Investigation of pipelines defect localization for fusion reactor by using T (0,1) mode ultrasonic guided waves

The stable operation of a fusion reactor depends on the reliable functioning of various accessory systems, many of which comprise extensive pipelines with different diameters and diverse cladding. Defects in pipelines can occur due to manufacture, thermal stress, and fatigue, threatening the systems' safety and reliability. Ultrasonic guided waves (UGWs) testing offers a promising approach for remotely locating these minute defects. The study explores non-dispersive fundamental torsional guided (T(0,1)) waves, particularly their influence on minor defect detection in stainless steel pipes. Both finite element simulations and experimental trials reveal that reflection coefficients, indicative of defect presence, rapidly escalate from 64 to 128 kHz. The optimal frequency for minor defect detection lies between 128 and 180 kHz. A significant finding from the circumferential distribution spectrum and angle profile reveals pipe diameter's dominant influence on the reflection energy distribution concentration. Furthermore, this highlights the unique ability of T(0,1) guided waves to precisely locate defects in the circumferential direction within large-diameter pipes over long distances. The results underscore the promising potential of UGWs testing in complex pipelines of fusion reactors.