05000455/LER-2018-001, Automatic Safety System Actuation Following a Trip of a Station Auxiliary Transformer and Subsequent Loss of Offsite Power
| ML18241A056 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 08/29/2018 |
| From: | Kanavos M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2018-0086 LER 2018-001-00 | |
| Download: ML18241A056 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 4552018001R00 - NRC Website | |
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Byron Generating Station Exe[onGeneration 445ONorthGerrnanChurchRd www.ex&oncorp.com August29, 2018 LTR:
BYRON 2018-0086 File:
1.10.0101 (1D.101) 2.07.01 00 (5A.1 08)
United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Unit 2 Renewed Facility Operating License No. NPF-66 NRC Docket No. STN 50-455
Subject:
Licensee Event Report (LER) No. 455-201 8-001 -00, Byron Station Unit 2 Automatic Safety System Actuation following a trip of a Station Auxiliary Transformer and subsequent Loss of Offsite Power.
Enclosed is Byron Station Licensee Event Report (LER) No. 455-201 8-001 -00 regarding automatic actuation of the Emergency Diesel Generators and the Auxiliary Feedwater Pumps in response to a Station Auxiliary Transformer trip and resulting Loss of Oftsite Power on Byron Unit
- 2. This condition is being submitted in accordance with 10 CFR 50.73, Licensee Event Report System.
There are no regulatory commitments in this report.
Should you have any questions concerning this submittal, please contact Mr. Douglas Spitzer, Regulatory Assurance Manager, at (81 5) 406-2800.
Respectfully, Mark E. Kanavos Site Vice President Byron Generating Station M EK/GC/rm
Enclosure:
LER 455-201 8-001 -00 cc:
Regional Administrator NRC Region Ill NRC Senior Resident Inspector Byron Generating Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/3112020 (04-2018)
Esmad, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information cotechon.
- 3. Page Byron Station Unit 2 05000455 1
OF 4
- 4. Title Byron Unit 2 AutomatiC Safety System Actuation due to System Auxiliary Transformer 242-2 Failure and Subsequent Unit 2 Loss of Offsite Power (LOOP).
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Se uential Rev Facility Name Docket Number Month Day Year Year Nmber No.
Month Day Year N/A N/A Facility Name Docket Number of 06 18 2018 001 00 08 29 18 N/A N/A
- 9. Operating Mode
- 11. This_Report is Submitted Pursuant to the Requirements of 10 CFR §: (Checkall that apply)
D 20.2201(b)
E 20.2203(a)(3)(i)
LI 50.73(a)(2)(ii)(A)
LI 50.73(a)(2)(viii)(A)
LI 20.2201(d)
LI 20.2203(a)(3)(ii)
E 50.73(a)(2)(ii)(B) fl 50.73(a)(2)(viii)(B)
LI 20.2203(a)(1 )
20.2203(a)(4)
LI 50.73(a)(2)(iii)
LI 50.73(a)(2)(ix)(A)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A)
H 50.73(a)(2)(x)
- 10. Power Level J
20.2203(a)(2)(ii)
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.Z1(a)(4)
D 20.2203(a)(2)(iii)
E:
50.36(c)(2)
D 50.73(a)(2)(v)(B)
LI 73.71(a)(5)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
LI 50.73(a)(2)(v)(C) 73.77(a)(1)
I 00 LI 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D)
LI 73.77(a)(2)(i)
El 20.2203(a)(2)(vi)
H 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii)
LI 50.73(a)(2)(i)(C)
E1 Other (Specify in Abstract below or in C.
Cause of Event
The root cause of the SAT 242-2 failure is indeterminate. The failure was the result of an aggregate contribution of multiple events, including operation with a sustained open phase in 2012 and a partial oil drain and refill to replace a degraded bushing in 201 8, which degraded the dielectric qualities of the SAT 242-2 transformer insulation.
D.
Safety Consequences
This event is not considered an event or condition that could have prevented fulfillment of a safety function.
This event consisted of the failure of one of two available Unit 2 SATs. Operations declared the Unit 2 SATs inoperable per TS 3.8.1 and entered Condition A. Operations met the Completion Time for TS 3.8.1 Required Action A.2 to restore required qualified circuits to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />; therefore, Byron was always in compliance with Technical Specifications. There are no past operability considerations with respect to SAT 242-2. There were no actual safety consequences associated with the event since the Unit 2 DG performed as expected and since Operations met the required action and completion time to restore the offsite power system. This event was not a Safety System Functional Failure, as the SATs are not considered within the scope of the Safety System Performance Indicator. The design bases event for the offsite power system is a loss of offsite power. Therefore, there would have been no additional safety consequences if this event had occurred during the design basis event for this system.
E.
Corrective Actions
Completed Corrective Actions
Operations isolated SAT 242-2 per plant procedures and aligned power supplies for single SAT normal operation througi SAT 242-1.
Planned Corrective Actions
Implement guidance within a fleet standard procedure that directs the review and consideration of OEM input for internal transformer maintenance and any associated oil drain and refill actions.
Purchase and install replacement transformer for SAT 242-2.
F.
Previous Occurrences
Byron Station Unit 1, Licensee Event Report (LER) 454-2014-003-00, Byron Unit I Diesel GeneratorActuation due to System Auxiliary Transformer 142-2 relay actuation and Loss of Offsite Power (LOOP), dated May 14, 2014. This LER involved an actuation of the Emergency DGs following loss of offsite power when the unit I SATs tripped upon a differential relay actuation that initiated a trip and lockout of the Unit I SAT feed breakers.
Licensee Event Report (LER) 455-2012-001-00, Unit 2 Loss of Normal Offsite Power and Reactor Trip and Unit I Loss of Normal Offsite Power Due to Failure of System Auxiliary Transformer Inverted Insulators, dated March 30, 2012. This LER involved an actuation of the Emergency DGs following loss of offsite power when switchyard porcelain insulators failed, resulting in an open phase non-faulted condition on one of the phases.
A review of these LERs concluded that these events are similar; however, the causes and corrective actions taken would not have been expected to prevent this event from occurring.
C.
Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number ASEA TRANSFORMER TMY-45 S/N 6311-318Page 4
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