Thermal Performance Analysis And Vibration State Identification Of Steam Pipe In Secondary Circuit System Of Nuclear Power Plant

Nuclear power,as the cleanest and most effective energy that is of great significance for promoting national energy restructuring and sustainable development.In the secondary circulation system of nuclear power system,steam pipeline is a very key component,which has great influence on the safety and economic performance of nuclear power system during working.The in-depth study of the thermodynamic behavior and vibration characteristics of the steam pipeline in the second loop can diagnose the problems in the pipeline,Guide pipeline design and operation,and reduce the occurrence of pipeline accidents,which is of great significance to ensure the safety and economic operation of nuclear power plant.Because the variation of medium pressure in pipeline has great effect on the stability of pipeline,especially the large diameter steam pipeline with steam-water two-phase flow is more prone to vibration.Therefore,the paper adopts the AP1000 unit as the object of study,then the influence of pressure loss on the economy of the thermal system and the recognition of the vibration state of the pipeline are studied.Compared with the thermal generator set,the nuclear turbine has a drainage device between the stages,so it is difficult to build a mechanism analysis model.To solve this problem,first of all,use EBSILON software to model the secondary circuit system of the AP1000 unit,change the pressure loss of the main steam pipe and each extraction pipe respectively,and record the change of the extraction port parameters.After that,the performance calculation program of nuclear conventional island thermal system is compiled using Python language,and the parameters output by EBSILON model are fitted and then imported into the program to calculate the impact of steam pipeline pressure loss changes on the unit economy.The research shows that the change of heat consumption is not the same after the same percentage of the pressure loss in the extraction line of different heaters;The lower the extraction pressure,the greater the impact of the same pressure loss change on the unit’s economy;Secondly,the influence of main steam pipe pressure loss on the unit economy is studied.The results show that the main steam pipe pressure loss increases,and the unit heat loss increases.The lower the working condition,the unit heat loss increases with the same percentage of pressure loss change.Finally,the vibration signal of the steam pipe from the high pressure discharge to the heater of the heating network is decomposed and reconstructed by wavelet packet transform,and the energy eigenvectors in x,y and z directions are established.In order to analyze the pipeline state more accurately,support vector machine and SOM neural network are proposed.By comparing the effect category and classification accuracy of the optimized SVM and the optimized SVM and SOM,An example shows that the improved support vector machine is more effective in pipe state recognition.This paper has completed the analysis of the impact of pipeline pressure loss change on the economy of the nuclear power second-loop system and identifies pipeline vibration status,providing reliable recommendations for pipeline design,maintenance,and improving the economic performance of nuclear power units,and providing important references for performance monitoring and fault diagnosis of nuclear power secondary loop pipeline systems.