05000425/LER-2019-003, Transformer Deenergization Results in Emergency Diesel Generator and Auxiliary Feedwater Systems Starting
| ML19338C617 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/04/2019 |
| From: | Taber B Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-19-1420 LER 2019-003-00 | |
| Download: ML19338C617 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 4252019003R00 - NRC Website | |
text
A Southern Nuclear DEC 0 4 201 9 Docket No:
50-425 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 B. Keith Taber Vice President Vogtle Units 1-2 Vogtle Electric Generating Plant - Unit 2 Licensee Event Report 2019-003-00 7821 River RD Waynesboro GA. 30830 706-848-0004 tel 706-848-3321 fax NL-19-1420 Transformer deenergization results in Emergency Diesel Generator and Auxiliary Feedwater Systems Starting Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report, 2019-003-00 for Vogtle Electric Generating Plant Unit 2. This letter contains no NRC commitments. If you have any questions, please contact Matthew Horn at (706) 848-1544.
Respectfully submitted, B. Keith Taber Vice President Vogtle 1&2 BKT/KCW Enclosure: Unit 2 Licensee Event Report 2019-003-00 Cc: Regional Administrator NRR Project Manager-Vogtle 1 & 2 Senior Resident Inspector - Vogtle 1 & 2 RType: CVC7000
Vogtle Electric Generating Plant-Unit 2 Licensee Event Report 2019-003-00 Transformer deenergization results in Emergency Diesel Generator and Auxiliary Feedwater Systems Starting Enclosure Unit 2 Licensee Event Report 2019-003-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRC may not conduct or sponsor. and a person is not required to respond to, the information collection.
. Page Vogtle Electric Generating Plant, Unit 2 05000425 1 OF2
- 4. Title Transformer deenergization results in Emergency Diesel Generator and Auxiliary Feedwater Systems Starting
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name pocket Number Month Day Year Year Month Day Year N/A Number No.
~5000 10 09 2019 2019
- - 003
- - 00
~~ D~ ~o1 Facility Name pocket Number N/A Psooo
- 9. Operating Modle N/A N/A N/A Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
At 1023 EDT, on October 9, 2019, with Unit 2 in Mode 1 and 100 percent power, an actuation of the Unit 2 A-Train Emergency Diesel Generator (EDG)[EK] and the Unit 2 A-Train Auxiliary Feedwater (AFW)[BA] Systems occurred. The reason for the EDG auto-start was the loss of power to the 4160V 1 E electrical bus 2AA02 [EB] due to a fault at an offsite electrical switchyard. The AFW system started as a result of the undervoltage condition on the safety bus. The EDG automatically started and energized the bus as designed.
Due to the automatic actuation of systems listed in 10 CFR 50.73(a)(2)(iv)(B), specifically the Emergency Diesel Generator and the Auxiliary Feedwater Systems, this event is reportable under 10 CFR 50.73(a)(2)(iv)(A).
Corrective actions have been taken to ensure that additional controls are in place over this offsite switchyard when the SAT is in operation.
The operating crew responded correctly to the event. The applicable abnormal operating procedures were properly entered, and documentation met expectations.
NRC FORM 366 (02-2018)
A.
Event Description
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 003 REV NO.
- - 00 On October 9, 2019, Unit 2 was operating in Mode 1 and 100 percent power with the 2A Reserve Aux Transformer (RAT) removed from service due to a prior emergent issue. The 2A RAT is the normal power supply to the 2AA02 bus, with the 2A RAT out of service the Standby Aux Transformer (SAT) was aligned to provide power supply to the 2AA02 bus. The SAT is a transformer whose power is supplied via an offsite power station. Testing being performed at the offsite station caused a fault in their switch yard. Due to a breaker failure the fault failed to clear automatically as required by design, this caused an upstream breaker to open which deenergized the feed supplying the Vogtle SAT causing the SAT to deenergize.
The resultant loss of the SAT caused an undervoltage condition on 2AA02 to be detected and the EDG and AFW systems started as a result. The EDG started and loaded the safety bus as designed. The AFW system also started and operated as designed. The EDG supplied the bus until the repair work was completed on the RAT, then the EDG was paralleled with the grid and the bus was transferred to the RAT at 1620 EDT and the EDG was shut down at 1623 EDT.
Because of the automatic actuation of the Emergency Diesel Generator and the Auxiliary Feedwater Systems, which are systems listed in 10 CFR 50.73(a)(2)(iv)(B), this event is reportable under 10 CFR 50.73(a)(2)(iv)(A).
B. Cause of Event
The cause of the event was a loss of power from an offsite source.
C. Safety Assessment
There were no safety consequences as a resu~ of this event.
The operating crew responded correctly to the event. The applicable abnormal operating procedures were properly entered, and documentation met expectations. The event was within the analysis of the UFSAR Chapter 15. There was not a release of radioactivity.
D. Corrective Actions
While this event was caused by a loss of power from an offsite source, corrective actions have been taken to ensure that additional controls over this offsite switchyard are put in place when the SAT is in operation.
E.
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