Physical design is a methodological approach within engineering and applied science concerned with defining the tangible form, structure, and material composition of complex systems and facilities. It investigates how scientific principles, such as those governing nuclear reactions, are embodied in physical components and integrated assemblies to achieve specific functional objectives, like energy conversion. Key characteristics include the detailed specification of spatial layouts, structural integrity, material properties, and safety features, often involving multidisciplinary collaboration and computational modeling. Its significance lies in translating theoretical knowledge and functional requirements into practical, buildable, and operable physical realities, crucial for the successful and safe deployment of advanced technologies.