Research Of Fast Modeling Technology For Nuclear Power Secondary Loop System Simulation

The secondary loop system is an essential part in nuclear power plant.In the nuclear power system,the second loop system transfers the heat from which the reactor generates,converting thermal energy into kinetic.The secondary loop system is occupying an important position in the process of energy conversion.At present,computer and simulation technology has played an increasingly important role in the system simulation for nuclear power plants.The simulation technology could achieve the performance and analysis well for the actual system.It could also provide support for research and development of digital nuclear power plant.Until now in the system simulation for nuclear power plant,reactor and primary loop system are the main research object generally.However,the forms like boundary condition and lumped parameters method are often used for the simulation of secondary loop system.There are different kinds of equipment requiring consideration in the simulation of secondary loop system.Most of the simulating and modeling methods are lumped parameter method and onedimensional simulation modeling approach.Although those method is the main path to deal with issues related with high and enough degree of calculation accuracy,but it could not reflect the internal parameter distribution of the actual equipment adequately.Some other unique features cannot be effectively calculated and simulated also.During the simulation and modeling process of overall nuclear power secondary loop system,some simulation models and programs are often constructed corresponding to specific objects,resulting in poor reusability and versatility of programs.The requirements differ from the objects of simulation system.Based on the research status mentioned above,the fast modeling technology research for the nuclear power secondary loop system simulation was carried out.The related work was implemented from the perspective of equipment modeling and overall system modeling respectively.According to the equipment composition in the secondary loop system,the research on different equipment modeling and simulation is firstly executed.Under the condition of satisfying the demand of calculation time and accuracy,the modeling method of refined parameter distribution simulation model based on structure and physical phenomenon is realized for each main typical equipment with two phase heat transfer process.Based on the three basic characteristics with zones-nodes modularization,parameterization and refinement,the simulation model which could serve as the foundation of fast modeling technology is developed.It is also the basic of fast modeling equipment simulation library.Then there is the research on the construction and formation of system modeling by applying developed equipment simulation model.From the overall system level,the fast modeling framework is proposed and constructed.Some problems during the system modeling process are solved.To meet the different requirements of simulation for different types of secondary loop system,the system model could be modeling fast and conveniently for operation characteristics simulation.In-depth modeling and simulation related research on nuclear power secondary loop system and equipment was conducted in several areas as followings:There is the research on modeling and simulation of feed water heat exchanger in nuclear power secondary loop systems with multiple refined degrees.In term of the actual physical structure of the actual equipment,reasonable simplified assumptions could be proposed.The physical model of the feed water heat exchanger is simplified according to the actual physical process inside.The division of the multi-node simulation model with the two zones for the feed water heat exchanger was promoted.The actual tube rows and partitions were the basis for the division as well as the basis for changes in different refined degree.The steady state verification is performed on the established simulation model which could prove the accuracy.The operation characteristics and different parameters distribution analysis for the feed water heat exchanger are performed under two dynamic conditions.Comparison of three different refined degrees of feed water heat exchanger simulation models under different operating conditions could also prove the feasibility of this modeling and simulation method well.For the condenser in the nuclear power secondary loop system,the modeling and simulation method based on the numerical integral method along the mainstream flow direction was studied.According to the physical structure and operating characteristics of the actual condenser,the mainstream working fluid flowing directions on the shell side and the tube side were selected as the basis for modeling.The related reasonable assumptions were proposed to simply the developed model based on these processes.The integration method was employed in conjunction with the concept of average parameters along the path to convert the basic equations.For each process in the condenser,the reasonable heat transfer models were selected such as the degradation factor correlations for non-condensable gas.The established simulation model was verified and compared with steady state design parameters.The dynamic characteristics of the condenser under different operating conditions were validated.The credibility of the simulation model could be proved.The internal parameters distribution and operation characteristics along with the flow direction of the condenser were analyzed.For the deaerator in the nuclear power secondary loop system,the quasi 2-D refined parameter distribution modeling and simulation method was conducted.According to the physical process and phenomenon in the actual deaerator,the model with the two areas of the droplets spraying zone and the steam bubbling zone was divided.In each zone,the respective mainstream fluids are determined according to the motion state.More nodes are continued to be divided to ensure the calculation precision,refinement and speed.The pressure difference-flow distribution method is proposed for flow calculation to realize 2-D parameter distribution simulation and calculation.The steady state and dynamic conditions verification of the established deaerator model were carried out with comparative analysis,which could prove the accuracy and credibility.The analysis of the two-dimensional parameter distribution and operation characteristics of the deaerator was performed.With the simulation models built for different equipment,the further research is made from the overall level of the system.The research and implementation of the fast modeling technology for the secondary loop system simulation was carried out.The software with humanmachine interface platform was established.The three common basic characteristics of the simulation model for each equipment in the nuclear power secondary loop system,namely modularization,parameterization and refinement are the basic of equipment simulation model library.From the overall perspective of the secondary loop system and the feature of fast modeling technology these three basic characteristics could meet the requirement for fast modeling technology and use for different simulation.According to the actual modeling and simulation requirements for total system with some existing problems,approaches are proposed.Different approaches are applied to different problems such as equipment and system input parameter preprocessing and feedback,equipment simulation model time step uniformity,equipment connection to form the system,etc.The human-machine interface of the fast modeling and simulation platform for nuclear power secondary loop system was designed and developed.The practical examples and simulation experiments were combined with actual cases.The equipment simulation model formed by JTopmeret software and the refined parameter distributed equipment simulation model developed are adopted to construct different nuclear power plant secondary loop systems.The operating simulation and calculation is carried out.Those could illustrate the feasibility of the fast modeling system.