ML20006E450

LER 89-010-01:on 890715 & 17,voltage Oscillations Noted on Div II Battery Charger,Resulting in Inoperability of HPCS Sys.Caused by Failure of Charger in High Voltage Shutdown Relay.Charger Energized & Relay replaced.W/900215 Ltr

ML20006E450
Person / Time
Site:	LaSalle
Issue date:	02/15/1990
From:	Diederich G, Vinyard H COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-010-02, LER-89-10-2, NUDOCS 9002230185
Download: ML20006E450 (6)

Text

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I ' Commonwealth Edison

. LaSalle County Nuclear Station

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RuralRoute #1. Box 220

.* MarseiWes, Illinois 61341 Telephone 815/357 6761 February 15, 1990 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Station P1-137 Washington, D.C. 20555

Dear Sir:

Licensee Event Report #89-010-01, Docket #050-374 is being ,

submitted to your office to supercede previously submitted '

Licensee Event Report 89-010-00. ,

YO ,

G. J. Diederich '

hStationManager LaSalle County Station GJD/HTV/kg

• Rnclosure xc: Nuclear Licensing Administrator NRC Resident Inspector NRC Region III Administrator .

INPO - Records Center ll 7d:

' 9002230185 900215 - ,3 ADOCK0500g4

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LICENSEE EVENT REPORT (LER) g Docket Neber (2) Paee (3) ,

f acility Name (1) , .

LaSalle County Station Unit 2 01 Sl 01 01 01 31 71 4 1 l of 0l5 Title (4)

Hlah Pressure Core Soav torable Due to 01 vision til Battery Chareer Oscillations Event Date (5) LER Neber (6) W rt Date (7) Other Facilities involved (8)

Year /// Sequential // Revision Month Day Year Fac111tv Names Docket Neber(s)

Month Day Year fjj/ /,,/j T/ Neber

// Neber LaSalle Unit 1 01 51 of 01 01 31 71 3 01 7 11 5 81 9 el 9 01110

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01 1 0IT 11 5 91 0 01510101of I l l TH15 REPORT IS SUBMillED PURSUANT TO THE REQUIREMENTS OF 10CFR

^ (Chock one or more of the followine) (11) t MODE N 1 20.402(b) _ _ ,

20.405(c) 50.73(a)(2)(lv) .,,,_,,

73.7)(b) 20.405(a)(1)(1) 50.36(c)(1) . X_ 50.73(a)(2)(v) _

13.il(c)

POWER _ _

Other (Specify LEVEL g 20.405(a)(1)(ll) .,_,,. 50.36(c)(2) 50.73(a)(2)(vil) ,,

in Abstract 50.73(a)(2)(vill)(A)

(10) 0 9I 5 ,_ 20.405(a)(1)(111) ,

50.73(a)(2)(1) '

50.73(a)(2)(ll) 50.73(a)(2)(vill)(B) below and in

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_ 20.405(4)(1)(iv) 20.405(a)(1)(v) 50.73(a)(2)(lil) 50.73(a)(2)(x) Text)

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LICENSEE CONTACT FOR THl$ LER (12)

TELEPHONE NUSER Neue AREA CODE Harold T. Vinvard. Technical staff Enoineer. extension 2499 - 8 l 1 15 315171-l6171611 Co @ LETE ONE LINE FOR EACH C09 0NEW FAILURE DESCRIDED IN THIS REPORT (13)

CAUSE' ' SYSTEM COMPONENT MANUFAC- REPORTABLE CAUSE SYSTEM C090NENT MANUFAC- REPORTABLE TURER 70 NPRDS TURER TO NPRDS '

l Rl Ll Y Fl21314 l l l l l l l X El J Y I l l l l l l l l l l l l l

Expected Month i Day l Year SUPPLEMENTAL REPORT EXPECTFD (14)

Submission lyes (If ves. conelete EXPECTED SUBM15510N DATE) TlNO l l l l

A8STRACT (Limit to 1400 spaces, i.e approximately fifteen single-space typewritten lines) (16) on July 15, 1999 with Unit 2 in Operational Condition 1 (Run) at 95% power, the Nuclear Station Operator (W50) noticed voltage oscillations (120-131YDC) on the Unit 2 Division 111 battery charger. These e t escillations were not constant, but would occur for 5-10 seconds at indeterminate intervals. The battery l

charger was declared inoperable at 2119 hours0.0245 days <br />0.589 hours <br />0.0035 weeks <br />8.062795e-4 months <br /> on July 15, 1989. This also rendered the Unit 2 High Pressure Core Spray (HPCS) system inoperable and a 14-day timeclock was initiated in accordance with Technical Specifications. Similar occurrences of these oscillations have been observed since this event. Because of the intemittent nature of the problem, the root cause could not be detemined. l)

The cause of these events appears to be related to the charger High Voltage Shutdown Relay (HYSR). The exact i

failure mode of this relay was not detemined. l' l

The consequences of this event (s) was minimal. Division I and II Emergency Core Cooling Systems (ECCS) were fully operable during this period. In addition, the Reactor Core isolation Cooling system was fully operable ,

asanalternatehighpressureinjectionsystem. The HPCS system was fully functional, although inoperable, during this event (s). The Unit 2 Olvision 111 DC emergency power supply (battery) was fully charged l throughout the event.

l A chart recorder was connected to the HVSR to monitor coil voltage and contact position. Had the charger voltage oscillations re-occurred, the recorder would have indicated the HYSR failure mode, This event is reportable pursuant to 10CFR50.73(a)(2)(v) due to a safety system being declared inoperable.

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i LICENSEE EVENT REPORT (LER) TEXT CONilWuA110N ' Form Rev 2.0  :

00CEEl WUSER (2) LER NUSER (6) Pace (3) l PACILilY NAME (1) .

" Year fj//f Sequential //

/ Revision .]

/// Nimber ,g/

// Number l te kile County Station Unit 2 0 l 5 1 0 1 0 1 0 1 31 11 4 819 - 0l110 - 0l 1 01 2 0F 01 5 ll I

TEX 1 Energy Industry identification System (Ells) codes are identified in the text as [XX] 1 I

PLAN 1 AND SYSTEM IDENilflCATION General Electric - Bolling Water Reactor ,

Energy Industry Identification System (LilS) codes are identified in the text as [XX).

A. CONDlil0N PRIOR 10 EVENT 1 1/2 Event Date: 7/15/09 _ Event Time: 2tl9 Hours Unit ('s):

Run/Run Power Level (s): 91%/95%

Reactor Mode (s); 1/1 Mode (s) Name:

j B. DESCRIPil0N OF EVENT On July 15, 1989 with Unit 2 in operational condition 1 (Run) a_t 95% power, the Nuclear Station Operator (NSO, licensed Reactor Operator) noticed voltage oscillations (120-131VDC) on the Unit 2 Division 111 .

battery charger (DC) [EJ). these oscillations were not constant, but would occur for 5-10 seconds at Indeterminate intervals. The battery charger was declared inoperable at 2119 hours0.0245 days <br />0.589 hours <br />0.0035 weeks <br />8.062795e-4 months <br /> on July 15,19h.

Per Technical Specification 3.8.2.3 action b, the Unit 2 High Pressure Core Spray system (HPCS) (HP) l i

[BG) was declared inoperable and a'14alay timeclock was initiated in accordance with lechnical '

Specification 3.5.1. . Work Request L91276 was intnedlately initiated to resolve the probism. i1he Unit 2 Division 111 battery and bus (213) were crosstled to the Unit 1 Division 111 charger so the Unit 2  !

charger could be isolated. Crosstying DC buses with both units in Condition 1 (Run) required that the Unit 1 HPCS system was also declared inoperable.

inspection of the battery charger control circuit cards under Work Request L91276 revealed a heat damaged area on the "A" phase firing board. This board was removed and replaced with a new board. The charger was then energized and observed for nonnal operation. No charger abnonnallties were observed at

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that time. The crosstle between Division 111 DC buses from Units 1 and 2 was removed and the Unit 1- i HPCS system declared operable. The Unit 2 battery charger and HPCS system were declared operable at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br /> on July 16, 1999.

l 04 July 17, 1989 at y proximately 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, the Unit 2 NSO again noticed voltage oscillations on the Unit 2 Division lit bettery charger. The ugnitude and duration of these oscillations were similar to '

the ones seen on July 13,1989. Technical Staff and Electrical Maintenar.ce personnel were lunedlately contacted to observe the oscillations. The Unit 2 Division lit battery charger and the HPCS system were declared inoperable at lHS hours on July 17, 1989. Work Request L91305 was initiated to troubleshoot the charger. The Division til DC ruses were crosstled and the Unit 1 HPCS system declared Inoperable.'

The battery charger was subsequently inspected by the vendor. As a result of this investigation and of the probisms described, the vendor reconnended changing out the "A" phase Silicon-Controlled-Rect)fler (SCR) asssably. This was perfonned on July 21, 1999. LaSalle Electrical Surveillance, t.ES-0C-103,

" Battery Charger Capacity Test," was then perfonned to verify Technical Specification capacity requirements were met following replacement of the "A" phase SCR assembly. The battery charger was declared operable at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on July 24, 1999.

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LICEW5EE EVENT REPORT (LER) TEXT CONilmt?,110W Forn Rev 2.0

< Pace (3)

DOCKET enter (2) LER WUISER (6) f ACILITY NAME II) sequential /j/j/ Revision Year ffj/

//

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/// lheiber /// thaber_  ;

oi1Io oI i ol 3 0F ol 5 l o I 5 1 0 I o I o i 31 71 4 8Ie - -

' EaSalle County Station unit 2 TEXT Energy Industry identification System (Ell 5) codes are identified in the text as [XXJ

8. DESCRIP110N OF EVENT (Continued)

P Dn July 27, 1989 at 1645 hours0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br />, voltage oscillations were again observed on the unit 2 Olvision lli charger. Charger voltage decreased to 120VDC and returned to normal (131VDC) in approximately I minutes. At 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, charger voltage again decreased to 120VDC and did not return to normal voltage ,

until approximately 4 minutes later. The charger was declared inoperable at 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on July 21, 1989. The Technical Staff Engineer was notified and troubleshooting activities began under Work Request L91558. At this time it was discovered that contacts on the High Voltage $hutdown Relay (HV5R) were not

-making sufficient contact. This relay is normally energized (with contacts closed) during normal charger operation. Should a high voltage condition exist on the charger output, this relay will drop out and remove power to the charger control boards, effectively shutting off the charger. Oscillations of the charger could be reproduced by physically separating the contacts of this relay. The HVSR was replaced under Work Request L91558. A vendor representative verified proper operation following replacement. The charger was then declared operable on July 28, 1989.

On August 3,1989 at 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, charger voltage dropped to 120VDC. The Technical Staff Engineer was inmediately notified and proceeded to investigate the charger. Contacts of _the HVSR were found to be slightlyoffsetandwereadjustedtotheproperposition. following this action, the' charger returned' -

to normal operatir'g voltage. The problem reaccurred at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br /> on August 3,1989. Chargervojtage dropped to 120VDC for 1 minute and then returned to normal. The HV5R contacts were again cleaned and contacts verlfled in their proper position. A chart recorder was connected to the HVSR to aid in the failure analysis should the problem have re 4ccurred. No further charger abnormalltles were experienced and the chart recorder was removed on Septent>cr 15, 1989.

C. APPARENT CAUSE OF EVENT The cause of this event appears to have been related to the HYSR, although the exact failure mode could not be determined since no further abnormalltles occurred with the chart recorder connected.

D. SAFETY ANALYSIS OF EVENT Olvision I and 11 Emergency Core Cooling Systems (ECCS) were fully operable during this period, in addition, the Reactor Core Isolation Cooling (RCIC) (RI) (BW) system was fully operable as an alternate highpressureinjectionsystem. The HPCS system was functional, although inoperable, during this event (s). The Unit 2 Division 111 DC emergency power supply (battery) was fully charged throughout the event. ,

E. CORRECTIVE ACTIONS The following is a chronology of the troubleshooting activities since the July 15, 1989 event:

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' rom Rev 2.0 l 11CEW5(t EWLWT RfPORT (LER) TEXT COWilWuATION LER WU9(R (6) Page (3)_ _ l

_ PACIL11Y WAML (1) . 00CWL1 WUSER (2)

Year //j/ Sequential // Revision ff Weber

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OI 5 l

taSalle County Station unit 2 015101010131il4 8I9 - 0l110 - 0I 1 01 4 0F j

TEKi Energy Industry Identification System (Ell 5) codes are identified in the text as (XXJ  !

f E. CORRECllVE ACTIONS (Continued) 1/16/89: An inspection was perfomed of the battery charger control cards under Work Request L91276 revealed a heat damaged area on the "A" phase firing board. This board was removed and replaced with a new board. The charger was then energized and observed for nonnal operation.

Wo charger abnonnalltles were observed at that time and the charger declared operable.

l 7/17/89: With the cherger energized, input / output current through the $llicon-Controlled-Rectifiers (SCR's) was meas 9 red on all three phases. (Each phase has its own SCR assen61y.) "B" phase ,

I current appears to oscillate more than the other two phases, inplying an unbalanced  ;

condition. The battery charger was shutdown and all balancing potentlometers were cleaned and centered, in addition, all control circuit cards were removed, their connections cleaned, and 3 boards replaced (same boards). The charger was energized and phase currents balanced using the balancing potentiumeters. Operating personnel were then instructed to observe the charger for oscillations. Voltage / current oscillations began approximately one hour following the phase balancing.

7/18/89: The' battery charger vendor (C & D Power Systems, Inc.) was contacted and arrived onsite at approximately 1700 hou'rs. Technical Staff and Electrical Maintenance personnel assisted,the i vendor in troubleshooting the charger. Voltage checkpoints were established at the power transfomer secondary (AC input to the SCR bridge) and at the charger output teminals (DC  !

output). At that time, the charger appeared to be operating properly. Approximately one hour later, the charger voltage began to oscillate. Power transfonner secondary voltage remained i

constant during the oscillation but output voltage dropped to 120VDC. The problem, therefore was isolated to the output side of the SCR's. Since voltage regulation is controlled by the voltage / current sensing board, the vendor reconnended changing out this board. This was accomplished under Work Request L91305. The charger was energizeJ,and Operating personnel instructed to monitor the charger. .

1/19/89: LES-DC-103, "Bettery charger Capacity lest," was successfully perfonned to ensure the battery charger would satisfy Technical Specification Requirements.

1/20/89: In discussions with the vendor, it was decided to replace the "A" phase SCR assen61y. This corrective action was reconmended by the vendor based on problem description and the location of the burnt spot on the "A" phase firing board.

7/21/89: The "A" phase SCR assembly was replaced under Work Request L91305. LES-0C-103 was repeated to ensure this replacement did not affect the ability of the charger to meet leJ M cal Specifications, f/23/89: A chart recorder was placed on the charger to continuously monitor phase currents and output l

voltage.

7/25/89: Chart recorder was removed. No abnonnalities were observed.

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[ j L Fom Rev 2.0

~ l LICENSEE EVENT REPORT (LER) TEXT CONTlWuATION LER WuSER (6) Pane (3) <

FACILITY WAME (l) DOCKL1 NUSER (2)  ;

Sequential //jj/ Revision Year / '

j/j/j/

// We$er j/// Wumber 0l110 01 1 01 5 0F 01 5 l 0 1 5 1 0 1 0 1 0 1 31 71 4 819 - -

ta$alle County Station Unit 2 1EKT Energy Industry identification System (Ell 5) codes are identified in the text as [XX]  !

E. CORRECT!YE ACTIDWS (Continued) 7/27/89: Charger voltage oscillations were reported and Work Request L91558 initiated to investigate.

During this investigation, it was discovered that contacts on the High Voltage Shutdown Relay I (HYSR) were intemittently breaking contact. This relay is nomally energized, with contacts closed. in the event of a high voltage condition at the charger output teminals, this relay i

drops out and the battery charger is shutdown. Further investigation revealed that the '

charger oscillations could be recreated by physically opening one set of contacts of the HV5R >

relay. (The relay has 3 sets of contacts, I for each phase.) A call was made to C & D Power Systems to verify that failure of this relay could cause the erratic behavior exhibited by the charger. This was confinned by the vendor.

7/28/89: -The HVSR was replaced with assistance from the vendor. The vendor representative then verlfled proper operation of the relay and charger following replacement.

8/03/89: Charger voltage dropped to 120VDC at 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />. The Technical Staff Engineer discovered the "B"phasecontactsoftheHVSRwereslightlyoffsetandadjustedthemtotheproper. position. ~

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The charger then returned to its nonnal operating voltage. Probism re-occurred at 2215 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.428075e-4 months <br />; where charger voltage dropped to 120VDC for one minute and then returr.ed to normal. , ,

A chart recorder was connected to the HYSR to monitor coil voltage and contact position. Had the ,

charger voltage oscillatio% re-occurred, the recorder would have indicated its exact failure mode.

Unless this event, re-occurs, no further corrective action is necessary.

F. PREVIOUS EVENTS None.

'O. COMPONENT FA1LUPE DATA Nomenclature Model Number MFG Part Nunber Manufacturer 41NB30AF147P

! Furnas Elect. Relay /Contactor MN4 l-l L

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