ISO 4917-5:2024

Overview

ISO 4917-5:2024 - "Design of nuclear power plants against seismic events - Part 5: Seismic instrumentation" defines how seismic detection and recording systems are used and specified at nuclear power plants with water‑cooled reactors. The standard ensures seismic instrumentation can detect if design ground motion limits have been exceeded and that recorded acceleration time histories are suitable for reliable post‑seismic analysis. It applies to other nuclear facilities after applicability is verified and explicitly excludes instrumentation that implements nuclear safety functions (e.g., automatic shutdown systems) or equipment requiring IEC hardware qualification.

Key topics and technical requirements

• Purpose: Detect seismic events, measure accelerations, record time histories and enable comparison with plant design quantities (walk‑down and inspection levels).
• Instrumentation types: Acceleration sensors, recording devices, triggers and complete acceleration acquisition systems (sensors + recording + trigger logic).
• Performance: Measurements must produce comparable results (within tolerances) across the relevant time and frequency ranges; attention to amplitude‑frequency response and avoidance of aliasing.
• Location & mounting:
  • Free‑field acquisition systems are required; additional systems recommended inside reactor buildings.
  • Sensor mounting, local topography and soil inhomogeneity must have negligible effect on free‑field measurements.
  • Minimum siting distances: free‑field stations should be at least twice the largest length of the reactor building foundation from the reactor building; distances to other buildings should be at least the building’s largest ground‑plan dimension (exceptions allowed if justified).
  • Sensors must be fixed so no relative movement occurs and oriented to the seismic analysis coordinate axes.
• Operational requirements:
  • Seismic classification per IEC 61226 and seismic qualification per IEC/IEEE 60980‑344 (and general qualification IEC/IEEE 60780‑323) or equivalents.
  • Immediate display/availability of recorded time histories and response spectra after an event to assess inspection/shutdown criteria.
• Data needs: Recorded acceleration time histories must be suitable for dynamic calculations and post‑seismic engineering verifications.

Applications and users

Who benefits from ISO 4917-5:

• Nuclear plant designers and structural engineers (seismic design validation)
• Seismologists and instrumentation specialists (sensor siting and performance)
• Nuclear operators and maintenance teams (post‑event inspections and walk‑downs)
• Regulators and safety assessors (compliance review and post‑seismic analysis) Practical uses include site monitoring, event detection, automated alarms for inspections, and providing input for structural response and equipment qualification analyses.

Related standards

• ISO 4917‑1 (Principles), ISO 4917‑6 (Post‑seismic measures)
• IEC 61226 (function categorization)
• IEC/IEEE 60780‑323 and IEC/IEEE 60980‑344 (qualification)
• IEC 63186 (seismic reactor trip systems)

Keywords: ISO 4917-5, seismic instrumentation, nuclear power plants, acceleration acquisition system, seismic qualification, free‑field sensors, post‑seismic analysis.