In the intake structure of a nuclear power plant, undesirable pump operating characteristics such as vortices and nonuniform pump-approach flow around the pump bells take place frequently due to poorly arranged intake geometry. Therefore, prior to the construction or renovation of intake structure or internal auxiliary facilities, a hydraulic modeling test should be performed to predict the undesirable hydraulic phenomena. In this study, a three-dimensional turbulence model was applied for a numerical modeling test, and a 1:10 scale, geometrically undistorted physical model was employed to investigate the hydraulic behavior and simulate pump operating conditions in the intake structure of Kori Nuclear Units 3 and 4 in Korea. The results from these numerical and physical model tests were compared, and an antivortex device was also proposed to ensure a stable suction condition of the pumps.