Development And Application Of Thermal Hydraulics And Related Multiphysics Coupling Code For Advanced Nuclear Reactors

Multiphysics coupling phenomena exist in various reactors,especialy the advanced nuclear reactors.Multiphysics coupling besides with big scale parallel computing are the key techniques of numerical reactor.Traditional coupling method,which is based on the extra coupling interface between different codes,can't meet the strong coupling,high precision and big scale parallel requirement.The essence of Multiphysics coupling is partial differential equations.Developing the Multiphysics code based on an integrate platform is the tendency of numerical reactor.In this paper,authors developed a series of numerical code based on an open source CFD code:OpenFOAM,analyzing the magnetohydrodynamic phenomena in liquid metal blanket of fusion reactor and neutronics coupling with thermal hydraulics phenomena in fission reactors,in order to explore the key techniques and difficulties of multiphysics coupling in advanced nuclear systems.1)Magnetohydrodynamics code based on OpenFOAM used for liquid metal flow under strong magnetic field was developed.Electric potential method was used to solve the Maxwell fluid coupling equations.Conservative and consistent scheme was adopted to solve the electric potential gradient and electric current.PISO algorithm was used to solve NS equations.In order to validate the correctness of the MHD code,SHERCLIFF,HUNT,ALEX rectangular pipe and round pipe were chosen as the benchmark cases.The results showed that the numerical code can accurately solve the liquid metal flow under uniform and non-uniform magnetic field,orthogonal and non-orthogonal meshes.Complex geometries,such as sudden expansion pipes will frequently exist in the liquid metal blankets.There will be obvious 3D MHD effect in these components.Numerical analysis of MHD flow in expansion pipes with different expansion lengths and different expansion ratios have been performed.From the comparison,MHD flow mechanism in expansion pipes have been concluded.These conclusions can be used to the design of liquid metal blankets.Besides,the magneto-convection will be the dominant flow when liquid metal creep flow in blankets.So MHD code have been coupled with heat transfer.The magneto-convection in vertical squre under different magnetic field have been investigated.2)Point kinetic model have been coupled with CFD thermal hydraulics based on OpenFOAM platform,besides,the fuel pin pellet have been implemented in it.This neutronics/thermal hydraulics coupling code aims at explore the using of multi meshes in a single code.Mathmaticaly speaking,point kinetic model is in ordinary differential equations,and CFD and fuel pin pellet are in partial differential equations forms.Key techniques of coupling between these two kinds of equations have been drawn.Separate validation of these three module and integrate validtation of the coupling code have been done.The results showed the correctness of the coupling code.3)To meet the requirement of non-symmetry cooling,local disturbance and other transient accident analysis,neutron diffusion model have been added in OpenFOAM.Critical sphere,critical cylinder and IAEA,TWIGL and some other benchmark cases are used to examine the neutron diffusion code.After that,the preliminary coupling between neutron diffusion and CFD thermal hydraulics have been done.4)Neutronics/CFD thermal hydraulics coupling code based on point kinetics model have been used to do some application research,which aims to explore the adapatiblity of the coupling code.First one is the sensitivity analysis of small modular natural circulation lead cooled fast reactor with 100MWth,which caused by the burn up the core;Second is the lost trip analysis of ADS subcritical reactors;Third one is the non-symmetry activity insertion accident.This paper developed a series Multiphysics coupling code including liquid metal MHD code and neutronics/CFD thermal hydraulics coupling code based on an object oriented CFD framework.Finite volume method was used to discretise the partical differential equations and coupling between different partial differential equations have been performed.These codes have been validated and used to the specific phenomena analysis.The key techniques of Multiphysics coupling code based on a integrate platform have been explored.These resreaches help improving the quality of nuclear software of our country.It has some kind of engineer value.