Research On Location And Mass Estimation Method Of Reactor Vessel Loose Parts

Nuclear power plant reactor structure is complex,there are a large number of parts.With the continuous flow of the primary circuit coolant,there is a risk of loosening and falling off of the components in the reactor.The existence of loose parts in the reactor makes the operation of the reactor a safety hazard.Accurate localization and mass estimation of the loose parts are beneficial to quickly find the position of the loose parts and judge the degree of failure of the loose parts,providing effective suggestions for the follow-up maintenance of the reactor,and ensure the safety of the reactor operation.In this paper,the method of localization and mass estimation of loose parts is researched.Deriving the theoretical calculation formula of loose part mass according to the analysis of the collision process based on the Hertz collision theory.According to the flexural wave equation,the vibration wave propagation process caused by the collision of loose parts is analyzed,and the wave velocity calculation formula is derived.The main research contents are as follows:(1)Concentrating on the fact that the existing loose parts localization methods have low accuracy,this paper performs EMD(Empirical Mode Decomposition)processing on the signal to eliminate the interference of other vibration wave components in the impact signal,so that the signal arrival time and wave velocity calculations are more accurate,and adopt a multi-sensor layout and develop a sensor selection strategy,selecting the optimal positioning sensor combination for localization analysis,and further improve localization accuracy;(2)Aiming at the problems of large errors and poor consistency in the existing loose parts mass estimation methods,this paper derives the theoretical calculation formula for the mass of the loose part based on the collision response law.The mass estimation feature is calculated by the effective value of the impact signal and the main frequency of the signal,and the mass estimation function model is established according to the relationship between the mass estimation feature and the mass.Finally,the accuracy and reliability of the proposed localization and mass estimation method of loose parts were verified by plate and vessel tests.