Design of Fiber Bragg Grating Acoustic Sensor for Structural Health Monitoring of Nuclear Power Plant

Jung-Ryul Lee1,a See Yenn Chong1,b, Chang Yong Yun1,c, Hoon Sohn2,d

1Dept. of Aerospace Engineering, Chonbuk National University, 664-14 Duckjin-dong, Duckjin-gu, Jeonju, Chonbuk, 561-756, Republic of Korea

2Dept. of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejon, Korea

aleejrr@jbnu.ac.kr, bchongandy@live.com, cchyun0207@nate.com, dhoonsohn@kaist.ac.kr

Keywords: Structural health monitoring, Nuclear power plant, Metal-coated optical fiber, Fiber Bragg grating acoustic sensor

Abstract. Nuclear power plant (NPP) is commonly categorized as a harsh environment that gives rise age-related degradation on the structures of plant and eventually leads to radiation leakage that threatens to human. Integrated structural health monitoring (ISHM) technology is a strong candidate for NPP accidents. The emergence of optical fiber technology into SHM system for NPP was greatly interested by researchers, and also prior research works have shown that the fiber Bragg grating (FBG) was able to retain its reflectivity under radiation exposure. In this paper, a metal-coated fiber was newly used to develop a FBG acoustic sensor for ISHM of NPP. The 7 mm length of aluminum, copper/carbon coatings were successfully removed with sodium hydroxide and nitric acid solutions. A 5 mm FBG was successfully inscribed in the silica core through the 7 mm long coating-removed silica section of copper/carbon-coated fiber and the initial reflectivity was 71%. Then, the FBG acoustic sensor was developed in one-end-free FBG configuration on the stainless steel vessel using a high temperature metallic adhesive. The reflective power of the sensor was stabilized at 345°C during the high temperature elevation cyclic process. The FBG acoustic sensor showed good response to the acousto-ultrasonic waves during pencil-lead breaking and laser ultrasounics tests. The high temperature FBG acoustic sensor written in the cost-effective metal/carbon is feasible to be used for ISHM of the NPP.

Note: The proceeding paper has published in Advanced Materials Research

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