05000366/LER-2019-001, Emergency Diesel Generator Valid Actuation Signal Due to Inadvertent Electrical Bus De-Enerqization
| ML19113A264 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/23/2019 |
| From: | Vehec T Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-19-0459 LER 2019-001-00 | |
| Download: ML19113A264 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 3662019001R00 - NRC Website | |
text
-~ Southern Nuclear APR 2 3 2019 Docket Nos.: 50-366 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Thomas A. Vehec Vice President-Plant Hatch Edwin I. Hatch Nuclear Plant Unit 2 Batch l\\udear Plant I I 028 Hatdt l'arlm iiY Nnnh B:Lxl~y. Gt\\ 31513
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\\II::! 166 ::!077 fax NL-19-0459 LER 2019-001-00 Emergency Diesel Generator Valid Actuation Signal Due to Inadvertent Electrical Bus De-Enerqization Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a}{2)(iv)(A), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report.
This letter contains no NRC commitments. If you have any questions, please contact the Hatch Licensing Manager, Jimmy Collins at (912) 537-2342.
Respectfully submitted, T.A. Vehec Vice President-Hatch TAVIPDB Enclosure: LER 2019-001-00 Cc:
Regional Administrator, Region II NRR Project Manager-Hatch Senior Resident Inspector-Hatch RTYPE: CHA02.004
Edwin I. Hatch Nuclear Plant Unit 2 LEA 2019-001-00 Emergency Diesel Generator Valid Actuation Signal Due to Inadvertent Electrical Bus De-Energization Enclosure LEA 2019*001*00
NRC FORM3SG U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3160-0104 EXPIRES: 03131/2020
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- 3. Page Edwin I Hatch Nuclear Plant Unit 2 05000 366 1
OF 2
- 4. Title Emergency Diesel Generator Valid Actuation Signal Due to Inadvertent Electrical Bus De-Energization
- 6. Event Date
- 6. LER Number
- 7. Report Date B. Other Facilities Involved I
Soquonllol I Rov Focll\\ty Nomo Cockol Number Month Coy Yo or Yo:~r Numbor llo.
Month Coy Yc:u Edwin I. Hatch Nuclear Plant U1 06000 321 Foe lilly Nomo Oockol Number 02 23 2019 2019 -
001.
00 o'-1 62.3 ~OI't 06000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: {Check all that apply) 0 20 ::01(b) 0
- 20 2:203(a)(3)(*)
D 50 73(a)(1)(n)(A)
D 50 73(a)(:)(VIn)(A)
D 10 1:01(d)
D :0 ::::03(a)(3)(n)
D 50 73(a)(2}(n)(B)
D 50 73(a)(:)(vm)(B) 5 D
D D 50 i3(a)(2)(n*)
D
- 20 ::03(a)(1) 20 2103(a)(4) 50 73(a)(::!)(IX}(A) 0 :0 ::03(a)(2)(*)
0 50 36(c)(1)(*)(A) 0 50 73(a)(: (1v)(A) 0 50 73(a)(::!){x)
- 10. Power Level 0 ::a ::o3(a)(:!)(n) 0 50 36(c)(1)(n)(A) 0 50 73(a)(:)('l)(A) 0 73 71(a)(--1) 0 10 1:!03(a)(2)(m) 0 50 36(c)(:!)
0 50 73(a)(::!)(v)(B)
D 73 71(a)(5) 0 10 1:203(a)(2l(*v) 0 50 46(a)(3)(il)
D 50 73(a)(:)(v)(C) 0 73 77(a)(1) 000 0 20 1:!03(a)(2)(v) 0 50 73(a)(:)(i)(A) 0 50 73(a)(:)(v)(D) 0 73 77(a)(2)(i) 0 10 1:203(a)(2)(vl) 0 50 73(a)(:!)(*)(B) 0 50 73(a)(2)(vn) 0 73 77(a)(:!)(n) 0 50 73(a){2)(*Hct 0 Other (Specify in Abstract below or in NRC Form 366A)
- 12. Licensee Contact for this LER Licensee Contact Telephone Number (Include Area Code)
Edwin I. Hatch I Jimmy Collins-Licensing Manager 912-537-2342 C:zusa Systam I Component
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- 14. Supplemental Report Expected Month Coy Yc:1r 0 Yes {If yes complete 15 Expected Subrrnssron Dale) 0
- 16. Expected Submission Date No Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewntten lines)
At 0212 EST on February 23, 2019, with Unit 2 in MODE 5, an actuation signal for the 2C Emergency Diesel Generator (EDG) was received during the Loss of Coolant Accident I Loss of Offsite Power logic system functional test. The 2C EDG was running and tied onto the 2G 4160 Volt emergency bus when the alternate supply breaker was closed as required per the test procedure.
Immediately upon closing the alternate supply breaker, both the alternate supply breaker and 2C EDG output breaker tripped open. Additionally, the power circuit breakers supplying power to the 1 C Station Auxiliary Transformer (SAT) and 2C SAT also tripped open. This placed Unit 1, which was in MODE 1, into Required Action Statement 3.8.1.A for one required offsite circuit inoperable. The 2C EDG output breaker reclosed once the 2G 4160 Volt bus undervoltage relays sensed a deenergized bus. An 8-hour notification was made on February 23, 2019 (Event Notification 53893) per 10 CFR 50.72(b)(3)(iv)(A) due to the valid actuation of an emergency AC electrical power system that was not part of a pre-planned sequence.
Subsequent investigation and analysis determined that the Potential Transformers and Current Transformers for 2C SAT had been wired incorrectly, which allowed the 2C EDG and 2C SAT to be paralleled out of phase. Corrective actions were taken to correct the wiring. Independent and concurrent verifications were immediately put in place for ongoing degraded grid electrical work.
NRC FOPM 366 (04-:2018) (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3160~104 EXPIRES: 03131/2020
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LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
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- 3. LER NUMBER Edwin I. Hatch Nuclear Plant Unit 2 05000-1 366 NARRATlVE
Event Description
At 0212 EST on February 23, 2019, with Unit 2 in MODE 5 at 0 percent power, and in a refueling outage, and Unit 1 in MODE 1 at 100 percent power, an actuation signal for the 2C Emergency Diesel Generator (EDG) (EllS Code DG) was received during the Loss of Coolant Accident I Loss of Offsite Power logic system functional test. The 2C EDG was running and tied onto the 2G 4160 Volt emergency bus when the alternate supply breaker was closed as required per the test procedure. Immediately upon closing the alternate supply breaker, both the alternate supply breaker and 2C EDG output breaker tripped open. Additionally, the power circuit breakers (PCB) supplying power to the 1 C Station Auxiliary Transformer (SAn (EllS Code XFMR) and 2C SAT (EllS Code XFMR) also tripped open. This placed Unit 1 into Required Action Statement 3.8.1 A for one required offsite circuit inoperable. The 2C EDG output breaker reclosed once the 2G 4160 Volt emergency bus undeNoltage relays sensed a deenergized bus, resulting in a valid actuation signal to the2CEDG.
An 8-hour notification was made on February 23,2019 (Event Notification 53893) per 10 CFR 50.72(b)(3)(iv)(A) due to the valid actuation of an emergency AC electrical power system that was not part of a pre-planned sequence.
Event Cause Analysis
S1,1bsequent investigation and analysis determined that the Potential Transformers and Current Transformers for 2C SAT had been wired incorrecUy, which allowed the 2C EDG and 2C SAT to be paralleled out of phase. The incorrectly wired Potential Transformers and Current Transformers were caused by a lack of questioning attitude by the contract electricians. The physical layout drawing used to install conduits to the Potential Transformers contained an error, contributing to the wiring error. Ineffective wiring validation of the circuit during the post maintenance test also contributed, as it simply verified new wire installation and not the entire circuit.
Safety Assessment
Unit 2 was in a refueling outage with Division I power supplying required emergency loads. Division I power was not impacted by this event and was available to mitigate an accident if one had occurred during this event. The Decay Heat Removal (DHR) system was providing shutdown cooling at the time of the event. DHR is powered from a separate power supply that was not impacted. Because there was no loss of shutdown cooling and the outage safety assessment was not impacted by this event, this event had low safety consequence for Unit 2.
Unit 1 was operating at full power during the event. The alternate power supply to the emergency buses is from the 1 C SAT. During this event, the 1C SAT PCB's were tripped due to the Unit 2 2C SAT being paralleled out of phase.
Although the alternate power supply was lost to the emergency buses, the normal power supply, 1 D SAT, continued to provide power. All Unit 1 EDG's were operable during this event. Therefore, this event had low safety consequence for Unit 1.
Corrective Actions
Actions were taken to correct the wiring errors on both the Potential and Current Transformers. Independent and concurrent verifications were immediately put in place for ongoing degraded grid electrical work. The entire circuit was validated as part of the functional testing to ensure the wiring was correct. Additionally, an extent of condition review was performed for the other newly installed transformers on Unit 2.
Previous Similar Events
None NRC FORM 388A (114-2018)
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