ML20084S172

Ro:On 730409,during Surveillance Insp of Main Steam Line Low Pressure Switches,Set Point for Barksdale Switch 3-261-30A Found to Have Drifted.Cause Not Stated.Switch Setting Reset. Switch Type Under Investigation by Manufacturer

ML20084S172
Person / Time
Site:	Dresden
Issue date:	04/17/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S175	List: ML20084S172 ML20084S200
References
308-73, NUDOCS 8306160199
Download: ML20084S172 (2)

Text

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O O 50-249 f Commonwealth Edison Company ONE FIRST NATIONAL PLAZA ilt C H I C A G O. ILLtNOtt Addreu E.pfr to post o e ric e so m re r

• cnic Ao o. ILilN OIS 40p9 0 ende Nuclear Power Station p Morris, Illinois 60450 g5 .k WPW Ltr. #308-73 April 17, 1973 *

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ig. hFR191973.:.- c Mr. A. Giambusso N@,'8 '" [

Deputy Director for Reactor Projects \.h yf9- f J Directorate of Licensing $e,.

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U. S. Atomic Ehergy Cornission h(V

, Washington, D.C. 20545

SUBJECT:

LICENSE DPR 25. DRESDDI NUCLEAR PC'ER STATION. UNIT #3.

SECTION 6.6.B.3 CF THE TECHNICAL SFECIFICATIONS.

Dear Mr. Giambusso:

This is to report a condition relatine to the operatien of the unit in which on April 9,1973, a rain steam line pressure switch setting was found to have drifted. Pressure switch PSIr-3-261-30A was fourd tripping at 816 PSI which is below the Technical Specification limit of 850 PSI as described in Secticn 3.2.a.

PROBLFM AND INVESTIGATION During a surveilla ,ce inspection of the main steam line low pressure switches the set point for Barksdale switch 3-261-30A was found to have drifted to 816 PSI. The switch had been previously set at 871 PSI. The purpose of the pressure switch is to sense a drop in pressure due to a break in,a main steam line, and initiate a ereup I isolation. The electrical arrangement for

. le{,,] 3 a group I isolation initiation from a main steam line break is s. one-out-of-two-M twice logic. Therefore, it wenld have required two switch failures to prevent J an isolation at 850 PSI.

M{m UT Had a main steam line break occurred while the pressure setting of 3f the PSL-3-261-30A switch was 816 PSI all the main steam isolation valves would Ip have closed at 850 PSI. Thus, the failure of switch 3-261-30A did not present a hazard to the public safety since an isolation would have occurred at 850 PSI as designed.

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.- c o O CORRECTIVE ACTION ThePSI.

setting to 872 imediate corrective action was to reset the pressure switch The PSL-3-261-30A switch will be replaced prior to the unit startup

'29,1972). due to its failure history (Reference our letter dated December In addition, this switch type is presently under investigation by the manufacturer ard the Station Instrument Department to determine the cause of set point drift. Findings of the investigatien will dictate future corrective actions.

Sincerely, y A 1.l k i W. P. Werden

• Superintendent WPW:TL:jw cc: WPW Ltr. File 0

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