CFD Modeling of Hydrodynamic Jet Breakup of Molten Nuclear Fuel in the Coolant

During a severe accident, the molten nuclear fuel jet breakup in a liquid sodium pool received considerable attention from the Sodium-cooled Fast Reactor (SFR) community. The jet breakup phenomenon assumes importance in the in-vessel cooling of core debris on the core catcher after the accident. The Volume-of-Fluid (VoF)-based solver available in Ansys Fluent with appropriate initial and boundary conditions is used to simulate the jet breakup behavior. To capture the interface accurately and with less computational effort adaptive mesh refinement technique is employed. In the present study molten fuel jet of diameter (D) varying from 1 to 25 mm and with an inlet velocity of 5 m/s is allowed to fall into a column of liquid sodium, the width and height of the sodium column are chosen such that the wall effects are negligible. For cases under investigation, dimensionless breakup length (Lbrk/D) lies between 20 and 35 in the Atomization regime and is close to 35 in the sinuous regime.