Study On Thermal Fatigue Resulting Influence On Nuclear Class Pipe Life And Pipe Monitoring Technology

In nuclear reactor engineering field,the thermal stratification phenomenon widely exists in pressurizer surge line,feed water pipe and other nuclear pipes.Operating experience shows that this kind of phenomenon would influence the safe operation of the nuclear reactor and equipment,lead pressurizer surge line thermal fatigue failure and pipe cracks,then pipeline rupture due to crack propagation,result serious loss of coolant accident in nuclear power plant.IAEA also explicitly request new nuclear power plant must consider the effect of thermal stratification on the integrity of pressurizer surge line,and monitor thermal fatigue of nuclear pipes where thermal stratification exists.In this study,CFD method is used to analysis the temperature and stress distribution of pressurizer surge line,and the initial thermal fatigue monitoring system is designed based on the C-M equation.The three-dimensional entity modeling method is used to establish the analysis model for thermal stratification phenomenon in the pressurizer surge line.The finite element method is adopted to simulate thermal stratification,and the temperature distribution of pressurizer surge line is obtained.Moreover,the stress distribution of pressurizer surge line is calculated with existing thermal stratification.According to the French RCC-M PWR nuclear machinery design and construction guidelines,the structure safety of pressurizer surge line is assessed and the vulnerable position of pressurizer surge line is determined.Considering the reactor heating process,the monitoring technology of thermal fatigue life is studied and C # language is used to design and construct the thermal fatigue monitoring system based on circulation and the life prediction.The fixed stress calculation formula is used to calculate the stress intensity of pressurizer surge line,the rain flow method is utilized to count stress amplitude and the C-M equation is applied to predict the fatigue life of pipes in the program.Test results show that the program can correctly realize computing functions and completely monitor the thermal fatigue life,accomplish providing accurate life status for the staff.Life monitoring technology research provides theory and data support for nuclear power plant equipment aging management and life prolongation.