05000285/LER-1980-003-03, /03L-0:on 800122,during Special 24-h Diesel Generator Test,While Attempting to Load Generator,Generator Field Went to Max Excitation.Caused by Faulty Zener Diode & Corresponding Draft in A-C Regulator Panel

/03L-0:on 800122,during Special 24-h Diesel Generator Test,While Attempting to Load Generator,Generator Field Went to Max Excitation.Caused by Faulty Zener Diode & Corresponding Draft in A-C Regulator Panel

ML19294B014
Person / Time
Site:	Fort Calhoun
Issue date:	02/15/1980
From:	Mueller R OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19294B012	List: 05000285/LER-1980-003, Forwards LER 80-003/03L-0 05000285/LER-1980-003-03, /03L-0:on 800122,during Special 24-h Diesel Generator Test,While Attempting to Load Generator,Generator Field Went to Max Excitation.Caused by Faulty Zener Diode & Corresponding Draft in A-C Regulator Panel
References
LER-80-003-03L, LER-80-3-3L, NUDOCS 8002260585
Download: ML19294B014 (4)

LER-1980-003, /03L-0:on 800122,during Special 24-h Diesel Generator Test,While Attempting to Load Generator,Generator Field Went to Max Excitation.Caused by Faulty Zener Diode & Corresponding Draft in A-C Regulator Panel

Event date:
Report date:
2851980003R03 - NRC Website

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LICENSEE EVENT REPORT YI ke CONTactsLcCx.l l

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EVENT DESCAIPTICN AND PACB A8LE CONSECUENCES h

) I2 l'4hile attenttine to icad the die el :=ners- ~- 0G-2. durin: -ha er' m'rea -f a l

ai3I lspecial 2L-hcur diesel zenerstor test recy irad in resconse to !E Eu'letin 77-2?, the I

aiA lgeners. tor field vent to es:cimum axcitation; therefore, *he diesel vis shutievn to 1

o s Icrevent generst0r dsmage. The fsilure was 1 result of s reference 2ener diode irift I

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le n vas discovered. This le n was repaired per maintenance order and the 2L-hr. diesel laia I test vac restrated and satisf actortiv cercleted vi* tent furt h e r in e i lan -

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CAUSE CESCRIPTION AND COARECTIVE ACTIONS h i t.3 l'~he irift of the refernece :ener :icde 2nd corresrondinziv -he renerator Out ut chsr-I seteristics was celieved 50 have been :sused 'cy 1 faulty :ener dicie.

The liade was l replaced per M.3. *3762 snd the diesel oper'.ted satisfsetcrilf Ehe diesei %-h e r i

i l test was resu=ed.

Following the li de fsilure k restart, the liesel was se2ir shutdcv't i

3 lfol10ving 1 radiator tube led which deve?.ated du-ing the restar e1 'um. -'his len wasl l repaired ind the diesel test res'=e'i vithout further incident.

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Safety Analysis

The Fort Calhoun Station Uni 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 genera:cr DG-2 was inoperable, Diesel Generator No. I was operatie as were the 161K7 and 3L5K7 supplies thus providing nore than adequate capability for safe shutd:vn of the plant in the case of an accident.

The reacter was in a refueling shutdown condition during -he tine of thia 2h-hour diesel *est.

C:nsequently, the technical specification governing diesel generator operability requirenents, technical specification 2.7, was not applicable.

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Corrective Action

'4hile initially trying to lead diesel generator CG-2, Onto Sus LAk in an attempt to perfor= the 2L-hour diesel load test, which was required by response to II Sulletin 79-23, it was noticed tha: the generator field vent to maxi excitation with no additicnal input to the governor.

Therefore, the diesel generator was shutdevn and a maintenance order vritten to correct the problem.

The problem vus found to be a reference :ener dicde in the A-C regulator panel which would not holi ne required voltage.

This di:de <as replaced with a new diode, lnd ilesel generatcr CG-2 operability was restored.

Sub-sequently, the diesel generator 2L hour test was resu=ed.

Ten hcurs into the 2k hcur test the diesel generator DG-2 was again shutdevn due to increasing cccling water temperatures and the corresponding radia:cr tube leak which was disecvered.

A naintensnce order was vritten to investigate the leakage and repair it.

fhe radiator tube leak was postulated to have cecurred due to a piece cf metal which may have richochetted off the radia cr f an blades and punctured the radiatcr fins and tube sheet sufficiently to cause the leakage.

Ecvever, co etal pieces / sharp objects etc. vere found in the area and cc pieces cf the radiator assembly cr hcusing vere found to be =issing. The tube leak vas repaired, the ccciant systen filled and the 2L-hcur test was restarted and :c=pleted satisfactorily with-out further incident.

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