Test Analysis And Improvement Research On Thermal Performance Of Nuclear Power Plant Condenser

The condenser is one of the important equipment on the conventional island of a nuclear power plant.In order to ensure that the power generation capacity of the nuclear power plant is maintained at the design standard and the system operation is safe and reliable,it is necessary to test whether the key parameters of the condenser are in the normal range during the operation of the condenser,and adjust and adjust the operation mode of the unit.Maintenance provides a basis for technical decision-making.In accordance with the requirements of ASME PTC12.2 and in combination with the characteristics of condenser equipment in a coastal nuclear power plant in southwest China,parameters such as condenser back pressure,circulating cooling water temperature rise,condenser end difference,condensate subcooling degree,overall heat transfer coefficient,cleanliness of heat transfer pipe and circulating cooling water flow rate were selected as the monitoring target parameters for the condenser thermal performance test.On the basis of the existing nuclear power plant condenser thermal performance test methods,in order to solve the problem that the accuracy of the circulating cooling water flow online ultrasonic measuring device cannot meet the precise evaluation of the thermal performance,the test data acquisition and analysis,the circulating water density and specific heat capacity calculation modules are deeply studied and optimization.The main research contents include:1.According to the thermal balance principle of the condenser inlet and outlet,calculate the heat load discharged into the condenser.By measuring the temperature of the circulating water inlet and outlet,the circulating water flow can be calculated,reducing the influence of the online ultrasonic flow measurement error on the test results;2.The experimental calculation software considers the introduction of TEOS-10 seawater thermodynamic equations to calculate the circulating water density and constant pressure specific heat capacity.Compared with the original experimental system software using the interpolation method,the results show that the new equation can improve the accuracy of the experimental results.The segmented fitting method is adopted to correct the circulating water flow and temperature,and the error after fitting can meet the requirements of engineering calculation accuracy.3.Since the original test system needs to export the data for processing and calculation after the test data collection is completed,by adopting the distributed arrangement of IMP acquisition boards,using DDE dynamic data exchange to enter the test data into the calculation and analysis software,real-time data processing is realized and avoided The test failed due to abnormal measurement point data.According to the results of field experiments,the reasons for the low overall heat transfer coefficient during the operation of the condenser were analyzed and improved methods were proposed.Revise the upgrade test procedure to better guide the development of the cycle thermal performance test of the power station.By analyzing and calculating the influencing factors of the deviation of test results,it is found that the measurement error of inlet and outlet temperature of circulating cooling water differs by 0.1℃,that is,the deviation of circulating water flow of condenser can be about 1%.Using seawater thermodynamic equation TEOS-10 to calculate seawater density and specific heat capacity at constant pressure,the results show that the measurement error of condenser pressure is 1mbar,which can lead to the calculation error of actual heat transfer coefficient K of the condenser,and the corrected value of seawater density is less than 0.005 kg·m^-3.The historical data of each major overhaul of 6 units in a nuclear power base in South China were randomly selected,and the software was used for comparative analysis.The maximum deviation of cleanliness calculation was only 0.004.The results of two experiments before and after the first overhaul of Unit 1 of a coastal nuclear power plant in southwest China show that the overall heat transfer coefficient of the condenser during operation is lower than the designed value.According to the experimental data,the main reasons are high back pressure of the condenser and low cleaning coefficient of the cooled titanium tube.The high back pressure may be related to the unreasonable arrangement of the titanium tube bundle,and the cleaning coefficient is greatly affected by the local seawater quality.Moreover,the high-pressure water flushing of the titanium tube during the overhaul has a poor recovery effect on the cleaning coefficient of the condenser,so a more advanced titanium tube cleaning method should be introduced in the improvement direction.The results of this paper have good reference significance in the thermal performance test implementation and result evaluation of condenser in coastal nuclear power station,which can meet the needs of operation adjustment and maintenance strategy arrangement of condenser in power plant.