Keywords: loose parts monitoring system, LPMS, impact location estimation, continuous wavelet transform, time-frequency analysis, reliability, power plants, nuclear steam supply system, structural integrity monitoring, nuclear reactors, nuclear energy, nuclear power, nuclear technology, nuclear science
Application of continuous wavelet transform to the impact location estimation of the Loose Parts Monitoring System (LPMS)
The Loose Parts Monitoring System (LPMS) provides information on the location of a loosened or detached metal impacted onto the inner surface of a primary pressure boundary and on a mass or energy of the impact signal. For the conventional system, it is popular to employ the group delay among the sensors installed within 3 ft range from the impact source in a collection zone as stated in the Reg. Guide 1.133. However, there exist inherent errors for the estimation of the true location of the impact since it is highly dependent on the plant personnel's decision to determine the arrival time differences of the generated wave group among the neighbouring sensors. To overcome this problem in this study, the two-dimensional approach has been proposed and applied to effectively estimate the arrival time differences of the impact signal by using continuous wavelet transform which is one of the linear time-frequency analysis methods. The experiment has been implemented on the plate model and the steam generator's lower part in a real plant using steel balls. It is expected that the reliability of the location estimation could be enhanced when the proposed time-frequency method is introduced into the LPMS system.