ENS 52398
ENS Event | |
|---|---|
02:05 Nov 29, 2016 | |
| Title | Secondary Containment Technical Specification Not Met |
| Event Description | On November 28, 2016, starting at 2105 hrs. EST, high wind conditions encountered on site resulted in the Technical Specification (TS) for secondary containment pressure boundary not being met numerous times. The duration of time that the secondary containment Technical Specification was not met was approximately 1 second for each instance.
All plant equipment responded as required to the changing environmental conditions and Reactor Building HVAC returned secondary containment pressure within TS limits. At 0055 EST on November 29, 2016, high wind conditions had subsided and secondary containment vacuum was greater than the TS operability limit of 0.125 inches of vacuum water gauge (TS SR 3.6.4.1.1) and steady, and the LCO was exited. There were no radiological releases associated with this event. Declaring secondary containment inoperable is reportable under 10CFR50.72(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.
On November 29, 2016, at 0242 EST, high wind conditions encountered on site resulted in the Technical Specification (TS) for secondary containment pressure boundary not being met numerous times following the initial event notification. The duration of time that the secondary containment Technical Specification was not met was approximately 1 second for each instance. All plant equipment responded as required to the changing environmental conditions and Reactor Building HVAC returned secondary containment pressure to within TS limits. High wind conditions are expected to decrease throughout the day. If additional instances are identified that require entry into the Technical Specifications (TS) for secondary containment pressure boundary not being met, another follow up notification will be performed. There were no radiological releases associated with this event. Declaring secondary containment inoperable is reportable under 10CFR50.72(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. Notified R3DO (Stoedter).
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:+-0.4 h-0.0167 days <br />-0.00238 weeks <br />-5.4792e-4 months <br />) | |
| Opened: | Jeff Yeager 01:41 Nov 29, 2016 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Mar 17, 2017 |
| 52398 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |