Multifrequency Eddy Current System for Steam Generator Tubing Inspection Volume 2:Analytical Studies

摘要

A multifrequency eddy current testing system has been developed to test nuclear steam generator tubes and has been evaluated on a steam generator mockup. Results to date show that use of more than one inspection frequency facilitates electronic assessment of flaw depth, thereby reducing reliance on visual interpretation of signal information by operators.nThis interim report on Research Project 403 consists of two volumes. Volume I, "Progress Summary," provides details on the system design and an evaluation of the system's performance on a steam generator mockup. The system consists of a four frequency signal generator, which excites the inspection coil, followed by a Walsh function instrument which extracts information from any two of the four frequencies present in the composite test signal. The extracted information is processed to discriminate against unwanted signals, such as those from probe wobble, and is then transmitted to the defect decision circuitry for additional processing. Results of the mockup tests show that the system has a higher probability of flaw detection in many cases than does a conventional single frequency test.