ENS 46021
ENS Event | |
|---|---|
10:19 Jun 17, 2010 | |
| Title | |
| Event Description | At 0519 CDT on June 17th, Unit 2 was closing the 2CS009B, Containment Spray Recirc Sump Isolation Valve, as part of post maintenance testing when the valve stopped stroking (i.e. mid position). The 2CS009B valve was being stroked closed for restoration from a successful timed stroke in the open direction. The 2CS009B valve was manually closed and verified closed via limit switch indication.
With the 2CS009B valve unable to be closed from the Main Control Room, an unanalyzed condition may have existed where, during a large break LOCA requiring cold leg recirc, the Refueling Water Storage Tank (RWST) had an additional flow path to the containment recirc sump. This potentially challenges the operators to complete the switchover prior to the RWST reaching 9%, the point at which pumps taking a suction from the RWST only are shutdown. This condition is still being evaluated. The licensee notified the NRC Resident Inspector.
At 0509 on June 17, 2010, Unit 2 was closing the 2CS009B, Containment Spray (CS) Recirculation Sump Isolation Valve, as part of post maintenance testing when the valve stopped stroking (i.e., mid-position). The 2CS009B was being stroked closed for restoration from a successful timed stroke in the open direction. The 2CS009B was manually closed and verified closed via limit switch indication. With the 2CS009B unable to close from the Main Control Room, an unanalyzed condition may have existed where, during a large break LOCA requiring cold leg recirculation, the Refueling Water Storage Tank (RWST) had an additional flow path to the recirculation sump. This potentially challenged the operators to complete the switchover prior to the RWST reaching 9%, the point at which pumps taking a suction from the RWST only are shutdown. While this condition was being evaluated, an ENS notification was made per ENS 46021 under 10CFR50.72(b)(3)(ii)(B). As the evaluation approached the 60-day reporting period, LER 2010-002 was issued in accordance with 10 CFR 50.73(a)(2)(ii)(B), assuming the results would yield an unanalyzed condition. Since then, an evaluation was completed. The results concluded the operators would have performed the switchover steps within the allowed time, before reaching the RWST empty alarm set point. Therefore, the Emergency Core Cooling System (ECCS) and CS system would have performed their design functions. The evaluation also determined the RWST outflows with 2CS009B in the open position during the ECCS switchover sequence did not affect the RWST vortex analysis. Based on no loss of design function, the plant was not in an unanalyzed condition and this event is not reportable per 10CFR 50.72(b)(3)(ii)(B) or 10CFR 50.73(a)(2)(ii)(B). This event was screened for additional reportability criteria contained in the Exelon Reportability Manual. Again, since there was no loss of design function there is no reportability requirement. Therefore ENS notification 46021 is being retracted. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Braidwood  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+3.93 h0.164 days <br />0.0234 weeks <br />0.00538 months <br />) | |
| Opened: | James E. Muraida 14:15 Jun 17, 2010 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Feb 1, 2011 |
| 46021 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 519592016-05-25T19:15:00025 May 2016 19:15:00
[Table view]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 Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 517712016-03-07T02:00:0007 March 2016 02:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Involving Diesel Driven Auxiliary Feedwater Pump Air Intakes ENS 513342015-08-20T22:10:00020 August 2015 22:10:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Condition That Could Prevent Pressurizer Porv Block Valves from Operating ENS 502822014-07-15T14:42:00015 July 2014 14:42:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Low Containment Spray Flow Rate ENS 502272014-06-25T20:55:00025 June 2014 20:55:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Loss of Ultimate Heat Sink Capacity Due to Low Level ENS 501892014-06-11T19:34:00011 June 2014 19:34:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition One Containment Spray Train Chemical Additive Flow Out of Specifications ENS 493712013-09-09T22:00:0009 September 2013 22:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Leakage of Containment System Isolation Valve Controlled Leakage Devices ENS 468682011-05-20T23:00:00020 May 2011 23:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Marine Life Inside Afw Piping ENS 467072011-03-30T01:00:00030 March 2011 01:00:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Voiding in Auxiliary Feedwater Alternate Suction Line ENS 464152010-11-12T19:00:00012 November 2010 19:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Inaccurate Information Provided in License Amendment Request ENS 462032010-08-24T16:40:00024 August 2010 16:40:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Essential Service Water Placed in a Line-Up That May Have Prevented Its Safety Function ENS 460212010-06-17T10:19:00017 June 2010 10:19:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Containment Spray Recirc Sump Isolation Valve Failure to Stroke Closed 2016-05-25T19:15:00 | |