Uranium dioxide (UO₂) has been broadly employed as nuclear fuel in nuclear reactors. However, the poor thermal conductivity of UO₂ compromises the safety of the reactor owing to possible sharp temperature gradients. Graphene oxide (GO) is a promising additive to improve the thermal conductivity of UO₂ owing to its excellent thermal performance.

This study aims to achieve uniform distribution of GO in UO₂ pellets, effectively controlling the doping amounts to enhance the thermal conductivity of UO₂ pellets.

GO-doped UO₂ powders with different doping amounts were prepared using solid-liquid mixing and ammonium diuranate (ADU) co-precipitation methods. After establishing the optimized powdering process, UO₂-GO composite fuel pellets were prepared by spark plasma sintering (SPS). Properties of the UO₂-GO composite fuel pellets, such as density, grain size, physical phase, and thermal conductivity, were examined using scanning electron microscope (SEM), energy dispersion spectrometer (EDS), metallographic microscope, laser pulse thermal conductivity meter, etc., and compared with those of conventional pure UO₂ pellets.

The results showed that the density of UO₂-GO pellets can reach up to 97.6% T.D.. The thermal conductivity of UO₂-GO pellets with 1.5 wt.% doped GO is 85.9% higher than that of conventional UO₂ pellets at 1 000 ℃. The grain size of the UO₂-GO pellets is uniform, and the GO is homogeneously distributed at the grain boundary to form a bridging thermal conduction network.

The thermal conductivity of UO₂ pellets is successfully improved through GO doping.