ML20198F728
| ML20198F728 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 11/11/1977 |
| From: | Cox T Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-1153 NUDOCS 8605290064 | |
| Download: ML20198F728 (8) | |
Text
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NOV 1119'I7 Docket Nos. 50-460 !
and 50-513 i
APPLICANT: Washington Public Power Supply System (WPPSS) l
SUBJECT:
SUMARY OF MEETING WITH WPPSS AND USGS TO RECEIVE DESCRIPTI0tl 0F WPPSS' RECENT WORK ON' 1872 EARTHQUAKE EVALUATION 1
l On October 17,1977 representatives of the Office of Nuclear Reactor Regulation (NRC), WPPSSs and the U. S. Geological Survey, (USGS) met in l
Denver, Colorado to receive a presentation by WPPSS on the content of Amendment 23 to the WNP-1, 4 PSAR, which amendment was submitted to the NRC on October 11, 1977. Representatives of the Portland General Electric Company, Pacific Power and Light Company, and the PugetsSound Power and
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Light Company were also present.
Background
i The applicant's stated purpose in requesting this meeting was to familiarize the staff and USGS members with the technical scope and content of Amendment 23.
The familiarization was an effort by WPPSS to assist in anteXpeditious review of the material. Amendment 23 was submitted in response to the staff's request dated April 18, 1977, vhich asked WPPSS to reassess the December 14, 1872 earthquake with respect to the design basis seismic acceleration selected by WPPSS for the WNP-1, 4 projects. WPPSS stated, in their letter transmitting l
Amendment 23, their need for a NRC conclusion on the 1872 earthquake issue.
l The construction schedule now in effect at the Hanford sites involves both WNP-1 and WNP-4. The WNP-1 project has received construction pemit number i
CPPR-134 while work at WNP 4, 3000 feet to the north of WNP-1, is proceeding l
under altimited Work AuthoFization most recently amended on March 28, 1977.
WPPSS indicated that a full construction permit for WNP-4 is needed by March 1,1978 if a significant cutback in the on-site work force is to be avoided.
Sumary L. Grume (WPPS), in introductory remarf., listed the significant milestones completed.in the work done to this time on the 1872 earthquake. He noted that the principal efforttby WPPSS since February 1977 has been to (1) better define the location of the December 14, 1072 earthquake by either identifying the source structure or associating the earthquake with a geologic province, and (2) to evaluate the possibility of a similar earthquake occurring in the Columbia Plateau.
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The program of studies reported on in Amendment 23 includes all of the effort undertaken by WPPSS since February 1977, some of which work was reported in a meeting with the staff on July 14,1977.
L. Grume pointed out that all of the work reported on in July 1977 has been updated and integrated with extensive new work done in the period June through September 1977. WPPSS' total effort on evaluation of the 1872 earthquake is now doctmented as Appendix 2R of the WNP-1, 4 preliminary Safety Analysis Report. WPPSS' sumary report regarding the 1872 earthquake and th.e earthquake's relationship to the seismic design of the WNP-1, 4 plants is in Appendix 2R.
The conclusions of this report are included as Enclosure 1 to this sumary.
WPPSS concludes that their original design basis seismic acceleration of i
0.25 g for the safe shutdown earthquake is still adequate and conservative.
The detailed technical presentations at this meeting were a comprehensive exposition of the material contained in individual sub-appendices 2R-A through 2R-L of Amendment 23, which support the sumary and conclusions in Appendix 2R. These presentations were made by representatives of the individual consultants involved. ' Enclosure 2 is a list of the sub-appendices and their titles. Enclosure 3 is a list of persons attending the meeting.
Original Signed D T.Cos Thomas H. Cox, Project Manager Light Water Reactors Branch No. 3 Division of Project Management l
Enclosures:
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1.
Pages 2R-4, 2R-5, and 2R-6 from Amendnent 23 to WNP-1/4 PSAR l
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2.
L'ist of Sub-Appendices (page 2R-iv of Amendnent 23 to WNP-1/4 PSAR) 3.
Atteddees List, October 17, 1977 Meeting i
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Washington Public Power Supply System ATIN: Mr. N. O. Strand Managing Director 3000 George Washington Way Richland, Washington 99352 cc:
Joseph B. Knotts, Jr., Esq.
Debevoise & Liberman Shoreham Builoing, Suite 700 800 35th Street, N.W.
Washington, D. C.
20005 Richard Q. Quigley, Esq.
Washington Public Power Supply System 3000 George Washington Way Richland, Washington 99352 O
A
WNP-1/4 Amendment 23 PSAR ENCLOSURE 1 2.0 SCMMARY AND CO!CLUSICt3 Although the exact epicenter location for the December 14, 1872 earthquake has not been established unegaivocally, most investiga'wrs who have studied this event have concluded that the epicentral area is in the Northern Cascades-Okanogan region. The evidence for this location comes fr a the results of an intensive search for all historical information by h?PSS and a critical evaluation of that material by two separate geotechnical consulting firms (WPPSS [WGR],1974; WGR,1976; WPPSS (WCC],1977) and an independent panel of expert geologists and seismologists (Coombs et al,1976, Shappendix 2R A).
In addition, all earlier investigations plus new data (see Sub-appendix 2R E) have been re-evaluated and result in the same conclusion (see Sub-appendix 2R B).
The same region is suspect as a general epicenter for geologic reasons because it contains major faults that had been mapped and described in the literature (Sub-appendix 2R D).
These faults are major in that some involve strike-slip displacements measured in tens of kilcceters and all have mapped lengths of may tens of kilcneters. Reactivation of these faults under the present north-south stress regime (Sub-appendix 2R C) is a possibility. The abundance of major faults in the epicentral region provide candidates for the scurce c.f this earthquake. However, it has proven difficult to establish the time of R. test movement on these faults as late Cenozoic sediments, that escally help to bracket the time of movement on faults, are almost ccepletely lacking in the epicentral area.
Determination of a precise location of the epicenter has also proven difficult because of the almost ecuplete lack of people within the remote epicentral area in 1872 who could communicate first-hand accounts of the event. W.erefore, reliance is placed on the reports of people and damage to structures in the fringe area i.nediately surrounding the general epicenter.
This approach helps to constrain the shape of the meizoseismal arec and provides a reasonable means of estimating the size of the earthgaake for
. engineering design purposes.
Considering the existing information and the new geological, geophysical, and seismolcgical information (presented as Sub-appendices 2R A through 2R L in this am ndment), the follcwing conclusions have been reached by h7PSS and the Technical Advisory Panel regarding the Dece:2er 14,1872 earthgaake and its relevance in determining the seismic design bases for WPPSS Nuclear Project 1 and 4:
o The December 14, 1872 earthquake occurred in the Northern Cascades-Okanogan area. The epicenter for the earthquake is located within a meizoseismal zone that extends from Lake Chelan in the south to southern British Columbia in the north. It is constrained to the east by the balanced rock at Chak Lake. There is little data for constraint 'a the west.
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WNP-1/4 Amendment 23 PSAR b
o There appears to have been one main earthquake that occurred around 10 PM, the evening of Decerter 14, 1872. Two to four earthquakes of slightly smaller magnitude probably occurred over a broad area after the main shock during the night of Decerter 14-15, 1872. These aftershocks may have unduly expanded the felt area attributed to the main earthquake.
o If the large felt area previously ascribed to the December 14, 1872 earthquake is valid, and is not ccuplicated by widely dispersed aftershocks, then the earthquake had a magnitude near 7 and an intensity of VIII over a broad region. Alternatively, if the felt area is a ecmposite of multiple seismic events, then the magnitude of the largest of these events was probably less than 7.
o A diligent examination of most of the major faults in the epicentral area has failed to reveal positive evidence of Quaternary displacement with the possible exception of one zone of faulting (Hcpe-Straight Creek).
o If the focal depth of the December 14, 1872 earthquake was shallcw, i.e.,
less than 25 km, and if the earthquake had a magnitude near 7, then the ground surface should have been broken in the epicentral area by faulting. No exceptiens to this depth-magnitude-surface faulting relationship are known frcm the historic seismic records of the western United States.
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If a shallow earthquake of 1872-type and magnitude had cccurred in the Columbia Plateau in the late Cenozoic period, it would have produced extensive surface rupture. A thorough geologic examinaticn of the plateau shcws that there has been no surface faulting ccepatible with an 1872-type event since at least the beginning of Holecene time (11,000 years).
o Similarly, detailed geologic and aeremagnetic studies in the area of overlap of Columbia River basalts across older basement rocks of the Northern Cascades-Cka~nogan epicentral terrane derenstrate that none of the major basement structures appear to have significantly affected the Columbia Plateau basalts since mid-Pleistecene (1 millicn years). No evidence of late Pleistocene or Holocene faulting ccupatible with a
.shallcw 1872-type event was found in the Columbia Plateau boundary area, o
If the December 14, 1872 earthquake was deep, i.e., greater than 25 km, it may have occurred either in the lower crust or upper mantle. Surface rupture by attendant faulting would not be expected. In contrast, an earthquake of this focal depth beneath the central Columbia Plateau would be restricted to the upper mantle because the crust there is cnly 25 km, or less, thick. Since the mantle beneath the central Columbia Plateau and that beneath the Northern Cascades-Ckanogan epicentral area can be distinguished by physical differences (Figure 2R 2), there appears to be no reasonable basis for ;cstulating that a deep earthquake of the 1872-type could equally well be generated in the mantle beneath the Colurtia Plateau.
o Frcm the standpoint of postulating the occurrence of an 1872-type earthquake in the Columbia Plateau, the focal depth of the Decer.ter 14, 1872 earthquake, whether shallow (< 25 km) er deep (> 25 )ca), does not appear to be relevant. In neither case can an earthgaake of the type and magnitude known to have occurred in the Northern Cascades-Okanogan region in 1872, be geologically justified as likely to occur in the Columbia Plateau, nor is there any evidence that such an earthgaake has occurred in the Columbia Plateau since mid-Pleistocene time.
In conclusion, the seismic design that is being used for WPPSS Nuclear Projects 1 and 4 is based on.a postulated intensity VIII earthqaake occurring on the closest geologic structure (Rattlesnake) considered to be capable under 10 CFR 100, Appendix A at a distance of 13 miles. Assuming no attenuation of energy, the attendant acceleration value at the site is estimated to be 0.25g (see Chapter 2.5.2.10).
In light of the fact that: (1) the largest historic earthquake known to have occurred in the site vicinity was an intensity VII at a distance of over 50 miles; and (2) that an 1872-type earthgaake occurring on a structure in the site vicinity is highly unlikely, we therefore conclude that the present seismic design of 0.25g is both adegaate and conservative.
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WNP-1/4 Amerdtent 23 PSAR ENCLOSURE 2 APPDDIX 2R LIST CF SUB-APPDDICES 2R A
" REPORT CF U!E REVIEW PANEL CN THE DECDiBER 14, 1872 EARUlQUAKE" by H. A. Coombs, W. G. Milne, O. W. Nuttli ard D. B. Slemons (December,1976 Report, reproduced in part) 2R B
" REVIEW OF THE NCRTH CASCADE, EARTHQUAKE OF DECDiBER 14, 1872" by Woodward-Clyde Consultants 2R C "TECICNIC EWLUTION CF THE PACIFIC lORTHWEST:
PRECAMBRIAN TO PRESENr" by G.A. Davis 2R D "GECIOGIC EVALL%TICNS OF :smAcavaES IN THE 1872 EARTHQUAKE EPICD7rRAL REGION" by Shannon & Wilson, Inc.
2R E "GECPHYSICAL AND SEISMOICGICAL STUDIES IN M 1872 EARU! QUAKE EPICDTIPAL REGICN" by Weston Geophysical Research, Inc.
2R F
" IMAGERY AND TCPIPAPHIC INTEFGPETATICN CF GECICGIC STRUCIURES IN CD?rRAL WASHDX7IGN" by C.E. Glass and D.B. Slemons
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2R G "RDCTE SDEING ANALYSIS OF THE 1872 EARTHQUAKE EPICDTfRAL REGION" by D.B. Slenzens, Gary Carver, and D.T. Trexler 2R H "GECIOGIC EVALL%TICNS CF STRUCTJFIS IN THE CCID!BIA PIATEAU" by Shannon & Wilson, Inc.
2R I
" GEOPHYSICAL EVALL%TICNS OF STRLCTURES IN DIE CCLCMBIA PIATEAU" by Weston Gecphysical Research, Inc.
2R J "EVALL% TION CF MICPCEARTHQUAKE ACTIVITY IN EASTEEN IGSHINGICN" by Weston Gecphysical Research, Inc.
2R K "RDicrE SCEniG ANALYSIS CF THE CCLCMSIA PIATEAU" by C.E. Glass 2R L "MICPCEARTFQUAKE SCRVEYS AND EVALL%TICN CF STPESS CRIENIATION IN CENTRAL IGSHINGICN" by Woodward-Clyde Censultants 2R iV
ENCLOSURE 3 ATTENDANCE LIST OCTOBER 17, 1977 MEETING ON 1872 EARTHQUAKE WPPSS Portland General Electric Co.
L. Grumme R. Halicki D. T111 son J. Frewine A. Hosler W. Kiel NRC C Cox Pacific Power & Light Co.
R. McMullen R. Kent C. Stepp J. Kelleher Woodward-Clyde D. Tocher Weston Geoohysical Research J. Hobgood G. Leblanc W. Savage J. Doherty L. Cluff G. Simmons T. Turcotte V. Murphy G. Carver J. McCleary R. Withers Hanford Engineering Development J. Dohrenwend Laboratories D. Simpson Puget Sound Power & Light Co.
J. Mecca Perkins Law Firm G. Jacobsen D. Little USGS Techtel ST Trockman (Denver)
R. Talmage M. Hopper W. Hays R. Morris Independent Consultants W. Spence G. Davis 1
J. Devine (Reston)
H. Coombs P. Hanshaw R. Couch S. Malone C. Glass Shannon & Wilson D. Slemmons H. Waldron R. Deacon R. Kienle l
S. Farooqui l
T. Olmsted D. Clayton l
B. Ryan l
R. Bentley l
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