A fretting/wear degradation at the tube support in the U-bend region of a steam generator (SG) of a pressurized water reactor (PWR) has been reported. Simulated fretted flaws were machined on SG tubes of 195 mm in length. A pressure test was carried out with the tubes at room temperature by using a high pressure test facility which consisted of a water pressurizing pump, a test specimen section and a control unit. Water leak rates just after a ligament rupture or a burst were measured. Tubes degraded by up to 70% of the tube wall (TW) showed a high safety margin in terms of the burst pressure during normal operating conditions. Tubes degraded by up to 50% of the TW did not show a burst. Burst pressure depended on the defect depths rather than on the wrap angles. The tube with a wrap angle of 0° showed a fish mouth fracture, whereas the tube with a 45° wrap angle showed a three way fracture.
- Nuclear Engineering Division
Ligament Rupture Pressure of Fretted SG Tubes of PWRs
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Hwang, SS, Jung, MK, Kim, HP, & Kim, JS. "Ligament Rupture Pressure of Fretted SG Tubes of PWRs." Proceedings of the 14th International Conference on Nuclear Engineering. Volume 1: Plant Operations, Maintenance and Life Cycle; Component Reliability and Materials Issues; Codes, Standards, Licensing and Regulatory Issues; Fuel Cycle and High Level Waste Management. Miami, Florida, USA. July 17–20, 2006. pp. 415-418. ASME. https://doi.org/10.1115/ICONE14-89211
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