ML20084U052

Telecopy Ro:On 720909,two Electrohydraulic Control Low Oil Pressure Scram Switches Found Below Tech Spec Limits & on 720910,control Valve 4 Failed to Indicate Half Scram When Fast Closed.Setpoint Drift Corrected

ML20084U052
Person / Time
Site:	Dresden
Issue date:	09/11/1972
From:	COMMONWEALTH EDISON CO.
To:	Bloch E US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8306270034
Download: ML20084U052 (1)

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TLXA191 LX-W-UA072 HA RELAY (K VEB119) PDB TDVE MORRI9 ILL 09-11 352P CDT EDUARD BLOCH ACTING DIR DIRECTORATE OF LICENSING US ATOMIC ENERGY COMMISSION nASHDC 20545

SUBJECT:

DPR-25 DRESDEN NUCLEAR PO'.t'ER STATION UNIT 3.

THIS WILL CONFIRM A CONVERSATION 9ITH MR F DANCE OF YOUR OFFICE AT !!45 HOURS THIS DATE CONCERT!iUG TWO SEPARATE INCIDEf;TS 09 UNIT 3.

ON 9-9-7E UHILE MAKIN3 A CALLABRATION ON EHC LD'A DIL PRESSURE SCRAM SUITCHES, THE SET POINT' ON TE'O SUITCHES '!AS FOUND BELO',!

THE 900 PSIG TECHNICAL SPECIFICATION LIMITS. P S-1. S - 1 HAD DRIFTED DOWN TO A SET POINT OF E95PSIG. PS-LS-4 HAD DRIFTED EOMN TO A SET POINT OF E!EPF.TG, PS-LS-1 HAS A HISTORY OF DRIFTING SET "0 INT "HILE PS-LS-4 IS A NEV MODEL SUITCH WITH A SUPPOSEDLY GREATER ACCURACY. THE SET POINT ON ALL S*!ITC 'ES HAS Bi?EN INCREASED TO 935PSIG. IN ADDITION A CALL ARR ATION CHECK t'ILL BE i'ADE ON PS-LS-4 ON A UEEKLY BASIS UNTIL THIS PROBLEM OF EXCESSIVE SET POINT DRIFT CAN BE CORRECTED.

THE SECOND INCIDENT OCCURED ON 9-10-72 AT 0300 HOURS. 'e'HILE CONDUCTING TURRINE UEEKl.Y CHECKS NUMBER 4 CONTROL VALUF FAILED TO INDICATE A HALF SCRAM WifEN IT WAS FAST Cl.0 SED. FUSE F5H WAS PULLED TO ACCUATE A HALF SCRAM UNTIL REPAIRS COULD SE COMPLETED.

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