ML17083B376
| ML17083B376 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/07/1984 |
| From: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| To: | Knighton G Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML16341C157 | List: |
| References | |
| NUDOCS 8405180168 | |
| Download: ML17083B376 (48) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 NAY 0 V 1984 MEMORANDUM FOR:
George Knighton, Chief Licensing Branch No.
3 Division of Licensing FROM:
SUBJEC):
Robert E. Jackson, Chief Geosciences Branch Division of Engineeri'ng STATUS OF DRAFT ELEMENTS FOR THE DIABLO CANYON LICENSE CONDITION Attached are the staff's draft elements for the Diablo Canyon License Condition.
Also attached are draft explanations for each of the elements and a draft of the staff parallel effort.
These drafts will be used by the staff in discussions with PGSE at the meeting on May 8, 1984.
Attachment:
As stated cc:
w/attachment J. Knight R. Jackson L. Reiter S.
Brocoum R.
Rothman R. McMullen D. Gupta H. PoIk G. Lear P. T.
Kuo L
Chandi er A. Thadani Robert E. Jackson, ref Geosciences Branch Divisi of Er(gineering
Ii
Diablo Canyon Nuclear Plant License Conditions PG&E shall develop and implement a State-of-the-Art Program to revalidate the seismic design bases used for Diablo Canyon.
PGIIE shall submit for NRC staff review and approval the proposed Program Plan and proposed schedule for implementation by January 30, 1985.
The program shall be completed and final report submitted to the NRC by July 1, 1988.*
The program shall consist, at a minimum, of the following proposed conditions:
(1)
The applicant shall identify, examine, and evaluate all relevant geologic and seismic data, information, and interpretations that have become available since the 1979 ASLB hearing, including but not limited to the following:
(a) data collected as a result of research by government agencies and others, and as a result of extensive oil exploration off the coast and onshore in central California since 1978, including seismic reflection data, geological
- mapping, and exploratory well boring logs; (b) reprocessed, pre-1979 seismic reflection data obtained by PGSE during licensing activities, and by the USGS during research activities.
These data will be selected in critical areas based on the results of (a),
and reprocessed using modern techniques.
- The Commission approved this paragraph on March 27, 1984, and made it a.
condition of the Low Power License on April 13, 1984
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The final results of these efforts will be used as input to Condition (2).
(2)
PG&E shall reevaluate the magnitude of the safe shutdown earthquake.
This element shall include reevaluation of the maximum earthquake for the Hosgri fault and also evaluation of the max'imum earthquake on any other capable fault in the site region which might be considered as controlling for the ground motion.
The parameters to be considered in this reevaluation are:
(a) Fault length to estimate magnitude (b) Rupture length to estimate magnitude (c) Slip rate to estimate magnitude (d) Maximum displacement from a single event to estimate. magnitude (e) Historical seismicity (f) Other approaches, such as total area of fault to estimate magnitude.
(3)
PGEE shall revalidate the ground motion at the site based on the magnitude of the safe shutdown earthquake.
A.
(a) Perform regression analysis of spectral values to get estimates of both horizontal and vertical spectra for Diablo Canyon (DCNPP) site specific conditions.
(b) Estimate site specific horizontal and vertical spectra.
(c) Perform. earthquake numerical modeling study using the most recent techniques calibrated to a suite of nearfield data.
(d) Consider and evaluate the relevant soil-structure interaction effects such as, but not limited to, embedment and foundation averaging.
Both analytical and empirical techniques may be appropriate.
All of the above will take into account the site specific conditions valid for DCNPP such as: distance to the fault, focal mechanism, attenuation and site geology.
(4)
PG8E shall assess the significance of conclusions drawn from seismic reevaluation and revalidation studies in item 1, 2 and 3, utilizing the following two elements:
(a)
PGSE shall perform an up-to-date realistic seismic probabilistic risk assessment (PRA) assuming the seismic capacity of the plant as it is actually constructed.
The PRA shall adequately represent the uncertainty involved and include estimates of core-melt and consequences to the public of different ground motion levels up to and beyond the existing seismic, design basis.
(b) If the results or the scope of the PRA indicate the need, PGSE shall also make deterministic estimates of seismic capability of selected structures, systems or components to better estimate existing seismic margins.
PGKE shall keep the staff informed on the progress of the revalidation program by quarterly progress reports and by semi-annual meetings in Bethesda.
The applicant will also present annual progress reports to the ACRS subcommittee on Diablo Canyon.
EXPLANATION OF EACH LICENSE CONDITION FOR DIABLO CANYON LICENSE CONDITION I:
UPDATE AND REPROCESS DATA This condition is necessary:
(a)
To reexamine the characteristics at depth of the Hosgri fault zone and other fault zones in the vicinity to determine whether or not they are vertical faults as assumed in the past, or low angle thrust faults.
If the latter is true it is necessary to know the approximate depth the faults may be beneath the site.
This information is needed to calculate earthquake ground motions at the site.
(b)
To confirm the overall length of the Hosgri zone, and, if possible, the lengths of segments that have ruptured during a single earthquake.
This information is needed to determine the maximum earthquake the Hosgri is capable of generating; (c)
To determine the effects of the Hosgri fault zone and other faults in the site area on the strata in the shallow subsurface such as, seafloor offset and their relation to folding in the shallow sediments.
These data are important in calculating the recurrence intervals of large earthquakes used in seismic risk assessment; (d)
To confirm that there are no thrust splays of the Hosgri fault zone or other faults, nearer to the site, that have not been detected.
LICENSE CONDITION 2:
REEVALUATION OF THE SAFE SHUTDOWN EARTH(UAKE I
I The safe shutdown earthquake for Diablo Canyon is based on the assumption of the occurrence of a magnitude (N ) 7.5 earthquake on the Hosgri fault 5 km from the plant.
The magnitude of the assumed earthquake was estimated from an interpretation of the tectonics of coastal California and the relation of the Hosgri to this regime.
A key element of this estimation was the assumption that the 1927 Lompoc earthquake (H
7.3) occurred on the Hosgri.
This assumption was made because the error bounds of the epicentral location of this earthquake are so large that the Hosgri could not be eliminated as a possible source.
Another important assumption in the magnitude estimation for the safe shutdown earthquake was that the Hosgri is a continuous system of anastomosing faults stretching from the Transverse Range faults to the San Simeon and San Gregorio faults.
Since the completion of the Hosgri reanalysis and the Diablo Canyon ASLB hearings more information has become available as to the geology and tectonics of coastal California.
This new data and interpretations may have relevance to the magnitude estimation for the Diablo Canyon safe shutdown earthquake.
In addition, the techniques for estimating the possible magnitude of earthquakes from the geologic record have become better understood and more acceptable.
These techniques include the estimation of the maximum earthquake magnitude on a fault from the length of the fault, the length of rupture during a single earthquake, the slip rate of the fault, the maximum displacement from a single earthquake, and the area of the rupture surface during an earthqdake.
LICENSE CONDITION 3:
REVALIDIATIONOF THE VIBRATORY GROUND NOTION BASED ON THE MAGNITUDE OF THE CONTROLLING EARTHQUAKE At the time of the Hosgri reanalysis for Diablo Canyon there was very little strong ground motion data which had been recorded in the near field of large earthquakes.
Because of this, the spectrum used by Dr.
Newmark for estimating the ground motion was based primarily on the strong ground motion of the 1971 San Fernando Valley earthquake recorded at Pocoima Dam.
This record had the highest peak horizontal ground acceleration recorded to that time.
Since then there have been a number of near field recordings made from large earthquakes.
This enhanced data base has been used to derive predictive equations for vibratory ground motion as a function of earthquake size, distance from source, and site conditions such as geology, and fault type.
This data base has also been used to calibrate theoretical numerical modeling studies as a
means of improving their reliability.
Using the recent data and newly derived predictive methods more certain estimates of ground motion may be made.
In the Hosgri analysis the staff, on the recommendation of Dr. Newmark, allowed for reduction of the ground motion for larger structures based on the "tau effect" (foundation averaging).
This has been subject to controversy.
The "tau effect" is one of several effects, due to the presence of large embedded structures, that may act to modify the level of earthquake motion actually experienced in nuclear plant structures.
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These effects, their interactions and implications may be estimated utilizing sophisticated analytical and empirical techniques.
LICENSE CONDITION 4:
ASSESSMENT OF SIGNIFICANCE OF CONCLUSIONS FROM ESTIMATION STUDIES The purpose of this condition is to assess the significance of differences, if any, between the existing seismic design basis and that inferred from the new information presented in the previous tasks.
Since PRA allows us to associate risk with different levels of ground motion, it can put into context the impact of changing geological, seismological and analytical assumptions.
It also serves as a screening device to identify so-called weak links where focussed attention may bring about significant improvement in calculated risk. If necessary, limited deterministic analysis may be called upon to better define seismic margins in specific selected areas.
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PARALLEL STAFF EFFORTS
'I'IITH REGARD TO THE DIABLO CANYON PLANT LICENSE CONDITION tiost of the technical work will be provided by PGSE for staff review.
Technical assistance and limited independent analysis will be utilized as needed for the review.
Examples of staff and staff consultant efforts are listed below:
'1)
Review and perform some independent analysis of the evaluation of geologic and seismologic data, information and interpretation provided by the applicant and some data we may acquire independently.
The staff will be aided by its advisor, the USGS and its consultant Dr. David B. Slemmons.
Such new data may include seismic reflection profiles which may be available from the oil
- industry, new exploratory (for oil and gas) well data, publications in geology, tectonics, and seismology about the central California Coast.
(2) 'The staff will make independent assessments of and review the applicants revalidation of the magnitude of the safe shutdown earthquake.
The staff will be assisted, as necessary, by the U.S.G.S.
and Dr. David B. Slemmons.
(3)
The staff will review with the assistance, as necessary, of our
- advisors, the U.S.G.S
, the National Laboratories, and others, the Applicant's ground motion estimates and soil-structure interaction studies.
Utilizing recent USGS and other studies, the staff will make independent estimates in selected areas of groundmotion.
(4)
The staff,, with the assistance of the USGS and National Laboratories, will review the PRA.
(5)
The staff, through a National Laboratory, will set up advisory review panels to advise the staff on technical issues on the seismic revalidation.
r DIABLO CANYON OPERATING LICENSE CONDITIONS IN GEOLOGY SEISNOLOGY AND SEISYiI C DESIGN I
INTRODUCTION AND BACKGROUND I I SIGNIFICANCE OF NEM INFORNATION III CONNISSION APPROVAL (IN GENERAL)
OF CONDITIONS IV LICENSE SEISNIC CONDITIONS V
DESCRIPTION OF PARALLEL. STAFF REPORT VI REPORTING PROGRESS AND SCHEDULING
I.
INTRODUCTION 8 BACKGROUND A,
OBLIGATION OF NRC 8 UTILITIES TO KEEP UP MITH SCIENCE AND UPDATE ANALYSES B,
EXTENSIVE INVESTIGATIONS CONDUCTED OFFSHORE BY THE OII INDUSTRY SINCE 1978, C.
ACRS 14 JULY 1978 LETTER RECOMMENDING SEISMIC DESIGN REEVALUATION IN 10 YEARS D,
1983 - COMMISSIONERS QUESTIONED TAU EFFECT THOUGHT PROCESS E,
EARLY 1984 FEBRUARY DE l'lANAGEMENT, IN ANTICIPATION OF THE NEED TO TAKE SOME KIND OF ACTION ON THE ABOVE ACTIVITIES, REQUESTED GSB TO RECOMMEND TASKS TO UPDATE AND REASSESS THE SEISMIC DESIGN OF DIABLO CANYON
F.
INITIAL CONDITIONS TO THE OL FOR THE SEISNIC PgP~ yg REEVALUATION OF THE PLANT MERE DEVELOPED G.
CROUCH ET AL PAPER (NOTIFIED BY PGRE ON 22 MARCH 84)
INTERPRETS COASTAL FAULTS AS BEING PREDOMINANTLY THRUST-NOT STRIKE-SLIP 1,
NEM DATA HIGH RESOLUTION SEISM, REFLECT.
2, BETTER DATA 3,
BETTER REPROCESS ING TECHNIQUES 4.
SUPPORTED BY DRILLING DATA 5,
SUPPORTED BY FOCAL SOLUTIONS OF EARTHQUAKES
0 II, SIGNIFICANCE OF NEW FINDINGS P
A.
DATA SUGGEST LOW EARTHQUAKE RECURRENCE INTERVAL B
NO SEA FLOOR (RECENT)
OFFSET C,
FAULT FlATTENING AND LOCATION TO EAST COULD BE CLOSER TO SITE (BENEATH) THAN 5,8 KM PREV, ASSUMED D,
CHARACTER OF GROUND MOTION MAY BE DIFFERENT (THRUST VS, STRIKE-SLIP - HIGHER OR LOWER OR NO DIFFERENT)
III.
IN APRIL 1984i THE COMMISSION VOTED IN FAVOR OF PLACING SEISMIC CONDITIONS TO OPERATING LICENSE NRR TO DEVELOP THE SPECIFICS
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IV, LICENSE SEISMIC CONDITIONS A,
PROCEDURE 1,
PGaE A
PREPARE PROPOSED PROGRAM 8 SUBMIT TO NRC B,
TAKE LEAD IN CARRYING OUT PROGRAM 2.
NRC STAFF AND ADVISORS (NAT'I
- LABS, USGS 8
DR, SLEMMONS)
A, REVIEW 8 APPROVE OF PG8E PROGRAM B
REVIBl RESULTS OF PROGRAM c,
PERFORM AN INDEPENDENT PROGRAH
B, CONDITION 1 - UPDATE GEOLOGY 8 SEISf'10LOGY 1.
REQUIRENENTS A,
EVALUATE POST-1979 ASLB HEARING INFORNATION B
REEVALUATE SELECTED PRE-1979 DATA THAT NAY BE NEEDED TO FILL IN GAPS IN THE NEW DATA'SING NEW REPROCESS ING TECHNIQUES 2,
PURPOSES AD CONFIRN CHARACTER OF HOSGRI AT DEPTH B
CONFIRN OVERALL LENGTH OF HOSGRI IN LIGHT OF THRUSTING HYPOTHESIS c,. CONFIRN RECENCY OF LAST NOYENENT 8, DETERNINE RECURRENCE D.
CONFIRN THAT THERE ARE NO SIGNIFICANT THRUST SPLAYS CLOSER TO SITE
C.
CONDITION 2 REEVALUATE THE SSE
.1, REQUIREMENTS MAGNITUDE OF SSE A
FAULT LENGTH B
RUPTURE LENGTH c.
SLIP RATE D
MAXIMUM DISPLACEMENT FROM SINGLE EVENT E
HISTORICAL SEISMICITY F
OTHER APPROACHES SUCH AS AREA OF FAULT PLANE TO ESTIMATE MAGNITUDE 2
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REASONS A
NEW DATA ON GEOLOGY AND TECTONICS OF COASTAL CALIFORNIA THAT MUST BE. TAKEN INTO ACCOUNT B,
NEW TECHNIQUES FOR ES1 IMATING MAGNITUDE FROM GEOLOGICAL RECORD (1)
LENGTH OF FAULT (2)
LENGTH OF.RUPTURE DURING SINGLE EARTHQUAKE (5) SLIP RATE (0)
MAXIMUM DISPLACEMENT FROM SINGLE EARTHQUAKE (5)
AREA OF RUPTURE SURFACE DURING EARTHQUAKE
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D, CONDITION 3 - REVALIDATE GROUND MOTION AT THE SITE 1,
REQUIREMENTS A,
REGRESSION ANALYSIS HORIZ, 8 VERT, SPECTRAL VALUES FOR SITE SPECIFIC CONDITIONS B, SITE SPECIFIC SPECTRA (VERT, R HORIZ. )
c.
EARTHQUAKE NUMERICAL MODELLING STUDY.USING MODERN TECHNIQUES D,
SOIL-STRUCTURE INTERACTION EFFECTS 2,
REASONS A,
MORE RECENT NEAR-FIELD RECORDINGS THAT SHOULD BE TAKEN INTO ACCOUNT B
MODELLING STUDY ALl OWS FOR SENSITIVITY STUDY C,
SOIL-STRUCTURE INTERACTION ANALYSIS TO EVALUATE THE EFI-ECT OF STRUCTURES ON THE GROUND MOTION
E, CONDITION 4 ASSESS THE SIGNIFICANCE OF THE RESULTS OF CONDITIONS 1, 2
a 3 WITH RESPECT TO DESIGN R
CONSTRUCTION 1.
REQUIREMENTS A, SEISMIC PRA B,
IF NECESSARY DETERMINISTIC ESTIMATES OF SEISMIC CAPABILITY OF SELECTED STRUCTURES
- SYSTEMS, OR COMPONENTS 2.
REASONS A,
ASSESS SIGNIFICANCE OF ANY DIFFERENCES BETWEEN EXISTING SEISM, DESIGN BASIS AND THAT RESULTING FROM PREVIOUS 3 CONDITIONS B
LIMITED DETERMINISTIC ANALYSIS CAN BE USED TO BETTER DEFINE SPECIFIC SEISMIC MARGINS
V, PARALLEL STAFF EFFORTS A,
CONDITION 1 1,
REVIEM DATA PROVIDED BY PGRE 2,
SOME ANALYSIS OF 'INDEPENDENTLY ACQUIRED DATA 3,
USGS AND DR,
- SLEMMONS, ADVISORS B,
CONDITION 2 1,
REVIEM OF PG8E ANALYSES 2,
INDEPENDENT ASSESSMENT OF SSE MAGN 3,
ADVISORS (AS NECESSARY)
USGS R DR, SLEMMONS C.
CONDITION 3 1,
REVIB'5 PGRE ANALYSIS 2,
ADVISORS (AS NECESSARY)
NATIONAL LAB's a USGS D,
CONDITION 4 1,
REVIEW PGRE'S PRA 2,
ADVISORS (AS NECESSARY)
NAT'L LABS 8 USGS E,
SENIOR ADVISORY REVIEH PANELS OR PANELS'O REVIEW RESULTS
VI, PROGRESS REPORTING AND SCHEDULING A.
PROGRESS REPORTS 1.
QUARTERLY PROGRESS REPORTS 2,
SEMI-ANNUAI MEETINGS IN BETHESDA B,
SCHEDULE 1,
PGRE SUBMIT PROPOSED PROGRAM JAN 30, 1985 2,
PROGRAM COMPLETED AND FINAL REPORT SUBMITTED 3
YEARS AFTER APPROVAL BY THE NRC STAFF
General Features of the Geology/Seismology Reevaluation Program Proposed by PGB E:
~ Review existing Geosciences data base
~ Identify new Geosciences data since 4978, including geophysical, geologic, and seismologic data
~ Review interpretations of geologic features and seismologic phenomena elsewhere for possible application to Diablo Canyon
~ Evaluate need to acquire new data; gather such data as required
~ Evaluate geophysical data processing techniqes for optimum results in varying conditions; have data processed as needed
~ Interpret and integrate all data to achieve updated geologic and seismologic understanding of the region of interest for Diablo Canyon
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Major Goals of the Geology/Seismology Reevaluation Program:
~ Updated map of the central and southern Santa Maria Basin and adjacent on-land area, with data relating to the subsurface dimension o Updated map of the San Gregorio-Hosgri fault system, also with data relating to the subsurface dimension
~ improved understanding of the pattern and rate of tectonism in the region of Diablo Canyon
~ Reevaluation of the seismic capability of the Hosgri fault and any other faults found to be significant to the design earthquake for Diablo Canyon
MEETING
SUMMARY
DISTRIBUTION
+Dock-et No(s),
50 275'0. 323~
NRC PDR Local PDR NSIC PRC System LB3 Reading
- Attorney, OELD GWKnighton Proiect Manager H. Schierling JLee NRC PARTICIPANTS D. Eisenhut G. Knighton T. Novak R. Vollmer A. Thadani R. Jackson ST Brocoum J.
P. Knight L. Chandler L. Reiter R.
Rothman R. McMullen D. Gupta A. Ibrahim H. Schier ling R. Savio S. Israel bcc:
Applicant
& Service List
C