Síntese e caracterização do combustível nuclear avançado UO2 - grafeno

Abstract

The development of advanced nuclear fuels aimed at enhancing the thermal conductivity of uranium dioxide (UO2) pellets represents a significant step toward improving the performance and safety of nuclear reactors. In this context, the present research investigated the effects of graphene—a material known for its high thermal conductivity— as an additive to UO2 pellets. Pellets containing 2% and 6% graphene were produced and sintered, and their properties were analyzed in comparison with pure UO2 samples. Dilatometric analysis revealed that the addition of graphene promoted greater macroscopic shrinkage and higher sintering rates. Furthermore, the diffusivity and thermal conductivity of the graphene-containing pellets were consistently higher than those of the pure sample, indicating a substantial improvement in heat transfer capability. However, microstructural characterization yielded contrasting results. The analysis of porosity and grain size demonstrated that graphene modified the microstructure of the pellets. The residual porosity became more irregular, with larger and often interconnected pores. At the same time, graphene inhibited grain growth, leading to a progressive reduction in average grain size with increasing concentration. Although graphene contributes to macroscopic densification and improves thermal properties, it compromises the microstructural integrity of the material. The inhibition of grain growth and the formation of detrimental porosity may be attributed to the presence of carbon residues acting as pinning agents at grain boundaries.