ML15301A557

Supplement to Staff Assessment of Response to 10 CFR 50.54(f) Information Request Flood Causing Mechanisms Reevaluations

ML15301A557
Person / Time
Site:	Harris
Issue date:	11/02/2015
From:	Juan Uribe Japan Lessons-Learned Division
To:	Waldrep B Duke Energy Progress
Govan, Tekia, NRR/JLD 415-6197
References
CAC MF1103
Download: ML15301A557 (16)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 2, 2015 Mr. Benjamin C. Waldrep, Site Vice President Shearon Harris Nuclear Power Plant 5413 Shearon Harris Rd.

M/C HNP01 New Hill, NC 27562-0165

\\.

SUBJECT:

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 - SUPPLEMENT TO STAFF ASSESSMENT OF RESPONSE TO 10 CFR 50.54{f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION (CAC NO.

MF1103)

Dear Mr. Waldrep:

The purpose of this letter is to transmit the supplement to the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of Shearon Harris Nuclear Power Plant, Unit 1 (HNP) reevaluated flood hazard information that was issued to you by letter dated April 29, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15104A370). The supplement updates the original staff assessment to address changes in the NRC's approach to the steps following the review of the flood hazard reevaluations as directed by the Commission. The letter also addresses the next steps associated with the mitigation strategies assessment with respect to the reevaluated flood hazards.

By letter dated March 12. 2012 (ADAMS Accession No. ML12053A340), the NRC issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Section 50. 54(f)

(hereafter referred to as the 50.54(f) letter). The request was :ssued as part of implementing lessons-learned from the accident at the Fukushima Dai-ichi nuclear power plant in Japan. to the 50.54(f) letter requested licensees to reevaluate flood-causing mechanisms using present-day methodologies and guidance. By letter dated March 12, 2013 (ADAMS Accession No. ML13079A253), Duke Energy Progress, Inc. (the Hcensee) responded to this request for HNP. This response was supplemented by letters dated March 24, 2014 (ADAMS Accession No. ML14087A165), and April 1, 2015 (ADAMS Ac.cession No. ML15091A590). By letter dated March 31, 2015, the staff transmitted to you the staff assessment of the information provided in the aforementioned letters. The NRC staff has cbrnpleted its review of the information pro.vided, as documented 1n the staff assessment and the enclosed supplement to the staff assessment. This closes out the NRC's efforts associated with CAC No. MF1103.

The enclosed supplement to the NRC staff assessment updates the staff's conclusions in accordance with the flood hazard reevaluation approach desci,:bed in NRC letter dated September 1, 2015 (ADAMS Accession No. ML15174A257), coi1cerning the coordination of requests for information regarding flooding hazard reevaluations and mitigating strategies for beyond-design-basis external events. This letter describes the changes in the NRC's approach to the flood hazard reevaluations that were approved by the CviT*mission in its Staff Requirements Memorandum (ADAMS Accession No. ML ~5209A682) to COMSECY-15-0019

(ADAMS Accession No. ML15153A104) that described the NRC's mitigating strategies and flooding hazard reevaluation action plan.

As documented in the NRC staff assessment and the enclosed supplement, the staff has concluded that the licensee's reevaluated flood hazard information is suitable for the assessment of mitigation strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in guidance documents currently being finalized by the industry and staff) for HNP. Further, the licensee's reevaluated flood hazard information is suitable for other assessments associated with Near-Term Task Force Recommendation 2.1 "Flooding."

The reevaluated flood hazard results for local intense precipitation, streams and rivers, and storm surge were not bounded by the current design-basis flood hazard. In order to complete its response to Enclosure 2 to the 50.54(f) letter, the licensee is expected to submit a revised integrated assessment or focused evaluation(s), as appropriate, to address these reevaluated flood hazards, as described in the NRC's September 1, 2015, letter.

If you have any questions, please contact me at (301) 415-3809 or email at Juan.Uribe@nrc.gov.

Docket No. 50-400

Enclosure:

Supplement to Staff Assessment of Flood Hazard Reevaluation Report cc w/encl: Distribution via Listserv Juan F. Uribe, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation

SUPPLEMENT TO STAFF ASSESSMENT BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO FLOODING HAZARD REEVALUATION REPORT NEAR-TERM TASK FORCE RECOMMENDATION 2.1 SHEARON HARRIS NUCLEAR POWER PLANT. UNIT 1 DOCKET NO. 50-400

1.0 INTRODUCTION

This document is a supplement to the U.S. Nuclear Regulatory Commission (NRC) staff assessment that was transmitted by letter dated April 29, 2015 (NRC, 2015a) to Duke Energy Progress, Inc. (Duke, the licensee) for Shearon Harris Nuclear Power Plant, Unit 1 (HNP, Harris). With the exceptions of the Table 3.1-1 and the Reference section, this supplement only contains the sections that were changed to resolve the open item and reflect the changes in the NRC's approach to the flood hazard reevaluations that were approved by the Commission in its Staff Requirements Memorandum (SRM) (NRC, 2015b) to COMSECY-15-0019 (NRC, 2015c),

which described the NRC's mitigating strategies and flooding hazard reevaluation action plan.

Table 3.1-1 at the end of the supplement is copied from the staff assessment for convenience.

Instead of repeating the Reference section in its entirety, only the additions to the list of references are included in the supplement.

2.0 REGULATORY BACKGROUND 2.1 Applicable Regulatory Requirements There are no changes or updates to this section of the NRC staff assessment.

2.2 to the 50.54(f) Letter There are no changes or updates to this section of the NRC staff assessment.

2.2.1 Flood-Causing Mechanisms There are no changes or updates to this section of the NRC staff assessment.

2.2.2 Associated Effects There are no changes or updates to this section of the NRC staff assessment.

2.2.3 Combined Effect Flood Enclosure 2.2.3 Combined Effect Flood There are no changes or updates to this section of the NRC staff assessment.

2.2.4 Flood Event Duration There are no changes or updates to this section of the NRC staff assessment.

2.2.5 Actions Following the Flooding Hazard Reevaluation Report (FHRR)

For the sites where the reevaluated flood hazard is not bounded by the current design-basis (COB) flood hazard for all flood-causing mechanisms, the request for information issued Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(f) (hereafter referred to as the 50.54(f) letter) (NRC, 2012a) requests licensees and construction permit holders to:

Submit an interim action plan with the FHRR documenting actions planned or already taken to address the reevaluated hazard(s)

Perform an integrated assessment subsequent to the FHRR to: (a) evaluate the effectiveness of the current licensing basis (i.e., flood protection and mitigation systems);

(b) identify plant-specific vulnerabilities; and (c) assess the effectiveness of existing or planned systems and procedures for protecting against and mitigating consequences of flooding for the flood event duration.

After issuance of the.50.54(f) letter, the NRC changed the approach to the steps following the review of the flood hazard reevaluations, as directed by the Commission, to permit use of focused evaluations as an alternative to an integrated assessment. The NRC letter dated September 1, 2015 (NRC, 2015d), describes the changes in the NRC's approach to the flood hazard reevaluations.

If the reevaluated flood hazard is bounded by the COB flood hazard for all flood-causing mechanisms at the site, licensees are not required to perform an integrated assessment or a focused evaluation(s) at this time.

3.0 TECHNICAL EVALUATION

There are no changes or updates to this section of the NRC staff assessment.

3.1 Site Information There are no changes or updates to this section of the NRC staff assessment.

3.2 Local Intense Precipitation (LIP) and Associated Site Drainage There are no changes or updates to this section of the NRC staff assessment.

3.2.1 Site Drainage There are no changes or updates to this section of the NRC staff assessment.

3.2.2 Local Intense Precipitation There are no changes or updates to this section of the NRC staff assessment.

3.2.3 Runoff Analyses There are no changes or updates to this section of the NRC staff assessment.

3.2.4 Sumps and Containment Areas There are no changes or updates to this section of the NRC staff assessment.

3.2.5 Hydraulic Model There are no changes or updates to this section of the NRC staff assessment.

3.2.6 Sensitivity Analyses There are no changes or updates to this section of the NRC staff assessment.

3.2.7 Flood Event Duration The NRC staff notes that the bases and justification for flood duration parameters (e.g., warning time based on existing forecasting resources or agreements) may be further evaluated as part of the focused evaluation consistent with the process and guidance discussed in COMSECY-15-0019 (NRC, 2015c). The staff issued a request for additional information (RAI) to the licensee (NRC, 2014a) to supplement the HNP, Unit 1, FHRR. The licensee's response (Duke, 2014b, RAI No. 18 response), is discussed in Section 3 of this supplemental staff assessment.

The staff notes that longer duration Probable Maximum Precipitation (PMP) events, such as the 72-hr PMP, generate greater volumes of runoff; and, the shorter duration PMP events, such as the 1-hour PMP, result in (potentially significantly) shorter warning time with greater peak event magnitude, and likewise may result in flooding above the elevation of openings to plant structures.

The NRC staff notes that a reasonable estimate of the site's LIP PMP is the application of an appropriate National Oceanic Atmospheric Administration (NOAA) Hydro Metereological Report (HMR) estimate for any rainfall duration used in NUREG/CR-7046, regardless of temporal distribution of the rainfall. The licensee obtained 1-sq. mile PMP depths for durations ranging between 5-minutes and 1-hour using HMR 52 (HMR-52). Therefore, the NRC staff confirmed that the licensee selected appropriate rainfall rate values to satisfy the 50.54(f) information request.

3.2.8 Conclusion The NRC staff confirmed the licensee's conclusion that the reevaluated flood hazard for LIP and associated site drainage is not bounded by the COB flood hazard. Therefore, the licensee is expected to submit a focused evaluation for LIP and associated site drainage consistent with the process outlined in COMSECY-15-0019 (NRC, 2015c) and associated guidance that will be issued. Under this approach, the NRC staff anticipates that licensees will perform and document a focused flooding evaluation for LIP and associated site drainage that evaluates the impact of the LIP hazard on the site and implements any necessary programmatic, procedural or plant modifications to address this hazard exceedance. The NRC staff anticipates that licensees will submit letters providing a summary of the evaluation and, if needed, regulatory commitments to implement and maintain appropriate programmatic, procedural or plant modifications to protect against the LIP hazard.

3.3 Streams and Rivers There are no changes or updates to this section of the NRC staff assessment.

3.3.1 Probable Maximum Precipitation There are no changes or updates to this section of the NRC staff assessment.

3.3.2 Precipitation Losses There are no changes or updates to this section of the NRC staff assessment.

3.3.3 Snyder Coefficients There are no changes or updates to this section of the NRC staff assessment.

3.3.4 Unit Hydrographs There are no changes or updates to this section of the NRC staff assessment.

3.3.5 Spillway Rating Curves There are no changes or updates to this section of the NRC staff assessment.

3.3.6 Runoff and Probable Maximum Flood Elevations There are no changes or updates to this section of the NRC staff assessment.

3.3.7 Coincident Wind and Wave Activity There are no changes or updates to this section of the NRC staff assessment.

3.3.8 Conclusion The NRC staff confirmed the licensee's conclusion that the reevaluated flood hazard for site flooding from streams and rivers is not bounded by the COB flood hazard; therefore, the licensee should address flooding from streams and rivers, including combined effects, such as wind setup and wave runup, within the scope of the integrated assessment or focused evaluation consistent with the process and guidance discussed in COMSECY-15-0019 (NRC, 2015c). The information on flooding from streams and rivers that is specific to the data needs of the integrated assessment or focused evaluation is described in Section 4 of this staff assessment.

3.4 Failure of Dams and Onsite Water Control/Storage Structures There are no changes or updates to this section of the NRC staff assessment.

3.5 Storm Surge The licensee stated in its FHRR, that the reevaluated hazard, including associated effects, for site flooding due to storm surge near HNP, Unit 1 is 254.5 ft (77.57 m). This flood-causing mechanism is described in the licensee's COB. The COB hazard for site flooding due to storm surge at the HNP, Unit 1 site is 254.9 ft (77.69 m). At the Auxiliary Dam, the reevaluated hazard elevation of 257.9 ft (78.61 m) is not bounded by the design basis of 256.2 ft (78.09 m). No design-basis was evaluated at the Main Dam, where the reevaluated hazard elevation is 233.4 ft (71.14 m).

To estimate the effects from storm surge, the FHRR referenced current methods supplemented with guidance from NUREG/CR-7046 (NRC, 2011e). Additionally, the licensee used NOAA Technical Report National Weather Service (NWS) 23 (NWS-23) in its FHRR to determine parameter values used in the Probable Maximum Hurricane (PMH) calculation.

The meteorological characteristics used by the licensee to calculate the PMH were obtained from National Oceanic and Atmospheric Administration (NOAA) Technical Report NWS 23 (NOAA, 1979) for Milepost 2200 and 35.6 degrees latitude. The licensee computed wave runup using the methods in the U.S. Army Corps of Engineers (USAGE) (2008) and wind setup using the methods in USAGE (1997).

To determine the fetch, the licensee used five straight line fetch distances in the PMH-induced wave runup and wave setup calculations. Since several headlands interrupt the fetches when the Main Reservoir level is at the present lower level of 220 ft (67.1 m), the licensee stated that the calculated fetches were conservative for present conditions.

The licensee determined the PMH-induced wave runup and wind setup at the Main and Auxiliary Reservoirs assuming normal operating water levels in the Auxiliary and Main Dams, and by following the procedure given in the USAGE Coastal Engineering Manual, Engineer Manual 1110-2-1100 (USAGE, 2008). The licensee calculated the average water depth of the reservoirs by taking the storage volume at the stillwater elevation divided by the surface area but used the higher value from the Harris Advanced Reactor, 1 Units 2 and 3 combined license application final safety assessment report (Revision 3) (PEC, 2011) in subsequent calculations.

The licensee did not evaluate the COB flood hazard level for PMH-induced storm surge for the Main Dam, but noted that both the Main and Auxiliary Dams and HNP, Unit 1 are protected up to elevation 260 ft (79.2 m).

The licensee noted that the reevaluated PMH-induced storm surge flood level for the Auxiliary Dam exceeds the COB flood level by 1.65 ft (0.50 m), but remains below the Auxiliary Dam flood protection level by 2.15 ft (0.66 m). In addition, water wave phase speed and water velocity would produce significantly smaller dynamic forces with floating debris compared to dynamic forces produced by hurricane/tornado wind projectiles.

The licensee stated the embankment of the plant island along the Main Reservoir is protected by 300 ft (91.4 m) of sacrificial spoil fill at elevation 245 ft (74.7 m). The extent of erosion due to the 2 worst fetches is estimated by the licensee to be 150 ft (45. 7 m) resulting from a PMH duration of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. Therefore, the licensee stated that the sacrificial spoil fill provides a conservative design.

The NRC staff agrees with the licensee that dynamic forces from floating debris are minimal compared to those resulting from hurricane/tornado wind projectiles and concludes that the COB is bounded for hydrodynamic loading on the safety-related structures, except for the Auxiliary Dam, which is not bounded by the COB. The staff further concludes that the loading from waterborne projectiles and debris are bounded by loading from other hazards such as tornado wind and tornado missiles. The staff confirmed the fetch lengths, straight-line fetches, wind speed, and calculation of wind-wave runup and setup associated with the HNP, Unit 1 and Auxiliary/Main dams. The staff agrees with the licensee's use of the USAGE (2008) as the source of applicable methodology for the performing relevant wave action calculations. The staff also agrees that the sacrificial spoil fill erosion of 50 percent provides a conservative design.

The NRC staff confirmed the licensee's conclusion that the reevaluated hazard at the Auxiliary Dam for flooding from storm surge is not bounded by the COB flood hazard; therefore, the licensee should include flooding from storm surge within the scope of the integrated assessment or focused evaluation consistent with the process and guidance discussed in COMSECY 0019 (NRC, 2015c). The information on flooding from storm surge that is specific to the data needs of the integrated assessment or focused evaluation is described in Section 4 of this staff assessment.

3.6 Seiche There are no changes or updates to this section of the NRC staff assessment.

3.7 Tsunami There are no changes or updates to this section of the NRC staff assessment.

1 Harris Advanced Reactor is a proposed addition of new Units 2 and 3 to the HNP, Unit 1 site, and is located adjacent to HNP, Unit 1.

3.8 Ice-Induced Flooding There are no changes or updates to this section of the NRC staff assessment.

3.9 Channel Migrations or Diversions There are no changes or updates to this section of the NRC staff assessment.

4.0 REEVALUATED FLOOD HEIGHT. EVENT DURATION AND ASSOCIATED EFFECTS FOR HAZARDS NOT BOUNDED BY THE COB The NRC staff confirms that the reevaluated hazard results for LIP, streams and rivers, and storm surge are not bounded by the COB flood hazard. Therefore, the NRC staff anticipates that the licensee will perform additional assessments (i.e., integrated assessment or focused evaluation) of plant response for HNP, Unit 1, as described, in NRC letter dated September 1, 2015 (NRC, 2015d).

The NRC staff reviewed the following flood hazard parameters needed to perform the additional assessments or evaluations of plant response:

Flood event duration, including warning time and intermediate water surface elevations that trigger actions by plant personnel, as defined in Japan Lessons-Learned Directorate (JLD) Interim Staff Guidance (ISG) JLD-ISG-2012-05. Flood event durations for the flood-causing mechanisms identified above are shown in Table 4.0-1.

Flood height and associated effects, as defined in JLD-ISG-2012-05. Flood height and associated effects for the flood-causing mechanisms identified above are shown in Table 4.0-2.

4.1 Flood Event Duration The NRC staff requested the licensee to provide the applicable flood event duration parameters associated with mechanisms that are not bounded by the COB. The applicable flood duration parameters include the warning time the site will have to prepare for the event, the period of time the site is inundated, and the period of time necessary for water to recede from the site.

The staff also requested the licensee to provide the flood height and associated effects for these mechanisms:

(a) Local Intense Precipitation - The warning time stated by the licensee for an inundation of the site as a consequence of a LIP event is zero, since it may occur without warning from localized storms (Duke, 2014b). The site is assumed by the licensee to be inundated for a period of one hour (Duke, 2014b). The water level is then expected by the licensee to recede below site grade within one hour (Duke, 2014b). In its FHRR, the licensee identified the flood height as 0.4 ft (0.12 m) at the Waste Process Building and 0.4 ft (0.12 m) at the Diesel Fuel Oil Storage Tank Building. The hydrodynamic loadings at these locations are minimal when compared to the strength of the buildings; (b) Streams and rivers - The warning time for flooding from rivers and streams is 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> (Duke, 2014b) based on information from the National Weather Service; the site is not inundated from this flood mechanism; (c) Storm surge - The warning time for flooding from storm surge is 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> (Duke, 2014b) based on information from the NWS; the site is not inundated from this flood mechanism.

4.2 Conclusion Based upon the preceding analysis, NRC staff confirmed that the reevaluated flood hazard information is appropriate input to other assessments or evaluations associated with Near-Term Task Force Recommendations, including the assessment of mitigation strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in guidance documents currently being finalized by the industry and staff).

5.0 CONCLUSION

The NRC staff has reviewed the information provided for the reevaluated flood-causing mechanisms of HNP, Unit 1. Based on its review, the staff concludes that the licensee conducted the hazard reevaluation using present-day methodologies and regulatory guidance used by the NRC staff in connection with early site permit and combined license reviews.

Based on the preceding analysis, the NRC staff confirmed that the licensee responded appropriately to Enclosure 2, Required Response 2, of the 50.54(f) letter, dated March 12, 2012.

In reaching this determination, the NRC staff confirmed the licensee's conclusions that (a) the reevaluated flood hazard results for local intense precipitation, streams and rivers, and storm surge are not bounded by the current design-basis flood hazard, (b) additional assessments of plant response will be performed for the local intense precipitation, streams and rivers, and the storm surge flood-causing mechanisms, and (c) the reevaluated flood-causing mechanism information is appropriate input to additional assessments or evaluations of plant response, as described in the 50.54(f) letter and COMSECY-15-0019 (NRC, 2015b), including the assessment of mitigation strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in guidance documents currently being finalized by the industry and staff).

The NRC staff has no additional information needs at this time with respect to the FHRR.

6.0 REFERENCES

U.S. Nuclear Regulatory Commission Documents and Publications NRC (U.S. Nuclear Regulatory Commission), 2015a, letter from Juan F. Uribe, NRC, to Benjamin C. Waldrep, Vice President, Shearon Harris Nuclear Power Plant, "Shearon Harris Nuclear Power Plant, Unit 1 - Staff Assessment of Response to 10 CFR 50.54(f) Information Request Flood-Causing Mechanism Reevaluation (TAC No. MF1103), April 29, 2015, ADAMS Accession No. ML15104A370.

NRC (U.S. Nuclear Regulatory Commission), 2015b, SRM-COMSECY-15-0019-Closure Plan for the Reevaluation Of Flooding Hazards for Operating Nuclear Power Plants,"

COMSECY-15-0019, July 28, 2015, ADAMS Accession No. ML15209A682.

NRC (U.S. Nuclear Regulatory Commission), 2015c, "COMSECY-15-0019 - Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants," June 30, 2015, ADAMS Accession No. ML15153A104.

NRC (U.S. Nuclear Regulatory Commission), 2015d, letter from William M. Dean, Director, to Power Reactor Licensees, "Coordination of Requests for Information for Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events," September 1, 2015, ADAMS Accession No. ML15174A257.

Codes and Standards There are no additions to the references in this section.

Other References There are no additions to the references in this section.

Table 3.1-1. Current Design Basis Flood Hazards at HNP Stillwater Level Flood Level1 Section in Flooding Mechanism ft (m) NGVD29 Associated Effects ft (m) NGVD29 FHRR (Duke, 2013)

Local Intense 261.27 (79.64)

Negligible 261.27 (79.64) 2.1.1, 4.1 and Precipitation and at powerblock Table 6 Associated Drainage buildings (based on 1-hr PMP) 256.0 (78.03) 1.7 ft (0.52 m) at Plant 257.7 (78.55) at 2.1.2, 2.1.3, at Plant Island Island, wind setup Plant Island 2.1.8, 4.2, and wave runup and Table 6 Streams and Rivers 4.2 ft (1.28 m) at Main (using PMF resulting 238.9 (72.82) at Dam, wind setup and 243.1 (74.10) at from 36-hr PMP)

Main Dam wave runup Main Dam combined with wind setup and wave runup 2.0 ft (0.61 m) at Auxiliary Dam, wind 256.0 (78.03) at setup and wave runup 258.0 (78.64) at Auxiliary Dam Auxiliary Dam Failure of Dams and Bounded by None (below site Bounded by 2.1.9 and 4.9 Onsite Water Streams and grade)

Streams and Control/Storage Rivers at Rivers at Structures Auxiliary Dam Auxiliary Dam 252.0 (76.81) at 2.9 ft (0.88) at Plant 254.9 (77.69) at 2.1.8 and Plant Island Island, wind setup Plant Island Table 6 and wave runup Storm Surge No analysis at Main (based on PMH)

No analysis Dam NoCDB at Main Dam at Main Dam 4.2 ft (1.28 m) at 252.0 (76.81 ) at Auxiliary Dam, wind 256.2 (78.09) at Auxiliary Dam setup and wave runup Auxiliary Dam NIA NIA Not discussed in 2.1.4 and 4.4 Seiche current design basis NIA NIA Not discussed in 2.1.5 and 4.5 Tsunami current design basis NIA NIA Not discussed in 2.1.6 and 4.6 Ice-Induced current design basis Channel Migrations or NIA NIA Not discussed in 2.1.7and4.7 current design Diversions basis NIA = Not Applicable 1 Site grade at elevation 260.0 ft (79.25 m) NGVD29.

Table 4.0-1. Flood Event Duration for Reevaluated Hazards for Flooding-Causing Mechanisms Not Bounded by COB Hazard Flood-Causing Time for Period of Site Time for Site Preparation Recession of Mechanism for Flood Event Inundation Water from Site Local Intense Precipitation and 0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> 1 hour1 1 hour1 Associated Drainaqe Storm Surge 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> Site not inundated Site not inundated Flooding in Streams 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> Site not inundated Site not inundated and Rivers 1These values are estimates by licensee, as analysis was limited to steady-state one-dimensional modeling.

Table 4.0-2. Reevaluated Flood-Causing Mechanisms and Associated Effects for Flooding-Causing Mechanisms Not Bounded by COB Hazard Flood-Causing Stillwater Elevation1 Associated Flood Hazard1*2 Reference Mechanism NGVD29 Effects NGVD29 261.41 ft (79.68 m) at Diesel Fuel Oil Assumed drain Storage Tank Building Local Intense Varies with maximum blockages due to (protected to 262.0 ft Precipitation and of 261.4 ft (79. 7 m) sediment, debris, or (79.86 m)); not Associated at the Diesel Fuel Oil ice. Other bounded by COB of Drainage Storage Tank and associated effects:

261.27 ft (79.64 m)

FHRR, Table 3 Waste Processing wind (N/A),

and Table 6 (based on 1-hr Buildings hydrodynamic force 261.36 ft (79.66 m)

PMP)

(minimal), and at Waste Processing groundwater effects Building (protected to (none).

261.06 ft (79.57 m);

not bounded by COB of 261.27 ft (79.64 m)

Streams and 256.50 ft (78.18 m) 1.14 ft (0.35 m)3 at 257.64 ft (78.53 m)

Rivers at Plant Island; Plant Island, wind at Plant Island; not bounded by COB setup and wave bounded by COB of (based on PMF of 256.0 ft (78.03 m) run up 257.7 ft (78.55 m) resulting from design storm 243.84 ft (74.32 m) 5.96 ft (1.82 m)3 at 249.80 ft(76.14 m) consisting of at Main Dam; Main Dam, wind at Main Dam; FHRR, Section antecedent storm not bounded by COB setup and wave not bounded by COB 3.2.1.5 and at 0.4 x 72-hr PMP of 238.9 ft (72.82 m) run up of243.1 ft(74.10 m)

Table 6 followed by 72-hr dry period followed 256.50 ft (78.18 m) 2.84 ft (0.87 m)3 at 259.34 ft (79.05 m) by 72-hr PMP, at Auxiliary Dam; Auxiliary Dam at Auxiliary Dam; combined with not bounded by COB Upstream, wind not bounded by COB wind setup and of 256.0 ft (78.03 m) setup and wave of 258.0 ft (78.64 m) wave runup) run up 252.0 ft (76.81 m) 2.47 ft (0.75 m) at 254.47 ft (77.56 m) at Plant Island Plant Island, wind at Plant Island; setup and wave bounded by COB of run up 254.9 ft (77.69 m)

Storm Surge 220.0 ft (67.06 m) 13.43 ft (4.09 m) at 233.43 ft (71.15 m)

(based on PMH, at Main Dam Main Dam, wind at Main Dam; no COB FHRR, Table 4 combined with setup and wave and Table 6 wind setup and run up wave runup) 252.0 ft (76.81 m) 5.85 ft (1.78 m) at 257.85 ft (78.59 m) at Auxiliary Dam Auxiliary Dam at Auxiliary Dam; Upstream, wind not bounded by COB setup and wave of 256.2 ft (78.09 m) run up N/A = Not Applicable 1 Numbers of significant figures in elevation and flood hazard values reflect those presented by the licensee in its FHRR 2 Protected to 260.0 ft (79.25 m) NGVD29 unless otherwise noted.

3 Deduced from hazard elevation and stillwater elevation.

Table 5.0-1: Integrated Assessment Open Items Deleted

ML15153A104) that described the NRC's mitigating strategies and flooding hazard reevaluation action plan.

As documented in the NRC staff assessment and the enclosed supplement, the staff has concluded that the licensee's reevaluated flood hazard information is suitable for the assessment of mitigation strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in guidance documents currently being finalized by the industry and staff) for HNP. Further, the licensee's reevaluated flood hazard information is suitable for other assessments associated with Near-Term Task Force Recommendation 2.1 "Flooding."

The reevaluated flood hazard results for local intense precipitation, streams and rivers, and storm surge were not bounded by the current design-basis flood hazard. In order to complete its response to Enclosure 2 to the 50.54(f) letter, the licensee is expected to submit a revised integrated assessment or focused evaluation(s), as appropriate, to address these reevaluated flood hazards, as described in the NRC's September 1, 2015, letter.

If you have any questions, please contact me at (301) 415-3809 or email at Juan.Uribe@nrc.gov.

Docket No. 50-400

Enclosure:

Supplement to Staff Assessment of Flood Hazard Reevaluation Report cc w/encl: Distribution via Listserv DISTRIBUTION:

Sincerely, IRA/

Juan F. Uribe, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation PUBLIC JHMB R/F JUribe RidsNroDseaResource RidsNrrPMShearonHarrisResource BHarvey RidsNrrDorllpl2-2Resource RidsNrrLASLentResource RidsOgcMailCenterResource MShams CCook KErwin ARivera-Varona SF landers LQuinn-Willingham ACampbell ADAMS Accession No.: ML15301A557

• via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/JHMB/PM NRR/JLD/LA NAME MMarshall JUribe SLent DATE 10/ 28 /2015 11/2/2015 11/2/2015 OFFICE NRO/DSEA/RHM1/BC NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME CCook*

MShams*

JUribe DATE 10/24/2015 10/25/2015 11/2/2015