DS498 - External Events Excluding Earthquakes in the Design of Nuclear Installations

Status: STEP 5

Beteiligte IAEO-Komitees: NUSSC, WASSC

STEP 3 Kommentare der SSCs und IAEO-Bewertung IAEO Zusammenstellung nach dem STEP 3

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Background Information

The document (NS-G-1.5) was first published in 2003. The scope of the safety guide will be extended to all nuclear installations. This safety guide considers design protection measures of nuclear installations against external hazards covered by the existing IAEA Safety Standards.

The current revision (DS 498) was initiated to

  • Ensure consistency with applicable requirements for site evaluation and design of nuclear installations (SSR-1/DS484, SSR-2/1, SS-R-3 and SSR-4/DS478)
  • Ensure coherency and consistency with other relevant IAEA Safety Standards (e.g. SF-1 and GSRs),
  • Incorporate the lessons learned and address challenges highlighted IAEA Report on Fukushima-Daiichi NPP Accident.
     

The new information in DS498 includes

  • Will address hazards induced Common Cause Failures
  • Will address design basis for external hazards including combination of hazards
  • DEC against external hazards (when applicable)
  • Recommendations for achieving adequate safety margins to avoid cliff edge effects consistent with applicable safety requirements.
     

Other Changes

  • The terminology will be made consistent with the new definitions in the safety requirements and the safety glossary
  • References will be updated
     

Fukushima Daiichi Implications

  • Importance of adequate design basis
  • Appropriate considerations of uncertainties
  • Common-cause effects of external events can compromise several layers of defense in depth at the same time
  • Combined effects of natural events need to be considered