Application of an IR Thermography Technique to the Inspection of Local Wall-Thinning Defects in Nuclear Piping Components

Abstract

In this study, infrared (IR) thermography was tested on pipe specimens with artificial wall-thinning defects of various dimensions, in order to determine optimal thermal injection conditions and the capability of the procedure for detecting wall-thinning defects in small-bore nuclear piping components. An active IR method was employed in the experiment. The specimen was thermally activated using two halogen lamps, and thermal images were captured via an IR camera. The thermal injection condition that provided the best images of wall-thinning defects was dependent on the pipe geometry; the optimal object distance decreased with decreasing pipe diameter. Under the optimal conditions, IR thermography was able to detect all wall-thinning defects with depth d/t ≥ 0.5, except for a defect that was very short and narrow, in a pipe specimen of length 500 mm at one time. However, the wall-thinning defects with depth of d/t = 0.25 were only detected when they had a suitable length and circumferential angle.