Experimental Studies on Guided Waves for the On-Line Inspection of Steam Generator Tubes

Deployment of an advanced on-line monitoring of the component integrity offers the prospect of improved performance, enhanced safety, and reduced overall cost for nuclear power plants. Guided ultrasonic waves have been known as one of promising techniques that could be utilized for on-line monitoring. The present work is aimed at developing a new method for on-line monitoring of the pipes during the operation period of nuclear power plants. For this purpose, Steam generator (S/G) tube was selected as the object of the experiment. Dispersion curves and the incident angles corresponding to the specific modes were calculated for the S/G tube. The modes of guided wave were identified by time-frequency diagrams obtained by short time Fourier transform. Group velocities were also determined from the time-frequency diagrams obtained at the different separations of transducers. It was experimentally confirmed that there was no mode conversion when the guided ultrasound passed curved region of the S/G tube. The optimum mode of guided wave for the S/G tube was suggested and verified by experiments