Ultrasound in Lead-Bismuth Eutectic

SCKCEN is in the process of designing MYRRHA, a fast spectrum research reactor cooled with lead-bismuth eutectic. As liquid metal is opaque to visual light, ultrasonic measurement techniques are selected to fulfill essential tasks that will be demanded by licensing authorities: fuel assembly identification and localization of a lost fuel assembly. To that end, a considerable research effort at SCKCEN is devoted to study ultrasonic propagation in LBE. As ultrasonic experiments in LBE are elaborate and expensive to set up, we are particularly interested in to what extent experiments in water can be extrapolated to LBE. We present results of a first experiment which shows that the signal to noise ratio is better in LBE and that we even see small diffuse reflections up to 40 degrees off normal. On the other hand, we do not see internal reflections in stainless steel which we do in water. Therefore, we conclude that experiments in water can be used to validate algorithms for LBE on the condition that they do not rely on internal reflections. We also present solutions to tackle the essential tasks: fuel assembly identification and lost object localization. The requirements for the ultrasonic equipment implementing these solutions are discussed.