Physico-chemical properties of (U,Ce)O2

Abstract

The high-temperature X-ray diffraction analysis of (U,Ce)O2 with CeO2 contents ranging from 0 to 20 mol.% CeO2 was performed to obtain the variation of the linear thermal expansion coefficient with the CeO2 content. Ultrasonic pulse-echo measurements were also carried out from room temperature to 673 K to estimate the change in the mechanical properties of (U,Ce)O2 with the CeO2 content. The variation in the linear thermal expansion coefficient at the low CeO2 content region is more steep than that expected from the linear thermal expansion coefficient of UO2 and CeO2. The Young's and shear moduli of all (U,Ce)O2 were found to decrease with rising temperature. This was due to the increase of the bond length accompanied by the thermal expansion. Although the lattice parameter decreased with CeO2 content, the moduli of (U,Ce)O2 were found to decrease with increasing CeO2 content at room temperature. These results show that in the range from 0 to 20 mol.% of CeO2, as CeO2 content increases, the bottom of the potential energy in (U,Ce)O2 is shallower and broader.