A real-time model describing the dynamic behaviour of a nuclear power shell-and-tube condenser is presented, according the structure and working characteristics of the condensor. The model can be used under steady-state as well as transient conditions, and is also able to predict vapour and condensate flow rates, and the temperatures of the vapour, condensate, wall and coolant. The results of several simulations are analyzed after the simulation of normal and malfunction state. The results show that the model can be used for real-time simulation of nuclear power condensers.