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{{Adams
#REDIRECT [[RS-15-064, Limerick, Units 1 and 2 - Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Report]]
| number = ML15084A586
| issue date = 03/12/2015
| title = Limerick, Units 1 and 2 - Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Report
| author name = Barstow J
| author affiliation = Exelon Generation Co, LLC
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000352, 05000353
| license number = NPF-039, NPF-085
| contact person =
| case reference number = RS-15-064
| package number = ML15093A216
| document type = Letter
| page count = 7
}}
 
=Text=
{{#Wiki_filter:AoExeton Generation 10 CFR 50.54(f)RS-1 5-064March 12, 2015U.S. Nuclear Regulatory Commission ATTN: Document Control DeskWashington, DC 20555Limerick Generating
: Station, Units 1 and 2Renewed Facility Operating License Nos. NPF-39 and NPF-85NRC Docket Nos. 50-352 and 50-353
 
==Subject:==
 
Exelon Generation
: Company, LLC Response to March 12, 2012, Request forInformation Enclosure 2, Recommendation 2.1, Flooding, Required Response 2,Flood Hazard Reevaluation Report
 
==References:==
: 1. NRC Letter, Request for Information Pursuant to Title 10 of the Code of FederalRegulations 50.54(f)
Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi
: Accident, dated March 12,2012.2. NRC Letter, Prioritization of Response Due Dates for Request for Information Pursuantto Title 10 of the Code of Federal Regulations 50.54(f)
Regarding Flooding HazardReevaluations for Recommendations 2.1 of the Near-Term Task Force Review ofInsights From the Fukushima Dai-ichi
: Accident, dated May 11, 2012.3. U.S. Nuclear Regulatory Commission, NUREG/CR-7046, Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America, datedNovember 2011.4. Letter from David L. Skeen, U.S. Nuclear Regulatory Commission, to Joseph E. Pollock,Nuclear Energy Institute
-Trigger Conditions for Performing an Integrated Assessment and Due Date for Response, dated December 3, 2012.5. U.S. Nuclear Regulatory Commission, JLD-ISG-2012-05, Guidance for Performing theIntegrated Assessment for External
: Flooding, dated November 30, 2012.6. Letter from Exelon Generation
: Company, LLC to U.S. Nuclear Regulatory Commission, "180-day Response to NRC Request for Information Pursuant to 10 CFR 50.54(f)Regarding the Flooding Aspects of Recommendation 2.3 of the Near-Term Task ForceReview of Insights from the Fukushima Dai-ichi
: Accident, dated November 19, 2012(RS-1 2-172).ADo U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 2On March 12, 2012, the NRC issued Reference 1 to request information associated with Near-Term Task Force (NTTF) Recommendation 2.1 for Flooding.
One of the Required Responses inthis letter directed licensees to submit a Flood Hazard Reevaluation Report, including theinterim action plan requested in Item 1 .d of Reference 1, Enclosure 2, if appropriate.
On May11, 2012, the NRC issued the prioritization plan developed by the NRC and resultant FloodHazard Reevaluation due dates for all sites. Reference 2, Enclosure 1 identified LimerickStation, Units 1 and 2, as a Category 3 Site requiring a Flood Hazard Reevaluation Reportsubmittal due date of March 12, 2015. The information in the enclosed provides LimerickStation, Units 1 and 2, Flood Hazard Reevaluation Report. The Limerick
: Station, Units 1 and 2,Flood Hazard Reevaluation Report follows the reevaluation process described in Reference 3.Information Requested in Reference 1, Enclosure 2a. Site information related to the flood hazard. Relevant SSCs important to safety andthe UHS are included in the scope of this reevaluation, and pertinent data concerning these SSCs should be included.
Other relevant site data includes the following:
: i. Detailed site information (both designed and as-built),
including present-day sitelayout, elevation of pertinent SSCs important to safety, site topography, as well aspertinent spatial and temporal data sets;Response:
* Site layout and topography
-See Section 2.1 and Figures 2.1.1 and 2.1.2 ofEnclosure 1.* Pertinent Site Data is provided in Enclosure 2.ii. Current design basis flood elevations for all flood causing mechanisms;
 
===Response===
* See Section 2.2 of Enclosure 1, which describes the current design basis floodhazards for all flood causing mechanisms.
iii. Flood-related changes to the licensing basis and any flood protection changes(including mitigation) since license issuance;
 
===Response===
* See Section 2.3 of Enclosure 1 for a description of flood-related changes to thelicensing basis and any flood protection changes (including mitigation) sincelicense issuance.
U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 3iv. Changes to the watershed and local area since license issuance;
 
===Response===
* See Section 2.4 of Enclosure 1 for a description of changes to the watershed andlocal area since license issuance.
: v. Current licensing basis flood protection and pertinent flood mitigation features atthe site;Response:
* See Section 2.5 of Enclosure 1 for a description of Current Licensing Basis (CLB)flood protection and pertinent flood mitigation features at the site.vi. Additional site details, as necessary, to assess the flood hazard (i.e., bathymetry, walkdown
: results, etc.)Response:
* See Reference 6 for results of the flooding walkdowns.
" See Section 3 of Enclosure 1 for additional site and watershed information usedto assess the flood hazard.b. Evaluation of the flood hazard for each flood causing mechanism, based on present-day methodologies and regulatory guidance.
Provide an analysis of each floodcausing mechanism that may impact the site including local intense precipitation andsite drainage, flooding in streams and rivers, dam breaches and failures, storm surgeand seiche, tsunami, channel migration or diversion, and combined effects.Mechanisms that are not applicable at the site may be screened-out;
: however, ajustification should be provided.
Provide a basis for inputs and assumptions, methodologies and models used including input and output files, and other pertinent data.Response:
A description of the flood hazard reevaluation for each flood causing mechanism and thebasis for inputs, assumptions, methodologies, and models are referenced below. PerNRC/NEI public meeting dated January 16, 2013, input-output files are not included with thissubmittal package but are available upon request.* Local Intense Precipitation (LIP) and Site Drainage:
See Section 3.1 of Enclosure 1.* Flooding in Streams and Rivers: See Sections 3.2 of Enclosure
: 1.
U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 4* Dam Breaches and Failures:
See Section 3.4 of Enclosure 1." Storm Surge: See Section 3.3 of Enclosure 1.* Seiche: See Section 3.3 of Enclosure 1." Tsunami:
See Section 3.3 of Enclosure 1.* Ice-Induced Flooding:
See Section 3.6 of Enclosure 1.* Channel Migration or Diversion:
See Section 3.7 of Enclosure 1." Combined Effects (including wind-waves and runup effects):
See Section 3.5 ofEnclosure 1." Other Associated Effects (i.e. hydrodynamic
: loading, including debris; effects causedby sediment deposition and erosion; concurrent site conditions; and groundwater ingress) are addressed in the respective flood-causing mechanism sections andSections 3.9 and 4 of Enclosure 1." Flood Event Duration Parameters (i.e. warning time, period of site preparation, period of inundation, and period of recession) are addressed in the respective flood-causing mechanism sections and Sections 3.9 and 4 of Enclosure 1.* Error/Uncertainty analysis for the governing flood scenarios is addressed in Section3.8 of Enclosure 1.c. Comparison of current and reevaluated flood causing mechanisms at the site.Provide an assessment of the current design basis flood elevation to the reevaluated flood elevation for each flood causing mechanism.
Include how the findings fromEnclosure 4 of the 50.54(f) letter (i.e., Recommendation 2.3 flooding walkdowns) support this determination.
If the current design basis flood bounds the reevaluated hazard for all flood causing mechanisms, include how this finding was determined.
 
===Response===
The current design basis flood does not bound the reevaluated hazard for all applicable flood-causing mechanisms, combined-effect floods, associated
: effects, and/or flood eventduration parameters.
A complete comparison of current design basis and reevaluated floodhazards is provided in Section 4 of Enclosure 1 that describes how this finding wasdetermined for the applicable flood hazards.
Surge, Seiche, Tsunami, Ice Induced Flooding, Channel Migration or Diversion, and Combinations in Section H.1 and H.2 of Reference 3for the Schuylkill River and Sanatoga Creek (which includes the "Flooding in Streams andRivers" and "Dam Breaches and Failures" mechanisms) were either determined to beimplausible or completely bounded by the current design basis or other mechanisms.
Limerick Station is considered potentially exposed to the flood hazards listed below. Some U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 5individual flood-causing mechanisms (i.e. Flooding in Streams and Rivers, Dam Breachesand Failures, and Surge) are addressed in one or more of the combined-effect floods.1. Local Intense Precipitation (LIP)The maximum reevaluated flood elevation (218.4 feet Mean Sea Level (MSL)) isbounded by the design basis flood elevation (218.6 feet MSL). The associated effects are also bounded or not applicable, as described in Section 4 of Enclosure 1.Flood event duration parameters are not applicable to the LIP flood since manualactions are not credited in the Current Licensing Basis (CLB) with providing protection.
: However, the south side of the plant, near the emergency dieselgenerators, was not analyzed with the design basis LIP flood, as it was with thereevaluated LIP flood. Therefore, LIP was considered to be unbounded in this area.2. Combined-Effect Flood in Section H.1, Reference 3, Floods Caused by Precipitation Events (including hydrologic dam failure) for Possum Hollow RunThe three alternative precipitation-event combinations specified in Section H.1 ofReference 3, plus hydrologically-induced upstream dam failure, were evaluated forthe Possum Hollow Run watershed.
The maximum reevaluated stillwater elevation (167.8 feet MSL) for the prevailing alternative is not bounded by the design basisstillwater elevation for the same stream (159.0 feet MSL). However, the reevaluated flood elevation for Possum Hollow Run is bounded by the design basis floodelevations of the Schuylkill River (207 feet MSL). Note that the nominal plant gradeelevation is 217 feet MSL Therefore, no further actions are required for this scenarioas the station is bounded by the Schuylkill River Flood.d. Interim evaluation and actions taken or planned to address any higher floodinghazards relative to the design basis, prior to completion of the integrated assessment described below, if necessary.
 
===Response===
Per Enclosure 2 of Reference 1, an Integrated Assessment is required for plants where thecurrent design basis floods do not bound the reevaluated hazard for all flood causingmechanisms.
Reference 4 presents four approaches for performing an Integrated Assessment based on the results of the flood hazard reevaluation.
Scenario 1 -Reevaluated Hazard Bounded by Design BasisScenario 2 -Only Local Intense Precipitation Scenario 3 -All Permanent and Passive Flood Protection Scenario 4 -Integrated Assessment RequiredAn Integrated Assessment is not necessary in Scenario
: 1. Limited evaluations can beconducted and submitted with the Flood Hazard Reevaluation Report under Scenarios 2and 3 that only address specific sections of the Integrated Assessment Interim StaffGuidance (Reference 5). Licensees in Scenario 4 and those not including limited U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 6evaluations in the Flood Hazard Reevaluation Report under Scenarios 2 and 3 are requiredto perform a full Integrated Assessment.
Per "Part c" above, the current design basis flood bounds the reevaluated hazard for allflood causing mechanisms except LIP. Therefore, Scenario 2 (above) applies.
Reference 4states (regarding Scenario 2):If local intense precipitation is the only portion of the reevaluated hazard that is notbounded by the current design basis, the licensee can limit the evaluation to only the sitedrainage.
This evaluation should be performed using Section A. 1.1.6 of Appendix A tothe integrated assessment interim staff guidance (ISG) and the application of guidancecontained in NUREG-0800, "Standard Review Plan for the Review of Safety AnalysisReports for Nuclear Power Plants: LWR [light-water reactor]
Edition."
The results of thisevaluation should be submitted with the hazard report.Limerick Station opted to include a limited Integrated Assessment with this submittal basedon a limited evaluation of the effects of the LIP flood in the unanalyzed area on the southside of the plant, near the emergency diesel generators.
Section A. 1.1.6 of Reference 5does not apply in this case since the reevaluated LIP flood elevation is lower than the designbasis LIP (Enclosure 1, Table 4.0.2). The focus of this limited Integrated Assessment is todetermine the impact of LIP at the emergency diesel generators and if additional compensatory measures are needed to maintain plant safety.Engineering Technical Evaluation 01550669-36 was prepared to analyze the ingress volumeof floodwater entering the doors to the diesels.
This evaluation reviewed the amount ofwater that could enter the rooms through a small door undercut and compared it to theallowable volume in the diesel rooms in the diesel pit area. The results of the evaluation showed that there is no effect on safety related equipment in the diesel generator roomsduring the LIP flood and no compensating actions are necessary.
Interim ActionsNo interim actions are required since the limited evaluation, discussed above, demonstrates that the reevaluated LIP flood does not impact plant safety under current configuration.
: e. Additional actions beyond Requested Information item 1.d taken or planned toaddress flooding
: hazards, if any.Response:
* None required.
This letter contains no new regulatory commitments and no revision to existing regulatory commitments.
U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 -Flood Hazard Reevaluation Submittal for Limerick Generating
: Station, Units 1 and 2March 12, 2015Page 7If you have any questions regarding this submittal, please contact Ron Gaston at (630) 657-3359.I declare under penalty of perjury that the foregoing is true and correct.
Executed on the 12thday of March 2015.Respectfully submitted, James BarstowDirector
-Licensing
& Regulatory AffairsExelon Generation
: Company, LLC
 
==Enclosures:==
: 1. Limerick Generating
: Station, Flood Hazard Reevaluation Report, Revision
: 02. CD-R labeled:
"Limerick Generating
: Station, Flood Hazard Reevaluation, Pertinent SiteData"Document Components:
Pertinent Site Data (requires AutoCAD or similar program)cc: Director, Office of Nuclear Reactor Regulation (w/o Enclosure 2)Regional Administrator
-NRC Region I (w/o Enclosure 2)NRC Senior Resident Inspector
-Limerick Generating
: Station, Units 1 and 2NRC Project Manager, NRR -Limerick Generating
: Station, Units 1 and 2Mr. Robert F. Kuntz, NRR/JLD/JHMB, NRCMr. Victor E. Hall, NRR/JLD/JHMB, NRCDirector, Bureau of Radiation Protection
-Pennsylvania Department of Environmental Resources (w/o Enclosure 2)R. R. Janati, Chief, Division of Nuclear Safety, Pennsylvania Department ofEnvironmental Protection, Bureau of Radiation Protection (w/o Enclosure 2)}}

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