Vertical crack imaging in a nuclear structure using Ultrasonic Pulse Velocity and Ultrasonic Tomography Techniques

Ensuring the integrity of concrete structures used for the containment of short-lived low- and intermediate-level radioactive waste is critical for long-term safety. Cracking, particularly from expansive mechanisms like alkali-silica reaction (ASR) originating in the waste, can compromise the durability of the aforementioned structures and must be carefully assessed. This study evaluates the effectiveness of non-destructive testing (NDT) methods—Ultrasonic Pulse Velocity (UPV) and Ultrasonic Tomography (UT)—for crack detection and characterization. UPV mapping revealed velocity drops and spatial non-uniformity in cracked zones, enabling crack detection and crack pattern identification. Further UPV measurements provided an estimation of the crack depth, which was validated by core samples. UT provided additional insights into internal features, including rebar and backwall positioning. Cracks were identified via backwall echo shadowing. Both techniques proved valuable, with UPV offering straightforward interpretation and UT requiring in-depth analysis. These findings support the integration of NDTs into routine structural assessments to enhance reliability while minimizing invasiveness.