ML20084U478

LER BFAO-50-260/763W:on 760412,fire Reed Relay Failures Discovered.Caused by Failed Contacts.Voltage Monitoring Circuit Will Be Added to Rod Sequence Control Sys & Rod Withdrawal Prohibit Circuit Added

ML20084U478
Person / Time
Site:	Browns Ferry
Issue date:	05/12/1976
From:	Fox H TENNESSEE VALLEY AUTHORITY
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
LER-BFAO-50-260-763, NUDOCS 8306290065
Download: ML20084U478 (3)

Text

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p O LICENSEE EVENT REPOR CONTROL BLOCK:l l l l l l l (PLEASE PRINT ALL REQUIRED INFORMATION) 1 6 Avt LCENSE NUMBER E T PE Oi Llt IB lR lF l214l lo Io l-I ol ol ol ol ol-lo loj l4 l1 ItItItl lo Ii l 7 89 15 25 26 30 31 3P CAttcony "I7pU r EE occutt HuusEn EvtNr oArt AEPORT DATE ECON i l l*1 Loj [L_j lol5lol-lol216lol 1014ltl2l7161 l l l l l l l 7 8 57 59 59- 60 61 68 69 74 75 80 EVENT DESCRIPis0N ,

@ ;Diring RMCS retesting, five reed relay failures were discovered, four of which would l 7 89 80 S{ l permit the sequential selection and withdrawal of adiacent control rods when in tha l 7 o9 80 h ! REFUEL inode. and one of which would allow two < nntrol rode to ha ufcharnun  !

7 H9 80 gg l simultaneously in all but shutdown mode of operation. (BFAo-50-260/ 763W) l 7 89 80

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' CNE CIO[ COMPONENf' c0DE MANuF votAtoN Q dj (_BJ l R l E l Ll Al Yl X] [NJ l Cl 3l 4l 5l lN_,)

7 O9 10 11 12 17 43 44 47 48 CAUSE DESCRipT;ON DE l Failed contacts on C. P. Claire reed relays (model MR4Mc-1023) l 7 89 83 UE I l 7 8g 80 i

l 1 sta s  % POWER OTHER STA?dS DSC VERY - OrSCOVE Av OESCA@ TON y l ol ol 0l l NA l d45 l NA l 7 8 9 10 12 13 44 46 80 h 3E AMOUNT OF ACTMTV LOCATCN OF RELEASE E

7 0 0 dE Or $t 111 10 m I 44 45 I n 80 l

PERSONNEL EXPOSURES NUVBEA fvPE DESCAPTCN Q l0 l0 l0 l @

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PE4SONNEL INJURIES NUME*En ClSCR PTCN H I ol ol of I n l 7 89 11 12 60 0FFSITE CONSEQUENCES NA (IE I l 7 89 80 LOSG OR OAMAGE TO FACILITY TVN DESCR#?CN u LzJ 7 89 10 l n 80 l

FUOLCT'l DE I m l 7 60 80 AD3ITIONAL FACTORS hl SEE ATTACHMENT j

7 89 80 8306290065 760512 i

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ADDCK 05000260 PDR J

ec NAME. PHCNE:

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l ADDITIONAL FACTURS ,

Simultaneous withdrawal of two control rods require the following conditions coinci-dentally:

1. Control rod with the failed (contacts closed) reed relay relected first, and

a. In the startup and run modes, the second control rod must be selected within the first 0.4 second of the withdrawal cycle of the first control rod, or

b. In the refuel mode, there is no time ristraint in selecting and withdrawing the second control rod.

Sequential withdrawal of two adjacent control rods requires:

1. Control rod with the failed (contacts open) reed relay selected and withdrawn, it is then possible to select and withdraw a secced adjacent control rod, without a time restraint.

To correct this problem, a voltage monitoring circuit will be added to the RSCS and a rod withdrawal prohibit circuit will be added to the RMCS on all units. Defective reed relays were replaced and proper circuit functions verified.

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Q Q TENNESSEE VALLEY Ah0RITY

$ CHATTANOOGA, TENNEOcEE 07401

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MAY1419765 2 Mr. !!orutn C. Moscley, Director U.C. Nuclear EcJulatory Co d ssion ( u.s.

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EcGion II /f 230 reachtree atreet, IM.,- 5th Floor  %

Atlanta, Georgia 30303 ~ N Doar In'. Moseley:

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THUTE38EB Ypm AUT.iCRITY - B205m3 FuhY UUCImR FIAIIT U11IT 2 -

DOCl27 1:0. 50-2c - JACILI'I' cit 2A'HilG LICHISE D2R ABIDINAL OccUnanicE TBFAc-50-250/763W

' Die enclosed report in to provido details concerning five reed relay failurca 1.hich voro discovered during RIES rotesting and is succitted in accordanco with A;pendi:c E to EcGulator/ Guido 1.15, Revision 4, August IVls. 'dlis event occurrod on Erovns Airry Euc1 car Plant unit 2.

Very truly yours, TZtCEESEE VALLEY AITHIORITY

- . H. S. Fox I

1. ' Director of Power Pn> duction

• O Enclosure (3) .

CC (Diclosuro):

Director (3) -

' Ofnco or IAnacemnt Inforniion and Progra::1 Control U.S. Ituelcar Reculatory Co:ssinaion Washincton,DCf20M5 nn cctor (40) <

Offico or Inspection and D1torce:ent U.S.1;ticlear Regulatory Cotuission f Waabington, DC .'.X. )555

, 4887 l

An Equal Opportunity Employer i wt*1 titXr IQXi10N t -

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