Nuclear security infrastructure is a multifaceted academic concept and research domain that examines the integrated systems, processes, and capabilities designed to prevent unauthorized access, theft, sabotage, or diversion of nuclear materials and facilities. This concept investigates the design, implementation, performance, and evolution of the physical, technical, human, and institutional elements constituting the protective framework for nuclear assets. Key characteristics include its complexity, layering of defense-in-depth principles, reliance on technological advancements, and the critical interplay between technical measures, human reliability, and regulatory regimes. Its significance lies in its crucial role in mitigating proliferation risks, ensuring the safety and security of nuclear energy and research activities, and contributing to international stability.