RS-14-054, Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Report (FHRR)

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Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Report (FHRR)
ML14079A419
Person / Time
Site: Clinton Constellation icon.png
Issue date: 03/12/2014
From: Gaston R
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-14-054
Download: ML14079A419 (7)
v • d • e


Text

Exelon Generation, 10 CFR 50.54(f)

RS-14-054 March 12, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. STN 50-461

Subject:

Exelon Generation Company, LLC Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Report (FHRR)

References:

1. NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations 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 Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Flooding Hazard Reevaluations for Recommendations 2.1 of the Near-Term Task Force Review of Insights 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", dated November 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 the Integrated 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 Force Review of Insights from the Fukushima Dai-ichi Accident," dated November 27, 2012 (RS-12-166).

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U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 2 On 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 in this letter directed licensees to submit a Flood Hazard Reevaluation Report, including the interim action plan requested in Item 1.d of Reference 1, Enclosure 2, if appropriate. On May 11, 2012, the NRC issued the prioritization plan developed by the NRC and resultant Flood Hazard Reevaluation due dates for all sites. Reference 2, Enclosure 1 identified Clinton Power Station, Unit 1, as a Category 2 Site requiring a Flood Hazard Reevaluation Report submittal due date of March 12, 2014. The information in the enclosures provides Clinton Power Station, Unit 1 Flood Hazard Reevaluation Report. The Clinton Power Station, Unit 1 Flood Hazard Reevaluation Report follows the reevaluation process described in Reference 3.

Information Requested in Reference 1, Enclosure 2

a. Site information related to the flood hazard. Relevant SSCs important to safety and the UHS are included in the scope of this reevaluation,and pertinentdata concerning these SSCs should be included. Other relevant site data includes the following:
i. Detailedsite information (both designed and as-built), includingpresent-day site layout, elevation of pertinent SSCs important to safety, site topography,as well as pertinentspatialand temporal data sets;

Response

  • Site layout and topography - See Section 2.1 and Figures 2.1.1 and 2.1.2 of Enclosure 1 (FHRR).
  • Pertinent Site Data is provided in Enclosure 2.

ii. Currentdesign basis flood elevations for all flood causing mechanisms;

Response

  • See Section 2.2 of Enclosure 1, which describes the current design basis flood hazards for all flood causing mechanisms.

iii. Flood-relatedchanges to the licensing basis and any flood protection changes (includingmitigation) since license issuance;

Response

  • See Section 2.3 of Enclosure 1 for a description of flood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance.

iv. Changes to the watershed and local area since license issuance;

Response

U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 3

  • See Section 2.4 of Enclosure 1 for a description of changes to the watershed and local area since license issuance.
v. Currentlicensing basis flood protection and pertinentflood mitigation features at the site;

Response

  • See Section 2.5 of Enclosure 1 for a description of Current License 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 used to assess the flood hazard.

b. Evaluation of the flood hazardfor each flood causing mechanism, based on present-day methodologiesand regulatoryguidance. Provide an analysis of each flood causing mechanism that may impact the site including local intense precipitationand site drainage,flooding in streams and rivers, dam breaches and failures, storm surge and seiche, tsunami, channel migrationor diversion, and combined effects.

Mechanisms that are not applicableat the site may be screened-out; however, a justification should be provided. Provide a basis for inputs and assumptions, methodologiesand 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 the basis for inputs, assumptions, methodologies, and models are referenced below. Per NRC/NEI public meeting dated January 16, 2013, input-output files are not included with this submittal package but are available upon request. In addition to the flood-causing mechanisms listed in Requested Information "Item B" of Reference 1, Enclosure 2 (above),

the FHRR (Enclosure 1) provides results for associated effects, flood duration parameters, and error/uncertainty.

  • Local Intense Precipitation (LIP) and Site Drainage: See Section 3.1 of Enclosure 1.

" Flooding in Streams and Rivers: See Section 3.2 of Enclosure 1.

" Dam Breaches and Failures: See Section 3.4 of Enclosure 1.

  • Storm Surge: See Section 3.3 of Enclosure 1.

U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 4

  • Seiche: See Section 3.3 of Enclosure 1.

" Tsunami: See Section 3.8 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 of Enclosure 1.

" Other Associated Effects (i.e. hydrodynamic loading, including debris; effects caused by sediment deposition and erosion; concurrent site conditions; and groundwater ingress): See Sections 3.10 and 4 of Enclosure 1.

  • Flood Event Duration Parameters (i.e. warning time, period of site preparation, period of inundation, and period of recession): See Sections 3.10 and 4 of Enclosure 1.
  • Error/Uncertainty analysis for the governing flood scenarios is addressed in Section 3.9 of Enclosure 1.
c. Comparisonof currentand reevaluatedflood 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 from Enclosure 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 bounds the reevaluated hazard for all applicable flood-causing mechanisms, combined-effect floods, associated effects, and flood event duration parameters. A complete comparison of current design basis and reevaluated flood hazards is provided in Section 4 of Enclosure 1. The summary below describes how this finding was determined for the applicable flood hazards. The seiche, tsunami, ice-induced flooding, channel migration or diversion, and combined-effect floods H.2 (seismically-induced dam failure) and H.4.1 (floods along the shores of enclosed bodies of water, shore location)

(Reference 3) flood-causing mechanisms were either determined to be implausible or completely bounded by other mechanisms. Some individual flood-causing mechanisms (i.e.

flooding in streams and rivers, dam breaches and failures, and surge) are addressed in one or more of the combined-effect floods.

1. Local Intense Precipitation (LIP)

The maximum reevaluated flood elevation (736.8 feet MSL) is bounded by the design basis flood elevation (736.8 feet MSL). The associated effects are also

U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 5 bounded, as described in Section 4 of Enclosure 1. Flood event duration parameters are not applicable to the LIP flood since manual actions are not credited in the CLB) with providing protection.

2. Combined-Effect Flood in Section H.1, Reference 3, Floods Caused by Precipitation Events (including hydrologic dam failure) for Lake Clinton The three alternative precipitation-event combinations specified in Section H.1 of Reference 3, plus hydrologically-induced upstream dam failure, were evaluated for Lake Clinton, which collects drainage from the North Fork and Salt Creek watersheds. The maximum reevaluated stillwater elevation (708.5 feet MSL) for the prevailing alternative (Alternative 1) is bounded by the design basis stillwater elevation (708.9 feet MSL). The maximum reevaluated wind-wave elevation (712.04 feet MSL) for the prevailing alternative (Alternative 1) is bounded by the design basis wind-wave elevation (713.8 feet MSL). The other associated effects are also bounded, as described in Section 4 of Enclosure 1. Flood event duration parameters are not applicable to this combined-effect flood since manual actions are not credited in the CLB with providing protection at SSCs important to safety.
3. Combined-Effect Flood in Section H.4.2, Reference 3, Floods along the Shores of Enclosed Bodies of Water (Stream Location)

Section H.4.2, Reference 3, presents three alternatives (three streamside locations) for flooding along shores of enclosed bodies of water that considers the combined-effects of precipitation-induced flooding, surge, and wind-wave runup. The maximum reevaluated stillwater elevation (701.18 feet MSL) for the prevailing alternative (Alternative 1) is bounded by the design basis stillwater elevation (708.9 feet MSL).

The maximum reevaluated wind-wave elevation (713.3 feet MSL) for the prevailing alternatives (Alternatives 1 and 2) is bounded by the design basis wind-wave elevation (713.8 feet MSL). The other associated effects are also bounded, as described in Section 4 of Enclosure 1. Flood event duration parameters are not applicable since manual actions are not credited in the CLB with providing protection to SSCs important to safety.

d. Interim evaluation and actions taken or planned to addressany higher flooding hazardsrelative to the design basis, prior to completion of the integratedassessment describedbelow, if necessary.

Response

Per Enclosure 2 of Reference 1, an Integrated Assessment is required for plants where the current design basis floods do not bound the reevaluated hazard for all flood-causing mechanisms. 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 Basis Scenario 2 - Only Local Intense Precipitation Scenario 3 - All Permanent and Passive Flood Protection

U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 6 Scenario 4 - Integrated Assessment Required An Integrated Assessment is not necessary in Scenario 1. Limited evaluations can be conducted and submitted with the FHRR under Scenarios 2 and 3 that only address specific sections of the Integrated Assessment Interim Staff Guidance (Reference 5). Licensees in Scenario 4 and those not including limited evaluations in the FHRR under Scenarios 2 and 3 are required to perform a full Integrated Assessment.

Per "Part c" above, the current design basis flood bounds the reevaluated hazard for all flood-causing mechanism, combined-effect floods, associated effects, and flood event duration parameters. Therefore, Scenario 1 in Reference 4 applies; Scenarios 2, 3, and 4 are not applicable; and interim evaluations/actions and an Integrated Assessment are not required.

e. Additional actions beyond Requested Information item 1.d taken or planned to address flooding hazards,if any.

Response

  • None required.

This letter contains no new regulatory commitments and no revision to existing regulatory commitments.

If 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 12th day of March 2014.

Respectfully submitted, Ronald W. Gaston Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosures:

1. Clinton Power Station, Flood Hazard Reevaluation Report, Revision 0
2. CD-R labeled: "Clinton Power Station, Pertinent Site Data" Document Components:

Pertinent Site Data (requires AutoCAD or similar program)

U.S. Nuclear Regulatory Commission NTTF Recommendation 2.1 - Flood Hazard Reevaluation Submittal for Clinton Power Station March 12, 2014 Page 7 cc: Director, Office of Nuclear Reactor Regulation (w/o Enclosure 2)

Regional Administrator - NRC Region III (w/o Enclosure 2)

NRC Senior Resident Inspector - Clinton Power Station NRC Project Manager, NRR - Clinton Power Station Mr. G. Edward Miller, NRR/DORL/LPL2-1, NRC Illinois Emergency Management Agency - Division of Nuclear Safety (w/o Enclosure 2)

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