05000373/LER-2013-002-02, Regarding Unusual Event Declared Due to Loss of Offsite Power and Dual Unit Reactor Scram
| ML14022A064 | |
| Person / Time | |
|---|---|
| Site: |  |
| Issue date: | 01/22/2014 |
| From: | Vinyard H Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA14-001 LER 13-002-02 | |
| Download: ML14022A064 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 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)(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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 3732013002R02 - NRC Website | |
text
RA14-001 January 22, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374 10 CFR 50.73
Subject:
Licensee Event Report 2013-002-02 Unusual Event Declared Due to Loss of Offsite Power and Dual Unit Scram In accordance with 10 CFR 50.73(a)(2)(iv)(A), Exelon Generation Company (EGC), LLC, is submitting supplemental Licensee Event Report Number 2013-002-02 for LaSalle Units 1 and 2. This supplement revises the previous reports to state that the event was not reportable under 10 CFR 50.73(a)(2)(v)(D), and did not constitute safety system functional failure.
There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Mr. Guy V. Ford, Regulatory Assurance Manager, at (815) 415-2800.
Harold T. Vinyard Plant Manager LaSalle County Station
Enclosure:
Licensee Event Report cc:
Regional Administrator-NRC Region Ill NRC Senior Resident Inspector-LaSalle County Station
(
{
NRCFORM366 U.S. NUClEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRE~: 10/31/2013 (10.2010)
Estimated burden per rasponse to comply with this mandatory collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned ara Incorporated Into the licensing process and fed back to ind~ Send comments ragardng burden estimate to the FOIA/Prlvacy Section
- - 5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by Internet e-mail to LICENSEE EVENT REPORT {LER) infocollects.rasourceOn~, and to the Desk Officer, Office of Information and Regulatory Affairs, N 10202, (315().()1 04), Office of Management and Budget, Washington, DC 20503. H a means used to impose an information (See reverse for required number of collection does not display a currantly valid OMB control number, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to raspond to, the information collection.
- 1. FACIUTY NAME
- 2. DOCKET NUMBER r.PAGE LaSalle County Station, Unit 1 05000373 1 OF 3
~.TITLE Unusual Event Declared Due to Loss of Offsite Power and Dual Unit Reactor Scram
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACIUTY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR LaSalle County Station, Unit 2 05000374 FACIUTY NAME DOCKET NUMBER 04 17 2013 2013 -
002 -
02 01 22 2014 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 0 20.2201 (b) 0 20.2203(a)(3){i) 0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 0 20.2201 {d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73{a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 0 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A) 0 50.73(a)(2)(iii) 0 50.73{a)(2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a){2)(ii) 0 50.36{c)(1)(ii)(A) 181 50. 73(a)(2)(iv)(A) 0 50.73(a)(2)(x) 0 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) 100 0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 0 73.71(a)(5) 0 20.2203(a)(2)(v) 0 50.73(a){2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER 0 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form ~A
- 12. UCENSEE CONTACT FOR THIS LER FACIUTY NAME I
TELEPHONE NUMBER (Include Area Code)
John Kowalski, Site Engineering Director 815-415-3800
- 13. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TOEPIX FACTURER TOEPIX c
FK XPT W120 y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 181 NO SUBMISSION DATE
~BSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On April17, 2013, LaSalle Units 1 and 2 were operating in Mode 1 at 100% power, with a severe thunderstorm in progress. At 1457 hours0.0169 days <br />0.405 hours <br />0.00241 weeks <br />5.543885e-4 months <br /> COT, lightning struck 138KV Line 0112, resulting in a phase-to-ground fault which subsequently cleared. At 1459 hours0.0169 days <br />0.405 hours <br />0.00241 weeks <br />5.551495e-4 months <br />, a second phase-to-ground fault on Line 0112 occurred and all 345 KV oil circuit breakers (OCBs) in the main switchyard opened, resulting in a loss of offsite power and reactor scrams on both Units. All emergency diesel generators automatically started and loaded onto their respective busses. All control rods fully inserted, and all systems responded as expected.
An Unusual Event was declared due to a loss of offsite power for greater than 15 minutes. Offsite power was restored to all ESF busses by 2301 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.755305e-4 months <br /> on April17, 2013, and the Unusual Event was terminated at 0814 hours0.00942 days <br />0.226 hours <br />0.00135 weeks <br />3.09727e-4 months <br /> on Apri118, 2013.
The root cause of the event was determined to be degradation of the 138kV switchyard grounding system that allowed a lightning induced fault to flash over onto the DC protective system. The ground system in the 138kV switchyard was repaired, and corrective actions include improving lightning shielding in the 138kV switchyard.
NRC FORM 366 (10.2010)
- 6. LER NUMBER I
SEQUENTIAL I REV NUMBER NO.
002 02
- 3. PAGE 2
OF 3
LaSalle County Station Units 1 and 2 are General Electric Company Boiling Water Reactors with 3546 Megawatts Rated Core Thermal Power.
A. CONDITION PRIOR TO EVENT
Unit(s): 1/2 Event Date: April17, 2013 Reactor Mode(s): 1/1 Mode(s) Name: Power Operation
B. DESCRIPTION OF EVENT
Event Time: 1459 COT Power Level: 1 00%
On April17, 2013, LaSalle Units 1 and 2 were operating in Mode 1 at 100% power, with a severe thunderstorm in progress. At 1457 hours0.0169 days <br />0.405 hours <br />0.00241 weeks <br />5.543885e-4 months <br /> COT, lightning struck 138KV Line 0112, resulting in a phase-to-ground fault which subsequently cleared. At 1459 hours0.0169 days <br />0.405 hours <br />0.00241 weeks <br />5.551495e-4 months <br />, a second phase-to-ground fault on Line 0112 occurred and all 345 KV oil circuit breakers (OCBs) in the main switchyard (SY)[FK] opened, resulting in a loss of offsite power and reactor scrams on both Units. All emergency diesel generators (DG)[EK] automatically started and loaded onto their respective busses.
Plant systems on both Units responded as expected. All control rods went full in. The main steam isolation valves closed, with decay heat being removed via the safety relief valves. High Pressure Core Spray (HPCS)[BG] automatically started on both Units on low reactor water level; Reactor Core Isolation Cooling (RCIC)[BN] was used for level control. At 1511 hours0.0175 days <br />0.42 hours <br />0.0025 weeks <br />5.749355e-4 months <br />, LaSalle declared an Unusual Event due to a loss of offsite power (LOOP) for greater than 15 minutes.
Primary containment pressure increased as expected, consistent with the loss of containment cooling due to the loss of non-ESF AC power. Primary containment pressure reached the Primary Containment Isolation System (PCIS)[JM] isolation setpoint on April 17, 2013, at 1721 hours0.0199 days <br />0.478 hours <br />0.00285 weeks <br />6.548405e-4 months <br /> on Unit 2 and at 2004 hours0.0232 days <br />0.557 hours <br />0.00331 weeks <br />7.62522e-4 months <br /> on Unit 1.
Offsite power was restored to all ESF busses by 2301 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.755305e-4 months <br /> on April17, 2013. Containment cooling was restored on April18, 2013, by 0055, and the PCIS signals were cleared on Unit 1 by 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> and on Unit 2 by 0814 hours0.00942 days <br />0.226 hours <br />0.00135 weeks <br />3.09727e-4 months <br />. The Unusual Event was terminated at 0814 hours0.00942 days <br />0.226 hours <br />0.00135 weeks <br />3.09727e-4 months <br /> on April18, 2013.
This occurrence is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event which resulted in the automatic actuation of the reactor protection system (RPS)[JC], emergency core cooling systems (ECCS), and ESF systems as listed in 10 CFR 50.73(a)(2)(iv)(B). An ENS report was made to the NRC (EN 48939) at 1559 COT on April17, 2013, and was updated as required throughout the event.
This event constitutes an unplanned scram with complications for both LaSalle Units 1 and 2.
C. CAUSE OF EVENT
The initiating event was a lightning strike on 138KV Line 0112 in the main 345/138 KV switchyard. Line 0112 was inspected in the field and had sustained heavy damage to phase "C" insulators.
The root cause of the event was determined to be degradation of the 138kV switchyard grounding system that allowed a lightning induced fault to flash over onto the DC protective system. The grounding system degradation was due to poor workmanship during original construction. This degradation allowed a fault (10.2010)
LICENSEE EVENT REPORT (LEA) u.s. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET
- 1. FACIUTY NAME
- 2. DOCKET YEAR LaSalle County Station, Unit 1 05000373 2013 NARRA11VE
- 6. LER NUMBER I
SEQUENTIAL I REV NUMBER NO.
002 02
- 3. PAGE 3
OF initiated by a lightning strike on the L0112 C phase capacitance coupled voltage transformer (CCVT) in the 138kV switchyard to damage the shared DC protection system. Another contributor to the event was determined to be inadequate lightning shielding of the 138kV switchyard.
D. SAFETY ANALYSIS
3 The safety significance of this event was minimal. On the loss of offsite power, all emergency diesel generators automatically started and loaded onto their respective busses. Both reactors automatically scrammed, with all control rods fully inserting. All ESF and ECCS systems were operable at the time of the event. 345 KV Lines 01 01 and 0102 from Plano, and 345 KV Lines 01 03 and 01 04 from Braidwood remained energized during the event.
This event was determined not to be reportable under 10 CFR 50.73(a)(2)(v)(D) as an event that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. NUREG-1022, Revision 3, does not require a LOOP to be reported under this requirement. An engineering review of UFSAR Chapter 6 "Engineered Safety Features" and 15 "Accident Analyses" was performed that validated that the non safety-related offsite power system is not required to mitigate the consequences of an accident. In the event of loss of offsite power, the ESF loads are automatically connected to the EDGs in sufficient time to provide for safe reactor shutdown and to mitigate the consequences of a design basis accident such as a LOCA. Therefore, the event did not constitute a safety system function failure.
E. CORRECTIVE ACTIONS
Offsite power was restored to the ESF busses on both Units by 2301 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.755305e-4 months <br /> on April17, 2013.
All degraded connections and ground cables in the 138kV switchyard were repaired.
Lightning shielding in the 138kV switchyard have been improved.
F. PREVIOUS OCCURRENCES
A search identified no previous occurrences within the past 1 0 years of a scram or a loss of offsite power at LaSalle County Station resulting from a lightning strike.
G. COMPONENT FAILURE DATA
Westinghouse PCA-5 type capacitance coupled voltage transformer.