An advanced infrared thermography (IRT) technique, known as lock-in mode IRT, has been developed and employed to improve the detection capability of defects in materials with high thermal conductivity. Lock-in mode IRT has been shown to provide better detection capability than conventional active IRT. Therefore, to investigate application of this technique to nuclear piping components, we conducted lock-in mode IRT tests on pipe specimens containing simulated wall-thinning defects. We obtained phase images of the wall-thinning defects and compared them with thermal images obtained from conventional active IRT tests. The results indicated that the ability to size the detected wall-thinning defects in piping components was improved by using lock-in mode IRT. The improvement was especially apparent when detecting short and narrow defects, and defects with slanted edges. However, the detection capability for shallow wall-thinning defects did not improve much when using lock-in mode IRT.

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