An improved pressurizer model with bubble rise and condensate drop dynamics

Abstract The dynamic prediction of pressurizer performance in a pressurized water nuclear power plant can be improved by incorporating the bubble rise and condensate drop velocity concepts. The pressurizer is divided into two stratified elements separated by a water vapor interface. The bottom element contains subcooled or boiling liquid and the top element contains superheated or condensing vapor. Bubbles forming in the bottom element rise and enter the top element after an appropriate transport delay. Condensate forming in the top element falls and enters the bottom element after an appropriate time lag. Using this mass exchange concept and applying the equations of continuity, energy and steam-water properties for top and bottom elements combined with the pressurizer pressure control features, a comprehensive analytical model is developed. The predictions of this mathematical model are in good agreement with available data on the Shippingport pressurizer performance. Unlike previous pressurizer models, this improved model provides unique solutions and does not require changing the interface evaporation and condensation coefficients to match the experimental data.