Semantic search
| Discovered date | Reporting criterion | Title | Event description | |
|---|---|---|---|---|
| ENS 56570 | 13 June 2023 03:33:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Accident Mitigation - High Pressure Coolant Injection Declared Inoperable | The following information was provided by the licensee via email: At 2333 EDT on June 12, 2023, the division 2 Mechanical Draft Cooling Tower (MDCT) Fan `D' was declared inoperable due to a trip of the fan while running in high speed. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High-Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI room cooler. The cause of MDCT Fan `D' trip is currently unknown with trouble shooting being developed for remediation of the condition. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The NRC Senior Resident Inspector has been notified.
The purpose of this notification is to retract a previous event notification (EN) 56570 reported on June 13, 2023, at 0602 EDT. The cause of the fan trip was a failed vibration switch. At 0429 EDT on June 14, 2023, the vibration switch was replaced, the MDCT fan "D" was tested satisfactory for operability, and the UHS, emergency diesel generator 13/14, and MDCT were declared operable. Following the initial EN, further analysis of the condition was performed utilizing a previously performed gothic analysis model (to perform HPCI room heat-up calculations) which bounded this condition. Based on the initial conditions at the time of the indication loss, specifically HPCI room and suppression pool temperature, it was determined that the resulting worst case post-accident room temperature was sufficiently low enough to provide margin to HPCI operability without the room cooler in service for the required mission time. No other concerns were noted during the event. HPCI remained operable and there was no loss of safety function. The fan trip did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). Therefore, the NRC non-emergency 10CFR50.72(b)(3)(v)(D) report was not required and the NRC report 56570 can be retracted, and no licensee event report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The licensee notified the NRC Resident Inspector. Notified R3DO (Nguyen) |
| ENS 56295 | 4 January 2023 06:48:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Inoperable | The following information was provided by the licensee via email: At 0148 EST on January 4, 2023 it was identified that P4400F603B, Division 2 Emergency Equipment Cooling Water (EECW) Supply Isolation Valve, lost position indication. Division 2 EECW System was declared inoperable due to the potential that this valve may not be capable of performing its safety function to automatically isolate the safety related Division 2 EECW system from the non-safety related Reactor Building Closed Cooling Water (RBCCW) system. Because the Division 2 EECW system provides cooling to the High Pressure Coolant Injection (HPCI) room cooler, HPCI was also declared inoperable; therefore, this condition is being reported as an eight-hour, non--emergency notification per 10 CFR 50.72(b)(3)(v)(D). At 0240 EST, position indication was restored and Division 2 EECW and HPCI was returned to operable following inspection of the associated motor control center (MCC) and testing of the associated fuses. The cause of the loss of indication is under investigation. The Senior NRC resident inspector has been notified.
The following retraction was received from the licensee via email: The purpose of this notification is to retract a previous Event Notification, EN 56295, reported on 1/4/2023. Following the initial EN, further analysis of the condition was performed utilizing a gothic analysis model to perform HPCI room heat-up calculations. Based on the initial conditions at the time of the indication loss, specifically HPCI room and Suppression Pool temperature, it was determined that the resulting worst case post-accident room temperature was sufficiently low enough to provide margin to HPCI operability without the room cooler in service for the required mission time. No other concerns were noted during the event. Therefore, HPCI remained operable and there was no loss of safety function. The event did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). Therefore, the NRC non-emergency 10 CFR 50.72(b)(3)(v)(D) report was not required and the NRC report 56295 can be retracted and no Licensee Event Report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The NRC Senior Resident Inspector has been notified. Notified R3DO (Ruiz). |
| ENS 56241 | 28 November 2022 09:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection System Inoperable | The following information was provided by the licensee via email: At 0400 EST on November 28, 2022, during the performance of Division 2 Residual Heat Removal (RHR) cooling tower fan operability and RHR Service Water valve lineup verification, it was reported that the Mechanical Draft Cooling Tower (MDCT) Fan 'B' was making a loud metallic noise. The cause of the metallic noise is unknown at this time. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on inoperable cooling water to the HPCI room cooler, per LCO 3.0.6. Investigation into the Division 2 MDCT Fan 'B' abnormal noise is in progress. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The NRC Resident Inspector has been notified.
The following information was provided by the licensee via email: The purpose of this notification is to retract a previous Event Notification 56241 reported on 11/28/2022. On 11/28/22, an event notification to the NRC was made when mechanical draft cooling tower (MDCT) Fan B was declared inoperable and issued Limited Condition of Operation (LCO) 2022-0428 for Division 2 MDCT Fan B abnormal noise. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS) (Technical Specification (TS) 3.7.2). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system (TS 3.7.2), which cools various safety related components, including the High-Pressure Coolant Injection (HPCI) system room cooler (TS LCO 3.0.6). Subsequent inspection and evaluation determined that the brake noise is expected while fans are running at low speeds. This is supported by plant technical procedure, 24.205.10 `Div. 2 RHR Cooling Tower Fan Operability and RHRSW Valve Line-up Verification' (line item 2.2 in Precautions and Limitations) which states `Chatter from the brakes of the MDCT Fans is expected and no cause for discontinuing the test.' The equipment vendor stated that brake chatter is possible and common given that the internal components are free to move along the splined connections. Internal Operating Experience from experienced station operators and maintenance technicians confirmed that the condition is normal and expected. Both Division 2 MDCTs exhibited the same behavior at low speed and passed surveillance testing satisfactorily. No other concerns were noted during fan operation. Therefore, HPCI remained operable and there was no loss of safety function. The event did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). EN 56241 is retracted and no Licensee Event Report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The NRC Resident Inspector has been notified. Notified R3DO (Stoedter). |
| ENS 56054 | 18 August 2022 01:08:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Safety System Inoperability | The following information was provided by the licensee via email: At 2108 EDT on August 17, 2022 the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The Division 2 EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) room cooler and Division 2 Control Center HVAC (CCHVAC) chiller. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. At the time of the event, Division I CCHVAC was inoperable for maintenance (but was running for a maintenance run) and the event caused an inoperability of Division 2 CCHVAC. This resulted in an inoperability of both divisions of CCHVAC. Failure of the Division 2 MDCT Fan brake inverter occurred due to a trip of the DC input breaker. The breaker was reset at 2128 EDT restoring Division 2 UHS Operability. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfilment of the safety function of structures or systems that are needed to mitigate the consequences of an accident based on a loss of a single train safety system and loss of both divisions of a safety system. The Senior NRC Resident Inspector has been notified
The following information was provided by the licensee via email: On 8/17/22 at 2108 EDT the Division 2 (Div. 2) mechanical draft cooling tower (MDCT) brake inverter input breaker tripped for an unknown cause. The result of the loss of power was the inoperability of the MDCT fan brakes which impacts the ultimate heat sink (UHS) (TS 3.7.2). The UHS cascades to the EECW (emergency equipment cooling water) (TS 3.7.2) which is a support system for Div. 2 CCHVAC (Control Cell) Chiller A/C system (TS 3.7.4). This resulted in the inoperability of the Div. 2 CCHVAC Chiller. The cause for the breaker to trip is an intermittent electrical transient. Immediate corrective action was to reset the breaker, and the long-term action is to implement a modification to mitigate susceptibility to voltage variations. Div. 1 has implemented this long-term mod and no unexpected trips have occurred to date. Div. 1 CCHVAC Chiller was previously inoperable from equipment issues which was repaired, and the unit was in service for a 24-hour confidence run. Although licensed personnel had not completed the administrative actions for documenting operability during the 24-hour confidence run to monitor parameters, the (post maintenance test) PMT related to the maintenance was already completed, which included a 4-hour run in accordance with surveillance 24.413.01, Div. 1 and Div. 2 Chilled Water Pump and Valve, to verify normal operation and motor current. These PMT's were completed prior to the identified inoperability of the Div. 2 UHS due to the tripped breaker on the brake power supply. At the time of the MDCT brake inverter trip, the Operations' Senior License and the Night Shift Manager were aligned that, although still operating as part of the 24-hour confidence run, the unit was in service and capable of performing its safety function, but the administrative tasks were not completed, the Limited Condition of Operation (LCO) sheet had not been cleared, and no log entries were made. Since the Div. 1 Chiller was, in fact, operable at the time of the trip of the breaker on the inverter, this would allow the use of Technical Specification (TS) 3.0.9 'Barriers'. Per Operations Department Expectation (ODE)-12 `LCOs' (standard guidance and expectations for preparing and implementing an LCO), Operations determined that the MDCT brakes are barriers to a tornado event and TS 3.0.9 could be utilized. By invoking TS 3.0.9, as long as all other supported systems in the other division are operable, Div. 2 supported systems relying upon the UHS can remain operable and the Automatic Depressurization System (ADS) and Reactor Core Isolation Cooling (RCIC) system can be used as backup to the High Pressure Coolant Injection (HPCI) system. Based on this information, there was no loss of safety function with CCHVAC A/C system or HPCI. Therefore, the NRC non-emergency 10CFR50.72(b)(3)(v)(D) report was not required and the NRC report 56054 can be retracted. The NRC Resident Inspector has been notified. Notified R3DO (Orlikowski) |
| 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. |
| ENS 54293 | 25 September 2019 16:03:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Declared Inoperable | At 1203 EDT, on September 25, 2019, during a Division 2 Emergency Equipment Service Water (EESW) pump and valve surveillance test, the Division 2 Emergency Equipment Cooling Water (EECW) Temperature Control Valve was found to be approximately 80 percent open rather than in its required full open position during fail safe testing. The Division 2 EESW system is required to support operability of the Division 2 EECW system. The Division 2 EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. An investigation is underway into the cause of the failure. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The NRC Senior Resident Inspector has been notified. The licensee is in 72-hour shutdown action statement.
Subsequent engineering evaluation has determined that the EECW TCV was capable of passing sufficient flow to perform its design basis functions, including supporting the HPCI room cooler, while approximately 80% open. Therefore, HPCI remained operable and there was no loss of safety function. The event did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). EN 54293 is retracted and no Licensee Event Report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The NRC Resident Inspector has been notified. Notified R3DO (Cameron). |
| ENS 54188 | 30 July 2019 14:14:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unplanned High Pressue Coolant Injection Inoperability | On July 30, 2019, at 1014 EDT, the Division 2 Mechanical Draft Cooling Tower (MDCT) Fan D was declared inoperable due to a trip of the fan while placing in it high speed. The MDCT Fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation revealed that a high speed breaker control power fuse had blown. The control power fuse was replaced, the MDCT Fan D was tested satisfactorily, and HPCI was declared operable at 1431 EDT. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The licensee has notified the NRC Senior Resident Inspector |
| ENS 53772 | 4 December 2018 14:35:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | En Revision Imported Date 1/31/2019 | EN Revision Text: HPCI INOPERABLE DUE TO MECHANICAL DRAFT COOLING TOWER FAN BRAKE INVERTER FAILURE At 0935 EST on December 4, 2018, the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation into why the Division 2 MDCT fan over speed brake inverter failed is in progress. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The NRC Resident Inspector has been notified. Fermi 2 is in a 14-day LCO for inoperability of HPCI and a 72-hour LCO for UHS inoperability.
The purpose of this notification is to retract EN 53772 made on December 4, 2018. Subsequent to the initial notification, the event and site Technical Specifications (TS) were reviewed further. An evaluation determined that TS Limiting Condition for Operation (LCO) 3.0.9 for barriers could be applied to the MDCT fan brakes. As a result of applying TS LCO 3.0.9 to the MDCT fan brakes, it was not necessary to declare the UHS inoperable. With the Division 2 UHS operable on December 4, 2018, the HPCI system was also operable. With HPCI operable, there was no event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). Therefore, EN 53772 is retracted and no Licensee Event Report (LER) under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The licensee has notified the NRC Resident Inspector. Notified R3DO (Cameron). |
| ENS 53537 | 3 August 2018 04:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Declared Inoperable | At 0940 EDT on August 3, 2018, the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation into why the Division 2 MDCT fan over speed brake inverter failed is in progress. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) based on an unplanned HPCI inoperability. The NRC Resident Inspector has been notified. |
| ENS 53300 | 29 March 2018 18:44:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Due to Inoperability of Emergency Equipment Cooling Water Pump | At 1344 on March 29, 2018, it was determined (engineering evaluation) that an unanalyzed condition that significantly degraded plant safety previously existed. During a postulated control room abandonment due to a fire, and concurrent with a Loss of Offsite Power (LOOP), the required number of Emergency Equipment Cooling Water (EECW) pumps would not have been available from 10/28/2015 to 3/10/2018. On March 8, 2018, during relay functional testing it was discovered that the C3 Emergency Equipment Cooling Water (EECW) pump closing springs did not recharge with the breaker transfer switch in emergency. On August 23, 2012, a wire modification was performed that contained a drawing error resulting in wire placement on the incorrect connection points for the C3 EECW pump. On March 10, 2018, the C3 EECW pump breaker wiring was corrected and subsequent testing was completed satisfactorily. Prior to 10/28/2015, Brown's Ferry Nuclear Plant (BFN) adhered to Appendix R fire protection requirements which did not credit the C3 EECW pump for fire protection from the backup control location. On 10/28/2015, BFN transitioned to National Fire Protection Association (NFPA) 805 fire protection requirements which takes credit for the C3 EECW pump from the backup control location. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B), 'Any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety'. This is also reportable as a 60-day written report in accordance with 10 CFR 50.73(a)(2)(ii)(B). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified of this event. |
| ENS 53049 | 1 November 2017 19:25:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Design Deficiencies Identified During Engineering Review | At 1425 (CDT) on November 1, 2017, Operations was notified of a condition affecting Unit 3 4kV Shutdown Boards 3EA, 3EB, 3EC, and 3ED. It was discovered that multiple potential transformer (PT) primary fuses are GE type EJ1 size 0.5 AMP which does not coordinate with the PT's secondary fuses. A fault on the associated cable could clear the primary PT primary fuses for the 4kV Shutdown Board. This would result in the board tripping 4kV motor loads, disconnecting from Off-site power and connecting to the Emergency Diesel Generator. However, since the PT fuse is cleared, the under-voltage trips on the 4kV motors would remain in if there is no Common Accident Signal (CAS) present. The 4kV motor loads include Residual Heat Removal (RHR) Pumps, Core Spray (CS) Pumps, Residual Heat Removal Service Water (RHRSW) Pumps, and Emergency Equipment Cooling Water (EECW) pumps. Review of NFPA 805 analyses show the cables for all four U3 4kV Shutdown Boards are routed in Fire Area 03-03 and Fire Area 16. Therefore a fire in either area could result in a loss of all four U3 4kV Shutdown Boards motor loads. Cables for 4kV Shutdown Board 3EA and 3EB are both routed in Fire Area 21 which could result in a loss of both Division I Shutdown Board motor loads. Compensatory fire watch measures have been established. This event requires an 8 hour report in accordance with 50.72(b)(3)(ii)(B), 'Any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety.' The NRC Resident Inspector has been notified. CR 1354129 was initiated in the Corrective Action Program. |
| ENS 52958 | 9 September 2017 14:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Mechanical Draft Cooling Tower Fans Declared Inoperable | At 1000 EDT on September 9, 2017, the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation into why the Division 2 MDCT fan over speed brake inverter failed is in progress. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident based on a loss of a single train safety system. The licensee entered two (2) LCO Action Statements (AS); 14-day LCO AS 3.5.1 for ECCS (HPCI Inoperable) and 72-hour AS 3.7.2 for UHS. The licensee has two spare inverters on-site. After replacement and successful post-maintenance testing the licensee expects to exit both AS before 72-hours. The NRC Resident Inspector has been notified. |
| ENS 50265 | 10 July 2014 09:45:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Technical Specification Required Shutdown | 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. |
| ENS 49801 | 6 February 2014 17:54:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Emergency Equipment Cooling Water in Manual Override Due to Human Performance Error | At 1254 (EST) on February 6, 2014, while shutting down Division 2 Emergency Equipment Cooling Water (EECW), a human performance error occurred resulting in the Division 2 EECW isolation override switch being placed in manual override. Division 2 EECW remained running and continued to operate normally. The Division 2 EECW system cools various safety related components including the High Pressure Coolant Injection (HPCI) system room cooler. With the Division 2 EECW isolation override switch in manual override, Division 2 EECW may have been prevented from performing its safety function during a loss of power event. An unplanned HPCI inoperability occurred due to the Division 2 EECW inoperability which may have prevented HPCI from performing its safety function. A 14 day Limiting Condition for Operation (LCO) was entered for HPCI via T.S. LCO 3.5.1 and subsequently exited 36 seconds later upon returning the Division 2 EECW isolation override switch to normal. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on a loss of a single train safety system. The NRC Resident Inspector has been notified. The licensee reported that the individuals involved have been removed from licensee duties pending further investigation.
The Fermi 2 Engineering staff has completed a comprehensive evaluation of the momentary mispositioning of the Division 2 EECW system overide switch initially reported on February 6, 2014. The evaluation determined that HPCI room temperature would remain below the HPCI room steam leak detection isolation logic setpoint in the unlikely event that the momentary mispositioning resulted in the temporary interruption of the cooling water flow to the HPCI system room cooler. Over the brief period of time for which EECW would have been unavailable to support the effective operation of the room cooler, its function was not necessary for HPCI to perform its required safety functions. Therefore, event notification 49801 is retracted. The licensee notified the NRC Resident Inspector. Notified R3DO (Passehl). |
| ENS 48886 | 3 April 2013 14:53:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Cooling Water Makeup Pump Failed to Start During a Surveillance Test | At 1053 (EDT) on April 3, 2013, during the performance of a surveillance test on the Division 2 Emergency Equipment Cooling Water (EECW) system the EECW system was declared inoperable due to the Division 2 EECW makeup pump failing to start during the surveillance. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) room cooler. A 14 day Limiting Condition for Operation (LCO) was entered for HPCI via (Technical Specification) LCO 3.5.1. Investigation into why the makeup pump did not start is currently in progress. This report is being made pursuant to 10 CFR 50.72 (b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on a loss of a single train safety system. The NRC Resident Inspector has been notified.
An evaluation of Event 48886 has determined that the Division 2 Emergency Cooling Water (EECW) system was capable of supporting HPCI Room Cooler and HPCI operation for a period of time in excess of that required to perform the required safety functions as assumed in the accident analysis. Therefore, this event is retracted. The licensee notified the NRC Resident Inspector. Notified the R3DO (Orth). |
| ENS 47834 | 13 April 2012 20:25:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Impacting Emergency Diesel Generator Loading | On March 14, 2012, it was determined that in the event of an Appendix R fire, fire damage to cables in certain fire areas could cause a Residual Heat Removal Service Water System (RHRSW) pump to spuriously start, overload EDG A and B, and render them inoperable during certain Appendix R fires. This was reported as an unanalyzed condition (Ref. EN #47764). An extent of condition analysis was completed on April 13, 2012. From this analysis it was determined that EDG A, D, 3EC, and 3ED could exceed the maximum rated loading due to the potential for an automatic or spurious start of RHRSW Pumps B3 and D3 that supply Emergency Equipment Cooling Water (EECW) to essential safety equipment. The following are the Fire Areas (FA) affected: EDG A in FA 21 EDG D for FA 2-3 and 9 EDG 3EC in FA 1-1, 1-3, and 20, and EDG 3ED in FA 1-1, 1-3, 1-4, and 20. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B). This is also reportable as a 60 day written report IAW 10 CFR 50.73(a)(2)(ii)(B). This event was entered into the licensee's Corrective Action Program as PER 536176. The NRC Resident Inspector has been notified of this event. |
| ENS 47638 | 11 May 2010 06:00:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | UNANALYZED CONDITIONS DISCOVERED DURING NFPA 805 TRANSITION REVIEW
During the licensee's NFPA 805 transition review process, several unanalyzed conditions were discovered but determined to be not reportable at that time. During subsequent review, the licensee determined these conditions did meet reporting requirements. The following unanalyzed conditions affect all three Browns Ferry units: "On 5/11/2010, it was determined that in the event of an Appendix-R fire, multiple hot shorts affecting reactor pressure instrument loops, Safety Relief Valves (SRV) overpressure logic or ADS (Automatic Depressurization System) logic could cause 2 to 13 SRVs to spuriously open, for certain fire areas. The current Appendix R safe shutdown analysis only assumes 2 SRVs spuriously open. The issue has significant safety impact due to the potential for one fire scenario to result in spurious opening of multiple SRVs, loss of low pressure inventory makeup, and loss of the condensate system for inventory makeup, which would challenge adequate core cooling during performance of Safe Shutdown Instructions. "On 8/18/2010, it was determined that in the event of an Appendix-R fire, fire induced circuit damage can potentially result in the inability to manually close the following Motor Operated Valves: Residual Heat Removal Heat Exchanger outlet valves and Emergency Equipment Cooling Water pump cross-tie valves. The failure to be able to manually close these valves could result in the loss of decay heat removal function and loss of credited diesel generators to power required safe shutdown equipment. These issues have significant safety impact since the capability to manually close these valves is necessary to ensure adequate core cooling during performance of BFN Safe Shutdown Instructions. "On 9/30/2010, it was determined that in the event of an Appendix-R fire, fire induced multiple hot shorts could cause both Inboard and Outboard RHR test return valves, and Drywell Spray and Suppression Pool Spray valves to spuriously open due to damage to the valve control circuit cables. This could result in draining of the Pressure Suppression Chamber Head Tank and the affected low pressure Emergency Core Cooling System loop piping (RHR or CS). Consequently, the discharge pipe in the credited Residual Heat Removal (RHR) loop may not be filled and vented when the Safe Shutdown Instructions (SSIs) call for the RHR pump to be started. The resulting water hammer could result in piping system damage resulting in loss of core cooling and decay heat removal functions and loss of suppression pool inventory. Additionally, single spurious actuation of Core Spray (CS) test return valves due to fire damage to their control circuits could have the same results. These issues have significant safety impact since they would challenge the ability to provide adequate core cooling during performance of Safe Shutdown Instructions. On 8/22/2011, two unanalyzed conditions were discovered: First, "it was determined that, in the event of an Appendix-R fire in certain areas, fault propagation due to loss of the breaker control circuit in conjunction with power cable damage could result in de-energization of the associated 4kV Shutdown Board. This potential exists since some 4kV Shutdown Board load breakers are not equipped with separate fuses for trip circuits extending beyond the board. This condition could result in a loss power to credited safe shutdown equipment that would challenge the ability to provide adequate core cooling during performance of BFN Safe Shut down Instructions. Second, "it was determined that in the event of an Appendix-R fire in certain areas, Multiple Spurious Operations (MSO) could result in the Main Steam Isolation Valves failing to close, or to re-open. This potentially results in a challenge to control inventory loss during performance of Safe Shut down Instructions. The following unanalyzed condition only affects Unit 2: "On 8/18/2010, it was determined that in the event of an Appendix-R fire, fire induced circuit damage can potentially result in the inability to manually close certain Main Steam Drain Line Motor Operated Valves. The current Appendix R safe shutdown analysis credits manual closure of these valves. Failure to close these valves results in loss of suppression pool inventory which could challenge adequate core cooling during performance of BFN Safe Shutdown Instructions." Compensatory actions in the form of fire watches to mitigate all these conditions are in place in accordance with the BFNP Fire Protection Report. The licensee will make the required 60-day written reports in accordance with 10CFR50.73(a)(2)(ii)(B). These events were entered into the licensee's Corrective Action Program. The licensee has notified the NRC Resident Inspector. | |
| ENS 44811 | 28 January 2009 12:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection System Inoperable | On January 28, 2009 at 0730 the Division 2 Emergency Equipment Cooling Water System (EECW) was declared inoperable due to a blown control power fuse in the bucket for the P4400F604 - Div 2 EECW Supply to Control Rod Drive (CRD) pumps. This is a normally open valve and is required to close upon EECW initiation to remove non-essential loads. The blown control power fuse would have prevented this action from occurring. The ECCW System cools various safety related components including the High Pressure Coolant Injection (HPCI) System Area Cooler. An unplanned HPCI inoperability occurred due to the Division 2 EECW inoperability based on a loss of the HPCI System Area Cooler. A 14 day Limiting Condition for Operation (LCO) was entered for HPCI per LCO 3.5.1. The control power fuse was replaced, EECW and HPCI were declared operable, and LCO 3.5.1 exited on January 28, 2009 at 1025. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on loss of a single train safety system. The NRC Resident Inspector has been notified.
The As-Found condition of the Division 2 Emergency Equipment Cooling Water (EECW) Control Rod Drive (CRD) Pump Supply Valve and High Pressure Coolant Injection (HPCI) System Room Cooler were evaluated. The HPCI System Room Cooler was operable with P4400-F604, Division 2 EECW to the CRD supply valve open. Based on an Engineering evaluation of EECW flow during a Loss of Coolant Accident (LOCA) and Non-LOCA conditions with the valve open, there is adequate flow margin in the EECW system. The HPCI Room Cooler had adequate cooling flow to perform its design function. The HPCI room temperature would have been maintained below the HPCI equipment room high temperature isolation setpoint. Additionally, plant procedures provide directions for bypassing the HPCI equipment room high temperature trip. Consequently, there was no loss of HPCI safety function. Declaring HPCI inoperable was conservative and based on initial considerations. Therefore, event notification 44811 is retracted. The Licensee notified the NRC Resident Inspector. Notified R3DO (Lara). |
| 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. |
| ENS 42622 | 6 June 2006 20:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Failure to Meet Emergency Equipment Service Water Surveillance Requirement | On June 6, 2006 at 1600 EDT the Division 2 Emergency Equipment Service Water System (EESW) was in service for a planned surveillance test when the system failed to achieve required flows as specified in the surveillance. These flow rates are acceptance criteria and therefore resulted in system inoperability. EESW cools the Emergency Equipment Cooling Water (EECW) System which in turn cools various safety related components including the High Pressure Coolant Injection (HPCI) System Area Cooler. Unplanned HPCI inoperability occurred due to the Division 2 EECW/EESW inoperability based on loss of the HPCI System Area Cooler. A 14 day Limiting Condition for Operation (LCO) was entered for HPCI per LCO 3.5.1. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on loss of a single train safety system." The licensee notified the NRC Resident Inspector.
On June 6, 2006 at 1600 EDT, during the performance of the quarterly pump and valve operability surveillance test on Division 2 of the Emergency Equipment Service Water System (EESW), the minimum pump flow required by the procedure to perform the test could not be established. Because minimum pump flow could not be established, Division 2 of EESW was declared inoperable. EESW cools the Emergency Equipment Cooling Water (EECW) System which in turn cools various safety related components including the High Pressure Coolant Injection (HPCI) System Area Cooler. HPCI was declared inoperable based on loss of the HPCI System Area Cooler due to the Division 2 EECW/EESW inoperability. A 14 day Limiting Condition for Operation (LCO) was entered for HPCI per LCO 3.5.1. A report was made to the NRC pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on loss of a single train safety system. On June 7, 2006, the test was re-performed with the valve in the bypass line around the heat exchanger Temperature Control Valve (TCV) throttled open. The required pump flow was established and the surveillance was successfully completed at 1815 EDT. Further Engineering evaluation concluded that minimum pump flow could not be established on June 6, 2006 due to normal pump wear and heat exchanger fouling. The pump flow required for performing the pump and valve operability surveillance test was established to monitor pump degradation and is higher than the flow required for the EESW system to perform its safety function. It has been verified that the measured flow exceeds the system design basis required flow with an adequate margin and that the pump and heat exchanger remain adequate to support the HPCI room cooling operation. The HPCI safety function was maintained throughout this period; therefore, this event is being retracted. The licensee notified the NRC Resident Inspector. Notified the R3DO (Louden). |
| ENS 42224 | 23 December 2005 03:25:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Eecw Temperature Control Valve Not Fully Open | While performing Div. 1 & 2 Emergency Equipment Cooling Water (EECW)/Emergency Equipment Service Water (EESW) Valve Lineup Verification surveillance on 12/22/05, the temperature control valve (TCV) on both divisions of EECW were found to be approximately 95% open rather than their required full open position. The system design requires that the TCV, or the associated TCV bypass valve, be in the full open position during system startup to avoid a potentially damaging pressure transient from occurring. Both divisions of EECW and all supported systems (including HPCl, both divisions Core Spray, and both divisions of RHR) were declared INOPERABLE at 2225 EST. Multiple LCO Required Actions were entered, including entry into LCO 3.0.3. At 2250 EST, Div. 1 EECW was restored to OPERABLE status by fully opening the TCV bypass valve and isolating the TCV, and LCO 3.0.3 was exited. At 2252 EST, Div. 2 EECW was restored to OPERABLE status by fully opening the TCV bypass valve and isolating the TCV, and all associated LCO Required Actions were exited. Reactor power remained at 100% throughout the event. The NRC resident inspector has been notified. This report is being made pursuant to 10CFR50.72(b)(3)(ii)(B) as an unanalyzed condition and 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident. The licensee is investigating the cause of the valve not being fully open. The licensee notified the NRC Resident Inspector.
This is a retraction of NRC Event #42224. Based on further engineering review, it is concluded that no potential damage from a pressure transient would occur as a result of the TCV being approximately 95% open. System startup pressure transient concerns reflected in the operating procedures originated from a previously-experienced pressure transient resulting from void collapse against a closed TCV. System startup with the as-found TCV position still provides a sufficiently-open flow path to preclude void collapse against a closed boundary. Additionally, Engineering has determined that system operation with a 90% open TCV would have no significant impact on total system flow and the cooling function. Therefore, both divisions of EECW and all other supported systems (including HPCI, both divisions of Core Spray, and both divisions of RHR) were operable with the TCV in the approximately 95% open position. The licensee notified the NRC Resident Inspector. Notified R3DO (Ring). |
| ENS 41354 | 24 January 2005 21:10:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Due to Unidentified Leakage Greater than 10 Gpm | The licensee reported that it had indications of unidentified reactor coolant leakage greater than 10 gpm which placed the licensee into an unusual event emergency action level (EAL). Indication of drywell sump level increase and pump out rate gave an approximate leak rate of 30 gpm. The licensee also indicated that drywell pressure was above the normal range. The unusual event declaration was made at 1610 EST. At 1619 EST, the licensee manually scrammed the reactor. The scram was uncomplicated with all rods fully inserting and all systems functioning as required. Decay heat is being rejected to the main condenser. There has been no ECCS injection actuation and reactor water level is being maintained by feed pumps. The licensee has no significant safety related equipment out of service. The licensee stated that there is no indication of further degradation of the leak rate and the source of the leak is still under investigation The licensee has notified the NRC Resident Inspector along with State, Local, and other government agencies.
At 1640 EST, the licensee upgraded to an ALERT following additional leak rate calculations that indicated the leak rate was approximately 75 - 80 gpm based on drywell sump pump out rate. The licensee's EAL for an alert is RCS leakage greater than 50 gpm. The NRC entered the monitoring mode at 1653 EST. The licensee stated that there has been no increase in drywell radiation levels and that sump water chemistry analysis is in progress. In addition to the normal government agencies notified, the NRC also notified the Canadian Nuclear Safety Commission Duty Officer (R. Chamberlaine).
The licensee has indications that the leakage may not be reactor coolant leakage. Chemistry results show that the sump water radiation levels are at a level less than would be expected for RCS leakage. In addition, a secondary cooling system was found in a lineup configuration that could have masked leakage from the system. The licensee is waiting to get additional chemistry results on the presence of corrosion inhibitors in the sump water to provide additional confirmation that the leakage is not from the RCS.
The licensee confirmed the presence of corrosion inhibitors in the drywell sump. In addition, based on manipulations of the Reactor Building Closed Cooling Water system and the Emergency Equipment Cooling Water system the licensee believes that the leakage is from the Reactor Building Closed Cooling Water system and not RCS leakage. The plant is stable and the licensee is continuing to cool down with pressure now at 180 psi and decreasing.
The licensee terminated its Alert and Unusual Event at 22:28 EST based on sump water chemistry, activity, and Reactor Building Closed Cooling Water System manipulations that indicate the leakage is secondary cooling water and not from the RCS. The NRC secured from the monitoring mode at 22:36 EST. Notified DHS (Belt), FEMA (Caldwell), DOE (Dasilva), EPA (Baumgartner) USDA (Sykes), and HHS( Pyles). The Canadian Nuclear Safety Commission Duty Officer (R. Chamberlaine) was also notified. |