ML20084S288

Ro:On 730108,switches DPIS 3-2352 & 3-2353 for HPCI Sys High Flow Isolation Drifted Above Tech Spec Limit.Cause Unknown.Locking Devices Will Be Installed on Switch Calibr Screws

ML20084S288
Person / Time
Site:	Dresden
Issue date:	01/17/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S289	List: ML20084S288 ML20084S290
References
44-73, NUDOCS 8306160449
Download: ML20084S288 (2)

Text

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. .- .a 2 O O U Ug 50-249 Commonwealth Edison Company 72 WE9T ADAMS STREET

• C H I C A G O, ILLINOIS m . u.ar POST OFFICE SOX 7 4 7

• C H I C A G O, ILLINOIS 40690 Dresden Nuclear Power Station R. R. #1 .

Of Morris, Illinois 60450 f8 O WFW Ltr. #44-73 January 17, 1973 l9N./M k'e)]^ s ll. ] Yfy s -

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r,N n.:.c Mr. A. Giambusso bN s O

Deputy Director for Reactor Projects g Directorate of Licensing i'7 U. S. Atomic Energy Conmission Washington, D.C. 20545

SUBJECT:

LICENSE DPR-95. DRESDEN NUCLEAR POWER STATION._ UNIT #3 __

SECTION 6.6.B.2 0F THE TECHNICAL SPECIFIC ATIONS.

Dear Mr. Giambusso:

This is to report a condition relating to the unit in which, on January 8, 1973, the switches for the High Pressure Coolant Injection System (HPCI) high flow isolation drifted above the Technical Specification limit of a differential pressure of:5150 inches of water. The switches were ic=ediately recalit: ated to ecmply with the Technical Specification limits.

PROBLEM AND INVFSTIGATION The switches are Barton Model #288 differential pressure sensors identified as DPIS 3-2352 and DPIS 3-2353. The history of these switches shows drift in both the increasing and decreasing direction. This drift problem has been investigated and the manufacturers suggested correction is to install locking devices on the calibrating screws to prevent screw movement caused by normal plant vibration. -

The function of DPIS 3-2352 and DPIS 3-2353 is to isolate the HPCI system in the event of a breakage in the HPCI steam supply piping.

Although the switches drifted above the Technical Specifications, they did operate, and in the event of a break in the steam piping would have isolated the HPCI system at 150.5 inches differential pressure. Consequently, we conclude that this slight switch drift presented no safety hazard.

g6260449730is7 8 ADDCM 05000249 PDR 533 i j

o O CORRECTIVE ACTION As mentioned above, the manufacturer of Barton Model #288 switches has been censulted concerning this drift problem, and has made specific recom.cndations as to a corrective action. This corrective '

action consists of' installing locking devices on the switch calibrating screws. The locking devices have been received and are presently being processed through Con:monwealth Edison Quality Assurance. The devices will be installed, after Quality Assurance approval, on all Parton Medel

1. 288 switches and any other switch with similar problems, with an esti-mated completion date of March 1,1973. A follow up study will be per-formed to assure that the locking devices have corrected the drift problem on the Barton Model #288 switches. A follow up letter will be provided upon completion of this study. .

l p Sincerely, j

h. . M6b W. P. Worden WPW:WH:jlw

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cc: WFW Ltr. File O

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