ML18026A426

LER 90-007-01:on 900705,primary Power Supply to RPS a Power Distribution Panel Lost When One Electrical Protection Assembly (EPA) Breaker Tripped.Epa Logic Cards Reviewed & RPS Power Supply Will Be redesigned.W/930609 Ltr

ML18026A426
Person / Time
Site:	Susquehanna
Issue date:	06/09/1993
From:	Meter J, Stanley H PENNSYLVANIA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-007, LER-90-7, PLAS-566, NUDOCS 9306150200
Download: ML18026A426 (7)

Text

~ ACCELE D DOCUlVHKNT DISTQISUTION SYSTEM REGUL - RY INFORMATION DISTRIBUTIu.< SYSTEM (RIDS)

ACCESSION NBR:9306150200 DOC.DATE: 93/06/09 NOTARIZED: NO DOCKET ¹ FACIL:50-368 Susquehanna Steam Electric Station, Unit 2, Pennsylva 05000388 AUTH. NAME AUTHOR AFFILIATION METER,J.J. Pennsylvania Power & Light Co.

STANLEY,H.G. Pennsylvania Power & Light Co.

RECIP . NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-007-01:on 900705,primary power supply to RPS A power distribution panel lost whrn one electrical protection assembly (EPA) breakers tripped.EPA logic cards reviewed &

RPS power supply will be redesigned.W/930609 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PDl-2 LA 1 1 PD1-2 PD 1 1 CLARK,'R 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 NRR/DRPW/OEAB 1 1 NRR/DRSS/PRPB 2 2 198R/~DSSA SPLB 1 1 NRR/DSSA/SRXB 1 1 REG FILE- 02 '1 1 RES/DSIR/EIB 1 1 GN1 FILE 01 1 1 EXTERNAL'G&G BRYCE g J ~ H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYiG.A 1 1 NSIC POOREgW. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTETH CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 ENCL 32

- Pennsylvania Power 8 Light Company Two North Ninth Street ~ Allentown, PA 18101 ~ 215/ 7705151 June 9, 1993 U.S. Nuclear Regulatory Control Desk Commission'ocument Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 90-007.-01 FILE R41-2 PLAS 566 Docket No. 50-388 License No. NPF-22 Attached is Licensee Event Report 90-007-01 which is an update to LER 90-007-00. The event was determined reportable per 10CFR50.73(a)(2)(iv) in that unplanned actuations of Engineered Safety Features occurred due to the loss of the primary power supply to the Division 1 Reactor Protection System power distribution panel when one Electrical Protection Assembly breaker tripped.

'H.G.

~ltanley VP Nuclea Operations JJM/mjm cc: Mr. T. T. Martin Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. G. S. Barber Sr. Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 35 Berwick, PA 18603-0035 X40nsa 9306150200 930609 PDR ADOCK 05000388 8 PDR

NRC FORM 386 V.S. NUCLEAR REGULATORY COMMISSION (64)9) APPAOVEO OMB NO. 31500104 EXPIRES: 4I30I92 ESTIMATED BURDEN PEA RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD L(CENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P630), U.S. NUCLEAR REGVLATORY COMMISSION, WASHINGTON, DC 20565, AND TO THE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET. WASHINGTON, OC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) PAGE 3 S eharna Steam Electric Station Unit 2 p 5 p p p 3 8 81 DF TITLE (4)

ESF Actuations Doe to HPS EPA Breaker Spurious Trip EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR ~< SSQVSNTIAL NVMSEA II8 Inslors MONTH tvVMSSII OAY YEAR FACILITYNAMES DOCKET NUMBER(SI 0 5 0 0 0 0 7 0 5 9 0 9 0 0 0 7 0 1 0 6 0 9 9 3 0 5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PURSUANT T 0 THE RLOUIREMENTS OF 10 CFR (): IChectr one or more of the follovrlnpi (11 MODE (1) 20A02(S) 20.405(c) 50,73( ~ l(2) livl 73.71(II)

POWER 20A06 (4) (I ) (I) 50.38(cl(1) 60.73(el l2)(vl 73.71(c)

I EYEL 1 0 0 20A05 (4) (1) (6 I 50.38(cl(2) 60.73(s) l2)(vill OTHER ISpecily in Ahttrect helow end In Text, HRC Form 20A05(s)(1) liiil 50.73( ~ l(2)(i) 50.73(s) (2 H vi i i) (A) 366AI 20.405(s l(1) (Iv) 50.7 3(s) (2) (ii) 50.73(sl(2)(vii() (Bl 20A05(s) l1) (v) 50.73(s) (2) (iii) 50.73 (4) (2) (x I LICENSEE CONTACT FOR THIS LFR (12)

NAME TELEPHONE NUMBER AREA CODE J. J. Meter Powm Production Engineer COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBEO IN THIS REPORT (13) 717542-187 "IX X' r .%O.

g MANUFAC. MANUFAC.

CAUSE SYSTEM COMPONENT TURER TO NPROS CAUSE SYSTEM COMPONENT TURER TO N)yv r 5 2 G 0 8 0 Y SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED SUBMISSION DATE I15I YES Ilf yet, complete EXPECTED SVBMISSIOH DA TEI X No ABSTRACT ILlmlt to f400 tpecer, I e., epproxlmetely fifteen sinpreepece typewritten Iinerl (18)

At 1633 on July 5, 1990, with the Unit operating at, 1004 power, the primary power supply to the "A" Reactor Protection System (RPS) power distribution panel was lost when one of its Electrical Protection .

Assembly (EPA) breakers tripped. This interruption caused the Reactor Water Cleanup system, and various other Primary Containment Isolation system components to isolate and the Standby Gas Treatment System and Control Room Emergency Outside Air Supply System to auto initiate.

plant systems and components functioned properly and as expected in All response to the event. No reactor parameters were affected and no Emergency Core Cooling Systems were actuated. EPA breaker was reset at 1640 and all isolation signals were reset byThe 1646. Full power operation of the unit continued without interruption. The cause of this EPA breaker trip as well as others at the Station have been investigated.

In general, the majority of the EPA breaker trips have been linked to a failure/anomaly of an electrical subcomponent on the EPA logic card.

Logic cards have undergone subcomponent lifetime upgrades and other RPS power supply components have been cleaned, inspected and optimized. The long term action is to modify the RPS supply systems such that the latest version of EPA logic cards willpower replace the existing models and forced cooling to the EPA cards will be provided.

NRC Form 366 (669)

(6+9)'.S.

NRC FORM 366A LICENSEE EVENT REPORT (LER)

NUCLEAR REGULATOAY COMMISSION APPROVED OMB NO. 31500104 EXP IR ESI 4/30/92 ESTIMATED BURDEN PER AESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (F430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2)

LER NUMBER (6) PAGE (3)

YEAR SLS< SEQUENTIAL REVISION

%M NUMSER NUMSER Unit 2 Su ehanna Steam Electric Station TEXT /I/ mom Spoco /4 ntqu/Iud, uoo oddldooo//VRC FomI 36M'4/ () 7) 38890 007 0102 oF 0 5 DESCRIPTION OF EVENT At 1633 on July 5, 1990 with the Unit operating at 1004 power, the primary power supply to the "A" Reactor Protection System (RPS; EIIS Code: JC) power distribution panel 2Y201A was lost when one of its Electrical Protection Assembly (EPA) breakers, 2CB-S003A-C, tripped. This power interruption resulted in Primary Containment Isolation System (EIIS Code: JM) actuations and automatic system initiations. RPS as well as other plant systems functioned as designed in response to the event. The major actuations were as follows:

1) Reactor Building Isolated.

HVAC (EIIS Code: VA) Zones II and III

2) Reactor Water Cleanup System (EIIS Code: CE) inboard isolation valve closed.

3) Cooling water isolation valves to the Reactor Recirc Pumps closed (EIIS Code: CC).

4) "A" Standby Gas Treatment System (EIIS Code: BH) auto initiated.

5) "A" Control Room Emergency Outside Air Supply System (EIIS Code: BH) auto initiated.

The EPA breaker was reset at 1640, all reset by 1646, and all affected systems isolation were subsequently signals were restored. Full power operations of the Unit continued without interruption.

CAUSE OF EVENT The loss of power to the "A" RPS bus was due to an unexpected trip of the downstream primary power supply EPA breaker. The EPA logic cards monitor RPS power for conditions of undervoltage, and underfrequency and trip the EPAovervoltage, breakers when these conditions exist or when the logic card fails. EPA breakers are in series and the trip of either breaker will interrupt power to the distribution panel.

The cause of this EPA breaker trip as well as others at the Station have been investigated. In general, the majority of the EPA breaker trips at the station have been linked to a failure/anomaly of an electrical subcomponent on the EPA logic NRC F oRR 366A (64)9)

NRC FORM SSSA V.S. NUCLEAR REGULATORY COMMISSION (609( APPROVED OMB NO. 31500104 EXPIRFSI 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (PJ)30), U.S, NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500(04), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) (.ER NUMBER (6) PAGE (3)

SEQUENTIAL ~?' REVISION YEAR @( NUMBER '.~ NUMBER Unit 2 Susquehanna Steam Electric Station TEXT ///moIP 4F444/4 IRTII/IPd, II44 Pddir4IIM//VRC FamI 3SS/(3/ (12) o s o o o 3 8 8 9 0 0 0 7 0 l 0 3 op 05 card. A subcomponent failure such as a capacitor or a transistor would cause the logic card to fail and subsequently trip the EPA breaker.

Contributing factors to subcomponent failures were increasing subcomponent age and higher than optimum temperature of the subcomponent environment. As a subcomponent life increases, particularly capacitors, the EPA cards with subcomponents become less reliable and eventually fails. This "aging" process was found to be applicable when the EPA logic card was both in service and in storage. The higher the temperature a subcomponent is subjected to, the shorter its reliable life becomes. In May of 1991 a task team was formed to address the reliability of the RPS power supply systems at the Station.

Prior to the task team being formed and reaching its conclusions, logic cards that experienced a trip were not examined on a subcomponent basis. Failed logic cards were typically returned to the manufacturer for analysis. The manufacturer would then replace the subcomponent(s) that failed. The card would then be returned and either put into service or stored for future use.

In both instances the logic cards contained both new and used subcomponents. The temperature of the EPA. logic card environment was found to be greater than optimum. The ambient room temperature were EPA cards are located was near 90 degrees F. In addition the EPA cards were mounted in a sealed junction box which further increased subcomponent temperature.

CORRECTIVE ACTIONS As described above, in May of 1991 a task team was formed to address the reliability of the RPS power supply systems at the Station. Two main objectives were established. The first objective was short term and was to reduce the number of spurious RPS power supply trips by enhancing and better maintaining the components in the present systems. The second was long term and was to reduce spurious RPS power supply trips and increase reliability via the modification process.

In the short term, EPA logic cards were reviewed on an individual basis and subcomponents lifetime upgrades were performed so that each card could be reasonably expected not to fail within a five year lifetime. The junction boxes that house the EPA logic cards were equipped with ventilation louvers thereby reducing the ambient temperatures for the logic card subcomponents. Other short term actions included cleaning, inspecting and optimizing performance of RPS power supply components such as motor-NRC Form 366A (BBS)

NAC FORM &$6A U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO. 31500104 (6P9)'

EXPIRES: 4/30/92

'ESTIMATED BURDEN PEA RESPONSE TO COMP(.Y WTH THIS LICENSEE EVENT REPORT (LER) INFOAMATION COLLECTION REOUEST: 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P4)30), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555. ANO TO THE PAPERWORK REDUCTION PROJECT (3)504)104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

+~+ SEQUENTIAL 3'P REVISION YEAR NUMBER '- NUMBER Unit Susquehanna 2

Steam Electric Station TEXT /// more eoece /4 rerler)ed. Iree odd/I/one/NRC Form 3664'4/ (IT) 60o03890 007 01 0 4 oF 0 5, generator sets, regulating transformers, relays and connection panels.

The long term corrective action was to develop an RPS power supply modification that reduced spurious trips and increased reliability. After extensive analysis, modifications have been designed for the RPS power supply systems. The redesigned RPS power supply will utilize an improved version of EPA logic cards in lieu of the existing models and forced cooling to the EPA enclosures will be provided.

REPORTABILITY ANALYSIS This event. was determined to be reportable under 10CFR50.73(a)(2)(iv) in that unplanned actuations of Engineered Safety Features (ESF) occurred when the RPS EPA breaker tripped.

Since all ESF systems and components functioned properly and per design, there were no safety consequences or compromises to the health or safety of the public.

Had this event occurred with the Unit in cold shutdown or refueling, the safety significance would have been greater due to the fact that shutdown cooling could have been temporarily lost.

Even under these conditions the safety significance would be minimal since the plant is more than adequately designed to safely handle this type of event.

In accordance with the guidance provided in NUREG 1022 Supplement 1 items 14.1 and 14.10, the original submission date for this report was 8-6-90. No further updates to this report are expected.

ADDITIONAL INFORMATION Failed Component Information:

Component EPA Logic Card Model 147D8652 G001 & G003 Manufacturer General Electric A review of past Licensee Event Reports (LERs) for the station identified twelve other events where EPA breakers trips resulted in ESF actuations.

NRC Form 366A (669)

NRC FORM 366A

(&BI()

l LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION U.S. NUCLEAR AEGULATOAYCOMMISSION APPAOVED OMB NO. 31500104 EXP IR ESI 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFOAMATION COLLECTION REQUEST: 505) HAS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP.530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWOAK REDUCTION PROJECT (31500)04). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (21 LER NUMBER (6) PAGE (3)

SEQUENTIAL v~~ REVISION YEAR g> NUMSER NUMBER Unit 2 S ehanna Steam Electric Station o s o o o 3 8 8 9 0 0 0 7 0105 OF 0 5:

TEXT /ffmoro Snooo ir ooqo/rod, Irro odd/)/ono/HRC Form 36(/4'4/(11)

UNIT 1 (Docket No. 50-387/License No. NPF-14)

LER 92-007 LER 87-024 LER 92-001 LER 86-029 LER 91-006 LER 86-023 LER 91-004 LER 83-172 LER 90-005 UNIT 2 (Docket No. 50-388/Licensee No. NPF-22)

LER 91-008 LER 91-007 LER 88-005 NRC Form 366A (BBB)