Fabrication of UO2-BeO composite pellets with superior thermal conductivity based on multi-parameter theoretical analyses

In this paper, the fabrication process of UO2-BeO composite pellets was optimized for improving the thermal conductivity based on multi-parameter theoretical analyses and experimental investigations. It was found that the density of BeO and UO2/BeO interfacial thermal resistance (ITR) are crucial parameters that affect the thermal conductivity of UO2-BeO. To effectively increase BeO density and decrease UO2/BeO ITR, the fabrication method of pressureless sintering with a spheroidizing process was proposed. Through this method, UO2-BeO composite with high thermal conductivity was obtained. 89.2% and 71.4% enhancements of the thermal conductivity over UO2 were achieved at room temperature and 673 K, respectively. This enhancement is higher than all the reported results in the previous literatures that fabricated UO2-BeO using normal sintering temperatures (<2023 K). The results of finite element modelling showed that the centerline temperatures of our fabricated pellets in the reactor decreased remarkably compared with UO2 fuel, which would significantly improve the safety of the reactor. (C) 2020 Elsevier B.V. All rights reserved.