ML20248D979

Forwards Request for Addl Info Re Pipe Stresses Due to Differential Settlement Between Svc Bldg & Main Steam Valve House.Responses Should Be Provided in Forthcoming License Amend Request

ML20248D979
Person / Time
Site:	North Anna
Issue date:	08/03/1989
From:	Engle L Office of Nuclear Reactor Regulation
To:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
References
TAC-67985, TAC-67986, NUDOCS 8908110184
Download: ML20248D979 (4)

Text

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. August 3, 1989

? Docket Hos. 50-338 DISTRIBUTION and 50-339 Docket FileM DMiller NRC'8 Tocal PDRs LEngle PDII-2 R/F OGC (info. only)

SVarga, 14/E/4 EJordan, 3302 MNBB Mr. W. R. Cartwright Glainas, 14/H/3 BGrimes, 9/A/2 Vice President - Nuclear HBerkow ACRs (10)

Virginia Electric and Power Company MSinkule, RII .

5000 Dominion Blvd.

l Glen Allen, Virginia 23060

SUBJECT:

PIPE STRESSES DUE TO DIFFERENTIAL SETTLEMENT BETWEEN SERVICE BUILDING AND MAIN STEAM VALVE HOUSE - NORTH ANNA POWER STATION UNITS 1 AND 2 (NA-1&2) REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. 67985 AND 67986)

Our ongoing review of your submittals dated March 10, 1988 and liarch 23, 1989, as well as the Stone and Webster Engineering Corporation Report entitled

" Engineering Pipe Stress Analysis Calculation" dated May 8,1981, has identified a list of comments that require clarification. These comments are provided in the enclosure to this letter.-

Your responses should be provided in your forthcoming license amendment request which addresses the long-term resolution of the subject as noted above.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than 10 respondents; therefore, OMB clearance is not required under P.L. 36-01).

Sincerely, Original signed by:

Leon B. Engle, Project itanager .

Project Directorate 11-2 Division of Reactor Projects-I/II Office of Nuclear Reactor Regulation

Enclosure:

Request for Additional Information cc w/ enclosure:

See next page

[TACfiOS 67985/67986]

LA1,%{I-2 PMdD -c D:PD ?-d DM fler LEngle: bid HBerkow i g 07/p/89 07/3)/89 07/W89 8908110184 890803 PDR ADOCK 05000338 P PDC

Mr. W. R. Cartwright North Anna Power Station Virginia Electric & Power Company Units 1 and 2 cc:

- Mr. William C. Porter, Jr. C. M. G. Buttery, M.D. , M.P.H.

County Administrator Department of Health Louisa County 109 Governor Street P.O. Box 160 Richnend, Virginia - 23219 Louisa, Virginia 23093 Regional Administrator, Region II Michael W. Maupin, Esq. U.S. Nuclear Regulatory Commission Hunton and Williams 101 Marietta Street N.W., Suite 2900 P. O. Box 1535 Atlanta, Georgia 30323 Richmond, Virginia 23212 Mr. W. T. Lough Virginia Corporation Commission Mr. G. E. Kane, Manager Division of Energy Regulation North Anna Power Station P. O. Box 1197 P.O. Box 402 Richmond, Virginia 23209 Mineral, Virginia 23117 Old Dominion Electric Cooperative c/o Executive Vice President Innsbrcok Corporate Center 4222 Cox Road, Suite 102 Glen Allen, Virginia 23060 Mr. W. L. Stewart Senior Vice President - Power Virginia Electric and Power Co.

Post Office Box 26666 Richmond, Virginia 23261 Mr. Patrick A. O' Hare Office of the Attorney General Supreme Court Building 101 North 8th Street Richmond, Virginia 23219 l Senior Resident Inspector North Anna Power Station i U.S. Nuclear Regulatory Commission Route 2 Box 78 Mineral, Virginia 23117

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ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION Review of Pipe Stresses due to Differential Settlement between Service Building and Main Steam Valve House, North Anna Power Station, Units 1 and 2

References:

1. SWEC Report " Engineering Pipe Stress Analysis Calculation," dated May 8,1981.

2.. VEPCo letter dated March 10, 1988.

3. VEPCo letter dated March 23, 1989.

1. The results indicate that the relative displacement of the encased pipes is much larger than that of the o)en pipes (Reference 1, page 488, nodes SC, 25C and 400) although t1e rigidity of the encased pipes is much greater than that of the open pipes. This appears inconsistent and should be explained. It is recognized that the elastic spring assumed for the soil will also control the displacement values.

2. Please provide the following information:

a) The basis for the subgrade coefficient and the anchor stiffness values tssumed in the analysis, b) A layout drawing of the pipe line including the attachments at anchor points.

3. Please justify the use of the formula for a rectangular cross section in computing the soil spring stiffness value for the open pipes.

4. Since it is difficult to accurately estimate the analysis parameters (e.g., soil spring constant, spacing of springs, anchor stiffness), the effect of variation of the parameters should be investigated considering bounding values.

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5. Reference 2 mentions a stress value of 44,176 psi corresponding to a settlement of 0.047 ft. This stress value apparently does not correspond to that computed in Reference 1. This apparent inconsistency may be addressed in the "1981 Report" which is not available at NRC. Please  ;

provide this report and explain the inconsistency.

6. Since a small amount of settlement (e.g., on the order of 1/2 inch) produces a stress value comparable to tha allowable limit, the true relative displacements and the resulting strains should be more carefully l nonitored rather than depending on the survey results of the buildings. j

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l 1 For this small value, the actual relative displacements between two ends of the pipe line may be significantly different than from what are being predicted by the survey results.. It is recognized that some consideration to alternate monitoring methods has been discussed in Reference 3. Hcwever, it(e.g.

is suggested that the

, strain gauges, feasibility etc.) of monitoring be further explored. (by direct fiote that measurement the survey results indicate a higher settlement at point 114 than that at point 117).

7. It is not clear whether VEPCo is requesting removal of the settlenent monitoring requirements in the Technical Specifications for both the old and the new (replacement). pipes or for only the old pipes that have been removed (Reference 2, Attachment 2, first iage, Discussion Section).

This should be clearly stated.

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