ENS 40632
ENS Event | |
|---|---|
01:19 Apr 1, 2004 | |
| Title | New Worst Case Single Failure May Exceed 10 Cfr 50.46 Acceptance Criterion for Sbloca |
| Event Description | A new worst case single failure was identified on 03-31-04 for the small break LOCA analysis of record due to a postulated loss of a DC power bus. This condition may result in the analysis of record exceeding 10 CFR 50.46 acceptance criterion of 2200 F when a small break LOCA with this failure is postulated.
The current small break LOCA analysis of record assumes a single failure of one Emergency Diesel Generator (EDG) and credits flow from one charging pump. The peak cladding temperature for the analysis of record is 1929 F compared to the acceptance criteria of less than or equal to 2200 F. Half of the flow from a charging pump is assumed to go to the RCS and half is assumed to flow out the break. It was identified on 03-31-04 that a single failure of a DC power bus would be more limiting than the currently assumed single failure of an EDG. The DC bus failure will result in the EDG failure to start and also cause a charging loop isolation valve to the RCS to fail closed on loss of DC power. The other charging flow path to the RCS is on the assumed broken RCS leg so it is assumed to be spilled to the containment resulting in no charging flow to the RCS. Therefore, no charging flow would be delivered to the RCS as assumed in the current small break LOCA analysis of record. This condition has not been analyzed. Engineering judgment indicates that in the event of a small break accident the 10 CFR 50.46 acceptance criterion of 2200 F may be exceeded if the charging flow is not credited in the analysis of record. Therefore, this condition is reportable pursuant to 10 CFR 50.46 and 10 CFR 50.72(b)(3)(ii)(B). The current conservatism in the analysis of record and previous Westinghouse SBLOCA non-design basis scoping analyses using the NOTRUMP code provide assurance the plant is operating in a safe manner and is operable. The NOTRUMP analyses included cases with no changing flow. The peak clad temperature for these analyses were significantly below the acceptance criteria of 2200 F by more than 200 F. Thus, if an analysis were performed for Waterford 3 with the NOTRUMP code there is reasonable assurance due to the large margins that acceptable results would be achieved without any charging flow. This report is based on conservative judgment and available information. This report may be retracted based on the results of further evaluation. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Waterford  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Other Unspec Reqmnt | |
| Time - Person (Reporting Time:+-0.58 h-0.0242 days <br />-0.00345 weeks <br />-7.94484e-4 months <br />) | |
| Opened: | Robert Murillo 00:44 Apr 1, 2004 |
| NRC Officer: | Mike Ripley |
| Last Updated: | Apr 1, 2004 |
| 40632 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 568492023-11-10T21:45:00010 November 2023 21:45:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 523372016-10-31T16:00:00031 October 2016 16:00:00 Other Unspec Reqmnt Supplemental Cooling Inoperable During Movement of Dry Cask Storage Hi-Track Transfer Cask ENS 498752014-03-05T15:12:0005 March 2014 15:12:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Impact on Unfused Direct Current Ammeter Circuits in the Main Control Room ENS 493262013-09-05T21:00:0005 September 2013 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Loss of Auxiliary Component Cooling Water Systems ENS 468242011-05-06T07:09:0006 May 2011 07:09:00 Other Unspec Reqmnt Discovery of an After-The-Fact Unusual Event ENS 406322004-04-01T01:19:0001 April 2004 01:19:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition New Worst Case Single Failure May Exceed 10 Cfr 50.46 Acceptance Criterion for Sbloca ENS 405192004-02-13T11:25:00013 February 2004 11:25:00 Other Unspec Reqmnt 24 Hour Notification Per Licensee Condition 2.F 2023-11-10T21:45:00 | |