Comprehensive overview of external hazard assessment international and national guidelines for siting of Small Modular Reactors

Small Modular Reactors (SMRs) face a broad set of external hazards whose treatment depends critically on siting and the explicit derivation of site-specific parameters. This paper synthesizes and critiques international and national guidelines to assess how external events should be identified, quantified, and integrated into the design and operation of SMRs. Methods combine a comparative overview of safety standards with cross-hazard reasoning that aligns deterministic and probabilistic assessments and extracts implementable design and emergency preparedness recommendations. The scope spans natural hazards, technological and industrial hazards, and security and malicious risks. The research is motivated by the fact that the translation of IAEA standards into national rules remain uneven in depth ad perspectives, leading to asymmetrical treatment of siting and passive safety of SMRs. In addition, there are significant gaps in certain risks specific to SMRs, such as those posed by nearby industrial areas. The results indicate a high degree of similarity in regulations around the world, although differences exist in terms of thresholds and the use of different units. A overview of international and national regulations finds a broad alignment in protecting nuclear installations, including SMRs, from external hazards such as explosions, earthquakes, aircraft impact, flooding, extreme weather, and human-induced threats. The recommendations advocate for the standardization of certain international regulations in order to facilitate the development of SMR projects. In addition, there is a strong need for safety studies concerning certain risks specific to SMRs, particularly with regard to interactions with hazards from surrounding industries.