Metallurgical Examination of Cracked Feedwater Pipes from Nine Pressurized Water Reactors

A metallurgical failure analysis was performed on feedwater nozzle cracks from the steam generators of pressurized water reactors. The types of cracking observed have been categorized into three general classifications. The failures are considered to be caused by low cycle, stress-induced fatigue, probably enhanced by the corrosion process. Prior machine marks appeared to form initiation sites for cracks, while metallurgical structure had no apparent effect on crack location or propagation.