Monitoring of pipe wall thinning using high-temperature thin-film UT sensor

摘要

Periodical measurement of pipe wall thinning for nuclear power plant is performed manually with a conventional UT sensor and it is performed based on "JSME S NG1/NH1" code which is Japanese rules on pipe wall thinning management. However, there are following concerns. i) Measured values may vary depending on the stability of measurement position and condition of contact. ii) The additional work for installation and removal of heat insulating material and a scaffold is required at every measurement. iii) The stable measurement is difficult on complex geometry, such as T-jointing of small pipe, because of the curvature. iv) The continuous wall thinning monitoring in plant operating is impossible because of high-temperature. Therefore, the thin-film UT sensor for high-temperature use was developed. Since the thickness of the sensor is thin (less than 1. Omm), it can be installed under the heat insulating material of pipe. And its flexibility enables to measure the thickness on complex geometry, such as T-jointing of small pipe. Moreover, it has the high-temperature durability and it can be continuously attached during plant operation. Verification tests of measurement accuracy and load test of heat, heat cycle and radiation were performed. Furthermore, field trial was performed at actual nuclear power plant in plant operating. In this paper, features of the thin-film UT sensor, results of the verification tests and field trial are introduced. And finally several applications will be proposed.