Characteristics for crack detected by eddy current test in the steam generator tube

The flaws detected at the steam generator tube of the Nuclear Power Plant are the wear indications by anti-vibration bars and circumferential cracks at the top of the tubesheet. It is easy to detect and size wear indications. Also the wear indications are commonly found at the steam generator tubes. However, the steam generator tube which includes crack indication is plugged because it is very difficult to predict the growth rate and the sizing error is high. The motorized rotating pancake coil has been used for the detection of circumferential crack since it is not possible to detect using the conventional bobbin probe. This paper describes the characteristics for the circumferential crack at the steam generator tubes of the Korean Standard Nuclear Power Plants.