Densification kinetics and sintering behavior of UO 2 and 0.5 wt.%MnO‐doped UO 2

Abstract In this work, the sintering kinetics of pure UO 2 and 0.5 wt.%MnO‐doped UO 2 was studied by a high‐temperature dilatometer heated up to 1500°C. In addition, the sintering behavior of pure UO 2 and 0.5 wt.%MnO‐doped UO 2 was studied by pressureless sintering technique. The results showed that MnO doping enhanced the grain boundary diffusion of UO 2 , which can effectively decrease the densification temperature and promote grain growth. The sintering temperature of UO 2 was significantly reduced by about 200°C with the addition of 0.5 wt.%MnO. The microscopic morphology studies showed that there were still fine particles agglomerated, forming sintered spheres in the matrix even if no severe agglomeration and bimodal size distribution were observed in raw UO 2 powder. The microstructure evolution of the sintered sphere and UO 2 matrix during the densification process was studied by isothermal sintering. Finally, the present analyses indicated that the densification of UO 2 matrix can be accelerated by adding MnO or increasing the sintering temperature, thus improving the densification inhomogeneity of UO 2 matrix.