Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 55867 | 29 April 2022 03:38:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Assessment Capability | The following information was provided by the licensee via fax: On 4/28/2022, at 2338 EDT, Sequoyah received an unexpected alarm for seismological recording initiated. At 2341 EDT, unexpected alarm 1/2 Safe Shutdown Earthquake response spectra exceeded was received. The National Earthquake Information Center was contacted to confirm there was no seismic activity, and this was also confirmed on the U.S. Geological Survey website. The alarms were determined to be invalid, and they occurred due to a failure in the seismic monitoring system. This failure results in loss of ability to assess the Emergency Action Level for Initiating Condition HU2 `Seismic event greater than Operating Basis Earthquake (OBE) levels' per procedure EPIP-1, `Emergency Plan Classification Matrix.' If an actual seismic event had occurred, HU2 could not be assessed. However, compensatory measures have been implemented and include assessing OBE criteria based on alternative criteria contained in procedure AOP-N.05, `Earthquake,' which provides conservative guidance when seismic instruments are unavailable. This is an eight-hour, non-emergency notification for an event resulting in a major loss of Emergency Assessment Capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii). There is no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified." The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The faulty detector was removed from service, so the remaining detector provides conservative detection as the only source to make-up the logic for a seismological alarm. | ||
| ENS 55742 | 16 February 2022 16:28:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Offsite Communication Capability | The following information was provided by the licensee via fax or email: At 1128 EST on 2/16/2022, the SQN (Sequoyah Nuclear) Shift Manager was notified that TVA (Tennessee Valley Authority) attempted to notify Tennessee Emergency Management Agency (TEMA) regarding routine siren testing at 0750. 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, 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 54977 | 1 November 2020 09:56:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Seismic Assessment Instrumentation | At 0556 EST on 11/01/2020, Sequoyah received unexpected alarms for seismological recording initiated and (Units) 1/2 Safe Shutdown Earthquake response spectra exceeded. No seismic event was felt on site, the National Earthquake Information Center was contacted to confirm there was no seismic activity, and this was also confirmed on the U.S. Geological Survey website. The alarms were determined to be invalid, and they occurred due to a failure in the seismic monitoring system. This failure results in loss of ability to assess the Emergency Action Level for Initiating Condition HU2 'Seismic event greater than Operating Basis Earthquake (OBE) levels' per procedure EPIP-1. If an actual seismic event occurred, HU2 could not be assessed. However, compensatory measures have been implemented and include assessing OBE criteria based on alternative criteria contained in procedure AOP-N.05 'Earthquake' which provides conservative guidance when seismic instruments are unavailable. This is an eight hour, non-emergency notification for an event resulting in a major loss of Emergency Assessment Capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii). There is no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | ||
| ENS 54380 | 12 November 2019 12:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Emergency Operations Facility Out of Service | 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 EDT on January 31, 2020. The NRC Resident Inspector has been notified. Notified R2DO (Baptist). | ||
| ENS 54276 | 13 September 2019 09:27:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | En Revision Imported Date 9/17/2019 | 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 52172 | 11 August 2016 14:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Control Room Emergency Ventilation System Declared Inoperable | At 1015 (EDT) on August 11, 2016, it was discovered that a Fire Protection damper associated with the Control Room Emergency Ventilation System had closed unexpectedly due to component failure. The closure rendered both trains of the Control Room Emergency Ventilation System (CREVS) inoperable requiring both Unit 1 and 2 to enter Technical Specification Limiting Condition of Operation (LCO) 3.7.10 Condition G. Condition G requires immediate entry into LCO 3.0.3. At 1159 on August 11, 2016, actions were taken to block the deficient damper in the open position restoring both trains of CREVS to a fully operable condition and allowing exit of LCO 3.0.3 and 3.7.10 Condition G. The purpose of CREVS is to provide a protected environment from which occupants can control the (respective) unit following an uncontrolled release of radioactivity, hazardous chemicals, or smoke. In the event of a design basis accident, emergency ventilation components realign to supply filtered air and to pressurize the Control Room Envelop (CRE). While the damper was closed both trains of CREVS were incapable of supplying the Relay Room as well as the Technical Support Center and its associated support spaces. These locations constitute part of the CRE, therefore both trains of CREVS were inoperable. Both trains of CREVS being inoperable affected the habitability of the TSC where the assessment capability of the facility for all emergencies was adversely effected. The NRC Resident Inspector has been notified. | Control Room Emergency Ventilation | |
| ENS 50853 | 27 February 2015 18:05:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Emergency Notification System and Health Physics Network Telephone Lines Out of Service | On February 27, 2015, from 1305 to 1323 (EST), a loss of the ENS (Emergency Notification System) communication line, the HPN (Health Physics Network) line, and the other communication systems that the MCR (Main Control Room) operators use as part of the emergency plan occurred at TVA Sequoyah Units 1 and 2. A loss of these systems was experienced when transferring from a backup generator to an uninterruptible power supply (UPS) during fueling of the backup generator. Earlier in the day the normal power supply to the two (2) plant communications buildings was deenergized due to an unrelated electrical issue and backup diesel generators were supplying power to the buildings. While refueling one of the backup generators, the power supply was transferred to the UPS for personal safety reasons, however, the load on the UPS was greater than its capacity and its output (breaker) tripped. This loss of communications was corrected in approximately 18 minutes once the fuel tank was filled and the generator was started. Phone line capability has been restored and verified to be functional. Sequoyah is currently investigating why the load was greater than the UPS capacity. The radiological emergency plan (REP) was reviewed and other acceptable methods for communications were available. There were no personnel injuries as a result of this event and no impact on plant operations. Both units remain at 100% power. The NRC Resident Inspector has been notified. This notification is being made in accordance with 10CFR50.72(b)(3)(xiii) due to the loss of communications capability which includes events that would significantly impair the ability of the licensee to implement the functions of its emergency plans if an emergency were to occur. | ||
| ENS 46790 | 27 April 2011 14:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Emergency Sirens Due to Loss of Electric Power | At approximately 1030 EDT on April 27, 2011, (Sequoyah Nuclear Plant) received notification from TVAs Operations Duty Specialist that >30% of offsite sirens are not functional resulting in a 'major loss' of offsite (automatic) public notification (capabilities). The loss of offsite sirens is due to loss of electrical power caused by severe thunderstorms and high winds in the area. Thirty five sirens are not functioning (32 sirens are considered 30%). Efforts are in place to restore offsite sirens to service. At 1044 EDT on April 27, 2011, power was restored to 2 offsite sirens leaving 33 offsite sirens not functional. At 1050 EDT on April 27, 2011, TVA's Operations Duty Specialist made a notification to Tennessee Emergency Management Agency (TEMA) and Hamilton County Emergency Response. The licensee has notified the NRC Resident Inspector.
Sequoyah Nuclear Plant reported that 28 of 108 sirens are not functional (26%) which is below the 'major loss' of offsite automatic public notification capabilities threshold. The licensee has notified the Tennessee Emergency Management Agency (TEMA) and Hamilton County Emergency Response. The licensee will notify the NRC Resident Inspector. Notified R2DO (Seymour). | ||
| ENS 45370 | 20 September 2009 22:26:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Major Loss of Communications Due to Lightning Strike | At 1826 on Sept 20, 2009, a lightning strike caused a disruption of power to offsite communications. At 1853, ENS communications from Sequoyah Nuclear Plant to the NRC were verified. At 2129, Sequoyah Nuclear Plant was notified the ERDS was not linked to the CECC (Offsite Emergency Operating Facility) or the NRC. At 2218, it was discovered the NRC could not contact Sequoyah Nuclear Plant by the ENS, but Sequoyah Nuclear Plant could still contact the NRC using ENS. At 2240, backup phone communications with satellite phone and cell phones were established between Sequoyah Nuclear Plant and the NRC. Efforts are in progress to restore power to the communications NODE building to restore normal communications. At 0155 the NRC verified 2 way communications via ENS with the licensee. The licensee will notify the NRC Resident Inspector. | ||
| ENS 43543 | 1 August 2007 16:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | 77 Out of 108 Prompt Notification System Sirens Failed Their Monthly Test | On August 1, 2007, at 1200 Eastern Daylight time the prompt notification system (PNS) monthly test was performed and 77 of the 108 PNS sirens were not responsive to the test. This is considered to be a major loss of offsite response capability. Testing is being performed to ensure operability of the PNS sirens, trouble shooting has not identified the current problem with the system. 34 of the 77 sirens have been successfully tested and testing of the remaining sirens is being conducted. State, Local and the NRC Resident Inspector have been notified of this by the licensee. | ||
| ENS 42857 | 24 September 2006 08:30:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Emergency Notification System and Commercial Telephone Line Problems | On 9/24/06 at approximately 0430 EST, the NRC Duty Officer attempted to contact the plant via the ENS (Emergency Notification System) phone for the daily plant status. Communications via the ENS phone had apparently failed, and attempts by NRC to use the commercial lines for Unit 1, Unit 2 and the Shift Manager were also unsuccessful. The plant was notified at approximately 0650 by the TVA ODS (Operations Duty Specialist) that the NRC was apparently unable to communicate with Sequoyah via the ENS phone and commercial lines. Sequoyah staff was able to communicate with the NRC Duty Officer with a commercial line, however, the ENS phone line was not functional at that time. At approximately 0700, the ENS phone was successfully utilized to communicate with the NRC Duty Officer. This event is being reported under 10CFR50,72(b)(3)(xiii), Loss of Emergency Preparedness Capabilities. An investigation will follow to determine the cause and required corrective actions. The licensee notified the NRC Resident Inspector. |