Surveillance of defects under cyclic loads and during hot and cold hydro-tests by acoustic emission, UT and potential drop techniques (German HDR-programme)

Abstract

Abstract In the framework of the German HDR reactor safety programme a selected area of the reactor pressure vessel was loaded with 9500 thermal cycles. In 3 saw cut regions several crack fields were generated and monitored with on-line and off-line NDE-procedures. With potential drop and ultrasonic testing, crack front profiles could be described off-line with sufficient resolution. During the trials the crack growth was measured with stationary potential drop and ultrasound probes. With on-line acoustic emission crack growth of about 5 mm could be detected. On the basis of an interpretation model a classification of the acoustic emission signals in crack growth and crack surface friction phenomena was possible. The crack growth during the cooling phase is caused by fatigue; the reason for crack growth during the heating up phase is corrosion influence. All cracks are growing at different time periods and have different stress conditions.