Part A- Comments - Continued

DOE-STD-1024-92

LLNL-10

We recommend that Peak Ground Acceleration (PGA) values for DOE sites with

moderate and/or high hazard facilities located in the EUS, east of longitude

104W, be computed by both approaches, corrected for curve shape differences,

and tabulated by one organization. These should then be reviewed and made

available to all DOE sites for their use in design and evaluation. This is much

more reliable and cost effective than each site conducting independent studies.

LLNL-11

A marked-up copy of the interim position is also attached. The comments are

essentially editorial, but important to avoid misuse.

LLNL-12

In general, we conclude that the interim position is reasonable and attempts to

take advantage of the relative strengths of the LLNL and EPRI studies. We do

not offer specific recommendations for changes to the document. However, we

do have a few relatively minor questions regarding the methodology proposed in

the interim position. Clarification of these questions would serve to further

strengthen the document.

LLNL-13

A major strength of the interim position is that it explicitly incorporates both of

the methodologies, through a geometric averaging of the peak accelerations at

the target probability level. Such an approach circumvents the messy

problems that could be associated with other schemes for aggregating the

results of the two studies (e.g., assigning relative weights, component-level

aggregation, etc.). Further, the use of the most stable descriptor of the hazard,

the median peak acceleration, also appears to be the most reasonable point

for combining the two studies.

It has only been in the past 5 years that a complete description of the

uncertainties in seismic hazard have become nearly as important as the

central estimates in Probabilistic Seismic Hazard Analysis for licensing

purposes. Perhaps due to the increasing number of probabilistic risk

assessments being done for commercial nuclear plants and the probabilistic

components of the IPEE program, the state of the practice in seismic hazard

analysis is a full description of the seismic hazard and careful attention to

characterization of uncertainty.

LLNL-14

The interim position is said to apply to all sites east of about 104W "except for

sites within about 50 kilometers of active seismogenic sources, such as the

Paducah, Kentucky Site." How is an active seismogenic source defined?

Clearly in the example, the Paducah site is near the New Madrid seismic zone.

A-8