Study On The Wear Reliability Of Steam Generator Tubes In Nuclear Power Plants

With the increase of nuclear power installed capacity,the safety and reliability of nuclear pressurized components become more and more important.Steam Generator(SG)as one of the main pressure parts of the nuclear power plant,its structure is complicated and the number of heat transfer tubes is large.The Flow Induced Vibration(FIV)between the tubes and support plates or anti-vibration bars becomes more serious.Therefore,it is of great significance to study the FIV in nuclear steam generator for nuclear safety and reliability.At present,many research institutions and scholars have studied the FIV phenomenon in the SG,and done some wear tests for the tubes.However,less research for the wear failure of tubes caused by FIV with reliability method has been investigated.This paper preliminary simulates the FIV in SG.The scatter of wear coefficient is studied with probabilistic approach.Then,the wear volume is estimated with Archard formula.At last,reliability analysis has been performed for the tubes,to predict the practical time.The main work and achievements are as follows:(1)The statistical analysis for the uncertainty of the wear coefficient is carried out.As for a set of wear coefficient data which obey Weibull distribution,moment estimation and Bayesian estimation are adopted to solve the parameters.It is found that the parameters obtained by this method can reflect the sample data distribution better.(2)A preliminary study on the FIV is carried out.The vortex shedding frequency,the natural frequency and the critical flow velocity of the heat transfer tube are calculated firstly,and then the ANSYS modal analysis is used to analyze the vibration situation of different bend radius tubes.The result suggests that the greater bend radius,the smaller corresponding modal frequencies,which means the tubes are more sensitive to external incentives.Hence,the analysis can provide the necessary input for wear load.(3)The residual wall thickness of tubes under different wear scars are analyzed according to Archard formula,predicting the usable life and failure probabilities of tubes under different wear work rates.The innovations of this paper: 1)the proposed parameters estimate method combines Bayesian estimation and moment estimation 2)the practical pipe working time is computed through the wear scars,also studied the relationship with the pipe wear depth and the pipe practical working time,the relationship with the wear working rate and the failure probability.It is hope to expand the sample data to get a more reliable wear coefficient distribution.This thesis can provide some references for the design and the eddy current testing interval of the SG.