Improving Ultrasonic Examination Procedures for Detection of Thermal Fatigue

This paper describes improvements to the ultrasonic procedures to be used for the detection of thermal fatigue in nuclear power plants in accordance with the requirements of the Electric Power Research Institute (EPRI) Material Reliability Program (MRP) inspection and evaluation guidelines. These examinations have been performed at nuclear plants in the USA since the 1980s with very few detections of degradation. However, since 2013 there have been ten instances of thermal fatigue cracks. The MRP formed a thermal fatigue focus group to analyze these leaks and flaws related to thermal fatigue inspection programs. Then the group developed recommendations to address these recent operational experiences. The MRP has been developing improvements to the ultrasonic examination process and this paper will share these. A computer based training program for the ultrasonic personnel has been developed that will be described. And finally, the MRP has fabricated a variety of thermal fatigue mockups that are loaned to member utilities prior to an outage so the ultrasonic personnel can practice detecting thermal fatigue just prior to the examinations. Implementation of these mockups will also be described.