Research On Reconfigurable Simulation Models Of Pipe Networks And Equipments In NPP

In different life sections for nuclear power plants,the operating characteristics is one of the most important focus point and research area.In addition to experimental way,simulation has become an important method due to its high safety,good economy and strong repeatability.However,in current researches,all simulation stages in nuclear power plant lifetime are simulated by same model,possibly it is difficult to model when the parameters are missing,or the accuracy is insufficient when the parameters are detailed;the resistance coefficients were fully based on calculating or giving,which lead to rough results under dynamic operations or large errors with actual data;homogeneous model cannot simulate the separate phenomena in vessel,while the separated model cost too much calculation source and the astringency is low;general equipment models cannot show the inner characteristics,and inner-characteristic models do not have a good coupling performance with pipe network model;the connection relationship of nodes and flows cannot be changed quickly lead to a bad reconfigurability,which cannot meet the requirements of designing simulation,evaluation simulation and training simulation.In order to solve the above problems,a multi-objective application,reconfigurable pipe network and equipment model for nuclear power plant was proposed in this paper.The model is aiming at the process system simulation needs of different stages of nuclear power plant.For the design stage,design simulation model has the ability to predict unknown operating conditions;for the demonstration stage,evaluation simulation model has a high degree of refinement;for the operation stage,the training simulation model can reproduce the given design operating conditions.In the single-phase pipe network model present in this paper,the on-way resistance coefficients are calculated to meet the simulation requirements under low velocity flow in long pipeline,and the whole local resistance coefficient is given to fit the actual or designing data.Conservation models of mass,momentum and energy are used to simulate the flow process,and the transient term in momentum equation is carried out as the mark to distinguish the multi-objective application model.It is considered in the design simulation model and the evaluation simulation model,while not considered in the training simulation model.At the same time,the pressure wave transmission model is considered in the evaluation simulation model to meet the needs of fine evaluation.In the two-phase pipe network model,in order to ensure the stability,rapidity and accuracy of the solution,this paper establishes a model based on the l conservation models of mass,momentum and energy,considering steam,water and air 3 kinds of medium,aiming at different simulation objects,presents two kinds of calculation sub models: the five equation model of the flow between pipes and the six equation model of the flow between separators.For the equipment models in pipe network model,inner-characteristic models based on pipe network components are developed,which not only meets the coupling requirements,but also meets the needs of refined simulation.The multi-objective application are reflected in number of nodes divisions.Both of the pipe network model and equipment models are inserted a connection relation sign matrix.Based on the Doolittle method,a two-dimensional dynamic solving method of pressure and enthalpy are proposed in this paper.Using this two-dimensional dynamic solving method,nodes and flows connections can be changed quickly and dynamically.A different reconfigured model can be reconstructed quickly which do not need to start from the drawing of simulation digraph,greatly reduces the workload of modeling personnel in the design,evaluation and training stages.The accuracy and reconfigurability of the pipe network and equipment models proposed in this paper are verified by the simulation of actual systems and equipment.In the single-phase pipe network,the models for design simulation,evaluation simulation and training simulation application can reflect their respective calculation differences;and by comparing with the calculation results of Jtopmeret,the accuracy,stability and application scopes of the models can be verified.In the two-phase pipe network model,the phase change caused by energy change can be simulated accuracy,and the simulation results in the pipeline and vessel can reflect the characteristics different.Comparing with Jtopmeret,the calculation results of some parameters are more accurate.The equipment models can get the refined parameter distribution inside,which has a high degree of refinement;the components of the pipe network model are directly used for modeling,which has strong coupling with the pipe network model.By modifying the symbols of the parameters in connection relation sign matrix,the pipe network model was tested by adding pipes and modifying the break positions,the fast reconfigurability of the model is verified.The calculation results of the model before and after reconstruction are analyzed.The simulation ability and accuracy of the model before and after reconstruction are the same.By using the pipe network and equipment models built in this paper,the third loop model of China Experimental Fast Reactor(CEFR)was modeled and tested.The models were connected by boundaries and implanted into the CEFR full range simulator of Harbin Engineering University.Dynamic testing the model under power reducing from 100%FP to the lowest operating state of the third loops and the inverse process.The fluid includes subcooled water,saturated water,two-phase,saturated steam and superheated steam,pressure range from 14 MPa main steam pipe to 0.02 MPa condenser,and the conditions include single-phase flow and phase changing flow.The test results show that the calculation results of the proposed model are in line with the theoretical analysis,and the stability is not divergent when the model is switched.It has good simulation ability for severe conditions,and the calculation results can reflect the advantages of the model.Through the work of this paper,it is concluded that the single-phase and two-phase pipe network model and equipment models proposed in this paper have high calculation accuracy and good calculation stability,can meet the needs of multi-objective simulation applications,models can reconfigure quickly.Designing schemes are changed frequently in the design stage,the evaluation and comparison of multiple similar systems in the demonstration stage,and the breach is added at any position in the training stage.For those stages use,the solution method based on two-dimensional matrix makes the model have the ability of fast reconfiguration,which greatly reduces the workload of modeling and debugging on the modelling programmer.The model after reconstruction has the same simulation ability and accuracy as the original model,can be reconstructed infinitely in theory.