ML19254F414
| ML19254F414 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 10/29/1979 |
| From: | Lefevre H Office of Nuclear Reactor Regulation |
| To: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19254F415 | List: |
| References | |
| NUDOCS 7911090257 | |
| Download: ML19254F414 (4) | |
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UNITED STATES f f y v, c ' g g
NUCLEAR REGULATORY COMMISSION
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C WASHINGTON, D. C. 20555 j
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g 29 99 MEMORANDUM FOR:
Robert E. Jackson, Chief Geosciences Branch, DSS THRU:
Leon Reiter, Section Leader k/ ~
Geology and Seismology Section Geoscien us Branch, DSS FROM:
Harold E. Lefovre, Geologist Geology and Seismology Section Geosciences Branch, DSS
SUBJECT:
GECLCGIC FEATURES IN THE SERVICE SP!LL'.!AY AREA 0F THE.4A.; CAM - WCLF CREEK GEHERATI:?3 STATIO:1 UNIT I (STN 50-482)
On Tuesday afternoon, September 25, 1979, C. R. Oberg (NRC I&E Region IV) notified H. Lefevre (NRC staff Geologist, Wolf Creek) that faulting had bet.n identified in the excavation for the Service Spillway of the Main Dam for the Wolf Creek Generating Station. The Service Spillway (a non-safety related structure) is located approximately 3 miles south of the main plar' area.
Mr. Oberg had been informed by the applicant's(Kansas Gas and Elr ric Company's (KG&E) geologic consultants, Dames and Moore, that the.aulting was similar in age (at least 280 million years old) and mode of deformation (during or shortly after deposition of the original sediments) to that previous observed and reported upon by NRC staff geologists in 1977 and 1978. The earlier faulting had been observed in the Power Block area and in the Outlet Tunnel area of the Main Dam. Mr. Oberg was further informed by Dames and Moore personnel that Mr. Frank W. Wilson of the Kansas Geological Survey had been contacted by Dames and Moore and would visit the site the following day, September 26, 1979.
H. Lefevre contacted Mr. Wilson later in the afternoon of September 25, and confirmed that he would be making a site visit on September 2ti.
It should be noted that Mr. Wilson is quite familar with the site and regional geology and has visited the Wolf Creek facility on several occasions both on State matters as well as with NRC geologists. Mr. Wilson is considered by the NRC staff to be well qualified to coment upon geologic conditions observed at the site.
1 04 351 7 91100 0 h
OCT 2 9 m79 Rcbert E. Jackson Discussion with F. Wilson, Xansas Geolooical Survey, Sect. 27, 1979 At approximatelf 1:00 a.m., Thursday, September 27, 1979, b. Lefere (NRC staff) cortacted Frank Wilson regarding his observations of the previous day at the Service Spillway area of the Wolf Creek site. Mr.
Wilson indicated that he had examined a shale exposure containing a thin (8") coal bed where two types of features were visible - (1) shear zones with minor displacements (about 2 inches) and (2) zones where snale appeared to have been " injected" through the coal bed. Mr. Wilsen stated that the features are localized, die out within a few inches of their ends, and are overlain and underlain by undisturbed strata. According to Mr. Wilson these features, like those cbserved in the power block area in 1977 (MRC-Kansas. Geological Survey site visit) and in the Main Dam area in 1978 (observ'.J Loth by the NRC and F. Wilson) are penecontemporaneous (formed during the Pennsylvanian time more than 280 million years ago) and were not caused by tectonic activity. Mr. Wilson indicated that he would submit the report.of his observations to the NRC. This September 27, 1979 report has been received and is appended to this memorandum.
Mr. C. Oberg of NRC Region IV was informed on the same day at 11:30 a.m.
regarding F. Wilson's observations and conclusions.
Discussions with Acolicant's Geolooic Consultants F. Wilson's September 27,.1979 letter mentions a " pop-up" relief structure in the non-Category I Service Spillway excavation. According to Mr. Wilson this feature has an amplitude and width of 2-3 inches, an estimated length of 15-20 feet and a strike of about NSO W.
Mr. Wilson is uncertain of the origin of the " pop-up" but mentions three possible causes:
(1) air slaking of the uncovered shale, (2) local stress, or (3) regional stress.
Subsequent staff conversations with Dames and Moore (geologic consultants to the applicant) on October 12,17,18 and 19 revealed the following:
1304 352
CCT 2 s 1979 Robert E. Jackson
_3_
1.
The " pop-up" is 12. feet long and is confined to the central portion of the Service Spillway. The amplitude and width are as described by F. Wilson. to further movement was detected following Mr. Wilson's observations.
2.
The '.' pop-up" occurs along a portion of the 60 ft. long 0.1" wide sub-vertical sandstone dike within the Ireland Member of the Penn-sylvanian Lawrence Formation.
3.
The " pop-up" occurred sametime between opening of the excavation on September 21 an< 3eptember 26, the time of F. Wilson's site visit.
4.
The Ireland Member projected northward underlies the power block at a depth of at least MO fi..
5.
Undisturbed sandy sbale beds were traced across the sand dike where exposed in the excavation walls to the northwest and southeast of the
" pop-up" with no disruption or offset.
6.
Neither '.' pop-ups" nor sand dikes have been obserhed elsewhere within the excavations at the Wolf Creek site.
7.
Vertical holes drilled at various locations throughout the site area (Power Block, the ESWS Pump House, and.in the Main Dam area) for the purpose of. pre-splitting of an excavation face. prior to blasting remained undeformed after opening of the excavation, thus indicating an absence of observable stress affecting the bedrock.
Conclusions The shear and injection features expcsed in the Service Spillway area of the Main Dam, some 3 miles south of the power block area, are not capable within the maning of Appendix A to 10 CFR Part 100 and consequently pose no hazard to the Wolf Creek facility. The Service Spi.llway features, like those observed in 1977 and 1978 by NRC geologists, are clearly old (greater than 280 million years) and.are confined to small zones within the Pennsylvanian age Lawrence Formation. The features are clearly localized since neither overlying nor underlying strata have been disturbcd.
Thesmallpop-upobservedintheflooroftheSerhiceSpillwayexcavation occurred within.a few days of opening of the excavation. No similar features have been observed in other excavations within the Wolf. Creek site. No wall dislocations resulting from excessive stress have been detected at the site. Based upon the localization of the " pop-up" at a non-safety-related location about 3 miles from the Power Block area, confinement to a geologic 1304 353
OCT 29 679 Robert E. Jackson 4-unit stratigraphically at least 140 feet below the Power Block area, and an absence of similar structure within other portions of the site area, the NRC staff concludes that the mechanism causing the " pop up" poses no hazard to the safety-related structures at the Wolf Creek Generating Station. The NRC staff concludes that the feature.is most likely the result of stress relief (rebound) resulting from excavation within the Ireland Member of the Pennsylvanian Lawrence Formation combined with the discontinuity caused by the thin sand dike within an otherwise essentially homogeneous shale medium.
WO b
.,4fofW Harold E. Lefevre, Geologist Geology and Seismology Section Geosciences Branch Divisien of Systems Safety
Attachment:
As stated cc: w/ attachment
- 0. Eisenhut W. Gammill J. Knight
- 0. Parr E. Licitra E. O'Donnell L. Reiter H. Lefevre J. Greeves F. Wilson, Kansar Geol. Survey C. Oberg, Region IV S. Lewis R. G. Ryan POR Local POR ACRS (17) 1304 354