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Category:LICENSEE EVENT REPORT (SEE ALSO AO
MONTHYEARML20046B4841993-07-30030 July 1993 LER 93-006-00:on 930703,auxiliary Feedwater Signal Inadvertently Actuated Due to Personnel Error.Equipment Reset to Normal Lineup & Fuses Removed for Reinstallation Prior to Reactor startup.W/930730 Ltr ML20045H7611993-07-16016 July 1993 LER 93-007-00:on 930626,CR Alarm Received,Indicating Excessive Temp on Reactor Coolant Pump Motor Stator 1-04 & Manual Trip Initiated.Caused by RTD Failure.Rtd Terminations Disconnected & AOP revised.W/930716 Ltr ML20045A9911993-06-11011 June 1993 LER 93-004-00:on 930514,failure to Satisfy TS Surveillance for Verification of Valve Position Due to Valve Discrepancies Discovered During DBD Review.Valve Cap & Clearance installed.W/930611 Ltr ML20045A4681993-06-0303 June 1993 LER 93-003-00:on 930504,manual Reactor Trip Occurred Following Inadvertent Closure of Fwiv.Caused by Instrumentation Channel Error.Maint Performed on Affected Instrumentation channels.W/930603 Ltr ML20044G4071993-05-26026 May 1993 LER 93-006-00:on 930426,failure to Satisfy TS Surveillance Requirement for Primary Plant ESF Exhaust Filtration Unit Noted.Caused by Poor Labeling,Specification of Wrong Procedure & Discrepancy in Parts list.W/930526 Ltr ML20024H1581991-05-21021 May 1991 LER 91-016-00:on 910418,failure of Check Valve to Prevent Backflow Discovered.Caused by Mfg Error in Machining Process of Valve Body Casting.Valves Reassembled & Scheduled to Receive testing.W/910521 Ltr ML20024G7211991-04-25025 April 1991 LER 91-012-00:on 910326,potential Gas Binding of Centrifugal Charging Pumps Due to Voids in Boric Acid Gravity Feed Line Identified.Caused by Hydrogen Coming Out of Solution in Lower Pressure Ccp Suction header.W/910425 Ltr ML20024G6801991-04-22022 April 1991 LER 91-010-00:on 910322,unit 1 Operated Outside Tech Spec Due to Auxiliary Feedwater Sys Test Line Isolation Valve Not Closed.Root Cause Not Determined.Providing Addl Guidance to Operators & Operators Monitoring valves.W/910422 Ltr ML20029B6421991-03-12012 March 1991 LER 91-004-00:on 910210,potential Transformer Drawer Opened at Bottom of Switchgear Bus 1A3 Auxiliary Cubicle,Causing Load Shed Signal & Reactor Trip.Caused by Personnel Error. Labels Attached to Switchgear bus.W/910312 Ltr ML20028G9551990-09-27027 September 1990 LER 90-026-00:on 900828,surveillance Missed Due to Inadequate Procedural Requirements.Caused by Inadequate Manual Surveillance Scheduling Methods.Station Procedures revised.W/900927 Ltr ML20044A1351990-06-26026 June 1990 LER 90-017-00:on 900527,main Feedwater Flow Control Valve Failed Closed,Resulting in Reduced Feedwater Flow & Decreasing Steam Generator Water Level.Caused by Failure of Solenoid Valve Coil.Solenoid Coil replaced.W/900626 Ltr ML20044A3281990-06-22022 June 1990 LER 90-016-00:on 900521,engineering Determined That Three Atmospheric Relief Valves Declared Inoperable Resulting in Entry Into Tech Spec Limiting Condition for Operation 3.0.3. Pneumatic Controls Drifted Out of calibr.W/900622 Ltr ML20043H1971990-06-19019 June 1990 LER 90-015-00:on 900520,chemistry Sample Special Condition Surveillance Missed.Caused by Procedural Error.Procedures Revised to Provide Appropriate Cautions Re Required Sample. W/900619 Ltr ML20043G1121990-06-13013 June 1990 LER 90-014-00:on 900514,containment Penetration Improperly Isolated While Containment Isolation Valve Made Inoperable for Repairs.Caused by Inadequate Review of Work Order. Supervisor Counseled & Shift Order issued.W/900613 Ltr ML20043F1571990-06-0808 June 1990 LER 90-013-00:on 900509,while Installing Jumpers Across Feedwater Pump Speed Controllers,Pump Coastdown Occurred, Resulting in Loss of Feedwater Flow & Reactor Trip.Caused by Inadequate Procedure Review.Review performed.W/900608 Ltr ML20043E4511990-06-0707 June 1990 LER 90-012-00:on 900508,control Room Personnel Failed to Satisfy Time Limit for Completion of Action Required by Tech Specs Re Plant Radiation Monitoring.Caused by Personnel Error.Individual Counseled & Procedure revised.W/900607 Ltr ML20043F4941990-06-0404 June 1990 LER 90-011-00:on 900504,Pressure Instrument Root Isolation Valve 1SI-8961 Open When Procedure Indicated Valve Should Be Locked Closed.Caused by Lack of Clear Instructions Re Definition of Physical Work. Valve locked.W/900604 Ltr ML20043C0201990-05-29029 May 1990 LER 90-010-00:on 900428 & 29,2-h Surveillance Interval, Including 25% Extension Allowed by Tech Spec 4.0.2,exceeded. Caused by Personnel Error.Procedure Enhancements Initiated & Personnel Involved counseled.W/900529 Ltr ML20043A6691990-05-18018 May 1990 LER 90-009-00:on 900421,reactor Trip Occurred Due to Accidental Bumping of Source Range Reactor Trip Reset/Block Previously Bypassed for Power Operation.Order Issued Suspending Cleaning of Control boards.W/900518 Ltr ML20043A6131990-05-16016 May 1990 LER 90-008-00:on 900416,Train a Diesel Generator Rendered Inoperable Due to Failure to Complete post-work Operability Testing on Starting Air Receiver Check Valve 01. Caused by Inadequate Review.Procedure revised.W/900516 Ltr ML20043A6111990-05-16016 May 1990 LER 90-007-00:on 900416,ESF Actuation Signal Occurred, Resulting in Train a of Control Room Air Conditioning Sys Shifting to Emergency Recirculation Mode.Caused by Personnel Error.Handswitch Added to Radiation monitor.W/900516 Ltr ML20043A4201990-05-14014 May 1990 LER 90-006-00:on 900412,P-6 Permissive Signal Received & Source Range Flux Doubling (Srfd) Actuation Occurred.Caused by Inadvertent Reset of Srfd Block.Integrated Plant Operations Procedures changed.W/900514 Ltr ML20012B6491990-03-0909 March 1990 LER 90-001-00:on 900209,reactor Protection Sys Actuation Occurred Due to Spike on Range Channel.Appropriate Source Range Procedures Revised to Require Insertion of Flux Doubling Signal Block Prior to withdrawal.W/900309 Ltr 1993-07-30
[Table view] Category:RO)
MONTHYEARML20046B4841993-07-30030 July 1993 LER 93-006-00:on 930703,auxiliary Feedwater Signal Inadvertently Actuated Due to Personnel Error.Equipment Reset to Normal Lineup & Fuses Removed for Reinstallation Prior to Reactor startup.W/930730 Ltr ML20045H7611993-07-16016 July 1993 LER 93-007-00:on 930626,CR Alarm Received,Indicating Excessive Temp on Reactor Coolant Pump Motor Stator 1-04 & Manual Trip Initiated.Caused by RTD Failure.Rtd Terminations Disconnected & AOP revised.W/930716 Ltr ML20045A9911993-06-11011 June 1993 LER 93-004-00:on 930514,failure to Satisfy TS Surveillance for Verification of Valve Position Due to Valve Discrepancies Discovered During DBD Review.Valve Cap & Clearance installed.W/930611 Ltr ML20045A4681993-06-0303 June 1993 LER 93-003-00:on 930504,manual Reactor Trip Occurred Following Inadvertent Closure of Fwiv.Caused by Instrumentation Channel Error.Maint Performed on Affected Instrumentation channels.W/930603 Ltr ML20044G4071993-05-26026 May 1993 LER 93-006-00:on 930426,failure to Satisfy TS Surveillance Requirement for Primary Plant ESF Exhaust Filtration Unit Noted.Caused by Poor Labeling,Specification of Wrong Procedure & Discrepancy in Parts list.W/930526 Ltr ML20024H1581991-05-21021 May 1991 LER 91-016-00:on 910418,failure of Check Valve to Prevent Backflow Discovered.Caused by Mfg Error in Machining Process of Valve Body Casting.Valves Reassembled & Scheduled to Receive testing.W/910521 Ltr ML20024G7211991-04-25025 April 1991 LER 91-012-00:on 910326,potential Gas Binding of Centrifugal Charging Pumps Due to Voids in Boric Acid Gravity Feed Line Identified.Caused by Hydrogen Coming Out of Solution in Lower Pressure Ccp Suction header.W/910425 Ltr ML20024G6801991-04-22022 April 1991 LER 91-010-00:on 910322,unit 1 Operated Outside Tech Spec Due to Auxiliary Feedwater Sys Test Line Isolation Valve Not Closed.Root Cause Not Determined.Providing Addl Guidance to Operators & Operators Monitoring valves.W/910422 Ltr ML20029B6421991-03-12012 March 1991 LER 91-004-00:on 910210,potential Transformer Drawer Opened at Bottom of Switchgear Bus 1A3 Auxiliary Cubicle,Causing Load Shed Signal & Reactor Trip.Caused by Personnel Error. Labels Attached to Switchgear bus.W/910312 Ltr ML20028G9551990-09-27027 September 1990 LER 90-026-00:on 900828,surveillance Missed Due to Inadequate Procedural Requirements.Caused by Inadequate Manual Surveillance Scheduling Methods.Station Procedures revised.W/900927 Ltr ML20044A1351990-06-26026 June 1990 LER 90-017-00:on 900527,main Feedwater Flow Control Valve Failed Closed,Resulting in Reduced Feedwater Flow & Decreasing Steam Generator Water Level.Caused by Failure of Solenoid Valve Coil.Solenoid Coil replaced.W/900626 Ltr ML20044A3281990-06-22022 June 1990 LER 90-016-00:on 900521,engineering Determined That Three Atmospheric Relief Valves Declared Inoperable Resulting in Entry Into Tech Spec Limiting Condition for Operation 3.0.3. Pneumatic Controls Drifted Out of calibr.W/900622 Ltr ML20043H1971990-06-19019 June 1990 LER 90-015-00:on 900520,chemistry Sample Special Condition Surveillance Missed.Caused by Procedural Error.Procedures Revised to Provide Appropriate Cautions Re Required Sample. W/900619 Ltr ML20043G1121990-06-13013 June 1990 LER 90-014-00:on 900514,containment Penetration Improperly Isolated While Containment Isolation Valve Made Inoperable for Repairs.Caused by Inadequate Review of Work Order. Supervisor Counseled & Shift Order issued.W/900613 Ltr ML20043F1571990-06-0808 June 1990 LER 90-013-00:on 900509,while Installing Jumpers Across Feedwater Pump Speed Controllers,Pump Coastdown Occurred, Resulting in Loss of Feedwater Flow & Reactor Trip.Caused by Inadequate Procedure Review.Review performed.W/900608 Ltr ML20043E4511990-06-0707 June 1990 LER 90-012-00:on 900508,control Room Personnel Failed to Satisfy Time Limit for Completion of Action Required by Tech Specs Re Plant Radiation Monitoring.Caused by Personnel Error.Individual Counseled & Procedure revised.W/900607 Ltr ML20043F4941990-06-0404 June 1990 LER 90-011-00:on 900504,Pressure Instrument Root Isolation Valve 1SI-8961 Open When Procedure Indicated Valve Should Be Locked Closed.Caused by Lack of Clear Instructions Re Definition of Physical Work. Valve locked.W/900604 Ltr ML20043C0201990-05-29029 May 1990 LER 90-010-00:on 900428 & 29,2-h Surveillance Interval, Including 25% Extension Allowed by Tech Spec 4.0.2,exceeded. Caused by Personnel Error.Procedure Enhancements Initiated & Personnel Involved counseled.W/900529 Ltr ML20043A6691990-05-18018 May 1990 LER 90-009-00:on 900421,reactor Trip Occurred Due to Accidental Bumping of Source Range Reactor Trip Reset/Block Previously Bypassed for Power Operation.Order Issued Suspending Cleaning of Control boards.W/900518 Ltr ML20043A6131990-05-16016 May 1990 LER 90-008-00:on 900416,Train a Diesel Generator Rendered Inoperable Due to Failure to Complete post-work Operability Testing on Starting Air Receiver Check Valve 01. Caused by Inadequate Review.Procedure revised.W/900516 Ltr ML20043A6111990-05-16016 May 1990 LER 90-007-00:on 900416,ESF Actuation Signal Occurred, Resulting in Train a of Control Room Air Conditioning Sys Shifting to Emergency Recirculation Mode.Caused by Personnel Error.Handswitch Added to Radiation monitor.W/900516 Ltr ML20043A4201990-05-14014 May 1990 LER 90-006-00:on 900412,P-6 Permissive Signal Received & Source Range Flux Doubling (Srfd) Actuation Occurred.Caused by Inadvertent Reset of Srfd Block.Integrated Plant Operations Procedures changed.W/900514 Ltr ML20012B6491990-03-0909 March 1990 LER 90-001-00:on 900209,reactor Protection Sys Actuation Occurred Due to Spike on Range Channel.Appropriate Source Range Procedures Revised to Require Insertion of Flux Doubling Signal Block Prior to withdrawal.W/900309 Ltr 1993-07-30
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20217E8021999-10-0707 October 1999 CPSES Unit 1 Cycle 8 Colr ML20217G4151999-09-30030 September 1999 Monthly Operating Repts for Sept 1999 for Cpses,Units 1 & 2 ML20212F7671999-09-24024 September 1999 SER Granting Relief Request C-4 Pursuant to 10CFR50.55a(g)(6)(i) for Unit 2,during First 10-year ISI Interval & Relief Requests B-15,B-16 & B-17 Pursuant to 10CFR50.55a(g)(6)(i) ML20216J5701999-09-16016 September 1999 Rev 2 to CPSES Unit 2 Cycle 5 Colr TXX-9920, Monthly Operating Repts for Aug 1999 for Cpses.With1999-08-31031 August 1999 Monthly Operating Repts for Aug 1999 for Cpses.With ML20211M2981999-08-0606 August 1999 Rev 1 to CPSES Fuel Storage Licensing Rept, CPSES Credit for Soluble Boron & Expansion of Spent Fuel Storage Capacity, Consisting of Revised Title Page and 4-1 ML20210U4081999-07-31031 July 1999 Monthly Operating Repts for July 1999 for Cpses,Units 1 & 2 ML20210D8321999-07-23023 July 1999 Safety Evaluation Accepting Relief Requests Re Use of 1998 Edition of Subsections IWE & Iwl of ASME Code for Containment Insp ML20209H7661999-07-15015 July 1999 Safety Evaluation Accepting GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power-Operated Gate Valves, for Comanche Peak Steam Electric Station,Units 1 & 2 ML20209H2721999-07-0909 July 1999 2RF04 Containment ISI Summary Rept First Interval,First Period,First Outage ML20209H2631999-07-0909 July 1999 2RF04 ISI Summary Rept First Interval,Second Period,Second Outage ML20209G7501999-07-0808 July 1999 SER Finding That Licensee Individual Plant Exam of External Events Complete with Regard to Info Requested by Suppl 4 to GL 88-20 & That IPEEE Results Reasonable Given Design, Operation & History of Comanche Peak Steam Electric Station ML20196L0191999-07-0808 July 1999 Safety Evaluation Granting Request Relief B-6 (Rev 2),B-7 (Rev2),B-12,B-13,B-14 & C-9,pursuant to 10CFR50.55a(g)(6)(i).Technical Ltr Rept Also Encl ML20210J9391999-06-30030 June 1999 CPSES Commitment Matl Change Evaluation Rept 0003,for 970802-990630 ML20209G0801999-06-30030 June 1999 Monthly Operating Repts for June 1999 for Cpses,Units 1 & 2 ML20196J0621999-06-29029 June 1999 Safety Evaluation Supporting Proposed Changes to Emergency Plan Re Licenses NPF-87 & NPF-89 Respectively ML20195G5141999-05-31031 May 1999 Monthly Operating Repts for May 1999 for Comanche Peak Steam Electric Station,Units 1 & 2.With ML20216E0711999-05-21021 May 1999 1999 Graded Exercise - Comanche Peak Steam Electric Station ML20206Q0091999-05-14014 May 1999 Safety Evaluation Accepting GL 92-08, Thermo-Lag 330-1 Fire Barriers, Dtd 921217,for Comanche Peak Electric Station,Unit 1 ML20206H2061999-05-0606 May 1999 SER Accepting Exemption to App K Re Leading Edge Flowmeter for Plant,Units 1 & 2 ML20196L2241999-04-30030 April 1999 Monthly Operating Repts for Apr 1999 for Cpses,Units 1 & 2 ML20205R5701999-04-14014 April 1999 Rev 6 to ER-ME-067, TU Electric Engineering Rept,Evaluation of Thermo-Lag Fire Barrier Sys ML18016A9011999-04-12012 April 1999 Part 21 Rept Re Defect in Component of DSRV-16-4,Enterprise DG Sys.Caused by Potential Problem with Connecting Rod Assemblies Built Since 1986,that Have Been Converted to Use Prestressed Fasteners.Affected Rods Should Be Inspected ML20205J7831999-04-0101 April 1999 Rev 0 to ERX-99-001, CPSES Unit 2 Cycle 5 Colr ML20205N3101999-03-31031 March 1999 Monthly Operating Repts for Mar 1999 for Cpses,Units 1 & 2 ML20204H6371999-02-28028 February 1999 Monthly Operating Repts for Feb 1999 for Comanche Peak Units 1 & 2 ML20205N1481999-02-28028 February 1999 Corrected Monthly Operating Rept for Feb 1999 for CPSES, Units 1 & 2 ML20203A4881999-02-0303 February 1999 Safety Evaluation Granting Requests for Relief B-3 - B-6,C-2 & C-3 for Plant,Unit 2 ML20210J9201999-02-0101 February 1999 CPSES 10CFR50.59 Evaluation Summary Rept 0008,for 970802- 990201 ML20202D0101999-01-27027 January 1999 Safety Evaluation Supporting First 10-yr Interval ISI Program Plan Requests for Relief B-9,B-10 & B-11 for CPSES, Unit 1 ML20199E9961998-12-31031 December 1998 Monthly Operating Repts for Dec 1998 for Cpses,Units 1 & 2 ML20207D6091998-12-31031 December 1998 1998 Annual Operating Rept for Cpses,Units 1 & 2. with ML20197K2371998-11-30030 November 1998 Monthly Operating Repts for Nov 1998 for Cpses,Units 1 & 2 ML20195F3161998-10-31031 October 1998 Monthly Operating Repts for Oct 1998 for Cpses,Units 1 & 2 ML20154M8841998-09-30030 September 1998 Monthly Operating Repts for Sept 1998 for Cpses,Units 1 & 2 ML20154B5741998-09-30030 September 1998 Safety Evaluation Re Licensee Response to GL 96-05, Periodic Verification of Design-Basis Capability of Safety- Related Motor-Operated Valves. Licensee Has Established Acceptable Program ML20151W0361998-08-31031 August 1998 Monthly Operating Repts for Aug 1998 for Cpses,Units 1 & 2. with ML20151Q1211998-08-14014 August 1998 Rev 0 to Control of Hazard Barriers ML20237C4061998-08-14014 August 1998 Safety Evaluation Supporting Request to Implement Risk Informed IST Program ML20237C6721998-07-31031 July 1998 Monthly Operating Repts for July 1998 for Cpses,Units 1 & 2 ML20236V3121998-07-29029 July 1998 Final Part 21 Rept Re Enterprise DSR-4 & DSRV-4 Edgs.Short Term Instability Was Found During post-installation Testing & Setup as Part of Design mod/post-work Testing Process. Different Methods Were Developed to Correct Problem ML20236R0711998-06-30030 June 1998 Monthly Operating Repts for June 1998 for Cpses,Units 1 & 2 ML20249B2581998-05-31031 May 1998 Monthly Operating Repts for May 1998 for Cpses,Units 1 & 2 ML20248A1671998-05-22022 May 1998 Interim Part 21 Re Enterprise DSR-4 & DSRV-4 Emergency diesel.Post-installation Testing Revealed,High Em/Rfi Levels Affected New Controllers,Whereas Original Controllers Were unaffected.Follow-up Will Be Provided No Later than 980731 ML20247G3241998-04-30030 April 1998 Monthly Operating Repts for Apr 1998 for Cpses,Units 1 & 2 ML20216B8661998-04-0101 April 1998 Rev 0 to ERX-98-001, CPSES Unit 1 Cycle 7 Colr ML20216J3061998-03-31031 March 1998 Monthly Operating Repts for Mar 1998 for Cpses,Units 1 & 2 ML20216J1861998-02-28028 February 1998 Monthly Operating Repts for Feb 1998 for Comanche Peak Steam Electric Station ML20197A6951998-02-24024 February 1998 Inservice Insp Summary Rept,First Interval,Second Period, First Outage ML20199J5391998-02-0202 February 1998 CPSES Commitment Matl Change Evaluation Rept 0002 for 960202-970801 1999-09-30
[Table view] |
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Log # TXX-91180 _-
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file # 10200 TUll FC1RK: 910.4 c Ref. Voluntary (
w mi.m J < .u, Jr. May 21, 1991 i,,,,,,,, .. , nm a. .,. j .,
A U. S. Nuclear Regulatory Conunission 5 Attn: Document Control Desk 46' Washington, D. C. 20555 .J
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STA110N (CPSES)
DOCKET NO. 50 445 REPORT Of EVENT WITH GENERIC INTEREST - - -
LICENSEE EVENT REPORT 91-016-00 Gentlemen:
Enclosed is Licensee Event Report 91-016 00 for Comanche Peak Steam Electric '
Station Unit 1, " Manufacturing Error Leading to the f ailure of a Check Valve to Prevent Backflow."
Review of this event has been corducted with due regard to the previous history and corrective actions associated with these check valves at CPSES.
Based on this review, it was concluded that the current plans for continued use of these valves remains technically sound.
Sincerely, William J. Cahill, Jr.
/ /
s By.
A. B. Scott, Jr.
Vice President, Nuclear Operations JAA/bm c - Mr. R. D. Martin, Region IV Resident inspectors, CPSES (2)
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LICENSEE EVENT REPORT (LER) iMANCHIP 64 U.S NUCtt AR REGut ATOHY COWWIS$ON. WASHWGTON T. 20%6, AND TO THE P APE RWORK REDUCTON PROJECT (3160 010s) 3F FICC Or W ANACd WtNT AND BJCoC1, W ASHNGTCM CC A%03
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Sutmsewsi h Y.s (# y . cortsv.t. Ino.ded Sobevesseor, De!.i % l l l cw eit-noi4x. .... - .e* m . - i - ..,o, ion On April 18,1991, reverse flow testing was being perinrmed on check valves in the Auxiliary Feedwater System. One of eight check valves in the system branch lines failed to meet the test acceptance criteria. The cause of the failure was determined to be a manufacturing deficiency in the finish machining of the rough casting of the valve body.
The incomplete machining resulted in excess casting materialinside the valve body which interfered with full stroke motion of the swing arm counterweight. Corrective action included finish machining of the affected check valve, inspection of similar valves in the system, and procedure review. A voluntary report is being submitted due to interest resulting from previous experience with check valves in the Auxiliary Feedwater System.
Enclosure to TXX 1.i 194 NHC FORM 3H6A U S NUCLE AR REGULATOHV COMW.550N ggg ggg g g EXPIRES: 4'30112 E STIMATED BURDEN PER HESPONSE TO COMPLY WITH THIS INFORMA?ON
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LICEfJSEE EVENT REPORT (LER) BURDEN ESilWATE TO THE RECORDS AND REPOR18 WANAGEMEN1 .
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TEXT CONTINUATION DC. P06S6. AND TO THE PAPE RWORK REDUCTON PROJECT (31600104) 0FFICE OF WANAGE MI NT AND BUDGET. W ASHINGTON. DC. 20503.
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010 012 OF 018 L DESCRIPTION OF THE REPORTABLE EVENT A. PLANT CONDITIONS PRIOR TO THE EVENT On April 18,1991, Comanche Peak Steam Electric Station (CPSES) Unit 1 was in Mode 5, Cold Shutdown, with the Reactor Coolant System at a temperature of 100 degrees F and pressure of approximately 15 psia.
B. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT There were no inoperable structures, systems, or components that contributed to the event, C. NARRATIVE
SUMMARY
OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On April 18,1991, backflow testing was being performed on check valves (Ells:(V))
in the Auxiliary Feedwater (AFW) System (Ells:(BA)). One of the check valves included in the test did not satisfy the test acceptance criteria, and action was initiated to identify the cause of the test failure. Radiography revealed that the valve disk was being held off of its seat by mechanicalinterference between the disk counterweight and the valve body. The valve was disassembled and it was discovered that the valve body casting had not been fully finish machined by the manufacturer. A lip of excess casting material at the back of the valve body had caused the disk counterweight to catch on the opening stroke and hang the valve disk in the open position.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL OR PERSONNEL ERROR The condition was identified during work activity initiated following the failure of the check valve to meet the reverse flow test acceptance criteria.
Enclosure to TXX-91180 NRC FORM 3 64 U S. NUCLE AR RE GUL ATORY COMWissoN APPROVED OMB NO. 3160 0104 EXPIRES er10W E811M ATED BURDEN PER RESFVNSE TO COMPLY WITH THIS INrORMAtlON i
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- 11. COMPONENT OR SYSTEM FAILURES A. FAILED COMPONENT INFORMATION l
Component
Description:
Pressure seal check valve,4 inch,900 pound Manufacturer: Borg Warner / International Pump, Inc (BW/IP).
Manufacturer's Part Number: 75560 i B. FAILURE MODE, MECHANISM, AND EFFECT OF EACH FAILED COMPONENT The affected check valve stuck open due to interference between the disk counterweight and a tip of excess casting material on the valve body, allowing reverse flow in one branch of the AFW system.
C. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE A manufacturing errorin the machining process of the valve body casting allowed excess casting material to remain on the inside surface of the valve body.
D. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS The Auxiliary Feedwater System is designed to provide flow to the steam generators for heat removal from the primary system after certain design basis accidents as described in the CPSES Final Safety Analysis Report and serves as the feedwater source during hot standby and cooldown from power operations. The system can also be used to adjust steam generator water levels prior to and during plant startup, to establish wet layup in tho steam generators, or to maintain steam generator water levels following a loss of coolant accident. The check valve failure described in this report would not inhibit the ability of the system to deliver flow to the steam generators for performance of any of the functions for which the system is designed.
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0IO OI4 OF 0I6 i..m .. .. . . - ., o n Ill. ANALYSIS OF THE EVENT A. SAFETY SYSTEM RESPONSES THAT OCCURRED Not applicable - there were no safety system actuations associated with this event.
B. DURATION OF SAFETY SYSTEM TR AIN INOPER ABILITY There were no safety systems rendered inoperable as a result of the event.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT For each of the design functions of the AFW system, the failure described in this report would not prevent the system from delivering flow to the associated steam generator, and additional check valves in the system would prevent or inhibit backflow, in the absence of a line break or manual valve misoperation, the check valve failure would lack significance in any plant mode because of the absence of a backflow path, it is concluded that the condition did not adversely affect the safe operation of CPSES Unit 1 or the health and safety of the public.
IV. CAUSE OF THE EVENT Immediate cause High flow rates through the branch hne in conjunction with a manufacturing deficiency caused the check valve to stick in the open position. On April 12,1991, dynamic testing was performed on the motor operated isolation valve down stream of the affected check valve. The test is conducted to meet the requirements of Generic Letter 89-10 to ensure that the motor-operated valve will close during a main feedwater line break accident. The test simulates, to the extent possible, expected AFW flow to a faulted steam generator during the accident. The test involves a flow rate of approximately 660 gallons per minute, and caused the swing arm and counterweight to impact the excess casting material with sufficient force to cause plastic deformation to the casting and wedge the disk in the open position. The test flow rate is wellin excess of the flow rate required during normal surveillance testing of components in the AFW system.
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Roolcause The component was not manufactured in accordance with design. During the manufacture of the valve body, finish machining of the rough casting was not adequately performed. The incomplete machining resulted in excess casting material inside the valve body (Refer to Figure 1) which interfered with full stroke motion of the swing arm counterweight. Information related to valve port dimensions is BW/IP proprietory information and not an inspectable attribute during receipt inspection.
The counterweight was added in April,1990, as a design modification to the eight check valves in the AFW branch lines. Post modification testing consisted of manual full stroke manipulation of each set of internals on an uninstalled test valve body. Since the test valve was the same model and vintage as the installed plant valves, it was assumed that no significant differences existed in the valve bodies. In an unmodified condition the valve would not have stuck open, and the condition described should not be considered a generic problem for this model check valve in other applications.
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0IO OI6 OF 016 r..m - .. ... ~ . ~ a.,on V. CORRECTIVE ACTIONS IMMEDIATE The affected valve was machined to remove excess casting material from the valve body and restore the design contour of the valve port. The remaining seven check valves in the AFW branch lines were disassembled, photographed, and inspected to ensure that finish machining had been adequately performed. Measurements inside the valve body were taken for each of the valves and revealed that finish machining had been performed correctly. The valves were reassembled and are scheduled to receive forward and reverse flow testing prior to piant restart.
ACTIONS TO PREVENT RECURRENCE Procedures will be reviewed and revised as appropriate to ensure that in the event that replacement of one of the AFW branch line check valves is required, sufficient inspection and testing will be performed to prevent a similar condition.
VI. PREVIOUS SIMILAR EVENTS There have been no previous similar events reported pursuant to 10CFR50.73.
Vll. ADDITIONAL INFORMATION Although the event does not meet the reporting criteria of 10CFR50.73, a voluntary report is being submitted because of the significance and generic interest of the event resulting from pievious experience with BW/IP cneck valves in the AFW system.
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