ENS 42526
ENS Event | |
|---|---|
10:12 Mar 4, 2006 | |
| Title | Invalid Emergency Diesel Generator Start |
| Event Description | This telephone notification is provided in accordance with 10 CFR 50.73(a)(1), to report an invalid actuation reportable under 10 CFR 50.73 (a)(2)(iv)(A).
On March 4, 2006, with Unit 1 in Mode 5 'Refuel,' Instrument Maintenance (IM) technicians were installing a Barton level indicator for reactor vessel level indicator 1B21-R452A as part of a system modification. At 0512 hours0.00593 days <br />0.142 hours <br />8.465608e-4 weeks <br />1.94816e-4 months <br />, momentary 'Reactor Vessel Water Low Level 2' alarms were received in the Main Control Room, and the Unit 1 High Pressure Core Spray (HPCS) Emergency Diesel Generator (1B EDG) auto-started. A Reactor Vessel Water Level Low 2 condition sends a start signal to HPCS and the 1B EDG; however, because the HPCS pump control switch was in pull-to-lock, the pump did not start and did not inject water into the reactor vessel. The initiating signal was reset, and at 0524 hours0.00606 days <br />0.146 hours <br />8.664021e-4 weeks <br />1.99382e-4 months <br /> the 1B EDG was shutdown with the Maintenance Switch placed in 'Maintenance.' Investigation determined that the 1B EDG had auto-started approximately 15 minutes after the IM technicians had completed work and placed the 1B21-R452A indicator back in service. The computer point alarm typer data was reviewed, and it was observed that only a single set of alarm points were received. Typically, when an alarm is caused by improperly valving in an instrument, multiple alarm points are received due to 'ringing.' Based on the 15 minute time delay and the lack of ringing, the apparent cause was determined to be an air bubble that was introduced during the modification and then migrated to the level transmitter, resulting in an invalid low level signal and an auto-start of the 1B EDG. Corrective actions included reviewing the remaining Barton installation modification work packages for unusual piping configurations that could contribute to air entrapment, and-for adequate system isolation requirements; i.e., bypassing trip units or removing components from service in order to prevent inadvertent actuations. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an invalid actuation of an EDG. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Lasalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1255.13 h52.297 days <br />7.471 weeks <br />1.719 months <br />) | |
| Opened: | Coley Chappell 16:20 Apr 25, 2006 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Apr 25, 2006 |
| 42526 - NRC Website
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WEEKMONTHYEARENS 552402021-03-10T13:15:00010 March 2021 13:15:00
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