DS564 - Design of Nuclear Installations Against External Events Excluding Earthquakes

Status: STEP 3

Revision von SSG-68

Beteiligte IAEO-Komitees: NUSSC, WASSC

Specific Safety Guide

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The current edition of IAEA Safety Standards Series No. SSG-68, published in 2021, provides recommendations for the design of nuclear installations against external events excluding earthquakes. It was developed in response to evolving international safety requirements following the Fukushima Daiichi accident, with particular emphasis on addressing design extension conditions and enhancing resilience to extreme external hazards. However, since the major drafting in 2016-2017, there have been changes in both the external risk landscape, such as increasing climate change impacts, space weather, and innovative designs leading to non-traditional site environments, and the broader framework of IAEA Safety Standards, which prompts a revision of SSG-68.

This revision will include recommendations on the design provisions to address new external hazard conditions arising from evolving siting environments, such as remote, underground, or repurposed industrial sites, and from increased deployment of innovative reactor technologies, including small modular reactors (SMRs), floating nuclear power plants (FNPPs), transportable nuclear power plants (TNPPs), non-water-cooled reactors, and other types of advanced design reactors.

It will also take into account the growing frequency and severity of combined climate-related events that may challenge the performance of safety-related structures, systems, and components.

The update will enhance the existing recommendations by incorporating recent developments in external hazard characterization, safety assessment methodologies, and design provisions for evolving conditions. In particular, the revised Safety Guide will provide recommendations for addressing:

• Combined and cascading events, such as extreme precipitation combined with flooding, wildfires coupled with infrastructure failure, and long-duration severe weather scenarios.
• New siting contexts, including remote locations, post-industrial (brownfield) areas, and co-location with existing infrastructures, such as former coal- or gas-fired power stations.
• Advanced reactor technologies, including SMRs, non-water-cooled reactors, floating nuclear power plants (FNPPs), transportable nuclear power plants (TNPPs), and other innovative designs that require updated design considerations for protection against external hazards.

This revision will include all nuclear installations. For the same purpose, the IAEA Safety Standards Series No. SSG-67, Seismic Design for Nuclear Installations is under revision as well. Owing to the differing modes of impact on structures, systems and components, it is considered necessary that SSG-67 and SSG-68 be revised as separate safety guides. However, the revision of SSG-68 will be developed in close coordination with the revision of SSG-67 to ensure consistency in design approaches and criteria, as well as to address the combination of external events.