ML20235J724

Submits Responses to NRC 870820 Request for Addl Info Re Settlement Monitoring Program.Encl Proprietary Sketch SK-2-C-330 Provides Plan View of Major Power Block Structures.Sketch Withheld

ML20235J724
Person / Time
Site:	Vogtle
Issue date:	09/22/1987
From:	Bailey J GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20235J726	List: ML20235J724 ML20266J887
References
GN-1398, NUDOCS 8710020069
Download: ML20235J724 (7)

Text

• Georgja Fbwer Company

• Post O$ce Box W,2 Waynesboro, Georgia 30830 Telephone 404 554-9961 404 724 8114

n. s Southern Company Services, Inc.

Post Office Box 2625 Birmingham, Alabama 35202 h

Telephone 205 870-6011 VOgtle Project September 22, 1987 U. S. Nuclear Regulatory Commission Attn: Document Control Desk File: X7BC35 Washington, D.C. 20555 Log: GN-1398 Ref: 1) Letter GN-1368, Dated May 22, 1987

2) Letter dated August 20, 1987, M. A. Miller to J. P. O'Reilly NRC DOCKET NUMBERS 50-424 and 50-425 i OPERATING LICENSE NPF-68 CONSTRUCTION PERMIT NUMBER CPPR-109 V0GTLE ELECTRIC GENERATING PLANT - UNITS 1 AND 2 SETTLEMENT MONITORING PROGRAM Gentlemen:

In regard to the above Reference 2 request for additional information,  ;

we are providing the following responses:

Request 1(a)

In view of Georgia Power Company's (GPC's) previous (September, 1986) commitment to continue settlement monitoring through the first year following issuance of an operating license for Unit 2 at a frequency of approximately 60-day intervals, justify the recent (May 22, 1987) proposal to change the monitoring frequency on 71 markers from 60-day intervals to 6-month intervals by providing more complete information and evaluation than that given in the May 22, 1987, letter.

Specifically:

Provide a detailed drawing showing only the affected markers, and the location, type and amount of loading (such as structures, equipment, backfill, etc.) that are yet to be imposed and that are likely to cause additional settlement of structures.

Response

e p$ Attached Sketch S K-2-C- 330 provides a plan view of the major power block structures and shows those markers whose frequency is proposed ylA o to be changed from 60-day intervals to 6-month intervals. Also mo delineated on the sketch are the remaining areas to be backfilled, o, including their depth and associated loads. Placement of structural concrete and equipment is essentially complete. However, some j[E t ey < oms to Fite s SOM

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, a U. S. Nuclear Regulatory Commission September 22, 1987 r Settlement Monitoring Program Page Two File: X7BC35 Log: GN-1398 L

structures, such as tanks, will have additional hydrostatic loads applied when they are filled with water, and the fuel pools will have additional loads due to spent fuel assemblies, Unit 2 racks, and water. These loads, their locations, and their forecast date of application are provie,a on the sketch.

Request 1(b) {

Provide a discussion (with sketches where necessary) to show whether the locations of the affected markers are within the zone of influence of the expected future loading, and identify any markers (out of the 71 markers) that may be recording time-dependent slow consolidation settlements referred to in SSER 4, dated December, 1986.

Response

As was noted above, with the exception of some minor local areas to be backfilled and tanks and other equipment to be filled with water, the placement of structural concrete, major equipment, and catecory 1 backfill is virtually complete for both Units 1 and 2. No significant additional settlement of the markers is anticipated due to the remaining loads. Of the markers being considered for a 6-month reading frequency, only the Control Building - Tunnel 2T4A/4B interface (Markers 268/269) and the markers in the Fuel Handling Building area are close enough to future loading areas to see the influence of the loads to be applied.

It is anticipated that any such influence near the tunnels will be minor and that the influence on the differential between Markers 268 and 269 will be negligible.

It is also anticipated that the additional localized water loads in the Fuel Handling Building will have little affect on the markers in trat area. The Fuel Handing Building basemat has settled approximately 2-inches to-date. The total load to be applied is approximately 12,000 kips or 0.72 KSF. The gross static loading pressure for the Fuel Building will be approximately 8.1 KSF. Therefore, the loads to be applied represent about 8.9 percent of the total applied load.

Assuming a linear relationship between applied loads and settlement '

to-date, the Fuel Building would settle an additional 0.2 inches.

However, the expectt, additional settlement would actually be less since much of the Fuel Handling Building settlement to-date is the resul t of loads applied by adjacent structures and backfilling. It should also be noted that the portion of the load applied from the fuel assemblies (approximately 3,600 kips or 30 percent of the total future load) will be applied over a period of several years. Based on the above, it is concluded that the future settlement of the Fuel Handling Building will be adequately monitored by readings made at 6-month intervals.

U. S. Nuclear Regulatory Commission September 22, 1987 Settlement Monitoring Program Page Three File: X7BC35 Log: GN-1398 The date when each structure was complete is provided on Sketch SK-2-C-330 and is based on the date by which at least 97 percent of the concrete has been placed. It can be seen that, for Unit 1, the placement of - structural concrete has been essentially complete since late 1984 although some work continued until mid-1985. Unit 2 structures

.have been essentially complete since late 1986 although some work continued until mid-1987. Heavy equipment (excluding water) is typically installed prior to a structure's completion.

Backfill adjacent to Unit 1 structures has been essentially complete since mid-1986. The last major Unit 1 areas to be backfilled were on. the south and southeast portions of the power block. Backfill adjacent to Unit 2 structures has been essentially complete since the beginning of 1987, although some isolated areas remain as described above. The last major Unit 2 areas to be completed were on the south and southwest portions of the power block. Some minor backfilling also occurred near the Turbine Building.

The 71 markers for which a reading frequency of 6-months is proposed were chosen because -their settlement record indicated that they had leveled off to the extent that changes within a 6-month period were i negligible. This. can be seen by reviewing the settlement graphs transmitted per Reference 1. SER Section 2.5.4.4.3 states that ". . .the 60-day interval between readings [has been] spaced close enough to properly monitor the slow consolidation settlements." While some consolidation settlement (the vertical component of the volume decrease resulting from pore' water being squeezed out of clay) is to be expected, this is not of concern because these settlements will be small and occur over a long pe riod ~ of time. FSAR Section 2.5.4.10.2 (Page 2.5.4-28) states:

" Total settlements include both elastic and consolidation settlements of the marl stratum and elastic settlements of the sand backfill and the lower sand stratum. Due to the highly reconsolidated nature of the marl stratum, the consolidation settlements are small compared to the elastic settlements'."

Based on the above discussion and, more importantly, the settlement records themselves, it is concluded that a 6-month reading frequency is spaced close enough to properly monitor the 71 markers under review.

Request 2 Identify the settlement markers reported to be subsequently placed in the same general area as Markers 308 and 310 that GPC proposes to discontinue reading (refer to GPC's letter of August 3, 1987). Show the location of these unidentified markers in the drawing requested I above.

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U; S. Nuclear Regulatory Commission September 22, 1987 Settlement Monitoring Program Page Four

' File: X7BC35 Log: GN-1398

Response

Sketch SK-2-C-330 shows the location of Markers 308 and 310 and indicates they are located close to Marker- No.101. These markers were installed

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subsequent to the erosion which occurred in the power block in 1979.

They were installed at the initiative of GPC construction and were not requested by engineering or the NRC personnel _ present at the time.

They were not located in areas where erosion had occurred. They are not a part 'of the original settlement marker scheme; but because their readings were submitted to NRC at the time of the erosion, we are informing you of our proposal.to discontinue reading them.

Request 3 While GPC had stated in response to Q241.19 that some addition, subtraction and . relocation of settlement markers might occur, GPC's letters dated May 22, 1987, and August 3, 1987, indicate that approximately 100 of the original 175 markers at the site are proposed

.to be relocated. Confirm that the correlation of new settlement readings with the original settlement readings (including Marker 235 already relocated) will be checked and certified to be correct by qualified engineers.

. Response The revised locations of the relocated markers will be reviewed by engineering to verify that the new locations are consistent with the plan view locations of the original markers. The elevations of the relocated markers will be established by a double run in both the forward and backward direction from the original markers using the standards for . first-order Class II leveling. The resulting settlement data will be reviewed by qualified engineers to ensure no anomalies exist in the settlement pattern. Any significant changes in the settlement pattern of the relocated markers will be investigated by engineering to determine if the change is' related to the marker relocation. The original markers will not be destroyed or disturbed and will, therefore, be available should any future correlation be required.

Should your staff require further information, please inquire.

Sincerely, 1

J. A. Bailey Project Licensing Manager JAB /KWK/jc Enclosures (Drawings listed in Appendix A)

U. S. Nuclear Regulatory Commission September 22, 1987 Settlement Monitoring Program Page Five l File: X7BC35 Log: GN-1398 xc: J. P. O'Reilly R. E. Conway l P. D. Rice L. T. Gucwa R. A. Thomas J. E. Joiner, Esquire B. W. Churchill, Esquire M. A. Miller (2)

G. Bockhold, Jr.

NRC Regional Administrator NRC Resident Inspector R. Goddard, Esquire D. Feig R. W. McManus Vogtle Project File l

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