ENS 48056
ENS Event | |
|---|---|
14:28 Jun 29, 2012 | |
| Title | Unanalyzed Condition Due to Increase in Probable Maximum Flood Level |
| Event Description | On June 29, 2012, TVA issued an updated calculation titled 'PMF Determination for Tennessee River Watershed' The calculation resulted in an increase in the Watts Bar Nuclear (WBN) probable maximum flood (PMF) level from Elevation 734.9 to Elevation 739.2. All flood sensitive safety related systems, structures, and components have been reviewed and been determined to remain unaffected by the revised PMF surge elevation, with the exception of the Thermal Barrier Booster Pump Motors and Essential Raw Cooling Water (ERCW) equipment required for flood mode operation located on Elevation 722 of the Intake Pumping Station (IPS). The updated PMF of Elevation 739.2 could impact the ability of the thermal barrier booster pumps and the Elevation 722 IPS ERCW equipment to perform their design accident protection function. Because of the unanalyzed condition. the potential existed for WBN to exceed its PMF design basis and adversely affect plant safety.
This notification is being made pursuant to 10 CFR 50.72(b)(3)(ii)(B). Compensatory measures have been prepared to install a temporary flood protection barrier around the thermal barrier booster pumps and provide additional protection of Elevation 722 of the IPS in the event of a flood alert. The potential for the increased PMF level and the associated compensatory measures were previously discussed in a public meeting between TVA and the NRC on May 31, 2012 and in correspondence between TVA and the NRC dated June 13, 2012 and June 25, 2012. All safety related equipment is currently operable. There are no indications of conditions that might result in a flood in the near term. The licensee notified the NRC Resident Inspector of this condition.
Based upon continuing engineering reviews, the chilled water circulating pump motors for the Train A and B Main Control Room and 6.9kV Shutdown Board Room, including various sub-components, would be partially submerged during a Probable Maximum Flood (PMF) event. These components were not previously considered as affected by the PMF. The affected components are located on floor elevation 737.0 of the auxiliary building. This notification is being made pursuant to 10 CFR 50.72(b)(3)(ii)(B). Compensatory measures have been prepared to install temporary flood protection barrier around the chilled water circulating pump motors and provide additional protection of Elevation 722 of the IPS in the event of a flood. All safety related equipment is currently operable. There are no indications of conditions that might result in a flood in the near term. The licensee notified the NRC Resident Inspector of this condition. Licensee Event Report 50-390/2012-002-00 will be supplemented to include a description of the potential PMF affects on the chilled water circulating pump motors. Notified the R2DO (Ernstes). |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-1.4 h-0.0583 days <br />-0.00833 weeks <br />-0.00192 months <br />) | |
| Opened: | Charles Broesche 13:04 Jun 29, 2012 |
| NRC Officer: | Joe O'Hara |
| Last Updated: | Nov 29, 2012 |
| 48056 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 569102023-12-28T16:29:00028 December 2023 16:29:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 565412023-05-25T17:45:00025 May 2023 17:45:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition of Emergency Diesel Generator ENS 538012018-12-20T05:00:00020 December 2018 05:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Containment Air Return Fan System Inoperable ENS 533492018-04-19T23:44:00019 April 2018 23:44:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to Emergency Core Cooling Gas Accumulation Acceptance Criteria ENS 528502017-07-12T16:38:00012 July 2017 16:38:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to Gdc-5 (General Design Criterion-5) for Dual Unit Operation ENS 519952016-06-08T19:26:0008 June 2016 19:26:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition That Could Potentially Degrade Plant Safety ENS 509602015-04-06T21:00:0006 April 2015 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Volume Control Tank Isolation Time Analysis Error ENS 508872015-03-13T15:00:00013 March 2015 15:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 505962014-11-05T18:10:0005 November 2014 18:10:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Regarding Appendix R Procedures ENS 505402014-10-15T21:00:00015 October 2014 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Appendix R Unanalyzed Condition Affecting the Turbine Driven Aux Feedwater Pump ENS 502452014-07-01T02:46:0001 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 498182014-02-11T23:00:00011 February 2014 23:00:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 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 Nonconservative Operator Manual Actions Identified in Appendix R Analysis ENS 495412013-11-14T21:00:00014 November 2013 21:00:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 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, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Postulated Fire Induced Failure of Centrifugal Charging Pumps ENS 493892013-09-27T16:45:00027 September 2013 16:45:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Calculation Error Resulted in Unanalyzed Condition for Appendix R Event ENS 480562012-06-29T14:28:00029 June 2012 14:28:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Increase in Probable Maximum Flood Level ENS 487232009-07-28T05:00:00028 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 2023-05-25T17:45:00 | |