ML16341F353
| ML16341F353 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/29/1989 |
| From: | Rood H Office of Nuclear Reactor Regulation |
| To: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| References | |
| TAC-55305, TAC-68049, NUDOCS 8910050113 | |
| Download: ML16341F353 (32) | |
Text
September 29, 1989 Docket Nos.
50-275 and 50-323 Mr. J.
D. Shiffer, Vice President Nuclear Power Generation c/o Nuclear Power Generation, Licensing Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco, California 94106
Dear Mr. Shiffer:
DISTRIBUTION
[QDD J GH NRC
& LPDRs GBagchi MVirgilio RPichumani JLee RRothman HRood LReiter EJordan BGrimes ACRS (10)
PDV Plant File OGC (for.info only)
SUBJECT:
TRANSMITTAL OF DOCUMENTS RELATING TO NRC STAFF REVIEW OF DIABLO CANYON LONG TERM SEISMIC PROGRAM (LTSP)
(TAC NOS.
55305 AND 68049)
Enclosed for your information and use are two reports by NRC staff consultants which relate to the NRC staff review of the Diablo Canyon Seismic Reevaluation Program.
The enclosed material is as follows:
2.
Letter report re: "Evaluation of Responses Provided to Comments on Final Report for Long Term Seismic Program for the Diablo Canyon Nuclear Power Plant," August 31, 1989, by Carl J. Costantino, Professor of Civil Engineering, City College of the City University of New York.,
Letter report re: "Further Comments and guestions on PG&E's Final Report of the Diablo Canyon Long Term Seismic Program,"
September 25, 1989, by A. S. Veletsos, Professor of Civil Engineer ing, Rice Univer si ty, Houston, Texas.
The comments and questions in the enclosed reports will be discussed at our Soil-Structure Interaction (SSI) meeting to be held on November 2/3, 1989 in San Francisco.
It is our goal to resolve all outstanding SSI issues at the meeting.
Therefore, we request that you be prepared to address all areas covered by the enclosed reports at that meeting.
Sincerely,
Enclosures:
as stated cc w/encl:
See next pa e
original signed by Harry Rood Harry Rood, Senior Project Manager Project Directorate V
Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation DRS /PD5 HRood 09/pg/89 DR G0/
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Docket Nos.
50-275 and 50-323 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 September 29, 1989 Mr. J.
D. Shiffer, Vice President Nuclear Power Generation c/o Nuclear Power Generation, Licensing Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco, California 94106
Dear Mr. Shiffer:
SUBJECT'RANSMITTAL OF DOCUMENTS RELATING TO NRC STAFF REVIEW OF DIABLO CANYON LONG TERN SEISMIC PROGRAM (LTSP)
(TAC NOS.
55305 AND 68049)
Enclosed for your information and use are two reports by NRC staff consultants which relate to the NRC staff review of the Diablo Canyon Seismic Reevaluation Program.
The enclosed material is as follows:
1.
Letter report re: "Evaluation of Responses Provided to Coments on Final Report for Long Term Seismic Program for the Diablo Canyon Nuclear Power Plant," August 31, 1989, by Carl J. Costantino, Professor of Civil Engineering, City College of the City University of New York.
2.
Letter report re: "Further Cooments and guestions on PG&E's Final Report of the Diablo Canyon Long Term Seismic Program,"
September 25, 1989, by A. S. Veletsos, Professor of Civi'i Engineering, Rice University, Houston, Texas.
The comments and questions in the enclosed reports will be discussed at our Soil-Structure Interaction (SSI) meeting to be held on November 2/3, 1989 in San Francisco.
It is our goal to resolve all outstanding SSI issues at the meeting.
Therefore, we request that you be prepared to address all areas covered by the enclosed reports at that meeting.
Sincerely,
Enclosures:
as stated cc w/encl:
See next page Harry Rood, Senior Project Manager Project Directorate V
Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
-ilk)'
Mr. J.
D. Shiffer Pacific Gas and Electric Company Diablo Canyon CC:
Richard F. Locke, Esq.
Pacific Gas 5 Electric Company Post Office Box 7442 San Francisco, California 94120 Ms. Sandra A. Silver 660 Granite Creek Road Santa Cruz, California 95065 Mr. Peter H. Kaufman Deputy Attorney General State of California 110 West A Street, Suite 700 San Diego, California 92101 Managing Editor The Count Tele ram Tribune 1
o nson venue P. 0.
Box 112 San Luis Obispo, California 93406 Ms. Nancy Culver 192 Luneta Street San Luis Obispo, California 93401 Regional Administrator, Region V
U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 Mr. John Hickman Senior Health Physicist Environmental Radioactive Mgmt. Unit Environmental Management Branch State Department of Health Services 714 P Street, Room 616 Sacramento, California 95814 NRC Resident Inspector Diablo Canyon Nuclear Power Plant c/o U.S. Nuclear Regulatory Commission P. 0.
Box 369 Avila Beach, California 93424 Y
Br uce Norton, Esq.
c/o Richard F. Locke, Esq.
Pacific Gas and Electric Company Post Office Box 7442 San Francisco, California 94120 Dr. R. B. Ferguson Sierra Club - Santa Lucia Chapter Rocky Canyon Star Route Creston, California 93432 Chairman San Luis Obispo County Board of Supervisors Room 270 County Government Center San Luis Obispo, California 93408 Michael M. Strumwasser, Esq.
Special Assistant Attorney General State of California Department of Justice 3580 Wilshire Boulevard, Room 800 Los Angeles, California 90010
ck
Mr. J.
D. Shiffer Pacific Gas and Electric Company Diablo Canyon Long Term Seismic Program CC:
Dr. Keiiti Aki Department of Geological Sciences University Park University of Southern California Los Angeles, California 90089-0741 Dr. Ralph J. Archuleta Department of Geological Sciences University of California Santa Barbara Santa Barbara, California 93106 Dr. Steven M. Day Department of Geological Science San Diego State University San Diego, California 92182 Dr. George Gazetas Dept. of Civil Engineering 212 Ketter Hall SUNY-Buffalo Buffalo, New Yor k 14260 Dr. Robert D. Brown, Jr.
U.S. Geological Survey Mail Stop 977 345 Middlefield Road Menlo Park, California 94025 Dr. David B. Slemmons Center for Neotectonic Studies MacKay School of Mines University of Nevada-Reno
- Reno, Nevada 89557-0047 Dr. Robert Fitzpatrick Building 130 Brookhaven National Laboratory
- Upton, New Yor k 11973 Dr. Jean Savy Mail'ode L-196 Lawrence Livermore National Laboratory P. 0.
Box 808 Livermore, California 94550 Dr. Anestis S. Veletsos 5211 Paisley Avenue
- Houston, Texas 77096 Dr.
Ken Campbell U.S. Geological Survey P.O.
Box 25046, Mail Stop 966 Denver Federal Center Denver, Colorado 80225 Dr. C. J. Costantino Building 129 Brookhaven National Laboratory
- Upton, New York 11973 Dr. M. K. Ravindra EQE 3150 Bristol Street, Suite 350 Costa Mesa, California 92626 Dr. Michael Bohn Sandia Lab. - Organization 6412 Post Office Box 5800 Albuquerque, New Mexico 87185 Dr. J. Johnson EQE 595 Market Street - 18th Floor San Francisco, California 94105
ENCLOSURE 1
DEPARTMENT OF CIVIL ENGINEERING CITY COLLEGE OF THE CITY UNIVERSITY OF NEV YORK New York, New York 10031 212-690-8145 31 August 1989 Dr. Morris Reich Head, Structural Analysis Division Department of Nuclear Energy Brookhaven National Laboratory
- Upton, Long Island, New York 11973 Re:
Evaluation of Responses Provided to Comments on Final Report for Long Term Seismic Program for the Diablo Canyon Nuclear Power Plant
Dear Dr. Reich:
This letter re ort p
presents a
summary of my evaluation of the responses provided b the DCLTS na Report issued y
SP Project 'Team to my comments to the Final by PG&E in 1988.
M comme y
omments at that time were restri t d 1
c e on y to those items of'he Final Report with which our c
our panel had been associated, although the SSI program obviously has been impacted b and im e
y an mpacts other aspects of the program.
My comments on the PG & E res onses an sponses and other aspects of the Final Report with which I am interested follow.
1.
In the discussions of Chapter 5 which are associated with the descriptions and usages of the CLASSI/SASSI computer programs, the DC Project Team did not quantify the adequacy of the SSI calculations in the Final Report.
Based on the results of the audit of J o
une 87, they were asked to provide a detailed re or p t on their computational program t b
d o
e ma e a part of the Final Re ort fo p
r both comparison problems as well f
h as or those used for the DC site specific calculations.
Th 1
ese atter results were to be
presented so as to clearly specify the limitations of the numerical results based on the computational limitations of the computer codes.
The Pro)ect Team has now provided four volumes describing their calculational program to justify the adequacy of these computer programs for this evaluation.
These reports are in general complete and detailed enough to allow me to judge the applicability of the approach for the DCLTSP.
As I stated in previous reports to you, I feel that the Project Team did an outstanding job of justifying the application.
- However, some apparent confusion still remains with the response provided to Question 21.
At the time of our review of the CLASSI/SASSI evaluations, we requested that the Team clearly provide us with indications of the frequency ranges over which the calculations are applicable, that is, the frequency cutoffs above which the SSI calculations are inadequate.
- Instead, the response provided listed the criteria used in the specific computations of Green's functions, impedances, discretization, etc., for each computer code used for both the comparison problems as well as the site specific calculations summarized ia the reports. If the numerical results indicate that the SSI calculations are adequate up, to a frequency of 33 hz (as indicated by the various spectra presented in the Final Report),
they should so indicate this and show how the comparison problems support this conclusion.
If the SSI calculations are not adequate to this frequency
- range, the figures should clearly indicate the frequency cutoffs for each problem.
2.
The issue of potential lift-offeffects and its impact on SSI predictions for the DCNPP was brought up at the licensing hearings for Unit I and was questioned at the SSI workshop held in November 1987 and in my review of the Final Report.
The Project Team performed calculations for the SSI response of the Reactor Building, using three of the original suite of empirical records unmodified for site specific effects.
They found in these calculations that lift-offeffects were negligible, provided that lateral sidewall stiffnesses (which were found to be important) were not seriously degraded.
Their analyses, described at several workshops, made use of several assumptions with.which I was concerned and which were not adequately
described in the Final Report.
These items can be summarized in the following issues:
a.
The impact of the potential loss of sidewall support due to compaction of the surrounding backfill during the predicted rocking motions of the Reactor Containment Building was addressed in the Final Report by comparing results obtained for the original problem and one in which sidewall springs were reduced to half their value.
Justification of the adequacy of this approach was requested.
It is my opinion that the response provided to Question 25 is a reasonable engineering approach to evaluating the potential impact of loss of sidewall support on the computed seismic response of the Reactor Containment Building.
The results indicate that even assuming full tension cutoff on 'one side throughout the rocking motion leads to only a small change in spectra, while not severely overstressing the foundation bedrock through excessive bearing pressure.
Since this conclusion is relatively important to the SSI evaluation, I
would recommend that these calculations be audited at our next meeting for completeness of our review.
b.
The effects of slap-down following any separation of the base slab from the soil, which results in coupling between vertical and horizontal motions through the mechanism of modified interaction
- damping, was shown in an earlier presentation by the Project Team to cause a
frequency shift in the SSI response.
In my original review of the uplift documentation provided to us by the Project Team, it was my impression that this effect was not accounted for in the calculations presented at that time.
The response to Question 26 indicates that this effect was included in all cases.
If this is the
- case, I
recommend that the documentation of the uplift calculations be modified to clearly incorporate this point.
For the study of the hazards associated with higher spectral accelerations required for the hazards assessment
- study, the Project
Team states that lift-offeffects at the higher acceleration levels will not be significant.
I have no way of assessing this judgment, since I did not perform any of the lift-offcalculations.
However, I do not think that such a judgment can be easily made without some support applicable to the Diablo Canyon Reactor Containment Building.
The Project Team indicates in the response to Question 27 that in the six sets of uplift calculations
- made, the effects of small pertur-bations in the time phasing between horizontal and vertical input motions on potential lift-offeffects and equipment support point spectra were'ncluded.
This may be so, but some support for this conclusion should be provided.
In particular, the response should indicate what the perturbations were for the six sets of calculations.
d.
The three suites of input seismic motions used for the lift-off calculations were different from those site specific inputs defined and used for.t'e remainder of the SSI study. It was requested that the specific differences should be included in the Final Report, with reasons for the differences discussed and evaluated.
The response to Question 27 on this point does not appear to me to be appropriate.
In addition to these comments on specific responses, several concerns remain which I feel have not been adequately responded to by the Project Team.
I list these in the following paragraphs in no particular order of importance.
More detail on some of these may be found in my previous correspondence to you.
a.
The Final Report presents an evaluation of the deterministic seismic margins of the plant by comparison of the HCLPF capacities for various structures and equipment with the 50%
and 848 probability of non-exceedance spectral accelerations.
Although the report continually states I
that the HCLPF capacity estimates contain large conservatisms, much of these estimates are subjective and difficult to assess.
For example, it is stated on page 6-17 that margins between the onset of significant
strength degradation and total collapse are large.
Such an assessment is difficult to support, for example, for many reinforced concrete type structures or subsystems.
Special mention is made for shear walls, but no other assessment is presented to support this general statement.
Of more importance, the Final Report does not make an attempt to relate the new deterministic response calculations to the results from any deterministic calculations made during the Hosgri reevaluation, and with which some difficulties were found in the design.
Examples such as the capacities of the pipeway structure, several block walls in the Turbine Building, the turbine pedestal in the Turbine Building, the bolted connections in the Turbine Building, and the buried diesel fuel tanks come to mind.
The 84% site specific spectra for the Turbine Building, for example, is shown to be significantly higher than that used in the Hosgri reevaluation, and one would normally conclude that those difficultproblem areas would be made worse.
Thus, although the seismic margins assessment presented in the Final Report states that adequate margins exist in the
- plant, such conclusions are difficult to accept without such specific comparisons.
b.
On pages 4-48 and 4-51 of the Final Report, it is stated that discre-pancies in energy content of the numerically generated ground motions noted at the low frequency range (below 3 hz) are unimportant. Yet, at one of the workshops, results were presented for the nonlinear analyses conducted for the Turbine Building indicating frequency shifts due to nonlinear effects down to near 1 hz.
Since the Turbine. Building is the structure with the lowest safety margin, the sensitivity of the results on safety margins to these low frequency spectral accelerations is unclear.
c.
On page 4-30, it is stated that topographic effects at the DC site were shown by finite difference calculations to be insignificant.
I did not see any of these results at any of the Ground Motion panel discussions that I attended, although I understand that such information was presented
C'
at the last panel meeting. If such results are available, they should be specifically included in the responses.
In addition, if the specific weighing factors listed in Table 4-4 were chosen to remove topographic influences, as I understood from one of the recent meetings, it seems that these effects should be specifically reintroduced to determine the site specific spectra applicable to DC site.
d.
The Final Report indicates that site specific response spectra for both horizontal and vertical motions, generated from the regression studies of
- Sadigh, were used as input data to the SSI analyses.
As I recall, no vertical input motions were used in the deterministic SSI studies, except for the lift-offevaluations.
In this case, actual vertical records were used which were not scaled to achieve the site-specific spectral content described in the Final Report.
The record sets sent to the SSI panel did not contain any vertical components, and we were told that a single site specific spectra (no time history) was used in any SSI evaluation.
The responses should be clarified in this respect.
Finally, the major concern in the plant evaluation must reside in the questions associated with the development of the site-specific spectra used as input to the SSI and fragility studies.
These were raised in the past by several people and clearly presented by Professor Veletsos in his recent report.
Clearly, the margins assessment is directly related to the spectral acceleration levels assumed in the mid-frequency range of interest.
Questions associated with weighing factors, sensitivity of the target spectra to weighting factors, sensitivity of the target spectra to change in earthquake magnitude, topographic effects, etc.,
should all be addressed to provide as clear a description of the procedures used to arrive at the overall margins assessment as possible.
Obviously, many of these questions must be addressed by the Ground Motion Panel members.
As a comment separate from the specific evaluation of the Diablo Canyon plant, it should be noted that the SSI procedures presented in the Final Report do not address one particular issue which was mentioned in the recent
A-40 discussions, and that has to do with the requirement imposed on new licensing applications to limit the reductions in foundation input motions due to depth of burial effects.
Any potential impact of omission of this factor from the DC evaluation on future procedures to be followed by NRC should be evaluated.
It would be instructive to know what the depth of embedment reductions are for the DC structures.
I think this data is available from the SSI site specific evaluations and can be easily determined.
Respectfully submitted, Carl J.
C tantino Professor of Civil Engineering
~ SEP 26 '89 15:26 ENCLOSURE 2
P. 3/7 A. S. VELETSOS SSOR
~ DEPhRTMENT OF CIVILENOINEERINO BRO%'N &. ROOT FROFE RICE UNIVERSITY
~ HOUSTON, TEXhS 77001
~ (713) 527.8IOI, KXT. 2388 CONSULTANT
~ 5211 PAISLEY ~ HOUSTON, TEXAS 77096
~ (713) 729-4348 September 25, 1989 Dr, Horrfs Reich, Head Structura1 Analgsfs Division Brookhaven National Laboratory Department of Nuclear Energy Bufldfng 129
- Upton, Long Island, New York 11973 Re: Further Comments and guestfons on PGSF's Final Report of the Diablo Canyon Long Term Seismic Program
Dear Norris:
The following comments pertain to Chapter 7 of the above-referenced report (Ref. 1), and are complementary to those made fn my report to you of November 4,
1988 (Ref. 2).
They are presented fn order of more or less decreasing importance, with the general comments grouped separately from the specific.
6eneral Comnents
). The site-spec1ffc response spectra for the basemat and floor'seudo-accel-erat1ons p~esented fn Figs.
7-6 through 7 39 of the Final Report correspond to the free-field response spectra displayed fn Ffg, 7-2.
Several questfons have been raised fn Refs, 2.
3 and 4 regardfng the appropriateness of the latter spectra and the associated ground motions, and the same questions also apply to the material of Chapter 7.
It was basically suggested that these ground motions and response spectra may underestimate the severity of the most intense ground shak1ng that may occur at the plant site, I should stress, however, that as of this wr1t-fng, I have had no opportunity to review PGSF's recent answers to the questions posed by NRC following the March 1-3, 1989 meetfng ef the Ground Notion Panel fn San Francisco.
SEP 26 '89 15:26 P.4i7
- 2. Mhfle I do not pretend to know what precisely is the required scope of the deterministic, studies of plant responses, and wh1le I recognize that the evaluation of the sefsmfc margfns for the structures and equipment is beyond the scope of my responsibilities, I feel that.ft would not be in-appropriate for me to observe that the study reported in Chapter 7 fs not as comprehensive and conclusive as I would have expected 1t to be.
~ A I would have thought that this phase of the Long Term Seismic Program would have:
- a. Identified. the "weak 11nks" of the structures and equipment as deter-mined in the original design; b.
Compared the load demands for these links as determined in the site-specific, recent studies with those established in the original design; and
- c. Evaluated fn deterministic terms the design implications of the result-ing differences.
Alternatively, I, would have expected to be shown that the site-specific des1gn spectra for all structures and crft1cal equfpment items determfned in the latest study are, for all frequencies of interest, lower than the corresponding spectra used in the original design.
This has
- not, of
- course, been demonstrated.
As used 1n Chapter 7 of the Final Report, the terms "determin1stfc evalua-tion" and "determinfstic seismic margfn 'assessment" 1mpress me as being mfsnomers.
The evaluatfons of seismic capacities presented are high-con-fidence-of-low-probabflfty-of-failure (HCLPF) estimates based on probabi-lfstfc risk assessmant, fragility consideratfons.
Specfffc Cewents and guestfons
- 1. In the comparisons of basemat response spectra presented fn Figs.
7-20 through 7-29, are the Hosgrf evaluation spectra the same as the "qualifi-cation basis" spectra referred to on p. 7-1 of the Report?
If not, are they higher or lower than the latter spectra?
SEP 26 '8'9 15:27 P.Sr7 2 ~ In the discussion of the fnterrelatfonshfp of the two sets of spectra on p.
7-23 of the Final Report, ft fs observed that the 84th percentile site-specific response spectra exceed the Hosgri evaluation spectra at certain frequencfes, but that "the average values pf the exceedances" range only "from about 5 percent for the containment building interior structure to about 10 percent for the auxiliary building". It fs further observed that "these exceedances are not sfgnfffcant as they can be accom-modated by the existing design margin".
It f s notewor thy that the exceedances for the contafnment buildf ng exterior structure are substantially higher, partfcularly ff provision is made for the uncertainties involved in the computation of its fundamental natural frequency.
More importantly though, tHe exceedances for the auxi-liary structure reach values of the order of 33K't selected frequencies within the frequency range of interest.
Are these larger exceedances also fnsfgnfffcant for all parts of the structures, fncludfng their weakest 1fnks7 The exceedances bf the 84 percentile site-specific response spectra over the Hosgri evaluation spectrum for the turbine building are, of course, significantly higher, The effect of these exceedances appears to have been evaluated only in probabilfstfc terms.
- 3. Although not specifically stated, the equipment damping for the floor re-sponse spectra presented fn Figs.
7-30 through 7-38 of the Final Report appears to be 5 percent of critical damping.
Is this dampfng value appro-priate for all equipment items fnvolvedf 4,
The peak values of the sefsmfc qualification basfs floor response spectra
. fn Figs.
7-30 and 7-31 are approximately twice as large as those for the 84 percentile site-specific spectra, Do both sets of spectra, refer to the same amount of damping, and ff so what fs the source of this dffference7 Despite the fact that the 84 percentile site-speciffc basemat response spectrum for the turbine building fn Ffg.
7-29 fs substantially higher than that for the Hosgri evaluation
- spectrum, the opposite fs true of the
'orresponding'loor response spectra displayed in Ffg. 7-39, Again, what
k
SEP 26 '89 1S:27
(
4
'I P.6's the reason-for this difference?
Are both sets of spectra for the same structural and equipment damping values?
If not, why not?
6.
An explanation is requested of precisely what is meant by the term peak-and-valley variability of response spectra referred to on p, 7-46 of the Final
- Report, If this term refers to the peak-to-valley spread of the spectral ordinates obtained.for different possible ground motions at the plant site, normalized with respect to their means, then the 20 percent value impresses me as being small.
The same coment was made in my reports to you given as Refs.
3 and 5.
I have also reviewed PG&E's answers to the questions posed by others regard-ing Chapter 5 of the Final Report on soil-structure interaction issues, but have no questions or comments to make in this regard.
Sincerely yours, A. S. Yeletsos
I
SEP 26 '89 15:28 P.7/7 REFERENCES I. Pacific Gas 5 Electric
- Company, "Final Report of the Diablo Canyon Long Term Seismic Program," Docket Nos.
50-275 and 50-323,,July, 1988 V
(
2, Veletsos, A. S,,
"Comments on PGSE's Final Report on Long Term Seismic Program for Diablo Canyon./lant,"
Letter Report to Dr.
M.
Reich of Brookhaven National. Laboratory, Long Island, New York, November 4, 1988
- 3. Yeletsos, A.. S.,
- Tang, Y.,
and
- Prasad, A. N.,
"Studies of Earthquake Ground Notiorts and Soil-Structure Interaction for Diablo Canyon Nuclear Power Plant,"
Report to Brookhaven National Laboratory, Long Island>
New York, December 10, 1988
- 4. Yeletsos, A.
S.,
"March 1-3, 1989 Meeting of Ground Motion Panel for Diablo Canyon Long Term Seismic Studies,"
Letter Report to Or.
M. Reich of Brookhaven National Laboratory, Long Island, New York, May 9, 1989
- 5. Veletsos, A. S.,
"Long Term Seismic Program for Diablo Canyon Nuclear Power Plant," Letter Report to Dr.
M. Reich of Brookhaven National Labora-tory, Long Island, New York, June 22, 1988
I I
t