Study on corium jet breakup and fragmentation in sodium with a GPU-accelerated color-gradient lattice Boltzmann solver

•A GPU-accelerated color-gradient lattice Boltzmann solver is developed.•The solver is used to simulate hydrodynamic corium jet breakup and fragmentation in sodium.•The mechanisms and characteristics of corium jet breakup and fragmentation are analyzed. In this paper, the color-gradient lattice Boltzmann model (Saito et al., Phys. Re. E 98, 013,305, 2018) is used to study 3D hydrodynamic corium jet breakup and fragmentation in sodium. Firstly, an in-house GPU-accelerated color-gradient lattice Boltzmann solver is introduced in detail. Then, the solver is validated by comparing the simulation results with two demo Wood's metal jet experiments. Finally, the solver is used to study the characteristics and mechanisms of molten corium jet breakup and fragmentation in sodium under severe accident scenarios in a sodium-cooled fast reactor. The corium jet morphologies, breakup and fragmentation mechanisms, penetration depth, breakup length and fragment size distribution are extensively studied.