ML20084S278

Ro:On 730303,while Conducting Calibr Checks,Barton Differential Pressure Switch on LPCI Sys Loop Selection Logic Found Damaged.Caused by Damaged Internal micro-switch During Locking Device Installation.Switch Replaced

ML20084S278
Person / Time
Site:	Dresden
Issue date:	03/30/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S282	List: ML20084S278 ML20084S283
References
252-73, NUDOCS 8306160428
Download: ML20084S278 (2)

Text

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• C H I C A G O, I L L I N o t s 6 0.6 9 0 WPW Ltr.#252-73 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 g March 30, 1973 /

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{ J.i Mr. A. Giambusso 2 gpg3 1973* ~--'

Deputy Director for Reactor Projects US-l$!:f[

h#CI 11 Directorate of Licensing 4 # p U. S. Atomic Energy Commission Washington, D. C. 20545 m ,

SUBJECT:

LICENSE DPR-25, DRESDEM NUCLEAR POWER STATION, UNIT 3, SECTION 6.6.C.1 0F THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This is to report a condition relating to the operation of the unit in which on March 3,1973, a Barton dif ferential pressure switch on the Low Pressure Coolant Injection, LPCI, system loop selection logic was found damaged.

PROBLEM AND INVESTIGATION While conducting calibration checks following a modification to the Barton pressure switches, which added a locking device to the calibra-tion adjustments, a damaged switch was discovered. Barton switch 3-261-35D, which monitors the differential pressure across thu 3B recirculation pump and sets up the logic for the LPCI system loop selection circuitry, had jammed in the closed position.

l An investigation revealed that a micro-switch internal to the Barton switch was inadvertently damaged during the locking device instal-i lation. It is believed the close proximity of the locking device to the micro-switch may have contributed to the inadvertant damaging of the micro-ewitch.

The differential pressure switches for the LPCI injection loop select circuitry, shown on P&ID M-357, are arranged in a one-out-of-two twice logic array. It would have required the failure of two differential pressure switches to disable the "B" loop injection logic. Since the switch failure did not render the "B" loop inoperable and the redundant "A" loop i

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! was available, the safety function of the LPCI system was not jeopardized.

8306160428 730330 b' ) O f j l PDR ADOCK 05000249 fn S PDR 2177

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Mr. A. Gitm' so March 30, 1973 CORRECTIVE ACTION Since the micro-switch is believed to have been inadvertantly damaged during the locking device installation, the corrective action was to replace and calibrate the damaged Barton switch. In addition, all the other Barton pressure switches on both Units 2 and 3 have been recalibrated af ter the locking device installation to insure proper switch operation.

Sincerely, kO . . Mw W. P. Worden Sitperintendent WPW:do cc: WPW Ltr. File u

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