Semantic search
| Entered date | Site | Region | Reactor type | Event description | |
|---|---|---|---|---|---|
| ENS 57126 | 13 May 2024 16:40:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 0917 EDT on May 13, 2024, a control room operator erroneously rendered the `B train of the Unit 2 residual heat removal (RHR) system inoperable. This occurred while the `A train of the Unit 2 RHR system was out of service for preplanned maintenance. RHR serves as the low head safety injection (LHSI) subsystem for the emergency core cooling system (ECCS) and because of this, Unit 2 was without a required train of ECCS from 0917 EDT to 0921 EDT. No other equipment issues were identified. The LHSI subsystem is credited by the analysis for a large break loss of coolant accident at full power. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC resident inspector has been notified. There is no release of radioactive material associated with this event. |
| ENS 57077 | 15 April 2024 14:38:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: At 2224 EST on February 15, 2024, with both units 1 and 2 in Mode 1 at 100 percent power, an invalid start of the emergency diesel generator (EDG) system on 1A-A, 1B-B, and 2B-B EDGs occurred while removing clearances. The 2A-A EDG did not start because it was still under a clearance. The 1A-A, 1B-B, and 2B-B EDGs started and functioned successfully. The start signal for the 1A-A, 1B-B, and 2B-B EDGs was generated from the common emergency start of the 2A-A EDG. The signal was not from a loss of offsite power (LOOP) to any shutdown board or from any parameters that would initiate a safety injection (SI) signal, for which the EDG is designed to provide a design basis safety function. Also, the starts were not from intentional manual actuation. Starting the EDGs did not make them inoperable and each EDG was able to perform its design (basis) safety function. The common emergency start relay for each diesel is not safety related. It is an anticipatory and redundant circuit to start other EDGs in the event of a LOOP or SI related to the specific EDG. With the 2A-A EDG out of service, the associated common emergency circuit would not be required to perform any function. The starts were not initiated in response to actual plant conditions or parameters satisfying the requirements for initiation of the system. This event was originally reported under EN 56970 on February 16, 2024, at 0205 EST in accordance with 10 CFR 50.72(b)(3) (iv)(A) as an event that results in a valid actuation of the emergency diesel generator system. This EN was retracted on February 21, 2024, at 1549 EST. This event is being reported in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) as an event that results in an invalid actuation of the emergency diesel generator system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57006 | 5 March 2024 04:14:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: At 0132 EST, with Unit 2 in Mode 1 at 100 percent power, the reactor automatically tripped due to a main feedwater isolation signal which resulted in steam generator lo-level reactor trip. The reactor trip was not complex, with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed using the auxiliary feedwater and steam dump systems. Unit 1 is not affected. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the auxiliary feedwater system (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72(b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. All control rods are fully inserted. The cause of the main feedwater isolation is being investigated. |
| ENS 56970 | 16 February 2024 02:05:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: At 2224 EST on February 15, 2024, with both units 1 and 2 in mode 1 at 100 percent power, an actuation of the emergency diesel generator (EDG) system on 1A-A, 1B-B, and 2B-B EDGs occurred while removing clearances. The 2A-A EDG did not start because it was still under a clearance. The reason for the emergency diesel generator system auto-start was clearance removal sequencing errors. The emergency diesel generator system automatically started as designed when the common emergency start signal was received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the emergency diesel generator system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The following information was provided by the licensee via email: In accordance with NUREG-1022, Section 2.8 and Section 4.2.3, Watts Barr is retracting the previous report EN 56970 pursuant to 10 CFR 50.72(b)(3)(iv)(A). The start signal for the 1A-A, 1B-B, and 2B-B emergency diesel generators (EDG)s was from activation of the common emergency start of the 2A-A EDG. The actuation was not from a loss of offsite power (LOOP) to any shutdown board or from any parameters that would initiate a safety injection (SI) signal, for which the EDG is designed to provide a design basis safety function. Also, the starts were not from intentional manual actuation. Starting the EDGs did not make them inoperable and each EDG was able to perform its design safety function. The common emergency start relay for each diesel is not safety related. It is an anticipatory and redundant circuit to start other EDGs in the event of a LOOP or SI related to the specific EDG. With the 2A-A EDG out of service, the associated common emergency circuit would not be required to perform any function. The starts were not initiated in response to actual plant conditions or parameters satisfying the requirements for initiation of the system. Since the starts were not initiated via an automatic signal from a LOOP, SI, or traditional operator action, the signal is not a valid actuation in accordance with 10 CFR 50.72(b)(3)(iv)(A). Therefore, EN 56970 is being retracted. The NRC Resident Inspector has been notified of this retraction. Notified R2DO (Miller) |
| ENS 56935 | 27 January 2024 23:39:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: At 2141 EDT, with Unit 2 in Mode 1 at 100 percent power, the reactor automatically tripped due to a main turbine trip. The trip was not complex, with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed using the auxiliary feedwater and steam dump systems. Unit 1 is not affected. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the auxiliary feedwater system (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72(b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. All control rods are fully inserted. The cause of the turbine trip is being investigated. The licensee notified the NRC Resident Inspector. |
| ENS 56910 | 28 December 2023 18:55:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: Plant alignment caused an unanalyzed condition regarding unit 1 and unit 2 Appendix R procedures. (Watts Bar Nuclear) (WBN) unit 1 and unit 2 Appendix R procedures require manual operator action times including (volume control tank) (VCT) isolation. They are calculated with an assumed hydrogen cover gas constant at 20 psig. This is to preclude hydrogen ingestion into the charging pumps with an operator action time of 70 minutes. Due to recent lower hydrogen concentration in the (reactor coolant system) (RCS), (unit 2) VCT hydrogen regulator set point was increased to 28 psig. This increased pressure set point invalidated the initial assumptions made in the Appendix R calculations for manual operator action times. WBN unit 1 VCT hydrogen regulator was also verified high out of band at 22 psig. WBN has restored unit 1 and unit 2 VCT hydrogen regulators to the required specification. The NRC Resident Inspector has been notified of this condition. |
| ENS 56850 | 12 November 2023 22:02:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: On November 12, 2023, at 0300 EST, a Watts Bar contractor was transported offsite for medical treatment due to a work-related injury. Upon arrival at an offsite medical facility, medical personnel determined the injury required the individual to be admitted into the hospital and will be kept overnight. The individual was inside of the Radiological Controlled Area, however was free released with no contamination. The injury and hospitalization were reported to the Occupational Safety and Health Administration (OSHA) under 29 CFR 1904.39(a)(2). The contracting agency informed OSHA at 1319 EST. Watt Bar Operations personnel were officially notified by the contracting agency of the report made to OSHA at 1945 EST. This is a four-hour notification, non-emergency for a notification of other government agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). The NRC Resident Inspector has been notified. |
| ENS 56809 | 21 October 2023 09:25:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via fax and email: Fire potentially degrading the level of safety of the plant. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At 0907 EST, the licensee declared a notification of unusual event, under emergency action level HU.4, due to multiple fire alarms and CO2 discharge in the emergency diesel building. When the plant fire brigade entered the building, there was no indication of fire or damage to any plant equipment. The cause of the multiple alarms is under investigation. State and local authorities were notified and no offsite assistance was requested. Both units remain at 100 percent power. The NRC Resident Inspector has been notified. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
At 1007 EDT, Watts Bar terminated the notification of unusual event. The basis for termination was that no fire or damaged plant equipment was found. The NRC Resident Inspector has been notified. Notified R2DO (Miller), IR-MOC (Crouch), NRR-EO (Felts), DHS-SWO, FEMA Ops Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
Watts Bar Nuclear Plant (WBN) is retracting Event Notice 56809, Notice of Unusual Event, based on the following additional information, not available at the time of the initial notification. Specifically, in accordance with the emergency preparedness implementing procedures, WBN reported a condition that was determined to meet emergency action level (EAL) HU4, Initiating criteria number 1, receipt of multiple (more than 1) fire alarms or indicators and the fire was within any Table H2 plant area, which includes the diesel generator building. It was further determined that multiple fire detection zones actuated (spurious and invalid) enabling the discharge of installed fire suppression (CO2) into the space. Upon entry by the site fire brigade, it was determined that no smoke or fire existed and reported to the Shift Manager at 0930 EDT. All fire alarms were reset. Troubleshooting activities are in progress to determine the cause. A fire watch has been established and CO2 has been isolated. The required compensatory measures for the affected areas will remain in place until completion of the investigation, and CO2 suppression is restored to functional. Notified R2DO (Miller), IR-MOC (Crouch), NRR-EO (Felts), DHS-SWO (email), FEMA Ops Center (email), CISA Central (email), FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email). |
| ENS 56660 | 4 August 2023 20:51:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 1746 EDT on 08/04/2023, with Unit 2 in Mode 1 at 100 percent power, the reactor automatically tripped due to number 2 steam generator low low level. The trip was not complex, with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed by using the auxiliary feedwater and steam dump systems. Unit 1 is not affected. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the auxiliary feedwater system (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. All control rods are fully inserted. The cause of the number 2 steam generator low low level is being investigated. |
| ENS 56593 | 27 June 2023 19:04:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 1626 EDT, with Unit 2 in Mode 1 at 100 percent power, the reactor automatically tripped due to a main turbine trip. The (reactor) trip was not complex with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed using the auxiliary feedwater and steam dump systems. Unit 1 is not affected. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the auxiliary feedwater system (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. All control rods are fully inserted. The cause of the turbine trip is being investigated. |
| ENS 56541 | 25 May 2023 17:02:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 1345 EDT on May 25, 2023, it was determined that a fire barrier for area 737-A1B was not installed, and would render the 2A Emergency Diesel Generator (EDG) not operable in the event of a fire on the Unit 2 side of elevation 737 in the Auxiliary Building. The 2A EDG is the credited power source for fire safe shutdown for a fire located in this area. Without the credited source of power, this places WBN U2 (Watts Bar Nuclear Unit 2) in an unanalyzed condition. A fire watch has been established in the area until the issue is resolved. Therefore, this event is being reported as an eight-hour non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. |
| ENS 56274 | 15 December 2022 12:52:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via email: This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 1. On November 24, 2022, at 1621 Eastern Standard Time (EST), the Train B CVI actuated due to an invalid high radiation signal from 1-RM-90-131, Containment Purge Air Exhaust Monitor. Upon investigation, the high radiation signal was caused by a failed power supply. Corrective action included replacing the power supply, 1-RM-90-131 ratemeter, and restoring the system to service. Prior to and following the invalid high radiation alarm, all radiation monitors except 1-RM-90-131 were stable at their normal values; therefore, the CVI was invalid. Control room operators performed appropriate checks and confirmed that all required automatic actuations occurred as designed. This event has been entered into the corrective action program as Condition Report 1819098. The NRC Resident Inspector was notified. |
| ENS 55741 | 16 February 2022 16:42:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | The following information was provided by the licensee via fax or email: At 1159 EST, on 2/16/2022, the Watts Bar Nuclear, Shift Manager was notified that Tennessee Valley Authority (TVA) attempted to notify Tennessee Emergency Management Agency (TEMA) regarding routine siren testing at 0750 EST. TVA was unable to reach TEMA via telephone land line or the Emergency Communication and Notification System (ECNS). TEMA Watch Point staff were located at their back-up facility. TVA subsequently notified TEMA via cell phone that there were communication issues with the primary and backup notification methods. It was determined that the TEMA back-up facility was not able to receive incoming calls. At 0820 EST, TEMA positioned personnel at their primary facility in order to respond to notifications. This restored primary and backup means of notifying the state because the primary facility was not affected by the communication issues. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) as a Major Loss of Offsite Communications Capability because it affected TVA's ability to notify the State of TN. The licensee has notified the NRC Resident Inspector. |
| ENS 55590 | 18 November 2021 02:21:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 2238 Eastern Standard Time (EST), on 11/17/2021, a Watts Bar Nuclear Plant contractor was transported offsite for treatment at an offsite medical facility. The offsite medical facility notified Watts Barr Nuclear Plant at 2310 EST that the individual had been declared deceased. The fatality was not work-related and the individual was inside of the Unit 1 Radiological Controlled Area. The individual was confirmed not to be contaminated. This is a four-hour notification, non-emergency for a notification of other government agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The licensee will notify OSHA. |
| ENS 55550 | 28 October 2021 14:19:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1340 EDT on October 28, 2021, Watts Bar Nuclear Plant (WBN) Units 1 and 2 initiated voluntary communication to the State of Tennessee and local officials as part of the Nuclear Energy Institute (NEI) Groundwater Protection Initiative (GPI), after receiving analysis results for two on-site monitoring wells that indicated tritium activity above the GPI voluntary communication threshold. The suspected source, a permitted release line, has been isolated, and additional corrective actions are in progress. This condition did not exceed any NRC regulations or reporting criteria. This notification is being made solely as a four-hour, non-emergency notification for a Notification of Other Government Agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 55143 | 17 March 2021 12:59:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1004 EDT on March 17, 2021, with Unit 2 in Mode 1 at 90 percent power, the reactor automatically tripped due to a main turbine trip. The trip was not complex, with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed by the Auxiliary Feedwater and Steam Dump Systems. Unit 1 is not affected. Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. All controls rods fully inserted and the electrical system is in normal shutdown alignment. The cause of the turbine trip is being investigated. |
| ENS 55118 | 1 March 2021 16:38:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1511 EST on March 1, 2021, it was discovered that the main control room (MCR) envelope was inoperable due to a MCR door being found ajar; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The door was closed, restoring the MCR envelope to operable at 1513 EST. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 55083 | 26 January 2021 15:46:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | A licensed operator had a confirmed positive alcohol test during a random fitness-for-duty test. The employee's access to the plant has been terminated. The NRC Resident Inspectors have been notified. |
| ENS 54997 | 15 November 2020 06:11:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 0144 EST on November 15, 2020, with Unit 1 in Mode 1 at 100 percent power and Unit 2 in Mode 5 at 0 percent power, an actuation of the Emergency Diesel Generator (EDG) system occurred while transferring the 2A-A 6.9 kV Shutdown Board (SDBD) from the maintenance feed to its normal power supply. The reason for the 2A-A 6.9 kV SDBD failing to transfer to the normal power supply is under investigation. The EDGs automatically started as designed when the valid actuation signal was received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the EDGs. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 54994 | 11 November 2020 16:11:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1311 EST on November 11, 2020, it was determined, after evaluation of the Watts Bar Nuclear Plant (WBN) Unit 2 Steam Generator (SG) tube eddy current test data collected during the on-going refueling outage, that the WBN Unit 2 Reactor Coolant System pressure boundary did not meet the performance criteria for SG tube structural integrity. Specifically, SG number 3 failed the condition monitoring assessment for conditional burst probability. WBN has completed tube plugging and additional corrective actions are in progress. This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 54870 | 31 August 2020 15:30:00 | Watts Bar | NRC Region 2 | This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report two invalid Containment Ventilation Isolation (CVI) actuations at Watts Bar Nuclear Plant (WBN) Unit 1. On July 23, 2020, at 0956 Eastern Daylight Time (EDT), the Train A CVI actuated due to an invalid high radiation signal from 1-RM-90-130, Containment Purge Air Exhaust Monitor. Upon investigation, the high radiation signal was caused by a failed power supply. Corrective action included replacing the power supply, 1-RM-90-130 detector, and restoring the system to service. On August 7, 2020, at 2017 EDT, the Train A CVI actuated due to an invalid high radiation signal from 1-RM-90-130, Containment Purge Air Exhaust Monitor. Upon investigation, a small tear was identified in the foil covering the scintillation detector. This defect caused erratic indication and the system actuation. The foil was replaced and the system was restored to service. Prior to and following the invalid high radiation alarms, all radiation monitors except 1-RM-90-130 were stable at their normal values; therefore, the CVI was invalid. Control room operators performed appropriate checks and confirmed that all required automatic actuations occurred as designed. These events were entered into the corrective action program as CR 1625135 and CR 1628904. The NRC Resident Inspector was notified. | |
| ENS 54781 | 15 July 2020 14:58:00 | Watts Bar | NRC Region 2 | At 0835 EDT on July 15, 2020, it was discovered that the main control room (MCR) envelope was inoperable due to a MCR door being found ajar; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The door was closed, restoring the MCR envelope to operable at 0839 EDT. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54753 | 22 June 2020 13:45:00 | Watts Bar | NRC Region 2 | At 1304 EDT on June 22, 2020, Watts Bar Nuclear Plant (WBN) Units 1 and 2 initiated voluntary communication to the State of Tennessee and local officials as part of the Nuclear Energy Institute (NEI) Groundwater Protection Initiative (GPI), after receiving analysis results for one on-site monitoring well that indicated tritium activity above the GPI voluntary communication threshold. WBN identified and corrected the cause. This condition did not exceed any NRC regulations or reporting criteria. This notification is being made solely as a four-hour, non-emergency notification for a Notification of Other Government Agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54720 | 20 May 2020 12:07:00 | Watts Bar | NRC Region 2 | At 0521 EDT on May 20, 2020, with Unit 2 in Mode 3 at 0 percent power and Unit 1 defueled, an actuation of the Emergency Diesel Generator (EDG) System occurred while transferring the 1B-B 6.9kV Shutdown Board (SDBD) from the maintenance feed to its normal power supply. The reason for the 1B-B 6.9kV SDBD failing to transfer to the normal power supply is under investigation. The EDGs automatically started as designed when a valid actuation signal was received. The event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the EDGs. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54718 | 19 May 2020 19:57:00 | Watts Bar | NRC Region 2 | At 1329 EDT on May 19, 2020, it was discovered that the main control room (MCR) envelope was inoperable due to a control room envelope (CRE) door being found ajar; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The CRE door was closed, restoring the MCR envelope to operable at 1331 EDT. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54531 | 19 February 2020 10:20:00 | Watts Bar | NRC Region 2 | EN Revision Imported Date : 2/21/2020 NOTIFICATION OF UNUSUAL EVENT DUE TO FIRE IN CONTROL BUILDING At 0957 EST on February 19, 2020, a Notification of Unusual Event (NOUE) has been determined to be present at the Watts Bar plant Unit 1 under criteria HU4 for a fire potentially degrading the safety of the plant (fire for more than 15 minutes). The NRC Senior Resident Inspector has been notified for this event. Notified DHS SWO, FEMA Operations Center, CISA IOCC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).
The fire was declared extinguished at 1033 EST. The NOUE was terminated at 1126 EST. The investigation into the cause of the fire is in progress. Notified R2DO (Musser), NRR EO (Miller), and IRD MOC (Kennedy). Additionally, notified DHS SWO, FEMA Operations Center, CISA IOCC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).
Watts Bar Nuclear Plant (WBN) is retracting Event Notice 54531 (NOUE notification) based on the following additional information. WBN reported a condition that was determined to meet the definition of a FIRE in the plant Emergency Preparedness Implementing Procedures (EPIP) based on indications available to the decision-maker at the time the declaration was made. A fire, without observation of flame, is considered present if large quantities of smoke and heat are observed. Moderate quantities of smoke were observed coming from an electrical cabinet not required to support safe plant operation. Once Fire Brigade personnel were able to access the affected room, no evidence of flame or significant heat was observed. Plant personnel ultimately determined that an overheated electrical component (transformer) resulted in the smoke. As such, the actual conditions did not meet the EPIP definition of a fire. The NRC Resident Inspector has been notified of this retraction. Notified R2DO (Musser), NRR EO (Miller), and IRD MOC (Kennedy). | |
| ENS 54532 | 19 February 2020 10:20:00 | Watts Bar | NRC Region 2 | At 0936 EST on February 19, 2020, the Watts Bar Unit 1 reactor was manually tripped while operating at 100 percent power in response to loss of control of water level for steam generator number 3. All control and shutdown bank rods inserted properly in response to the manual reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. There is no impact to Unit 2. The manual actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50. 72(b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. | |
| ENS 54390 | 16 November 2019 03:02:00 | Watts Bar | NRC Region 2 | At 2234 Eastern Standard Time (EST) on November 15, 2019, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 2236 EST, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10 Control Room Emergency Ventilation System (CREVS) was declared not met for both trains. Watts Bar Unit 1 and Unit 2 entered Condition B. At 2236 EST on November 15, 2019, the alarm cleared, CREVS was declared operable and LCO 3.7.10 Condition B was exited for both units. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54391 | 16 November 2019 03:02:00 | Watts Bar | NRC Region 2 | At 2353 EST on November 15, 2019, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 2355 EST, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10 Control Room Emergency Ventilation System (CREVS) was declared not met for both trains. Watts Bar Unit 1 and Unit 2 entered Condition B. At 2355 EST on November 15, 2019, the alarm cleared, CREVS was declared operable and LCO 3.7.10 Condition B was exited for both units. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. See similar EN #54390. The licensee has taken compensatory measures while investigating the cause. | |
| ENS 54379 | 12 November 2019 07:57:00 | Watts Bar | NRC Region 2 | On November 12, 2019, the Central Emergency Control Center (CECC) was removed from service for a planned facility upgrade project. The CECC is a common Emergency Operations Facility (EOF) for the TVA Nuclear sites (Browns Ferry / Sequoyah / Watts Bar). The duration of the upgrade project is approximately 75 days. If an emergency is declared requiring CECC activation during this period, an alternate CECC will be used. During this period, the alternate CECC will be staffed and activated using existing emergency procedures. This is an eight-hour, non-emergency notification for a Loss of Emergency Assessment Capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the CECC will be unavailable for more than 72 hours. The Emergency Response Organization has been notified that the CECC will be unavailable during the upgrade project and to report to the alternate CECC in the event of an emergency. There is no impact on the health and safety of the public or plant employees. The NRC Resident Inspector has been notified.
The CECC facility upgrade project is sufficiently complete such that the CECC was returned to a functional status at 1400 EST on January 31, 2020. The NRC Resident Inspector has been notified. Notified R2DO (Baptist) | |
| ENS 54277 | 13 September 2019 12:21:00 | Watts Bar | NRC Region 2 | EN Revision Text: EMERGENCY OPERATING FACILITY UNAVAILABLE DUE TO ACCESS ISSUES This is an eight-hour, non-emergency notification for a loss of Emergency Assessment Capability. A condition impacting access to the Emergency Operating Facility, Central Emergency Control Center (CECC), located in the TVA Chattanooga Office Complex occurred on September 13, 2019 at 0527 EDT. Fire suppression capabilities for the TVA Chattanooga Office Complex are currently impacted by a water main failure rendering access to the facility unsafe for personnel. If an emergency is declared requiring CECC activation during this period, other emergency response centers will be activated and staffed using existing emergency planning procedures and have the capability to perform the functions normally performed by the CECC. This is an eight-hour, non-emergency notification for a loss of Emergency Assessment Capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the condition affects the functionality of an emergency response facility. The condition does not affect the health and safety of the public. The NRC Resident Inspector has been notified.
Water lines impacting the Chattanooga Office Complex were repaired, and as of time 0734 EDT on 9/16/19, the CECC was returned to a functional status. The NRC Resident Inspector has been informed of this event update. Notified R2DO (Ehrhardt). | |
| ENS 54252 | 1 September 2019 00:09:00 | Watts Bar | NRC Region 2 | While operating at 100 percent power, the Watts Bar Unit 1 reactor was manually tripped at 2055 EDT on August 31, 2019 due to loss of steam generator #2 level control. The trip was not complex. All control and shutdown bank rods inserted properly in response to the manual reactor trip. All safety systems, including Auxiliary Feedwater, actuated as designed. Operations responded and stabilized the plant. Decay heat is being removed by the Auxiliary Feedwater and the Steam Dump System. Unit 2 is not affected. The cause of the loss of steam generator water level control is being investigated. The manual actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The automatic actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector was notified. | |
| ENS 54220 | 14 August 2019 20:00:00 | Watts Bar | NRC Region 2 | This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 2. On July 26, 2019, at 1003 Eastern Daylight Time (EDT), the Train A CVI actuated due to an invalid High Radiation signal from 2-RM-90-130, Containment Purge Air Exhaust Monitor. Prior to and following the invalid High Radiation alarm, all radiation monitors except 2-RM-90-130 were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid High Radiation alarm was due to a failed ratemeter for 2-RM-90-130. Control room operators performed appropriate checks and confirmed that the subject indication was an invalid high radiation signal. The ratemeter for 2-RM-90-130 was replaced and the monitor returned to service. At the time of the event, plant conditions for a High Radiation alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified. | |
| ENS 54127 | 20 June 2019 17:59:00 | Watts Bar | NRC Region 2 | At 1340 EDT on June 20, 2019, a breach in excess of allowable margin in the Unit 2 Shield Building annulus was identified. T.S. LCO 3.6.15, Condition A was entered. The breach is expected to be repaired within the 24 hours allowed LCO time. No other equipment issues were identified. The Shield Building ensures that the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C). NRC Resident Inspector has been notified. The breach consists of a tear in a flexible boot seal for a penetration associated with the suction path for gas treatment fans. There is no release of radioactive material associated with this event. | |
| ENS 54112 | 12 June 2019 11:55:00 | Watts Bar | NRC Region 2 | At 0849 (EDT), a significant air leak on an inline air filter was identified. At 0908, the leak on the filter was isolated. A subsequent review of this situation determined that this air leak impacted operation of the A Train of the Control Room Emergency Air Temperature Control System (CREATCS) which is required to be operable in accordance with Technical Specification 3.7.10. At the time of this event, the B Train of CREATCS was out of service for planned maintenance. With both trains of CREATCS out of service, both Watts Bar Units entered a condition that could have prevented fulfillment of a safety function. This condition was terminated when the leaking air filter was isolated. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified. | |
| ENS 54077 | 22 May 2019 05:45:00 | Watts Bar | NRC Region 2 | On May 22, 2019, at 0233 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 reactor was manually tripped due to a failure of the #2 Main Feedwater Regulating Valve during power ascension following a refueling outage. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and Steam Dumps. Unit 2 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10 CFR 50.72(b)(3)(iv)(A) and 10 CFR 50.72(b)(2)(iv)(B). There was no impact to WBN Unit 1. The NRC Senior Resident has been notified. | |
| ENS 54021 | 23 April 2019 09:44:00 | Watts Bar | NRC Region 2 | At 0232 EDT on April 23, 2019, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 0233 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10 Control Room Emergency Ventilation System (CREVS) was declared not met for both trains. Watts Bar Unit 1 entered Condition B. Watts Bar Unit 2 was not performing movement of irradiated fuel assemblies and did not meet the APPLICABILITY for CREVS per LCO 3.7.10. At 0233 EDT on April 23, 2019, the alarm cleared, CREVS was declared operable and LCO 3.7.10 Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 0232 EDT to 0233 EDT, (Watts Bar Nuclear) WBN was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. | |
| ENS 53840 | 22 January 2019 09:41:00 | Watts Bar | NRC Region 2 | This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 1. On December 2, 2018 at 0028 Eastern Standard Time (EST), the Train A CVI actuated due to an invalid High Radiation signal from 1-RM-90-130, Containment Purge Exhaust Radiation Monitor. In addition to the Train A CVI, instrument malfunction alarms were received for 1-RM-90-106, Lower Containment Radiation Monitor and 1-RM-90-112, Upper Containment Radiation Monitor as the associated valves isolated for the CVI. A common instrument malfunction alarm was also received for 1-RM-90-130 and 1-RM-90-131, Containment Purge Exhaust Radiation Monitors. Prior to and following the invalid High Radiation alarm, all radiation monitors except 1-RM-90-130 were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid High Radiation alarm was due to a failed ratemeter for 1-RM-90-130. Control room operators performed appropriate checks and confirmed that the subject indication was an invalid high radiation signal. The ratemeter for 1-RM-90-130 was replaced and the monitor returned to service. At the time of the event, plant conditions for a High Radiation alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified. | |
| ENS 53801 | 21 December 2018 00:02:00 | Watts Bar | NRC Region 2 | At 1642 Eastern Standard Time (EST) on December 20, 2018, it was determined that both trains of Containment Air Return Fan (CARF) were simultaneously INOPERABLE from 0817 (EST) to 1129 (EST) on November 20, 2018. This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. | |
| ENS 53697 | 27 October 2018 16:52:00 | Watts Bar | NRC Region 2 | On October 27, 2018, at 1533 EDT, Watts Bar Nuclear (WBN) Plant Unit 1 reactor was manually tripped due to a failure of the #3 Reactor Coolant Pump normal feeder breaker to close during the planned power transfer to unit power following startup. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. (Main Steam Isolation Valves) MSIVs were required to be isolated due to cooldown. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and Steam Generator Atmospheric Dump Valves. Unit 1 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72 (b)(2)(iv)(B). There was no effect on WBN Unit 2. The NRC Senior Resident has been notified. | |
| ENS 53593 | 11 September 2018 05:17:00 | Watts Bar | NRC Region 2 | At 0113 EDT on September 11, 2018, it was discovered both trains of CREVS (control room emergency ventilation system) were simultaneously inoperable; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The door to the main control room habitability zone from the turbine building was left open and unattended for about a minute, breaking the pressure boundary in the room, resulting in an alarm. The door was closed, clearing the alarm and the CREVS was considered operable. | |
| ENS 53557 | 22 August 2018 11:23:00 | Watts Bar | NRC Region 2 | At 0943 EDT on August 22, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 100 percent power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The reactor automatically tripped due to a main turbine trip signal. An investigation is in progress. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. | |
| ENS 53467 | 22 June 2018 12:14:00 | Watts Bar | NRC Region 2 | At 0841 EDT on June 22, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 95% power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The reactor automatically tripped due to a main turbine trip. The turbine trip was caused by main generator electrical trip. An investigation is in progress. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip. | |
| ENS 53398 | 11 May 2018 15:19:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1011 EDT on May 11, 2018, Containment Shield Building Annulus differential pressure exceeded the required limit. The Shield Building was declared inoperable requiring entry into Technical Specification (TS) 3.6.15 Conditions A and B. The event was initiated by failure of the operating annulus vacuum fan. Main Control Room Operators manually started the stand-by annulus vacuum fan to recover pressure. Shield Building Annulus differential pressure was restored to the required value at 1016 EDT and TS 3.6.15 Condition A and B were exited on May 11, 2018 at 1016 EDT. The failure mechanism for the annulus vacuum fan is being investigated. The Containment Shield Building ensures the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). The Emergency Gas Treatment System (EGTS) would have automatically started and performed its design function to maintain the Shield Building Annulus differential pressure within required limits. The event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D). The NRC Resident has been notified. |
| ENS 53356 | 22 April 2018 04:28:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | On April 22, 2018 at 0222 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 entered TS (Technical Specifications) LCO (Limiting Condition for Operation) 3.0.3 due to both trains of the Residual Heat Removal System (RHRS) becoming inoperable. During surveillance testing, the gas void values on Emergency Core Cooling System (ECCS) piping common to both trains did not meet acceptance criteria. This caused both RHRS trains to become inoperable. Operations subsequently vented the RHRS to meet the acceptance criteria and exited TS LCO 3.0.3 at 0227 EDT. More frequent surveillances will be conducted to monitor gas void volumes while additional analysis is being performed to determine corrective actions. The NRC Resident Inspector has been notified.
This event is being retracted. The initial report was based on a conservative acceptance criteria for gas accumulation adopted on April 19, 2018 when it was determined that the previously used acceptance criteria for gas accumulation in the ECCS was non-conservative. Additional analysis has subsequently been performed and determined that a higher gas accumulation acceptance criteria does not challenge operability. With a void of less than the acceptance criteria, in the event of ECCS actuation, the system piping support loads will remain within structural limits and the piping system will remain operable. Therefore, both trains of Unit 2 RHRS were operable and the previously reported 10 CFR 50.72(b)(3)(v)(B) event is being retracted. The NRC Resident Inspector staff has been informed of this event retraction. Notified R2DO (Desai) of this retraction. |
| ENS 53355 | 22 April 2018 02:34:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | On April 21, 2018 at 2152 EDT, Watts Bar Nuclear Plant (WBN) Unit 1 entered TS (Technical Specifications) LCO (Limiting Condition for Operation) 3.0.3 due to both trains of the Residual Heat Removal System (RHRS) becoming inoperable. During surveillance testing, the gas void values on Emergency Core Cooling System (ECCS) piping common to both trains did not meet acceptance criteria. This caused both RHRS trains to become inoperable. Operations subsequently vented the RHRS to meet the acceptance criteria and exited TS LCO 3.0.3 at 2222 EDT. More frequent surveillances will be conducted to monitor gas void volumes while additional analysis is being performed to determine corrective actions. The NRC Resident Inspector has been notified.
This event is being retracted. The initial report was based on a conservative acceptance criteria for gas accumulation adopted on April 19, 2018 when it was determined that the previously used acceptance criteria for gas accumulation in the ECCS was non-conservative. Additional analysis has subsequently been performed and determined that a higher gas accumulation acceptance criteria does not challenge operability. With a void of less than the acceptance criteria, in the event of ECCS actuation, the system piping support loads will remain within structural limits and the piping system will remain operable. Therefore, both trains of Unit 1 RHRS were operable and the previously reported 10 CFR 50.72(b)(3)(v)(B) event is being retracted. The NRC Resident Inspector has been informed of this event retraction. Notified R2DO (Ehrhardt). |
| ENS 53349 | 20 April 2018 00:55:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | On April 19, 2018 at 1944 EDT, Watts Bar Nuclear Plant (WBN) determined that a preliminary analysis shows current acceptance criteria for gas accumulation in the WBN Unit 1 and Unit 2 Safety Injection System (SIS) and Residual Heat Removal System (RHRS) discharge piping may be non-conservative. The surveillances that check void values and allow venting of the systems are to be performed utilizing conservative criteria at more frequent intervals to ensure gas void volumes remain under acceptable limits. Additional analysis is being performed to determine final actions. The NRC Resident Inspector has been notified. |
| ENS 53327 | 12 April 2018 12:14:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 0920 EDT on April 12, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 100 percent power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The cause of the automatic reactor trip is being investigated. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip. |
| ENS 53291 | 26 March 2018 20:07:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1839 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1840 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10, Control Room Emergency Ventilation System (CREVS), was declared not met for both trains and Condition B entered. At 1840 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO (Limiting Condition for Operation) 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 1839 EDT to 1840 EDT, WBN (Watts Bar Nuclear) was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). A watch has been posted at the door to prevent recurrence. The NRC Resident Inspector has been notified. |
| ENS 53288 | 26 March 2018 11:51:00 | Watts Bar | NRC Region 2 | Westinghouse PWR 4-Loop | At 1058 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1100 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10, Control Room Emergency Ventilation System (CREVS), was declared not met for both trains and Condition B entered. At 1100 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO (Limiting Condition for Operation) 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 1058 EDT to 1100 EDT, WBN (Watts Bar Nuclear) was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. |