Development of Acoustic Leak Detection and Localization Methods for Inlet Piping of Fugen Nuclear Power Plant

• Published in: Journal of nuclear science and technology 2004-02, Vol.41 (2), p.183-195
• Main Authors: SHIMANSKIY, Sergey, IIJIMA, Takashi, NAOI, Yosuke
• Format: Article
• Language: English
• Subjects: acoustic monitoring; Applied sciences; ATR Fugen; coolant leakage; correlation matrix; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Installations for energy generation and conversion: thermal and electrical energy; leak detection; leak localization; leakage sound; microphone; multi-channel processing; wavelet decomposition
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/18811248.2004.9715475

The development work carried out on Fugen NPP is focused on detection of a small leakage on the reactor's inlet feeder pipes at an early stage by an acoustic leak detection method with usage of high-temperature resistant microphones. Specifically, the leak rate of 0.046 m 3 /h has been chosen as a target detection capability for this system. A cross-correlation technique has been studied for leak detection under low signal-noise ratios. The study shows that the sound diffusion on piping causes distortion of leak signals that results in their low correlation. A leak-location estimator and multi-channel correlation value, associated with estimated leak position, have been employed to detect such low-correlated leak signals. A method based on cross-correlation of signal spectral components has been proposed to deal with non-stationary leak signals. Joint-Time-Frequency-Analysis has been applied to analyze such signals, whilst a Wavelet decomposition technique has been used to extract their short-term spectral fluctuations. Since the spectral components are less affected by signal distortion, they provide higher correlation value and can be applied for leak detection under lower signal-noise ratios. The possibility of detecting and locating a small leakage by the methods proposed has been demonstrated by a number of simulation tests conducted on the Fugen NPP site.