Experimental techniques for investigating thermal transport in nuclear materials

The unique combination of large energy density and extreme environment inside a nuclear reactor imposes strict requirements on the thermal transport property of nuclear materials, which is significantly deteriorated by the irradiation damage, leading to increased service temperature, complex microstructural changes, and compromised integrity. To address this issue, tremendous efforts have been made over the years to measure, comprehend, and enhance thermal transport regulated by radiation-induced defects in advanced nuclear materials. Such efforts would be laborious and time-consuming without revolutionary innovations in characterization techniques. Herein, we review recent experimental studies on the thermal transport properties of nuclear materials, with a focus on the advancements in the measurement techniques with improved spatial resolutions. We provide a brief introduction to the mechanisms of thermal transport in nuclear materials and the impact of irradiation damage on thermal transport. A comprehensive review is presented of advanced thermal characterization techniques that encompass different length scales, ranging from millimeter to nanometer, along with their respective experimental outcomes. Finally, the practicality of each measurement technique is assessed, and research opportunities are discussed in regard to the development of physics-based fuel models.