ML20128N378

Forwards Addl Info Re Plans for Settlement Assessment & long-term Settlement Monitoring of safety-related Structures & Piping,Per 850516 Commitment

ML20128N378
Person / Time
Site:	Vogtle
Issue date:	05/21/1985
From:	Bailey J GEORGIA POWER CO.
To:	Adensam E Office of Nuclear Reactor Regulation
References
GN-623, NUDOCS 8506030253
Download: ML20128N378 (3)

Text

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t'*~ ~ GeorgisPower Company -

Rcuta 2. Box 299A -

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W1ynisboro. Georgia 30830

- Telephone 404 554-9961' 404 724-8114 f Southern Company Services,Inc.-

Post Office Box 2625

. Birmingham, Alabama 35202 Telephone 205 870-6011

, May 21, 1985 l.

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Director of Nuclear Reactor' Regulation Log: GN-623

' Attention: Ms. E. G. Adensaa File: X6BK10 Licensing Branch No. 4

' Division.of-Licensing U.S. Nuclear Regulatory Commission l

Washington, D.C. 20555 NRC DOCKET NUMBERS 50-424 AND 50-425

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CONSTRUCTION PERMIT NUMBERS CPPR-108 AND CPPR-109 V0GT E E M CTRIC GENERATING PLANT - UNITS l'AND 2 RESOLUTION OF V0GT2 SETTE)ENT OPEN ITEMS

Dear Mr. Denton:

' During a conference call on May .16, .1985, with members of the NRC staff we

! agreed to supply additional information on our plans for settlement assessment and long-tern settlement monitoring of safety-related structures and piping.

' Enclosed is the additional information requested. If your staff requires further information, please do not hesitate to contact me.

Sincerely, t- .

i J. A. Bailey l Project Licensing Manager l JAB /caa Enclosure

, xc: D. O. Foster ls R. A. Thomas J. E. Joiner, Esquire B. W. - Churchill, Esquire M. A. Miller r

B. Jones, Esquire (W/o Enclosure) '

'L. T. Gucwa G. Bockhold, Jr.

H. H. Gregory, III T. Johnson (W/o Enclosure)

D. C. Teper (W/o Enclosure) \

L. Fowler Vogtle Project File 1 I

[- g, a m

[~ $ 9883 g g PDR

7 ATTACHMENT

1. Assessment of Differential Settlement Effects of Structures An update of total and differential settlements will be provided in a report to NRC staff three months prior to fuel load of Unit 1. The report will include an assessment of the effects of differential settlement on structural stresses if the net slope of the deflection curve (6/L) relative to structural tilt is equal to or greater than 1/670 as calculated from the measured structural settlements. The review to determine the need for such an assessment will be performed for the control building, the auxiliary building and the fuel handling building. These large power block structures contain the number of markers required and the accessibility for a similar review of these structures). The maximum 6/L ratio presented in the responses to Question 241.18 is limited differential settlement which has occurred within safety related structures to date. The containment and NSCW cooling towers are only accessible at their periphery and therefore not suitable to the development of contours and the application of the 1/670 type criteria. The report will, however, include the total and differential settlement for these and all other safety related structures to insure that reasonable settlements are occurring within predicted limits. The level of survey accuracy will also be defined.

It should be noted that the containment and NSCW cooling tower structures are very rigid and will settle as rigid bodies without significant deformation of the mats or superstructures.

2. Review of Total and Differential Settlement In the report to be submitted in Item 1, actual total structure settlements will be compared with the predicted totals in FSAR figure 2.5.4.8. If total predicted settlements are exceeded the settlement analysis will be reevaluated. Actual differential settlements between structures will be compared with those used in design. This will consist primarily of updating the data presented in Table 241.18-1, Differential Settlement for Representative Piping. If future evaluations of the actual differential settlement indicate that 75 percent of the amount used in design has been reached the situation will be reviewed. If it appears that the design differential settlement may be exceeded, the piping will be reanalyzed for an increased differential settlement and/or the supports will be adjusted or modified to satisfy the design requirements.

3. Maintenance of Settlement Markers Throughout the life of the plant important settlement markers which are destroyed or become inaccessible will be replaced with markers as near as possible to their original locations. Important settlement markers will not be deleted from the program nor will their reading frequency _be modified except as provided for in item 4. Important setticment markers are defined as those markers located in safety related structures whose total settlements have exceeded one inch and/or which are needed to continue the determination of differential settlements across a structure or to establish differential settlements at piping penetrations.

As plant construction is finalized some markers may become inaccessible. Wherever possible, these markers will be transferred to new locations and continuous readings provided so that the total settlement of the original marker can be obtained.

4. Settlement Monitoring Frequency and Summaries Settlement monitoring for both units will be continued for important markers (see item 3) through the first year following issuance of operating license for Unit 2 at a frequency interval not to exceed 90 days. At the end of this period, the licensee will provide a brief technical report with supporting settlement data and graphical plots, and an evaluation of the settlement effects which justifies any propcsed reduction in the frequency and number cf markers monitored.

Future plans for continuing the settlement monitoring program will be identified by the licensee at the time of the submittal.

5. Settlement monitoring will be performed immediately af ter any earthquake event equal to or exceeding a free-field acceleration of 1/2 OBE (.06g ). A settienent survey will also be performed if the groundwater level in the power block area drops more than 10 feet below the reference groundwater level in more than one observation well monitoring the backfill. The reference level will be verified through monitoring the observation wells in the power block backfill for a two year period (June 1987).

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