ENS 52850
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ENS Event | |
|---|---|
16:38 Jul 12, 2017 | |
| Title | Unanalyzed Condition Related to Gdc-5 [General Design Criterion-5] for Dual Unit Operation |
| Event Description | On July 12, 2017, at 1238 Eastern Daylight Time (EDT), Watts Bar Nuclear Plant (WBN) determined that a preliminary analysis shows adequate Essential Raw Cooling Water (ERCW) flow may not be in place during dual unit limiting design basis conditions of one unit in Hot Shutdown on Residual Heat Removal (RHR) cooling when the other unit experiences a Loss of Coolant Accident (LOCA). Based on preliminary analysis, during a Unit 1 LOCA, Unit 1 receives adequate flow when following existing procedural guidance; however, Unit 2 may not receive adequate flow to meet cool-down requirements with design basis maximum temperatures. During a Unit 2 LOCA, however, current procedural guidance is not adequate to ensure the proper system alignment to establish correct ERCW Component Cooling Water (CCS) Heat Exchanger A and B flow rates for either unit's cool down requirements.
Unit 2 has been shutdown for an extended period of time such that the flow delivered by ERCW is adequate to serve both Unit 1 in a LOCA and Unit 2 in less than Mode 3. The NRC Resident Inspector has been notified. |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-0.55 h-0.0229 days <br />-0.00327 weeks <br />-7.5339e-4 months <br />) | |
| Opened: | David Allen 16:05 Jul 12, 2017 |
| NRC Officer: | Dong Park |
| Last Updated: | Jul 12, 2017 |
| 52850 - 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 | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
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 | |
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