Detection of underclad defects by non destructive testing

Discovery of underclad cold cracking phenomenon in steam generator tube sheets and under the cladding of reactor vessel nozzles led FRAMATOME to study, develop and qualify non destructive examination methods capable of detecting and characterizing these types of defects. To reach this objective, FRAMATOME started by studying the possibilities of various NDT methods, after which the following two techniques were retained: a) ultrasonic testing for examination of tube sheet before drilling and of reactor vessel nozzles; b) Eddy current testing by internal probe for examination of drilled tube sheets with tubes installed