Analysis of Minimum Gap for U-bends of Steam Generator Tube Bundle

During the fabrication and tubing of the tube bundle for steam generator, some local deformations in the U-bend area might occur, which will result in a smaller gap or even contact between tubes. According to the design principles for tube bundle, taking CPR1000 steam generator（Type 55/19B） as the analysis model, the gap for the U-bends is analyzed and evaluated from the views of flow-induced vibration（FIV）, wear, dry-out and stress analysis. Based on the analysis results, it is concluded that the minimum gap for the U-bends should be larger than the turbulent amplitudes to avoid unacceptable flow-induced vibration, wear and dry-out which means enough safety margins should be considered during U-bends gap design.