CSA N289.3:20 pdf download – Design procedures for seismic qualification of nuclear power plants.
3 Definitions and abbreviations 3.1 Definitions The following definitions shall apply in this Standard: Acceleration — the most common parameter for categorizing seismic motion; it is usually expressed in mm/s 2 , gals (cm/s 2 ), or “g” units. Note: By international agreement, the value of “g” is 9806.65 mm/s 2 . Authority having jurisdiction (AHJ) — the organization having jurisdiction over the design, procurement, fabrication, installation, testing, operation, inspection, maintenance, and decommissioning of a nuclear facility. Notes: 1) AHJ is also referred to as “regulatory authority”. 2) In Canada, the regulatory authority is the Canadian Nuclear Safety Commission (CNSC) who receives its authority pursuant to the Nuclear Safety and Control Act (NSCA). Checking/review level earthquake (CLE/RLE) — an engineering representation of earthquake ground motion chosen to have a lower probability of occurrence exceedance than the design basis earthquake (DBE). Notes: 1) The CLE is used to identify any nuclear-safety-related SSCs that can have insufficient seismic ruggedness, ductility, or inelastic response capability to withstand and perform their safety function for earthquakes exceeding the DBE. 2) The RLE is usually applied to existing plants, or existing designs of proposed plants, as part of seismic evaluation. The CLE/RLE is usually used for new designs to ensure prescribed safety margins for earthquakes exceeding the DBE. 3) The probability level of exceedance of the CLE/RLE is generally agreed upon by the operating organization and the AHJ. The mean probability of exceedance is normally set at one order of magnitude lower than the one used for DBE. A mean probability level of exceedance of 1 × 10 -4 to 1 × 10 -5 per year is typically selected for CLE. 4) See Annexes C and D of CSA N289.1 for methods of evaluation for beyond the design basis and experience- based seismic qualification methods. Closely spaced modes — a group of modes having the lowest and highest frequency within 10% of each other.
4 Application of seismic ground motion to engineering design 4.1 General 4.1.1 Design intent The nuclear power plant seismic qualification process shall demonstrate that SSCs required to be seismically qualified have the capability to safely withstand the effects of the plant site seismic hazard. Note: CSA N289.2 defines an acceptable process for determination of site-specific seismic hazard and seismic ground motion parameters. 4.1.2 Design ground motion Seismic design of nuclear power plant SSCs shall be based on DBSGMs representing the seismological, geological, and geotechnical conditions of the site, expressed in a form applicable to dynamic analysis of the plant SSCs. Seismic dynamic analyses of the nuclear power plant SSCs shall be performed using ground response spectra (standard-shape or site-specific) or ground time-histories that have been conservatively defined to account for uncertainties in the site seismic hazard, in accordance with Clauses 4.1.3 and 4.1.4. The design ground response spectra shall be based on the free-field ground motion or reference ground condition modified to incorporate the site-specific geological conditions, in accordance with Clause 4.1.3.
4.1.3 Determination of design seismic ground motion Clause 4.2 specifies the minimum seismic ground motions consistent with conservative seismic design for nuclear power plant SSCs. These minimum requirements shall be followed, even in regions of low seismicity. Clause 4.3 establishes the requirements and describes the methods for developing design ground response spectra used in the design of nuclear power plant SSCs requiring seismic qualification. Spectrum compatible time-histories may be used in the dynamic analysis. In this case, the requirements for the time-histories of ground motion as specified in Clause 4.4 shall be used. 4.1.4 Annual probabilities and confidence levels The free-field design ground response spectrum shall be specified at an annual frequency of 1 × 10 -4 or lower, at the statistical mean confidence level as a minimum. Notes: 1) Probabilistic safety assessment can be performed using the checking level earthquake. For further guidance on probabilistic safety assessment, see CSA N289.1. 2) Authorities having jurisdiction might specify different design requirements for lower probability and/or increased confidence levels. 4.2 Minimum design ground response spectra The minimum design horizontal response spectra used in the design of a new nuclear power plant shall a) be the standard-shape ground response spectrum anchored to a peak ground acceleration of 0.1 g on rock (see Clause 4.3.2 and Figure 1); and b) take into account the site-specific geological conditions.CSA N289.3:20 pdf download.
