ML14087A011

LER 14-001-00 for St. Lucie, Unit 1, Regarding Internal RAB Flooding During Heavy Rain Due to Degraded Conduits Lacking Internal Flood Barriers

ML14087A011
Person / Time
Site:	Saint Lucie
Issue date:	03/10/2014
From:	Jensen J Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2012-066 LER 14-001-00
Download: ML14087A011 (4)

Text

FFPL.March 10, 2014L-2012-066 10 CFR 50.73U. S. Nuclear Regulatory Commission Attn: Document Control DeskWashington, D.C. 20555Re: St. Lucie Unit 1Docket No. 50-335Reportable Event: 2014-001Date of Event: January 9, 2014Internal RAB Flooding During Heavy Rain Due to Degraded Conduits Lacking InternalFlood BarriersThe attached Licensee Event Report 2014-001 is being submitted pursuant to the requirements of10 CFR 50.73 to provide notification of the subject event.Respectfully, Site Vice President St. Lucie PlantJJ/KWFAttachment Florida Power & Light Company6501 S. Ocean Drive, Jensen Beach, FL 34957 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 licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Information CollectionsLICENSEE EVENT REPORT (LER) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byLI E E T Rinternet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and(See Page 2 for required number of Regulatory

Affairs, NEOB-10202, (3150-0104),

Office of Management and Budget, Washington, DCfor each block) 20503. It a means used to impose an information collection does not display a cun-ently valid OMBdigits/characters control number, the NRC may not conduct or sponsor, and a person is not required to respond to,the intormation collechon.

1. FACILITY NAME 2. DOCKET NUMBER 3. PAGESt. Lucie Unit 1 05000335 1 OF4. TITLEInternal RAB Flooding During Heavy Rain Due to Degraded Conduits Lacking Internal Flood Barriers5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVEDFACILITY NAME DOCKET NUMBERMONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR 05000FACILITY NAME DOCKET NUMBER1 9 2014 2014- 001 -0 3 10 2014 050009. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)D1 20.2201(b)

F1 20.2203(a)(3)(i)

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

D 50.73(a)(2)(vii)

[] 20.2201(d)

F] 20.2203(a)(3)(ii)

[] 50.73(a)(2)(ii)(A)

[] 50.73(a)(2)(viii)(A)

D 20.2203(a)(1)

[ 20.2203(a)(4)

" 50.73(a)(2)(ii)(B)

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

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

[ 50.36(c)(1)(i)(A)

[ 50.73(a)(2)(iii)

[ 50.73(a)(2)(ix)(A)

10. POWER LEVEL F1 20.2203(a)(2)(ii)

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

[] 50.73(a)(2)(iv)(A)

F1 50.73(a)(2)(x)

ED 20.2203(a)(2)(iii)

[ 50.36(c)(2)

[] 50.73(a)(2)(v)(A)

D 73.71(a)(4)

El 20.2203(a)(2)(iv)

[ 50.46(a)(3)(ii)

D 50.73(a)(2)(v)(B)

D 73.71(a)(5) 100E] 20.2203(a)(2)(v)

[ 50.73(a)(2)(i)(A)

[ 50.73(a)(2)(v)(C)

[ OTHERr5 5Specify in Abstract below or in______________

20.2203(a)(2)(vi) 50.73(a)(2)(t)(B)

5) _ NRC Form 366A12. LICENSEE CONTACT FOR THIS LERLICENSEE CONTACT TELEPHONE NUMBER (include Area Code)K. W. Frehafer, Licensing Engineer 1 (772) 467-774813. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTCAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM OPNN FACTURE R TEPORTBLFACTURER TO EP[X 1 FACTURER TO EPIXB N/A N/A N/A N/A14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEARSUBMISSION 5] YES (Ifyes complete

15. EXPECTED SUBMISSION DAT"E) [ NO DATE 5 2014ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)On January 9, 2014, the St. Lucie site was experiencing heavy rainfall.

Storm drain blockage caused water to backupwithin the emergency core cooling system (ECCS) pipe tunnel. Water entered the reactor auxiliary building (RAB)through two degraded conduits that lacked internal flood barriers.

At 1803 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.860415e-4 months <br /> St. Lucie declared an Unusual Event.(UE) due to storm drain capacity degradation.

The UE was terminated at 0001 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> on January 10, 2014, when thestorm had passed and the drains had been cleared.The extent of condition identified four additional conduits that lacked the required internal flood barriers.

All the affectedconduits subsequently had qualified internal water seals installed.

During this event there was no loss of any safety related accident mitigation or safe shutdown equipment.

The safetysignificance of this event is being evaluated by FPL. This LER will be revised to reflect the results.NRC FORM 366 (02-2014)

NRC 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.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

",j .Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byLICENSEE EVENT REPORT (LER) intemet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of nformation and Regulatory

Affairs, NEOB-10202, (3150-0104),

Office of Management and Budget,CONTINUATION SHEET Washington, DC 20503. If 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. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEYEAR SEQUENTIAL REVIYEAR NUMBER NO.St. Lucie Unit 1 05000335 j 2 OF 32014 001 -0NARRATIVE Description of the EventOn January 9, 2014, St. Lucie Unit 1 was in Mode 1 operation at 100 percent reactor power. The St. Lucie sitewas experiencing heavy rainfall.

In the early afternoon the site storm drain system was challenged as the stormwater basins started to back up.At -1610 hours, operators reported that water was backing up through the -0.5 feet elevation floor drains in thereactor auxiliary building (RAB) and into the emergency core cooling system (ECCS) pump room sumps atthe -10.0 feet elevation.

The water was observed entering the RAB through an electrical junction box which wasbelow the elevation for which the RAB flood protection was designed.

At -1620 hours, the control room received the B Safeguards Pump Room Sump Level High/High-High alarms.At -1628 hours the operators entered procedure 1-AOP-24.01, "RAB Flooding,"

and immediately closed theECCS sump isolation valves to preclude flooding of the ECCS pump room. However, the water level in the RAB-0.5 feet elevation continued to rise.At -1635 hours, after deliberation between the field operators and the Control Room, the operators decided tocontrol the RAB flooding by cycling the ECCS sump isolation valves to allow batch removal of RAB water via theECCS sump pumps.At -1732 hours, a higher capacity temporary pump at the yard sump was used to reduce the rate of water entryinto the RAB.At -1803 hours, an Unusual Event (UE) was declared as the significant rainfall exceeded the site's storm drainsystem capacity.

The UE was terminated at -0001 hours on January 10, 2014, after the significant rains subsided and the stormdrain were observed draining site water accumulation.

All safety related accident mitigation and safe shutdown equipment remained operable prior to, during, and afterthe event.Cause of the EventThe cause of the RAB flooding was due to' legacy installation issues with two non-safety electrical conduits[EIIS:CND]

in the ECCS pipe tunnel that lacked the required internal flood barriers.

Degradation of the conduitsprovided a water entry path into the R.AB. The extent of condition identified four more conduits with the samelegacy installation issue, for a total of six conduits without internal flood seals. Qualified flood seals have nowbeen installed where these conduits terminate in the building in order to restore the RAB to a waterproofed condition.

The Organizational and Programmatic portion of the root cause evaluation is on-going at the time theLER was submitted.

This LER will be supplemented once the evaluation is completed, approximately 60 daysfrom the date of this LER.The direct cause of the storm water basin back up that allowed the ECCS pipe tunnel to flood was blockage ofthe piping that connects east storm water basin to the overflow basin. The blockage that contributed to thestorm drain system flow restriction has been removed.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. PAGEY SEQUENTIAL REVA NUMBER NO.St. Lucie Unit 1 05000335 YA3 OF 32014 -001 0NARRATIVE Analysis of the EventThis condition is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an event or condition that resultedin the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety. Althoughthis event did not result in any loss of function, postulated external flooding events could result in RAB waterlevels exceeding the analyzed RAB internal flooding event, as a result of the discovery of these missing conduitseals. This is contrary to design as it is assumed that design features seal the RAB below the +17.2 feetelevation from water sources external to the RAB.The site is comprised of an east and a west drainage system that outflows to the east and west storm waterbasins, which in turn flow to the southwest overflow basin and to the southeast overflow basin through a 36-inchinterconnection.

The southeast overflow basin has a high level outflow valve that can be opened duringexcessive rainfall events. Due to flow blockage from the east storm water basin to the overflow basins, thesevere rainfall caused the water level of the east storm water basin to rise above its banks and flood the plantarea west of the G1 and G2 warehouses.

Once the water level exceeded the elevation of the Unit 1 component cooling water (CCW) building floor (elevation

+12 feet) the building no longer drained and allowed the backflowto flood the adjacent ECCS pipe tunnel and yard sump. The degraded conduit within the ECCS pipe tunnel,along with the lack of internal conduit flood barriers in the RAB side, provided a direct path for water to enter theRAB.The water intrusion into the RAB continued until the storm drain blockage was corrected and the remaining volume of water in the ECCS pipe tunnel drained into the building.

Operators took action to remove the floodwater, by cycling the ECCS room sump isolation valves in order to utilize the installed sump pumps.As previously noted, during this event there was no loss of safety related accident mitigation or safe shutdownequipment.

Florida Power & Light (FPL) is currently evaluating various external flooding scenarios to determine if any postulated conditions could have resulted in, the loss of safety related accident mitigation or safeshutdown equipment.

Once this evaluation is complete, FPL will provide a supplement to this LER.Safety Significance The safety significance of the RAB flood protection bypass provided by the degraded conduits is currently beingassessed by FPL, and will be provided in a supplement to this LER.Corrective Actions1. All conduits identified as lacking internal flood barriers during the extent of condition reviews were providedwith qualified seals.Failed Component(s)

Various non-safety conduitsSimilar EventsOn December 27, 2012, FPL reported degraded penetration seals within electrical manways that bypassed St.Lucie Unit 1 RAB external flood protection features in LER 50-335/2012-010.

This original construction legacyissue was discovered during the Fukushima 50.54(f) flooding walkdowns that were performed as part of theNRC-approved NEI walkdown scope. Unit 2 was also identified to have unsealed conduit penetrations, but wasnot included in that LER as a flooding evaluation performed at the time concluded Unit 2 was bounded by itsinternal flooding analysis.

Once complete, the insights developed from the detailed St. Lucie flooding modelsbeing developed for the recent event will be applied to the 2012 LER condition.

If any conditions are identified that exceed previous analysis

results, those conditions will be reevaluated for impact on equipment operability and reportability.