ML20213E029
| ML20213E029 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/03/1982 |
| From: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| To: | Knight J Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0451, CON-WNP-451, CON-WPN-451 NUDOCS 8203090261 | |
| Download: ML20213E029 (4) | |
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.g MEMORAUDUM FOR:
James P. Knight, Assistant Director for Components and Structures Engineering, DE kjBggl i
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Robert E. Jackson, Chief
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Geosciences Branch, DE 1
SUBJECT:
U"P-2 REVIEW STATUS l'
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My menorandum of 23 January,1932, provided a sumary of 5 outstanding issues concerning the geology and seismology of the UMP-2 site. In that
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meno I indicated that a follow-up meno which would include a nore detailed 4
j discussion of the subelenents to these 5 issues, plus the new DOE report.
The following sections includd a discussion of the more specific aspects 4
l of the issues.
l A.
Cle Elum - Hallula Fault Zone (CLEU) l 1.
The oeologic boundary of CLEU (a laroe zone that the staff has assumed i
to be capable since the CP stage) is in question. The boundary of this zone i
which was delineated by the applicant on topographic maps in answer to 0350.14 telexed to them on Novenber 20, and received at URC in January, if:2 appears to be sormwhat arbitrarily drawn with respect to known topographic featuras and structurcs assuned to be related to the zone. An examination j
of Landsat inagery of the region revealed a rectilinear feature 90 kn long that is subparallel to CLEU, but intersects it at its southeast end at Hallula Cap. It does not appear to us to be a coincident alignnent of three separate geonorphic features as reported by the applicant.
4 Three factors suggest that the Cold Creek Lineanent could be a fault:
a.
The abrupt, continuous color contrast onthe false-color Iandsat
- image, b.
An apparent cast-dipping planar surface where the linear crosses the eastern end of Umtanum Ridge as observed on aerial photographs.
Anapparenthydrologicbarrierhasbeendetectedalonahisljnear c.
by Rockwell and reported in their ST-5 report (Pg. III-103).
The importance of resolving the nature of the Cold Creek Linea ent lies in its proxinity to the UMP 2 site. The applicant has placed the closest approach of the CLEU structure at a snall 7 km long f ault near the crest of Dattlesnake Mt. about 19 km from the site.
If the Cold Creek Lineanent is a fault, it probably should be considered as part of the CLEU. Such a deternination would bring the closest approach of CLEW to about 11.5 km from the site. This could have a significant icpact on ground notion estinates for -the site.
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Capability of CLEll flone of the exposed faults within the CLEW zone of deformation can be shown to be non-capable within Appendix A to 10 CFR 100 on bhe basis of the overlying sediments which cap the faults.
The Wallula Gap fault, exposed across the river fron Van Sycle and Warr.
Spring Canyons has fault segments which offset older colluvium but are capped by unfaulted 13,000 year old glacial deposits jIn other locations these fault segments are expressed as young-appearing scarps.
The Yellepit trench indicates that the fault present there is capped by the unfaulted Kennewick fanglomerate, the age of which was originally reported as 55,000 years old, but subsequently changed by the anplicant to 21,000 years old. Although a mathematical correction was nade in February,1901, the t!RC was not informed until it appeared in Amendnent 18 of the FSAD. in October, 1981. Only in response to Q350.15 (received December 20, ISG1) did it becoae clear that the evidence at Yellepit could not preclude capability of the Wallula Gap Fault.
At Finley Quarry, nultiple novements are apparent in three reverse f aults within a span of 40 ft. The largest fault juxtaposes two basalts that normally are separated by at least 90 noters of other basalt flows betteen them. Two of the faults are capped by unfaulted gracels that are dated by caliche rinds of 70,000 to 250,000 years old. The largest fault is only covered with unfaulted Holocene colluvium and loess ( 13,000 years). There-fore, the 500,000 year Appendix A criteria for multiple movenent has not been met.
In addition, a linear feature on the alluvial f an along the base of Rattlesnake Ridge about 13 kn northwest of the site, which was observed by the staff and its consultant during the site visit last Decerber, appears to be a young fault. This feature is also located within the CLEU zone.
A document received en January 29 (ST-142) from Rockwell interprets this linear as a normal fault on the flank of Rattlesnake ridw. Unless more precise age dating of the faults is obtained, the Cl.EW probably will be assumed to be capable for about 140 km, with its nearest boundary possibly located about 11.5kkm from the site.
3.
Segmentation The applicant interprets the CLEU as a segmented zone of snall, discontinuous f aults, and determines estinates of potential earthquake magnitudes based on these lengths. As an example, the chain of small doubly-plunging anticlines that appear to be the southeastern continuation of Cattlesnake Ridge, have I
short faults nepped at their northeast side. According to the applicant, the l
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I i also infomed of this fact by the Applicant on Febrtiary 1,1992. The age and proximity to the surface of these faults is not known by us.
Because of the recent receipt of this document, the Staff has not had an opportunity to study it or to assess its significance. To the best of our knowledge, it has not been reviewed by the applicant.
D.. The expected ground motion from faults and geologic structures which have been fcund to be capable remains in question. The tuo significant geologic structures are the RAW segment of CLEW and Gable flountain - South-east Anticline. The applicant has completed estinatep assuming a !>6.5 event occurred on CLEll,19.5 kn from the site and a i1=5.0 on Gable l'ountain, 15 km from the site.
These events do not exceed the design of the plant.
However, as discussed above, the closest aprroach of the CLEU and the signi-ficance of the southeast atticline are still in question. Dependino on the outcorne of these issues, the applicants assumptions may not be valid.
For example,'if the closest approach of CLEU is assuued to be 11.5 km, potential exceedances above the present design are possible. The same may hold true for the Southeast Anticline. The resolution of the groundnotion issue depends upon the resolution of the above geologic issues.
E.
The staff has identified an issue regarding the it, 6.1 site specific
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response (Q3Gl.17} which at present is. unresolved. The site specific spectrun response spectrum uns received for review on January 18, 1902. This issue involves the shear velocity profile which the applicant has assuned for the LdP-2 site (the geotechnical engineer is also involved with this). There is a sharp shear velocity contrast at a depth of 100 feet belou the site.
The recording sites chosen by the applicant for the site specific spectrun do not match that shear vel 0 city contrast. The applicant states that the shear velocity decreases at a depth of 250 feet. This is questiened by the staff geotechnical engineer. This issue could be significant because it could alter the selection cf strong notion records chosen for the site specific spectrum develep.r.cnt. The present site specific spectrum is for a f1, = G.1 at a distance of about IC km.
It is about equal to the design of the plaht. This issue could be resolved in a ceeting with the applicant depending upon discussions and infomation relating to the shear velocity profile assuned for the site and how the site conditions of the strong notion sites chosen for the site specific spectrum conf &rm to that profile. In addition, the Staff needs three sensitivity tests provided on the present site specific spectrun. These tests will help the staff resolve other open issues. These tests are:
a) Run the site specific saectrum (SSP) leaving out one of the two recordings at San Juan Bautista overpass, b) Run the SSP achieving a nea1 rupture distance of 11.5 kn.
c) Run the SSP achieving a nean rupture distance of 15 km.
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/ DISTRIBUTION:.JOCKET FILE FGSB RDG Also the applicant is preinring a discussion of the nagnitude of the n = G.1 i
event. They nay take the position that an P, = 6.1 is not correct and that this event was actually smaller. This may Peduce the l's = 6.1 assuned fcr the site specific spectrum. In addition, the response to question 3G1.17, regarding the association of this carthquake with a north trending fault (possibly Hite fault).seems to contradict the applicant's position in the FSAR (section 2.5.2.3.3).which states that no association has been made between the source of the 1936 event and a specific structure of fault. This apparent l
l contradiction needs to be c1 cared up by the applicant.
F.
The ground motion from near field swam earthquakIs renains open. The applicant states in response to question 361.16 that they are still doing vork in order to answer the staff questions. The response to Q3G1.16 was received for review by the staff on January 13,19C2. They need to infom use of j!
when this response will be received, as well as their position on the significance of this issue with resocct to the seismic desinn adequacy of the plant.
l In order to nake progress in resolving the open issues, we have scheduled a meeting with the applicant for February 10, 1932 in order to allow the applicant to present any other infomation available on the open issues as ecl1 as comit-I nents on documentation. We propose the following two approaches in order of preference with regard to the Ui:P-2 SER schedule.
1.
Delay the Geosciences SER input. This would allow the IT.C reviewers and the applicant time to review the new infomation, espeddelly the extensive studies in ST-14. liew questions may be generated by this review. It is also cpparent that the need for further f
field investigation including mapping, trenching and diilling nay be necessary to resolve these issues. The benefit of this approach is that a SER input with few or no open issues nay be issoc '.
The disadvantage is that the SER input is delayed.
2.
Issue our SER input in tine for the issuance of the SER on !' arch 12, 1982. Such an SER is likely to have significant open issues, because l
of the inadequacies of the applicants current geological and seisnological studies.
l Robert E. Jackson, Chief Geosciences Branch Division of Engineering l
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