ENS 40557
ENS Event | |
|---|---|
01:11 Mar 1, 2004 | |
| Title | Unit 2 Automatic Feedwater Isolation System (Afis) Declared Inoperable |
| Event Description | The licensee reported that both digital trains of the automatic feedwater isolation system were declared inoperable when one channel's input failed to zero and about the same time the second channel showed a shift in readouts which was fairly significant that they also declared it inoperable. These two channels have a shared neutral bus and it is believed that there may be a loose connection somewhere in the circuit. They are currently troubleshooting the problem. Plant will initiate a unit shutdown if the problem cannot be corrected by 0600 on 03/01/04 (12-hour LCO A/S).
The NRC Resident Inspector will be notified.
Update- FNS 40557, dated 3-1-04, addressed an apparent loss of safety function on Oconee Unit 2. Specifically, the Automatic Feedwater Initiation System (AFIS) was considered inoperable, and therefore unable to perform its required safety functions. During that event, Operations shift personnel conservatively declared AFIS Channel 2 inoperable because it demonstrated an unexpected shift in readout concurrent with the failure of Channel 1. Subsequently Duke power concluded that Channel 2 remained capable of performing its safety function despite the shift in readout, which was in the conservative direction. Therefore, Duke Power has concluded that there was no reportable loss of safety function associated with this event and hereby retracts ENS notification 40557. Duke Power notes that, during the event, both channels were intentionally disabled for a brief period as a planned part of the repair activity. This was done to prevent the possibility of a spurious actuation during the repair. However, per guidance in NUREG 1022, removal of both trains of a safety function as part of a planned activity which results in entry into a Tech Spec action statement is not reportable. Initial Safety Significance: Operations declared TS 3.3.13 Condition B, which allowed 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to come to Mode 3. Repairs were completed prior to initiation of shutdown. Corrective Action(s): A loose wiring connection was repaired. The NRC Resident Inspector was informed. |
| Where | |
|---|---|
Oconee  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.1 h0.129 days <br />0.0185 weeks <br />0.00425 months <br />) | |
| Opened: | Randy Todd 04:17 Mar 1, 2004 |
| NRC Officer: | Chauncey Gould |
| Last Updated: | Mar 23, 2004 |
| 40557 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (96 %) |
| After | Power Operation (96 %) |