Progress in defect detection and characterization with multi-frequency-eddy-current and current perturbation testing

This paper is devided into two parts. The first one decribes a new eddy current inspection device which is designed especially for the defect testing of heat exchanger tubes in nuclear power plants. It was the aim of the development to improve the defect detection sensitivity and the signal interpretation in the critical part of the tube sheet with its expansion. Fig.1 shows this inspection area with three typical defect types. The objective of the second part is the electric current perturbation method for the inspection on surface or near surface defects especially in austenitic components. The interpretation of the measured signals is supported by computer results coming out from numerical models.