Fig. 1. Process flowchart for UO₂ powder via ADU co-precipitation method (a) and solid-liquid mixing method (b)

Fig. 2. Process curve of spark plasma sintering for GO-doped UO₂ pellets

Fig. 3. Diagram of sampling position for doping uniformity test

Fig. 4. Element distribution of UO₂-GO powder for GO doping amounts of 0.5 wt.% (a), 1.5 wt.% (b) and 5.0 wt.% (c)

Fig. 5. SEM morphology of UO₂-GO powder for GO doping amounts of 0.5 wt.% (a), 1.5 wt.% (b) and 5.0 wt.% (c)

Fig. 6. Effects of different SPS sintering parameters on pellets properties

Fig. 7. Metallographic structure of UO₂-GO pellets for GO doping amounts of 0.5 wt.% (a), 1.5 wt.% (b) and 5.0 wt.% (c)

Fig. 8. Thermal conductivity (a) and increase of thermal conductivity compared to those of conventional UO₂ pellets (b) for UO₂ pellets prepared under different conditions