ENS 57459
ENS Event | |
|---|---|
04:58 Dec 6, 2024 | |
| Title | Emergency Diesel Generators Declared Inoperable |
| Event Description | The following information was provided by the licensee via phone and email:
At 2358 Eastern Standard Time (EST) on December 5, 2024, emergency diesel generator (EDG) '1' was declared inoperable due to a failure in the standby lube oil temperature control circuit. At this time, EDG '2' was already inoperable due to failure of a relay in the starting air circuity. As a result, both EDGs were simultaneously inoperable; therefore, this condition is being reported as a non-emergency notification per 10 CFR 50.72(b)(3)(v)(D), as an event or condition that could have prevented fulfillment of a safety function. Offsite power, EDG '3', and EDG '4' were operable during the entire time period that EDGs '1' and '2' were inoperable. The effective safety function was restored at time 0148 on December 6, 2024, when lube oil temperature was restored and EDG '1' was declared operable. EDG '1' was inoperable concurrently with EDG '2' for approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 50 minutes. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The inoperability of two EDGs placed the plant in LCO 3.8.1.
The purpose of this Notification is to retract EN 57459 which was made on December 6, 2024, at 1700 EST. At 2358 EST on December 5, 2024, emergency diesel generator (EDG) '1' was declared inoperable due to low lube oil temperature. At this time, EDG '2' was already inoperable. The condition of EDG `1' and EDG `2' being inoperable at the same time was reported as a non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). Subsequent to this, it was determined that the identified EDG `1' low lube oil temperature reading was not representative of the temperature of the lube oil in the crankcase and sump, and therefore had no impact on EDG `1' operability. A component failure in the standby lube oil flow control circuit resulted in lube oil flow bypassing the lube oil circuit leg where temperature is sensed, allowing this uncirculated oil in the temperature sensing leg to stagnate and cool. Lube oil flow continued to recirculate through the heater circuit leg to the EDG and remained above the operability limit. The operability determination for EDG `1' has been updated indicating that EDG `1' operability was never lost for this event. As a result, there was not a condition that could have prevented the system from fulfilling the safety function. Offsite power, EDG `1', EDG '3', and EDG '4' were operable during this time. The NRC Resident Inspector has been notified. Notified R2DO (Franke) |
| Where | |
|---|---|
| Unswick North 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:+12.03 h0.501 days <br />0.0716 weeks <br />0.0165 months <br />) | |
| Opened: | Jason Wiley 17:00 Dec 6, 2024 |
| NRC Officer: | Karen Cotton-Gross |
| Last Updated: | Dec 12, 2024 |
| 57459 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unswick with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 574592024-12-06T04:58:0006 December 2024 04:58:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Emergency Diesel Generators Declared Inoperable 2024-12-06T04:58:00 | |