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Category:LICENSEE EVENT REPORT (SEE ALSO AO
MONTHYEARML17313B0751999-08-27027 August 1999 LER 99-002-00:on 990730,test Mode Trip Bypass for EDG Output Breakers Not Surveilled.Cause Under Investigation.Operations Personnel Conservatively Invoked SR 3.0.3 for SR 3.8.1.13. with 990827 Ltr ML17313B0191999-07-16016 July 1999 LER 99-005-00:on 990618,RT on Low DNBR Was Noted.Caused by Hardware Induced Calculation Error.Cr Operator Was Taken to Place Reactor in Stable Condition IAW Appropriate Operating Procedure ML17313A9281999-05-0707 May 1999 LER 99-004-00:on 990408,PSV Lift Pressures Were Outside of TS Limits.Caused by Lift Pressure Setpoint Drift.Psvs Have Been Tested,Disassembled,Inspected,Reassembled & Certified at Wyle Labs ML17313A8951999-04-14014 April 1999 LER 99-003-00:on 990317,required Surveillance Requirement Not Completed Due to Deficient Procedure,Was Determined. Caused by Cognitive Personnel Error.St Procedures Revised to Require Chiller to Be Operating & Oil Temperature Checked ML17313A8921999-04-13013 April 1999 LER 98-003-01:on 980902,discovered That MSSV as-found Lift Pressures Were Outside TS Limits.Caused by Bonding of Valve Disc to Nozzle Seat.Affected Valves Were Adjusted,Retested & Returned to Svc ML17313A8891999-04-0909 April 1999 LER 99-001-00:on 990310,RT on High Pressurizer Pressure Was Noted.Caused by Loss of Heat Removal.Cr Supervisor Was Removed from Shift Duties for Diagnostics Skills Training. with 990409 Ltr ML17313A8361999-03-0101 March 1999 LER 99-001-00:on 990103,TS Violation for Power Dependent Insertion Limit Alarm Being Inoperable.Caused by Personnel Error.Revised Procedure to Clarify How Computer Point Is to Be Returned to Scan Mode.With 990302 Ltr ML17313A7701999-01-15015 January 1999 LER 96-008-00:on 960507,inadequate Procedure Results in Nuclear Power Channels Not Calibrated During Power Ascension Tests Occurred.Caused by Deficient Procedure.Procedure Revised ML17313A6611998-10-24024 October 1998 LER 98-008-00:on 980729,EQ of Electrical Connectors Were Not Adequately Demonstrated.Caused Because Test Was Conducted with Only Single Lv Connector & Without Fully Ranged Inputs. Revised EQ Requirements ML17313A5961998-09-14014 September 1998 LER 98-002-00:on 980814,B Train H Recombiner Was Noted Inoperable Due to cross-wired Power Receptacle.Cause of Event Is Under investigation.Cross-wired Power Supply Receptacle for B Train H Recombiner Was re-wired ML17313A5761998-09-0808 September 1998 LER 98-003-01:on 980113,discovered That One Channel of RWT Level Sys Had Failed High.Caused by Water Intrusion Into Electrical Termination Pull Box.Weep Holes Were Drilled Into Bottoms of Pull Boxes Nearest Level Transmitters ML17313A5591998-08-28028 August 1998 LER 98-001-00:on 980730,entered TS 3.0.3 Due to Safety Injection Flow Instruments Being Removed from Svc.Caused by Personnel Error.Transmitters Were Unisolated & Returned to svc.W/980828 Ltr ML17313A5201998-07-30030 July 1998 LER 98-004-00:on 980630,personnel Discovered That Pressure Safety Valve Had Not Received Periodic Set Pressure Test for ASME Class 1 Pressure Safety Valve.Caused by Personnel Error.Pressure Safety Valve reviewed.W/980730 Ltr ML17313A4671998-06-19019 June 1998 LER 98-007-00:on 980520,CR Personnel Observed Flow & Pressure Perturbations on Chemical & Vol Control Sys Letdown Sys.Caused by Cyclic Fatigue Due to Dynamic Pressure Transients.Unit Letdown Piping Replaced ML17313A4131998-06-0505 June 1998 LER 98-006-00:on 980507,determined That Plant Was Outside Design Basis Due to SI Discharge Check Valve Reverse Flow. Check Valve Was Disassembled,Examined & Reassembled, Whereupon Valve Met Acceptance Criteria ML17313A3951998-05-26026 May 1998 LER 98-005-00:on 980428,noted That Required Response Time Testing Had Not Been Performed.Caused by Personnel Error. Coached I&C Personnel Responsible for Reviewing Work Authorization Documentation ML17313A3251998-04-0101 April 1998 LER 98-004-00:on 980304,safety Valves as-found Pressures Out of Tolerance.Cause of Event Is Under Investigation.Three Mssv'S & Psv Will Be Replaced W/Refurbished & Recertified Valves During Refueling Outage U1R7 ML17313A3131998-03-21021 March 1998 LER 98-001-00:on 980301,surveillance Test Deficiency Found During Qaa Leads to TS 3.0.3/4.0.3 Entry.Caused by Personnel Error.Personnel Responsible for Inadequately Performed SR Were Coached ML17313A2251998-03-0505 March 1998 LER 93-005-00:on 930309,CR Personnel Discovered Missed TS LCO Action & Subsequently Performed Surveillance Satisfactorily.Caused by Personnel Error.Appropriate Disciplinary Action issued.W/980305 Ltr ML17313A2241998-02-26026 February 1998 LER 98-001-00:on 980130,reactor Protection & ESFAS Instrumentation Not Bypassed within one-hour Allowed by TS Occurred.Caused by Inadequate Procedures.Expectation to Detect Alarm Conditions Was Emphasized to CR Personnel ML17313A2081998-02-10010 February 1998 LER 97-007-00:on 971006,TS Violation Occurred Due to Inadequate Shutdown Cooling Flow During Modes 5 & 6 Operation.Independent Investigation of Event Was Conducted IAW APS CA program.W/980210 Ltr ML17313A2041998-02-0505 February 1998 LER 97-006-00:on 971028,missed TS 4.0.5 SR Was Noted.Caused by Personnel Error.Independent Investigation of Event Is Being Conducted IAW W/Aps Corrective Action Program ML17313A1201997-11-12012 November 1997 LER 97-006-00:on 971020,manual Reactor Trip Occurred Due to Vibration & Bearing Temp Increases in Reactor Coolant Pump. Caused by Failed Lower Journal Bearing.Bearing Assembly Was Disassembled,Inspected & Rebuilt ML17312B7181997-10-0707 October 1997 LER 97-003-00:on 970907,inadvertent Loss of Power & EDG Start Occurred Due to Procedural Error.Changed Train a & Train B Edg/Ist ST Procedures to Consistently Reflect Proper Pretest Staging Hand switches.W/971007 Ltr ML17312B7051997-09-26026 September 1997 LER 97-003-01:on 970215,seven Main Steam Safety Valves Were Found Out of Tolerance Prior to Refueling Outage.Safety Analysis Performed Based Upon as-found MSSV Data Which Demonstrated That MSSVs Would Perform Safety Functions ML17312B5531997-07-0707 July 1997 LER 97-002-00:on 970528,SR for Core Protection Was Not Performed Due to Inadequate Procedures.Revised Procedures ML17312B5501997-07-0707 July 1997 LER 97-003-00:on 970211,notified of Trevitest Activities Indicating That Total of Seven MSSVs Had as-found Lift Set Pressures Greater than 3 Percent Allowed by TS 3.7.1.1. Investigation Conducted.Seven MSSVs replaced.W/970707 Ltr ML17312B4971997-06-13013 June 1997 LER 97-002-00:on 970531,RT Occurred.Caused by Spurious Opening of All Four Rt Switchgear Breakers.Independent Investigation of Event Being Conducted in Accordance W/Util Corrective Action Program ML17312B1461996-12-17017 December 1996 LER 96-007-00:on 961119,surveillance Test Deficiencies Were Found During GL 96-01 Review Leading to TS 3.0.3 Entries. Caused by Increase in Scope of Required Testing.Supplement Will Be submitted.W/961217 Ltr ML17312A9511996-09-0404 September 1996 LER 96-003-00:on 960809,open Auxiliary Bldg Door Caused Full Bldg Essential Filtration Inoperability.Caused by Personnel Error.C/As Under consideration.W/960904 Ltr ML17312A8641996-07-17017 July 1996 LER 96-001-00:on 960621,inaccurate Gas Calculations for Post Accident Sampling Sys Occurred.Caused by Surveillance Test Worksheet Errors.Independent Investigation of Event Being conducted.W/960717 Ltr ML17300B2541996-06-11011 June 1996 LER 96-001-01:on 960404,inappropriate Grounding of Equipment Resulted in Condition Outside Design Basis of Plant. Established Fire Watches Required for Affected Areas ML17312A8081996-06-0909 June 1996 LER 96-002-00:on 960514,Tech Spec Violation Occurred Due to Erroneous Surveillance Requirement.Caused by Incorporation of C-E Generic Ts.Investigation Being conducted.W/960609 Ltr ML17312A7751996-05-17017 May 1996 LER 96-003-00:on 960122,missed Surveillance for Logic Check of Logs 1 & 2 Safety Excore Bypasses.Caused by Procedural Error.Log Power Functional Test Revised to Check Logs 1 & 2 Bypasses Regardless of Power level.W/960517 Ltr ML17312A7511996-05-0606 May 1996 LER 96-001-00:on 960404,smoke Discovered in Back Boards Area of CR by Security Officer,Performing Hourly Fire Watch Tour. Caused by Improperly Grounded Circuit.Investigation for Inappropriate Grounding of Low Voltage Power Sys Initiated ML17312A7241996-04-25025 April 1996 LER 96-002-00:on 960401,inappropriate Work Practice Resulted in Esfa of Train B Edg.Night Order Was Issued to All Three Units Describing event.W/960425 Ltr ML17312A6861996-04-0606 April 1996 LER 95-007-01:on 950512,determined That Bench Settings of air-operated Letdown & Containment Isolation Valves Adversely Affected Ability of Valves to Perform 10CFR50 App R Safety Function.Affected Valves Modified ML17312A5631996-02-22022 February 1996 LER 95-016-00:on 951212,containment Spray TS Violation Occurred Due to Unrecognized Valve Failure.Shim/Band Was Placed Around Stator of 1JSIBUV665 Motor Operator to Maintain Stator in Correct position.W/960222 Ltr ML17311B3381996-01-0909 January 1996 LER 95-014-00:on 951209,reactor Tripped Following Degradation of Main FW Flow.Caused by Malfunction of Fwcs Power supply,NNN-D11,transfer switch.NNN-D11 Aligned to Normal Power supply.W/960109 Ltr ML17311B3331995-12-31031 December 1995 LER 95-013-00:on 951201,AFW Sys Was Outside Design Basis of Plant.Caused by Design Error.Performed Assessment to Demonstrate That Existing Condition Does Not Pose Addl Safety concerns.W/951231 Ltr ML17311B2801995-11-23023 November 1995 LER 95-011-00:on 951018,identified Procedural Deficiency W/Msiv & FWIV ISTs Due to Personnel Error.Verified Operability of MSIVs & FWIVs.W/951123 Ltr ML17311B2531995-10-20020 October 1995 LER 95-002-00:on 950924,identified That Abnormal Blowdown Valves to Blowdown Flash Tank (Bft) Isolated,Resulting in Reactor Core Power Exceeding 3,800 Mwt Due to Personnel Error.Procedure for Aligning Blowdown to Bft Revised ML17311B1991995-09-21021 September 1995 LER 95-010-00:on 950727,equipment Qualification of Air Handling Unit Caused Essential Cw Pump to Be Inoperable. Used Work Orders to Drill Weep Holes in Motor Lead Connection boxes.W/950921 Ltr ML17311B1741995-09-0404 September 1995 LER 95-004-01:on 950329,containment Electrical Penetration Overcurrent Protective Devices Found Outside Design Basis. Caused by Error on Part of Original Architect Engineer. Modified Affected Circuits Critical to Normal Operational ML17311B1561995-08-27027 August 1995 LER 95-003-00:on 950729,switchyard Voltage Dropped Below Administratively Imposed Limit of 524 Kv for Approx 10 Seconds Due to Transient Grid Voltage.No C/A Taken Since Transmission Sys Transient Short duration.W/950827 Ltr ML17311B1551995-08-25025 August 1995 LER 95-002-01:on 950303,identified That Slb Analyses Failed to Consider as Initial Condition One Percent SDM for All Rods in (ARI) Due to Lack of Coordination & Unclear Div of Responsibilities.Ari Core Data Book SDM Curves Modified ML17311B1211995-08-16016 August 1995 LER 95-005-00:on 950717,RT on Low SG Water Level Was Result Following Degradation of MFW Flow.Completed Evaluation of Event ML17311B0841995-07-28028 July 1995 LER 94-005-01:on 941019,completed TS Required Shutdown Due to Expiration of LCO Time Limit.Design Change Options Identified & Will Be Reviewed to Determine If Valve &/Or Motor Operator Replacement or Mod Necessary ML17311B0721995-07-20020 July 1995 LER 95-004-00:on 950706,identified Four Occassions Between 950407 & 0630 When Conditional Surveillance in TS LCO 3.8.4.1 Action a Not Performed Due to Inattention to Detail. CR Copy of Temporary Procedure 40TP-9ZZ04 Corrected ML17311B0081995-07-0606 July 1995 LER 95-003-00:on 950613,TS LCO 3.0.3 Entered Following Loss of Both Trains of Essential Cw Sys & Both Hydrogen Recombiners.Caused by Spurious Actuations Due to Broken EDG Speed Probe Connector.Connector replaced.W/950706 Ltr 1999-08-27
[Table view] Category:RO)
MONTHYEARML17313B0751999-08-27027 August 1999 LER 99-002-00:on 990730,test Mode Trip Bypass for EDG Output Breakers Not Surveilled.Cause Under Investigation.Operations Personnel Conservatively Invoked SR 3.0.3 for SR 3.8.1.13. with 990827 Ltr ML17313B0191999-07-16016 July 1999 LER 99-005-00:on 990618,RT on Low DNBR Was Noted.Caused by Hardware Induced Calculation Error.Cr Operator Was Taken to Place Reactor in Stable Condition IAW Appropriate Operating Procedure ML17313A9281999-05-0707 May 1999 LER 99-004-00:on 990408,PSV Lift Pressures Were Outside of TS Limits.Caused by Lift Pressure Setpoint Drift.Psvs Have Been Tested,Disassembled,Inspected,Reassembled & Certified at Wyle Labs ML17313A8951999-04-14014 April 1999 LER 99-003-00:on 990317,required Surveillance Requirement Not Completed Due to Deficient Procedure,Was Determined. Caused by Cognitive Personnel Error.St Procedures Revised to Require Chiller to Be Operating & Oil Temperature Checked ML17313A8921999-04-13013 April 1999 LER 98-003-01:on 980902,discovered That MSSV as-found Lift Pressures Were Outside TS Limits.Caused by Bonding of Valve Disc to Nozzle Seat.Affected Valves Were Adjusted,Retested & Returned to Svc ML17313A8891999-04-0909 April 1999 LER 99-001-00:on 990310,RT on High Pressurizer Pressure Was Noted.Caused by Loss of Heat Removal.Cr Supervisor Was Removed from Shift Duties for Diagnostics Skills Training. with 990409 Ltr ML17313A8361999-03-0101 March 1999 LER 99-001-00:on 990103,TS Violation for Power Dependent Insertion Limit Alarm Being Inoperable.Caused by Personnel Error.Revised Procedure to Clarify How Computer Point Is to Be Returned to Scan Mode.With 990302 Ltr ML17313A7701999-01-15015 January 1999 LER 96-008-00:on 960507,inadequate Procedure Results in Nuclear Power Channels Not Calibrated During Power Ascension Tests Occurred.Caused by Deficient Procedure.Procedure Revised ML17313A6611998-10-24024 October 1998 LER 98-008-00:on 980729,EQ of Electrical Connectors Were Not Adequately Demonstrated.Caused Because Test Was Conducted with Only Single Lv Connector & Without Fully Ranged Inputs. Revised EQ Requirements ML17313A5961998-09-14014 September 1998 LER 98-002-00:on 980814,B Train H Recombiner Was Noted Inoperable Due to cross-wired Power Receptacle.Cause of Event Is Under investigation.Cross-wired Power Supply Receptacle for B Train H Recombiner Was re-wired ML17313A5761998-09-0808 September 1998 LER 98-003-01:on 980113,discovered That One Channel of RWT Level Sys Had Failed High.Caused by Water Intrusion Into Electrical Termination Pull Box.Weep Holes Were Drilled Into Bottoms of Pull Boxes Nearest Level Transmitters ML17313A5591998-08-28028 August 1998 LER 98-001-00:on 980730,entered TS 3.0.3 Due to Safety Injection Flow Instruments Being Removed from Svc.Caused by Personnel Error.Transmitters Were Unisolated & Returned to svc.W/980828 Ltr ML17313A5201998-07-30030 July 1998 LER 98-004-00:on 980630,personnel Discovered That Pressure Safety Valve Had Not Received Periodic Set Pressure Test for ASME Class 1 Pressure Safety Valve.Caused by Personnel Error.Pressure Safety Valve reviewed.W/980730 Ltr ML17313A4671998-06-19019 June 1998 LER 98-007-00:on 980520,CR Personnel Observed Flow & Pressure Perturbations on Chemical & Vol Control Sys Letdown Sys.Caused by Cyclic Fatigue Due to Dynamic Pressure Transients.Unit Letdown Piping Replaced ML17313A4131998-06-0505 June 1998 LER 98-006-00:on 980507,determined That Plant Was Outside Design Basis Due to SI Discharge Check Valve Reverse Flow. Check Valve Was Disassembled,Examined & Reassembled, Whereupon Valve Met Acceptance Criteria ML17313A3951998-05-26026 May 1998 LER 98-005-00:on 980428,noted That Required Response Time Testing Had Not Been Performed.Caused by Personnel Error. Coached I&C Personnel Responsible for Reviewing Work Authorization Documentation ML17313A3251998-04-0101 April 1998 LER 98-004-00:on 980304,safety Valves as-found Pressures Out of Tolerance.Cause of Event Is Under Investigation.Three Mssv'S & Psv Will Be Replaced W/Refurbished & Recertified Valves During Refueling Outage U1R7 ML17313A3131998-03-21021 March 1998 LER 98-001-00:on 980301,surveillance Test Deficiency Found During Qaa Leads to TS 3.0.3/4.0.3 Entry.Caused by Personnel Error.Personnel Responsible for Inadequately Performed SR Were Coached ML17313A2251998-03-0505 March 1998 LER 93-005-00:on 930309,CR Personnel Discovered Missed TS LCO Action & Subsequently Performed Surveillance Satisfactorily.Caused by Personnel Error.Appropriate Disciplinary Action issued.W/980305 Ltr ML17313A2241998-02-26026 February 1998 LER 98-001-00:on 980130,reactor Protection & ESFAS Instrumentation Not Bypassed within one-hour Allowed by TS Occurred.Caused by Inadequate Procedures.Expectation to Detect Alarm Conditions Was Emphasized to CR Personnel ML17313A2081998-02-10010 February 1998 LER 97-007-00:on 971006,TS Violation Occurred Due to Inadequate Shutdown Cooling Flow During Modes 5 & 6 Operation.Independent Investigation of Event Was Conducted IAW APS CA program.W/980210 Ltr ML17313A2041998-02-0505 February 1998 LER 97-006-00:on 971028,missed TS 4.0.5 SR Was Noted.Caused by Personnel Error.Independent Investigation of Event Is Being Conducted IAW W/Aps Corrective Action Program ML17313A1201997-11-12012 November 1997 LER 97-006-00:on 971020,manual Reactor Trip Occurred Due to Vibration & Bearing Temp Increases in Reactor Coolant Pump. Caused by Failed Lower Journal Bearing.Bearing Assembly Was Disassembled,Inspected & Rebuilt ML17312B7181997-10-0707 October 1997 LER 97-003-00:on 970907,inadvertent Loss of Power & EDG Start Occurred Due to Procedural Error.Changed Train a & Train B Edg/Ist ST Procedures to Consistently Reflect Proper Pretest Staging Hand switches.W/971007 Ltr ML17312B7051997-09-26026 September 1997 LER 97-003-01:on 970215,seven Main Steam Safety Valves Were Found Out of Tolerance Prior to Refueling Outage.Safety Analysis Performed Based Upon as-found MSSV Data Which Demonstrated That MSSVs Would Perform Safety Functions ML17312B5531997-07-0707 July 1997 LER 97-002-00:on 970528,SR for Core Protection Was Not Performed Due to Inadequate Procedures.Revised Procedures ML17312B5501997-07-0707 July 1997 LER 97-003-00:on 970211,notified of Trevitest Activities Indicating That Total of Seven MSSVs Had as-found Lift Set Pressures Greater than 3 Percent Allowed by TS 3.7.1.1. Investigation Conducted.Seven MSSVs replaced.W/970707 Ltr ML17312B4971997-06-13013 June 1997 LER 97-002-00:on 970531,RT Occurred.Caused by Spurious Opening of All Four Rt Switchgear Breakers.Independent Investigation of Event Being Conducted in Accordance W/Util Corrective Action Program ML17312B1461996-12-17017 December 1996 LER 96-007-00:on 961119,surveillance Test Deficiencies Were Found During GL 96-01 Review Leading to TS 3.0.3 Entries. Caused by Increase in Scope of Required Testing.Supplement Will Be submitted.W/961217 Ltr ML17312A9511996-09-0404 September 1996 LER 96-003-00:on 960809,open Auxiliary Bldg Door Caused Full Bldg Essential Filtration Inoperability.Caused by Personnel Error.C/As Under consideration.W/960904 Ltr ML17312A8641996-07-17017 July 1996 LER 96-001-00:on 960621,inaccurate Gas Calculations for Post Accident Sampling Sys Occurred.Caused by Surveillance Test Worksheet Errors.Independent Investigation of Event Being conducted.W/960717 Ltr ML17300B2541996-06-11011 June 1996 LER 96-001-01:on 960404,inappropriate Grounding of Equipment Resulted in Condition Outside Design Basis of Plant. Established Fire Watches Required for Affected Areas ML17312A8081996-06-0909 June 1996 LER 96-002-00:on 960514,Tech Spec Violation Occurred Due to Erroneous Surveillance Requirement.Caused by Incorporation of C-E Generic Ts.Investigation Being conducted.W/960609 Ltr ML17312A7751996-05-17017 May 1996 LER 96-003-00:on 960122,missed Surveillance for Logic Check of Logs 1 & 2 Safety Excore Bypasses.Caused by Procedural Error.Log Power Functional Test Revised to Check Logs 1 & 2 Bypasses Regardless of Power level.W/960517 Ltr ML17312A7511996-05-0606 May 1996 LER 96-001-00:on 960404,smoke Discovered in Back Boards Area of CR by Security Officer,Performing Hourly Fire Watch Tour. Caused by Improperly Grounded Circuit.Investigation for Inappropriate Grounding of Low Voltage Power Sys Initiated ML17312A7241996-04-25025 April 1996 LER 96-002-00:on 960401,inappropriate Work Practice Resulted in Esfa of Train B Edg.Night Order Was Issued to All Three Units Describing event.W/960425 Ltr ML17312A6861996-04-0606 April 1996 LER 95-007-01:on 950512,determined That Bench Settings of air-operated Letdown & Containment Isolation Valves Adversely Affected Ability of Valves to Perform 10CFR50 App R Safety Function.Affected Valves Modified ML17312A5631996-02-22022 February 1996 LER 95-016-00:on 951212,containment Spray TS Violation Occurred Due to Unrecognized Valve Failure.Shim/Band Was Placed Around Stator of 1JSIBUV665 Motor Operator to Maintain Stator in Correct position.W/960222 Ltr ML17311B3381996-01-0909 January 1996 LER 95-014-00:on 951209,reactor Tripped Following Degradation of Main FW Flow.Caused by Malfunction of Fwcs Power supply,NNN-D11,transfer switch.NNN-D11 Aligned to Normal Power supply.W/960109 Ltr ML17311B3331995-12-31031 December 1995 LER 95-013-00:on 951201,AFW Sys Was Outside Design Basis of Plant.Caused by Design Error.Performed Assessment to Demonstrate That Existing Condition Does Not Pose Addl Safety concerns.W/951231 Ltr ML17311B2801995-11-23023 November 1995 LER 95-011-00:on 951018,identified Procedural Deficiency W/Msiv & FWIV ISTs Due to Personnel Error.Verified Operability of MSIVs & FWIVs.W/951123 Ltr ML17311B2531995-10-20020 October 1995 LER 95-002-00:on 950924,identified That Abnormal Blowdown Valves to Blowdown Flash Tank (Bft) Isolated,Resulting in Reactor Core Power Exceeding 3,800 Mwt Due to Personnel Error.Procedure for Aligning Blowdown to Bft Revised ML17311B1991995-09-21021 September 1995 LER 95-010-00:on 950727,equipment Qualification of Air Handling Unit Caused Essential Cw Pump to Be Inoperable. Used Work Orders to Drill Weep Holes in Motor Lead Connection boxes.W/950921 Ltr ML17311B1741995-09-0404 September 1995 LER 95-004-01:on 950329,containment Electrical Penetration Overcurrent Protective Devices Found Outside Design Basis. Caused by Error on Part of Original Architect Engineer. Modified Affected Circuits Critical to Normal Operational ML17311B1561995-08-27027 August 1995 LER 95-003-00:on 950729,switchyard Voltage Dropped Below Administratively Imposed Limit of 524 Kv for Approx 10 Seconds Due to Transient Grid Voltage.No C/A Taken Since Transmission Sys Transient Short duration.W/950827 Ltr ML17311B1551995-08-25025 August 1995 LER 95-002-01:on 950303,identified That Slb Analyses Failed to Consider as Initial Condition One Percent SDM for All Rods in (ARI) Due to Lack of Coordination & Unclear Div of Responsibilities.Ari Core Data Book SDM Curves Modified ML17311B1211995-08-16016 August 1995 LER 95-005-00:on 950717,RT on Low SG Water Level Was Result Following Degradation of MFW Flow.Completed Evaluation of Event ML17311B0841995-07-28028 July 1995 LER 94-005-01:on 941019,completed TS Required Shutdown Due to Expiration of LCO Time Limit.Design Change Options Identified & Will Be Reviewed to Determine If Valve &/Or Motor Operator Replacement or Mod Necessary ML17311B0721995-07-20020 July 1995 LER 95-004-00:on 950706,identified Four Occassions Between 950407 & 0630 When Conditional Surveillance in TS LCO 3.8.4.1 Action a Not Performed Due to Inattention to Detail. CR Copy of Temporary Procedure 40TP-9ZZ04 Corrected ML17311B0081995-07-0606 July 1995 LER 95-003-00:on 950613,TS LCO 3.0.3 Entered Following Loss of Both Trains of Essential Cw Sys & Both Hydrogen Recombiners.Caused by Spurious Actuations Due to Broken EDG Speed Probe Connector.Connector replaced.W/950706 Ltr 1999-08-27
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML17300B3811999-09-30030 September 1999 Monthly Operating Repts for Sept 1999 for Pvngs,Units 1,2 & 3.With 991007 Ltr ML17300B3271999-08-31031 August 1999 Monthly Operating Rept for Aug 1999 for Pvngs,Units 1,2 & 3 ML17313B0751999-08-27027 August 1999 LER 99-002-00:on 990730,test Mode Trip Bypass for EDG Output Breakers Not Surveilled.Cause Under Investigation.Operations Personnel Conservatively Invoked SR 3.0.3 for SR 3.8.1.13. with 990827 Ltr ML17313B0611999-07-31031 July 1999 Monthly Operating Repts for July 1999 for Pvngs,Units 1,2 & 3.With 990810 Ltr ML17313B0191999-07-16016 July 1999 LER 99-005-00:on 990618,RT on Low DNBR Was Noted.Caused by Hardware Induced Calculation Error.Cr Operator Was Taken to Place Reactor in Stable Condition IAW Appropriate Operating Procedure ML17300B3151999-06-30030 June 1999 Monthly Operating Repts for June 1999 for Pvngs,Units 1,2 & 3.With 990714 Ltr ML17313A9921999-06-21021 June 1999 Special Rept:On 990525,RMS mini-computer Was Removed from Service to Implement Yr 2000 Mod & Was OOS Longer than 72 H Allowed.Caused by Planned Y2K Mods.Preplanned Alternate Sampling Program Was Initiated ML17313A9911999-06-18018 June 1999 Special Rept:On 990510,loose-part Detection Sys Channel 2 Was Declared Inoperable.Caused by Malfunction of Mineral Cable Connector to Accelerometer.Licensee Will Implement Modifications Which Will Enhance loose-part Detection Sys ML17313A9731999-05-31031 May 1999 Monthly Operating Repts for May 1999 for Pvngs,Units 1,2 & 3.With 990608 Ltr ML17313A9281999-05-0707 May 1999 LER 99-004-00:on 990408,PSV Lift Pressures Were Outside of TS Limits.Caused by Lift Pressure Setpoint Drift.Psvs Have Been Tested,Disassembled,Inspected,Reassembled & Certified at Wyle Labs ML17313A9201999-04-30030 April 1999 Monthly Operating Repts for Apr 1999 for Pvngs,Units 1,2 & 3.With 990512 Ltr ML17313A8951999-04-14014 April 1999 LER 99-003-00:on 990317,required Surveillance Requirement Not Completed Due to Deficient Procedure,Was Determined. Caused by Cognitive Personnel Error.St Procedures Revised to Require Chiller to Be Operating & Oil Temperature Checked ML17313A8921999-04-13013 April 1999 LER 98-003-01:on 980902,discovered That MSSV as-found Lift Pressures Were Outside TS Limits.Caused by Bonding of Valve Disc to Nozzle Seat.Affected Valves Were Adjusted,Retested & Returned to Svc ML17313A8891999-04-0909 April 1999 LER 99-001-00:on 990310,RT on High Pressurizer Pressure Was Noted.Caused by Loss of Heat Removal.Cr Supervisor Was Removed from Shift Duties for Diagnostics Skills Training. with 990409 Ltr ML17300B3071999-03-31031 March 1999 Seismic Portion of Submittal-Only Screening Review of Palo Verde Nuclear Generating Station Units Ipeee. ML17313A8801999-03-31031 March 1999 Monthly Operating Repts for Mar 1999 for Pvngs,Units 1,2 & 3.With 990412 Ltr ML20207M9231999-03-12012 March 1999 Amended Part 21 Rept Re Cooper-Bessemer Ksv EDG Power Piston Failure.Total of 198 or More Pistons Have Been Measured at Seven Different Sites.All Potentially Defective Pistons Have Been Removed from Svc Based on Encl Results ML20207H7471999-03-10010 March 1999 1999 Emergency Preparedness Exercise 99-E-AEV-03003 ML17313A8361999-03-0101 March 1999 LER 99-001-00:on 990103,TS Violation for Power Dependent Insertion Limit Alarm Being Inoperable.Caused by Personnel Error.Revised Procedure to Clarify How Computer Point Is to Be Returned to Scan Mode.With 990302 Ltr ML17313A8501999-02-28028 February 1999 Monthly Operating Repts for Feb 1999 for Palo Verde Nuclear Generating Station.With 990311 Ltr ML17313A7791999-02-0505 February 1999 Safety Evaluation Accepting Licensee Rev to Emergency Plan That Would Result in Two Less Radiation Protection Positions Immediatelu Available During Emergencies ML17313A8061999-01-31031 January 1999 Monthly Operating Repts for Jan 1999 for Pvngs,Units 1,2 & 3.With 990218 Ltr ML17313A7701999-01-15015 January 1999 LER 96-008-00:on 960507,inadequate Procedure Results in Nuclear Power Channels Not Calibrated During Power Ascension Tests Occurred.Caused by Deficient Procedure.Procedure Revised ML17313A7381998-12-31031 December 1998 Monthly Operating Repts for Dec 1998 for Palo Verde Nuclear Generating Station,Units 1,2 & 3.With 990113 Ltr ML20206H2101998-12-31031 December 1998 SCE 1998 Annual Rept ML17313A7031998-11-30030 November 1998 Monthly Operating Repts for Nov 1998 for Pvngs,Unit 1,2 & 3. with 981209 Ltr ML17313A6701998-11-0404 November 1998 Rev 2 to PVNGS Unit 2 Colr. ML17313A6741998-10-31031 October 1998 Monthly Operating Repts for Oct 1998 for Pvngs,Units 1,2 & 3.With 981109 Ltr ML17313A6611998-10-24024 October 1998 LER 98-008-00:on 980729,EQ of Electrical Connectors Were Not Adequately Demonstrated.Caused Because Test Was Conducted with Only Single Lv Connector & Without Fully Ranged Inputs. Revised EQ Requirements ML17313A6561998-09-30030 September 1998 Monthly Operating Rept for Sept 1998 for PVNGS Units 1,2 & 3.With 981007 Ltr ML17313A5961998-09-14014 September 1998 LER 98-002-00:on 980814,B Train H Recombiner Was Noted Inoperable Due to cross-wired Power Receptacle.Cause of Event Is Under investigation.Cross-wired Power Supply Receptacle for B Train H Recombiner Was re-wired ML17313A5761998-09-0808 September 1998 LER 98-003-01:on 980113,discovered That One Channel of RWT Level Sys Had Failed High.Caused by Water Intrusion Into Electrical Termination Pull Box.Weep Holes Were Drilled Into Bottoms of Pull Boxes Nearest Level Transmitters ML17313A5591998-08-28028 August 1998 LER 98-001-00:on 980730,entered TS 3.0.3 Due to Safety Injection Flow Instruments Being Removed from Svc.Caused by Personnel Error.Transmitters Were Unisolated & Returned to svc.W/980828 Ltr ML20151S0941998-08-21021 August 1998 Rev 6 to COLR for PVNGS Unit 3 ML20151S0861998-08-21021 August 1998 Rev 4 to COLR for PVNGS Unit 1 ML20151S0901998-08-21021 August 1998 Rev 1 to COLR for PVNGS Unit 2 ML18066A2771998-08-13013 August 1998 Part 21 Rept Re Deficiency in CE Current Screening Methodology for Determining Limiting Fuel Assembly for Detailed PWR thermal-hydraulic Sa.Evaluations Were Performed for Affected Plants to Determine Effect of Deficiency ML17313A5401998-08-13013 August 1998 Special Rept:On 980715,declared PASS Inoperable.Caused by Failure of Offgas Flush/Purge Control Handswitch HS0101. Handswitch Replaced & Post Maintenance Retesting Was Initiated ML17313A5301998-07-31031 July 1998 Monthly Operating Repts for July 1998 for Pvgns,Units 1,2 & 3.W/980812 Ltr ML17313A5201998-07-30030 July 1998 LER 98-004-00:on 980630,personnel Discovered That Pressure Safety Valve Had Not Received Periodic Set Pressure Test for ASME Class 1 Pressure Safety Valve.Caused by Personnel Error.Pressure Safety Valve reviewed.W/980730 Ltr ML17313A5791998-07-0707 July 1998 to PVNGS SG Tube ISI Results for Seventh Refueling Outage Mar & Apr 1998. ML17313A5001998-06-30030 June 1998 Monthly Operating Repts for June 1998 for Palo Verde Nuclear Generating Station,Units 1,2 & 3.W/980710 Ltr ML17313A4671998-06-19019 June 1998 LER 98-007-00:on 980520,CR Personnel Observed Flow & Pressure Perturbations on Chemical & Vol Control Sys Letdown Sys.Caused by Cyclic Fatigue Due to Dynamic Pressure Transients.Unit Letdown Piping Replaced ML17313A4521998-06-19019 June 1998 Rev 5 to COLR for Pvngs,Unit 3. ML17313A4501998-06-19019 June 1998 Rev 4 to COLR for Pvngs,Unit 3. ML17313A4131998-06-0505 June 1998 LER 98-006-00:on 980507,determined That Plant Was Outside Design Basis Due to SI Discharge Check Valve Reverse Flow. Check Valve Was Disassembled,Examined & Reassembled, Whereupon Valve Met Acceptance Criteria ML17313A4211998-05-31031 May 1998 Monthly Operating Repts for May 1998 for Pvngs,Units 1,2 & 3.W/980609 Ltr ML17313A3951998-05-26026 May 1998 LER 98-005-00:on 980428,noted That Required Response Time Testing Had Not Been Performed.Caused by Personnel Error. Coached I&C Personnel Responsible for Reviewing Work Authorization Documentation ML17313A3691998-04-30030 April 1998 Monthly Operating Repts for Apr 1998 for PVNGS.W/980412 Ltr ML17313A3251998-04-0101 April 1998 LER 98-004-00:on 980304,safety Valves as-found Pressures Out of Tolerance.Cause of Event Is Under Investigation.Three Mssv'S & Psv Will Be Replaced W/Refurbished & Recertified Valves During Refueling Outage U1R7 1999-09-30
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Text
LlCENSEE EVENT REPORT (LER)
ACIUTYNAME (1) DOCKET NUMBER (2) PAGE (3) oF Palo Verde Unit 2 0 5 0 0 0 5 2 9 1 0 7 ITLE (6)
Reactor Tri Followin the De radation of Main Feedwater Flow EVENT DATE 5 LER NUMBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED 8 MONTH DAY TEAR YEAR SEOUENTIAL REVISION MONTH DAY TEAR FACIUTYNAMES 1 NVMSERS NUMBER tIVMBER NIA 0 5 0 0 0 0 7 1 7 9 5 9 5 0 0 5 0 0 0 8 1 6 9 5 NIA 0 5 0 0 0 REPQRT Is sUBMITTED PURsUANT To THE REQUIREMENTs oF 10 cFR C (check one or mora ot the toltovvrno) (11)
MODE (0) 20A02(b) 20.45(c) 50.73(a)(2)(rv) 73.71(b)
POWER 20.405(a)(t) 0) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) 20.45(a)(1)(ri) 50.35(c)(2) 50.73(a) (2)(vti) OTHER (Specify in Abstract LEVEL<<0) 0 0 20,45(a)(1) (iii) 5073(a)(2)O) 50.73(a)(2)(vib)(A) beiovv and in Text, NRC Form 20.405(a)(t) Ov) 50.73(a)(2) 50.73(a) (2) (vtii)(B) 366A) 20.45(a)(1) 50.73(a)(2)(x)
<i'0.73(a)
(v) (2) (iii)
LICENSEE CONTACT FOR THIS LER (1 2)
AME E NUMBER Burton A. Grabo, Section Leader, Nuclear Regulatory Affairs 6 0 2 3 9 3 - 6 4 9 2 COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN TI6S REPOR T(13)
MANUFAG. REPORTABLE . MANUFAG. REPORTABLE TURER TO NPRDS TURER TO NPRDS MPX No SUPPLEMENTALREPORT EXPECTED(te) EXPECTED DAY YEAR SUBMISSCN YES ol yea. comptete EXPECTED SUBMISSCN DATE)
TllxcrNJlel e N00 aopN, I ~, wwrelewy r On July 17, 1995, le ~~ ~at Inelr (ei approximately 2331 MST, Palo Verde Unit 2 was in Mode 1 DATE (1 5)
(POWER OPERATION), operating at approximat:ely 100 percent power when a reactor trip occurred when Steam Generator Number 2 (SG-2) water level reached the Reactor Protection System (RPS) trip setpoint for low SG water level following the degradation of main'feedwater (FW) flow. Immediately following the reactor trip an Engineered Safet:y Feature Actuation System (ESFAS) actuation of both Auxiliary Feedwater Actuation Systems (AFAS) was received on SG-1 and SG-2 low levels. The loss of FW flow was the result of a momentary power loss (from NNN-Dll) to the FW control system (FWCS) during a switching operation of the non-Class 1E 13.8 kV (NAN-S05) switchgear from the normal power supply (startup transformer X01) to the 'alternate power supply (startup transformer X02) in order to take startup transformer X01 out of service for maintenance.
When the switching operation was carried out, the breaker indications for startup transformers X01 and X02 did not change. Plant multiplexer (PMUX) indication problems led the operating crew to believe that the switching operation did not occur. Concerned about an inadvertent breaker closure, the operating crew reset the alternate supply breaker X02. This resulted in the deenergization of NAN-S05, NAN-S03, and the class 1E 4.16 kV bus (PBA-S03).
The root cause for the Unit 2 reactor trip was determined to be a failure of the initial design to consider FWCS responses to momentary power interruptions.
An evaluation of the adequacy of NNN-Dll to support the FWCS and steam bypass control system (SBCS) is ongoing. Any corrective actions identified will be tracked under the APS Commitment Action Tracking System.
Previous similar events were reported pursuant to 10 CFR 50.73 in LERs 528/95-008, 530/94-007, 530/94-005, 530/93-001 and 529/92-001.
9508230041 950816 PDR 'ADO(."K 0500052tyi S PDR
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ACIUTYNAME DOCKET NUMBER LER NUMBER PAGE SEQUENTIAL EVISIO NUM8ER ; NUMSER Palo Verde Unit 2 0 5 0 0 0 5 2 9 9 5 0 0 5 0 0 0 2 OF 0 7 EXT 1 ~ REPORTING REQUIREMENT:
This LER 529/95-005 is being written to report an event that resulted in an automatic actuation of an Engineered Safety Feature (ESF), including the Reactor Protection System (RPS) as specified in 10 CFR 50.73(a)(2)(iv).
Specifically, on July 17, 1995, at approximately 2331 MSTg Palo Verde Unit 2 was in Mode 1 (POWER OPERATION), operating at approximately 100 percent power when a reactor trip occurred when Steam Generator Number 2 (SG-2) (AB) water level reached the Reactor Protection System (RPS)(JC) trip setpoint for low SG water level following the degradation of main feedwater (FW)(SJ) flow. Immediately following the reactor trip an Engineered Safety Feature Actuation System (ESFAS)(JE) actuation of both Auxiliary Feedwater Actuation Systems (AFAS)(JE, BA) was received on SG-1 and SG-2 low levels. The loss of FW flow was the result of a momentary power loss to the FW control system (FWCS) during a switching operation of the non-Class 1E 13.8 kV (NAN-S05)(EA) switchgear from the normal power supply (startup transformer (XH4R) X01) to the alternate power supply (startup transformer X02) in order to take staztup transformer X01 out of for maintenance. 'ervice When the switching operation was carried out, the breaker indications for startup transformers X01 and X02 did not change. Plant multiplexer (PMUX) indication problems led the operating crew (utility, licensed) to believe that the switching operation did not occur. Concerned about an inadvertent breaker closure, the operating crew reset the alternate supply breaker X02.
This resulted in the deenergization of NAN-S05, NAN-S03, and the class 1E 4.16 kV bus (PBA-S03)(EB). The loss of power to the class 1E 4.16 kV bus resulted in a valid ESFAS signal starting the Train A Emergency Diesel Generator (EDG)(EK) ~ Required plant equipment and safety systems responded to the event as designed. No other safety actuations occurred and none were required. By approximately 0000 MST on July 18, 1995, the plant was stabilized in Mode 3 (HOT STANDBY).
2 ~ EVENT DESCRIPTION:
On July 17, 1995, at approximately 2315 MST, Unit 2 was in Mode 1 (POWER OPERATION) at approximately 100 percent power when Control Room personnel (utility, licensed) were preparing to transfer the non-Class 1E 13.8 kV switchgear (NAN-S05) from the normal power supply (startup transformer X01) to the alternate power supply (startup transformer X02) in order to take startup transformer X01 out of service for maintenance. When the, Reactor Operator (RO) (utility, licensed) closed the alternate breaker, there was no indication from the main control board that either breaker position had changed, (normal or alternate). After conferring with the Control Room Supervisor (CRS) (utility, licensed), believing that the alternate breaker had not closed and concerned about an inadvertent breaker closure, the RO opened the alternate breaker which resulted in the deenezgization of NAN-S05, NAN-.S03, and the Class 1E 4.16 kV bus (PBA-S03). The loss of power to the class 1E 4.16 kV bus resulted in a valid ESFAS signal starting the Train A EDG which restored power to PBA-S03.
LICENSEE EVENT REPORT (LER) TEXT CONTINuATION AGILITYNAME DOCKET NUMBER LER NUMBER PAGE
'EQUENTIAL EVISIO NUMBER NUMBER Palo Verde Unit 2 0 5 0 0 0 5 2 9 9 5 - 0 0 5 0 0 0 3 OF 0 7 EXT When the alternate power supply breaker X02 was opened, NNN-D11 (power supply for FWCS and steam bypass control system (SBCS)(JI)) recognized the undervoltage condition on bus PBA-S03 and the undervoltage relay dropped out which forced the transfer switch to transfer to the "Normal" power source. (Note: NNN-D11 was lined up to the "Emergency" power supply per Operation's procedures, as the preferred power source.) The automatic transfer switch is a break before make switch which caused the output voltage to drop for approximately 0.5 second.
This voltage drop caused the FWCS to go to manual operation and SBCS to go to emergency off without any automatic functions. The FWCS went to zero output which resulted in the main FW pumps going to minimum speed and the economizer flow control valves closing.
At approximately 2331 MST on July 17, 1995, the Unit 2 reactor (AC) tripped when SG-2 water level reached the RPS trip setpoint foz low SG water level following the degradation of main FW flow.
With the SBCS in emergency off (without any automatic functions) reactor coolant system (RCS) temperature and SG pressure were controlled by a main steam safety valve (MSSV)(SB, RV) and atmospheric dump valves (ADVs)(SB) until the SBCS was available for use. Required plant equipment and safety systems responded to the event as designed. No other safety system actuations occurred and none were required.
The SS diagnosed the event as an uncomplicated reactor trip. At approximately 0000 MST on July 18, 1995, the plant was stabilized in Mode 3 (HOT STANDBY).
- 3. ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATION OF THIS EVENT:
This Unit 2 reactor trip can be classified as a Loss of Normal Feedwater which is an infrequent event of the "decreasing heat removal by the secondary system" category and is bounded by the limiting event for this category which is the Loss of Condenser Vacuum (LOCV). Additionally, equipment and systems, assumed in Safety Analysis, were functional and plant response was normal for the situation that occurred. Scenarios defined in Updated Final Safety Analysis Report (UFSAR) Chapter 15 and design assumptions of the reactor protection system are bounding for this Unit 2 reactor trip. Scenarios defined in UFSAR Chapter 6, concerning Loss of Coolant Accidents (LOCA), were not challenged during this transient.
The reactor coolant system (RCS)(AB) pressure increased to approximately 2275 pounds per square inch absolute (psia) during this event. The peak pressure criteria of 110 percent of design (2750 psia) was not challenged during this RCS pressure transient. The steam generator peak pressures of 1258 and 1260 (SG-1 and SG-2 respectively) psia were reached at approximately 2332 MST. The main steam safety valve operated as designed to maintain SG pressure until the atmospheric dump valves (ADVs) were used to maintain SG pressure. The ADVs were used until the SBCS became available to maintain SG pressure. The maximum SG pressure was below the 110 percent of design pressure (1397 psia),
I
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AGILITYNAME DOCKET NUMBER YEAR
'ER NUMBER SEQUENTIAL EVISIO PAGE NUMBER ~ NUMBER Palo Verde Unit 2 0 5 0 0 0 5 2 9 9 5 0 0 5 0 0 0 4oFO 7 EXT The transient did not cause any violation of the Specified Acceptable Fuel Design Limits (SAFDLs). This event did not result in any challenges to the fission product barriers or result in any releases of radioactive materials'herefore, there were no adverse safety consequences or implications as a result of this event. This event did not adversely affect the safe operation of the plant or the health and safety of the public.
CAUSE OF THE EVENT:
An incident investigation for the Unit 2 reactor trip is being performed in accordance with the APS Corrective Action Program. The cause for the Unit 2 reactor trip was that the initial design did not consider the FWCS responses to momentary power interruptions (SALP Cause Code B: Design, Manufacturing, Construction/Installation). The FWCS design does not ~
provide immediate transfer of power upon loss of power. The current plant configuration is in accordance with design; however, the 500 milliseconds that it takes to transfer power is not adequate to ensure that the FWCS is not interrupted.
In addition to the root cause there were two contributing factors that led to the loss of power on NNN-D11 and subsequent reactor trip and AFAS:
- 1. The failure of the PMUX system provided inaccurate breaker information to the control room staff. The temperature sensitive equipment in PMUX=
had failed due to high temperatures in the 25RMT cabinet, which was the initiating cause. There are no control room alarms associated with a RMT failure and the Operations Computer Systems personnel, responsible for the PMUX equipment, were unaware of the high temperatures in the 25RMT cabinet.
- 2. When the expected response was not achieved during the switching operation, PMUX system was providing inaccurate information, the RO conferred with the CRS (believing that the breaker might inadvertently close), and took actions with the intention to prevent parallel sources for the bus and personnel injury of the Auxiliary Operator sent out to inspect the breaker. However, had the RO checked additional indications that exist in the control room, the true condition of the power source for the bus could have been ascertained. P No unusual characteristics of the work location (e.g., noise, heat, or poor lighting) directly contributed to this event. There were no procedural errors which contributed to this event.
If the evaluation results differ from this determination or if information is developed which would affect. the readers understanding oz perception of this event, a supplement to this report will be submitted.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ACIUTY NAME DOCKET NUMBER LER NUMBER PAGE YEAR SEOUENTIAI. EVISIO NUMBER NUMBER Palo Verde Unit 2 0 5 0.0 0 5 2 9 9 5 0 0 5 0 0 0 5 OF 0 7
- 5. STRUCTURES, SYSTEMS, OR COMPONENTS INFORMATION:
On July 14, 1995, at approximately 1530 MST, remote multiplexer terminal (RMT) cabinet 25 failed due to excessive heat in the 25RMT cabinet. This failure froze all of the NAN-S05 input/output signals in their present state without the control room operators knowledge. This failure was determined to be a causal factor in the reactor trip. A description of the PMUX system is provided in Section 8 "Additional Information" of this LER.
On July 11, 1995, one of the air conditioning units that provide cooling for 25RMT was identified to be out of service. A work request was written and repairs were scheduled to begin on July 18, 1995. The 25RMT room has two air conditioning (AC) units to provide cooling, however, recognized that during this time one AC unit was unable to provide it was not sufficient cooling.
On July 13, 1995, an OCS technician found that 25RMT (multiplexer for NAN-S05) had experienced a communication error which was caused by a intermittent failure of the PCM. The technician performed a download and was able to clear the communication error, and 25RMT was brought back on line.
Following the reactor trip, the investigation showed that on July 14, 1995, 25RMT had another communication error at 1430 and 1530 MST. Apparently 25RMT was able to perform a download at 1430 successfully and reboot itself, however, at 1530 25RMT failed due to high temperature in the 25RMT cabinet.
Subsequently, all of the NAN-SOS input/output signals froze in their present state without the control room operators knowledge. This led to the control zoom staff believing that the breaker manipulations taken did not occur when in fact they did.
The investigation conducted as a result of this event revealed that the overall PMUX systems availability since 1992 is 98.5 percent. In 1994 and 1995 the PMUX systems availability was 99.5 percent.
There are no indications that any other structures, systems, or components were inoperable at the start of the event which contributed to this event.
No failures of components with multiple functions were involved. All safety system actuations that were required actuated as designed.
- 6. CORRECTIVE ACTIONS TO PREVENT RECURRENCE:
The evaluation of the event has not been completed to date. Any corrective actions identified will be tracked under the APS Commitment Action Tracking System.
On July 18, 1995, the PMUX equipment malfunctions were troubleshot. The supply breaker to 25RMT's air conditioner was repaired, PCM-99 card was replaced, and 25RMT was placed in service. A walkdown of all the air conditioners for RMTs was completed and found no additional concerns.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ACILITYNAME DOCKET NUMBER LER NUMBER PAGE YEAR . SEQUENTIAL EVISIO NUMBER NUMBER Palo Verde Unit 2 0 5 0 0 0 5 2 9 9 5 0 0 5 0 0 0 6 OF 0 7 I'EXT As an interim corrective action, a functional check of the PMUX status will be performed during the normal working day by Operations Computer System (OCS) technicians (utility, nonlicensed).
Long term corrective actions for the PMUX system being considered are:
~ Develop a remote indication monitoring system accessible to the Unit 1 Control Room Operators. To be completed by October 17, 1995.
~ Establish local monitoring of temperature in the PMUX cabinets.
To be completed by September 19, 1995.
~ OCS will install a monitor of the PMUX system in the OCS maintenance shop to ensure that switchyard PMUX systems are properly monitored. To be completed by October 17, 1995.
On July 19, 1995, a night order was issued to inform all Operations personnel that Auxiliary Operators are to be dispatched to the switch yard to observe evolutions of the nature until it can be demonstrated that the multiplexer problems have been corrected. Additionally, when anticipated results are not achieved following an "Action" step, and plant conditions permit, an investigation should be initiated prior to taking additional actions.
On July 21, 1995, a night order was issued to inform-all licensed Operations personnel that described the potential for a loss of function from both the PCS and SBCS during a transfer of NNN-D11.
This event will be presented to operators during the requal cycle in industry events. Additionally, Nuclear Training is to review the lesson plans and clarify how the automatic bus transfer for NNN-D11 works. To be completed by November 17, 1995.
Long term corrective actions for NNN-Dll being considered aze:
~ Evaluate existing design adequacy and modification options to support FWCS and SCBS during momentary power interruptions in accordance with the existing PVNGS Design Modification Process.
Present any proposed design modifications to the Plant Modification Committee (PMC) for approval by December 29, 1995.
The PMC will determine modif ication.
if the evaluation warrants a design Zf the evaluation results differ from this determination or if information is developed which would affect the readers understanding or perception of this event, a supplement to this report will be submitted.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AGILITYNAME DOCKET NUMBER LER NUMBER PAGE YEAR S MUEN IIAI EVISIO NUMBER NUMBER Palo Verde Unit 2 0 5 0 0 0 5 2 9 9 5 0 0 5 0 0 0 7 OF 0 7 7 ~ PREVIOUS SIMILAR EVENTS:
Reactor trips attributed to a Feedwater Control System (FWCS) malfunction have been previously reported in LERs 528/95-008, 530/94-007, 530/94-005, 530/93-001 and 529/92-001. However, in the previous events, the cause of the specific FWCS component failure and corrective actions taken were not the same as in this event and would not have prevented this event.
However, there is some indications that had previous issues been properly addressed this event may have been prevented.
- 8. ADDITIONAL INFORMATION:
On July 19, 1995, at 1344 MST, Palo Verde Unit 2 was in MODE 1 (POWER OPERATIONS) and synchronized to the grid.
The following is a description of the PMUX system manufactured by Teledyne Controls.
The design function of remote multiplexer terminal (RMT) cabinet 25 in the plant multiplexer (PMUX) system is to gather information of various plant analog/digital instrument, input signals of the switchyazd and transmit them to the local multiplexer terminal (LMT) so that indications of switchyard breakers can be monitozed by Control Room personnel.
There are no fails, control room alarms associated with a RMT failure.
the central master control unit simply drops that RMT out of the If a RMT loop and continues operation with the remaining RMTs. There aze a total of five RMTs per unit, plus an additional RMT that provides switch yard information to the Transmission Control Center and Salt River Pro)ect (load dispatchers).
Three of the five RMTs are'sed for indication and control of the cooling tower (KE) fans (one RMT per cooling tower), the remaining RMTs are used for indications on NAN-S05 and NAN-S06 (one RMT pez bus).
It should be noted that the PMUX system is configured such that control signals for the switchyard breakers are transmitted through normal cabling while switchyard indications such as breaker position, bus voltage, and amperage rely on multiplex signals.
V 4