Hydromechanical investigation on 3 PWR upper plenum core structures Original Research Article

In this paper, experiments with three upper plenum core structures—the upper plenum core structure of active 300 MW PWR in the Peopleʹs Republic of China and its two improved core structures, respectively—are carried out in a 1/4 scale transparent model of the active 300 MW PWR upper plenum with water. The horizontal across velocity in the upper plenum model is measured with an N-J type dynamic resistance strain foil velocity meter (N-J DRSFV). The axial velocity is obtained by using a laser Doppler velocity measuring system (LDV). The experimental results are compared and analyzed carefully. The complex flow velocity distribution is obtained in the experiment with each core structure. Finally, it is concluded that the improved upper plenum core structure can reduce the hydraulic load on the drop of control rods.