Preparation process and performance of graphene oxide-doped UO2 pellets

[Background] 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. [Purpose] 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. [Methods] 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. [Results] The results showed that the density of UO2GO 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. [Conclusions] The thermal conductivity of UO2 pellets is successfully improved through GO doping. © 2024 Science Press. All rights reserved.