[en] The report describes the theoretical study and the experiment of ultrasonic guided waves and AE which are attractive for the online and real time inspection of pipes installed in nuclear power plants. The following list presents the main contents of the report. Techniques using guided ultrasound have been investigated for the on-line monitoring of stainless steel pipe of 2 inches diameter. Guided waves were generated by using wedges. The received signals from various artificial flaws were analyzed. The pattern matching technique was developed in order to identify the modes of the received guided waves. The phased array technique was studied in order to control the modes of the generated guided waves, and multi-channel transducers and multi-channel ultrasonic pulser/receiver have been designed. The principle and measurement of Acoustic Emission(AE) technique was reviewed and summarized. Also basic tensile/fatigue experiments which are necessary for applying AE to on-line monitoring have been performed