Document: NUREG-0800
Document ID: 585516eb-af20-45dc-a470-9638ec9381f3
Document Type: srp
Title: Each calculated spectrum of the artificial time history is considered to envelop
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070640306.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
0 Hz / ) 8 ( ) S f o f At any frequency the average PSD is computed over a frequency band width of ±20 f , percent, centered on the frequency (e.g., 4 Hz to 6 Hz band width for = 5 Hz). f f The power above 24 Hz for the target PSD is so low as to be inconsequential so that checks above 24 Hz are unnecessary. (However, note that the response spectrum calculations are required beyond 24 Hz as governed by RG 1.60 definitions.) Similarly, power below 0.3 Hz has no influence on stiff nuclear plant facilities, so that checks below 0.3 Hz are unnecessary. This 3.7.1-23 Revision 3 - March 2007 minimum check is set at 80 percent of the target PSD so as to be sufficiently high to prevent a deficiency of power over any broad frequency band, but sufficiently low that this requirement introduces no additional conservatism over that already embodied in the Regulatory Guide 1.60 response spectrum. A time history meeting this minimum PSD requirement will produce a response spectrum that lies below the RG 1.60 response spectrum at all frequencies. To produce a response spectrum that accurately fits the 2 percent damped, 1.0 g, Regulatory Guide 1.60 response spectrum at all frequencies above 0.25 Hz, the PSD defined by Equation (2) can be used with the resulting time history being clipped at ±1.0 g (see NUREG/CR-3509). To produce a response spectrum that conservatively envelops the 1.0 g, RG 1.60 response spectrum at 2 percent damping and greater, a PSD set at 130 percent of the PSD defined by Equation (2) can be used with the resulting time history being clipped at ±1.0 g. REFERENCES 1. Regulatory Guide 1.60, "Design Response Spectra for Seismic Design of Nuclear Power Plants." 2. NUREG/CR-3509, "Power Spectral Density Functions Compatible with NRC Regulatory Guide 1.60 Response Spectra," June 1988. 3. NUREG/CR-5347, "Recommendations for Resolution of Public Comments on USI A-40, Seismic Design Criteria," June 1989. 3.7.1-24 Revision 3 - March 2007 ( ) ( ) S f F f T o D = 2 2 2