An Investigation of High Order and Low Order Dynamic Modeling of a Complete Pressurized Water Reactor Nuclear Power Plant

A reference high order PWR system model was developed resulting in a 57th order, lumped parameter, state variable dynamic model. Included in the model are representations of the reactor core, pressurizer, U-tube recirculation type steam generator, connecting piping, and turbine-feedwater heaters. Also included are the models of three-element feedwater flow control, nonlinear reactor control, pressurizer pressure control, and megawatt-frequency turbine control systems.

A low order PWR system model was developed by reducing the 57th order model to a 25th order model by physical methods.

A further reduction on the low order model was demonstrated by a numerical method called the "pole-zero deletion method."

The results of the physically reduced low order model were compared to the results of the reference high order model. This comparison showed that the low order model could simulate the desired output of turbine shaft power equally as well as the reference high order model. Other intermediate system outputs were also shown to give good results for the low order model as compared to the reference high order model.