Design, Assembly, and Inspection of Advanced U-Bend/Antivibration Bar Configurations for PWR Steam Generators

Tube vibration and wear potential in the U-bend region of pressurized water reactor (PWR) steam generators is reduced by enhanced design bases and fabrication procedures. Applicable vibration mechanisms are described and related to field experience to focus the development program which led to the enhancements. Technical bases were developed from flow-induced vibration tests and shaker tests in which the tube/antivibration bar (AVB) wear-producing forces and motions were characterized in terms of work rate. Fixtures to control weld shrinkage and instruments to measure tube/AVB fit-up were developed for fabrication. Assembly and application experience, including measurement of fabricated tube bundle/AVB fit-up, is summarized for several advanced steam generators. Implications for enhanced operating experience relative to conventional design configurations are noted.