ML17261A783

LER 87-008-00:on 871223,failure of Safeguards Circuit Breakers Occurred Due to Zero Clearance Between Ampector Actuator Arm & Breaker Trip Bar.Caused by Inadequate Design Info from Vendor.Clearance reset.W/880122 Ltr

ML17261A783
Person / Time
Site:	Ginna
Issue date:	01/22/1988
From:	Backus W, Snow B ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-87-008, LER-87-8, NUDOCS 8801280254
Download: ML17261A783 (10)

Text

yl REGULA Y INFQRt'IATIQN DISTR lBUTI YSTEM (R IDS)

ACCESSION NBR: 8801280254 DOC. DATE: 88/01/22 NOTARIZED: NO DOCKET j FACIL: 50-244 Robert Emmet Ginna Nuclear Plant> Unit 1> Rochester G 05000244 AUTH. NAME AUTHOR AFF ILlATION BACKUS. W. H. Rochester Gas 8c Electric Corp.

SNOW> B. A. Rochester Gas 8c Electric Corp.

RECIP. NAME RECIPIENT AFFILIATION

SUBJECT:

LER 87-008-00: on 8?1223> failure of safeguards circuit breakers occurred due to zero clearance between ampector actuator arm 8c breaker tY ip bar. Caused bg inadequate design info from vendor. Clearance reset. W/880122 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR TITLE: 50. 73 Licensee Event Report (LER)>

J Incident ENCL Rpt>

+etc.SIZE:

NOTES: License Exp date in accordance with 10CFR2> 2. 109(9/19/72). 05000244 RECIPIENT COPIES REC IP I ENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD1-3 LA 1 1 PD1-3 PD 1 1 STAHLE C 1 INTERNAL: ACRS MICHELSON 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEQD/DSP/NAS 1 1 AEOD/DSP/ROAB 2 2 AEQD/DSP/TPAB 1 1'

ARt't/DCTS/DAB 1 DEDRQ 1 NRR/DEST/ADS 0 NRR/DEST/CEB 1 1 NRR/DEBT/ELB 1 NRR/DEST/ICSB 1 1 NRR/DEST/t'tEB 1 NRR/DEST/MTB 1 NRR/DEST/PSB 1 1 NRR/DEBT/RSB 1 1 NRR/DEST/SGB 1 1 NRR/DLPG/HFB 1 1 NRR/DLPG/GAB NRR/DOEA/EAB 1 1 NRR/DREP/RAB 1 1 NRR/DREP/RPB 2 2 flR SIB 1 1 NRR/PMAS/ILRB 1 1 02 1 1 RES TELFORD> J 1 1 RES/DE/EIB 1 1 RES/DRPS DIR 1 1 RGNl FILE 01 1 1 EXTERNAL: EGSG GROH> M 5 5 FORD BLDG HOY> A H ST LOBBY WARD 1 1 LPDR NRC PDR 1 1 NSIC HARRIS> J NSIC MAYS> G 1 1 TOTAL NUMBER OF CQP IES REGUIRED: LTTR 46 ENCL 45

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CATE 11EI YEE (It yw, ceeWw EXPECTEO SUEJJJETIOJT OATN AMTlhACTJ kali N JtOJ NItN, I.A, tttMe eHyMywt tyyeaeNM Neat OEJ On December 21, 1987 at. 1411 EST with the unit at 100% Reactor Power the 1B RHR Pump. failed to start for testing due to zero clearance between its breakers amptector actuator arm and the tripper bar. Follow up testing of selected safeguards breakers revealed a second failure on December 23, 1987 of the 1B Safety Injection Pump. Because a majority of the safety related breakers are of this same design, a possibility of. common mode failure existed.

Immediate corrective action was to inspect, adjust .and test the affected breakers and return them to oper'able status.

The root cause of the event was determined to be inadequate design information provided by the vendor during modification installation of the amptector devices.

Corr'ective action to prevent recurrence includes checking and setting, if necessary, the clearance between the amptector actuator arm and breaker tripper bar during preventive maintenance on these breakers.

8801280254 880122 PDR ADQCK 05000244 S PDR

U.t. NUCLCAII IICOULATOIIYCOMMIttION NAC Setm tttA I04S LICENSEE EVENT REPORT ILER1 TEXT CONTINUATION ASSIIOVtO OMt NO. 1150&10l tXrlttt:tnllt5 SACII.ITY NANt Ill OOCKtT NUMttll (1l Ltll NUMttll ltl ~ AOt Itl tt QM M M t N7 INAL VNION MUM CA 0 0 0 OF ar Power Plant S 0 T%XT It'mac ~

R.E. Ginna Nuc N mtMtrC Mrr eAWstW NPC Form ~'ll(ITI PRE-EVENT PLANT CONDITIONS The unit was at 1004 Reactor Power and the Results and Test (R&T) department was commencing Periodic Test Procedure PT-2.2 (Residual Heat Removal System).

DESCRIPTION OF EVENT A. EVENT:

On December 21, 1987 at 1411 EST, the Control Room operator attempted to start the 1B Residual Heat Removal (RHR) pump per procedure PT-2.2. The breaker to switch white disagreement light illuminated and the pump did not start. The Control Room operator turned the switch to the stop position clearing the white disagreement light and notified operations supervision.

Operations supervision notified maintenance of the RHR pump failure to start problem and declared the 1B RHR pump inoperable. Technical Specification (TS) 3.3.1.5 allows one Residual Heat Removal pump to be out of service provided the pump is restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Follow up testing of other selected safety revealed a second failure on December 23, related'reakers 1987. The 1B Safety In)ection Pump failed to start on the 8th test cycle.

B. INOPERABLE STRUCTURES s COMPONENTS s OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

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R.E. Ginna Nuclear -Power Plant o 5 o o o2 4487 00 00 03 o~ 0 S 7gCT Idrsee ~ 4 aeskeC f>> ~ASIC Ana ~'flIITI C. DATES A'ND APPROXIMATE TIMES FOR MAJOR OCCURRENCES:

o December 21, 1987, 1411 EST: Event date and time o December 21, 1987, 1411 EST: Discovery date and time o December 21, 1987, 1411 EST: 1B RHR pump declared inoperable o December 21, 1987, 1431 EST: 1B RHR pump is successfully started o December 22, 1987, 0825 EST: 1B RHR pump declared operable o December 23, 1987, 1545 EST: 1B Safety In)ection Pump fails to start on 8th cycle of testing.

This pump was already declared inoperable for testing o December 23, 1987, 1635 EST: 1B Safety In)ection Pump declared operable D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None E~ METHOD OF DISCOVERY:

The 1B RHR pump failure to start was discovered by the Control Room operator while attempting to start it during performance of procedure PT-2.2.

The 1B Safety In)ection Pump failure to start was discovered during subsequent testing of selected safety related breakers.

MAC f01M SSSA Iaaa I

U.S. NUCLSAII ASOULATOIIYCOMMISSION NIIC Pena SSSA 10471 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION AttIIOVSO OMS NO. S150&I&

SX ~ llltt SISIISS tAC ILITYNANt Ill OOCKST NVINSN Ql Ltll NUMSSA Itl VSAA + SSOVSNTIAL tVISION N M N M A R.E. Gonna Nuclear Power Plant 0 5 0 0 0 2 4 4 7 0 80 004 OF 0 8 TSXT IS Awe ~ II eeJW ~ ~hNC Ana ~'4 (ltl F. OPERATOR ACTION:

o After the 1B RHR pump failed to start, the Control Room operator turned the pump switch to the OFF position and notified operations supervision.

Normal operator action at this time, had the 1B RHR pump been required to operate, would have been to attempt a restart. This was not done at this time but was subsequently done successfully after the electricians had visually checked the breaker and found no visible problems.

o No operator action was required with the sub-sequent failure of the 1B Safety In)ection pump as the pump had already been declared inoperable for testing.

III'AUSE OP EVENT A. IMMEDIATE CAUSE:

The safeguard pumps failed to start because their electrical breakers failed to remain closed.

B. INTERMEDIATE CAUSE:

It was concluded that the safeguard breakers failed to remain closed due to zero or pumps electrical negative clearance between the amptector actuator arm and the breaker trip bar. The slight pressure of the amptector actuator arm adds to the likelihood of the tripper bar bouncing during a breaker closure thus tripping the breaker after closures. There is a potential that tripper bar bouncing is more likely to occur when the batteries supplying D.C. control power to the breakers are on equalizing charge at 140 volts D.C. Normal battery voltage is 130 volts D.C. The "B" battery was on equalizing charge during the event. This battery feeds control power to the two failed breakers. Testing results indicated that if the amptector clearance is set properly the battery voltage does not contribute to the failure mode.

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Ug. NUCLCAN ACCULATOAVCOMM/ttION NIIC Pena $ NA It'll LICENSEE EVENT REPORT ILER) TEXT CONTINUATION AftlIOVtOOMt NO. $ 1$ 0&IIH tXP//1$ $ . t/$ 1/$ $

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The root cause o f the event. was determined to be Inadequate Design Information provided by the vendor (Westinghouse) of the amptector devices. Prior to June 1987 following some failures of non class lE breakers, where the amptector modification had been made, the vendor issued a recommendation to leave a clearance of approximately 1/32 of an inch, verified visually, between the amptector actuator arm and the breaker trip bar. Westinghouse also stated that this approximately 1/32 of an inch clearance was a recommen-dation not a requirement. All amptector modifications after this recommendation was received, were installed using the approximately 1/32 of an inch, verified visually, clearance between actuator arm and tripper bar.

ANALYSIS OF EVENT This event is reportable in accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(vii)(D) which requires reporting of, "any event where a single cause or condition caused at least one independent train or channel to become inoperable in multiple systems or two or channels to become inoperable in a single system independent'rains designed to mitigate the consequences of an accident," in that the cause of the failure of the safeguards pump breakers could have been a common mode failure in other safety related breakers that had the amptector modification prior to June 1987.

An assessment was performed considering both the safety consequences and implications of this event with the following results and conclusions:

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~ LICENSEE EVENT REPORT ILER) TEXT CONTINUATION UJ. NUCLKAH IIIOUlAYOIIYCOMMlCQOH AttIIOVf0 OMI HO. 31IOWIOA EXtlllES 10I45 fACILIZYNAMC lll OOCKKT NUIIII Ql I.III NUMOCN Ill y YAH tOVAHYIAl II

OVISIOH HVM H M R.E. Gonna Nuclear Power Plant 24 487 008 00 06 oF 0 8 ma <~AMHWeeN~ ~~NNC~~+IIn There were no operational or safety consequences attributed to the failure to remain closed of the safeguards pump breakers because:

o The two safeguards pumps failed to start during a test of the pumps and not during an operational or accident mitigation demand.

o The 1B Safety In)ection pump did not fail to start until the 8th cycle of testing.

o The 1B RHR pump started on the second attempt after electricians visually checked the breaker.

o The 1A RHR pump was operable and capable of performing the minimum safeguards functions.

o Two safety injection pumps were operable and capable of performing the minimum safeguards functions.

Implications of the event were that the failure mechanism could be a common mode failure and may be affecting other safety related breakers that the amptector modification had been. performed on prior to June 1987. A review by the plant staff was made of all amptector modifications made both before and after the vendors recommendation to leave approximately 1/32 inch clearance between the amptector actuator arm and the breaker tripper bar. This review was necessary to address both operability of equipment and any generic implications based on this one failure mechanism.

o The number of documented cycles the above breakers had experienced since modification was reviewed.

This was considered a good indication of operability if the breaker had had 10 or more cycles without failure.

US. NUCLKAIIN40ULATOIIYCOMMISSION NAC lena 444A I444I 4I50&10i LICENSEE EVENT REPORT (LERI TEXT CONTINUATION ASSAOV4D OM4 NO.

4XWA44 4aII45 Ltll NUM44II ISI ~ A04 ISI 4 ACILITY NAM4 III SSOUSNTI*L ASVISlON N M 1 NUM A R.E. Gonna Nuclear Power Plant 0 5 0 0 0 2 4 4 0 8 0 0 07 oF mrrIi~MSSANMSMMC ~~rWCa maWIITI As' result of the above review, a number of safety related breakers were selected for inspection and testing on a priority basis. These inspections and tests were performed on the selected breakers and one more failure was identified. The 1B safety in)ection pump failed to start on the 8th cycle. All other selected breakers were found operational.

An assessment of the implications of the common mode failure was made with the following results:

o The identified failures were sporadic (i.e. the breakers would close most of the time).

The Emergency procedures direct the operators to check the emergency equipment running and to start manually, equipment that is not running.

Based on the above, it can be concluded that if the safety related breakers did not close when required, they could have been closed manually by the operator.

V. CORRECTIVE ACTION A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

0 The clearance between the amptector actuator arm and the breaker tripper bar of the 1B RHR pump breaker and the 1B safety infection pump breaker were adjusted, the breakers tested satisfactorily and the pumps were returned to operable status.

B. ACTION TAKEN OR PLANNED TO PREVENT RECTJEGKNCE:

0 All breakers with. the amptector modification will have the clearance between the actuator arm if and the tripper bar checked and ad)usted, needed, during performance of preventive mainten-ance of these breakers.

NAC SOAM SSSA I444l

US. IIUCLTA1 IISOULATOAYCOMMISNOSI IIAC Pena 000A IOOSI LlCENSEE EVENT REPORT (LER) TEXT CONTINUATION ASSIIOV EO OMO HO, 3I 60MI OS ESSIIITS SIBI ITS I'ACILITYISAMS III OOCIIKT IIUS<<ill IZI LRII IIUMOEII ISI ~ AOS ISI YSAII S S 0 M S II T I A L M II R.E. Ginna Nuclear Power Plant 0 S 0 0 0 2 4 4 8 7 008 00 0 oF08 TSCt IS'A<<M <<s<<O <<S<<ML ~ ~ASIC Aee ~'Sl IITI VI ~ ADDITIONAL NFORMA ION A. FAILED COMPONENTS:

The failed components were amptector kits Class 1E, Style No. 6472C21G10 LIG 800/600/400 For: DB-50 Breakers.

B. PREVIOUS LERs ON SIMILAR EVENTS:

A similar LER event. historical search was conducted with the following results: No documentation of similar LER events could be identified.

C. SPECIAL COMMENTS:

The amptector modifications were made to upgrade the old type series trip overcurrent units which are thermal/mechanical direct acting devices. The newer amptectors are solid state overcurrent devices.

The old devices were factory, set and not resettable in the field where as the new device is resettable in the field and much easier to test.

The industry was notified of this event through Nuclear Network on December 29, 1987.

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ROCHESTER GAS AND ELECTRIC CORPORATION ~ 89 EAST AVENUE, ROCHESTER, N.K 14649.0001 Tf.LCI'>OPEC ARcA coDf. 7ld 5A6 2700 January 22, 1988 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

LER 87-008, Inoperable Safeguards Equipment Circuit Breakers Due To Zero Clearance Between Amptector Actuator Arm And The Breaker Trip Bar Causes Possibil-ity of Common Mode Failure R.E. Ginna Nuclear Power Plant Docket No. 50-244 In accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(vii)(D) which requires a report of, "any event where a single cause or condition caused at least one independent train or channel to become inoperable in multiple systems or two independent trains or channels to become inoperable in a single system designed to mitigate the consequences of an accident", the attached Licensee Event Report LER 87-008 is hereby submitted.

This event has in no way affected the public's health and safety.

Very truly yours, Bruce A. Snow Superintendent of Nuclear Production xco U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 Ginna USNRC Resident Inspector