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| Entered date | Event description | |
|---|---|---|
| ENS 51487 | 21 October 2015 18:33:00 | The isolation function when transferring control from the Main Control Room to the Alternate Shutdown Panel (AI-185) for Pressurizer Heater Bank No. 4 (including Groups No. 10, No. 11, and No. 12) has been identified as a potential circuit failure. Identification of the potential circuit failure vulnerability is for Pressurizer Heater Bank No. 4 when isolated from Alternate Shutdown Panel (AI-185) and operated locally from Motor Control Center (MCC-4C1) for Alternate Shutdown Fire Areas 41 (Cable Spreading Room) and 42 (Main Control Room). The vulnerability involves an external hot short affecting the conductor connecting to the control room switch which may keep the 94/10 relay energized and defeat MCC control of the heaters. In a postulated event, a fire in the control room could prevent the heaters from energizing when demanded, or cause the heaters to unintentionally energize. This condition is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. Per National Fire Protection Association (NFPA) 805, fire watch is an adequate compensatory measure. Therefore, this vulnerability has been added to the existing NFPA 805 Fire Protection compensatory measure for Fire Area 41. For Fire Area 42, the Main Control Room is continuously staffed, which has been credited as the compensatory measure. The NRC Resident Inspector has been notified. |
| ENS 51270 | 27 July 2015 18:01:00 | On July 8, 2015, Fort Calhoun Station was in Mode 1, 100% when personnel identified an increase in the Reactor Coolant System unidentified leakage rate. As a result, personnel performed a containment entry and identified the source coming from the Reactor Coolant Pump 3A seal area. Based on this observation, a monitoring plan was established and on July 20, 2015 the leak rate exceeded the pre-establish leak limit and operators manually shutdown the reactor. On July 22, 2015, at approximately 1330 CDT, personnel identified the source of the seal leak as a crack on the middle seal inlet line, which is part of the reactor coolant system boundary. Maintenance personnel have since repaired the seal line and it has passed post-maintenance testing. The 8-hour verbal report is being made post event due to additional review of the leakage condition identifying the leakage constituted a degraded condition due to be material defects in the primary coolant system. The leak rate was between 1 and 2 gpm. The licensee notified the NRC Resident Inspector. |
| ENS 48148 | 1 August 2012 13:24:00 | At 0327 CDT, a call was received from the NRC Operations Center for Emergency Notification System (ENS) phone status check on the commercial phone line. The ENS phone system had no incoming rings, nor a dial-tone. The NRC Headquarters Operations Officer (HOO) was to submit a trouble ticket. At 0949 CDT, Emergency Planning personnel were working with Verizon Communications to determine the cause of the loss of the ENS phone. Verizon had isolated the problem to the American Broadband network and was working to resolve the problem. At 1010 CDT, Emergency Planning personnel identified that the Health Physics Network (HPN) line, the Protective Measures Counterpart (PMC) and Reactor Safety Counterpart (RSC) lines with the NRC had also been lost. The Conference Operations Network (COP) and all other commercial phone lines were functional and remained available. All areas were reachable by commercial phone lines. At 1022 CDT, the FCS Control Room was informed by Emergency Planning personnel of the communication means that were lost. The Emergency Plan per EPIP-OSC-1 was reviewed and verified no initiating conditions applied. At 1034 CDT, Emergency Planning personnel verified the communications problem with ENS, HPN, the Protective Measures Counterpart and Reactor Safety Counterpart lines was limited to the Fort Calhoun site. The Emergency Operations Facility (EOF) was not affected. At 1054 CDT, the ENS phone was restored to the FCS Control Room. This was verified by FCS placing a call to the NRC Operations Center. The NRC Operations Center then returned the call. All communications were satisfactorily restored. At 1132 CDT, the Protective Measures Counterpart line was restored. At 1142 CDT, the HPN and Reactor Safety Counterpart lines were restored. This is being reported per 10CFR50.72(b)(3)(xiii) for 'Any event that results in a major loss of emergency assessment capability, off site response capability, or communications capability.' The licensee notified the NRC Resident Inspector. |