Determination of interaction effect between cracked tube and eggcrate support plate on the burst pressure

Steam generator is one of the major components in the nuclear power plant comprising pressure-retaining boundary. Typically, there are thousands of thin-walled tubes as well as several support plates in a steam generator. According to the operating experience of the steam generators, a lot of cracks have been found in the tubes. Therefore, an accurate integrity assessment of the tubes is crucial for maintaining safety as well as reliability of a nuclear power plant. The steam generator tubes are supported by several support plates, and deformations of the tubes are partially restrained depending on the crack location and the gap between the tube and the support plate. In the authors' previous study, it has been reported that burst pressures for circumferentially cracked tubes are significantly affected by the support plate and existing solutions differ from the actual burst pressure. However, this interaction effect for axially cracked tubes has not been fully investigated while those are frequently occurred during operation. In this paper, therefore, a number of elastic-perfectly plastic finite element analyses were performed considering the contact interaction between the tube and the support plate. The burst pressure is then evaluated in accordance with the lower bounding limit theorem and the support-induced interaction effects on the burst pressure were determined.