Evaluation of the Integrity of Steam Generator Tubes Subjected to Flow Induced Vibrations

Flow-induced vibrations (FIV) continue to affect the operations of nuclear power plant components such as heat exchanger tube bundles. The negative effect of FIV is in the form of tube fatigue, cracking, and fretting wear at the supports. Fretting wear at the supports is the result of tube/support impact and friction. Fluidelastic and turbulence forces are the two main excitation mechanisms that feed energy into the system causing these violent vibrations. To minimize this effect all support clearances must be kept at a very small value. This paper investigates the consequences of losing the effectiveness of a particular support as a result of corrosion or excessive fretting wear. A full U-bend tube subjected to both fluidelastic and turbulence forces is utilized in this work. The performance of countermeasures such as the installation of additional flat bars in the U-bend region is thoroughly investigated. The investigation utilized both deterministic and probabilistic techniques.