The preparation and performance of graphene oxide-doped UO2 pellets

[Background]: Uranium dioxide (UO2) has been broadly employed as nuclear fuel in nuclear reactors. The poor thermal conductivity of UO2, however, reduces the safety of the reactor due to possible sharp temperature gradients. Graphene oxide (GO) is a kind of promising additive to improve the thermal conductivity of UO2 for its excellent thermal performance. [Purpose]: This work aimed at achieving uniform distribution of GO in UO2 pellets, effectively controlling the doping amounts, and finally enhancing the thermal conductivity of UO2 pellets. [Methods]: GO-doped UO2 powders with different doping amounts were prepared by solid-liquid mixing method and ammonium diuranate (ADU) co-precipitation method. After selecting the optimized powdering process, the UO2-GO composite fuel pellets were prepared by spark plasma sintering (SPS). The properties of the UO2-GO composite fuel pellets, such as density, grain size, physical phase, thermal conductivity, etc., were examined and compared with that of the conventional pure UO2 pellets. [Results]: The results showed that the density of UO2-GO pellets could reach up to 97.6% T.D. The thermal conductivity of UO2-GO pellets with 1.5 wt. % doped GO was 85.9% higher than that of conventional UO2 pellets at 1000 ℃. The grain size of the UO2-GO pellets was uniform, and the GO was homogeneously distributed at the grain boundary to form a bridging thermal conduction network. [Conclusions]: The thermal conductivity of the UO2 pellets was successfully improved through GO doping.