Development of eddy current test technology for steam generator tube in PWR plant

When ISI of steam generator heat transfer tubes is enforced by use of the eddy current test method (ECT method), many signals are detected regardless of presence of flaw or not. In order to detect flaw occurring in the heat transfer tube, therefore, it is necessary to develop a technique for evaluating defective signals buried in these signals separately or a probe having a special function. In this paper, these signals are arranged and studied, a method of evaluating signals and the performance of a special probe developed by our company on the basis of ample ISI experience are introduced and furthermore, it is explained that the entire zone of the heat transfer tube can be tested thoroughly by use of the present ECT technique. An outline and features of multiplex ECT method now under study as a precision flaw detecting method are described next and its effect on the improvement of S/N and elimination of harmful signals is reported. (author)