This publication covers two main aspects of safety against external events including the site hazard assessment and the robustness of the installation against external hazards. This publication provides practical guidance and information for the development of the technology-neutral safety framework for assessing the applicability of site evaluation requirements considering site-installation interactions and taking into account the innovative safety features of the advanced reactors. A methodology is provided for an overall optimization of safety measures against external hazards, including the use of a risk-informed approach, supporting the effective and balanced implementation of the defence in depth concept. This methodology covers the application of grading that considers the safety features of the nuclear installation, allowing for a reduced implementation time/cost while ensuring robustness of the installation for applicable hazards. This publication is useful for both new and existing nuclear installations and is intended to be used by regulatory bodies, designers, operating organizations, vendors, research institutes, and technical support organizations working in the area of nuclear safety.