Detection of Pipe Contents with Ultrasonic Pulse Echo Technique

Abstract

In the decommissioning work at the Fukushima Daiichi Nuclear Power Plant, many pipes that may be contaminated with radioactive material need to be cut and removed. In order to cut pipes safely, the presence of deposits inside them must be detected before cutting. Generally, in the ultrasonic pulse echo method, ultrasonic transducer is pressed against the target pipe by hand. However, considering the risk of radiation exposure, this study proposes a method which makes the transducer attached to a rod and pressed against the target pipe. When using the transducer at the edge of a rod, it is difficult to stably make the transducer surface attached to the pipe surface with a proper angle. To overcome this issue, a function to perform contact determination was added in this study. Furthermore, a method was developed to detect the presence or absence of adhesions based on differences in reflection ratio.