Degradation Mechanism of Dissimilar Metal Weld Joints on Steam Generator Collectors VVER 440MW Type

Indications were detected on dissimilar metal welds (DMW) of steam generators (SG) after 20 years of operation during NDT inspections. Indications started slowly growth every year. DMW on SGs had to be repaired. Paper describes experimental analysis and degradation mechanism of SG weld joints failures.