Experimental and numerical tools for the characterization of ultrasonic propagation for nuclear reactor application

Due to being cooled by liquid metal, the next generation of nuclear reactors requires an ultrasonic visualization system for internal inspection and object detection. In such environment, acoustic propagation is submitted to peculiar conditions in terms of temperature and velocity gradients. In the core of the nuclear reactor, temperature gradients are 5K over 0.1 m and the velocity gradients reach 1 m/s over 0.2 m. The effects of these conditions on the ultrasonic propagation are investigated in a specific water facility, reproducing conditions similar to the nuclear application. The design and the characteristics of this new facility are presented in this paper. This includes a shadowgraph system for the visualization of the propagation of the acoustic wave in various conditions. The acoustic similitude between water and liquid metal is discussed for ensuring the validity of the water test for nuclear application. The propagation of ultrasonic waves in the full scale application is modeled by using a ray tracing algorithm. The validation of this algorithm has been performed by comparing the results with data from literature and numerical acoustic calculation. Preliminary results obtained with this algorithm are shown in the paper.