Ultrasonic imaging in liquid sodium: Topological energy for damages detection

Under-sodium imaging at high temperature is an important requirement in sodium cooled fast reactors during structural inspection. It aims at checking the integrity of immersed structures and assessing component degradation. The work presented in this paper focuses on designing an advanced ultrasound methodology for detecting damages such as deep crack defects. For that purpose, a topological imaging approach was implemented. This method takes advantage of all available prior knowledge about the environment through the integration of differential imaging and time reversal techniques. The quality of the topological energy distribution (the image) is further enhanced by applying a time gating related to each reconstructed pixel. Numerical and experimental results are presented using this method in order to confirm its reliability. These images are compared to a B-scan to emphasize the localization performances of this method.