0CAN031404, ANO, Units 1 & 2 - Seismic Hazard and Screening Report (CEUS Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force (Nttf)Review of Insights from the Fukushima

ANO, Units 1 & 2 - Seismic Hazard and Screening Report (CEUS Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force (Nttf)Review of Insights from the Fukushima Da

ML14092A021
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/28/2014
From:	Jeremy G. Browning Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
0CAN031404
Download: ML14092A021 (121)

Text

Entergy Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Jeremy G. Browning Site Vice President Arkansas Nuclear One OCAN031404 March 28, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852

SUBJECT:

Seismic Hazard and Screening Report (Central Eastern United States (CEUS)

Sites), Response to NRC Request for Information (RFI) Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force (NTTF)

Review of Insights from the Fukushima Dai-ichi Accident Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6

REFERENCES:

1. NRC letter to Entergy, RF Pursuantto Title 10 of the Code of Federal Regulations 50.54(0 Regarding Recommendations 2.1, 2.3, and 9.3 of the NTTF Review of Insights from the Fukushima Dai-ichiAccident, dated March 12, 2012 (OCNA031208) (ML12053A340)

2. Nuclear Energy Institute (NEI) Letter to NRC, Proposed Path Forwardfor NTTF Recommendation 2.1: Seismic Reevaluations, dated April 9, 2013 (ML13101A379)

3. NRC Letter, Electric Power Research Institute (EPRI) FinalDraft Report XXXX)O(, "SeismicEvaluation Guidance:Augmented Approach for the Resolution of Fukushima NTTF Recommendation 2.1: Seismic," as an Acceptable Alternative to the March 12, 2012, Information Request for Seismic Reevaluations, dated May 7, 2013 (ML13106A331)

4. EPRI Report 1025287, Seismic Evaluation Guidance, Screening, Prioritizationand Implementation Details (SPID) for the Resolution of Fukushima NTTF Recommendation 2.1: Seismic, (ML12333A170)

5. NRC Letter, Endorsementof EPRI Final Draft Report 1025287, "Seismic Evaluation Guidance, "dated February 15, 2013, (OCNA021302)

(ML12319A074)

6. Entergy Letter to NRC, Response to NRC RFI Pursuantto 10 CFR 50.54(0 Regarding the Seismic Aspects of Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-ichiAccident -

1.5-Year Response for CEUS Sites, dated September 12, 2013, (OCAN091301) (ML13255A373)

OCAN031404 Page 2 of 3

Dear Sir or Madam:

On March 12, 2012, the NRC issued Reference 1 to all power reactor licensees. Enclosure 1 of Reference 1 requested each addressee located in the CEUS to submit a seismic hazard evaluation within 1.5 years from the date of Reference 1.

In Reference 2, NEI requested NRC agreement to delay submittal of the final CEUS seismic hazard evaluation so that an update to the EPRI ground motion attenuation model could be completed and used to develop that information. NEI proposed that descriptions of subsurface materials and properties and base case velocity profiles be submitted to the NRC by September 12, 2013 (Reference 6), with the remaining seismic hazard and screening information submitted by March 31, 2014. NRC agreed with the proposed path forward in Reference 3.

Reference 4 contains industry guidance and detailed information to be included in the seismic hazard evaluation submittal. NRC endorsed this industry guidance in Reference 5.

The enclosed Seismic Hazard and Screening Reports for Arkansas Nuclear One (ANO) provide the information described in Section 4 of Reference 4 in accordance with the schedule identified in Reference 2.

This letter contains no new regulatory commitments. If you have any questions or require additional information, please contact Stephenie Pyle at 479.858.4704.

I declare under penalty of perjury that the foregoing is true and correct. Executed on March 28, 2014.

Sincerely, JGB/nbm

Enclosures:

1. Seismic Hazard and Screening Report for ANO-1

2. Seismic Hazard and Screening Report for ANO-2

0CAN031404 Page 3 of 3 cc: Mr. Marc L. Dapas Regional Administrator U. S. Nuclear Regulatory Commission, Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Peter Bamford MS O-8B3 One White Flint North 11555 Rockville Pike Rockville, MD 20852

Enclosure 1 to 0CAN031404 Seismic Hazard and Screening Report for ANO-1

Seismic Hazard and Screening Report for Arkansas Nuclear One Unit I 1

Table of Contents Page 1.0 Introduction ............................................................................................................................. 3 2.0 Seism ic Hazard Reevaluation ............................................................................................ 4 2,1 Regional and Local Geology ........................................................................................ 6 2,2 Probabilistic Seismic Hazard Analysis ................................. 6 2.2.1 Probabilistic Seism ic Hazard Analysis Results .................................................. 6 2.2.2 Base Rock Seism ic Hazard Curves .................................................................. 8 2.3 Site Response Evaluation ............................................................................................ 8 2.3.1 Description of Subsurface Material ..................................................................... 8 2.3.2 Development of Base Case Profiles and Nonlinear Material Properties ............ 8 2.3.2.1 Shear Modulus and Dam ping Curves ................................................... 13 2.3.2.2 Kappa ................................................................................................... 14 2.3.3 Random ization of Base Case Profiles .............................................................. 14 2.3.4 Input Spectra ...................................................................................................... 15 2.3.5 Methodology ..................................................................................................... 15 2.3.6 Am plification Functions ..................................................................................... 15 2.3.7 Control Point Seism ic Hazard Curves .............................................................. 20 2.4 Control Point Response Spectrum ............................................................................ 20 3.0 Plant Design Basis and Beyond Design Basis Evaluation Ground Motion ...................... 23 3.1 Safe Shutdown Earthquake Description of Spectral Shape ....................................... 23 3.2 Control Point Elevation .............................................................................................. 24 3.3 IPEEE Description and Capacity Response Spectrum .............................................. 24 4.0 Screening Evaluation ........................................................................................................ 26 4.1 Risk Evaluation Screening (1 to 10 Hz) ..................................................................... 26 4.2 High Frequency Screening (> 10 Hz) ....................................................................... 26 4.3 Spent Fuel Pool Evaluation Screening (1 to 10 Hz) ................................................... 26 5.0 Interim Actions ...................................................................................................................... 26 6.0 Conclusions .......................................................................................................................... 27 7.0 References ............................................................................................................................ 27 Appendix A .................................................................................................................................. 30 Appendix B .................................................................................................................................. 42 2

1.0 Introduction Following the accident at the Fukushima Daiichi nuclear power plant resulting from the March 11, 2011, Great Tohoku Earthquake and subsequent tsunami, the Nuclear Regulatory Commission (NRC) established a Near-Term Task Force (NTTF) to conduct a systematic review of NRC processes and regulations and to determine if the agency should make additional improvements to its regulatory system. The NTTF developed a set of recommendations intended to clarify and strengthen the regulatory framework for protection against natural phenomena. Subsequently, the NRC issued a 50.54(f) letter (U.S. NRC, 2012) that requests information to assure that these recommendations are addressed by all U.S.

nuclear power plants. The 50.54(f) letter (U.S. NRC, 2012) requests that licensees and holders of construction permits under 10 CFR Part 50 reevaluate the seismic hazards at their sites against present-day NRC requirements. Depending on the comparison between the reevaluated seismic hazard and the current design basis, the result is either no further risk evaluation or the performance of a seismic risk assessment. Risk assessment approaches acceptable to the staff include a seismic probabilistic risk assessment (SPRA), or a seismic margin assessment (SMA). Based upon the risk assessment, the NRC staff will determine whether additional regulatory actions are necessary.

This report provides the information requested in items (1) through (7) of the "Requested Information" section and Attachment 1 of the 50.54(f) letter (U.S. NRC, 2012) pertaining to NTTF Recommendation 2.1 for the Arkansas Nuclear One (ANO) - Unit 1 plant, located in Pope County, Arkansas. In providing this information, Entergy followed the guidance provided in the Seismic Evaluation Guidance:Screening, Prioritization,and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (EPRI, 2013a). The Augmented Approach, Seismic Evaluation Guidance:Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (EPRI, 2013c),

has been developed as the process for evaluating critical plant equipment as an interim action to demonstrate additional plant safety margin prior to performing the complete plant seismic risk evaluations.

The original geologic and seismic siting investigations for ANO - Unit 1 was performed in accordance with Appendix A to 10 CFR Part 100 and meet General Design Criterion 2 in Appendix A to 10 CFR Part 50. The Safe Shutdown Earthquake (SSE) Ground Motion was developed in accordance with Appendix A to 10 CFR Part 100 and used for the design of seismic Category I systems, structures and components.

In response to the 50.54(f) letter (U.S. NRC, 2012) and following the guidance provided in the SPID (EPRI, 2013a), a seismic hazard reevaluation was performed. For screening purposes, a Ground Motion Response Spectrum (GMRS) was developed. Based on the results of the screening evaluation, ANO - Unit 1 screens-in for a Spent Fuel Pool evaluation and a High Frequency Confirmation. Additionally, based on the results of the screening evaluation, ANO -

Unit 1 screens-out of a risk evaluation.

3

2.0 Seismic Hazard Reevaluation The Arkansas Nuclear One site is located approximately six miles west-northwest of Russellville, Arkansas, on a peninsula formed by the Dardanelle Reservoir which acts as the water source for each Unit. The Arkansas Nuclear One site is in the center of the Arkansas Valley section of the Ouachita province. The Arkansas Valley lies within the area of outcrop of Paleozoic rocks which occupy essentially the northwestern half of the state. The rocks of the Arkansas Valley are nearly all of sedimentary origin. They include only a few bodies of igneous rock. The beds in the valley consist chiefly of non-fossiliferous shale and sandstone, all of Carboniferous age, and most of them belonging to the lower part of the Pennsylvanian series.

The rocks are generally highly carbonaceous and in some places are coal bearing. They contain little or no calcareous material. (Entergy, 2014a), (Entergy, 2014b)

The site is underlain by 8 to 30 ft of moderate to stiff, plastic, red and tan clay with occasional zones of silty clay, which overlies black, dense, horizontally bedded shale and sandstone of the McAlester formation. (Entergy, 2014a)

The nature of the structural features of the Arkansas Valley and their relation to the structure of the adjacent Ouachita and Boston Mountains show that the dominant force in the production of those features was horizontal pressure exerted from the south. It is believed that the folding and thrust faulting developed in post-Paleozoic pre-Cretaceous time due to the subsidence of a land mass to the south which supplied sediments in the place where this land mass once stood. The normal faults were also connected with this episode of deformation. These are believed to have formed either contemporaneously with folding, before folding, or as a result of tension developed after the period of folding. Some normal faults are also believed to have formed during deposition and subsidence of the Pennsylvanian sediments. In the Arkansas Valley, the southward-dipping faults terminate against northward-dipping normal faults. The precise dating of the folds and faults of the Arkansas Valley cannot be done with assurance, but it is known that they are very old geologic structures and probably were formed before Cretaceous time.

(Entergy, 2014a)

East-west trending folds are mapped in the area of the site. From about three miles north to three miles south of the site are two anticlines and one syncline. From north to south these structures are as follows: London anticline, Scranton syncline, and the Prairie View anticline.

The plant site is located on the Scranton syncline in which the maximum dip rarely exceeds 10 degrees except locally where contorted beds may dip as steeply as 20 degrees. (Entergy, 2014a)

The London anticline extends from about four and one-half miles northwest of the town of London, east to about three miles northwest of the site. This anticline may continue east to connect with the anticline which is mapped northeast of the site to a point three and one-half miles north of Russellville. The south limb of the London anticline is steeper than the north limb.

(Entergy, 2014a) 4

The Scranton syncline, also known as the Ouita syncline, extends from northeast of Russellville, west to a point where it probably dies out about five miles northwest of Scranton. Here it is presumably terminated by the Dublin fault, which is an east-west-trending fault over nine miles west of the site. On the western part of the Scranton syncline the south limb is steeper than the north limb. However, on the eastern portion of the syncline the north limb is steeper than the south limb. (Entergy, 2014a)

The Prairie View anticline is mapped from a point three miles southwest of the town of Scranton, east to at least as far as Russellville. This nearly symmetrical anticline is broken by northward-dipping normal faults. (Entergy, 2014a)

There are a number of old faults mapped in the vicinity of the Arkansas River, particularly to the northwest and west of the site. These are in the main, east-west-trending faults. Of these, the London and Prairie View faults are the closest to the site. The London fault and an accompanying unnamed small branch fault trend east-west about four miles north of the site. A small fault which branches from the unnamed fault lies about two and one-half miles northeast of the site. The London fault is a high-angle south-dipping normal fault. It is best exposed about eight miles northwest of the site at Big Piney Creek where the western part of the fault ends. At this locality, the fault plane dips 580 south and has an apparent displacement of about 20 ft. The fault is also exposed to the east along Flat Rock Creek and in a drainage ditch along a country road about eight miles from the site. The unnamed eastwest-trending fault lies about one mile south of the London fault. The trend of this unnamed fault changes toward the east to generally northwest-southeast and appears to intersect the London fault in the vicinity of the north fork of Mill Creek. This fault is at least pre-Cretaceous in age. (Entergy, 2014a)

The Prairie View fault is concealed under alluvium about six miles west of the site. Another six miles to the west, the fault is exposed. It is an east-west-trending high-angle north-dipping normal fault. This fault extends to the west as far as three miles northwest of Subiaco. The maximum displacement along the fault is 350 ft two miles west of the town of Prairie View. Near the western end of the fault there is about 170 ft of maximum displacement and the fault plane dips about 650 northward. About three miles from the western end of the fault is a small branch fault which is downthrown on the southside and is assumed to be dipping south. The Prairie View anticline is faulted by the Prairie View fault and is similar to the faulted anticlines discussed by Hendricks and Parks. It is their opinion that the faulted anticlines in the Fort Smith district were either faulted then folded, or contemporaneously faulted and folded. Therefore, the Prairie View fault is at least as old as the folding in this area, which is pre-Cretaceous. (Entergy, 2014a)

In summary, the only faults within five miles of the site are the Prairie View fault, and the London fault and its branch faults. The closest fault is only a small branch fault and approaches within about two and one-half miles of the site. The last movement of these faults is believed to have occurred prior to the Cretaceous. (Entergy, 2014a)

Considering the historic seismicity of the site region, Entergy determined that because of the excellent formation conditions and the recent general quiescence of the area that a low 5

earthquake intensity could be selected. However, considering the New Madrid earthquake, which is the only severe earthquake experienced in the central United States in historic time, an intensity of VII on the Modified Mercalli Intensity Scale of 1931 (Maximum Earthquake) has been assigned for the site. This is considered to be conservative and corresponds to a design spectrum of 0.20g for the SSE. (Entergy, 2014a)

2. 1 Regional and Local Geology The Arkansas Valley is essentially a Paleozoic basin which had its most significant development during the Mississippian and Pennsylvanian. The greatest accumulations occurred during the Lower (Morrowan) and Lower Middle (Atokan) Pennsylvanian. Deformation of the Ouachitas occurred during Mid-Pennsylvanian time. During this time, the Ouachitas were strongly folded, with some thrust faulting, especially in Oklahoma. The Arkansas Valley section lies between the essentially flat-lying rocks of the Boston Mountains on the north and complexly folded strata of the Ouachita Mountains on the south. Its structure, therefore, has some of the characteristics of both its bounding regions, but is generally a region of broad, gentle folds which trend east-west and are only moderately faulted. Faulting is related to the folding and is pre-Cretaceous in age.

(Entergy, 2014a) (Entergy, 2014b)

Since Cretaceous (and probably late Paleozoic) time, erosion has been the primary agent in the development of land forms in the region. No sediments younger than Pennsylvanian are found in the region, except for Quaternary terrace and alluvial deposits along the stream valleys. In a few places, intrusive rocks, mapped by as mid-Cretaceous cut the Paleozoic sediments. In the Arkansas Valley, these rocks consist of scattered dikes and sills of varying composition. None occur at the plant site. (Entergy, 2014a) (Entergy, 2014b)

The site is about six miles northwest from Russellville, and about two miles from the small town of London. The plant is situated on a peninsula formed by the Corps of Engineers' Dardanelle Reservoir. The plant is located on a broad, nearly flat bench adjacent to the floodplain of the Arkansas River. This bench is at about Elevation 353 ft, at the lower of the two Pleistocene terrace levels. Soil on the terrace consists of clay and silty clay, and is from eight to 30 ft thick at the site. The broad floodplain of the Arkansas River is now covered with the waters of the Dardanelle Reservoir in the vicinity of the site. The low hills adjacent to the site are formed by the gently upturned strata along the flaghksof the Scranton-Ouita syncline. Relief within the limits of the site area is less than 10 ft. (Entergy, 2014a) (Entergy, 2014b) 2.2 ProbabilisticSeismic HazardAnalysis 2.2.1 ProbabilisticSeismic Hazard Analysis Results In accordance with the 50.54(f) letter (U.S. NRC, 2012) and following the guidance in the SPID (EPRI, 2013a), a probabilistic seismic hazard analysis (PSHA) was completed using the recently developed Central and Eastern United States Seismic Source Characterization (CEUS-SSC) for Nuclear Facilities (CEUS-SSC, 2012) together with the updated Electric Power 6

Research Institute (EPRI) Ground-Motion Model (GMM) for the Central and Eastern United States (CEUS) (EPRI, 2013b). For the PSHA, a lower-bound moment magnitude of 5.0 was used, as specified in the 50.54(f) letter (U.S. NRC, 2012). (EPRI, 2013d)

For the PSHA, the CEUS-SSC background seismic sources out to a distance of 400 miles (640 km) around the ANO - Unit 1 site were included. This distance exceeds the 200 mile (320 km) recommendation contained in Reg. Guide 1.208 (U.S. NRC, 2007) and was chosen for completeness. Background sources included in this site analysis are the following (EPRI, 2013d):

1. Extended Continental Crust-Gulf Coast (ECCGC)

2. Gulf Highly Extended Crust (GHEX)

3. Illinois Basin Extended Basement (IBEB)

4. Mesozoic and younger extended prior - narrow (MESE-N)

5. Mesozoic and younger extended prior - wide (MESE-W)

6. Midcontinent-Craton alternative A (MIDCA)

7. Midcontinent-Craton alternative B (MIDCB)

8. Midcontinent-Craton alternative C (MIDCC)

9. Midcontinent-Craton alternative D (MIDC_D)

10. Non-Mesozoic and younger extended prior - narrow (NMESE-N)

11. Non-Mesozoic and younger extended prior - wide (NMESE-W)

12. Oklahoma Aulacogen (OKA)

13. Paleozoic Extended Crust narrow (PEZN)

14. Paleozoic Extended Crust wide (PEZ-W)

15. Reelfoot Rift (RR)

16. Reelfoot Rift including the Rough Creek Graben (RR-RCG)

17. Study region (STUDYR)

For sources of large magnitude earthquakes (designated Repeated Large Magnitude Earthquake (RLME) sources), in NUREG-2115 (CEUS-SSC, 2012) modeled for the CEUS-SSC, the following sources lie within 1,000 km of the site and were included in the analysis (EPRI, 2013d):

1. Cheraw

2. Commerce

3. Eastern Rift Margin Fault northern segment (ERM-N)

4. Eastern Rift Margin Fault southern segment (ERM-S)

5. Marianna

6. Meers

7. New Madrid Fault System (NMFS)

8. Wabash Valley For each of the above background and RLME sources, the mid-continent version of the updated CEUS EPRI GMM was used. (EPRI, 2013d) 7

2.2.2 Base Rock Seismic Hazard Curves Consistent with the SPID (EPRI, 2013a), base rock seismic hazard curves are not provided as the site amplification approach referred to as Method 3 has been used. Seismic hazard curves are shown below in Section 2.3.7 at the SSE control point elevation. (EPRI, 2013d) 2.3 Site Response Evaluation Following the guidance contained in Seismic Enclosure 1 of the 50.54(f) Request for Information (U.S. NRC, 2012) and in the SPID (EPRI, 2013a) for nuclear power plant sites that are not founded on hard rock (defined as 2.83 km/sec), a site response analysis was performed for ANO - Unit 1. (EPRI, 2013d) 2.3.1 Descriptionof Subsurface Material Arkansas Nuclear One - Unit 1 is located on a peninsula formed by the Dardanelle Reservoir about 57 miles (92 km) northwest of Little Rock, Arkansas. The site is situated in the center of the Arkansas Valley in the Ouachita Physiographic Province. The site is founded on Pennsylvania McAlester formation which is hard, dense shale at the top of about 5,000 ft (1,524 m) of firm sedimentary rock. The SSE was specified at an elevation of 326 ft (99.4 m) within the Pennsylvanian shale (Entergy, 2014a).

2.3.2 Development of Base Case Profiles and NonlinearMaterial Properties The basic information used to create the site geologic profile at the ANO - Unit 1 site was taken from plant specific information in the Safety Analysis Report (SAR) (Entergy, 2014a) with the following description (Entergy, 2014a) (Entergy, 2014b):

The reactor containment building is founded on shale of the McAlester Formation with embedment depth of around 26 ft. with tendon galleries of about 36 ft. below grade. Basement rock is estimated to be at a depth of 5,000 ft. The site seismic P-wave varies from 11,000 to 14,500 fps (Entergy, 2014a; Figures 2-21 and 2-30), and Poisson's ratio of 0.18 for 'rock' and 0.25 for 'shale' at the site (Entergy, 2014a, Tables 2-2 and 2-5). The ANO - Unit 1 SAR does not specifically provide a S-wave velocity; however, the ANO - Unit 2 SAR indicates site P-wave velocities form 10,000 to 14,500 fps, and S-wave (not measured but calculated P-wave of 10,000 fps and a Poisson's ration of 0.30) of 5,350 fps. While this information is not identical it is appropriate to use for both units. The site seismic profiles are shown in Figure 2-21 of the SAR (Entergy, 2014a).

The location of the SSE at elevation 326 ft (99.4 m) is within the Pennsylvanian shale with firm sedimentary rocks extending to Precambrian basement at a depth of about 5,000 ft (1,524 m)

(Entergy, 2014a).

8

Shear-wave velocities for the profile were unspecified with compressional-wave velocities listed between 10,000 and 14,500 ft/s (3,048 m/s and 4,419 m/s respectively), likely based on shallow refraction surveys (Entergy, 2014a) (Entergy, 2014b). To develop a mean base-case shear-wave velocity profile, a shallow velocity of 5,300 ft/s (1,616 m/s) was assumed. This value reflects an assumption of a reasonable Poisson ratio of about 0.30 and the lower value of the compressional-wave velocity for the top of the Pennsylvanian McAlester Formation. (EPRI, 2013d)

Provided the materials to basement depth reflect similar sedimentary rocks and age, the shear-wave velocity gradient for sedimentary rock of 0.5 m/m/s (EPRI, 2013a) was assumed to be appropriate for the site. The shallow shear-wave velocity of 5,300 ft/s (1,616 m/s) was taken at the surface of the profile with the velocity gradient applied at that point, resulting in a base-case shear-wave velocity of about 7,772 ft/s (2,369 m/s) at a depth of 5,000 ft (1,524 m). The mean or best estimate base-case profile is shown as profile P1 in Figure 2.3.2-1. (EPRI, 2013d)

Based on the uncertainty in shear-wave velocities due to the lack of measurements, a scale factor of 1.57 was adopted to reflect upper and lower range base-cases. The scale factor of 1.57 reflects a Opin of about 0.35 based on the SPID (EPRI, 2013a) 1 0 th and 9 0 th fractiles which implies a 1.28 scale factor on up. (EPRI, 2013d)

Using the best estimate or mean base-case profile (P1), the depth independent scale factor of 1.57 was applied to develop lower and upper range base-cases profiles P2 and P3 respectively with the stiffest profile (P3) reaching reference rock velocities at a depth of about 1,200 ft (366 m). Base-case profiles P1 and P2 have a mean depth below the SSE of 5,000 ft (1,524 m) to hard reference rock, randomized +/-1,500 ft (+/-457 m). The base-case profiles (P1, P2, and P3) are shown in Figure 2.3.2-1 and listed in Table 2.3.2-1. The depth randomization reflects +/-30%

of the depth to provide a realistic broadening of the fundamental resonance rather than reflect actual random variations to basement shear-wave velocities across a footprint. (EPRI, 2013d) 9

Vs profiles for Arkansas Site Vs (ft/sec) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

500 1000 1500 2000 2000

-Profile 1 ZF2500 ~ 2500-Profile 2

-Profile 3 3000 3500 4000 4500 5000 5500 Figure 2.3.2-1. Shear-wave velocity profiles for ANO - Unit 1. (EPRI, 2013d) 10

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 1 site. (EPRI, 2013d)

Profile 1 Profile 2 Profile 3 thickness depth Vs thickness depth Vs thickness depth. Vs (ft) (ft) (ft/s) (ft) (ft) MIJS) (ft) (ft) (fJs) 0 5,302 0 3,378 0 8,325 10.0 10.0 5,302 10.0 10.0 3,378 10.0 10.0 8,325 10.0 20.0 5,307 10.0 20.0 3,381 10.0 20.0 8,332 10.0 30.0 5,312 10.0 30.0 3,384 10.0 30.0 8,340 10.0 40.0 5,317 10.0 40.0 3,387 10.0 40.0 8,348 10.0 50.0 5,322 10.0 50.0 3,390 10.0 50.0 8,356 10.0 60.0 5,327 10.0 60.0 3,393 10.0 60.0 8,364 10.0 70.0 5,332 10.0 70.0 3,397 10.0 70.0 8,372 10.0 80.0 5,337 10.0 80.0 3,400 10.0 80.0 8,379 10.0 90.0 5,342 10.0 90.0 3,403 10.0 90.0 8,387 10.0 100.0 5,347 10.0 100.0 3,406 10.0 100.0 8,395 10.0 110.0 5,352 10.0 110.0 3,409 10.0 110.0 8,403 10.0 120.0 5,357 10.0 120.0 3,413 10.0 120.0 8,411 10.0 130.0 5,362 10.0 130.0 3,416 10.0 130.0 8,419 10.0 140.0 5,367 10.0 140.0 3,419 10.0 140.0 8,427 10.0 150.0 5,372 10.0 150.0 3,422 10.0 150.0 8,434 10.0 160.0 5,377 10.0 160.0 3,425 10.0 160.0 8,442 10.0 170.0 5,382 10.0 170.0 3,428 10.0 170.0 8,450 10.0 180.0 5,387 10.0 180.0 3,432 10.0 180.0 8,458 10.0 190.0 5,392 10.0 190.0 3,435 10.0 190.0 8,466 10.0 200.0 5,397 10.0 200.0 3,438 10.0 200.0 8,474 10.0 210.0 5,402 10.0 210.0 3,441 10.0 210.0 8,481 10.0 220.0 5,407 10.0 220.0 3,444 10.0 220.0 8,489 10.0 230.0 5,412 10.0 230.0 3,448 10.0 230.0 8,497 10.0 240.0 5,417 10.0 240.0 3,451 10.0 240.0 8,505 10.0 250.0 5,422 10.0 250.0 3,454 10.0 250.0 8,513 10.0 260.0 5,427 10.0 260.0 3,457 10.0 260.0 8,521 10.0 270.0 5,432 10.0 270.0 3,460 10.0 270.0 8,529 10.0 280.0 5,437 10.0 280.0 3,464 10.0 280.0 8,536 10.0 290.0 5,442 10.0 290.0 3,467 10.0 290.0 8,544 10.0 300.0 5,447 10.0 300.0 3,470 10.0 300.0 8,552 10.0 310.0 5,452 10.0 310.0 3,473 10.0 310.0 8,560 10.0 320.0 5,457 10.0 320.0 3,476 10.0 320.0 8,568 10.0 330.0 5,462 10.0 330.0 3,479 10.0 330.0 8,576 10.0 340.0 5,467 10.0 340.0 3,483 10.0 340.0 8,584 10.0 350.0 5,472 10.0 350.0 3,486 10.0 350.0 8,591 10.0 360.0 5,477 10.0 360.0 3,489 10.0 360.0 8,599 10.0 370.0 5,482 10.0 370.0 3,492 10.0 370.0 8,607 11

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 1 site. (EPRI, 2013d)

______Profile 1 Profile 2 Profile 3 thickness depth Vs thickness depth Vs thickness depth Vs j(ft) (ifts) (ft) (ft) MItS) (ft ft ft/S) 10.0 380.0 5,487 10.0 380.0 3,495 10.0 380.0 8,615 10.0 390.0 5,492 10.0 390.0 3,499 10.0 390.0 8,623 10.0 400.0 5,497 10.0 400.0 3,502 10.0 400.0 8,631 10.0 410.0 5,502 10.0 410.0 3,505 10.0 410.0 18,638 10.0 420.0 5,507 10.0 420.0 3,508 10.0 420.0 8,646 10.0 430.0 5,512 10.0 430.0 3,511 10.0 430.0 8,654 10.0 440.0 5,517 10.0 440.0 3,514 10.0 440.0 8,662 10.0 450.0 5,522 10.0 450.0 3,518 10.0 450.0 8,670 10.0 460.0 5,527 10.0 460.0 3,521 10.0 460.0 8,678 10.0 470.0 5,532 10.0 470.0 3,524 10.0 470.0 8,686 10.0 480.0 5,537 10.0 480.0 3,527 10.0 480.0 8,693 10.0.. 490.0 5,542 10.0 490.0 3,530 10.0 490.0 8,701 10.0 500.0 5,547 10.0 500.0 3,534 10.0 500.0 8,709 100.0 600.0 5,572 100.0 600.0 3,550 100.0 600.0 8,748 100.0 700.0 5,622 100.0 700.0 3,581 100.0 700.0 8,827 100.0 800.0 5,672 100.0 800.0 3,613 100.0 800.0 8,905 100.0 899.9 5,722 100.0 899.9 3,645 100.0 899.9 8,984 100.0 999.9 5,772 100.0 999.9 3,677 100.0 999.9 9,062 100.0 1,099.9 5,822 100.0 1,099.9 3,709 100.0 1,099.9 9,141 100.0 1,199.9 5,872 100.0 1,199.9 3,741 100.0 1,199.9 9,219 100.0 1,299.9 5,922 100.0 1,299.9 3,772 100.0 1,299.9 9,285 100.0 1,399.9 5,972 100.0 1,399.9 3,804 100.0 1,399.9 9,285 100.0 1,499.9 6,022 100.0 1,499.9 3,836 1 100.0 1,499.9 9,285 100.0 1,599.9 6,072 100.0 1,599.9 3,868 100.0 1,599.9 9,285 100.0 1,699.9 6,122 100.0 1,699.9 3,900 100.0 1,699.9 9,285 100.0 1,799.9 6,172 100.0 1,799.9 3,932 100.0 1,799.9 9,285 100.0 1,899.9 6,222 100.0 1,899.9 3,964 100.0 1,899.9 9,285 100.0 1,999.9 6,272 100.0 1,999.9 3,995 100.0 1,999.9 9,285 100.0 2,099.9 6,322 100.0 2,099.9 4,027 100.0 2,099.9 9,285 100.0 2,199.9 6,372 100.0 2,199.9 4,059 100.0 2,199.9 9,285 100.0 2,299.9 6,422 100.0 2,299.9 4,091 100.0 2,299.9 19,285 100.0 12,399.9 6,472 100.0 2,399.9 4,123 100.0 2,399.9 9,285 100.0 2,499.9 6,522 100.0 2,499.9 4,155 100.0 2,499.9 9,285 100.0 2,599.9 6,572 100.0 2,599.9 4,186 100.0 2,599.9 9,285 100.0 2,699.9 6,622 100.0 2,699.9 4,218 100.0 2,699.9 9,285 100.0 12,799.8 16,672 1 100.0 2,799.8 4,250 100.0 2,799.8 19,285 100.0 12,899.8 6,7221 100.0 2,899.8 4,282 100.0 2,899.8 9,285 100.0 12,999.8 6,772 1 100.0 12,999.8 4,31'4 1 100.0 2,999.8ý 9,285 12

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 1 site. (EPRI, 2013d)

Profile 1 Profile 2 Profile 3 thickness depth Vs thickness depth Vs thickness depth Vs (ft t (ftls) (f) (f) (ft/s) Ot) () (ftis) 100.0 3,099.8 6,822 100.0 3,099.8 4,346 100.0 3,099.8 9,285 100.0 3,199.8 6,872 100.0 3,199.8 4,378 100.0 3,199.8 9,285 100.0 3,299.8 6,922 100.0 3,299.8 4,409 100.0 3,299.8 9,285 100.0 3,399.8 6,972 100.0 3,399.8 4,441 100.0 3,399.8 9,285 100.0 3,499.8 7,022 100.0 3,499.8 4,473 100.0 3,499.8 9,285 100.0 3,599.8 7,072 100.0 3,599.8 4,505 100.0 3,599.8 9,285 100.0 3,699.8 7,122 100.0 3,699.8 4,537 100.0 3,699.8 9,285 100.0 3,799.8 7,172 100.0 3,799.8 4,569 100.0 3,799.8 9,285 100.0 3,899.8 7,222 100.0 3,899.8 4,600 100.0 3,899.8 9,285 100.0 3,999.8 7,272 100.0 3,999.8 4,632 100.0 3,999.8 9,285 100.0 4,099.8 7,322 100.0 4,099.8 4,664 100.0 4,099.8 9,285 100.0 4,199.8 7,372 100.0 4,199.8 4,696 100.0 4,199.8 9,285 100.0 4,299.8 7,422 100.0 4,299.8 4,728 100.0 4,299.8 9,285 100.0 4,399.8 7,472 100.0 4,399.8 4,760 100.0 4,399.8 9,285 100.0 4,499.8 7,522 100.0 4,499.8 4,792 100.0 4,499.8 9,285 100.0 4,599.8 7,572 100.0 4,599.8 4,823 100.0 4,599.8 9,285 100.0 4,699.8 7,622 100.0 4,699.8 4,855 100.0 4,699.8 9,285 100.0 4,799.7 7,672 100.0 4,799.7 4,887 100.0 4,799.7 9,285 100.0 4,899.7 7,722 100.0 4,899.7 4,919 100.0 4,899.7 9,285 100.0 4,999.7 7,772 100.0 4,999.7 4,951 100.0 4,999.7 9,285 3,280.8 8,280.6 9,285 3,280.8 8,280.6 9,285 3,280.8 8,280.6 9,285 2.3.2.1 Shear Modulus and Damping Curves Nonlinear dynamic material properties were not available for ANO - Unit 1 for sedimentary rocks. The rock material over the upper 500 ft (150 m) was assumed to have behavior that could be modeled as either linear or non-linear. To represent this potential for either case in the upper 500 ft of sedimentary rock at the ANO - Unit 1 site, two sets of shear modulus reduction and hysteretic damping curves were used. Consistent with the SPID (EPRI, 2013a), the EPRI rock curves (model Ml) were considered to be appropriate to represent the upper range nonlinearity likely in the materials at this site and linear analyses (model M2) was assumed to represent an equally plausible alternative rock response across loading level. For the linear analyses, the low strain damping from the EPRI rock curves were used as the constant damping values in the upper 500 ft. (EPRI, 2013d) 13

2.3.2.2 Kappa Base-case kappa estimates were determined using Section B-5.1.3.1 of the SPID (EPRI, 2013a) for a firm CEUS rock site. Kappa for a firm rock site with at least 3,000 ft (1 km) of sedimentary rock may be estimated from the average S-wave velocity over the upper 100 ft (V,0oo) of the subsurface profile. For the ANO - Unit 1 site, with at least 3,000 ft (1 km) of firm rock, the corresponding average shear-wave velocities over the top 100 ft (31 m) were 5,325 ft/s (1,623 m/s) (P1), 3,391 ft/s (1,034 m/s) (P2), and 8,360 ft/s (2,548 m/s) (P3). The corresponding kappa estimates were 0.014 s, 0.023 s, and 0.009 s respectively. The range of kappa from 0.009 s to 0.023 s reflects a reasonable assessment of epistemic uncertainty. The suite of kappa estimates and associated weights are listed in Table 2.3.2-2. (EPRI, 2013d)

Table 2.3.2-2. Kappa Values and Weights Used for Site Response Analyses. (EPRI, 2013d)

Velocity Profile Kappa(s)

P1 0.014 P2 0.023 P3 0.009 Weights P1 0.4 P2 0.3 P3 0.3 I

_____________________________________________I G/Gmax and Hysteretic Damping Curves M1 0.5 M2 0.5 2.3.3 Randomization of Base Case Profiles To account for the aleatory variability in dynamic material properties that is expected to occur across a site at the scale of a typical nuclear facility, variability in the assumed shear-wave velocity profiles has been incorporated in the site response calculations. For the ANO - Unit 1 site, random shear wave velocity profiles were developed from the base case profiles shown in Figure 2.3.2-1. Consistent with the discussion in Appendix B of the SPID (EPRI, 2013a), the velocity randomization procedure made use of random field models which describe the statistical correlation between layering and shear wave velocity. The default randomization parameters developed in (Toro,1997) for United States Geological Survey "A" site conditions were used for this site. Thirty random velocity profiles were generated for each base case profile. These random velocity profiles were generated using a natural log standard deviation of 0.25 over the upper 50 ft and 0.15 below that depth. As specified in the SPID (EPRI, 2013a),

correlation of shear wave velocity between layers was modeled using the footprint correlation model. In the correlation model, a limit of +/-2 standard deviations about the median value in each layer was assumed for the limits on random velocity fluctuations. (EPRI, 2013d) 14

2.3.4 Input Spectra Consistent with the guidance in Appendix B of the SPID (EPRI, 2013a), input Fourier amplitude spectra were defined for a single representative earthquake magnitude (M 6.5) using two different assumptions regarding the shape of the seismic source spectrum (single-corner and double-corner). A range of 11 different input amplitudes (median peak ground accelerations (PGA) ranging from 0.01g to 1.5g) were used in the site response analyses. The characteristics of the seismic source and upper crustal attenuation properties assumed for the analysis of the ANO - Unit 1 site were the same as those identified in Tables B-4, B-5, B-6 and B-7 of the SPID (EPRI, 2013a) as appropriate for typical CEUS sites. (EPRI, 2013d) 2.3.5 Methodology To perform the site response analyses for the ANO - Unit 1 site, a random vibration theory (RVT) approach was employed. This process utilizes a simple, efficient approach for computing site-specific amplification functions and is consistent with existing NRC guidance and the SPID (EPRI, 2013a). The guidance contained in Appendix B of the SPID (EPRI, 2013a) on incorporating epistemic uncertainty in shear-wave velocities, kappa, non-linear dynamic properties and source spectra for plants with limited at-site information was followed for the ANO - Unit 1 site. (EPRI, 2013d) 2.3.6 Amplification Functions The results of the site response analysis consist of amplification factors (5% damped pseudo absolute response spectra) which describe the amplification (or de-amplification) of hard reference rock motion as a function of frequency and input reference rock amplitude. The amplification factors are represented in terms of a median amplification value and an associated standard deviation (sigma) for each oscillator frequency and input rock amplitude. Consistent with the SPID (EPRI, 2013a) a minimum median amplification value of 0.5 was employed in the present analysis. Figure 2.3.6-1 illustrates the median and +/-1 standard deviation in the predicted amplification factors developed for the eleven loading levels parameterized by the median reference (hard-rock) peak acceleration (0.01g to 1.50g) for profile P1 and EPRI (EPRI, 2013a) rock G/Gmax and hysteretic damping curves. The variability in the amplification factors results from variability in shear-wave velocity, depth to hard-rock, and modulus reduction and hysteretic damping curves. To illustrate the effects of nonlinearity at the ANO - Unit 1 firm rock site, Figure 2.3.6-2 shows the corresponding amplification factors developed with linear site response analyses (model M2). Between the linear and nonlinear (equivalent-linear) analyses, Figures 2.3.6-1 and Figure 2.3.6-2 respectively show only a minor difference for 0.5g loading level and below. Above about the 0.5g loading level, the differences increase significantly but only above about 20 Hz. Tabular data for Figure 2.3.6-1 and Figure 2.3.6-2 is provided For Information Only in Appendix A. (EPRI, 2013d) 15

0 C3 0 INPUT MlOTIONI0.05G 0

C) 0:

INPUT MOTION'0,20G 4-2 0

CZ c c0I I PT0 N . 0 C3 INPUT MOTION 0.40G to -1 to 0 10 ( 10 2 io - 1 1o 0 10 1 102 Frequency (Hz) Frequency (Hz)

AMPLIFICATION, ARKANSAS, MIPIKI M 6.5,. 1 CORNER: PAGE I OF 2 Figure 2.3.6-1. Example suite of amplification factors (5% damping pseudo-absolute acceleration spectra) developed for the mean base-case profile (P1), EPRI rock modulus reduction and hysteretic damping curves (model Ml), and base-case kappa (K1) at eleven loading levels of hard-rock median peak acceleration values from 0.01g to 1.50g. M 6.5 and single-corner source model (EPRI, 2013a). (EPRI, 2013d) 16

1 I 111111 I IIIIIIII I I 115111 C3 0

0 E 0-II SINPUT rIOTIGIOSUCQ INPUT MOTION' 0.75G 0

0 0

INPUT MOTICtl 1.OOG INPUT MOTIONI 1.25G 03 CC-INPUT MOTIONI 1.50G 0

10 -1 LO 0 10 1 a 2 Frequency (Hz)

AMPLIFICATION, ARKANSAS, MIPIKI M 6.5, 1 CORNER: PAGE 2 OF 2 Figure 2.3.6-1 .(cont.)

17

C-4-J E

a:

INPUiT MOTcION .OIG INPUT MO TION 0.05G C-

- "- --..--. *Fz INPUT MOTION~ 0. OG 2 INPUTr NOTION~ 0.20G 0

U INPUT MOTION~ 0.40C; 1 10 2 10 I- 10 2 t -1 to 0 IQ I 100 10I Frequency (Hz) Frequency (Hz)

AMPLIFICATION, ARKANSAS, M2PIKI M 6.5, 1 CORNER: PAGE 1 OF 2 Figure 2.3.6-2.Example suite of amplification factors (5% damping pseudo absolute acceleration spectra) developed for the mean base-case profile (P1), linear site response (model M2), and base-case kappa (K1) at eleven loading levels of hard rock median peak acceleration values from 0.01 g to 1.50g. M 6.5 and single-corner source model (EPRI, 2013a). (EPRI, 2013d) 18

C

.0 (

C3 U

INPUT MOTION' 0.50G INPUT MOTIO 0,7--

C)

Cc 0

INPUT MOTICtI I.OOG 1.25G INPUT MIOTIONI 4j0 CC 4-12 INPUT MlOTION~ 1.50G io-1 to 0 10o1 10 2 Frequency (Hz)

AMPLIFICATION, ARKANSAS, M2PIK1 M 6.5, 1 CORNER: PRAGE 2OF 2 Figure 2.3.6-2.(cont.)

19

2.3.7 Control Point Seismic Hazard Curves The procedure to develop probabilistic site-specific control point hazard curves used in the present analysis follows the methodology described in Section B-6.0 of the SPID (EPRI, 2013a).

This procedure (referred to as Method 3) computes a site-specific control point hazard curve for a broad range of spectral accelerations given the site-specific bedrock hazard curve and site-specific estimates of soil or soft-rock response and associated uncertainties. This process is repeated for each of the seven spectral frequencies for which ground motion equations are available. The dynamic response of the materials below the control point was represented by the frequency- and amplitude-dependent amplification functions (median values and standard deviations) developed and described in the previous section. The resulting control point mean hazard curves for ANO - Unit 1 are shown in Figure 2.3.7-1 for the seven spectral frequencies for which ground motion equations are defined. Tabulated values of mean and fractile seismic hazard curves and site response amplification functions are provided in Appendix A. (EPRI, 2013d)

Total Mean Soil Hazard by Spectral Frequency at Arkansas 1E-2 ....

1E3 U

03 -25 Hz S.-10 Hz U~~ -- 5Hz

... PGA

@1 -2.5 Hz 03 -1 Hz "M -0.5 Hz 1E-6 1E-7 . . . . -. . . . .. .

0.01 0.1 1 10 Spectral acceleration (g)

Figure 2.3.7-1. Control point mean hazard curves for spectral frequencies of 0.5, 1.0, 2.5, 5.0, 10, 25 and PGA (100 Hz) at ANO - Unit 1. (EPRI, 2013d) 2.4 Control PointResponse Spectrum The control point hazard curves described above have been used to develop uniform hazard response spectra (UHRS) and the GMRS. The UHRS were obtained through linear 20

interpolation in log-log space to estimate the spectral acceleration at each spectral frequency for the 10-4 and 10-5 per year hazard levels. Table 2.4-1 shows the UHRS and GMRS accelerations for a range of spectral frequencies. (EPRI, 2013d) 21

Table 2.4-1. UHRS and GMRS for ANO - Unit 1. (EPRI, 2013d)

Freq. (Hz) 14UHRS 109UHRS GMRS (g) 100 1.82E-01 4.88E-01 2.40E-01 90 1.82E-01 4.91E-01 2.42E-01 80 1.83E-01 4.97E-01 2.44E-01 70 1.86E-01 5.09E-01 2.50E-01 60 1.96E-01 5.42E-01 2.65E-01 50 2.20E-01 6.22E-01 3.03E-01 40 2.59E-01 7.42E-01 3.61E-01 35 2.79E-01 8.02E-01 3.89E-01 30 3.02E-01 8.67E-01 4.21E-01 25 3.26E-01 9.32E-01 4.53E-01 20 3.54E-01 9.85E-01 4.82E-01 15 3.81E-01 1.03E+00 5.06E-01 12.5 3.90E-01 1.03E+00 5.10E-01 10 3.86E-01 1.OOE+00 4.96E-01 9 3.80E-01 9.71E-01 4.83E-01 8 3.76E-01 9.46E-01 4.72E-01 7 3.64E-01 9.06E-01 4.53E-01 6 3.50E-01 8.54E-01 4.29E-01 5 3.32E-01 7.91E-01 3.99E-01 4 2.92E-01 6.90E-01 3.48E-01 3.5 - 2.71E-01 6.36E-01 3.22E-01 3 2.44E-01 5.67E-01 2.87E-01 2.5 2.11E-01 4.87E-01 2.47E-01 2 1.91E-01 4.35E-01 2.21E-01 1.5 1.73E-01 3.84E-01 1.96E-01 1.25 1.57E-01 3.43E-01 1.76E-01 1 1.41E-01 3.01E-01 1.55E-01 0.9 1.28E-01 2.76E-01 1.42E-01 0.8 1.20E-01 2.59E-01 1.33E-01 0.7 1.13E-01 2.47E-01 1.27E-01 0.6 1.OOE-01 2.20E-01 1.13E-01 0.5 8.46E-02 1.88E-01 9.62E-02 0.4 6.77E-02 1.51 E-01 7.70E-02 0.35 5.92E-02 1.32E-01 6.74E-02 0.3 5.08E-02 1.13E-01 5.77E-02 0.25 4.23E-02 9.41E-02 4.81E-02 0.2 3.38E-02 7.53E-02 3.85E-02 0.15 2.54E-02 5.65E-02 2.89E-02 0.125 2.12E-02 4.71E-02 2.41E-02 0.1 1.69E-02 3.76E-02 1.92E-02 22

The 1 E-4 and 1 E-5 UHRS are used to compute the GMRS at the control point and are shown in Figure 2.4-1. (EPRI, 2013d)

Mean Soil UHRS and GMRS at Arkansas 1.2 1.

-1E-5 UHRS 0.8

.2 WU -GMRS 0.6

-1E-4 UHRS CA 0.4 0.2 0.

0.1 1 10 100 Spectral frequency, Hz Figure 2.4-1. UHRS for 10"4 and 10' and GMRS at control point for ANO - Unit I (5%-damped response spectra). (EPRI, 2013d) 3.0 Plant Design Basis and Beyond Design Basis Evaluation Ground Motion The design bases for ANO - Unit 1 are identified in the Updated Final Safety Analysis Report (Entergy, 2014a).and other pertinent documents.

An evaluation for beyond design basis (BDB) ground motions was performed in the Individual Plant Examination of External Events (IPEEE). The IPEEE capacity response spectrum is included below for screening purposes.

3.1 Safe Shutdown Earthquake Descriptionof Spectral Shape The SSEs for ANO - Unit 1 were developed in accordance with 10 CFR Part 100, Appendix A through an evaluation of the maximum earthquake potential for the region surrounding the site.

Considering the historic seismicity of the site region, Entergy determined that because of the excellent formation conditions and the recent general quiescence of the area that a low earthquake intensity could be selected. However, considering the New Madrid earthquake, which is the only severe earthquake experienced in the central United States in historic time, an 23

intensity of VII on the Modified Mercalli Intensity Scale of 1931 has been assigned for the site.

This is considered to be conservative and corresponds to a design spectrum of 0.20g for the SSE. (Entergy, 2014a)

The SSE is defined in terms of a PGA and a design response spectrum. Table 3.1-1 shows the spectral acceleration (SA) values as a function of frequency for the 5% damped horizontal SSE.

(EPRI, 2013d)

Table 3.1-1. SSE for ANO - Unit 1. (EPRI, 2013d)

Freq.

(Hz) SA (g) 0.5 0.10 1.0 0.17 2.5 0.29 5.0 0.31 10 0.24 25 0.20 100 0.20 3.2 Control Point Elevation The SSE control point elevation is at Elevation 326 ft. It is defined to be at the bottom of the foundation of the highest safety-related building, which is the Reactor Building. The bottom of the foundation for the Reactor Building is at 326 ft within the Pennsylvanian shale (Entergy, 2014a).

3.3 IPEEE Descriptionand Capacity Response Spectrum A "modified" full-scope Seismic Margin Assessment (SMA) was performed to support the IPEEE for ANO - Unit 1. The results of the IPEEE were submitted to the NRC (Entergy, 1996). Results of the NRC review are documented in reference (U.S. NRC, 2001).

The ANO - Unit 1 Seismic IPEEE was performed using the Seismic Margins assessment option per the EPRI methodology of EPRI-6041 (EPRI, 1991). With this method, a seismic margins earthquake (SME) was postulated and the items needed for safe shutdown were then evaluated for the SME demand. Components and structures that were determined to have sufficient capacity to survive the SME without loss of function were screened-out. Items that did not screen were subjected to a more detailed evaluation, including calculation of a high-confidence of low-probability of failure (HCLPF) PGA for that item. A 0.30 PGA earthquake level and the NUREG/CR-0098 (U.S. NRC, 1978) median response spectra shape were used.

The IPEEE was reviewed for adequacy utilizing the guidance provided in Section 3.3 of the SPID (EPRI, 2013a). The IPEEE Adequacy Determination according to SPID (EPRI, 2013a)

Section 3.3.1 is included in Appendix B.

24

The results of the review have shown, in accordance with the criteria established in SPID (EPRI, 2013a) Section 3.3, that the IPEEE is adequate to support screening of the updated seismic hazard for ANO - Unit 1. The review also concluded that the risk insights obtained from the IPEEE are still valid under the current plant configuration.

The Safety-related structures at ANO - Unit I are founded on rock. As stated in NUREG 1407 Section 3.2.1, a plant in the full scope category that is located on a rock site is not required to perform a soil failure evaluation.

The 5% damped horizontal IPEEE HCLPF Spectrum (IHS) spectral acceleration for ANO - Unit I is provided in Table 3.3-1. The SSE and the IHS are shown in Figure 3.3-1.

Table 3.3-1. IHS for ANO - Unit I IPEEE (Entergyl 996).

Freq. HIS (Hz) (g) 0.5 0.15 1.0 0.29 2.2 0.64 8.0 0.64 10 0.57 25 0.35 33 0.30 100 0.30 0.7

-SSE

-SS

- IHS 0.5 0.4 0.3 0.2 0.1 0

0.1 1 10 100 Frequency (Hz) 25

Figure 3.3-1. SSE and IHS Response Spectra for ANO - Unit 1.

4.0 Screening Evaluation In accordance with SPID (EPRI, 2013a) Section 3, a screening evaluation was performed as described below.

4.1 Risk Evaluation Screening (1 to 10 Hz)

In the 1 to 10 Hz part of the response spectrum, the IHS exceeds the GMRS for ANO - Unit 1.

Based on this comparison, a risk evaluation will not be performed.

4.2 High Frequency Screening (> 10 Hz)

For a portion of the range above 10 Hz, the GMRS exceeds the SSE. Therefore, ANO - Unit 1 screens-in for a High Frequency Confirmation.

4.3 Spent Fuel Pool Evaluation Screening (1 to 10 Hz)

In the 1 to 10 Hz part of the response spectrum, the GMRS exceeds the SSE. Therefore, ANO

- Unit 1 screens-in for a Spent Fuel Pool evaluation.

5.0 Interim Actions Based on the screening evaluation, the expedited seismic evaluation described in EPRI 3002000704 (EPRI, 2013c) will be performed as proposed in a letter to NRC (ML13101A379) dated April 9, 2013 (NEI, 2013a) and agreed to by NRC (ML13106A331) in a letter dated May 7, 2013 (U.S. NRC, 2013).

Consistent with NRC letter (ML14030A046) dated February 20, 2014 (U.S. NRC, 2014), the seismic hazard reevaluations presented herein are distinct from the current design and licensing bases of ANO - Unit 1. Therefore, the results do not call into question the operability or functionality of SSCs and are not reportable pursuant to 10 CFR 50.72, "Immediate notification requirements for operating nuclear power reactors," and 10 CFR 50.73, "Licensee event report system".

The NRC letter also requests that licensees provide an interim evaluation or actions to demonstrate that the plant can cope with the reevaluated hazard while the expedited approach and risk evaluations are conducted. In response to that request, NEI letter dated March 12, 2014 (NEI, 2014), provides seismic core damage risk estimates using the updated seismic hazards for the operating nuclear plants in the Central and Eastern United States. These risk estimates continue to support the following conclusions of the NRC GI-199 Safety/Risk Assessment (U.S. NRC, 2010):

26

Overall seismic core damage risk estimates are consistent with the Commission's Safety Goal Policy Statement because they are within the subsidiary objective of 10-4/year for core damage frequency. The GI-1 99 Safety/Risk Assessment, based in part on information from the U.S. Nuclear Regulatory Commission's (NRC's) Individual Plant Examination of External Events (IPEEE) program, indicates that no concern exists regarding adequate protection and that the current seismic design of operating reactors provides a safety margin to withstand potential earthquakes exceeding the original design basis.

ANO - Unit 1 is included in the March 12, 2014 risk estimates (NEI, 2014). Using the methodology described in the NEI letter, all plants were shown to be below 10-4/year; thus, the above conclusions apply.

In accordance with the Near-Term Task Force Recommendation 2.3, ANO - Unit 1 performed seismic walkdowns using the guidance in EPRI Report 1025286 (EPRI, 2012). The seismic walkdowns were completed and captured in Fukushima Seismic Walkdown Report (Entergy, 2013). The goal of the walkdowns was to verify current plant configuration with the existing licensing basis, to verify the current maintenance plans, and to identify any vulnerabilities. The walkdown also verified that any vulnerabilities identified in the IPEEE (Entergy, 1996) were adequately addressed. The results of the walkdown, including any identified corrective actions, confirm that ANO - Unit 1 can adequately respond to a seismic event.

6.0 Conclusions In accordance with the 50.54(f) request for information (U.S. NRC, 2012), a seismic hazard and screening evaluation was performed for Arkansas Nuclear One - Unit 1. A GMRS was developed solely for the purpose of screening for additional evaluations in accordance with the SPID (EPRI, 2013a). Based on the results of the screening evaluation, ANO - Unit 1 screens-in for a High Frequency Confirmation and a Spent Fuel Pool evaluation. Additionally, based on the results of the screening evaluation, ANO - Unit 1 screens-out of a risk evaluation.

7.0 References 10 CFR Part 50. Title 10, Code of Federal Regulations, Part 50, "Domestic Licensing of Production and Utilization Facilities," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 50.72. Title 10, Code of Federal Regulations, Part 50.72, "Immediate Notification Requirements for Operating Nuclear Power Reactors," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 50.73. Title 10, Code of Federal Regulations, Part 50.73, "Licensee Event Report System," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 100. Title 10, Code of Federal Regulations, Part 100, "Reactor Site Criteria," U.S.

Nuclear Regulatory Commission, Washington DC.

27

CEUS-SSC (2012). "Central and Eastern United States Seismic Source Characterization for Nuclear Facilities, U.S. Nuclear Regulatory Commission Report," NUREG-2115; EPRI Report 1021097, 6 Volumes; DOE Report# DOE/NE-0140.

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28

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"Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)

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U.S. NRC (2014). NRC Letter, Eric J. Leeds to All Power Reactor Licensees, "Supplemental Information Related to Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Seismic Hazard Reevaluations for Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident," dated February 20, 2014.

29

Appendix A Tabulated Data 30

Table A-la. Mean and Fractile Seismic Hazard Curves for 100 Hz (PGA) at ANO - Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 8.02E-02 4.31E-02 6.64E-02 8.12E-02 9.51E-02 9.93E-02 0.001 6.09E-02 2.76E-02 4.77E-02 6.09E-02 7.66E-02 8.72E-02 0.005 1.83E-02 7.77E-03 1.16E-02 1.69E-02 2.29E-02 3.84E-02 0.01 9.30E-03 3.73E-03 5.35E-03 8.23E-03 1.20E-02 2.25E-02 0.015 6.06E-03 2.1OE-03 3.05E-03 5.27E-03 8.23E-03 1.51E-02 0.03 2.60E-03 5.50E-04 8.60E-04 1.92E-03 4.25E-03 7.34E-03 0.05 1.22E-03 1.77E-04 2.92E-04 6.93E-04 2.16E-03 4.19E-03 0.075 6.12E-04 7.45E-05 1.27E-04 2.96E-04 9.93E-04 2.32E-03 0.1 3.57E-04 4.07E-05 7.34E-05 1.67E-04 5.20E-04 1.38E-03 0.15 1.55E-04 1.74E-05 3.42E-05 7.66E-05 2.04E-04 5.75E-04 0.3 3.21E-05 3.47E-06 7.77E-06 1.92E-05 4.50E-05 1.04E-04 0.5 9.43E-06 7.89E-07 2.01E-06 5.91E-06 1.51E-05 2.92E-05 0.75 3.38E-06 1.82E-07 5.42E-07 1.98E-06 5.66E-06 1.11E-05

1. 1.55E-06 5.35E-08 1.84E-07 8.23E-07 2.68E-06 5.42E-06 1.5 4.76E-07 7.03E-09 3.19E-08 1.98E-07 8.12E-07 1.82E-06

3. 4.66E-08 2.39E-10 9.11E-10 1.02E-08 7.23E-08 2.1OE-07

5. 6.22E-09 1.42E-10 1.84E-10 8.35E-10 8.12E-09 3.01E-08 7.5 1.02E-09 1.32E-10 1.60E-10 2.13E-10 1.20E-09 5.12E-09

10. 2.51E-10 1.21E-10 1.32E-10 1.82E-10 3.57E-10 1.36E-09 31

Table A-i b. Mean and Fractile Seismic Hazard Curves for 25 Hz at ANO -

Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 8.59E-02 5.58E-02 7.34E-02 8.72E-02 9.93E-02 9.93E-02 0.001 6.98E-02 3.90E-02 5.83E-02 7.03E-02 8.23E-02 9.37E-02 0.005 2.62E-02 1.21E-02 1.84E-02 2.46E-02 3.19E-02 5.12E-02 0.01 1.45E-02 6.64E-03 9.24E-03 1.32E-02 1.79E-02 3.19E-02 0.015 9.81E-03 4.25E-03 5.91E-03 8.85E-03 1.27E-02 2.22E-02 0.03 4.61E-03 1.49E-03 2.16E-03 3.90E-03 6.73E-03 1.07E-02 0.05 2.41E-03 5.42E-04 8.35E-04 1.79E-03 4.01E-03 6.54E-03 0.075 1.36E-03 2.25E-04 3.68E-04 8.60E-04 2.39E-03 4.25E-03 0.1 8.75E-04 1.25E-04 2.1OE-04 4.98E-04 1.51E-03 3.01E-03 0.15 4.45E-04 5.66E-05 1.01E-04 2.35E-04 6.93E-04 1.62E-03 0.3 1.19E-04 1.51E-05 2.96E-05 6.73E-05 1.64E-04 3.84E-04 0.5 4.05E-05 5.20E-06 1.10E-05 2.64E-05 6.OOE-05 1.13E-04 0.75 1.65E-05 1.98E-06 4.50E-06 1.15E-05 2.60E-05 4.56E-05

1. 8.51E-06 9.37E-07 2.22E-06 5.91E-06 1.40E-05 2.39E-05 1.5 3.19E-06 2.80E-07 7.13E-07 2.13E-06 5.42E-06 9.51E-06

3. 4.77E-07 2.19E-08 6.54E-08 2.57E-07 8.60E-07 1.64E-06

5. 9.36E-08 2.25E-09 7.66E-09 3.90E-08 1.67E-07 3.57E-07 7.5 2.19E-08 3.95E-10 1.16E-09 6.83E-09 3.73E-08 9.11E-08

10. 7.14E-09 2.01E-10 3.57E-10 1.82E-09 1.15E-08 3.09E-08 32

Table A-ic. Mean and Fractile Seismic Hazard Curves for 10 Hz at ANO -

Unit 1. (EPRI, ý013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.37E-02 7.34E-02 8.00E-02 9.37E-02 9.93E-02 9.93E-02 0.001 8.1OE-02 5.75E-02 6.83E-02 8.12E-02 9.37E-02 9.93E-02 0.005 3.41E-02 1.79E-02 2.46E-02 3.37E-02 4.31E-02 5.35E-02 0.01 1.86E-02 9.24E-03 1.25E-02 1.79E-02 2.35E-02 3.23E-02 0.015 1.25E-02 6.09E-03 8.23E-03 1.18E-02 1.62E-02 2.25E-02 0.03 6.11E-03 2.57E-03 3.57E-03 5.58E-03 8.47E-03 1.16E-02 0.05 3.41E-03 1.10E-03 1.62E-03 2.96E-03 5.20E-03 7.45E-03 0.075 2.02E-03 5.05E-04 7.77E-04 1.57E-03 3.33E-03 5.12E-03 0.1 1.34E-03 2.76E-04 4.37E-04 9.37E-04 2.29E-03 3.79E-03 0.15 6.90E-04 1.13E-04 1.87E-04 4.19E-04 1.16E-03 2.22E-03 0.3 1.78E-04 2.46E-05 4.50E-05 1.02E-04 2.57E-04 5.83E-04 0.5 5.54E-05 7.55E-06 1.51E-05 3.52E-05 7.89E-05 1.67E-04 0.75 2.06E-05 2.68E-06 5.75E-06 1.40E-05 3.14E-05 5.83E-05

1. 1.00E-05 1.16E-06 2.64E-06 7.03E-06 1.60E-05 2.84E-05 1.5 3.47E-06 3.01E-07 7.66E-07 2.35E-06 5.91E-06 1.05E-05

3. 4.83E-07 1.67E-08 5.58E-08 2.57E-07 8.72E-07 1.72E-06

5. 9.34E-08 1.21E-09 4.98E-09 3.57E-08 1.67E-07 3.79E-07 7.5 2.20E-08 2.32E-10 6.54E-10 6.09E-09 3.73E-08 9.65E-08

10. 7.22E-09 1.82E-10 2.39E-10 1.60E-09 1.16E-08 3.28E-08 33

Table A-id. Mean and Fractile Seismic Hazard Curves for 5.0 Hz at ANO -

Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.55E-02 7.55E-02 8.23E-02 9.65E-02 9.93E-02 9.93E-02 0.001 8.43E-02 6.OOE-02 6.93E-02 8.47E-02 9.93E-02 9.93E-02 0.005 3.61 E-02 1.79E-02 2.49E-02 3.52E-02 4.77E-02 5.50E-02 0.01 1.89E-02 8.98E-03 1.25E-02 1.82E-02 2.57E-02 3.01E-02 0.015 1.23E-02 5.83E-03 8.OOE-03 1.18E-02 1.67E-02 2.01E-02 0.03 5.64E-03 2.35E-03 3.33E-03 5.35E-03 8.OOE-03 9.93E-03 0.05 3.08E-03 9.65E-04 1.49E-03 2.72E-03 4.70E-03 6.36E-03 0.075 1.78E-03 4.25E-04 6.73E-04 1.40E-03 2.92E-03 4.31E-03 0.1 1.14E-03 2.22E-04 3.63E-04 8.OOE-04 1.92E-03 3.23E-03 0.15 5.60E-04 8.47E-05 1.44E-04 3.33E-04 8.98E-04 1.90E-03 0.3 1.29E-04 1.53E-05 2.80E-05 6.45E-05 1.69E-04 4.98E-04 0.5 3.54E-05 3.95E-06 8.OOE-06 1.92E-05 4.70E-05 1.20E-04 0.75 1.16E-05 1.23E-06 2.68E-06 7.03E-06 1.72E-05 3.52E-05

1. 5.13E-06 4.90E-07 1.15E-06 3.28E-06 8.12E-06 1.53E-05 1.5 1.58E-06 1.15E-07 3.01E-07 1.01E-06 2.68E-06 4.98E-06

3. 1.85E-07 5.75E-09 1.95E-08 9.24E-08 3.23E-07 6.83E-07

5. 3.21E-08 5.20E-10 1.72E-09 1.10E-08 5.35E-08 1.34E-07 7.5 6.96E-09 1.92E-10 3.14E-10 1.67E-09 1.05E-08 3.14E-08

10. 2.17E-09 1.55E-10 1.87E-10 4.77E-10 3.01E-09 1.01E-08 34

Table A-le. Mean and Fractile Seismic Hazard Curves for 2.5 Hz at ANO -

Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.00E-02 6.73E-02 7.55E-02 8.98E-02 9.93E-02 9.93E-02 0.001 7.37E-02 4.77E-02 5.75E-02 7.34E-02 9.11E-02 9.93E-02 0.005 2.44E-02 1.18E-02 1.57E-02 2.32E-02 3.33E-02 4.01E-02 0.01 1.17E-02 5.42E-03 7.34E-03 1.1OE-02 1.60E-02 1.98E-02 0.015 7.39E-03 3.23E-03 4.50E-03 7.03E-03 1.02E-02 1.29E-02 0.03 3.35E-03 1.04E-03 1.62E-03 3.05E-03 5.05E-03 6.73E-03 0.05 1.74E-03 3.52E-04 6.09E-04 1.40E-03 2.92E-03 4.31E-03 0.075 9.27E-04 1.31E-04 2.35E-04 6.09E-04 1.62E-03 2.80E-03 0.1 5.49E-04 6.OOE-05 1.11E-04 3.01E-04 9.37E-04 1.95E-03 0.15 2.35E-04 1.84E-05 3.57E-05 1.01E-04 3.57E-04 9.65E-04 0.3 4.12E-05 2.13E-06 4.70E-06 1.38E-05 5.05E-05 1.64E-04 0.5 9.27E-06 3.73E-07 9.65E-07 3.33E-06 1.16E-05 3.09E-05 0.75 2.61E-06 8.12E-08 2.46E-07 1.05E-06 3.63E-06 8.47E-06

1. 1.04E-06 2.53E-08 8.72E-08 4.31E-07 1.60E-06 3.57E-06 1.5 2.82E-07 4.19E-09 1.72E-08 1.10E-07 4.70E-07 1.08E-06

3. 2.84E-08 2.72E-10 7.89E-10 6.93E-09 4.50E-08 1.29E-07

5. 4.43E-09 1.82E-10 1.98E-10 7.45E-10 5.91E-09 2.07E-08 7.5 8.72E-10 1.32E-10 1.82E-10 2.19E-10 1.04E-09 4.07E-09

10. 2.52E-10 1.21E-10 1.32E-10 1.82E-10 3.52E-10 1.21E-09 35

Table A-if. Mean and Fractile Seismic Hazard Curves for 1.0 Hz at ANO -

Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 6.70E-02 3.63E-02 4.77E-02 6.73E-02 8.47E-02 9.51E-02 0.001 4.59E-02 2.04E-02 2.96E-02 4.56E-02 6.09E-02 7.23E-02 0.005 1.18E-02 4.63E-03 6.83E-03 1.10E-02 1.64E-02 2.13E-02 0.01 5.95E-03 2.01E-03 3.19E-03 5.50E-03 8.60E-03 1.13E-02 0.015 4.OOE-03 1.1OE-03 1.87E-03 3.63E-03 6.09E-03 8.OOE-03 0.03 1.92E-03 2.84E-04 5.75E-04 1.55E-03 3.28E-03 4.77E-03 0.05 9.45E-04 7.89E-05 1.79E-04 6.26E-04 1.74E-03 2.88E-03 0.075 4.54E-04 2.42E-05 5.91E-05 2.39E-04 8.35E-04 1.60E-03 0.1 2.42E-04 9.79E-06 2.46E-05 1.07E-04 4.31E-04 9.37E-04 0.15 8.57E-05 2.49E-06 6.54E-06 3.01E-05 1.40E-04 3.57E-04 0.3 1.01E-05 1.84E-07 5.75E-07 2.80E-06 1.42E-05 4.25E-05 0.5 1.77E-06 2.01E-08 7.77E-08 4.77E-07 2.49E-06 7.23E-06 0.75 4.57E-07 2.88E-09 1.36E-08 1.1OE-07 6.73E-07 1.98E-06

1. 1.86E-07 7.45E-10 3.68E-09 3.79E-08 2.68E-07 8.47E-07 1.5 5.52E-08 2.16E-10 6.09E-10 7.77E-09 7.13E-08 2.64E-07

3. 6.63E-09 1.44E-10 1.82E-10 4.77E-10 5.91E-09 2.96E-08

5. 1.17E-09 1.32E-10 1.46E-10 1.82E-10 8.OOE-10 4.50E-09 7.5 2.58E-10 1.21E-10 1.32E-10 1.82E-10 2.42E-10 9.51E-10

10. 8.12E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 3.52E-10 36

Table A-lg. Mean and Fractile Seismic Hazard Curves for 0.5 Hz at ANO -

Unit 1. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 3.27E-02 1.62E-02 2.25E-02 3.19E-02 4.31E-02 5.20E-02 0.001 1.92E-02 8.72E-03 1.25E-02 1.82E-02 2.60E-02 3.28E-02 0.005 4.97E-03 1.51E-03 2.49E-03 4.56E-03 7.45E-03 9.79E-03 0.01 2.75E-03 4.83E-04 9.79E-04 2.39E-03 4.50E-03 6.26E-03 0.015 1.86E-03 2.07E-04 4.77E-04 1.49E-03 3.28E-03 4.77E-03 0.03 7.82E-04 3.42E-05 9.65E-05 4.43E-04 1.49E-03 2.64E-03 0.05 3.24E-04 7.03E-06 2.16E-05 1.27E-04 5.83E-04 1.32E-03 0.075 1.35E-04 1.77E-06 5.75E-06 3.79E-05 2.16E-04 6.OOE-04 0.1 6.59E-05 6.26E-07 2.07E-06 1.44E-05 9.37E-05 3.01E-04 0.15 2.1OE-05 1.27E-07 4.63E-07 3.33E-06 2.53E-05 9.51E-05 0.3 2.17E-06 5.58E-09 2.76E-08 2.35E-07 2.07E-06 9.11E-06 0.5 3.56E-07 5.05E-10 2.60E-09 3.05E-08 3.14E-07 1.55E-06 0.75 8.87E-08 1.92E-10 4.63E-10 5.35E-09 7.13E-08 4.07E-07

1. 3.54E-08 1.82E-10 2.16E-10 1.53E-09 2.42E-08 1.62E-07 1.5 1.04E-08 1.32E-10 1.82E-10 3.42E-10 5.12E-09 4.37E-08

3. 1.26E-09 1.21E-10 1.32E-10 1.82E-10 4.07E-10 3.79E-09

5. 2.27E-10 1.21E-10 1.32E-10 1.82E-10 1.82E-10 5.83E-10 7.5 5.06E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 2.13E-10

10. 1.61E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 1.82E-10 37

Table A-2. Amplification Functions for ANO - Unit 1. (EPRI, 2013d)

Median Sigma Median Sigma Median Sigma Median Sigma PGA AF In(AF) 25 Hz AF In(AF) 10 Hz AF In(AF) 5 Hz AF In(AF) 1.00E-02 1.08E+00 4.75E-02 1.30E-02 9.47E-01 5.76E-02 1.90E-02 1.02E+00 9.03E-02 2.09E-02 1.17E+00 9.85E-02 4.95E-02 9.08E-01 6.43E-02 1.02E-01 7.27E-01 1.11E-01 9.99E-02 9.80E-01 1.06E-01 8.24E-02 1.16E+00 1.04E-01 9.64E-02 8.49E-01 7.06E-02 2.13E-01 6.89E-01 1.24E-01 1.85E-01 9.67E-01 1.09E-01 1.44E-01 1.15E+00 1.05E-01 1.94E-01 8.OOE-01 7.61E-02 4.43E-01 6.59E-01 1.32E-01 3.56E-01 9.50E-01 1.12E-01 2.65E-01 1.14E+00 1.08E-01 2.92E-01 7.74E-01 7.92E-02 6.76E-01 6.41E-01 1.35E-01 5.23E-01 9.37E-01 1.14E-01 3.84E-01 1.13E+00 1.09E-01 3.91 E-01 7.56E-01 8.13E-02 9.09E-01 6.27E-01 1.38E-01 6.90E-01 9.26E-01 1.17E-01 5.02E-01 1.12E+00 1.11E-01 4.93E-01 7.42E-01 8.27E-02 1.15E+00 6.16E-01 1.41 E-01 8.61 E-01 9.16E-01 1.18E-01 6.22E-01 1.11E+00 1.12E-01 7.41E-01 7.18E-01 8.48E-02 1.73E+00 5.94E-01 1.45E-01 1.27E+00 8.96E-01 1.21E-01 9.13E-01 1.1OE+00 1.15E-01 1.O1E+00 7.OOE-01 8.61E-02 2.36E+00 5.77E-01 1.47E-01 1.72E+00 8.79E-01 1.24E-01 1.22E+00 1.08E+00 1.17E-01 1.28E+00 6.85E-01 8.65E-02 3.01 E+00 5.61 E-01 1.50E-01 2.17E+00 8.64E-01 1.26E-01 1.54E+00 1.07E+00 1.18E-01 1.55E+00 6.74E-01 8.65E-02 3.63E+00 5.49E-01 1.51E-01 2.61 E+00 8.51 E-01 1.26E-01 1.85E+00 1.06E+00 1.19E-01 Median Sigma Median Sigma Median Sigma 2.5 Hz AF In(AF) 1 Hz AF In(AF) 0.5 Hz AF In(AF) 2.18E-02 1.09E+00 8.96E-02 1.27E-02 1.39E+00 1.12E-01 8.25E-03 1.25E+00 1.19E--01 7.05E-02 1.08E+00 8.90E-02 3.43E-02 1.38E+00 1.07E-01 1.96E-02 1.24E+00 1.15E--01 1.18E-01 1.08E+00 8.87E-02 5.51E-02 1.37E+00 1.05E-01 3.02E-02 1.24E+00 1.14E--01 2.12E-01 1.08E+00 8.88E-02 9.63E-02 1.37E+00 1.03E-01 5.11 E-02 1.24E+00 1.13E--01 3.04E-01 1.07E+00 8.89E-02 1.36E-01 1.37E+00 1.02E-01 7.1OE-02 1.24E+00 1.13E--01 3.94E-01 1.07E+00 8.91E-02 1.75E-01 1.38E+00 1.01E-01 9.06E-02 1.24E+00 1.13E-01 4.86E-01 1.07E+00 8.92E-02 2.14E-01 1.38E+00 1.OOE-01 1.10E-01 1.24E+00 1.13E--01 7.09E-01 1.07E+00 8.96E-02 3.10E-01 1.38E+00 9.89E-02 1.58E-01 1.25E+00 1.13E-01 9.47E-01 1.06E+00 9.09E-02 4.12E-01 1.39E+00 9.80E-02 2.09E-01 1.25E+00 1.13E-01 1.19E+00 1.06E+00 9.32E-02 5.18E-01 1.39E+00 9.76E-02 2.62E-01 1.25E+00 1.14E-01 1.43E+00 1.06E+00 9.45E-02 6.19E-01 1.39E+00 9.71 E-02 3.12E-01 1.25E+00 1.14E-01 38

Tables A-3a and A-3b are tabular versions of the typical amplification factors provided in Figures 2.3.6-1 and 2.3.6-2. Values are provided for two input motion levels at approximately 5 These factors are unverified and are 1 0 -4 and 10- mean annual frequency of exceedance.

provided for information only. The figures should be considered the governing information.

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Table A-3a. Median AFs and sigmas for Model 1, Profile 1, for 2 PGA levels.

For Information Only M1P1K1 Rock PGA=0.194 M1P1K1 PGA=0.741 Freq. med. Freq. med.

(Hz) Soil SA AF sigma ln(AF) (Hz) Soil SA AF sigma ln(AF) 100.0 0.161 0.828 0.081 100.0 0.516 0.697 0.100 87.1 0.162 0.814 0.082 87.1 0.520 0.679 0.101 75.9 0.164 0.788 0.083 75.9 0.525 0.648 0.103 66.1 0.168 0.740 0.086 66.1 0.535 0.592 0.107 57.5 0.176 0.662 0.092 57.5 0.554 0.509 0.114 50.1 0.190 0.596 0.105 50.1 0.591 0.445 0.129 43.7 0.209 0.554 0.118 43.7 0.641 0.408 0.144 38.0 0.232 0.559 0.134 38.0 0.703 0.413 0.162 33.1 0.254 0.578 0.148 33.1 0.771 0.435 0.176 28.8 0.280 0.638 0.150 28.8 0.847 0.485 0.186 25.1 0.299 0.675 0.142 25.1 0.920 0.530 0.177 21.9 0.313 0.741 0.149 21.9 0.969 0.596 0.176 19.1 0.326 0.783 0.145 19.1 1.012 0.641 0.175 16.6 0.339 0.846 0.139 16.6 1.060 0.708 0.169 14.5 0.350 0.914 0.154 14.5 1.105 0.782 0.170 12.6 0.358 0.959 0.161 12.6 1.145 0.842 0.177 11.0 0.350 0.963 0.136 11.0 1.130 0.860 0.163 9.5 0.344 0.989 0.112 9.5 1.106 0.890 0.134 8.3 0.342 1.065 0.110 8.3 1.099 0.968 0.126 7.2 0.336 1.117 0.105 7.2 1.097 1.040 0.125 6.3 0.328 1.161 0.091 6.3 1.070 1.087 0.101 5.5 0.314 1.164 0.113 5.5 1.027 1.100 0.118 4.8 0.302 1.144 0.101 4.8 0.989 1.091 0.115 4.2 0.284 1.109 0.108 4.2 0.929 1.063 0.120 3.6 0.276 1.107 0.089 3.6 0.904 1.069 0.097 3.2 0.261 1.110 0.103 3.2 0.866 1.093 0.106 2.8 0.246 1.102 0.090 2.8 0.827 1.106 0.100 2.4 0.225 1.093 0.083 2.4 0.760 1.106 0.090 2.1 0.208 1.110 0.070 2.1 0.703 1.131 0.069 1.8 0.191 1.142 0.092 1.8 0.642 1.161 0.086 1.6 0.184 1.270 0.102 1.6 0.614 1.287 0.098 1.4 0.166 1.328 0.076 1.4 0.550 1.347 0.077 1.2 0.152 1.377 0.078 1.2 0.498 1.392 0.077 1.0 0.141 1.415 0.070 1.0 0.458 1.428 0.068 0.91 0.121 1.334 0.078 0.91 0.390 1.344 0.076 0.79 0.105 1.288 0.077 0.79 0.338 1.296 0.075 0.69 0.095 1.299 0.084 0.69 0.300 1.305 0.082 0.60 0.082 1.287 0.067 0.60 0.257 1.291 0.065 0.52 0.069 1.266 0.066 0.52 0.214 1.270 0.065 0.46 0.058 1.284 0.087 0.46 0.179 1.286 0.086 0.10 0.002 1.205 0.033 0.10 0.007 1.195 0.035 40

Table A-3b. Median AFs and sigmas for Model 2, Profile 1, for 2 PGA levels.

For Information Only M2P1K1 PGA=0.194 M2P1K1 PGA=0.741 Freq. med. Freq. med.

(Hz) Soil SA AF sigma In(AF) (Hz) Soil SA AF sigma ln(AF) 100.0 0.169 0.872 0.055 100.0 0.613 0.828 0.058 87.1 0.171 0.858 0.055 87.1 0.620 0.811 0.059 75.9 0.173 0.833 0.055 75.9 0.632 0.781 0.059 66.1 0.178 0.785 0.055 66.1 0.655 0.725 0.059 57.5 0.188 0.709 0.057 57.5 0.703 0.646 0.063 50.1 0.206 0.647 0.069 50.1 0.789 0.594 0.081 43.7 0.230 0.610 0.084 43.7 0.894 0.569 0.098 38.0 0.257 0.619 0.096 38.0 1.005 0.590 0.108 33.1 0.282 0.642 0.109 33.1 1.101 0.621 0.118 28.8 0.311 0.707 0.105 28.8 1.208 0.692 0.112 25.1 0.328 0.740 0.113 25.1 1.262 0.728 0.118 21.9 0.341 0.808 0.123 21.9 1.298 0.799 0.127 19.1 0.353 0.847 0.117 19.1 1.326 0.840 0.121 16.6 0.364 0.909 0.117 16.6 1.353 0.904 0.119 14.5 0.373 0.973 0.137 14.5 1.370 0.970 0.139 12.6 0.378 1.013 0.138 12.6 1.373 1.010 0.140 11.0 0.370 1.015 0.112 11.0 1.329 1.012 0.114 9.5 0.361 1.038 0.089 9.5 1.286 1.035 0.090 8.3 0.356 1.111 0.089 8.3 1.258 1.108 0.090 7.2 0.348 1.156 0.088 7.2 1.217 1.153 0.089 6.3 0.339 1.199 0.085 6.3 1.177 1.196 0.085 5.5 0.323 1.196 0.104 5.5 1.114 1.194 0.104 4.8 0.310 1.172 0.095 4.8 1.061 1.170 0.095 4.2 0.290 1.131 0.098 4.2 0.987 1.130 0.098 3.6 0.281 1.127 0.083 3.6 0.951 1.125 0.083 3.2 0.263 1.120 0.098 3.2 0.886 1.119 0.097 2.8 0.247 1.108 0.088 2.8 0.828 1.107 0.088 2.4 0.225 1.094 0.080 2.4 0.750 1.092 0.080 2.1 0.208 1.109 0.071 2.1 0.688 1.108 0.070 1.8 0.191 1.141 0.094 1.8 0.630 1.139 0.093 1.6 0.184 1.269 0.102 1.6 0.604 1.266 0.102 1.4 0.166 1.325 0.075 1.4 0.540 1.322 0.075 1.2 0.151 1.375 0.079 1.2 0.491 1.371 0.078 1.0 0.140 1.413 0.071 1.0 0.452 1.408 0.070 0.91 0.120 1.332 0.078 0.91 0.385 1.328 0.077 0.79 0.105 1.287 0.077 0.79 0.335 1.284 0.076 0.69 0.095 1.299 0.084 0.69 0.298 1.296 0.082 0.60 0.082 1.286 0.067 0.60 0.255 1.284 0.066 0.52 0.069 1.266 0.067 0.52 0.213 1.264 0.066 0.46 0.058 1.284 0.087 0.46 0.179 1.281 0.087 0.10 0.002 1.205 0.033 0.10 0.007 1.193 0.035 41

Appendix B IPEEE Adequacy Review 42

Table of Contents Page 1.0 Background ........................................................................................................................... 44 2.0 General Considerations ................................................................................................... 44 2.1 Relay Chatter ................................................................................................................. 45 2.2 Soil Failure Evaluation .............................................................................................. 45 3.0 Prerequisites ......................................................................................................................... 45 4.0 Adequacy Dem onstration ................................................................................................. 47 4.1 Structural Models and Structural Response Analysis ................................................ 47 4.2 In-Structure Dem and and ISRS ................................................................................ 48 4.3 Selection of Seismic Equipment List (SEL)/Safe Shutdown Equipment List (SSEL) ..... 48 4.4 Screening of Com ponents ......................................................................................... 49 4.5 W alkdowns ..................................................................................................................... 50 4.6 Fragility Evaluation ................................................................................................... 52 4.7 System Modeling ....................................................................................................... 53 4.8 Containm ent Perform ance ....................................................................................... 54 4.9 Peer Review ................................................................................................................... 55 5.0 Conclusion ............................................................................................................................ 55 6.0 References ............................................................................................................................ 56 43

1.0 Background

The Nuclear Regulatory Commission (NRC) staff issued Generic Letter (GL) 88-20, Supplement 4 on June 28, 1991 (Reference 6.10), requesting that each licensee conduct an individual plant examination of external events (IPEEE) for severe accident vulnerabilities. Concurrently, NUREG-1407, "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities" (Reference 6.9) was issued to provide utilities with detailed guidance for performance of the IPEEE.

A seismic margin assessment (SMA) was performed for the seismic portion of the Arkansas Nuclear One (ANO) - Unit 1 IPEEE (Reference 6.1) using the Electric Power Research Institute (EPRI) SMA methodology, EPRI NP-6041 (Reference 6.3) with enhancements identified in NUREG-1407 (Reference 6.9). ANO-1 performed a 0.3g "modified" full scope SMA utilizing a NUREG/CR-0098 (Reference 6.4) spectral shape for a rock site. The "modified" full scope SMA involved developing a Safe Shutdown Equipment List (SSEL) and performing High-Confidence of Low-Probability of Failure (HCLPF) calculations only for components that potentially had a capacity less than the 0.3g review level earthquake (RLE). Capacities for reactor internals and soil-related failures were not included in the "modified" full scope SMA. The calculated plant-level HCLPF for ANO - Unit 1 resulting from performance of the IPEEE was greater than 0.3g.

The results of the ANO - Unit 1 IPEEE (Reference 6.1) were provided to the NRC on May 31, 1996.

The NRC staff submitted a request for additional information (RAI) in two letters dated April 3, 1998 (Reference 6.11) and May 7, 1998 (Reference 6.12), relating to ANO - Unit 1 and ANO -

Unit 2. ANO responded to the RAI letters with additional information by letter dated March 30, 1999 (Reference 6.13). The NRC staff later submitted a request for supplemental information concerning the RAI responses in a letter dated February 7, 2000 (Reference 6.14). ANO responded to the request for supplemental information by letter dated June 14, 2000 (Reference 6.15).

The NRC issued its Staff Evaluation Report (SER) on February 27, 2001 for the ANO - Unit 1 and ANO - Unit 2 IPEEEs (Reference 6.2). The SER concluded that the ANO-1 and ANO-2 IPEEE process was capable of identifying the most likely severe accidents and severe accident vulnerabilities, meeting the intent of GL 88-20 (Reference 6.10).

2.0 General Considerations The plant safe shutdown earthquake (SSE) is a Housner type spectrum anchored to 0.2g peak horizontal ground acceleration and 0.133g peak vertical ground acceleration.

The ANO-1 IPEEE is a modified full scope EPRI seismic margin assessment. The EPRI SMA was selected as the method for the IPEEE evaluation because it was compatible with the Unresolved Safety Issue (USI) A-46 assessment being conducted in parallel with the IPEEE work. The Seismic Qualification Utility Group (SQUG) Generic Implementation Procedure (GIP) 44

(Reference 6.16) used for USI A-46 allowed for coordination of activities to support both projects. The Review Level Earthquake (RLE), based on the NUREG/CR-0098 (Reference 6.4) spectrum applicable to a rock site and anchored to a 0.3g peak ground acceleration, was used for the determination of component HCLPFs. The minimum component HCLPFs was found to be at least a 0.3g PGA value, after addressing any HCLPFs that fell below that level, resulting in a plant HCLPF of at least 0.3g. Therefore, the IPEEE HCLPF Spectrum (IHS) that can be used for comparison against the new GMRS is equal to the RLE spectrum anchored at a 0.3g PGA.

The IPEEE commitments and modifications that were required to achieve the plant level HCLPF have been completed. Verification of the completion of these commitments and modifications were provided in the ANO - Unit 1 Response (Reference 6.17) to 10 CFR Part 50.54(f) Request for Information Recommendation 2.3 Seismic (Reference 6.18) and are further discussed below in Section 3.0 Prerequisites. Confirmation that these modifications are still in place is described in the Prerequisites section of this report.

The following sections summarize the results of the IPEEE adequacy evaluation according to the guidance of the Screening, Prioritization and Implementation Details (SPID) (Reference 6.5).

2. 1 Relay Chatter The ANO - Unit 1 relay evaluation for IPEEE was consistent with the requirements of a full-scope evaluation, as described in NUREG-1407.

The following is included in the SER (Reference 6.2) for ANO-1: "The relay review program at ANO-1 exceeded this [the IPEEE] requirementbecause full capacity versus demand screening, in accordance with the GIP (Reference 6.16), was performed on all relays associated with small break LOCA and containment performance. The evaluation was performed accordingto the GIP (Reference 6.16) using the Design Basis SSE Response Spectra as the basis. This also meets the RLE in the IPEEE SMA due to the conservative amplification factors used for USI A-46 and the more liberal response spectra peak clipping allowed for an SMA."

2.2 Soil FailureEvaluation The safety-related structures at ANO - Unit 1 are founded on rock. As stated in NUREG-1407 (Reference 6.9), Section 3.2.1, a plant in the full-scope category that is located on a rock site is not required to perform a soil failure evaluation.

3.0 Prerequisites The following items have been addressed in order to use the IPEEE analysis for screening purposes and to demonstrate that the IPEEE results can be used for comparison with the GMRS:

1) Confirmation that commitments made under the IPEEE have been met.

45

2) Confirmation that all of the modifications and other changes credited in the IPEEE analysis are in place.

3) Confirmation that any identified deficiencies or weaknesses to NUREG-1407 in the ANO

- Unit 1 IPEEE NRC SER are properly justified to ensure that the IPEEE conclusions remain valid.

4) Confirmation that major plant modifications since the completion of the IPEEE have not degraded/impacted the conclusion reached in the IPEEE.

Response

The IPEEE commitments and modifications have been completed. Verification of the completion of these commitments and modifications were provided in the ANO - Unit 1 Seismic Walkdown Report (Reference 6.17) Attachment A. Attachment A provides: a description of the action taken, whether the vulnerability continues to be addressed, and when the resolution actions were completed.

The ANO - Unit 1 NRC SER (Reference 6.2) on the seismic portion of the IPEEE states that the ANO - Unit 1 IPEEE appears to meet the objectives of Generic Letter 88-20; addresses all the USIs and Generic Safety Issues (GSIs) requested in NUREG-1407 (Reference 6.9); and contains suitable discussion of seismic/fire interaction, seismic/flood interaction, and containment performance.

The ANO - Unit 1 NRC SER (Reference 6.2) did note that details of operator actions credited when defining success paths were not included in the IPEEE submittal (Reference 6.1).

However, the operator actions were discussed in detail in the responses to RAIs.

Major new or replacement equipment was identified, as described in the Walkdown Report (Reference 6.17) and placed on the list of equipment to be examined during the walkdowns.

The IPEEE SSEL was used as the starting point for developing an equipment list for the walkdowns, so that all the equipment on the IPEEE SSEL was walked down again.

No conditions were identified that could adversely affect IPEEE conclusions and, therefore, risk insights in the IPEEE analysis remain valid.

46

4.0 Adequacy Demonstration 4.1 StructuralModels and StructuralResponse Analysis Methodology used:

Structural Models Pertinent resources, including IPEEE (Reference 6.1), SAR (Reference 6.19), structural calculations, and drawings (References 6.20 through 6.46) were reviewed.

Major structures for the ANO - Unit 1 site considered in the SMA are the Reactor Building -

Internal Structure, Reactor Building - Containment Shell, Auxiliary Building, Intake Structure, and Diesel Fuel Storage Vault. Structural models were developed in the '70s for the purposes of generating modal properties for dynamic analysis. The Review Level Earthquake for the IPEEE SMA is the median shaped NUREG/CR-0098 (Reference 6.4) spectrum, applicable to a rock site, anchored to a 0.3g peak ground acceleration.

The dynamic models were developed such that they can accurately predict the building response, including in-structure response spectra, in the frequency range of interest. The ANO - Unit 1 dynamic models of the structures are adequate to represent frequencies in excess of 20 Hz and, as such, are adequate for the assessments focused on the 1 Hz to 10 Hz range.

The structural models for these buildings consist of massless beam elements and lumped masses at major floor elevations. The massless beam elements represent the stiffness properties of concrete walls. The beam elements, in general, are rigidly linked to each other and to a lumped mass at each major floor elevation. Thus, each floor elevation acts as a rigid body.

For structures where there are no major floors, such as the Containment Shell, the mass is modeled uniformly along the height of the structure. The Reactor Building - Containment Shell does not have any significant structural eccentricity between the center of mass and center of rigidity. Reactor Building - Internal Structure, Auxiliary Building and Intake Structure have some torsional irregularities. However, the structural models are detailed enough to capture the overall structural responses for both the horizontal and vertical components of ground motion.

The ANO - Unit 1 structures are founded on rock, which is typical of the area and consists primarily of shale and sandstone.

For the dynamic analyses, the bedrock on which the structure is founded was modeled using soil springs.

47

Compliance with NUREG-1407:

This methodology meets the guidance and requirements of EPRI NP-6041 and the enhancements specified in NUREG-1407.

Adequate for Screening:

The IPEEE methodology and structural modeling are in compliance with NUREG-1407 (Reference 6.9) and are adequate for screening purposes.

4.2 In-Structure Demand and ISRS Methodology used:

The ANO-1 in-structure response spectra (ISRS) for the IPEEE SMA are presented in (Reference 6.1). The ISRS were generated using time history analyses. The IPEEE SMA ISRSs were compared against the original ISRSs (References 6.47 through 6.49). The comparison shows matching amplification frequencies and modal characteristics. The IPEEE SMA ISRSs are deemed reasonable.

Compliance with NUREG-1407:

In-structure response spectra were developed for the IPEEE SMA (Reference 6.1). The IPEEE SMA was done in accordance to the guidance and requirements of EPRI NP-6041 (Reference 6.3) and the enhancements specified in NUREG-1407 (Reference 6.9). The IPEEE ISRS are consistent with the design basis spectra and deemed acceptable for screening purposes.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE in-structure demands and ISRS results are adequate for screening purposes.

4.3 Selection of Seismic Equipment List (SEL)/Safe Shutdown Equipment List (SSEL)

Methodology used:

The selection of equipment in the IPEEE (Reference 6.1) is done to address USI A-46 and to support the IPEEE. Equipment selection to address USI A-46 issues is based on the GIP (Reference 6.16), Section 3 and Appendix A. Equipment selection to support the IPEEE is based on NUREG-1407 (Reference 6.9) and EPRI NP-6041-SL (Reference 6.3). The list of equipment provided in Appendix B of the IPEEE (Reference 6.1) addresses both USI A-46 and 48

IPEEE requirements and is the equipment that would be used for the safety functions required to establish and maintain a safe shutdown condition, including a primary and alternate success path.

The following safety functions were satisfied by the IPEEE success paths: reactivity control, reactor coolant pressure control, reactor coolant inventory control, and decay heat removal. In addition, equipment required to prevent early containment failure was included on the SSEL.

Equipment was selected that provided redundancy for each of the safe shutdown functions (secondary success path). The list of components includes an indication of the component location and the equipment class defined in the GIP (Reference 6.16).

Support system requirements for the above functional success paths were identified. Equipment in support systems required for the operation of safe shutdown equipment or for indication of plant conditions showing safe shutdown were included in the SSEL.

The passive and active components included in the IPEEE scope are identified in Appendix B of the ANO- Unit 1 IPEEE submittal (Reference 6.1).

Compliance with NUREG-1407:

This methodology meets the guidance and requirements of EPRI NP-6041 (Reference 6.3) and the enhancements specified in NUREG-1407 (Reference 6.9). Section 3.2.5.1 of NUREG-1407 (Reference 6.9) requires a complete set of potential success paths be identified and the narrowing/elimination of paths to be documented in detail. Section 3.9 of the ANO - Unit 1 IPEEE (Reference 6.1) documents in detail the system analysis and the selection of equipment for the primary and backup success paths.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE seismic equipment selection results are adequate for screening purposes.

4.4 Screening of Components Methodology used:

The Seismic Review Team (SRT) screened from further margin review structures and components for which the SRT could document HCLPFs at or above the specified RLE of 0.3g based on their combined experience and judgment and use of earthquake experience data.

49

The screening guidance given in EPRI NP-6041 (Reference 6.3) was used. This is the same procedure used for the resolution of USI A-46.

Structures and equipment that could not be screened were further evaluated as documented in the IPEEE submittal (Reference 6.1) in section 3.5. The unscreened components were subjected to a Conservative Deterministic Failure Margin (CDFM) analysis as described in EPRI NP-6041 (Reference 6.3) to determine HCLPFs for the components and documented in Table 3.5-1 of the IPEEE (Reference 6.1). Plant walkdowns provided information about components, such as anchorage details, required for the HCLPF evaluation.

Compliance with NUREG-1407:

The above methodology meets the requirements of NUREG-1407 (Reference 6.9) Section 3.2.5.5 Screening Criteria which states that screening guidance given in the GIP (Reference 6.16) may be used provided review/screening is performed at the appropriate RLE, caveats included in the margins report are observed and use of the generic equipment ruggedness spectrum are observed. NUREG-1407 (Reference 6.9) also requires that spatial interaction evaluations such as assessing the effects of flooding, as noted in EPRI NP-6041 (Reference 6.3), be performed.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE screening of component results are adequate for screening purposes.

4.5 Walkdowns Methodology used:

IPEEE Walkdowns Seismic walkdowns for USI A-46 and for the IPEEE were performed concurrently. Components common to both programs were inspected only once. Two walkdowns were performed at ANO-1, the first walkdown was performed during an outage and included equipment inside the containment, the second walkdown was performed a few months later and included the equipment outside of containment. The IPEEE walkdown scope included passive components and structures, containment isolation and performance, and seismic interactions.

The IPEEE walkdowns are documented in the IPEEE report (Reference 6.1) and in the Seismic Evaluation Work Sheets (SEWS) in accordance with EPRI NP-6041 (Reference 6.3) and the SQUG (Reference 6.16).

50

Major structures and components were walked down. Components within the IPEEE scope but not within the A-46 evaluation scope were identified so that combined walkdowns could be performed to address both A-46 and IPEEE. With the exception of some anchorage or interaction issues, equipment walked down for A-46 and IPEEE was judged to screen at 0.3g.

Seismic outliers were identified for resolution at a later date by modifications or further analysis.

Walkdowns were conducted by a combination of one S&A engineer and one ANO seismic engineer, with access to an ANO systems engineer and operations personnel. Seismic Review Team members were SQUG trained and certified.

The potential for spatial system interactions was considered during seismic walkdowns. System interaction issues were considered and noted on the SEWS for the IPEEE. The following provides examples of what was considered either previously as part of A-46 walkdowns or as part of the IPEEE:

Proximity: The proximity of structures to components and components to components was considered during walkdowns. For example, the proximity of valve operators to structures and other components was considered. Masonry block walls were revisited during the IPEEE analysis and were screened for the SMA. To ensure that block walls have capacity above 0.3g, HCLPF calculation was performed for the worst case block wall that was not upgraded during the IE-80-1 1 program (Reference 6.50). This block wall was calculated to have a capacity of 0.39g.

• Seismic II over I: Interactions with overhead equipment or nearby equipment, including block walls, were evaluated during the walkdowns.

" Seismic Spray & Flooding: The possibility of water spray and flooding impact on systems was considered during the walkdown. No tanks were found in areas with SSEL equipment and fire water piping was judged to have supports with sufficient capacity.

" Seismic Fires: The potential for seismic induced fires impacting SSEL equipment was evaluated during the walkdowns. No cabinets (fire sources) were found in areas containing SSEL equipment.

The above spatial interactions were evaluated and found acceptable.

Near-Term Task Force (NTTF) Recommendation 2.3 Walkdowns On March 12, 2012 NRC issued a generic letter (Reference 6.18) requesting, in part, information relating to seismic walkdowns. In response, Entergy performed the requested seismic walkdowns and area walk-bys over a three week period during September and October of 2012. Walkdown inspections focused on anchorages and seismic spatial interactions, but also included inspections for other potentially adverse seismic conditions. The NTTF Recommendation 2.3 walkdowns are documented in a walkdown report (Reference 6.17).

51

Verification of the resolution of commitments made to address seismic vulnerabilities identified in the IPEEE are provided in the ANO - Unit 1 Seismic Walkdown Report (Reference 6.17)

Attachment A. Attachment A provides: a description of the action taken, whether the vulnerability continues to be addressed, and when the resolution actions were completed. The walkdown report (Reference 6.17) was submitted to the NRC on November 27, 2012.

Compliance with NUREG-1407:

Walkdowns were conducted and documented in accordance with EPRI NP-6041 (Reference 6.3) as required by Section 3.2.5.2 of NUREG-1407 (Reference 6.9).

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE walkdown results are adequate for screening purposes.

4.6 FragilityEvaluation Methodology used:

ANO - Unit 1 developed and implemented a program to satisfy the requirements of the IPEEE seismic margins evaluation. The SMA program concentrated on verifying the seismic adequacy of structures, equipment, large tanks, cable tray conduit raceway systems and other distribution systems, and relays. The screening and verification walkdowns verified that the equipment, tanks, distribution systems, structures and relays are able to withstand the 0.3g Review Level Earthquake at the plant and still provide for its safe shutdown.

• Components were screened using the criteria contained in Tables 2-3 and 2-4 of EPRI NP-6041 (Reference 6.3).

• Components that are screened are judged to have a seismic capacity in excess of the RLE demand. HCLPF capacities are determined for those items that are not screened out.

" CFDM HCLPF capacity calculations were typically required for equipment anchorages, large tanks, and block walls.

All the Class I Structures were screened out based on the EPRI NP-6041 (Reference 6.3) screening criteria.

Compliance with NUREG-1407:

ANO - Unit 1 calculated HCLPFs for all outlier components in accordance with the guidance of EPRI NP-6041 (Reference 6.3) and NUREG-1407 (Reference 6.9) Section 3.2.5.7.

52

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE fragility evaluation results are adequate for screening purposes.

4.7 System Modeling Methodology used:

Functional success paths were developed for the four safety functions: reactivity control, Reactor Coolant System (RCS) pressure control, RCS inventory control, and decay heat removal. Primary and alternate success paths for each safety function were identified. Alternate success paths involve the same systems as the primary success paths by using the opposite train. Plant-specific Success Path Logic Diagrams (SPLDs) are provided in the RAI response (Reference 6.13) for both loss of off-site power (LOSP) and small Loss of Coolant Accident (LOCA) with both the primary and alternate success path. Dependency matrices are also provided in the RAI responses that identify the support systems required for operation of the front-line systems in the SPLD.

The evaluation of non-seismic failures and human actions was not addressed explicitly in the IPEEE (Reference 6.1) evaluation of seismic risk; however, both are discussed in the responses to RAIs (Reference 6.13). A fault tree was developed from the detailed plant fault tree, taking no credit for components on the IPEEE SSEL and quantified to determine the conditional core damage probability. The conditional core damage probability was combined with the frequency of a 0.3g earthquake at the ANO site from EPRI NP-6395-D (Reference 6.51) to estimate a Core Damage Frequency (CDF) below 1.OE-06. It was concluded that the risk from a 0.3g seismic event was therefore insignificant.

The identification of success paths and components was based on nominal credit for operator actions, given that sufficient manpower, time, and procedures were available. Specific operator actions necessary for safe shutdown are not discussed in the IPEEE submittal (Reference 6.1),

but are discussed in the responses to RAIs.

Compliance with NUREG-1407:

NUREG-1407 (Reference 6.9), Section 3.2.5.1 states that for IPEEE purposes, it is desirable that to the maximum extent possible, that the alternate path involve operational sequences, systems, piping runs and components different from those used in the preferred path. As indicated above and documented in the IPEEE, different components and trains were selected, but from the same systems at ANO - Unit 1.

53

Taking into account the information supplied in RAI responses, the treatment of non-seismic failures and human actions in the ANO - Unit 1 IPEEE meets the requirements of Section 3.2.5.8 of NUREG-1407 (Reference 6.9).

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE system modeling results are adequate for screening purposes.

4.8 Containment Performance Methodology used:

Containment performance was evaluated for gross containment failure, containment system failure, containment bypass, containment isolation failure, and interactions with containment.

The containment structure was evaluated using the methodology and guidance of EPRI NP-6041 (Reference 6.3).

For containment isolation and bypass, containment penetrations were evaluated with respect to seal failure, valve failure, and failure of piping between penetrations and isolation valves.

The containment evaluation found that no significant vulnerabilities exist that would impact containment performance for the RLE.

Compliance with NUREG-1407:

The review of containment meets the requirements of Section 3.2.6 of NUREG-1407 (Reference 6.9) to evaluate the containment integrity, isolation, bypass and suppression functions to identify vulnerabilities that involve early failure of the containment functions.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE containment performance results are adequate for screening purposes.

54

4.9 PeerReview Methodology used:

An independent peer review of the SMA was conducted by Mr. Harry Johnson of Programmatic Solutions. Mr. Johnson conducted two days of walkdowns as part of his review. Mr. Johnson's review report is included in the IPEEE submittal (Reference 6.1) in Appendix D. Mr. Johnson concluded that the methods used were appropriate, the methods have been correctly implemented, and the actions recommended in the IPEEE to address seismic vulnerabilities are reasonable.

In addition to the independent peer review by Mr. Johnson, a peer review of the SSEL was conducted by Dr. Robert Budnitz of Future Resources Associates, Inc. Dr. Budnitz's review report is also included in the IPEEE (Reference 6.1) in Appendix D. Comments consisted of editorial comments related to clarification of IPEEE text and were incorporated in the IPEEE report (Reference 6.1).

Two engineers from Enercon, Mr. Sean Smolarek and Mr. Eric Dilbone reviewed the IPEEE, as described in the Walkdown Report (Reference 6.17).,

"In-house" review is evidenced by the reviewer sign-off on IPEEE cover sheets, but there is no discussion of in-house review in the IPEEE report body.

Compliance with NUREG-1407:

The above review process, using a combination of independent in-house review and two external consultants for seismic review, meets the requirements of Section 7 of NUREG-1407 (Reference 6.9) for peer review.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE peer review results are adequate for screening purposes.

5.0 Conclusion The ANO - Unit 1 IPEEE was a modified full scope seismic margin submittal and requires the performance of a detailed review of relay chatter. The modified scope of the ANO - Unit 1 IPEEE excluded soil-related failures.

55

The following is included in the SER (Reference 6.2) for ANO-1: "The relay review program at ANO-1 exceeded this [the IPEEE]requirementbecause full capacity versus demand screening, in accordance with the GIP (Reference 6.16), was performed on all relays associatedwith small break LOCA and containment performance. The evaluation was performed according to the GIP (Reference 6.16) using the Design Basis SSE Response Spectra as the basis. This also meets the RLE in the IPEEE SMA due to the conservative amplification factors used for USI A-46 and the more liberal response spectra peak clipping allowed for an SMA."

Based on the IPEEE adequacy review performed consistent with the guidance contained in EPRI 1025287 (SPID) (Reference 6.5) and documented herein, the ANO - Unit 1 IPEEE results are considered adequate for screening and the risk insights gained from the IPEEE remain valid under the current plant configuration.

6.0 References 6.1 Arkansas Nuclear One Document, 96-R-1006-02, Rev. 000, "IPEEE Seismic Margins Assessment (SMA) of Arkansas Nuclear One, Unit 1."

6.2 United States Nuclear Regulatory Commission, "Staff Evaluation Report of Individual Plant Examination of External Events (IPEEE) Submittal on Arkansas Nuclear One, Units 1 & 2," Enclosure 1 to Letter Dated February 27, 2001 [OCNA020113].

6.3 Electric Power Research Institute, "A Methodology for Assessment of Nuclear Power Plant Seismic Margin," EPRI NP-6041-SL, Revision 1, August 1991.

6.4 "Development of Criteria for Seismic Review of Selected Nuclear Power Plants,"

NUREG/CR-0098, US NRC, May 1978.

6.5 Electric Power Research Institute, TR-1025287, "Seismic Evaluation Guidance:

Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," November 2012.

6.6 NEI Letter, Kimberly A. Keithline to David L. Skeen, NRC "Relay Chatter Reviews for Seismic Hazard Screening," dated October 3, 2013 [ML13281A308].

6.7 NEI Letter, A.R. Pietrangelo to D.L. Skeen, NRC "Proposed Path Forward for NTTF Recommendation 2.1: Seismic Reevaluations," dated April 9, 2013 [ML13101A379].

6.8 NRC Letter, E. Leeds to J. Pollock, NEI "Acceptance Letter for NEI Submittal of Augmented Approach, Ground Motion Model Update Project, and 10CFR50.54(f)

Schedule Modifications Related to the NTTF Recommendation 2.1, Seismic Reevaluations," dated May 7, 2013 [ML13106A331].

6.9 United States Nuclear Regulatory Commission, "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities," NUREG-1407, June 1991.

6.10 "Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities - 10CFR50.54(f)," Generic Letter No. 88-20, Supplement 4, US NRC, June 28, 1991 6.11 NRC Letter to Entergy, Request for Additional Information Pertaining to the Arkansas Nuclear One (ANO) Summary Reports for the Individual Plant Examination of External Events (IPEEE), dated April 3, 1998 [0CNA049807, 0CNA049808].

6.12 NRC Letter to Entergy, Request for Additional Information Pertaining to the Arkansas Nuclear One (ANO) Summary Reports for the Individual Plant Examination of External Events (IPEEE), dated May 7, 1998 [0CNA059806].

56

6.13 Entergy Letter to NRC "Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 Additional Information Pertaining to GL 87-02 and 88-20," dated March 30, 1999 [0CAN0399011.

6.14 NRC Letter to Entergy, Request for Supplemental Information Concerning Entergy Operations Previous Responses Dated March 30, 1999, dated February 7, 2000

[OCNA020004].

6.15 Entergy Letter to NRC "Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 IPEEE Supplemental RAI Response," dated June 14, 2000 [0CAN060003].

6.16 Seismic Qualification Utility Group (SQUG), "Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment," Revision 2, March, 1993.

6.17 Entergy Letter to NRC, "ANO-1 Seismic Walkdown Report," Attachment 1 to letter 1CAN111201, dated November 27, 2012.

6.18 NRC Generic Letter "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident," dated March 12, 2012 [ML12053A340].

6.19 Arkansas Nuclear One Unit 1, Safety Analysis Report, Amendment No. 26.

6.20 Arkansas Nuclear One Drawing, C-148, Rev. 13, "Reactor Building Reinforced Concrete Basement Floor Elevation 336'-6"."

6.21 Arkansas Nuclear One Drawing, C-149, Rev. 8, "Reactor Building Reinforced Concrete Ground Floor Elevation 357'-0"."

6.22 Arkansas Nuclear One Drawing, C-150, Rev. 7, "Reactor Building Reinforced Concrete Intermediate Floor Elevation 376'-6"."

6.23 Arkansas Nuclear One Drawing, C-1 51, Rev. 2, "Reactor Building Reinforced Concrete Plans Elevation 362'-0" to Elevation 376'-6"."

6.24 Arkansas Nuclear One Drawing, C-152, Rev. 7, "Reactor Building Reinforced Concrete Operating Floor Elevation 401'-6"."

6.25 Arkansas Nuclear One Drawing, C-153, Rev. 6, "Reactor Building Reinforced Concrete Shielding Floor Elevation 424'-6"."

6.26 Arkansas Nuclear One Drawing, C-201, Rev. 4, "Concrete Auxiliary Building Plan at Elevation 317'-0"."

6.27 Arkansas Nuclear One Drawing, C-202, Rev. 14, "Concrete Auxiliary Building Plan at Elevation 335'-0"."

6.28 Arkansas Nuclear One Drawing, C-203, Rev. 11, "Concrete Auxiliary Building Plan at Elevation 354'-0"."

6.29 Arkansas Nuclear One Drawing, C-204, Rev. 13, "Concrete Auxiliary Building Plan at Elevation 372'-0"."

6.30 Arkansas Nuclear One Drawing, C-205, Rev. 11, "Concrete Auxiliary Building Plan at Elevation 386'-0"."

6.31 Arkansas Nuclear One Drawing, C-206, Rev. 17, "Concrete Auxiliary Building Plan at Elevation 404'- '."

6.32 Arkansas Nuclear One Drawing, C-213, Rev. 13, "Concrete Auxiliary Building Section -

A."

6.33 Arkansas Nuclear One Drawing, C-214, Rev. 9, "Concrete Auxiliary Building Section - B and C."

6.34 Arkansas Nuclear One Drawing, C-215, Rev. 8, "Concrete Auxiliary Building Section -

D."'

6.35 Arkansas Nuclear One Drawing, C-216, Rev. 12, "Concrete Auxiliary Building Section -

E."

57

6.36 Arkansas Nuclear One Drawing, C-217, Rev. 8, "Concrete Auxiliary Building Section -

F."

6.37 Arkansas Nuclear One Drawing, C-223, Rev. 3, "Concrete Auxiliary Building Section -

H."

6.38 Arkansas Nuclear One Drawing, C-224, Rev. 4, "Concrete Auxiliary Building Section -

J.,,

6.39 Arkansas Nuclear One Drawing, C-225, Rev. 4, "Concrete Auxiliary Building Section -

K."

6.40 Arkansas Nuclear One Drawing, C-226, Rev. 6, "Concrete Auxiliary Building Plan at Elevation 327'-0 & Elevation 355'-4."

6.41 Arkansas Nuclear One Drawing, C-229, Rev. 5, "Concrete Auxiliary Building Sections."

6.42 Arkansas Nuclear One Drawing, C-80, Rev. 5, "Intake Structure Foundation Plan Elevation 315'-0" & 322'-6"."

6.43 Arkansas Nuclear One Drawing, C-81, Rev. 18, "Intake Structure Plan at Elevation 354'-

0,.1, 6.44 Arkansas Nuclear One Drawing, C-82, Rev. 22, "Intake Structure Plans & Sections."

6.45 Arkansas Nuclear One Drawing, C-83, Rev. 14, "Intake Structure Sections."

6.46 Arkansas Nuclear One Drawing, C-84, Rev. 10, "Intake Structure Sections & Details."

6.47 Arkansas Nuclear One Unit 1, 6600-C-1 01, Rev. 1, "Specification for Earthquake Resistance Design of Equipment Located in the Reactor Building for Arkansas Power &

Light Company Arkansas Nuclear One Little Rock, Arkansas 72203."

6.48 Arkansas Nuclear One Unit 1, APL-C-501, Rev. 2 , "Earthquake Resistance Design of Structures and/or Components Located in the Reactor Building for the Arkansas Nuclear One Unit 1 Power Plant."

6.49 Arkansas Nuclear One Unit 1, AP&L-C-502, Rev. 2, "Earthquake Resistance Design of Structures and/or Components Located in the Auxiliary Building for the Arkansas Nuclear One Unit I Power Plant."

6.50 "Masonry Wall Design," IE Bulletin No. 80-11, US NRC May 8, 1980.

6.51 Electric Power Research Institute, NP-6395-D, "Probabilistic Seismic Hazard Evaluation at Nuclear Plant Sites in the Central and Eastern United States: Resolution of the Charleston Issue," April 1989.

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Enclosure 2 to OCAN031404 Seismic Hazard and Screening Report for ANO-2

Seismic Hazard and Screening Report for Arkansas Nuclear One Unit 2 1

Table of Contents Page 1.0 Introduction ............................................................................................................................. 3 2.0 Seism ic Hazard Reevaluation ............................................................................................ 4 2.1 Regional and Local Geology ........................................................................................ 6 2.2 Probabilistic Seism ic Hazard Analysis ....................................................................... 6 2.2.1 Probabilistic Seism ic Hazard Analysis Results .................................................. 6 2.2.2 Base Rock Seism ic Hazard Curves .................................................................. 8 2.3 Site Response Evaluation ............................................................................................ 8 2.3.1 Description of Subsurface Material ..................................................................... 8 2.3.2 Development of Base Case Profiles and Nonlinear Material Properties ............ 8 2.3.2.1 Shear Modulus and Dam ping Curves ................................................... 13 2.3.2.2 Kappa ................................................................................................... 14 2.3.3 Random ization of Base Case Profiles .............................................................. 14 2.3.4 Input Spectra ...................................................................................................... 15 2.3.5 Methodology ..................................................................................................... 15 2.3.6 Am plification Functions ..................................................................................... 15 2.3.7 Control Point Seism ic Hazard Curves .............................................................. 20 2.4 Control Point Response Spectrum ............................................................................ 20 3.0 Plant Design Basis and Beyond Design Basis Evaluation Ground Motion ...................... 23 3.1 Safe Shutdown Earthquake Description of Spectral Shape ................... 23 3.2 Control Point Elevation .............................................................................................. 24 3.3 IPEEE Description and Capacity Response Spectrum .............................................. 24 4.0 Screening Evaluation ........................................................................................................ 26 4.1 Risk Evaluation Screening (1 to 10 Hz) ..................................................................... 26 4.2 High Frequency Screening (> 10 Hz) ....................................................................... 26 4.3 Spent Fuel Pool Evaluation Screening (1 to 10 Hz) ................................................... 26 5.0 Interim Actions ...................................................................................................................... 27 6.0 Conclusions .......................................................................................................................... 28 7.0 References ............................................................................................................................ 28 Appendix A .................................................................................................................................. 30 Appendix B .................................................................................................................................. 42 2

1.0 Introduction Following the accident at the Fukushima Daiichi nuclear power plant resulting from the March 11, 2011, Great Tohoku Earthquake and subsequent tsunami, the Nuclear Regulatory Commission (NRC) established a Near-Term Task Force (NTTF) to conduct a systematic review of NRC processes and regulations and to determine if the agency should make additional improvements to its regulatory system. The NTTF developed a set of recommendations intended to clarify and strengthen the regulatory framework for protection against natural phenomena. Subsequently, the NRC issued a 50.54(f) letter (U.S. NRC, 2012) that requests information to assure that these recommendations are addressed by all U.S.

nuclear power plants. The 50.54(f) letter (U.S. NRC, 2012) requests that licensees and holders of construction permits under 10 CFR Part 50 reevaluate the seismic hazards at their sites against present-day NRC requirements. Depending on the comparison between the reevaluated seismic hazard and the current design basis, the result is either no further risk evaluation or the performance of a seismic risk assessment. Risk assessment approaches acceptable to the staff include a seismic probabilistic risk assessment (SPRA), or a seismic margin assessment (SMA). Based upon the risk assessment, the NRC staff will determine whether additional regulatory actions are necessary.

This report provides the information requested in items (1) through (7) of the "Requested Information" section and Attachment 1 of the 50.54(f) letter (U.S. NRC, 2012) pertaining to NTTF Recommendation 2.1 for the Arkansas Nuclear One (ANO) - Unit 2 plant, located in Pope County, Arkansas. In providing this information, Entergy followed the guidance provided in the Seismic Evaluation Guidance:Screening, Prioritization,and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (EPRI, 2013a). The Augmented Approach, Seismic Evaluation Guidance:Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (EPRI, 2013c),

has been developed as the process for evaluating critical plant equipment as an interim action to demonstrate additional plant safety margin prior to performing the complete plant seismic risk evaluations.

The original geologic and seismic siting investigations for ANO - Unit 2 was performed in accordance with Appendix A to 10 CFR Part 100 and meet General Design Criterion 2 in Appendix A to 10 CFR Part 50. The Safe Shutdown Earthquake (SSE) Ground Motion was developed in accordance with Appendix A to 10 CFR Part 100 and used for the design of seismic Category I systems, structures and components.

In response to the 50.54(f) letter (U.S. NRC, 2012) and following the guidance provided in the SPID (EPRI, 2013a), a seismic hazard reevaluation was performed. For screening purposes, a Ground Motion Response Spectrum (GMRS) was developed. Based on the results of the screening evaluation, ANO - Unit 2 screens-in for a Spent Fuel Pool evaluation and a High Frequency Confirmation. Additionally, based on the results of the screening evaluation, ANO -

Unit 2 screens-out of a risk evaluation.

3

2.0 Seismic Hazard Reevaluation The Arkansas Nuclear One site is located approximately six miles west-northwest of Russellville, Arkansas, on a peninsula formed by the Dardanelle Reservoir which acts as the water source for each Unit. The Arkansas Nuclear One site is in the center of the Arkansas Valley section of the Ouachita province. The Arkansas Valley lies within the area of outcrop of Paleozoic rocks which occupy essentially the northwestern half of the state. The rocks of the Arkansas Valley are nearly all of sedimentary origin. They include only a few bodies of igneous rock. The beds in the valley consist chiefly of non-fossiliferous shale and sandstone, all of Carboniferous age, and most of them belonging to the lower part of the Pennsylvanian series.

The rocks are generally highly carbonaceous and in some places are coal bearing. They contain little or no calcareous material. (Entergy, 2014a), (Entergy, 2014b)

The site is underlain by 8 to 30 ft of moderate to stiff, plastic, red and tan clay with occasional zones of silty clay, which overlies black, dense, horizontally bedded shale and sandstone of the McAlester formation. (Entergy, 2014a)

The nature of the structural features of the Arkansas Valley and their relation to the structure of the adjacent Ouachita and Boston Mountains show that the dominant force in the production of those features was horizontal pressure exerted from the south. It is believed that the folding and thrust faulting developed in post-Paleozoic pre-Cretaceous time due to the subsidence of a land mass to the south which supplied sediments in the place where this land mass once stood. The normal faults were also connected with this episode of deformation. These are believed to have formed either contemporaneously with folding, before folding, or as a result of tension developed after the period of folding. Some normal faults are also believed to have formed during deposition and subsidence of the Pennsylvanian sediments. In the Arkansas Valley, the southward-dipping faults terminate against northward-dipping normal faults. The precise dating of the folds and faults of the Arkansas Valley cannot be done with assurance, but it is known that they are very old geologic structures and probably were formed before Cretaceous time.

(Entergy, 2014a) (Entergy, 2014b)

East-west trending folds are mapped in the area of the site. From about three miles north to three miles south of the site are two anticlines and one syncline. From north to south these structures are as follows: London anticline, Scranton syncline, and the Prairie View anticline.

The plant site is located on the Scranton syncline in which the maximum dip rarely exceeds 10 degrees except locally where contorted beds may dip as steeply as 20 degrees. (Entergy, 2014a) (Entergy, 2014b)

The London anticline extends from about four and one-half miles northwest of the town of London, east to about three miles northwest of the site. This anticline may continue east to connect with the anticline which is mapped northeast of the site to a point three and one-half miles north of Russellville. The south limb of the London anticline is steeper than the north limb.

(Entergy, 2014a) (Entergy, 2014b) 4

The Scranton syncline, also known as the Ouita syncline, extends from northeast of Russellville, west to a point where it probably dies out about five miles northwest of Scranton. Here it is presumably terminated by the Dublin fault, which is an east-west-trending fault over nine miles west of the site. On the western part of the Scranton syncline the south limb is steeper than the north limb. However, on the eastern portion of the syncline the north limb is steeper than the south limb. (Entergy, 2014a) (Entergy, 2014b)

The Prairie View anticline is mapped from a point three miles southwest of the town of Scranton, east to at least as far as Russellville. This nearly symmetrical anticline is broken by northward-dipping normal faults. (Entergy, 2014a) (Entergy, 2014b)

There are a number of old faults mapped in the vicinity of the Arkansas River, particularly to the northwest and west of the site. These are in the main, east-west-trending faults. Of these, the London and Prairie View faults are the closest to the site. The London fault and an accompanying unnamed small branch fault trend east-west about four miles north of the site. A small fault which branches from the unnamed fault lies about two and one-half miles northeast of the site. The London fault is a high-angle south-dipping normal fault. It is best exposed about eight miles northwest of the site at Big Piney Creek where the western part of the fault ends. At this locality, the fault plane dips 58' south and has an apparent displacement of about 20 ft. The fault is also exposed to the east along Flat Rock Creek and in a drainage ditch along a country road about eight miles from the site. The unnamed eastwest-trending fault lies about one mile south of the London fault. The trend of this unnamed fault changes toward the east to generally northwest-southeast and appears to intersect the London fault in the vicinity of the north fork of Mill Creek. This fault is at least pre-Cretaceous in age. (Entergy, 2014a) (Entergy, 2014b)

The Prairie View fault is concealed under alluvium about six miles west of the site. Another six miles to the west, the fault is exposed. It is an east-west-trending high-angle north-dipping normal fault. This fault extends to the west as far as three miles northwest of Subiaco. The maximum displacement along the fault is 350 ft two miles west of the town of Prairie View. Near the western end of the fault there is about 170 ft of maximum displacement and the fault plane dips about 650 northward. About three miles from the western end of the fault is a small branch fault which is downthrown on the southside and is assumed to be dipping south. The Prairie View anticline is faulted by the Prairie View fault and is similar to the faulted anticlines discussed by Hendricks and Parks. It is their opinion that the faulted anticlines in the Fort Smith district were either faulted then folded, or contemporaneously faulted and folded. Therefore, the Prairie View fault is at least as old as the folding in this area, which is pre-Cretaceous. (Entergy, 2014a)

(Entergy, 2014b)

In summary, the only faults within five miles of the site are the Prairie View fault, and the London fault and its branch faults. The closest fault is only a small branch fault and approaches within about two and one-half miles of the site. The last movement of these faults is believed to have occurred prior to the Cretaceous. (Entergy, 2014a) (Entergy, 2014b) 5

Considering the historic seismicity of the site region, Entergy determined that because of the excellent formation conditions and the recent general quiescence of the area that a low earthquake intensity could be selected. However, considering the New Madrid earthquake, which is the only severe earthquake experienced in the central United States in historic time, an intensity of VII on the Modified Mercalli Intensity Scale of 1931 (Maximum Earthquake) has been assigned for the site. This is considered to be conservative and corresponds to a design spectrum of 0.20g for the SSE. (Entergy, 2014a) (Entergy, 2014b)

2. 1 Regional and Local Geology The Arkansas Valley is essentially a Paleozoic basin which had its most significant development during the Mississippian and Pennsylvanian. The greatest accumulations occurred during the Lower (Morrowan) and Lower Middle (Atokan) Pennsylvanian. Deformation of the Ouachitas occurred during Mid-Pennsylvanian time. During this time, the Ouachitas were strongly folded, with some thrust faulting, especially in Oklahoma. The Arkansas Valley section lies between the essentially flat-lying rocks of the Boston Mountains on the north and complexly folded strata of the Ouachita Mountains on the south. Its structure, therefore, has some of the characteristics of both its bounding regions, but is generally a region of broad, gentle folds which trend east-west and are only moderately faulted. Faulting is related to the folding and is pre-Cretaceous in age.

(Entergy, 2014b)

Since Cretaceous (and probably late Paleozoic) time, erosion has been the primary agent in the development of land forms in the region. No sediments younger than Pennsylvanian are found in the region, except for Quaternary terrace and alluvial deposits along the stream valleys. In a few places, intrusive rocks, mapped by as mid-Cretaceous cut the Paleozoic sediments. In the Arkansas Valley, these rocks consist of scattered dikes and sills of varying composition. None occur at the plant site. (Entergy, 2014b)

The site is about six miles northwest from Russellville, and about two miles from the small town of London. The plant is situated on a peninsula formed by the Corps of Engineers' Dardanelle Reservoir. The plant is located on a broad, nearly flat bench adjacent to the floodplain of the Arkansas River. This bench is at about Elevation 353 ft, at the lower of the two Pleistocene terrace levels. Soil on the terrace consists of clay and silty clay, and is from eight to 30 ft thick at the site. The broad floodplain of the Arkansas River is now covered with the waters of the Dardanelle Reservoir in the vicinity of the site. The low hills adjacent to the site are formed by the gently upturned strata along the flanks of the Scranton-Ouita syncline. Relief within the limits of the site area is less than 10 ft. (Entergy, 2014b) 2.2 ProbabilisticSeismic HazardAnalysis 2.2.1 ProbabilisticSeismic HazardAnalysis Results In accordance with the 50.54(f) letter (U.S. NRC, 2012) and following the guidance in the SPID (EPRI, 2013a), a probabilistic seismic hazard analysis (PSHA) was completed using the 6

recently developed Central and Eastern United States Seismic Source Characterization (CEUS-SSC) for Nuclear Facilities (CEUS-SSC, 2012) together with the updated Electric Power Research Institute (EPRI) Ground-Motion Model (GMM) for the Central and Eastern United States (CEUS) (EPRI, 2013b). For the PSHA, a lower-bound moment magnitude of 5.0 was used, as specified in the 50.54(f) letter (U.S. NRC, 2012). (EPRI, 2013d)

For the PSHA, the CEUS-SSC background seismic sources out to a distance of 400 miles (640 km) around the ANO - Unit 2 site were included. This distance exceeds the 200 mile (320 km) recommendation contained in Reg. Guide 1.208 (U.S. NRC, 2007) and was chosen for completeness. Background sources included in this site analysis are the following (EPRI, 2013d):

1. Extended Continental Crust-Gulf Coast (ECCGC)

2. Gulf Highly Extended Crust (GHEX)

3. Illinois Basin Extended Basement (IBEB)

4. Mesozoic and younger extended prior - narrow (MESE-N)

5. Mesozoic and younger extended prior - wide (MESE-W)

6. Midcontinent-Craton alternative A (MIDCA)

7. Midcontinent-Craton alternative B (MIDCB)

8. Midcontinent-Craton alternative C (MIDCC)

9. Midcontinent-Craton alternative D (MIDCD)

10. Non-Mesozoic and younger extended prior - narrow (NMESE-N)

11. Non-Mesozoic and younger extended prior - wide (NMESE-W)

12. Oklahoma Aulacogen (OKA)

13. Paleozoic Extended Crust narrow (PEZN)

14. Paleozoic Extended Crust wide (PEZW)

15. Reelfoot Rift (RR)

16. Reelfoot Rift including the Rough Creek Graben (RR-RCG)

17. Study region (STUDYR)

For sources of large magnitude earthquakes (designated Repeated Large Magnitude Earthquake (RLME) sources), in NUREG-2115 (CEUS-SSC, 2012) modeled for the CEUS-SSC, the following sources lie within 1,000 km of the site and were included in the analysis (EPRI, 2013d):

1. Cheraw

2. Commerce

3. Eastern Rift Margin Fault northern segment (ERM-N)

4. Eastern Rift Margin Fault southern segment (ERM-S)

5. Marianna

6. Meers

7. New Madrid Fault System (NMFS)

8. Wabash Valley 7

For each of the above background and RLME sources, the mid-continent version of the updated CEUS EPRI GMM was used. (EPRI, 2013d) 2.2.2 Base Rock Seismic Hazard Curves Consistent with the SPID (EPRI, 2013a), base rock seismic hazard curves are not provided as the site amplification approach referred to as Method 3 has been used. Seismic hazard curves are shown below in Section 2.3.7 at the SSE control point elevation. (EPRI, 2013d) 2.3 Site Response Evaluation Following the guidance contained in Seismic Enclosure 1 of the 50.54(f) Request for Information (U.S. NRC, 2012) and in the SPID (EPRI, 2013a) for nuclear power plant sites that are not founded on hard rock (defined as 2.83 km/sec), a site response analysis was performed for ANO - Unit 2. (EPRI, 2013d) 2.3.1 Descriptionof Subsurface Material Arkansas Nuclear One - Unit 2 is located on a peninsula formed by the Dardanelle Reservoir about 57 miles (92 km) northwest of Little Rock, Arkansas. The site is situated in the center of the Arkansas Valley in the Ouachita Physiographic Province. The site is founded on Pennsylvania McAlester formation which is hard, dense shale at the top of about 5,000 ft (1,524 m) of firm sedimentary rock. The SSE was specified at an elevation of 326 ft (99.4 m) within the Pennsylvanian shale (Entergy, 2014b).

2.3.2 Development of Base Case Profiles and NonlinearMaterial Properties The basic information used to create the site geologic profile at the ANO - Unit 2 site was taken from plant specific information in the Safety Analysis Report (SAR) with the following description (Entergy, 2014a) (Entergy, 2014b):

The reactor containment building is founded on shale of the McAlester Formation with embedment depth of around 26 ft. with tendon galleries of about 36 ft. below grade. Basement rock is estimated to be at a depth of 5,000 ft. The site shear-wave (S-wave) velocity of 5,350 fps (was) calculated using a Poisson's ratio of 0.30 and the range of values of the compressional-wave (P-wave) velocity from 10,000 to 14,500 fps for McAlester shale. The site seismic profiles are shown in Figure 2.5-21 of the SAR (Entergy, 2014b)

The location of the SSE at elevation 326 ft (99.4 m) is within the Pennsylvanian shale with firm sedimentary rocks extending to Precambrian basement at a depth of about 5,000 ft (1,524 m)

(Entergy, 2014b).

Shear-wave velocities for the profile were unspecified with compressional-wave velocities listed between 10,000 and 14,500 ft/s (3,048 m/s and 4,419 m/s respectively), likely based on shallow refraction surveys (Entergy, 2014a) (Entergy 2014b). To develop a mean base-case shear-8

wave velocity profile, a shallow velocity of 5,300 ft/s (1,616 m/s) was assumed. This value reflects an assumption of a reasonable Poisson ratio of about 0.30 and the lower value of the compressional-wave velocity for the top of the Pennsylvanian McAlester Formation. (EPRI, 2013d)

Provided the materials to basement depth reflect similar sedimentary rocks and age, the shear-wave velocity gradient for sedimentary rock of 0.5 m/m/s (EPRI, 2013a) was assumed to be appropriate for the site. The shallow shear-wave velocity of 5,300 ft/s (1,616 m/s) was taken at the surface of the profile with the velocity gradient applied at that point, resulting in a base-case shear-wave velocity of about 7,772 ft/s (2,369 m/s) at a depth of 5,000 ft (1,524 m). The mean or best estimate base-case profile is shown as profile P1 in Figure 2.3.2-1. (EPRI, 2013d)

Based on the uncertainty in shear-wave velocities due to the lack of measurements, a scale factor of 1.57 was adopted to reflect upper and lower range base-cases. The scale factor of 1.57 reflects a Otpln of about 0.35 based on the SPID (EPRI, 2013a) 101h and 9 0 th fractiles which implies a 1.28 scale factor on o. (EPRI, 2013d)

Using the best estimate or mean base-case profile (P1), the depth independent scale factor of 1.57 was applied to develop lower and upper range base-cases profiles P2 and P3 respectively with the stiffest profile (P3) reaching reference rock velocities at a depth of about 1,200 ft (366 m). Base-case profiles P1 and P2 have a mean depth below the SSE of 5,000 ft (1,524 m) to hard reference rock, randomized +/-1,500 ft (+/-457 m). The base-case profiles (P1, P2, and P3) are shown in Figure 2.3.2-1 and listed in Table 2.3.2-1. The depth randomization reflects +/-30%

of the depth to provide a realistic broadening of the fundamental resonance rather than reflect actual random variations to basement shear-wave velocities across a footprint. (EPRI, 2013d) 9

Vs profiles for Arkansas Site Vs (ft/sec) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

500 1000 1500 2000 - Profile 1

- Profile 2 2500

• 3000 ... Profile 3 3500 4000 4500 5000 5500 Figure 2.3.2-1. Shear-wave velocity profiles for ANO - Unit 2. (EPRI, 2013d) 10

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 2 site. (EPRI, 2013d)

______Profile 1 _____Profile 2 _ ___ Profile 3 ____

thickness depth Vs thickness depth Vs thickness depth Vs 0 5,302 0 3,378 0 8,325 10.0 10.0 5,302 10.0 10.0 3,378 10.0 10.0 8,325 10.0 20.0 15,307 10.0 20.0 3,381 10.0 20.0 18,332 10.0 30.0 5,312 10.0 30.0 3,384 10.0 30.0 8,340 10.0 40.0 5,317 10.0 40.0 3,387 10.0 40.0 8,348 10.0 50.0 5,322 10.0 50.0 3,390 10.0 50.0 8,356 10.0 60.0 5,327 10.0 60.0 3,393 10.0 60.0- 8,364 10.0 70.0 5,332 10.0 70.0 3,397 10.0 70.0 8,372 10.0 80.0 5,337 10.0 80.0 3,400 10.0 80.0 8,379 10.0 90.0 5,342 10.0 90.0 3,403 10.0 90.0 8,387 10.0 100.0 5,347 10.0 100.0 3,406 10.0 100.0 8,395 10.0 110.0 5,352 10.0 110.0 3,409 10.0 110.0 8,403 10.0 120.0 5,357 10.0 120.0 3,413 10.0 120.0 8,411 10.0 130.0 5,362 10.0 130.0 3,416 10.0 130.0 18,419 10.0 140.0 5,367 10.0 140.0 3,419 10.0 140.0 8,427 10.0 150.0 5,372 10.0 150.0 3,422 10.0 150.0 8,434 10.0 160.0 5,377 10.0 160.0 3,425 10.0 160.0 8,442 10.0 170.0 5,382 10.0 170.0 3,428 10.0 170.0 8,450 10.0 180.0 5,387 10.0 180.0 3,432 10.0 180.0 8,458 10.0 190.0 15,392 10.0 190.0 3,435 10.0 190.0 8,466 10.0 200.0 5,397 10.0 200.0 3,438 10.0 200.0 8,474 10.0 210.0 5,402 10.0 210.0 3,441 10.0 210.0 8,481 10.0 220.0 5,407 10.0 220.0 3,444 10.0 220.0 8,489 10.0 230.0 5,412 10.0 230.0 3,448 10.0 230.0 8,497 10.0 240.0 5,417 10.0 240.0 3,451 10.0 240.0 8,505 10.0 250.0 5,422 10.0 250.0 3,454 10.0 250.0 8,513 10.0 260.0 5,427 10.0 260.0 3,457 10.0 260.0 8,521 10.0 270.0 5,432 10.0 270.0 3,460 10.0 270.0 8,529 10.0 1280.0 5,437 10.0 280.0 3,464 10.0 280.0 8,536 10.0 290.0 5,442 10.0 290.0 3,467 10.0 290.0 8,544 10.0 300.0 5,447 10.0 300.0 3,470 10.0 300.0 8,552 10.0 310.0 5,452 1 10.0 310.0 3,473 10.0 310.0 8,560 10.0 320.0 5,457 10.0 320.0 3,476 10.0 320.0 8,568 10.0 330.0 5,462 10.0 330.0 3,479 10.0 330.0 8,576 10.0 1340.0 5,467 10.0 340.0 3,483 10.0 340.0 8,584 10.0 350.0 5,472 10.0 350.0 3,486 10.0 350.0 8,591 10.0 360.0 5,477 10.0 360.0 3,489 10.0 360.0 8,599 10.0 370.0 5,482 10.0 1370.0 3,492 1 10.0 370.0 8,607 11

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 2 site. (EPRI, 2013d)

Profile 1 Profile 2 Profile 3 thickness depth Vs thickness depth Vs thickness depth Vs 10.0 380. 5, 487 10.0 380.0 3, 495 10.0 380.0 8, 615 10.0 390.0 5,492 10.0 390.0 3,499 10.0 390.0 8,623 10.0 400.0 5,497 10.0 400.0 3,502 10.0 400.0 8,6231 10.0 410.0 5,502 10.0 410.0 3,505 10.0 410.0 8,638 10.0 420.0 5,507 10.0 420.0 3,508 10.0 420.0 8,646 10.0 430.0 5,512 10.0 430.0 3,511 10.0 430.0 8,6546 10.0 440.0 5,517 10.0 440.0 3,514 10.0 440.0 8,662 10.0 450.0 5,522 10.0 450.0 3,518 10.0 450.0 8,670 10.0 460.0 5,527 10.0 460.0 3,5218 10.0 460.0 8,678 10.0 470.0 5,5327 10.0 470.0 3,524 10.0 470.0 8,6786 10.0 480.0 5,537 10.0 480.0 3,527 10.0 480.0 8,693 10.0 490.0 5,542 10.0 490.0 3,530 10.0 490.0 8,701 10.0 500.0 5,547 10.0 500.0 3,534 10.0 500.0 8,709 100.0 600.0 5,5472 100.0 600.0 3,550 100.0 600.0 8,748 100.0 700.0 5,622 100.0 700.0 3,581 100.0 700.0 18,782 100.0 800.0 5,672 100.0 800.0 3,6813 100.0 800.0 8,905 100.0 899.9 5,6722 100.0 899.9 3,645 100.0 899.9 8,984 100.0 999.9 5,772 100.0 999.9 3,677 100.0 999.9 89,06 100.0 1,99.9 5,822 100.0 1,99.9 3,6709 100.0 1,99.9 9,141 100.0 1,199.9 5,872 100.0 1,199.9 3,741 100.0 1,199.9 9,2191 100.0 1,299.9 5,922 100.0 1,299.9 3,772 100.0 1,299.9 9,285 100.0 1,399.9 5,972 100.0 1,399.9 3,804 100.0 1,399.9 9,285 100.0 1,499.9 6,022 100.0 1,499.9 3,836 100.0 1,499.9 9,285 100.0 1,599.9 6,072 100.0 1,599.9 3,8368 100.0 1,599.9 9,285 100.0 1,699.9 6,122 100.0 1,699.9 3,900 100.0 1,699.9 9,285 100.0 1,799.9 6,172 100.0 1,799.9 3,932 100.0 1,799.9 9,285 100.0 1,899.9 6,222 100.0 1,899.9 3,964 100.0 1,899.9 9,285 100.0 1,999.9 6,272 100.0 1,999.9 3,995 100.0 1,999.9 9,285 100.0 2,099.9 6,3272 100.0 2,099.9 4,027 100.0 2,099.91 9,285 100.0 2,199.9 6,372 100.0 2,199.9 4,059 100.0 2,199.9 9,285 100.0 2,299.9 6,422 100.0 2,299.9 4,0591 100.0 2,299.9 9,285 100.0 2,399.91 6,472 100.0 2,399.9 4,012 100.0 2,399.9 9,285 100.0 2,499.9 6,522 100.0 2,499.9 4,155 100.0 2,499.9 9,285 100.0 2,599.9 6,572 100.0 2,599.9 4,186 100.0 2,599.9 9,285 100.0 2,699.9 6,622 100.0 2,699.9 4,2186 100.0 2,699.9 9,285 100.0 2,799.8 6,672 100.0 2,799.8 4,250 100.0 2,799.8 9,285 100.0 2,899.8 6,6722 100.0 2,899.8 4,`282 100.0 2,899.8 9,285 100.0 2,999.8 6,772 100.0 2,999.8 4,314 100.0 2,999.8 9,285 12

Table 2.3.2-1. Layer thicknesses, depths, and shear-wave velocities (Vs) for 3 profiles, ANO -

Unit 2 site. (EPRI, 2013d)

Profile 1 Profile 2 Profile 3 thickness depth Vs thickness depth Vs thickness depth Vs 100.0(ft) (ft/s) (ft) (ft) (f34s) (ft) 3 ft9 9,S) 100.0 3,099.8 6,822 100.0 3,099.8 4,346 100.0 3,099.8 9,285 100.0 3,199.8 6,872 100.0 3,199.8 4,378 100.0 3,199.8 9,285 100.0 3,299.8 6,922 100.0 3,299.8 4,409 100.0 3,299.8 9,285 100.0 3,399.8 6,972 100.0 3,399.8 4,441 100.0 3,399.8 9,285 100.0 3,499.8 7,022 100.0 3,499.8 4,473 100.0 3,499.8 9,285 100.0 3,599.8 7,072 100.0 3,599.8 4,505 100.0 3,599.8 9,285 100.0 3,699.8 7,122 100.0 3,699.8 4,537 100.0 3,699.8 9,285 100.0 3,799.8 7,172 100.0 3,799.8 4,569 100.0 3,799.8 9,285 100.0 3,899.8 7,222 100.0 3,899.8 4,600 100.0 3,899.8 9,285 100.0 3,999.8 7,272 100.0 3,999.8 4,632 100.0 3,999.8 9,285 100.0 4,099.8 7,322 100.0 4,099.8 4,664 100.0 4,099.8 9,285 100.0 4,199.8 7,372 100.0 4,199.8 4,696 100.0 4,199.8 9,285 100.0 4,299.8 7,422 100.0 4,299.8 4,728 100.0 4,299.8 9,285 100.0 4,399.8 7,472 100.0 4,399.8 4,760 100.0 4,399.8 9,285 100.0 4,499.8 7,522 100.0 4,499.8 4,792 100.0 4,499.8 9,285 100.0 4,599.8 7,572 100.0 4,599.8 4,823 100.0 4,599.8 9,285 100.0 4,699.8 7,622 100.0 4,699.8 4,855 100.0 4,699.8 9,285 100.0 4,799.7 7,672 100.0 4,799.7 4,887 100.0 4,799.7 9,285 100.0 4,899.7 7,722 100.0 4,899.7 4,919 100.0 4,899.7 9,285 100a.0 4,999.7 7,772 100.0 4,999.7 4,951 100.0 4,999.7 9,285 3,280.8 8,280.6 9,285 3,280.8 8,280.6 9,285 3,280.8 8,280.6 9,285 2.3.2.1 Shear Modulus and Damping Curves Nonlinear dynamic material properties were not available for ANO - Unit 2 for sedimentary rocks. The rock material over the upper 500 ft (150 m) was assumed to have behavior that could be modeled as either linear or non-linear. To represent this potential for either case in the upper 500 ft of sedimentary rock at the ANO - Unit 2 site, two sets of shear modulus reduction and hysteretic damping curves were used. Consistent with the SPID (EPRI, 2013a), the EPRI rock curves (model Ml) were considered to be appropriate to represent the upper range nonlinearity likely in the materials at this site and linear analyses (model M2) was assumed to represent an equally plausible alternative rock response across loading level. For the linear analyses, the low strain damping from the EPRI rock curves were used as the constant damping values in the upper 500 ft. (EPRI, 2013d) 13

2.3.2.2 Kappa Base-case kappa estimates were determined using Section B-5.1.3.1 of the SPID (EPRI, 2013a) for a firm CEUS rock site. Kappa for a firm rock site with at least 3,000 ft (1 km) of sedimentary rock may be estimated from the average S-wave velocity over the upper 100 ft (Vsioa) of the subsurface profile. For the ANO - Unit 2 site, with at least 3,000 ft (1 km) of firm rock, the corresponding average shear-wave velocities over the top 100 ft (31 m) were 5,325 ft/s (1,623 m/s) (P1), 3,391 ft/s (1,034 m/s) (P2), and 8,360 ft/s (2,548 m/s) (P3). The corresponding kappa estimates were 0.014 s, 0.023 s, and 0.009 s respectively. The range of kappa from 0.009 s to 0.023 s reflects a reasonable assessment of epistemic uncertainty. The suite of kappa estimates and associated weights are listed in Table 2.3.2-2. (EPRI, 2013d)

Table 2.3.2-2. Kappa Values and Weights Used for Site Response Analyses. (EPRI, 2013d)

Velocity Profile Kappa(s)

P1 0.014 P2 0.023 P3 0.009 Weights P1 0.4 P2 0.3 P3 0.3 G/Gmax and Hysteretic Damping Curves M1 0.5 M2 0.5 2.3.3 Randomization of Base Case Profiles To account for the aleatory variability in dynamic material properties that is expected to occur across a site at the scale of a typical nuclear facility, variability in the assumed shear-wave velocity profiles has been incorporated in the site response calculations. For the ANO - Unit 2 site, random shear wave velocity profiles were developed from the base case profiles shown in Figure 2.3.2-1. Consistent with the discussion in Appendix B of the SPID (EPRI, 2013a), the velocity randomization procedure made use of random field models which describe the statistical correlation between layering and shear wave velocity. The default randomization parameters developed in (Toro,1997) for United States Geological Survey "A" site conditions were used for this site. Thirty random velocity profiles were generated for each base case profile. These random velocity profiles were generated using a natural log standard deviation of 0.25 over the upper 50 ft and 0.15 below that depth. As specified in the SPID (EPRI, 2013a),

correlation of shear wave velocity between layers was modeled using the footprint correlation model. In the correlation model, a limit of +/-2 standard deviations about the median value in each layer was assumed for the limits on random velocity fluctuations. (EPRI, 2013d) 14

2.3.4 Input Spectra Consistent with the guidance in Appendix B of the SPID (EPRI, 2013a), input Fourier amplitude spectra were defined for a single representative earthquake magnitude (M 6.5) using two different assumptions regarding the shape of the seismic source spectrum (single-corner and double-corner). A range of 11 different input amplitudes (median peak ground accelerations (PGA) ranging from 0.01g to 1.5g) were used in the site response analyses. The characteristics of the seismic source and upper crustal attenuation properties assumed for the analysis of the ANO - Unit 2 site were the same as those identified in Tables B-4, B-5, B-6 and B-7 of the SPID (EPRI, 2013a) as appropriate for typical CEUS sites. (EPRI, 2013d) 2.3.5 Methodology To perform the site response analyses for the ANO - Unit 2 site, a random vibration theory (RVT) approach was employed. This process utilizes a simple, efficient approach for computing site-specific amplification functions and is consistent with existing NRC guidance and the SPID (EPRI, 2013a). The guidance contained in Appendix B of the SPID (EPRI, 2013a) on incorporating epistemic uncertainty in shear-wave velocities, kappa, non-linear dynamic properties and source spectra for plants with limited at-site information was followed for the ANO - Unit 2 site. (EPRI, 2013d) 2.3.6 Amplification Functions The results of the site response analysis consist of amplification factors (5% damped pseudo absolute response spectra) which describe the amplification (or de-amplification) of hard reference rock motion as a function of frequency and input reference rock amplitude. The amplification factors are represented in terms of a median amplification value and an associated standard deviation (sigma) for each oscillator frequency and input rock amplitude. Consistent with the SPID (EPRI, 2013a) a minimum median amplification value of 0.5 was employed in the present analysis. Figure 2.3.6-1 illustrates the median and +/-1 standard deviation in the predicted amplification factors developed for the eleven loading levels parameterized by the median reference (hard-rock) peak acceleration (0.01g to 1.50g) for profile P1 and EPRI (EPRI, 2013a) rock G/Gmax and hysteretic damping curves. The variability in the amplification factors results from variability in shear-wave velocity, depth to hard-rock, and modulus reduction and hysteretic damping curves. To illustrate the effects of nonlinearity at the ANO - Unit 2 firm rock site, Figure 2.3.6-2 shows the corresponding amplification factors developed with linear site response analyses (model M2). Between the linear and nonlinear (equivalent-linear) analyses, Figures 2.3.6-1 and Figure 2.3.6-2 respectively show only a minor difference for 0.5g loading level and below. Above about the 0.5g loading level, the differences increase significantly but only above about 20 Hz. Tabular data for Figure 2.3.6-1 and Figure 2.3.6-2 is provided For Information Only in Appendix A. (EPRI, 2013d) 15

C*

00 U

0 0

C3 INPUT MOTION4 0OaI INPUT MIOTION'0.05G 00 0 02 ro 0

C3 0'

43 4-'

INPUT MOTIONI 0 tOG INPUT MOTION~0,20G 0

C3 CE

.-0 0 - '-'-S.,

CE 0 INPUJT NOTION 0.30G INPUT M¶OTION~

0.40G Z q i I ZDIII i I i I IRI*I i l i R 0 IO2 1a 2 1 1 to to I 10 -1 100 ]a I Frequencu (Hz) Frequency (Hz)

AMPLIFICATION, ARKANSAS, MIPIKI M 6.5, 1 CORNER: PAGE I OF 2 Figure 2.3.6-1 .Example suite of amplification factors (5% damping pseudo-absolute acceleration spectra) developed for the mean base-case profile (P1), EPRI rock modulus reduction and hysteretic damping curves (model M1), and base-case kappa (K1) at eleven loading levels of hard-rock median peak acceleration values from 0.Olg to 1.50g. M 6.5 and single-corner source model (EPRI, 2013a). (EPRI, 2013d) 16

C

~1 0

00 03 INPUT MIOTION' 0.50G INPUT MOTION 0.75G CL E

0 03 0

03 INPUT MOTION' l.00G INPUT MOTIONI1.25C 0-03 CC INPUT NOTIONi 1.50G 10 -1 to 0 to 1 10 2 Frequency (Hz)

AMPLIFICATION, ARKANSAS, MIPIKI M 6.5, 1 CORNER: PAGE 2 OF 2 Figure 2.3.6-1 .(cont.)

17

C -

0 ob U

C) 0 IraiT MiOTION G.OIG INPUT MOTION~ O.05C a:

0 CC.

0 C) 1INPUT MIOTION G04CC 0 INPUT MOTION4 0.20r.

0 V-.-

INPUT MlOTIONI0.30G lT MOTION 0.40C

• i l li*l$ I l I EI*I@L I

• I IRII 10 -1 w 0 10 1 1o 2 I0 -1 10 0 10 1 10 2 Frequency (Hz) Frequency (Hz)

AMPLIFICATION, ARKANSAS, M2PIK1 M 6.5, 1 CORNER: PAGE I OF 2 Figure 2.3.6-2. Example suite of amplification factors (5% damping pseudo absolute acceleration spectra) developed for the mean base-case profile (P1), linear site response (model M2), and base-case kappa (K1) at eleven loading levels of hard rock median peak acceleration values from 0.01g to 1.50g. M 6.5 and single-corner source model (EPRI, 2013a). (EPRI, 2013d) 18

C3 I-)

0 ar- 0~

INPUT MOTION1 0,50G IPT MOTIONI 0.75G cn3 0

003 0

C3 INPUT MOTIONI L.0G INPUT MOTIONI 1.25G 42-,

E 0r C3 INPUT MO0TION~ 1.50G loa- toaoO 1 ,a 2 Frequencql (Hz)

AMPLIFICATION, ARKANSAS, M2P1KI M 6.5, 1 CORNER; PAGE 2 OF 2 Figure 2.3.6-2.(cont.)

19

2.3.7 Control Point Seismic Hazard Curves The procedure to develop probabilistic site-specific control point hazard curves used in the present analysis follows the methodology described in Section B-6.0 of the SPID (EPRI, 2013a).

This procedure (referred to as Method 3) computes a site-specific control point hazard curve for a broad range of spectral accelerations given the site-specific bedrock hazard curve and site-specific estimates of soil or soft-rock response and associated uncertainties. This process is repeated for each of the seven spectral frequencies for which ground motion equations are available. The dynamic response of the materials below the control point was represented by the frequency- and amplitude-dependent amplification functions (median values and standard deviations) developed and described in the previous section. The resulting control point mean hazard curves for ANO - Unit 2 are shown in Figure 2.3.7-1 for the seven spectral frequencies for which ground motion equations are defined. Tabulated values of mean and fractile seismic hazard curves and site response amplification functions are provided in Appendix A. (EPRI, 2013d)

Total Mean Soil Hazard by Spectral Frequency at Arkansas 1E-2 1E-3 W -25 Hz 3 *-10 Hz IE-4 5 Hz PGA C<

W -- -1Hz 0.5 Hz

=1E-56---

0 0-0.5 Hz C

E-7 1E-6 - - ----- ----

0.01 0.1 1 10 Spectral acceleration (g)

Figure 2.3.7-1. Control point mean hazard curves for spectral frequencies of 0.5, 1.0, 2.5, 5.0, 10, 25 and PGA (100 Hz) at ANO - Unit 2. (EPRI, 2013d) 2.4 Control Point Response Spectrum The control point hazard curves described above have been used to develop uniform hazard response spectra (UHRS) and the GMRS. The UHRS were obtained through linear 20

interpolation in log-log space to estimate the spectral acceleration at each spectral frequency for the 10 4 and 10- per year hazard levels. Table 2.4-1 shows the UHRS and GMRS accelerations for a range of spectral frequencies. (EPRI, 2013d) 21

Table 2.4-1. UHRS and GMRS for ANO - Unit 2. (EPRI, 2013d) 1g 4 UHRS 5 Freq. (Hz) 1- UHRS GMRS (g) 100 1.82E-01 4.88E-01 2.40E-01 90 1.82E-01 4.91E-01 2.42E-01 80 1.83E-01 4.97E-01 2.44E-01 70 1.86E-01 5.09E-01 2.50E-01 60 1.96E-01 5.42E-01 2.65E-01 50 2.20E-01 6.22E-01 3.03E-01 40 2.59E-01 7.42E-01 3.61E-01 35 2.79E-01 8.02E-01 3.89E-01 30 3.02E-01 8.67E-01 4.21E-01 25 3.26E-01 9.32E-01 4.53E-01 20 3.54E-01 9.85E-01 4.82E-01 15 3.81E-01 1.03E+00 5.06E-01 12.5 3.90E-01 1.03E+00 5.10E-01 10 3.86E-01 1.OOE+00 4.96E-01 9 3.80E-01 9.71E-01 4.83E-01 8 3.76E-01 9.46E-01 4.72E-01 7 3.64E-01 9.06E-01 4.53E-01 6 3.50E-01 8.54E-01 4.29E-01 5 3.32E-01 7.91E-01 3.99E-01 4 2.92E-01 6.90E-01 3.48E-01 3.5 2.71E-01 6.36E-01 3.22E-01 3 2.44E-01 5.67E-01 2.87E-01 2.5 2.11E-01 4.87E-01 2.47E-01 2 1.91E-01 4.35E-01 2.21E-01 1.5 1.73E-01 3.84E-01 1.96E-01 1.25 1.57E-01 3.43E-01 1.76E-01 1 1.41E-01 3.01E-01 1.55E-01 0.9 1.28E-01 2.76E-01 1.42E-01 0.8 1.20E-01 2.59E-01 1.33E-01 0.7 1.13E-01 2.47E-01 1.27E-01 0.6 1.00E-01 2.20E-01 1.13E-01 0.5 8.46E-02 1.88E-01 9.62E-02 0.4 6.77E-02 1.51 E-01 7.70E-02 0.35 5.92E-02 1.32E-01 6.74E-02 0.3 5.08E-02 1.13E-01 5.77E-02 0.25 4.23E-02 9.41E-02 4.81E-02 0.2 3.38E-02 7.53E-02 3.85E-02 0.15 2.54E-02 5.65E-02 2.89E-02 0.125 2.12E-02 4.71E-02 2.41E-02 0.1 1.69E-02 3.76E-02 1.92E-02 22

The 1 E-4 and 1E-5 UHRS are used to compute the GMRS at the control point and are shown in Figure 2.4-1. (EPRI, 2013d)

Mean Soil UHRS and GMRS at Arkansas 1.2 1.

--1-1E-5 UHRS o 0.8

-GMRS U 0.6

-1E-4 UHRS w 0.4 0.2 0.

0.1 1 10 100 Spectral frequency, Hz Figure 2.4-1. UHRS for 104 and 10-5 and GMRS at control point for ANO - Unit 2 (5%-damped response spectra). (EPRI, 2013d) 3.0 Plant Design Basis and Beyond Design Basis Evaluation Ground Motion The design bases for ANO - Unit 2 are identified in the Updated Final Safety Analysis Report (Entergy, 2014b) and other pertinent documents.

An evaluation for beyond design basis (BDB) ground motions was performed in the Individual Plant Examination of External Events (IPEEE). The IPEEE capacity response spectrum is included below for screening purposes.

3.1 Safe Shutdown Earthquake Descriptionof Spectral Shape The SSEs for ANO - Unit 2 were developed in accordance with 10 CFR Part 100, Appendix A through an evaluation of the maximum earthquake potential for the region surrounding the site.

Considering the historic seismicity of the site region, Entergy determined that because of the excellent formation conditions and the recent general quiescence of the area that a low earthquake intensity could be selected. However, considering the New Madrid earthquake, which is the only severe earthquake experienced in the central United States in historic time, an 23

intensity of VII on the Modified Mercalli Intensity Scale of 1931 has been assigned for the site.

This is considered to be conservative and corresponds to a design spectrum of 0.20g for the SSE. (Entergy, 2014a)

The SSE is defined in terms of a PGA and a design response spectrum. Table 3.1-1 shows the spectral acceleration (SA) values as a function of frequency for the 5% damped horizontal SSE.

(Entergy, 2014b)

Table 3.1-1. SSE for ANO - Unit 2 (Entergy, 2014b)

Freq.

(Hz) SA (g) 0.5 0.11 1.0 0.20 2.5 0.40 5.0 0.40 10 0.33 25 0.22 100 0.20 3.2 Control Point Elevation The SSE control point elevation is at Elevation 326 ft. It is defined to be at the bottom of the foundation of the highest safety-related building, which is the Reactor Building. The bottom of the foundation for the Reactor Building is at 326 ft within the Pennsylvanian shale (Entergy, 2014b).

3.3 IPEEE Descriptionand Capacity Response Spectrum The IPEEE was performed as a focused scope SMA using the EPRI approach. The results of the IPEEE were submitted to the NRC (Entergy,1996). Results of the NRC review are documented in reference (U.S. NRC, 2001).

The ANO - Unit 2 Seismic IPEEE was performed using the Seismic Margins assessment option per the EPRI methodology of EPRI- 6041 (EPRI, 1991). With this method, a seismic margins earthquake (SME) was postulated and the items needed for safe shutdown were then evaluated for the SME demand. Components and structures that were determined to have sufficient capacity to survive the SME without loss of function were screened out. Items that did not screen were subjected to a more detailed evaluation, including calculation of a high-confidence of low-probability of failure (HCLPF) PGA for that item. A 0.30 PGA earthquake level and the NUREG/CR-0098 (U.S. NRC, 1978) median response spectra shape were used.

The IPEEE was reviewed for adequacy utilizing the guidance provided in Section 3.3 of the SPID (EPRI, 2013a). The IPEEE Adequacy Determination according to SPID (EPRI, 2013a)

Section 3.3.1 is included in Appendix B.

24

The results of the review have shown, in accordance with the criteria established in SPID (EPRI, 2013a) Section 3.3, that the IPEEE is adequate to support screening of the updated seismic hazard for ANO - Unit 2. The review also concluded that the risk insights obtained from the IPEEE are still valid under the current plant configuration.

The safety-related structures at ANO - Unit 2 are founded on rock. As stated in NUREG 1407 Section 3.2.1, a plant in the full scope category that is located on a rock site is not required to perform a soil failure evaluation.

The 5% damped horizontal IPEEE HCLPF Spectrum (IHS) spectral acceleration for ANO - Unit 2 is provided in Table 3.3-1. The SSE and the IHS are shown in Figure 3.3-1.

Table 3.3-1. IHS for ANO - Unit 2 (Entergy, 1996).

Freq. IHS (Hz) (g) 0.5 0.15 1.0 0.29 2.2 0.64 8.0 0.64 10 0.57 25 0.35 33 0.30 100 0.30 25

0.7 0.6 0.5 8 0.4

.2 "U 0.3 U

0.2 0.1 0

0.1 1 Frequecy 100 Frequency (Hz)

Figure 3.3-1. SSE and IHS Response Spectra for ANO - Unit 2.

4.0 Screening Evaluation In accordance with SPID (EPRI, 2013a) Section 3, a screening evaluation was performed as described below.

4.1 Risk Evaluation Screening (1 to 10 Hz)

In the 1 to 10 Hz part of the response spectrum, the IHS exceeds the GMRS for ANO - Unit 2.

Based on this comparison, a risk evaluation will not be performed.

4.2 High Frequency Screening (> 10 Hz)

For a portion of the range above 10 Hz, the GMRS exceeds the SSE. Therefore, ANO - Unit 2 screens-in for a High Frequency Confirmation.

4.3 Spent Fuel Pool Evaluation Screening (1 to 10 Hz)

In the I to 10 Hz part of the response spectrum, the GMRS exceeds the SSE. Therefore, ANO

- Unit 2 screens-in for a Spent Fuel Pool evaluation.

(Hz 26

5.0 Interim Actions Based on the screening evaluation, the expedited seismic evaluation described in EPRI 3002000704 (EPRI, 2013c) will be performed as proposed in a letter to NRC (ML13101A379) dated April 9, 2013 (NEI, 2013a) and agreed to by NRC (ML13106A331) in a letter dated May 7, 2013 (U.S. NRC, 2013). The full evaluation of soil failures required in SPID (EPRI, 2013a) is not required as the supporting medium for safety related structures is rock with a Vs = 3500fps or more. Item 2.7 of Enclosure 3 to the NRC SER (US NRC, 2001) observes: "The principal structures at ANO-2 are founded on bedrock; therefore, a soil evaluation is not required."

Consistent with NRC letter (ML14030A046) dated February 20, 2014 (U.S. NRC, 2014), the seismic hazard reevaluations presented herein are distinct from the current design and licensing bases of ANO - Unit 2. Therefore, the results do not call into question the operability or functionality of SSCs and are not reportable pursuant to 10 CFR 50.72, "Immediate notification requirements for operating nuclear power reactors," and 10 CFR 50.73, "Licensee event report system".

The NRC letter also requests that licensees provide an interim evaluation or actions to demonstrate that the plant can cope with the reevaluated hazard while the expedited approach and risk evaluations are conducted. In response to that request, NEI letter dated March 12, 2014 (NEI, 2014), provides seismic core damage risk estimates using the updated seismic hazards for the operating nuclear plants in the Central and Eastern United States. These risk estimates continue to support the following conclusions of the NRC GI-199 Safety/Risk Assessment (U.S. NRC, 2010):

Overall seismic core damage risk estimates are consistent with the Commission's Safety Goal Policy Statement because they are within the subsidiary objective of 1004/year for core damage frequency. The GI-199 Safety/Risk Assessment, based in part on information from the U.S. Nuclear Regulatory Commission's (NRC's) Individual Plant Examination of External Events (IPEEE) program, indicates that no concern exists regarding adequate protection and that the current seismic design of operating reactors provides a safety margin to withstand potential earthquakes exceeding the original design basis.

ANO - Unit 2 is included in the March 12, 2014 risk estimates (NEI, 2014). Using the methodology described in the NEI letter, all plants were shown to be below 10-4/year; thus, the above conclusions apply.

In accordance with the Near-Term Task Force Recommendation 2.3, ANO - Unit 2 performed seismic walkdowns using the guidance in EPRI Report 1025286 (EPRI, 2012). The seismic walkdowns were completed and captured in Fukushima Seismic Walkdown Report (Entergy, 2013). The goal of the walkdowns was to verify current plant configuration with the existing licensing basis, to verify the current maintenance plans, and to identify any vulnerabilities. The walkdown also verified that any vulnerabilities identified in the IPEEE (Entergy, 1996) were 27

adequately addressed. The results of the walkdown, including any identified corrective actions, confirm that ANO - Unit 2 can adequately respond to a seismic event.

6.0 Conclusions In accordance with the 50.54(f) request for information (U.S. NRC, 2012), a seismic hazard and screening evaluation was performed for Arkansas Nuclear One - Unit 2. A GMRS was developed solely for the purpose of screening for additional evaluations in accordance with the SPID (EPRI, 2013a). Based on the results of the screening evaluation, ANO - Unit 2 screens-in for a High Frequency Confirmation and a Spent Fuel Pool evaluation. Additionally, based on the results of the screening evaluation, ANO - Unit 2 screens-out of a risk evaluation.

7.0 References 10 CFR Part 50. Title 10, Code of Federal Regulations, Part 50, "Domestic Licensing of Production and Utilization Facilities," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 50.72. Title 10, Code of Federal Regulations, Part 50.72, "Immediate Notification Requirements for Operating Nuclear Power Reactors," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 50.73. Title 10, Code of Federal Regulations, Part 50.73, "Licensee Event Report System," U.S. Nuclear Regulatory Commission, Washington DC.

10 CFR Part 100. Title 10, Code of Federal Regulations, Part 100, "Reactor Site Criteria," U.S.

Nuclear Regulatory Commission, Washington DC.

CEUS-SSC (2012). "Central and Eastern United States Seismic Source Characterization for Nuclear Facilities, U.S. Nuclear Regulatory Commission Report," NUREG-2115; EPRI Report 1021097, 6 Volumes; DOE Report# DOE/NE-0140.

Entergy (1996). Report Number 96-R-2016-02, "Individual Plant Examination of External Events (IPEEE) for Seismic SMA at ANO-2," dated April 1996.

Entergy (201-2). "EPRI Data Request for Site Amplification Calculations, Arkansas Nuclear One-Units 1 & 2," Informal report transmitted from Entergy to EPRI in July, 2012.

Entergy (2013). "Updated Arkansas Nuclear One, Unit 2 Seismic Walkdown Report,"

Calculation ANO2-CS-12-00001, Revision 1, Transmitted to NRC via Letter 1CAN091302, dated September 30, 2013.

Entergy (2014a). "Arkansas Nuclear One - Unit 1, SAR Amendment 26," Docket Number 50-313, February 2014.

Entergy (2014b). "Arkansas Nuclear One - Unit 2, SAR Amendment 25," Docket Number 50-368, January 2014.

EPRI (1991). "A Methodology for Assessment of Nuclear Power Plant Seismic Margin,"

Revision 1, NP-6041-SLR1, Aug 1991.

EPRI (2012). "Seismic Walkdown Guidance for Resolution of Fukushima Near-Term Task Force Recommendation 2.3: Seismic," EPRI 1025286, June 2012.

28

EPRI (2013a). "Seismic Evaluation Guidance Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," Electric Power Research Institute, Report 1025287, Feb. 2013.

EPRI (2013b). "EPRI (2004, 2006) Ground-Motion Model (GMM) Review Project," Electric Power Research Institute, Palo Alto, CA, Report. 3002000717, 2 volumes, June 2013.

EPRI (2013c). EPRI 3002000704, "Seismic Evaluation Guidance, Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," May 2013.

EPRI (2013d). "Arkansas Seismic Hazard and Screening Report," Electric Power Research Institute, Palo Alto, CA, dated December 23, 2013.

NEI (2013a). NEI Letter to NRC, "Proposed Path Forward for NTTF Recommendation 2.1:

Seismic Reevaluations," April 9, 2013.

NEI (2013b). NEI Letter, Kimberly A. Keithline to David L. Skeen, NRC "Relay Chatter Reviews for Seismic Hazard Screening," dated October 3, 2013.

NEI (2014). NEI Letter to NRC, "Seismic Risk Evaluations for Plants in the Central and Eastern United States," March 12, 2014.

Toro (1997). Appendix of: Silva, W.J., Abrahamson, N., Toro, G., and Costantino, C. (1997).

"Description and Validation of the Stochastic Ground Motion Model", Report Submitted to Brookhaven National Laboratory, Associated Universities, Inc., Upton, New York 11973, Contract No. 770573.

U.S. NRC (1978). "Development of Criteria for Seismic Review of Selected Nuclear Power Plants," NUREG/CR-0098, May 1978.

U.S. NRC (2001). "Arkansas Nuclear One, Units 1 and 2 - Individual Plant Examination of External Events (TAC Nos. M83588 and M83589)," dated February 27, 2001.

U.S. NRC (2010). "Implications of Updated Probabilistic Seismic Hazard Estimates in Certral and Eastern United States on Existing Plants," GI-1 99, September 2, 2010.

U.S. NRC (2007). "A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion," U.S. Nuclear Regulatory Commission Reg. Guide 1.208.

U.S. NRC (2012). NRC (E Leeds and M Johnson) Letter to All Power Reactor Licensees et al.,

"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," March 12, 2012.

U.S. NRC (2013). NRC Letter, Eric J. Leeds to Joseph E. Pollock, NEI "Electric Power Research Institute Final Draft Report XXXXXX, Seismic Evaluation Guidance:

Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic, As an Acceptable Alternative to the March 12, 2012, Information Request for Seismic Reevaluation," dated May 7, 2013.

U.S. NRC (2014). NRC Letter, Eric J. Leeds to All Power Reactor Licensees, "Supplemental Information Related to Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Seismic Hazard Reevaluations for Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident," dated February 20, 2014.

29

Appendix A Tabulated Data 30

Table A-la. Mean and Fractile Seismic Hazard Curves for 100 Hz (PGA) at ANO - Unit 2. (EPRI, 2013d)

AMPS(q) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 8.02E-02 4.31E-02 6.64E-02 8.12E-02 9.51E-02 9.93E-02 0.001 6.09E-02 2.76E-02 4.77E-02 '6.09E-02 7.66E-02 8.72E-02 0.005 1.83E-02 7.77E-03 1.16E-02 1.69E-02 2.29E-02 3.84E-02 0.01 9.30E-03 3.73E-03 5.35E-03 8.23E-03 1.20E-02 2.25E-02 0.015 6.06E-03 2.1OE-03 3.05E-03 5.27E-03 8.23E-03 1.51E-02 0.03 2.60E-03 5.50E-04 8.60E-04 1.92E-03 4.25E-03 7.34E-03 0.05 1.22E-03 1.77E-04 2.92E-04 6.93E-04 2.16E-03 4.19E-03 0.075 6.12E-04 7.45E-05 1.27E-04 2.96E-04 9.93E-04 2.32E-03 0.1 3.57E-04 4.07E-05 7.34E-05 1.67E-04 5.20E-04 1.38E-03 0.15 1.55E-04 1.74E-05 3.42E-05 7.66E-05 2.04E-04 5.75E-04 0.3 3.21E-05 3.47E-06 7.77E-06 1.92E-05 4.50E-05 1.04E-04 0.5 9.43E-06 7.89E-07 2.01E-06 5.91E-06 1.51E-05 2.92E-05 0.75 3.38E-06 1.82E-07 5.42E-07 1.98E-06 5.66E-06 1.11E-05

1. 1.55E-06 5.35E-08 1.84E-07 8.23E-07 2.68E-06 5.42E-06 1.5 4.76E-07 7.03E-09 3.19E-08 1.98E-07 8.12E-07 1.82E-06

3. 4.66E-08 2.39E-10 9.11E-10 1.02E-08 7.23E-08 2.1OE-07

5. 6.22E-09 1.42E-10 1.84E-10 8.35E-10 8.12E-09 3.01E-08 7.5 1.02E-09 1.32E-10 1.60E-10 2.13E-10 1.20E-09 5.12E-09

10. 2.51E-10 1.21E-10 1.32E-10 1.82E-10 3.57E-10 1.36E-09 31

Table A-i b. Mean and Fractile Seismic Hazard Curves for 25 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 8.59E-02 5.58E-02 7.34E-02 8.72E-02 9.93E-02 9.93E-02 0.001 6.98E-02 3.90E-02 5.83E-02 7.03E-02 8.23E-02 9.37E-02 0.005 2.62E-02 1.21E-02 1.84E-02 2.46E-02 3.19E-02 5.12E-02 0.01 1.45E-02 6.64E-03 9.24E-03 1.32E-02 1.79E-02 3.19E-02 0.015 9.81E-03 4.25E-03 5.91E-03 8.85E-03 1.27E-02 2.22E-02 0.03 4.61E-03 1.49E-03 2.16E-03 3.90E-03 6.73E-03 1.07E-02 0.05 2.41E-03 5.42E-04 8.35E-04 1.79E-03 4.01E-03 6.54E-03 0.075 1.36E-03 2.25E-04 3.68E-04 8.60E-04 2.39E-03 4.25E-03 0.1 8.75E-04 1.25E-04 2.1OE-04 4.98E-04 1.51E-03 3.01E-03 0.15 4.45E-04 5.66E-05 1.01E-04 2.35E-04 6.93E-04 1.62E-03 0.3 1.19E-04 1.51E-05 2.96E-05 6.73E-05 1.64E-04 3.84E-04 0.5 4.05E-05 5.20E-06 1.10E-05 2.64E-05 6.OOE-05 1.13E-04 0.75 1.65E-05 1.98E-06 4.50E-06 1.15E-05 2.60E-05 4.56E-05

1. 8.51E-06 9.37E-07 2.22E-06 5.91E-06 1.40E-05 2.39E-05 1.5 3.19E-06 2.80E-07 7.13E-07 2.13E-06 5.42E-06 9.51E-06

3. 4.77E-07 2.19E-08 6.54E-08 2.57E-07 8.60E-07 1.64E-06

5. 9.36E-08 2.25E-09 7.66E-09 3.90E-08 1.67E-07 3.57E-07 7.5 2.19E-08 3.95E-10 1.16E-09 6.83E-09 3.73E-08 9.11E-08

10. 7.14E-09 2.01E-10 3.57E-10 1.82E-09 1.15E-08 3.09E-08 32

Table A-ic. Mean and Fractile Seismic Hazard Curves for 10 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.37E-02 7.34E-02 8.00E-02 9.37E-02 9.93E-02 9.93E-02 0.001 8.1OE-02 5.75E-02 6.83E-02 8.12E-02 9.37E-02 9.93E-02 0.005 3.41E-02 1.79E-02 2.46E-02 3.37E-02 4.31E-02 5.35E-02 0.01 1.86E-02 9.24E-03 1.25E-02 1.79E-02 2.35E-02 3.23E-02 0.015 1.25E-02 6.09E-03 8.23E-03 1.18E-02 1.62E-02 2.25E-02 0.03 6.11E-03 2.57E-03 3.57E-03 5.58E-03 8.47E-03 1.16E-02 0.05 3.41E-03 1.10E-03 1.62E-03 2.96E-03 5.20E-03 7.45E-03 0.075 2.02E-03 5.05E-04 7.77E-04 1.57E-03 3.33E-03 5.12E-03 0.1 1.34E-03 2.76E-04 4.37E-04 9.37E-04 2.29E-03 3.79E-03 0.15 6.90E-04 1.13E-04 1.87E-04 4.19E-04 1.16E-03 2.22E-03 0.3 1.78E-04 2.46E-05 4.50E-05 1.02E-04 2.57E-04 5.83E-04 0.5 5.54E-05 7.55E-06 1.51E-05 3.52E-05 7.89E-05 1.67E-04 0.75 2.06E-05 2.68E-06 5.75E-06 1.40E-05 3.14E-05 5.83E-05

1. 1.00E-05 1.16E-06 2.64E-06 7.03E-06 1.60E-05 2.84E-05 1.5 3.47E-06 3.01E-07 7.66E-07 2.35E-06 5.91E-06 1.05E-05

3. 4.83E-07 1.67E-08 5.58E-08 2.57E-07 8.72E-07 1.72E-06

5. 9.34E-08 1.21E-09 4.98E-09 3.57E-08 1.67E-07 3.79E-07 7.5 2.20E-08 2.32E-10 6.54E-10 6.09E-09 3.73E-08 9.65E-08

10. 7.22E-09 1.82E-10 2.39E-10 1.60E-09 1.16E-08 3.28E-08 33

Table A-ild. Mean and Fractile Seismic Hazard Curves for 5.0 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.55E-02 7.55E-02 8.23E-02 9.65E-02 9.93E-02 9.93E-02 0.001 8.43E-02 6.OOE-02 6.93E-02 8.47E-02 9.93E-02 9.93E-02 0.005 3.61E-02 1.79E-02 2.49E-02 3.52E-02 4.77E-02 5.50E-02 0.01 1.89E-02 8.98E-03 1.25E-02 1.82E-02 2.57E-02 3.01E-02 0.015 1.23E-02 5.83E-03 8.OOE-03 1.18E-02 1.67E-02 2.01E-02 0.03 5.64E-03 2.35E-03 3.33E-03 5.35E-03 8.OOE-03 9.93E-03 0.05 3.08E-03 9.65E-04 1.49E-03 2.72E-03 4.70E-03 6.36E-03 0.075 1.78E-03 4.25E-04 6.73E-04 1.40E-03 2.92E-03 4.31E-03 0.1 1.14E-03 2.22E-04 3.63E-04 8.OOE-04 1.92E-03 3.23E-03 0.15 5.60E-04 8.47E-05 1.44E-04 3.33E-04 8.98E-04 1.90E-03 0.3 1.29E-04 1.53E-05 2.80E-05 6.45E-05 1.69E-04 4.98E-04 0.5 3.54E-05 3.95E-06 8.00E-06 1.92E-05 4.70E-05 1.20E-04 0.75 1.16E-05 1.23E-06 2.68E-06 7.03E-06 1.72E-05 3.52E-05

1. 5.13E-06 4.90E-07 1.15E-06 3.28E-06 8.12E-06 1.53E-05 1.5 1.58E-06 1.15E-07 3.01E-07 1.01E-06 2.68E-06 4.98E-06

3. 1.85E-07 5.75E-09 1.95E-08 9.24E-08 3.23E-07 6.83E-07

5. 3.21E-08 5.20E-10 1.72E-09 1.10E-08 5.35E-08 1.34E-07 7.5 6.96E-09 1.92E-10 3.14E-10 1.67E-09 1.05E-08 3.14E-08

10. 2.17E-09 1.55E-10 1.87E-10 4.77E-10 3.01E-09 1.01E-08 34

Table A-le. Mean and Fractile Seismic Hazard Curves for 2.5 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 9.00E-02 6.73E-02 7.55E-02 8.98E-02 9.93E-02 9.93E-02 0.001 7.37E-02 4.77E-02 5.75E-02 7.34E-02 9.11E-02 9.93E-02 0.005 2.44E-02 1.18E-02 1.57E-02 2.32E-02 3.33E-02 4.01E-02 0.01 1.17E-02 5.42E-03 7.34E-03 1.10E-02 1.60E-02 1.98E-02 0.015 7.39E-03 3.23E-03 4.50E-03 7.03E-03 1.02E-02 1.29E-02 0.03 3.35E-03 1.04E-03 1.62E-03 3.05E-03 5.05E-03 6.73E-03 0.05 1.74E-03 3.52E-04 6.09E-04 1.40E-03 2.92E-03 4.31E-03 0.075 9.27E-04 1.31E-04 2.35E-04 6.09E-04 1.62E-03 2.80E-03 0.1 5.49E-04 6.00E-05 1.11E-04 3.01E-04 9.37E-04 1.95E-03 0.15 2.35E-04 1.84E-05 3.57E-05 1.01E-04 3.57E-04 9.65E-04 0.3 4.12E-05 2.13E-06 4.70E-06 1.38E-05 5.05E-05 1.64E-04 0.5 9.27E-06 3.73E-07 9.65E-07 3.33E-06 1.16E-05 3.09E-05 0.75 2.61E-06 8.12E-08 2.46E-07 1.05E-06 3.63E-06 8.47E-06

1. 1.04E-06 2.53E-08 8.72E-08 4.31E-07 1.60E-06 3.57E-06 1.5 2.82E-07 4.19E-09 1.72E-08 1.10E-07 4.70E-07 1.08E-06

3. 2.84E-08 2.72E-10 7.89E-10 6.93E-09 4.50E-08 1.29E-07

5. 4.43E-09 1.82E-10 1.98E-10 7.45E-10 5.91E-09 2.07E-08 7.5 8.72E-10 1.32E-10 1.82E-10 2.19E-10 1.04E-09 4.07E-09

10. 2.52E-10 1.21E-10 1.32E-10 1.82E-10 3.52E-10 1.21E-09 35

Table A-if. Mean and Fractile Seismic Hazard Curves for 1.0 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 6.70E-02 3.63E-02 4.77E-02 6.73E-02 8.47E-02 9.51E-02 0.001 4.59E-02 2.04E-02 2.96E-02 4.56E-02 6.09E-02 7.23E-02 0.005 1.18E-02 4.63E-03 6.83E-03 1.10E-02 1.64E-02 2.13E-02 0.01 5.95E-03 2.01E-03 3.19E-03 5.50E-03 8.60E-03 1.13E-02 0.015 4.OOE-03 1.1OE-03 1.87E-03 3.63E-03 6.09E-03 8.OOE-03 0.03 1.92E-03 2.84E-04 5.75E-04 1.55E-03 3.28E-03 4.77E-03 0.05 9.45E-04 7.89E-05 1.79E-04 6.26E-04 1.74E-03 2.88E-03 0.075 4.54E-04 2.42E-05 5.91 E-05 2.39E-04 8.35E-04 1.60E-03 0.1 2.42E-04 9.79E-06 2.46E-05 1.07E-04 4.31E-04 9.37E-04 0.15 8.57E-05 2.49E-06 6.54E-06 3.01E-05 1.40E-04 3.57E-04 0.3 1.01E-05 1.84E-07 5.75E-07 2.80E-06 1.42E-05 4.25E-05 0.5 1.77E-06 2.01E-08 7.77E-08 4.77E-07 2.49E-06 7.23E-06 0.75 4.57E-07 2.88E-09 1.36E-08 1.1OE-07 6.73E-07 1.98E-06

1. 1.86E-07 7.45E-10 3.68E-09 3.79E-08 2.68E-07 8.47E-07 1.5 5.52E-08 2.16E-10 6.09E-10 7.77E-09 7.13E-08 2.64E-07

3. 6.63E-09 1.44E-10 1.82E-10 4.77E-10 5.91E-09 2.96E-08

5. 1.17E-09 1.32E-10 1.46E-10 1.82E-10 8.OOE-10 4.50E-09 7.5 2.58E-10 1.21E-10 1.32E-10 1.82E-10 2.42E-10 9.51E-10

10. 8.12E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 3.52E-10 36

Table A-lg. Mean and Fractile Seismic Hazard Curves for 0.5 Hz at ANO -

Unit 2. (EPRI, 2013d)

AMPS(g) MEAN 0.05 0.16 0.50 0.84 0.95 0.0005 3.27E-02 1.62E-02 2.25E-02 3.19E-02 4.31E-02 5.20E-02 0.001 1.92E-02 8.72E-03 1.25E-02 1.82E-02 2.60E-02 3.28E-02 0.005 4.97E-03 1.51E-03 2.49E-03 4.56E-03 7.45E-03 9.79E-03 0.01 2.75E-03 4.83E-04 9.79E-04 2.39E-03 4.50E-03 6.26E-03 0.015 1.86E-03 2.07E-04 4.77E-04 1.49E-03 3.28E-03 4.77E-03 0.03 7.82E-04 3.42E-05 9.65E-05 4.43E-04 1.49E-03 2.64E-03 0.05 3.24E-04 7.03E-06 2.16E-05 1.27E-04 5.83E-04 1.32E-03 0.075 1.35E-04 1.77E-06 5.75E-06 3.79E-05 2.16E-04 6.OOE-04 0.1 6.59E-05 6.26E-07 2.07E-06 1.44E-05 9.37E-05 3.01E-04 0.15 2.1OE-05 1.27E-07 4.63E-07 3.33E-06 2.53E-05 9.51E-05 0.3 2.17E-06 5.58E-09 2.76E-08 2.35E-07 2.07E-06 9.11E-06 0.5 3.56E-07 5.05E-10 2.60E-09 3.05E-08 3.14E-07 1.55E-06 0.75 8.87E-08 1.92E-10 4.63E-10 5.35E-09 7.13E-08 4.07E-07

1. 3.54E-08 1.82E-10 2.16E-10 1.53E-09 2.42E-08 1.62E-07 1.5 1.04E-08 1.32E-10 1.82E-10 3.42E-10 5.12E-09 4.37E-08

3. 1.26E-09 1.21E-10 1.32E-10 1.82E-10 4.07E-10 3.79E-09

5. 2.27E-10 1.21E-10 1.32E-10 1.82E-10 1.82E-10 5.83E-10 7.5 5.06E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 2.13E-10

10. 1.61E-11 1.21E-10 1.32E-10 1.82E-10 1.82E-10 1.82E-10 37

Table A-2. Amplification Functions for ANO - Unit 2. (EPRI, 2013d)

Median Sigma Median Sigma Median Sigma Median Sigma PGA AF In(AF) 25 Hz AF In(AF) 10 Hz AF In(AF) 5 Hz AF In(AF) 1.OOE-02 1.08E+00 4.75E-02 1.30E-02 9.47E-01 5.76E-02 1.90E-02 1.02E+00 9.03E-02 2.09E-02 1.17E+00 9.85E-02 4.95E-02 9.08E-01 6.43E-02 1.02E-01 7.27E-01 1.11E-01 9.99E-02 9.80E-01 1.06E-01 8.24E-02 1.16E+00 1.04E-01 9.64E-02 8.49E-01 7.06E-02 2.13E-01 6.89E-01 1.24E-01 1.85E-01 9.67E-01 1.09E-01 1.44E-01 1.15E+00 1.05E-01 1.94E-01 8.O0E-01 7.61E-02 4.43E-01 6.59E-01 1.32E-01 3.56E-01 9.50E-01 1.12E-01 2.65E-01 1.14E+00 1.08E-01 2.92E-01 7.74E-01 7.92E-02 6.76E-01 6.41E-01 1.35E-01 5.23E-01 9.37E-01 1.14E-01 3.84E-01 1.13E+00 1.09E-01 3.91E-01 7.56E-01 8.13E-02 9.09E-01 6.27E-01 1.38E-01 6.90E-01 9.26E-01 1.17E-01 5.02E-01 1.12E+00 1.11E-01 4.93E-01 7.42E-01 8.27E-02 1.15E+00 6.16E-01 1.41E-01 8.61E-01 9.16E-01 1.18E-01 6.22E-01 1.11E+00 1.12E-01 7.41E-01 7.18E-01 8.48E-02 1.73E+00 5.94E-01 1.45E-01 1.27E+00 8.96E-01 1.21E-01 9.13E-01 1.10E+00 1.15E-01 1.01E+00 7.OOE-01 8.61E-02 2.36E+00 5.77E-01 1.47E-01 1.72E+00 8.79E-01 1.24E-01 1.22E+00 1.08E+00 1.17E-01 1.28E+00 6.85E-01 8.65E-02 3.01E+00 5.61E-01 1.50E-01 2.17E+00 8.64E-01 1.26E-01 1.54E+00 1.07E+00 1.18E-01 1.55E+00 6.74E-01 8.65E-02 3.63E+00 5.49E-01 1.51E-01 2.61E+00 8.51E-01 1.26E-01 1.85E+00 1.06E+00 1.19E-01 Median Sigma Median Sigma Median Sigma 2.5 Hz AF In(AF) 1 Hz AF In(AF) 0.5 Hz AF In(AF) 2.18E-02 1.09E+00 8.96E-02 1.27E-02 1.39E+00 1.12E-01 8.25E-03 1.25E+00 1.19E-01 7.05E-02 1.08E+00 8.90E-02 3.43E-02 1.38E+00 1.07E-01 1.96E-02 1.24E+00 1.15E-01 1.18E-01 1.08E+00 8.87E-02 5.51E-02 1.37E+00 1.05E-01 3.02E-02 1.24E+00 1.14E-01 2.12E-01 1.08E+00 8.88E-02 9.63E-02 1.37E+00 1.03E-01 5.11E-02 1.24E+00 1.13E-01 3.04E-01 1.07E+00 8.89E-02 1.36E-01 1.37E+00 1.02E-01 7.1OE-02 1.24E+00 1.13E-01 3.94E-01 1.07E+00 8.91E-02 1.75E-01 1.38E+00 1.01E-01 9.06E-02 1.24E+00 1.13E-01 4.86E-01 1.07E+00 8.92E-02 2.14E-01 1.38E+00 1.OOE-01 1.IOE-01 1.24E+00 1.13E-01 7.09E-01 1.07E+00 8.96E-02 3.10E-01 1.38E+00 9.89E-02 1.58E-01 1.25E+00 1.13E-01 9.47E-01 1.06E+00 9.09E-02 4.12E-01 1.39E+00 9.80E-02 2.09E-01 1.25E+00 1.13E-01 1.19E+00 1.06E+00 9.32E-02 5.18E-01 1.39E+00 9.76E-02 2.62E-01 1.25E+00 1.14E-01 1.43E+00 1.06E+00 9.45E-02 6.19E-01 1.39E+00 9.71E-02 3.12E-01 1.25E+00 1.14E-01 38

Tables A-3a and A-3b are tabular versions of the typical amplification factors provided in Figures 2.3.6-1 and 2.3.6-2. Values are provided for two input motion levels at approximately 104 and 105 mean annual frequency of exceedance. These factors are unverified and are provided for information only. The figures should be considered the governing information.

39

Table A-3a. Median AFs and sigmas for Model 1, Profile 1, for 2 PGA levels.

For Information Only MI1P1iK1 Rock PGA=0.194 MI1P1iK1 PGA=0.741 Freq. med. Freq. med.

(Hz) Soil SA AF sigma ln(AF) (Hz) Soil SA AF sigma In(AF) 100.0 0.161 0.828 0.081 100.0 0.516 0.697 0.100 87.1 0.162 0.814 0.082 87.1 0.520 0.679 0.101 75.9 0.164 0.788 0.083 75.9 0.525 0.648 0.103 66.1 0.168 0.740 0.086 66.1 0.535 0.592 0.107 57.5 0.176 0.662 0.092 57.5 0.554 0.509 0.114 50.1 0.190 0.596 0.105 50.1 0.591 0.445 0.129 43.7 0.209 0.554 0.118 43.7 0.641 0.408 0.144 38.0 0.232 0.559 0.134 38.0 0.703 0.413 0.162 33.1 0.254 0.578 0.148 33.1 0.771 0.435 0.176 28.8 0.280 0.638 0.150 28.8 0.847 0.485 0.186 25.1 0.299 0.675 0.142 25.1 0.920 0.530 0.177 21.9 0.313 0.741 0.149 21.9 0.969 0.596 0.176 19.1 0.326 0.783 0.145 19.1 1.012 0.641 0.175 16.6 0.339 0.846 0.139 16.6 1.060 0.708 0.169 14.5 0.350 0.914 0.154 14.5 1.105 0.782 0.170 12.6 0.358 0.959 0.161 12.6 1.145 0.842 0.177 11.0 0.350 0.963 0.136 11.0 1.130 0.860 0.163 9.5 0.344 0.989 0.112 9.5 1.106 0.890 0.134 8.3 0.342 1.065 0.110 8.3 1.099 0.968 0.126 7.2 0.336 1.117 0.105 7.2 1.097 1.040 0.125 6.3 0.328 1.161 0.091 6.3 1.070 1.087 0.101 5.5 0.314 1.164 0.113 5.5 1.027 1.100 0.118 4.8 0.302 1.144 0.101 4.8 0.989 1.091 0.115 4.2 0.284 1.109 0.108 4.2 0.929 1.063 0.120 3.6 0.276 1.107 0.089 3.6 0.904 1.069 0.097 3.2 0.261 1.110 0.103 3.2 0.866 1.093 0.106 2.8 0.246 1.102 0.090 2.8 0.827 1.106 0.100 2.4 0.225 1.093 0.083 2.4 0.760 1.106 0.090 2.1 0.208 1.110 0.070 2.1 0.703 1.131 0.069 1.8 0.191 1.142 0.092 1.8 0.642 1.161 0.086 1.6 0.184 1.270 0.102 1.6 0.614 1.287 0.098 1.4 0.166 1.328 0.076 1.4 0.550 1.347 0.077 1.2 0.152 1.377 0.078 1.2 0.498 1.392 0.077 1.0 0.141 1.415 0.070 1.0 0.458 1.428 0.068 0.91 0.121 1.334 0.078 0.91 0.390 1.344 0.076 0.79 0.105 1.288 0.077 0.79 0.338 1.296 0.075 0.69 0.095 1.299 0.084 0.69 0.300 1.305 0.082 0.60 0.082 1.287 0.067 0.60 0.257 1.291 0.065 0.52 0.069 1.266 0.066 0.52 0.214 1.270 0.065 0.46 0.058 1.284 0.087 0.46 0.179 1.286 0.086 0.10 0.002 1.205 0.033 0.10 0.007 1.195 0.035 40

Table A-3b. Median AFs and sigmas for Model 2, Profile 1, for 2 PGA levels.

For Information Only M2P1K1 PGA=0.194 M2P1K1 PGA=0.741 Freq. med. Freq. med.

(Hz) Soil SA AF sigma ln(AF) (Hz) Soil SA AF sigma In(AF) 100.0 0.169 0.872 0.055 100.0 0.613 0.828 0.058 87.1 0.171 0.858 0.055 87.1 0.620 0.811 0.059 75.9 0.173 0.833 0.055 75.9 0.632 0.781 0.059 66.1 0.178 0.785 0.055 66.1 0.655 0.725 0.059 57.5 0.188 0.709 0.057 57.5 0.703 0.646 0.063 50.1 0.206 0.647 0.069 50.1 0.789 0.594 0.081 43.7 0.230 0.610 0.084 43.7 0.894 0.569 0.098 38.0 0.257 0.619 0.096 38.0 1.005 0.590 0.108 33.1 0.282 0.642 0.109 33.1 1.101 0.621 0.118 28.8 0.311 0.707 0.105 28.8 1.208 0.692 0.112 25.1 0.328 0.740 0.113 25.1 1.262 0.728 0.118 21.9 0.341 0.808 0.123 21.9 1.298 0.799 0.127 19.1 0.353 0.847 0.117 19.1 1.326 0.840 0.121 16.6 0.364 0.909 0.117 16.6 1.353 0.904 0.119 14.5 0.373 0.973 0.137 14.5 1.370 0.970 0.139 12.6 0.378 1.013 0.138 12.6 1.373 1.010 0.140 11.0 0.370 1.015 0.112 11.0 1.329 1.012 0.114 9.5 0.361 1.038 0.089 9.5 1.286 1.035 0.090 8.3 0.356 1.111 0.089 8.3 1.258 1.108 0.090 7.2 0.348 1.156 0.088 7.2 1.217 1.153 0.089 6.3 0.339 1.199 0.085 6.3 1.177 1.196 0.085 5.5 0.323 1.196 0.104 5.5 1.114 1.194 0.104 4.8 0.310 1.172 0.095 4.8 1.061 1.170 0.095 4.2 0.290 1.131 0.098 4.2 0.987 1.130 0.098 3.6 0.281 1.127 0.083 3.6 0.951 1.125 0.083 3.2 0.263 1.120 0.098 3.2 0.886 1.119 0.097 2.8 0.247 1.108 0.088 2.8 0.828 1.107 0.088 2.4 0.225 1.094 0.080 2.4 0.750 1.092 0.080 2.1 0.208 1.109 0.071 2.1 0.688 1.108 0.070 1.8 0.191 1.141 0.094 1.8 0.630 1.139 0.093 1.6 0.184 1.269 0.102 1.6 0.604 1.266 0.102 1.4 0.166 1.325 0.075 1.4 0.540 1.322 0.075 1.2 0.151 1.375 0.079 1.2 0.491 1.371 0.078 1.0 0.140 1.413 0.071 1.0 0.452 1.408 0.070 0.91 0.120 1.332 0.078 0.91 0.385 1.328 0.077 0.79 0.105 1.287 0.077 0.79 0.335 1.284 0.076 0.69 0.095 1.299 0.084 0.69 0.298 1.296 0.082 0.60 0.082 1.286 0.067 0.60 0.255 1.284 0.066 0.52 0.069 1.266 0.067 0.52 0.213 1.264 0.066 0.46 0.058 1.284 0.087 0.46 0.179 1.281 0.087 0.10 0.002 1.205 0.033 0.10 0.007 1.193 0.035 41

Appendix B IPEEE Adequacy .Review[PDWl]

42

Table of Contents Page 1.0 Background ........................................................................................................................... 44 2.0 General Considerations ................................................................................................... 44 2.1 Relay Chatter ................................................................................................................. 45 2.2 Soil Failure Evaluation .............................................................................................. 45 3.0 Prerequisites ......................................................................................................................... 46 4.0 Adequacy Demonstration ................................................................................................. 47 4.1 Structural Models and Structural Response Analysis ................................................ 47 4.2 In-Structure Demands and In-Structure Response Spectra ...................................... 48 4.8 Selection of Seismic Equipment List (SEL)/Safe Shutdown Equipment List (SSEL) ..... 48 4.4 Screening of Com ponents ....................................................................................... 49 4.5 W alkdowns .................................................................................................................... 50 4.6 Fragility Evaluation ................................................................................................... 52 4.7 System Modeling ....................................................................................................... 53 4.8 Containment Performance ....................................................................................... 54 4.9 Peer Review ................................................................................................................... 55 5.0 Conclusions .......................................................................................................................... 56 6.0 References ............................................................................................................................ 56 43

1.0 Background

The Nuclear Regulatory Commission (NRC) staff issued Generic Letter (GL) 88-20, Supplement 4 on June 28, 1991 (Reference 6.10), requesting that each licensee conduct an individual plant examination of external events (IPEEE) for severe accident vulnerabilities.

Concurrently, NUREG-1407, "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities" (Reference 6.9) was issued to provide utilities with detailed guidance for performance of the IPEEE.

A seismic margin assessment (SMA) was performed for the seismic portion of the Arkansas Nuclear One (ANO) - Unit 2 IPEEE using the Electric Power Research Institute (EPRI) SMA methodology, EPRI NP-6041 (Reference 6.3) with enhancements identified in NUREG-1407 (Reference 6.9). ANO - Unit 2 performed a 0.3g "modified" focused scope SMA utilizing a NUREG/CR0098 (Reference 6.4) spectral shape for a rock site. The "modified" focused scope SMA involved developing a Safe Shutdown Equipment List (SSEL) and performing High-Confidence of Low-Probability of Failure (HCLPF) calculations only for components that potentially had a capacity less than the 0.3g review level earthquake (RLE). Capacities for reactor internals and soil-related failures were not included in the "modified" focused-scope SMA. The calculated plant-level HCLPF for ANO - Unit 2 resulting from performance of the IPEEE was greater than 0.3g. The results of the ANO - Unit 2 IPEEE were provided to NRC in a letter dated May 31, 1996.

The NRC staff submitted a request for additional information (RAI) in two letters dated April 3, 1998 (Reference 6.11) and May 7, 1998 (Reference 6.12), relating to ANO Unit 1 and ANO - Unit 2. ANO responded to the RAI letters with additional information by letter dated March 30, 1999 (Reference 6.13). The NRC staff later submitted a request for supplemental information concerning the RAI responses in a letter dated February 7, 2000 (Reference 6.14). ANO responded to the request for supplemental information by letter dated June 14, 2000 (Reference 6.15).

The NRC issued its staff Staff Evaluation Report (SER) (Reference 6.2) on February 27, 2001 for the ANO - Unit 1 and ANO - Unit 2 IPEEEs. The SER concluded that the ANO-1 and ANO - UNIT 2 IPEEE process was capable of identifying the most likely severe accidents and severe accident vulnerabilities, meeting the intent of GL 88-20 (Reference 6.10).

2.0 General Considerations The plant safe shutdown earthquake (SSE) is a Housner type spectrum anchored to 0.2g peak horizontal ground acceleration and 0.133g peak vertical ground acceleration.

The ANO-2 IPEEE is a modified focused scope EPRI seismic margin assessment. The EPRI SMA was selected as the method for the IPEEE evaluation because it was compatible with the Unresolved Safety Issue (USI) A-46 assessment being conducted in parallel with 44

the IPEEE work. The Seismic Qualification Utility Group (SQUG) Generic Implementation Procedure (GIP) (Reference 6.16) used for USI A-46 allowed for coordination of activities to support both projects. The Review Level Earthquake (RLE), based on the NUREG/CR-0098 (Reference 6.4) spectrum applicable to a rock site and anchored to a 0.3g peak ground acceleration, was used for the determination of component HCLPFs. The minimum component HCLPFs was found to be at least a 0.3g PGA value, after addressing any HCLPFs that fell below that level, resulting in a plant HCLPF of at least 0.3g. Therefore, the IPEEE HCLPF Spectrum (IHS) that can be used for comparison against the new GMRS is equal to the RLE spectrum anchored at a 0.3g PGA The IPEEE commitments and modifications that were required to achieve the plant level HCLPF have been completed. Verification of the completion of these commitments and modifications were provided in the ANO - Unit 2 Response to 1 OCFR 50.54(f) Request for Information Recommendation 2.3 Seismic (Reference 6.17) and are further discussed below in Section 3.0 Prerequisites. Confirmation that these modifications are still in place is described in the Prerequisites section of this report.

The following sections summarize the results of the IPEEE adequacy evaluation according to the guidance of the Screening, Prioritization and Implementation Details (SPID) (Reference 6.5).

2.1 Relay Chatter The ANO - Unit 2 relay evaluation for IPEEE used the same methodology as the ANO - Unit 1 relay evaluation and meets the requirements of a full-scope evaluation, as described in NUREG-1407 (Reference 6.9), even though ANO - Unit 2 is a focused-scope plant. In terms of relays identified, ANO-2 identified 2956 relays of which 2255 were classified "non-essential" and 273 were placed on the Essential Relay List. ANO- Unit 1 was a full scope plant and 2314 relays were identified of which 2002 were classified as "non-essential" and 223 were placed on the Essential Relay List.

The following is included in the SER (Reference 6.2) for ANO-2: "The relay review program at ANO-2 exceeded this [the IPEEE]requirement because full capacity versus demand screening, in accordance with the GIP (Reference 6.16), was performed on all relays associatedwith small break LOCA and containment performance. The evaluation was performed according to the GIP (Reference 6.16) using the Design Basis SSE Response Spectra as the basis. This also meets the RLE in the IPEEE SMA due to the conservative amplification factors used for USI A-46 and the more liberal response spectra peak clipping allowed for an SMA."

2.2 Soil FailureEvaluation The safety-related structures at ANO - Unit 2 are founded on rock. The full evaluation of soil failures required in SPID (EPRI, 2013a) is not required as the supporting medium for safety related structures is rock with a Vs = 3500fps or more. Item 2.7 of Enclosure 3 to the NRC SER (US NRC, 2001) observes: "The principal structures at ANO-2 are founded on bedrock; therefore, a soil evaluation is not required."

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3.0 Prerequisites The following items have been addressed in order to use the IPEEE analysis for screening purposes and to demonstrate that the IPEEE results can be used for comparison with the GMRS:

1. Confirmation that commitments made under the IPEEE have been met.

2. Confirmation that all of the modifications and other changes credited in the IPEEE analysis are in place.

3. Confirmation that any identified deficiencies or weaknesses to NUREG-1407 in the ANO

- Unit 2 IPEEE NRC SER are properly justified to ensure that the IPEEE conclusions remain valid.

4. Confirmation that major plant modifications since the completion of the IPEEE have not degraded/impacted the conclusion reached in the IPEEE.

Response

The IPEEE commitments and modifications have been completed. Verification of the completion of these commitments and modifications were provided in the ANO - Unit 2 Seismic Walkdown Report (Reference 6.17) Attachment A. Attachment A provides: a description of the action taken, whether the vulnerability continues to be addressed, and when the resolution actions were completed.

The ANO - Unit 2 NRC SER (Reference 6.2) on the seismic portion of the IPEEE states that the ANO - Unit 2 IPEEE appears to meet the objectives of Generic Letter 88-20 (Reference 6.10); addresses all the USIs and Generic Safety Issues (GSIs) requested in NUREG-1407 (Reference 6.9); and contains suitable discussion of seismic/fire interaction, seismic/flood interaction, and containment performance.

The ANO - Unit 2 NRC SER (Reference 6.2) did note that details of operator actions credited when defining success paths were not included in the IPEEE submittal (Reference 6.1). However, the operator actions were discussed in detail in the responses to RAIs.

Major new or replacement equipment was identified, as described in the Walkdown Report (Reference 6.17) and placed on the list of equipment to be examined during the walkdowns.

The IPEEE SSEL was used as the starting point for developing an equipment list for the walkdowns, so that all the equipment on the IPEEE SSEL was walked down again.

No conditions were identified that could adversely affect IPEEE conclusions and, therefore, risk insights in the IPEEE analysis remain valid.

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4.0 Adequacy Demonstration 4.1 Structural Models and StructuralResponse Analysis Methodology used:

Structural Models Pertinent resources, including IPEEE (Reference 6.1), Safety Analysis Report (SAR)

(Reference 6.18), structural calculations (Reference 6.19 and 6.20) and drawings (Reference 6.21-6.26) are reviewed.

Major structures for the ANO - Unit 2 site considered in the SMA are the Reactor Building -

Internal Structure, Reactor Building - Containment Shell, Auxiliary Building, Intake Structure, and Diesel Fuel Storage Vault. Structural models were developed in the '70s for the purposes of generating modal properties for dynamic analysis. The Review Level Earthquake for the IPEEE SMA is the median-shaped NUREG/CR-0098 (Reference 6.4) spectrum, applicable to a rock site, anchored to a 0.3g peak ground acceleration.

The dynamic models were developed such that they can accurately predict the building response, including in-structure response spectra, in the frequency range of interest. The ANO - Unit 2 dynamic models of the structures are adequate to represent frequencies in excess of 20 Hz and, as such, are adequate for the assessments focused on the 1 Hz to 10 Hz range The structural models for these buildings consist of massless beam elements and lumped masses at major floor elevations. The massless beam elements represent the stiffness properties of concrete walls. The beam elements, in general, are rigidly linked to each other and to a lumped mass at each major floor elevation. Thus, each floor elevation acts as a rigid body. For structures where there are no major floors, such as the Containment Shell, the mass is modeled uniformly along the height of the structure. The Reactor Building -

Containment Shell does not have any significant structural eccentricity between the center of mass and center of rigidity. Reactor Building - Internal Structure, Auxiliary Building and Intake Structure have some torsional irregularities. However, the structural models are detailed enough to capture the overall structural responses for both the horizontal and vertical components of ground motion.

The ANO structures are founded on rock, which is typical of the area and consists primarily of shale and sandstone.

The seismic analysis of the structures was performed using a fixed base.

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Compliance with NUREG-1407:

This methodology meets the guidance and requirements of EPRI NP-6041 (Reference 6.3) and the enhancements specified in NUREG-1407 (Reference 6.9).

Adequate for Screening:

The IPEEE methodology and structural modeling are in compliance with NUREG-1407 (Reference 6.9) and are adequate for screening purposes.

4.2 In-Structure Demands and In-Structure Response Spectra Methodology used:

The ANO - Unit 2 in-structure response spectra (ISRS) for the IPEEE SMA are presented in (Reference 6.1). The ISRS were generated using time history analyses. The IPEEE SMA ISRS were compared against the original ISRS (Reference 6.19) and (Reference 6.20). The comparison shows matching amplification frequencies and modal characteristics. The IPEEE SMA ISRS are deemed reasonable.

Compliance with NUREG-1407:

In-structure response spectra were developed for the IPEEE SMA (Reference 6.1). The IPEEE SMA was done in accordance to the guidance and requirements of EPRI NP-6041 (Reference 6.3) and the enhancements specified in NUREG-1407 (Reference 6.9). The IPEEE ISRS are consistent with the design basis spectra and deemed acceptable for screening purposes..

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE in-structure demands and ISRS results are adequate for screening purposes.

4.3 Selection of Seismic Equipment List (SEL)/Safe Shutdown Equipment List (SSEL)

The selection of equipment in the IPEEE (Reference 6.1) is done to address USI A-46 and to support the IPEEE. Equipment selection to address USI A-46 issues is based on the GIP (Reference 6.16), Section 3 and Appendix A. Equipment selection to support the IPEEE is based on NUREG-1407 (Reference 6.9) and EPRI NP-6041-SL (Reference 6.3). The list of equipment provided in Appendix B of the IPEEE (Reference 6.1) addresses both USI A-46 and IPEEE requirements and is the equipment that would be used for the safety functions 48

required to establish and maintain a safe shutdown condition, including a primary and alternate success path.

The following safety functions were satisfied by the IPEEE success paths: reactivity control, reactor coolant pressure control, reactor coolant inventory control, and decay heat removal.

In addition, equipment required to prevent early containment failure was included on the SSEL. Equipment was selected that provided redundancy for each of the safe shutdown functions (secondary success path). The list of components includes an indication of the component location and the equipment class defined in the GIP (Reference 6.16).

Support system requirements for the above functional success paths were identified.

Equipment in support systems required for the operation of safe shutdown equipment or for indication of plant conditions showing safe shutdown were included in the SSEL.

The passive and active components included in the IPEEE scope are identified in Appendix B of the ANO - Unit 2 IPEEE submittal (Reference 6.1).

Compliance with NUREG-1407:

This methodology meets the guidance and requirements of EPRI NP-6041 (Reference 6.3) and the enhancements specified in NUREG-1407 (Reference 6.9). Section 3.2.5.1 of NUREG-1407 (Reference 6.9) requires a complete set of potential success paths be identified and the narrowing/elimination of paths to be documented in detail. Section 3.9 of the ANO - Unit 2 IPEEE (Reference 6.1) documents in detail the system analysis and the selection of equipment for the primary and backup success paths. It is noted in the SER (Reference 6.2) that only one success path exists for small break Loss of Coolant Accidents (LOCAs), however, the responses to RAIs (Reference 6.13) state that only one success path is required for small break LOCAs.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE seismic equipment selection results are adequate for screening purposes.

4.4 Screening of Components Methodology used:

The Seismic Review Team (SRT) screened from further margin review structures and components for which the SRT could document HCLPFs at or above the specified RLE of 0.3g based on their combined experience and judgment and use of earthquake experience data.

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The screening guidance given in the GIP for Seismic Verification of Nuclear Power Plant Equipment (Reference 6.16) was used. This is the same procedure used for the resolution of USI A-46.

Structures and equipment that could not be screened were further evaluated as documented in the IPEEE submittal (Reference 6.1) in section 3.5. The unscreened components were subjected to a Conservative Deterministic Failure Margin (CDFM) analysis as described in EPRI NP-6041 (Reference 6.3) to determine HCLPFs for the components and documented in Table 3.5-1 of the IPEEE (Reference 6.1). Plant walkdowns provided information about components, such as anchorage details, required for the HCLPF evaluation.

Compliance with NUREG-1407:

The above methodology meets the requirements of NUREG-1407 (Reference 6.9) Section 3.2.5.5 Screening Criteria which states that screening guidance given in the GIP (Reference 6.16) may be used provided review/screening is performed at the appropriate RLE, caveats included in the margins report are observed and use of the generic equipment ruggedness spectrum are observed. NUREG-1407 (Reference 6.9) also requires that spatial interaction evaluations such as assessing the effects of flooding, as noted in EPRI NP-6041 (Reference 6.3), be performed.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE screening of component results are adequate for screening purposes.

4.5 Walkdowns Methodology used:

IPEEE Walkdowns Seismic walkdowns for USI A-46 and for the IPEEE were performed concurrently.

Components common to both programs were inspected only once. Two walkdowns were performed at ANO - Unit 2, the first walkdown was performed during an outage and included equipment inside the containment,and the second walkdown was performed a few months later and included the equipment outside of containment. The IPEEE walkdown scope included passive components and structures, containment isolation and performance, and seismic interactions.

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The IPEEE walkdowns are documented in the IPEEE report (Reference 6.1) and in the Seismic Evaluation Work Sheets (SEWS) in accordance with EPRI NP-6041 (Reference 6.3) and the SQUG (Reference 6.16).

Major structures and components were walked down. Components within the IPEEE scope but not within the A-46 evaluation scope were identified so that combined walkdowns could be performed to address both A-46 and IPEEE. With the exception of some anchorage or interaction issues, equipment walked down for A-46 and IPEEE was judged to screen at 0.3g. Seismic outliers were identified for resolution at a later date by modifications or further analysis.

Walkdowns were conducted by a combination of one S&A engineer and one ANO seismic engineer, with access to an ANO systems engineer and operations personnel. Seismic Review Team members were SQUG trained and certified.

The potential for spatial system interactions was considered during seismic walkdowns.

System interaction issues were considered and noted on the SEWS for the IPEEE. The following provides examples of what was considered either previously as part of A-46 walkdowns or as part of the IPEEE:

Proximity: The proximity of structures to components and components to components was considered during walkdowns. For example, the proximity of valve operators to structures and other components was considered. Masonry block walls were revisited during the IPEEE analysis and were screened for the SMA. To ensure that block walls have capacity above 0.3g, HCLPF calculation was performed for the worst case block wall that was not upgraded during the IE-80-11 program. This block wall was calculated to have a capacity of 0.35g.

• Seismic II over I: Interactions with overhead equipment or nearby equipment, including block walls, were evaluated during the walkdowns.

• Seismic Spray & Flooding: The possibility of water spray and flooding impact on systems was considered during the walkdown. No tanks were found in areas with SSEL equipment and fire water piping was judged to have supports with sufficient capacity.

• Seismic Fires: The potential for seismic induced fires impacting SSEL equipment was evaluated during the walkdowns. No cabinets (fire sources) were found in areas containing SSEL equipment.

The above spatial interactions were evaluated and found acceptable.

Near-Term Task Force (NTTF) Recommendation 2.3 Walkdowns On March 12, 2012 NRC issued a generic letter (Reference 6.27) requesting, in part, information relating to seismic walkdowns. In response, Entergy performed the requested seismic walkdowns and area walk-bys over a three week period during September and October of 2012. Walkdown inspections focused on anchorages and seismic spatial 51

interactions, but also included inspections for other potentially adverse seismic conditions.

The NTTF Recommendation 2.3 walkdowns are documented in a walkdown report (Reference 6.17).

Verification of the resolution of commitments made to address seismic vulnerabilities identified in the IPEEE are provided in the ANO - Unit 2 Seismic Walkdown Report (Reference 6.17) Attachment A. Attachment A provides: a description of the action taken, whether the vulnerability continues to be addressed, and when the resolution actions were completed. The walkdown report (Reference 6.17) was submitted to the NRC on November 27, 2012.

Compliance with NUREG-1407:

Walkdowns were conducted and documented in accordance with EPRI NP-6041 (Reference 6.3) as required by Section 3.2.5.2 of NUREG-1407 (Reference 6.9).

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE walkdown results are adequate for screening purposes.

4.6 Fragility Evaluation Methodology used:

ANO - Unit 2 developed and implemented a program to satisfy the requirements of the IPEEE seismic margins evaluation. The SMA program concentrated on verifying the seismic adequacy of structures, equipment, large tanks, cable tray conduit raceway systems and other distribution systems, and relays. The screening and verification walkdowns verified that the equipment, tanks, distribution systems, structures and relays are able to withstand the 0.3g RLE at the plant and still provide for its safe shutdown.

" Components were screened using the criteria contained in Tables 2-3 and 2-4 of EPRI NP-6041 (Reference 6.3).

" Components that are screened are judged to have a seismic capacity in excess of the RLE demand. HCLPF capacities are determined for those items that are not screened out.

• CFDM HCLPF capacity calculations were performed for equipment anchorages, large tanks, and a worst-case block wall.

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All the Class I Structures were screened out based on the EPRI NP-6041 (Reference 6.3) screening criteria.

Compliance with NUREG-1407:

ANO - Unit 2 calculated HCLPFs for all outlier components in accordance with the guidance of EPRI NP-6041 (Reference 6.3) and NUREG-1407 (Reference 6.9) Section 3.2.5.7.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE fragility evaluation results are adequate for screening purposes.

4.7 System Modeling Methodology used:

Functional success paths were developed for the four safety functions: reactivity control, Reactor Coolant System (RCS) pressure control, RCS inventory control, and decay heat removal. Primary and alternate success paths for each safety function were identified.

Alternate success paths involve the same systems as the primary success paths by using the opposite train. Plant-specific Success Path Logic Diagrams (SPLDs) are provided in the RAI response (Reference 6.13) for both loss of off-site power (LOSP) and small LOCA with both the primary and alternate success path. Dependency matrices are also provided in the RAI responses that identify the support systems required for operation of the front-line systems in the SPLD.

The evaluation of non-seismic failures and human actions was not addressed explicitly in the IPEEE evaluation of seismic risk; however, both are discussed in the responses to RAIs (Reference 6.13). A fault tree was developed from the detailed plant fault tree, taking no credit for components on the IPEEE SSEL and quantified to determine the conditional core damage probability. The conditional core damage probability was combined with the frequency of a 0.3g earthquake at the ANO site from EPRI NP-6395-D (Reference 6.28) to estimate a Core Damage Frequency (CDF) below 1.OE-06. Itwas concluded that the risk from a 0.3g seismic event was therefore insignificant.

The identification of success paths and components was based on nominal credit for operator actions, given that sufficient manpower, time, and procedures were available.

Specific operator actions necessary for safe shutdown are not discussed in the IPEEE submittal (Reference 6.1), but are discussed in the responses to RAIs.

Compliance with NUREG-1407:

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NUREG-1407 (Reference 6.9), Section 3.2.5.1 states that for IPEEE purposes, it is desirable that to the maximum extent possible, that the alternate path involves operational sequences, systems, piping runs and components different from those used in the preferred path. As indicated above and documented in the IPEEE, different components and trains were selected, but from the same systems at ANO - Unit 2.

Taking into account the information supplied in RAI responses, the treatment of non-seismic failures and human actions in the ANO - Unit 2 IPEEE meets the requirements of Section 3.2.5.8 of NUREG-1407 (Reference 6.9).

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE system modeling results are adequate for screening purposes.

4.8 Containment Performance Methodology used:

Containment performance was evaluated for gross containment failure, containment system failure, containment bypass, containment isolation failure, and interactions with containment.

The containment structure was evaluated using the methodology and guidance of EPRI NP-6041 (Reference 6.3).

For containment isolation and bypass, containment penetrations were evaluated with respect to seal failure, valve failure, and failure of piping between penetrations and isolation valves.

The containment evaluation found that no significant vulnerabilities exist that would impact containment performance for the RLE.

Compliance with NUREG-1407:

The review of containment meets the requirements of Section 3.2.6 of NUREG-1407 (Reference 6.9) to evaluate the containment integrity, isolation, bypass and suppression functions to identify vulnerabilities that involve early failure of the containment functions.

Adequate for Screening:

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The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE containment performance results are adequate for screening purposes.

4.9 PeerReview Methodology used:

An independent peer review of the SMA was conducted by Mr. Harry Johnson of Programmatic Solutions. Mr. Johnson conducted two days of walkdowns as part of his review. Mr. Johnson's review report is included in the IPEEE submittal (Reference 6.1) in Appendix D. Mr. Johnson concluded that the methods used are appropriate, the methods have been correctly implemented, and the actions recommended in the IPEEE to address seismic vulnerabilities are reasonable.

In addition to the independent peer review by Mr. Johnson, a peer review of the SSEL was conducted by Dr. Robert Budnitz of Future Resources Associates, Inc. Dr. Budnitz's review report is also included in the IPEEE (Reference 6.1) in Appendix D. One minor comment was provided that did not impact Dr. Budnitz's conclusion that the SSEL development was satisfactory.

Two engineers from Enercon, Mr. Sean Smolarek and Mr. Eric Dilbone reviewed the IPEEE, as described in the Walkdown Report (Reference 6.17).

"In-house" review is evidenced by the reviewer sign-off on IPEEE cover sheets, but there is no discussion of in-house review in the IPEEE (Reference 6.1) report body.

Compliance with NUREG-1407:

The above review process, using a combination of independent in-house review and two external consultants for seismic review, meets the requirements of Section 7 of NUREG-1407 (Reference 6.9) for peer review.

Adequate for Screening:

The methodology used is in compliance with NUREG-1407 (Reference 6.9) and the IPEEE peer review results are adequate for screening purposes.

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5.0 Conclusions The ANO - Unit 2 IPEEE was a modified focused scope seismic margin submittal and requires the performance of a detailed review of relay chatter. The ANO - Unit 2 relay evaluation for IPEEE used the same methodology as the ANO - Unit 1 relay evaluation and meets the requirements of a full-scope evaluation, as described in NUREG-1407 (Reference 6.9), even though ANO - Unit 2 is a focused-scope plant.

The following is included in the SER (Reference 6.2) for ANO-2: "The relay review program at ANO-2 exceeded this [the IPEEE] requirementbecause full capacity versus demand screening, in accordance with the GIP (Reference 6.16), was performed on all relays associatedwith small break LOCA and containment performance. The evaluation was performed accordingto the GIP (Reference 6.16) using the Design Basis SSE Response Spectra as the basis. This also meets the RLE in the IPEEE SMA due to the conservative amplification factors used for USI A-46 and the more liberal response spectra peak clipping allowed for an SMA."

The modified scope of the ANO IPEEE excluded soil-related failures. The safety-related structures at ANO - Unit 2 are founded on rock. As stated in NUREG-1407 (Reference 6.9),

Section 3.2.1, even a plant in the full-scope category that is located on a rock site is not required to perform a soil failure evaluation.

Based on the IPEEE adequacy review performed consistent with the guidance contained in EPRI 1025287 (SPID) (Reference 6.5) and documented herein, with the exception of the completion of the detailed relay chatter review, the ANO - Unit 2 IPEEE results are considered adequate for screening and the risk insights gained from the IPEEE remain valid under the current plant configuration.

6.0 References 6.1 Engineering Report for Arkansas Nuclear One, 96-R-2016-02, Rev. 0, "Individual Plant Examination of External Events (IPEEE) for Seismic SMA at ANO - UNIT 2."

6.2 United States Nuclear Regulatory Commission, "Staff Evaluation Report of Individual Plant Examination of External Events (IPEEE) Submittal on Arkansas Nuclear One, Units 1 & 2," Enclosure 1 to Letter Dated February 27, 2001 [OCNA020113].

6.3 Electric Power Research Institute, "A Methodology for Assessment of Nuclear Power Plant Seismic Margin," EPRI NP-6041-SL, Revision 1, August 1991.

6.4 "Development of Criteria for Seismic Review of Selected Nuclear Power Plants,"

NUREG/CR- 0098, US NRC, May 1978.

6.5 Electric Power Research Institute, TR-1025287, "Seismic Evaluation Guidance:

Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," November 2012.

6.6 NEI Letter, Kimberly A. Keithline to David L. Skeen, NRC "Relay Chatter Reviews for Seismic Hazard Screening," dated October 3, 2013.

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6.7 NEI Letter, A.R. Pietrangelo to D.L. Skeen, NRC "Proposed Path Forward for NTTF Recommendation 2.1: Seismic Reevaluations," dated April 9, 2013 [ML13101A379].

6.8 NRC Letter, E. Leeds to J. Pollock, NEI "Acceptance Letter for NEI Submittal of Augmented Approach, Ground Motion Model Update Project, and 10CFR50.54(f)

Schedule Modifications Related to the NTTF Recommendation 2.1, Seismic Reevaluations," dated May 7, 2013 [ML13106A331].

6.9 "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities," NUREG-1407, US NRC, June 1991

[OCNA20113].

6.10 "Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities - 10CFR 50.54(f)," Generic Letter No. 88-20, Supplement 4, US NRC, June 28, 1991.

6.11 NRC Letter to Entergy, "Request for Additional Information Pertaining to the Arkansas Nuclear One (ANO) Summary Reports for the Individual Plant Examination of External Events (IPEEE)," dated April 3, 1998 [0CNA049807, 0CNA049808].

6.12 NRC Letter to Entergy, "Request for Additional Information Pertaining to the Arkansas Nuclear One (ANO) Summary Reports for the Individual Plant Examination of External Events (IPEEE)," dated May 7, 1998 [0CNA059806].

6.13 Entergy Letter to NRC "Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 Additional Information Pertaining to GL 87-02 and 88-20," dated March 30, 1999 [0CAN039901].

6.14 NRC Letter to Entergy, "Request for Supplemental Information Concerning Entergy Operations' Previous Responses," dated March 30, 1999, dated February 7, 2000

[OCNA020004].

6.15 Entergy Letter to NRC "Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 IPEEE Supplemental RAI Response," dated June 14, 2000 [OCAN060003].

6.16 Seismic Qualification Utility Group (SQUG), "Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment," Revision 2, March, 1993.

6.17 Entergy, "ANO - UNIT 2 Seismic Walkdown Report," Attachment 1 to letter 2CAN111201, dated November 27, 2012.

6.18 Arkansas Nuclear One Unit 2, Safety Analysis Report, Amendment No. 25.

6.19 Arkansas Nuclear One Unit 2, APL-C-2501, Rev. 3, "Earthquake Resistance Design of Structures and/or Components Located in the Reactor Building for the Arkansas Nuclear One Unit 2 Power Plant."

6.20 Arkansas Nuclear One Unit 2, AP&L-C-2502, Rev. 2, "Earthquake Resistance Design of Structures and/or Components Located in the Auxiliary Building for the Arkansas Nuclear One Unit 2 Power Plant."

6.21 Arkansas Nuclear One (Unit 2) Drawing, A-2100, Rev. 19, "Architectural Floor Plan @

Elevation 317'-0" & Category I Key Plans for Conc. Unit Masonry."

6.22 Arkansas Nuclear One (Unit 2) Drawing, A-2101, Rev. 41, "Architectural Floor Plan at Elevation 335'-0"."

6.23 Arkansas Nuclear One (Unit 2) Drawing, A-2102, Rev. 31, "Architectural Floor Plan at Elevation 354'-0"."

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6.24 Arkansas Nuclear One Drawing, A-2103, Rev. 34, "Architectural Floor Plan at Elevations 368'- 0" 372'-0" & 374'-6"."

6.25 Arkansas Nuclear One Drawing, A-2105, Rev. 31, "Architectural Floor Plan at Elevations 404'- 0" & 422'-0"."

6.26 Arkansas Nuclear One Drawing, A-2106, Rev. 24, "Architectural Roof Plan."

6.27 NRC Generic Letter "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(o Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident," dated March 12, 2012 [ML12053A340].

6.28 Electric Power Research Institute, NP-6395-D, "Probabilistic Seismic Hazard Evaluation at Nuclear Plant Sites in the Central and Eastern United States: Resolution of the Charleston Issue," April 1989.

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