Semantic search
Jump to navigation
Jump to search
| Entered date | Event description | |
|---|---|---|
| ENS 55200 | 20 April 2021 15:36:00 | A non-licensed, employee supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been terminated. The licensee notified the NRC Resident Inspector. |
| ENS 54709 | 13 May 2020 13:10:00 | 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. |
| ENS 54332 | 16 October 2019 10:22:00 | 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. |
| ENS 53070 | 14 November 2017 15:13:00 | 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. |
| ENS 50925 | 25 March 2015 21:37:00 | On March 25, 2015, at approximately 1413 CDT, a Browns Ferry Nuclear (BFN) employee fell approximately 6 feet and sustained a laceration to his forehead and potential other injuries. The individual had been working in the Unit 2 drywell, which is a contaminated area. The individual was able to be removed from his anti-contamination clothing prior to leaving the Radiological Controlled Area (RCA). The individual was surveyed by a Radiation Protection (RP) technician and had slight contamination (150 cpm (counts per minute)) on his forehead in the area near the laceration. No survey of his back was performed due to being on a stretcher. At 1457 CDT, the individual was transported to an off-site medical facility. A BFN RP technician accompanied the individual to the hospital. Subsequent survey of the individual at the medical facility determined that no other areas of contamination existed. The individual was successfully decontaminated at the medical facility during initial treatment and all locations have been free released. All contaminated materials have been properly controlled. This event is reportable in accordance with 10CFR50.72(b)(3)(xii) any event requiring the transport of a radioactively contaminated person to an offsite medical facility for treatment. This event has been entered into the Corrective Action Program (CAP) in SR# 1004507. The NRC Resident Inspector has been notified. The individual was transported to Decatur Morgan General Hospital in Decatur, Alabama for decontamination and follow-up medical treatment. |
| ENS 50265 | 10 July 2014 09:17:00 | At 0445 (CDT) on July 10, 2014, Browns Ferry Unit 2 initiated actions to commence a reactor shutdown to comply with TS LCO 3.0.3. TS LCO 3.0.3 was entered at 0355 (CDT) and was required due to the 'C' Emergency Diesel Generator becoming inoperable after isolating a leak on the Emergency Equipment Cooling Water System. Currently, a 7 day TS LCO Action 3.5.1.A is in effect due to ongoing scheduled Core Spray Loop I maintenance outage. The declaration of inoperability of the equipment supported by the 'C' Emergency Diesel Generator, Core Spray Loop II, along with the redundant Core Spray system inoperable for maintenance resulted in TS LCO 3.0.3 for Unit 2. TS LCO 3.0.3 requires actions to be initiated within one hour; to place the unit in MODE 2 within 10 hours; MODE 3 within 13 hours; and MODE 4 within 37 hours. This event requires a 4 hour report lAW 50.72(b)(2)(i), 'The initiation of any nuclear plant shutdown required by the plant's Technical Specifications.' Actions were taken to restore the Core Spray System to Operable status and LCO 3.0.3 was exited at 0735 (CDT) on July 10, 2014. The NRC Resident Inspector has been notified. This event was entered into the Corrective Action Program. Browns Ferry Unit 2 had reduced power to 98% when LCO 3.0.3 was exited, the power reduction was suspended, and preparations are being made to return power to 100%. There is no impact on Units 1 or 3. |