ENS 54977
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ENS Event | |
|---|---|
09:56 Nov 1, 2020 | |
| Title | Loss of Seismic Assessment Instrumentation |
| Event Description | 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. |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | |
| Time - Person (Reporting Time:+1.13 h0.0471 days <br />0.00673 weeks <br />0.00155 months <br />) | |
| Opened: | Zachary Patterson 11:04 Nov 1, 2020 |
| NRC Officer: | Thomas Herrity |
| Last Updated: | Nov 1, 2020 |
| 54977 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 558672022-04-29T03:38:00029 April 2022 03:38:00
[Table view]10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Assessment Capability ENS 557422022-02-16T16:28:00016 February 2022 16:28:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Offsite Communication Capability ENS 549772020-11-01T09:56:0001 November 2020 09:56:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Seismic Assessment Instrumentation ENS 543802019-11-12T12:00:00012 November 2019 12:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Emergency Operations Facility Out of Service ENS 542762019-09-13T09:27:00013 September 2019 09:27:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness En Revision Imported Date 9/17/2019 ENS 521722016-08-11T14:15:00011 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 ENS 508532015-02-27T18:05:00027 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 ENS 467902011-04-27T14:30:00027 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 ENS 453702009-09-20T22:26:00020 September 2009 22:26:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Major Loss of Communications Due to Lightning Strike ENS 435432007-08-01T16:00:0001 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 ENS 428572006-09-24T08:30:00024 September 2006 08:30:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Emergency Notification System and Commercial Telephone Line Problems 2022-04-29T03:38:00 | |
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