Seismic qualification of safety class electrical equipment for nuclear power plants
1 Scope
This standard specifies the implementation method and documentation requirements of seismic qualification for verifying that safety level electrical equipment can perform its safety function during and/ or after an earthquake.
This standard is applicable to seismic qualification of safety level electrical equipment in nuclear power plants, including any interface components or equipment whose failure will have harmful effects on the performance of safety system.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 12727 Qualification of safety class electrical equipment for nuclear power plants
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
broadband response spectrum
response spectrum that describes motion in which amplified response occurs over a wide (broad) range of frequencies
3.2
coherence function
comparative relationship between two times histories. It provides a statistical estimate of how much two motions are related, as a function of frequency. The numerical range is from zero for unrelated, to +1.0 for related motions
3.3
correlation coefficient function
comparative relationship between two time histories. It provides a statistical estimate of how much two motions are related, as a function of time delay. The numerical range is from zero for unrelated, to +1.0 for related motions
3.4
critical seismic characteristics
design, material, and performance characteristics of an equipment item that provide assurance that the item will perform its required function under seismic loads
3.5
cutoff frequency
frequency in the response spectrum where the ZPA asymptote begins. This is the frequency beyond which the single-degree-of-freedom (SDOF) oscillators exhibit no amplification of motion and indicate the upper limit of the frequency content of the waveform being analyzed
3.6
damping
energy dissipation mechanism that reduces the amplification and broadens the vibratory response in the region of resonance. It is usually expressed as a percentage of critical damping. Critical damping is defined as the least amount of viscous damping that causes a SDOF system to return to its original position without oscillation after initial disturbance.
3.7
earthquake experience spectrum; EES
response spectrum that defines the seismic capacity of a reference equipment class based on earthquake experience data
3.8
flexible equipment
equipment, structures and components whose lowest resonant frequency is less than the cutoff frequency on the response spectrum
3.9
inclusion rules
rules that define the bounds of equipment included in a reference equipment class based on an acceptable range of equipment physical characteristics, dynamic characteristics, and functions for which seismic ruggedness has been demonstrated by experience data
3.10
independent items
components and equipment that (a) have different physical characteristics or (b) experienced different seismic motion characteristics, e.g., different earthquakes, different sites, different buildings, or different orientations/locations in the same building
3.11
narrowband response spectrum
response spectrum that describes the motion in which amplified response occurs over a limited (narrow) range of frequencies
3.12
natural frequency
frequency(s) at which a body vibrates due to its own physical characteristics (mass and stiffness) when the body is distorted in a specific direction and then released
3.13
operating basis earthquake; OBE
earthquake that could reasonably be expected to occur at the plant site during the operating life of the power plant considering the regional and local geology and seismology and specific characteristics of local subsurface material
Note: For the vibratory ground motion produced by the earthquake, those features of the nuclear power plant, necessary for continued operation without undue risk to the health and safety of the public, are designed to remain functional.
3.14
power spectral density; PSD
mean squared amplitude per unit frequency of a waveform, and it is expressed in g2/Hz versus frequency
GB/T 13625-2018 The following standards are cited：
