ENS 45331
ENS Event | |
|---|---|
01:20 Sep 8, 2009 | |
| Title | Discovery of After-The-Fact Emergency Condition Unusual Event |
| Event Description | This report documents a condition in which WBN [Watts Bar Nuclear] Unit 1 met the criteria to declare a NOUE [Notification of Unusual Event] based on RCS [Reactor Coolant System] unidentified leakage. Prior to declaration, the event was terminated thus no declaration was made. This event is reportable within one hour as an acceptable alternative to reporting in accordance with 10CFR50.72(a)(1)(i) - declaration of any of the emergency classes specified in the licensees approved emergency plan.
During tagout installation in support of planned maintenance on the cation bed flush valve (1-FLV-62-921) in the CVCS/Letdown system, isolation boundary valve leakage of approximately 80 gpm was present for approximately three minutes. The leakage was terminated by reclosing opened vent (1-VTV-62-917) and drain valves (1-DRV-62-920). Cation Bed Inlet (l-ISV-62-915) and Outlet (1-ISV-62-916) and all other boundary valve isolations were verified to be in the correct, closed position per the tagout instructions. This RCS leakage was directed to the Tritiated Drain Collector Tank, thus all leakage was contained within plant systems and no radiological releases resulted. A work order will be initiated to troubleshoot and repair the faulty isolation valve. This amount of leakage is in excess of the amount specified in WBN Emergency Plans for declaration of an NOUE based on >10 gpm unidentified leakage per EAL 2.5. Prior to declaration, the event was terminated, thus no declaration was made. The State of Tennessee and the NRC Resident Inspector has been notified.
Event Notice 45331 reported a condition in which WBN Unit 1 conservatively determined it met the criteria to declare a NOUE based on RCS unidentified leakage. Prior to declaration, the event was terminated thus no declaration was made. Based upon further review and discussion with others in the industry, the NOUE criterion cited, EAL 2.5, applies to specific sources of excessive RCS leakage. The source of the leakage discussed in the event has been confirmed as CVCS leakage, not RCS leakage. An action to clarify the basis and scope of this EAL is being pursued within TVA's Corrective Action Program. Therefore, Event Notice 45331 is being retracted. The NRC resident has been notified. Notified the R2DO (Blamey). |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| Other Unspec Reqmnt | |
| Time - Person (Reporting Time:+-3.3 h-0.138 days <br />-0.0196 weeks <br />-0.00452 months <br />) | |
| Opened: | Newton Lacy 22:02 Sep 7, 2009 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Sep 15, 2009 |
| 45331 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 476092012-01-17T22:46:00017 January 2012 22:46:00
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