Nonlinear dynamic modeling of U-tube steam generators in pressurized water reactors

A new model and solution method has been proposed for U-Tube Steam Generators in Pressurized Water Reactors to be used in dynamic model and control studies. The steam generator is separated into 14 nodes. These nodes are investigated by applying the mass and energy conservation equations in differential form. A nonlinear differential equation system has been obtained. The system of equation has been numerically analyzed utilizing the Julia programming language through a fourth order Runge–Kutta method. Instantaneous accurate data for thermodynamic properties have been taken from the Coolprop library. Three-element PI control has been applied as the control system in the model. Changes in feedwater flow rate, steam outlet flow rate, primary fluid inlet flow rate, feedwater inlet temperature and primary fluid inlet temperature have been investigated and the response of the steam generator has been simulated using the proposed model.It has been seen that the proposed model gives responses for U-Tube Steam Generators comparable to those in previous studies and that it can be utilized in control simulations and dynamic model. Exergy analysis has been performed for thermodynamic performance analysis for Pressurized Water Reactors and the developed U-Tube Steam Generators model. Exergy destruction and efficiency have been obtained and compared for each component of typical Pressurized Water Reactors and all nodes of the developed U-Tube Steam Generators model. Changes in the primary fluid inlet flow rate, primary fluid inlet temperature, feedwater inlet temperature and U-tubes diameter ratio have been investigated and the response of the steam generator has been presented with the developed model. In the pressurized water reactor exergy analysis, it has been observed that the highest exergy destruction rate was in the reactor (61.80%), condenser (14.27%) and turbines (8.28%). In the U-tube steam generator exergy analysis, it was determined that the exergy destruction rate was higher in the downcomer and boiling zone nodes.