Simulation and control of an integral pressurized water reactor, with multiple units that operate in parallel and feed steam to a single turbine, is presented. Such a configuration requires mixing steam from two or more units in a steam header, with the steam from all the units maintained at the same operating conditions, with efficient operation of this configuration requiring advanced control strategy. The objective of this research is to evaluate and quantify the performance of a nuclear power plant comprised of two IRIS reactor units. The steam from two reactors flow into a common header connected to a single turbine, resulting in a steam-mixing control problem with respect to “load-following” scenarios, such as reduced consumption during weekends. To solve this problem, a single-unit IRIS Simulink® model, previously developed at the University of Tennessee, was modified to include a second unit, and was used to develop the control strategies under various operation transients.