ML17238A720

Letter Regarding Drift Beyond the Limit of Accuracy in the Calibration So Some of the Low Electro Hydraulic (EHC) Oil Pressure Scram Switches

ML17238A720
Person / Time
Site:	Dresden
Issue date:	07/24/1972
From:	Worden W Commonwealth Edison Co
To:	Bloch E US Atomic Energy Commission (AEC)
References
Download: ML17238A720 (1)

Text

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• . SSF234 EAWA Q NND166 CCH 206NN305166)PD W U TELEX JOL ORIBP EDt0?/24/72 ..**~egula.t,orY file Cy.

• ZCZC 002 NA PDF TDJL MORR IS ILL 24 *42op CDT ED'r/ARD G BLOCH-ACTING DIR DIRECTORATE- OF LICENCY U S ATOMIC COMM liJASHDC 20545

• BT SUBJECT DPR19 AND DPR 25 DRESDEN ~UCLEAR POWER SlATIO~

UNITS 2 AND ,3.. . ..

T iU S 1iJI LL C0 NF I RM C0 NV ER SAT I ON AT I 5 : ,<, 0 !': 0 UR S T E I S DATE

~!ITH MR ):{ D!\MPE OF YOUR OFF I CE REGARD I NG DR I FT BEYOND T!*(E LIMIT OF INSTRUMENT ACCVHACY,° IN TnE CALIBRATION SO SOME OF THE LOl.*1 ELECTRO HYDR/'!ULIC CONTROL CE/'.!C) OIL PRESSURE SCR-AM

$'.)ITCHES, BUT RESULTED IN SET POI NT BEYOND THOSE ALLO\-!ED IN SECT I 0 N :~

• 1 0 F TE CF: NI CA I.. SPEC I F I Cf\ T I ON

• DURING ROUTINE CALIBRATION JULY 15 1972 THE SWITCHES WERE FOUND SET AT VALUES AANGING FROM q66PSIG TO P85PSIG COMPARED TO LIMIT TO 900 PSIG DECREASING, ~ND INVOLVED TWO SWITCHES ON UMIT 2 AND ALL FOUR S\:JITCHES ON UNIT *3. THE SVITCHES, B~.RKSD.~LE MODEL TC9622-3 '*VERE H1Mt:DIATELY RECf\LIBRtHED ANO fiN .

INVESTIGATION Wf\S REGLIN T0.DETERM1NE THE CAUSE OF THE DRIFT.

INSPECTION OF THE Sv!ITCi-! INTERNAL HEVL~LED NO APPARANT ARMORf*JAL n* I ES. A REV I E'.1 OF A CAL I RRA fI_ON HI ST ORY OF TJ1ESE S11JITCl!ES SlW\)ED A TENDANCY TO DRIFT !JUT* NOT BEYOND THE LIMITS. IN ADDITION Tf.iE CALIBR/HION PlWCEDURE lr.'AS

_REVIEWED AND FOU~D TO BE SATISFACTORY.

TJlf. CAUSE OF T:ns LARGE SET POINT c::fl\NGE IS UNEXPLAfNED AND BECAUSE OF TRE PAST TENDENCY OF TUESE S\ITCHES to DRIFT .SOME\-!.HAT, urEY 1o'!ILL BE CALIBRATED NEXT MOMTlt RtHHER THAN JUST *FUNCTIONALLY CHECKED AS REQUIRED BY THE TEC~NICAL SPECIFICATION W P WORDEN SUPT *DRESDEN NUCLEAR STATION NNNNCOR25P EDT)

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1215A EDT USAEC MQS GHIN 40G8.(

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