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| Entered date | Event description | |
|---|---|---|
| ENS 52331 | 28 October 2016 21:58:00 | On October 28, 2016, at 1500 EDT, the Standby Liquid Control system was declared inoperable. Technical Specification (TS) Limiting Condition for Operation (LCO) 3.1.7 Condition B was entered due to sodium pentaborate concentration not within limits. Standby Liquid Control sodium pentaborate concentration was found to be low outside of the acceptable region following a Standby Liquid Control system tank high level alarm in the Main Control Room. Sodium pentaborate was added to the Standby Liquid Control tank by chemistry personnel and the concentration was then verified to be acceptable. Standby Liquid Control was declared Operable on 10/28/16 at 1935 EDT. The cause of the out-of-acceptable concentration was due to make-up water leaking by a closed valve. (The licensee cycled this valve and closed an upstream valve.) Declaring the Standby Liquid Control system inoperable is reportable under 10 CFR 50.72(b)(3)(v)(A), (C), and (D) as an event or condition that could have prevented the fulfillment of a safety function of a system needed to shut down the reactor and maintain it in a safe shutdown condition, control the release of radioactive material, and mitigate the consequences of an accident. The licensee has notified the NRC Resident Inspector. |
| ENS 52205 | 27 August 2016 17:48:00 | On August 27, 2016, at 1500 EDT a severe thunderstorm occurred in Monroe County, including the Fermi 2 site. Due to high winds encountered during the thunderstorm, the Technical Specification (TS) for secondary containment pressure boundary was not met numerous times. The duration of time that the secondary containment Technical Specification was not met was approximately 1 second for each event. All plant equipment responded as required to the changing environmental conditions and Reactor Building HVAC returned secondary containment pressure within TS limits. At 1540 EDT, 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 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). |