Study on the Ultrasonic Characterization Method of Liquid Heavy Metals

Due to their specific thermo-physical and chemical properties, heavy metals such as lead (Pb) and its alloy, the Pb-Bi eutectic (lead-bismuth), have been chosen as the main coolants for generation IV nuclear reactors, the LFR (Lead Cooled Fast Reactor) series. For operational safety reasons, it is necessary to monitor the capacity of structural materials to withstand the intended operating conditions, the configuration of the fuel core, and the flow of liquid metal in the reactor circuit throughout the entire operating period. Given the opacity of the liquid metal environment at high temperatures, ultrasonic waves are the only viable physical method for obtaining internal information during reactor operation. The practical implementation of ultrasound technology under such extreme conditions is not yet fully validated and requires extensive experimental investigations. For this purpose, dedicated test facilities, specialized equipment and measurement methods adapted to the liquid metal environment are required. In this regard, within the Institute for Nuclear Research (ICN) Pitesti, activities are being carried out to develop the experimental infrastructure for ultrasonic measurements regarding the determination of the acoustic parameters of liquid lead. The paper presents general aspects regarding ultrasonic technology, the equipment used, signal processing means, and preliminary results for the verification of the test system for ultrasonic measurements in the molten lead environment.