Information Notice 1991-51, Inadequate Fuse Control Programs
_1 I4UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555August 20, 1991NRC INFORMATION NOTICE NO. 91-51: INADEQUATE FUSE CONTROL PROGRAMS
Addressees
- All holders of operating licenses or construction permits for nuclear powerreactors.
Purpose
- _This information notice is intended to alert addressees to potential problemscaused by inadequate programs to control activities related to fuses. It isexpected that recipients will review the information for applicability to theirfacilities and consider actions, as appropriate, to avoid similar problems.However, suggestions contained in this information notice do not constitute NRCrequirements; therefore, no specific action or written response is required.
Description of Circumstances
- -During recent inspections, the U.S. Nuclear Regulatory Commission (NRC) hasidentified numerous deficiencies involving fuse control programs. Thesedeficiencies included inadequate root cause evaluations of blown fuses,inadequate verification of design information for installed and replacementfuses, inadequate identification and labeling of fuses, and lack of coordina-tion between fuses and circuit breakers.Other fuse control problems, especially those resulting from personnel errors,have been reported in licensee event reports (LERs). As reported in the LERs,these personnel errors have caused inadvertent operation or loss of vital plantequipment and, in some cases, have resulted in a loss of offsite AC power andthe spurious actuation of engineered safety features (ESF).Discussion:The main function of a fuse is to prevent or minimize damage to the electricaldistribution system (EDS) and related components and to limit the effect andextent of service interruptions whenever any portion of the system is subjectedto a fault. Fuses are relied upon to isolate electrical faults to ensureminimum disturbance to the system. Fuses are also uses as electrical isolationdevices between a class 1E power supply and non-class 1E electrical equipment.Proper protection is achieved through the careful selection of the type and therating of the fuse. If an oversized fuse is selected that has a higher capa-city than the upstream fuse or breaker, the oversized fuse could make the entireS4 2T~ , 7:V /16'
IN 91-51August 20, 1991 -bus unavailable in case of a fault within the circuit. In addition, a faultedcircuit with an oversized fuse can degrade the voltage of a bus and impartexcessive heat to adjacent cables. On the other hand, .if an undersized fuse isselected, the undersized fuse could lead to a loss of the safety.function ofequipment by prematurely opening the protected circuit. Therefore, whenselecting fuses, it is important to consider the voltage, current, interruptingrating, fuse type, and coordination with other fuses and circuit breakers.Common deficiencies identified during recent NRC inspections of fuse controlprograms are as follows:Inadequate Root Cause Evaluation of Blown FusesDuring an NRC inspection at Zion Nuclear Power Station, Unit 2 (NRC Inspec-tion Report 50-295/90-13)i the staff noted that on July 7, 1990, Unit 2personnel declared an alert condition because of a partial loss of theannunciators in the control room for the nuclear steam supply system (NSSS)and the balance-of-plant (BOP) systems. The loss of the annunciatorsapparently resulted from blown fuses in the power supplies for the annun-ciators. On 11 different occasions between July 1 and July 7, 1990, fusesblew in various NSSS and BOP annunciator power supplies. The licensee'selectrical maintenance personnel and operators continued to replace-theblown fuses without contacting the technical staff engineers to determinethe root causes of the excessive fuse failures until after the event onJuly 7, 1990. Subsequently, the licensee determined that some of thefuses installed in 125 VDC power supplies were rated for 32 VOC.Inadequate Verification of Design Information for Installed andReplacement FusesIn June 1990, during an NRC maintenance team inspection at KewauneeNuclear Power Plant (NRC Inspection Report 50-305/90-11), the NRC identi-fied a number of discrepancies between design documents and fuses in-stalled in AC and DC safety-related fuse panels. In addition, the NRCfound that many design documents did not contain information regarding thesize, rating, type, or manufacturer of the fuse. The discrepant fuses andthe lack of design information could have caused inadequate system andcomponent protection.Inadequate Identification and Labeling of FusesIn July and August 1990, during an electrical distribution system func-tional inspection (EDSFI) at the Trojan Nuclear Plant (NRC InspectionReport 50-344/90-200), the NRC determined that tbL licensee did not havean adequate program to control the identification, labeling, and replace-ment of fuses. The NRC also determined that the lack of a fuse controlprogram had contributed to past problems with incorrectly installed fuse K 9<_ IN 91-51August 20, 1991 Improper Coordination of Fuses and Circuit BreakersIn May 1990, during a routine inspection at the Palisades Nuclear Generat-ing Plant (NRC Inspection Report 50-255/90-10), three examples were foundin which fuses and breakers did not coordinate in all regions on thecoordination curves. This, in turn, might have resulted in a disturbanceto the system under fault conditions not being minimized. In addition,the NRC found that the licensee's fuse procedure specified voltage andcurrent ratings for fuse replacements but did not include the model andtype. Without all of the proper information, such as the time/currentcharacteristics of the fuse, proper coordination and protection. may nothave been obtained.Personnel ErrorsAlthough personnel errors cannot be totally eliminated from routine,emergency, or corrective plant maintenance, a review of LERs indicatesthat most errors are caused by either the plant staff not being adequatelytrained or plant procedures not being adequately detailed. Some examplesof these LERs are included in Attachment 1. A well designed fuse controlprogram along with trained personnel and clear procedures could reduceerrors in fuse control significantly.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Zelig Falevits, RIII(708) 790-5772Roger Mendez, RIII(708) 790-5589Fred Burrows, NRR(301) 492-3260
Attachments:
-<1. Examples of LERs Related to Fuse ProblemsCaused by Personnel Errors2. List of Recently Issued NRC Information Notices QAttachment 1IN 91-51August 20, 1991 Examples of LERs Related to Fuse ProblemsCaused by Personnel ErrorsFacility: Dresden Unit 2LER No.:Abstract:Facility:LER No.:Abstract:Facility:LER No.:Abstract:Facility:50-237/88-023On December 31, 1988, with the unit in the refueling mode, an ESFactuation occurred and subsequently caused initiation of the standbygas treatment system and isolation of the reactor building ventila-tion system. The ESF actuation occurred-when the wrong fuses werepulled after an operating shift foreman erroneously changed the fusenumbers on the equipment outage checklist. The operating shift fore-man believed that the fuse numbers originally listed on the equipmentoutage checklist were incorrect. He changed the fuse numbers butfailed to have a second operator independently verify the change. Asa result of this error, the wrong fuses were pulled and an unexpectedESF actuation occurred.Peach Bottom Unit 250-277/88-006On March 3, 1988, the unit experienced an actuation of the primarycontainment isolation system as the result of a loss of power to then"A" residual heat removal system logic bus. The loss of power wascaused by an improperly filled out blocking permit which directedthe individual performing the block to remove a fuse from a wrongpanel.Zion Unit 150-295/87-009On April 30, 1987, with the unit in hot shutdown, the unit experi-enced a safety injection and opening of the main steam isolationvalves which pressurized the steam line to approximately 800 psig(from approximately 80 psig). The event occurred because an elec-trical equipment operator failed to pull fuses in the requiredsequence.Fort Calhoun Unit 1LER No.:Abstract:50-285/87-009 -WCAOn April 4, 1987, the unit experienced an unplanned loss of alloffsite AC power because of personnel error. The loss of offsite ACpower occurred when electrical maintenance personnel were performingmaintenance on a transformer's secondary side non-segregated busduct. They inadvertently pulled the wrong transformer fuses,resulting in the tripping of an on-line transformer, the opening ofthe secondary side breakers and, ultimately, the temporary loss ofall offsite AC power to the plan eAttachment 2IN 91-51August 20, 1991 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to91-5091-4991-4891-4789-56,Supp. 291-4691-45A Review of Water HammerEvents After 1985Enforcement of SafetyRequirements for Radiog-raphersFalse Certificates of Con-formance Provided by West-inghouse Electric SupplyCompany for Refurbished Com-mercial-Grade CircuitBreakersFailure of Thermo-LagFire Barrier Material toPass Fire-Endurance TestQuestionable Certificationof Material Supplied tothe Defense Department byNuclear SuppliersDegradation of EmergencyDiesel Generator Fuel OilDelivery SystemsPossible Malfunction ofWestinghouse ARD, BFD, andNBFD Relays, and A200 DCand DPC 250 Magnetic Con-tactors08/20/91 All holders of OLs or CPsfor nuclear power reactors.08/15/91 All Nuclear Regulatory Com-mission (NRC) licenseesauthorized to use sealedsources for industrialradiography.08/09/91 All holders of OLs or CPsfor nuclear power reactors.08/06/91 All holders of OLs or CPsfor nuclear power reactors.07/19/91 All holders of OLs or CPs.for nuclear power reactors.07/18/91 All holders of OLs or CPsfor nuclear power reactors.07/05/91 All holders of OLs or CPsfor nuclear power reactors.91-44Improper Control ofChemicals in Nuclear FuelFabrication07/08/91-441 nuclear fuel facilities.OL = Operating LicenseCP = Construction Permi IN 91-51-August 20, 1991 Improper Coordination of Fuses and Circuit BreakersIn May 1990, during a routine inspection at the Palisades Nuclear Generat-ing Plant (NRC Inspection Report 50-255/90-10), three examples were foundin which fuses and breakers did not coordinate in all regions on thecoordination curves. This, in turn, might have resulted in a disturbanceto the system under fault conditions not being minimized. In addition,the NRC found that the licensee's fuse procedure specified voltage andcurrent ratings for fuse replacements but did not include the model andtype. Without all of the proper information, such as the time/currentcharacteristics of the fuse, proper coordination and protection may nothave been obtained.Personnel ErrorsAlthough personnel errors cannot be totally eliminated from routine,emergency, or corrective plant maintenance, a review of LERs indicatesthat most errors are caused by either the plant staff not being adequatelytrained or plant procedures not being adequately detailed. Some examplesof these LERs are included in Attachment 1. A well designed fuse controlprogram along with trained personnel and clear procedures could reduceerrors in fuse control significantly.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Zelig Falevits, RIII(708) 790-5772Roger Mendez, RIII(708) 790-5589Fred Burrows, NRR(301) 492-3260
Attachments:
1. Examples of LERs Related to Fuse ProblemsCaused by Personnel Errors2. List of Recently Issued NRC Information Notices*SEE P VIOUS CONCURRENCES_NEEI "<t/OGCB:DOEA:NRR *RPB:ADM *D/DRIS:NRR *D/DST:NRRCHBerlinger TechEd BKGrimes AThadani08/1 08/ /91 08/07/91 08/06/91 08/05/91*OGCB:DOEA RR *RIII *RIII *SELB:DST:NRR*C/SELB:DST:NRRPCWen ZFalevits RMendez FHBurrows FRosa07/26/91 07/26/91 07/26/91 07/29/91 07/31/91DOCUMENT NAME: IN 91-51 (0IN 91-XXAugust xx, 1991 Improper Coordination of Fuses and BreakersIn May 1990, during a routine inspection at the Palisades Nuclear Generat-ing Plant (NRC Inspection Report 50-255/90-10), three examples were foundin which fuses and breakers did not coordinate in all regions on thecoordination curves. This, in turn, might not have minimized the distur-bance to the system under fault conditions. In addition, the NRC foundthat the licensee's fuse procedure specified voltage and current ratingsfor fuse replacements but did not include the model and type. Without allof the proper information, such as the time/current characteristics of thefuse, proper coordination and protection may not have been obtained.Personnel ErrorsAlthough personnel errors cannot be totally eliminated from routine,emergency, or corrective plant maintenance, a review of LERs indicatesthat most errors are caused by either the plant staff not being adequatelytrained or plant procedures not being adequately detailed. Some examplesof these LERs are included in Attachment 1. A well designed fuse controlprogram along with trained personnel and clear procedures could reduceerrors in fuse control significantly.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Zeli Falevits, RIII(708) 790-5772Roger(708)Mendez, RIII790-5589Fred Burrows, NRR(301) 492-3260
Attachments:
1. Examples of LERs Related to Fuse ProblemsCaused by Personnel Errors2. List of Recently Issued NRC Information NoticesDocument Name: IN FOR FUSE CONTROL INSPE*SEE PREVIOUS CONCURRENCESD/DOEA:NRR C/OGCB:DOEA:NRR *RPB:ADMCERossiod CHBerlinger! TechEd08/ /91 08/12491 ¶ 08/07/91*OGCB:DOEA:NRR *RIII *RIIIPCWen ZFalevits RMendez07/26/91 07/26/91 07/26/91*D/DRIS:NRR *D/DST:NRRBKGrimes AThadani08/06/91 08/05/91*SELB:DST:NRR*C/SELB:DST:NRRFHBurrows FRosa07/29/91 07/31/91
--vt @* This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.?'iCharles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Zelig Falevits, RIII(708) 790-5772Roger Mendez, RIII(708) 790-5589Fred Burrows, NRR(301) 492-3260
Attachments:
1. Examples of LERs Related to Fuse ProblemsCaused by Personnel Errors2. List of Recently Issued NRC Information NoticesDocument Name: IN FOR FUSE CONTROL INSPECTIOND/DOEA:NRRCERossi07/ /91OGCB:DOEA:N RPCWen07/9b/C/OGCB:DOEA:NRR RPB:ADMCHBerlinger 7flw TechEd07/ /91 p07/ /9:RI I I ?J RIIIiCVFaldvits 4vpMendez8 7/ab6/91 1 07/9/9KR aCA~~s pER -,W. E, 0JI