Integration of technical processes: practical examples from the experiences made for the design of ITER fusion reactor systems

The design of complex systems requires the application of a robust Systems Engineering methodology, which integrates the different technical processes. The field of "Big Science", which includes nuclear fusion experiments, in particular calls for the use of niche technologies beyond the state of arts. Within this context, relevant uncertainty is often on input data and constraints, e.g. projects are organized into contract frameworks, for which the contractor is constrained to work within precise boundaries and has not the possibility to influence what lies outside.In general, the technical activities to be performed for the design of systems can be referred to different main topics: Requirements management, Design, Virtual prototyping (for performance and structural assessment), RAMS, Validation and qualification of components. For complex systems, the adoption of a "traditional" design process is typically not effective, and the above topics cannot be assessed sequentially during the project, in a single iteration loop. Indeed, many interdependent activities must be performed for each topic, with complex input-output relations among them, that vary during the different phases of the project. An effective and efficient design process requires the identification of the relevant workflows and iteration loops, which requires the definition of a conceptual framework to be taken as reference, concerning the above main topics, the technical activities to be performed for each topic and the input-output relationships among them. These workflows and iteration loops should be reflected by the project schedule and used for the project monitoring.In this paper, examples are presented of the strategies that have been implemented for the design of ITER fusion reactor systems, highlighting the variability of the integration workflow and the results obtained.