Stress corrosion crack length and depth evolution on pulled SG tubes from a PWR

Eddy current test (ECT) data collected from the in-service inspection (ISI) of pulled steam generator (SG) tubes were evaluated in terms of the primary water stress corrosion crack (PWSCC) length and depth evolution. After shot peening, the evaluated crack length and the number of cracks did not increase, but the Eddy current voltages that were related to the crack depth increased continuously. In the analysis of all the tubes of the plant, the evaluated crack lengths saturated at around 6 mm, while the voltage of the defects increased with time. As a result, shot peening was considered effective for suppressing crack length increase, but not so successful from the point of preventing crack deepening. It was also found that tube bundles that were susceptible to PWSCC were located in a special area depending on the steam generators of the analyzed plant.