ENS 43894
ENS Event | |
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20:10 Jan 11, 2008 | |
Title | Discovery of an After the Fact Unusual Event |
Event Description | At 1510, "[Watts Bar Nuclear (WBN)] had identified RCS leakage in excess of 25 gallons per minute (gpm). The leakage was estimated at 105 gpm. This is a report notification only and not a declaration. The EAL that was exceeded was 2.6, RCS identified leakage. While placing a mixed bed demineralizer in service VCT level was observed to have dropped 10%. The demineralizer was immediately removed from service. This terminated the drop in VCT level. In accordance with WBN EPIP-1 Emergency Classification Flowchart, section 3.0 step 3.3.7, if an EAL was exceeded but the emergency has been totally resolved (prior to declaration), the emergency condition that was appropriate shall not be declared but reported only. The duration of the leakage was approximately 15 minutes. The unit remains at mode 1 and 100% power. The cause for the unexpected level decrease is under investigation at this time. There were no radiological releases associated.
The licensee will notify the NRC Resident Inspector.
The original report contains a typographical error. The leak duration was reported as 15 minutes. The correct time period is 1.5 minutes. Notified R2DO(Moorman)
On January 11, 2008, TVA notified the NRC of the discovery of an after the fact unusual event. The reported event described potential RCS leakage in excess of 25 GPM that was approximately 1 and 1/2 minutes in duration. The estimated magnitude of this leak was based on a step change in Volume Control Tank (VCT) level that occurred when placing the 1A Mixed Bed Demineralizer in service. TVA's post-event investigation concluded the cause of the VCT level change was the filling of a void in the 1A Mixed Bed Demineralizer. The cause of the void was a procedural deficiency in the flush methodology used when returning the demineralizer to service. Based on the evaluation of this event, TVA has concluded that no actual RCS leakage occurred. The RCS pressure boundary remained intact throughout this evolution. Based on the result of this evaluation and the subsequent successful alignment of the demineralizer without incident, TVA is retracting this event. The licensee has notified the NRC Resident of this retraction. Notified the R2DO (Munday) and NRR EO (Brown). |
Where | |
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Watts Bar Tennessee (NRC Region 2) | |
Reporting | |
Emergency class: | Unusual Event |
10 CFR 76.120(a)(4) | |
Time - Person (Reporting Time:+-4.4 h-0.183 days <br />-0.0262 weeks <br />-0.00603 months <br />) | |
Opened: | Greg Evans 15:46 Jan 11, 2008 |
NRC Officer: | Pete Snyder |
Last Updated: | Feb 8, 2008 |
43894 - NRC Website
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Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
WEEKMONTHYEARENS 438942008-01-11T20:10:00011 January 2008 20:10:00
[Table view]10 CFR 76.120(a)(4) Discovery of an After the Fact Unusual Event 2008-01-11T20:10:00 | |