ML20213D717
| ML20213D717 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 04/29/1981 |
| From: | Knight J Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0067, CON-WNP-356A, CON-WNP-67 NUDOCS 8105040570 | |
| Download: ML20213D717 (9) | |
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James P. Knight, Assistant Director for 4
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SUBJECT:
WASHINGT0!! NUCLEAR PLAf4T f0. 2: GEOSCIENCES
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BRA!<CH REQUEST FOR ADDITION #L INFORMATI0rl i
Enclosed are questions for the Washington f;uclear Plant'No. 2.
The subjects covered had been discussed by the Geosciences Branch at the March 31, 1981 l
Bethesda neeting. 0360,11 thru Q350.13 and 0361.9 thru Q3G1.13 have been provided by the staff's advisor, the U. S. Geological Survey. Please encourage the Supply System personnel to naintain direct contact with the Geosciences Branch concerning these questions.
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James P. Knight, Assistant Director for Components and Structures Engineering Division of Engineering
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GEOSCIENCES BRANCH REQUEST FOR ADDITIONAL INFORMATION WASHINGTON NUCLEAR PLANT NO. 2 WASHINGTON PUBLIC POWER SUPPLY SYSTEM DOCKET NO. 50-397 360.6 Tectonic Framework and Mechanisms. Provide a neotectonic model or alternative models of the Columbia Plateau and adjacent provinces with emphasis on the possible seismic source zones in the Plateau under and around WNP-2.
I 360.7 Capable Faults. The following geologic or topographic features are faults or they are surface features that strongly suggest the presence of faults: the faults associated with Umtanum Ridge, Gable Mountain, Rattlesnake Mountain, Toppenish Ridge, Saddle Mountains, Yakima Ridge, " Alphabet Hills" in the Rattlesnake-Wallula linear zone; the straignt course of the Columbia River east of the site and north of Richland; Trimble's lineaments; and other prominent lineaments in the region. Which of these features do you consider to be capable faults within the meaning of Appendix A, 10 CFR Part 1007 Present the bases for eliminating those that you do not consider to be i
capable faults. Those that you consider to be capable f aults, determine their lengths, their relationship to each other and their relationship to regional tectonic structures. Also, determine the nature and amount of movenent, and the history of displacements along the faults, including the estimated maximum Quaternary displacement related to a single earthquake.
360.8 Surface faulting. Provide an assessment of any surface fauit potential l
at the site. Consider in this evaluation the Cold Creek Syncline, the I
hypothesized Wooded Island monocline (Rothe, 1978), thrust faults i
I associated with nearby anticlinorial ridges, the Gable Moantain faults, am.
3 and the faults discovereo in nearby drill core, such as at 0B-10.
The evaluation should consider the possible effects caused by man's activities.
360.9 Volcanic Hazards. Assess the potential volcanic hazards to WNP-2 in light of the effects of the 1980 eruptions of Mount St. Helens.
What is the significance of the nearly three feet of 6000-year-old compacted ash discovered in 1980 near Richland?
360.10 Work plans. Provide details of your trenching program and geosciences workplan and the expected goals of these programs.
360.11 What models of subsurface structure in the basalt pile are required (USGS) or excluded by a detailed structural and kinematic analysis based on the fold and thrust geometry mapped at the ground surface, deep wells, seismic,'and magnetics?
These analyses should help explain:
a.
Intersections of folds.
b.
Cross structures, c.
Differences in fold spacing and trend.
d.
Curving structures--Cleman Mountain anticline.
360.12 What are the merits of explaining the obvious structures and l
trenas by vertical tectonics through the basalt pile or by horizontal tectonics within the basalt pile?
360,13 What is the structural geometry below and between the anticlines QSGS) of Frenchman Mountain, Saddle Mountain, Gable Mountain, and Ratt1 snake Ridge?
a 361.1 Provide a discussion of possible ground motion from potential swarm earthquakes in the immediate vicinity of the site. What is the largest magnitude swarm earthquake which could occur close to the site? At what distance from the site is this event assumed to occur? Provide supporting bases. Compare the ground motion (including peaks and response spectra) from this potential earthquake to the SSE and actual design used.
361.2 As noted in the WNP-2 FSAR the peak acceleration was determined to be 0.25g by assuming an intensity MMl=VIII event occurred on the Rattle-snake structure and allowing for no attenuation. A report by Woodward-Clyde " Seismological Review of the July 16, 1936 Milton Freewater Earth-quake Source Region" states that the 1936 earthquake had a magnitude of ML = 6.1.
This earthquake is the largest magnitude earthquake (historical) within the Columbia Plateau Tectonic Province which has not been associated with a tectonic structure. Since magnitude may be a more realistic estimate of earthquake size than intensity, compare the ground motion (incluaing peaks and response spectra) assuming that a magnitude M = 6.1 L
reoccurred in the vicinity of the WNP-2 site. One method of making such a comparison is to analyze accelerograms from similar magnituce earthquakes, recorded at appropriate distances, and site conditions.
It has been the staff's position that the representation appropriate for use in comparing a " site specific spectra" with the SSE is the 84th percentile of the response spectra as derived directly from the real time histories.
. 361.3 Evaluate the maximum earthquake potential of faults which have been found to be capable within the meaning of Appendix A, 10 CFR Part 100, and regional tectonic structures associated with the capable faults.
Compare the ground motion (both peaks and response spectra) from potential earthquakes on these structures to'the proposed SSE and actual design used.
Include such consideration as: fault length, fault displacement, slip rate, magnitude or range of magnitude assumed for each structure, and the distance at which these events are' assumed to occur fran the site.
361.4 Provide a discussion on the effect, if any, of newly acquired data (geological, geophysical and seismological) has on your position with regard to the 1872 earthquake. This should include but not be limited to the magnitude, depth, tectonic province in which a similar event could occur, and any ground motion effects at the site.
361.5 Provide a discussion, with supporting bases, of the possibility that the 1872 earthquake could occur in the mantle under the WNP-2 site.
361.6 Provide the location ano dates of operation of the strong motion instruments mentioned in your January 27, 1981 work plan.
361.7 A report entitled " Fault and Earthquake Hazard Evaluation of Five U. S.
Corps of Engineers Dams in Southeastern Washington" by David B. Slemmons and Peg 0'Malley discusses potential earthquake hazard for Southwestern Washington. The authors estimate a magnitude of 6.3 to 6.8 (Richter) for the CLEW zone based on the Wallula Gap fault being probably active or capable and having a length of 40 km. Evaluate these findings and any impact they may have on the seismic design adequacy ot' the plant.
. 361.8 Provide a discussion of the possible relationship of the earthquakes with depths greater than 9 km to the grabens whose bounding faults may extend for significant distances south under the Plateau, into the Pasco Basin.
361.9 The FSAR (vol. 2) lists the epicenter of the July 15, 1936 (local time)
(USGS)
Milton-Freewater, Oregon earthquake at 46.0N., ll8.5W., with a magnitude of 5 3/4 (vol. 2, page 2.5-110). A report by Wooaward-Clyde consultants,
" Seismological Review of the July 16, Milton-Freewater Earthquake Source Region" prepared for WPPSS has' relocatea the epicenter of this shock at 46 12.5N., 118 14.0W., and computed a magnitude of M 6.1.
How does this L
discrepancy affect the ground motion at the site?
361.10 With regard to the Woodward-Clyde Consultants report referreo to in question 9,' above, the report states that the teleseismic location program, MEVENT (Dewey, 1971) was used to relocate the Milton-Freewater earthquake.
The program MEVENT allows for flexibility in assigning weightings to recorded earthquake arrival times. How were the station readings weighted in the relocation and how do stations with large residuals (for example, 8.5 and 9.9 seconds) affect the relocationir 361.11 Would relocation of other significant earthquakes in the area affect (USGS) estimation of the ground motion at the site?
361.12 If the assumptions of Davis (p. 2R-C-3, PSAR, vol. 2A) that the 1872 (USGS) earthquake "..almost certainly occurred within the North American plate...."
and that "the hypothesized Olympic-Wallowa lineament is not an expression of a fundamental change in crustal character..." (p. 2R C-4, PSAR, vol. 2A) are correct, what is the justification for limiting the maximum magnitude earthquake within 100 km of the site to approximately magnitude 6?
. 361.13 A great amount of geological and seismological data has been
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collected that is pertinent to evaluation of ground motion at the site.
If these cata were integrated into one or more possible tectonic models and these models were then used in a probabilistic analysis of ground motion, how would the ground motion at the site be affected? As an example, in the report " Factors Influencing Seismic Exposure of the Southeast Washington Region" prepared by Woodward-Clyde Consultants for WPPSS, how would the levels of ground motion estimated at the site in this report be affected by the following parameter changes:
a) Modeling of the recently recorded seismicity near the site
("Recent Seismicity of the Hanford Region', Woodward-Clyde Consultants report for WPPSS) as discrete seismic sources rather than " random sources" and estimating maximum magnitude within these discrete sources according to several viable, but alternate, tectonic hypotheses.
b)
Increasing the maximum magnitude of an earthquake in " random source" to an 1872 type earthquake to account for the possibility of a large event in this area, c) Throughout the area, developing seismic source zones for probabilistic modeling through the consideration of several different tectonic hypotheses. For example, Sengor, Burke and Dewey (1978) have hypo-thesized "impactogens", rifts striking at high angles to orogenic belts behind an active subduction zone that accommodate both extensional and transucurrent crustal movements. The example they use is the Graben. Another possible example. night be regional right lateral linea-ments and faults zones existing in central and southern Oregon (Lawrence, l
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. 1976). These lineaments might possibly be considered analogous to the Olympic-Wallowa lineament, as they are in the same regional tectonic framework.
361.14 Provide a discussion on any correlation of historic and recent earthquake activities and tectonic structures within the Columbia Plateau Tectonic Province.
If any correlation exists, determine if an earthquake larger than that of the maximum historical earthquake should be assumed to occur on these structures. Provide supporting evidences. Compare the ground motion (including peaks and response spectra) from these potential earth-quakes to the SSE and actual design used.
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REFERENCES Lawrence, R.D., 1976, Strike-Slip Faulting Terminates the Basin and Range Province in Oregon, Geological Society of America Bulletin, v. 87, p. 846-850.
Sengor, Celal A.M., Burke, Kevin, and Dewey, John F.,1978, Rifts at High Angles to Orogenic Belts: Tests for their origin and the upper Rhine Graben as an example, American Journal of Science v. 278, p. 24-40.
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