ML14121A079

LER 14-001-00 for LaSalle County Station, Units 1 & 2 Regarding Secondary Containment Inoperable Due to Interlock Doors Open

ML14121A079
Person / Time
Site:	Lasalle
Issue date:	04/18/2014
From:	Vinyard H T Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA14-013 LER 14-001-00
Download: ML14121A079 (6)

Text

Ad o LaSalle StationA2601 North 21st RoadExelon Generation Marseilles, IL 61341815 415 2000 Telephone www.exeloncorp.com 10 CFR 50.73RA14-013April 18, 2014U.S. Nuclear Regulatory Commission ATTN: Document Control DeskWashington, DC 20555-0001 LaSalle County Station, Units 1 and 2Facility Operating License Nos. NPF-1 1 and NPF-1 8NRC Docket Nos. 50-373 and 50-374

Subject:

Licensee Event Report 2014-001-00 Secondary Containment Inoperable Due to Interlock Doors OpenIn accordance with 10 CFR 50.73(a)(2)(v)(C) and (D), Exelon Generation Company(EGC), LLC, is submitting Licensee Event Report Number 2014-001-00 for LaSalleCounty Station 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. VinyardPlant ManagerLaSalle County Station

Enclosure:

Licensee Event Reportcc: Regional Administrator

-NRC Region IIINRC Senior Resident Inspector

-LaSalle County Station NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:

01/31/2017 (02-2014)

Estimated burden per response 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 are incorporated into the lcensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Infornation Collections LICENS EEVENT REPORT (LER) Branch (1-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byL intemet e-mail to Infocollects.Resourcefnrtgov, and to the Desk Officer, Office of Information and(See Page 2 for required number of Regulaty Affirs, NEOB-1 02OZ (3150-0104),

Oce of Management and Budget, Washington, DC,. .e for each block) 2o3. f a means used to impose an informnaton collection does not display a cunently valid OMBdigits/characters focontrol number, the NRC may not conduct or sponsor, and a person is not requred to respond to,the information collection.

1. FACIUTY NAME 2. DOCKET NUMBER 3. PAGELaSalle County Station Unit 1 05000373 1 --OF 5"4. TITLESecondary Containment Inoperable Due to Interlock Doors Open5. EVENT DATE 6. LER NUMBER 7. REPORT DATE S. OTHER FACILTIES INVOLVEDI FACILITY NAME DOCKET NUMBERMONTH DAY YEAR YEAR NEUMENTIA NO.-E MONTH DAY YEAR LaSalle C. yountySainUit20007 Station Unit 2 05000374FACILITY NAME DOCKET NUMBER02 18 2014 2014 -001 -00 04 21 2014 050009. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)El 20.2201(b)

El 20.2203(a)(3)(i)

[] 50.73(a)(2)(i)(C)

C] 50.73(a)(2)(vii)

El 20.2201(d)

[] 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

E] 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

_ _ 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

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

El 50.36(c)(1)(ii)(A)

El 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

El 20.2203(a)(2)(Iii)

El 50.36(c)(2)

El 50.73(a)(2)(v)(A)

El 73.71 (a)(4)00 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71 (a)(5)00E 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)

El OTHERSpecify in Absb'act below or in__ 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)

NReC Form3WA12. UCENSEE CONTACT FOR THIS LERLICENSEE CONTACT TELEPHONE NUMBER (Indude Ama Code)Joe Kutches, Maintenance Director (815) 415-250013. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTC I MANU- REPORTABLE CAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM COMPONENT FACTURER TO EPIX C S FACTURER TO EPIXX NG IMEC Locknetics Y14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEARSUBMISSION

[E YES (If yes, complete

15. EXPECTED SUBMISSION DATE) O NO DATES SABSTRACT (Limit to 1400 spaces, i.e., approdimately 15 single-spaced typewritten lines)On February 18, 2014, Unit 1 was in Mode 5 with fuel moves in progress during refueling outage Li R1 5, and Unit 2 wasin Mode 1 at 100% power. At 1820 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.9251e-4 months <br /> CST, it was reported that both air-lock doors of the Unit 2 Reactor Building710' elevation between the Unit 2 diesel generator corridor and the Unit 2 Reactor Building were open at the same timefor approximately 3 seconds.

While both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2

("Verify one secondary containment access door in each access opening is closed")

was notmet. Secondary containment was declared inoperable for the time that both interlock doors were open. TS 3.6.4.1Required Action (RA) C.1 to suspend fuel movements on Unit 1 and RA A.1 to restore secondary containment toOPERABLE status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> were entered and exited at 1820 CST on February 18, 2014.The cause of the event was degradation of the door closure mechanism and door frame seal. A contributing cause was aless than robust design of the door interlock assembly.

Corrective actions from the previous occurrences to identify, procure and install a more robust interlock assembly design were still in progress at the time of the event. Additional corrective actions included creating a periodic preventative maintenance task to inspect,

tighten, and replace fasteners as necessary.

NRC FORM 366 (02-2014)

UNRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:

01/31/2017 (02-2014)

Estimated burden per response 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 are incorporated into the licensing process and fed back to industry.r sSend comments regarding burden estimate to the FOIA, Pnivacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byLICENSEE EVENT REPORT (LER) internet e-mail to lnfocodlects.Resource@nrc.gov, and to the Desk Officer, Office at infonmation and Regulatory

Affairs, NEO8-102.,

(3150-0104),

Office of Management and Budget,CONTINUATION SHEET Washington, DC 20503. H a means used to impose an information collection does not display acurrently valid OMB control number, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information collection.

1. FACIUTY NAME 2. DOCKET 6. LER NUMBER 3. PAGESEQUENTIAL REVYEAR NUMBER NO.LaSalle County Station, Units 1 and 2 05000373 j 2 OF 5r2014 -001 -00 /NARRATIVE 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: February 18, 2014 Event Time: 1820 CSTReactor Mode(s):

5/1 Mode(s) Name: Refueling/Power Operation Power Level: 0% / 100%B. DESCRIPTION OF EVENT:On February 18, 2014, Unit 1 was in Mode 5 with fuel moves in progress during refueling outage Li R15, andUnit 2 was in Mode 1 at 100% power. At 1820 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.9251e-4 months <br /> CST, it was reported that both air-lock doors of the Unit 2Reactor Building 710' elevation between the Unit 2 diesel generator corridor and the Unit 2 Reactor Buildingwere open at the same time for approximately 3 seconds.While both interlock doors were open, Technical Specification (FS) Surveillance Requirement (SR) 3.6.4.1.2

('Verify one secondary containment access door in each access opening is closed")

was not met. Secondary containment

[NG] was declared inoperable for the time that both interlock doors were open. TS 3.6.4.1Required Actions (RA) C.1, C.2 and C.3 to immediately suspend irradiated fuel movements, core alterations, and OPDRVs on Unit 1 and RA A.1 to restore secondary containment to OPERABLE status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> wereentered and exited at 1820 CST on February 18, 2014.This occurrence is reportable under 10 CFR 50.73(a)(2)(v)(C) and (D) as an event or condition that could haveprevented the fulfillment of the safety function of the structures or systems that are needed to control therelease of radioactive material and to mitigate the consequences of an accident.

An ENS report was made tothe NRC at 2215 EST (EN# 49840) on February 18, 2014, pursuant to 10 CFR 50.72(b)(3)(v)(C).

An Engineering Evaluation has determined this event did not meet the NEI 99-02 definition of a Safety SystemFunctional Failure.C. CAUSE OF EVENT:Troubleshooting found that the door closure mechanism and door seal were degraded for door #507 (ReactorBuilding side of the interlock),

which prevented the electro-mechanical solenoid operated bolt from properlyaligning with the door-mounted catch. This malfunction resulted in the capability to open both interlock doors#507 and #402 at the same time, and was similar to a previous occurrence on October 22, 2013.The degradation of the door closure mechanism and door seal was determined to be due to repeatedchallenges of the door during personnel ingress/egress.

The design of the interlock mechanism wasconsidered a contributing cause, as it was considered less than robust for the application.

Corrective actions from the previous occurrences to identify, procure and install a more robust design were stillin progress at the time of the event. Interim corrective actions were in place to perform quarterly inspections ofthe assemblies and to tighten the fasteners as required.

NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEYER SEQUENTIAL REVYE500NUMBER NO.05000 3 OF 5NARRATIVE D. SAFETY ANALYSIS:

The safety significance of this event was minimal.

The Reactor Building-to-outside differential pressureremained negative throughout the period that the secondary containment was inoperable.

The secondary containment was inoperable for approximately 3 seconds, which was significantly less than the four-hour Completion Time to restore the secondary containment to operable status allowed by TS 3.6.4.1 RequiredAction A.1.The function of the secondary containment is to contain, dilute, and hold up fission products that may leak fromthe primary containment following a Design basis Accident (DBA). Engineering Evaluation (EC 396711) wasperformed to show that this event had no impact on the safety function associated with secondary containment.

The time that both doors were simultaneously opened was less than 10 seconds.

This event did not result in thereactor enclosure differential pressure dropping below the design bases set point of -0.25 inches w.g. Both theinner and outer doors were promptly closed by station personnel which ended the event. This event did notinvolve any kind of door or airlock material condition preventing door closure.

Additionally, both the inner andouter doors were closed by normal expected means and were capable of remaining closed as designed.

The computed dose for EC 396711 was based on the door opening during the 780 second time period prior toStandby Gas Treatment (SBGT) system drawdown and filtration.

This discounts the initial 120 seconds of anevent where no release takes place, per calculation L-003068, "Re-Analysis of Loss of Coolant Accident(LOCA) Using Alternative Source Terms".The approximate 3 second opening of the secondary containment doors is bounded by calculation L-003068, "Re-Analysis of Loss of Coolant Accident (LOCA) Using Alternative Source Terms". Should an event occur, withboth secondary containment doors open simultaneously for 30 seconds or less, this would result in a potential dose increase of approximately 3.85%. The 3.85% decrease in margin is inconsequential compared to the 10CFR 100 regulatory limits.EC 396711 also evaluated the pressure impact on the secondary containment and the ability of the SBGTsystem to achieve the TS required negative pressure.

The results of the evaluation show SBGT would restoresecondary containment pressure within 3 minutes which is well below the 15 minute maximum drawdown timerequired by TS.Based on the short duration of door opening (approximately 3 seconds),

no material condition preventing doorclosure or maintaining the doors closed and attendance by knowledgeable personnel who closed the doorsimmediately, the secondary containment safety function was maintained.

E. CORRECTIVE ACTIONS:* The door closure mechanism and door frame seal for door #507 was repaired.

• Efforts to install a more robust design for the interlock assembly are in progress.

" Quarterly preventative maintenance to inspect the assemblies and fasteners and tighten or replace asnecessary remain in progress.

NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEI SEQUENTIAL REVYEAR NUMBER NO.05000 4 OF 5NARRATIVE F. PREVIOUS OCCURRENCES:

LER 2013-007-01 On October 22, 2013, both Units 1 and 2 were in Mode 1 at 100% power. At 1129 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.295845e-4 months <br /> CDT, it was reportedthat both air lock doors on the Unit 1 Reactor Building 710' elevation between the Chemistry Hot Lab and theReactor Building were open at the same time for approximately 10 seconds.

While both interlock doors wereopen, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2

("Verify one secondary containment access door in each access opening is closed")

was not met. Secondary containment wasdeclared INOPERABLE for the time that both interlock doors were open. TS 3.6.4.1 Required Action A.1 forboth Units 1 and 2 to restore secondary containment to OPERABLE status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> was entered andexited at 1129 CDT on October 22, 2013.The cause of the event was a less than robust design of the door interlock assembly.

Troubleshooting foundthat the mounting fasteners that secure the entire locking assembly to the frame of door # 226 (Reactor Buildingside of the interlock) were loose, which prevented the electro-mechanical solenoid operated bolt from properlyaligning with the door-mounted catch. This misalignment prevented the bolt from entering the catch on door #226 when door # 225 (Chemistry Hot Lab side) was opened. This malfunction resulted in the capability to openboth interlock doors at the same time, and was similar to a previous occurrence on February 28, 2013.LER 2013-001-02 On February 28, 2013, Unit 1 was in Mode 1 at 100% power and Unit 2 was in Mode 5 for refueling outageL2R14. At 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> CST, it was reported that both air lock doors on the Unit 1 Reactor Building 710'elevation between the Chemistry Hot Lab and the Reactor Building were open at the same time forapproximately 10 seconds.

While both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2

("Verify one secondary containment access door in each access opening isclosed")

was not met for Unit 1. Secondary containment was declared INOPERABLE for the time that bothinterlock doors were open. TS 3.6.4.1 Required Action A.1 to restore secondary containment to OPERABLEstatus within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> was entered and exited for Unit 1 at 0400 CST on February 28, 2013.The cause of the event was determined to be a less than robust design of the door interlock assembly.

Troubleshooting found that the mounting fasteners that secure the entire locking assembly to the frame of door# 226 (Reactor Building side of the interlock) were loose, which prevented the electro-mechanical solenoidoperated bolt from properly aligning with the door-mounted catch. This misalignment prevented the bolt fromentering the catch on door # 226 when door # 225 (Chemistry Hot Lab side) was opened. This malfunction resulted in the capability to open both interlock doors at the same time.This occurrence was similar to the October 2013 event. In addition to repairing the interlock assembly bytightening the fasteners, actions were initiated to periodically inspect the assemblies and to identify and install amore robust design. The new design had been identified but not installed when the October 2013 eventoccurred.

LER 2012-001-00 On September 18, 2012, Units I and 2 were in Mode 1 at 100% power. At 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br /> CDT, an Equipment Operator (EO) reported the Unit 2 Reactor Building 761'elevation Interlock Doors 424/314 were both open atthe same time for approximately 10 seconds.

During the time that both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2

("Verify one secondary containment access door inNRC FORM 368A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACIUTY NAME 2. DOCKET 6. LER NUMBER 3. PAGEYEAR SEOUENTIAL I REVNUMBER NO.05000 5 OF 5NARRATIVE each access opening is closed")

was not met. The secondary containment was declared INOPERABLE for thetime that both interlock doors were open. LaSalle Station entered and exited TS 3.6.4.1 Required Action A.1 for'both Units 1 and 2 to restore secondary containment to OPERABLE status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.The cause of the event was determined to be the solenoid bracket being loose on Unit 2 Reactor Building 761'interlock door 424. Two screws that hold the locking solenoid bracket in place were found loose. The two loosescrews on the locking solenoid mounting bracket caused the electric lock assembly to become misaligned.

Themisalignment of the electric lock assembly prohibited the locking solenoid plunger from being fully engaged withthe door catch and damaged the limit switch, which resulted in the capability to open both interlock doors at thesame time.G. COMPONENT FAILURE DATA:Locknetics/SDC style lockNRC FORM 366A (02-2014)