Seismic Design/Evaluation Input

DOE-STD-1020-2002

the AR range from 2 to 6. These risk reduction ratios support achieving performance goals

between about 3x10-5 to 5x10-6. In the primary region of interest of AR between 2 and 3, risk

reduction ratios from about 8 to 17 are achieved as compared to the target level of 10 for PC 4

and sites not near tectonic plate boundaries.

The risk reduction ratio achieved may be improved by using a variable formulation of

SF which is a function of AR. In order to justify use of the variable scale factor approach, the site

specific hazard curve must have a rigorous pedigree. Reference C-20 demonstrates that the SF

factors shown in Reference C-20 give the best fit of RR over the AR range of primary interest

from about 2 to about 6. The use of the scale factors given in Figures in Reference C-20

combined with Equation C-6 improves the RR values compared to target values as shown in

Figures in Reference C-20 for PC 3 (RR = 4) and PC 4 (RR = 10), respectively. Figures in

Reference C-20 demonstrate that when the variable scale factors are used, risk reduction factors

achieved are within about 10% of the target values of 4 and 10, respectively. As a result, target

performance goals would be met within about the same 10%.

It is to be noted that the information in Ref. C-20 may need to be adjusted to new PH

value of 4x10-4 for PC-3 SSCs, with RR = 4. The variable scale Factor is altered from that in Ref.

C-20 and becomes, SF = maxium (0.9, .6AR 0.4). If the variable scale factor is significantly

larger, it should be used instead of 0.9 and 1.25 for PC-3 and PC-4 respectively. This is

particularly significant at low seismicity sites.

For sites near tectonic plate boundaries for which AR is in the range of about 1.5 to 2.25,

such as LLNL, SNL-Livermore, SLAC, LBL, and ETEC. Figures in Reference C-20

demonstrate that larger risk reduction ratios are achieved than the target levels of 4 for PC 3 and

10 for PC 4, respectively. Therefore, it is acceptable to use twice the hazard probabilities for

these sites combined with the appropriate constant scale factors. Hence, for sites near tectonic

plate boundaries, target performance goals may be adequately achieved with hazard

probabilities and seismic scale factors of 1x10-3 and 1.0 for PC 3 and 2x10-4 and 1.25 for PC 4.

C.3

Seismic Design/Evaluation Input

The seismic performance goals presented in Tables C-1 and C-2 are achieved by

defining the seismic hazard in terms of a site-specified design response spectrum (called herein,

the Design/Evaluation Basis Earthquake, [DBE]). Either a site-specific design response

spectrum specifically developed for the site, or a generic design response spectrum that is

appropriate or conservative for the site may be used as the site-specified design response

spectrum. Probabilistic seismic hazard estimates are used to establish the DBE. These hazard

curves define the amplitude of the ground motion as a function of the annual probability of

exceedance PH of the specified seismic hazard.

An annual exceedance probability for the DBE, PH is specified from which the

maximum ground acceleration (or velocity) may be determined from probabilistic seismic hazard

curves. Evaluating maximum ground acceleration from a specified annual probability of

C-11