Mechanical damage experience in major light water reactor systems

This paper describes the nuclear power industry's experience with mechanical (as opposed to thermal or electrochemical) damage in the major systems of light water reactor (LWR) plants. Almost all of the occurrences of damage were caused by mechanical vibration. The sources of vibration include flow-induced vibration, water-hammer events, and pump and valve vibration. However, the damage has sometimes been initiated or aggravated by other sources, such as stress corrosion cracking, loss of preload, or corrosion-fatigue. Mechanical vibration can also cause metal loss in the walls of thin tubes when they impact with their supports. Some of the components that have experienced mechanical damage are reactor coolant pump shafts, PWR and BWR reactor vessel internals, PWR instrument tubes, thermal sleeves in piping, and steam generator tubes. Various mitigation methods can e implemented to reduce or eliminate these problems