Abstract: In severe accidents of a nuclear power plant, the released radioactive aerosols can be removed by pool scrubbing effect. Two-phase numerical simulation of the pool scrubbing process is necessary. The boundary conditions at the bubble injection point need to be determined before using the two-phase CFD program. Based on the framework of Integration of Pool scrubbing Research to Enhance Source-term Calculations (IPRESCA) project and the volume of fluid (VOF) method, a numerical simulation of gas injected bubble dynamics from single submerged orifice was carried out. Bubble size, shape, and detachment frequency at the orifice were captured. Sensitivity analysis of the influence of bubble injection speed on bubble detachment frequency was carried out. The bubble centroid height was obtained by DBSCAN clustering algorithm, and the bubble rising velocity at different heights was calculated. The distribution of the mean void fraction along the z-axis direction and the distribution of mean void fraction and mean mixture velocity along the horizontal lines and radius in central plane at different height are given.