Thermal properties of MnO-Al2O3 doped UO2 fuel pellets

Improving fuel performance to reduce fission gas release and increase resistance to PCI (pellet cladding interaction) is a technical challenge. Both goals can be achieved with large grain microstructures, since grain size enlargement is expected to enhance fuel plasticity as well as fission gas retention capability. Many researchers have investigated the effects of the processing parameters on the grain size of UO2 pellets. Those parameters include the additives, a higher sintering temperature, a longer sintering time, the sintering atmosphere, and so on. Among those, the technology regarding the doping of additives has been studied widely because this technology can increase the grain size significantly and is quite compatible with an industrial pellet fabrication process. The oxide additives (such as Nb2O5, TiO2, MgO, SiO2 and the corundum type of M2O3 with M= Al, Cr, etc.) have been known to promote a grain growth of UO2. Doped cations in the UO2 matrix or grain boundary enhance the chemical mobility of the U cation thereby promoting the sintering ability and the grain growth. The solubility of doped cations and their valence state are determined directly by the thermodynamic state of the sintering conditions. Thermal properties are one of the most important properties of nuclear fuel. Thermal diffusivity and thermal expansion of MnO-Al2O3 doped UO2 fuel pellets is unknown. This paper describes the thermal diffusivity and thermal expansion of MnO-Al2O3 doped UO2 pellets with a large grain size