ML20084U098

Telecopy Ro:On 720718,during Routine Calibr,Switch PS-3-263-55A Found Set at Value Beyond Limits of Instrument Accuracy.Switch Recalibr.Investigation Underway

ML20084U098
Person / Time
Site:	Dresden
Issue date:	07/25/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084U094	List: ML20084U093 ML20084U098
References
NUDOCS 8306270051
Download: ML20084U098 (1)

Text

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PMS BOYCE mIER DIR FDIVN OF COMPLIANCE REGION 3 US ATOMIC ENGY COMM 799 ROOSEVELT RD GLEN ELLYN ILL 60137 SUBJECTJ DPR-25 DRESDEN NUCLEAR POWER STATION UNIT 3 THIS IS TO CONFIRM A CONVERSATION WITH MR H DANCE OF YOUR OFFICE AT 1345 HOURS THIS DATE CONCERNING A DRIFT BEYOND THE LIMITS ,-

0F INSTRUMENT ACCURACY IN THE CALIBRATION OF A HIGH REACTOR s 2 'I' E PRESSURE SCRAM SWITCH THAT RESLLTED IN A SET POINT BE _.

ALLOVED IN SECTION 3 10F THE TECHNICAL SPECIFICATIONS.

DURING ROUTINE CALIBRATION ON JULY 18 1972 SWITCH PS-3-263-55A WAS FOUND SET AT A VALUE CORRESPONDING TO 1075 PSIG COMPARED TO THE sr.miLIMITS met OFJUL1060 PSIG INCREASINGING. THE SWITCH, A MELETRON, MODEL 2 81977 u _m_ -

372-oSSd49A, WAS IMMEDIATELY RECALIBRATED AND A INVESTIGATION WASBEGUN TO DETERMINE THE CAUSE OF THE DRIFT.

A REVIEW OF THE CALIBRATION HISTORY OF THESE SWITCHES SHOWED A TENDEN CY FOR THE SET POINT TO DRIFT UPUARD DURING THE SUMMER MONTHER AND DOWNWARD IN THE WINTERMONTHS.

UtRIL THE CAUSE OF THIS BEHAVIOR IS DISCOVERED THE SWITCHES WILL BE CALIBRATED MONTHLY DURING THE SUMMER MONTHS. A FURTHER INVESTIGATION WILL BE BEGUN TO DETERMINE THE CAUSE OF THIS SET PINT SHIFT AND VILL BE REPORTED AS RECUIRED BY SEC 6.B.2 0F THE TECHNICAL SPECIFICATIONS.

W P WORDEN SUPT DRESDEN NUCLEAR POWER STATION.

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