Thermal expansion of simulated thoria–urania fuel by high temperature XRD

The thermal expansion behavior of polycrystalline samples of ThO2–3.45% UO2 and SIMFUEL corresponding to burn-up of 43,000 MWd/Te has been investigated from room temperature to 1473 K, and for SIMFUEL corresponding to burn-up of 28,000 MWd/Te has been investigated from room temperature to 1173 K, using a high temperature X-ray diffraction (HTXRD). Linear and volumetric thermal expansion data like, percentage thermal expansion, average or mean coefficient of thermal expansion (CTE) was generated using the lattice parameters. It is observed that SIMFUEL has a lower lattice parameter compared to ThO2–3.45% UO2 and this is attributed to the dissolution of the rare earths and part of the Zr and Ce in fuel matrix. Also SIMFUEL has slightly higher thermal expansion than ThO2–3.45% UO2 and this is related to the lower melting point of SIMFUEL.