Research On Modular Modeling Method Of Reactor Coolant System

The reactor core and the primary reactor coolant system are the central parts of the nuclear power plant.The modeling method based on the concept of "control volume” is mainly used to the primary reactor coolant system.The method is mainly used in some large thermal-hydraulic program such as Relap5,THEATRe and so on.The major feature of the modeling method is that the calculation accuracy and the speed are affected by the number of control volume.The finer the body divides,the higher precision it calculates,but it will also increase the computing time.Modular modeling method has some advantages of a short development cycle,high modeling accuracy,an easy way to modify,high resource utilization and low calculation cost and so on.However,due to the characteristics of multivariate,large inertia,and nonlinear,time-varying distribution parameters and so on,the modular modeling method was rarely used in modeling the primary reactor coolant system to ensure stability calculations.The purpose of this article is aimed at researching loosely coupled interface scheme and analyzing a suitable modular modeling method for the primary reactor coolant system.The simulation models of the primary reactor coolant system equipment modules,including the core physics-thermal model,the natural circulation steam generator model,the steam generator model,the pressurizer model and the main pump model were firstly built by using thermal-hydraulic simulation program THEATRe in this study.The solution is the node momentum and node pressure method(NPNM),which can not only accurately simulate a wider range of conditions,but can also improve the computing speed.Secondly,according to the structural characteristics of the reactor core and the primary reactor coolant system,researching the model interface Loosely coupling scheme,selecting the suitable boundary conditions,the pressurizer data exchange and oscillating flow calculation methods,physical-thermal coupling scheme and data exchange frequency,and using the coupling scheme to build modular simulation model of the reactor core and the primary reactor coolant system.Finally,the modular modeling method and the traditional modeling method are compared in steady-state and transient working conditions,include the varying load conditions,the reactivity insertion accident and loss of flow accident.In addition,in order to meet the requirement of real-time calculation of refinement model,MPI technology is used to build multi-machines(nodes)distributed simulation platform,and modify and transplant THEATRe program,so that the model can meet the requirements of parallel computing.According to the complexity of the models,the suitable assignment scheme is used to achieve parallel real-time simulation.