ML19331D980

Forwards Description of Fault Zone in Rock Foundation for Unit 1 Control & Diesel Generator Bldgs.Drawing Encl

ML19331D980
Person / Time
Site:	Phipps Bend
Issue date:	08/22/1980
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML19331D981	List: ML19331D980 ML19331D983
References
NUDOCS 8009040484
Download: ML19331D980 (4)

Text

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tCO CheJtnut Street Tcwer II August 22, 1980

er. Harold R. Denton, Director .

Office of Muclear Beactor Regulation U.S. luelear Regulatory Commissien

'!ashin.tten, DC 20555

Dear Mr. Denton:

In the "atter of the Apolication of ) Docket Nes. ST'l 50-553 Tennessee Valey Authority ) ST:I 50-554 In a July 29, 1080, telephone conversatien with the !iRC Eeologist, Dick cMullen, notification was made of discovery of additional faults at our Phipps Send !!uclear Plant in the area of the unit 1 control and diesel generator buildings. Enclosed is a detailed description of these features wnich was provided in the July 20, 1C30, telephone conversation.

We do not consider this minor fault to be cacable trithin the deaning of Appendix A to 10 CPR Part 100.

Very truly yours, TEN!!ESSEE VALLEY AUTHORITY L. M. " ills, Manager Nuclear Regulation and Safety Enclosure 3ool S

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PHIPPS BEND NUCLEAR PLANT Fault Zone In The hock Foundation For The Unit 1 Control And Diesel Generator (Division 1) Buildings Final excavation for the unit 1 control and diesel generator (division 1) buildings has exposed a series of reverse and thrust faults near the dntersection of the two buildings. The faults are described as Fault 23, Fault Zone 24, and Fault 25. (See attached phctographs.)

Fault 23, which intersects station W 1+33 at station N 0+31.5, extends from the west wall of the fuel building eastward, across the excavation (see attached map). The fault, which strikes N. 40 E. and dips 84 SE., truncates the south limb of an overturned anticline. The fault plane is defined by a tight calcite-filled fracture that displays minimal deformation of adjacent beds.

I Fault Zone 24 consists of interconnecting thrust and reverse faults which truncate the north limb of a syncline. The thrust fault, which intersects station W 1+33 at station N 0+18.5, is vertical and strikes N. 49 E. This fault, defined by a tight calcite-filled fracture showing a minimum amounL of deformation of adjacent beds, truncates the north limb of a syncline. At stations N 0+08 and W 1+33, a reverse fault strikes N. 35 E., dips 70 SE.,

and intersects the axis of a syncline. This reverse fault is defined by a tight calcite-filled fracture which shows little deformation of adjacent beds.

Fault 25 is a thrust fault which intersects station S 0+06 at station W 0+85. This fault dips 33 NW. in the north section and 6 SE. in the south

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, section, forming an anticlinal pattern. The fault plane, which strikes N. 51 E.,

is defined by a weathered zone 1 to 3 inches wide with little deformation of adjacent beds.

These are typical faults for the immediate area of the Phipps Bend Nuclear Plant, a'd n represent a continuation of faults already reported to NRC (Fault 3, May 8, 1979).

These faults were formed by stress relief due to tectonic pressure from I

the northwest and southeast during formation of the Saltv111e Fault Family (250 mybp). Having been stable for approximately 250 million years, these faults are not considered to be capable of producing ground offsets or generating earthquakes. Therefore, we do not classify them as capable faults, within the meaning of Appendix A to 10 CFR part 100.

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1 Thrust Fault 25 Located at north end of Unit 1 Control Building. View S