The development of simulators for complex systems like nuclear power plants is a hard task where many different factors have to be considered. This paper presents a simulation environment composed by a simulation kernel and supported by a set of tools and simulation models that allow the real-time simulation of the control room of nuclear power plants. The developed simulators allow the training of the operators for the operations and maintenance of the power plant in a safe way and they are being used in full scope simulations for different real power plants. In this type of systems, where many components have to interoperate between them, the communications play a main role. The main contribution of the paper is to show the lessons learned from the utilization of CORBA and Real-time CORBA in the development of this type of simulators.