[en] The off-take and liquid entrainment on the air-water interface is experimentally investigated in the T-junction that has a vertical upward branch. In case of the pressurizer manway opening during a shutdown operation the steam generated in the core flows into the pressurizer via the surge line and is discharged through the manway, where the steam flow accompanies the coolant entrainment by off-take below the inlet of surge line. scaling analysis is performed to scale down the experimental facility to the reference prototype, Korea Standard NPP. The horizontal leg and the surge line are scaled down as the horizontal main pipe and the vertical branch pipe, respectively. Two different diameters of the branch pipe are proposed to have proper scaling relations between prototype and model. The main pipe diameter (D) is 0.295 m and the surge line diameters are 50 mm and 70 mm, which have higher scales than those of the previous break flow experiments. The system pressures are slightly over the atmospheric pressure and no water flow exists. An off-take phenomenon is visually observed using the transparent pipes. The onset of liquid entrainment and the branch quality are investigated for the changes of the water level in the horizontal pipe and the air flow rate. The scale effect of the branch pipe diameter (d) is investigated in the present work compared with the previous small break loss of coolant accident (SB-LOCA) experiments for the top break on which the correlations does not represent the d-scale effect. The scaling effect clearly exists in the present works that have large scales of d and d/D. Stratified to slug transition in the horizontal pipe strongly affects the branch quality and occurs at larger gas velocities than those of previous results. (author)