05000461/LER-2018-004, Undervoltage Condition Caused by an Offsite Ameren Transformer Bushing Failure Initiates an Automatic Start of an Emergency Diesel Generator
| ML18331A164 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 11/21/2018 |
| From: | Kapellas B Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| U-604456 LER 2018-004-00 | |
| Download: ML18331A164 (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) |
| 4612018004R00 - NRC Website | |
text
Clinton Power Station 8401 Power Road Clinton, IL 61727
~,,*
~~¥ Exelon.Generation U-604456 November 21, 2018 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001
Subject:
Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRG Docket No. 50-461 Licensee Event Report 2018-004-00 10 CFR 50.73 SRRS 5A.108 Enclosed is Licensee Event Report (LER) 2018-004-00: Undervoltage Condition Caused by an Offsite Ameren Transformer Bushing Failure Initiates an Automatic Start of an Emergency Diesel Generator. This report is being submitted in accordance with the requirements of 1 O CFR 50.73.
There are no regulatory commitments contained in this report.
Should you have any questions concerning this report, please contact Mr. Dale Shelton, Regulatory Assurance Manager, at (217) 937-2800.
KP/lam Attachment: License Event Report 2018-004-00 cc:
Regional Administrator - Region Ill NRG Senior Resident Inspector -
Clinton Power Station Office of Nuclear Facility Safety -
Illinois Emergency Management Agency
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRG may not conduct or sponsor, and a person is not required to respond to, the infoanation collection.
3.Page Clinton Power Station, Unit 1 05000461 1
OF 4
- 4. Title Undervoltage Condition Caused by an Offsite Ameren Transformer Bushing Failure Initiates an Automatic Start of an Emergency Diesel Generator
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rev Facility Name Docket Number Month Day Vear Vear Number No.
Month Day Vear 05000 Facility Name Docket Number 09 26 2018 2018 -
004 00 11 21 2018 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
- D 20.2201 (bl D 20.2203(a)(3)(il D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201 (dl D 20.2203(a)(3)(iil D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B) 1 D 20.22os(a)(1J D
D D
20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(il D 50.36(c)(1)(i)(A)
~ 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x) 1 O. Power Level D 20.22os(a)(2)(iil D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4l D 20.2203(~)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(s)
D 20.2203(a)(2)(iv)
D so.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1 i 099 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)*
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(iil D 50.73(a)(2)(i)(C)
D Other (Specify in Abstract below or in C.
Cause of the Event
SEQUENTIAL NUMBER 004 REV NO.
00 The cause of the event was a failure of the high side bushing on offsite Clinton Route 54 Substation Transformer No. 2 which caused the south feed to the Tabor Substation to cycle. Cycling of the south feed to the Tabor Substation caused the transient on the station 138 kV feed, which resulted in the subsequent station equipment responses.
D.
Safety Consequences
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as*any event or condition that resulted in manual or automatic actuation of emergency electrical power systems. The failure occurred at an offsite Ameren substation and did not directly involve CPS equipment.
The condition which caused a trip of the 138 kV supply line is bounded by the analysis in the Updated Safety Analysis Report section 15.2.6, "Loss of AC Power." The condition described in this report is less severe and involved no safety consequences since it only involved a loss of offsite power supply and not a trip of the unit. Electrical power sources are designed with sufficient redundancy to ensure the availability of necessary power to plant systems, structures, and components. All station equipment responded as,designed to this event with no malfunctions.
E.
Corrective Actions
The ERAT was restored to normal configuration at 1354 CDT on September 26, 2018. Ameren has completed installation of a 138 kV ring bus {Tabor Station) to improve the reliability of the 138 kV feed to CPS and is in the process of upgrading the feeds to the new substation.
F.
Previous Similar Occurrences SEQUENTIAL NUMBER 004 REV NO.
00 There were no previous occurrences involving the loss of 138 kV line and ERAT trip due to failure of an offsite transformer. However, several similar occurrences involving loss of the 138 kV line have occurred. These events are summarized below.
Licensee Event Report 2017-001-00: Failure of the 138 kV Offsite Power Source Results in a Loss of Secondary Containment Vacuum On February 24, 2017, at approximately 2239 hours0.0259 days <br />0.622 hours <br />0.0037 weeks <br />8.519395e-4 months <br /> CDT the ERAT and the associated SVC tripped due to a loss of the 138 kV line owned and maintained by Ameren Illinois. The 138 kV line was successfully re-energized at 0053 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> on February 25, 2017 and the ERAT off-site source was restored and declared OPERABLE at 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />. The cause of this event was identified by Ameren as an air flow spoiler failure.
Licensee Event Report 2016-004-00: Trip of Emergency Reserve Auxiliary Transformer Static VAR Compensator Causes Positive Secondary Containment Pressure Following Lightning Strike on 138 kV Offsite Source On March 30, 2016, at 1545 CDT, the ERAT SVC [COMP] tripped when the 138 kV line cycled open and closed due to a lightning strike. During the event, Division 1 Secondary Containment (SC) isolation dampers went shut due to the momentary loss of power and SC vacuum exceed o inches water gauge (WG). EOP-8 and TS LCO 3.6.4.1, Required Action A.1 were entered as a result of this abnormal condition. At 1547, the Standby Gas Treatment System (VG) Train A was started per CPS procedures. At 1550, SC vacuum had been restored to TS limits. Procedure EOP-8 and TS LCO 3.6.4.1 Required Action A.1 were exited. The ERAT was restored at 1926 hours0.0223 days <br />0.535 hours <br />0.00318 weeks <br />7.32843e-4 months <br /> and TS LCO 3.8.1 Required Actions A.1 and A.2 were exited.
The event on September 26, 2018 did result in a momentary reduction in SC vacuum. However, due to an approved change to the CPS TS, that event did not require declaring SC inoperable or entry into associated TS Actions.
G.
Component Failure Data
The failed component that caused the fault on the 138 kV feed and subsequent ERAT trip is owned by Ameren. There were no CPS component failures associated with this event. Page _4_ of _4_