ML17238A719

Letter Regarding Dresden Nuclear Power Station Unit 3 - Concerning a Drift Beyond the Limits of Accuracy in the Calibration of a High Reactor Pressure Scram Switch

ML17238A719
Person / Time
Site:	Dresden
Issue date:	07/25/1972
From:	Worden W Commonwealth Edison Co
To:	Bloch E US Atomic Energy Commission (AEC)
References
Download: ML17238A719 (1)

Text

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~JU \*JSH TLXA244 ~*JAF157Ci'510)(1-017243C207)PD 07/25/72 .14'54 res IPMJLIA JOL ZCZC 183 BJ PD TDJ( MORRIS ILL 25 218P CDT PMS EDWARD J BLOCH ACT DIR DIRECTORATE OF LICENSING U S ATOMIC ENERGY COMM WASHDC 20545 SUBJ DPR-25 DRESDEN .NUtLEAR POWER STATION UNIT 3 THIS IS TO GONFIRM A CONVERSATION WITH MR H DANCE OF YOUR OFFICE AT 1345 BOURS IBIS DATE CONCERNING A DRIFT BEYOND THE LIMITS OF INSTRUMENT  ;

ACCURACY IN THE CALIBRATION OF A HIGH RE~CTOR ~RESSURE SCRAM SWITCH THAT RESULTED IN A SET POINT BEYOND THAT ALLOWED IN SECTION 3.1 OF THE TECHNICAL SPECIFICATIONS.

DURING RETINE CAL1~RATION ON JULY 18 1972 SWITCH PS-3-263-55A WAS FOUND SET AT A VALUE CORRE'SPONDING TO 1075 PSIG COMPARED TO THE LIMITS OF 1060 PSIG INCREASING. TBE SWITCH, A MELETRON, ~ODEL 372-6SS-49A, WAS IMMEDIATELY ~ECALIBRATED AND AN INVESTIGATION WAS BEGUN TO DETERMINE.

THE CAUSE OF THE DRIFT.

• A ~EVIEW OF THE CALIBRATION HISTORY OF THESE S~ITCHES SHOWED A TENDENCY FOR THE SET POiNT TQ DRIFT UPWARD DURING THE SUMMtR MONTHS **

AND DOWNWARDNIN TRE WINTER MONTHS.

UNTIL IRE CAUSE OF TRIS BEHAVIOR IS DISCOVERED THE SWITCHES WCLL BE

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CALIBRATED MONTHLY DURING THE SUMMER MONTES. A FURTHER ~NVESTIGATION WILL BE BEGUN TO DETERMINE THE CAUSE OF TRIS SET POI.NT SHIFT .AND WILL .

BE REPORTED AS RQUIRED BY SEC 6.B.2 *OF THE TECHNICAL SPECIF'IC.DiTIONS~

VP WPDEM S/PT DRESDEN NUCLEAR POWER*STATION.

540P EDT USA EC HQS GTW N *

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