ML20084Q408

Ro:On 731108,isolation Valve on RHR HX B Found Partially Closed W/Stem Uncoupled from Disc.Cause Not Stated.Valve Will Be Disassembled & Insp

ML20084Q408
Person / Time
Site:	Quad Cities
Issue date:	12/04/1973
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084Q404	List: ML20084Q401 ML20084Q408
References
NUDOCS 8306130257
Download: ML20084Q408 (2)

Text

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'?f%  % - - .a q .9 9 J. F. O ' Leary, Director Directorate of Licensing U. S. ATOMIC ENERGY COMMISSION Washington, D. C. 20545

REFERENCE:

Quad-Cities Nuclear Power Station, Unit 2 Docket #50-265, License DPR-30, Appendix A, Section 6.6.B.2.

Dear Mr. O ' Leary:

The purpose of this latter is to report an unusual event concerning the Resi-dual Heat Removal (RHR) Service Water System of Unit 2 at quad-Cities Nuclear Power Station. On November 8,1973, an isolation valve on "B" RHR heat ex-changer was found partially closed with its stem uncoupled from its disc.

This event was discussed with Mr. J. Fishbaugher of the Directorate of Regu- '

latory Operations, Region li t .

PROBLEM AND INVESTIGATION While performing routine surveillance on the RilR service water system it was discovered that M0-2-1001-1o53 would go only. partially closed end stop; however, it could be returned to the open position. This valve is the dwn stream service water Isolation valve for the B RHR system heat exchanger.

Investigations by maintenance personnel subsequently determined that the valve was stuck approximately I 1/2 inches open and the stem was disconnected from the disc. The design of the stem and disc is such that the notched disc slips over a flared stem. However, since there was play in the valve disc as it moved off its seat, the disc fell off the stem when it was approximately 1 1/2 Inches off its seat.

Due to the buildup of deposits on the valve body and disc from river water, it appeared that this situation had existed for some time; however, how long is 1 uncertain.

EVALUATION AND CORRECTIVE ACTION To prevent any future failures of this kind the stem was attached to the disc  ;

by drilling a 1/4 inch hole perpendicular to the disc on either side of the- I disc notch and bolting a 1/4 inch thick strap on either side of the disc over ]

the flared stem. Nuts were tightened and welded to the bolts.

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, s ' ' John F . O ' Leary, Di rector , December 4, 1973 A review of previous surveillance tests showed that the RHR service water pumps which feed the "B" heat exchanger performed satisfactorily and met the Techni-cal Specification requirements of greater than 3570 gpm at 198 psig even though flow was restricted by the M0-2-1001-1853 valve. Followint the repair, both pumps in the "B" residual heat removal loop were started and the M0-2-1001-185B valve was slowly closed manually until the valve was approximately 1 1/2 inches open. At this position 6000 gpm was flowing through the heat exchanger at a pressure greater than 200 psig which further verified the operability of the system at all times.

Although the valve disc was off its stem in a partially closed position for a long time as evidenced by the markings, no limiting conditions for operation were exceeded since all previous surveillance flow tests have been completed satisf actorily with the most recent test being October 24, 1973.

A thorough review of station records indicated that there are five valves of this type in the station; two in Unit I and three in Unit 2. All these valves are used for RhR heat exchanger Isolation and were manufactured by the Ohio injector Co. (0IC) which was subsequently acquired by the Lunkenheimer Valve Co. All of these valves have been checked for disc-stem attachment by attempt-Ing to rotate the stem with the valve in an intermediate position. Since these are gate valves rotation of the stem should not be possible; no abnormalities were detected. Furthermore, one of these valves will be completely disassembled for inspection.

Yours very truly, a- ,

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'~B. B.'Stephenson

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Station Superintendent BBS:RAN/dkp BBS-73-266 cc: Reginal Director Directorate of Regulatory Operations - Region ill

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