Part A- Comments - Continued

DOE-STD-1024-92

OR-1

The evaluation to obtain the pseudo-mean peak ground acceleration has been

changed to include the LLNL hazard results with expert #5 instead of the LLNL

hazard results without expert #5, which were used in the previous draft. We do

not recommend using LLNL hazard results with expert #5 included. The

guidelines themselves discuss numerous studies which have been performed to

justify not using the LLNL results with expert #5 included. The LLNL results with

expert #5 for the 85th percentile and the mean are outliers, and should not be

used to determine the pseudo-mean peak acceleration in the guidelines.

Including expert #5 in the evaluation increases the pseudo-mean peak

acceleration about 25-40 percent, which we believe is not appropriate for use

with the evaluation requirements defined in UCRL-15910.

The guidelines state that the rationale for including expert #5 "relates to the fact

that resulting peak accelerations have a conservative bias, making engineering

assessments more stable in that final resolution to the LLNL EPRI issue to 1.5 to

2 years away. If engineering assessments conclude that major upgrades are

necessary for existing facilities, an explicit assessment should also be made

using the pseudo-mean peak accelerations without LLNL attenuation expert 5."

There are numerous steps in performing seismic evaluations where small extra

conservatism has a tendency to be introduced at each step. These extra

conservatisms are accumulated through the total evaluation process and can

increase the demands 2-3 times or greater in the final evaluation results. The

seismic evaluation must also be tied to an overall risk assessment of the facility

which could be significantly impacted by these extra conservatisms. Therefore

we recommend that extra conservatism not be included this way. We

recommend the input parameters for seismic evaluations be determined without a

conservative bias, and then evaluate the sensitivity of the input parameters to

determine if the evaluation conclusions, and risk assessments are affected. This

is the philosophy of the evaluation procedures defined in UCRL-15910.

OR-2

We agree with the additional information on how to develop a deterministic site

specific spectral shape. We recommend only the EPRI uniform hazard spectra

be used to determine the dominant earthquake parameters for the site-specific

spectra shapes because the LLNL uniform hazard spectra are controlled by

standard spectral shape models as discussed in the guidelines. Therefore, the

LLNL spectra do not actually represent uniform hazard spectra and should not be

used to determine the dominant earthquake parameters for the site-specific

studies. The guidelines could be improved by including a case study on how to

develop the site-specific spectra.

A-14