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Category:LICENSEE EVENT REPORT (SEE ALSO AO
MONTHYEARML18064A8631995-08-14014 August 1995 LER 95-004-00:on 950714,determined That Redundant DG Circuits Not Separated Per App R Due to Insufficient App R Program Documentation.Hourly Fire Tour Established in EDG 1-1 Room & Review of LERs for App R Completed ML18100B2981994-05-24024 May 1994 LER 94-014-00:on 940426,SG 1-2 Automatically Started When Two Indicating Light Sockets Shorted Together Due to Personnel Error.Description of Event & Lessons Learned Will Be Published in Operations Incident Summary.W/940524 Ltr ML20024E4541983-08-0404 August 1983 LER 83-017/03L-0:on 830706,power Supply Circuit Breaker for Oily Water Separator Effluent Flow Monitor (FR-251) Tripped Open & Would Not Reset.Cause Undetermined.Breaker Replaced. W/830804 Ltr ML20052E1721982-04-29029 April 1982 LER 82-005/03L-0:on 820330,during Surveillance Testing,Steam Generator Blowdown Tank Liquid Radiation Monitor RM-23 Failed Quarterly Functional Test.Caused by Failure of Photo Multiplier Tube ML20052A3861982-04-22022 April 1982 LER 82-003/03X-1:on 820212,prior to Fuel Load,Vital Instrument Ac Panel Undervoltage Alarm Received in Control Room.Inverter IY-11 & Panel PY-15 Tripped When Manually Switched Off.Cause Unknown ML20052C2951982-04-15015 April 1982 LER 81-001/01X-1:on 810922,during Review of Reportability of Inoperable Plant Vent Rod Monitoring Channels,Discovered Required STS Action Statements Had Not Been Entered.Caused by Personnel Error.Personnel Retrained ML20042C4071982-03-24024 March 1982 LER 82-002/03L-0:on 820222,air Sample Pumps for Plant Vent Radiation Monitors (RM 14A & B) Found Tripped.Caused by Clogging of Rad Monitor Filter Paper W/Debris from Const Activities ML20042C3511982-03-24024 March 1982 LER 82-004/03L-0:on 820223 & 26,oily Water Separator Effluent Line Flow Rate Measurement Device (FR-251) Inoperable.Caused by Faulty Electronic Component on First Occasion & by Breakdown of Oscillator on Second ML20042A8701982-03-16016 March 1982 Updated LER 81-002/01X-6:on 810927,error Discovered in Diagram Used to Locate Vertical Seismic Floor Response Spectra for Equipment & Sys Seismic Design.Caused by Erroneous Use of Unit 2 Diagram for Unit 1 ML20042A7761982-03-15015 March 1982 LER 82-003/03L-0:on 820212,prior to Fuel Load,Operators Received Vital Instrument Ac Panel Under Voltage Alarm in Control Room.Caused by Tripped Feeder Breaker to PY-15. Event Under Investigation ML20041E3911982-03-0101 March 1982 LER 82-001/03L-0:on 820129,during Audit Prior to Fuel Load, Communication Phone Mounted on Front Section of Hot Shutdown Panel Was Discovered Excluded from Seismic Analysis.Caused by Coordination Failure.Panel Will Be Reanalyzed ML20040D8191982-01-25025 January 1982 Updated LER 81-002/01X-5:on 810927,prior to Fuel Loading, Engineer Discovered Error in Diagram Used to Locate Vertical Seismic Floor Response Spectra for Use in Plant Equipment & Sys Seismic Design.Unit 2 Diagram Used for Unit 1 Annulus ML20040B4721982-01-15015 January 1982 LER 81-010/03L-0:on 811217,prior to Fuel Load,Documentation for Gross Gamma Analysis of Weekly Composite Sample for Oily Water Separator Discovered Missing for 811029-1119.Sheets Apparently Misplaced.Procedure Revised ML20040A5191982-01-14014 January 1982 Updated LER 81-005/01X-1:on 811015,during Insp,Battery Cell Case Found Weeping.Further Insp Revealed 17 Cells W/Cracks Near Molded Support Ribs on Bottom of Cases.Caused by Inadequate Support of Cells.Racks Modified & Cells Replaced ML20040A0721982-01-11011 January 1982 LER 81-009/03L-0:on 811211,operator Failed to Perform Daily Channel Check on Iodine Sampler Flow Rate Monitor.Caused by Inadequate Instructions for Verifying Annunciator Window Operability.Procedure Change Issued ML20039G9421982-01-11011 January 1982 Updated LER 81-002/01X-4:on 810927,error Found in Diagram Used to Locate Vertical Seismic Floor Response (Vsfr) Spectra.Caused by Use of Unit 2 Diagram for Unit 1 Annulus Area ML20039D3601981-12-18018 December 1981 Updated LER 81-002/01X-3:on 810927,discovered Error in Diagram Used to Locate Vertical Seismic Floor Response Spectra Inplant Equipment & Sys Seismic Design.Caused by Using Incorrect Diagram.Sys Being Reviewed & Modified ML20039C5861981-12-17017 December 1981 LER 81-007/03L-0:on 811125,discovered That Tech Specs Surveillance Requirement 4.11.2.4.1 Re Project Doses Due to Gaseous Releases from Plant Not Performed within Required Time Interval.Caused by Personnel Oversight ML20039C5791981-12-17017 December 1981 LER 81-008/03L-0:on 811130,discovered That Gross Alpha Activity Analysis Had Not Been Performed within Required Time Interval.Caused by Personnel Oversight.Sample Counted on 811130 ML20038B9381981-12-0202 December 1981 LER 81-006/03L-0:on 811103,daily Channel Check on Plant Vent Flow Recorder Not Performed.Caused by Operator & Reviewer Failure to Note Step on Checklist.Operators Instructed & Procedure Simplified 1995-08-14
[Table view] Category:RO)
MONTHYEARML18064A8631995-08-14014 August 1995 LER 95-004-00:on 950714,determined That Redundant DG Circuits Not Separated Per App R Due to Insufficient App R Program Documentation.Hourly Fire Tour Established in EDG 1-1 Room & Review of LERs for App R Completed ML18100B2981994-05-24024 May 1994 LER 94-014-00:on 940426,SG 1-2 Automatically Started When Two Indicating Light Sockets Shorted Together Due to Personnel Error.Description of Event & Lessons Learned Will Be Published in Operations Incident Summary.W/940524 Ltr ML20024E4541983-08-0404 August 1983 LER 83-017/03L-0:on 830706,power Supply Circuit Breaker for Oily Water Separator Effluent Flow Monitor (FR-251) Tripped Open & Would Not Reset.Cause Undetermined.Breaker Replaced. W/830804 Ltr ML20052E1721982-04-29029 April 1982 LER 82-005/03L-0:on 820330,during Surveillance Testing,Steam Generator Blowdown Tank Liquid Radiation Monitor RM-23 Failed Quarterly Functional Test.Caused by Failure of Photo Multiplier Tube ML20052A3861982-04-22022 April 1982 LER 82-003/03X-1:on 820212,prior to Fuel Load,Vital Instrument Ac Panel Undervoltage Alarm Received in Control Room.Inverter IY-11 & Panel PY-15 Tripped When Manually Switched Off.Cause Unknown ML20052C2951982-04-15015 April 1982 LER 81-001/01X-1:on 810922,during Review of Reportability of Inoperable Plant Vent Rod Monitoring Channels,Discovered Required STS Action Statements Had Not Been Entered.Caused by Personnel Error.Personnel Retrained ML20042C4071982-03-24024 March 1982 LER 82-002/03L-0:on 820222,air Sample Pumps for Plant Vent Radiation Monitors (RM 14A & B) Found Tripped.Caused by Clogging of Rad Monitor Filter Paper W/Debris from Const Activities ML20042C3511982-03-24024 March 1982 LER 82-004/03L-0:on 820223 & 26,oily Water Separator Effluent Line Flow Rate Measurement Device (FR-251) Inoperable.Caused by Faulty Electronic Component on First Occasion & by Breakdown of Oscillator on Second ML20042A8701982-03-16016 March 1982 Updated LER 81-002/01X-6:on 810927,error Discovered in Diagram Used to Locate Vertical Seismic Floor Response Spectra for Equipment & Sys Seismic Design.Caused by Erroneous Use of Unit 2 Diagram for Unit 1 ML20042A7761982-03-15015 March 1982 LER 82-003/03L-0:on 820212,prior to Fuel Load,Operators Received Vital Instrument Ac Panel Under Voltage Alarm in Control Room.Caused by Tripped Feeder Breaker to PY-15. Event Under Investigation ML20041E3911982-03-0101 March 1982 LER 82-001/03L-0:on 820129,during Audit Prior to Fuel Load, Communication Phone Mounted on Front Section of Hot Shutdown Panel Was Discovered Excluded from Seismic Analysis.Caused by Coordination Failure.Panel Will Be Reanalyzed ML20040D8191982-01-25025 January 1982 Updated LER 81-002/01X-5:on 810927,prior to Fuel Loading, Engineer Discovered Error in Diagram Used to Locate Vertical Seismic Floor Response Spectra for Use in Plant Equipment & Sys Seismic Design.Unit 2 Diagram Used for Unit 1 Annulus ML20040B4721982-01-15015 January 1982 LER 81-010/03L-0:on 811217,prior to Fuel Load,Documentation for Gross Gamma Analysis of Weekly Composite Sample for Oily Water Separator Discovered Missing for 811029-1119.Sheets Apparently Misplaced.Procedure Revised ML20040A5191982-01-14014 January 1982 Updated LER 81-005/01X-1:on 811015,during Insp,Battery Cell Case Found Weeping.Further Insp Revealed 17 Cells W/Cracks Near Molded Support Ribs on Bottom of Cases.Caused by Inadequate Support of Cells.Racks Modified & Cells Replaced ML20040A0721982-01-11011 January 1982 LER 81-009/03L-0:on 811211,operator Failed to Perform Daily Channel Check on Iodine Sampler Flow Rate Monitor.Caused by Inadequate Instructions for Verifying Annunciator Window Operability.Procedure Change Issued ML20039G9421982-01-11011 January 1982 Updated LER 81-002/01X-4:on 810927,error Found in Diagram Used to Locate Vertical Seismic Floor Response (Vsfr) Spectra.Caused by Use of Unit 2 Diagram for Unit 1 Annulus Area ML20039D3601981-12-18018 December 1981 Updated LER 81-002/01X-3:on 810927,discovered Error in Diagram Used to Locate Vertical Seismic Floor Response Spectra Inplant Equipment & Sys Seismic Design.Caused by Using Incorrect Diagram.Sys Being Reviewed & Modified ML20039C5861981-12-17017 December 1981 LER 81-007/03L-0:on 811125,discovered That Tech Specs Surveillance Requirement 4.11.2.4.1 Re Project Doses Due to Gaseous Releases from Plant Not Performed within Required Time Interval.Caused by Personnel Oversight ML20039C5791981-12-17017 December 1981 LER 81-008/03L-0:on 811130,discovered That Gross Alpha Activity Analysis Had Not Been Performed within Required Time Interval.Caused by Personnel Oversight.Sample Counted on 811130 ML20038B9381981-12-0202 December 1981 LER 81-006/03L-0:on 811103,daily Channel Check on Plant Vent Flow Recorder Not Performed.Caused by Operator & Reviewer Failure to Note Step on Checklist.Operators Instructed & Procedure Simplified 1995-08-14
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20211A9981999-07-12012 July 1999 Draft,Probabilistic Safety Assessment, Risk Info Matrix, Risk Ranking of Systems by Importance Measure DCL-99-045, 1998 Annual Financial Rept for PG&E Corp. with1998-12-31031 December 1998 1998 Annual Financial Rept for PG&E Corp. with ML20217G5151997-12-31031 December 1997 1997 PG&E Corp Annual Rept ML20205F5881997-07-24024 July 1997 Decommissioning Cost Estimate for Diablo Canyon Power Plant,Units 1 & 2 ML17264A9381997-07-10010 July 1997 Deficiency Rept Re Potential Safety Hazard Associated w/FM-Alco 251 Engin,High Pressure Fuel tube-catalog: 4401031-2 in Which Dual Failure Mode Exists.Caused by Incorrect Forming Process ML18102B6911997-01-31031 January 1997 Monthly Operating Repts for Jan 1997 for Diablo Canyon Power Plant,Units 1 & 2.W/970218 Ltr ML16342D5351997-01-31031 January 1997 WCAP-14826, Instrumentation Calibr & Drift Evaluation Process for Diablo Canyon Units 1 & 2,24 Month Fuel Cycle Evaluation. ML16343A4741997-01-31031 January 1997 WCAP-11595,Rev 2, W Improved Thermal Design Procedure Instrument Uncertainty Methodology Diablo Canyon Units 1 & 2 24 Month Fuel Cycle Evaluation. ML17083C6231997-01-31031 January 1997 Rev 4 to WCAP-13705, W Setpoint Methodology for Protection Sys Diablo Canyon Units 1 & 2,24 Month Fuel Cycle Evaluation. DCL-97-045, Pacific Gas & Electric Co 1996 Annual Rept1996-12-31031 December 1996 Pacific Gas & Electric Co 1996 Annual Rept ML16342D5541996-12-31031 December 1996 Non-proprietary Nrc/Util Meeting on Model 51 SG Tube Integrity & ARC Methodology. ML20129J4311996-10-18018 October 1996 Safety Evaluation Approving Corporate Restructuring & Establishment of Holding Company Under Temporary Name PG&E Parent Co.,Inc of Which PG&E Would Become Wholly Owned Subsidiary DCL-96-155, Revised Special Rept SR 95-05:on 950806,EDG 1-2 to Achieve Rated Output Frequency within TS Limits.Caused by Degraded Electronic Governor Performance.Replaced Electronic Governor Motor Operated Potentiometer & Electronic Governor1996-07-22022 July 1996 Revised Special Rept SR 95-05:on 950806,EDG 1-2 to Achieve Rated Output Frequency within TS Limits.Caused by Degraded Electronic Governor Performance.Replaced Electronic Governor Motor Operated Potentiometer & Electronic Governor ML20116B8491996-07-22022 July 1996 Revised Special Rept SR 95-03:on 950621,EDG 1-2 Failed to Load During Surveillance Testing.Caused by Loose Fuse Holder Contact Clip.Retensioned Loose Fuse Holder Contact Clip & Tightened Loose Wire Connection ML20116B8521996-07-22022 July 1996 Revised Special Rept SR 95-04:on 950718,EDG 1-2 Load Swings Occurred.Caused by Defective Electronic Governor Stability Potentiometer.Replaced Electronic Governor ML20236Q2611996-04-15015 April 1996 Rev 0 to DCP M-050284, Design Change Package for Installation of CCW Surge Tank Pressurization Sys for Unit 1 ML20094M6251995-11-21021 November 1995 Final Part 21 Rept of Investigation & Analysis of Suspect Fasteners Event 29257.B&G-Cardinal Discontinued Using Heat Treatment Equipment at Cardinal Facility Until Such Time That Satisfactory Mods Made to Hardware & Procedures ML18064A8631995-08-14014 August 1995 LER 95-004-00:on 950714,determined That Redundant DG Circuits Not Separated Per App R Due to Insufficient App R Program Documentation.Hourly Fire Tour Established in EDG 1-1 Room & Review of LERs for App R Completed ML18100B2981994-05-24024 May 1994 LER 94-014-00:on 940426,SG 1-2 Automatically Started When Two Indicating Light Sockets Shorted Together Due to Personnel Error.Description of Event & Lessons Learned Will Be Published in Operations Incident Summary.W/940524 Ltr ML16342C3091993-12-31031 December 1993 Monthly Operating Repts for Dec 1993 for Dcnpp Units 1 & 2 ML16342A3691993-08-31031 August 1993 Revised MOR for Aug 1993 for Dcnpp Unit 1 ML16342A3681993-07-31031 July 1993 Revised MOR for July 1993 for Dcnpp Unit 1 ML20046A6611993-07-21021 July 1993 Cycle 6 Startup Rept. ML20059G6811993-06-30030 June 1993 Revised MOR for June 1993 for Dcnpp Unit 1 ML16342A3671993-05-31031 May 1993 Revised MOR for May 1993 for Dcnpp Unit 1 ML20045D1731993-05-31031 May 1993 Monthly Operating Repts for May 1993 for Diablo Canyon,Units 1 & 2 ML20126J5961992-12-31031 December 1992 Part 21 Rept Re Potential Loss of RHR Cooling During Nozzle Dam Removal.Nozzle Dams May Create Trapped Air Column Behind Cold Leg Nozzle Dam.Mod to Nozzle Dams Currently Underway. Ltrs to Affected Utils Encl ML20141M0471991-12-31031 December 1991 Pge Annual Rept - 1991 ML20086T1001991-12-31031 December 1991 Adequacy of Seismic Margins Assuming Increase in Amplitude of Diablo Canyon Seismic Long-Term Program Horizontal & Vertical Ground Motions Described in Sser 34 ML16341G4871991-11-30030 November 1991 Nonproprietary Technical Justification for Eliminating Large Primary Loop Pipe Rupture as Structural Design Basis for Diablo Canyon Units 1 & 2 Nuclear Power Plants. ML20085D2951991-08-21021 August 1991 Field Exercise Scenario,Aug 1991 ML20070S7311990-12-31031 December 1990 Analysis of Capsule X from Diablo Canyon Unit 2 Reactor Vessel Radiation Surveillance Program ML20065R8731990-11-30030 November 1990 Monthly Operating Repts for Diablo Canyon Units 1 & 2 for Nov 1990 ML20058P5181990-05-11011 May 1990 Accident Sequence Precursor Program Event Analysis 323/87-005 R2, Loss of RHR Cooling Results in Reactor Vessel Bulk Boiling ML20058P5131990-04-0505 April 1990 Accident Sequence Precursor Program Event Analysis 424/PNO-IIT-90-02A, Loop,Diesel Generator Failure & 36 Min Interruption of SDC During Mid-Loop Operation ML20058P5221990-02-0303 February 1990 Accident Sequence Precursor Program Event Analysis Loss of Reactor Protection Sys Bus B Causes Loss of Shutdown Cooling ML20006E5441989-11-30030 November 1989 Review of Flow Peaking & Tube Fatique in Diablo Canyon Units 1 & 2 Steam Generators. ML20006C6681989-11-30030 November 1989 Nonproprietary WCAP-12416, Evaluation of Thermal Stratification for Diablo Canyon Units 1 & 2 Pressurizer Surge Line. ML20246E4891989-06-30030 June 1989 Quarterly Sys Status Rept,2nd Quarter 1989,Sys 65 120V Instrument AC Sys,Sys 66 120V Security UPS Sys & Sys 67 125/250VDC Sys ML20245G9881989-06-16016 June 1989 Has Been Canceled.Resolution of LERs Missing from Lertrk/Scss/Dcs Discussed DCL-89-117, Special Rept:On 890406,main Steam Line Radiation Monitor 1RM-71 Alarmed & Declared Inoperable.Caused by Failure of Detector Tube.Tube Replaced.Monitor Returned to Svc on 8904181989-04-27027 April 1989 Special Rept:On 890406,main Steam Line Radiation Monitor 1RM-71 Alarmed & Declared Inoperable.Caused by Failure of Detector Tube.Tube Replaced.Monitor Returned to Svc on 890418 ML20247M6281989-03-31031 March 1989 Nonproprietary Advanced Digital Feedwater Control Sys Median Signal Selector for Diablo Canyon Units 1 & 2 ML20246P4461989-03-23023 March 1989 Corrected Diablo Canyon Power Plant Unit 2 Second Refueling Outage Inservice Insp (ISI) Rept ML20236E0581988-12-31031 December 1988 Pacific Gas & Electric Co Annual Rept 1988 ML20247H0761988-11-30030 November 1988 Vol 1 to Bit Elimination Study for Diablo Canyon Units 1 & 2 ML20205S9071988-10-31031 October 1988 Steam Generator U-Bend Tube Fatigue Evaluation ML20153E5331988-08-29029 August 1988 Safety Evaluation Supporting Amends 31 & 30 to Licenses DPR-80 & DPR-82,respectively ML20206E7181988-05-30030 May 1988 Analysis of Capsule U from PG&E Diablo Canyon Unit 2 Reactor Vessel Radiation Surveillance Program ML20195G3301988-04-30030 April 1988 Corrected Monthly Operating Repts for Apr 1988 for Diablo Canyon ML20153B0411988-03-31031 March 1988 Comments on ACRS Subcommittee on Diablo Canyon Meeting on 880223-24 in Burlingham,Ca Re Status of Long Term Seismic Program of Plant 1999-07-12
[Table view] |
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Pacific Gas am! Electric Gompany 77 Beale Strfft f1.~c;'l 1451 Gregory M. Rueger P.O. B~,,. 77DOJO Senior Vice President and San Francis:o. CA 9417' General Manager 41 :J/973-4684 ~~uclear Power Generation Fax 415/973-2313 May* 24, 19-94 PG&E Letter DCL-94-11 6 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Docket No. 50-275, OL-DPR-80 Diablo Canyon, Unit 1 Licensee Event Report 1-94-014-00 Unplanned Diesel Generator Start (ESF Actuation) When Two Indicating Light Sockets Shorted Together Due to Personnel Error Gentlemen:
Pursuant to 1 0 CFR 50. 73 (a)(2)(iv), PG&E is submitting the enclosed Licensee Event Report regarding an unplanned diesel generator start (ESF actuation) when, due to a personnel error during startup bus potential circuit indicating lamp replacement, two indicating light sockets shorted together, causing the circuit's protective fuse to open resulting in a loss of potential sensing voltage.
Sincerely, cc: L. J. Callan Mary H. Miller Kenneth E. Perkins Sheri R. Peterson Diablo Distribution INPO Enclosure DC 1-94-0P-N026 64 7 2S/KWR/2246 I
i ii -
I 9406010063 940524 {I f
PDR ADDCK 05000275 l S PDR
LICENSEE EVENT REPORT (LE-FACILITY NAME (11 I DOCKET NUMBER (21 I PAGE (31 Diablo Canyon, Unit 1 lo 5IOIOIOl217l5lll°F 6 nT~~ Unplanned Diesel Generator Start (ESF Actuation) When Two Indicating Light Sockets Shorted Together Due to Personnel.Error EVENT DATE (61 LER NUMBER !Bl REPORT DATE (71 OTHER FACILITIES INVOLVED (8)
MON DAY YR YR SEQUENTIAL REVISION MON DAY YR DOCKET NUMBER !SI FACILITY NAMES NUMBER NUMBER 04 26 94 94 - 0 I 1 I4 - 0 I0 05 24 94 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR: (11)
MODE (9) 5 POWER LEVEL I ---'x"'-- 10 CFR 50.73Ca)(2)(iv) 10 i
...... ( .
o I oI o
_ _ _ OTHER - - - - - - - - -
(Specify in Abstract below and in text,* NRC Form 366A)
LICENSEE CONTACT FOR THIS LER (121 TELEPHONE NUMBER David P. Sisk; Senior Regulatory Compliance Engineer AREA CODE 805 545-4420 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE ("*/(*::.:/:::::_ CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE _(/*<;."".'}":<<
TURER TO NPRDS : : ) :: TURER TO NPRDS : \ "
. :.:::****** ::.=:*"*":*:: .
>-.:.*<**"' *******::::.:=:
I I I I :*.:.* *::-.=:.::* *: ... :.*.*****
I I I I* MONTH SUPPLEMENTAL REPORT EXPECTED (141
- EXPECTED DAY YEAR SUBMISSION DATE (15)
I I YES (if yes, complete EXPECTED SUBMISSION DATE) *1 X I NO ABSTRACT (16)
On April 26, 1994, at 1332 PDT, with Unit 1 in Mode 5 (Cold Shutdown), Diesel Generator (DG) 1-2 automatically started from an apparent loss of the startup power source when the "C-phase" and "B-phase" potential transformer sensing circuits were inadvertently shorted together while an operator was replacing an indicating light bulb. This event constitutes an engineered safety feature (ESF) actuation. The contra l room operators verified that auxiliary power was available and returned all act~ated equipment to normal status. A four-hour~ non-emergency report was made to the NRC in accordance with 10 CFR 50.72(b)(2)(ii) on April 26, 1994, at 1136 PDT.
The root cause of this event is personnel error (noncognitive), due to a lack of knowledge concerning the task at hand, in that the operator was not aware that the ac potential circuits could be inadvertently shorted together while attempting to replace an indicating light bulb. This inadvertent short between the C-phase and the adjacent B-phase socket resulted in the C-phase secondary potential fuse opening. This caused the DG 1-2 circuitry to sense startup bus undervoltage (U/V), resulting in an inadvertent automatic start of the DG. The DG did not load onto the bus since auxiliary power to the vital 4160-volt bus was not interrupted and, therefore, no 4160-volt U/V was sensed.
A description of the event and lessons learned will be published in an Operations Incident Summary and distributed to personnel involved in minor maintenance activities, such as replacement ~fan indicating bulb .
. 6472S
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., LICENSEE EVENT REPORT (LER) TEXT cor9NuATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)
YEAR SEQUENTIAL . . REVISION NUMBER ,::*' NUMBER Diablo Canyon, Unit 1 oIs I o I o I o I 2 I 7 I s 94 - oI 114 - o Io 2 IOF I 6 TEXT (17)
I. Plant Conditions Unit 1 was in Mode 5 (Cold Shutdown) with an average reactor coolant system temperature less than 200 degrees Fahrenheit.
II. Description of Problem A. Summary On April 26, 1994, at 1332 PDT, with Unit 1 in Mode 5 (Cold Shutdown), Diesel Generator (DG) [EB][DG] 1-2 automatically started from an apparent loss of the startup power [EA] source when the C-phase and B-phase potential transformer [EC][XPT]
11 11 11 11 sensing circuits [EC][CBL4] were inadvertently shorted together, resulting in the C-phase secondary potential fuse [EC][FU]
opening, while an operator was replacing an indicating light bulb [EC][IL]. This caused the DG 1-2 circuitry to sense startup bus undervoltage (U/V) [EA][27], resulting in an inadvertent automatic start of the DG. The DG did not load onto the bus since auxiliary power to the vital 4160-volt bus
[EA][BU] was not interrupted. This event constitutes an engineered safety feature (ESF) actuation. The control room operators verified that auxiliary power [EA] was available and returned all actuated equipment to normal status. A four-hour, non-emergency report was made to the NRC in accordance with 10 CFR 50.72(b)(2)(ii) on April 26, 1994, at 1136 PDT:
B. Background None.
C. Event Description On April 26, 1994, by routine observation, a non-licensed electrical watch operator found the C-phase potential indicating light burned out on the 4160-volt breaker [EA][52] for the startup power source feeder to vital Bus G. In attempting to replace the indicating light bulb, the operator found it necessary to remove the retaining ring for the indicating light socket. While removing the retaining ring, the entire indicating light socket was rotated resulting in an inadvertent short of the C-phase socket to the adjacent B-phase socket. The C-phase secondary potential fuse opened as a result of the short.
On April 26, 1994, at 0834 PDT, DG 1-2 circuit~y sensed an apparent startup power source U/V and DG 1-2 cranking alarms annunciated in the main control room. Control room operators observed DG 1-2 start and achieve rated speed and voltage.
6472S
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LICENSEE cVENT REPORT {LER) TEXT CO-NUATION i
'i FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)
YEAR *.. :*. SEQUENTLAL j :<::::::: REVISION I:::',:* NUMBER :/:\: NUMBER Diablo Canyon, Unit 1 TEXT (17)
On April 26, 1994, at 0905 PDT, control room operators placed DG 1-2 in manua 1 , defeated the automatic start .feature at the startup feeder breaker cubicle per the annunciator response procedure guidance, _and
. DG 1-2 was shutdown and the control switch [EA][HS] returned to the "auto" position. The safety injection and 4160-volt bus U/V starts are still enabled in this configuration.
Electrical maintenance investigation determined that the C-phase potential transformer fuse in the 4160-volt Bus G secondary potential sensing circuitry had opened. The opened fuse caused a loss of sensed potential on the startup power source, initiating a DG automatic start. The DG did not load onto the vital 4160-volt bus since the auxiliary power source was available and aligned to the vital 4160-volt Bus G for the duration of the event.
The fuse was replaced and the startup feeder circuit DG 1-2 automatic start feature was returned to service.
On April 26, 1994, at 1136 PDT, a four-hour, non-emergency report was made pursuant to 10 CFR 50.72(b)(2)(ii).
D. Inoperable Structures, Components, or Systems that Contributed to the Event None.
E. Dates and Approximate Times for Major Occurrences
- 1. April 26, 1994, at 0834 PDT: Event Date/Discovery Date:
Inadvertent start of DG 1-2 during indicating light bulb replacement.
- 2. April 26, 1994, at 1136 PDT: A four-hour, non-emergency report was made to the NRC in accordance with 10 CFR 50.72 (b)(2)(ii).
F. Other Systems or Secondary Functions Affected None.
G. Method of Discovery The event was immediately apparent to plant* operators due to alarms and indications received in the control room.
6472S
LICENSE VENT REPORT_ (LER) TEXT co91NUATION FACILITY NAME (1) DDCKET NUMBER (2) LER NUMBER (6) PAGE (3)
YEAR SEQUENTlAL ~:_:;:.::::._: REVISKlN NUMBER I::{::\: NUMBER Diablo Canyon, Unit 1 TEXT (17)
H. Operator Actions DG 1-2 was placed in manual, the automatic start feature at the startup feeder breaker cubicle was defeated in accordance with the annunciator response procedure guidance, and DG 1-2 wis shutdown and the control switch returned to the "auto" position.
I. Safety System Responses DG 1-2 started but did not load onto.its associated 4160-volt bus since auxiliary power was available.
III. Cause of the Problem A. Immediate Cause The opened fuse caused a loss of sensed potential on the startup power source, initiating a DG automatic start.
B. Root Cause The root cause of this event is personnel error (noncognitive), due to a lack of knowledge concerning the task at hand, in that the operator was not aware that the ac potential circuits could be inadvertently shorted together while attempting to replace an indicating light bulb.
This inadvertent short between the C-phase and the adjacent B-phase socket resulted in the C-phase secondary potential fuse opening. This caused the DG 1-2 circuitry to sense startup bus U/V, resulting in an inadvertent automatic start of the DG. The DG did not load onto the bus since auxiliary power to the vital 4160-volt bus was not interrupted and, therefore, no 4160-volt U/V was sensed.
C. Contributing Cause None.
IV. Analysis of the Event Since all equipment performed as designed during this event, the inadvertent actuation of the DG ESF component did not adversely affect the health and safety of the public.
V. Corrective Actions A. Immediate Corrective Actions The fuse was replaced.
6472S
LICENSE .::VENT REPORT (LER} TEXT coi9NUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)
Diablo Canyon, Unit 1 oIs I oI oI oI 2 I 1 I s 94 - oI 114 - oIo
B. Corrective Actions to Prevent Recurrence A description of the event and lessons learned was published in an Operations Incident Summary and distributed to personnel involved in minor maintenance activities, such as replacement of an indicating bulb. The summary described how much action an operator should take with regard to repair of a problem-indicating light and when to request Electrical Maintenance personnel involvement in the repair.
VI. Additional Information A. Failed Components None.
B. Previous LERs on Similar Problems LER 1-94-007, dated April 28, 1994, and LER 1-94-011, dated May 11, 1994, describe two events regarding a short-to-ground on the second level U/V sensing circuit for 4160-volt Bus H. This short-to-ground resulted in opening the potential transformer sensing circuit fuse, which started and *loaded the associated DG. The corrective actions for these LERs are related to preventing the short-to-ground and were under investigating at the *time of this event. Therefore, these corrective acti~ns could not have prevented the current event.
LER 2-91-001-00, dated July 15, 1991, describes an Instrumentation and Controls (I&C) technician inadvertently dropping a screw on the power switch for power supply NM51 while performing maintenance. This resulted in a voltage transient to the output relays of radiation protection monitors RM-11 and RM-12, which caused a solid state protection system Train B CVI actuation. The corrective actions to prevent recurrence included (1) counseling the technician invol~ed regarding the necessity for establishing a temporary electrical .
barrier when working around energized equipment, when practical, and (2) issuance of a maintenance bulletin that describes the event and discusses current policies and procedures applicable to performing work on energized equipment. These corrective actions could not have prevented the current event since the maintenance bulletin was issued for I&C personnel only. The cause of the current event was a lack of knowledge concerning the task at hand, 1n that the operator was not aware that the ac.potential circuits could be inadvertently shorted together while attempting to replace an indicating light bulb.
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LICENSEE EVENT REPORT (LER) TEXT CO-NUATION FACILITY NAME (l) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)
VEAR L::::::: SEQUENTIAL 1::::::::::: REVISION -
r/{- NUMBER F:::::? NUMBER Diablo Canyon, Unit 1 oIs.I oI oI oI 2 I 7 I s 94 - oI 114 - o Io 6 IOF I 6 TEXT (17)
LER 1-90-019-00, dated December 27, 1990, describes how a contract electrician was performing design modifications in an energized radiation monitor cabinet. As the electrician removed the pliers fro~
the cabinet, the pliers came in contact with the terminals on a fuse block, causing a voltage transient on an inverter, and ultimately resulting in a CVI. The root cause was determined to be personnel error in that if the electrician had taped the tool in accordance with standard work practices for wo~king in energized cabinets, electrical contact w.ith the fuse block may not have occurred. A contributory cause was determined to be a previously issued maintenance bulletin regarding work on energized equipment, which recommends taping tools, had not been reviewed with *the technician. Corrective actions included distributing and training on relevant maintenance bulletins to the general construction crews who also perform work on energized equipment within the plant. The corrective actions from this event concentrated on the use of tools within energized cabinets or in the vicinity of energized equipment.
6472S