Calculation of Correction Factors

DOE-STD-1024-92

These frequencies were not selected given the above discussion and

concerns regarding how the Uniform Hazard Spectrum were derived. Given

these issues the decision was made to use the peak ground acceleration.

4.1

Calculation of Correction Factors

Appendix D, provided by Dr. Cornell, describes the specific formulation of

the pseudo-mean correction factor. The general steps, using the information

at a peak acceleration of 0.20g, are as follows (the number provided for

these steps exclude LLNL-AE5): Quantify the difference between LLNL and

EPRI for the ratio of the 85th percentile to the median for 0.20g (about 2)

and derive a composite 85th/median factor using this value and the EPRI

absolute ratio of the 85th/median (composite ratio about 5; a similar result is

obtained by calculating the geometric mean of the EPRI and LLNL

85th/median ratios); assume an underlying lognormal distribution and derive

a mean/median hazard multiplier (about 3.6); and using this hazard

multiplier and representative slopes of seismic hazard curves derive a ratio

for mean/median ground motion.

Using the above steps, estimates of the pseudo-mean correction factor were

made for the following: Information for the peak acceleration values of 0.1g,

0.2g, and 0.4g; LLNL data that includes and excludes LLNL-AE5; slopes of

EPRI and LLNL seismic hazard curves for the nuclear reactor sites; and

probability levels and range of median ground motion appropriate for DOE

sites. Appendix E provides the data associated the above range of

parameters. The following summarized the values selected for the

correction factor.

For the probabilities of 2 x 10-3/yr. and 10-3/yr. associated with UCRL-

15910 (DOE-STD-1029) use the LLNL and EPRI slope information for

probabilities of 10-3 /yr. to 10-4/yr.

For the probability of 2 x 10-4/yr. associated with UCRL-15910 (DOE-

STD-1020) use the LLNL and EPRI slope information for probabilities

of 10-4/yr. to 10-5/yr.

For the probabilities of 2 x 10-3/yr. and 10-3 /yr. associated with UCRL-

15910 (DOE-STD-1020) use the LLNL and EPRI seismic hazard

ratios at a peak acceleration of 0.10g.

For the probability of 2 x 10-4/yr. associated with UCRL-15910 (DOE-

STD-1020) use the LLNL and EPRI seismic hazard ratios at a peak

acceleration of 0.20g.