DEVELOPMENT OF AN IN-SERVICE INSPECTION TECHNIQUE FOR THE INTERMEDIATE HEAT-EXCHANGER TUBES OF THE HIGH-TEMPERATURE ENGINEERING TEST REACTOR

A n experimental study is carried out to clarify the performance of an eddy current testing probe and probe-inserting equipment for the in-s ervice inspection of the intermediate heat exchanger tubes of the High -Temperature Engineering Test Reactor. Artificial discontinuities are made with reference to the American Society of Mechanical Engineers st andards for steam generator tubes in a light water reactor. It is conf irmed that the probe can detect these discontinuities as well as small er ones, such as a 0.5-mm-diam 100% through-wall hole and a 0.5-mm-wid e groove, in a base-metal tube. For the welded joints, the back-excess weld metal is a main noise contributor, and a multiple-frequency meth od can remove the noise. The inspection performance, however, is lower . The probe-inserting equipment can smoothly insert and extract the pr obe. The winding of the cable causes a scattering in the probe traveli ng velocity values and a measurement error regarding the probe's locat ion in the tube.