ML17252A990

Letter Reporting a 03/03/1973 Condition Relating to a Barton Differential Pressure Switch on the Low Pressure Coolant Injection System Loop Selection Being Found Damaged - Dresden Unit 3

ML17252A990
Person / Time
Site:	Dresden
Issue date:	03/30/1973
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
WPW Ltr. #252-73
Download: ML17252A990 (2)

Text

50-249 Commonwealth Edison Company

- 7 2 W ES T A DA M S S T R EE T

• C H I CA G 0, I L L I N 0 IS -

Addrus Reply to, POST OFFICE BOX 767 *CHICAGO, ILLINOIS 60690 WPW Ltr.1/252-73 Dresden Nuclear Power Station R. R. 1/1 Morris, Illinois 60450 March 30, 1973 Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. s. Atomic Energy Commission Washington, D. C. 20545

SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT 3, SECTION 6.6.C.l OF 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 differential 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 differentiai pressure across the 3B recirculation pump and sets up the logic for the LPCI system loop selection cir'cul-try, had jaI1D11ed in the closed_ position.

• An investigation revealed that a micro-switch internal to the Barton switch was inadvertently damaged during the locking device instal-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-switch.

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 r~quired 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 was available, the safety function of the LPCI system was not jeopardized.

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~ "' J Since the micro-switch is believed to have beeii,:i~~dve~-.tantly damaged during the locking device installation, the corrective .... .. t ac"'tion 1 was to replace and calibrate ~be damaged Barton switch. In ~d~ion, all the other Barton pressure switches on both Units 2 and 3 have been recalibrated

• after the locking device installation to insure proper switch operation.

Sincerely, W. P. Worden Superintendent

• WPW:do cc: WPW Ltr. File

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