalline 〈UN〉, 〈UO2〉, 〈UO2·ThO2〉 solid solution, and 〈ThO2〉 were determined between room temperature and ca 1000°C by means of x-ray diffraction techniques. For the range 26° to 1000°C, the values of the average linear thermal expansion coefficients (ᾱ×106/∘C) are 8.61, 10.52, 10.18, and 9.32, respectively. A comparison of the observed 〈UO2·ThO2〉 lattice constants with those calculated by the method of E—an Zen indicates that the solid solution becomes less ideal as the temperature increases.