ML20065M856

Special Rept:On 901102,differential Settlement Between Unit Containment & Main Steam Valve House Exceeded TS Value. Caused by Stresses Placed on Piping.Tech Spec Change Request Submitted to Delete Monitoring Requirement

ML20065M856
Person / Time
Site:	North Anna
Issue date:	12/06/1990
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
90-745, NUDOCS 9012110234
Download: ML20065M856 (2)

Text

- _ _ _ _

, VinaINIA EI.ECTHIC ANI) POWER COMPANY

- 1tiennown,Vinaixa encon December 6,1990-U.S. Nuclear Regulatory Commission Serial No. 90 745 1 Attention: Document Control Desk NAPS /RCS/rcs '

Washington, D.C. 20555 Docket No. 50-339 License No. NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 2 DIFFERENTIAL SETTLEMENT BETWEEN THE UNIT 2 CONTAINMENT AND THE UNIT 2 MAIN STEAM VALVE HOUSE On November 2,1990, the differential settlement between the Unit 2 containment (survey point 131) and the Unit 2 main steam valve house (survey point 124), specified in Table 3.7 5 of Technical Specification 3.7.12.1, was confirmed to have exceeded 75 percent of the allowable value of 0.030 feet. The differential settlement between survey points 131 and 124, calculated during the performance of Periodic Test I PT-112, " Category I Structures - Settlement Monitoring", on November 2,1990 was 0.025 feet, or 83 percent of 0.030 feet. There is no difference in the differential settlement between points 131 and 124 measured on November 2,1990 and that measured on May 30,1990, the date of the last previous performance of 1 PT-112. This special report is submitted pursuant to the requirements of Technical Specification 3.7.12.1.

The bases for monitoring the differential settlement-between the Unit 2 containment and the Unit 2 main steam valve house are the stresses placed on the main steam, feedwater, service water, and condenser air ejector piping. These lines possess adequate flexibility to absorb 0.030 feet of differential settlement as described in earlier special reports, Serial No. 09 540, submitted July 28,1989 and Serial No.90-385, submitted June 29,1990. Both the July 1989 submittal and the June 1990 submittals were the result of survey points 131 and 124 exceeding 75 percent of 0.030 feet differont!al settlement based on results of differential settlemert surveys conducted in R y 1989 and May 1990, respectively.

On October 2,1989, Virginia Electric and Power Company submitted a technical specification change request (Serial No.89-682) which proposed the deletion of the requirement to mo'11 tor survey points 131= and 124 along with other rock founded structures. Technical Report," Evaluation of Settlement Monitoring Program for Main

' Plant Structures in Sapport of Proposed Changes to Technical Specification 3/4.7.12,"

which was Attachmer t 4 to this October 1989 submittal, provides the technical basis for deletion of the requimment to monitor these and other points, ggk21ggggggeog8%37 IE2_2_

e rm p p

l' l:

' Based on the above, the structural Integrity of the piping represented by points 131 and 124 has not been compromised. -This special report has been reviewed by the Station Nuclear Safety and Operating Committes.-

.Should you have any questions regarding this report, please contact us.

'L '

Very

, truly

.- yl

/ Q" .

W. L. Ste art '

Senior V ce President Nuclear l .

cc: U.S. Nuclear Regulatory Commission

. Region ll 101 Marietta Street, N.W.

-Suite 2900.

Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station l

1

- , , .- . _ , , , . , . . . . ,