Multi-physical Coupling Research For Thorium Molten Salt Fast Reactor

The Molten Salt Reactor(MSR) with special liquid molten salt fuel is one of the sixadvanced reactor concepts identified by the Generation IV International Forum(GIF) as acandidate for cooperative development, which is characterized by remarkable advantages ininherent safety, fuel cycle, miniaturization, effective utilization of nuclear resources andproliferation resistance. In view of the main GIF goals and the perfect capable of breeding,actinide transmutation and safety in the thoium molten salt fast reactor(TMSFR), since2005,R&D in the countries of the world has focused on the development of fast-spectrum MSRconcepts combining the generic assets of fast neutron reactors with those relating to molten saltfluorides as fluid fuel and coolant, especially, for can-type TMSFR without solid moderator inthe core. The peculiar design and operation in TMSFR make inherent tightly coupling relationsbetween the neutron fux, the delayed neutron precursor, the heat transfer and the turbulent fow,which can result in new and important physical effect. Besides, the multi-physical couplingtechnology in the nuclear reactor is becoming the research frontier of the nuclear engineering athome and abroad. Hence, to bulid the thorium molten salt reactor integrated simulationplatform(TMSRINS) and develop the throrium motlen salt fast reactor three dimentionmulti-physical coupling code as an effective tool for multis-cale and multi-physics analysis inTMSFR have important significance in academic research and engineering application forunderstanding the characteristics of multi-physical coupling and optimizing the design in thethorium molten salt fast reactor.In the dissertation, firstly, the development and status of the molten salt reactor, themulti-physical coupling technology and the mutli-physical coupling research in molten saltreactor are reviewed and summaried. And then the neutron transport equation with the effect ofthe fluid flow is derived in detail, and the multi-group neutron diffusion equation of the moltensalt reactor is established by P1approximation,grouping theory and Reynolds-averaged method.The six-group delayed neutron precursor conservation equations with the effect of the turbulenttransport are derived detailly based on the principle of conservation of components. On the basisof baisc principles of conservation of mass, momentum and energy, adopting Reynolds-averagedmethod and Boussinesq eddy viscosity assumption, the turbulent Navier-Stokes equation, thegoverning euqation for turbulent kinetic energy k, the governing equation for the rate of viscous dissipation ε and the energy equation expressed as the temperature T in the TMSFR are buildcompletely. Ultimately, these equations with relevant boundary conditions constitute themulti-physical coupling model in TMSFR. In order to shoose suitable numerical method to solvethe PDEs of the multi-physical model for the thorium molten salt fast reactor, in the dissertation,the spatial discretisation methods, the temporal discretisation methods and the multi-physicalcoupling chemes are analyzed and compared, at the same time, the numerical algorithms forthese discretised linear equations are also introduced.After bluiding the TMSRINS platform, in the light of multi-physical coupling model forTMSFR, finite volume method for saptical discretisation, Euler fully implicit method fortemporal discretisation, Gauss-Seidel method, relaxation method, conjugate gradient method,bi-conjugate gradient, preconditioned conjugate gradient method and preconditionedbi-conjugate gradient method for discretised linear equations, and serial, implicit, direct couplingscheme, the three dimension multi-physical coupling code-TMSR3D for TMSFR is develpedand validated. The TMSR3D code support structured and unstructured mesh, uses the same meshin different modules, fully implicit coupling scheme in coupling solvers, three dimensionvisualization in post-processing, C++object-oriented programming language, modular-basedcode design and so on. With the purpose of demonstrating the the functions and features of theTMSR3D code, a concept design of the small thoium molten salt fast reactor is present, then theTMSR3D code is applied to analyze the effect of the fuel inlet velocity, the effect of the fuelresident time out of the core and the effect of the turbulent diffusion at the steady state. Inaddition, the transient characteristics in the core, particularly, the effect of the turbulent diffusion,are simulated and analyzed after a step reactivity addition. The results indicate that the TMSR3Dcode can adequately and effectively simulates the multi-physical coupling phenomena at steadystate and transient in the core of TMSFR，and can especially well refect the transport effect ofthe convective term and the turbulent diffusion term, which is peculiar to TMSFR.