Verifying that complex systems such as power plants satisfy the requirements that ensure their proper operation, in particular with respect to safety, dependability and environmental regulations, is difficult due to the large number of potential situations to be explored in terms of initiating events and their chain of consequences on the behavior of the system. The paper presents a new framework for supporting a methodology that aims at reconciling innovation (ability to modify the system) and safety (ability to comply with regulatory requirements). The general principle is to produce independently formal models of the requirements, of the possible variants of the design, and of the dynamic behavior of the system for the possible designs, then assemble them together to simulate the full system's behavior to automatically detect possible violations of the requirements.