Flaw Depth Evaluation of Primary Water Stress Corrosion Cracking in Steam Generator Tubings

Flaw depth evaluation was performed on the primary water stress corrosion cracking in steam generator tubing, with the eddy current test results such as signal amplitude and phase angle. The relationship between crack length and crack depth was also investigated, based on the metallographic results of pulled-out tubings. This study yields the following results and conclusions: (1) there is no direct correlation between crack length and crack depth. (2) it is not easy to correlate the crack depth with phase angle, (3) although signal amplitude appears to be related with crack length, the latter cannot exactly be obtained from the former value, (4) it would be helpful to sleeve or plug those tubings with crack lengths greater than 5mm, taking into account the present ECT measurement error of 1.5mm, and the fact that most cracks with the length above 7mm could be a through-crack