Results and experiences of ISI austenitic and dissimilar welds using SH-waves and EMUS-probes

Increasing demands for In-Service-Inspection (ISI) of austenitc and dissimilar metal welds in NPP's in Germany and other european countries from the motivation of the application of new NDE-techniques with potential to improve the inspectability of these types of welds. In this context also the requirements of the german code KTA 3201.4 (revision 6.1990) of ultrasonic inspection of dissimilar metal welds has to be considered. Up to now in the most cases standar and special UT-techniques are only covering the HAZ's ; to fulfill the code requirements the inspection has to be performed from both sides of the weld. Dissimilar metal welds are in many cases only accessible from one side. Therefore US-techniques are necessary which are capable to inspect the whole weld even if there is only access from one side. Among the different ultrasonic wave modes - Longitudinal (L-) waves, Shear waves with polarization in the plane of incidence (Sv-waves) and Shear waves with polarization perpendicula to the plane of incidence (SH-waves), Sh-waves show most promising advantages for the inspection for longitudinal defects in austenitic and dissimilar metal welds, as was demonstrated in different cases.