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{{Adams
#REDIRECT [[05000327/LER-2015-003]]
| number = ML15322A054
| issue date = 11/13/2015
| title = LER 15-003-00 for Sequoyah, Unit 1, Regarding Manual Reactor Trip Due to Loss of Power to the Vital Instrument Power Board 1-II
| author name = Carlin J T
| author affiliation = Tennessee Valley Authority
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000327
| license number = DPR-077
| contact person =
| document report number = LER 15-003-00
| document type = Letter, Licensee Event Report (LER)
| page count = 7
}}
 
=Text=
{{#Wiki_filter:Tennessee Valley Authority, Post Office Box,2000, Soddy Daisy, Tennessee 37384-2000November 13, 201510 CFR 50.73AI-FN: Document Control DeskU.S. Nuclear Regulatory CommissionWashington, D.C. 20555-0001Sequoyah Nuclear Plant, Unit 1Renewed Facility Operating License No. DPR-77NRC Docket No. 50-327
 
==Subject:==
Licensee Event Report 50-327/2015-003-00, "Manual Reactor Trip due toLoss of Power to the Vital Inverter Power Board 1-Il"The enclosed Licensee Event Report provides details concerning a manual reactor tripfollowing a loss of power to the Vital Instrument Power Board 1-Il. This report is beingsubmitted in accordance with 10 CFR 50.73 (a)(2)(iv)(A), as an event that resulted in amanual or automatic actuation of the Reactor Protection System and the AuxiliaryFeedwater System. This condition had no impact on Unit 2.There are no regulatory commitments contained in this letter. Should you have anyquestions concerning this submittal, please contact Jon Johnson, Acting Sequoyah SiteLicensing Manager, at (423) 843-8129.Si President-rah Nuclear Plant
 
==Enclosure:==
Licensee Event Report 50-327/2015-003cc: NRC Regional Administrator -Region IINRC Senior Resident Inspector -Sequoyah Nuclear Plant NINNRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 01131/2017(02-2014)burden per response to comply with this mandatory collection request: 80 hours.=..y°`,Reported lessons learned are incorporated into the licensing process and fed back to industry... * =Send comments regarding burden estimate to the FOIA, Pdtvacy and Information Collections.... LICE SEE VEN REP RT (ER) Branch (T-5 F53), U.S. Nuclear Regalatory Commission, Washington, DC 20555-0001, or byLICE SEE VEN REP RT (ER) internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and(See Page 2 for required number of Regulatory Atfairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC20503. If a means sused to impose an information collection does not display a currently valid 0MBdigits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to,the information collection.1. FACILITY NAME 2. DOCKET NUMBER 13. PAGESequoyah Nuclear Plant Unit 1 05000327[1O 64. TITLEManual Reactor Trip due to Loss of Power to the Vital Instrument Power Board 1-115. EVENT DATE 6. LER NUMBER I 7. REPORT DATE J8. OTHER FACILITIES INVOLVEDMONT1DA7YER1iFACILITY NAME DOCKET NUMBERMOT A ER YA SEOUENTIALI REV IMONTH DAY YEAR NAIEAIINUMBER INO.NI ~ ~ iFACILITY NAME DOCKET NUMBER09 14 2015 2015 -003 -00I1 13 2015 NA9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)'[] 20.2201(b) [] 20.2203(a)(3)(i) lii 50.73(a)(2)(i)(C) D] 50.73(a)(2)(vii)[] 20.2201(d)' [ 20.2203(a)(3)(ii) [] 50.73(a)(2)(ii)(A) [] 50.73(a)(2)(viii)(A)[] 20.2203(a)(1) E] 20.2203(a)(4) E] 50.73(a)(2)(ii)(B) L] 50.73(a)(2)(viii)(B)D] 20.2203(a)(2)(i) [] 50.36(c)(1)(i)(A) [] 50.73(a)(2)(iii) fl 50.73(a)(2)(ix)(A)10. POWER LEVEL [] 20.2203(a)(2)(ii) [] 50.36(c)(1)(ii)(A) X 50.73(a)(2)(iv)(A) [] 50.73(a)(2)(x)L] 20.2203(a)(2)(iii) [] 50:36(c)(2) [] 50.73(a)(2)(v)(A) LI 73.71(a)(4)[] 20.2203(a)(2)(iv) [] 50.46(a)(3)(ii) [] 50.73(a)(2)(v)(B) [] 73.71 (a)(5)10 f 20.2203(a)(2)(v) [] 50.73(a)(2)(i)(A) [] 50.73(a)(2)(v)(C) LI OTHEREl 20.2203(a)(2)(vi) [] 50.73(a)(2)(i)(B) [] 50.73(a)(2)(v)(D) Specifyin.Abstract beloworin_________________ ___________________________________________ NRC Form 366A12. LICENSEE CONTACT FOR THIS LERLICENSEE CONTACTITEPOENME(IcueAaCoe13._COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTCAUSEE SYSTEME I COMPONs14. SUPPLEMENTAL REPORT EXPECTEDEl YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [] NOA.BSTRACT (Limit to 1400 spaces, i e., approximately 15 single-spaced typewritten lines)On September 14, 2015, at 0426 Eastern Daylight Time, Sequoyah Nuclear Plant (SQN) Unit 1 reactor wasmanually tripped due to a loss of power to the Vital Instrument Power Board (VIPB) 1-11. Prior to the reactortrip, operators were in the process of realigning Vital Inverter 1-Il for planned maintenance. During thisevolution, VIPB 1-Il became de-energized. Operators entered Abnormal Operating Procedure AOP-P.03, "Lossof Unit 1 Vital Instrument Power Board" which required a manual reactor trip. Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply at 0550. All plant safety systems responded asdesigned, all control rods fully inserted, and auxiliary feedwater automatically initiated from the feedwaterisolation signal as expected. It was determined that an Alternating Current (AC) output switch failed causingthe loss of power to the VIPB 1-Il. The direct cause of the switch failure was due to increased friction of bearingsurfaces caused by lack of appropriate lubrication. The lack of lubrication was related to a failure to implementacorrective action following an operating experience review at SQN in 2000 of a similar event at McGuireNuclear Station. The failure to implement a corrective action was determined to be the root cause of this event.Corrective actions to prevent recurrence include ensuring the existing requirement for management review ofall corrective action closures remains in the Corrective Action Program. Unit 2 was unaffected by this event.NRC FORM 366 (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 011311201702-2014).burden per response to comply with this mandatory collection request: 80 hours.,* *Reported lessons learned are incorporated into the licensing process and fed back to industry.Send comments regarding burden estimate to the FOIA, Privacy and Information Collections(~ ) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by".- LICENSEE EVENT REPORT (LER) internet e-mail to Infocollects.Resource@nro.gov, and to the Desk Officer, Office of InformationadRegulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget,CONTINUATION SHEET Washington, DC 20503. If a means used to impose an information collection does not display acurrenhly valid 0MB control number, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information collection.1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEIIj SEQUENTIAL REVYEARNUMBER NO.Sequoyah Nuclear Plant Unit I1 05000327 YER2 OF. 6__ _ _ _ _ _ __ _ _ _ _ _ __ _ _ _jJ 2015 -003 -00NARRATIVEI. Plant Operating Conditions Before the EventAt the time of the event, Sequoyah Nuclear Plant (SQN) Unit 1 reactor was operating at 100 percentrated thermal power (RTP). The condition described in this LER did not impact SQN Unit 2.II. Description of EventsA. Event:On September 14, 2015, at 0426 Eastern Daylight Time (EDT), SQN Unit 1 reactor wasmanually tripped due to a loss of power to the Vital Instrument Power Board (VIPB) 1-Il [EllSCode EE]. Prior to the reactor trip, operators were in the process of realigning Vital Inverter 1-Il[Ells Code INVT] for planned maintenance. During this evolution, the VIPB 1-Il became de-energized. Operators entered Abnormal Operating Procedure AOP-P.03, "Loss of Unit 1 VitalInstrument Power Board" which required a manual reactor trip. Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply at 0550. All plant safety systemsresponded as designed, all control rods fully inserted as required, and auxiliary feedwaterautomatically initiated from the feedwater isolation signal as expected.The manual trip was in response to an alternating current (AC) output switch (EllS Code JS)failure that occurred on the Vital Inverter 0-Il. This failure resulted in the loss of power to VIPB 1-I1. The switch failure occurred due to increased friction of bearing surfaces caused by lack of'appropriate lubrication.B. Status of structures, components, or systems that were inoperable at the start of the eventand contributed to the event:There were no inoperable structures, components or systems that contributed to this event.C. Dates and approximate times of occurrences:The event occurred during the realignment of the Vital Inverter 1-Il for plannedmaintenance. The realignment involved placing Vital Inverter 0-Il into service to feed theVIPB 1-11. During the realignment, VIPB 1-11 lost power. The loss of power required entryinto Technical Specification (TS) Limiting Condition of Operation (LCO) 3.8.2.1 and amanual reactor trip in accordance with AOP-P.03. Following the manual reactor trip,power was restored to the VIPB 1-Il.NRC FORM 366A (02-201 4)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEIISEQUENTIAL IREVYEAR NUMBER NOSequoyah Nuclear Plant Unit 1 05000327 I13 OF 6NARRATIVEDates and Times Description..September 14, 2015 at Clearance approved for placing Vital Inverter 0-Il into0102 EDT service as an alternate feed to VIPB 1-11.September 14, 2015 at Vital Inverter 0-11.placed into service to the VIPB 1-Il.0405 EDTSeptember 14, 2015 at Loss of power to VIPB 1-1l occurred.0421 EDTSeptember 14, 2015 at TS LCO 3.8.2.1 entered due to loss of VIPB 1-Il.0423 EDTSeptember 14, 2015 at Unit 1 reactor manually tripped as directed by AOP-0426 EDT P.03.September 14, 2015 at* VIPB 1-Il restored to normal power supply.0550 EDTD. Manufacturer and model number of each component that failed during the event:The failed component was an AC molded case output switch on Vital Inverter 0-Il. The switchfailure led to a loss of power to the VIPB 1-Il. The switch manufacturer is General Electric (GE),part # TQD22Y225.E. Other systems or secondary functions affected:There were no other systems or functions affected by this event.F. Method of discovery of each component or system failure or procedural error:Observations and functional testing of the 0-11 vital inverter identified erratic operation of the 0-IlAC inverter output switch. The output switch exhibited failure to latch and stay latched duringbench testing. It was concluded that this switch failure resulted in the loss of the VIPB 1-Il andsubsequent manual reactor trip.NRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(o2-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER j 3. PAGEIISEQUENTIAL REVuYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 4 OF 61[2015 -003 -00NARRATIVEG. The failure mode, mechanism, and effect of each failed component, if known:The failed component for this event is the vital inverter 0-1l output switch. The switch failed tolatch and stay latched due to increased friction of bearing surfaces caused by lack of appropriatelubrication.H. Operator actions: -Upon receipt of multiple alarms, bi-stables lit, rods stepping in, and the centrifugal charging pumpsuction valve from the refueling water storage tank open, the operators verified no runback wasin progress and placed the rod control system in manual. Operators entered AOP-P.03, "Loss ofUnit 1 Vital Instrument Power Board," tripped the reactor, and entered Emergency Procedure E-0"Reactor Trip or Safety Injection," while continuing in AOP-P.03. The operators then transitionedto Emergency Subprocedure ES-0. 1, "Reactor Trip Response." Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply.I. Automatically and manually initiated safety system responses:Following the manual reactor trip, plant safety systems responded as designed. All controlrods fully inserted as required. Auxiliary automatically initiated from the feedwaterisolation signal as expected.Ill. Cause of the eventA. The cause of each component or system failure or personnel error, if known:The direct cause of the event was failure of the output switch on Vital Inverter 0-Il. This outputswitch failed open causing loss of power to the VIPB 1-Il resulting in entry into AOP-P.03directing a manual reactor trip.B. The cause(s) and circumstances for each human performance related root cause:The root cause was determined to be failure to implement a corrective action from SQN'sreview of an operating experience event in 2000. The root cause is documented incondition report (CR) 1081482.IV. Analysis of the event:SQN Unit I reactor was manually tripped in response to loss of power to VIPB 1-Il on.September 14,2015. The loss of power was due to a failed AC output switch on Vital Inverter 0-I1. The switch faileddue to increased friction of bearing surfaces caused by lack of appropriate lubrication.The plant transient response including reactor power, reactor coolant system (RCS) pressure, RCStemperature, pressurizer level, RCS secondary side pressure, and AFW flow remained withintechnical specification limits and were bounded by the Updated Final Safety Analysis Report(UFSAR) analysis. Containment pressure, temperature, and radiation were unaffected by thisNRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME j2. DOCKET 6. LER NUMBER [ 3. PAGEI ISEQUENTIAL IREVYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 I 5 OF 6I _____ 2015 -003 -00NARRATIVEtransient. Steam generator level experienced during this event was bounded by UFSAR analysis.The plant responded as expected for the conditions of the trip.Observations and functional testing of Vital Inverter 0-Il identified erratic operation of the 0-Il1ACinverter output switch. The output switch exhibited failure to latch and stay latched during benchtesting. No other discrepancies were identified with the inverter. It was concluded that this switchfailure resulted in the loss of VIPB 1-Il and the subsequent manual reactor trip.V. Assessment of Safety ConsequencesThere were no safety consequences as a result of the event. Safety systems functioned asdesigned and no complications were experienced. No Technical Specification limits were exceededand the UFSAR analyses of the event remained bounding.A. Availability of systems or components that could have performed the same function as thecomponents and systems that failed during the event:There were no other components that could have performed the same function as the vitalinverter 0-Il AC output switch.B. "For events that occurred when the reactor was Shut down, availability of systems orcomponents needed to shutdown the reactor and maintain safe shutdown conditions,remove residual heat, control the release of radioactive material, or mitigate theconsequences of an accident:This event did not occur when the reactor was shut down. Safety-related systems thatwere needed to shut down the reactor, maintain safe shutdown conditions, removeresidual heat or mitigate the consequences of an accident remained available throughoutthe event.C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsedtime from discovery of the failure until the train was returned to service:There was no failure that rendered a train of a safety system inoperable during this event.VI. Corrective ActionsCorrective Actions are being managed by TVA's corrective action program under CR 1081482.A. Immediate Corrective Actions:* Vital Inverter 1-Il reenergized and placed back into service feeding the VIPB 1-Il.Trouble shooting was initiated. Testing was performed on the inverter, AC outputswitch, cabling, and the transfer switch on the VIPB.* Initial troubleshooting and testing identified the failed open AC output switch. Noother issues were identified.NR* FORM 366A (02-201 4)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME J2. DOCKET 6. LER NUMBER [ 3. PAGEIIISEQUENTIAL i REVYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 [6 OF 6j2015 -003 -00NARRATIVE* Extent of condition was initiated to identify any other molded case switches withGE Part # TQD22Y225.B. Corrective Actions to Prevent Recurrence or to reduce probability of similar eventsoccurring in the future:Ensure the existing requirement for management review of all corrective action closuresremains in the Corrective Action Program by "source noting" this requirement in TVA'sCAP procedure. The requirement for management review of corrective action closureshas been in effect since 2012. Had this requirement been in effect in 2000, the eventdescribed in this LER could have been prevented.VII. Additional InformationA. Previous similar events at the same plant:A review of the previous reportable events for the past 3 years at SQN found no similar eventscaused by failure to implement corrective actions from operating experience events. A review ofreportable events back to 1994 found one similar vital inverter switch failure that occurred duringa maintenance activity. It was also a GE TQD22Y225 switch. This resulted in LER 50-327/94016 and the cause was attributed to mechanical failure.B. Additional Information:Institute of Nuclear Power Operations operating experience item QE1 1056 documented a reactortrip at McGuire in 2000 following a vital inverter output switch failure. A SQN review of this OEfailed to implement a corrective action that could have prevented the event described in thisLER. Due to the similarities in OE and the failures attributed to this specific component, TVA isplanning to formally screen the component failure under 10 CFR Part 21.C. Safety System Functional. Failure Consideration:This event did not result in a safety system functional failure in accordance with 10 CFR50.73(a)(2)(v).D. Scrams with Complications Consideration:This event did not result in an unplanned scram with complications.VIII. Commitments:None.NRC FORM 366A (02-2014)
Tennessee Valley Authority, Post Office Box,2000, Soddy Daisy, Tennessee 37384-2000November 13, 201510 CFR 50.73AI-FN: Document Control DeskU.S. Nuclear Regulatory CommissionWashington, D.C. 20555-0001Sequoyah Nuclear Plant, Unit 1Renewed Facility Operating License No. DPR-77NRC Docket No. 50-327
 
==Subject:==
Licensee Event Report 50-327/2015-003-00, "Manual Reactor Trip due toLoss of Power to the Vital Inverter Power Board 1-Il"The enclosed Licensee Event Report provides details concerning a manual reactor tripfollowing a loss of power to the Vital Instrument Power Board 1-Il. This report is beingsubmitted in accordance with 10 CFR 50.73 (a)(2)(iv)(A), as an event that resulted in amanual or automatic actuation of the Reactor Protection System and the AuxiliaryFeedwater System. This condition had no impact on Unit 2.There are no regulatory commitments contained in this letter. Should you have anyquestions concerning this submittal, please contact Jon Johnson, Acting Sequoyah SiteLicensing Manager, at (423) 843-8129.Si President-rah Nuclear Plant
 
==Enclosure:==
Licensee Event Report 50-327/2015-003cc: NRC Regional Administrator -Region IINRC Senior Resident Inspector -Sequoyah Nuclear Plant NINNRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 01131/2017(02-2014)burden per response to comply with this mandatory collection request: 80 hours.=..y°`,Reported lessons learned are incorporated into the licensing process and fed back to industry... * =Send comments regarding burden estimate to the FOIA, Pdtvacy and Information Collections.... LICE SEE VEN REP RT (ER) Branch (T-5 F53), U.S. Nuclear Regalatory Commission, Washington, DC 20555-0001, or byLICE SEE VEN REP RT (ER) internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and(See Page 2 for required number of Regulatory Atfairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC20503. If a means sused to impose an information collection does not display a currently valid 0MBdigits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to,the information collection.1. FACILITY NAME 2. DOCKET NUMBER 13. PAGESequoyah Nuclear Plant Unit 1 05000327[1O 64. TITLEManual Reactor Trip due to Loss of Power to the Vital Instrument Power Board 1-115. EVENT DATE 6. LER NUMBER I 7. REPORT DATE J8. OTHER FACILITIES INVOLVEDMONT1DA7YER1iFACILITY NAME DOCKET NUMBERMOT A ER YA SEOUENTIALI REV IMONTH DAY YEAR NAIEAIINUMBER INO.NI ~ ~ iFACILITY NAME DOCKET NUMBER09 14 2015 2015 -003 -00I1 13 2015 NA9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)'[] 20.2201(b) [] 20.2203(a)(3)(i) lii 50.73(a)(2)(i)(C) D] 50.73(a)(2)(vii)[] 20.2201(d)' [ 20.2203(a)(3)(ii) [] 50.73(a)(2)(ii)(A) [] 50.73(a)(2)(viii)(A)[] 20.2203(a)(1) E] 20.2203(a)(4) E] 50.73(a)(2)(ii)(B) L] 50.73(a)(2)(viii)(B)D] 20.2203(a)(2)(i) [] 50.36(c)(1)(i)(A) [] 50.73(a)(2)(iii) fl 50.73(a)(2)(ix)(A)10. POWER LEVEL [] 20.2203(a)(2)(ii) [] 50.36(c)(1)(ii)(A) X 50.73(a)(2)(iv)(A) [] 50.73(a)(2)(x)L] 20.2203(a)(2)(iii) [] 50:36(c)(2) [] 50.73(a)(2)(v)(A) LI 73.71(a)(4)[] 20.2203(a)(2)(iv) [] 50.46(a)(3)(ii) [] 50.73(a)(2)(v)(B) [] 73.71 (a)(5)10 f 20.2203(a)(2)(v) [] 50.73(a)(2)(i)(A) [] 50.73(a)(2)(v)(C) LI OTHEREl 20.2203(a)(2)(vi) [] 50.73(a)(2)(i)(B) [] 50.73(a)(2)(v)(D) Specifyin.Abstract beloworin_________________ ___________________________________________ NRC Form 366A12. LICENSEE CONTACT FOR THIS LERLICENSEE CONTACTITEPOENME(IcueAaCoe13._COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTCAUSEE SYSTEME I COMPONs14. SUPPLEMENTAL REPORT EXPECTEDEl YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [] NOA.BSTRACT (Limit to 1400 spaces, i e., approximately 15 single-spaced typewritten lines)On September 14, 2015, at 0426 Eastern Daylight Time, Sequoyah Nuclear Plant (SQN) Unit 1 reactor wasmanually tripped due to a loss of power to the Vital Instrument Power Board (VIPB) 1-11. Prior to the reactortrip, operators were in the process of realigning Vital Inverter 1-Il for planned maintenance. During thisevolution, VIPB 1-Il became de-energized. Operators entered Abnormal Operating Procedure AOP-P.03, "Lossof Unit 1 Vital Instrument Power Board" which required a manual reactor trip. Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply at 0550. All plant safety systems responded asdesigned, all control rods fully inserted, and auxiliary feedwater automatically initiated from the feedwaterisolation signal as expected. It was determined that an Alternating Current (AC) output switch failed causingthe loss of power to the VIPB 1-Il. The direct cause of the switch failure was due to increased friction of bearingsurfaces caused by lack of appropriate lubrication. The lack of lubrication was related to a failure to implementacorrective action following an operating experience review at SQN in 2000 of a similar event at McGuireNuclear Station. The failure to implement a corrective action was determined to be the root cause of this event.Corrective actions to prevent recurrence include ensuring the existing requirement for management review ofall corrective action closures remains in the Corrective Action Program. Unit 2 was unaffected by this event.NRC FORM 366 (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 011311201702-2014).burden per response to comply with this mandatory collection request: 80 hours.,* *Reported lessons learned are incorporated into the licensing process and fed back to industry.Send comments regarding burden estimate to the FOIA, Privacy and Information Collections(~ ) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by".- LICENSEE EVENT REPORT (LER) internet e-mail to Infocollects.Resource@nro.gov, and to the Desk Officer, Office of InformationadRegulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget,CONTINUATION SHEET Washington, DC 20503. If a means used to impose an information collection does not display acurrenhly valid 0MB control number, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information collection.1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEIIj SEQUENTIAL REVYEARNUMBER NO.Sequoyah Nuclear Plant Unit I1 05000327 YER2 OF. 6__ _ _ _ _ _ __ _ _ _ _ _ __ _ _ _jJ 2015 -003 -00NARRATIVEI. Plant Operating Conditions Before the EventAt the time of the event, Sequoyah Nuclear Plant (SQN) Unit 1 reactor was operating at 100 percentrated thermal power (RTP). The condition described in this LER did not impact SQN Unit 2.II. Description of EventsA. Event:On September 14, 2015, at 0426 Eastern Daylight Time (EDT), SQN Unit 1 reactor wasmanually tripped due to a loss of power to the Vital Instrument Power Board (VIPB) 1-Il [EllSCode EE]. Prior to the reactor trip, operators were in the process of realigning Vital Inverter 1-Il[Ells Code INVT] for planned maintenance. During this evolution, the VIPB 1-Il became de-energized. Operators entered Abnormal Operating Procedure AOP-P.03, "Loss of Unit 1 VitalInstrument Power Board" which required a manual reactor trip. Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply at 0550. All plant safety systemsresponded as designed, all control rods fully inserted as required, and auxiliary feedwaterautomatically initiated from the feedwater isolation signal as expected.The manual trip was in response to an alternating current (AC) output switch (EllS Code JS)failure that occurred on the Vital Inverter 0-Il. This failure resulted in the loss of power to VIPB 1-I1. The switch failure occurred due to increased friction of bearing surfaces caused by lack of'appropriate lubrication.B. Status of structures, components, or systems that were inoperable at the start of the eventand contributed to the event:There were no inoperable structures, components or systems that contributed to this event.C. Dates and approximate times of occurrences:The event occurred during the realignment of the Vital Inverter 1-Il for plannedmaintenance. The realignment involved placing Vital Inverter 0-Il into service to feed theVIPB 1-11. During the realignment, VIPB 1-11 lost power. The loss of power required entryinto Technical Specification (TS) Limiting Condition of Operation (LCO) 3.8.2.1 and amanual reactor trip in accordance with AOP-P.03. Following the manual reactor trip,power was restored to the VIPB 1-Il.NRC FORM 366A (02-201 4)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEIISEQUENTIAL IREVYEAR NUMBER NOSequoyah Nuclear Plant Unit 1 05000327 I13 OF 6NARRATIVEDates and Times Description..September 14, 2015 at Clearance approved for placing Vital Inverter 0-Il into0102 EDT service as an alternate feed to VIPB 1-11.September 14, 2015 at Vital Inverter 0-11.placed into service to the VIPB 1-Il.0405 EDTSeptember 14, 2015 at Loss of power to VIPB 1-1l occurred.0421 EDTSeptember 14, 2015 at TS LCO 3.8.2.1 entered due to loss of VIPB 1-Il.0423 EDTSeptember 14, 2015 at Unit 1 reactor manually tripped as directed by AOP-0426 EDT P.03.September 14, 2015 at* VIPB 1-Il restored to normal power supply.0550 EDTD. Manufacturer and model number of each component that failed during the event:The failed component was an AC molded case output switch on Vital Inverter 0-Il. The switchfailure led to a loss of power to the VIPB 1-Il. The switch manufacturer is General Electric (GE),part # TQD22Y225.E. Other systems or secondary functions affected:There were no other systems or functions affected by this event.F. Method of discovery of each component or system failure or procedural error:Observations and functional testing of the 0-11 vital inverter identified erratic operation of the 0-IlAC inverter output switch. The output switch exhibited failure to latch and stay latched duringbench testing. It was concluded that this switch failure resulted in the loss of the VIPB 1-Il andsubsequent manual reactor trip.NRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(o2-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER j 3. PAGEIISEQUENTIAL REVuYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 4 OF 61[2015 -003 -00NARRATIVEG. The failure mode, mechanism, and effect of each failed component, if known:The failed component for this event is the vital inverter 0-1l output switch. The switch failed tolatch and stay latched due to increased friction of bearing surfaces caused by lack of appropriatelubrication.H. Operator actions: -Upon receipt of multiple alarms, bi-stables lit, rods stepping in, and the centrifugal charging pumpsuction valve from the refueling water storage tank open, the operators verified no runback wasin progress and placed the rod control system in manual. Operators entered AOP-P.03, "Loss ofUnit 1 Vital Instrument Power Board," tripped the reactor, and entered Emergency Procedure E-0"Reactor Trip or Safety Injection," while continuing in AOP-P.03. The operators then transitionedto Emergency Subprocedure ES-0. 1, "Reactor Trip Response." Following the reactor trip,operators restored power to VIPB 1-Il with the normal supply.I. Automatically and manually initiated safety system responses:Following the manual reactor trip, plant safety systems responded as designed. All controlrods fully inserted as required. Auxiliary automatically initiated from the feedwaterisolation signal as expected.Ill. Cause of the eventA. The cause of each component or system failure or personnel error, if known:The direct cause of the event was failure of the output switch on Vital Inverter 0-Il. This outputswitch failed open causing loss of power to the VIPB 1-Il resulting in entry into AOP-P.03directing a manual reactor trip.B. The cause(s) and circumstances for each human performance related root cause:The root cause was determined to be failure to implement a corrective action from SQN'sreview of an operating experience event in 2000. The root cause is documented incondition report (CR) 1081482.IV. Analysis of the event:SQN Unit I reactor was manually tripped in response to loss of power to VIPB 1-Il on.September 14,2015. The loss of power was due to a failed AC output switch on Vital Inverter 0-I1. The switch faileddue to increased friction of bearing surfaces caused by lack of appropriate lubrication.The plant transient response including reactor power, reactor coolant system (RCS) pressure, RCStemperature, pressurizer level, RCS secondary side pressure, and AFW flow remained withintechnical specification limits and were bounded by the Updated Final Safety Analysis Report(UFSAR) analysis. Containment pressure, temperature, and radiation were unaffected by thisNRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME j2. DOCKET 6. LER NUMBER [ 3. PAGEI ISEQUENTIAL IREVYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 I 5 OF 6I _____ 2015 -003 -00NARRATIVEtransient. Steam generator level experienced during this event was bounded by UFSAR analysis.The plant responded as expected for the conditions of the trip.Observations and functional testing of Vital Inverter 0-Il identified erratic operation of the 0-Il1ACinverter output switch. The output switch exhibited failure to latch and stay latched during benchtesting. No other discrepancies were identified with the inverter. It was concluded that this switchfailure resulted in the loss of VIPB 1-Il and the subsequent manual reactor trip.V. Assessment of Safety ConsequencesThere were no safety consequences as a result of the event. Safety systems functioned asdesigned and no complications were experienced. No Technical Specification limits were exceededand the UFSAR analyses of the event remained bounding.A. Availability of systems or components that could have performed the same function as thecomponents and systems that failed during the event:There were no other components that could have performed the same function as the vitalinverter 0-Il AC output switch.B. "For events that occurred when the reactor was Shut down, availability of systems orcomponents needed to shutdown the reactor and maintain safe shutdown conditions,remove residual heat, control the release of radioactive material, or mitigate theconsequences of an accident:This event did not occur when the reactor was shut down. Safety-related systems thatwere needed to shut down the reactor, maintain safe shutdown conditions, removeresidual heat or mitigate the consequences of an accident remained available throughoutthe event.C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsedtime from discovery of the failure until the train was returned to service:There was no failure that rendered a train of a safety system inoperable during this event.VI. Corrective ActionsCorrective Actions are being managed by TVA's corrective action program under CR 1081482.A. Immediate Corrective Actions:* Vital Inverter 1-Il reenergized and placed back into service feeding the VIPB 1-Il.Trouble shooting was initiated. Testing was performed on the inverter, AC outputswitch, cabling, and the transfer switch on the VIPB.* Initial troubleshooting and testing identified the failed open AC output switch. Noother issues were identified.NR* FORM 366A (02-201 4)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION(02-2014) LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME J2. DOCKET 6. LER NUMBER [ 3. PAGEIIISEQUENTIAL i REVYEAR NUMBER NO.Sequoyah Nuclear Plant Unit 1 05000327 [6 OF 6j2015 -003 -00NARRATIVE* Extent of condition was initiated to identify any other molded case switches withGE Part # TQD22Y225.B. Corrective Actions to Prevent Recurrence or to reduce probability of similar eventsoccurring in the future:Ensure the existing requirement for management review of all corrective action closuresremains in the Corrective Action Program by "source noting" this requirement in TVA'sCAP procedure. The requirement for management review of corrective action closureshas been in effect since 2012. Had this requirement been in effect in 2000, the eventdescribed in this LER could have been prevented.VII. Additional InformationA. Previous similar events at the same plant:A review of the previous reportable events for the past 3 years at SQN found no similar eventscaused by failure to implement corrective actions from operating experience events. A review ofreportable events back to 1994 found one similar vital inverter switch failure that occurred duringa maintenance activity. It was also a GE TQD22Y225 switch. This resulted in LER 50-327/94016 and the cause was attributed to mechanical failure.B. Additional Information:Institute of Nuclear Power Operations operating experience item QE1 1056 documented a reactortrip at McGuire in 2000 following a vital inverter output switch failure. A SQN review of this OEfailed to implement a corrective action that could have prevented the event described in thisLER. Due to the similarities in OE and the failures attributed to this specific component, TVA isplanning to formally screen the component failure under 10 CFR Part 21.C. Safety System Functional. Failure Consideration:This event did not result in a safety system functional failure in accordance with 10 CFR50.73(a)(2)(v).D. Scrams with Complications Consideration:This event did not result in an unplanned scram with complications.VIII. Commitments:None.NRC FORM 366A (02-2014)}}

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