Research on the grain growth and the mechanism of (U,Ti)O2 dispersion fuel microspheres

This paper studies the preparation of UO2 dispersion fuel microspheres with 0.3 wt% of doped titanium by the sel–gol method. The experimental results show that between 1250 °C and 1450 °C, grain growth speeds are different with a rapid growth of some grains and a “double peaks” feature of grain sizes distribution, while at 1550 °C, the grain sizes have normal distribution with the average grain size of about 42 μm. Based on the calculation, between 1250 and 1550 °C, the average activation energy of the grain growth of (U,Ti)O2 microspheres, Ea, was 232.79 kJ/mol, which is significantly lower than that of the UO2 microspheres. In the later sintering period of (U,Ti)O2 microspheres, U4O9 is formed in some parts of the microspheres, accelerating the U-atom diffusion rate and the grain growth.