Fatigue monitoring of power plant components

Numerous investigations in the field of material fatigue have been performed in recent years. The reason for these activities was the occurence of particular crack formations in feed-water lines and feed-water nozzles of steam generators of pressurized-water reactors, and in pressure vessels of boiling-water reactors. Material investigations pointed out that crack initiation and crack propagation was primarily caused by fatigue. Temperatures and strain measurements performed during plant operation indicated thermal cycles. A structural assessment was performed to determine the effects of thermal cycles which showed significant fatigue damage. In order to gain information on the material fatigue status in a most economical way, a fatigue monitoring system has been developed which is described in this paper. (orig.)