Computational Fluid Dynamics Analysis of the MELODIE Bubble Column for PbLi Tritium Extraction

Lead-lithium (PbLi), a eutectic metal, is a key liquid breeder material for tritium generation in the tritium-deuterium fusion reaction for fusion energy. Once tritium is produced, efficient extraction from PbLi is critical to the reactor’s safety and tritium fueling economy. The MELODIE facility conducted hydrogen extraction experiments with a PbLi bubble column; however, the resulting analysis was limited.This study developed a computational fluid dynamics (CFD) model by using a Eulerian-Eulerian two-fluid approach to analyze hydrogen extraction from PbLi in the MELODIE bubble column configuration. The results obtained from the model were compared against the MELODIE experimental data. Interfacial models were surveyed and selected based on their validation against mercury experiments reported in the literature, as mercury exhibits physical properties similar to PbLi. Mass transfer models ranging from rigid to mobile mechanisms were surveyed and analyzed under varying solubility conditions, and a comparative assessment of the interfacial mass transfer models was performed.While the mobile and semi-mobile interface models agreed well with the experimental data at low to moderate gas-to-liquid flow ratios, the highest gas-to-liquid flow ratio results aligned with a rigid interface assumption. The CFD results suggest a possible transition in bubble interface behavior, which is highly unlikely. However, when the Aiello solubility is slightly reduced, the experimental data aligned with the rigid interface assumption, restoring physical consistency.