ML20054E835

Advises That Util 820208 Commitments Re Svc Water Pond Structures (SER Item 1.8.20) Acceptable Except for Interpretation of Insp Schedule.Addl Discussion of NRC Bases for Conclusions in Suppl 3 to SER Encl

ML20054E835
Person / Time
Site:	Summer
Issue date:	06/04/1982
From:	Youngblood B Office of Nuclear Reactor Regulation
To:	Nichols T SOUTH CAROLINA ELECTRIC & GAS CO.
References
NUDOCS 8206140315
Download: ML20054E835 (5)

Text

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Decument

Control-(50-395) w NRC PDR L PDR Ji#l NSIC 41982 TERA ACRS (16)

D:cket No.: 50-395 LB#1 Rdg.

MRushbrook Mr. T. C. Nichols, Jr. WKane Senior Vice President-Power Operations Attorney, OELD South Carolina Electric & Gas Company 0IE Post Office Box 764 GLear(2)

Columbia, South Carolina 29218

Subject:

Virgil C. Sunmer Nuclear Station - Service Water Pond Structures SER Item 1.8.20 We have reviewed your letter of February 8,1982 on above subject. We conclude that your commitments to monitor the embankment novements, to survey the sub-merged west embankment siope, and to perform underwater inspection of the intake structure are acceptable.

However, your interpretation of the inspection schedule, is not acceptable.

Since the service water pond was impounded in 1978 without an appropriate inspec-tion progran, none of the above was included in the inspection. An inspection to establish the reference bases should be carried out as soon as practicable.

The date when that inspection takes place should be considered as "the date of impoundment" and the schedule specified in Regulatory Guide 1.127 (or an acceptable alternative to it) should be carried out thereafter, i.e., annual inspections for the next four years. Less frequent inspections may be acceptable if the results of the future inspections warrant such relaxation.

In reading your February 8,1982 letter, we felt there may have been some misunderstanding on your part as to the bases for some of our conclusions in Supplement No. 3 to the Safety Evaluation Report. In the enclosure we have provided for your information some additional discussion of the bases for those conclusions.

Sincerely, originni signed b78

p. J. Ycurgblood.,

B. J. Youngblood, Chief 8206140315 820604 Licensing Branch No. 1 PDR ADOCK 05000395 Division of Licensing E PDR

Enclosure:

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Mr. T. C. Nichols, Jr.

Vice President & Group Executive Nuclear Operations

• South Carolina Electric & Gas Company.

Post Office Box 764 '

Columbia, South Carolina 29218 _,

cc: Mr. Henry Cyrus Senior Vice President ~

South Carolina Public Service Authority '

- 223 North Live Oak Drive

1. Moncks Corner, South Carolina 29461 J. B. Knotts, Jr. , Esq. - -

' Debevoise & Liberman .

- 1200 17th Street, N. W. -

Washington, D. C. 20036 Mr. Mark B. Whitaker, Jr.

Group Manager - Nuclear Engineering & Licensing South Carolina Electric & Gas Company Post Office 764 Columbia, South Carolina 29218 Mr. Brett Allen Bursey Route 1, Box 93C Little Mountain, South Carolina 29076 Resident Inspector / Summer NPS c/o U. S. NRC ~ -

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Route 1, Box 64 Jenkinsville, South Carolina 29065 -

Mr. James P. O'Reilly .

U. S. NRC, Region II 101 Marietta Street Suite 3100 *

_ Atlanta, Geo.rgia 30303 9 e

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Enclosure Staff Review of Applicant's Comments Contained in the Letter to H. Denton from T. Nichols dated February 8, 1982 Factors Contributing to the Structural Settlement

.The staff's bases for concluding that the select fill below the foundation level (El 385.0'), was too wet when placed are:

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1. On-site borrow soils, not selected fill, were used for the west embankment below elevation 386.0' (this is stated on p. 2.5-147 of the FSAR).

2. The allowable compaction moisture content had been modified 'by the applicant from "within 2 percent below and 4 percent above the optimum moisture content" to "within 1 percent below and 6 percent above the optimum moisture content". Weather conditions were cited in the FSAR for causing

. the construction delay and the increased moisture content in the fill. A test fill program was carried out to justify the soil strength aspects of an increase in the moisture content to 6 percent above the optimum (pp.

2.5-86, 146, 146a and 147 of FSAR).

3. The west embankment was raised to El. 390' in August 1973. Block samples taken from the west. embankment during construction showed that the moisture contents of samples taken below El. 385' ranged from 22.9 to 26.9 percent, which is about 5.4 to 9.4 percent above optimum, while samples from the north and south dams were within the specified moisture content limits (see Table 2.5-59 of the FSAR). The service water pond was not filled until 1978.

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Encl'osure 4. The groundwater level prior to reservoir filling was at El. 365' based on -

piezometric readings from WE-6 and 7 taken from September 12 to November 29,

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1977, as shown in the Woodward-Clyde (W-C) Report. The soil moisture contents ranged from 22.0 to 24.0 percent for samples taken between El. 365'

, and El. 380'. The soil moisture content at El. 360', below the groundwater level, showed a range from 24.5 to 26.8 percent, about 2 percent higher than the samples above the groundwater level. We.noted that this noisture

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range is about the same as the block samples shown on FSAR Table 2,5-59,

5. After reservoir filling to El. 425' on March 5,1978, the' groundwater level rose to El. 378.6 on August 18,1978 (see WE-8 and 12 of the W-C October 1979 Report) and was at El. 423' in December of 1980 (see the W-C Report submitted March 6,1981). The soil moisture contents shown in the 1981 report ranged from 24.7 to 28.9 percent between El, 360' and 375', again about 2 percent higher than what is shown in the orange 1977 Gilbert /W-C repo rt.

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Factors Contributing to the Cracking of the Intake Structure The staff's basis for concluding that the thickness of the fill and saprolite is different than that assumed in the settlement analysis is:

Figure 2.5-109 of the FSAR, depicts the intake structure founded across a valley with steep slopes after stripping. Compressible saprolite was assumed not to exist beneath the tunnel according to the orange 1977 Gilbert /W-C re po rt. The most recent borings,14 and 15, indicate that up to 35 feet of saprolite was found to exist below the foundation level about 10 feet north of the intake structure.

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.. .r Enclosure .

The staff's basis for concluding that the more heavily loaded pumphouse would be expected to settle more than the lightly loaded intake structure is:

The applicant's calculation submitted in September 1980 showed that the

.. average load under the pumphouse at El. 367' is 7026 psf while the average load under the tunnel at Sta.1 + 64, where the tunnel connects to the pumphouse, is 5490 psf at El. 367'. The applicant's modified 1980 settlement analysis indicated that the pumphouse should settle about 12 inches while the tunnel, at Sta.1 + 64, should settle 7 inches.

Future Settlements The staff's basis for anticipating potential settlement of structures and embankments and creep of slopes over the plant lifetime is the interpretation of the applicant's docketed laboratory and field data. The staff believes that the applicant's

, additional monitoring program will provide sufficient information to determine whether additional settlement or creep of the west embankment will take place.

Monitoring Requirements The staff's position with' respect to the inspection schedule outlined in Regulatory Guide 1.127 is that an inspection to establish the reference bases should be carried out as soon as practi. cable since the essential service water pond was l impounded in 1978 without an appropriate R.G.1.127 inspection. The date when I that inspection takes place should be considered as "the date of impoundment" and the schedule specified in R.G.1.127 (or an acceptable alternative to it) should be carried out thereafter.

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