Evaluation method of ultrasonic testing for steam generator tubes in nuclear power plants

For inservice inspection of steam generator (SG) tubes in nuclear power plant, ultrasonic testing (UT) technique is getting attention as one inspection method. In the delectability of cracks, UT seems to be much more superior than the conventional ECT. However, accuracy of sizing, especially sizing for the depth of cracks, is not sufficient yet, thus many methods have been proposed and developed to improve the sizing accuracy of UT. In this paper, the authors describe their evaluation methods of UT for SG tubes in nuclear power plant of pressurized water reactor (PWR) system.