Condition monitoring and on-line surveillance of a pipe in a BWR large scale earth quake experiment

Safety rules ask for special design of components of LWR's in order to avoid damage or failure. One design criterion is protection against earth quakes. The contribution refers to the development and application of a dc potential drop technique for the on-line surveillance and condition monitoring of a predamaged tube (starter notch at the inner side with a fatigue crack) in a large scale primary circuit experiment in the German Nuclear Safety Research programme (HDR-Programme). It will be demonstrated that the technique can control the crack growing starting at the inner side of the tube by a potential drop application from the outside. For interpretation, software (analytical and FE-codes) is available. Progressive crack propagation can be observed and an alarm can be derived. The tube fails with leak before break.