Acoustic emission monitoring during thermal shock fatigue with an acoustic emission signal parameter processor

In the framework of a reactor safety research programme thermal shocks of a cladded feed water nozzle have been carried out during simulated operating conditions (temperature = 300 degree = 11 MPa). The objective of these trials is to contribute to the understanding of crack initiation and propagation under realistic thermal shock conditions, to monitor crack initiation and growth by NDT on-line as well as off-line. Up to now the nozzle corner has been shocked 5200 times. The shocked area was surveilled by acoustic emission (AE). During the last 800 thermal shocks a new AE-equipment with optimized capabilities for detection, location of AE sources and interpretation of AE signals has been used. This AE-system and the results obtained during the last 800 shocks will be described. One important result is that it is possible to separate crack growth signals from friction noise of the cracks by signal analysis when the AE signals are received with broadband transducers.