A numerical simulation method for molten material behavior in nuclear reactors

•A numerical simulation method based on computational fluid dynamics for calculating molten materials behavior is proposed.•A new Poisson solver is developed which drastically improves the computational performance of the JUPITER algorithm.•Verification and validation was performed by estimating fundamental problem characteristics and comparing with experimental data of molten material behavior. Projections obtained from JUPITER are in good agreement with these results.•Our conclusion is that JUPITER has a potential to efficiently evaluate molten material behavior.