ENS 52076
ENS Event | |
|---|---|
00:05 Jul 9, 2016 | |
| Title | Secondary Containment Technical Specification Not Met |
| Event Description | On July 8 2016, at 19:09 [EDT] a severe thunderstorm warning was issued for Monroe County. This severe thunderstorm warning included the Fermi 2 site. Due to the high winds encountered during the thunderstorm, the Technical Specification (TS) for the secondary containment pressure boundary was not met two times during the storm for a duration time of 2 seconds total (one second for each event).
At 20:05:21 Secondary Containment pressure went positive (0.22 inches of water gauge) and at 20:05:22 returned back below plant TS limits (-0.35 inches of water gauge). At 20:06:33 Secondary Containment pressure went greater than TS limits (-0.10 inches of water gauge) and at 20:06:34 returned below TS limits (-0.28 inches of water gauge). All plant equipment responded as required to the changing environmental conditions and Reactor Building HVAC returned the secondary containment pressure below the TS limits. There were no radiological releases associated with this event. The severe thunderstorm warning for the area was cancelled at 20:30. The TS requirement is to maintain secondary containment greater than or equal to 0.125 inches of vacuum water gauge (TS SR 3.6.4.1.1) for secondary containment operability. Declaring secondary containment inoperable is reportable under 10 CFR 50.72(b)(3)(v)(C) as an event or condition that could have prevented the fulfillment of a safety function needed to control the release of radioactive material. The licensee has notified the NRC Resident Inspector.
In this event notification, DTE Electric Company (DTE) reported conditions whereby the Fermi 2 secondary containment was believed to have exceeded Technical Specification Surveillance Requirements due to high winds. DTE hereby retracts this event notification as the Fermi 2 secondary containment has been determined to have been operable during this event as described below. The Fermi 2 secondary containment pressure is maintained at a pressure less than the external pressure to contain, dilute, hold up, and reduce the activity level of fission products prior to release to the environment, and to isolate and contain fission products that are released during a Design Basis Accident or certain operations. Secondary containment pressure is monitored by a number of differential pressure (dP) sensors. High wind gusts have resulted in momentary negative pressure on the leeward side of the building, causing a more positive pressure indication from one or more dP sensors. The secondary containment building pressure remains relatively constant during these 'wind events.' In December 2016, DTE implemented a software design change to display a 120-second rolling average for secondary containment dP indication. A 120-second rolling average recorded every second provides the operator a more accurate report of actual secondary containment conditions, while mitigating the signal noise and wind gust effects. The conditions associated with the subject event notification were re-reviewed in light of the improved secondary containment dP indication and it was determined that the Fermi 2 secondary containment was operable during this event. Specifically, the secondary containment pressure did not exceed Technical Specification Surveillance Requirements during this event. In summary, the above event notification is retracted because the Fermi 2 secondary containment was determined to have been fully operable during the conditions identified in the subject report. The licensee notified the NRC Resident Inspector. Notified R3DO (Stoedter). |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
| Time - Person (Reporting Time:+-0.85 h-0.0354 days <br />-0.00506 weeks <br />-0.00116 months <br />) | |
| Opened: | Derek Etue 23:14 Jul 8, 2016 |
| NRC Officer: | Bethany Cecere |
| Last Updated: | Mar 17, 2017 |
| 52076 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |