ML13330A148
| ML13330A148 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/05/1980 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Dietch R Southern California Edison Co |
| References | |
| TASK-16, TASK-RR NUDOCS 8011210005 | |
| Download: ML13330A148 (11) | |
Text
DISTRIBUTION Docket File JRoe NRC PDR.
OELD Docket No.:
50-206 Local PDR OI&E (3)
ORB Reading GCwalina NRR Reading NSIC William T. Russell TERA Hazel -Smith ACRS (16)
Mr. R. Dietch, Vice President Nuclear Engineering and Operations SNowicki SEP File (2)
DEisenhut RDiggs Southern California Edison Company RPurple JWetmore 2244 Walnut Grove Avenue TNovak Post Office Box 800 Teovak Rosemead, California 91770 dGLainas
Dear Mr. Dietch:
JHeltemes, AEOD SUBJECT. SAN ONOFRE -
SEP TOPIC XVI, TECHNICAL SPECIFICATIONS The objective of SEP Topic XVI, "Technical Specifications" is to assure that safety limits and operational safety measures are specified in order to minimize the probability or consequences of accidents. In orderto assure that the implementation of-appropriate technical specifications will conform to the overall objective of the SEP program, we have decided to delay completion of SEP Topic XVI, Technical Specifications, until the completion of all other SEP Topic reviews and the Integrated Safety Assessment. This will allow for an integrated evaluation of current Technical Specifications with any proposed Technical Specification changes resulting from individual SEP topic reviews.
If you have any questions or comments toward this regard please inform the NRC in a timely manner.
Sincerely, ginal signed byl Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing cc:
See next page
- See previous yellow for additional concurrences.
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NOV 05 19804 DISTRIBUTION Do"ckt File JRoe NRC PDR OELD Local PDR OI&E (3)
Docket No.:
50-206 ORB Reading GCwalina NRR Reading NSIC William T. Russell TERA Hazel Smith ACRS (16)
TWambach SEP File (2)
Mr. R. Dietch, Vice President DEisenhut RDiggs Nuclear Engineering and Operations RPurple JWetmore Southern California Edison Company TNovak 2244 Walnut Grove Avenue RTedesco Post Office Box 800 GLainas Rosemead, California 91770 JHeltemes, AEOD
Dear Mr. Dietch:
SUBJECT:
SAN ONOFRE -
SEP TOPIC XVI, TECHNICAL SPECIFICATIONS The objective of SEP Topic XVI, "Technical Specifications" is to assure that safety limits and operational safety measures are specified in order to minimize the probability of accidents. In order to assure that the implementation of appropriate technical specifications will conform to the overall objective of the SEP program, we have decided to delay revision of your present Thchnical Specifications until the completion of all other SEP Topic reviews-an&the Integrated Safety Assessment. This will allow for an integrated evaluation of current Technical Specifications with any proposed Technical Specification changes resulting from individual SEP topic reviews.
If you have any questions or comments toward this regard please inform the NRC in a timely manner.
Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing cc:
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0 UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 NOV 0 5 1980 Docket No.:
50-206 Mr. R. Dietch, Vice President Nuclear Engineering and Operations Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Dietch:
SUBJECT. SAN ONOFRE - SEP TOPIC XVI, TECHNICAL SPECIFICATIONS The objective of SEP Topic XVI, "Technical Specifications" is to assure that safety limits and operational safety measures are specified in order to minimize the probability or consequences of accidents. In order to assure that the implementation of appropriate technical specifications will conform to the overall objective of the SEP program, we have decided to delay completion of SEP Topic XVI, Technical Specifications, until the completion of all other SEP Topic reviews and the Integrated Safety Assessment. This will allow for an integrated evaluation of current Technical Specifications with any proposed Technical Specification changes resulting from individual SEP topic reviews.
If you have any questions or comments toward this regard please inform the NRC'in a timely manner.
Sincerely, Dennis M. Crutchfield, hie Operating Reactors Br nch No. 5 Division of Licensing cc:
See next page
Mr. R. Dietch cc Charles R. Kocher, Assistant Director, Technical Assessment General Counsel Division Southern California Edison Company Office of Radiation Programs Post Office Box 800 (AW-459)
Rosemead, California 91770 U..S. Environmental Protection Agency David R. Pigott Crystal Mall #2 SSamuel B. Casey Arlington, Virginia 20460 Chickering & Gregory Three Embarcadero Center U. S. Environmental Protection Twenty-Third Floor Agency San Francisco, California 94111 Region IX Office ATTN: EIS COORDINATOR Jack E. Thomas 215 Freemont Street Harry B. Stoehr San Francisco, California 94111 San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector c/o U. S. NRC P. 0. Box AA Oceanside, California 92054 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego San Diego, California 92101 California Department of Health ATTN: Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814
NRC-SONGS Box NRCSONGS_0027 Accession 8012030379
Review of the Reports Dealing with the Simulation of Earthquake Ground Moticns for San Onofre Nuclear Generators Station Unit I for the Nuclear Regulatory Canissicn.
by D. L. Bernreuter, Leader Engineering Geosciences Group At the outset, I would like to reafirm my overall support for the general approach used by 'ERA-DETA in attempting to estimate the strong ground motion characteristics at the San Onofre site.
I believe that the approach is useful and sheds light on a number of important questions.
A number of negative comments follow.
These arise because TERRA-DELTA is attempting to solve a very difficult problem - a problem for which most (if not all) researchers agree that we do not yet even understand the basic physics of the earthquake rupture process much less know how to solve the problem.
TERA-DELTA has
- nttempted to overceme our lack of knowledge by use of a simplified fault re process and the introduction of randamness.
It is interesting to note a-zch of the "improved" models developed by TERA-DELTA that are of the major inprovements was the introduction of more 'randomness.
This seems counter-productive to the basic goal of a calculational effort.
In my view of
'the usefulness of a calculational effort lies in our ability to say that we it-derstand the basic physics of the problem, that our model incorporates in a reasonably correct way the basic important parameters and physics.
Then by bounding the various parameters we can calculate reasonable worst case results appropriate for -
in our case - the earthquake in the posulate offshores zone cf deformaticn at the San Onofre site.
I accept that there is considerable randomness in the earthquake faulting process.
Hcwever, the continued introduction of more and more randomness in place of understanding the physics of the problem is very troublesome -
thus I cannot agree that the model has been properly calibrated.
In fact one key problem that I have with TERA-DELTA's work is over the criteria they used to argue that they have adequately calibrated their model.
They argue that approximate equality of peak acceleration and "same match" to smoothed response spectra is more than adequate to show that their model cniservatively models the possible earthquakes at the San Onofre site.
I, on the other hand, feel that same match of the more important phases of the time series are necessary before we can argue that the model used is reasonable.
If, for example as I strongly feel is the case, the initial slip velocity behind the rupture front is highly variable rather than uniform as modeled by
'IENA-DELTA, then it is important to know where the energy which gives rise to tio peak ground moticn originates before one can use such a match to judge what values of slip velocity are reasonable.
This can only be done by matching the important features of time series.
The next report by Day, (Ref. 1.), shcws that the introduction of variaticns in tectonic stress along the fault has a very significant effect on 8O012o0 3 3
both rupture velocity and slip velocity. This report by Day also shows that (at least for one reasonable model) that the slip velocity is a function of the stress drop and introduces rapid changes in rupture and slip velocity.
These rapid changes in rupture and slip velocities could have significant effect on the time series of the ground acceleration and on the high frequency end of the response spectra.
In my past reports (References 2 and 3), I also indicated that in my view the major deficiency of the TERA-DELTA's reports is that they have not established conservative bounds for the key parameters of their model appropriate for the postulated SSE for the San Onofre site.
TERA-DELTA's studies show that the really iportant parameters of model that ontrol the higher frequency ground motion (; z) are:
- 1.
Vo = initial slip velocity (dynamic stress drop)
- 2.
Rupture velocity
- 3.
Both the micro-incoherence and the maro-randemness introduced
- 4.
Q values used
- 5.
Geologic structure Not included in the TERA-DEDTA study, but in my view of considerable importance, is the nonlinear behavior of the soils at the various sites used for calibration pirposes..
In my past reports I discussed why I felt that TERA-DELTA's-calibration of Vo was inadequate.
My views are still much the same as I do not feel that Supplements II and III address my prime concerns, which were with the modeling of Vo, Q and the randomness introduced into the model.
The study by Day (Ref 1) serves to underline these concerns and introduces a new concern which deals with low rupture velocity was modeled.
My understanding of the TERA-DELUA report is that the rupture velocity is always less than the shear wave velocity.
The time of rupture was randomly chosen, but is always slower than 0.90 (1= shear wave velocity).
The study by day and the work of DAS and Aki suggest that the rupture velocity can be larger than the shear wave velocity - in fact in Day's study it generally was larger.
In addition, we can expect randon variation in rupture time, but at least Day's study suggests that as the rupture grows the rupture velocity grows.
This potential correlation does not seem to be included in the TERA-DELTA model.
Of potential importance is the fact that the slip function studied is always a member of the same family of functions and very smooth except at the start and stopping of the rupture.
The slip velocities calculated by Day show additional character which could have significant influence on the high frequency content of the spectrum.
The,potential importance of such variations in the slip function seems to need study.
All of the randomness introduced by TERA-DEDIA may cover the ranges of variation in the slip function that might be postulated including different functional form of the slip function, but this is not at all evident frau the sensitivity studies presented.
In Supplements II and III TERA-DELTA attempted to provide added verification for their choice of Vo = 800 cm/se.
In Supplement II the Long Beach earthquake of 1933 and the San Fernando earthquake were modeled, and in Supplement III the recent Imperial Valley earthquake was modeled.
The first problem that I have with the Long Beach earthquake modeling is that the resultant time series is shorter than the recorded time series.
I comented on this point with regard to TERA-DELThAs modeling of the 1940 Imperial Valley record at El Centro.
This shortness could came fran the Q's used and or lack of complexity in the rupture model such as variations of Vo, starting and stopping of the rupture etc.
In addition, the modeling seems to give to high a peak acceleration.
It is hard, to make judgements about the modeling because of the late start of the instruments and lack of other studies to pin down some of the important parameters of the rupture process.
The San Fernando earthquake has received considerable study.
Many of the studies of this event suggest that the rupture process was highly variable with the most energetic part of the rupture occurring on the laser part of the-fault.
The only way to check to see if in fact the uniform modeling used by TERA-DELTA provides a calibration for Vo is to be able to determine if higher values of Vo should have been used on the lower fault and lower values on the upper fault under the recording site.- We also need to assess what impact this might have on the 'TRA-DELTJ model.
Haever, as we do not have the cnputed time series to compare with the recorded data it is very difficult to assess how reasonable the model is.
In addition, it is very hard to assess the correctness of the topographic amplification factor used.
The problem is once again related to a question of needing a comparison of where the energy is coming fran for both the model and the recorded data.
The Imperial Valley earthquake of 1979 provides a number of stations as well as stations with obsolete time which could be used to calibrate TERA-DELTA's model.
They have made little use of such data and once again use a uniform stress drop model with randon rupture velocity and other random parameters.
As I discussed in Ref. 4 the location of the center of energy release could be a number of kilameters fram the El Centro array.
Also as I pointed out in Ref. 4 there is some evidence that a major barrier could have existed several kilometers south of El Centro array.
The TERA-DELTA model would put the effective center of every release much closer to the El Centro array.
It seems to me that this can be resolved because we know when in time the energy arrived.
The initial wave shapes should also provide additional, insight into the correctness of any model.
I find it noteworthy to contrast the difference in duration between the records recorded on the El Centro array and by the Bonds Corner Station.
Also, the Mexican is much longer duration (like Bonds Corner) than that
recorded by the El Centro array.
This indicates to me the rupture process was very complex and nonunifoarm.
Once again this could only be resolved by comparison of wave shapes and arrival time (which for the first time are available).
One of the important questions that the TERA-DELTA reports attempts to address is the focusing of the seismic energy towards the site. Considerable randomness is introduced in the model bo reduce the focusing effects.
Day raises one interesting objectian.to the TERA-DELTA model on Page 30 of this report.
Also, the nonlinear behavior of the soil is of possible irportance when comparing calculated linear results to recorded results.
Without some assessment of the nonlinear effect and comparison of wave shape, type and arrival time I find it impossible to judge hw real and necessary both the micro and marco randamness used are.
In addition, the computed spectra for Imperial Valley seems to lack energy in the period range of 1 to 4 seconds.
These larger period waves seem to show upon the recorded accelerograms at.
a number of stations suggesting that there may be.large coherent--zones of rupture.
The potential implication of this is that there might be too much randanness in the TERA-DELTA model - or the scale (1 km) is too small for same zones of the fault.
Too bad TERA-DELTA didn't compute the ML fran recorded motion data to comipare to the MIs of their simulated earthquake.
The ML s of the simulated earthquake appear to be low suggestions that more 1 sec wave energy is needed.
The geologic structure and Q's are important parameters.
For example, Fig. 4-13 of May, 1978 shows a considerable variation (factor of 2 or more) in the cmputed spectra as a function of geologic structure for several different sites.
The importance of Q is hard to determine as to some extent the value of Vo was chosen relative to the Q model used.
But what isn't clear is how much the Q model might effect the spectrum for longer and larger fault rupture sequences.
If indeed Q is independent of frequency, then changes in-Qwould most likely be a second order effect relative to some of the other concerns discussed above.
On the other hand, Q is not independent of frequency but increases with frequency, then how Q is modeled could be important.
The sensitivity studies do not really address the role and importance of variations in Q.
In order to provide added caparisons TERA-DELTA used the data and a regression analysis to determine how the ground motion varies with distance.
In my view, the regression model given in Chapter 2 of Supplement III also appears to use a question of metrics, of distance from fault trace and yet was an attenuation of 1/CRF20)1.75 for horizontal accelerations and 1/CR+10) 1. 7 5 for vertical.
Such a model might suggest that the main source of energy is at same depth.
Very near the fault changes in distances of a few kilometers are very important.
To simply use the closest distance to the fault trace can introduce cchsiderable.confusion.
This is discussed in same detail by Shakal (Ref. 5).
In closing, I still feel that TERA-DELTA has not yet properly calibrated their model.
If the strong ground motion recorded at the various sites used for comparison and calibration was due to:
(1) high stress drop earthquakes (2) the region of large stress drop was very near the recording site as modeled (3) nonlinear behavior of the soil is of second order of importance (4) the scale of randanness used by TERADEDIA and the amount of randamness introduced to reduce focusing is appropriate then the results can play the role TERA-DELTA wasn't there to play.
On the other hand I feel that several of the earthquakes used were not high stress drop earthquakes or that the zone of high stress drop was at some distance fra the recording site.
I also suspect that the noninear behavior of the soiL is important.
In addition, I think that the manner in which randomness is introduced and its scale needs more careful calibration.
Overall I think that to acceptably calibrate their model, TIRA-DELTA must look at wave shapes and arrival times in order to address the above points.
If my analysis given in Ref. 4 (Table VII, which updates Table I of Ref.
2), is correct, then the May 1940 Imperial Valley event for the event nearest El Centro, Parkfield, the 1979 Imperial Valley and Coyote Lake earthquakes are low stress drop earthquakes.
I applied the same analysis to the 1933 earthquake and also found it to be a low stress drop event of the same order as the other earthquakes.
This only leaves San Fernando as a high stress drop event used to calibrate the model.
However, as discussed above there.is considerable questian about the way TERA-DELTA modeled San Fernando.
For these reasons I feel that we must consider the results of TERRA-DELTA's modeling to be mean values.
I would think that we could well expect a factor of 2 uncertainty at all frequencies including peak acceleration.
This factor of 2 would correspond to the one sigma level.
This is assuming that high dynamic stress drop earthquake is possible in the offshore zone of dezonation.
If only low dynamic stress drop event like Parkfield or Imperial Valley can occur then the Housner -spectra at 0.679 seems reasonable in light of TERA-DELTA's modeling.
b
-g REFERENCES
- 1.
Day, S. M., "Three-Dizensional Finite Difference Simulation of Fault
,Dynamics."
System, Science and Software Report SSS-R-80-4295.
- December, 1979.
- 2.
Bernreuter, D. L., "Review of Reports on Simulation of Ground Motions for the San Orofre Nuclear Generating Station - Unit I."
LLNL Letter Report to NRC, December 4, 1979.
- 3.
Bernreuter, D. L., "Cornments on the Report Simulation of Earthquake Ground Motion for San Onofre Nuclear Generating Station - Unit I."
LL Letter Report to NRC, September 7, 1978.
- 4.
Bernreuter, D. L., "Scaling and Estimation of Earthquake Ground motion as a Function of the Earthquake Source Parameters and Distance."
Draft Report to NRC,August 14, 1980.
- 5.
Shakal, A. "Analysis of Peak Ground at Near-Source Distance."
Draft Report to NRC, October, 1980.
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