ML19241A362

LER 79-012/01T-0 on 790618:relay 62x2B/RC1A Failed to Drop Out When Coil Was de-energized.Caused by Notch in Operating Rod.Of 48 Relays inspected,25 Notches Were Found & Removed

ML19241A362
Person / Time
Site:	Three Mile Island
Issue date:	07/06/1979
From:	Stanley W METROPOLITAN EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19241A361	List: ML19241A360 ML19241A362
References
FOIA-81-159 LER-79-012-01T, LER-79-12-1T, NUDOCS 7907180482
Download: ML19241A362 (2)

Text

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July 6, 1979 Three Mile Is11nd Nuclear Station, Unit 1 Docket '.io. 50-239 Attachment to LER 79-12/OlT-0 During .r.spection o f the phcsphor brcnze operating reds cn rela"s s in the Engineered Safeguards Actuation Syste=, relay 62x23/RCIA failed in the energized positicn. The relay did not " drop out" when the coil cas de-energized. The inspection was being conducted to check fer E.ct:hes in operating rods that could possibly result in failure. The failed relay had a notch apprcximately 0.002 inches deep. The failed relay is part of the 2-of-3 coincidence logic for Actuation A, Block 3.

The ec ;cnents affected would be Decay Heat Closed Cooling Pump A and

.;uclear Services Closed Cooling Pump A (or 3). The relay failure would not prevent ec ponent starting but wculd result in a 2-of-2 lo-ic.s Although the individual relay f ai]ure is not eportable by TMI-l Technical Specifications, the event is,being reported in accordance with Technical Specification 2.9.2. A(9) as a potentially generic problem.

31 ilar relays failed and were repcrted in LEE 76-5 2nd 76-16. Two (2) relay failures occurred in 1977 that were ac: reportable. Cne relay failed in January 1979 The failure in Jan . 1979 was attributed to the notch in the operating rod. The other i ar h) failures were attributed to other causes.

The cause for the failure is believed to be che notch on the operating rod; however, the failure =cde has not been pr sitively identified. The notch in the operating rod occurs where the rt 1 ribrates against the magnet assembly due to coil hun. An inspection of L8 relays was conducted.

Twenty-five (25) of the relays had detectable notches ranging frc 0.C01 to 0.003 inches deep. The notches were secothed out using crocus cloth. The remaining relays will be inspected; notches vill be recoved or the Operating rod 2nd magnet assembly will be replaced prior to startup. A charfered

~1gnet assembly is being investigated that would pre'vnt the operating rod frc hanging up cn the magnet assembly.

The failed relay is a GTE Sylvanie, Type FM Eulletin 7:05, Catalog 5U12-ll with a 1207 AC coil.

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f] EVENT DESCRIPTION AND p ACB A SLE CCNSECUENCES h'E 60 61 ;OCK ET NVMf ER ' 69 ENT C ATE 74 75 AEPORT OATE l During inspection of relays in the Engineered Safecuards Actuation Cvstem. I oI2 Individual 1 j o i3] ] relay.62x23/ECIA failed to drop out when the coil was deenercised.

I o 4 l failure not renertable, but is beine retorted rer TS 6.o.9.3/0' " a 1

g ; cotenti ally generic problem. Failed relay would have reduced 2-of-3 coincidence

[O !s l logic to 2-of-2, affectin;; Decay Heat C1csed Cooline Furn A & '!!c 9rvices 1 l CC Pr:n A or 3. Tnis event had no ef fec' cn the nublic healtk or safatv.

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, 7 l Bulletin 7305, Catalog SU12-11 v/120 v.AC Coil. Of L8 relavs subsecuentiv 1

, inspected, 25 notches, 0.001 to 0.003 inches deep, were found L removed.

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