As more variable renewable energy enters the grid, peaking power is increasingly supplied by carbon-emitting natural gas plants. Significant greenhouse gas emissions can be avoided if these gas plants are replaced with carbon-neutral nuclear facilities to provide power to complement renewable generation and meet overall power demand. There is a significant body of work regarding reactor power shaping, especially with control rod movement in mechanical shim control strategies, for both currently operating nuclear power plants and future plant designs, but the literature on load following to meet rapidly varying power demand is less extensive. We have selected the Westinghouse IRIS IPWR as our demonstration for modeling, simulation, and control studies. The current plant model, developed with the aid of the TRANSFORM Library in Modelica, has a point reactor kinetics model, the steam generator system, and a simple balance of plant. The reactor core model has been augmented to include multiple axial nodes, the xenon reactivity contribution, and loss of excess reactivity during burnup to explore plant performance and control over a period of time of up to several hours and at different stages of the reactor life cycle. Preliminary results for load following operation in the IRIS Simulink model developed at the University of Tennessee suggest candidate actuators and strategies for control, especially in the balance of plant for fast transients. The control scheme for the load following operation of the IRIS IPWR model would ultimately lead to the development of real operational mechanisms and principles for SMRs in a grid with a large renewables share. Such principles include the consideration of figures of merit regarding the effect of maneuvers and actuation on plant economics. In the future the model will be augmented with a higher fidelity balance of plant model and integrated with a realistic grid demonstration to evaluate feasibility and performance.