ENS 48725
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ENS Event | |
|---|---|
05:00 Jul 28, 2009 | |
| Title | Unanalyzed Condition That Could Have Resulted in an Increased Maximum Flood Level |
| Event Description | On July 28, 2009, TVA identified, in the Corrective Action Program, the potential to overtop and fail earthen embankments at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams. This condition could have resulted in an increase in the probable maximum flood (PMF) level at Sequoyah Nuclear (SQN) Units 1 & 2. TVA initiated immediate actions to address the condition by conducting additional analyses and developing contingent actions. Additional actions were developed including the installation of modular flood barriers [which were] completed in December 2009. The barriers increase the effective height of the affected embankments preventing their overtopping and failure. The increase in PMF could have affected plant equipment including the emergency diesel generator system and the essential raw cooling water system.
Additional details regarding the modular flood barriers and the results of TVA's subsequent hydrologic analyses for SQN were discussed in public meetings between TVA and the NRC staff on July 7, 2010 and May 31, 2012, and provided in TVA letters to the NRC dated August 10, 2012, October 30, 2012, and January 18, 2013. This report addresses a condition as described in 10 CFR 50.72 (b)(3)(ii)(B). Affected safety-related equipment is currently operable. The NRC Resident Inspector has been notified of this condition. See related event notifications from Watts Bar (EN#48723) and Browns Ferry (EN#48724). |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+30947.17 h1,289.465 days <br />184.209 weeks <br />42.391 months <br />) | |
| Opened: | Harold Howle 17:10 Feb 6, 2013 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Feb 6, 2013 |
| 48725 - NRC Website
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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 544872020-01-22T03:18:00022 January 2020 03:18:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition ENS 521872016-08-17T21:22:00017 August 2016 21:22:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Not Meeting Single Failure Criteria ENS 519942016-06-08T19:26:0008 June 2016 19:26:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition That Could Potentially Degrade Plant Safety ENS 519352016-05-17T01:05:00017 May 2016 01:05:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition That Significantly Degrades Plant Safety ENS 518542016-04-07T19:07:0007 April 2016 19:07:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - High Pressure Fire Suppression Isolated from Containment ENS 515272015-11-10T20:02:00010 November 2015 20:02:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 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 Unanalyzed Condition Due to Debris Dropped Into Reactor Cavity Equipment Pit ENS 502442014-07-01T02:46:0001 July 2014 02:46:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition That Could Have Resulted in an Increased Maximum Flood Level ENS 496902014-01-03T20:00:0003 January 2014 20:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Abgts Potentially Inoperable for Both Units Under Worst-Case Conditions ENS 485842012-12-13T00:14:00013 December 2012 00:14:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Risk of Possible Flooding to Ercw Building During Design Basis Flood ENS 487252009-07-28T05:00:00028 July 2009 05:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition That Could Have Resulted in an Increased Maximum Flood Level ENS 448142009-01-28T19:25:00028 January 2009 19:25:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to a Postulated Appendix R Fire Scenario 2020-01-22T03:18:00 | |
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