Detection of concrete-emdedded steel liner corrosion using nonlinear ultrasound

The gas-tight steel containment liner plate is one of the protective barriers employed in Nuclear Power Plants (NPPs) to shield the exterior environment from the release of radioactive particles in the event of an accident or an attack. In certain NPPs the containment liner is embedded in concrete, making it challenging to inspect by non-destructive means.

Concrete is inherently heterogeneous which means that sound propagating in concrete behaves in an almost unpredictable manner due to the vast amount of internal scatters. This leads to a high level of acoustic attenuation and other phenomena which makes concrete inspection using ultrasound a challenging task. Conventional ultrasound typically measures attenuation or time-of-flight (to estimate sound velocity). The resolution is proportional to the wavelength and small defects require small wavelengths. These small wavelengths are effectively attenuated in concrete, thus impairing the detection capabilities of conventional techniques.

In contrast to conventional ultrasound techniques, nonlinear ultrasound studies waveform distortion, i.e. changes to the spectral content of the transmitted elastic wave. Defects may distort elastic waves considerably even if the wavelengths are some order of magnitude greater than the defect size. As such, these techniques are generally well suited for the detection of precursors to critical deterioration in solids.

This project aims to assess the feasibility of employing advanced nonlinear ultrasonic techniques to detect and image corrosion damage in concrete-embedded steel liners.

This project is funded by Energiforsk (BET165) and the Swedish Radiation Safety Authority (SSM2019-1114).