Study And Application Of SPH On FCI Resulting From Fast Reactor Core Disruptive Accident

Smoothed Particle Hydrodynamics（SPH）is a meshfree particle method which is based on Lagrangian.For the better performance to model complex hydrodynamics problem with freesurface,moving interface,deformation of boundary compared with the traditional grid-based method,SPH is widely applied to ship hydrodynamics,hydraulic engineering,aerospace,petrochemical engineering and mechanical engineering.This paper achieves the application of SPH to study the nuclear reactor accident by simulating the fuel-coolant interaction（FCI）resulting from fast reactor core disruptive accident with Fortran code.Firstly,the basic theoretical study of SPH is discussed in this paper and the SPH formulation of fluid governing equation is derived.The neighbouring particle search,solid boundary condition,solidification phase transformation and other related computational technologies are studied.A particle group search algorithm is developed to search pieces and the Poisson equation considering the pressure Dirichlet boundary condition is given.The calculation procedure is generally introduced.Secondly,models are calculated to verify the capacity of codes on simulating the free surface flow,heat conduction and solid–fluid mixture flow.The collapse of a water column is modeled and tested by comparing with numerical result from MPS and Fluent simulation,and experimental data.The comparative analysis between numerical and analytical solutions of flat heat conduction is given.The modelling of a square body drifted in water is achieved by importing PMS to SPH.Lastly,SPH is applied to simulate single molten metal droplet,continuous droplets and jet flow interact with coolant and heat transfer,solidification,solid-liquid mixture flow and surface tension are generally taken into account.The penetration process of single droplet with various initial temperature and velocity are simulated and it is concluded that the fragmentation of droplet is influenced by fragmentation-controlled and freezing-controlled regime.The falling interval and height of continuous droplets both influence the degree of fragmentation.The simulation of jet flow model presents a phenomenon that the coolant on both sides of the cavity smash together and form a jet injection.The impact of the jet injection leads to the molten metal smash tempestuously in short time which is agreed with a conclusion from another research.For the original SPH discretization scheme is limited to solve the problem with high density ratio,this paper employs an improved scheme to model a UO₂ ball falling into the coolant and eliminate the pressure instability on the interface.