[Federal Register Volume 62, Number 187 (Friday, September 26, 1997)]
[Notices]
[Pages 50632-50642]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-25632]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-361 and 50-362]


Southern California Edison Company, Et Al., San Onofre Nuclear 
Generating Station, Units 2 and 3; Issuance of Director's Decision 
Under 10 CFR 2.206

    Notice is hereby given that the Director, Office of Nuclear Reactor 
Regulation, has acted on a Petition for action under 10 CFR 2.206 
received from Mr. Stephen Dwyer dated September 22, 1996, as 
supplemented by letter dated December 10, 1996, two e-mails of March 
26, 1997, and an e-mail of May 28, 1997, for the San Onofre Nuclear 
Generating Station (SONGS), Units 2 and 3.
    The Petition requests that the Commission shut down the San Onofre 
Nuclear Generating Station pending a complete review of the ``new 
seismic risk.'' As a basis for the request, the Petitioner asserts that 
a design criterion for the plant, which was ``0.75 G's acceleration,'' 
is ``fatally flawed'' on the basis of the new information gathered at 
the Landers and Northridge quakes. The Petitioner asserts (1) that the 
accelerations recorded at Northridge exceeded ``1.8 G's and it was only 
a Richter 7+ quake,'' (2) that there were horizontal offsets of up to 
20 feet in the Landers quake, and (3) that the Northridge fault was a 
``Blind Thrust and not mapped or assessed.''
    The Director of the Office of Nuclear Reactor Regulation has 
determined that the request should be denied for the reasons stated in 
the ``Director's Decision Under 10 CFR 2.206'' (DD-97-23), the complete 
text of which follows this notice and which is available for public 
inspection at the Commission's Public Document Room, the Gelman 
Building, 2120 L Street, N.W., Washington, D.C. 20555, and at the Local 
Public Document Room located at the Main Library, University of 
California, P. O. Box 19557, Irvine, California 92713.

    Dated at Rockville, Maryland, this 19th day of September 1997.

    For the Nuclear Regulatory Commission.
Samuel J. Collins,
Director, Office of Nuclear Reactor Regulation.

Director's Decision Under 10 CFR 2.206

I. Introduction

    By Petition dated September 22, 1996, Stephen Dwyer (Petitioner) 
requested that the Nuclear Regulatory Commission (NRC) take action with 
regard to San Onofre Nuclear Generating Station (SONGS). The Petitioner 
requested that the NRC shut down the SONGS facility ``as soon as 
possible'' pending a complete review of the ``new seismic risk.'' 
<SUP>1</SUP> The Petitioner asserted as a basis for this request that a 
design criterion for the plant, which was ``0.75 G's acceleration,'' is 
``fatally flawed'' on the basis of new information gathered at the 
Landers and Northridge earthquakes. The Petitioner asserted (1) That 
the accelerations recorded at Northridge exceeded ``1.8G's and it was 
only a Richter 7+ quake,'' (2) that there were horizontal offsets of up 
to 20 feet in the Landers quake, and (3) that the Northridge fault was 
a ``Blind Thrust and not mapped or assessed.'' On November 22, 1996, 
the NRC staff acknowledged receipt of the Petition as a request 
pursuant to 10 CFR 2.206 and informed the Petitioner that there was 
insufficient evidence to conclude that the requested immediate action 
was warranted. Notice of the receipt of the Petition indicating that a 
final decision with respect to the requested action would be 
forthcoming at a later date was published in the Federal Register on 
November 29, 1996 (61 FR 60734).
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    \1\ In his e-mail dated March 26, 1997, supplementing his 
Petition, the Petitioner also requested removal of ``all spent fuel 
out of the southern California seismic zone.''
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    The Petitioner provided supplemental information in support of his 
Petition in a letter dated December 10, 1996, two e-mails dated March 
26, 1997, and an e-mail dated May 28, 1997.<SUP>2</SUP> My Decision in 
this matter follows.
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    \2\ By letter dated June 26, 1997, the NRC staff advised the 
Petitioner that his e-mail dated April 25, 1997, concerning the 
ability of the SONGS steam generators to withstand a major seismic 
event, would be treated as a separate 10 CFR 2.206 Petition.
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II. Discussion

A. Regulatory Requirements Associated With Potential Earthquake Motion 
and the Licensing Basis for SONGS

    The design bases for each nuclear power plant must take into 
account the potential effects of earthquake ground motion.<SUP>3</SUP> 
The seismic design basis, called the safe-shutdown earthquake (SSE), 
defines the maximum ground motion that certain structures, systems, and 
components necessary for safe shutdown are designed to 
withstand.<SUP>4</SUP> SONGS Units 2 and 3 seismic design basis is 
consistent with the siting criteria set forth in Title 10 of the Code 
of Federal Regulations, Part 100, Appendix A, ``Seismic and Geologic 
Siting Criteria for Nuclear Power Plants.'' Appendix A describes the 
nature of the investigations required to

[[Page 50633]]

obtain the geologic and seismic information necessary to determine site 
suitability and provide reasonable assurance that a nuclear power plant 
can be constructed and operated at a site without undue risk to health 
and safety of the public. Among other particulars, Appendix A requires 
<SUP>5</SUP>--
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    \3\ See 10 CFR Part 50, Appendix A, Criterion 2 and 10 CFR 
50.34(a)(1)(i); see also 10 CFR Part 100, Appendix A, V.(a) which 
provides, in part, that ``the design of each nuclear power plant 
shall take into account the potential effects of vibratory ground 
motion caused by earthquakes.'' The investigative obligations of 10 
CFR Part 100, Appendix A, which are only imposed explicitly on 
applicants for construction permits, were effective December 13, 
1973 (38 FR 31279, November 13, 1973). The Licensing Board issued 
its decision regarding the SONGS Units 2 and 3 construction permits 
on October 15, 1973. However, the SONGS site was reviewed against 
the Appendix A criteria during the construction permit licensing 
review which was updated at the operating license review stage.
    \4\ The SSE is defined, in part, as ``that earthquake which is 
based upon an evaluation of the maximum earthquake potential 
considering the regional and local geology and seismology and 
specific characteristics of local subsurface material. It is that 
earthquake which produces the maximum vibratory ground motion for 
which certain structures, systems, and components are designed to 
remain functional.'' See 10 CFR Part 100, Appendix A. III.(c).
    \5\ See 10 CFR Part 100, Appendix A. IV.
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    <bullet> Determination of the lithologic, stratigraphic, 
hydrologic, and structural geologic conditions of the site and the 
region surrounding the site.
    <bullet> Identification and evaluation of tectonic structures 
underlying the site and the region surrounding the site, whether buried 
or expressed at the surface.
    <bullet> Evaluation of physical evidence concerning the behavior 
during prior earthquakes of the surficial geologic materials and 
substrata underlying the site.
    <bullet> Determination of the static and dynamic engineering 
properties of the materials underlying the site, such as seismic wave 
velocities, density, water content, porosity, and strength.
    <bullet> Listing of all historically reported earthquakes that 
affected or that could reasonably be expected to have affected the 
site.
    <bullet> Correlation of epicenters of historically reported 
earthquakes, where possible, with tectonic structures, any part of 
which is located within 320 kilometers (200 miles) of the site. 
Epicenters that cannot be correlated with tectonic structures shall be 
identified with tectonic provinces, any part of which is located within 
320 kilometers (200 miles) of the site.
    <bullet> For capable faults <SUP>6</SUP> that may be of 
significance in establishing the SSE or that are longer than 330 meters 
(1000 feet) and within 8 kilometers (5 miles) of the site, 
determination of the length of the fault; the relationship of the fault 
to the regional tectonics structures; and the nature, amount, and 
geologic history of displacements along the fault, including the 
estimated amount of maximum Quaternary displacement related to any one 
earthquake along the fault are required.
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    \6\ A capable fault is a fault which has exhibited one or more 
of the following characteristics: (1) Movement at or near the ground 
surface at least once within the past 35,000 years or movement of a 
recurring nature within the past 500,000 years, (2) Macro-seismicity 
instrumentally determined with records of sufficient precision to 
demonstrate a direct relationship with the fault, and (3) A 
structural relationship to a capable fault according to 
characteristics (1) or (2), above, such that movement on one could 
be reasonably expected to be accompanied by movement on the other. 
See 10 CFR Part 100, Appendix A.III(g).
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    The information collected in these investigations is used to 
determine the vibratory ground motion at the site, assuming that the 
epicenters of the earthquakes are situated at the point on the tectonic 
structures or in the tectonic provinces nearest to the site. The 
earthquake that could cause the maximum vibratory ground motion at the 
site is designated the SSE. The vibratory ground motion produced by the 
SSE is defined by response spectra, which are smoothed design spectra 
developed from a set of vibratory ground motions caused by more than 
one earthquake.
    SONGS was licensed consistent with the seismic and geologic siting 
criteria for nuclear power plants set forth in 10 CFR Part 100, 
Appendix A, described above. The site has undergone geologic, 
geophysical, geotechnical, and seismic investigations and reviews that 
are at least as thorough and comprehensive as those of any critical 
facility.<SUP>7</SUP> The SONGS SSE is based on the assumed occurrence 
of a surface-wave (M<INF>S</INF>) <SUP>8</SUP> magnitude 7 earthquake 
on the offshore zone of deformation (OZD), a right lateral strike slip 
fault zone, approximately 8 kilometers from the site at its closest 
approach. This magnitude 7 event is larger than any earthquake known to 
have occurred on the OZD, and the resulting ground motion estimate is 
larger than that which could reasonably be expected at the SONGS site 
from any other seismic source. The determination of the SSE was made in 
accordance with the criteria and procedures specified in Appendix A to 
10 CFR Part 100 and using a multiple hypothesis approach in which 
several different methods were used to determine each parameter; 
sensitivity studies were performed to account for the uncertainties in 
the earth sciences.
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    \7\ The findings of these investigations were reviewed 
extensively by the staff and were litigated in proceedings 
concerning the issuance of the construction permit and operating 
licenses for SONGS Units 2 and 3. See LBP-73-36, 6 AEC 929 (1973); 
ALAB-248, 8 AEC 957 (1974) and see LBP-82-3, 15 NRC 61 (1982); ALAB-
673, 15 NRC 688 (1982); ALAB-717, 17 NRC 346 (1983); and see 
Carstens v. NRC 742 F.2d 1546 (D.C. Cir. 1984), cert. denied, 471 
U.S. 1136 (1985) (the Court of Appeals affirmed the Commission's 
granting of the operating licenses for SONGS Units 2 and 3, noting 
the voluminous record and substantial evidence supporting the 
seismic review).
    \8\ In 1935, Charles Richter introduced the concept of magnitude 
to describe the size of earthquakes. His original formula was based 
on events in southern California recorded on torsion seismographs 
within 600 km of the epicenter. This is the magnitude labeled 
M<INF>L</INF>. Over the years Richter and others developed formulas 
to compute magnitudes from body and surface waves (m<INF>b</INF> and 
M<INF>S</INF>) at distant (teleseismic) stations as well as other 
methods to compute magnitudes for local events in other areas of the 
world. Most of these methods of computing magnitude use as the 
measured variable the amplitude of one or more seismic waves. All of 
these magnitude procedures, including the moment magnitude 
M<INF>W</INF>, have been developed to produce a number which 
represents the size of an earthquake, and each was shingled onto 
Richter's original procedure so that the formulas would produce 
similar values at particular places on the magnitude scale. Each 
computation procedure has its own magnitude or distance range over 
which it is valid. Surface wave magnitude is normally calculated 
from the amplitudes of waves with periods near 20 seconds. Moment 
magnitude is based on the seismic moment. Seismic moment is 
calculated from recordings on digital seismographs and compared to 
the waveforms synthetic seismograms from numerical models of the 
fault rupture to determine the moment.
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    In addition, the plant has design margins (capability) well beyond 
the demands of the SSE. The ability of a nuclear power plant to resist 
the forces generated by the ground motion during an earthquake is 
thoroughly incorporated in the design and construction of the plant. 
The codes that govern the construction of residential and commercial 
buildings are far less stringent than the requirements for nuclear 
power plants. As a result, nuclear power plants are able to resist 
earthquake ground motions well beyond their design basis, the SSE, and 
far above the ground motion that would result in damage to buildings 
designed and built to commercial codes.
    The geologic and seismic siting and the design of SONGS were 
reviewed by the NRC staff, the U. S. Geologic Survey, the National 
Oceanic and Atmospheric Administration, the Advisory Committee on 
Reactor Safeguards and were litigated before the Atomic Safety 
Licensing Board before they were licensed by the 
Commission.<SUP>9</SUP> The NRC continually monitors the adequacy of 
the design of nuclear power plants in order to protect the public 
health and safety. The SONGS licensee performed an individual plant 
examination of external events (IPEEE).<SUP>10</SUP> The IPEEE is a 
program that involves the evaluation of the capability of a nuclear 
power plant to withstand the effects of several natural phenomena such 
as earthquakes, fires, and floods, well beyond its design bases. The 
most recent geologic and seismic information for the southern 
California region was used in the probabilistic analysis to quantify 
the seismic hazard and the uncertainties for the SONGS site for this 
program.
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    \9\ See cases cited supra note 7.
    \10\ See response to Generic Letter 88-20, Supplement 4, 
Individual Plant Examination of External Events (IPEEE) dated 
December 15, 1995, discussed, infra, at pages 22-24.
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    The ground motion from an earthquake at a particular site is a 
function of the magnitude and focal mechanism (type of faulting, i.e., 
normal, reverse, strike slip) at the earthquake source. It is also a 
function of the distance of the facility from the

[[Page 50634]]

fault and the geology immediately under the facility site. The 
estimates of SSE ground motion for the SONGS site conform with the 
procedures and criteria specified in 10 CFR Part 100, Appendix A and 
the Standard Review Plan (SRP) <SUP>11</SUP> Sections 2.5.1 and 2.5.2 
(NUREG-0800). As previously stated, the earthquake that was determined 
to control the design of SONGS is a M<INF>S</INF>=7 located on the OZD 
at a distance of 8 kilometers from the site. The appropriate level of 
conservatism for characterizing the ground motion through a site-
specific spectrum as specified in SRP 2.5.2 is the 84th percentile. 
This level of conservatism was used in the design and licensing review 
of SONGS, Units 2 and 3.
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    \11\ Standard Review Plan (SRP) is used as guidance for the 
Office of Nuclear Reactor Regulation staff responsible for the 
review of applications to construct and operate nuclear power 
plants.
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    Since the SONGS plants were licensed, a new magnitude scale, moment 
magnitude (M<INF>W</INF>), has come into common usage. The most 
recently published ground motion attenuation relationships 
<SUP>12</SUP> use M<INF>W</INF>. An attenuation relationship is a 
relationship between sized earthquake, distance to fault and the 
amplitude of the ground motion. Since magnitude 7 M<INF>W</INF> is 
equal to magnitude 7 M<INF>S</INF>,<SUP>13</SUP> there is no need to 
make a conversion between M<INF>W</INF> and M<INF>S</INF> when 
comparing the ground motion estimates obtained using the recent 
attenuation relationships to the SONGS SSE ground motion.
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    \12\ N. A. Abrahamson and W. J. Silva, ``Empirical Response 
Spectral Attenuation Relations for Shallow Crustal Earthquakes,'' 
Seismological Research Letters, 68, 94-127 (1997); David M. Boore, 
William B. Joyner, and Thomas E. Fumal, ``Equations for Estimating 
Horizontal Response Spectra and Peak Acceleration From Western North 
American Earthquakes: A Summary of Recent Work,'' Seismological 
Research Letters, 68, 128-153 (1997); K. W. Campbell, ``Empirical 
Near-Source Attentuation Relationships for Horizontal and Vertical 
Components of Peak Ground Acceleration, Peak Groud Velocity and 
Pseudo-Absolute Aceleration Response Spectra,'' Seismological 
Research Letters, 68, 154-179; K. Sadigh, C.Y. Chang, J. A. Egan, F. 
Makdisi, and R. R. Yongs, ``Attentuation Relationships for Shallow 
Crustal Earthquakes Based on California Strong Motion Data,'' 
Seismological Research Letters, 68 180-189 (1997).
    \13\ Thorne Lay and Terry C. Wallace, Modern Global Seismology, 
Academic Press, Inc., San Diego, California; K. W. Campbell (1995).
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B. Responses to the Petitioner's Concerns

1. Concern that SONGS is in a High Seismic Hazard Area
    In the enclosure to his letter,<SUP>14</SUP> the Petitioner 
referenced ``a recent paper by M. D. Petersen et al. (Seismic Hazard 
Analysis, AEG, 1-20-96)'' and stated that it concludes that the entire 
Los Angeles, Ventura, and Orange Counties are high hazard areas. The 
Petitioner stated that the paper also concludes that accelerations of 
0.4g (pga), 1.0g (0.3-sec SA), and 0.5g (1-sec SA) can occur nearly 
everywhere.
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    \14\ Stephen Dwyer, Letter to Dr. Shirley Jackson and Frank J. 
Miraglia, Jr., with enclosure, dated December 10, 1996.
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    The NRC staff attempted to find the reference mentioned by Mr. 
Dwyer but was unsuccessful. Mark D. Petersen of the California Division 
of Mines and Geology informed the staff that the correct reference is 
an article that he and his coauthors published in the Bulletin of the 
Seismological Society of America.<SUP>15</SUP> Dr. Petersen made a 
presentation at a workshop on seismic hazard in southern California in 
January 1996 and gave participants in the workshop preprints and 
reprints of some of his recent publications. The cited reference was 
one of these handouts.
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    \15\ Mark D. Petersen, Chris H. Cramer, William A. Bryant, 
Michael S. Reichle, and Tousson R. Toppozada, ``Preliminary Seismic 
Hazard Assessment for Los Angeles, Ventura, and Orange Counties, 
California, Affected by the 17 January 1994 Northridge Earthquake,'' 
Bulletin of the Seismological Society of America, 86, S247-S261 
(1996).
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    In the section of the paper entitled ``Hazard Maps,'' the authors 
state:

    The DMG probabilistic seismic hazard maps (10% exceedance in 50 
years) for peak ground acceleration (pga) and 5% damped spectral 
acceleration (SA) at 0.3-and 1-sec periods on alluvial site 
conditions are shown in Figures 3 through 5. These maps may be 
useful in characterizing regional variations in seismic hazard in 
southern California but should not be used as input for detailed 
site-specific estimates of ground shaking in the earthquake-
resistant design of individual structures.<SUP>16</SUP>

    \16\ Id.
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    The paper then states--

    The three maps show similar hazard patterns that indicate high 
hazard over the entire tri-county area. The expected peak 
accelerations exceed 0.4g (pga), 1.0g (0.3 s SA), and 0.5g (1 s SA) 
nearly everywhere in the tri-county area.'' <SUP>17</SUP>

    \17\ Id.
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    To address the acceleration values mentioned by the Petitioner with 
respect to SONGS, the NRC staff has produced Figure 1, which contains a 
plot of the SONGS SSE seismic response spectrum at 5 percent of 
critical damping and the values quoted from the Petersen paper. Since 
period in seconds is the reciprocal of frequency in Hertz, the 1-second 
period spectral acceleration (0.5g) is plotted at a frequency of 1 
Hertz, the 0.3-second period acceleration (1.0g) is plotted at a 
frequency of 3.33 Hertz and the peak ground acceleration (0.4g) is 
plotted at a frequency of 33 Hertz. The figure demonstrates that the 
spectral accelerations (accelerations plotted in the response spectra) 
used in the design of SONGS are significantly higher than those from 
the Petersen paper, thus showing the conservatism of the design basis 
for SONGS.
2. Concern About a Large Earthquake on the San Andreas Fault
    In the enclosure to his letter dated December 10, 1996, entitled 
``Uncertainty Factors Affecting Seismic Risk Risk Modelling in Southern 
California,'' the Petitioner stated ``We must prepare for a great event 
on the Southern San Andreas Fault.'' He also mentioned an earthquake on 
the San Andreas in his e-mail message.<SUP>18</SUP>
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    \18\ Stephen Dwyer, e-mail message to Dr. Jackson, Subject: San 
Onofre Nuclear Power Plant Risk, dated September 22, 1996.
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    The NRC staff agrees that there must be preparation for a large 
event on the San Andreas fault and finds that the SONGS seismic design 
is well able to withstand the demands of a large earthquake on the 
southern San Andreas fault. Although the geologic evidence appears to 
indicate that the largest event to have occurred on the southern San 
Andreas in the Quaternary Period (the last 2 million years) is 
estimated to have been in the moment magnitude (Mw) range of 7.5 to 8; 
to evaluate the potential ground motion at the SONGS site from a large 
earthquake on the southern San Andreas fault, the staff made the very 
conservative assumption of a moment magnitude 8.25 strike-slip 
earthquake at the closest distance of the San Andreas fault to the site 
(90 kilometers). This assumption was made to calculate the effects of a 
large earthquake on the San Andreas fault. The results are plotted in 
Figure 2 which demonstrates that the design basis (SSE) spectrum for 
SONGS is much higher than the ground motion estimates from the Mw 8.25 
on the San Andreas fault using four recent attenuation relationships. 
These four empirical attenuation relationships were developed after the 
occurrence of the Northridge and Landers earthquakes, and include the 
recent strong ground motion from these events. They were performed by 
internationally known experts in earthquake ground motion analysis and 
were published in the Seismological Research Letters,<SUP>19</SUP> the 
peer-reviewed journal of the Seismological Society of America. The 
assumption of a moment magnitude 8.25 strike-slip earthquake and the

[[Page 50635]]

SONGS site foundation geology were used as input parameters for these 
four earthquake ground motion attenuation relationships.<SUP>20</SUP> 
The ground motion estimates were made at the 84th percentile level 
recommended by SRP Section 2.5.2. The plots of the results obtained 
from these four attenuation relationships and the SONGS Units 2 and 3 
SSE design response spectrum are shown in Figure 2. The plotted 
information in the figure demonstrates that the SONGS design is well 
able to accommodate the demand of the ground motion of the large 
earthquake on the southern San Andreas fault since it envelopes the 
estimates of the four relationships at all frequencies.
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    \19\ Abrahamson and Silva, supra note 12.
    \20\ Id.
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3. Concern About the SONGS Design Basis in Light of the Landers and 
Northridge Earthquakes
    In an e-mail message to Chairman Jackson dated September 22, 1996, 
the Petitioner stated--

    I am a geologist in Southern California, and I am deeply 
concerned by the current situation at San Onofre NPP. The design 
criteria for this old plant was 0.75 G's acceleration. With the new 
information gathered at the Landers and Northridge Quakes, this 
criteria is fatally flawed. The accelerations recorded at Northridge 
exceeded 1.8 G's !!! and it was only a Richter 7+ quake. Horizontal 
offsets of up to 20 feet in the Landers quake were also way beyond 
geologists and seismologists estimates. The whole science is in 
disarray. Also the Northridge fault was a ``Blind Thrust' and not 
mapped or assessed. If we have a larger quake here on the San 
Andreas, or a smaller one closer to the plant, well I hate to 
imagine * * *. What's even worse is the fact that scientists are not 
able to give us the info we need to evaluate the situation.

    The main points of the Petitioner's message appear to be--
    <bullet> A peak ground acceleration recorded from the Northridge 
magnitude Mw 6.7 earthquake exceeded 1.8 g.
    <bullet> The Northridge earthquake occurred on a blind fault that 
had not been mapped or assessed.
    <bullet> The maximum horizontal displacement of almost 20 feet due 
to the Landers magnitude 7.3 earthquake is much larger than would be 
estimated.
    <bullet> Scientists are not able to provide the information to 
evaluate the situation.
    The magnitude 6.7 Northridge earthquake of January 17, 1994, 
occurred on a buried thrust fault in the San Fernando Valley and was 
similar to the 1971 San Fernando Valley earthquake. The distance from 
this earthquake epicenter to the SONGS site is about 130 kilometers (80 
miles). The Northridge earthquake was felt at SONGS. A free-field 
seismic instrument at SONGS recorded a peak ground acceleration of 
0.025g, which is significantly less than the SSE peak ground 
acceleration of 0.67g, thus indicating that an earthquake in the 
epicentral region of Northridge poses no threat to the plant.
    The peak ground acceleration of 1.8g from the Northridge earthquake 
referred to by the Petitioner was recorded by the California Division 
of Mines and Geology station in Tarzana. The anomalous character of the 
seismic response at the Tarzana site is well known.<SUP>21</SUP> The 
intense shaking at the Tarzana site is a condition of the site and is 
not characteristic of the Northridge earthquake. This fact is 
demonstrated by the unusually strong ground motion that was also 
observed there during the 1987 Whittier Narrows earthquake 
<SUP>22</SUP> and during the aftershocks following both the Northridge 
and Whittier Narrows mainshocks. In recognition of the unusually high 
ground motion recordings at Tarzana, there have been a number of 
studies of this site <SUP>23</SUP> to try to determine the cause of the 
high recordings. These studies have attributed the high peak ground 
accelerations to the site's specific geology. The anomalous site effect 
was found to be confined to a small area 50 meters in radius around the 
station; beyond this area, the ground motion recordings were down to 
their normally expected values. It is, therefore, inappropriate to rely 
on data recorded at the unique Tarzana site to make judgments about 
ground motion estimates at other locations. The geologic formations 
under the SONGS site differ from those at the Tarzana site. The SONGS 
site does not anomalously amplify the earthquake ground motion as the 
Tarzana site does. During the evaluation of the site no geologic 
formations under SONGS were identified that would result in 
exceptionally high earthquake ground motions. Further, recorded 
earthquakes at SONGS have not exhibited any unusual amplifications.
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    \21\ J. A. Rial, ``The Anomalous Seismic Response of the Ground 
Motion at the Tarzana Hill Site During the Northridge 1994 Southern 
California Earthquake: A Resonant, Sliding Block?'' Bulletin of the 
Seismological Society of America, 86, 1714-1723 (1996).
    \22\ A. M. Shakal, M. Huang, and T. Cao, ``The Whittier Narrows, 
California, Earthquake of October 1, 1987: CSMIP Strong Motion 
Data,'' Earthquake Spectra, 4 75-100 (1988).
    \23\ R. D. Catchings and W. H. K. Lee, ``Shallow Velocity 
Structure and Poisson's Ratio at the Tarzana, California Strong-
Motion Accelerometer Site,'' Bulletin of the Seismological Society 
of America, 86 1704-1713; Rial, loc. cit.; Paul Spudich, Margaret 
Hellweg, and W. H. K. Lee, ``Directional Topographic Site Response 
at Tarzana Observed in Aftershocks of the 1994 Northridge, 
California, Earthquake: Implications for Mainshock Motions,'' 
Bulletin of the Seismological Society of America, 86, S193-S208 
(1996).
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    As a result of their studies of the near field ground motions from 
thrust faults, Somerville et al.<SUP>24</SUP> found that the ground 
motions from the Northridge earthquake, in general, are within the 84th 
percentile when compared to previously developed empirical attenuation 
relations for thrust faults. This finding indicates that the Northridge 
ground motion data would not cause seismologists to revise ground 
motion estimates for thrust fault earthquakes. The data from this 
earthquake have been incorporated into the strong ground motion 
databases and have not significantly altered the results of the 
attenuation relationships. In addition, it is inappropriate to use the 
ground motions from thrust faults for estimates in a region in which 
there is no potential for this type of faulting, such as the South 
Coast Borderland where SONGS is located.
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    \24\ Paul Somerville, Chandan Saikia, David Wald, and Rover 
Graves, ``Implications of the Northridge Earthquake for Strong 
Ground Motions from Thrust Faults,'' Bulletin of the Seismological 
Society of America, 86 S115-S125 (1996).
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    To address the issue of whether there is a potential for buried 
thrust faults at the SONGS site, the staff referred to a book by Yeats 
et al.<SUP>25</SUP> that contains a list and a map of the regions of 
the world that have the potential for large reverse-fault earthquakes. 
Thrust faults are low angle reverse faults. In California, the regions 
listed are the northern California coast, the Coast Ranges of central 
California, and the western Transverse Ranges. The 1994 Northridge 
earthquake and the 1971 San Fernando Valley earthquake are related to 
the western Transverse Ranges. There is no indication of reverse-fault 
earthquakes in the South Coast Borderland where SONGS is located.
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    \25\ Robert S. Yeats, Kerry Sieh, and Clarence R. Allen, The 
Geology of Earthquakes, Oxford University Press, Oxford, England 
(1997).
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    In southern California, the mountain ranges flanking the ``Big 
Bend'' of the San Andreas fault (the Transverse Ranges) strike east-
west and are bounded on the south by north-dipping range-front reverse 
faults, part of a discontinuous system of faults that extends from the 
Santa Barbara Channel eastward to the eastern end of the San Gabriel 
Mountains. Other important reverse faults in this region include the 
Pleito fault in the southern margin of the South San Joaquin Basin; the 
south-dipping Oak Ridge fault in the Ventura Basin which extends 
eastward to the San Fernando Valley as a blind thrust that produced the 
1994 Northridge

[[Page 50636]]

earthquake; and a blind reverse-fault system beneath the Santa Monica 
Mountains North of the Los Angeles basin. Major earthquakes generated 
by these reverse faults include the 1952 Kern County earthquake in the 
South San Joaquin Valley (M<INF>S</INF> 7.7), the 1971 San Fernando 
earthquake at the eastern edge of the Ventura basin (M<INF>W</INF> 
6.7), the 1978 Santa Barbara earthquake in the western Ventura basin 
(M<INF>L</INF> 5.9), the 1987 Whittier Narrows earthquake in the Los 
Angeles basin (M<INF>L</INF> 5.9), the 1991 Sierra Madre earthquake at 
the southern edge of the San Gabriel Mountains northeast of Los Angeles 
(M<INF>L</INF> 6.0), and the 1994 Northridge earthquake in the San 
Fernando Valley (M<INF>L</INF> 6.7). Of these, only the 1952 and 1971 
earthquakes produced surface rupture. Global Positioning System 
satellite geodesy confirms the high convergence rate as a result of 
reverse slip on these faults,<SUP>26</SUP> indicating this is an active 
thrust fault area. These indications were not seen in the SONGS area.
---------------------------------------------------------------------------

    \26\ Id.
---------------------------------------------------------------------------

    To state that the Northridge earthquake occurred on a blind fault 
that had not been mapped or assessed is an oversimplification. Blind 
thrust faults are recognized as significant sources of seismic hazard 
in areas of active folding, and the Transverse Ranges-Los Angeles basin 
has long been recognized as such an area. If, before the Northridge 
earthquake, such a fault had been sought as part of a siting 
investigation, it or the active folding indicative of such a fault 
would have been found and would have been considered in the seismic 
hazard estimate. In addition, the potential occurrence of a 
M<INF>W</INF> 6.5 to 7 on a buried fault has been assumed in the 
commercial design and construction codes for the area where the 
Northridge earthquake occurred, so in effect, the potential for blind 
faults has been accounted for.
    The types of site investigations, borehole drilling, and seismic 
survey profiles normally performed for critical facilities such as 
nuclear power plants are not used for normal residential or commercial 
structures because of the high costs of such work. For residences or 
commercial buildings, the codes rely on more generalized hazard 
estimates, such as those found in Petersen et al.<SUP>27</SUP> These 
hazard studies incorporate all the known geologic information in their 
ground motion estimates.
---------------------------------------------------------------------------

    \27\ Mark D. Peterson, et al., supra note 15.
---------------------------------------------------------------------------

    The most promising new data for the identification of areas of 
potential buried thrust faults comes from geodetic measurements of the 
satellite-based Global Positioning System, which is capable of 
determining convergence rates across folded terranes. Geomorphic 
studies are important in that the deformation of late Quaternary stream 
or coastal terraces provides quantitative data on the uplift rates or 
lack of uplift of postulated active folds over buried faults. In fact, 
the locale of the 1987 Whittier Narrows, California, earthquake was 
identified more than 70 years ago <SUP>28</SUP> as an active anticline 
on the basis of warped geomorphic surfaces.
---------------------------------------------------------------------------

    \28\ F.F. Vickery, ``The Interpretation of the Physiography of 
the Los Angeles Coastal Belt,'' Bulletin of the American Association 
of Petroleum Geologists, 11, 417-424 (1927).
---------------------------------------------------------------------------

    The SONGS site lies in a relatively stable structural block bounded 
by major northwest-southeast trending strike-slip faults. The relative 
motion between the Pacific plate and the North American plate is 
accommodated, in part, by dextral strike slip along the San Andreas 
fault system and faults in the borderlands, extension in the Gulf of 
California, and contraction in the Transverse Ranges and the Los 
Angeles basin region.<SUP>29</SUP>
---------------------------------------------------------------------------

    \29\ M.L. Zoback and R.E. Anderson, ``Cenozoic Evolution of the 
State of Stress and Style of Tectonism in Western United States,'' 
Philosophical Transactions of the Royal Society of London, 300, 407-
434 (1981); R. Weldon and E. Humphreys, ``A Kinematic Model of 
Southern California,'' Tectonics, 5, 38-48 (1986); D.F. Argus and 
R.G. Gordon, ``Sierra Nevada-North America Motion From VLBI and 
Paleomagnetic Data--Implications for the Kinematics of the Basin and 
Range, Colorado Plateau, and California Coast Ranges,'' EOS 
Transactions, American Geophysical Union, 69, 1418 (1988); R.S. 
Stein and R.S. Yeats, ``Hidden Earthquakes,'' Scientific American, 
260, 48-57 (1989).
---------------------------------------------------------------------------

    The tectonic setting of the SONGS site is significantly different 
from the complex regime of the Transverse Ranges and the Los Angeles 
basin. This difference is reflected in the higher seismicity in the 
Transverse Range and the Los Angeles basin than in the SONGS site area. 
The presence or absence of blind thrust faults in a region is indicated 
by the presence or absence of significant uplift and folding of late 
Quaternary period deposits and geomorphic surfaces <SUP>30</SUP> as 
evidenced in the Transverse Ranges and the Los Angeles basin region. 
Mapping of marine terraces along the western flank of the San Joaquin 
Hills to the north of the SONGS site indicates a uniform uplift rate 
for the past 80 to 120 thousand years.<SUP>31</SUP> Lajoie et 
al.<SUP>32</SUP> reported on the coastal region between San Onofre 
Bluff and Torrey Pines north of Soledad Mountain in San Diego and noted 
that there has been no significant crustal tilt perpendicular to the 
coastline during much of the Quaternary Period. There is also no 
indication from the marine terrace studies of significant tilt parallel 
to the coastline during much of the Quaternary Period. The marine 
terrace data, along with other geological mapping and geophysical 
surveys, have not identified geologically young folds or blind thrust 
faults in the SONGS site vicinity. The closest capable fault to the 
site is the OZD 8 kilometers from the site, and it is the postulated 
earthquake on this fault that dominates the seismic hazard at SONGS. 
Therefore, the statement that the Northridge earthquake occurred on a 
blind fault that had not been mapped or assessed, and the implication 
that such a condition could also exist at the SONGS site, are not 
valid.
---------------------------------------------------------------------------

    \30\ Stein and Yeats, supra notes 25 and 29.
    \31\ D.T. Barrie, T. Totnall, and E. Gath, ``Neotectonic Uplift 
and Ages of Pleistocene Marine Terraces, San Joaquin Hills, Orange 
County, California,'' in E.G. Heath and W.L. Lewis (editors), The 
Regressive Pleistocene Shoreline Coastal Southern California, South 
Coast Geological Society, Inc., 1992 Annual Field Trip Guide Book 
No. 20, 115-122 (1992).
    \32\ K.R Lajoie, D.J. Ponti, C.L. Powell, II, S.A. Mathieson, 
and A.M. Sarna-Wojcicki, ``Emergent Marine Strandlines and 
Associated Sediments, Coastal California; a Record of Quaternary 
Sea-Level Fluctuations, Vertical Tectonic Movements, Climatic 
Changes, and Coastal Processes,'' in E.G. Heath and W.L. Lewis 
(editors), The Regressive Pleistocene Shoreline Coastal Southern 
California, South Coast Geological Society, Inc., 1992 Annual Field 
Trip Guide Book No. 20, 81-104 (1992).
---------------------------------------------------------------------------

    The Landers magnitude M<INF>W</INF> 7.3 earthquake of June 28, 
1992, was in the Eastern California Shear Zone (ECSZ) approximately 140 
kilometers from the SONGS site. The ECSZ is a complex zone of 
predominantly right lateral strike-slip faulting. The earthquake was 
caused by strike-slip faulting on five fault segments with a total 
rupture length of about 70 kilometers.<SUP>33</SUP>
---------------------------------------------------------------------------

    \33\ Yeats, et al., supra note 25.
---------------------------------------------------------------------------

    Campbell and Bozorgnia <SUP>34</SUP> used 167 accelerograms 
recorded during the Landers earthquake to study the ground motions from 
this event. A comparison of these recordings with ground motions 
predicted by contemporary attenuation relationships indicated that 
relationships developed before the Landers earthquake made a reasonable 
prediction of the Landers ground motions within 60 kilometers of the 
fault, and relationships developed after

[[Page 50637]]

the Landers earthquake did a reasonably good job of predicting the 
Landers ground motions within the distance ranges for which they were 
applicable. This information shows that there was nothing extraordinary 
about the ground motions from the Landers earthquake that would 
challenge the adequacy of the near field ground motion estimates made 
for the SONGS SSE. To demonstrate the adequacy of the SONGS SSE ground 
motion, Figure 3 contains a plot of the SSE response spectrum and the 
84th percentile response spectra obtained from the four recent 
earthquake ground motion attenuation relationships to estimate the 
ground motion for a magnitude M<INF>W</INF> 7 earthquake at a distance 
of 8 kilometers. The SONGS response spectrum envelopes the response 
spectra of all four relationships at all frequencies.
---------------------------------------------------------------------------

    \34\ K.W. Campbell and Y. Bozorgnia, ``Empirical Analysis of 
Strong Ground Motion from the 1992 Landers, California, 
Earthquake,'' Bulletin of the Seismological Society of America, 84, 
573-588 (1997).
---------------------------------------------------------------------------

    To address the issue of the 20 feet (6 meters) of fault 
displacement as a result of the Landers earthquake, the staff has 
reviewed the work of researchers on this subject. Post-earthquake 
investigations have found that slip on the Landers earthquake faults 
was extremely heterogeneous both along strike and down dip. The 
magnitude of the horizontal offset varied along the fault trace, but 
was typically 2 to 3 meters with maximum strike-slip offset of about 6 
meters.<SUP>35</SUP> This offset is not unusual and is within the range 
of offsets for an earthquake of this size.<SUP>36</SUP> The U.S. 
Geological Survey, with NRC sponsorship, has conducted paleoseismic 
studies of the fault segments that ruptured during the Landers 
earthquake. Trenches across the faults provide clear evidence of the 
two most recent pre-1992 surface faulting events. The most recent 
faulting, Holocene age, has displacements essentially the same as the 
1992 event. Evidence from the trenches also indicates that the segments 
that ruptured during the 1992 event had ruptured during the previous 
events.<SUP>37</SUP> If, before the Landers earthquake, these faults 
had been subjected to the type of investigations that nuclear power 
plant sites undergo, the earthquake and fault rupture potential would 
have been identified.
---------------------------------------------------------------------------

    \35\ Carlos Lazarte, Jonathan D. Bray, Arvid M. Johnson, and 
Robert E. Lemmer, ``Surface Breakage of the 1992 Landers Earthquake 
and Its Effects on Structures,'' Bulletin of the Seismological 
Society of America, 84, 547-561 (1994).
    \36\ Donald L. Wells and Kevin J. Coppersmith, ``New Empirical 
Relationships Among Magnitude, Rupture Length, Rupture Width, 
Rupture Area, and Surface Displacement,'' Bulletin of the 
Seismological Society of America, 84, 974-1002 (1994).
    \37\ David P. Schwartz. Personal communication with Dr. Robert 
Rothman, of the NRC staff, June 1997. Dr. Schwartz is a senior 
geologist employed by the U.S. Geological Survey in Menlo Park, 
California and a international authority on paleoseismology.
---------------------------------------------------------------------------

    There are no faults at the SONGS site capable of surface offset. 
The fault nearest to the SONGS site capable of significant surface 
offset is the OZD, which is 8 kilometers from the site. Assuming that 
there were to be offsets on the order of 6 meters or more on the OZD, 
they would have no detrimental effect on SONGS because of the distance 
of the fault, the orientation of the fault, and the potential ground 
motion to which the plant is designed.
    With respect to the Petitioner's statement that scientists are not 
able to provide the information to evaluate the situation, the staff 
notes that numerous papers have been published in the scientific 
literature and presentations made at national and international 
scientific meetings on these two earthquakes. In addition, the 
Seismological Society of America has devoted one issue of its Bulletin 
<SUP>38</SUP> to the Northridge earthquake and another issue to the 
Landers earthquake.<SUP>39</SUP> The information about these events is 
understood and is widely distributed in the professional community.
---------------------------------------------------------------------------

    \38\ Bulletin of the Seismological Society of America, Volume 
86, Number 1, Part B Supplement, February 1996.
    \39\ Bulletin of the Seismological Society of America, Volume 
84, Number 3, June 1994.
---------------------------------------------------------------------------

4. Concern About ``Seismic Analysis Uncertainties''
    In the enclosure to his letter dated December 10, 1996, the 
Petitioner provided a list of 10 seismic analysis uncertainties 
<SUP>40</SUP> and implies that these must be addressed because new 
surprises will occur with each event.
---------------------------------------------------------------------------

    \40\ List of Seismic Analysis Uncertainties: (1) How to quantify 
slip rates and maximum magnitudes along with their uncertainties for 
all fault sources. (2) How to incorporate blind thrusts with 
appropriate weighting. (3) What seismogenic zone widths to use for 
various fault zones. (4) Which magnitude distributions are most 
appropriate for various faults. (5) How to incorporate background 
seismicity and which ``b'' value is most appropriate for 
exponentially distributed earthquakes. (6) Whether to use source 
zones or simple point sources in modelling background seismicity. 
(7) Which alternative segmentation models are viable (including 
alternative cascades models for ``A'' zones). (8) How to incorporate 
geodetic data directly in the model. (9) Which attenuation relations 
are most appropriate and how to model ground motion from large (M>8) 
earthquakes. (10) How to resolve the discrepancy between the rate of 
earthquakes in this and other seismic hazard models and the historic 
earthquake record (especially in the Transverse Ranges).
---------------------------------------------------------------------------

    The Petitioner appears to have compiled a list of uncertainties in 
estimating seismic hazard from the Petersen paper.<SUP>41</SUP> There 
is nothing unique about this list. These are the types of issues a 
geologist or a seismologist performing earthquake hazard investigations 
must routinely confront. They are among the points that the NRC Seismic 
and Geologic Siting Criteria for Nuclear Power Plants and the NRC SRP 
were developed to address.
---------------------------------------------------------------------------

    \41\ Peterson, et al., supra note 15.
---------------------------------------------------------------------------

    The geologic and seismic investigations and reviews that were 
performed for the licensing of SONGS Units 2 and 3 were deterministic 
in nature. In the deterministic method, the uncertainties were not 
explicitly quantified. Rather, a multi-method approach with sensitivity 
studies was used. For instance, to determine the maximum magnitude 
estimate for a fault empirical relationship, such as magnitude as a 
function of the parameters slip rate, the fault length, the rupture 
length per event, the rupture area, and the historical seismicity were 
used. Also, various fault segmentation models were used in magnitude 
estimates. To determine the ground motion from a magnitude 7 earthquake 
at a distance of 8 kilometers, attenuation relationships from the 
statistical analysis of empirical ground motion data, theoretical 
numerical modeling studies, and the response spectra from magnitude 6.5 
and larger earthquakes recorded at distances of 13 kilometers and less 
were used. The SSE for the SONGS site enveloped all of these estimates. 
The geology in the site region was investigated by geologic mapping, 
excavation of faults, offshore and onshore seismic reflection profiles, 
onshore refraction profiles, geophysical surveys, drill holes, well 
logs, trenching, geomorphic surveys, and geodetic studies. The 
information from these various studies was analyzed by experienced 
professional geologists and geophysicists, and the site characteristics 
were thus developed in a conservative manner. Independent studies and 
reviews were performed by the NRC staff, the U.S. Geologic Survey, the 
National Oceanic and Atmospheric Adminstration, and the Advisory 
Committee on Reactor Safeguards. These studies and reviews confirmed 
the licensee's determinations.
    The uncertainties in seismic hazard estimates can be addressed 
quantitatively through a probabilistic seismic hazard analysis. In 
1991, the NRC issued Supplement 4 to Generic Letter 80-20 requesting 
licensees of nuclear power plants to perform an IPEEE to identify 
plant-specific vulnerabilities to severe accidents. Among the events to 
be assessed were earthquakes, internal fires, high winds and tornadoes, 
external floods, and transportation and nearby facility accidents. As 
part of the SONGS IPEEE

[[Page 50638]]

program, a state-of-the-art probabilistic seismic hazard analysis was 
performed. In response to an NRC request for information, Southern 
California Edison submitted its contractor's final report on the 
seismic hazard study.<SUP>42</SUP> In the seismic hazard study, ground 
motion exceedance probabilities were calculated using hypotheses about 
the causes and characteristics of earthquakes in the region. Scientific 
uncertainty about the causes of earthquakes and about the physical 
characteristics of potentially active tectonic features lead to 
uncertainty in the inputs to the seismic hazard calculations. These 
uncertainties were quantified using the tectonic interpretations 
developed by earth scientists knowledgeable about the region. These 
experts evaluated the likelihood associated with alternative tectonic 
features and with alternative characteristics of these potential 
sources. These and other uncertainties were propagated through the 
entire analysis. The result of the analysis is a spectrum of hazard 
curves and their associated weights. These curves quantify the seismic 
hazard at the site and its uncertainty.
---------------------------------------------------------------------------

    \42\ Risk Engineering, Inc., ``Seismic Hazard at San Onofre 
Nuclear Generating Station, ``Prepared for Southern California 
Edison Co., Final Report (1995).
---------------------------------------------------------------------------

    The major components of the probabilistic seismic hazard analysis 
are the identification of the seismic sources, the determination of the 
earthquake magnitude distribution and rate of occurrence for each 
source, the estimation of the ground motion, and the incorporation of 
these factors by the probability analysis into the hazard curves. The 
Risk Engineering, Inc., report <SUP>43</SUP> more than adequately 
demonstrates how the uncertainties of the type the Petitioner listed in 
the enclosure to his letter were addressed. The comparison of the 
probabilistic seismic hazard results to the SSE indicates that the SSE 
response spectrum has an annual probability of being exceeded in the 
range of 5 x 10<SUP>-6</SUP> to 4 x 10<SUP>-4</SUP>, depending on the 
frequency. This estimate is similar to the probabilistic hazard 
estimates for other critical facilities in the western United States. 
The low frequency of exceedance of the SSE ground motion provides 
further assurance that the licensing basis for SONGS provides adequate 
protection of the health and safety of the public.
---------------------------------------------------------------------------

    \43\ Id.
---------------------------------------------------------------------------

5. Concern About the Failure of Welded-Steel Frames in Commercial 
Buildings During the Northridge Earthquake
    In an e-mail message to Dr. Shirley Jackson,<SUP>44</SUP> the 
Petitioner stated--

    \44\ Stephen Dwyer, e-mail message to Dr. Shirley Jackson, 
Subject: 2.206 Petition Re: SONGS Seismic Hazards, dated May 28, 
1997.
---------------------------------------------------------------------------

    The breaking of welds in steel buildings in the San Fernando 
Valley is a warning that all sorts of steel welds and fittings are 
vulnerable. The number of such welds and fittings at SONGS is almost 
uncountable, and it's therefore unrealistic to believe that they 
will all be undamaged or broken at forces far below the Design Basis 
Event of 67%g.

    It appears that the Petitioner is referring to the failure of 
welded-steel moment-resisting frames (WSMFs) in high-rise residential 
and commercial buildings during the 1994 Northridge earthquake. 
Following the Northridge earthquake, inspections of many otherwise 
intact buildings indicated structural damage to WSMFs. The WSMFs were 
specifically designed on the basis of the assumption that they would be 
capable of extensive yielding and plastic deformation. The deformation 
was assumed to be accomplished by the yielding of plastic hinges in the 
beams at their connections to the columns. Damage was expected to 
consist of moderate yielding at the connections and localized buckling 
of the steel elements. However, contrary to the design assumption, the 
WSMF failures were brittle fractures with unanticipated deformations in 
girders, cracking in column panel zones, and fractures in beam-to-
column weld connections. A number of factors related to seismic 
analysis and design, materials, fabrication, and construction have been 
identified as contributing to the failure of the WSMFs and are the 
focus of research projects sponsored by the Federal Emergency 
Management Agency.<SUP>45</SUP>
---------------------------------------------------------------------------

    \45\ FEMA 267, ``Interim Guidelines: Evaluation, Repair, 
Modification and Design of Welded Steel Moment Frame Structures, 
Program to Reduce the Earthquake Hazards of Steel Moment Frame 
Structures,'' Federal Emergency Management Agency, Washington, DC 
(1995).
---------------------------------------------------------------------------

    The method of computing seismic loads, their combination with other 
non-seismic loads, the acceptance criteria, and the quality assurance 
requirements for nuclear power plants are significantly more 
conservative than those for non-nuclear buildings designed using 
building codes for residential or commercial structures. For nuclear 
power plants, two levels of ground motion, based on very conservative 
siting criteria, are determined for designing the safety-related 
structures, systems, and components. For the lower level of vibratory 
motion, the operating-basis earthquake,<SUP>46</SUP> the load factors, 
and acceptable allowable stresses ensure that the stresses in plant 
structures remain at least 40 percent below the yield stress of the 
material. For the higher level vibratory motion, the SSE, the 
associated load factors, and allowable stresses ensure that the 
stresses in steel structures do not exceed the yield stress of the 
material. The NRC staff design review guidance specified in SRP Section 
3.7.2 does not accept the use of inelastic deformation of any steel 
member or connection in nuclear power plants for design-basis seismic 
events. Also, the use of broadband design response spectra, 
conservatively defined structural damping values, consideration of 
amplified forces at higher elevations in the plants, and consideration 
of all three components of the design-basis vibratory motion in the 
dynamic analysis ensure that the loads and load paths of the seismic 
events are properly considered in the design, as opposed to the use of 
static shear forces in non-nuclear structures. For these reasons, the 
failure of WSMFs in residential and commercial buildings as a result of 
the Northridge earthquake is not relevant to nuclear power plants.
---------------------------------------------------------------------------

    \46\ See 10 CFR Part 100, Appendix A, III(d).
---------------------------------------------------------------------------

    On the basis of its review of the Petitioner's request that the 
SONGS units be shutdown due to inadequate protection against potential 
earthquake ground motion, the staff has concluded that the Petitioner 
has not presented a basis for such an action.

III. Conclusion

    On the basis of the above assessment, I have concluded that no 
substantial health and safety issues have been raised by the Petitioner 
that would require taking the action requested by the Petitioner. As 
explained above, the SONGS site has undergone extensive geologic, 
geophysical, geotechnical, and seismic investigations and reviews, 
including a recent analysis to quantify the seismic hazard and 
uncertainties for the SONGS site. Furthermore, SONGS was licensed 
consistent with the seismic and geologic siting criteria for nuclear 
power plants set forth in 10 CFR Part 100, Appendix A. The Petitioner 
has not provided any information in support of his concerns and 
requested actions, including information regarding recent earthquakes, 
which the NRC staff was not already aware. Accordingly, the 
Petitioner's requested action, pursuant to Section 2.206, is denied.
    A copy of this Decision will be filed with the Secretary of the 
Commission

[[Page 50639]]

for the Commission to review in accordance with 10 CFR 2.206(c) of the 
Commission's regulations. As provided by this regulation, the Decision 
will constitute the final action of the Commission 25 days after 
issuance, unless the Commission, on its own motion, institutes a review 
of the Decision within that time.

    Dated at Rockville, Maryland, this 19th day of September 1997.

    For The Nuclear Regulatory Commission.
Samuel J. Collins,
Director, Office of Nuclear Reactor Regulation.
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