PIPE INSPECTION USING UT SMART FLEXIBLE TRANSDUCER
G. Cattiaux, S. Mahaut, O. Roy, O. Casula,
8ème Conférence Européenne pour les Contrôles Non Destructifs, Barcelone, Espagne, juin 2002,
The inspection of primary and secondary circuit components of French pressurized water reactors is mainly performed with contact ultrasonic transducers. The irregular state of surface and the complex geometry of such components (nozzles, elbows) may lead to degraded inspection performances. The unmatched contact between the wedge and the component due to an irregular surface geometry would result to loss of sensitivity and beam distortions. Complex geometry could also limit the scanning displacement of the probe, therefore the area would not be entirely covered. To improve such inspections, a new concept of contact transducer has been developed for several years by CEA, with the support of the safety authorities (IRSN). This “smart contact transducer” is a flexible phased array transducer, able to fit a complex profile, and to compensate the beam distortions using optimised delay laws computed in real-time using a specific instrumentation inserted in the transducer. Thus, the integrated phased array probe just needs to be positioned above the inspection area. The process is self-adaptive, and the data acquired are presented directly in the inspected component referential. Inspections of mock-ups of realistic irregular profiles, including artificial defects, have been carried out, which allowed to estimate the enhanced performances of the smart contact transducer compared to conventional contact probes. Results obtained using this new concept under irregular profile are similar to those obtained through a flat interface, while conventional probes cannot be efficiently used.