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FENOC, Perry Nuclear Power Plant - Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Ac
	ML15069A056
Person / Time
Site:	Perry
Issue date:	03/10/2015
From:	Harkness E; FirstEnergy Nuclear Operating Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	L-15-074
	Download: ML15069A056 (39)
	v • d • e

FE NOC' FirstEnergy Nuclear Operating Company ErnestJ. Harkness Vice President March 10, 2015 L-15-074 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852

SUBJECT:

Perry Nuclear Power Plant Docket No. 50-440, License No. NPF-58 Perry Nuclear Power Plant P.O. Box 97 10 Center Road Perry, Ohio 44081 440-280-5382 Fax: 440-280-8029 10 CFR 50.54(f)

FirstEnergy Nuclear Operating Company (FENOC) Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued a letter titled, "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," to all power reactor licensees and holders of construction permits in active or deferred status. Enclosure 2 of the 10 CFR 50.54(f) letter addresses NTTF Recommendation 2.1 for flooding. One of the required responses is for licensees to submit a Hazard Reevaluation Report (HRR) in accordance with the NRC's prioritization plan. By letter dated May 11, 2012, the NRC placed the Perry Nuclear Power Plant (PNPP) in Category 3 requiring a response by March 12, 2015. The Flood HRR for PNPP is enclosed.

As discussed in the enclosed report, three flood levels (riverine, local intense precipitation and probable maximum storm surge) determined during the hazard reevaluation exceed the current licensing basis (CLB) flood levels. Actions planned to address the reevaluated hazards are also described in the enclosed report.

Perry Nuclear Power Plant L-15-074 Page 2 In accordance with the guidance provided by NRC letter dated December 3, 2012, titled "Trigger Conditions for Performing an Integrated Assessment and Due Date for Response," an integrated assessment is required if flood levels determined during the hazard reevaluation are not bounded by the CLB flood levels. The 10 CFR 50.54(f) letter specifies that the integrated assessment be completed and a report submitted within two years of submitting the HRR. Therefore, FENOC intends to submit an Integrated Assessment Report for PNPP prior to March 12, 2017.

There are no regulatory commitments contained in this letter. If there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, Manager -

Fleet Licensing, at 330-315-6810.

I declare under penalty of perjury that the foregoing is true and correct. Executed on March Id, 2015.

Respectfully,

~~-

Ernest J. Harkness

Enclosure:

Flood Hazard Reevaluation Report cc:

Director, Office of Nuclear Reactor Regulation (NRR)

NRC Region Ill Administrator NRC Resident Inspector NRR Project Manager

Enclosure L-15-074 Flood Hazard Reevaluation Report (36 pages follow)

FLOOD HAZ/ARD REEVALUATIOil REPORT IN RESPONSE TO THE 50.5/T(f}

INFORUATION REQUEST REGARDING NEAR-TERI' TASK FORCE RECOHTENDATION 2.I: FLOODING for ths PERRY HUCLEAR POWER PLANT f 0 Ctnttr Road North Perry, OH {4081 Firret Energy Corporation 76 South Main Street Akron, OH 44308 Preparad by:

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NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Table of Gontents Revision 0

February 23,2015

1. PURPOSE

......3 1.1. Background

..........3 1.2. Requested Actions

..........3 1.3. Requested Information

...-.-..4

2. SITE INFORMATION

......5 2.1. Current Design Basis..

..........7 2.1.1. Local Intense Precipitation (LlP).....

......7 2.1.2. Flooding in Streams and Rivers

......7 2.1.g. Dam Breaches and Failures 2.1.4. Storm Surge and Seiche

...'..7 2.1.5. Tsunami......

.....7 2.1.6. lce-lnduced Flooding

.........7 2.1.7. Channel Migration or Diversion

..,....7 2.1.8. Combined Effect Flood (including

\\Mnd-Generated Waves)

...........8 2.1.9. Low Water 2.2. Flood-Related Changes to the License Basis

......8 2.3. Changes to the Watershed and Local Area since License lssuance

.....8 2.4. Current Licensing Basis Flood Protection and Pertinent Flood Mitigation Features............8

3.

SUMMARY

OF FLOOD HATARD REEVALUATION

........9 3.1. Flooding in Streams and Rivers (Reference PNPP 2015a, PNPP 2015b, PNPP 2015c, PNPP 2015d, PNPP 2015e, PNPP 2015f

, PNPP 2015n, PNPP 2015r, and PNPP 2015s)

........10 3.1.1. Basisoflnputs:...

..........11 3.1.2. Computer Software Programs

....-12 3.1.3. Methodology

....12 3.1.4. Results

.......16 3.2. Dam Assessment (Reference PNPP 2015h) 3.2.1. Basis of Inputs....

.....18 3.2.2. Computer Software Programs

....1 8

3.2.3. Methodology

....1 I

3.2.4. Results

....... 1 I 3.3. lce-lnduced Flooding (Reference PNPP 2015i)

....'..18 3.3.1. Basis of Inputs....

....18 3.3.2. Computer Software Programs

.......18 3.3.3. Methodology

...18 3.3.4. Resutts

....'..19 3.4. Channel Migration or Diversion (Reference PNPP 2015i)

...'20 PERRY NUCLEAR POWER PLANT Page 1 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2015 3.4.1. Basis of Inputs....

...20 3.4.2. Computer Software Programs

......24 3.4.3. Methodology

...20 3.4.4. Results

....20 3.5. Storm Surge (Reference PNPP 2015j, PNPP 2015k, PNPP 20151, PNPP 2A15o, and PNPP 2015p)

...20 3.5.1. Basis of lnputs....

........21 3.5.2. Computer Software Programs

......21 3.5.3. Methodology

.....21 3.5.4. Results

....23 3.6. Tsunami Assessment (Reference PNPP 2015m).

....24 3.6.1. Basis of Inputs....

....24 3.6.2. Computer Software Programs

.......24 3.6.3. Methodology

...24 3.6.4. Results

......25 3.7. Combined Effect Flood (including

\\Mnd-Generated Waves) (Reference PNPP 2015q)...26 3.7.1. Basisoflnputs....

....26 3.7.2. Computer Software Programs

...27 3.7.3. Methodology

.....27 3.7.4. Results

......27 3.8. Local Intense Precipitation (Reference PNPP 20159)

.....28 3.8.1. Basis of Inputs....

...28 3.8.2. Computer Software Programs

.....28 3.8.3. Methodology

...28 3.8.4. Results

.....29

4. COMPARISON WITH CURRENT DESIGN BASIS...

.......29

5. INTERIM AND PLANNED FUTURE ACTIONS

.......33

6. REFERENCES

......34 PERRY NUCLEAR POWER PLANT Page 2 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation

1. PURPOSE Revision 0

February 23,2015 1.1. Background In response to the nuclear fuel damage at the Fukushima Dai-ichi power plant due to the March 11, 2011 earthquake and subsequent tsunami, the United States Nuclear Regulatory Commission (NRC) established the Near Term Task Force (NTTF) to conduct a systematic review of NRC processes and regulations, and to make recommendations to the NRC for its policy direction. The NTTF reported a set of recommendations that were intended to clarify and strengthen the regulatory framework for protection against natural phenomena.

On March 12,2012 the NRC issued an information request pursuant to Title 10 of the Code of Federal Regulations, Section 50.54 (f) (10 CFR 50.54(0 or 50.54(D letter) which included six (6) enclosures:

1. NTTF Recommendation 2.1: Seismic

2. NTTF Recommendation 2.1 : Flooding

3. NTTF Recommendation 2.3: Seismic

4. NTTF Recommendation 2.3: Flooding

5. NTTF Recommendation 9.3: EP

6. Licensees and Holders of Construction Permits f n Enclosure 2 of the NRC-issued information request (Reference NRC March 2A12), the NRC requested that licensees reevaluate the flooding hazards at their sites against present-day regulatory guidance and methodologies being used for early site permits (ESP) and combined operating license reviews.

On behalf of FirstEnergy Nuclear Operating Company (FENOC) for the Perry Nuclear Power Station (PNPP), this Flood Hazard Reevaluation Report (Report) provides the information requested in the March 12, 2012 50.54(D letter; specifically, the information listed under the "Requested Information" section of Enclosure 2, paragraph 1 ('a' through 'e'). The "Requested f nformation" section of Enclosure2, paragraph 2 ('a'through

'd'), Integrated Assessment

Report, will be addressed separately if the current design basis floods do not bound the reevaluated hazard for all flood-causing mechanisms.

1.2. Requested Actions Per Enclosure 2 of the NRO-issued information

request, 50.54(0 letter, FENOC is requested to perform a reevaluation of all appropriate external flooding sources for PNPP, including the effects from local intense precipitation (LlP) on the site, the probable maximum flood (PMF) on streams and rivers, lake flooding from storm surges, seiches, and tsunamis, and dam failures. lt is requested that the reevaluation apply present-day regulatory guidance and methodologies being used for ESPs, combined operating license reviews, and calculation reviews including current techniques,

software, and methods used in present-day standard engineering practice to develop the flood hazard. The requested information will be gathered in Phase 1 of the NRC staffs two-phase process to implement Recommendation 2.1, and will be used to identify potential "vulnerabilities" (see defi nition below).

PERRY NUCLEAR POWER PI-ANT Page 3 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2Q15 The NRC prioritization of responses letter (Reference NRC May 2012) identifies PNPP as a Category 3 site. Licensees in this category are expected to report the results of the reevaluation within three years of the March 12, 2012 50.54(f) letter issuance.

For the sites where the reevaluated flood exceeds the design basis, addressees are requested to submit an interim action plan documenting planned actions or measures implemented to address the reevaluated hazards.

Subsequently, addressees shall perform an integrated assessment of the plant to fully identify vulnerabilities and detail actions to address them. The scope of the integrated assessment report will include full power operations and other plant configurations that could be susceptible due to the status of the flood protection features. The scope also includes those features of the ultimate heat sink (UHS) that could be adversely affected by flood conditions (the loss of UHS from non-flood associated causes is not included). lt is also requested that the integrated assessment address the entire duration of the flood conditions.

A definition of vulnerability in the context of Enclosure 2 is as follows: Plant-specific vulnerabilities are those features important to safety that when subject to an increased demand due to the newly calculated hazard evaluation have not been shown to be capable of performing their intended functions.

1.3. Requested Information Per Enclosure 2 of the NRC-issued information request 50.54(D letter, the Report should provide documented results, as well as pertinent PNPP information and detailed analysis, and include the following:

1. Site information related to the flood hazard. Relevant structure, systems, and components (SSCs) important to safety and the UHS are included in the scope of this reevaluation, and pertinent data concerning these SSCs should be included.

Other relevant site data include the following:

1. Detailed site information (both designed and as-built), including present-day site layout, elevation of pertinent SSCs important to safety, site topography, and pertinent spatial and temporal data sets; Current design basis flood elevations for all flood-causing mechanisms; Flood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance; Changes to the watershed and local area since license issuance; Current licensing basis flood protection and pertinent flood mitigation features at the site; and

6. Additional site details, as necessary, to assess the flood hazard (e.g., bathymetry and walkdown results).

2. Evaluation of the flood hazard for each flood-causing mechanism, based on present-day methodologies and regulatory guidance. Provide an analysis of each flood-causing mechanism that may impact the site, including LIP and site drainage, flooding in streams and rivers, dam breaches and failures, storm surge and seiche, tsunamis, channel migration or diversion, and combined effects. Mechanisms that are not applicable at the site may be screened out; however, a justification should be provided. A basis for inputs and 2.

3.

4.

5.

PERRY NUCLEAR POWER PLANT Page 4 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0

February 23,2415 or planned to address any higher flooding hazards completion of the integrated assessment described assumptions, methodologies and models used, including input and output files, and other pertinent data should be provided.

3. 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 from Enclosure 2 of the 50.54(D letter (i.e., Recommendation 2.1, flood hazard reevaluations) support this determination.

lf the current design basis flood bounds the reevaluated hazard for all flood-causing mechanisms, include how this finding was determined.

4.

5.

Interim evaluation and actions taken relative to the design basis, prior to below, if necessary.

Additional actions beyond requested flooding hazards, if any.

information item 1.d taken or planned to address

2. SITE INFORMATION PNPP is located in Lake County, Ohio, approximately seven miles northeast of Painesville.

The southern plant site boundary line is 3,100 feet from the shoreline of Lake Erie on the west side of the site and 8,000 feet on the east side (USAR, Section 2.4.1.1). Lake Erie is the major hydrologic feature of the location.

In the vicinity of the site, the coastal watershed is drained by several small streams (USAR, Section 2.4.1.2).

Two nameless, parallel streams run close to the plant area. The larger (Major Stream) has a drainage basin of 7.16 square miles and runs northwestward within 1,000 feet of the southwest corner of the plant. The smaller stream (Minor Stream),

which has a drainage area of only 0.76 square miles, borders the plant area to the east.

The safety-related structures of the plant are located within the drainage basin of the small stream. Final grade elevations in the immediate plant area vary from 617 to 620 feet (USGS)

(USAR, Section 2.4.2.2).

The floors at plant grade are set at Elevation 620.5 feet (USGS) (USAR, Section 2.4.2.3).

Note that the Updated Safety Analysis Report (USAR) presents elevations using a USGS datum that is equivalent to the National Geodetic Vertical Datum of 1929 (NGVD 29).

The present-day site layout is shown in Figure 2.0.1.

PERRY NUCLEAR POWER PLANT Page 5 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Figure 2.0.1 - Present-Day Site Layout PERRY NUCLEAR POWER PLANT Revision 0 February 23,2015 Page 6 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2015 2,1. Current Design Basis The current design basis is defined in the PNPP USAR. The following is a list of flood-causing mechanisms and their associated water surface elevations that were considered for the PNPP current design basis.

2.1.1. Local Intense Precipitation (LlP)

The USAR indicates that the precipitation value of 26.7 inches over a 6-hour period, with the maximum hourly rainfall of 13.1 inches occurring during the first hour, is utilized for the LIP analysis.

In the case of complete blockage of the storm drainage system, the plant site has been graded so that overland drainage will occur away from the plant site buildings and will not allow the accumulated storm water to exceed Elevation 620.5 feet (USGS) (USAR, Section2.4.2.3).

2.1.2. Flooding in Streams and Rivers The USAR identifies a flow rate of 31,250 cubic feet per second (cfs) for the Major Stream and 7,000 cfs forthe Minor Stream (USAR, Section 2.4.3). The Major Stream water surface elevation upstream of the plant access road for the PMF was found to be 624.0 feet (USGS) until this surface met the normal depth of flow in the existing stream. This water surface elevation will safely pass beneath the railroad bridge (USAR, Section 2.4.3.5\\.

The Minor Stream water surface efevation was found to be 619.5 feet (USGS) (USAR, Figure 2.4-8).

2.1.3. Dam Breaches and Failures The USAR identifies no impoundments upstream of the plant. Therefore, dam failure is not included as a design condition (USAR, Section 2.4.4).

2.1.4. Storm Surge and Seiche The probable maximum meteorological event in Lake Erie results in a maximum stillwater surface etevation of 580.5 feet (USGS) (USAR, Section 2.4.5.2.2).

The probable maximum storm (PMS) was assumed to occur over a 72-hour period, during which the winds increased from 20 miles per hour to the maximum speed of approximately 103 miles per hour over the lake and then decreased to less than 35 miles per hour in the Perry area (USAR, Section 2.4.5.1.3).

2.1.5. Tsunami Since the site is located on Lake Erie, an inland lake, tsunami occurrence (USAR, Section 2.4.6).

2.1.6. lce-lnduced Flooding not applicable lce flooding cannot occur because of the high bluffs between the buildings and the lake. Also, safety-related onshore buildings are set back from the top of the 4S-foot high bluff to preclude ice forces being a problem (USAR, Section 2.4.7.4).

2.1.7. Channel Migration or Diversion Channel diversion is not applicable to PNPP since no cooling water channels exist from which ffow could be diverted (USAR, Section2.4.9).

PERRY NUCLEAR POWER PLANT Page 7 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2415 2.1.8. Combined Effect Flood (including Wind-Generated Waves)

\\Mnd wave activity, including runup, was evaluated as part of the surge analysis. Runup occurring coincidentally with the probable maximum setup would extend to about elevation 607.9 feet (USGS) on the bluff at the lake shore (USAR, Section 2.4.2.2).

2.1.9. Low Water No water is taken from the Major Stream or Minor Stream. Therefore, low flows in the streams will not affect PNPP operation.

The UHS for PNPP is Lake Erie. Submerged offshore intakes supply water to the emergency service water pumphouse.

All safety-related pumps and equipment are located above elevation 586.5 feet (USGS) in the emergency service water pumphouse (USAR, Section 2.4.10). The emergency service water pumphouse and emergency service water pumps are designed to provide service capacity under all lake level conditions down to 565.26 feet (USGS) level caused by the probable maximum setdown superimposed on the minimum monthly mean lake level (USAR, Section 2.4.11.6).

Two vertical shafts convey water into the intake tunnel. The intake heads are covered with a velocity cap to prevenUminimize whirlpooling.

With the inverts of the intake ports at an average elevation of 552.65 feet (USGS), inflow of sufficient cooling water is assured (USAR, Section 2.4.11.5).The corresponding water level in the emergency service water pump chamber would be at elevation 562.09 feet (USGS).

2.2. Flood-Related Changes to the License Basis There were no changes to the flood-related license basis since the initial license issuance.

2.3. Changes to the Watershed and Local Area since License lssuance Thewatershed contributory to the Major Stream is determined to be 7.44 square miles based on the most current data available (Reference PNPP 2015c). The watershed contributory to the Minor Stream is determined to be 0.69 square miles based on the most current data available (Reference PNPP 2015e). Based on aerial images of the watershed, the changes to the watershed include commercial development within the watershed area, which is a small percentage of the overall watershed area.

The nominal design elevation of site power block buildings (buildings important to nuclear safety) are at elevation 620.5 feet (USGS) or higher. Review of the site Corrective Action program determined the actuat current elevation of some of the power block buildings are up to 1.5 inches lower (PNPP Condition Report 2009-68678).

The changes to the local area sub-watershed for PNPP include buildings that have been added or removed and security barrier upgrades that have been added to the site since license issuance.

2.4. Gurrent Licensing Basis Flood Protection and Pertinent Flood Mitigation Features The maximum flood level in the design basis is below the site finished floor elevation of 620.5 feet (USGS). Therefore, no mitigation actions were initiated or taken for flooding at the site.

While performing this flooding reevaluation, it was discovered that the original analysis that supports the Minor Stream probable maximum flood in the USAR could not be located. A functionality assessment was conducted and determined that the maximum water level at the site buildings due to flooding of the Minor Stream does not exceed the ground floor elevation of Unit 1 and Unit 2 site buildings or affect the ability to achieve and maintain cold shutdown conditions following a PMP/PMF event (PNPP Condition Report 2013-05625).

No compensatory actions are credited.

PERRY NUCLEAR POWER PLANT Page 8 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation

3.

SUMMARY

OF FLOOD HAZARD REEVALUATION Revision 0

February 23,2015 NUREG ICR-7046, Design-Basis Ftood Estimation for Site Characterization at Nuelear Power Plants in the tJnited Sfafes of America (Reference NUREG/CR-7046),

by reference to the American Nuclear Society (ANS), states that a single flood-causing event is inadequate as a design basis for power reactors and recommends that combinations should be evaluated to determine the highest flood water elevation at the site. For PNPP, the combination that produces the highest flood water elevation at the site safety-related structures is the PMF on the Minor Stream with the effects of coincident wind wave activity, as provided below.

The USAR reports elevations corresponding to a USGS datum that is equivalent to the NGVD 29 vertical datum. The recent site survey, United States Geological Survey (USGS) topographic maps, and other reference documents report elevation in the North American Vertical Datum of 1988 (NAVD 88). The Lake Erie elevations are typically referenced to the International Great Lakes Datum of 1985 (IGLD 85). In order to compare the reevaluated flood elevations with the existing design basis elevations reported in the USAR, the final pertinent elevations have been converted to the NGVD 29 datum. The conversion from NAVD 88 to NGVD 29 at PNPP is represented as: feet NGVD 29 = feet NAVD 88 + 0.72 feet. The conversion from IGLD 85 to NGVD 29 at PNPP is represented as: feet NGVD 29= feet IGLD 85 + 0.94feet.

Calculation 50:40.000 (Reference PNPP 2015e) defines the Minor Stream maximum water surface elevation of 623.0 feet NGVD 29 at PNPP adjacent to the east side of the power block, which occurs at the Unit 2 Turbine Building.

This elevation is due to an all-season PMF event.

The maximum water surface elevation is above the site nominal finished floor elevation of 620.5 feet NGVD 29 for a duration of 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months and 15 minutes.

Calculation 50:55.000 (Reference PNPP 2015q) defines the coincident wind wave runup, The maximum wave runup elevation of the PMF coincident with wind wave activity is determined by adding the wind wave runup to the water surface flood elevation due to the PMF. The maximum wave runup elevation in the vicinity of the power block is 628.3 feet NGVD 29. The wave runup elevations in the vicinity of the power block are above the site nominal finished floor elevation of 620.5 feet NGVD 29.

Calculation 50:42.OOO (Reference PNPP 20159) defines the maximum water surface elevation resulting from the LIP event adjacent to the entire west side of the power block. The maximum water surface elevation due to the LIP event is 621.2feet NGVD 29. The LIP maximum water surface elevation is above the site nominal finished floor elevation of 620.5 feet NGVD 29. Note that because the Minor Stream drainage area is relatively small (less than 1 square mile), the PMP applied to the Minor Stream is equal to the LlP. Therefore the PMF results for the Minor Stream are equivalent to the effects of the LIP on the east side of the power block.

The methodology used in the flooding reevaluation for PNPP is consistent with the following standards and guidance documents:

o NRC Standard Review Plan, NUREG-0800, revised March 2007 (Reference NUREG-0800) o NRC Office of Standards Development, Regulatory Guides, RG 1.102 - "Flood Protection for Nuclear Power Plants", Revision 1, dated September 1976 (Reference NRC RG 1.102) and RG 1.S9-"Design Basis Floods for Nuclear Power Plants", Revision 2, dated August 1977 (Reference NRC RG 1.59)

NUREG/CR-7046, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America," dated November 2011 (Reference NUREG/CR-7046)

PERRY NUCLEAR POWER PLANT Page 9 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2015 o NUREG/CR-6966, "Tsunami Hazard Assessment at Nuclear Power Plant Sites in the United States of America", dated March 2009 (Reference NUREG/CR-6966)

"American National Standard for Determining Design Basis Flooding at Power Reactor Sites", dated July 28, 1992 (Reference ANSI/ANS-2.8-1992)

NEI Report 12-08, "Overview of External Flooding Reevaluations" (Reference NEI August 2012) o NRC JLD-ISG

-2012-06, "Guidance for Performing a Tsunami, Surge or Seiche Flooding Hazard Assessment",

Revision 0, dated January 4,2013 (Reference JLD-ISG-2012-06) o NRC JLD-lSG-2013-01, "Guidance for Assessment of Flooding Hazards due to Dam Failure",

Revision 0, dated July 29, 2013 (Reference JLD-lSG-2O13-01)

The flood hazard reevaluation, including inputs and methodology, are beyond the current PNPP design and license basis. Consequently, the analytical results project beyond the capability of the current design basis. The following provides the flood-causing mechanisms and their associated water surface elevations that are considered in the PNPP flood hazard reevaluation:

3.1. Flooding in Streams and Rivers (Reference PNPP 2015a, PNPP 2015b, PNPP 2015c, PNPP 2015d, PNPP 2015e, PNPP 2015f, PNPP 20{5n, PNPP 2015r, and PNPP 2015s)

The PMF in rivers and streams adjoining the site is determined by applying the probable maximum precipitation (PMP) to the drainage basin in which the site is located. Because the watersheds analyzed are small, the representative PMP is point precipitation.

This is identical to the LlP. Furthermore, the proximity of the Minor Stream to PNPP creates a condition where the Minor Stream flooding based on point precipitation PMP is identical to the LIP analysis for the Minor Stream and the adjacent SSCs.

The PMF is based on a translation of PMP rainfall in the watershed to flood flow. The PMP is a deterministic estimate of the theoretical maximum depth of precipitation that can occur at a certain time of year for a specified area at a particular geographical location.

A rainfall-to-runoff transformation

function, as well as runoff characteristics, based on the topographic and drainage system network characteristics and watershed properties, are needed to appropriately develop the PMF hydrograph.

The PMF hydrograph is a time history of the discharge and serves as the input parameter for other hydraulic models that develop the flow characteristics, including flood flow and elevation.

The PMF is a function of the combined events defined in NUREG/CR-7046 for floods caused by precipitation events.

Alternative 1 - Combination of:

Mean monthly base flow o Median soil moisture Antecedent or subsequent rain: the lesser of (1) rainfall equal to 40 percent of PMP and (2) a 500-year rainfall The All-Season PMP Waves induced by Z-year wind speed applied along the critical direction Alternative 2 - Combination of:

Mean monthly base flow PERRY NUCLEAR POWER PLANT a

o Page 10of35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0

February 23,2015 Snowmelt from the probable maximum snowpack A 1O0-year, snow-season rainfall o Waves induced by Z-year wind speed applied along the critical direction Alternative 3 - Combination of:

o Mean monthly base flow Snowmelt from a 1O0-year snowpack Snow-season PMP Waves induced by 2-year wind speed applied along the critical direction 3.1.1. Basis of Inputs:

The inputs used in the PMP, snowmelt, and PMF analyses are based on the following:

All-Season PMP Analysis and Cool-season PMP with Snowmelt Analysis

. PNPP, Major Stream, and Minor Stream watershed locations;

. Probable Maximum Precipitation Study for the State of Ohio; o Site-specific, all-season PMP point rainfall short duration estimates determined using a storm-based approach in accordance with NOAA Hydrometeorological Reports and the World Meteorological Organization approach;

. Site-specific, cool-season PMP point rainfall estimates determined using a storm-based approach in accordance with NOAA Hydrometeorological Reports and the World Meteorological Organization approach; o The 100-year, all-season point rainfall estimates from the National Oceanic and Atmospheric Administration (NOAA) Precipitation Frequency Data Server, and ratio of cool-season to all-season rainfall depths determined from the regional Rainfall Frequency Atlas of the Midwest; o Daily snow depth and density by month for Ohio, data is downloaded from NOAA; and

. Snowmelt rate (energy budget) equations and constants are based on U.S. Army Corps of Engineers (USACE)

Engineering Manual EM-1 11A-2'1406.

PMF Analysis-Hydrologic and Hydraulic Analysis

. PNPP, Major Stream, and Minor Stream watershed locations, areas, boundaries and configurations; Precipitation and associated

snowmelt, as applicable, for the subject watershed area; Base flow: Historic flow rate data collected by USGS at gauge 04212100 on the Grand River, which is used to determine the base flow for the Major Stream and Minor Stream; Site topography developed from aerial photogrammetry; Digital terrain model (DTM) developed from site topography; Manning's roughness coefficients are based on a visual assessment of aerial photography and selected using standard applicable engineering guidance references; and Site data for the rail line bridge crossing the Major Stream.

o a

a O

a PERRY NUCLEAR POWER PLANT Page 11 of35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation 3.1.2. Computer Sofhryare Programs Revision 0

February 23,2015 PMP and Snowmelt analysis ArcGlS Desktop 10.1 o Microsoft Excel o SPAS 9.5 PMF analysis AutoCAD Civil 3D 2012 ArcGlS Desktop 10.0 ArcGlS Desktop 10.1 HEC-HMS 3.5 HEC-RAS 4.1 HEC-GeoRAS 10.1 o Microsoft Excel 3.1.3. Methodology The site-specific PMP analysis included the following steps:

o An extensive storm search to identify storms which could be used for PMP studies in the region.

Largest precipitation events which were determined to be transpositionable to the PNPP site were then maximized in-place and transpositioned to the site.

Site-Specific, All-Season PMP All the storms evaluated in the previous PMP studies in the region, and considered to be transpositionable to the PNPP site were evaluated.

This resulted in 20 events that were evaluated to determine the short duration 1-hour depth for the site-specific, all-season PMP. Ten of these storms were previously analyzed in Hydrometeorological Report No.

33 and Hydrometeorological Report No. 51 by the National Weather Service (NWS) and the USACE. The remaining 1O were analyzed for the Probable Maximum Precipitation Study for the State of Ohio.

Each storm is then maximized by an in-place maximization factor to represent what the storm would have looked like had the atmospheric conditions and moisture available for rainfall production been at maximum levels when the storm occurred versus what was actually observed.

The in-place maximized values for each storm are then adjusted to transpose the storm from its original location to the PNPP site. The transposition calculation adjusts for differences in available moisture at the site versus the original storm location. The ratios to determine sub-hourly increments in Hydrometeorological Report No. 52, are applied to the resulting site-specific, 1-hour PMP estimate to determine 5-, 15-, and 3O-minute duration estimates.

Site-Specific, Cool-Season PMP A site-specific, cool-season depth-area-duration relationship is developed for durations from 1 to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months and area sizes from 1 to 20,000 square miles. In addition, hourly temperature, dew point, and wind speed time series are maximized for cool-season PMP for input parameters of associated snowmelt. Ten extreme rainfall storms that occurred from October to May within the Great Lakes region are identified.

Although the cool-season months are October through Aprit, storms during the month of May that represent PERRY NUCLEAR POWER PLANT Page 12 of 35

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Flooding First Energy Corporation Revision 0 February 23,2015 cool-season characteristics are included in the analysis for determining the site-specific, cool-season PMP SPAS software analysis is completed for three storms that were not analyzed previously by the NWS or USACE, or occurred after the publication of the hydrometeorological documents.

The moisture content of each storm is maximized to provide the upper limit rainfall estimation for each storm at the location where it occurred.

The maximized storms are then transpositioned from the original storm location to PNPP to the extent supportable by similarity of topographic and meteorological conditions. Maximum precipitation values, adjusted for in-place maximization and transposition factors, are enveloped to define the cool-season PMP.

The PMF analysis includes the following steps:

Delineate watershed and sub-watersheds and calculate sub-watershed areas for input into the USACE HEC-HMS rainfall-runoff hydrologic computer model.

Determine rainfall.

Estimate HEC-HMS rainfall-runoff model input parameters: National Resources Conservation Service (NRCS) unit hydrograph method.

o Adjust unit hydrograph to account for the effects of nonlinear basin response.

Perform PMF simulation with PMP input using HEC-HMS model with no precipitation losses.

o Estimate water surface elevation using HEC-RAS unsteady-state model by using runoff hydrograph from the HEC-HMS model as an input.

Watershed Delineation For the purposes of the hydrologic modeling effort, the Major Stream is evaluated using one watershed.

The Minor Stream watershed is subdivided into three (3) sub-watersheds (the Minor Stream south of the site, the Minor Stream and site area contributing to the Minor Stream at the lateral swale between the two cooling towers, and the unnamed tributary east of the site) based on the topography of the site.

Rainfall and Snowmelt Each atternative contains rainfall defined either by the all-season PMP (Alternative 1), the 1O0-year, cool-season rainfall (Alternative 2), or the cool-season PMP (Alternative 3).

Each rainfall event is considered to be a72-hour duration event. Note that an antecedent rainfall occurs prior to the all-season PMP. Because of the small drainage areas of the Major Stream and Minor Stream and the 72-hour dry period between the antecedent storm and the PMP event, the streams return to baseflow conditions prior to the PMP event. Therefore, the antecedent storm is determined to have no influence on the PMP storm. The all-season event incorporates no rainfall runoff losses.

Snowmelt is included in the two cool season alternatives.

Alternative 2 includes snowmelt from the probable maximum snowpack.

Alternative 3 includes snowmelt from the 100-year snowpack.

For rain-on-snow conditions dew point temperature and wind speed are obtained from the site-specific PMP analysis.

The basin wind coefficient is conservatively assumed to maximize snowmelt.

The snowpack is assumed to be at its maximum at the onset of rainfall events and cover the entire watershed.

Soil is assumed to be frozen with no precipitation losses during the cool-season months of October through April. For the probable maximum

snowpack, the snowpack depth is assumed to provide continuous snowmelt for the entire duration of the coincident rainfall event.

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February 23,2015 Alternative I -All-Season PMP The all-season PMP is determined by using the site-specific PMP estimates defined by the PMP study for the State of Ohio (Reference ODNR 2013) for durations from 6to72 hours. The PNPP site-specific analysis defines the PMP estimates for t hour and sub-hourly increments.

lntermediate S-minute incremental PMP depths are determined for point precipitation (1 square mile).

The temporal distribution of the PMP is arranged in accordance with recommendations in HMR-52, wherein individual rainfall increments decrease progressively to either side of the greatest rainfall increment.

Various temporal distributions for each rainfall scenario are then evaluated to further maximize the runoff. Front, onethird, center, twothirds, and end-loading temporal distributions are considered in an effort to capture the distribution that maximizes runoff.

Alternative 2 - Probable Maximum Snowpack and 100-Year Gool-Season Rainfall

\\l/hile snowpack can be determined directly from the snow depth, adequate data is not available to extrapolate any historical observations up to the magnitude of the probable maximum event. To maximize snowmelt contribution, the probable maximum snowpack is conservatively assumed not to deplete during the duration of the coincident rainfall.

The 1O0-year, cool-season rainfall is determined forthe PNPP location and a duration of 72-hours using precipitation frequency estimates defined by NOAA Atlas 14 guidance and applying regional seasonal guidance. NOAA Atlas 14 provides all-season point precipitation rainfall estimates via the NOAA precipitation frequency data server. The NOAA Atlas 14 values are adjusted to reflect cool-season rainfall rather than all-season rainfall.

The 100-year, cool-season rainfall is equivalent for all the cool-season months.

Furthermore, the maximized dew point temperature and wind speed time series determined by site-specific analysis is applicable to all cool-season months.

To maximize snowmelt at each time step, the dew point temperature and wind speed are reordered to match the 72-hour temporal distributions of the rainfall.

Alternative 3 - 1O0-Year Snowpack and Cool-Season PMP A 10O-year snow depth is calculated by performing a statistical analysis based on the historical data obtained from the NOAA National Climatic Data Center daily snow depth records. A Fisher-Tippett Type l (FT-l) distribution frequency analysis is performed to determine the maximum snow depth with an annual exceedance probability of 1 percent (i.e. 100-year snow depth) for each month from October through April. The FT-l distribution is applicable for long-term statistical analyses and specifically for extreme value calculations.

The maximum snowpack bulk density is applied to determine the available snow water equivalent.

The maximum 100-year snowpack occurs in March and is combined with the site-specific, cool-season PMP. To maximize snowmelt at each time step, the dew point temperature and wind speed are reordered to match the 72-hour temporal distributions of the rainfall.

Hydrologic Model (HEC-HMS)

The PMF is the flood resulting from the72-hour duration all-season PMP or a combination of cool-season rainfall and snowmelt.

The temporal distribution of the PMP is determined in accordance with the recommendations in HMR-52, wherein individual increments decrease progressively to either side of the greatest increment.

Front, one-third,

center, two-thirds, and end-loading temporal distributions are considered in an effort to capture PERRY NUCLEAR POWER PLANT Page 14 of 35

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Flooding First Energy Corporation Revision 0 February 23,2015 the distribution that maximizes runoff. Because of the small drainage areas of the Major Stream and Minor Stream and the 72-hour dry period between the antecedent storm and the PMP event, the antecedent storm is determined to have no influence on the PMP storm.

USACE HEC-HMS hydrologic software is used to convert rainfall to runoff. A rainfall hyetograph is applied to the Major Stream watershed and each sub-watershed of the Minor Stream and transformed to runoff using unit hydrograph methodology.

Generally, a unit hydrograph is developed using historical data obtained from various rain and stream gauges in the watershed.

The Major Stream and Minor Stream watersheds are ungauged.

Thus, no historical observations are available to use as a basis to create a unit hydrograph.

Therefore, a synthetic unit hydrograph is developed. NRCS unit hyd rog raph methodology is used for rai nfal l-to-runoff transformation.

ANSI/ANS-2.8-1992 suggests that base flow should be based on mean monthly flow. As mean monthly flow is not available for the Major Stream or Minor Stream, the base flow is approximated based on the mean monthly flow in an adjacent watershed.

The USGS gauge station on the Grand River near Painesville, OH is used. The Grand River is in the same hydrologic unit as the Major Stream and Minor Stream and has similar watershed characteristics.

Therefore, it is an acceptable approach to use the base flow information for the Grand River as the basis for estimation of the base flow for Major Stream and Minor Stream.

To conservatively maximize runoff, no precipitation losses are incorporated into the all-season PMF alternative analysis.

Additionally, no precipitation losses are incorporated into the cool-season PMF alternatives due to the assumption that the ground is frozen.

The unit hydrographs for the Major Stream watershed and each sub-watershed of the Minor Stream are modified to account for the effects of nonlinear basin response in accordance with NUREG/CR-7046.

The peak of each unit hydrograph is increased by one-fifth and the time-to-peak is reduced by one-third. The remaining hydrograph ordinates are adjusted to preserve the runoff volume to a unit depth over the drainage area.

Hydraulic Model (HEC-RAS)

The unsteady flow simulation module within the USACE HEC-RAS software is used to transform the resulting flow hydrographs from the controlling alternative into a water surface elevation hydrograph under unsteady flow conditions. For reference and comparison, all three alternatives are evaluated with the HEC-RAS model.

Channel and floodplain geometry for the Major Stream and the Minor Stream is modeled by developing cross sections of the streams. The cross sections are placed at locatlons that define geometric characteristics of the stream and overbanks. Cross sections are also placed at representative locations where changes occur in discharge, slope, shape, and roughness, as well as at hydraulic and inline structures (e.9., bridges culverts).

Stream banks, blocked obstructions, and ineffective flow areas are also incorporated into the HEC-RAS model.

Three crossings are incorporated into the Major Stream model. The plant access road includes a culvert and is modeled using topographic survey data and USAR data. The upstream rail line bridge is modeled using topographic survey data and site records.

The upstream secondary access road is included as an inline structure and all flow overtops the road.

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Flooding First Energy Corporation Revision 0 February 23,2015 One crossing is incorporated into the Minor Stream model. The downstream Lockwood Road crossing is modeled as an inline structure and all flow overtops the road.

The PMF flow hydrographs obtained from the time-series outflow results of the HEC-HMS models are entered into the HEC-RAS models.

A bounding water level in Lake Erie is used as a downstream boundary condition for the HEC-RAS software program.

The HEC-RAS model is evaluated for the all-season PMF (Alternative

1) and the cool-season PMF (Alternative 2 and Alternative 3).

3.1.4. Results Major Stream The Major Stream is not directly adjacent to PNPP safety-related structures.

However, overtopping at the rail line bridge structure results in overflow from the Major Stream that contributes to flooding effects in the Minor Stream and the LIP area.

The Alternative 1 PMF is the controlling combination and is a result of the all-season PMP, The one-third, center, and two-thirds temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation overtopping the rait line bridge structure is 630.9 feet NGVD 29, with a maximum flow of 30,100 cfs at the bridge. The resulting maximum water levels for the Major Stream are not adjacent to the power block.

Overtopping of the rail line causes backwater to accumulate and flow toward the site through two access points of the secondary access road. The peak flow through the two access points is74 cfs. This flow is incorporated into the LIP area analysis by combination with rainfall runoff for the area directly south of the plant.

Backwater also overflows the secondary access road further to the east. The peak flow into the Minor Stream watershed is 1754 cfs. This flow is incorporated into the Minor Stream analysis by application directly to the upstream cross section of the Minor Stream hydraulic model.

Alternative 2 does not overtop the rail line bridge structure and no overflow to the Minor Stream or LIP area occurs. The one-third, center, and twothirds temporal distributions produce identical peak results and the maximum water levels. The maxlmum water surface elevation at the rail line bridge structure is 621.1 feet NGVD 29 with a maximum flow of 9,500 cfs at the bridge.

Alternative 3 does not overtop the rail line bridge structure and no overflow to the Minor Stream or LIP area occurs. The one-third, center, and two-thirds temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation at the rail line bridge structure is 623.1 feet NGVD 29 with a maximum flow of 14,900 cfs at the bridge.

The all-season PMF is determined to be the controlling PMF scenario.

An additional combined effect analysis, including the effects of wind wave activity, is performed as discussed in Section 3.7. The contribution to LIP flooding is incorporated into the analysis discussed in Section 3.8.

Minor Stream Overtopping flow from the Major Stream watershed is added to the HEC-RAS modeling for the Alternative 1 PMF. Overtopping flow from the Major Stream watershed does not occur for Alternative 2 or Alternative 3.

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February 23,2015 The Alternative 1 PMF is the controlling combination and is a result of the all-season PMP. The one-third, center, and two-thirds temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation occurs at the Unit 2 Turbine Building and is 623.0 feet NGVD 29. The maximum flow overtopping Lockwood Road downstream is 5,300 cfs. Alternative 1 peak flooding overflows the Minor Stream channel banks and contributes to LIP flooding on the west side of the power block.

For Alternative 2, the one-third, center, and two-thirds temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation occurs at the Unit 2 Turbine Building and is 620.6 feet NGVD 29. The maximum flow overtopping Lockwood Road downstream is 1,000 cfs. Alternative 2 peak flooding overflows the Minor Stream channel banks and contributes to LIP flooding on the west side of the power block.

For Alternative 3, the one-third, center, and two-thirds temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation occurs at the Unit 2 Turbine Building and is 621.1 feet NGVD 29. The maximum flow overtopping Lockwood Road downstream is 1,600 cfs. Alternative 3 peak flooding overflows the Minor Stream channel banks and contributes to LIP flooding on the west side of the power block.

The all-season PMF (Alternative 1) is determined to be the controlling PMF scenario.

The maximum water surface elevations at each safety-related structure adjacent to the Minor Stream flooding and the duration of flooding above the nominal finished floor elevation of 620.5 feet NGVD 29 are provided in Table 1. An additional combined effect analysis is performed as discussed in Section 3.7. The contribution to LIP flooding is incorporated into the analysis discussed in Section 3.8.

Table I - Minor Stream Flooding Elevations and Durations at PNPP Structure Maximum Water Surface Elevation (feet NGVD 29)

Flood Duration above 620.5 feet (NGVD 29)

Unit 2 Turbine Building 623.0 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 15 minutes Unit 2 Auxiliary Building 622.9 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 10 minutes Unit 2 Reactor Building 622.3 t hour 10 minutes lntermediate Building 622.2 t hour 10 minutes Unit 1 Reactor Building 622.2 t hour 10 minutes Unit 1 Auxiliary Building 622.2 t hour 10 minutes Unit 1 Turbine Building 621.1 40 minutes PERRY NUCLEAR POWER PLANT Page 17 of 35

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Flooding First Energy Corporation 3.2. Dam Assessment (Reference PNPP 2015h) 3.2.1. Basis of Inputs Inputs used for the dam assessment evaluation include:

o PNPP, Major Stream, and Minor Stream watershed locations.

USGS topographic quadrangle maps.

o The USACE National Inventory of Dams (NlD) database is used to identify any watershed dams.

3.2.2. Computer Software Programs None 3.2.3. Methodology The PNPP Major Stream and Minor Stream watershed locations are approximated using USGS topographic quadrangle maps. The USACE NID database is reviewed to determine that no dams are located in the Major Stream or Minor Stream watersheds.

3.2.4. Results No dams are located in the combined watershed of the Major Stream and Minor Stream.

Therefore, dam failure is not applicable.

3.3. lce-lnduced Flooding (Reference PNPP 2015i)

As identified by NUREG/CR-7046, ice jams and ice dams can form in rivers and streams adjacent to a site, and may lead to flooding by two mechanisms:

Collapse of an ice jam or an ice dam upstream of the site can result in a dam breach-like flood wave that may propagate to the site; and o An ice jam or an ice dam downstream of a site may impound water upstream of itself, thus causing a flood via backwater effects.

3.3.1. Basis of Inputs USACE ice jam database.

o Site topography.

Bridge geometry (upstream and downstream of PNPP) topography and site records.

using site 3.3.2. Computer Software Programs Microsoft Excel 3.3.3. Methodology Per NUREG/CR-7046, ice-induced flooding is assessed by reviewing the USACE ice jam database to determine the most severe historical events that have occurred. No historical records are available for the Major Stream or the Minor Stream. The nonexistence of ice jam records is explained by the absence of stream monitoring stations on the two streams. Based on ice jam occurrences recorded for rivers within adjacent watersheds, it is determined that ice jam events are possible.

Revision 0

February 23,2015 PERRY NUCLEAR POWER PLANT Page 18 of 35

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Flooding First Energy Corporation Revision 0 February 23,2015 assumes the Lockwood the road. Therefore, by The maximum ice jam is determined by selecting the historic event produced the that location.

maximum flood stage relative to the normal water surface elevation Regardless of the specific conditions that produced the historic flood stage at a specific

location, the full height is conservatively assumed to represent the ice jam.

Historical ice jam data for the adjacent watersheds for the Grand River and the Ashtabula River are considered.

Although no records are available for the actual height of the ice jams, the maximum recorded stage is used to represent the ice jam. The ice jam is transposed to the site and compared with other flooding causing mechanisms.

3.3.4. Results The maximum reported ice jam stage in the regional vicinity of PNPP is estimated to be 18 feet. For the Minor Stream, no significant upstream crossings or structures are present that could facilitate significant ice jam formation. The only upstream access road is an unimproved road with a low profile and a small drainage structure. The elevation characteristics of the area at that drainage structure indicate in the unlikely event an ice jam did occur, it would be limited to less than 2 feet in height. Furthermore, any ice jam and subsequent failure would only release a flow rate at the maximum capacity of the small drainage structure.

By qualitative comparison, the PMF analysis includes rainfall runoff contribution from the entire drainage area resulting in a peak flow rate magnitudes greater than the capacity of a small drainage structure.

Any upstream ice jam collapse is bounded by the PMF analysis.

The only downstream location on the Minor Stream conducive to an ice jam is at Lockwood Road. The assumed transposition of the maximum ice jam would produce a maximum water surface elevation of 608.7 feet NGVD 29 (608 feet NAVD 88). Assuming the culvert at Lockwood Road is completely blocked, any coincident flow would eventually that nat overtop Lockwood Road. The PMF analysis for Minor Stream Road culvert is completely blocked and the PMF overtops qualitative comparison with the PMF analysis, any downstream bounded by the PMF analysis.

ice jam flooding is For the Major Stream, the upstream rail line bridge has a clear height of greater than 20 feet from natural grade to the bottom of the low chord. The assumed transposition of the maximum estimated 18 feet ice jam would allow normal flows overtopping the ice jam to flow through the remaining bridge opening below the low chord. The PMF analysis for the Major Stream results in overtopping of the rail line bridge. Any ice jam failure at this location would be transposed downstream to the plant access road.

The access road includes a large elliptical culvert 35'-11" by 23'-5". Based on site topography the clear height is approximately 18 feet above the normal water surface elevition. Assumed transposition of the maximum estimated 18 feet ice jam would produce a maximum water surface elevation below the plant access road. Assuming the culvert at the plant access road is completely blocked, any coincident flow would eventually overtop the plant access road. The PMF analysis for Major Stream results in overtopping of the plant access road. Therefore, by qualitative comparison with the PMF

analysis, any ice jam flooding is bounded by the PMF analysis The downstream sediment control structure is the only other location possibly conducive to an ice jam. The assumed transposition of the maximum ice jam would produce a maximum water surface elevation of 604.7 feet NGVD 29 (604 feet NAVD 88). The results of the PMF analyses for the Major Stream exceed the estimated ice jam elevation.

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February 23,2015 lce-induced flooding at PNPP is bounded by the PMF analyses, and no further consideration is required.

3.4. Ghannel Migration or Diversion (Reference PNPP 2015i)

NUREG/CR-7046 indicates historical records and hydrogeomorphological data should be used to determine whether an adjacent

channel, stream, or river has exhibited the tendency to migrate towards the site.

3.4.1. Basis of Inputs Ohio Department of Natural Resources surficial geology map USGS topographic quadrangle maps, including aerial images 3.4.2. Gomputer Software Programs o None 3.4.3. Methodology Surficial geology along with historic and current topographic quadrangle maps that include aerial images are reviewed to examine the condition and alignment of rivers and streams over time.

3.4.4. Results The surficial geology map indicates the area in the immediate vicinity of PNPP is characterized by layers of sand, silt and clay, and till or clayey to silty till over shale bedrock. This characterization represents the entire watershed of the Minor Stream and the majority of the Major Stream. The upstream portion of Major Stream is characterized by additional areas of sand and gravel or clayey to silty till over shale bedrock.

Alluvium or organic material, which are more susceptible to erosion, are not present in the Major Stream or the Minor Stream watersheds.

Topographic maps for the years of 1905 (Reprinted 1943), 1960 (Revised 1992), 1994, and 2010 are reviewed to assess historic channel migration.

The Minor Stream was rerouted as part of the plant construction. These modifications have remained unchanged.

The topographic and aerial images provide no evidence of oxbows, braided

streams, or alluvial fans that could indicate a potential for channel migration of the Major Stream or the Minor Stream.

The streams in the vicinity of PNPP do not exhibit characteristics of channel migration.

3.5. Storm Surge (Reference PNPP 20151, PNPP 2015k, PNPP 20151, PNPP 20{5o' and PNPP 20{5p)

Probable Maximum Storm Surse (PMSSl In accordance with JLD-ISG -2012-06, all coastal nuclear power plant sites and nuclear power plant sites adjacent to cooling ponds or reservoirs subject to potential hurricanes, windstorms and squatl lines must consider the potential for inundation from storm surge and waves. JLD-ISG-2012-06 also suggests that for the storm surge hazard assessment, historical storm events in the region should be augmented by a synthetic storm parameterized to account for conditions more severe than those in the historical records and considered reasonably possible on the basis of technical reasoning.

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Flooding First Energy Gorporation Revision 0 February 23,2015 3.5.1. Basis of Inputs The inputs used in PMSS analysis are based on the following:

Historical wind and pressure field data from NOAA for the Great Lake Region o Probable maximum windstorm (PMWS)

Lake Erie bathymetry from the NOAA geophysical database Supporting GIS data 3.5.2. Computer Software Programs

. ArcMap 10.1 Deft3D software suite (Delft3D-FLOW Delft3D-WAVE, Delft3D-RGFGRID, and Delft3D-QUICKIN) lGLD85 Height Conversion Tool R Computer Language 2.15.1 Microsoft Excel 3.5.3. Methodology Several physical processes contribute to the generation of a storm surge. The contribution of wind to a storm surge is often called wind setup. \\Mnd blowing over the water causes a shear stress that is exerted on the surface of the water, pushing water in the direction of the wind. Atmospheric pressure gradients are another forcing mechanism that contributes to changes in water level, as water is forced from regions of high atmospheric pressure toward regions of low atmospheric pressure.

The following describes the methodologies used in the PMSS calculation:

Development of the PMWS The PMWS storm-based approach is specific to the characteristics of the site. Past extreme events in a region are analyzed and considered transpositionable.

As part of the PMWS, different storm types (such as synoptic, squall line, and hybrid) that impacted the Great Lakes region are considered in order to determine the storm event that will generate the maximum surge and seiche. Each storm's input parameters are quantified and plotted based on the location of low/high pressure centers, concurrent wind/pressure fields, and how they evolve through time and space.

Most of the synoptic storms occur in association with deep areas of low pressure which move through the region from southwest to northeast. The general synoptic pattern is one in which the deep area of low pressure results in a very strong pressure gradient force between its low pressure center and a corresponding region of higher pressure to the north or west. The larger the gradient between the two systems over a given distance is, the stronger the resulting winds.

Squall line (or derecho) events create a widespread straight-line windstorm that is associated with a fast-moving band of severe thunderstorms.

These winds have produced some of the highest instantaneous gusts on record, but last for only a short time (less than 30 minutes) at a given location.

The short duration of these events, as they quickly traverse a given location, means they will not control the PMSS. Further, these events do not occur within deep low pressure systems or remnant tropical systems' Therefore, their wind and pressure data are not combined with the other storm types in this analysis, as this would result in a PMWS that is not physically possible.

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February 23,2015 Although deep tow pressure systems often produce the longest duration large-scale winds, other storm types also produce strong winds over the region. In rare cases, land-falling tropical systems along the Gulf Coast or Atlantic Seaboard move inland across the Appalachians or up the Mississippi and Ohio River valleys. By the time these storms reach the Great Lakes region, they are no longer tropical systems, but instead have transitioned into extra-tropical cyclones.

Their general circulation and center of deep low pressure persists. Much like the deep low pressure scenario previously discussed, strong and persistent winds can result. The remnants of Hurricane Hazel (October 1954) and Hurricane Sandy (October 2012) are classic examples of this storm type. This storm scenario provided some of the strongest winds from the northwest through the northeast directions over Lake Erie (with durations of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months or more).

Delft3D Galibration The Delft3D hydrodynamic model is set up using the Delft3D software suite. The wave setup contribution to the total storm surge values are modeled by coupling the Delft3D-WAVE and Delft3D-FLOW surge models.

The general approach to storm surge modeling using coupled Delft3D-FLOW and Delft3D-WAVE models consists of the following steps:

o Developing the bathymetric dataset and model grid mesh for the lake system; o Assembling input files for atmospheric forcing (wind and pressure fields);

Assembling input files for initial water level, boundary conditions, and the physical and numerical parameters of the model; Assembling measured water levels and wave data for model calibration and verification; Testing and refining the initial model setup; I

Validating the model for historical extreme storm events; and o Assessing model sensitivity to various factors and adjustable parameters such as bottom friction and wind drag coefficient.

The Delft3D model is calibrated based on historical data obtained from NOAA meteorological and water level recording stations located in the Lake Erie region.

Review of historical data shows that various parts of Lake Erie respond differently to any one particular storm. The storm that produces extreme water levels in one part of Lake Erie might not, and probably does not, produce extreme levels in other parts. Therefore the number of calibration and validation storms selected, to assess model prediction accuracy, covered all parts of the lake shoreline.

Calibration and verification of the coupled Delft3D-FLOW and Delft3D-WAVE models is performed by a time series comparison of measured and predicted/modeled storm surge values at different water level recording stations on Lake Erie. A similar time series comparison is also performed for wave heights.

The Delft3D models are calibrated using extreme historic wind and pressure data from multiple meteorological and water level recording stations.

Calibration and verification of the coupled Delft3D-FLOW and Delft3D-WAVE models demonstrates that the hydrodynamic model is capable of computing the storm surge and seiche dynamics for Lake Erie, as well as the significant wave heights and periods at PNPP from PMWS events.

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NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2015 PMSS The calibrated Delft3D model is used to determine the PMSS. The historic wind and pressure field data is replaced with candidate PMWS events, and the model is run to determine the critical PMWS.

JLD-lSG -2012-06 and ANSI/ANS 2.8-1992 require the antecedent (pre-storm) water level equal to the 1O0-year maximum recorded water level to be applied as the initial storm surge model still water level. The 1O0-year water level of 575.6 feet NGVD 29 (574.6 feet IGLD 85) is used as the initial condition/antecedent water level in all the Delft3D-FLOW models. Since the probable minimum low water level at PNPP could occur at a time when the monthly mean lake level is at the long-term mean low probable level, the antecedent water level for low water evaluation is set to the long-term low probable level at Lake Erie, which is equal to 568.9 feet NAVD 29 (568 feet IGLD 85).

Various topographic features affect the storm surge propagation towards PNPP. The site is located on the bluffs adjacent to the shores of Lake Erie. The bluffs at the site are more than 40 feet above the 100-year water level of the lake.

Maximum Historical and 2S-year Storm Surge The historical maximum storm surge is the largest of the determined yearly maximum storm surge heights. The historicat maximum storm surge height is used in combined flooding scenarios as discussed in Section 3.7.

Storm surges are calculated from monthly data as the difference between monthly maximum and monthly mean based on guidance provided by USACE. The Log Pearson Type lll distribution is the commonly accepted frequency procedure for annual maximum water levels. A frequency analysis on the yearly maximum storm surge heights obtained from the Fairport and Erie stations is performed using a Log Pearson lll statistical analysis.

The 25-year storm surge height is used in combined flooding scenarios.

3.5.4. Results Simulations of all the candidate PMWS events showed that the critical PMWS event is the transpositioned September 1989 wind storm event maximized over the PNPP site.

This storm is the most intense of all the PMWS events with a maximum wind speed of 106 miles/hour and is aligned along the north-south direction. The maximum PMSS resulting from this PMWS event produced a maximum water surface elevation of 582.6 feet NGVD 29, which is well below the site. Wave runup effects are evaluated with combined flooding scenarios as discussed in Section 3.7.

Surge, Seiche, and Resonance Results show that the level of the rise due to a seiche is significantly less than the calculated surge height. For this reason, seiches are not the controlling flood event at PNPP.

Resonance generated by waves can cause problems in enclosed water bodies such as harbors and bays when the period of oscillation of the water body is equal to the period of the incoming waves. However, the PNPP site is not located in an enclosed embayment.

Additionalty, the period of oscillation of Lake Erie near the PNPP site is determined to be in the range of 1 1 to 15 hours1.736111e-4 days 0.00417 hours 2.480159e-5 weeks 5.7075e-6 months . This is much greater than that of the peak spectral period of the incident shallow water storm waves. Consequently, resonance is not a detriment at PNPP during the critical PMWS event.

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Flooding First Energy Corporation Revision 0 February 23,2415 Probable Minimum Low Water Level resulting from the PMWS Simulations of all the candidate PMWS storm events show that the critical PMWS event that woutd result in probabte minimum low water level (drawdown) is the transpositioned November 1998 storm event maximized over the PNPP site. This storm had the most intense southeasterly winds of the examined storm events, with a maximum wind speed of 93 miles/hour.

The probable minimum low water elevation (drawdown) associated with the transposed November 1998 storm produces a probable minimum low water level of 563.0 feet NGVD 29 near the PNPP site. The inverts of the PNPP intake ports are at an average elevation of 552.65 feet NGVD 29.

3.6. Tsunami Assessment (Reference PNPP 2015m)

NUREG/CR-6966 identifies that earthquakes, landslides, and volcanoes can initiate tsunamis, with earthquakes being the most frequent cause. Dip-slip earthquakes (due to vertical movement) are more efficient at generating tsunamis than strike-slip earthquakes (due to horizontal movement).

To generate a major tsunami, a substantial amount of slip and a large rupture area is required.

Consequently, only large earthquakes with magnitudes greater than 6.5 generate observable tsunamis.

3.6.1. Basis of Inputs o National Center for Earthquake Engineering Research (NCEER) database Natural Resources Canada seismicity data NOAA natural hazards tsunami database NOAA natural hazards volcano database o Ohio Department of Natural Resources (ODNR) seismicity data o USGS earthquake hazards program database 3.6.2. Gomputer Sofhrare Programs None 3.6.3. Methodology As identified by NUREG/CR-7046, tsunami assessment is referenced to NUREG/CR-6966 and NOAA Technical Memorandum OAR PMEL-136.

In addition, the more recently issued NRC guidance, JLD-lSG

-2012-06, also addresses tsunami assessment.

However, JLD-ISG

-2012-OO provides guidance on detailed tsunami modeling and is beyond the scope of this assessment.

Technical Memorandum OAR PMEL-136 reflects a similar tsunami screening assessment described by NUREG/CR-6966.

The NUREG/CR-6966 screening assessment is based on a regional screening and a site screening.

The regional screening consists of researching historical records for tsunami records and the potential for tsunami-generating sources. The site screening evaluates the site based on the horizontal distance from a coast, the longitudinal distance measured along a river, and the grade elevation in comparison to the effects of a tsunami. This assessment approach is based on a review of historical records and databases.

NUREG/CR-6966 identifies that tsunamis are generated by rapid, large-scale disturbances of a body of water. The most frequent cause of tsunamis is an earthquake; however, landslides and volcanoes can also initiate tsunamis.

Because of the tsunami-generation sequence associated with earthquakes, dip-slip earthquakes (due to vertical movement) are more efficient at generating tsunamis than strike-slip earthquakes (due to horizontal movement).

Furthermore, to generate a major tsunami, a substantial amount PERRY NUCLEAR POWER PLANT Page 24 of 35

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February 23,2415 of slip and a large rupture area is required.

Consequently, only large earthquakes with magnitudes greater than 6.5 generate observable tsunamis.

As part of the assessment, the NOAA natural hazards tsunami database is used to review historical tsunami events and associated runups for the east coast of the United States and Canada. Of the total events, there were 7 tsunami events that produced 14 runups occurring in the Great Lakes region from 1755 to 1954. The USGS hazard fault database findings are reviewed for strong earthquakes or the vertical displacements necessary to induce a tsunami. Additionally, the USGS earthquake hazards program, the NCEER database, and the Natural Resources Canada database are reviewed for historical earthquakes in the region.

ODNR data is atso reviewed for earthquake-generated tsunami and landslide-induced tsunami. Lastly, the NOAA natural hazards volcano database is reviewed to assess volcanoes in the Lake Erie region.

3.6.4. Results According to ODNR, an earthquake-generated tsunami in Lake Erie would require a very large earthquake on the order of magnitude 7.A or greater and significant vertical displacement.

Historically, in the Lake Erie region, the largest earthquakes are in the magnitude 5.0 range. Preliminary analysis of post-glacial sediments in the region has not yielded evidence of a large earthquake in the last few thousand years. Furthermore, earthquakes in the region, for which sufficient data are available, show primarily horizontal rather than vertical movement, which is not as conducive to tsunami generation.

Tsunamis can also be generated by the downslope movement of a very large volume of rock or sediment, either from a rockfall above the water or from a submarine landslide.

Although large amounts of unconsolidated sediments are washed into Lake Erie each year when shoreline bluffs are undercut by wave action, these masses lack sufficient volume and rapid collapse to displace a volume of water that would create a tsunami.

Lake Erie also has a very gentle bottom profile, particularly in the western and central basins. The eastern basin has steeper slopes, but not steep enough for a large amount of sediment to suddenly flow downslope in a submarine landslide.

The NOArA nstural hazards tsunami database identifies only two occurrences of non-seiche (or non-wind-induced) tsunami events in the Great Lakes region. The two occurrences yielded slight or small wave effects.

The USGS Earthquake Hazards Program fault database contains no known Quaternary faults (or current faults) in this region because geologists have not found any faults at the Earth's surface. Consequently, no potential exists for strong earthquakes or the vertical displacement necessary to induce a tsunami. Various earthquake databases, including the USGS Earthquake Hazards Program earthquake

database, the National Center for Earthquake Engineering research catalog, and Natural Resources Canada, identify that the largest events in the vicinity are no greater than magnitude 5.0.

Lastly, no volcanoes are located in the Lake Erie hazards volcano database.

according to the NOAA natural Tsunami is not the controlling flood event at PNPP.

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February 23,2015 of:

seiche with wind-wave activity; and the maximum controlled water level in the enclosed 3.7. Gombined Effect Flood (including Wind-Generated Waves) (Reference PNPP 20{5q}

Evaluation of floods caused by precipitation events is covered in Appendix H.1 of NUREG/CR-7046. The three alternatives are addressed in flooding on streams and rivers (Section 3.1), which identifies the resulting water surface elevations. Combined effect flooding evaluates the component of added waves induced by 2-year wind speed along the critical direction.

Evaluation of floods along the shores of enclosed bodies of water is covered in Appendix H.4.1 of NUREG/CR-7046 and includes one alternative:

Combination of:

Probable maximum surge and seiche with wind-wave activity.

The lesser of the 100-year or the maximum controlled water level in the enclosed body of water.

Three alternatives are specified in Appendix H.4.2 of NUREG/CR-7046 for streamside locations of enclosed bodies of water. Each of the alternatives considered has three components contributing to the water surface elevation.

Alternative 1 - Gombination of:

The lesser of one-half of the PMF or the 500-year flood; Surge and seiche from the worst regional hurricane or windstorm activity; and The lesser of the 100-year or the maximum controlled water level body of water.

Alternative 2 - Combination of:

PMF in the stream; A 2S-year surge and seiche with wind-wave activity; and The lesser of the 1OO-year or the maximum controlled water level body of water.

a with wind-wave in the enclosed in the enclosed o Afternative 3 -Gombination

- A Z5-year flood in the stream; Probable maximum surge and The lesser of the 100-year or body of water.

3.7.1. Basis of Inputs Inputs include the following:

Major Stream all-season PMF and HEC-RAS modeling from Calculation 50:38.000 Major Stream cool-season PMF and HEC-RAS modeling from Calculation 50:39.000 o Minor Stream all-season PMF and HEC-RAS modeling from Calculation 50:40.000 o Minor Stream cool-season PMF and HEC-RAS modeling from Calculation 50:41.000 o PMSS from Calculation 50:47.000 o Wave parameters for Lake Erie at PNPP from Calculation 50:47.000 1OO-year or maximum controlled water level in Lake Erie from Calculation 50:46.000 Lake Erie historical maximum surge from Calculation 50:46.000 o Lake Erie 2S-year surge from Calculation 50:46.000 Z-year wind speed Site topography PERRY NUCLEAR POWER PLANT Page 26 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation Revision 0 February 23,2015 3.7.2. Gomputer Sofhrvare Programs ArcGlS Desktop 10.1 o HEC-GeoRAS 10.1 o HEC-RAS 4.1 Microsoft Excel 3.7.3. Methodology Each combination includes coincident wind-wave activity. Coincident wind-wave activity is determined for the critical flooding combination using the USACE guidance outlined in USACE Coastat Engineering Manual. Wind setup is the effect of horizontal stress on the water surface. Runup is the maximum elevation of wave uprush above stillwater level.

H.4.1 Gombination Probable maximum surge and seiche is discussed In Section 3.5. \\Mnd wave activity includes wave height, wind setup, and wave runup. Wave height and wind setup are included as part of the PMSS developed using Delft3D model. Wave runup is determined in accordance with USACE guidance on the shoreline and bluff slopes adjacent to Lake Erie.

H.4.2 Com bi nation Alternatives As a bounding

approach, the maximum Lake Erie water level from all three alternatives, including the initial water level and surge effects, is used as the downstream boundary condition for Major Stream and Minor Stream flooding, and combined with the PMF for each stream. lt is determined that the maximum Lake Erie water level has no significant effect on the PMF analyses.

The Major Stream and Minor Stream HEC-RAS models are updated and the results are compared to the H.1 Combination results to determine the bounding combination for wind wave activity. The 2-year wind speed is applied to the longest fetch length based on the inundation area of the PMF. Wave height and wind setup are determined in accordance with USACE guidance. Significant wave height is used to determine wave runup in accordance with USACE guidance on vertical walls.

3.7.4. Results The H.4.1 Combination maximum water surface elevation is 582.6 feet NGVD 29, including wind setup, and occurs west of the power block along the shoreline bluff slopes.

The maximum effects due to wind wave activity occur at a location just east of the power block along a section of shoreline with steeper bluff slopes. Wave action analysis concludes that a maximum wave runup of 27.5 feet may be generated on the shoreline bluff slopes. The PMSS maximum water surface elevation at this location is 581.7 feet NGVD 29. The maximum wave runup elevation during the controlling PMSS is equal to 609.2 feet NGVD 29, which is well below the site.

The maximum combined water surface elevation for the Major Stream and the Minor Stream are the PMF results.

The bounding H.4.2 Combination includes the PMF for Major Stream and Minor Stream utilizing the PMSS as a downstream boundary condition.

This results in maximum water surface elevations equal to the PMF results for the Minor Stream. For the Major Stream the maximum water surface elevations are equal to the PMF results upstream of the plant access road. Downstream of the plant access road are slight variances. However, the resulting water levels are maintained within the Major Stream watershed boundaries away from the power block and well below the nominal PERRY NUCLEAR POWER PLANT Page 27 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding First Energy Corporation finished floor elevation of PNPP safety-related structures.

minimal.

Revision 0

February 23,2015 Therefore, the variances are The Major Stream is not directly adjacent to PNPP safety-related structures.

Therefore, wind wave activity has no specific consequence.

The maximum PMF water surface elevation for the Minor Stream as shown in Table 1 is 623.0 feet NGVD 29. Wave action analysis concludes that a maximum combined wind setup and wave runup of 5.3 feet may be generated on the vertical face of the power block structures.

The maximum wave runup elevation during the controlling flooding for the Minor Stream and east side of the power block is equal to 628.3 feet NGVD 29.

3.8. Local Intense Precipitation (Reference PNPP 20159)

The LIP is an extreme precipitation event at a given location. The effects of the LIP are evaluated for the west side of the power block. The effects of the LIP on the east side of the power block are identical to the Minor Stream reevaluation.

The LIP evaluation is performed in accordance with NUREG/CR-7046.

3.8.1. Basis of Inputs Site topography Site-specific, all-season PMP o Combined probable maximum snowpack snowmelt and rainfall Combined 1OO-year snowpack snowmelt and site-specific, Contribution flow from Major Stream all-season PMF o Contribution flow from Major Stream cool-season PMF Contribution flow from Minor Stream all-season PMF o Contribution flow from Minor Stream cool-season PMF 3.8.2. Gomputer Software Programs ArcGlS Desktop 10.1 HEC-HMS 3.5 Microsoft Excel 3.8.3. Methodology The LIP is equal to the all-season, point precipitation PMP or the comblned effects of cool-season snowmelt and rainfall.

The three alternatives for the PMF are also evaluated for the effects of the LlP. The duration of the LIP event is 72-hours.

The all-season and coot-season alternatives are evaluated using 5-minute increments for various temporal distributions to maximize runoff. Front, onethird, center, two-thirds, and end-loading temporal distributions are considered in an effort to capture the distribution that maximizes runoff.

The site is subdivided into four (4) sub-basin areas based on the topography of the site.

1O0-year, cool-season cool-season PMP A rainfall using unit a basis to NRCS unit USACE HEC-HMS hydrologic software is used to convert rainfall to runoff.

hyetograph is applied to the sub-basin areas and transformed to runoff hydrograph methodology.

No historical observations are available to use as create a unit hydrograph.

Therefore, a synthetic unit hydrograph is developed.

hyd rog raph methodology is used for rainfall-to-runoff transformation.

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February 23,2015 The entire roof drainage is assumed to be contributing to the surface runoff.

Conservatively, no precipitation losses are incorporated into the analysis. Naturally for the site area, base flow is zero. Active and passive drainage system components (e.9.,

pumps, gravity storm drain systems, small culverts, and inlets) were considered non-functionat or clogged during the LIP event, per Case 3 in NUREG/CR-7046.

No adjustment of the unit hydrographs is made to account for the effects of nonlinear basin response, because the unit hydrographs are developed to conservatively maximize the response time.

The sub-basin areas are modeled as reservoirs using USACE HEC-HMS hydrologic software and an elevation-area relationship.

The reservoir areas are modeled with broad crested weir flow to account for outflow locations and barrier structures. Split flow between reservoir areas is modeled as an auxiliary connection between the reservoir areas. Overflow contributions from the Major Stream and Minor Stream are added as applicable.

Outflow from the model drains north toward Lake Erie.

3.8.4. Results For the all-season PMP event (Alternative 1), the one-third, center, twothirds, and end-loading temporal distributions produce identical peak results and the maximum water levels. The maximum water surface elevation along the entire west side of the power block for Alternative 1 is 621.2 feet NGVD 29.

Based on the results for Alternative 1 only the center temporal distribution is evaluated for the combined probable maximum snowpack and 1OO-year cool-season rainfall event (Alternative 2). The maximum water surface elevation along the entire west side of the power block for Alternative 2 is 620.0 feet NGVD 29.

Based on the results for Alternative 1 only the center temporal distribution is evaluated cool-season PMP event (Alternative 3). The for the combined 1OO-year snowpack and maximum water surface elevation along Alternative 3 is 620.2 feet NGVD 29.

the entire west side of the power block for The all-season PMP event (Alternative

1) is determined to be the controlling LIP scenario. The maximum water surface elevations at safety-related structures along the west side of the power block is 621.2 feet NGVD 29. The duration of flooding above the nominal finished floor elevation is t hour 3 minutes.

Coincident wind wave activity combined with the LIP is not designated by NUREG-CR/7046. Additionally, site obstructions, including structures and barrier blocks, and shallow water depths of flooding on the west side of the power block preclude development of significant fetch length and subsequent wave conditions.

4. COMPARISON WITH CURRENT DESIGN BASIS The reevaluated maximum water surface elevations due to the riverine flooding (PMF for the Major Stream and Minor Stream, including the combined effects of wind wave activity),

LlP, and lake flooding (PMSS) exceed the current licensing basis.

For riverine flooding, the current design basis incorporates superseded

guidance, which does not examine sub-hourly PMP increments, temporal distributions, or the effects of nonlinear basin response.

In addition, recent site topography is used for the hazard reevaluation.

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February 23,2015 For lake flooding, the current design basis assumes the surge acts only in one direction.

A site-specific wind and pressure field is developed as part of the reevaluation.

More recent storms provide the controlling wind for reevaluated surge flooding at PNPP.

As previously indicated, the PMSS maximum stillwater surface elevation exceeds the design basis elevation of 580.5 feet NGVD 29 by a maximum value of 2.1 feet. The UHS for PNPP is Lake Erie. Although the design basis is exceeded, the PMSS Stillwater surface elevation remains below the safety-related pumps and equipment located above elevation 586.5 feet NGVD 29 in the emergency service water pumphouse.

Additionally, the PMSS minimum stillwater surface elevation is lower than the design basis of 565.26 feet NGVD 29 by 2.3 feet.

However, previous evaluation determined that there is adequate net positive suction head and submergence of the emergency service water pumps for a resulting elevation as low as 559.0 feet NGVD 29 (Reference PNPP 2004).The maximum surge runup exceeds the design basis elevation of 607.9 feet NGVD 29 by a maximum value of 1.3 feet. However, the maximum effects of the PMSS event are maintained on the bluffs adjacent to Lake Erie. The site grade remains higher than the maximum effects of the PMSS event. Therefore, the resulting beyond design basis PMSS effects are inconsequential to safety-related structures.

For LIP flooding, the current design basis reduces the peak rainfall intensity to account for the roof drainage system and altow a build-up of six inches of rainfall depth over the entire plant site.

Additionally, runoff coefficients (losses) are incorporated into the analysis. As part of the hazard reevaluation, recent site topography is used, and no credit is taken for losses or the roof drainage system. Furthermore, the hazard reevaluation incorporates overflow contributions from the adjacent Major Stream and Minor Stream watersheds.

The comparisons of existing and reevaluated flood hazards are provided in Table 2.

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Table 2 - Comparison of Existing and Reevaluated Flood Hazards at PNPP Flood-Gausing Mechanism Design Basis Comparison Flood Hazard Reevaluation Results Flooding streams rivers In and Maior Stream PMF Elevation is 624.0 feet NGVD 29 (at rail line bridge).

PMF Flow is 31,250 cfs.

Cool-season is not evaluated.

Minor Stream PMF Elevation is 619.5 feet NGVD 29.

PMF Flow is 7,000 cfs.

Cool-season is not evaluated.

Not bounded.

Exceeds current design basis for both Major Stream and Minor Stream.

Maior Stream All-season PMF Elevation is 630.9 feet NGVD 29 (at rail line bridge).

All-Season PMF Flow is 30,100 cfs.

Cool-Season PMF Elevation is 623.1 feet NGVD 29.

Cool-season PMF Flow is 14,900 cfs.

Minor Stream All-season PMF Elevation is 623.0 feet NGVD 29.

All-season PMF Flow is 5,300 cfs.

Cool-season PMF Elevation is 621.1 feet NGVD 29.

Cool-season PMF Flow is 1,600 cfs.

Dam breaches and failures No upstream impoundments.

Bounded Dam assessment indicates no watershed dams.

Storm surge Water surface elevation is 580.5 feet NGVD 29.

Low water elevation is 565.26 feet NGVD 29.

Not bounded.

Exceeds current design basis.

Water surface elevation is 582.6 feet NGVD 29.

Low water elevation is 563.0 feet NGVD 29.

Seiche This flood-causing mechanism is not described specifically for the site in the USAR.

Bounded Bounded by storm surge.

Tsunami This flood-causing mechanism is identified as not applicable in the USAR.

Bounded Tsunami assessment indicates a slight possibility of tsunamis in the Great Lakes region. However, the seismicity in the region suggests no potential exists for strong earthquakes or the vertical displacement necessary to induce a substantial tsunami.

NTTF Recommendation 2.1 (Hazard Reevaluations):

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Table 2 - Comparison of Existing and Reevaluated Flood Hazards at PNPP (Continued)

Flood-Causing Mechanism Design Basis Comparison Flood Hazard Reevaluation Results lce-induced flooding This flood-causing mechanism is identified as not plausible in the USAR.

Bounded lce-induced flooding is bounded by the all-season PMF event.

Channel migration or diversion This flood-causing mechanism is identified as not applicable in the USAR.

Bounded Channel diversion is not characteristic for adjacent streams.

Combined effect flood (including wind-generated waves)

Wave runup on Lake Erie shoreline bluffs is 607.9 feet NGVD 29.

\\Mnd wave effects on streams is not described in the USAR.

Not bounded.

Exceeds current design basis.

Wave runup on Lake Erie shoreline bluffs is 609.2 feet NGVD 29.

Maximum wave runup elevation in the vicinity of the power block is 628.3 feet NGVD 29.

LIP Maximum water surface elevation is 620.5 feet NGVD 29.

Not bounded.

Exceeds current desiqn basis.

Maximum water surface elevation is 621.2 feet NGVD 29.

NTTF Recommendation

2. 1 First Energy Corporation (Hazard Reevaluations)

Flooding Plant monument elevations, used as a basis for plant design, have been reported to have an approximate 0.21 feet uncertainty with respect to the 2012 Sanborn topographic survey, being the survey basis of flooding evaluations.

The approximate 0.21 feet uncertainty ls in excess of the estimated 0.11 feet tolerance of the 2012 Sanborn survey. The 0.11 feet tolerance accounts for survey accuracy as well as for the accuracy of the conversion between NAVD 88 to NGVD 29 datums. The 0.21feet uncertainty shall be considered in addition to the stated 0.72 feet onsite conversion between the NADV 88 and NGVD 29 datums. Thus, accounting for an additional 0.21 feet of water depth at elevations listed herein. However, since the Report shows that flood levels significantly exceed the design basis flood levels, the conclusion of this report is unchanged, an interim action plan has been determined necessary.

The interim action plan as stated in the following section will account for this discrepancy and the power block building settlement of up to 1.5 inches discussed in Section 2.3, within the listed modifications as well as in all final design basis conditions.

Revision 0

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5. INTERIM AND PLANNED FUTURE ACTIONS Revision 0 February 23,2015 The Flooding Hazard Reevaluation Report evaluated the applicable flooding hazards for PNPP.

Four of the postulated reevaluated flood hazard events (riverine flooding, lake flooding, combined effects, and LIP) resulted in maximum flood water elevations higher than previously calculated for PNPP. These postulated flooding events are considered beyond design basis events and do not constitute an operability concern. The PMSS event and the combined effects for wave runup on the Lake Erie shoreline results are inconsequential.

Therefore, no interim or future actions are planned for this event.

The interim action plan is an engineering change package and supporting analyses to demonstrate maximum water surface elevations will not result in flooding of plant buildings important to nuclear safety. An engineering change package has been initiated to implement design changes to the Major Stream and the Minor Stream to address the design basis condition described in the functionality assessment (PNPP Condition Report 2013-05625) and accommodate the beyond design basis events. Although the functionality assessment removes some of the conservatism applied in the original evaluation, the results for the Minor Stream on the east side of the power block and the LIP results on the west side of the power block were equal to or less than the nominal finished floor elevation of PNPP safety-related structures.

Therefore, no additional interim actions are necessary.

The design changes will ensure that all flow will be maintained within the Major Stream watershed boundaries and within the banks of the Minor Stream. Because the Major Stream is not immediately adjacent to safety-related structures, the resulting water levels in the Major Stream are inconsequential.

However, overflow from the Major Stream is a contributor to Minor Stream water tevels. Therefore, flow needs to be maintained within the Major Stream watershed boundaries.

The engineering change package incorporates removal of a portion of the existing abandoned rail line embankment crossing the Major Stream. Removal of the embankment allows greater conveyance of flow in the overbanks of the Major Stream, preventing flow from overtopping the rail line. Furthermore, the secondary access road is raised to prevent any remaining backwater from overtopping the road. This modification results in the concentration of Major Stream runoff to be carried downstream to Lake Erie, rather than contributing to runoff to other areas of the site. The technical basis of the Major Stream modifications incorporates analysis of site-specific PMP as input, no precipitation losses, unit hydrograph rainfall runoff analysis, including the etfects of nonlinear basin response, and one-dimensional unsteady state hydraulic modeling.

The engineering change package incorporates an upstream diversion of the Minor Stream. The diversion channel diverts runoff flow east around the outside of the security barriers and north directly to Lake Erie. A berm is designed adjacent to the diversion channel between the channel and the site. Under PMF conditions the berm will maintain all flood water away from the site.

These modifications significantly reduce the runoff flow received by the Minor Stream, resulting in the design basis water levels of 619.5 feet NGVD 29. With the design basis water levels, the combined effect wind wave activity runup on the power block is no longer applicable.

The technical basis of the Minor Stream modifications incorporates analysis of Hydrometeorological No. 33 PMP as input, no precipitation losses, unit hydrograph rainfall runoff analysis, including the effects of nonlinear basin response, and one-dimensional unsteady state hydraulic modeling.

Hydrometeorological No. 33 PMP is determined to bound site-specific PMP.

These changes will result in eliminating the overflow contributions from the Major Stream and the Minor Stream to other areas of the site. Therefore, only the precipitation for the LIP contributes to flooding. Supporting the engineering change package, the interim action plan includes completion of an LIP analysis to determine the maximum water surface elevation.

Also, the evafuation will address the 0.21 feet datum discrepancy, discussed in Section 4, and the PERRY NUCLEAR POWER PLANT Page 33 of 35

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6. REFERENCES (ANSI/ANS-2.8-1992)

ANS, American Nationat Standard for Determining Design Basrs Flooding at Power Reactor Sr'fes, Prepared by the American Nuclear Society Standards Committee Working Group ANS-2.8, 1992.

(JLD-ISG-2013-01)

NRC, Guidance for Assessment of Flooding Hazards due to Dam Failure, Revision 0, July 2A13.

(JLD-ISG

-2012-06)

NRC, Guidance for Performing a Tsunami, Surge or Seiche Flooding Hazard Assessment, Revision 0, January 2013.

(NEf August 2012) NEl, Report 12-08, Overview of External Flooding Reevaluations, August 2012.

(NRC March 2012) NRC, Letterto Licensees, Requestfor Information Pursuantto Title 10 of the Code of Federal Regulations 50.54(0 Regarding Recommendations

2. 1,2.3, and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi

Accident, March 12,2012.

(NRC May 2012) NRC, Letter to Licensees, 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 Recommendation 2.1 of the Near-Term Task Force Review of lnsights from the Fukushima Dai-ichi

Accident, May 11,2012.

(NRC RG 1.59) NRC, Desrgn Basis Flood for Nuclear Power Plants, Regulatory Guide Revision 2, 1977.

(NRC RG 1.102) NRC, Ftood Protection for Nuclear Power Plants, Regulatory Guide 1.102, Revision 1, 1976.

(NUREG-O8OO)

NRC, NUREG-0800, Standard Review Ptan for the Review of Safety Analysis Reporfs for Nuclear Power Ptants: LWR Edition - Sde Characterisfics and Site Parameters (Chapter 2), ML070400364, March 2007.

(NUREG/CR-7046)

NRC, NUREG/CR-7046, PNNL-20091

, Design-Basis Flood Estimation for Site Characterization at Nuclear Power Ptants in the United Sfafes of America, ML11321A195, November 2011.

(NUREG/CR-6966)

NRC, NUREG/CR-6966, Tsunami Hazard Asses sment at Nuclear Pawer Ptant Sifes in the lJnited Sfafes of America, National Technical Information Service, March 2009.

(ODNR 2013) Ohio Department of Natural Resources, Probable Maximum Precipitation Study for the Sfafe of Ohio, prepared by Applied Weather Associates, LLC, February 2013.

(PNPP 2OO4)

FENOC Calculation P45-081, Evaluation of Nef Positive Suction Head (NPSH) and Submergence Requirements for the Emergency Service Water (ESW Sysfem Pumps, Revision 0.

(PNPP 2015a) FENOC Calculation 50:36.000, PNPP Sde-Specific All-Season PMP, Revision 0.

(PNPP 2015b) FENOC Calculation 50:37.000, PNPP Sde-specific Cool-season PMP, Revision 0.

PERRY NUCLEAR POWER PLANT Page 34 of 35

NTTF Recommendation 2.1 (Hazard Reevaluations):

Flooding Revision 0

First Energy Corporation February 23,2015 (PNPP 2015c) FENOC Calculation 50:38.000, PNPP Major Stream All-Seasan Probable Maximum Flood, Revision 0.

(PNPP 2015d) FENOC Calculation 50:39.000, PNPP Major Stream Cool-Season Probable Maximum Flood, Revision 0.

(PNPP 2015e) FENOC Calculation 50:40.000, PNPP Minor Stream A//-Season Probable Maximum Flood, Revision 0.

(PNPP 20150 FENOC Calculation 50:41.000, PNPP Minor Stream Cool-Season Probable Maximum Flood, Revision 0.

(PNPP 20159) FENOC Calculation 50:42.000, PNPP Effects of Local lntense Precipitation, Revision 0.

(PNPP 2015h) FENOC Calculation 50:43.000, PNPP Dams Assessmenf, Revision 0.

(PNPP 2015i) FENOC Calculation 50:44.000, PNPP lce Jam and Channel Assessmenf, Revision 0.

(PNPP 2015j) FENOC Calculation 50:45.000, PNPP Wind Climatology, Revision 0.

(PNPP 2015k) FENOC Calculation 50:46.000, PNPP Surge and Seiche Screemng, Revision 0.

(PNPP 20151)

FENOC Calculation 50:47.000, PNPP Surge and Seiche Analysis, Revision 0.

(PNPP 2015m) FENOC Calculation 50:48.000, PNPP Tsunami Assessment, Revision 0.

(PNPP 2015n) FENOC Calculation 50:52.000, PNPP Rainfall Runoff GIS Analysis, Revision 0.

(PNPP 2015o) FENOC Calculation 50:53.000, PNPP Surge and Seiche G/S Analysis, Revision 0.

(PNPP 2015p) FENOC Calculation 50:54.000, PNPP Surge and Seiche Calibration, Revision 0.

(PNPP 2015q) FENOC Calculation 50:55.000, PNPP Combined Events, Revision 0.

(PNPP 2015r) FENOC Calculation 50:59.000, PNPP Sde-Specific All-Season Sub-Hour Probable Maximum Precipitation Analysis for 1-10 Square Miles, Revision 0.

(PNPP 2015s) FENOC Calculation 50:60.000, PNPP Sife-Specific Cool-Season Probable Maximum (rainfall) Precipitation Analysis, Revision 0.

(USAR) Perry Nuclear Power Plant, Updated Safety Analysis Report, Revision 17.

PERRY NUCLEAR POWER PLANT Page 35 of 35

v t e Letter Sequence Response to RAI
TAC:MF6099, (Open)
Initiation Acceptance... Administration Questions Answers 10 March 2015 11 December 2015 Results Approval... Other: ML15153A145
MONTHYEAR2015-03-10 [Table View]

L-15-074, FENOC, Perry Nuclear Power Plant - Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Ac

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L-15-074, FENOC, Perry Nuclear Power Plant - Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Ac

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