Some aspects of the re-extension of the reactor plant life with VVER-440 on the example of Novovoronezh NPP UNIT 4

The drive of the reactor control and protection system (CPS) is a system of normal operation, important for safety. Malfunctions of the drives of the ARC type CPS are often the initial events for accidents leading to unauthorized downtime. The currently existing standard methods for monitoring the parameters of the CPS do not allow for a reliable assessment of the condition of the drives. In this paper, it is proposed to implement an approach that provides an increase in sensitivity when recognizing the states of the drives of the ARC control system by processing the initial signals, which are vibroacoustic signals registered on the lid of the upper unit of the VVER reactor. A procedure for processing diagnostic signals using singular spectrum analysis is proposed. The proposed approach differs from the known ones by the presence of a scaling procedure, which is implemented by multiplying the eigenvalue matrices by the gankelized matrices of the source data. Due to scaling, the necessary sensitivity increase is provided. The expected increase in sensitivity is based on the fact that the eigenvalues reflect the structure of the signals, which changes significantly under the influence of the defect. The proposed method was used to process vibroacoustic signals registered on the lid of the upper block of the VVER reactor unit. Experimental studies were carried out at the test stand of Izhorskiye Zavody OJSC. The results of processing experimental data indicate a high quality of diagnosis. The hypothesis was clearly confirmed that the difference in the structure of diagnostic signals of serviceable and faulty equipment can manifest itself in the eigenvalues of the gankel signal matrices. The approach proposed in the article to the processing of diagnostic signals is easily amenable to automation and can be implemented in the development of a diagnostic system for the drive of an ARC-type CPS.

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Improvement of methods for analyzing the technical condition of electromechanical equipment of nuclear power plants

Abidova

2023

GNS

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The article analyzes the problem of diagnostics of NPP electric drive valves. Failure of this type of equipment can become the initial event for design or beyond design accident. Therefore, during the period of preventive maintenance at NPPs diagnostics of up to 2000 units of valves is carried out mainly by registration and analysis of the motor current signal during opening and closing. However, the applied statistical and frequency analysis methods do not always provide the necessary quality of diagnostics. The article points out the disadvantage of the applied methods – insensitivity to the dynamics of electromechanical equipment in terms of nonlinear manifestations of defects. As a tool for analyzing these manifestations the phase-plane method is proposed and its theoretical basis is outlined. The diagnostic signal is described as a vector diagram of a harmonic series subjected to amplitude and phase modulation. The most characteristic forms of phase trajectories - cardioids, nephroids, epicycloids – are shown. The main advantages of the phase-plane method over traditional frequency methods – sensitivity, possibility to identify the type of modulation, phase shift, dynamic and chaotic manifestations – are demonstrated by examples of processing diagnostic signals of NPP equipment. An important advantage of signal representation in the form of phase portrait is the visualization of dynamic features of the signal. The result of the work is a new method that allows to extract additional information about the object state by analyzing the non-stationary component of the initial data. It is proposed to introduce the phase-plane method into the practice of processing diagnostic signals of electric drive valves and other electromechanical equipment operated at NPPs.

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Some aspects of the re-extension of the reactor plant life with VVER-440 on the example of Novovoronezh NPP UNIT 4

Abstract: И з в е с т и я в у з о в • Я д е р н а я э н е р г е т и к а • № 2 • 2 0 1 9 91

Cited by 3 publications

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Prerequisites for the Implementation of a Risk-Oriented MRO Strategy for NPP Valves

Prerequisites for the Implementation of a Risk-Oriented MRO Strategy for NPP Valves

Diagnostics of the drive of the control and protection system of the reactor plant ark type

Improvement of methods for analyzing the technical condition of electromechanical equipment of nuclear power plants

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