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| Entered date | Event description | |
|---|---|---|
| ENS 42943 | 28 October 2006 21:52:00 | An 8 hour notification per 10 CFR 50.72(b)(3)(ii)(B) is being made due to discovery of a previously unanalyzed plant condition. The chemical volume control system (CVCS) charging line is a high energy line susceptible, within design space, to a rupture that could result in pipe whip and an impingement condition. The containment penetration (M-3) for the charging line is directly below the high-pressure safety injection (HPSI) header penetrations (M-5 & M-6). Due to this proximity, a failure of the charging line could impact the SI-1503 class HPSI line (M-6) causing damage to the header and rendering it incapable of fulfilling its design function. The two HPSI headers are different class piping with the M-5 penetration being a 2500 psig (SI - 2501 Class) line and the M-6 penetration being a 1500 psig (SI-1503 Class) line. The 2500 psig line is constructed of robust enough piping to not be susceptible to failure, however both HPSI headers are cross connected prior to location of concern. Although both HPSI and CVCS breaks are isolable, operator action would be required to identify and isolate the break location. The possible result of a high energy line break of charging piping could result in all three pipe headers being inoperable until manual action could be taken to isolate leakage on the 1500 psig HPSI line. Plant is currently shutdown for refueling outage with scheduled startup of November 21, 2006. The licensee notified the NRC Resident Inspector.
Additional review of the stations design and licensing basis has determined that the charging and high pressure safety injection systems are correctly designed to the stations high energy line break criteria for lines inside containment. This situation is not reportable and therefore event notification 42943 is being withdrawn. The licensee notified the NRC Resident Inspector. Notified R4DO (Clark) |
| ENS 42781 | 17 August 2006 11:22:00 | Phone line maintenance is occurring today 8/17/06. Maintenance starting at 0900 and is planned until 1600 hours. Line maintenance may impact ENS, HPN, and ERDS capabilities. An 8 hour notification per 10CFR50.72(b)(3)(xiii) is being made due to expected failures during line interruptions. Affected communications will be verified subsequent to completion of line maintenance. The licensee notified the NRC Resident Inspector.
The ENS and HPN lines were tested and declared operable at 16:55 CDT. The ERDS line was verified operable at 17:25 by sending plant data to the NRC. The licensee notified the NRC Resident Inspector. R4DO (Blair Spitzberg) notified. |
| ENS 41446 | 27 February 2005 01:26:00 | The following information, in addition to the phone report, was obtained from the licensee via facsimile: Fort Calhoun Station Unit 1 experienced a reactor trip from 16.1% Reactor Power on a Loss of Turbine Load during a scheduled plant shutdown for a refueling outage. The turbine generator was tripped offline at 2101 per refueling outage schedule. A feedwater transient occurred (cause being investigated) during turbine testing, resulting in power rising rapidly from 12.6% to 16.1% . At which point the reactor tripped on loss of load due to being greater than 15% power with all turbine stop valves closed. All plant equipment functioned as designed. A Reactor Coolant System (RCS) cooldown resulted due to a feedwater transient. Main Feedwater was isolated, which terminated the cooldown. Auxiliary Feedwater (AFW) was established with the diesel driven auxiliary feed pump. Emergency Boration was manually initiated due to the RCS cooldown and secured after shutdown margin verification. Plant is currently stable in mode 3. This report is being made pursuant to 10 CFR 50.72(b)(2)(iv)(B) for an event that resulted in an event that resulted in an unplanned RPS actuation while the reactor was critical. All rods fully inserted, no ECCS actuation and no relief valves lifted. Steam generators are being used for heat sink. The NRC resident Inspector was notified |
| ENS 40382 | 10 December 2003 21:12:00 | Discovered vulnerability in a safeguard system that could allow access to a controlled access area for which compensatory measures have not been employed. The licensee will notify the NRC Resident Inspector. Contact the Headquarters Operations Officer for additional details.
The licensee provided additional information about this event. Contact the Headquarters Operations Officer for additional details. Notified R4DO (D. Graves) and TAS (J. Whitney) |