Study On Optimization Design Of Open Natural Circulation System By Improved Genetic Algorithm

Since the first nuclear power plant built,people more and more favor in the clean and efficient way of generating.In order to ensure as much as possible there is no accident during the operation of the nuclear power plant,systems are often equipped with heat removal device used for the residual heat removal at the time of the accident.But several serious accidents happened in recent decades,it shows that the plant wants to be safe by using power heat removal system in case of floods or strong vibrations tend to failure.So the passive safety system gradually being applied in the residual heat removal,including heat derived by using their density difference cycle of natural circulation system.this paper improved genetic algorithm in order to optimize the open natural circulation system,considering the heat and efficiency this paper produced a parameter named total heat transfer per unit area,then using the improved algorithm optimized the open natural circulation system.The parameters that maximize the total heat transfer per unit area are found by the algorithm.the results of this research are as follows:(1)This paper studied the operating principle of open natural circulation system and the variation of thermal parameters of the system.In order to facilitate the analysis of the results,the system structure is simplified.And the model was built by C# software.The trend of mass flow with time in the first 1400 s of the system is calculated.The calculation results are compared with the reference data,the differences between the calculated system initial 1400 s mass flow trend and the reference data were less than 5%,therefore,the accuracy of the established model and subsequent results has been proved.(2)In order to improve the computational power of genetic algorithm,the concept of marked interval is introduced.After a certain gene is arranged according to the numerical size,if the gene value of 10% individuals is relatively concentrated,which is less than15% of the maximum range of the gene,then mark the 5% scope of the center.The possible worse effective genes and the possible better effective genes could be marked.When a new individual gene falls into the marker range,it will be specially manipulated.This method can improve the effectiveness of crossover and mutation operations of genetic algorithms.And the algorithm in this paper and many other existing improved algorithms are used to calculate different complex functions.Therefore,the optimization effect of the algorithm in this paper is verified.(3)The system is studied by example optimization.Through the sensitivity analysis of parameters,the height of the pipe,the number of the pipe,the pipe diameter,insulation pipe diameter and the height of thermal insulation were determined as the optimization variables.The optimal goal is the accumulated heat of system initial 1400 s per unit area.The optimization design of the open natural circulation system has been carried out with the proposed improved genetic algorithm to find the optimal structure parameters under the constraint of stable circulation operation.The final optimized results obtained are as follows: the height of the pipe,the number of the pipe,the pipe diameter,insulation pipe diameter and the height of thermal insulation are 2.48 m,100,0.02 m,0.24 m and 5.76 m.After optimization,the accumulated heat of system initial 1400 s per unit area increased by20.8%,which proves that the optimization process of the algorithm can effectively improved the heat transfer capacity of the system.The research results can provide data support for the selection of system structural parameters and have certain theoretical reference value.