Abstract: The computational fluid dynamics（CFD） simulation was adopted to study the internal flow field in nozzle chamber,which was involved in the casting nozzle in the preparation process of UO₂ kernel particles.In particular,the flow flux uniformity analysis of each nozzle,which is the important determinant factor of UO₂ kernel size uniformity,was focused on.Four possible factors that may affect the flow flux uniformity of nozzle in the actual production process were investigated,including the inflow direction,the nozzle distribution,the nozzle chamber levelness and the nozzle orifice size.From the simulation results we can be found that,relative to the other three influencing factors,the nozzle orifice size is the key factor and is one of the main reasons for giving rise to the non-uniformity of particle size.The simulation results suggested that the size of the nozzle orifice should be particularly concerned about in the actual production processes.Furtherly,the mathematical analysis of the flow equation was given,and the theoretical validation of the simulation results was drawn out.The conclusions of this study can be used to develop targeted experimental studies further and also provide a reference to improve the uniformity of particle size.