ML20086A048

Special Rept:On 911029,differential Settlement Between Containment & Main Steam Valve House Exceeded 75% of Allowable Value of 0.030 Ft.Ts Change Request Submitted on 911002 to Delete Monitoring Survey Points 131 & 124

ML20086A048
Person / Time
Site:	North Anna
Issue date:	11/12/1991
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
91-664, NUDOCS 9111180212
Download: ML20086A048 (2)

Text

I ,, q VIRGINIA ELECTRIC AND POWER COMPANY RICIIMOND, VIRGINIA 23261 Ncvember 12, 1991 U.S. Nuclear Regulatory Commission Serial No.: 91-664 Attention: Document Control Desk NAPS /MJB

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

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT NO. 2 DIFFERENTIAL SETTLEMENT BETWEEN THE UNIT 2 CONTAINMENT AND THE UNIT 2 MAIN STEAM VALVE HOUSE On October 29, 1991, 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, as defined by survey, was confirmed to have exceeded 75 percent of the allowable value of 0.030 feet. A Deviation Report was prepared based on preliminary data on October 14,1991. The differential settlement between survey points 131 and 124, calculated during the performance of Periodic Test 1 PT-112, " Category 1 Structures - Settlement Survey",

was 0.025 feet, or 83 percent of 0.030 feet. During the last performance of 1-PT-112 on April 24,1991, the differential settlement between these two points was 0.015 feet.

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. 89 540, submitted July 28,1989, Serial No.90-385, submitted June 29,1990, and Serial No.90-745, submitted December 6,1990. The July 1989 submittal, June 1990 submittal, and the December 1990 submittal wers the results of survey points 131 and 124 exceeding 75 percent of 0.030 feet differential settlement based on results of differential settlement surveys conducted in May 1989, June 1990, and November 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 monitor survey points 131 and 124 along with other rock founded structures. Technical Report, " Evaluation of Settlement Monitoring Programs for Main Plant Structures in Support of Proposed Changes to Technical Specification 3/4.7,12,"

9111180212 911112 PDR ADoct 05000339 "0l

(\

i h

b PDR-

which was Attachment 4 to this October 1989 submittal, provides the technical bases for deletion of the requirement to monitor these and other points, h Based upon the above, the structuralintegrity of the piping represented by points 131 l and 124 has not been compromised. This special report has been reviewed by the Station Nuclear Safety and Operating Committee.

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

1 Very truly yours, i

(

p }  ;.}

?L W. L. Stewart

! Senior Vice President - Nuclear l

cc: U.S. Nuclear regulatory Commission Region ll 1 101 Marietta Street, N.W. l Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser

, NRC Resident inspector North Anna Power Station i

i l

t ,

- -- , , , ,