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{{Adams
#REDIRECT [[05000373/LER-2013-002]]
| number = ML13207A371
| issue date = 07/26/2013
| title = LER 13-002-01 for LaSalle, Unit 1 Regarding Unusual Event Declared Due to Loss of Offsite Power and Dual Unit Reactor Scram
| author name = Vinyard H T
| author affiliation = Exelon Generation Co, LLC
| addressee name =
| addressee affiliation = NRC/NRR, NRC/Document Control Desk
| docket = 05000373, 05000374
| license number = NPF-011, NPF-018
| contact person =
| case reference number = RA13-041
| document report number = LER 13-002-01
| document type = Letter, Licensee Event Report (LER)
| page count = 4
}}
 
=Text=
{{#Wiki_filter:10 CFR 50.73 RA13-041July 26, 2013 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
 
==Subject:==
Licensee Event Report 2013-002-01 Unusual Event Declared Due to Loss of Offsite Power and Dual Unit Scram In accordance with 10 CFR 50.73(a)(2)(iv)(A) and 73.(a)(2)(v)(D), Exelon Generation Company (EGC), LLC, is submitting supplemental Licensee Event Report Number 2013-002-01 for LaSalle Units 1 and 2.
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.
Respectfully, Harold T. Vinyard Plant Manager LaSalle County Station
 
==Enclosure:==
Licensee Event Report cc:Regional Administrator - NRC Region III NRC Senior Resident Inspector - LaSalle County Station I
NRC FORM 366U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104EXPIRES: 10/31/2013 (10-2010)
Estimated burden per response to comply with this mandatory collection request: 80 hours. Reported lessons learnedare incorporated into the licensing process and fed back to industry. Send comments regarding burden estimateto the FOIA/Privacy Section (T-5 F53), U.S. Nuclear Regulatory Commission,Washington,DC20555-0001,orbyintemete-mailtoLICENSEE EVENT REPORT (LER)infocollects.resource@nrc.gov
,and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and (See reverse for required number of Budget,Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the ifillinon coon.ormatect1. FACILITY NAME
: 2. DOCKET NUMBER
: 3. PAGELaSalle County Station, Unit 1 050003731OF 34. TITLEUnusual 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 MONTHDAYYEARYEARSEQUENTIAL REVMONTHDAYYEARFACILITY NAME Unit 2LaSalle County Station DOCKET NUMBER 05000374NUMBERNO.,FACILITY NAME DOCKET NUMBER 041720132013-002-0107262013N/AN/A9. OPERATING MODE
: 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:
(Check all that apply) q20.2201(b)q20.2203(a)(3)(i)q50.73(a)(2)(i)(C)q50.73(a)(2)(vii) 1q20.2201(d)q20.2203(a)(3)(ii)q50.73(a)(2)(ii)(A)q50.73(a)(2)(viii)(A) q20.2203(a)(1)q20.2203(a)(4)q50.73(a)(2)(ii)(B)q50.73(a)(2)(viii)(B) q20.2203(a)(2)(i)q50.36(c)(1)(i)(A)q50.73(a)(2)(iii)q50.73(a)(2)(ix)(A)
: 10. POWER LEVEL q20.2203(a)(2)(ii)q50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A)q50.73(a)(2)(x) q20.2203(a)(2)(iii)q50.36(c)(2)q50.73(a)(2)(v)(A)q73.71(a)(4) 100q20.2203(a)(2)(iv)q50.46(a)(3)(ii)q50.73(a)(2)(v)(B)q73.71(a)(5) q20.2203(a)(2)(v)q50.73(a)(2)(i)(A)q50.73(a)(2)(v)(C)qOTHERq20.2203(a)(2)(vi)q50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)Specify in Abstract below or in NRC Form 366A
: 12. LICENSEE CONTACT FOR THIS LERFACILITY NAME TELEPHONE NUMBER (Include Area Code)John Kowalski, Deputy Engineering Manager 815-415-3830
: 13. COMPLETE O NE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSESYSTEMCOMPONENT MANU-FACTURERREPORTABLECAUSESYSTEMTO EPIXCOMPONENT MANU-FACTURERREPORTABLE TO EPIXCFKXPTW120Y14. SUPPLEMENTAL REPORT EXPECTED15. EXPECTED MONTHDAYYEARSUBMISSION171YES(If yes, complete 15. EXPECTED SUBMISSION DATE)0NODATEABSTRACT(Limit to 1400 spaces, i.e.,
approximately 15 single-spaced typewritten lines)
On April 17, 2013, LaSalle Units 1 and 2 were operating in Mode 1 at 100% power, with a severe thunderstorm in progress. At 1457 hours CDT, lightning struck 138KV Line 0112, resulting in a phase-to-ground fault which subsequently cleared. At 1459 hours, a second phase-to-ground fault on Line 0112 occurred and all 345 KV oil circuit breakers (OCRs) 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 hours on April 17, 2013, and the Unusual Event was terminated at 0814 hours on April 18, 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)
NRC FORM 366AU.S. NUCLEAR REGULATORY COMMISSION (10-2010)LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
: 1. FACILITY NAME
: 2. DOCKET6. LER NUMBER3. PAGEYEARSEQUENTIALREVNUMBERNO.LaSalle County Station, Units 1 050003732OF32013-002-01NARRATIVE 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 / 2Event Date: April 17, 2013Event Time: 1459 CDT Reactor Mode(s): 1 / 1Mode(s) Name: Power OperationPower Level: 100%
B.DESCRIPTION OF EVENT:
On April 17, 2013, LaSalle Units 1 and 2 were operating in Mode 1 at 100% power, with a severe thunderstorm in progress. At 1457 hours CDT, lightning struck 138KV Line 0112, resulting in a phase-to-ground fault which subsequently cleared. At 1459 hours, 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 hours, 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 hours on Unit 2 and at 2004 hours on Unit 1.
Offsite power was restored to all ESF busses by 2301 hours on April 17, 2013. Containment cooling was restored on April 18, 2013, by 0055, and the PCIS signals were cleared on Unit 1 by 0230 hours and on Unit 2 by 0814 hours. The Unusual Event was terminated at 0814 hours on April 18, 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). It is also 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. An ENS report was made to the NRC (EN# 48939) at 1559 CDT on April 17, 2013, pursuant to 10 CFR 50.72(a)(1)(i), 50.72(b)(2)(iv)(A), 50.72(b)(2)(iv)(B), 50.72(b)(3)(iv)(A) and 50.72(b)(3)(v)(D), and was updated as required throughout the event.
This event constitutes an unplanned scram with complications and a safety system functional failure 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.
NRC FORM 366A (10-2010)
NRC FORM 366AU.S. NUCLEAR REGULATORY COMMISSION (10-2010)LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
: 1. FACILITY NAME
: 2. DOCKET
: 6. LER NUMBER3. PAGEYEARSEQUENTIALREVNUMBERNO.LaSalle County Station,Units 1050003733OF32013-002-01NARRATIVE 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 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:
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 0101 and 0102 from Plano, and 345 KV Lines 0103 and 0104 from Braidwood remained energized during the event.E.CORRECTIVE ACTIONS:Offsite power was restored to the ESF busses on both Units by 2301 hours on April 17, 2013.All degraded connections and ground cables in the 138kV switchyard were repaired.Lightning shielding in the 138kV switchyard will be improved.
F.PREVIOUS OCCURRENCES:
A search identified no previous occurrences within the past 10 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.
NRC FORM 366A (10-2010)}}

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