Research On Three-dimensional Nuclear-thermal Coupling Method Based On JMCT And FLUENT

There is a strong feedback mechanism between physics and thermodynamic water in reactor core.The pile of physics-thermal coupling can accurately obtain the steady state and transient behavior in the runtime,thermal parameter distribution,improve the accuracy of the safety design,reduce the safety margin,improve efficiency,has important significance for reactor design and analysis.Within the core of fission power distribution determines the change of the thermal hydraulic parameters,and the distribution of thermal hydraulic parameters and by the doppler effect and moderator temperature fuel effect to influence the change of reactivity.In the process of studying the complex feedback mechanism between physics and thermal hydraulic power,various coupling methods and coupling procedures are continuously developed and improved.Using Monte Carlo program,can be applied to complex geometry,have a lot of nuclear database,and CFD sequence based on first principles,can solve,fine data accurate,better able to feature analysis of the reactor.In this paper,the coupling study between the two processes is carried out.Using both procedures coupling research need to separate modeling,physical model and the thermal-hydraulic models and then the grid matching,meshing dimensions will affect the calculation accuracy and computation time.Based on the mature and reliable MCNP5 Monte Carlo software and computer fluid dynamics software Fluent as the research object,to carry out the coupling process of grid scale optimization research,analysis the influence of different grid scale to the computing result,get the most suitable physical and thermal coupling of grid scale,put forward in view of the pressurized water reactor in the process of component model grid optimization scheme,and to establish a model to validate the result.The JMCT program is a neutron-photon coupled Monte Carlo particle transport simulation software with fine physical computation and geometric description.In this paper,we developed the coupling program based on the homemade monte-carlo software JMCT2.2 and computational fluid mechanics software Fluent6.3.26 by using C++ language and used the Tally6 card to count on the fission deposition.Through the interface program,the deposition can be extracted and converted into power density and exported.Through the Fluent UDF function,the output of power is completed,and the output of density and temperature is achieved.Through grid optimization,we analyzed the result of the typical pressurized water reactor model and found that temperature and density as the neutronics model selection criterion of grid scale modeling can greatly reduce workload,improve the computational efficiency and ensure the calculation accuracy.Coupling calculation results by comparing JMCT-FLUENT coupled with MCNP-FLUENT calculation results,and analyzes each grid computing power and temperature distribution,as well as the overall model calculation results of the evaluation,evaluation JMCT and the accuracy of the FLUENT program coupling.It is found that the JMCT-FLUENT coupling can accurately introduce the feedback of temperature and density,and can accurately calculate the parameters in the reactor.