| Abstract Scope |
Gadolinium (Gd) and europium (Eu) oxides have been extensively studied as burnable absorbers. Gd2O3 is very suitable, due to its high neutron cross-section of the Gd isotopes. Moreover, the addition of Gd is commonly used in boiling water reactors (BWR). Also, the Gd2O3 cubic phase is stable to 1200 °C, and readily forms a solid solution with the cubic UO2. Several studies have
focused on the dopant behavior, but discrepancies remain, such as micro-cracking. Additionally, the accommodation of Gd3+ depends on the oxygen availability, resulting in the formation of either vacancies or the formation of U5+. Here we prepared several sets of Gd and Eu-doped UO2, using solid-state synthesis (6, 10 and 15 wt%). Phase purity was determined via X-ray diffraction and elemental analysis. We performed thermal physical analysis (thermal diffusivity, heat capacity, dilatometry) to obtain thermal conductivity results. In addition, we used state-of-the-art
synchrotron X-ray Absorption Spectroscopy (XAS) to study the local structure and defects in doped-UO2. Our data shows that Gd and Eu doping greatly impacts the thermal conductivity due to the formation of defects in the UO2 lattice. XAS in addition, suggest the formation of vacancies. We will discuss in detail our results and the subtleties of UO2 defect chemistry and compare these to historical data. |