Mesoscale Thermal Transport Measurements of Multi-phase and Porous Nuclear Fuels Using a Square-wave Pulse Thermoreflectance Technique

The safe and efficient operation of nuclear reactors require accurate knowledge of peak temperatures in the fuel assemblies. The temperature profiles are governed by the thermal transport properties of the fuel, namely the thermal conductivities (k) and thermal diffusivities (D). These properties can be very difficult to measure as they can vary considerably from the measured bulk values of the fresh fuel, and quickly degrade with increasing burnup [1-3]. Laser-based techniques have been effectively used for nondestructive and non-contact thermal transport measurements of a wide variety of materials, including nuclear materials [4-6] that would otherwise prove too hazardous or difficult to measure otherwise. In this study, a new thermoreflectance technique known as square-pulse transient thermoreflectance (SPTR) is