ML20132B954
| ML20132B954 | |
| Person / Time | |
|---|---|
| Issue date: | 03/30/1984 |
| From: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| To: | Knight J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20132B198 | List: |
| References | |
| FOIA-85-363 NUDOCS 8404160237 | |
| Download: ML20132B954 (1) | |
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UNITED STATES
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. NUCLEAR REGULATORY COMMISSION 2, " WASWNGTON, D. C. 20555 5
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MEMCRANDUM FOR: James P. Knight, Assistant Director for Components & Structures Engineering, DE FROM: Robert E. Jackson, Chief '
Geosciences Branch, DE
SUBJECT:
REVISION 10F DIVISION OF ENGINEERING GEOSCIENCES PLAN TO ADDRESS USGS CLARIFICATION RELATING TO SEISMIC DESIGN EARTHOUAKES IN THE EASTERN SEABOARD OF THE UNITED STATES Attached is our revised plan to address the U. S. Geological Survey's clarification of position relating to seismic design earthcuakes in the Eastern Seaboard of the United States.
The revisions are generally changes of the dates of completion of specified tasks with minor revisions of the tasks themselves. Tasks which are completed or currently underway are also indicated. -
.. We estimate that the preliminary hazard levels for the sites, along with
'. our reconinendations of which plants may need further evaluation should be completed early to mid-1985, instead of mid-1984 as originally planned. In addition, industry has undertaken an extensive parallel program to develop methodology for calculating hazard curves through the Electric Power Research Institute (EPRI) which is scheduled for ccmpletion early in 1985.
The deterministic portion of the program will be synthesized on or about January 1986. The delay from the original date of January 1985 is due to the time required to compete the necessary contracts through ORES.
In summary the probabilistic and deterministic parts of the programs are underway. There have been some delays of' 6 months to 1 year. The present schedule is for completion of the probabilistic part of the plan during 1985, and the detenninistic part early in 1986. .
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Robert E. Jacklion, Chief Geosciences ' Branch, DE cc: See next page isA 3
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R. Vollmer O. Eisenhut R. Arsenault L. Beratan A. Murphy i
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NUCLEAR REGULATORY COMMISSION WASMNCTON, O. C. 20555 -
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MAR 0 2 iC33 L ,
o MEMORANDUM FOR: Harold R. Denton, Director .
y Office of Nuclear Reactor Regulation '
FROM: Richard H. Vollmer, Director Division of Engineering SU3 JECT: DIVISION OF ENGINEERIttG GEOSCIENCE PLAtt TO ADDRESS'USGS CLARIFICATION RELATING TO SEISMIC DESIGil EARTHGUAXES It!
, THE EASTERN SEABOARD OF THE UtiITED STATES A plan for our proposed program to address the U. S. Geological Survey's clarification of position relating to seismic design earthcuakes in the Eastern Seaboard of the United SM*es is attached (enclosure 1). This plan elaborates en the outline provided as an attachment to a memorandum entitled, " Clarification of U. S. Geological Survey Position Relating to Seismic Design Earthquakes in the Eastern Seaboard of the United.
States", which was sent from the Executive Director of Operations to the -
Ccc21ssioners on November 19, 1982.
The plan is divided into two parts. Part one is a short term probabilistic assessment utilizing an extensive new seismic hazard study currently being develcped by Lawrence Liver =cre National Laboratory.
Part two is a longer tem deterministic assessment based primarily en icng range ORES research with the possible need for utility sponsored investigations at some loc:tions after an assessment of the long term research results. Additionaily, we recemend that an industry spenscred seismic hazard study be soliciud.
We estimate that the effort ta .stablish the seismic hazard level for the sites and make appropriate ccmparisons will take approximately three years to c0molete, utilizing staff rescurces of about 2.5-3.0 SY per -
year, and $300K per year in technical assistance funds. Our preliminary reccmmendations on which plants, if any, may need further evaluation ,,
shculd be completed in mid-1984. Because of the required research effort, the detarministic element will not be synthesized until 1985. -
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- The proposed program will cceplement engoing PRA reviews and the seismic 4
hazard spectra which are developed can also be used for future SEP evaluations. This program, therefore, is basically a centinuation, with modification, of our engoing work. This prcgram does not include rescurces to complete a reevaluation effort for plants for which design spectra may need to be reevaluated. We recommend that this contingency be censidered a 1 included in the operating plan for FY 84 This plan -
also presupcoD; that cur interim position for licensing reviews (encicsure 2) % fcund to be acceptable by ACRS and ASLS while we implement this program.
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,rs MAa 03 1333 There is evidence to sucport this assumption in the recent Appeal Scard decisien on Summer (ALAB-710).
We have also assessed our ability to implement this plan under the existing regulation, Appendix A to 10 CFR Part 100. We have concluded ;
that, although Appendix A itself does not explicitly reccgni:e the use of probabilistic methods, as a minimum they can be used to assist in reaching deterministic judgements (Seabrcok Remand, CLI80-33). It is not clear whether they can be used as the primary tool in setting appropriate ground motion leve? s. Therefore, we recc= mend that we implement a limited modification or clarification of Appendix A as previously planned in conjunction with ORES as a parallei, yet independent effort, along with the Charlesten plan. This modificatica has been recc= mended in SECY-79-300 and 2ndorsed by the Siting Policy Task Force in NUREG-0625 and is necessary to reflect the current state of art. This modification will require an aeditional 1.0 SY per year fer 2 years.
We recer=end that you consider placing this effort equally under three resource areas - Operating Reactor Licensing Actions or Safety Technology, Systematic Evaluation Program for older cperating plants, __
and Casework for ongoing OL review plants.
. -s This plan has been developed as a result of extensive discussion within 1
/ the Geosciences Branch, NRR; and discussions with the Earth Sciences Branch, ORES; and the U. S. Geological Survey.
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Richard H. Vollmer, Director Division of Engineering
Enclosure:
As stated cc: w/ enclosure -
E. Case A. Murphy -
O. Eisenhut . T. Schmidt R. Vollmer. W. Russell R. Mattson R. Bernero H. Thompson GSB Staff J. Knight Z. Ros:toczy R. Jackson P. Williams L. Reiter S. Broccum T. Sullivan L. Beratan R. Minogue F. Arsenault
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Recommended plan Eastern U. 5. Earthouakes Revision 1 -
Introduction On November 18, 1982, the U. S. Geological Survey (USGS) forwarded a letter to the Nuclear Regulatory Comission clarifying their past a position with respect to the 1886 Charleston earthquake. The USGS letter states that:
"Because the geologic and tectonic features of the Charleston region are similar to those in other regions of the eastern seaboard, we conclude that although there is no recent or historical evidence that other regions hav'e experienced strong earthquakes, the historical record is not, of itself, sufficient grounds for ruling out the occurrence in these other regions of strong seismic ground motions similar to those experienced near Charleston in 1886. Although the probability of strong ground motion due to an earthquake in any given year at a particular location in the eastern seaboard may be very low, deterministic and probabilistic evaluations of the seismic hazard should be made for individual sites in the eastern seaboard to establish the seismic engineering parameters for critical facilities."
(~#] We have evaluated the USGS clarification of position and have concluded that it can be addressed predominantly through existing programs at NRC with the possibility of additional requests for utility - sponsored work. We recomend that a two part program be implemented which will address both the deterministic and probabilistic elements mentioned by the USGS.
Part 1 of the proposed program is a short term probabilistic assessment of plants in the eastern seaboard. This part of the plan is necessary because many of the current tectonic working hypotheses are not amenable to investigation by deterministic methods in the short term.
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Part 2 of the proposed program is a longer term deterministic assessment of the causes of large earthquakes, such as the Charleston earthquake, in the eastern seaboard. Specific areas of relatively high seismicity e
and tectonic structures are identified which we recommend be addressed through the ORES long range research plan.
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Basec on our evaluation of the research results, some applicants or licensees may be required to investigate tectonic structures which may not have been previously identified during the licensing procedure.
Part 1 - Probabilistic Assessment __
cN NN,5 Discussion The November 18, 1982 letter from the USGS represents not so much a new understanding but rather a more explicit recognition of existing uncertair. ties with respect to the causative structure and mechanism of the 1886 Charleston earthquake. Many hypotheses have been proposed as to the locale in the eastern seaboard of future Charleston-size earthquakes. Some of these could be very restrictive in location while -
others would allow this earthquake to recur over very large areas.
Presently, none of these hypotheses are definitive and all contain a strong element of speculation.
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Traditional deterministic approaches such as that outlined in Section l l
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with this situation. Probabilistic methods which allow for the consideration of many hypotheses, their associated credibilities, and the explicit incorporation of uncertainty are much better equipped to provide rational frameworks for decision making. The question that needs to be answered is:
Taking uncertainties into account, have licensing decisions for plants in the eastern seaboard (i.e., in the region affected by the USGS clarified position on the Charleston Earthquake) resulted in acceptable levels of assumed seismic hazard (exposure to earthquake ground motion) at the individual sites? -
One means for answering the above question is a probabilistic assessment _
of seismic hazard at all nuclear power plant sites east of the Rocky
- t. j Mountains. Since adequate or acceptable levels of seismic hazard have not been explicitly defined in probabilistic tems, it is assumed that the probability of seismic ground motion exceeding design levels implicitly associated with licensing decisions based upon traditional methods in other regions of the U. S. east of the Rocky Mountains is adequate; these other regions include areas such as the Central Stable Region and the Gulf Coastal Plain. The prime tool for carrying out this assessment is an updated and revised version of the Uniform Hazard -
Methodology developed for the Systematic Evaluation Program by Lawrence Livemore National Laboratory (LLNL) and its subcontractor TERA Corporation. This methodology relies upon the incorporation of diverse expert opinion with regard to the input parameters needed to make probabilistic estimates. As such, it does not rely upon single
- hypotheses which do not account for existing uncertainties but rat.er N'
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attempts to incorporate the hypotheses and their uncertainties into the computations. Identification of plants (if any) in the eastern seaboard at which the probability of exceeding design-level ground motion is a
significantly greater than has been assumed at other locations may result in an integrated seismic evaluation and/or engineering reanalysis to assure the plant's ability to withstand a more severe earthquake.
This study may also identify selected plants outside of the eastern seaboard whose design levels may be inappropriate, relative to other plants, with respect to the seismic hazard.
In addition [i-we-are-alse-4m444at4mg] through a technical assistance _
., contract, a study to better estimate ground motion from a large i ,' earthquake the size of the 1886 Charleston event to gain a better understanding of how this ground motion should be represented [- ]. has recently been completed.
Major Activities - Probabilistic Assessment The probabilistic assessment portion of the proposed program is divided into the following elements. -
- 1. January 1983 thru [Apw&l-1983] September, 1984 - Continue development of LLNL study including expert opinion surveys on
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seismic hazard east of the Rocky Mountains. This study (Seismic Hazard Characterizaticn of the Eastern U.S.) is presently underway as a joint effort of NRR (FIN NO. A0428) and ORES. (FIN No. A03C61.
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[Ne] Additional resources above those [a%Feady] allocated [aFe]
were needed[,] because of cost overruns on this oroject (about 1.0 SY,S157,500).
- 2. [May-1983] January,1984 thru [9eesmber-1983] Sectember,1985 -
Calculation of seismic hazard spectra by LLNL for all nuclear power plant sites (approximately 75) east of the Rocky Mountains will be comoleted by early to mid-1985. An estimation of the probability of seismic ground motion exceeding the design level at each site, taking into account specific site conditiens, will be completed and provided as a report. [An-add 444enal-3,0-SV-4s-peeded-ser-bhNh-and Q,3-SV-fer-NRG-effert-dWF4mg-this-pep 4ed,] _
[31-September---Deeember-1983--] In addition, a comparison of LLNL
) study with existing probabilistic studies such as Algermissen and others (1982) will be comoleted. [An-add 4tiemal-Qv3-SV-4s-meeded fer-khNh-effert,] An additional 3.0 SY is needed for LLNL (FIN No.
A0448) and 0.3 SY for NRC effort during this period.
[4,] h [Mareh] December 1983 - [1983] March 1985 - Sponsorship by the utilities of a probabilistic estimation of seismic hazard for all nuclear power plants east of the Rocky Mountains. [This-study, wh41e-net-a-Pequirementi -4s-strengly-weeemmended-se-as-te -
semplement-the-bhNh-study-and-pwevide-anether-4mdependest assessment-of-se4sm4e-hazard,] An additional [0,1] 0.4 SY needed for LLNL FIN No. A0448) and 0.1 SY for NRC effort.
[b] 42 [9esember-1983-Mareh-1984] February,1985 - Seotember,1985
- Using LLNL and other studies, the NRC staff will int $ grate this
'~ information and maxe comparisons of the probability of seismic
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ground motion exceeding design levels in the eastern seaboard with probabilities calculated at plants in the rest of the Eastern and Central V. S. Comparisons will be made in several ways including a
comparison by regi.on alone a'nd by region and plant vintage. Plants in the eastern seaboard (if any) that are associated with significantly greater hazard than those elsewhere will then be identified. Other comparisons may be needed, but will be decided upon after review of initial results. An additional 0.7 SY is ,
needed for NRC effort.
[6,-Apr41-1984-September-1984---Assesswent-ef-4n444al-eene4ws4 ens regarding-hazard-4n-14ght-ef-feedbaek-frem-expert-spin 4en-en __
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resemmendatien-en-plants-wh4eh-need-reevalwatien,-An-add 444emal-0,2 SV-needed-for-bbHL-and-0,2-SV-fer-NRG-effert,]
[7,] 5. January 1983-December 1983 - Ground motien estimates at different distances and site conditions from a large Charleston type earthquake. Both theoretical and empirical estimates using data from recent earthquakes will be made. This study [4s presently-being-4n444ated-threwgh-a-teeknical-assistanee-eentrast w4*h-bbNk,--Ne-additiemal-ressurses-are-reew4 red,]hasbeen -
recently comoleted.
Status summary reports of research into probabilistic estimates of seismic hazard funded by CRES will be needed by December 1983 so as to incorporate them into task number 5.
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Imolementation of Probabilistic Assessment Results The implementation of results is outlined above in [ elements-i-and-6,]
element 4 4
NRR Staff and Cost Reauirements - Probabilistic Assessment The additional effort required for this portion of the program will be
[2,5) 4.4 SY for LLNL ([1,9] in FY 83. [0,6] 2.4 in FY 84) and 1.3 SY for NRC (0.3 in FY 83, 1.0 in FY 84). this staff effort can be accommodated with the currently available resources in the Geosciences Branch because this program complements ongoing staff activities and may replace other staff activities for individual sites. This program does not include resources to complete the seismic evaluation and/or __
engineering reanalysis which some plants may require as a result of the
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(/ probabilistic elements.
Utility-Sponsored Study in Conjunction with the Probabilistic Assessment A recommended utility-sponsored study is outlined above in element [4,]
3.-
Schedule - Probabilistic Assessment The proposed schedule for implementing this plan appears in Table 1.
Part 2 - Deterministic Asse,ssment Discussion The deterministic portion of the proposed program is designed to better understand the causes of large earthquakes, such as the Charleston earthquake, in the eastern seaboard. This effort may require some expansion of immediate and long term ORES programs. Increased
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understanding of the cause of seismicity in the eastern seaboard wi.ll allow a reduction in the uncertainty in estimating the seismic hazard for nuclear power plants. The primary problem with seismic hazard a
characterization in the eastern seaboard is that no causative mechanism for seismicity has been identified to date and no surface offsets due to earthquakes are known. Although there are literally thousands of crustal structures known in the eastern seaboard, which, if they were active, could produce strong earthquakes, none have been demonstrated to have been active during the Quaternary (the last two million years) or proved to be capable. The result is that, to date, there has been no generally accepted association between eastern seismicity and crustal __
structure.
( [! The overall approach of the deterministfc assessment is to study areas of relatively higher se.ismicity in the eastern seaboard to determine if tectonic features and processes responsible for the seismicity can be identified and correlated. This will be pursued by crustal studies at hypocentral depths to determine if there is any correlation between crustal structures et hypocentral depths and the earthquake hypocenters.
The primary tool for determining crustal structure at hypocentral depths will be the use of multi-channel seismic reflection profiles. The -
primary tools for locating the hypocenters will be the continued monitoring and analysis of earthquakes from the existing microearthquake nets. These nets will have to be maintained and upgraded in order to improve depth locations of hypocenters if there is to be an improved I ability to correlate between hypocenters and tectonic structures at depths of up to 25 kilometers.
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This research will be contracted and monitored by ORES, and does not represent a radical departure from past programs. Increased coordination between NRR and ORES will be required, however, to better a
define the problems that are to be resolved in order to improve our understanding of eastern seismicity in the licensing context. This portion of the program is designed to improve our ability to assess the adecuacy of the design of nuclear facilities on the eastern seaboard.
The result, in part, will be sumary reports which will represent the current status of research including a review and synthesis of available data. These results will be used to modify, if necessary, conclusions drawn from the probabilistic studies and identify individual features, _
if appropriate, for assessment by utilities.
t) y J0 Major Activities - Deterministic Assessment The deterministic assessment portion of the proposed program is divided into the following elements appropriate to each region listed.
A. Charleston Region Since the causative mechanism of the Charleston earthquake of 1886 continues to be one of the primary unresolved problems in evaluating seismicity in the eastern seaboard, research in the Charleston area -
should continue with the goal of testing the various hypotheses as to the cause of the earthquake. In particular, emphasis should be placed on determining if suggested features such as the Ashley River and -
Woodstock Fault zones constitute the source zones of the Charleston earthquakes.
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- 1. May 1983 " Workshop on the 1886 Charleston Earthquake and Its Implications for Today" - the U. S. Geological Survey and the scientific community [w411-present] presented a summary and a
evaluation of the tectonics and seismicity at Charleston.
- 2. [ September-1983] April 1984 - ORES in consultation with the U.
S. Geological Survey and the scientific community should have a program in place to test the most likely tectonic hypothesis ,
for seismicity.
- 3. June [1984] 1985 - ORES presents the results of the program of testing the highest-weighted hypothesis. Interim results will be presented as available.
, _ , 4. January [1985] 1986 - ORES presents summary report (perhaps a
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(.,;;p symposium) describing the results of the Charleston work testing the highest-weighted tectonic hypothesis.
B. Ramaoo Fault Zone 4
The Ramapo Fault Zone, a Precambrian fault zone that was intermittently active until the Mesozoic, is the northwestern boundary of the Newark Triassic Basin. Low level seismicity occurs in the area and may be associated with the fault zone, however, the seismicity in the region forms a band 40 kilometers wide. Detailed field work and limited -
trenching and core drilling suggest that the Ramapo Fault has not been recently reactivated. The purpose of studying the fault is to establish whether there is a causal relationship between Mesozoic or older faults such as the Ramapo Fault and current seismicity in this area by determining the location and geometry of these faults at hypocentral
[ . depths.
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- 1. April 1983 - ORES [4n444ates] initiated a new evaluation of the Ramapo Fault. The study (shewid-4aelude] includes multi-channel seismic reflection profiling and other geophysical techniques a
such as in-situ stress measurements and ge:detic measurements to determine the current state of stress at hypocentral depths.
- 2. [ January] February 1984 - ORES [ presents] g esented preliminary results of the program to fate, and plans for the coming year.
- 3. [Japwary] March 1985 - ORES presents summary report on this aspect of the Ramapo Fault Study including the identification -
and analysis of any seismic source zones. _.
.. C. Central Virginia Seismic Zone
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(1/ Recent work by earth scientists at Virginia Polytechnic Institute have suggested that there may be a relationship between the seismicity in Central Virginia and the northeast trending thrust faults and decollement of the piedmont crust of the Appalachian Orogenic Belt. The purpose of this part of the progran is to continue evaluation of the relationship between the faults and the earthquakes.
- 1. April 1983 - ORES [ presents] presented a plan for undertaking -
the seismic reflection profiling, and applying other geophysical techniques such as geodetic measurements and in-situ stress measurements.
- 2. [Jaswary] May 1984 - ORES presents the preliminary results or progress to date, and plans for the coming year.
[. 3. January 1985 - ORES presents a summary report on the v
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the Central Virginia Study including the potential identification and analysis of any seismic source zones.
D. Giles County, Virginia The Giles County Seismic Zone is a northeast trending linear zone of seismicity which apparently is located beneath the decollement and thrust faults associated with the Valley & Ridge Province of the Appalachian Orogenic Belt. It has been suggested that the seismic zone has occurred as a reactivated northeast trending normal fault associated with the opening of the Proto-Atlantic (called the Iapatus) in the late Proterozoic and early Paleozoic (800-500 million years ago).
,..s 1. April 1983 - ORES [4mit4ates] initiated planning for the k, l proposed research.
- 2. August 1983 - ORES [4n444ates] initiated study of the Giles County structure using seismic reflection profiling.
- 3. [ April] May 1984 - ORES presents preliminary results and plans for the coming year.
- 4. April 1985 - ORES presents summary results of this phase of the research including the potential identification and analysis of any seismic source zones. -
E. New England The research in New England has been underway for several years and will be continued. Increased emphasis should be placed on evaluation of the source mechanism for the New Brunswick and Gaza, N.H. earthquakes, the neotectonics of seismically active areas, and the orientation and
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0 magnitude of the stress field in the seismically active areas of the region. An in-situ stress measurement at hypocentral depths will be conducted at Moodus. Depending on the results of the seismic reflection f .
studies described above, additional seismic reflection surveys may be conducted in seismically active areas of New England such as Moodus, Connecticut; New Hampshire; Massena, New York and New Brunswick, Canada.
- 1. April 1983 - ORES [eempletes] comoleted plans for stress measurement at Moodus.
- 2. [ August] April 1983 - Conduct stress measurements at Moodus. -
Stress measurements will also be conducted in the Ramaco Fault area in May, 1984
- 3. [ App 44] July 1984 - ORES presents preliminary results of stress a measurements and their relationship to the local seismicity and tectonics.
4 January 1985 - ORES presents summary results of stress measurements and other studies (including neotectonics) described above.
Implementation of Deterministic Assessment Results As the results from the deterministic studies become available, they -
will be evaluated, and, the effect, if any, on operating plants and plants in the Operating 1.icense stage of review will be determined. The need for additional evaluations of particular structures by utilities will be assessed as the information becomes available. Two problems will .
1 be addressed by the deterministic portion of the program; (1) whether cr l not the deterministic findings warrant any reassessment of the
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O conclusions drawn from the probabilistic study; and (2) whether there are any particular tectonic structures which are associated with or similar to tectonic structures associated with seismicity which, because of their proximity to individual sites, should be analyzed by the utilities. The above effort will take about two to three years (early
[1986}1986) to complete. The impact of this research on nuclear power plants will be determined by the NRC staff with technical assistance contracts, if necessary.
f!RR Staff and Cast Reouirements - Deterministic Assessment This effort will recuire continuous communication among NRR, ORES and -
the contractors. As research funds are limited and the amount of time __
-- is short, careful interaction will be necessary to obtain the
(; information required to allow a resolution of eastern seismicity. It is estimated that one staff year per year for three years will be necessary for NRR to implement this deterministic part of the overall plan.
The research effort will be funded by ORES and technical assistance contracts will be funded by NRR. It is estimated that for the deterministic assessment, $200,000 may be required to implement the NRR technical assistance program to determine the impacts of the findings on the nuclear facilities in the eastern U. S. -
Utility-Soonsored Studies as Result of the Deterministic Asessment During FY 1983 no ' deterministic work by the utilities is currently recommended, beyond that necessary to pursue their normal efforts to continue to assess any hazards identified by them for their sites.
After the results of the research are available and if any source zones
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are identified which have particular importance to specific sites or s_ /
g s, have impact on the probabilistic program, some utilities may be required to investigate structures in the vicinity of their plants.
Schedule - Deterministic Assessment a
The proposed schedule for implementing this plan follows as Table 1.
Our ability to meet this proposed schedule may be somewhat optimistic and is contingent o,n implementing the appropriate contracts. We will be better able to assess this schedule when the work has been initiated.
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Calendar Year Schedule for Probabiilstic and Deterministic Seismic Hazard Program ,
1983 1984 1985 -
Part 1 ShNt Tenn Meet with ACRS to Meet with ACRS to discuss Program to discuss Preliminary Recommendations 1_ Update LLNL Seismic [+Gemplete-Methedelegy] 4 Complete Methodology llazard Methodology i
- 2. Calculate Seismic + [+Repert-with-Speetra] Report with Spectra llazard Spectra for Eastern Sites Report with i
[3,] Compare with other + [+ Report-with-Gemparisens] Comparisons available probability ,
^ studies +
Production of Ytudy Results
[4,] 3. Initiation of Industry- + [+Produetien-af-Study-Resultsj
- Sponsored Seismic llazard Study Letter Report with Reconenendations
[l-etter-Repert-wi th +
Preliminary-Resemendatiens] Final Reconwnendations
- 5. 4. Comparison of Seismic + [+] [+ Final--Reeomenda tiens]
liizard at Sites initate-Feedbaek Assess-impaet-on
[6 -Assessment-ef-impaet-ef +-----------------------+ Previous-Results]
Expert-Feedbaek initiate Tac with LLNL
[7,1 h Charleston Ground Motion + +1ssue Report (issued Jan, 1984, NilREG June,1984)
Study Table 1 l .
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Calendar Year Schedule for Probabilistic and Deterministic Seismic Ilazard Program .
e 1983 1984 1985 I
Part 2 Long Term Meet with ACRS to Heet with ACRS to discuss Program to discuss Preliminary Recminnenda tions l
Workshop-Interim Progress Report on Results of Synthesis liypothesis Testing Testing
- 1. Charleston Research + x [x] x [xx-----] x Initiate Preliminary Summa ry Study Report Report
- 2. Ramapo Fault Research + x x xx-----
Initiate Prelimina ry Summary Study Results Report Report
- 3. Central Va. Research + x [x] x xx------
Initiation Preliminary Summa ry RFP of Study Results Report
- 4. Giles County, Va. + x x x xx-----
Research Stress Measurenents Conduct Preliminary Sunmary Plan Measurenents Results Report
- 5. New England + x x x -------xx Seismotectonic Research Summarize Review Preliminary Evaluation Summary of of Determinsitic of Results of RES Source Zones Work
- 6. Assessment of Impact of + x x +
Detenninistic Studies on Sites Table 1 (cont'd) l ..
- Enclosure 2 D.
Interim Position on Charleston Earthcuake ,
ror L1censina Proceec1na The f!RR Staff position with respect to the Intensity X 1885 Charleston earthquake has been that, in the context of the tectonic province approach used for licensing nuclear power plants, this earthquake should a be restricted to the Charleston vicinity. This position was based, in part, on information provided by the United States Geological Survey (USGS) in a letter dated Decer-ber 30, 1980 from J. E. Devine to R. E.
Jackson (see Summer Safety Evaluation Report). The USGS has been reassessing its position and issued a clarification on Movember 18, 1982 in a letter from J. E. Devine to R. E. Jackson. As a result of this letter, a preliminary evaluation and cutline 'or NRC action was forwarded to the Commission in a memorandum from W. J. Dircks on November 19, 1982.
(.> The USGS letter states that:
"Because the geologic and tectonic features of the Charleston region are similar to tMse in other regions of the eastern seaboard, we conclude that eithough there is no recent or historical evidence that other regions have exoerienced strong earthquakes, the historical record is not, of itself, sufficient grounds for ruling out the occurrence in these other regions of strong seismic ground motions similar to those experienced near Charleston in 1886. Although the probability of strong ground motion due to an earthquake in any given year at a particular location in the eastern seaboard may be very low, deterministic and probabilistic evaluations of the seismic hazard should be made fpr individual sites in the eastern seaboarc to establish the seist:iic engineering parameters for critical facilities." -
The USGS clarification represents not so much a new understanding but rather a more explicit recognition of existing uncertainties with respect to the causative structure and mechanism of the 1886 Charleston earthquake. llany hypotheses have been proposed as to the locale in the i
- eastern seaboard of future Charleston-size earthquakes. Scre 0# :nese jm_
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- 2-t, could be very restrictive in location while others would alicw this earthquake to recur over very large areas. Presently, rone of these hypotheses are definitive and all contain a streng element of a speculation.
We are addressing this uncertainty in both longer-tern deterministic and shorter-term probabilistic programs. The deterministic studies, funded primarily by the Office of Research of the NRC shculd reduce the uncertainty by better identifyirg (1) the causal mechanism of the Charleston earthquake and (2) the potential for the occurrence of lar;e earthcuakes throughout the eastern seaboard. The probabilistic studies, primarily that being conducted for NRC by Lawrence Livermore National __
.7s1 Laboratory (LLNL) will take into account . existing uncerta.inties. They s / will have as their aim to cetermine differences, if any, between the probabilities of seismic gecund motion exceeding design levels in the eastern seaboard (i.e. as affected by the USGS clarified position en :ne Charleston earthquake) and the probabilities of seismic grcund motien exceeding design levels elsewhere in the central and eastern U. S.
Any plants where the prcbabilities of exceeding design level greurd motions are significantly higher than those calculated for other plants in the Central and Eastern U. S. will be identified and evaluated fo'r' ,
possible further engineerir.g analysis.
Given the speculative nature of the hypotheses with respect to the recurrence of large Charleston-type earthquakes as a result of our j i
limited scientific knculedge and the generalized low pecbability I associated with such events, we do not see a need for any action for i
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