Imaging of fatigue cracks in cladded pressure vessels with the SLIC-50

Abstract A two-step multibeam-multimode approach to ultrasonic in-service inspection of cladded reactor pressure vessels for near-surface fatigue cracks is presented. Detection of cracks is achieved with the SLIC-40 multibeam transducer, which yields a strong reflected-diffracted signal from the upper crack extremity (pulse 1). Sizing is accomplished with the SLIC-50 multimode transducer, which also yields a mode-converted (hence, well-separated) diffracted signal from the lower crack extremity (pulse 2). These SLIC transducers were used by the manual MBSP team (employing multiple beams and satellite pulses) in the PISC II international round-robin exercise and were qualified on the eight near-surface cracks in plate 2. Data from this exercise are discussed. The first sizing results obtained with a mechanized SLIC-50 and a computer-aided doublet acquisition and imaging system (DAISY) for three semi-elliptical underclad fatigue cracks are also compared with results reported by manual ultrasonic examiners as well as with the known crack depths.