Numerical Simulation of Corium Jet Fragmentation

Severe accident studies have become important for understanding the environmental impact of nuclear power following the Three Mile Island (TMI) accident. Severe accident phenomena are interdisciplinary since they can include the interaction of molten corium with reactor structures and water, and the transport and release of fission products that carry vapors and aerosols. During an accident, molten corium may fall in the form of a jet into a water pool. The fragmentation of the corium jet is a critical process concerning Fuel-Coolant Interactions (FCI). A steam explosion could occur depending on jet fragmentation and dispersion in the water. A 2-D in-house CFD MATLAB script has been developed by employing the Volume of Fluid Method (VOF) to simulate jet fragmentation in a water pool. This research is the first study to use the Multidimensional Universal Limiter for Explicit Solution (MULES) algorithm to capture the interface behavior in the jet breakup process. The effect of the compression constant, the mesh sensitivity, and the face correction loop on the MULES are investigated in this thesis. Moreover, the effects of the jet inlet velocity and jet diameter on the jet breakup length are numerically studied using the newly developed code. The simulation results compared well with the experimental results and another numerical study found in the literature.