05000461/LER-2017-001, Regarding Failure of the 138 Kv Offsite Power Source Results in a Loss of Secondary Containment Vacuum

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Regarding Failure of the 138 Kv Offsite Power Source Results in a Loss of Secondary Containment Vacuum
ML17114A470
Person / Time
Site: Clinton 
Issue date: 04/21/2017
From: Stoner T
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
U-604340 LER 17-001-00
Download: ML17114A470 (6)
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LER-2017-001, Regarding Failure of the 138 Kv Offsite Power Source Results in a Loss of Secondary Containment Vacuum
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)(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)
4612017001R00 - NRC Website
v • d • e

text

,IIiiA2Y Exelon Generation Clinton Power Station 8401 Power Road Clinton, IL 61727 U-604340 April 21, 2ID17 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 2017-001-00 10CFR50.73 SRRS 5A.108 Enclosed is Licensee Event Report (LER) 2017-001-00: Failure of the 138 kV Offsite Power Source Results in a Loss of Secondary Containment Vacuum. This report is being submitted in accordance with the requirements of 10 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.

Respectfully,

~<=s-Theodore R. Stoner Site Vice President Clinton Power Station KP/cac Attachment: Licensee Event Report 2017-001-00 cc:

Regional Administrator-NRG 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 OMB: NO. 3150*0104 EXPIRES: 10/31/2016 (11-2015) the NRG may not conduct or sponsor, and a person is not required to respond to, lhe Information collection.

3. PAGE Clinton Power Station, Unit 1 05000461 1 OF 5
4. TITLE Failure of the 138 kV Offsite Power Source Results in a Loss of Secondary Containment Vacuum
5. EVENT DATE
6. LEA NUMBER
7. REPORT DATE B. OTHER FACILITIES INVOLVED I

SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 02 24 2017 2017 - 001

- 00 04 21 2017 05000
9. OPERATING MODE
11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

D 20.2201 (b)

D 20.2203(aH3Hi>

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201(d)

D 20.2203(a)(3Hiil D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 1 D

D 50.13(a)(2)(m>

20.2203(a)(1)

D 20.2203(a)(4l D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1 )(i)(A)

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2)(ii)

D 50.36(c)(1 )(il)(A)

D 50.73(a)(2)(v)(A)

D 13.11(a)(4J D 20.2203(al(2)(iiil D so.3s(c)(2J D 50.73(a)(2)(v)(B)

D 13.11(a)(sJ D 20.2203(a)(2)(iv)

D so.4s(aH3Hlil IZ! 50.73(a)(2)(v)(C)

D 13.77(a)(1J 099 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

Oso. 73(a)(2)(v)(D)

D 13.77(a)(2)(il D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 1s.11(a)(2)(ii)

-*~-**,,.,,.

D 50.73(a)(2)(i)(C)

D OTHER

[_

i Specify in Abstract below or In =

PLANT AND SYSTEM IDENTIFICATION

6. LEA NUMBER I

SEQUENTIAL I NUMBER 001 REV NO.

00 2

General Electric-Boiling Water Reactor, 3473 Megawatts Thermal Rated Core Power Energy Industry Identification System (EllS) codes are identified in the text as [XX]

EVENT IDENTIFICATION

3. PAGE OF Failure of the 138 kV Offsite Power Source Results in a Loss of Secondary Containment Vacuum A.

Plant Operating Conditions before the Event

Unit: 1 Mode: 1 Event Date: 02/24/17 Mode Name: Power Operation B.

DESCRIPTION OF EVENT

Event Time: 2239 Reactor Power: 99 percent 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 Emergency Reserve Auxiliary Transformer (ERAT) and the associated Static VAR Compensator (SVC) tripped due to a loss of the 138 kV line owned and maintained by Ameren Illinois. The Main Control Room (MGR) entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.1, AC Sources-Operating, Required Actions A.1 and A.2. The Clinton area was experiencing very strong winds at the time of the 138 kV power loss and the ERAT trip.

As a result of the voltage transient caused by automatic transfer to the Reserve Auxiliary Transformer (RAT), the Division 1 Fuel Building Ventilation (VF) system isolation dampers closed causing a trip of the VF supply and exhaust fans. The effect of this condition was that Secondary Containment (SC) vacuum rose to slightly greater than O inches water gauge (WG) and exceeded the TS limit of -0.25 inch WG. Operations personnel entered Emergency Operating Procedure (EOP) -8, Secondary Containment Control, and TS LCO 3.6.4.1, Secondary Containment, Required Action A.1. As a result of the loss of power and subsequent bus transfer, the following additional system actuations occurred:

Division 1 MGR Ventilation Chiller tripped Division 1 Diesel Generator room Exhaust Fan 1 VD02CA tripped, Division 1 Shutdown Service Water Pump auto started, Fission Product Monitoring (FPM) skid isolation valves shut, Division 1 Hydrogen Monitoring system isolations valves shut, Containment Service Air system Outboard Isolation 1 SA029 shut Nuclear Systems Protection System Inverter Trouble alarms annunciation (due to loss of syncronization).

CONTINUATION SHEET

2. DOCKET 05000461 YEAR
6. LER NUMBER I

SEQUENTIAL I REV NUMBER NO.

2017 001 00

3. PAGE 3

OF The system actuations were addressed and plant equipment was restored to service in accordance with plant procedures. The Standby Gas Treatment System (VG) was manually started and SC vacuum was restored within TS limits at approximately 2242 hours0.0259 days <br />0.623 hours <br />0.00371 weeks <br />8.53081e-4 months <br />. The momentary loss of power did not adversely affect the safe operation of the plant or the restoration of SC.

During the investigation, Ameren determined that high winds caused a line fault external to the Station which resulted in the 138 kV supply line trip. 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 Ameren successfully re-energized the 138 kV line. The ERAT was returned to service and declared OPERABLE at 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />.

C.

CAUSE OF EVENT

The cause of the event was identified by Ameren as an air flow spoiler failure. The radial feed design of 138 kV offsite power to CPS is susceptible to single point failures. The Clinton area was experiencing very strong winds at the time of the air flow spoiler failure.

D.

SAFETY ANALYSIS

This event is reportable in accordance with 1 O CFR 50.73(a)(2)(v)(C) as a condition that could have prevented fulfillment of a safety function to control the release of radioactive material because SC was declared inoperable during the event.

The broken air flow spoiler which caused a trip of the 138 kV supply line and the ERAT is a condition bounded by the analysis in 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. The AC electrical power sources are designed with sufficient redundancy to ensure the availability of necessary power to plant systems, structures, and components.

The VG system was fully operable at the time of the event and capable of performing its required safety function. Operations entered EOP-8 for SC vacuum less than -0.25 inch WG and entered TS LCO 3.6.4.1 Required Action A.1. SC vacuum was restored to within TS limits within the associated completion time requirement. The SC vacuum is kept slightly negative relative to atmospheric pressure to prevent leakage to the* atmosphere. The VF system is a non-safety ventilation system which is normally in service to maintain SC vacuum. The VG system is the safety-related system which is relied upon to perform this function following an accident. During the event the VG system was manually placed in service and restored SC to operability consistent with its safety function. Therefore, the ability of the station to maintain SC vacuum in the event of an accident was never jeopardized or challenged by the VF system fan trip. Engineering analysis has determined that this event is not considered a safety system functional failure.

The event discussed in this report does not constitute a safety system functional failure.

E.

CORRECTIVE ACTIONS

The 138 kV line was successfully re-energized on February 25, 2017 at 0053 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br />. Following the restoration of the 138 kV line, the ERA T transformer and associated static VAR Compensator were returned to service. An additional corrective action includes installing a modification to preclude tripping of VF due to a momentary loss of power.

F.

PREVIOUS SIMILAR OCCURENCES

There were no previous occurrences involving the loss of 138 kV line and ERAT trip due to a broken air flow spoiler. However, several similar occurrences involving to loss of the 138 kV line have occurred. These events are summarized below.

License 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 Emergency Reserve Auxiliary Transformer (ERAT)

Static VAR Compensator (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.

Licensee Event Report 2015-004-00: Trip of Emergency Reserve Auxiliary Transformer Static VAR Compensator Causes Positive Secondary Containment Pressure Following Lightning Strike on 138 kV Offsite Source.

On June 25, 2015 at 0301 CDT, the Main Control Room received numerous annunciators that indicated a trip of the ERAT transformer Static VAR Compensator (SV.C)[COMP] caused by a voltage transient on the 138 kV offsite source due to thunderstorms in the area. The Division 1 Safety Bus [BU] was manually aligned from the reserve source to its normal source. As a result of the voltage transient, the Division 1 VF system isolation dampers closed causing a trip of VF supply and exhaust fans. SC vacuum increased to greater than O inches WG which exceeded the TS requirement. SC vacuum was restored within TS requirements by reopening the VF isolation dampers and restarting the VF supply and exhaust fans. The ERAT SVC was returned to service at 0457 CDT.

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

2. DOCKET
6. LEA NUMBER
3. PAGE OF 5

YEAR I SEQUENTIAL I REV NUMBER NO.

05000461 5

2017 001 00 G.

COMPONENT FAILURE DATA

The component failure which caused the 138 kV supply trip was owned by Ameren. There were no CPS component failures associated with this event.

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