A RELAP5/MOD3.1 model of a boiling water reactor and an interface originally developed as a real-time test platform for the Browns Ferry Unit 2 feedwater control system and turbine governors have been expanded to include feedwater heater systems and controls and to change the reactor recirculation pump controls from the current fluid-coupled drive to a future variable speed drive. The expanded model includes feedwater heater shell-side components, associated piping, steam supplies, and condensers, and allows simulation of the Foxboro digital feedwater heater level control system. The model was updated to RELAP5/MOD3.1.1, while the interface was expanded to handle additional communications and operator actions. The simulated feedwater heater level controls were tuned and benchmarked; benchmarking was performed against steady-state data at various power levels from plant heat balance data. After the model was benchmarked, various transients were simulated to identify potential flaws in the feedwater heater level control system.