Feasibility Study on HfO2/xGnP Composites for Enhanced Thermal Conductivity

Abstract

The commercial nuclear power industry is interested in advanced fuels and claddings that can produce higher power levels with a higher safety margin and be manufactured at low cost. Although UO2 fuel is chemically stable, its thermal conductivity is low. In the nuclear engineering field, the thermal conductivity of fuels is a very important parameter for the optimum design and safety analysis of a nuclear system. This is because the thermal conductivity of fuels significantly affects the internal energy of the nuclear fuel by heat transfer through the coolant. Higher thermal conductivity of nuclear fuel means that the fuel would be able to operate at lower temperatures, which would limit fission gas release and reduce the stored energy thus improving its safety margin. Therefore, the safety analysis using fuel thermal conductivity is necessary for the prediction of thermal-hydraulic behavior. If xGnP (Exfoliated Graphite Nanoplatelets) is mixed in UO2 fuel, it is chemically stable and its thermal conductivity will be enhanced. Advantages of xGnP are a high thermal conductivity and a low absorption cross section. In present work, HfO2 is selected as a substitute of UO2 due to the similar density of HfO2 and UO2. HfO2/xGnP composites were made by adding 10 vol. % of xGnP having a high thermal conductivity and the thermal conductivity of HfO2/xGnP composites were measured by LFA 447 NanoFlash.