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:
ugh 4. 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 25 Hz for the PSD targets for Western US Sites and Central and Eastern US Soil Sites is so low as to be inconsequential so that checks above 25 Hz are unnecessary. For Central and Eastern US Rock Sites checks above 50 Hz are unnecessary. (However, note that the response spectrum calculations are required beyond 25 Hz and 50 Hz, as appropriate.) Similarly, power below 0.3 Hz has no influence on stiff nuclear plant facilities, so that checks below 0.3 Hz are unnecessary. This 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 specified target response spectrum. A time history meeting this minimum PSD requirement will produce a response spectrum that lies below the target response spectrum at all frequencies. To produce a response spectrum that accurately fits the 2 percent damped, 1.0 g, target response spectrum at all frequencies 3.7.1-25 Revision 3 - March 2007 above 0.25 Hz, the PSD specified in Tables 1 through 4 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 target response spectrum at 2 percent damping and greater, a PSD set at 130 percent of the PSD specified in Tables 1 through 4 can be used with the resulting time history being clipped at ±1.0 g. Table 1 – Central and Eastern US Rock Sites Table 2 – Central and Eastern US Soil Sites frequency (hz) 0-50 km 50-100 km 0-10 km 10-50 km 50-100 km 100-200 km 0-10 km 10-50 km 50-100 km 100-200 km in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 in2/sec3 0.3 0.93 0.58 61.77