ML14007A140
| ML14007A140 | |
| Person / Time | |
|---|---|
| Site: | Docket Number  |
| Issue date: | 12/26/2013 |
| From: | Dougherty T J Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LG-13-157 LER 13-003-00 | |
| Download: ML14007A140 (5) | |
Text
LG-13-157 ICRO7December 26,2013.U.. Nuclear Regulatory Commission
.. ... .,.....ATTN: Document Control-Desk Wash o, 0 20550001
...Limerick Oenerating
- Station, Unit 2Facility Operating License No. NPF-8.NRC Docket No. SO-=Subject.
LE 2013.003-00, Condition That Could Have Prevented Fulfillment of theReactor Enclosure Secondary Containment Integrity Safety FunctionThis Licensee Event Re port (LER) addresses a condition that could have prevented fulfillment of the:reactor enclosure secondary containnent integrity safety function.
Both airlock doors onone reactor enclosure ailock were briefly opened simultaneously due to the airlock design anda worker failure to verify a door latch was fully engaged prior to eP-ting the airlock.
This LER Isbeing BtbMtted pursuant to the requirements of I OCFR5P.73(a)(2)(v)(C).
There are no commitments contained in this letter.If you have any questions, plEas contact Rober B. Dickinson at J610) 718-3400.
Respectfully, Thomas J. Dougherty Vice President
-Limerick Generating StationExelon Generation
- Company, LLCcc: Administrator Region I, USNRCUSNRC Senior Resident Inspector, LGS UAlltll , U.MUIAITORY COMIJMON APPROVED BY OMI: NO. 3150.0104 EXPIRES:
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- Station, Unit 2 05000353 1 OF 4ITLE .OF. 'Inoperable Reactor Enclosure Secondary Containment Integrity Due to Open Airlock"L EVENT ...... lE NUMBEUR 7. REPOIT DATE I; OTHF VMS RACIES iNVOLVEDI ONT AY I YEAR YEA NUM BE R N O .I MTH IMY YZ R*0 50 0 0--A-ITY NAME DOCKET NUMBER10 30 1 2013 2 -003 -00 12 26 2013 05000OPE VON , 1. S OWIs I PB= S -EWS If3F 6 W (-C=W all tha apply)0 20.2201(b)
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Specify in belowor in NRC Fami 366ATEPHONE NUMBER ,fIfx ,Ai Code)Robert B. Dickinson, Manager -Regulatory Assurance 610-718-3400 M1AN3U REPORTABLECH CAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM COMPONENT FACTURER TO EPIX CS MTFACTURER TO EPIXB NH OR W302 Y IIT10M MP5EPtE 15.I EXPECTED MNH DY YAeUBM-SON03 YES (if yes. complete
- 15. EXPECTED SUBMISSION DATE) I NO OATETRACT (Lm..t to 1400S pacos, Ie., lInes)A worker in the reactor enclosure was using the equipment airlockwhen a simultaneous opening of both airlock doors occurred.
Thebreach occurred when the outboard door was opened with the inboarddoor not properly latched.
Both doors were closed in less than 10seconds and the breach of secondary containment was terminated.
The cause of the airlock breach is the reactor enclosure airlockdesign does not prevent both doors from being openedsimultaneously.
A contributing cause was the airlock door self-closing feature failed to fully close and latch the airlock doorand the worker did not properly verify the door was latchedfollowing use. The airlock door self-closing feature was verifiedto be working properly but may require assistance to fully latch.A reactor enclosure airlock design change will be evaluated.
NRC FORM 366 (10-2010)
Umc FORIM 3NA h ~ U.S ?UM~5 RZOULATOR1Y COWMMISO(10-2010)
LUCEII@UE Y RIE flGVN )L.ECOlENTAIAio SHEETUmerick Generting Satio, Unit 2 06000353M 2N2013 -003 -00NARRATIVI Unit Conditions Prior to the EventUnit 2 was in Operational Condition (OPCON) 1 (Power Operation) at100% power. There were no other structures, systems or components out of service that contributed to this event.Description of the EventOn Wednesday, October 30, 2013, Limerick Unit 2 was operating at100% power. At 1550 hours0.0179 days <br />0.431 hours <br />0.00256 weeks <br />5.89775e-4 months <br />, the reactor enclosure low delta pressurealarm (EIIS:ALM) actuated and reactor enclosure pressure wasobserved recovering to a normal pressure of 0.33 inch of vacuumwater gauge.An investigation identified that a worker in the reactor enclosure (EIIS:NH) on the 313 foot elevation was using the equipment airlockwhen an opening of both airlock doors (EIIS:DR) occurred.
Theworker was exiting the reactor enclosure and entering the fan roomusing the airlock when the breach occurred.
The worker did noteffectively verify that the inboard door latch was engaged when thedoor was closed. The worker then opened the outboard door and theinboard door also opened due to the differential pressure on thedoor. Both doors were closed in less than 10 seconds and the breachof secondary containment was terminated.
The worker notifiedOperations shift management of the unexpected containment breach.Technical Specification (TS) 3.6.5.1.1 Reactor Enclosure Secondary Containment Integrity surveillance requirement 4.6.5.1.1.a requiresverification that reactor enclosure pressure is greater than orequal to 0.25 inch of vacuum water gauge which is performed on a 24hour frequency.
The TS surveillance requirement 4.6.5.1.1.b.2 requires at least one door in each access to the reactor enclosure be verified closed which is performed on a 31 day frequency.
TS3.6.5.1.1 is applicable in operational conditions (OPCON) 1, 2 and3.This LER is being submitted pursuant to the requirements of10CFR50.73(a)(2)(v)(C) for a condition that could have prevented thefulfillment of the safety function of structures or systems neededto control the release of radioactive material.
Analysis of the EventThere was no actual safety consequence associated with this event.The potential safety consequences of this event were minimal.
BothIRC FORM 326A (10-2010)
(10C2010)
UCENSEE EVENT REPORT ) u.S. NUCLEAR RGULTOYon CONTINUATION SHEET.FAC, NAMUmerck Generating
- Statijn, Unit 2 05000353 3 OF 42013 -003 -00NARRAmvEdoors on the airlock were open simultaneously for lees than 10seconds.To prevent an unplanned breach of secondary containment each reactorenclosure airlock is equipped with door open indicating lights whichare used to locally verify the door status. If both doors areopened simultaneously a local alarm is actuated.
If both doorsremain open for greater than 10 seconds an alarm is actuated in themain control room and operators are dispatched to verify the airlockdoors closed.UFSAR 6.2.3.2.1 describes the secondary containment design. Thereactor enclosure secondary containment (Zones I and II) aredesigned to limit the inleakage to 200% of their zone free volumeper day, and the refueling area secondary containment (Zone III) isdesigned to limit the inleakage to 50% of its zone free volume perday. These inleakage rates are based on a negative interior pressureof 0.25 in wg, while operating the standby gas treatment system(SGTS). Following a LOCA the affected zone is maintained at thisnegative pressure by operation of the SGTS.Cause of the EventThe cause of the airlock breach is the reactor enclosure airlockdesign does not prevent both doors from being opened simultaneously.
A contributing cause was the airlock door self-closing featurefailed to fully close and latch the airlock door and the worker didnot properly verify the door was latched following use.Corrective Action Completed The airlock door self-closing feature was functionally tested.Corrective Action PlannedA reactor enclosure airlock design change will be evaluated.
RCFORMPrevious Similar Occurrences Unit 2 LER 2013-002 was submitted due to a reactor enclosure airlockbreach caused by a non-functional airlock door open indicating lightnot providing the correct door status. There have also beenprevious similar occurrences in the prior three years based on areview of the operator logs. The events were identified by anactuation of the airlock seal open alarm which indicates that bothairlock doors were open for a period exceeding 10 seconds.3SA (10-2D10)
NRC(10201 UCENSEE EVENT REPORT (LER) u.8. C rEGLATORY COMMSONCONTINUATION SHEET1. FX(KJTY MAMIE L. PAOMT&LE~
tM GMELUmerick Generating
- Station, Unit 2 005000363 E -1 4 OF 41.2013 -003 -001NHARRAIWE Component DataComponent NumberComponent NameManufacturer Model NumberDoor-560Reactor Enclosure Fan Room DoorWoolley7790 DWG/HW SET BMRC FORM 386A (10-2010)