Development and application of guided wave technology for buried piping inspection in nuclear power plant

Guided wave (GW) technology, well used in petrochemical industries and academia for pipeline inspection, were studied to evaluate the integrity of buried pipes in nuclear power plant (NPP). Since GW inspection does not require direct access to the entire pipe surface and can be used to screen relatively large component areas from the probe location, this method can be developed to examine the inaccessible portions of pipeline, such as the buried pipes. However, the adhesion, due to soil pressure and anticorrosive coating, caused serious decay during GW propagation. Detection range and discrimination of GW inspection should be studied. In this research, a field experiment was conducted to verify and quantify the attenuation rate caused by coating, soil pressure and pipe size. The on-site inspection could offer not only the data but the uncertainty analysis for the pipeline surroundings. The profiles from a series of GW inspections on ten different pipes were compared and analyzed after an inter-pipe normalization. The test results indicate the relation between soil pressure and GW attenuation rate, so as the influence over decay by the coating/tape or the different GW operating frequencies. Moreover, a real on-site inspection was applied on a buried pipeline near NPP field. A successful GW evaluation was demonstrated.