Discrimination method of through-wall cracks in steam generator tubes using eddy current signals

A unique non-destructive technique to discriminate a through-wall crack and to measure the through-wall length of a through-wall crack was developed using the EDM notch specimens and verified by using real fatigue cracks. It is based on the distribution profile of the eddy current signal amplitude along the crack length direction. It was also verified that the internal pressurization of the in situ pressure test induced a plastic deformation of the crack, resulting in a remarkable increase of the signal amplitude.