Safety Assessment of Nuclear Installations Against Combinations Hazards Induced by External Events

External events pose significant challenges to nuclear installations, particularly when natural and human induced hazards occur in combination, leading to complex and increased risks. The Fukushima Daiichi accident highlighted the critical importance of addressing such hazard combinations in nuclear design, operation and safety assessment. In response, the IAEA has revised and updated its safety standards to improve the understanding and assessment of external event induced hazard combinations. However, detailed technical guidance remains necessary, especially for deterministic and probabilistic safety assessments. This TECDOC presents current state-of-practice approaches for assessing nuclear installations against combined external hazards. It offers a structured framework for identifying, grouping and analysing hazard combinations, assessing the performance of nuclear installations under their effects, and evaluating plant response, supported by practical examples from Member States. The TECDOC promotes good practices and enhances the resilience and safety of nuclear installations.