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Category:ABNORMAL OCCURRENCE REPORTS (SEE ALSO LER & RO)
MONTHYEARML20084F1431975-12-22022 December 1975 AO 251-75-12:on 751212,boron Concentration in Boron Injection Tank Measured 2% Below Lower Limit.Caused by Dilution of Unit 3 Bit W/Water from Safety Injection Sys Accumulator C Followed by Dilution of Boric Acid Tank ML20084F7031975-12-11011 December 1975 Supplementary Rept 3 to AO 251-75-4:on 750312,lateral Restraints for Spent Fuel Racks Found Broken.Cause Not Stated.All Spent Fuel Rack Seismic Restraint Springs Replaced ML20084F3451975-11-28028 November 1975 AO 250-75-9:on 751119,pressure Switch PS-3-2058 Setpoint Exceeded Max Limit.Caused by Setpoint Drift.Pressure Switch Recalibr & Setpoint Returned to Proper Value ML20084F1441975-11-21021 November 1975 AO 251-75-11:on 751112,boron Concentration in Boric Acid Storage Tank C Discovered Above Upper Limit.Caused by Addition of Concentrated Boric Acid Solution to Tank.Primary Grade Water Added to Tanks & Contents Diluted ML20084F4151975-11-0505 November 1975 AO 250-75-8:on 751026,MSIV C Malfunctioned.Cause Not Determined.Msiv Stem Packing & Pneumatic Cylinder Inspected. Investigation of Cause Continuing ML20084F3351975-10-31031 October 1975 AO 251-75-10:on 751021,unplanned Release of 880 G Radioactive Liquid to Underground Area Outside Plant Radiation Controlled Boundary Occurred.Caused by Personnel Error.Floor Drains to Be Labeled ML20084F3971975-10-13013 October 1975 AO 251-75-8:on 750525,diesel Generator Breaker 4A & Bus Stripping 4B Relay Malfunctioned During Engineered Safeguards & Emergency Power Sys Integrated Test. Intermittent Open Circuit Caused by Electrolytic Corrosion ML20084F4371975-10-0303 October 1975 AO 250-75-7:on 750924,high Pressure Comparator in Pressurizer Protection Sys Channel III Malfunctioned.Caused by Two Failed Capacitors in Dc Power Supply.Comparator PC-3-457A Replaced ML20084F5561975-08-0101 August 1975 AO 250-75-6:on 750623,during Rotation of Operating Equipment,Intake Cooling Water Pump 3A Malfunctioned.Rept Incomplete ML20084F5181975-07-24024 July 1975 Supplementary AO 251-75-9:on 750613,airlock Equalizing Valve Opened Breaching Containment Integrity.Operating Procedure 0202.1 Reactor Startup-Cold Condition to Hot Shutdown Condition, Will Be Revised ML20084F5991975-06-0606 June 1975 AO 250-75-4:on 750522,intake Cooling Water Pump Breaker 3A Malfunctioned.Cause Not Yet Determined.Pump Breaker Racked Out & Inspected for Damage ML20084F6081975-05-27027 May 1975 AO 250-75-3:on 750517,battery Charger Transformer 3A Failed. Caused by Unsatisfactory Original Insulation.Transformer Replaced.Vendor Examined Failed Transformer & Repaired Charger.Charger 3A Placed Back in Svc ML20084F6501975-05-0606 May 1975 AO 251-75-7:on 750426,during Refueling Operations,Fuel Assembly P41 Damaged.Caused by Procedural Deficiencies. Procedures Revised to Specify Fuel Assembly Must Be Lifted to full-up Position Before SFP Bridge Moved Away ML20084F6441975-05-0101 May 1975 AO 251-75-6:on 750422,during Valve & Steam Generator Maint, Containment Integrity Breached.Caused by Procedural Deficiencies.Administrative & Maint Procedures Will Be Revised ML20084F7291975-05-0101 May 1975 Supplemental AO 251-75-4:on 750312,broken Lateral Restraints for Spent Fuel Racks Discovered.Caused by Stress Corrosion. Original Springs Replaced.On 750321,broken Restraint Found on Unit 3.Insp Underway ML20084F7671975-04-23023 April 1975 AO 250-75-2:on 750414,steam Generator Protection Sys Channel II Low Level Comparator Failed.Caused by Failed Capacitor in 15-volt Dc Instrument Power Supply.Comparator Replaced ML20084G0771975-04-22022 April 1975 AO 251-75-1:on 750413,spent Fuel Pit Cooling Pump Bearing Failed.Caused by Procedural Deficiencies.Areas Affected Cleaned,Pump Repaired & Off-Normal-Condition Procedure 3508 Revised ML20084F6691975-04-22022 April 1975 AO 251-75-5:on 750413,unplanned Release of Liquid Radioactive Matl Occurred.Rept Incomplete ML20084F7451975-03-21021 March 1975 AO 251-75-4:on 750312,lateral Restraints for Spent Fuel Racks Discovered Broken.Cause Under Investigation.Springs Will Be Replaced ML20084F7881975-03-14014 March 1975 AO 251-75-3:on 750304,steam Generator Protection Sys Channel II Low Steam Line Pressure Comparator Failed.Caused by Failed Capacitor in 15-volt Dc Instrument Power Supply. Comparator Replaced ML20084F8041975-03-12012 March 1975 AO 250-75-1:on 750302,reactor Operated Outside Indicated Axial Flux Difference Target Band.Cause Attributed to Operators Not Understanding Tech Specs.New Procedures Will Be Discussed in Detail W/Operating Personnel ML20084G0811975-02-14014 February 1975 AO 251-75-1A:on 750103,zero Shift in Pressurizer Lead/Lag Controller PM-456A Occurred.Caused by Failure of Capacitor in Amplifier of Lead/Lag Controller.Controller Replaced W/ Calibr Spare Controller ML20084F8241975-01-30030 January 1975 AO 251-75-2:on 750120,low Boron Concentration Found in Boron Injection & Boric Acid Storage Tanks.Caused by Demineralized Water Being Used to Flush Temporary Hoses.Blocked Recirculation Line Will Be Cleared or Renewed ML20084C4961975-01-28028 January 1975 Supplemental AO 251-74-7:on 741108,leak Found in 3/4-inch Vent Line Assembly Upstream of Safety Injection Sys 10-inch Check Valve.Possibly Caused by Presence of Defect at Weld Root or Poor fit-up Between Pipe & Coupling ML20084G0861975-01-13013 January 1975 AO 251-75-1:on 750103,pressurizer Pressure Protection Channel II Lead/Lag Controller Failed.Caused by Zero Shift in Pressurizer Low Pressure Lead/Lag Controller.Controller Adjusted to Correct Zero Shift ML20084C1251975-01-0606 January 1975 AO 251-74-9:on 741227,newly Installed Digital Data Processing Sys Revealed Feedwater Temp Reading of Sys About 10 F Lower than Feedwater Temp Shown on Feedwater Temp Recorder.Caused by Incorrect Calibr Procedure ML20084C1171975-01-0606 January 1975 AO 250-74-12:on 741227,newly Installed Digital Data Processing Sys Revealed Feedwater Temp Reading Used by Sys About 10 F Lower than Feedwater Temp Shown on Feedwater Temp Recorder.Caused by Incorrect Calibr Procedure ML20084C1341974-12-12012 December 1974 AO 251-74-11:on 741203,while RCS Pressure Being Increased, Pressure Control Valve Indicated Closed & Pressure Reached Setpoint Above Tech Spec Limits Before Valve Opened.Caused by Automatic Closure of RHR Sys Valves ML20084C1701974-12-0202 December 1974 AO 251-74-8:on 741123,indication of Low Boric Acid Flow in Flow Path from Boric Acid Tanks to RCS Observed.Caused by Accumulation or Buildup of Boric Crystals in Line.Boric Acid Flow Path Isolated from RCS ML20084C5281974-11-0808 November 1974 AO 251-74-7:on 741029,routine Visual Insp of RCS Revealed Steam Leaking from 3/4-inch Vent Line Assembly Upstream of Safety Injection Sys.Cause Unknown.Vent Assembly Removed & Sent for Metallurgical Analysis.Supplemental AO Will Follow ML20084C5351974-10-23023 October 1974 AO 251-74-6:on 741013,analysis of Boron Injection Tank Boron Content Revealed Concentration Below Tech Spec Limit.Caused by Insufficient Recirculation Coupled W/Minor Inleakage. Boron Injection Tank Recirculated ML20084C5501974-09-23023 September 1974 AO 251-74-4:on 740913,routine Boron Analysis of Boric Acid Storage Tanks Revealed Tank C Boron Concentration Below Tech Spec Limit.Caused by Partially Open Primary Water Flush Valve.Valve Alignment Procedure Will Be Revised ML20084C5551974-09-16016 September 1974 AO 250-74-10:on 740906,one Steam Generator C lo-lo Water Level Comparator Would Not Trip at Required Value.Caused by Failure of 15 Volt Dc Power Supply Filter Capacitor. Comparator Replaced W/Calibr Spare Unit ML20084C5951974-08-22022 August 1974 AO 251-74-3:on 740812,counting of Daily Composite Steam Generator Secondary Sys Water Sample Revealed Significant Increase in Radiation Level.Caused by Plugged Sample Line to 4-R-19 Detector.Sampling Sys Being Evaluated ML20084C5781974-08-22022 August 1974 AO 251-74-2:on 740812,counting of Daily Composite Steam Generator Secondary Sys Water Sample Revealed Significant Increase in Radiation Level.Cause Unknown.Steam Generator a Will Be Examined by Reactor Vendor to Identify Source ML20084C6051974-08-0101 August 1974 AO 250-74-8:on 740219,personnel Overexposure Occurred While Attempting Maint on E Detector of Flux Mapping Equipment. Caused by Failure to Comply W/Radiation Work Permit ML20084C6231974-07-0505 July 1974 AO 251-74-8:on 740627,0701 & 02,boron Injection Tank Boron Concentration Found Below Tech Specs Limit.Caused by Insufficient Recirculation Coupled W/Minor Leakage. Investigation Continuing ML20084C7191974-05-17017 May 1974 AO 250-74-7:on 740508,while Attempting to Start Three Auxiliary Feedwater Pumps,Pumps a & B Failed to Start & C Started But Tripped When Attempt Made to Feed Steam Generators.Caused by Packing Too Tight.Packing Loosened ML20084C7441974-05-10010 May 1974 AO 250-74-6:on 740503,after Safety Injection Sys Pump 3A Started to Add Water to Safety Injection Accumulators,Pump Indicated Abnormally Low Running Current & Discharge Pressure.Cause Unknown.No Abnormalities Found ML20084C8811974-04-19019 April 1974 AO 250-74-5:on 740411,routine Boron Analysis of Boron Injection Tank Contents Indicated Boron Concentration Below Lower Tech Spec Limit.Cause Unknown.Contents Recirculated Through Boric Acid Storage Tank ML20084M2961974-03-15015 March 1974 Suppl to AO 3-73-1:on 730106,reactor Coolant Leaked Into Reactor Containment from Differential Pressure Cell.Caused by Flange Bolt Failure.Bolts Replaced ML20084C9941974-02-27027 February 1974 AO 250-74-4:on 740218,recent Monthly in-core Detector Flux Map Found to Not Meet Requirements of Change 11 to Tech Spec for Power Level Greater than 75%.Caused by Failure to Comply W/Recent Changes in Tech Specs ML20084M2511974-02-22022 February 1974 Suppl to AO 3-73-3:on 730319,emergency Diesel Generator a Failed to Automatically Start.Caused by Malfunctioned Starting Air Solenoid Valve.Valve Replaced & Defective Valve Subjected to Tests.Valve Spring Assemblies Replaced ML20084D0051974-02-15015 February 1974 AO 250-74-3:on 740206,engineered Safeguards Sys Energized & Reactor Tripped from Safety Injection Sys Signal.Caused by Improper Engaging of Two Air Driven Starting Motor Pinion Gears W/Engine Flywheel Ring Gear ML20084D0161974-02-15015 February 1974 AO 250-74-2:on 740205,safety Injection Pump 3A Failed to Start.Caused by Closing Spring Mechanical Indicator of Safety Injection Pump 3A Motor Circuit Breaker Being in Intermediate Position & Not Closed.Spring Mechanism Tested ML20084M3711973-11-26026 November 1973 Suppl to AO 3-72-8:on 721216,small Fire Discovered in Battery Charger Cubicle 3.Caused by Winding Short in Transformer.New Transformers Installed ML20084M1361973-11-24024 November 1973 Suppl to AO 4-73-3:on 730509,pump 4A Discovered Leaking.Insp Determined Pump in Satisfactory Condition.Components of Mechanical Seal Assembly Replaced ML20084D2371973-10-26026 October 1973 AO 3-73-10:on 731018,review of Chemistry Analysis Log Sheets for Boric Acid Storage Tanks & Boron Injection Tanks Indicated Boric Acid Storage Tank a Concentration in Excess of Tech Spec Limits.Caused by Personnel Oversight ML20084D2431973-10-16016 October 1973 AO 4-73-12:on 731007,approx 50 to 75 Gallons of Reactor Coolant Released to Charging Pump Room in Auxiliary Bldg Via Failed Bellows in Relief Valve 4-209.Caused by Increased Pressure on Bellows & Opening in Valve Bonnet ML20084D2491973-09-20020 September 1973 AO 4-73-11:on 730920,sample from Inlet Piping to Boron Injection Tank Analyzed & Found to Contain Less than Specified Min in Tech Specs.Caused by Valve Leaking in Suction of Boric Acid Transfer Pumps 1975-08-01
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20217L9371999-10-20020 October 1999 Safety Evaluation Supporting Licensee Proposed Alternative from Certain Requirements of ASME Code,Section XI for First 10-Yr Interval Request for Relief for Containment Inservice Insp Program ML17355A4471999-09-30030 September 1999 Monthly Operating Repts for Sept 1999 for Turkey Point,Units 3 & 4.With 991008 Ltr ML17355A4121999-08-31031 August 1999 Monthly Operating Repts for Aug 1999 for Turkey Point,Units 3 & 4.With 990909 Ltr ML17355A3981999-07-31031 July 1999 Monthly Operating Repts for July 1999 for Turkey Point,Units 3 & 4.With 990809 Ltr ML17355A3891999-07-20020 July 1999 LER 99-001-00:on 990623,manual Rt from 100% Power Following Multiple Control Rod Drops Was Noted.Caused by Manual Action Taken by Reactor Control Operator.Inspected & Repaired Stationary Gripper Regulating Cards.With 990720 Ltr ML17355A3841999-06-30030 June 1999 Monthly Operating Repts for June 1999 for Turkey Point,Units 3 & 4.With 990713 Ltr ML17355A3681999-06-30030 June 1999 Revised Update to Topical QA Rept, Dtd June 1999 ML17355A3611999-06-30030 June 1999 Refueling Outage ISI Rept. ML17355A3511999-05-31031 May 1999 Monthly Operating Repts for May 1999 for Turkey Point,Units 3 & 4.With 990609 Ltr ML17355A3331999-04-30030 April 1999 Monthly Operating Repts for Apr 1999 for Turkey Point,Units 3 & 4.With 990511 Ltr ML20217B9871999-04-0808 April 1999 Changes,Tests & Experiments Made as Allowed by 10CFR50.59 for Period Covering 971014-990408 ML17355A2881999-04-0505 April 1999 COLR for Turkey Point Unit 4 Cycle 18. ML17355A2911999-03-31031 March 1999 Monthly Operating Repts for Mar 1999 for Turkey Point,Units 3 & 4.With 990414 Ltr ML17355A2551999-02-28028 February 1999 Monthly Operating Repts for Feb 1999 for Turkey Point Nuclear Power Plant,Units 3 & 4.With 990315 Ltr ML17355A2261999-01-31031 January 1999 Monthly Operating Repts for Jan 1999 for Turkey Point,Units 3 & 4.With 990211 Ltr ML17355A2201999-01-20020 January 1999 Refueling Outage ISI Rept. ML17355A1911998-12-31031 December 1998 Monthly Operating Repts for Dec 1998 for Turkey Point,Units 3 & 4.With 990112 Ltr ML18008A0461998-11-30030 November 1998 Monthly Operating Repts for Nov 1998 for Turkey Point,Units 3 & 4.With 981209 Ltr ML17354B1921998-11-18018 November 1998 LER 98-007-00:on 981020,containment Purge Supply,Valve Opened Wider than TS Limit.Caused by Improper Setting of Mechanical Stops.Incorporated Improved Standard Method of Measuring Angular Valve Position Into Sp.With 981118 Ltr ML17354B1891998-11-0909 November 1998 Simulatory Certification Update 2. ML17354B1901998-10-31031 October 1998 Monthly Operating Repts for Oct 1998 for Turkey Point,Units 3 & 4.With 981112 Ltr ML17354B1591998-10-23023 October 1998 COLR for Turkey Point Unit 3 Cycle 17. ML17354B1361998-10-16016 October 1998 LER 98-004-00:on 980921,automatic Reactor Trip Occurred. Caused by Inadequate re-correlation of Intermediate Range Neutron Flux Instrumentation Reactor Trip Bistable. Enhanced Applicable Plant Procedures.With 981016 Ltr ML17354B1311998-09-30030 September 1998 Monthly Operating Repts for Sept 1998 for Turkey Point Unit 3 & 4.With 981012 Ltr ML17354B0971998-09-0909 September 1998 Part 21 Rept Re Possible Machining Defect in Certain One Inch Stainless Steel Swagelok Front Ferrules,Part Number SS-1613-1.Caused by Tubing Slipping Out of Fitting at Three Times Working Pressure of Tubing.Notified Affected Utils ML17354B0981998-08-31031 August 1998 Monthly Operating Repts for Aug 1998 for Turkey Points,Units 3 & 4.With 980915 Ltr ML17354B0771998-07-31031 July 1998 Monthly Operating Repts for July 1998 for Turkey Point,Units 3 & 4.W/980810 Ltr ML17354B0341998-07-15015 July 1998 LER 98-003-00:on 980619,discovered That Auxiliary Feedwater Sys Was Inoperable Due to Inadequate Inservice Testing of Valves.Caused by Misunderstanding of Testing Criteria.Util Revised Procedures & Verified Operability of Valves ML17354B0241998-06-30030 June 1998 Monthly Operating Repts for June 1998 for Turkey Point,Units 3 & 4.W/980709 Ltr ML17354B0171998-06-29029 June 1998 Rev 1 to PTN-FPER-97-013, Evaluation of Turbine Lube Oil Fire. ML17354A9841998-06-18018 June 1998 LER 97-007-01:on 970730,automatic Reactor Trip Occurred Due to Closure of B Msiv.Caused by Failed BFD22S Relay.Six Relays on 3A,3B & 3C MSIVs Were Replaced & Implemented Plant Change to Disable Electronic Trip Function on 3 AFW Pumps ML17354A9741998-06-0909 June 1998 LER 98-002-00:on 980513,discovered Potential LOCA-initiated Electrical Fault Which Places ECCS Outside Design Basis. Caused by Inadequate Review of Effect on non-safety Circuit failures.Re-powered PC-*-600A Relays ML20248F7441998-05-31031 May 1998 Reactor Vessel Working Group,Response to RAI Regarding Reactor Pressure Vessel Integrity ML17354A9711998-05-31031 May 1998 Monthly Operating Repts for Turkey Point,Units 3 & 4. W/980611 Ltr ML17354A9231998-04-30030 April 1998 Monthly Operating Repts for Apr 1998 for Turkey Point,Units 3 & 4.W/980511 Ltr ML17354A8821998-03-31031 March 1998 Monthly Operating Repts for Mar 1998 for Turkey Point,Units 3 & 4.W/980409 Ltr ML17354A8511998-03-24024 March 1998 LER 97-009-01:on 971114,discovered That CR Console Switch for 3B Sgfp Was Not in Start Position.Caused by Inadequate Procedural Guidance.Revised Procedures 3/4-OP-074,informed Personnel of Event & Performed Walkdown of CR ML17354B0001998-03-18018 March 1998 Florida Power & Light Topical Quality Asurance Rept, Dtd June 1998 ML17354A8441998-03-18018 March 1998 LER 98-001-00:on 980216,manual Reactor Trip Occurred Due to Loss of Turbine Control Oil Pressure W/Steam Leak in Auxiliary Feedwater Steam Supply Piping.Auxiliary Governor Maint Instructions Will Be revised.W/980318 Ltr ML17354A8311998-02-28028 February 1998 Monthly Operating Repts for Feb 1998 for Turkey Point,Units 3 & 4.W/980311 Ltr ML17354A7871998-01-31031 January 1998 Monthly Operating Repts for Jan 1998 for Turkey Point,Units 3 & 4.W/980209 Ltr ML17354A7581997-12-31031 December 1997 Monthly Operating Repts for Dec 1997 for Turkey Point,Unit 3 & 4.W/980112 Ltr ML17354A7361997-12-12012 December 1997 LER 97-009-01:on 971114,identified That CR Console Switch for 3B SG Feedwater Pump Was Not in Start Position.Caused by Inadequate Procedural Guidance.Procedures 3/4-OP-074,SGFP Were revised.W/971212 Ltr ML17354A7381997-11-30030 November 1997 Monthly Operating Repts for Nov 1997 for Turkey Point,Units 3 & 4.W/971215 Ltr ML17354A7211997-10-31031 October 1997 Monthly Operating Repts for Oct 1997 for Turkey Point,Units 3 & 4.W/971114 Ltr ML17354A7491997-10-13013 October 1997 SG Insp Rept. ML17354A8851997-10-13013 October 1997 FPL Units 3 & 4 Changes,Tests & Experiments Made as Allowed by 10CFR50.59 for Period Covering 960408-971013. ML17354A6801997-10-0808 October 1997 LER 97-008-00:on 970909,containment Sump Debris Screens Outside Design Basis Due to Stress Damage Was Discovered. Caused by Inadequate Procedural Guidance & Personnel Error. Discrepancies Found on Screens corrected.W/971008 Ltr ML17354A6791997-10-0606 October 1997 COLR Unit 4 Cycle 17, for Turkey Point ML17354A6811997-09-30030 September 1997 Monthly Operating Repts for Sept 1997 for Turkey Point,Units 3 & 4.W/971009 Ltr 1999-09-30
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November 26, 1973 i
Mr. John F. O' Leary, Directo h .g ,_ j Direcorate of Licensing -f" Office of Regulation Nj c4 U. S. Atomic Energy Commission Washington, D. C. 20545 TURKEY POINT UNIT NO. 3 DOCKET NUMBER 50-250 SUPPLEMENT TO ABNORMAL OCCURRENCE NO. 3-72-8 NO. 3 BATTERY CHARGER FIRE
Dear Mr. O' Leary:
I. INTRODUCTION On December 22, 1972, Abnormal occurence Report No. 3-72-8, which concerned No. 3 Battery Charger Fire, was submitted in accordance with Technical Specification No. 6.6.2.a for Turkey Point Unit No. 3, Operating License No. DPR-31.
This supplemental report presents the results and evaluation of tests and inspections performed to provide assurance that the cause of No. 3 Battery Charger fire was determined and corrected.
II. PROBLEM AND INVESTIGATIVE ACTION BACKGROUND On December 16, 1972 at 7:57 a.m. a small fire was discovered.
in No. 3 Battery Charger cubicle. Immediate actions were directed toward electrically isolating the No. 3 Battery.
Charger and extinguishing the fire. After No. 3 Battery Charger was isolated, No. 3S Battery Charger was placed in service.
At the time No. 3 Battery Charger fire was discovered, Unit No. 3 was in cold shutdown condition and Unit No. 4 was under construction. No. 3 Battery Charger was-supplying both units because of construction activities involving No. 4 Battery Room. The total electrical load was about 200 amps. This electrical load represents approximately
- 50% rated capacity of No. 3 Battery Charger.
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,00PY SENT REGION 4
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o Mr. John F. O' Leary, Director November 26, 1973
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. s INVESTIGATION AND RESULTS , ,
An immediate investigation by plant personnel revealed that the. fire involved one of two parallel input transformers in No. 3 Battery Charger. The insulation of this input transformer was charred and burned which indicated thatThe localized overheating of the insulation had occurred.
second input transformer which is located in the same cubicle and immediately to the left of the burned transformer did not appear to be damaged by the fire, however dark rings were noted on the insulation of the second transformer coils.
No. 3 Battery Charger control wiring, located immediately above the two parallel input transformers, showed no evidence of excessive temperature. An intense fire in No. 3 Battery Charger would have damaged the insulation of the left transformer and the insulation of the control wiring.
It was concluded that No. 3 Battery Charger fire was highly localized and involved the right transformer.
No. 3 Battery Charger was placed in service using the left input transformer to supply an electrical load of about 110 amps and performance was satisfactory. This test verified that the left transformer was not affected by the fire.
visual inspection of No. 3S Battery Charger revealed that the left transformer had moderately dark rings on the coil insulation._ Visual inspection of the right input transformer coil insulation revealed a normal appearance with no evidence of the_ dark rings. Visual inspection of No. 4 Battery Charger revealed dark rings present on the coils of the left input transformer and dark. rings with evidence of peeling on phase B coil of the right transformer.
The right input transformer from No. 3 Battery Charger which failed was returned to the manufacturer for further examination and tests.
When the failed transformer was disassembled, a winding short was revealed. The winding short extended from layer to layer in the center leg secondary coil, directly below the only turn in the top layer. This winding short caused i
several turns in B phase of the secondary side of the transformer to be shorted across.
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Mr.JohnF.O'Leey, Director o November 26, 1973
- N Analysis and evaluation of the consequences of a winding short involving several turns in the secondary side of the input transformer shows that the current flow in the secondary side will greatly increase as the result of a smaller number of effective turns in the secondary side of the transformer. An increase in current flow in the secondary windings will result in higher temperatures in the conductors and in the conductor insulation. Excessive temperature in the insulation could result in insulation failure. If the temperature reached the combustion temperature of the insulating material, the insulation will burn.
It was concluded that the fire in No. 3 Battery Charger right input transformer was caused by a winding short involving several turns in the center leg (B phase) secondary coil. The short caused a greatly increased current flow in the secondary coil which resulted in excessive temperature. When the insulation temperature reached the combustion temperature of the insulation, the material burned.
Tests were performed by the battery charger manufacturer which compared a transformer similiar to the failed trans-former with a new type transformer of an improved design.
This improved design provides for cooling air ducts between transformer coil layers and the use of larger size conductors in the transformer coil windings.
Review and analysis of the test results indicate that the transformer with the cooling air ducts had a maximum core temperature 6C lower than the maximum core temperature of the transformer similiar to the failed transformer. Com-parison of other winding temperatures revealed that temperatures were 21 to 27C lower in the improved design transformer compared to the transformer similiar to the failed transformer.
III CORRECTIVE ACTION TO PREVENT RECURRENCE Six new input transformers with cooling air ducts between transformer coil layers, larger size conductors in the transformer coil winding, and Class F insulation for the transformer coils were installed in Battery Charger Nos.
3, 3S, and 4.
--,..:. ) . . .
Mr., John F. O' Leary, Director November 26, 1973
'IV CONCLUSION Inspection and tests indicated that the design of the input transformers was marginal resulting in operating temperatures high enough to degrade the insulation which resulted in failure of one transformer.
Corrective action consisted of replacing all input transformers with tranformers of an improved design.
Very truly yours,
. D. Schmidt Director of Power Resources ADS /CMW/AA/VTC/
ldh Mr. Norman C. Moseley, Director Region II, Directorate of Compliance ,
U. S. Atomic Energy Commission Suite 818, 230 Peachtree Street, N.W.
Atlanta, Georgia 30303
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