Factor When Only Curve Exists

DOE-STD-1024-92

probabilities on the various steps used to develop the correction factor.

The revised correction factors are 1.80 for Low and Moderate Hazard

facilities and 1.65 for High Hazard facilities.

FACTOR WHEN ONLY ONE CURVE EXISTS

(NS-6)

For those sites which have only the LLNL or EPRI probabilistic seismic

hazard results the recommendation is to use the PGA correction factor on

an adjusted median curve. The adjusted median curve is calculated as

follows: for sites where only LLNL results are available with attenuation

expert #5, these results should be divided by 1.2. This factor represents the

difference between the LLNL and EPRI median hazard curves at both

reactor and DOE sites. For sites which have only the LLNL results without

attenuation expert 5, these median results can be used directly. For a site

that would have only EPRI results available (none are known to currently

exist) it is recommended that LLNL results be quantified for that site. If this

can not be accomplished the EPRI median should be increased by 1.2.

Note that this procedure is slightly different from that in the draft version of

the Standard, as pointed out by the comments. It was judged that

attempting to develop this factor at different probabilities was not warranted

by the data available.

DEVELOPING SITE SPECIFIC SPECTRA

(NS-7, LLNL-16, NP-3, EM-2, OR-2, OR-6)

Several comments requested enhanced guidance regarding the development

of site-specific spectra. Discussion related to this issue has been moved

from the body of the Standard into Appendix B. For those sites who choose

to develop a deterministic site-specific spectral shape, information contained

in the probabilistic seismic hazard analysis should be used to establish the

appropriate magnitude and distance. This Standard contains additional

information on the development of site-specific spectra (see Appendix B).

Department of Energy (NE-70) is developing a standard on developing site-

specific spectral shapes (DOE-STD-1023). At present DOE's Oak Ridge

office, working with Martin Marietta, is attempting to implement the guidance

in Appendix B at Paducah and Portsmouth as test cases. The interim

guidance developed in Appendix B considered information in NRC Standard

Review plan, Section 2.5.2, on developing site-specific spectra.

REGIONAL DEPENDENCY/LOG NORMALITY

(LLNL-2, LLNL-3)

The comments correctly point out that the assumption of log normality may

not apply to each individual site's seismic hazard curve. As a matter of

practicality the Standard is based on observed general trends versus

intensive site specific observations from the LLNL and EPRI results. The

full set of data for the ratio of mean to median hazard is provided as

Appendix C. One reason that the peak acceleration was used as the

ground motion parameter for the Standard was the increased instability of

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