Safety Reports

In recent years, significant experience of the effects of high wind and flooding on nuclear installations has been gained worldwide. These phenomena may simultaneously affect all the structures, systems and components important to safety at a nuclear installation site. By detailing the methodologies and providing case studies for the evaluation of meteorological and hydrological hazards, this publication supports IAEA Safety Standards Series No. SSG-18, Meteorological and Hydrological Hazards in Site Evaluation for Nuclear Installations. In the first part of the publication, wind hazards relating to tropical cyclones, tornadoes, extratropical storms, thunderstorms and wind-borne debris are discussed. The second part covers external flooding hazards (excluding tsunamis) relating to wind induced coastal flooding, wind generated waves on rivers, extreme precipitation and runoff events and the sudden release of impounded water.

This publication describes the updated version of the method for the assessment of comprehensiveness of defence in depth and demonstrates the overall improvement in assessment results when using it. For assessment of comprehensiveness, five levels of defence in depth are considered. To ensure that safety objectives are met at each level of defence in depth, the integrity of relevant fission product barriers is maintained by the safety functions. A set of challenges to the performance of safety functions and the mechanisms leading to the challenges are specified by the method. Finally, a comprehensive list of safety provisions, which contribute to preventing these mechanisms from occurring, is specified. These provisions encompass the inherent safety features, equipment, procedures, personnel availability, personnel training and safety culture aspects. The challenges, mechanisms and provisions for all levels of defence in depth are presented in the assessment method in the form of objective trees.