EXPERT-SYSTEM FOR THE CHARACTERIZATION OF DEFECT SIGNALS IN STEAM-GENERATOR TUBES

The automatic analysis, by computer, of defect signals in steam genera tor tubes, based on the eddy current multifrequency technique, is freq uently inefficient due to ''pilgrim noise''. The first step is to use a method that allows the noise to be eliminated: adaptive interpolatio n. Thanks to this method, which ensures reliable data on each channel, the analysis can be realised by taking account of the data correspond ing to each basic or mixed channel. By correlating these diverse data, the signals can be grouped according to two types of defects: single defects, and multiple defects (several at the same place). The second step is to use an expert system which allows a reliable diagnosis for whatever family the defect belongs to. According to this classificatio n, analysis is continued and results in the characterization of the de fect. The expert system has already been developed using the general-p urpose application expert-system shell SUPER, which is briefly describ ed. The knowledge base (SOCRATE) is described in detail. The first res ults obtained with signals corresponding to real defects, that have be en recorded in different places, are presented and discussed. The expe rt system is shown to be efficient in all the cases, even with signals obtained in very noisy environments.