This Safety Requirements publication establishes design requirements for safety functions and associated structures, systems and components important to the safe operation of a nuclear power plant. It also establishes requirements for a comprehensive safety assessment to identify potential hazards that may arise in the operation of a plant. In relation to the design process, preventive and mitigatory features for severe accidents, the management of safety, design management, plant ageing and wearing out effects, computer based safety systems, external and internal hazards, human factors, feedback of operational experience, and safety assessment and verification are considered. It supersedes Safety Series No. 50-C-D (Rev. 1), Code on the Safety of Nuclear Power Plants: Design (1988).