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This paper describes the development of a robot monitoring an aerial working environment in a high radiation area such as the Calandria face at a PHWR (pressurized heavy water reactor) of a nuclear power plant. The robot consists of three main parts: a mobile platform, a telescopic mast, and a mission tool. To access the target place across the guide rail ditch of a shielding door, the mobile platform is equipped with two front rubber wheels, two rear omni-wheels, and four flippers. The telescopic mast installed on the platform is able to lift up the mission devices to the height of 10 m. The mission devices are a radio hardened camera, a leak detecting sensor, a dosimeter detecting high radiation level, and a RAM operating device of a fuel exchange machine. In addition, a control system considering the emergency was developed.

Deployment of an advanced on-line monitoring of the component integrity offers the prospect of improved performance, enhanced safety, and reduced overall cost for nuclear power plants. Guided ultrasonic waves have been known as one of promising techniques that could be utilized for on-line monitoring. The present work is aimed at developing a new method for on-line monitoring of the pipes during the operation period of nuclear power plants. For this purpose, Steam generator (S/G) tube was selected as the object of the experiment. Dispersion curves and the incident angles corresponding to the specific modes were calculated for the S/G tube. The modes of guided wave were identified by time-frequency diagrams obtained by short time Fourier transform. Group velocities were also determined from the time-frequency diagrams obtained at the different separations of transducers. It was experimentally confirmed that there was no mode conversion when the guided ultrasound passed curved region of the S/G tube. The optimum mode of guided wave for the S/G tube was suggested and verified by experiments

This study was aimed at developing an effective method and a system for on-line health monitoring of pipes in nuclear power plants by using ultrasonic guided waves. For this purpose we developed a multi-channel ultrasonic guided wave system for a long-range inspection of pipes and a few techniques which can effectively find defects in pipes. To validate the developed system we performed a series of experiments and analyzed the results.