ML20151R134

Ro:On 880607,differential Settlement Between Svc Bldg & Main Steam Valve House Exceeded 75% of Allowable Value.Effect of Four Buried Svc Water Header Lines Running Between Two Structures of Primary Concern.Tech Spec Change Requested

ML20151R134
Person / Time
Site:	North Anna
Issue date:	08/05/1988
From:	Cruden D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
88-475, NUDOCS 8808120062
Download: ML20151R134 (2)

Text

-

L/

Vinoisi A Ih.ecruic Ann Pownu COMPANY l Ittennoxn, Vinoixr A 20061 l

August 5, 1988 D.N.Carpaw Vsta Punnspant-Nectuaa United States Nuclear Regulatory Commission Serial No.88-475 Attention: Document Control Desk NAPS /DEQ/deq Washington, D. C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AN_D_&

DIFFERENTIAL SETTLEMENT BETWEEN THE SERVICE BUILDING AND THE UNIT 2 MAIN STEAM VALVE HOUSE On June 7,1988, the differential settlement between the Service Building and the Unit 2 Main Steam Valve House (MSVH) was confirmed to exceed 75 percent of the allowable value, 0.03 feet, specified in Table 3.7-5 of Technical Specification 3.7.12.1. The differential settlement calculated during the performance of 1-PT-ll2, Category I Structures - Settlement Monitoring was 0.027 feet. Tnis 60 day Special Report is being submitted pursuant to the requirements of Technical Specification 3.7.12.1.

The primary concern of the differential settlement between the Service Building and the Unit 2 MSVH is the effect on the four buried service water header lines running between the two structures. The code allowable stress in the service water lines is 45,000 psi. This was explained in the Engineering Analysis attached to the Special Report submitted to you on August 14, 1987.

A Technical Specification change request was submitted on March 10, 1988, which would changa the allowable value of the differential settlement between the Service Building and the Unit 2 MSVH from 0.03 feet to 0.047 feet. This value, 0.047 feet, corresponds to a stress of 44,176 psi in the service water lines, which is still below the code allowable stress of 45,000 psi.

Approval of this Technical Specification change would mean that the 75 percent reportable threshold would increase to 0.035 feet and additional reviews would only be initiated when there is a significant concern. The differential settlement of 0.027 feet is less than 75 percent of the proposed allowable differential settlement value of 0.047 and therefore, has cosed no impact on the struc+. ural integrity of the service water lines.

Y 8808120062 880805 PDR S

ADOCK 05000339 lD PDC

The differential settlemeat between the Service Building and the Unit 2 MSVH will be monitored monthly, until the Technical Specification change has been approved, to confirm that there is no trend of increasirig differential settlement. Further reports will not be submitted if 75 percent of the present Technical Specification allowable limit is exceeded during the next six months, since this condition is considered to be addressed by this report.

Vgytrulyyours, b

o. S. O cc: U.S. Nuclear Regulatory Commission 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. J. L. Caldwell NRC Resident Inspector North Anna Power Station i

_