ML18059B006

LER 94-011-00:on 940425,discovered That Previously Unanalyzed Combination of Events Could Result in Slower than Specified Start of Edgs.Slow Starting Motor & Regulator replaced.W/940525 Ltr

ML18059B006
Person / Time
Site:	Palisades
Issue date:	05/25/1994
From:	Rogers D, Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-011, LER-94-11, NUDOCS 9405310216
Download: ML18059B006 (4)

Text

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consumers Power David W. Rogers

I Plant Safety and Licensing Director POWERINli MICRlliAN'S PRDliRESS PJtisades Nuclear Plant.

27780 Blue Star Memorial Highway, Covert, Ml 49043 I

I .

May 25, 1994 Nuclear Regulatory Commission

. Document Control Desk

• Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT LICENSEE EVENT REPORT 94-011 - PREVIOUSLY UNANALYZED COMBINATION OF EVENTS INDICATES POTENTIAL FOR INABILITY OF A SINGLE SOURCE TO RELIABLY START DIESEL GENERATORS.

Licensee Event Report (LER)94-011 is attached. This condition is reportable to the NRC per 10CFRS0.73(a)(2)(ii)(B) as a condition outside the design basis of the plant. *

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David W. Rogers ...

Plant Safety and Licensing Director CC Administrator, Region Ill, USNRC NRC Resident Inspector - Palisades Attachment

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9405310216 940525 PDR : ADOCK 05000255 S '\ PDR A CiHS' ENERGY COMPANY .

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NRC Form 388 U.S. NUCLEAR REGULATORY COMMISSION Cl-831 APPROVED !)MB NO. 31~104 EXPIRES: 8/31/86

-- LICENSEE EVENT REPORT (LERI FACILITY NAME 111 DOCKET NUMBER 121 PAGE 131 Palisades Plant I I I I I I I o s a* o o 2 s s 1 I O F I Q I J TITLEl41 PREVIOUSLY UNANALYZED COMBINATION OF EVENTS INDICATES POTENTIAL FOR INABILITY OF A SINGLE SOURCE TO RELIABLY START DIESEL GENERATORS.

EVENT DATE 161 LER NUMBER 161 REPORT DATE 161 OTHER FACILITIES INVOLVED 181 MONTH DAY' i "

YEAR YEAR SEQUENTIAL NUMBER  : REVISION NUMBER MONTH DAY YEAR FACILITY NAMES . *

' r **** N/A 0 Is I I~ I 0 0 I I ol4 215 9 4 914 0 I I1 1 o lo ols 215 914 N/A -

0 1 1°1°1°1*1 6

THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR I: (Ch<<:lc One"',,_,, ol rlwl follow/n(/J _111)

OPERATING N MODEIBI I -

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20.4061*111 )(iv) x 60.731all2lliil .60.731*ll2llviii11Bl NRC Form 386AJ 20.4061*111 llvl 60.731oll211iiil - 60.731*11211xl LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER Richard W. Smedley, Staff Licensing Engineer 6ARIEA1CI°~ I 7 I 6 I 4 I - I 8 I 9I I 3 1 CAUSE SYSTEM I

COMPONENT I I I I COMPLETE ONE LINE FOR EACH COMPONENT FAILURE _DESCRIBED IN THIS REPORT 1131 MANUFAC*

'TURER I* I REPORTABLE TO NPRDS I <***** t*

CAUSE SYSTEM I

COMPONENT I I I I MANUFAC*

TUR ER I I

.~ . -*I TO NPROS I' I I I I I I SUPPLEMENTAL REPORT EXPECTED !****************************

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I I I I I I I MONTH DAY

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.YEAR EXPECTED

- - , YES Uf yes, complete EXPECTED SUBMISSION D~TEI rx-i NO S\.!BMISSION DATE 1161 I I I ABSTRACT UJm/tto 1400llPllCOS. ie., epptTJJt/,,.,,to/y fifteen-aingle-spece typewritten linHI 1161 On Aprii 25; 1994, wi_th the plant in cold shutdown,* plant personnel discovered that, in certain circumstances, the ability of the plant's Emergency Diesel Generator's (EDGs) to start within the prescribed time frame could be adversely impacted. When loss of a station battery was considered as a single failure mechanism along with a design basis accident and loss of offsite power the result would be a reliance on only one starting circuit for each EDG .. That circuit is the "A" air start circuit for both diesel generators. The starting time for the "A" air start circuit for EOG 1-2 had previously exceeded the specified starting time. The single failure, station battery I a had not occurred in the past and availability of all starting circuits for both EDGs had not been impacted. However, the effect of the identified condition placed the plant outside its design basis .. The slow air start motor and its regulator have been replaced and tested satisfactorily.

Procedu.res used to control testing of both EDGs have been changed to reflect the information obtained as a result of this discovery.

J' NRC Form 386A U.S. NUCLEAR REGULATORY COMMISSION

{9-831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31 /86 LICENSEE EVENT REPORT (LERI TExT CONTINUATION FACILITY NAME 111 DOCKET-NUMBER 121 LEA NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisade's Plant 0500025594-011 0 0 0 2 OF 0 3 I *

• Event Descnot1on ** . . .

On Aprill 25, 1994, with the plant in...cold shutdown, itwas identified that there were a co.mbin~tion of circumstances which, when taken together, could result in a slower than specified start of Emergency Diesel Generators (l;DGs). The combination of events and circumstances which would impact EOG performance. was discovered by plant personnel wtio were addressing an issue raised by the NRC Diagnostic Evaluation Team (DET) staff. The. scenario which could result in a slow start requires the following: An event, such as a loss of coolant accident (LOCA) and resulting loss of offsite power, failure of a station battery, and start time of the "A" motor above 9.5 seconds. When offsite power would be lost, the undervoltage condition would initiate a start of EDGs utilizing both "A" and "B" starting motors. Plant experience as well as testing confirm EOG. starts within the Technical Specification time limit. However, with the loss of a station battery, only the "A" starting motor would be available. The "A" starting motor on EOG 1-2.has recently taken 9.99 seconds to start. Per procedure, a second.attempt using both motors was successfully completed. Though acceptable at the time, the procedure did not-consider the battery loss and resulting reliance on only the "A" motor which had exceeded its start time. The net effect of the condition placed. .

the plant outside its. design* basis

. as described in its FSAR.

Cause of Event The plant's investigation identified that there was an incomplete understanding of the implications of the undervoltage starting circuit arrangement and the slow start times for the "A" air start motor on EOG 1-2. The possibility for a single f~ilure, in this case a loss of a stati'on battery, placing reliance on the "A" starting circuit of one diesel generator was not recognized.

Analysis of Event Two starting circuits,. nAn and "B" are utilized for both Palisades Emergency Diesel Generators. If I

there were an event such as a LOCA, a concurrent loss of offsite power and a failure of either station battery 001 or D02, only the EOG "A" start circuitry capability would remain to start the associated diesel generator. Loss of station battery DO 1, in combination* with the other two

• events, would result in the loss of control power to both starting circuits for Emergency Diesel Generator EOG 1-1. This condition would a!so result in a loss of power to auxiliary relays which provide a start signal to the "B" air start motor for EOG 1-2. Because the "A" air start motor for EOG 1-2 had, at times in the past, exceeded its requirement to start EOG 1-2 within 9.5-seconds, -

the circumstances identified would have resulted in an inability of EOG 1-2 to meet design basis requirements. Because the failure was possible, this condition is reportable per*

10CFR50.73(a)(2)(ii)(B) as outside the plant's design basis.

NRC Form S88A 19-831 FACILITY NAME C11 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR "NUMBER NUMBER Palisades Plant

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- 'o lo Oil OF OIJ Safet\t lsignjficance I

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A loss of offsite power prompts a start of EOGs utilizing both air start motors. When both are used for a start, performance has met technical specification criteria.* Although the scenario described in this report notes a. potential for exceeding the 10-second start up requirement, the plant has not experienced .a loss of a station batt~ry which would force a reliance on only one circuit.

• Correc,ive Actions The following actions have been completed:

The slow starting motor and its regulator were replaced.

Procedu.res used for EOG start testing have been revised so that a slow start using the "A" air ,

start motor will result in declaring the EOG inoperable. J The following action will be completed:

l A* modification will. be completed during the 1995 refueling outage that will eiimiriate the potential depe~dance on a single* starting circuit capability.

Previous Occurrences None.

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