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Category:ABNORMAL OCCURRENCE REPORTS (SEE ALSO LER & RO)
MONTHYEARML20084S9121977-03-25025 March 1977 Telecopy Ao:On 770324,containmet Spray Pump a Out of Svc During Training Startup,Violating Tech Spec ML20084S9091976-05-31031 May 1976 Ao:On 770527,HPCI Pressure Switches E41-PSH-NO12 A,B,C & D Exceeded Tech Spec Calibr Limits.Switches Immediately Recalibr ML20086D4211976-02-0909 February 1976 AO 50-261/76-3:on 760128,high Level Alarm Received on Safety Injection Accumulator B.Caused by Check Valve 875 Leaking Resulting in Dilution.Accumulator Partially Drained & Refilled ML20086D4421976-02-0202 February 1976 AO 50-261/76-2:on 760121 & 22,failure of One & Delayed Operation of Two Reactor Trip Relays Occurred.Caused by Open Coil Winding.Three Defective Relays Replaced ML20086D4271976-01-29029 January 1976 Telecopy Ao:On 760128,sample of Safety Injection Accumulator B Indicated Boron Concentration of 1,939 Ppm,Below Tech Specs.Accumulator Partially Drained,Refilled & Verified ML20086D4391976-01-22022 January 1976 Ao:On 760124 & 22,discovered That Reactor Trip Relay RT3 in Reactor Protection Logic Train a Operating Erratically. Further Investigation Revealed That Relays RT-4 & RT-8 on Logic Train B Defective.Relays Replaced ML20086D4471976-01-13013 January 1976 AO 50-261/76-1:on 760102,failure of Boric Acid Transfer Pump Resulted in Failure of One ESF Component That Caused or Threatened to Render Sys Incapable of Functioning.Caused by Damaged Rotor ML20086F5211976-01-0202 January 1976 Ao:On 760102,boric Acid Pump B Stopped Running.Caused by Defective Stator & Damaged Rear Bearing.Investigation Continuing NG-75-2222, AO 50-261/75-20:on 751210,channel 950 of Containment Pressure Protection Found Inoperable.Caused by Open Output Fuse in Comparator PC-950.Fuse Replaced1975-12-23023 December 1975 AO 50-261/75-20:on 751210,channel 950 of Containment Pressure Protection Found Inoperable.Caused by Open Output Fuse in Comparator PC-950.Fuse Replaced NG-75-2210, AO 50-261/75-19:on 751208,boron Concentration Found Below Limits in Safety Injection Accumulator B.Cause Not Stated. Accumulator Partially Drained & Refilled from Refueling Water Storage Tank1975-12-22022 December 1975 AO 50-261/75-19:on 751208,boron Concentration Found Below Limits in Safety Injection Accumulator B.Cause Not Stated. Accumulator Partially Drained & Refilled from Refueling Water Storage Tank ML20086F5161975-12-0808 December 1975 Ao:On 751208,boron Sample from Safety Injection Accumulator B Indicated 1,915 ppm,35 Ppm Below Tech Specs.Cause Unknown. Accumulator Partially Drained & Refilled from Refueling Water Storage Tank NG-75-2017, AO 50-261/75-18:on 751102,auxiliary Feedwater Pump a Failed to Start Following Safety Injection Signal.Caused by Tarnished Contacts.Contacts within Local/Remote Switch Cleaned.Further Investigation Underway1975-11-13013 November 1975 AO 50-261/75-18:on 751102,auxiliary Feedwater Pump a Failed to Start Following Safety Injection Signal.Caused by Tarnished Contacts.Contacts within Local/Remote Switch Cleaned.Further Investigation Underway NG-75-2010, AO 50-261/75-17:on 751101,both Containment Personnel Air Lock Doors Opened Simultaneously W/Rcs Temp Above 200 F, Violating Tech Spec 3.6.1.a.Caused by Broken Rod,Bearing & Cam Follower on Outer Door Mechanism1975-11-12012 November 1975 AO 50-261/75-17:on 751101,both Containment Personnel Air Lock Doors Opened Simultaneously W/Rcs Temp Above 200 F, Violating Tech Spec 3.6.1.a.Caused by Broken Rod,Bearing & Cam Follower on Outer Door Mechanism NG-75-2001, AO 50-261/75-16:on 751028,svc Water Booster Pump B Failed to Start.Caused by Actuation of Pump Suction Pressure Switches Provided to Protect Pumps from Low Npsh.Containment Recirculation Fans Stopped to Prevent Overheating Motors1975-11-11011 November 1975 AO 50-261/75-16:on 751028,svc Water Booster Pump B Failed to Start.Caused by Actuation of Pump Suction Pressure Switches Provided to Protect Pumps from Low Npsh.Containment Recirculation Fans Stopped to Prevent Overheating Motors ML20086F5291975-11-0404 November 1975 Ao:On 751102,motor Driven Auxiliary Feedwater Pump a Failed to Start.Remote Electrical Contacts Cleaned ML20086F5401975-11-0303 November 1975 Ao:On 751101,containment Integrity Broken for Approx 10 Minutes Due to Simultaneous Opening of Both Personnel Air Lock Doors ML20086F5491975-10-29029 October 1975 Ao:On 751028,sequence of Switch Operations Resulted in Breakers for Both Svc Water Booster Pumps a & B Tripping on Overload NG-75-1575, AO 50-261/75-15:on 750921,more than One Inoperable Rod Present W/Reactor at Power as Result of Rod Control Urgent Failure.Caused by Defective Fuse in Ac Power Supply to Rod Control Cabinet 1AC.Fuse Replaced1975-10-0101 October 1975 AO 50-261/75-15:on 750921,more than One Inoperable Rod Present W/Reactor at Power as Result of Rod Control Urgent Failure.Caused by Defective Fuse in Ac Power Supply to Rod Control Cabinet 1AC.Fuse Replaced ML20086F5611975-09-22022 September 1975 Ao:On 750921,urgent Failure Alarm Received.Caused by Phase Failure in Cabinet 1AC Which Rendered 12 Rods Inoperable. Reactor Manually Tripped NG-75-1212, Revised AO 50-261/75-11:on 750527,RCS Oxygen Concentration Found to Be 0.16 Ppm,Exceeding Limit.Caused by Inattention to Hydrogen Concentration & Dilution of RCS to Hot Shutdown Boron Concentration.Vol Control Tank Vented1975-08-0404 August 1975 Revised AO 50-261/75-11:on 750527,RCS Oxygen Concentration Found to Be 0.16 Ppm,Exceeding Limit.Caused by Inattention to Hydrogen Concentration & Dilution of RCS to Hot Shutdown Boron Concentration.Vol Control Tank Vented NG-75-1158, AO 50-261/75-14:on 750715,valve V2-14B Steam Driven Auxiliary Feedwater Pump Discharge to Steam Generator B Failed to Open.Caused by Belleville Spring Being Filled W/Grease.Belleville Spring Packs & Shafts to Be Inspected1975-07-25025 July 1975 AO 50-261/75-14:on 750715,valve V2-14B Steam Driven Auxiliary Feedwater Pump Discharge to Steam Generator B Failed to Open.Caused by Belleville Spring Being Filled W/Grease.Belleville Spring Packs & Shafts to Be Inspected ML20086F5961975-07-16016 July 1975 Telecopy Ao:On 750715,steam Drive Auxiliary Feedwater Pump Discharge Valve V2-14B to Steam Generator B Failed to Open Electrically ML20086F6151975-07-14014 July 1975 Ao:On 750711,control Rod L-5 Dropped,Causing Load Runback to Approx 70% Power.Caused by Defective Stationary Gripper Coil NG-75-1089, Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve1975-07-11011 July 1975 Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve NG-75-1044, AO 50-261/75-12:on 750625,boric Acid Transfer Pump a Failed. Caused by Pump Shaft Being Broken at Keyway.Pump Rebuilt & Reinstalled.New Pump Model GVH-10K Will Be Installed Upon Receipt1975-07-10010 July 1975 AO 50-261/75-12:on 750625,boric Acid Transfer Pump a Failed. Caused by Pump Shaft Being Broken at Keyway.Pump Rebuilt & Reinstalled.New Pump Model GVH-10K Will Be Installed Upon Receipt ML20086F6081975-06-26026 June 1975 Telecopy Ao:On 750625,boric Acid Transfer Pump a Noted Off. Caused by Pump Shaft Being Broken at Keyway.Also on 750625, Employee Received Whole Body Dose of 3,080 Mrem for Quarter Ending 750630 ML20086F6741975-06-12012 June 1975 Revised AO 50-261/75-9:on 750501,reactor Coolant Pump Seal Failed,Resulting in Discharge of Reactor Coolant Fluid to Containment Floor.Caused by Pump Running W/Seal Leaking. Seals,Shaft,Impeller & Hearings Replaced ML20086F6201975-06-0606 June 1975 AO 50-261/75-11:on 750527,RCS Oxygen Concentration Noted to Be 0.16 Ppm,Exceeding Limit.Caused by Mixture of Hydrogen & Nitrogen in Vol Control Tank,Limiting Hydrogen to Rcs.Vol Control Tank Vented ML20086F6271975-06-0202 June 1975 AO 50-261/75-10:on 750521,boric Acid Transfer Pump B Failed.Caused by Shaft Being Broken at Keyway & Worn Pump Bearing.Pump Rebuilt ML20086F6231975-05-27027 May 1975 Ao:On 750527,RCS Sample Indicated 0.16 Ppm Oxygen,Exceeding Tech Specs.No Cause Stated.Concentration Reduced ML20086F6301975-05-21021 May 1975 Ao:On 750521,boric Acid Pump B Stopped.Caused by Broken Shaft in Keyway Area ML20086F5791975-05-12012 May 1975 AO 50-261/75-9:on 750501,reactor Coolant Pump Seal Failed, Resulting in Discharge of Reactor Coolant Fluid to Containment Floor.New Seal & Associated Parts Being Installed.Parts Shall Be Certified ML20086F6441975-05-0909 May 1975 AO 50-261/75-8:on 750429,RHR Pump Suction Valve RHR-862A Failed.Caused by Torque Switch on SMB-O Motor Operator Being Out of Adjustment.Torque Switch Adjusted.On 750430,complete Insp of Operator Found Excess Grease.Grease Removed ML20086F6911975-05-0202 May 1975 Telecopy Ao:On 750501,seal 1 on Reactor Coolant Pump C Failed,Producing Leak to Containment Floor.Seal 2 Failed on 750502.Cooldown Initiated.Rcs Depressurized & Drained to Below Pump Seals ML20086F6471975-04-29029 April 1975 Ao:On 750429,valve RHR-862A Failed to Open from RTGB When RHR Sys Being Aligned.Cause Under Investigation.Valve Opened Locally Using Manual Operator & All Flow Paths Restored ML20086F6981975-04-10010 April 1975 AO 50-261/75-7:on 750331,diesel B Tripped Due to Low Lube Oil Pressure.Caused by Lube Oil Filter High Differential Pressure Resulting from Dirty Filters.Lube Oil Filters Replaced ML20086F6961975-04-0101 April 1975 Telecopy Ao:On 750331,emergency Diesel B Tripped.Caused by Low Lube Oil Pressure.Filters Changed & Unit Returned to Svc ML20086F6991975-03-27027 March 1975 AO 50-261/75-6:on 750314,contractor Personnel Exposed to Radiation in Excess of Limits.Caused by Exceeding Stay Time in Localized Field of High radiation.Chem-Nuclear,Inc & Util Investigating Use of Addl Shielding ML20086F7001975-03-0707 March 1975 AO 50-261/75-5:on 750225 & 26,boric Acid Transfer Pump B Failed.Cause Not Identified.Pump Replaced ML20086F7011975-02-14014 February 1975 AO 50-261/75-4:on 750206,reactor Protection Overpower Channel Set I Failed to Generate Rod Stop Signal for Simulated Overpower Condition.Caused by Failure of Comparator Circuit in Dual Circuit Signal Comparator ML20086F7051975-02-0707 February 1975 Ao:On 750206,signal Comparator TO-412B Failed to Operate. Portion of Comparator Which Generates Rod Stop & Turbine Runback Signal Failed While Overpower Reactor Trip Signal Still Generated ML20086F7111975-02-0606 February 1975 AO 50-261/75-3:on 750126,component Cooling Water Pump C Tripped Due to Overcurrent.Caused by Backleakage Through Pump Discharge Side Check Valve Due to Debris.Leaking Mechanical Seal & Status Light Module Replaced ML20086F7201975-01-30030 January 1975 AO 50-261/75-2:on 750120,pressurizer Level Channel II Failed to Generate Reactor Trip Signal or Safety Injection Signal Upon Insertion of Simulated High & Low Levels.Caused by Malfunctioning Filter Capacitor C.3 ML20086F7281975-01-27027 January 1975 AO 50-261/75-1:on 750114,boric Acid Transfer Pump a Failed. Caused by Failed Shaft in Vicinity of Impeller Keyway.Pump Replaced.Replacement Pump Model GVH-10K on Order ML20086F7141975-01-27027 January 1975 Telecopy Ao:On 750126,component Cooling Pump C Failed to Start from Rtgb.Cause Under Investigation.Pump Breaker Racked Out,Inspected & Racked in ML20086F7241975-01-20020 January 1975 Telecopy Ao:On 750120,level Comparator LC-460A Failed to Operate.Cause Not Stated ML20086F7351975-01-15015 January 1975 Ao:On 750114,boric Acid Transfer Pump a Noted to Be in Off Indication at Rtgb.Caused by Broken Shaft ML20085D0621973-07-17017 July 1973 Ao:On 730628-0705 & 09-10,changes Performed on Safeguards Equipment W/O Demonstrating Operability of Redundant Equipment Before Removal.Safety Injection Pumps B & C Tripped & Circuit Breaker Tripped,Respectively ML20085D0661973-07-11011 July 1973 Telecopy Ao:On 730709,two Safety Injection Pumps Experienced Overcurrent Trips.Caused by New Overcurrent Trip Devices Tripping at Lower than Desired Value.Trip Setting Increased ML20085D0771973-07-10010 July 1973 Telecopy Ao:On 730710,circuit Breaker for Containment Cooler Fan 2 Tripped.Caused by Overcurrent Due to Misalignment of Calibr Spring in Overcurrent Trip Device.Spring Realigned 1977-03-25
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20217A1691999-09-22022 September 1999 Part 21 Rept Re Engine Sys,Inc Controllers,Manufactured Between Dec 1997 & May 1999,that May Have Questionable Soldering Workmanship.Caused by Inadequate Personnel Training.Sent Rept to All Nuclear Customers RA-97-0258, LER 97-S12-00:on 971119,discovered Uncompensated Security Zone.Caused by Inattention to Detail by Members of Security Force.Provided Event Info to Security Shift Personnel & Changed Practice Re Zone Review1997-12-19019 December 1997 LER 97-S12-00:on 971119,discovered Uncompensated Security Zone.Caused by Inattention to Detail by Members of Security Force.Provided Event Info to Security Shift Personnel & Changed Practice Re Zone Review ML20211M6491997-10-0808 October 1997 Addenda 1 to Part 21 Rept Re Weldments on Opposed Piston & Coltec-Pielstick Emergency stand-by Diesel gen-set lube-oil & Jacket Water Piping Sys.Revised List of Potentially Affected Utils to Include Asterisked Utils,Submitted ML20217Q2751997-06-30030 June 1997 CP&L Fitness for Duty Program Performance Data for Period 970101-0630 ML14183A6951995-09-18018 September 1995 Safety Evaluation Approving Relocation of Technical Support Ctr ML20059H7721994-01-17017 January 1994 Part 21 Rept Re Virginia Power Notifying Fairbands Morse Via Failure Analysis Rept NESML-Q-058 of Defective Air Start Distributor cam,16104412 ML17352A8691993-05-31031 May 1993 Technical Rept, Assessment of Aging Degradation of Civil/ Structural Features at Selected Operating Nuclear Power Plants. ML20125C7161992-12-0707 December 1992 Part 21 Rept Re Possibility for Malfunction of Declutching Mechanisms in SMB/SB-000 & SMB/SB/SBD-00 Actuators. Malfunction Only Occurs During Seismic Event.Balanced Levers May Be Purchased from Vendor.List of Affected Utils Encl ML20127P5861992-11-23023 November 1992 Followup to 921005 Part 21 Rept Re Potential Defect in SB/SBD-1 Housing Cover Screws.Procedure Re Replacement of SBD-1 Spring Cover Bolts Encl.All Fasteners Should Be Loosened & Removed.List of Affected Utils Encl ML20118B4391992-09-11011 September 1992 Part 21 Rept Re Degradation in Abb Type 27N Undervoltage Relays Used in Electrical Switchgear.Recommends That Users Review Applications Requiring Exposures Greater than 1E03 Rads TID W/Time Delay Function Option ML20079H1571991-09-30030 September 1991 Nonproprietary Evaluation of Revised Transfer to Cold Leg Recirculation Procedure,Hb Robinson Unit 2 ML20086T2951991-06-14014 June 1991 Rev 1 to EQ Documentation Package Eqdp 36.0, Boston Insulated Wire Cable ML20086T2861991-03-0808 March 1991 Rev 1 to EQ Documentation Package Eqdp 11.1, Dekoron Instrumentation Cables ML20086T2561991-03-0808 March 1991 Rev 1 to EQ Documentation Package 10.0, Continental Shielded Instrument Cable ML20065K6961990-10-31031 October 1990 Mechanical Licensing Rept for Hb Robinson High Thermal Performance Fuel Assemblies ML20065K6971990-10-31031 October 1990 Thermal Hydraulic Compatibility Analysis of Anf High Thermal Performance Fuel for Hb Robinson,Unit 2 ML20005G6831990-01-0505 January 1990 Part 21 Rept Re Installation Instructions for Grommet Use Range for Patel Conduit Seal P/N 841206.Conduit Seals in Environ Qualification Applications Inspected for Proper Wire Use Range & Grommets Replaced ML20247E0701989-07-20020 July 1989 Info Rept:On 890717-0804,fire Penetration Seals Will Be Removed from Svc to Allow Access for Ventilation Sys Mod. Addl Fire Barrier Penetrations Will Be Made in Wall Between RHR Pump Pit & Fuel Handling Bldg,Per Tech Spec 3.14.7.2 ML20246E9111989-03-31031 March 1989 PDC-3:Advanced Nuclear Fuels Corp Power Distribution Control for PWRs & Application of PDC-3 to Hb Robinson Unit 2 ML20245H0821989-01-25025 January 1989 Criticality Safety Analysis of Hb Robinson Spent Fuel Pool W/4.2% Nominal Enrichment Fuel Assemblies ML20205T0551988-10-31031 October 1988 Responses to NRC Questions on RTD Bypass Elimination Licensing Rept ML20147E2371988-02-29029 February 1988 1987 Annual Rept - Primary Coolant Iodine Spikes ML20147B1971987-12-31031 December 1987 1987 Annual Rept - Primary Safety & Relief Valve Challenges ML20236K7731987-10-31031 October 1987 Monthly Operating Rept for Oct 1987 ML20235W3781987-09-30030 September 1987 Monthly Operating Rept for Sept 1987 ML20238E2741987-08-31031 August 1987 Monthly Operating Rept for Aug 1987 ML20235H3151987-06-30030 June 1987 Monthly Operating Rept for June 1987 ML17261A5301987-06-18018 June 1987 Part 21 Rept Re Potential Util Failure to Comply W/Component Containment Isolation Licensing Commitment If Proposed Mods to Component Cooling Water Sys Instituted.Utils Advised to Evaluate Containment Isolation Sys ML20214W3241987-05-31031 May 1987 Monthly Operating Rept for May 1987 ML20214R5101987-04-30030 April 1987 Rev 1 to Monthly Operating Rept for Apr 1987,correcting Operation Statistics & Shutdown Experience Due to Mathematical Errors ML20215L4941987-04-30030 April 1987 Monthly Operating Rept for Apr 1987 ML20206F3561987-03-31031 March 1987 Monthly Operating Rept for Mar 1987 ML20210B4141987-03-31031 March 1987 Revised Monthly Operating Rept for Mar 1987 ML20205F6021987-03-23023 March 1987 Special Rept:On 870302,noble Gas Effluent Monitor for Main Steam Line B Declared Inoperable & Svc Not Returned Until 870312.Caused by Defective Detector.Detector Replaced.High Voltage for Detector Adjusted & Sys Operation Checked ML20212P3101987-02-28028 February 1987 Monthly Operating Rept for Feb 1987 ML20214Q7891987-01-31031 January 1987 Cycle 12,SAR ML20210R6341987-01-31031 January 1987 Monthly Operating Rept for Jan 1987 ML20207M2451986-12-31031 December 1986 Monthly Operating Rept for Dec 1986 L-18-120, Rev 0 to Supplemental Info in Support of Conservatisms in Criticality Analysis Performed for Hb Robinson Isfsi1986-12-18018 December 1986 Rev 0 to Supplemental Info in Support of Conservatisms in Criticality Analysis Performed for Hb Robinson Isfsi ML20215C7911986-11-30030 November 1986 Monthly Operating Rept for Nov 1986 ML20213F3121986-10-31031 October 1986 Monthly Operating Rept for Oct 1986 ML20215G1081986-09-30030 September 1986 Monthly Operating Rept for Sept 1986 ML20215F0361986-09-29029 September 1986 Special Rept:On 860902,during Cold Shutdown,Pressurizer PORV Lifted Twice to Prevent Overpressurization.Caused by Inadvertent Action by Unit Operators.Operations Personnel Counseled Re Importance of Breaker Position Indicators ML20211C0641986-09-0909 September 1986 Rev 0 to Final Rept Criticality Safety Analysis Hb Robinson Spent Fuel Storage Racks (Unpoisoned,Low Density) W/4.2% Enriched 15x15 Fuel Assemblies ML20211C0491986-09-0202 September 1986 Rev 0 to Final Rept Criticality Safety Analysis Hb Robinson New Fuel Storage Vault W/4.2% Enriched 15x15 Fuel Assemblies ML20212F5321986-07-31031 July 1986 Monthly Operating Rept for Jul 1986 ML20203D0221986-07-14014 July 1986 Part 21 Rept Re Air Monitoring Sys Probes Exhibiting Blue Tip Rather than Normal White Tip & Insensitive to Chlorine. Caused by Improper Handling/Storage.Advisory Bulletin Encl. Item Not Reportable Per Part 21 ML20202G3371986-06-30030 June 1986 Monthly Operating Rept for June 1986 ML20211B5601986-05-31031 May 1986 Monthly Operating Rept for May 1986 ML20197D2651986-04-30030 April 1986 Monthly Operating Rept for Apr 1986 1999-09-22
[Table view] |
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r February 14, 1975 $ Q = 2 6 ']
j File: NG-3513 (R) Serial: NG-75-231 1 Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission c) c)
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Dear Mr. Moseley:
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I H. B. ROBINSON UNIT NO.\2 LICENSENO.DPR-23$y\ #0 . '
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TAILURE OF COMPARATOR CIRCUIT C /
In accordance with 6.6.2.a of the Technical Specifications for H. B. Robinson Unit Ne. 2, the attached Abnormal Occurrence Report is submitted for your information. This report fulfills the. requirement for -
a written report within ten days of an Abnormal Occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16, Revision 1.
4 Yours very ,truly, i -
! 9 d) ~$- ;. {_ ~7'. G'" '
E. E. Utley i Vice-President Bulk Power Supply 4
TAW:KPY:mvp
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cc: Messrs. N. B. Bessac
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J. B. McGirt D. B. Waters i
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Abnormal Occurrence Report l 1. Report No. 50-261/75-4 2a. Date February 13, 1975
)
j 2b. Occurrence Date February 6, 1975
- 3. Facility H. B. Robinson Unit No. 2 Hartsville, South Carolina
- 4. _ Identification of Occurrence Failure of Reactor Protection Overpower Channel Set No. I to generate a rod stop signal for a simulated overpower condition. This constitutes an Abnormal' Occurrence as defined in Technical Specification 1.8.d.
- 5. Conditions Prior to Occurrence The reactor was at 100% power with all parameters normal. PT 5.1, "Overtemperature and Overpower Channel Set I" was being conducted.
- 6. Description of Occurrence '
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At approximately 1030 on February 6, 1975, Instrument and control Technicians began conducting PI 5.1 on Overtemperature and Overpower
] Channel Set I. PT 5.1 is a bi-weekly test which includes testing a
the overpower protection circuitry to determine if it will detect an overpower condition and send the appropriate rod stop or reactor trip signal to the reactor protection logic. This is accomplished by removing only one of the three channels at a time from service and simulating T flux and flux signals to the over-powercircuikEy.,TEyha,rying"EEEEesignalsf$0Erpowerconditionscan j be simulated and the appropriate rod stop or reactor trip signal checked.
At 1100 it was determined that no value or combination of values of delta T or delta flux would result in a rod stcp signal from Channel I.
A The reactor trip function of the protection channel was checked and determined to be operating properly. The technicians immediately '
reported the troubic and effected repairs to the overpower circuitry.
! Repairs vere completed at 1144.
j 7. Description of Apparent Cause of Occurrence i
One of the two comparator circuits in a dual circuit signal comparator, box number TC-412B, had failed in a nonconservative direction. This l comparator takes an overpower setpoint signal computed from flux i flux T , and T c deltdYpr,otbEEloncirE0kYr;y;omparesitwithasignalderivedin"ER8r, and then determines if an' overpower condition i
exists. If a rod stop or reactor trip is required, a signal-is sent to the reactor protection logic from this box.
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In this particular occurrence only the comparator circuit which deals with rod stop failed. Since the reactor trip comparator circuit operated properly, there is no possibility that a failure external to TC-412B precluded operation of the rod stop signal.
The exact cause of the comparator failure has not been determined, as described under Item 9, Corrective Action.
- 8. Analysis of Occurrence To obtain a rod stop signal from the overpower protection circuitry, i two of the three overpower channels must detect an overpower condition.
l Prior to commencing the teat on Overpower and Overtemperature Protection Channel I, the rod stop and reactor trip bistables for this channel were placed in the tripped position. Therefore, at the time TC-412B was l
found to be malfunctioning, the overpower protection logic was one out of two. This satisfies Technical Specification Table 3.5-2 which requires j a minimum of two overpower channels to be operable, with a minimum degree of redundancy of one. From the time the violation was discovered to the time the repairs were affected.and Channel I returned to service, no limiting operating conditions were violated.
{ I i Since PT 5.1 is a bi-weekly test, and the previous test detected no trouble with TC-412B, the comparator could have been out of service for a maximum of two weeks.
i 9. Corrective Action TC-412B was removed from the protection circuitry and replaced with an identical comparator. PT 5.1 was again run on Overpower and Over-temperature Protection Channel I with satisfactory results. The test was completed at 1144 on February 6, approximately.44 minutes after i the trouble was detected. In accordance with PT 5.1, the two remaining j Overpower and Overtemperature Channels were tested and found to be functioning normally. To determine the exact cause of the failure, ,
a number of tests have been conducted on TC-412B. These tests were:
(1) Power supply voltages checked.
j (2) Installed in a test rig and trip functions checked.
I (3) Installed in a spare location of a protection rack for two days, checking for possibl6 component failures due to heat.
l (4) Individual components heated.
I j
To date the comparator functions normally and no trouble has been found.
4 Since the problem now seems to no longer exist, the reliability of the I comparator is questionable. Therefore, this particular box will not
- be put into use in any reactor protection or safety. related control l circuitry until the cause of the failure is located anid repaired.
- Investigation as to the cause of the failure will continue to be ' pursued.-
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- 10. Failure Data (a) Two previous failures have occurred.
(1) October 3, 1974 - TC-412C, comparator in Overtemperature Protection Channel Set I failed due to defective 50,pf capacitor in the comparator power supply.
(2) January 20, 1975 - LC-460A, comparator in PressurJzer Water Level Protection Channel Set II due to defective 50 pf capacitor in the comparator power supply.
(b) The comparators are Westinghouse, Model 139-118, dual circuit comparators.
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- Cp&L oM Carolina Power & Light Company Raleigh. N. C. 27602 T e
l February 14, 1975 / p 7' 4 )
File: NG-3513 (R) Serial: NG-75-231 Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Cormission Region II, Suite 818 230 Peachtree Street, N.W.
Atlanta, Georgia 30303 Daar Mr. Moseley:
H. B. ROBINSON UNIT No. 2 LICENSE NO. DPR-23 FAILURE OF COMPARATOR CIRCUIT TC-412B In accordance with 6.6.2.a of the Technical Specifications for H. B. Robiason Unit No. 2, the attached Abnormal Occurrence Report is submitted for your information. This report fulfills the requirement for a written report within ten days of an Abnormel occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16 Revision 1.
Yours very truly, Oit!GINAL SIGNED BY v' Of1GK E. E. Utley Vice-President Bulh Power Supply TAW:KPY:mvp Attachment cc Messrs. N. B. Bessac P. W. Howe R. E. Jone D. Knuth J. B. McGirt D. B. Waters SP 'p(0 p)t" ,
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Abnormal Occurrence Report
- 1. Report No. 50-261/75-4 2a. Date February 13, 1975
, 2b. Occurrence Date February 6, 1975
- 3. Facility H. B. Robinson Unit No. 2 I Hartsville, South Carolina
- 4. Identification of Occurrence i
Failure of Reactor Protection Overpower Channel Set No. I to generate ,
a rod stop signal for a simulated overpower condition. This constitutes an Abnormal Occurrence as defined in Technical Specification 1.8.d. 1
- 5. Conditions Prior to Occurrence The reactor was at 100% power with all parameters normal. PT 5.1, "Overtemperature and Overpower Channel Set 1" was.being conducted.
- 6. Description of Occurrence At approximately 1030 on February 6, 1975, Instrument and Control Technicians began conducting PT 5.1 on Overtemperature and Overpower Channel Set 1. PT 5.1 is a bi-weekly test which includes testing 4
the overpower protection circuitry te determine if it will detect an overpower condition and send the appropriate rod stop or reactor trip signal to the reactor protection logic. This is accomplished by removing only one of the three channels at a time from service and simulating T ,T 1"* signals to the over-oldva'ryingu powercircuikg ry. Ey EEer ""d f1"#cse l signals,oweroverpower conditions c be simulated and the appropriate rod stop or reactor trip signal checked.
' At 1100 it was determined that no value or combination of values of.
delta T or delta flux would result in a rod stop signal from Channel I.
The reactor trip function of the protection channel was checked and determined to be operating properly. The technicians immediately reported the trouble and effected repairs to the overpower circuitry.
Repairs were completed at 1144.
- 7. Description of Apparent Cause of Occurrence One of the two comparator circuits in a dual circuit signal comparator, box number TC-412B, had failed in a nonconservative direction. This comparator takes an overpower setpoint signal computed from flux flux T , and T c
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and then.dctermines if an overpower condition exists. If a rod stop or reactor trip is required, a signal is sent to the reactor protection logic from this box.
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In this particular occurrence only the comparator circuit which deals with rod stop failed. Since the reactor trip comparator circuit operated properly, there is no possibility that a failure external to TC-4128 precluded operation of the rod stop signal.
The exact cause of the comparator failure has not been determined, as described under Item 9, Corrective Action.
- 8. Analysis of Occurrence To obtain a rod stop signal from the overpower protection circuitry, two of the three overpower channels must detect an overpower condition.
Prior to commencing the test on Overpower and Overtemperature Protection Channel I, the rod stop and reactor trip bistables for this channel were placed in the tripped position. Therefore, at the time TC-412B was found to be malfunctioning, the overpower protection logic was one out of two. This satisfies Technical Specification Table 3.5-2 which requires a minimum of two overpower channels to be operable, with a minimum degree of redundancy of one. From the time the violation was discovered to the time the repairs were affected_and Channel I returned to service, no limiting operating conditions were violated.
Since PT 5.1 is a bi-weekly test, and the previous test detected no trouble with TC-412B, the comparator could have been out of service for a maximum of two weeks.
- 9. Corrective Action TC-412B was removed from the protection circuitry and replaced with an identical comparator. PT 5.1 was again run on Overpower and Over-temperature Protection Channel I with satisfactory results. The test was completed at 1144 on February 6, approximately 44 minutes after the trouble was detected. In accordance with PT 5.1, the two remaining Overpower and Overtemperature Channels were-tested and found to be functioning normally. To determine the exact cause of the failure, a number of tests have been conducted on TC-412B. These tests were:
(1) Power supply voltages checked.
(2) Installed in a test rig and trip functions checked.
(3) Installed in a spare location of a protection rack'for two days, checking for possible component failures due to heat.
(4) Individual components heated.
To date the comparator functions normally and no trouble has been found.
Since the problem now seems to no longer exist, the reliability of the comparator is questionable. Therefore, this particular box will not be put into use in'any reactor protection or safety related control circuitry until-the cause of the failure is located and repaired.
Investigation as to the cause of the failure will continue to be pursued.
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- 10. Failure Data (a) Two previous failures have occurred.
(1) October 3, 1974 - TC-412C, comparator in Overtemperature Protection Channel Set I failed due to defective 50 pf capacitor in the comparator power supply.
(2) January 20, 1975 - LC-460A, comparator in Pressurizer Water Level Protection Channel Set II due to defective 50 pf capacitor in the comparator power supply.
(b) The comparators are Westinghouse, Model 139-118, dual circuit comparators.
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