ENS 40475
ENS Event | |
|---|---|
08:16 Jan 25, 2004 | |
| Title | Unplanned Auto Start of Turbine Driven Auxiliary Feedwater Pump |
| Event Description | At 0316, EST, on 25 January 2004, the Unit 2 turbine driven auxiliary feedwater pump (TDAFWP) was automatically started upon receipt of a valid start signal. The start of the pump was unplanned. At the time, the Unit 2 reactor was critical at [approximately] 0.001 % power as indicated on the Intermediate Range Nuclear Instruments (Unit 2 is emerging from a forced outage following main generator repairs). The steam generators were being supplied water by the motor-driven auxiliary feedwater pumps.
Shift operators were in the process of aligning the Unit 2 condensate system for cleanup and closed both (out of service) main feedwater pumps' suction isolation valves, as required by the procedure. Closure of a main feedwater pump's suction valve generates a main feedwater pump trip signal. Trip of both main feedwater pumps generates an automatic auxiliary feedwater system start signal. The start of the TDAFWP had no adverse effect on the unit. Operators reset one of the main feedwater pumps and secured the TDAFWP. The Licensee will notify the NRC Resident Inspector.
Background: On January 25, 2004, Unit 2 was being returned to operation following a maintenance outage. Unit 2 was critical (Mode 2) with auxiliary feedwater pumps 2A and 2B in service and both MFW pumps trip buses energized. Operations continued to align the condensate system, on long cycle for clean-up. This alignment requires the closure of the main feedwater pumps suction valves. The main feedwater pumps had already been aligned for service with the trip buses energized. The plant design results in an automatic start of the auxiliary feedwater pumps when both MFW pumps trip buses trip. On January 25, 2004 at approximately 0316 hours0.00366 days <br />0.0878 hours <br />5.224868e-4 weeks <br />1.20238e-4 months <br />, the Unit-2 TDAFW pump automatically started when an operator inappropriately closed the suction valves to both MFW pumps. The closure of the pumps suction valves initiated an invalid AFW pump start signal, resulting in the start of the TDAFW pump and the steam generator level control valves went to automatic. The two motor driven AFW pumps received a start signal though they were already in service for plant startup. This actuation was not the result of actual plant conditions or parameters (there was no feedwater flow through the MFW pumps); rather it was the result of an inappropriate action in closure of the MFW pumps suction valves with both MFW pumps trip buses energized. This event was originally reported on January 25, 2004 as a valid auxiliary feedwater system start signal. Further review has determined the signal to be invalid as described above. REPORT: This event was originally reported on January 25, 2004 as a valid auxiliary feedwater system start signal. Further review has determined the signal to be invalid as described above. The following information is provided in accordance with 10 CFR 50.73(a)(2)(iv)(A): 1. Both the Unit 2 Train A and B motor-driven auxiliary feedwater pumps were running, the turbine driven auxiliary feedwater pump started and the steam generator level control valves went to automatic. 2. Complete train actuation occurred. 3. The turbine-driven auxiliary feedwater pump start and the steam generator level control valves going to automatic were successful. Notified the R2DO (OGLE). The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+1.9 h0.0792 days <br />0.0113 weeks <br />0.0026 months <br />) | |
| Opened: | Herbert Eades 10:10 Jan 25, 2004 |
| NRC Officer: | Arlon Costa |
| Last Updated: | Feb 25, 2004 |
| 40475 - NRC Website | |
WEEKMONTHYEARENS 544462019-12-16T08:58:00016 December 2019 08:58:00
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