Semantic search
Start date | Reporting criterion | Title | Event description | System | LER | |
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ENS 55660 | 20 October 2021 13:05:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System |
This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of the Reactor Protection System (RPS). On October 20, 2021, at approximately 0705 hours Central Daylight Time (CDT), Browns Ferry, Unit 1, 1B RPS bus unexpectedly lost power. The loss of the bus resulted in a half scram, automatic Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolations, and Trains A, B, and C SBGT (Stand-By Gas Treatment) and A CREV (Control Room Emergency Ventilation system) started. All systems responded as expected. At 0720 hours CDT, the bus was placed on the alternate power supply and the half scram and PCIS isolations were reset. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The cause of the RPS bus loss was a trip of the underfrequency relay due to drift of the relay setpoint. The relay was replaced and 1B RPS bus was returned to the normal power supply on October 21, 2021, at 0510 hours CDT. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1729592. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup | |
ENS 55287 | 1 April 2021 18:02:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephonic Notification of Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of the 2A Reactor Protection System (RPS). On April 1, 2021, at 1302 (CDT), Browns Ferry Unit 2, 2A RPS (Motor Generator) MG set tripped causing a half scram. Unit 2 experienced an unexpected trip of the 2A RPS MG Set that resulted in automatic Primary Containment Isolation System (PCIS) Group 2, 3, 6, and 8 isolations and Trains A, B, and C Standby Gas Treatment (SGT) and Train A Control Room Emergency Ventilation (CREV) starts. At the time of the event, Unit 2 was in a refueling outage and the rods were already fully inserted. All systems responded as expected. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. Based on the troubleshooting conducted, the cause was determined to be a loose wiring connection in the motor circuit. The lugs were replaced with ring lugs. Operations reset the 2A RPS Half Scram and PCIS in accordance with 2-AOI-99-1 on April 1, 2021, at 1324 CDT thus correcting the condition and returning RPS to service. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1683358. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 54932 | 6 August 2020 22:49:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of an Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On August 6, 2020, at approximately 1749 CDT, Browns Ferry Nuclear Plant (BFN), Unit 2 experienced a loss of Reactor Protection System (RPS) Bus 2A. Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolated in response to this event. The PCIS isolations caused the initiation of Standby Gas Treatment (SBGT) trains A, B, and C, and Control Room Emergency Ventilation (CREV) subsystem A. Unit 2 declared RCS leakage detection instrumentation inoperable and entered TS LCO 3.4.5 condition A, B, and D with required action D.1 to enter LCO 3.0.3 immediately. Unit 2 entered TS LCO 3.0.3 with required actions to be in Mode 2 within 10 hours, Mode 3 within 13 hours, and Mode 4 within 37 hours. Upon investigation, it was discovered that an age-related overheating condition resulted in the failure of the 2A RPS Motor Generator (MG) set, causing the feeder beaker from the 2A 480v Remote Motor-Operated Valve distribution board to trip. On August 6, 2020, at approximately 1808 CDT, Operations personnel commenced restoration of Unit 2 to normal after transferring 2A RPS to its alternate power supply. The 2A RPS MG Set drive motor was replaced on August 24, 2020. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel (RV) Low Water Level or Drywell High Pressure. Plant conditions which initiate PCIS Group 3 actuations are RV Low Water Level or Reactor Water Cleanup Area High Temperature. Plant conditions which initiate PCIS Group 6 actuations are RV Low Water Level, High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation. Plant conditions which initiate PCIS Group 8 actuations are Reactor Vessel (RV) Low Water Level or Drywell High Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. All affected safety systems responded as expected. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1628707. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 54931 | 6 August 2020 06:28:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of an Invalid Specified System Actuation | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of an emergency service water system component that does not normally run and which provides an ultimate heat sink. On August 6, 2020, at approximately 0128 CDT, the A3 Emergency Equipment Cooling Water (EECW) pump received an auto-start signal while performing Post-Maintenance Testing (PMT) on the 3C Core Spray pump. Normally, the involved EECW pump would be started prior to testing to prevent an auto-start; however, in this case the pump was not running prior to the test. When the 3C Core Spray pump breaker was closed while in the test position, an unanticipated actuation of the A3 EECW pump occurred. Work was stopped and the workers reported to the Control Room to evaluate the condition. Based on a review of this event, individuals involved were coached on understanding system response prior to performing work. The A3 EECW pump responded in accordance with the plant design. No other plant equipment was affected during this event. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. Reference corrective action document CR 1628479. The NRC Resident Inspector has been notified of this event. | Service water Core Spray Emergency Equipment Cooling Water | |
ENS 54709 | 16 March 2020 06:02:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On March 16, 2020, at approximately 0102 CDT, Browns Ferry Nuclear Plant (BFN), Unit 3 received motor trip-out alarms and diagnosed Group 2 and 3 Primary Containment Isolation System (PCIS) Isolations, 3C Residual Heat Removal (RHR) Pump tripping and Reactor Water Cleanup (RWCU) system isolating. All affected safety systems responded as expected. BFN, Unit 3, was nearing the end of the U3R19 refueling outage at the time of the event, and was still dependent on the Shutdown Cooling (SDC) system. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. At the time of the event, these conditions did not exist: therefore, the PCIS actuation was invalid. The event was determined to have been caused by clearance restoration activities in an unprotected control panel. A fuse re-installation inadvertently created a fault condition between two different plant 120 VAC power sources when the fuse holder's lower spring clip contacted a different fuse. This was a result of age-related degradation of the fuse holder, its close proximity to other fuses, and the lack of insulating isolation barriers between fuses. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1594925. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Shutdown Cooling Residual Heat Removal Reactor Water Cleanup | |
ENS 54697 | 9 March 2020 01:21:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On March 8, 2020, at approximately 2021 CDT, Browns Ferry Nuclear Plant Unit 2 experienced an unexpected loss of the 2A Reactor Protection System (RPS). This resulted in Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations, and the initiation of Standby Gas Treatment Trains A and B, and Control Room Emergency Ventilation System Train A. All affected safety systems responded as expected. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The RPS MG Set trip was believed to have been caused by an intermittent short across a spike suppressor, which led to a loss of generator output signal to a voltage regulator. The affected components have been replaced. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1593265. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 54332 | 20 August 2019 16:33:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Specified System Actuation | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On August 20, 2019, at approximately 1133 hours Central Daylight Time (CDT), Browns Ferry Nuclear Plant (BFN), Unit 2 experienced an unexpected loss of the 2A Reactor Protection System (RPS). This resulted in Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations, and initiation of Standby Gas Treatment Trains A, B, and C and Control Room Emergency Ventilation System Train A. All affected safety systems responded as expected. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The cause of the RPS MG Set trip was dirty potentiometer windings on an Over Voltage Relay. The dirt prevented the potentiometer's wiper from contacting its windings, resulting in erratic setpoint values. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Reports 1542603, 1542608, and 1542569. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 54300 | 31 July 2019 21:50:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification Due to an Invalid Actuation of a Containment Isolation Signal | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On July 31, 2019, at approximately 1650 hours Central Daylight Time (CDT), Browns Ferry Nuclear Plant (BFN), Unit 1 experienced a Primary Containment Isolation System (PCIS) Group 6 isolation during performance of surveillance procedure 1-SR-3.3.6.2.3(A), Reactor/Refueling Zone Ventilation Radiation Monitor 1-RM-90-140/142 Calibration and Functional Test. The Group 6 isolation caused the initiation of Standby Gas Treatment (SBGT) Trains A, B, and C, and Control Room Emergency Ventilation (CREV) subsystem B. Unit 1 H2O2 Analyzer and Drywell Radiation Monitor CAM, 1-RM-90-256, were declared Inoperable and Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.5 Condition B was entered. All affected safety systems responded as expected. Plant conditions which initiate PCIS Group 6 actuations are Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. This condition was the result of two cleared fuses in the alarm logic. The apparent cause is a ground fault on the A6 Open Drain Input/Output Module. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Acton Program as Condition Report 1537358. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Reactor Building Ventilation Control Room Emergency Ventilation | |
ENS 54341 | 29 December 2018 07:20:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On December 29, 2018, at approximately 0220 Central Standard Time (CST), Browns Ferry Nuclear Plant (BFN), Unit 3 experienced an unexpected loss of power to the 3A Reactor Protection System (RPS) Bus due to the trip of the 3A RPS motor generator (MG) set. This resulted in Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations, and initiation of Standby Gas Treatment Trains A, B, and C and Control Room Emergency Ventilation System Train A. All affected safety systems responded as expected. This event is being reported as a late 60 day non-emergency notification. This missed notification was identified on August 23, 2019. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The cause of the trip of the RPS MG Set was a failure of the motor winding insulation of all three phases. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Reports 1478564 and 1543534. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 53661 | 16 August 2018 05:00:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On August 16, 2018, at approximately 1736 CDT, Browns Ferry Nuclear Plant (BFN), Unit 2 experienced an unexpected loss of the 2B Reactor Protection System (RPS). This resulted in Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations, and initiation of Standby Gas Treatment Trains A, B, and C and Control Room Emergency Ventilation System Train A. All affected safety systems responded as expected with the exception of the Unit 1 Refuel Zone Supply Fan Outboard Isolation Damper, 1-FCO-64-5, that failed to indicate closed position. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The cause of the RPS MG (Motor Generator) Set trip was a failed (shorted) operating coil associated with the 480 VAC motor starter inside the control box. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Reports 1440047 and 1440050. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 53070 | 10 January 2017 09:00:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On September 15, 2017, during a TVA (Tennessee Valley Authority) review of Operations logs, it was determined that a reportable condition occurred in January 2017 but no NRC report had been made. On January 10, 2017, at 0300 Central Standard Time (CST), Browns Ferry Nuclear Plant, Unit 3, received Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolation signals. The Group 2, 3, 6, and 8 isolations caused the initiation of all three trains of the Standby Gas Treatment (SBGT) system and Control Room Emergency Ventilation (CREV) subsystem 'A.' At 0311 CST, Operations personnel discovered that the 3A1 RPS circuit protector had tripped on undervoltage. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywall Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywall Pressure. At the time of the event, these conditions did not exist; therefore the actuation of the PCIS was invalid. All affected equipment responded as designed. This condition was the result of an undervoltage condition on the 3A1 circuit protector. During trouble shooting, the undervoltage setpoints were found to be 116 VAC and 115 VAC, when the normal as left acceptance band is 109.7 VAC to 111.3 VAC. The 3A RPS protective relays had been previously replaced in September 2016. The most likely cause of the undervoltage condition in these relays is infant mortality. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 51628 | 6 November 2015 14:15:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of an Emergency Diesel Generator | This 60-day telephone notification is being made per the reporting requirements specified by 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to describe an invalid actuation of the Emergency AC electrical power systems, due to invalid start of an emergency diesel generator (EDG). On November 6, 2015, at 0815 (CST), EDG A received a fast start signal inadvertently. Maintenance Fix-It-Now (FIN) personnel, working in the vicinity of the relay panel, made incidental contact with one of the relays in the Diesel Generator Logic Relay Panel which initiated the engine start. The engine started and obtained rated speed and voltage in single unit mode. This was not a valid initiation of EDG A. Operations personnel responded to the EDG actuation by ensuring that the engine was shut down and placed in standby condition in accordance to plant operating instructions. The plant conditions at the time of the EDG A initiation would not have actuated the EDG; therefore, the actuation of EDG A was invalid. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program (CAP) as Condition Report (CR) 1101730. The NRC Resident Inspector was notified of this event. | Emergency Diesel Generator | |
ENS 51085 | 5 April 2015 09:35:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification for an Invalid Primary Containment Isolation System Actuation | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting containment isolation valves in more than one system. On April 5, 2015 at 0435 CDT, during replacement of a failed fuse (2-FU1-64-16A-K33A), Unit 2 Primary Containment Isolation System (PCIS) logic received the B half of the Unit 2 Group 6 isolation signal. This caused initiation of the B and C Standby Gas Treatment, B Control Room Emergency Ventilation, isolation of the Unit 2 reactor zone and all three refueling zone ventilations. This was not a valid initiation of PCIS. Operations personal responded to the PCIS initiation, ensured that all equipment operated as designed, and returned the affected systems back to service. Plant conditions which initiate PCIS Group 6 actuations are Reactor Vessel Low Water (Level 3), High Drywell Pressure, and Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as PER 1010651. The NRC Resident Inspector was notified of this event. | Primary Containment Isolation System Reactor Building Ventilation Control Room Emergency Ventilation | |
ENS 50754 | 26 November 2014 20:27:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On November 26, 2014, at approximately 1427 hours Central Standard Time (CST), the Browns Ferry Nuclear Plant (BFN), 1A Reactor Protection System (RPS) Motor-Generator (MG) Set Power Supply unexpectedly de-energized resulting in a BFN Unit 1 half scram and Primary Containment Isolation System (PCIS) Groups 1, 2, 3, 6, and 8 isolation signals. The PCIS Groups 1, 2, 3, 6, and 8 isolations caused the initiation of all three trains of the Standby Gas Treatment (SBGT) system and Control Room Emergency Ventilation (CREV) subsystem 'A', and isolations of the BFN, Unit 1, Reactor Zone ventilation and BFN, Units 1 and 2, Refuel Zone ventilation (Unit 3 Refuel Zone ventilation was tagged out under 3-TO-2014-0001 at the time of this event). Operations personnel responded to the PCIS initiation, ensured all equipment operated as designed, placed the BFN 1A RPS on alternate power, and reset the RPS logic and PCIS isolations. Plant conditions which initiate PCIS Group 1 actuations are Reactor Pressure Vessel (RPV) Low Low Low Water Level (Level 1), Main Steam Line (MSL) High Flow, MSL Area High Temperature, or MSL Low Pressure. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The apparent cause for this condition was an intermittent problem with the BFN 1A RPS MG Set voltage adjust potentiometer. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 961518. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Pressure Vessel Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation Main Steam Line | |
ENS 50658 | 7 October 2014 15:35:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting containment isolation valves in more than one system. On October 7, 2014, at 2135 (CDT), while in a refueling outage with the reactor non-critical (Mode 5), work activities were in progress that included replacement of an excess flow check valve and execution of a Technical Specification Surveillance Procedure on the Automatic Depressurization System. Subsequent to valving in a level transmitter (LT), water levels in both the variable and reference legs of the LT were disturbed resulting in a Unit 1 full scram and Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolation signals due to receipt of an invalid low reactor water level signal. The PCIS Groups 2, 3, 6, and 8 isolations caused the initiation of Trains A, B, and C of the Standby Gas Treatment System and Control Room Emergency Ventilation Subsystem 'A'. The Reactor and Refuel Zone ventilation fans tripped and the secondary containment dampers isolated. Operations personnel responded to the PCIS initiation, ensured all equipment operated as designed, and placed affected systems back in service. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 943038. The NRC Resident Inspector has been notified of this event. | Secondary containment Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Standby Gas Treatment System Control Room Emergency Ventilation Automatic Depressurization System | |
ENS 50565 | 27 August 2014 16:09:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of General Containment Isolation Signals | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting containment isolation valves in more than one system. On August 27, 2014, at 1109 hours Central Daylight Savings Time (CDT), while in a forced unit outage with the reactor noncritical (Mode 3) and with all control rods fully inserted, instrument mechanics were attempting to backfill reactor water level transmitter (LT) 3-53 sensing lines following performance of LT replacement. During this effort, water levels in both the variable and reference legs of the LT were disturbed resulting in a Browns Ferry Nuclear Plant (BFN) Unit 1 full scram and Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolation signals due to receipt of an invalid low reactor water level signal. The PCIS Groups 2, 3, 6, and 8 isolations caused the initiation of Trains B and C of the Standby Gas Treatment (SBGT) System and Control Room Emergency Ventilation (CREV) Subsystem 'A'. The Reactor and Refuel Zone ventilation fans tripped and the secondary containment dampers isolated. Train A of the SBGT System was tagged out of service during the event. Operations personnel responded to the PCIS initiation, ensured all equipment operated as designed, and placed affected systems back in service. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 928777. The NRC Resident Inspector has been notified of this event. | Secondary containment Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation Control Rod | |
ENS 49942 | 21 January 2014 13:46:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Optional Telephone Notification of an Invalid Primary Containment Isolation Signal | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On January 21, 2014, at 0746 hours Central Standard Time (CST), during performance of the 3C Emergency Diesel Generator (EDG) post modification test instructions, the EDG was supplying a shutdown board in isochronous mode when the 3B Residual Heat Removal (RHR) pump was started causing the voltage to drop to 2100 volts. At this time, Browns Ferry Nuclear Plant (BFN) Unit 3, received a half scram and Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolation signals as a result of losing the 3B Reactor Protection System (RPS) Motor Generator (MG) set due to a time delay relay failure on under voltage. The PCIS groups 2, 3, 6, and 8 isolations caused the initiation of all three trains of the Standby Gas Treatment (SBGT) system, Control Room Emergency Ventilation (CREV) subsystem 'A', and the Refuel fans tripped and isolated. Operations personnel responded to the PCIS initiation, ensured all equipment operated as designed, and placed affected systems back in service. Plant conditions which initiate PCIS group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The apparent cause for this condition was a failure of a 3B RPS MG set time delay relay due to lack of a preventive maintenance strategy. The vendor manual for the time delay relay did not specify a qualified life. The replacement relay specified a replacement schedule of 10 years. The relay that failed was installed for approximately 13 years. To address this condition, preventive maintenance is being developed for MG set time delay relays. In addition, the only remaining relay, similar to the failed relay, is scheduled be replaced on August 25, 2014, for the 2A RPS MG set. The licensee has notified the NRC Resident Inspector. | Reactor Protection System Emergency Diesel Generator Primary Containment Isolation System Primary containment Reactor Building Ventilation Residual Heat Removal Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 49077 | 9 April 2013 10:06:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Report of an Invalid Primary Containment System Isolation Signal | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On April 9, 2013, at 0506 hours Central Daylight Time (CDT), during placement of clearance 2-TO-2013-0003, section 2-099-0001, Browns Ferry Nuclear Plant (BFN), Unit 2, received Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolation signals. The PCIS Groups 2, 3, 6, and 8 isolations caused the initiation of all three trains of the Standby Gas Treatment (SBGT) system and Control Room Emergency Ventilation (CREV) subsystem 'A', and isolations of the BFN, Unit 2, Reactor Zone ventilation and BFN, Units 1, 2, and 3, Refuel Zone ventilation. Operations personnel responded to the PCIS initiation, ensured all equipment operated as designed, and stopped the clearance placement. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The apparent cause for this condition was the outage tagging personnel did not prepare clearance 2-TO-2013-0003 section 2-099-0001 as a stand alone clearance, detail the effect on PCIS initiation on cover placement instructions, place clearance 2-TO-2013-0003 in the right sequence, and perform a thorough review of clearance 2-TO-2013-0003 section 2-099-0001 to identify the missing detail related to PCIS initiation. Personnel performance issues are being addressed in accordance with the Tennessee Valley Authority policies and processes. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 711266. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Primary containment Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 48690 | 23 November 2012 10:35:00 | 10 CFR 50.73(a)(1), Submit an LER | Primary Containment Isolation Actuation Signal During Surveillance | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting multiple Main Steam Isolation Valves (MSIVs). On November 23, 2012 at 0435 Central Standard Time, during performance of Surveillance Instruction 1-SI-3.3.1.A, ASME Section XI System Leakage Test of the Reactor Pressure Vessel and Associated Piping, as the Residual Heat Removal Loop II Shutdown Cooling was being placed in service, Group 1, Division II Primary Containment Isolation System (PCIS) logic groups A2 and B2 actuated resulting in an unanticipated Division II, Group 1 Complete Isolation and subsequent Inboard MSIV closure. The Outboard MSIVs had been previously tagged closed. Plant conditions which initiate Group 1 actuations are Reactor Vessel Low-Low-Low Water Level, Main Steamline Break, and Low Main Steamline Pressure at the Inlet to the Turbine. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The affected equipment responded as designed. This condition was the result of the reactor vessel water level being within two inches of the reactor head vent when Shutdown Cooling was placed into service, causing pressure perturbations. When these perturbations occurred, they gave an indication of low water level, causing the isolation and MSIV closure. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the (Browns Ferry Nuclear Plant) Corrective Action Program as Problem Evaluation Report 646607. The NRC Resident Inspector has been notified. | Main Steam Isolation Valve Primary Containment Isolation System Primary containment Shutdown Cooling Reactor Pressure Vessel Residual Heat Removal | |
ENS 48587 | 18 October 2012 05:01:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephone Notification of an Invalid System Actuation | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On October 17, 2012, at 2301 hours Central Daylight Time (CDT), the 3A Reactor Protection System (RPS) Motor Generator (MG) Set tripped, causing the loss of the 3A RPS Bus, resulting in a half scram. Loss of the 3A RPS Bus automatically isolated Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 which initiated 'A' Train of Control Room Emergency Ventilation (CREV) and 'A', 'B', and 'C' Trains of Standby Gas Treatment (SGT) while isolating the Reactor Water Cleanup System (RWCU). Plant Conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level, High Drywell Pressure, or Reactor Vessel High Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level, High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The affected equipment responded as designed. This condition was caused by the 3A RPS MG-Set motor winding's insulation failing due to age related degradation. To correct this condition, the 3A RPS MG Set was removed, rewound, refurbished, and re-installed. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 625651. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation | |
ENS 48568 | 9 October 2012 16:50:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephonic Notification of an Invalid System Actuation | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On October 9, 2012, at 1050 hours Central Daylight Time (CDT), the 2A Reactor Protection System (RPS) Motor Generator (MG) Set Voltage Regulator failed causing the 2A1 Circuit Protector to trip on undervoltage, resulting in a half scram. In addition, the loss of 2A RPS caused the isolation of Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8, which resulted in the initiation of Standby Gas Treatment (SGT) Trains 'A' and 'C' and the isolation of the 2-RM-90-256 Continuous Air Monitor (CAM), inboard valves, Drywell floor drain inboard isolation valve, and the Reactor Water Cleanup System (RWCU). Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level, High Drywell Pressure, or Reactor Vessel High Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level, High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level or High Drywell Pressure. At the time of the event, these conditions did not exist, therefore, the actuation of the PCIS was invalid. The affected equipment responded as designed. This condition was the result of the failure of the 2A RPS MG Set voltage regulator. To address this condition, the failed voltage regulator was replaced. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 621027. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup | |
ENS 48506 | 18 September 2012 06:45:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Actuation of Containment Isolation Signals | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On September 18, 2012, at 0045 hours Central Daylight Time (CDT), during performance of surveillance procedure 1-SR-3.3.6.2.3(B), Reactor/Refueling Zone Ventilation Radiation Monitor 1-RM-90-141/143 Calibration and Functional Test, a Primary Containment Isolation System (PCIS) partial Group 6 isolation occurred. The partial Group 6 isolation caused the initiation of Standby Gas Treatment (SBGT) subsystems 'A' and 'B' and Control Room Emergency Ventilation (CREV) subsystem 'A', and the isolation of the Unit 1 H2O2 analyzer and the 1-RM-90-256 Continuous Air Monitor (CAM). Due to the isolation of the 1-RM-90-256 CAM, Operations personnel declared the drywall CAM inoperable and entered Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.5 Condition B. Plant conditions which initiate PCIS Group 6 actuations are Reactor Vessel Low Water Level (Level 3), High Drywall Pressure, and Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). At the time of the event, these conditions did not exist, therefore, the partial actuations were invalid. The affected equipment responded as designed. On September 18, 2012, at 0123 hours CDT, Operations personnel commenced restoring the affected systems to normal. At 0132 hours CDT, the 1-RM-90-256 CAM was returned to service, the SBGT subsystems 'A' and 'B' were secured, and TS LCO 3.4.5.B was exited. At 0133 hours CDT, the CREV subsystem 'A' was secured and at 0138 hours CDT, the Unit 1 hours analyzer was returned to service. This condition was the result of improper test setup during performance of 1-SR-3.3.6.2.3(B). It was determined that a jumper installed during the performance of 1-SR-3.3.6.2.3(B) to prevent an invalid actuation was not installed correctly. When the detector lead was lifted, an isolation signal was received. The surveillance procedure was stopped and the equipment was restored to pre-test condition. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 611238. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Reactor Building Ventilation Control Room Emergency Ventilation | |
ENS 48505 | 17 September 2012 09:12:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Actuation of Containment Isolation Signals | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On September 13, 2012, Browns Ferry Nuclear Plant (BFN) personnel completed the installation of three metal-oxide varistors (MOVs), MOV1, MOV2, and MOV3, on the governor of the 3C Emergency Diesel Generator (EDG) as part of a design change. On September 17, 2012, at 0312 hours Central Daylight Time (CDT), during post-modification testing of the 3C EDG, the Direct Current (DC) control circuit breaker tripped, causing a loss of governor control power for the 3C EDG. This event resulted in the loss of the 3B Reactor Protection System (RPS) Bus. In addition, Primary Containment Isolation System (PCIS) groups 3, 6, and 8 successfully isolated. The Steam Vault Booster Fan tripped and the 3B Steam Jet Air Ejector isolated. Standby Gas Treatment (SGT) Trains 'A' and 'B' and Control Room Emergency Ventilation Train 'A' initiated. The SGT Train 'C' was already in service for BFN, Unit 3, Reactor Zone Ventilation. Plant Conditions which initiate PCIS Group 3 actuations are Reactor Vessel Low Water Level or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level, High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The affected equipment responded as designed. On September 17, 2012, at 0335 hours CDT, Operations personnel restored the 3B RPS Bus. This condition was the result of MOV1 and MOV3 operating due to induced current in their associated ground cables. This resulted in grounds which tripped the DC control power breaker. To address this condition, MOV1 and MOV3 were permanently removed. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Problem Evaluation Report 610091. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Emergency Diesel Generator Primary Containment Isolation System Reactor Building Ventilation Reactor Water Cleanup Control Room Emergency Ventilation Steam Jet Air Ejector | |
ENS 48082 | 19 May 2012 05:06:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Specified System Actuation | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On May 19, 2012, at 0006 hours Central Daylight Time (CDT), two fuses were inadvertently contacted with a spiral notebook in panel 9-42 of the auxiliary instrument room. The two blown fuses resulted in a Primary Containment Isolation System (PCIS) partial Group 6 isolation. The partial Group 6 isolation caused the initiation of Standby Gas Treatment subsystems 'A' and 'C', the initiation of Control Room Emergency Ventilation subsystem 'A', and the isolation of the inboard Group 6 valves and ventilation dampers. Plant conditions which initiate PCIS Group 6 actuations are Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, and Reactor Building Ventilation Exhaust High Radiation. At the time of the event, these conditions did not exist; therefore, the partial actuations were invalid. The affected equipment responded as designed. On May 19, 2012, at 0130 hours CDT, Operations personnel reset the partial Group 6 isolation. There were no safety consequences or impact on the health and safety of the public as a result of these events. This event was entered into the Corrective Action Program as Problem Evaluation Report 554165. The NRC Resident Inspector has been notified of this event. | Primary Containment Isolation System Reactor Building Ventilation Control Room Emergency Ventilation | |
ENS 48006 | 11 April 2012 20:15:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation Resulting from Post Maintenance Testing | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system. On April 11 , 2012, at 1515 hours Central Daylight Time (CDT), Operations personnel attempted to transfer the 3B 480V Reactor Motor Operated Valve (RMOV) Board to its alternate power supply for post maintenance testing on the alternate feeder breaker. The 3B 480V RMOV Board failed to transfer to the alternate power supply. Power to the 3B Reactor Protection System (RPS) Bus was lost resulting in a half-scram and actuation of Primary Containment Isolation System (PCIS) Group 6 with the initiation of all three trains (A, B, and C) of Standby Gas Treatment and the initiation of Train 'A' of the Control Room Emergency Ventilation System. Plant Conditions, which initiate PCIS Group 6 actuations, are Low Reactor Vessel Water Level, High Drywell Pressure, High Reactor Building Vent Radiation, or High Refuel Zone Radiation. At the time of the event, these conditions did not exist; therefore, the partial actuations were invalid. The affected equipment responded as designed. On April 11, 2012, at 1520 hours CDT, Operations personnel reset the half-scram from the loss of the 3B RPS Bus. This condition is the result of a bad connection of the breaker to panel contacts due to alignment and/or infrequent manipulation. There were no safety consequences or impact to the health and safety of the public as a result of these events. This event was entered Into the Corrective Action Program as Problem Evaluation Report 535537. The NRC Resident Inspector has been notified of this event. | Reactor Protection System Primary Containment Isolation System Control Room Emergency Ventilation | |
ENS 47450 | 19 September 2011 16:00:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Group 6 Isolation Signal | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation signal affecting more than one system. On September 19, 2011, at 1000 hours Central Daylight Time (CDT), during the performance of a maintenance activity on the Reactor/Refueling Zone Ventilation Radiation Monitor BFN-3-RM-090-0141/143, Browns Ferry Unit 3 received a Primary Containment Isolation System (PCIS) Group 6 isolation. This resulted in isolation of the reactor and refuel zone ventilation systems, initiation of the Standby Gas Treatment System (Trains A, B and C), and the initiation of the Control Room Emergency Ventilation System (Trains A and B). All plant systems responded as designed. There are two divisions of Reactor/Refueling Zone Ventilation Radiation Monitors: BFN-3-RM-090-0140/142 and BFN-3-RM-090-0141/143. A downscale or inoperable signal in both divisions will initiate the PCIS Group 6 isolation. Prior to the performance of the maintenance activity, BFN-3-RM-090-0140/142 was functional. However, during a field walkdown after the PCIS Group 6 isolation, relay BFN-3-RLY-064-16AK62A for BFN-3-RM-090-0140/142 was discovered to be chattering. A chattering relay could cause momentary loss of continuity between the contacts which would effectively generate a spurious isolation signal from that division. Thus, when 3-RM-090-0141/143 was made inoperable by the surveillance, the PCIS Group 6 logic was made-up. The PCIS Group 6 isolation was reset at 1008 CDT. This event was entered in the Corrective Action Program as Problem Evaluation Report (PER) 434799. There were no safety consequences or impact on the health and safety of the public as a result of these events. The NRC Senior Resident Inspector was notified. | Primary Containment Isolation System Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 47003 | 1 May 2011 07:44:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Rps (Scram) Actuation | This 60-day telephone notification is being made under the reporting requirements specified by 10 CFR 50.13(a)(2)(iv) and 10 CFR 50.73(a)(I) to describe an invalid RPS (Scram) actuation. On May 1, 2011, at 0244 hours Central Daylight Time (CDT), during a non-refueling outage, Browns Ferry Unit 2 was at 000 percent power in Mode 4 with all control rods already inserted into the core when an invalid full scram signal was received. The reactor scram signal was determined to be the result of a failure of the Unit 2 Unit Preferred Motor-Motor-Generator Set, which caused an electrical transient and resulted in noise In adjacent nuclear instrumentation cables. The scram signal was Initiated due to Invalid Indications (spikes) associated with the C and D Intermediate Range Monitors (IRMs). The spikes did not render the IRMs inoperable as these were momentary spikes. Therefore, the actuation was invalid. The scram was reset at 0312 CDT. This event was entered In the Corrective Action Program as Service Request (SR) 362127, which generated Problem Evaluation Report (PER) 362897. There were no safety consequences or impact on the health and safety of the public as a result of these events. The NRC Resident Inspector has been notified of this event. | Intermediate Range Monitor Control Rod | |
ENS 46880 | 30 March 2011 19:43:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephonic Notification of Invalid Rps Signal Due to Loss of Variable Leg of Level Transmitter | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv) and 10 CFR 50.73(a)(1) to describe an invalid RPS (SCRAM) actuation. On March 30, 2011, at 1443 hours Central Daylight Time (CDT), during a refueling outage, Browns Ferry Unit 2 received an invalid Common Accident Signal (CAS) as a result of maintenance activities. The CAS caused a full Unit 2 Reactor SCRAM and associated system initiations. The CAS was initiated due to invalid indications on both Channels A and B of low-low-low reactor water level, which did not exist; therefore, the actuation was invalid. The affected equipment responded as designed. All four Unit 1/2 Emergency Diesel Generators auto started and all four Unit 3 Emergency Diesel Generators auto started. Unit 2 received a full Reactor SCRAM and Core Spray Pumps A, B, C, and D auto started and injected into the reactor. Unit 2 Division I Residual Heat Removal (RHR) System was in Shutdown Cooling with only the C pump in service. The 'A' RHR pump auto started and Shutdown Cooling flow increased, as expected. Unit 2 Division II RHR System had been tagged out for maintenance and did not respond. High Pressure Coolant Injection and Reactor Core Isolation Cooling received auto initiation signals; however, their steam isolation valves were tagged closed and the systems did not start. The Inboard Main Steam Isolation Valves (MSIVs) isolated as a result of the CAS signal. The outboard MSIVs had been previously closed and tagged for refueling outage purposes. This event was entered in the Corrective Action Program as Service Request (SR) 346544, which generated Problem Evaluation Report (PER) 346568. There were no safety consequences or impact on the health and safety of the public as a result of these events. The NRC Senior Resident Inspector has been notified. The shutdown reactor water level transmitters share a common variable leg. When maintenance unrelated to the transmitters was performed, the variable leg was lost causing the low-low-low reactor water level SCRAM signal to be generated. | High Pressure Coolant Injection Emergency Diesel Generator Main Steam Isolation Valve Reactor Core Isolation Cooling Shutdown Cooling Core Spray Residual Heat Removal | |
ENS 46881 | 27 March 2011 01:05:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephonic Notification of Invalid Primary Containment Isolation Signal Due to Maintenance | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv) and 10 CFR 50.73(a)(1) to describe an invalid actuation of multiple secondary containment isolation signals affecting more than one system. On March 26, 2011, at 2005 hours Central Daylight Time (CDT), following planned maintenance activities, an unplanned actuation of secondary containment isolation signals affecting containment isolation valves in more than one system occurred and resulted in a partial Primary Containment Isolation System (PCIS) (Group 6, Secondary Containment) isolation and receipt of a Unit 2 Reactor Building Ventilation Abnormal Alarm. Unit 2 was in Mode 4, in a refueling outage, and at 0 percent power (0 MWT). Units 1 and 3 were both in Mode 1 and operating at approximately 100 percent power. Plant Conditions, which initiate PCIS (Group 6, Secondary Containment) actuations, are Low Reactor Vessel Water Level, High Drywell Pressure, High Reactor Zone Exhaust Radiation, or High Refueling Floor Exhaust Radiation. At the time of the event, these conditions did not exist; therefore, the partial actuations were invalid. For this occurrence, equipment normally affected by a complete Group 6 isolation responded as follows. Trains 'B' and 'C' of Standby Gas Treatment (SGT) System started while Train 'A' did not. Train 'B' of the Control Room Emergency Ventilation System (CREVS) started while Train 'A' did not. Secondary containment (Unit 1, 2, and 3 Reactor and Refuel Zones) normal ventilation isolated - fans stopped and dampers closed. Suppression Chamber Exhaust Inboard Isolation Valve 2-FSV-64-32 and Drywell Exhaust Inboard Isolation Valve 2-FCV-64-29 did not close. Because only a partial (B part of the logic) PCIS isolation was relayed, only the affected Group 6 equipment received the isolation demand. All equipment that received the isolation demand responded and performed as designed. Control Room personnel commenced actions of the applicable Alarm Response Procedure and the Group 6 Ventilation System Isolation Abnormal Operations Procedure. Train 'A' of the SGT System was later started. This event was entered in the Corrective Action Program as Service Request (SR) 344609 and Problem Evaluation Report (PER) 344680. There were no safety consequences or impact on the health and safety of the public as a result of these events. The NRC Resident Inspector has been notified of this event. Although Group 6 PCIS testing occurred earlier that day, the licensee could not determine the signal initiator and considered it spurious. | Secondary containment Primary Containment Isolation System Primary containment Reactor Building Ventilation Control Room Emergency Ventilation | |
ENS 46656 | 3 January 2011 21:15:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Telephone Notificaton Concerning Invalid Containment Isolation System Actuations | This 60-day telephone notification is being made under the reporting requirements specified by 10 CFR 50.73(a)(2)(iv) and 10 CFR 50. 73(a)(1) to report four closely-spaced invalid actuations of general containment isolation signals affecting more than one system. Four events of unplanned actuations of general containment isolation signals affecting containment Isolation valves in more than one system occurred during planned transfers of power between the normal and alternate power supply for the 3A 480V Shutdown Board. The first event occurred on January 3, 2011, at 1515 hours Central Standard Time (CST), with Unit 3 in a forced outage and at 0 percent power (0 MWT). The electrical power to the 3A Reactor Protection System (RPS) was interrupted during the planned transfer of the 3A 480V Shutdown Board from its normal supply to its alternate power supply. During the transfer, the alternate feeder breaker did not close. An attempt was made to return to the normal power supply; however, the normal feeder breaker did not initially close but did close on re-attempt. This resulted in the interruption of power to the 3A 480V Shutdown Board, which caused the 3A RPS to de-energize, resulting in a half scram and the actuation of Primary Containment Isolation System (PCIS) logic Groups 2, 3, 6, and 8, and the initiation of Trains A, B, and C Standby Gas Treatment and Train A Control Room Emergency Ventilation. Plant conditions, which require PCIS actuations and the associated system initiations (e.g., low reactor water level, high drywell pressure, abnormal area radiation level, or high area temperature), did not exist; therefore, the actuation was invalid. The affected equipment responded as designed. On January 3, 2011, at approximately 1620 hours CST, Unit 3 Operations personnel restored 3A RPS power and re-aligned affected equipment, as appropriate. This event was entered in the Corrective Action Program as Problem Evaluation Report (PER) 305070. Subsequent related failure to transfer events of the 3A 480V Shutdown Board occurred on January 4, 2011, at 2321 hours, on January 5, 2011, at 0448 hours, and on January 5, 2011, at 0841 hours. In each event the plant conditions which require PCIS actuations and the associated system initiation did not exist; therefore, the actuations were invalid. In each of the three subsequent events the affected equipment started and functioned successfully with one exception. During the last event, Main Control Room indication of a Secondary Containment outboard isolation damper closure was indeterminate (i.e., double-lit). The damper was declared inoperable, and the associated Technical Specification LCO 3.6.4.2 Action was taken. (A) work order (was) issued to investigate the problem repaired a damper limit switch. This problem was entered in the Corrective Action Program as PER 305062. PERs were generated for each of these events (PER 305865, PER 305421, and PER 305893). All of these events were consolidated into PER 305070. The Browns Ferry NRC Senior Resident Inspector has been notified. | Secondary containment Reactor Protection System Primary Containment Isolation System Control Room Emergency Ventilation | |
ENS 46066 | 2 July 2010 17:32:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System Actuation from a Loss of Power to the Reactor Protection System (Rps) 3A | This 60 day telephone notification is being made in-lieu of a written report under the requirements specified by 10 CFR 50.73(a)(2)(iv) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting more than one system. On May 12, 2010, at 1232 hours Central Daylight Time (CDT), with Unit 3 operating at 100 percent thermal power the electrical power to the 3A RPS was interrupted during the transfer of the 3A 480V shutdown board from its alternate supply to its normal power supply. During the transfer, the normal breaker did not close for several seconds. This resulted in the interruption of power to the 3A shutdown board which caused the 3A RPS to de-energize, resulting in a half scram and the actuation of PCIS logic Groups 2, 3, 6, and 8, and the initiation of Trains B and C of Standby Gas Treatment, and the initiation of Train A Control Room Emergency Ventilation. Plant conditions which require PCIS actuations and the associated system initiations (e.g., low reactor water level, high drywell pressure, abnormal area radiation level, or high area temperature) did not exist; therefore, the actuation was invalid. The affected equipment responded as designed. On May 12, 2010, by approximately 1342 hours CDT, Unit 3 operations personnel restored the 3A RPS power and realigned affected equipment as appropriate. There were no safety consequences or impact on the health and safety of the public as a result of this event. The event was entered into the corrective actions program as PER 229613. The NRC Senior Resident Inspector has been notified. | Reactor Protection System Primary Containment Isolation System Control Room Emergency Ventilation | |
ENS 46054 | 30 April 2010 21:48:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System (Pcis) Actuation from a Loss-Of-Power to Reactor Protection System (Rps) 1A | This 60-day telephone notification is being made in lieu of a written report, under reporting requirements specified by 10 CFR 50.73(a)(1), 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system. On April 30, 2010, at 1648 hours Central Daylight Time (CDT) with Unit 1 at 100 percent thermal power, while attempting to change a light bulb, the light socket shorted causing a loss of 1A RPS. The loss resulted in Groups 2, 3, 6, and 8 primary containment isolations, and initiation of Standby Gas Treatment and Control Room Emergency Ventilation. BFN's review of the event found that the bulb caused a direct short and caused the loss of RPS 1A. Plant conditions which require PCIS actuations and system initiations (e.g., low reactor water level, high drywall pressure, abnormal area radiation level, high area temperature) did not exist, therefore the actuation was invalid. The affected equipment responded as designed. On April 30, 2010, at approximately 1702 hours CDT Unit 1 operations personnel restored 1A RPS and by 1728 hours CDT, the recovery of the loss of 1A RPS was complete. This event had no safety consequences or impact on the health and safety of the public. The event is documented in the Corrective Action Program (PER 227662). The NRC Resident Inspector has been notified. | Reactor Protection System Primary Containment Isolation System Primary containment Control Room Emergency Ventilation | |
ENS 46046 | 27 April 2010 22:37:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Group 6 Containment Isolation | This notification is being made in lieu of a written report under the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a Group 6 containment isolation signal affecting more than one system. On April 27, 2010, at 1737 hours Central Daylight Time, with Unit 3 operating at 100 percent thermal power, Unit 3 received a Group 6 ventilation system isolation signal during the performance of a maintenance activity on a Unit 3 Reactor/Refuel Zone Radiation Monitor, 3 RM-90-141/143. This resulted in isolation of the reactor and refuel zone ventilation systems, initiation of Standby Gas Treatment system (Trains A, B, and C) and the Control Room Emergency Ventilation system (Train A). All equipment responded to the Group 6 ventilation system isolation signal in accordance with the plant design. However, during the recovery effort, one of the Unit 3 Reactor Building Ventilation dampers failed to indicate fully closed. Operations personnel verified by inspection that the damper was fully closed. There were no safety consequences or impact on the health and safety of the public as a result of this event. The event was entered into the Corrective Action Program (CAP) as PER 227125. From PER 227125, trouble shooting determined a relay coil had been installed upside down when the coils were recently replaced. The NRC Senior Resident Inspector has been notified. | Reactor Building Ventilation Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 44294 | 14 April 2008 18:08:00 | 10 CFR 50.73(a)(1), Submit an LER | Inadvertant Deenergization of Group Six Logic Circuit | This is a 60 day telephone notification is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) describing an invalid actuation of general containment isolation signal (Group 6) affecting more than one system. On April 14, 2008 at 1308 hours Central Daylight Time (CDT), with Unit 3 in mode 4, an unanticipated Group 6 primary containment isolation signal (PCIS) was generated during the placement of a clearance. During the placement of the clearance, plant personnel removed a fuse which deenergized Group 6 PCIS logic. This resulted in the auto start of train A of the control room ventilation system, auto start of trains A and C of the standby gas treatment (SGT) systems, and the isolation of the reactor zone and refuel zone normal ventilation systems. All systems responded according to plant design. Train B of the SGT system did not auto start because only the A channel PCIS was affected during the implementation of the clearance. Train B of SGT is only affected by the B channel PCIS logic. By 1444 hours CDT, the fuse was reinstalled, the affected systems were returned to standby readiness. There were no safety consequences or impact to the health and safety to the public. The event was entered into TVA's corrective action program. The reference corrective action document is PER 142243. The Senior Resident inspector had been notified of this report. | Primary containment | |
ENS 43083 | 10 November 2006 06:10:00 | 10 CFR 50.73(a)(1), Submit an LER | Edg Actuation Due to Accidental Switch Mispositioning | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of any of the equipment specified in paragraph 50.73(a)(2)(iv)(B). In this case, the equipment actuated was the four Unit 1 and 2 emergency diesel generators (EDG) A, B, C, and D. These EDGs are common equipment for Browns Ferry Units 1 and 2. On November 10, 2006, personnel were performing surveillance requirement (SR) test 0-SR-3.8.1.6, Common Accident Signal Logic. At this time Browns Ferry Unit 1 was shutdown and defueled, and Unit 2 was operating at 100% thermal power. During conduct of this testing, at 0010 hours CST, all four of the common U1/2 EDGs were inadvertently started. This occurred when test personnel (non-licensed) inadvertently placed a keylock switch in the wrong position during the equipment restoration portion of the testing. The SR test step being performed was correct, but it was incorrectly implemented. All affected equipment operated per the plant design in response to the switch manipulation, with each of the four EDGs properly starting and running in response to the invalid start signal. No loss of normal plant electrical power occurred, and none of the EDGs connected to its associated 4-Kv shutdown board. The EDGs were shutdown in accordance with plant operating procedures approximately 13 minutes after their start. Since no actual plant condition existed which required the EDGs to start, and since the starts occurred inadvertently as a result of a human error during a test performance, this event is classified as invalid. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. (Reference BFN corrective action document PER 114498). The NRC Senior Resident Inspector has been notified.
| Emergency Diesel Generator | |
ENS 42878 | 20 August 2006 01:02:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System Actuation | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of multiple main steam isolation valves. On August 19, 2006, at 2002 hours CDT, with Unit 3 shutdown in Mode 3 following an earlier manual scram of Unit 3 (reference Event Number 42787), the EHC System along with the turbine bypass valves was being used to cool down/depressurize the reactor. The EHC system is used to supervise the turbine control valves and turbine bypass valves to control reactor pressure. The EHC system was subsequently removed from service for the repair of a previously identified system fluid leak. Following the shutdown of EHC system, reactor pressure and temperature were allowed to slowly increase. At 2240 hours CDT upon completion of the leak repair, operations personnel placed an EHC pump back in service in accordance with the system operating instruction to support post-maintenance testing activities. However, when the EHC system was returned to service, the pressure control set point was lower than the reactor pressure. The significance of the delta between the EHC setpoint and the actual reactor pressure was not recognized by operations. Because the actual reactor pressure was higher than the existing control set point, the EHC system responded by opening turbine bypass valves to lower the reactor pressure. Operations personnel observed the bypass valve response, identified the cause, and raised the pressure control set point. This action caused the bypass valves to rapidly close. The abrupt cessation of steam flow caused by the rapid closure of the bypass valves initiated a reactor pressure transient that affected the reactor water level instrumentation. The affected level instruments' output signals exhibited a ringing effect of a magnitude sufficient to reach the low level set point for primary containment isolation system (PCIS) Group 1 actuation. The Group 1 isolation logic actuated in accordance with its design, and the main steam isolation valves and the main steam line drain valves automatically closed. Designed time delays in other logic circuits affected by these water level signals prevented additional equipment actuation during this event. Actual reactor water level did not change, remaining within the normal level band; therefore, the isolation signal is considered invalid. All equipment responded in accordance with the plant design. Upon verification that no actual water level anomaly existed and that the transient instrumentation response had stabilized, the affected PCIS logic was reset, and equipment was realigned as appropriate. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. The NRC senior resident inspector has been notified of this report. Reference corrective action document PER 109118. | Main Steam Isolation Valve Primary Containment Isolation System Main Steam Line | |
ENS 42877 | 19 August 2006 00:58:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System (Pcis) Actuation | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting more than one system. On August 18, 2006, at 1958 hours CDT, with Unit 2 operating at 100% thermal power, the electrical power to reactor protection system (RPS) bus 2B was interrupted during the performance of surveillance testing on RPS circuit protectors 2B1 and 2B2. The RPS buses 2A and 2B are normally powered from motor-generator (MG) sets 2A and 2B, respectively. During testing or maintenance intervals affecting either the MG set or the normal supply circuit protectors, the affected RPS bus is powered from a transformer supply through alternate power circuit protectors 2C1 and 2C2. Power to RPS bus 2B, which was being powered through the alternate power circuit protectors via a temporary transformer, was interrupted when circuit protector 2C1 actuated on a sensed under voltage condition. The Primary Containment Isolation System (PCIS) logic circuits powered from RPS bus 2B were de-energized, and PCIS logic Groups 2, 3, 6, and 8 were actuated. None of the plant conditions which require PCIS Groups 2, 3, 6, or 8 actuation (e.g., low reactor water level, high drywell pressure, abnormal area radiation levels, high area temperature, etc.) existed; therefore, these actuations are considered invalid. The following actuations/isolations occurred: Group 2: Isolation of the Pressure Suppression Chamber head tank pumps and Drywell Floor and Equipment Drains Isolation; Group 3: Isolation of the reactor water clean-up system; Group 6: Initiation of the Standby Gas Treatment System, Initiation of Control Room Emergency Ventilation, and Isolation of the reactor zone and refuel zone normal ventilation systems; Group 8: This logic isolates the Traversing In-core Probes (TIP) if they are inserted. The TIPs were not inserted at the time of this event. All equipment responded in accordance with the plant design. At the time of the loss of power from the alternate source, the surveillance testing had already been completed and activities were in progress to transfer the RPS bus back to its normal supply. These actions were completed and RPS Bus 2B was re-energized from RPS MG set 2B. The affected logic was reset, and equipment was realigned as appropriate. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. The NRC Senior Resident Inspector has been notified of this report. Reference corrective action document PER 109090. Also see similar NRC event number 42837. | Reactor Protection System Primary Containment Isolation System Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 42867 | 9 August 2006 14:51:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Eecw Pump Actuation During Testing | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of an emergency service water system component that does not normally run and which provides an ultimate heat sink. At 0951 hours CDT on August 9, 2006, with Unit 1 defueled and Units 2 and 3 operating at 100% power, the B3 Emergency Equipment Cooling Water (EECW) pump was tripped when an undervoltage relay was manually operated during functional testing of relaying associated with the 1B Core Spray (CS) pump breaker. While operations personnel were responding to the pump trip, but before the testing activity could be halted, performance of subsequent steps in the functional testing activity resulted in an automatic start of this same pump and then another trip when a companion undervoltage relay was manually operated. Auto-starting of associated EECW pumps upon CS pump starts is part of the equipment logic and had been anticipated, and the B3 EECW pump had been placed in service prior to beginning the relay functional testing to avoid an automatic start. The potential for tripping loads other than the 1B Core Spray pump breaker was discussed in the pre job briefing, however, the actual test instruction steps did not provide detail sufficient to ensure only specific undervoltage relay contacts were operated. Rather than operating only specific relay contacts, test personnel operated the entire relay, resulting in the unplanned trip, restart, and trip of the B3 EECW pump. The logic downstream from the manually operated undervoltage relays and the B3 EECW pump responded in accordance with the plant design. No other plant equipment was affected during this event, though the 2B Core Spray pump would have also tripped had it been running at the time the undervoltage relays were operated. The B3 EECW pump was secured, and the testing activity was suspended. Other operating EECW pumps were not affected and no degradation of EECW system function occurred. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. Reference corrective action document PER 108425. The licensee notified the NRC Resident Inspector. | Service water Core Spray Emergency Equipment Cooling Water | |
ENS 42837 | 18 July 2006 09:47:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System Actuation Due to Loss of Power to One Reactor Protection System Bus | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of general containment isolation signals affecting more than one system. On July 18, 2006, at 0447 hours CDT, with Unit 2 operating at 100% thermal power, the electrical power to reactor protection system (RPS) bus 2A was interrupted during the performance of surveillance testing on RPS circuit protectors 2A1 and 2A2. The RPS buses 2A and 2B are normally powered from motor-generator (MG) sets 2A and 2B, respectively. During testing or maintenance intervals affecting either the MG set or the normal supply circuit protectors, the affected RPS bus is powered from a transformer supply through alternate power circuit protectors 2C1 and 2C2. Power to RPS bus 2A, which was being powered through the alternate power circuit protectors via a temporary transformer, was interrupted when circuit protector 2C1 actuated on a sensed undervoltage condition. The Primary Containment Isolation System (PCIS) logic circuits powered from RPS bus 2A were de energized, and PCIS logic Groups 2, 3, 6, and 8 were actuated. None of the plant conditions which require PCIS Groups 2, 3, 6, or 8 actuation (e.g., low reactor water level, high drywell pressure, abnormal area radiation levels, high area temperature, etc.) existed, therefore these actuations are considered invalid. The following actuations/isolations occurred: Group 2: Isolation of the Pressure Suppression Chamber head tank pumps; and Drywell Floor and Equipment Drains Isolation Group 3: Isolation of the reactor water clean-up system Group 6: Initiation of the Standby Gas Treatment System; Initiation of Control Room Emergency Ventilation; and Isolation of the reactor zone and refuel zone normal ventilation systems. Group 8: This logic isolates the Traversing Incore Probes (TIP) if they are inserted. The TIPs were not inserted at the time of this event. All equipment responded in accordance with the plant design. Upon loss of power from the alternate source, the surveillance testing was suspended, and RPS Bus 2A was re energized from RPS MG set 2A. The affected logic was reset, and equipment was realigned as appropriate. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. The NRC senior resident inspector has been notified of this report. Reference corrective action document PER 106999. | Reactor Protection System Primary Containment Isolation System Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 42389 | 13 January 2006 17:57:00 | 10 CFR 50.73(a)(1), Submit an LER | Unplanned, Invalid Actuation of Emergency Diesel Generator | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of any of the equipment specified in paragraph 50.73(a)(2)(iv)(B). In this case, the equipment actuated was emergency diesel generator (EDG) A. This EDG is common equipment for Units 1 and 2. On January 13, 2006, troubleshooting was being conducted by maintenance personnel to determine the cause of observed alarm malfunctions on the EDG A local annunciator panel. Browns Ferry Unit 1 was shutdown and defueled and Unit 2 was operating at 100% thermal power. During this troubleshooting activity, at 1157 hours CST, EDG A was inadvertently started. The exact cause of the start could not be conclusively determined. EDG A properly started and ran in response to the invalid start signal. No loss of normal plant electrical power occurred, and the EDG did not connect to its associated shutdown board. The EDG was allowed to run for approximately one hour, and then it was shut down in accordance with plant operating procedures. Since no actual plant condition existed which required the EDG to start, and since the start occurred inadvertently, most likely as a result of a human error during the electrical circuit troubleshooting effort, this EDG start is classified as invalid. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. (Reference BFN corrective action document PER 96291). The licensee notified the NRC Resident Inspector. | Emergency Diesel Generator | |
ENS 42215 | 15 November 2005 14:05:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System (Pcis) Actuation | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system. On November 15, 2005, while operating at 100% thermal power, at 08:05 hours CST, Browns Ferry Unit 2 incurred an inadvertent, invalid actuation of the PCIS Group 6 logic. One reactor zone ventilation exhaust radiation monitor (the B channel) was indicating downscale due to a pre-existing maintenance issue, and, during activities to formally place the channel in a tripped status in accordance with the applicable Technical Specifications, the PCIS logic fuse for the opposite (A channel) radiation monitor was inadvertently removed rather than the fuse for the B channel. The PCIS logic responded as designed to the condition of both radiation monitors being downscale, and a Group 6 logic actuation resulted. The actuation was invalid because it resulted from an error related to an equipment tagging activity; there were no actual plant conditions which required the associated equipment actuations/isolations to occur. The following equipment actuations/isolations occurred: Unit 2 Group 6
* reactor zone and refuel zone normal ventilation systems * drywell-torus differential pressure compressor * drywell-torus Hydrogen/Oxygen analyzers * drywell radiation continuous air particulate monitor All equipment responded in accordance with the plant design. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for resolution. The NRC senior resident inspector has been notified. | Primary Containment Isolation System Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 41181 | 28 September 2004 18:02:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System Actuation from Loss-Of-Power to Reactor Protection System (Rps) Bus 2A | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system. On September 28, 2004, with Unit 2 operating at 100% thermal power, at 1302 hours CDT during maintenance work associated with protective relaying on 480 VAC Shutdown Board 2A, the board was inadvertently tripped. Associated RPS motor-generator (MG) set 2A lost power, and RPS bus 2A, which is powered from this MG set, was de-energized. Primary Containment Isolation System (PCIS) logic circuits powered from this bus lost power, and PCIS logic Groups 2, 3, 6, and 8 were actuated. The following actuations/isolations occurred: Group 2: Isolation of the Pressure Suppression Chamber head tank pumps (and) Drywell Floor and Equipment Drains Group 3: Isolation of the reactor water cleanup system. Group 6: Initiation of the Standby Gas Treatment System (and) Initiation of Control Room Emergency Ventilation (and) Isolation of the reactor zone and refuel zone normal ventilation system. Group 8: This logic isolates the Traversing Incore Probes (TIP) if they are inserted. The TIPs were not inserted at the time of this event. All equipment responded in accordance with the plant design. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for resolution. The NRC senior resident inspector has been notified. | Reactor Protection System Primary Containment Isolation System Reactor Water Cleanup Standby Gas Treatment System Control Room Emergency Ventilation | |
ENS 41180 | 25 September 2004 23:14:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System Actuation from Loss-Of-Power to Reactor Protection System (Rps) Bus 3B | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73 (a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system. On September 25, 2004, with Unit 3 operating at 100% thermal power, at 1814 hours CDT, a voltage regulator problem occurred on RPS motor-generator (MG) set 3B. The associated RPS circuit protectors sensed an undervoltage condition and opened, thereby de-energizing RPS bus 3B. Primary Containment Isolation System (PCIS) logic circuits powered from this bus lost power, and PCIS logic Groups 2, 3, 6, and 8 were actuated. The following actuations/isolations occurred: Group 2: Isolation of the Pressure Suppression Chamber head tank pumps, Drywell Floor and Equipment Drains Isolation. Group 3: Isolation of the reactor water clean-up system. Group 6: Initiation of the Standby Gas Treatment System, Initiation of Control Room Emergency Ventilation, Isolation of the reactor zone and refuel zone normal ventilation systems. Group 8: This logic isolates the Traversing Incore Probes (TIP) if they are inserted. The TIPs were not inserted at the time of this event. All equipment responded in accordance with the plant design, with the exception that Unit 2 refuel zone ventilation system supply inboard isolation damper 2-DMP-064-0006 failed to close. The series damper, 2-DMP-064-0005, fully closed, therefore there would have been no impact to secondary containment integrity had this been an actual event. The damper's failure to close resulted from a sticking solenoid valve which was subsequently replaced. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for resolution. The NRC senior resident inspector has been notified. | Secondary containment Reactor Protection System Primary Containment Isolation System Standby Gas Treatment System Control Room Emergency Ventilation |