Detection and analysis of defects in reactor pressure components by location and interpretation of acoustic emission sources

In the last years many hydrotests, cyclic fatigue tests and thermal shock tests have been carried out on reactor pressure vessels, which exhibited crack-like defects, with the aim to develop the conditions of detectability of growing and non-growing cracks by acoustic emission (AE). The AE generated during these experiments has been recorded and analyzed. Techniques for evaluation of AE-data have been developed which allowed the seperation of AE-events from crack growth and crack surface friction by risetime. Crack growth can be detected with high sensitivity at thermal shock and fatigue tests, whereas the detectability of crack surface friction increases, as the amount of compresssive stresses between the crack surface grows. At hydrotest only a low level AE is produced by non-growing cracks due to the lack of compressive stresses.