ML20039D592
| ML20039D592 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 05/11/1976 |
| From: | Nagl J OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20039D589 | List: |
| References | |
| RO-50-285-76-17, NUDOCS 8201050239 | |
| Download: ML20039D592 (4) | |
Text
LICENSEE EVENT REPORT 50-285/76-16 CONTROL BLOCK:l l l l l l l
[PLEASE PRINT ALL REIUlAED INFORM ATION 1 6 AME ECENSE NUMDEA 89 I Nle irI ci siil 14 lo lo l-lol ol ol of ol-lo lo l I b l i (111111 YPE TYPE l 0131 15 25 2G 30 31 3?
cATECOAY T7P DOCKU NUMBEA EVENT DATE REPORT DATE
[5E]Cou'l i I LLJ LLJ lo 15 lo 1-1 o 12 i 81 si lo l4121717 I 61 Io15lillIT16 7 8 57 58 59 60 61 68 69 74 75 BC EVENT DESCRIPT!CN o0 l At 1616 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.14888e-4 months <br /> on Acril 27, 1976', the primary air start motor for DG-2 failed to dis-7 89 l 80 03 b:ga~e after DG-2 was successfully started and at loo RPM. The redundant diesel 7 89 l 80
[0}4]
7 89 denerator, DG-1, was started and run to, prove operability; both redundant offsite l 05 00 l power sources, the 161 KV and the 3h5 M vere also operable. (LER 50-285/76-16) 7 89 l 36 l 7 89 l
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- EoE NE COMPONENT CCOE S A MM A VOLATON
@ l El El [A_l 7 89 10 l I l N l S l T) R] U l lAl l Xl 9l 9l 9l [N J 11 12 17 43 44 47 48 CAUSE DESCR;PTION h l""The aircan setting for the magnetic pickup unit for the airpax electronics switching l 80 h l tachometer wa s not set correctly.
7 89 l 1O I 80 7 89 I A US % POWE A OTHEA STATUS DISCO /EAY OfSCOVEAY DESCRIPTON 7 8 QJ 9
l ol 9l~ 8l l, NA l (BJ l Maintenance Test j 10 12 13 44 45 46 . 80 ACTMT Y CCSTEN T F4ELEASED OF PELE ASE AMOUNT OF ACTMTY 8
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L zJ 10 I na 11 44 l i n LOCATON OF AELEASE I
45 80 PERSONNEL EXPOSURES NUMBEA TYPE DESCAtPTON E@] lo Io I o I LzJ l n^
7 89 11 12 13 l 60 PERSONNEL INJURIES NUMBE A DESCAlpTON 14 lo l o l 0 l l NA .
7 89 11 12 ]
60 OFFSTTE CONSEQUENCES !
15 l NA 7 89 l LOSS OR OAMAGE TO FAC.1RY 80 TYPE DESCD9 TON *
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- 7 89 10 l PUBUCITY 17 l NA 7 09 l 00 ,
ADDITIONAL FACTORS O h l See Attachments 1, 2 and 3 l UD f8201050239 ADOCK ofoff} 5 %
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t NAME: John M. Nagl 'd ua pgggg, %W-W
I,1c:ncaa Ev:nt Report 50-285/76-16 Pagt. Two 4
. . Attachment No. 1 l Safety Analys' r
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Even though DG-2 did properly start at 1616 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.14888e-4 months <br /> on April 27,1976, it was administratively deemed inoperable since the primary air start motor failed to disengage at 100 rpm. At 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> DG-1 was started and run to ac=onstrate operability. While DG-2 was inoperable off-site 161 KV power was operable and supplying engineered safeguards buses lA3 and 1A4 with off-site 345 KV power available to buses lA3 and 1A4 should the 161 KV supply fail. In addition, DG-1 would have supplied bus lA3 (DG-2 feeds bus IAb) j had all off-site power been lost. There were no inoperable engineered safe-l guards components associated with bus lA3 while DG-2 .ias inoperable. All requirements of technical. specification 2.7.(2)i were satisfied, plant safety was not jeopardized end no limiting condition for operation was j violated with DG-2 inoperable.
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Licensee Event Report 50-285/76-16 ~
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Attach =ent No. 2 Corrective Action The magnetic sensing unit for the svitching tacho =eter (speed switch) had been removed on April 27, 1976, so that routine =aintenance could be per-formed on DG-2 cir start motors. This sensing unit is in close proxi=ity to the air sta.rt motors and interferes with accessability for air start motor maintenance. After co=pleting =aintenance on the air start motors, DG-2 was started to prove operability. This start was called for by pro-cedure. After sensing 100 rp= the speed switch generates a per=issive signal to disengage the air start =otors. Ecvever, due to the improper air gap setting, the speed switch failed to generate this per=issive and the air start motors consequently did not disengage. The air gap for the magnetic pick up unit was properly set and DG-2 successfully started with proper disengagement of the air start motors at 1710 S ours on April 27, 1976 (see Maintenance Order No. 10918). The error was procedural in that the maintenance procedure did not call for checking the air gap setting whenever the speed sensing unit is re-installed. Hereafter this setting vill be checked.
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' . Licensee Event Report 50-2b5/76-16 .
,',* Page Four l
, Attachment No. 3 ,
Failure Data This is the first occurrence of an improper air gap setting for the speed sensing unit for a diesel generator at the Fort Calhoun Station Unit No. 1.
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, , , , , l During the scnthly lead test of Diesel Generator Nc. 1 the field vent to =aximu= exci-I g,3, ,tation and was shut dev to prevent generator damage. The failure was a result of l yg,,, ; reference :ener dicde drift and probable bus conditions coupled with a positive feed- l 7,,3; ; back dreep c:=pensation. Se dicde vas replaced and the generator current restricted I
,g,gg fcr lead tests when paralleled to the bus. The generator vas retested successfully. I Ic i 71 1 I l3Idl l !
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Of the reference ener dicde and generator characteristics when paralleled jeje gi,3 j [the bus vas the failu e rechanis=. The :ener was reele.ced and airinistrative limits en J
,, , _ , , l parallel bus operation vert: impcsed. Sis is the second related failure. No fu ther I
,, ,3, jaction is anticipated. l ti!ai l I 7 8 9 80 F ACILtTv METHOO CF STATLS % POVsEE OTHER STATUS CIS00VERY CISCOVERY OESCRIPTICN l i i s j l g l@ l n l o l 8 !@l NA l l3I@l46 Su veillance test j 7 8 9 13 12 11 44 45 80 ACT1vtTY CON TENT RELEASED CFAELEASE AMOUNT OF ACTIVITY LOCATION OF AELEASE NA ii is 4! 31: l @ l z!@l 7 10 11 44 l l 45 NA 30 I
8535CNNEL EXPCSuaES NUveEE TYPE C E SCRIPTION li 17 ! 10 ! O 10 !@!Z l@l nA I 7 3 3 ti !? 13 50 PEASONNEL 84JuniES NUV8E4 DESCAiPTICN I li 8 ; l l 010 10 l@l NA I i ) 11 12 %
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LER 78-02k O=aha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000285 ATTACE ENT NO.1 Sa'ety Analysis The Fort Calhoun Station Unit No. 1 Engineered Safety Features Syste=
is so designed that no single failure can prevent the safe shutdown of the plant if required. During the time Diesel Generator No. 1 was inoperable (during repair and testing), Diesel Generator lio. 2 was operable and both the 161 Il and 3h5 El supplies vere available.
During the period of trouble shooting and testing on August 9, 1978, with the exciter manufacturer and subsequent testing on August 30, 1978, as recc== ended by the exciter manufacturer, the following infor=ation was discovered: .
(1) During the initial one hear run which lead to the failure of Diesel Ger.erator No. 1, it was noted the_ generator out-put current centinued to increase t'hroughout the entire run vithout any operator action.
(2) A bench test of the reference cener diode showed continual drift up. This vas the cener which was replaced and reported in IER 78-022. The drift was within =anufacturer tolerance. 'Ihe original diode was the.~sily co=pensated and exhibited a smaller drift, however, this exact replace-
=ent is no longer =anufactured.
(3) At the time the failure occurred, the generstor exciter was approxd -ately at its =axi=u= long time ex1tation 14'40, which was approaching the saturation limits of the machine.
(h) The gener-- A- ;(p ec=pensation is vired to boost cuErent if generator current-increases, rather than a nor=al machine set up for parallel operation on a bus, in which the droop co=pencation tencis to limit current.
Based on the data and info:=ation collected during testing and trouble-shooting Diesel Generator No. 1, the following hardware and procedure changes vere instituted:
(1) The cener diode referenced earlier was changed out to a 5C'4 cener diode to provide g eater stability. "he subsequent test showed the clicde did drift but to a =uch smal' er extent than the 10'4 cener.
3 (2) The generator exciter circuit vas designed to provide naxi-
! -"- cur ent boost in stan ing the Engineered Safety Features Loads. As a result of this , when paralleled to the bus , the i
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C=aha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000235 ATTACI2 ETT NO. 1 (centinued) drcop CT influence on the regulator operation may not be able to be ec=pensated for by a change in terminal voltage on the =achine '(parallel operation vill result in small ter=inal voltage changes with excitation and large current changes or power factor changes). To li=it current output of the generator, administrative centrols have been placed on the machine during parallel operatic to limit the current to below h00 amps at 2500 II (which is away frc= the saturatics region of the
=achine). A ce=putercalar= for the generator has also been provided to alar = at k00 a=ps.
In discussing this problem with the exciter =anufacturer and based on the test data,it has been deter =ined that though. the generator failed when paralleled to the bus, at no time vas it inoperable, if required, to perfer: its design function for Engineered Safety Feature operation.
Ecen the generater is operatec carrfing the ESF loads, after the. initial lead = starting, it vill provide c=1y the current required to maintain the lead.
Acy shift of the excitar circuit vill result in a drift of ter--
=inal voltage and a small drift-(4V/Z) of current, negating the droop cc=pensation effect.
The failure during parallel operation was deter =1=ed to result frc= .
tvo areas; the drift of the cener diode and a small load change on the bus during the generator test.
The cener diede drift and bus condition resulted in the generator being at approxi.-ately the =2xi=um long time excitation limits. Any s=all voltage dec ase or lead increase en the-bus at this time vould have required = ore current out of the generator, resulting in the drcop circuit positive feedback, increasing excitation vith little er no negative feedback frc= the exciter's voltage input.
At this tire '% ~M protection fuses. e vent to =axi=u= excitation and blev the field The generator vas subsequently retested and the current was . limited belev h00 a=ps. No proble=s vere encountered and no further action is anticipated.
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LEI 78-02h 0- aha Public Power District Fort Calhoun Station Unit No. 1 Decket No. 05000285 Al"ACSETI NO. 2 Fail =e Data A previcus failure was reported on LEt 78-022.
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REPORT DATE EVENT DESCRIPTION AND PRC8ABLE CCNSEQUENCES h Io (2 l l During preoperational testing of the ner offsite power lover system, Diesel Generator
, o ,3 ; gNo. 2 failed to auto close ento the bus. Breaker mode switch contacts27-27C failed to I o ! .i I ( =ake contact. Reference Technical Specification Section 2.7.
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7 8 9 SYSTEM CAUSE CAUSE C0v P. VAi v E C00E COCE SUSCOCE COMPCNENT COOE Sudeci SU C CE loist 7 8 II IE l@ l El@ LA_J@ Ic IK IT IB Ir la l@ .LsJ@ l 21 @
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.-EVENT YEA R REPORT NO. CCOE TYPE N O.
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_.21 22 23 24 26 27 28 29 30 - 31 32 ACTION , PUTURE EPPECT SHUTOCwN ATTACHu t NT NPRO4 PRiuf CCup. COMPCNENT TAKEN ACTICN CN PLANT METHCO HOURS 22 SUSMiTTE D FORM WS. SUPPU ER MANUP AC 1.sPER lX ]@l" l@ l25Z l@ lZl@
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.33 34 40 *1 -42 43 a4 CAUSE DESCRIPTION AND CCRRECTIVE ACTICNS Iitoll Contacts27-27C on General Electric svitch =odel vere not making contact. The vires
,, ,,,gwere moved to spare contacts25-25C. The generator was successfully retested. No .
,, ,, y further action is anticipated.
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5T s %PCWER OTHER STATUS 5O RY OtsCCVERY DESCRtP*ICN 32 lt i s i l H l@ l ol o I o l@l NA l l C l@l0PLS Testing (new Installation !
AbvlTV CO TENT r.ELEAst LoCAT:CN cP RELEASE @
l i j s l l Z l @o CP RELEASE AucuNT l Zl@l NAon ACTiviTv l 45 NA @ l SC l
7 a 9 to 11 44 PER$CNNEL EXPCSURES TYPE CESCRIPTICN /
NUM8ER l : j 7 l l o ] o l o l@l Z l@l NA _ l
,E sc~~EL ,~,uns NUveER cEsCRiPTiCN@
1: ntlololol@l 7 8 9 11 12 NA 30 i
LCSS OP OR CAMAGE TO PACluTV Q Tvet C ESCRIPTICN w/
NA I It191IZl@l 7 .3 9 10 so issuto PusuCtTV 3E30RIPTros g,f Q NRC USE CNLY I2ioiIn!@l NA l IiiiilIiiii!l
('a@ % p ) dNAeEg o, y pPaE,AnER 2 G 7 'M. Core /o.Petersonh
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n LIa 78-03S C=aha Public Power District Fcrt Calhoun Station Unit No. 1 Docket No. 05000285 Attachment No. 1 Safety Analysis During testing of the newly installed OPLS syste=, the failure of contacts27-27C en the auto close breaker = ode switch (h3-1/1AD2) vas discovered. Had the mal-function not been discovered during this special test, it vould have been dis-covered during the surveillance testing of the engineered safeguards system per ST-ESF-6.
At the time of the failure, the plant was in a refueling shutdown condition. In addition to the redundant generator, DG-1, which was fully operational,161 and 3k5 K7 power was available frc= off-site. The failure could have occurred during power operations, hence the reasen for i=nediate reporting. The failure was not annunciated since the ala:n is connected to different contacts of the switch.
The problem vas corrected by moving the vires frc= contacts27-27C to spare con-tacts25-25C en the same switch. This problem is considered an isolated case.
Ec Jever, to insure the problem does not occur in the future; positive verifica-tien of contact position and closure vill be made if possible on the six mode s dtches (breaker mode svitches h3-1/1AD1&2, breaker protection = ode switches h3-3/ LAD 1&2, and diesel mode switches h3-1/D1&2) prior to operation above 30C F.
Unless futu e failures dictate ctherwise, no further action is anticipated.
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l 1::R '78-038
- . Omaha Public ?cwer District-l Fort Calhoun Station. Uni No. 1
, Docket No.lo50co285 i
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Attachment No. 2 +
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. - Failure Data t s,.
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This is the first failure of a General Electric model switch at the Fort CaLhoun -t i Station. Unit No. 1. t i +
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LICENSEE EVENT REPORT M t rY)
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, l L Ql 0l 5 l 0 l 0 l 0 l 2 l 8 l 5 l@l 0 l 6 l 1 l 9 l 7 l 8 l@l0 60 61 68 69 EVENT QATE 74 75 l 7 l 013171880l@
HEPORT DATE j 8 DOCK ET NUMBER EVENT DESCRIPTION AND PROS ABLE CONSEQUENCES h
[O l 2 J l During the required ten second start and full load test of Diesel Generator No.1 l gg,3, y prior to plant startup, the generator field failed to reach rated h.16 KV terminal I
,g,,; ; voltage. At the time of failure, Diesel Generator No. 2, the 161 K7 supply and l 3h5 K7 supply were all available.
l 015 I i l 10 j61 I l 10671 1 I l 0 (8 l l l 7 8 9 80 SYSTEM CAUSE CAUSE COVP. VALVE CODE CODE SUSCODE COMPONENT CODE SU8 CODE SUSCODE lo191 7 8 l E I E l@ trLl@ LJ_l@ l C l Kl T l B l K I R lh W@20U @
9 to 11 12 13 18 19
_ SEOV ENTI AL OCCUR R E NCE REPORT R EVISION LE NRO EVENTYEAR REPORT NO, 4 CODE TYPE No.
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_ 21 22 23 24 26 27 28 29 31 32 N 'A C ON PL NT M HOURS S 8MI FO 8. PPLIE MA UF RER Lt_!@lz_J@ L2J@ L2.1@ l 0101 ol o f LLJ@ IUl@ IAl@ 1s1115161@
33 34 35 36 37 40 41 42 43 A4 ' 47 CA tSE DESCRIPTION AND CORRECTIVE ACTIONS h l i l 0 l lOne of the Shovnut 100 emp fuses supplying the generator field was found to have 1 l3 lil l failed. The fuse was replaced and the diesel tested satisfactorily. _
l li 121 l 1 11 131 l I l i 141 1 1 7 8 9 80 SA % POWER CTHER STATUS 015 RY DISCOVERY DESCRIPTION l1 l 5 l l Ol@ l 0l 0 l 0l@l NA l lBl@l Test Prior to Hestur l A ivlTY CO TENT FsELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE lusj lz l @ Lz_l@l 10 NA l I NA 45 80 7 8 9 11 44 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION li171 10 10 10 l@lz l@lNA '
l PE RSo~~E L ,NmLS NUMBER DESCRIPTION I
li ta 8l 101010 7 9 l@l12 11 UA 80 LOSS OF C A DAM AGE TO FACILITY TYPE DESCRIPTION NA l l t I s8 l 9l Z l@l10 7 80 12l0l i<;$UEf@DE A l 33CRIPTION [, ,1, l lllllllllllll%;
NA E P R. Mehaffey/G. Peterson PHONE:
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- LER 78-017 Czaha Public Power District Fort Calboun Station Unit No.1 Docket No. 03000285 Attach =ent No. 1 .
Safety Analysis The Fort Calhoun Station Unit No. 1 electrical distribution system is so designed that no single failure could prevent the safe shutdown of the plant if required.
At * '- a *d e of failure the plant was in a cold shutdown condition. Diesel Generster No. 2, the 161 K7 supply and the 3k5 KV supply were all operable.
The failure to reach terrinal voltage was due to the failure of a 100 a=p fuse in the generator field excitation circuit. The fuse was inspected and shoved no evidence of bleving and appears to have just opened on the protection
=etal strip. The fuse was replaced and the diesel returned to service. This is considered to be an isolated incident and no further action is anticipated.
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.T Iza 78-017 C:::aha Public Fover District Fort Calhoun Station Unit No.1 Docket No. 05000285 Attach =ent No. 2 Failu e Data This is the first failure of this type.
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7 6 60 61 COCKET NUM8ER 68 69 EVENT CATE REPORT DATE EVENT DESCRIPT!oN AND PROBABLE CONSEQUENCES h 10 62, I Transformer (TA) of DG-1 failed. This transformar fed onwer to the diesol's nil im l j o i3 i ; mersion heater as well as alarm circuitry correspondino to the followino items: I IOiA, I Low lube oil oressure. Low lube oil level, and Hich or low lube oil temoeratura. I 10651 i During the time of the transformer (T4) failurec DG-2 as well as the 161KV and 345 KT IOesj i systems were available and operable and would have been more than caoable of niti- l 1067) i gatinc.the circumstances of an accident should. the need arist In addition. .DG 1 I was considereo inoperable only during the time that the transformer was being i068i , changed out, i .e. only while DG-1 was in " local maintenance" l 80 7 8 9 C QE CO E SU OE COMPONENT COCE SUB Cdf SU E l0l9l 7 d l E ! E l@ l E l@ l A l@ lT lR lA lN 15 lF l@ lZ i@ lZ 9 10 11 12 13 18 19 20 l@
SE OUENTI AL OCCURRENCE REPORT REVISION .
LE n sr0 EVENTVEAR REPORT NO. CODE TYPE N O.
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28 29 lL l 30 l-l 31 10]
32 AKc A 10 ON PL T M MOURS 22 58 i O FOR 8. SU PLIER MANUFACT RER l33A l@lZ l@ l35Z l@ lZ l@ l 01 0l 0l l lN l@ lNlg lA l@ lW l1 12 p l@
34 36 33 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS tiiO, l Tre transformer failure was caused by a shorted coil. The transformer was replaced I witn an equivalent component ano suosequently the diesel generator, immersion neater
,siit , ; and all transformer related annunciation circuitry was satisfactorily tested and j
,,,,, [ returned to operation. The replacement transformer although eletrically eouivalent I i, i3; ( was of a different manufacturer. Thus an exact replacement transformer or the transi torner wnicn nas superceaea it will be procurreo anc instajied as soon as time ii iA i i permits. I 7 8 9 80
$A % POWEJt OTHER STATUS 015 O RY CISCOVERY DESCRIPTION Operator Observation Ii i s I l E l@ l 0 l 9 l 8 l@l NA l lAl@l l ACTIVITY CO TENT RELE ASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE NA l l NA l li 168l 9l Zl @ l toZ l@l 7 11 44 45 80 PERSONNEL EXPOSURES NUv9ER TYPE l i 171 l 0 l 0 l 0]@l Z j@lDESCRIPTION - NA l PERSONNEL NJuniES NUYBE R DESCRIPTION
' l i j a t l O ! G l 0 l@l E <
l 7 8 3 11 12 80 LOSS OF OR DAM 4GE TO FACILITY TYPE CE SCRIPTION I
li191lZl@l 7 8 9 10 NA 80 PUBLICITY NRc USE ONLY
- ISSUED DESCRIPTION ' h .
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LER 80-014 Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 ATTACHMENT N0. 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 transformer 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 fur.ction as described in the Final Safety Analysis Report.
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LER No.80-014 Omaha Public Power District Fort Calhoun Station Unit No.1
-Docket No. 05000285 ATTACHMENT NO. 2 Corrective Action M.C. #6421 was written to replace the failed Westinghouse 480/.20, 100 '.'a , Model 2-F-47-1 transformer. Since Westinghouse no longer manu-factures this transformer, (it was superseded by their model .lF0892) and no exact duplicate / spare was available, it was replaced using an equivalent GE 100 Va, 480/120 salt transformer. Upon replacement, the diesel was tested satisfactorily for operation as was all transformer related circuitry and the diesel DG-1 was returned to service.
As a further note, the Westinghouse model 1F0892 transformer which has superseded the failed model 2-F-47-1, and is electrically equivalent or superior to the model 2-F-47-1 has been ordered and will be installed in DG-1 circuitry as soon as procurement allows. -
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LER No.80-014 Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 ATTACHMENT N0. 3 Failure Data This is the first failure of this type at the Fort Calhoun Station.
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4 6J $1 OCCKET NUMSER EVENT DESCRIPTION ANo *RCBABLE CoNSECUENCES lo i:t i At 0850 during the cerformance of ST-ESF-6. F.2. diesel cenerator OG-1 was o-d f~
10 33; I and run to operating soeed. However, the bu :er which tests for DG-l " ready-to-load Io iai 1 within 10 seconds failed to sound within the-prescribed' time limit. Upon subsecuenti io t s! I retesting, the CG-1 diesel generator failed to start upon actuation of channel A I t o is 1 I full speed test switch. As a result of DG-1 failure to start, the redundant diesel I to: 7 l't generator was satisfactorily tested for operability and it was verified that there -I io,ai1 were no associated inoperable safeguards ecuipment. I
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12 61I known. It was costulated that certain relav contacts. switch contacts, etc. mav !
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tiistI diesel was retested and the diesel started and was " ready-to-load" within the cre- I 50 7 s a scribed time limit.
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LER No.80-028 Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000235 Attachment No. 1 Safety Analysis The Fort Calhoun Station Unit No.1 is so designed that no single failure, by itself, can adversely affect the ability of the plant to safely shutdown in the event of an accident. During the time DG-1 failed to start (automatically), the 161ky and 345kv offsite power feeds were energized and available. In addition, the redundant diesel generator CG-2 was verified to be operating correctly and it was further verified that no other engineered safeguards components associated with DG-1 were inoperable. As such, the consequences of an accident would have been more than adequately mitigated had the unlikely event of an accident occurred.
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LER No. S0-028 Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 Attachment No. 2 Corrective Action M.0. #7757 was written to investigate reasons for diesel generator DG-1 failure to start upon the second actuation of the Channel "A" full speed switch, as well as, the failure to get the buzzer, simulating the diesel is ready-to-load, when the ready to load light came on during the first actuation of the Channel "A" full speed test switch. As a result of this maintenance investigation, diesel emergency start circuitry was checked for loose wires, bad or faulty relays, failed or stuck switch contacts, etc. However, the results proved negative in that no probable cause of the diesel failures mentioned above has been positively deter-mi ned. In addition, a diesel air compressor was found to be operating improcerly, but still mainta'.ning adequate pressure to accommodate a diesel start.
After all applicable items had been checked, and found to be in operating order, the diesel generator DG-1 was again tested for operation per the channel "A" full speed test switch. The diesel s.arted ar.d was
" ready-to-load" within the prescribed time limit.
Therefore, the failures of the diesel to start have been undeter-minable.
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e LER No.80-02S Omaha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000285 Attachment No. 3 Failure Data This is the first failure of this type at Fort Calhoun Station Unit No. 1.
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EVENT DESCRIPT!CN AND PROS ASLE CCNSEQUENCES Q lOi2i l Wile atte=rtinz to lead the diesel eenere. tor, DG-2. durine the rerfor-ance of a 1 ioi3"l lspecial 2k-heu- diesel generater test recuired in rescense to II Bulletin 70-21. the 1 IOaA1 l genera:Or field vent to max"- axcitation; therefore, the diesel was shutdec to l l0esl Igrevent generater h M e. The failure was a result of a reference Zener diode drift i I o is 1 I in ehe A-C reculater canel. "he diede vas rerlaced and +he diasel renerster testin: 1 iTIT) I was resumed. Subse:uenetiv 10 heu-s later into the " resumed" test, a radiater tube I leak vas discovered. This leak vas repaired per :sintenance order and the 2L-hr. diesel Iosa1 l test was rest Nted and satisfactorily croleted without fu -her incident . 30 I
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[i47, l test was resumed. Following the diode failure L restart , the diesel was azzin shutdev:1 l i l 3 g l folleving a radiator tube leak which developed during the restarted ran. This leak vas l ii ,4i irepaired and the diesel test resumed without further incident. I 7 Q 3 80 PoCtLITY STATUS % POWER OTHER STATUS Q Q METHOOOP DISCOV E RY DISCOVERY QESCRIPTION 6 lt ( s8 l'l9 H l@ l 01 0l 0l@l N/A ,
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?crt Calhoun Statica Unit No. 1 Oceket 30. 050002S5 Attachnent No. 1 SafeTr Analysis The Fort Cal.kt.:n Stati0n Unit No.1 Ingineered Safety Features Systen is so designed that no single failure can prevent the safe shutdown of the plant if required. During the tine diesel generator CG-2 was inopersble, Diesel Generator No. 1 was operable as vere the 161K7 and 3h5KV supplies thus providing nore than adequate capability for safe shutdown of the plant in the case of an accident.
The reactor van in a refueling shutdovn condition during the tine of this 2h- hour diesel test. Consequently, the technical specification governing diesel generator operability requirenents, technical specification 2.7, vas not applicable.
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_ .. ... .. 2 Corrective Acticn 7 nile initially trying to lead diesel generator DG-2, Onto 3us lAh in er. atte=pt to perfor= the 2k-hour diesel load test, which was required by response to II Eulletin 79-23, it was noticed that the generator field vent
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the diesel generator was shut:10vn and a maintenance order vritten to correct the n.roblem.
The proble= vas found to be a reference zener diode in the A-C regulator
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vith a new diode, and diesel generater 2G-2 operability was restored. Sub-sequently, the diesel generator 2k hour test vas resumed.
Ten hours into the 2k hour test the diesel generatcr 2G-2 vas again shutdown due to increasing ecoling vater te=peratu' es and the correspending .
radiator tube leak which was discovered. A =aintenance orde= vas written to investigate the leakage and repair it. The radiator tube leak vas postulated to have cecurred due to a piece of =etal which may have rich 0chetted off the radiatcr fan blades and punctured the radia:Or fins and tube sheet sufficiently to cause the leakage. Ecvever, no metal pieces / sharp ob.jects etc. vere found in the area and no pieces ef the radiator asse:bly or housing vere found to be missing. The tube leak vra repaired, the ecclant syste filled and the 2h-hour test was restarted and co=pleted satisfactorily with-c1.....,s..,.
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