ML19347A931

LER 80-021/03L-0:on 800910,transformer T4 of DG-1 Failed. Transformer Feeds Diesel Oil Immersion Heater & Alarm Relays.Caused by Moveable Armature Located on Immersion Heater Contractor.Armature Repaired

ML19347A931
Person / Time
Site:	Fort Calhoun
Issue date:	09/11/1980
From:	Mueller R OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19347A923	List: ML19347A922 ML19347A931
References
LER-80-021-03L, LER-80-21-3L, NUDOCS 8009300539
Download: ML19347A931 (4)

Text

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RfRC FORM 366 U. S. NUCLEAR REGULATORY COMMIMlUN (7 77)

, LICENSEE EVENT REPORT l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

CONTROL BLOCK: l 1

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10111 7 8 9 l NLICENSEE I E I CODg F l C I S I l l@l 0101010 14 15 LiCENF l0.M8ER l0_l010 l0 l0 25 l026l@l 4! ll TYPE LICENSE ll ll JO l ll@l57 CAT 68 l@

con'T 10111 M l L l@l015101010121815 l@l 0191 68 69 110181 ol@lofol1111plol@

EVENT DATE 74 75 REPORT DATE 80 7 8 60 61 DOCKET NUMSER EVENT DESCRIPTION AND PROBABLE CONSEoVENCES Oio 10121 , Transformer (T4) of DG-1 failed. This transformer feeds the control circuitry for [

the 15 kw diesel oil imersion heater as well as supplying power to alarm relays for 1O lai ! the following items: low lube oil pressure, low lube oil level, hiah and/or low I 10141 I lube oil temperature, water temperature, water level and water pressure. Durino I iO Isi I the time of the transformer failure, DG-2 as well as the 161 kv and 345 kv systems 1 IO te i I were available and operable. In addition. DG-1 was considered inoperable only durind

!O I7I I the time that the transformer and associated eouipment were bei~n o chanaed out, i.e. I i c ie i i only while DG-1 was in " Local Maintenance". 2 I

'E'E #*"o'l CO 500EE COMPONENT CODi SUB E S bDE 10191 7 8 9 l E l E l@ IE l@ l A l@ l Tl RI Al NI S l F l@ lZ l@ l Zi@

10 11 12 13 58 19 20 SEQUENTI AL OCCUR RE NCE REPORT REVISION EVENT vEAR R EPORT NO. CODE TvPE NO.

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@ ,aegRO 18 10 I l-l I o f 2111 l-l 1013l lL l l-l 10l 21 22 23 24 26 27 28 29 30 31 32 K N

• AC O O PL NT M D HOURS S8 i FOR 8. SUPPL M NUFAC RER l3JA l@l34 Zl@ [Lj@

35 IZ 36 l@ 101010101 3, 40 l41 Hl@ lNI@

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43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS IilOII A moveable armature located on the immersion heater cnntactor was lonso nn the olunadr li li 1 I shaft & therefore. causina a slicht bindina orablem nn the enntactnr_ it ie 1 iii2i l oostulated that this bindino of the contactor caused the contactor control trans- I li13i I former to draw excessive current and eventually fail . The moveable armature was re-I ii ,4i I paired and the diesel satisfactorily tested and returned to service. I 80 7 8 9 STA  % POWER OTHER STATUS On O v DISCOVERv QESCRiPTION l i I s l [.E_,J@ l ll 01 Ol@l NA l [Aj@l OPERATOR OBSERVATION 80 l

' ' '2 n - 4s A!nviTv CarENT RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE lileIlZl @ [JJ@l NA l- l NA l

PERSO~~R ExPOSSES

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sVMBER oESCRiPTiON@

li lR l l 010101@L, NA 80 l

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'l li191lZl@l NA 8999300 PU8ETv NRc usE oNLY 12 l O l l Hl i@oESCRiPTiON iSSUEO NA UpS 5 3 o( '\ l 68 69 I l 1 1 l l 1 1 1 1 I l l :i 80 ;;

7 8 9 10

. . Mueller PHON E: dO7 d M -00ll NAM @ @F PR@ PAR @R< _

LER 80-021 Omaha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000285 ATTACHMENT NO. 1 Safety Analysis The Fort Calhoun Station Unit No.1 Engineered Safety Features System is so designed that no single failure can prevent the safe shut-down of the plant if necessary. During the time diesel generator DG-1 was inoperable, diesel generator DG-2 was operable as were the 161 KV and 345 KV supplies thus providing more than adequate capability for safe shutdown of the plant should the unlikely event of an accident occur.

It should be pointed out that DG-1 was considered inoperable only during the time that the transforner was being changed out since this transformer only feeds the oil immersion heater for DG-1 and associated annunciation. Should the need have arisen, DG-1 would still have automatically started per engineered safeguards and performed its design function as described in the Final Safety Analysis Report.

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LER 80-021 Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 ATTACHMENT NO. 2 Corrective Action M.0. #7057 was written to investigate possible causes for the failure of the control transformer. As a result, it was discovered that a moveable armature (moveable in the vertical direction) was loose on the immersion heater contgetor's giunger shaft, thus allowing the armature to rotate from 0 to 360 horizontally with respect to the plunger shaft. Normally, when the contactor is picked up or energized the plunger shaft is drawn vertically via magnetic forces until the armature mates with a designated seating surface on the contactor and correspondingly the main. contacts are completely closed. However, if the armature is allowed to rotate horizontally such that when the annature and plunger shaft are magnetically drawn upwards, the armature does not mate with its designated contactor seating surface; the "esult  !

is armature binding and partial closure of the contact main contacts. l Further the control transformer 5.ill draw excessive amps as it tries to fully close the contactor contacts.

To correct the problem, the armature was secured to the plunger shaft in such a position that proper seating between the armature and armature seating surface of the contact would be achieved.

As a further consequence of this problem, the emaining diesel con-trol panel (DG-2) was inspected for a similar problem. However, the armature shaft was found to be firmly riveted to the plunger shaft. l The failed control transformer was replaced with an electrically i equivalent transformer (See EEAR FC-80-101). Any wires or relays which l may have been damaged by the transformer overheating were also replaced '

with identical equipment. The diesel was satisfactorily tested and returned to service.

No further action is planned or scheduled in conjunction with this event.

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o LER 80-021 2

Omaha Public Power District Fort Calhoun Station Unit No.1 Docket NO. 05000285 ATTACHMENT NO. 3 Faiare Data This is the second failure of this type at the Fort Calhoun Station.

The first being documented per LER 80-014.

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