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| Entered date | Event description | |
|---|---|---|
| ENS 47419 | 6 November 2011 22:30:00 | At 1203 EST on 11/06/2011, the Safety Parameter Display System (SPDS) was removed from service for planned maintenance of the Plant Process Computer. The Plant Process Computer and the SPDS function were restored at 2015 EST on 11/06/2011. This event is reportable per 10 CFR 50.72(b)(3)(xiii) since the SPDS was out of service for greater than 8 hours resulting in a major loss of emergency assessment capability. The licensee will inform the NRC Resident Inspector. |
| ENS 47390 | 29 October 2011 19:46:00 | At approximately 1818 EDT on October 29, 2011, Three Mile Island Nuclear Generating Station received notification that 25 of 96 emergency notification system offsite sirens were not functional. The loss of >25% of the sirens is considered a Major Loss of Emergency Preparedness Capabilities (10CFR50.72(b)(3)(xiii)). The loss of offsite sirens was due to loss of electrical power caused by significant heavy snowfall in the area. Efforts are in place to restore offsite sirens to service. The licensee stated that compensatory measures are in place should their be a need to notify the areas affected by the lost sirens. The licensee has notified State and local authorities. The NRC Resident Inspector will be notified. |
| ENS 46194 | 21 August 2010 11:41:00 | On August 21, 2010 an inspection of the Air Intake Tunnel (AIT) sump identified missing flood barriers needed to protect safety related equipment in the plant. If enough flood water had entered into the AIT, water could have entered into the Auxiliary Building (AB) through the ventilation ductwork that connects the AIT and the AB. If flood water continued to enter the AB, then safety related equipment in the AB could have been affected. This condition could have resulted in the unavailability of equipment in the Auxiliary Building including the 1A and 1B Decay Heat pumps, the 1A and 1B Building Spray pumps and 1A, 1B and 1C Make-up Pumps. This is reportable as an 8 hour ENS notification under 10CFR50.72(b)(3)(v)(B) and 10CFR50.72(a)(1)(ii) as a condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. Flood protection barriers have been established for the affected penetrations. Inspections of the flood protection barriers are ongoing. Further engineering review is being performed to determine the impact of the potential water intrusion into the AIT and AB. The licensee notified the NRC Resident Inspector. The licensee will notify the Pennsylvania Bureau of Radiation Protection.
EN# 46194 made on August 21, 2010 at 1100 EDT is being retracted. Upon further Engineering review it was determined that the external flood barrier design deficiency in the Air Intake Tunnel (AIT) did not result in a condition that could have prevented the fulfillment of the safety function needed to remove residual heat. The AIT sump pump is in the cavity that had the degraded barrier where the in leakage of concern enters through conduits from yard electrical vaults. This pump starts automatically and has capacity in excess of the in leakage during the Probable Maximum Flood (PMF). The AIT sump pump's functional capability was confirmed to be available over the past three years. Therefore the ability to prevent flood water from the AIT reaching and impacting safety related equipment needed to remove residual heat was maintained. The event is therefore NOT reportable. The Licensee has notified the Resident Inspector. Notified R1DO. |