This Safety Guide provides recommendations on the seismic safety evaluation of nuclear installations. It addresses all types of new and existing nuclear installations. This Safety Guide presents three assessment methodologies: the deterministic approach, generally known as seismic margin assessment (SMA), seismic probabilistic safety assessment (SPSA), and a combination of SMA and SPSA known as ‘probabilistic safety assessment (PSA) based SMA. This Safety Guide provides specific recommendations on applying a performance-based graded approach to the seismic safety evaluation of nuclear installations other than nuclear power plants. It also covers the relation between seismic safety margins and defense-in-depth (DiD) level 3 and level 4. For new nuclear installations, this Safety Guide provides recommendations to assess adequacy of seismic margin to avoid cliff edge effects considering DiD level 3 and level 4. This publication is intended for use by regulatory bodies, operating organizations, and designers of nuclear installations.

• 1. INTRODUCTION
  • Background
  • Objective
  • Scope
  • Structure
• 2. DESIGN APPROACH CONSIDERING THE RADIOLOGICAL CONSEQUENCES OF ACCIDENTS
• 3. IMPLEMENTATION AND ASSESSMENT OF DESIGN EXTENSION CONDITIONS WITHIN THE CONCEPT OF DEFENCE IN DEPTH
  • Overall implementation of defence in depth
    • Normal operation and anticipated operational occurrences
    • Design basis accidents
    • Design extension conditions
  • Assessment of the implementation of defence in depth
  • Independence between levels of defence in depth
  • Assessment of the independence of the levels of defence in depth
• 4. PRACTICAL ELIMINATION OF PLANT EVENT SEQUENCES THAT COULD LEAD to AN EARLY RADIOACTIVE RELEASE OR A LARGE RADIOACTIVE RELEASE
  • Identification of relevant plant event sequences
  • Identification and assessment of safety provisions for demonstrating practical elimination
  • Demonstration of practical elimination
    • Practical elimination of plant event sequences because they would be physically impossible
    • Practical elimination of plant event sequences considered, with a high level of confidence, to be extremely unlikely to arise
  • Documentation of the approach to practical elimination
• 5. IMPLEMENTATION OF DESIGN PROVISIONS FOR ENABLING THE USE OF NON-PERMANENT EQUIPMENT FOR POWER SUPPLY AND COOLING
• REFERENCES
• Annex I EXAMPLES OF CASES OF PRACTICAL ELIMINATION
• Annex II APPLICATION OF THE CONCEPTS OF DESIGN EXTENSION CONDITIONS AND PRACTICAL ELIMINATION TO NUCLEAR POWER PLANTS DESIGNED TO EARLIER STANDARDS
• DEFINITION
  • Practical elimination
• CONTRIBUTORS TO DRAFTING AND REVIEW