Over the past few decades, the phase-field lattice Boltzmann method has emerged as an efficient and powerful tool for the numerical simulation of two-phase flows. In this study, a hybrid phase-field lattice Boltzmann method incorporating adaptive mesh refinement (AMR)[1] is developed to investigate the three-dimensional (3D) hydrodynamic breakup of corium jets in a liquid metal coolant pool. The proposed framework combines an improved finite volume method (FVM) for solving the conservative Allen-Cahn equation with a velocity-based lattice Boltzmann method (LBM) for the incompressible Navier-Stokes equations. The improved FVM mitigates numerical dispersion, thereby enhancing accuracy. To ensure robust simulation of high-Reynolds-number two-phase flows, the LBM employs a central-moment multiple-relaxation-time collision operator[2]. The method is validated against 3D Rayleigh-Taylor instability[3] and Wood’s metal jet breakup experiments[4], demonstrating good agreement between simulation and experimental results. Finally, the model is applied to simulate the breakup behavior of molten corium jets in sodium under severe accident conditions, highlighting its potential for accurately modeling liquid metal two-phase flows in nuclear safety analyses.