Text

Submits Revision to Seismic Hazard Evaluation to Include New Ground Motion Response Spectra (GMRS) Using New Geotechnical Data and Shear-Wave Testing
	ML15201A006
Person / Time
Site:	Robinson
Issue date:	07/17/2015
From:	Glover R; Duke Energy Progress
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	RNP-RA/15-0045
	Download: ML15201A006 (69)
	v • d • e

R. Michael Glover

(_~ DUKE H. B. Robinson Steam ENERGY~

Electric Plant Unit 2 Site Vice President Duke Energy Progress 3581 West Entrance Road Hartsville, SC 29550 0 : 843 857 1704 F: 843 857 1319 Mike.G/over@duke-energy.com 10 CFR 50.54(f)

Serial: RNP-RA/15-0045 JUL 17 2015 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO.2 DOCKET NO. 50-261 I RENEWED LICENSE NO. DPR-23

Subject:

Submittal of Revision to Seismic Hazard Evaluation to Include New Ground Motion Response Spectra (GMRS) Using New Geotechnical Data and Shear-Wave Testing for H. B. Robinson Steam Electric Plant, Unit No. 2

References:

1. Duke Energy letter to NRC, Seismic Hazard Evaluation, Response to NRC 10 CFR 50. 54(f) 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 31,2014 (ML14099A204)

2. NRC Summary of the June 30, 2014, Category 1 Public Meeting With Duke Energy Progress Inc. To Discuss Seismic Hazard Reevaluations Associated With Implementation of Japan Lessons-Learned Near-Term Task Force Recommendation 2.1, dated August 7, 2014 (ML14210A050)

Ladies and Gentlemen:

Reference 1 provided the NRC with Duke Energy's response for H. B. Robinson Steam Electric Plant, Unit No.2, in response to the NRC's 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 (ADAMS Accession No. ML12056A046).

The purpose of this letter is to provide further information regarding Duke Energy's response to the NRC's Request for Information regarding the Seismic Hazard Evaluation for H. B. Robinson Steam Electric Plant, Unit No. 2.

On June 30, 2014, the U.S. Nuclear Regulatory Commission (NRC) held a Category 1 public meeting (Meeting Notice ML14169A430) with Duke Energy Progress, Inc. (Duke Energy) for Brunswick Steam Electric Plant, Units 1 and 2 (Brunswick), and H. B. Robinson Steam Electric Plant, Unit No.2 (Robinson). The purpose of this meeting was to discuss issues resulting from the staff's screening and prioritization of Robinson related to Enclosure 1, Recommendation 2. 1:

Seismic of the March 12, 2012, NRC request for information per Title 10 to the Code of Federal Regulations, Part 50, Section 50.54(f) letter. By letter dated May 9, 2014, (ADAMS Accession No. ML14111A147) the NRC staff categorized Robinson, Unit No.2, as "screened in" to perform

U. S. Nuclear Regulatory Commission Serial: RNP-RA/15-0045 Page 2 of 2 additional seismic evaluations, prioritization group 1 plant, with a risk evaluation due by June 30, 2017, based on the staff's screening review. The public meeting supported information exchange and understanding of engineering differences to achieve subsequent technical resolution.

As stated in their August 7, 2014, Summary of the June 30, 2014, Category 1 Public Meeting With Duke Energy Progress Inc. to Discuss Seismic Hazard Reevaluations Associated With Implementation of Japan Lessons-Learned Near-Term Task Force Recommendation 2.1, (ML14210A050) the NRC summarized that Duke Energy planned to gather additional geotechnical data for the H. B. Robinson Site through onsite exploration during summer of 2014 and technical evaluations in fall of 2014. In addition, it was stated that this new site data will be used to revise the seismic GMRS hazard curve, as well as supporting the June 30, 2017 seismic Probabilistic Risk Assessment modeling. Duke Energy committed to working with the NRC Staff on exploration schedules and to continue information exchange in support of the staffs ongoing review.

As part of the ongoing information exchange, the enclosure to this letter provides the NRC with Duke Energy's revised GMRS Curve for H. B. Robinson Steam Electric Plant, Unit No.2, using new geotechnical data collected during onsite exploration and additional shear wave velocities testing.

Based on the results of the revised GMRS curve and the new geotechnical data collected during onsite exploration and additional shear wave velocity testing for H. B. Robinson Steam Electric Plant, Unit No. 2, Duke Energy is requesting a revised "Seismic Risk Evaluation (Prioritization Group)" from the current Group 1 as listed in the NRC letter dated May 9, 2014, (ADAMS Accession No. ML14111A147) to a Group 2 plant. If acceptable, the seismic probabilistic risk assessment (SPRA) for HBRSEP would be submitted to the NRC by December 31, 2019 instead of June 30, 2017.

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

Should you have any questions regarding this submittal , please contact Mr. Richard Hightower, Manager, Nuclear Regulatory Affairs at (843) 857-1329.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on :f~t-Cf 171 ~IS.

Sincerely, ct:t::~~

Site Vice President RMG/shc

Enclosure:

Duke Energy's Revised Seismic Hazard and Screening Report To Include a New GMRS Curve and Supporting Geotechnical Data for H. B. Robinson Steam Electric Plant, Unit No. 2 cc: Ms. M. C. Barillas, NRC Project Manager, NRR Mr. K. M. Ellis, NRC Sr. Resident Inspector Mr. V. M. McCree, NRC Region II Administrator Mr. N. J. DiFrancesco, NRC Senior Project Manager, JLD-NRR

U.S. Nuclear Regulatory Commission Enclosure to Serial: RNP-RA/15-0045 66 Pages Follow This Cover Sheet ENCLOSURE DUKE ENERGY'S REVISED SEISMIC HAZARD AND SCREENING REPORT TO INCLUDE A NEW GMRS CURVE AND SUPPORTING GEOTECHNICAL DATA FOR H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page i TABLE OF CONTENTS SECTION NO. PAGE 1.0 Introduction . .. . .. . .. .. .. . .. .. .. .. .. .. .. .. .. .. . .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. . . . 1 2.0 Seismic Hazard Reevaluation . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. . .. . . 2 2.1 Regional and Local Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Probabilistic Seismic Hazard Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3 Site Response Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 2.4 Ground Motion Response Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 39 3.0 Safe Shutdown Earthquake Ground Motion .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 42 3.1 Description of Spectral Shape and Anchor Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3.2 Control Point Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.0 Screening Evaluation . .. .. .. . .. .. .. .. .. .. .. .. . .. . . .. . .. . .. . .. . .. .. .. .. .. .. .. .. .. .. . .. .. .. .. . .. 43 4.1 Risk Evaluation Screening (1 to 10Hz).......................................... 43 4.2 High Frequency Screening (> 10 Hz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.3 Spent Fuel Pool Evaluation Screening (1 to 10 Hz) . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 5.0 Interim Actions and Assessments .. .. .... .. .. .. .. .. .. .. .. . . .. .... .. .. .. .. ... .... .. .... ... 44 5.1 Expedited Seismic Evaluation Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 5.2 Seismic Risk Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 5.3 Individual Plant Examination of External Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 45 5.4 Walkdowns to Address NRC Fukushima NTTF Recommendation 2.3 . . . 45 6.0 Conclusions . . . . . .. . . . . . . . . . . .. . .. . .. . .. . . . . .. . . . . . . . .. . .. . .. . . . . .. . . . . . . . .. . .. . . . . .. . . . . . . . .. . .. . . 46 7.0 References . . . . . .. . .. . .. . .. . . . . .. . .. . . . . .. . . . . .. . .. . .. . .. . .. . .. .... .. ...... .... .. ... . . . . . . . .. . .. . ... 47 Appendix A Tabulated Values of Mean and Fractlle Seismic Hazard Curves . . ... A-1 Appendix B Site-Specific Shear Modulus Degradation and Damping Curves .. .. B-1

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 1 of 51 1.0 Introduction Following the accident at the Fukushima Dai-ichi nuclear power plant resulting from the March 11, 2011, Great Tohoku Earthquake and subsequent tsunami, the NRC Commission 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 on March 12, 2012 (Reference 1), requesting information to assure that these recommendations are addressed by all U.S. nuclear power plants. The 50.54(f) letter 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 results, 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 pertaining to NTTF Recommendation 2.1 for the H.B. Robinson Steam Electric Plant (HBRSEP) site, located in Darlington County, South Carolina (SC). In providing this information, HBRSEP 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 1025287, 2013) (Reference 2). The Augmented Approach, Seismic Evaluation Guidance:

Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (EPRI3002000704, 2013) (Reference 3), 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 HBRSEP were performed using a detailed geologic study of the region and the site to establish the geologic suitability of the site for the nuclear unit. Additional data utilized in the geologic and seismic siting investigations were obtained from the U. S. Atomic Energy Commission (USAEC) Savannah River Operations Office (Appendix 2.5A of Reference 7), Dr.'s J. L. Stuckey and L. L. Smith (Appendix 2.5C of Reference 7), and Perry Byerly (Appendix 2.5D of Reference 7).

The Safe Shutdown Earthquake (SSE) was developed based on evaluation of historic earthquake activity, regional and local geology, and recommendation of Dr. G. W. Housner of

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 2 of 51 the California Institute of Technology. The SSE was used for the design of seismic Class I systems, structures and components.

The General Design Criteria (GDC) in existence at the time HBRSEP was licensed (July, 1970) for operation were contained in Proposed Appendix A to 10CFR50, General Design Criteria for Nuclear Power Plants, published in the Federal Register on July 11, 1967. (Appendix A to 10CFR50, effective in 1971 and subsequently amended, is somewhat different from the proposed 1967 criteria.) HBRSEP was evaluated with respect to the proposed 1967 GDC and the original Final Safety Analysis Report (FSAR) (Reference 7) contained a discussion of the criteria as well as a summary of the criteria by groups. FSAR, Sections 3.1.1.2 and 3.1.2 present that discussion without substantive change in order to preserve the original basis for licensing.

In response to the 50.54(f) letter and following the guidance provided in the SPID (Reference 2),

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, HBRSEP screens in for risk evaluation, a Spent Fuel Pool evaluation, and a High Frequency Confirmation.

Due to limited availability of data on dynamic material properties at the HBRSEP site, site investigations were performed in 2014 to obtain dynamic material properties including shear wave velocity profiles. New shear wave velocities were obtained using the P-S Suspension seismic velocity logging and Spectral Analysis of Surface Waves (SASW). Site-specific shear modulus degradation and damping curves were developed. Using the results of the new site investigations, a new GMRS was developed for the HBRSEP site.

The new GMRS revealed that seismic hazard at the HBRSEP site is not as high as previously determined in the March 2014 submittal. Therefore, it is requested that the HBRSEP be re-prioritized into Group 2 for completing the seismic risk evaluation. If acceptable, the seismic probabilistic risk assessment (SPRA) for HBRSEP should be submitted by December 31, 2019 instead of June 30, 2017.

2.0 Seismic Hazard Reevaluation HBRSEP is located in northwest Darlington County, SC, approximately 3 miles west-northwest of Hartsville, SC; 25 miles northwest of Florence, SC; 35 miles north-northeast of Sumter, SC; and 56 miles east-northeast of Columbia, SC. The plant is on the southwest shore of Lake Robinson, a cooling impoundment of Black Creek.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 3 of 51 Only one earthquake with intensity of V or greater has ever been recorded within 50 miles of the site. In 1959, an earthquake with intensity of V-VI (Modified Mercalli Scale) occurred about 15 miles from the site in the vicinity of McBee, SC. No permanent effects of this shock are noted in the literature or in a geologic reconnaissance, although it is presumed to have been felt at the location of the site. It is estimated that this shock had a magnitude no greater than 4.5 with an epicentral acceleration of well under 0.10 g.

On the basis of the historical data, it is expected that the site area could experience a shock on the order of the 1959 McBee shock once during the life of the plant. A Magnitude 4.5 earthquake with an epicentral distance of less than ten miles was selected as the design earthquake.

Although the probable ground acceleration for this earthquake would be 0.07 g to 0.09 g, a conservative value of 0.1 g was used for the Operational Basis Earthquake (OBE). An SSE with a maximum ground acceleration of 0.2 g was selected to provide an adequate margin of safety.

2. 1 Regional and Local Geology Regional Geology The HBRSEP site is located in the Coastal Plain physiographic province about 15 miles southeast of the Piedmont province. The basement crystallines in the Piedmont and below the Coastal Plain are composed largely of granite, gneiss, phyllite, and schist and dip to the southeast from 10 ft to 40 ft per mile. The normal regional dip of the Coastal Plain sediments is toward the southeast at about 8 ft to 30 ft per mile, the greater dips being in the deeper strata.

In South Carolina, the Coastal Plain is composed of largely unconsolidated sediments which overlie a slightly sloping surface of crystalline rock. These crystallines are of Precambrian and early Paleozoic age with subordinate sandstones and intrusive diorities of Triassic age. Triassic sediments have been faulted into the ancient crystallines. Faulted Triassic basins are evident in the Piedmont province and deep wells have located Triassic rocks in widely divergent areas beneath the Coastal Plain. Overlying the Precambrian, Paleozoic, and Triassic rocks, are the sediments of the Coastal Plain. These sediments are composed of sands, gravels, clays, shales, and limestones which range in age from Cretaceous to Pleistocene.

The Coastal Plain itself is divided into the upper Coastal Plain and the lower Coastal Plain by what has been termed the Orangeburg Scarp, an erosional feature representing a shoreline formed during Miocene times. The elevation of the Upper Coastal Plain ranges from approximately 210ft above Mean Sea Level, (MSL) at the Orangeburg Scarp, and 450ft to 500 ft above *MSL, at the Fall Zone. The Upper Coastal Plain is the outcrop zone of the Tuscaloosa (Middendorf) Formation of late Cretaceous age, but most of the area is blanketed by more recent alluvial deposits of sand and gravel. The elevation of the Lower Coastal Plain ranges

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 4 of 51 from approximately 210ft above MSL, at the Orangeburg Scarp to sea level at the coast. The major structural features of the region include Triassic grabens (downfaulted basins) and the Cape Fear Arch, a basement ridge which trends southeastward from the Fall Line to the Atlantic Coast just northeast of the North Carolina-South Carolina boundary. The Cape Fear Arch has caused the overlying Coastal Plain sediments to dip away from its structure, thereby modifying the normal regional dips on its flanks.

Local Geology The surficial materials above the Piedmont at the HBRSEP site are recent sands or soils developed from the underlying Middendorf Formation. The HBRSEP UFSAR notes that distinguishing the recent sands (defined as alluvial soils) from soils of the Middendorf Formation is difficult because the alluvial materials may have been derived from the Middendorf Formation and then transported by water movement to the HBRSEP site. The Middendorf Formation was formed by deposition of sediments transported by water from the west. Depositional environments are characterized by lateral and vertical variations in soil layers both in composition and thickness. Such variations were observed in the boring logs from historical and recent explorations. See section 2.3.1 for more details on local geology and description of subsurface materials at the HBRSEP site.

2.2 Probabilistic Seismic Hazard Analysis The seismic hazard analysis work follows the general guidance provided in Appendix B of Reference 2, but differs in some of the implementation details. These differences are discussed in the appropriate sections of this report and detailed information is available in Reference 49.

The seismic source model used for the HBRSEP PSHA is based on the CEUS-SSC project that was conducted from April2008 to December 2011 to provide a regional seismic source model for use in PSHAs for nuclear facilities. The CEUS-SSC project was based on Senior Seismic Hazard Analysis Committee (SSHAC) Study Level 3 methodology (References 25 and 26) to provide high levels of confidence that the data, models, and methods of the larger technical community had been considered and the center, body, and range of technically defensible interpretations had been included. For future use in site-specific applications, the CEUS-SSC report recommends that local data sets should be reviewed and possible site-specific refinements made to the model to account for local information as required by current regulations and regulatory guidance. Refinements to the CEUS-SSC model were evaluated as described in this report.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 5 of 51 2.2.1 Probabilistic Seismic Hazard Analysis Results In accordance with the 50.54(f) letter and following the guidance in the SPID (Reference 2), a probabilistic seismic hazard analysis (PSHA) was completed using recently developed data from 2012 "Central and Eastern United States Seismic Source Characterization (CEUS-SSC) for Nuclear Facilities" project (CEUS SSC) (Reference 4 ), the 2013 EPRI Ground Motion Characterization project for the CEUS (Reference 5), and site-specific dynamic properties in Reference 19. A site specific review of the CEUS-SSC earthquake catalog was also performed ,

and these results are incorporated into the PSHA for the HBRSEP site. For the PSHA, a lower-bound moment magnitude of 5.0 without use of the cumulative absolute velocity (CAV) model was used, as specified in the 50.54(f) letter.

Site-Specific CEUS-SSC Catalog Review There are two updates to the published CEUS-SSC model that are incorporated in this report.

The first update presents corrections to the maximum magnitude (Mmax) distributions for some of the seismic sources described in Reference 20. The second update presents revisions to the CEUS-SSC earthquake catalog in the southeastern US (Reference 21). The Youngs (2014) catalog revisions have been subsequently peer reviewed (Reference 20). Both of these revisions are used in this study. The earthquake catalog used in development of the CEUS-SSC model (EPRIIDOE/NRC, 2012) as updated in Reference 21 was complete through the end of 2008.

The earthquakes that have occurred in the CEUS in the intervening six years represent an important source of new information and are therefore reviewed and discussed.

For the seismic hazard model for HBRSEP, an updated earthquake catalog through October 15, 2014 was developed within a region that extends in Latitude from 29 to 39 degrees North and in Longitude from -74 to -86 degrees east. This region is sufficiently large to include all the seismicity within 200 mile (320 km) radius of the site. The process used to develop the CEUS-SSC catalog was used for the updated catalog. The portion of the CEUS-SSC catalog used for the HBRSEP PSHA is shown in Figure 2.2.1-1.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 6 of 51 Legend Stte c::::J 200 mi (320 krn) rad1us c:J Catalog search region CEUS sse catalog (r7*)

E[M)

25 0 30 0 40 0 50 60 70 Update (2009 - 2014)

E[M)

25 c, 30 0 40 G 5o

) 60 70 N

A 400ml 600 krn Figure 2.2.1-1: CEUS-SSC Earthquake Catalog and Updated Earthquake Catalog Recently published literature was reviewed to assess the need for refinements or updates to the seismic source model. A summary of the new information as it pertains to key aspects of the CEUS-SSC model is provided in Table 2.2.1-4. The review and evaluation of these new publications indicated that no adjustments to the model are needed. The updated earthquake catalog evaluated for the hazard analysis includes events from January 1, 2009 to October 15, 2014. Updated earthquake events were obtained from the following:

USGS National Earthquake Information Center website

Center for Earthquake Research and Information

Weston Observatory website

University of South Carolina

Virginia Tech Seismological Observatory

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 7 of 51 In addition, seismic moments and moment magnitudes were obtained from the Harvard Catalog of Moment Tensors and Catalog of Moment Tensors for parts of North America (Saint Louis University); macroseismic intensities were obtained from the USGS "Did You Feel It?" webpage.

In the CEUS-SSC source model (Reference 4), maximum magnitudes for distributed seismicity sources (source zones) were assessed using statistical methods that are based all or in part on the observed catalog of earthquakes that have occurred within the source zone boundaries with magnitudes E[M] > 4.3. The methodology is described under Section 5.2 of Reference 4.

Following the identification of an error in the maximum magnitudes for distributed seismicity source calculations (Reference 27), these distributions were subsequently updated for the seismotectonic zones IBEB, MID-C (A through D), PEZ-N, PEZ-W, and SLR. The corrected distributions for these zones are shown in Table 2.2.1-5.

A re-analysis of the CEUS-SSC earthquake catalog (Reference 21) led to the removal of a number of earthquakes from the south-eastern US portion of the catalog that are caused by impounding of reservoirs or are believed to be aftershocks of the Charleston earthquakes of 1886. Following that re-evaluation, a new set of earthquake recurrence rates were generated for the following seismicity source zones: ECC-AM, MESE-N, MESE-W, NMESE-N, PEZ-N, PEZ-W, and STUDY-R (Reference 48). Reference 21 catalog updates have been subsequently found to be acceptable by independent peer review (Reference 20). The updated recurrence rates are used in the HBRSEP PSHA.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 8 of 51 Table 2.2.1 -4: Review of Recent Literature Potentially Relevant to Seismic Source Zones Title Notes Model Modification Needed?

Reference 51 Estimating Earthquake New source: No No, The estimate of the 1886 Magnitudes from Reported Applicable to zone boundaries: earthquake being M 7.0 +/- 0.3 is Intensities in the Central and No consistent with the Charleston Eastern United States Applicable to zone magnitude: No RLME magnitude distribution that ranges from M 6.7-7.5 with the Applicable to RLME source highest weight given to parameters: This study uses a M 7.1.

new macroseismic intensity equation to estimate M 7.0 for the 1886 Charleston, South Carolina, earthquake, with an estimated uncertainty of 0.3 units at the 95% confidence level (based on a Monte Carlo analysis).

Reference 52 Pleistocene shorelines and New source: General locations No, variability in the future coastal rivers: Sensitive potential are hypothesized for potentially earthquake characteristics for the indicators of Quaternary active fault locations. ECC-AM and ECC-GC covers tectonism along the Atlantic Applicable to zone boundaries: the range of geometries and style Coastal Plain of North America No In this modeling study of of faulting of the potentially active landforms along the Atlantic faults inferred from this study.

coastline, three zones of NW- The geomorphic features trending active faults, three zones identified in this study do not of E-W-trending active faults and have sufficient information to one north-trending active fault characterize new RLME sources.

were identified. The NW- and E- The Charleston RLME source W- trending zones lie within the accounts for paleoliquefaction ECC-AM; the N-S-trending zones data.

lies within the ECC-GM.

Applicable to zone magnitude: No Applicable to RLME source parameters: No; the study postulates general fault orientation and relative uplift patterns.

Reference 53 Structural controls on intraplate New source: No No, the alternative Mmax and earthquakes in the eastern Applicable to zone boundaries: seismotectonic source zones in United States This study divides the the CEUS SSC model southeastern US into different encompass the postulated zones seismic zones based on the identified in this study. The concept that metamorphism at emphasis on reactivation of the edge of terranes prevent the Mesozoic brittle faults is an propagation of earthquakes underlying premise used to through these boundaries. Also, identify source zones in the modern seismicity is primarily CEUS SSC model. The variability occurring along postorogenic of future fault ruptures as brittle fracture sets. The study characterized for the ECC-AM

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 9 of 51 Title Notes Model Modification Needed?

concludes that seismicity within are consistent with fracture and the Appalachian accreted fault trends identified as favorable terranes of the Atlantic Coastal orientations in this study.

margin is consistent with reactivation of Mesozoic brittle fault zones.

Applicable to zone magnitude: No Applicable to RLME source parameters: No Reference 54 Regional Mesozoic structure and New source: No No.

seismicity in southeastern North Applicable to zone boundaries: The geometry and style of America No faulting of active faults inferred Applicable to zone magnitude: No from the historical seismicity are captured by the Charleston Applicable to RLME source RLME source.

parameters: This study examined seismicity in the Middleton Place-The postulated faults are within Summerville seismic zone and the Charleston Narrow zone, interpreted active NW -striking which is the highest weighted high-angle faults and NE-striking, geometry for the Charleston NW-dipping reverse faults.

RLME source.

Hypocenters were between 3 and 13 km .

The observed depths (3-13 km) are within the range of seismogenic crustal thickness Reference 55 Paleoseismites which formed New source: No No. The postulated surface prior to and during the 31 August Applicable to zone boundaries: rupture (along the trend of the 1886 Charleston earthquake in No Dorchester or Ashley River faults)

Colonial Dorchester, South Applicable to zone magnitude: No is included in the highest Carolina weighted zone (Narrow Zone)

Applicable to RLME source geometry for the Charleston parameters: This study looks at RLME source.

post-1760 deformation of buildings and concludes that a surface rupture displaced a kiln along an oblique reverse fault with a strike of -235°-315°, a slip vector of 96°-27 4 o, and a horizontal component of displacement of-1-2m. This surface displacement on the Dorchester fault, which is inferred to have occurred during the 1886 earthquake, is associated with evidence for earlier paleoliquefaction features . These observations are consistent with previous interpretation of the of the NW-trending, SE-dipping Ashley River seismic zone as the causative fault of the 1886

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 10 of 51 Title Notes Model Modification Needed?

Charleston earthquake based on analysis of joints and fractures in the walls of the Dorchester fort by Dutton (1889) after the 1886 earthquake.

Reference 56 Documentation for the 2014 New source: No. No. Although the SSC model Update of the United States The USGS report updated the used for the 2014 hazard maps National Seismic Hazard Maps treatment of earthquakes that are differs in detail from the CEUS potentially induced by sse model, there are no new underground fluid injection. As data, methods, or approaches shown on Figure 15 of this report, that would require modification of there is no recognized fluid- the CEUS-SSC model.

injection related induced seismicity in North Carolina, South Carolina or Georgia.

Applicable to zone boundaries No Applicable to zone magnitude:

The SSC model for the CEUS used in the 2014 maps updated the zonation for Mmax, keeping the two- zone (craton and margin) used in previous maps and adding a new four-zone model based on the CEUS SSC model. The study also updated the distribution for Mmax for background earthquakes based on a new analysis of global earthquakes in stable continental regions.

Applicable to RLME source parameters: The current model adopted the characterization of the Charleston RLME source as defined by the CEUS SSC (2012) model.

Reference 57 Discovery of a Sand Blow and New source: No No. The Sawmill branch of the Associated Fault in the Epicentral MPSSZ lies within the highest Applicable to zone boundaries:

Area of the 1886 Charleston weighted geometry for the No Earthquake Charleston RLME source.

Applicable to zone magnitude: No The maximum earthquake of M Applicable to RLME source 5.6 in this study is below the parameters: This study dated a range of expected magnitude (M

>3,500 ybp sand blow and linked 6.7-M 7.5) expected in the it to a maximum magnitude 5.6 Charleston RLME source and earthquake on the Sawmill therefore the source magnitude branch of the of the Middleton does not need to be updated to Place-Summerville seismic zone include this new data.

(MPSSZ)

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 11 of 51 Title Notes Model Modification Needed?

Reference 58 Crustal Structure in a Mesozoic New source: No No. The imaged faults lie within Extensional Terrane: The South Applicable to zone boundaries: the Charleston Narrow source Georgia Rift and the Epicentral No zone, which is the highest Area of the 1886 Charleston, weighted geometry for the Applicable to zone magnitude: No South Carolina, Earthquake Charleston RLME source.

Applicable to RLME source parameters: This thesis reprocesses seismic data and interprets Cenozoic aged faults in the vicinity of Edisto River, South Carolina. It does not draw any conclusions regarding the fault that ruptured during the 1886 Charleston earthquake.

Reference 59 Seismicity in the Triassic Deep New source: No No. The study does not identify River Basin, North Carolina Applicable to zone boundaries: any new sources in the study No region.

Applicable to zone magnitude: No Applicable to RLME source parameters: No A 12 station broadband seismic network surrounding the Sanford Sub-Basin of the Deep River Basin installed in 2012 to measure unrecorded seismicity did not record any natural seismicity over a 15-month period.

Reference 60 Reassessment of prehistoric New source: No No. the calculated magnitudes earthquake accelerations at the from this study (M 5 -7.5) are Applicable to zone boundaries:

Sam pit and Gapway sites in the generally within the range of No South Carolina coastal plain expected magnitudes for the Applicable to zone magnitude: No Charleston RLME source (M 6.7-Applicable to RLME source 7.5).

parameters: This study reevaluated the earthquake accelerations and magnitudes at two coastal paleoliquefaction sites taking into account the effects of sediment aging. The results of the study suggested that accelerations lower than previously estimated could cause liquefaction. Calculated magnitudes range from M 5 to M 7.5. This is a reevaluation of Hu et al. (2002a; 2002b).

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 12 of 51 Title Notes Model Modification Needed?

Reference 61 Hypocenter locations and focal New source: No No. This seismogenic zone (and mechanism solutions of Applicable to zone boundaries: postulated source fault) is within earthquakes in the epicentral No the Charleston Narrow source area of the 1886 Charleston, SC, zone, which is the highest Applicable to zone magnitude: No earthquake weighted geometry for the Applicable to RLME source Charleston RLME source. The parameters: This thesis uses depth of the proposed source is data from a local seismic network within the depth distribution for to interpret a south-striking, west- the Charleston RLME source.

dipping seismogenic zone in the upper 12 km of the crust. Many of the focal mechanisms show reverse faulting on approximately north-south trending nodal planes. The thesis proposes that the 1886 Charleston earthquake occurred on a south-striking, west dipping Mesozoic extensional fault.

Table 2.2.1-5: Corrected Mmax Distributions for Seismotectonic Source Zones Published in (Reference 4 )

MidC Weight IBEB (A through D) PEZ-N PEZ-W SLR 0.101 6.4 5.6 6.0 6.0 6.4 0.244 6.7 6.1 6.5 6.4 6.8 0.310 7.1 6.6 6.9 6.9 7.3 0.244 7.5 7.2 7.4 7.4 7.7 0.101 8.0 7.9 8.0 8.0 8.1 Probabilistic Seismic Hazard Analysis The seismic sources used for the HBRSEP PSHA are based on the CEUS-SSC model (Reference 4). Two types of seismic sources are included in this model:

Distributed Seismicity Sources

Repeated Large Magnitude Earthquake (RLME) sources.

The ground motion characterization and representation for aleatory (random) variability developed in Reference 5 were used to compute seismic hazard at the HBRSEP site. Reference 5 is based on the most recent published Ground Motion Prediction Equations (GMPE) for CEUS and it has been endorsed by the NRC.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 13 of 51 Distributed seismicity sources represent future seismicity that is broadly distributed and not related to specific features known to rupture repeatedly in large earthquakes. Two types of distributed seismicity source zones are defined based on different criteria and modeling approaches: maximum earthquake magnitude (Mmax) zones and seismotectonic zones. The Mmax zones are defined based solely on delineating regions where there are expected to be differences in the maximum magnitude of an earthquake that may occur, denoted as the Mmax of a seismic source zone. The seismotectonic zones are delineated based on seismotectonic data that may play a role in the distribution and characterization of future earthquakes (e.g., style of faulting, seismogenic thickness, and orientation of ruptures) in addition to the expected differences in Mmax. The distributed seismicity source zones allow for the occurrence of earthquakes at all locations in the CEUS. The distributed seismicity source zones delineate large regions of the CEUS within which the characteristics of future earthquakes are expected to be similar. The rate of seismicity is allowed to vary spatially within these large regions to capture the observed patterns of earthquake activity.

In contrast to the distributed seismicity zones, the RLME sources are geographically constrained to areas identified as capable of generating repeated large (M ~ 6.5) earthquakes as inferred from the historical or paleoseismic record (e.g., geologically young fault displacement and paleoliquefaction features). The RLME hazard is added to the seismic hazard computed from the distributed seismicity sources. RLMEs can be defined by the historical record, the paleoearthquake record or a combination of the two and are interpreted to occur along a specific fault or within a localized area.

The distributed seismicity source zones for the HBRSEP PSHA include those that are based on Mmax and those that are defined by seismotectonic characteristics. Distributed seismicity sources included in the PSHA are listed below; followed by the source acronym:

Mesozoic and younger extended crust, narrow and wide interpretations, MESE-N and MESE-W

Non-Mesozoic and younger crust, narrow and wide interpretations, NMESE-N and NMESE-W

Study Region, STUDY-R

Atlantic Highly Extended Crust, AHEX

Extended Continental Crust-Atlantic Margin, ECC-AM

Extended Continental Crust-Gulf Coast, ECC-GC

Gulf Coast Highly Extended Crust, GHEX

Illinois Basin Extended Basement, IBEB

Midcontinent-Craton alternative interpretations A-D, MIDC-A, MIDC-8, MIDC-C, and MIDC-D

Paleozoic Extended Crust, narrow and wide interpretations, PEZ-N and PEZ-W

Reelfoot Rift, RR The HBRSEP site is located within the ECC-AM seismotectonic zone and the MESE-N, MESE-W, and STUDY-R Mmax zones. The AHEX, ECC-GC, GHEX, IBEB, MIDC- A through -D, PEZ-

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 14 of 51 Nand PEZ-W, and RR seismotectonic zones and the NMESE-N and NMESE-W Mmax zones are also within the 1,000 km (625 mi) radius around the site. RLME sources are identified and characterized in either the Mmax zones or the seismotectonic zones branches of the master logic tree. The RLME sources included in the HBRSEP PSHA are as listed below.

Charlevoix

Charleston

New Madrid Fault Zone

Wabash Valley Other RLME sources in the Reelfoot Rift (i.e. the Commerce fault zone, the Eastern Rift Margin-South, the Eastern Rift Margin-North, and the Reelfoot-Marianna) were found to contribute in aggregate less than 1 percent to the total hazard.

For the HBRSEP PSHA, distributed seismicity source zones and RLME sources within a distance of 625 miles (1 ,000 km), and those RLME seismic sources at greater distances that contribute at least 1 percent to the hazard at the site were included. These distances exceed the nominal 200-mile (320 km) extent of the site region recommended in Reference 6 for defining design ground motions. The greater distance range was included in order to provide a more complete representation of the hazard over the full range of source zones that may potentially contribute to the hazard assessment.

2. 2. 2 Base Rock Seismic Hazard Curves The development of the soil hazard curves follows Approach 3 defined in Reference 46 and Appendix B of the SPID (Reference 2). The basic concept of Approach 3 is to convolve a probabilistic representation of site response with the probabilistic seismic hazard results for the base rock to produce probabilistic seismic hazard results at the desired horizon within the soil column. Seismic hazard curves at control point Elevation 216ft are shown in section 2.3.7.

2. 3 Site Response Evaluation Following the guidance contained in Seismic Enclosure 1 of the 3/12/2012 50.54(f) Request for Information and in the SPID (CEUS-SSC, 2013a) for nuclear power plant sites that are not sited on hard rock (defined as 2.83 km/sec), a site response analysis was performed for HBRSEP.

2.3.1 Description of Subsurface Material The HBRSEP is within the Coastal Plain Physiographic Province in South Carolina, and within the upper portion of that Province. At the Western edge of the Coastal Plain, which is approximately 15 miles Northwest of the site, Pre Cambrian basement rock of the Piedmont Physiographic is exposed. In the Piedmont, the basement rocks are covered with soil-like

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 15 of 51 material weathered in place from the original granitic rocks and the HBRSEP UFSAR (Reference 7) indicates this weathered material may be present below the Coastal Plain formations as well.

The materials above the Piedmont at the site are recent sands or soils developed from the underlying Middendorf Formation. The Middendorf Formation was formed by deposition of sediments transported by water from the west. A fluvial to deltaic depositional environment is described in Reference 33. Both types of depositional environments are characterized by lateral and vertical variations in soil layers, both in composition and thickness. Such variations were observed in the boring logs from historical and recent explorations. Overall, the Middendorf Formation is described as a sequence of alternating clay and sand layers. The sand layers vary from clean sands with some gravel zones to sands with varying proportions of silt and clay. The soils are generally hard or dense. Indurated to partly indurated layers of clay and sand are common within the Middendorf Formation.

The original site exploration at the HBRSEP is documented in a report by Dames and Moore report (Reference 18) and included borings to a maximum depth of 150 ft. The report describes the site soil profile as follows (in order of increasing depth):

1. "Approximately 30 feet of moderately compact to compact sandy soils;

2. Approximately 25 feet of moderately compact to compact sandy soils containing layers and pockets of compressible silty and clayey soils;

3. Approximately 30 feet of hard silty and clayey soils, and;

4. Very compact sandy soils containing partially cemented layers."

As discussed in section 1.0, due to limited geotechnical data at the HBRSEP site, soil investigations and borings were completed recently after the initial submittal in March 2014. The recent borings encountered materials within the upper 1OOft of the profile that are consistent with the above general descriptions. One layer was encountered consistently in essentially all historical and recent borings. This layer consists of clay (or occasionally silt) described on boring records as having resistances to penetration measured by various techniques in excess of 100 blows per foot which indicates a hard consistency. The layer is referred to as "Hard Clay", and commonly begins at elevation 170ft. with vertical variation on the order .+/-5ft. The layer thickness is commonly approximately 30ft., but variations of 1Oft. are seen. The "Hard Clay" layer often has dense sand seams on the order of 2 to 5ft. thick embedded within it.

The recent site exploration included a boring drilled to locate the Piedmont rock. Based on that boring, weathered rock material was encountered at an approximate depth of 378ft. below the ground surface (corresponds to approximate Elevation -154ft). The weathered rock consisted of hard clay to weak claystone with some hard seams. At an approximate depth of 400ft

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 16 of 51 (approximate El. -177ft), hard-green metavolcanic rock was encountered and extended to the boring termination depth of 431ft. The rock is similar in appearance to the published description of Persimmon Fork formation (http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=SCCAZpf;4, Accessed November 11, 2014 ).

Integration and comparison of the geotechnical boring logs and geophysical data from the recent site study (References 19 and 34) provided the basis for developing the stratigraphic profile.

Interpretation of the geophysical data, specifically the natural gamma, also aided in identifying stratigraphic formations. The general elevation of the HBRSEP plant is approximately 226 ft.

National Geodetic Vertical Datum of 1929 (NGVD29). This elevation is taken as the top of the stratigraphic profile.

A single stratigraphic profile is appropriate to represent the subsurface conditions at HBRSEP.

Table 2.3.1-1 provides a summary of the stratigraphic profile. Three basic soil layers are defined

-sand, hard clay and sand with variable silt and clay zones -above weathered rock and rock.

Because the geologic origin of the upper materials is not clearly separable into alluvial or Middendorf Formation layers, a single layer is defined above the clay. Similarly, due to the lateral and vertical variations in material types and thicknesses, a single layer is used between the clay and the weathered rock. The soil thickness is approximately 377 feet over weathered rock and bedrock, and the bedrock is at a depth of approximately 397 feet. Below a weathered zone, the bedrock below approximately 410 feet depth has a shear wave velocity in excess of 9,285 fps (2,830 m/s) and is taken to be the top of the reference hard rock velocity profile for the Reference 5 GMC. Category I structures are founded on or within the shallow portions of the soil column. Therefore, site response studies are used to model the modifying effects of the site soils on generic hard rock ground motions.

T a bl e 2..

3 1- 1Stra f1g ra p1h'1c Pro fil1e for th e HBRSEP Depth* Average Total Range Material Density Density (ft) (pcf) Range**

(pcf) 0 to 57 Silty/Clayey Sands 125 119 to 131 57 to 82 Hard Clay 129 123 to 135 Alternating layers of Clay, Silty Sand and Clayey 82 to 377 Sand; Occasional gravel zones; Thickness of 134 125 to 143 layers varies laterally and vertically 377 to 397 Weathered Rock 135 135

> 397 Metavolcanic Rock 177 174 to 179

Measured from grade (approximately El. 226ft.)

- Values shown based on average +/-.1 standard deviation where three or more are available.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 17 of 51 2.3.2 Development of Base Case Profiles and Nonlinear Material Properties The characterization of the dynamic properties of the HBRSEP site is described in Reference

19. Three alternative median shear wave velocity profiles for the H8RSEP site in the plant area were developed to represent the epistemic uncertainty in characterizing the materials beneath the Category I structures. The recommended shear wave velocities and unit weights with depth for the three Profiles A, B, and Care listed in Table 2.3.2-1 and the shear wave velocities are shown in Figure 2.3.2-1.

The three velocity profiles A, B, and C represent epistemic uncertainty in the median shear wave velocities (Vs) beneath the Category I structures. The profiles were developed from geophysical investigations conducted around the periphery of the Category I structures and are based on differing amounts of data. Profile A is based on P-S Suspension logging of the deep boring. It provides the most detailed data on variation of Vs with depth, but consists of only measurements at one location south of the Category I structures. Profile B is based on three SASW profiles obtained at locations south of the Category I structures, and Profile C is based on five SASW profiles obtained mainly north of the Category I structures. On the basis that, the measurements obtained around the periphery are considered equally likely to represent the conditions beneath the Category I structures, Profile C and the combined assessments of Profiles A and B are given equal weight. The relative weights between Profiles A and B are based partly on the relative amount of data available at each location (which favors Profile B), and partly on the fact that the P-S Suspension log from the deep borehole provides a more detailed picture of the variation in velocity with depth (which favors Profile A). The SASW technique (used to obtain Profile B) tends to provide more of a spatial and depth average picture of velocities. Balancing these two considerations, Profile 8 is favored over Profile A by a ratio of 2 to 1, leading to relative weights of 2/3 and 1/3 on Profiles B and A, respectively.

The above characterization of epistemic uncertainty in site median Vs differs somewhat from the approach described in Appendix 8 of Reference 2 in which a best estimate median Vs profile is defined and epistemic uncertainty in median Vs is represented by upper and lower profiles with velocities assigned based on an epistemic sigma for ln(Vs). However, the above characterization produces comparable epistemic uncertainty. Table 2.3.2-21ists the values of sigma In( median Vs) computed at various elevations from the weighted combinations of the median Vs for profiles A, B, and C. Appendix B of Reference 2 lists a recommended value for sigma In( median Vs) of 0.35 for sites with limited Vs data and indicates that for sites with multiple detailed shear wave velocity profiles, the appropriate value may be significantly smaller. As there is a substantial amount of velocity data for the HBRSEP site, the modeled epistemic uncertainty in median Vs listed in Table 2.3.2-2 is considered to be consistent with the SPI(Reference 2) recommendations.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 18 of 51 Table 2.3.2-1: Layer Thickness, Depth, and Median Shear Wave Velocity Profiles for Plant Area at the HBRSEP Profile A Layer Elevation Interval Layer Shear Wave Compressional Computed No (ft} Thickness Velocity Wave Velocity Poisson's (ft} (f ps} (f ps} Ratio 1 226 to 164 62 928 5703 0.4864 2 164 to 90 74 2431 7078 0.4331 3A 90 to 30 60 837 5453 0.4879 38 30 to -153 183 1917 6433 0.4513 4 -153 to -172 19 4686 10729 0.3822 5 -172 to -184 12 7513 15809 0.3541 6 -184 and below N/A 10369 18996 0.2878 Profile B Layer Elevation Interval Layer Shear Wave Compressional Computed No (ft} Thickness Velocity Wave Velocity Poisson's (ft) (fps) (fps) Ratio 1 226 to 168.5 57 .5 807 4959 0.4864 2 168.5 to 108.5 60 1847 5377 0.4331 3A 108.5 to 48.5 60 1032 6714 0.4879 38 48.5 to -153 201.5 3229 10839 0.4513 4 -153 to -172 19 4686 10729 0.3822 5 -172 to -184 12 7513 15809 0.3541 6 -184 and below N/A 10369 18996 0.2878 Profile C Layer Elevation Interval Layer Shear Wave Compressional Computed No (ft} Thickness Velocity Wave Velocity Poisson's

_{_f tl Jfp~ Jfps) Ratio 1 226 to 161 65 919 5648 0.4864 2 161 to -4.5 165.5 2315 6739 0.4331 3 -4.5 to -153 148.5 2835 9516 0.4513 4 -153 to -172 19 4686 10729 0.3822 5 -172 to -184 12 7513 15809 0.3541 6 -184 and below N/A 10369 18996 0.2878

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 19 of 51 Table 2.3.2-2: Epistemic Sigma In (Median Vs) for HBRSEP Plant Area Profiles Sigma Depth Elevation In( median (ft.) (ft.) Vs) 20 206 0.06 50 176 0.06 100 126 0.11 150 76 0.54 200 26 0.32 250 -24 0.32 300 -74 0.32 350 -124 0.32

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 20 of 51 250

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Figure 2.3.2-1: Plant Area Shear Wave Velocity Profiles A, B, C.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 21 of 51 2.3.2.2 Shear Modulus and Damping Curves The recent site investigation included developing site-specific non-linear material properties for the soil and weathered rock at HBRSEP. The work is described in detail in Reference 19.

As described in Reference 19, most of the soil layers beneath the site consist of a mixture of sands and clays. Accordingly, two sets of shear modulus degradation (G/Gmax) and damping relationships were developed using computational methods as described in Reference 19. One set is based on treating the soils as sands and the other set is based on treating the soils as clays. The G/Gmax and damping curves for sands typically show more non-linear behavior than those for clays in that there is a greater reduction in shear modulus and greater increase in damping level with increasing shear strain.

The alternative G/Gmax and damping relationships represent epistemic uncertainty in the dynamic behavior of the subsurface materials. Following the approach described in the SPID for treating epistemic uncertainty in G/Gmax and damping, the G/Gmax and damping relationships developed in Reference 19 were grouped into two sets: a "Sand" set representing a greater degree of nonlinearity and a "Clay" set representing a lesser degree of nonlinearity. This is consistent with the SPID use of the Reference 37 set and the more linear Peninsular Ranges subset of the SPID. The G/Gmax and damping behavior of the thin weathered rock layers was modeled using the SPID rock G/Gmax and damping relationships. For the more linear Clay set, the weathered rock was considered to behave linearly with damping set at the low strain level.

The shallowest layer at the site consists of sands, therefore only a sand curve was computed in Reference 19 for this layer. To provide a curve for the more linear Clay set, the Peninsular Ranges relationships were used for this layer. Figures in Appendix B of this report show median values for site-specific shear modulus degradation and damping curves computed in Reference 19.

Table 2.3.2.3-1 lists the six median dynamic soil property cases use to characterize epistemic uncertainty in site response for the HBRSEP site. The weights assigned to Profiles A, B, and C are described above. Equal weight is assigned to the two alternative sets of G/Gmax and damping relationships, the "Sand" set and the "Clay" set, as the soils are a mixture of sands and clays and this approach is consistent with the guidance provided in Appendix B of the SPID.

Table 2.3.2.3-2 summarizes the weights assigned to the 6 sets of dynamic soil properties.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 22 of 51 Table 2.3.2.3-1: Site Response Profile Designations Profile 10 Shear Wave Profile Material Curve Set PAsand A Sand set (more nonlinear)

PAclay A Clay set (more linear)

PBsand B Sand set (more nonlinear)

PBclay B Clay set (more linear)

PCsand c Sand set (more nonlinear)

PCclay c Clay set (more linear)

Table 2.3.2.3-2: Weights Assigned to Amplification Functions Amplification Material Curves Profile Weight Combined Weight Function Weight PASand 1/2 1/12 1/6 PACiay 1/2 1/12 PBSand 1/2 1/6 1/3 PBCiay 1/2 1/6 PCSand 1/2 1/4 1/2 PC Clay 1/2 1/4 2.3.2.3 Kappa The characterization of damping for the site soils used in the analysis does not make use of the parameter kappa (K). However, the equivalent value of K can be computed from the low strain damping values using the relationship from Reference 39:

H K=-- 2.3.2.3-1 QsVs where His the layer thickness, Vs the layer shear wave velocity, and Qs is the shear wave quality factor, equal to 1/2{ (Reference 39), where {is the damping ratio. Applying Equation (2.3.2.3-1) to each soil layer and summing the results provides the value of kappa contributed by the sediments above the hard rock. The weighted average value obtained for profiles A, B, and C is 5.2 ms. Combined with the 6 ms assigned to Reference 19 rock ground motion models leads to a total site Kof 11.2 ms (0.0112s). Reference 19 recommends use of the empirical

Seismic Hazard and Screening Report H.8. Robinson Steam Electric Plant (H8RSEP) Page 23 of 51 relationship developed in Reference 40 for sites with soil thickness less than 3,000 ft. to obtain the value of site kappa contributed by the soil profile:

K=0.0605H 2.3.2.3-2 where H is soil thickness in m and K is in ms. Using a thickness of 125 m (410 ft.), Equation (2.3.2.3-2) yields a K value of 7.6 ms. Combined with the 6 ms assigned to Reference 5 rock ground motion models leads to a total site K of 13.6 ms (0.0136s}. The difference between this value and the value obtained from the assigned soil damping, 2.4ms, is less than the standard error of 10 ms reported in Reference 40 for the empirical model. Therefore, the equivalent value of K derived from the damping relationships assigned to the H8RSEP site soils is considered consistent with the SPID recommendations.

2.3.3 Randomization of Base Case Profiles To account for the aleatory variability in dynamic material properties and following the general methodology given in the SPID, the dynamic material properties were randomized to capture variability within each soil layer across the site. The velocity profile randomization was accomplished using the velocity correlation model developed in Appendix C of Reference 41.

The specific correlation parameters used were those developed for USGS Category C sites, which represent firm alluvial sites such as the H8RSEP site. The standard deviation in ln(Vs) was specified according to the recommendations of the SPID, a value of 0.25 for the top 50 ft. of the profile, decreasing to 0.15 for greater depths. These values of sigma (ln(Vs) are larger than the values computed using the multiple individual SASW profiles that were used to develop Profiles 8 and C. Profile layering was based on the detailed soil stratigraphy information available for the H8RSEP site. Layer thicknesses were randomized over a range of approximately +/-5 percent based on the observed variation in layer boundaries in the individual profiles used to construct site Profiles 8 and C.

The velocity profiles developed in Reference 19 represent averages over relatively thick layers.

As evidenced in the P-S Suspension log data obtained at the site, within an individual major profile layer, there is variability in the velocity. Part of the intent of the velocity randomization is to represent that variability in the analyses. Accordingly, the major velocity layers listed in Table 2.3.2-1 were subdivided into two or three layers so that the randomization process could generate within-layer variability. This degree of subdivision represents the major degree of variability seen in the data without introducing a large number of velocity reversals, and thus additional damping.

Within the site response analyses, additional sublayers were introduced on the order of 5 feet in thickness in order to allow strain gradients to develop within the thick layers to capture the effects of loading on the equivalent-linear properties. Sixty (60) randomized velocity profiles were

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 24 of 51 developed for each of the three base case profiles. The G/Gmax and damping relationships were also randomized following the general guidance given in the SPID and the uncertainties defined in Reference 19. The randomization was performed assuming no correlation between random variations in G/Gmax and damping about the median curves. It is expected that inclusion of such correlation would have a second order effect on the results.

2.3.4 Input Spectra The input motions for this analysis were developed to represent the earthquakes contributing to the hazard. The representative earthquake ground motions were developed based on the Conditional Mean Spectrum (CMS) concept developed in Reference 42. The use of CMS is appropriate for the representative earthquake spectra as they are intended to represent the spectra of earthquakes that define the hazard for a limited frequency band. Reference 43 analyzed a large ground motion data set and developed relationships for the correlation between the variability in ground motion at two frequencies. Reference 43 model was extended in Reference 44 to cover a broader frequency range. The model was further extended in Reference 45 to account for differences in the high frequency content of the motions. The adjustments in Reference 45 are based on an assessment of the lowest spectral period at which the response spectrum is a factor of 1.5 times the PGA. For the data used in Reference 44, this occurs at a period of 0.1 s (1 0 Hz frequency). For CEUS ground motions this point occurs at a period less than 0.04 s, (25 Hz frequency) but is not clearly defined by Reference 19 Ground Motion Model. Therefore, a period of 0.04 s was used to apply Reference 45 adjustments to the Reference 44 correlation model.

Conditional Mean Spectra were developed for two frequency ranges, a high frequency range of 5 to 25 Hz and a low frequency range of 0.5 to 2.5 Hz. The CMS were broadened by setting the target frequency in the correlation model to each end of these two frequency bands. For example, the low frequency CMS was constructed by using a target frequency of 0.5 Hz for all frequencies less than 0.5 Hz and a target frequency of 2.5 Hz for all frequencies above 2.5 Hz.

Within the frequency band, the CMS was scaled to match the UHRS.

The use of CMS to represent earthquake ground motions for site response analyses represents a difference from the procedures described in Appendix B of the SPID. In the SPID, the ground motions used for site response are defined in terms of the median response spectra forM 6.5 earthquakes created using single corner and double corner source models. A range of loading levels is created by computing the median response spectra for a range of source to site distances. While the resulting median response spectra for M 6.5 earthquakes are not expected to be as broad-banded as UHRS, at high loading levels they are expected to be more broad-banded than the CMS created above, and therefore will impart greater demand on the soil columns in site response analyses, typically resulting in larger strains and lower site amplification

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 25 of 51 values, particularly at higher spectral frequencies. As a result, the use of CMS to develop input motions for site response analyses is expected to result in somewhat higher site amplification functions at high loading levels than the use of scaled median shapes. At low loading levels, the differences between the two approaches are expected to be minor.

Reference 42 CMS concept was originally developed around the use of a single target spectral frequency. Following the suggestion in Reference 45, for computational efficiency, the CMS developed in this study were broadened to cover two frequency ranges, 0.5 to 2.5 Hz and 5 to 25 Hz. While this represents a compromise between the use of a CMS for each of the seven Reference 19 spectral frequencies and the SPID approach of using median response spectral shapes at all loading levels, it is considered to provide an improved representation of ground motion demand on soil profiles at high loading levels over the use of broad-banded median spectra.

Input acceleration time histories were then developed for the site response analyses by loosely matching the time histories in Reference 46 CEUS time history database to the CMS. For each CMS, 30 time histories were selected from the magnitude-distance bin consistent with the mean magnitudes and distances contributing to the hazard in the HF or LF range, as indicated in Table 2.3.4-1. In this manner, a degree of the natural variability in the frequency content of earthquake ground motions is captured in the variability in site amplification. To more fully represent the range of input rock motions, the CMS matched time histories were scaled up and down by factors of approximately 1.5 to create 12 levels of input motions with PGA values ranging from approximately 0.005g to 1.5g, consistent with the range in input ground motion levels recommended in the SPID. Table 2.3.4-2 lists the time history sets used for each CMS from Reference 46.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 26 of 51 Table 2.3.4-1: Deaggregation Results Showing Mean Magnitude (M) and mean Distance (R, Km)

Peak Ground Acceleration 25 Hz Spectral Acceleration AFE Mean M MeanR AFE MeanM Mean R 1E-03 6.67 119.5 1E-03 6.64 118.0 1E-04 6.62 84.7 1E-04 6.60 83.1 1E-05 6.33 42.8 1E-05 6.30 42.2 1E-06 6.20 14.4 1E-06 6.18 14.9 1E-07 6.33 5.6 1E-07 6.35 6.4 10Hz Spectral Acceleration 5 Hz Spectral Acceleration AFE Mean M Mean R AFE Mean M Mean R 1E-03 6.70 121.4 1E-03 6.80 127.5 1E-04 6.70 89.1 1E-04 6.89 100.7 1E-05 6.43 49.0 1E-05 6.76 68.0 1E-06 6.27 19.0 1E-06 6.62 34.6 1E-07 6.42 7.8 1E-07 6.70 13.8 2.5 Hz Spectral Acceleration 1 Hz Spectral Acceleration AFE Mean M Mean R AFE MeanM Mean R 1E-03 6.93 141.1 1E-03 7.10 235.2 1E-04 7.10 115.9 1E-04 7.20 138.5 1E-05 7.12 93.8 1E-05 7.24 107.9 1E-06 7.08 66.1 1E-06 7.21 76.9 1E-07 7.06 36.7 1E-07 7.18 40 .1 0.5 Hz Spectral Acceleration AFE Mean M Mean R 1E-03 7.25 356.3 1E-04 7.29 200.3 1E-05 7.31 133.1 1E-06 7.32 96.4 1E-07 7.33 59.0 Note: Annual Frequency of Exceedance (AFE)

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 27 of 51 Table 2.3.4-2: Time History Data Sets from Reference 46 Used to Create Time Histories Representing Individual CMS.

Hazard Magnitude Distance NUREG/CR-6728 Designation Level (M) (km) CEUS Rock Data Set AFE 10-3 HF 6.7 122 M 6-7, D 100-200 km

~5Hz AFE 10-3 LF 7.1 228 M > 7, D 100-200 km 0.5 to 2.5 Hz AFE10-4 HF 6.7 89 M 6-7, D 50-100 km

~5Hz AFE10-4 LF 7.2 152 M > 7, D 100-200 km 0.5 to 2.5 Hz AFE 10- 5 HF 6.5 51 M 6-7, D 10-50 km

~5Hz AFE 10- 5 LF 7.2 112 M > 7, D 100-200 km 0.5 to 2.5 Hz AFE10-a HF 6.3 21 M 6-7, D 10-50 km

~5Hz AFE10-a LF 7.2 80 M > 7, D 50-100 km 0.5 to 2.5 Hz 2.3.5 Methodology Site response analyses are performed using suites of input acceleration time histories representing the hard rock hazard at the site. The results of the site response analyses are used to develop soil amplification functions for the site control point elevation (EI. 226ft). The amplification functions are then used to develop soil hazard curves for the control point from which horizontal UHRS and GMRS are developed.

2. 3. 6 Amplification Functions Site response analyses were performed for each of the 12 scaled CMS loading levels using the 60 randomized profiles and material curves and the 30 scaled acceleration time histories. The analyses were performed using a modified version of program SHAKE by Schnabel, et al., 1972 (Reference 47). The modifications to SHAKE program involved increasing the allowable length of time histories, the allowable number of soil layers, and the allowable number of G/Gmax and damping curves. In each analysis, the rock time history was input as an outcropping motion at the base of the profile and, after iteration, a surface time history was computed. Response

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 28 of 51 spectra for the input rock and computed surface motions were then used to compute the ratio of the response spectral ordinates at the 7 frequencies defined in Reference 19 ground motion model. Figure 2.3.6-1 shows the resulting amplification values for PGA for the six alternative characterizations of the HBRSEP site profile extending to the control point elevation of 226 ft.

For each analysis case, the amplification values were fit by a piece-wise continuous function defining the variation in In(amplification) and its standard deviation as a function of the level of input rock motion. The solid red lines on Figure 2.3.6-1 show the fitted relationships and the dashed red lines indicate+/- one standard deviation on In(amplification). Also shown on Figure 2.3.6-1 is the minimum amplification level of 0.5 recommended in the SPID. This minimum amplification level was implemented in the development of the soil hazard curves.

The computed effective shear strains in the soil layers were examined and found to be generally less than 1 percent at the higher loading levels. Therefore, the use of the equivalent linear approach is considered appropriate. It should be noted that at the highest loading levels, the imposition of a minimum site amplification of 0.5 means that the computed site amplification values at high strains are often not used in developing the soil hazard.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 29 of 51 o Amplification Data +/-One Sigma Fit of Modlan 0.5 Min1mum Amplification c:

Q

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Figure 2.3.6-1: PGA Amplification Values for the Three Profiles and Two Sets of G/Gmax and Damping Relationships at Control Point Elevation.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 30 of 51 2.3. 7 Control Point Seismic Hazard Curves Following the approach described in the SPID, the ground motion values at the control point elevation are developed in a hazard-consistent manner by applying Approach 3 in Reference 46.

Approach 3 involves characterizing the amplification of the site soils in terms of the median (mean log) amplification functions and their associated standard deviations. The PSHA for the site is repeated convolving the soil amplification functions with the ground motion predictions from the rock ground motion models to produce mean and fractile soil hazard curves. The mean soil hazard curves are used to compute soil UHRS for AFE of 104 and 1o*5 . The soil UHRS are then used to develop the initial horizontal GMRS.

The site response analyses for the HBRSEP site include three alternative soil profiles and two sets of dynamic properties (Table 2.3.2.3-1 ). The result is six alternative models used to develop probabilistic representations of site amplification. In applying Approach 3, this epistemic uncertainty in the site dynamic properties is incorporated into the analysis in the same manner as epistemic uncertainties in all of the other inputs to the site hazard calculation are incorporated. Each set of dynamic properties is used to develop a distribution for AFE on soil for the seven (7) frequencies at which the hard rock hazard is computed. Figure 2.3.7-1 shows the ground motion characterization logic tree that combines the epistemic uncertainty in the dynamic properties in logic tree format with the CEUS hard rock ground motions logic tree from Reference 19. The weights assigned to the alternative sets of dynamic properties are given in Table 2.3.2.3-2. The distributions for soil hazard are then used to develop mean soil hazard curves at the seven frequencies. These mean soil hazard curves are then used to develop the GMRS using the relationships defined in Reference 6.

The above approach differs from that described in Appendix 8 of the SPID in which the site amplification functions and their uncertainties are convolved with the mean hard rock hazard curves to produce mean soil hazard curves. Conceptually, the two approaches should yield the same mean hazard. The difference is that the above approach allows expression of the epistemic uncertainty in the site amplification in the soil hazard, contributing to the range in the soil hazard fractiles.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 31 of 51 G/Gmax and Rock Ground Motion Soil Profile Damping Characterization Sand Set EPRI (2013a) 0.5 Logic tree Profile A 1/6 Clay Set EPRI (2013a) 0.5 Logic tree Sand Set EPRI (2013a) 0.5 Logic tree Profile B 1/3 Clay Set EPRI (2013a) 0.5 Logic tree Sand Set EPRI (2013a) 0.5 Logic tree Profile C 1/2 Clay Set EPRI (2013a) 0.5 Logic tree Figure 2.3.7-1: Logic tree for soil hazard ground motion characterization.

Figures 2.3. 7-2 through 2.3. 7-8 show the mean and fractile soil hazard curves computed for the control point elevation for the seven Reference 5 ground motion frequencies. Tabulated values of mean and fractile seismic hazard curves are provided in Appendix A. The soil hazard fractiles are produced by the combination of the epistemic uncertainty in the CEUS rock hazard characterized by the logic trees, and the epistemic uncertainty in the site response model parameters, characterized by the logic tree shown on Figure 2.3.7-1. The epistemic uncertainty is quantified by the variance in AFE computed for each level of ground motion.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 32 of 51 Elevation 226 ft.

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Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 33 of 51 Elevation 226ft.

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Figure 2.3.7-3: Mean and fractile soil hazard curves for 1 Hz spectral acceleration (5% damping) for elevation 226ft.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP} Page 34 of 51 Elevation 226 ft.

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Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 35 of 51 Elevation 226ft.

1.E-01 l

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Figure 2.3.7-5: Mean and fractile soil hazard curves for 5Hz spectral acceleration (5% damping) for elevation 226ft.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 36 of 51 Elevation 226 ft 1.E..()1

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Figure 2.3. 7-6: Mean and fractile soil hazard curves for 10 Hz spectral acceleration (5% damping) for elevation 226ft.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 37 of 51 Elevation 226 ft.

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Figure 2.3.7-7: Mean and fractile soil hazard curves for 25Hz spectral acceleration (5% damping) for elevation 226ft.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 38 of 51 Elevation 226ft.

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Figure 2.3.7-8: Mean and fractile soil hazard curves for Peak Ground Acceleration for elevation 226 ft.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 39 of 51 2.4 Ground Motion Response Spectrum The control point elevation for the HBRSEP site is at elevation 226ft. The control point hazard curves described above have been used to develop the Uniform Hazard Response Spectra (UHRS) and the Ground Motion Response Spectrum (GMRS). The GMRS for the HBRSEP site is defined at the control point elevation. The materials underlying this point consist of approximately 400ft of firm to stiff soil and weathered rock overlying bedrock. The measured bedrock shear wave velocity is in excess of the reference rock velocity of 9285 fps for the Reference 5 Ground Motion Model.

The development of the smooth UHRS for AFE of 104 , 1o-5 , and 1a-s is performed in two steps.

The first step involves interpolation of the mean soil hazard curves to obtain the ground motion levels at the desired AFE levels for the seven Reference 5 ground motion frequencies. The second step involves developing smooth interpolation/extrapolation functions to provide smooth UHRS for the ground motion frequency range of 0.1 to 100 Hz (PGA). The performance-based GMRS is then computed from the 1o-4 and 1o-5 UHRS using the formulation in Reference 6 based on Reference 50 approach for defining a risk-consistent Design Response Spectrum (DRS). Figure 2.4-1 shows plots of 1E-4 and 1E-5 UHRS and GMRS for HBRSEP. The smoothed UHRS and the GMRS data are listed in Table 2.4-1.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 40 of 51 Table 2.4-1: Smoothed UHRS and GMRS for the HBRSEP Horizontal Horizontal Horizontal Horizontal Freq. (Hz) 104 UHRS 10"5 UHRS 10"6 UHRS GMRS 100.000 (PGA) 2.88E-01 5.82E-01 1.05E+OO 3.03E-01 90.090 2.88E-01 5.91 E-01 1.12E+OO 3.07E-01 83.333 2.88E-01 6.33E-01 1.20E+OO 3.25E-01 66.667 2.88E-01 7.43E-01 1.48E+OO 3.69E-01 60.241 2.88E-01 7.99E-01 1.64E+OO 3.91E-01 50.000 2.98E-01 9.35E-01 1.84E+OO 4.46E-01 40.000 3.34E-01 9.89E-01 1.95E+OO 4.77E-01 33.333 3.63E-01 9.87E-01 1.91E+OO 4.85E-01 25.000 4.45E-01 9.43E-01 1.78E+OO 4.87E-01 20.000 5.00E-01 1.01E+OO 1.86E+OO 5.24E-01 16.667 5.42E-01 1.05E+OO 1.92E+OO 5.52E-01 13.333 5.90E-01 1.12E+OO 2.01E+OO 5.92E-01 11.111 6.15E-01 1.19E+OO 2.10E+OO 6.24E-01 10.000 6.32E-01 1.23E+OO 2.15E+OO 6.44E-01 8.333 6.00E-01 1.20E+OO 2.11E+OO 6.28E-01 6.667 5.82E-01 1.17E+OO 2.06E+OO 6.11 E-01 5.882 5.95E-01 1.19E+OO 2.11 E+OO 6.23E-01 5.000 6.12E-01 1.22E+OO 2.17E+OO 6.36E-01 4.000 6.39E-01 1.26E+OO 2.27E+OO 6.59E-01 3.333 6.38E-01 1.22E+OO 2.21E+OO 6.45E-01 3.000 5.96E-01 1.18E+OO 2.13E+OO 6.17E-01 2.500 5.25E-01 1.07E+OO 1.94E+OO 5.59E-01 2.000 4.70E-01 1.03E+OO 1.85E+OO 5.28E-01 1.667 4.54E-01 9.71E-01 1.77E+OO 5.01E-01 1.333 4.05E-01 8.61E-01 1.59E+OO 4.44E-01 1.111 3.30E-01 7.29E-01 1.40E+OO 3.73E-01 1.000 2.84E-01 6.42E-01 1.30E+OO 3.27E-01 0Jl67 1 ::\!=IF-01 ::\ !=14F-01 !=! ORF-01 1 !=I?E-01 0.500 8.38E-02 2.60E-01 6.78E-01 1.24E-01 0.333 4.77E-02 1.47E-01 4.18E-01 7.03E-02 0.250 3.66E-02 1.07E-01 2.90E-01 5.20E-02 0.200 2.86E-02 8.53E-02 2.30E-01 4.11E-02 0.167 2.27E-02 7.04E-02 1.86E-01 3.37E-02 0.133 1.78E-02 5.39E-02 1.52E-01 2.59E-02 0.111 1.35E-02 4.34E-02 1.24E-01 2.06E-02 0.100 1.16E-02 3.67E-02 1.05E-01 1.75E-02

Seismic Hazard and Screening Report H. B. Robinson Steam Electric Plant (HBRSEP) Page 41 of 51 1.40 1.20 C) 1.00 M

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Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 42 of 51 3.0 Safe Shutdown Earthquake Ground Motion The design basis for HBRSEP is identified in the Updated Final Safely Analysis Report (Reference 7).

3. 1 Description of Spectral Shape and Anchor Point The Safe Shutdown Earthquake (SSE) was developed based on evaluation historic earthquake activity, regional and local geology, and recommendation of Dr. G. W. Housner of the California Institute of Technology.

Only one earthquake of intensity V or greater has ever been recorded within 50 miles of the site.

In 1959, an earthquake of intensity V-VI (Modified Mercalli Scale) occurred about 15 miles from the site in the vicinity of McBee, SC. No permanent effects of this shock are noted in the literature or in a geologic reconnaissance, although it is presumed to have been felt at the location of the site. It is estimated that this shock had a magnitude no greater than 4.5 with an epicentral acceleration of well under 0.10 g.

On the basis of historical data, it is expected that the site area could experience a shock in the order of the 1959 McBee shock once during the life of the plant. This shock could be as far distant as in 1959, or perhaps closer. On a conservative basis, Magnitude 4.5 earthquake was selected with an epicentral distance of less than ten miles. This earthquake is the design earthquake and although the probable ground acceleration would be .07 to .09g, a value of 0.1g is used. To provide an adequate margin of safety, a maximum earthquake ground acceleration of 0.2g was selected for the hypothetical Safe Shutdown Earthquake (SSE).

The SSE is defined in terms of a PGA and a design response spectrum. The SSE response spectra used for the seismic Class I SSCs for the HBRSEP site have a spectral shape conforming to a Housner curve (Section 2.5 of Reference 7). The horizontal design response spectrum for the SSE was normalized to 0.2g PGA as noted in HBRSEP UFSAR Figure 2.5.2-3 (Reference 7). Table 3.1-1 shows the spectral acceleration values as a function of frequency for the 5% damped horizontal SSE.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 43 of 51 Table 3.1-1. SSE for HBRSEP (Reference 16)

Frequency Spectral (Hz) Acceleration (g) 100 0.2 33 0.2 13.33 0.2 10 0.23 8 0.26 5 0.3 4 0.32 3 0.3 1.641 0.24 0.33 0.07 3.2 Control Point Elevation Based on information in Table 1 from Reference 16, the SSE control point elevation is defined at the top of ground surface (i.e., El. 226 feet MSL-NGVD 29, 0 ft depth).

4.0 Screening Evaluation In accordance with Section 3 of the SPID (Reference 2}, a screening evaluation was performed as described below.

4. 1 Risk Evaluation Screening (1 to 10 Hz)

In the 1 to 10Hz part of the response spectrum, the GMRS exceeds the SSE. Therefore, the plant screens in for a risk evaluation.

4.2 High Frequency Screening (> 10Hz)

For a portion of the range above 10 Hz, the GMRS exceeds the SSE. The high frequency exceedances can be addressed in the risk evaluation discussed in 4.1 above.

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

In the 1 to 10 Hz range of the response spectrum, the GMRS exceeds the SSE. Therefore, the plant screens in for a spent fuel pool evaluation.

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 44 of 51 5.0 Interim Actions and Assessments As described in Section 4, the GMRS developed in response to the NTTF 2.1: Seismic portion of the 10 CFR 50.54(f) Request for Information of 3/12/2012 exceeds the design basis SSE. The NRC 50.54(f) letter requests: "interim evaluation and actions taken or planned to address the higher seismic hazard relative to the design basis, as appropriate, prior to completion of the risk evaluation." These evaluations and actions are discussed below.

Consistent with NRC letter dated February 20, 2014 (Reference 10), the seismic hazard reevaluations presented herein are distinct from the current design and licensing bases of HBRSEP. 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," and10 CFR 50.73, "Licensee event report system.

5. 1 Expedited Seismic Evaluation Program An expedited seismic evaluation process (ESEP) has been completed for the HBRSEP in accordance with the methodology in EPRI 3002000704 as proposed in a letter to NRC dated April 9, 2013 (Reference 8) and agreed to by the NRC in a letter dated May 7, 2013 (Reference 9). Duke has submitted an ESEP to the NRC in accordance with the schedule in the April 9, 2013 letter (Reference 8).

For the ESEP, an equipment list was developed, inspections were completed and evaluations were performed per EPRI Guidance as described in Reference 3. Insights from the process revealed one case where cabinet anchorage analysis warranted increased capacity for higher than design basis loading, and another case where the seismic capacity of a group of instrument racks could be increased by relatively minor work scope.

Modifications were implemented for two cabinets. One cabinet required modification to achieve seismic capacity greater than 2 X SSE. The second cabinet was related to the first in configuration and function. Therefore, a similar modification was implemented for the second electrical cabinet to add seismic margin above 2 X SSE. Seismic margin above 2 X SSE was also added to a group of instrument racks by validating the bolting integrity of the top braces (a relatively minor scope of work).

Seismic Hazard and Screening Report H. B. Robinson Steam Electric Plant (HBRSEP) Page 45 of 51 5.2 Seismic Risk Estimates The NRC letter (Reference 10) also requests that licensees provide an interim evaluation or actions to address the higher seismic hazard relative to the design basis while the expedited approach and risk evaluations are conducted. In response to that request, NEIIetter dated March 12, 2014 (Reference 11 ), 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 Gl-199 Safety/Risk Assessment:

Overall seismic core damage risk estimates are consistent with the Commissio.n's Safety Goal Policy Statement because they are within the subsidiary objective of 1E-4/year for core damage frequency. The Gl-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.

HBRSEP is included in the March 12, 2014 (Reference 11) risk estimates. Using the methodology described in the NEI letter, the seismic core damage risk estimates for all plants were shown to be below 1E-4/year; thus, the above conclusions apply.

5.3 Individual Plant Examination of External Events The IPEEE investigations for the HBRSEP site followed the methodology for a full scope Seismic Margins Assessment (SMA) presented in NUREG-1407 entitled "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities,". Methodology from EPRI NP-6041-SL were applied. Walkdown screening was performed using a 0.30g NUREG/CR-0098 median soil spectrum as a Review Level Earthquake (RLE). The plant level IPEEE High Confidence of Low Probability of Failure (HCLPF) was 0.28g. The HCLPF was dependent on resolution of USI A-46 outlier conditions which have been completed.

5.4 Walkdowns to Address NRC Fukushima NTTF Recommendation 2.3 Walkdowns have been completed for HBRSEP in accordance with the EPRI seismic walkdown guidance (Reference 17); including inaccessible items. Potentially adverse seismic conditions (PASC) found were entered into the corrective action program (CAP) and resolved. None of the

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 46 of 51 PASC items challenged the operability of the plant. There were no vulnerabilities identified under IPEEE, however, identified enhancements were reviewed and found to be complete.

Duke confirmed through the walkdowns that the existing monitoring and maintenance procedures keep the plant consistent with the design basis.

6.0 Conclusions In accordance with the 50.54(f) request for information, a seismic hazard and screening evaluation was performed for HBRSEP. Due to limited shear wave velocity at HBRSEP, new site investigations were recently completed. Shear wave velocity profiles were obtained through P-S Suspension logging and Spectral Analysis of Surface Waves (SASW). A GMRS was developed in accordance with the SPID (Reference 2).

Based on the results of the screening evaluation, HBRSEP screens in for risk evaluation, a spent fuel pool evaluation and a High Frequency Confirmation. However, the new GMRS developed based on recent site investigation data revealed that seismic hazard at the HBRSEP site is not as high as previously determined. Therefore, it is requested that the HBRSEP be re-prioritized into Group 2 for completing the seismic risk evaluation. If acceptable, the seismic probabilistic risk assessment (SPRA) for HBRSEP should be submitted by December 31, 2019 instead of June 30, 2017.

Seismic Hazard and Screening Report H. B. Robinson Steam Electric Plant (HBRSEP) Page 47 of 51 7.0 References

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58. Buckner, J.C., 2011. Crustal Structure in a Mesozoic Extensional Terrane: The South Georgia Rift and the Epicentral Area of the 1886 Charleston, South Carolina, Earthquake. Master's thesis, Virginia Polytechnic Institute and State University, 49 pp.

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Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-1 Appendix A:

Tabulated Values of Mean and Fractile Seismic Hazard Curves

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-2 Table A-1: Soil Hazard Results for 0.5 Hz Spectral Acceleration (5% Damping) for Elev. 226ft.

0.5 Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-05 1.37E-01 1.05E-01 1.18E-01 1.35E-01 1.51 E-01 1.62E-01 5.00E-05 1.10E-01 7.24E-02 8.71E-02 1.10E-01 1.29E-01 1.41E-01 1.00E-04 8.66E-02 5.01E-02 6.46E-02 8.51E-02 1.05E-01 1.20E-01 5.00E-04 3.35E-02 1.66E-02 2.34E-02 3.24E-02 4.47E-02 5.50E-02 1.00E-03 1.97E-02 9.55E-03 1.32E-02 1.91E-02 2.69E-02 3.55E-02 5.00E-03 5.26E-03 1.74E-03 2.75E-03 5.01 E-03 8.13E-03 1.07E-02 1.00E-02 2.74E-03 5.89E-04 1.10E-03 2.40E-03 4.57E-03 6.46E-03 2.00E-02 1.19E-03 1.38E-04 3.24E-04 9.12E-04 2.14E-03 3.39E-03 3.00E-02 6.53E-04 4.90E-05 1.29E-04 4.27E-04 1.20E-03 2.09E-03 5.00E-02 2.64E-04 1.05E-05 3.16E-05 1.29E-04 4.79E-04 1.00E-03 1.00E-01 7.18E-05 1.32E-06 4.07E-06 2.14E-05 1.18E-04 3.24E-04 3.00E-01 7.46E-06 4.68E-08 1.59E-07 1.02E-06 8.51 E-06 3.39E-05 5.00E-01 2.16E-06 8.71E-09 3.31E-08 2.29E-07 2.09E-06 9.33E-06

?.OOE-01 9.24E-07 2.57E-09 1.10E-08 8.32E-08 8.13E-07 3.98E-06 1.00E+OO 3.47E-07 5.75E-10 2.88E-09 2.63E-08 2.82E-07 1.48E-06 2.00E+OO 4.04E-08 1.86E-11 1.35E-10 1.86E-09 2.75E-08 1.86E-07 3.00E+OO 1.13E-08 1.91E-12 1.78E-11 3.31E-10 6.46E-09 5.13E-08 5.00E+OO 2.30E-09 7.94E-14 1.07E-12 3.16E-11 8.71 E-10 9.33E-09 1.00E+01 2.43E-10 6.31E-16 1.45E-14 8.32E-13 4.17E-11 7.08E-10 2.00E+01 1.96E-11 2.88E-1B 1.12E-16 1.32E-14 1.26E-12 3.63E-11

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-3 Table A-2: Soil Hazard Results for 1 Hz Spectral Acceleration (5% Damping) for Elevation 226ft.

1Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-04 1.30E-01 9.33E-02 1.07E-01 1.29E-01 1.48E-01 1.59E-01 5.00E-04 8.90E-02 4.68E-02 6.17E-02 8.71 E-02 1.12E-01 1.29E-01 1.00E-03 6.38E-02 2.95E-02 4.17E-02 6.17E-02 8.51E-02 1.02E-01 5.00E-03 1.96E-02 8.32E-03 1.18E-02 1.86E-02 2.88E-02 3.89E-02 1.00E-02 1.05E-02 4.17E-03 6.03E-03 1.00E-02 1.62E-02 2.14E-02 2.00E-02 5.38E-03 1.78E-03 2.82E-03 5.13E-03 8.51 E-03 1.18E-02 3.00E-02 3.54E-03 9.77E-04 1.66E-03 3.24E-03 5.75E-03 8.13E-03 5.00E-02 1.96E-03 3.89E-04 7.59E-04 1.70E-03 3.31E-03 4.79E-03 7.00E-02 1.26E-03 1.95E-04 4.17E-04 1.05E-03 2.19E-03 3.31E-03 1.00E-01 7.46E-04 8.51 E-05 2.00E-04 5.75E-04 1.32E-03 2.09E-03 2.00E-01 2.20E-04 1.35E-05 3.47E-05 1.32E-04 3.98E-04 7.59E-04 3.00E-01 8.83E-05 3.98E-06 1.05E-05 4.27E-05 1.55E-04 3.31 E-04 5.00E-01 2.15E-05 7.24E-07 1.91E-06 7.94E-06 3.47E-05 8.71E-05 7.00E-01 7.66E-06 1.95E-07 5.25E-07 2.29E-06 1.12E-05 3.24E-05 1.00E+OO 2.40E-06 3.63E-08 1.12E-07 5.75E-07 3.16E-06 1.00E-05 2.00E+OO 2.30E-07 7.08E-10 3.72E-09 3.72E-08 2.69E-07 9.77E-07 3.00E+OO 5.96E-08 6.92E-11 5.25E-10 7.41 E-09 6.76E-08 2.63E-07 5.00E+OO 1.12E-08 4.17E-12 4.47E-11 9.33E-10 1.12E-08 5.01 E-08 1.00E+01 1.12E-09 7.59E-14 1.20E-12 4.07E-11 7.94E-10 4.57E-09 2.00E+01 9.21 E-11 8.32E-16 1.95E-14 1.15E-12 3.72E-11 3.02E-10

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-4 Table A-3: Soil Hazard Results for 2.5 Hz Spectral Acceleration (5% Damping) for Elev. 226ft.

2.5Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-04 1.38E-01 1.05E-01 1.18E-01 1.35E-01 1.51 E-01 1.62E-01 S.OOE-04 1.18E-01 7.94E-02 9.33E-02 1.15E-01 1.35E-01 1.48E-01 1.00E-03 9.61E-02 5.89E-02 7.08E-02 9.33E-02 1.18E-01 1.32E-01 S.OOE-03 3.94E-02 2.19E-02 2.75E-02 3.89E-02 5.50E-02 6.46E-02 1.00E-02 2.27E-02 1.29E-02 1.62E-02 2.34E-02 3.31E-02 3.98E-02 2.00E-02 1.18E-02 6.61E-03 8.71 E-03 1.26E-02 1.78E-02 2.19E-02 3.00E-02 7.70E-03 4.07E-03 S.SOE-03 8.13E-03 1.18E-02 1.48E-02 S.OOE-02 4.35E-03 2.00E-03 2.88E-03 4.57E-03 6.76E-03 8.71E-03

?.OOE-02 2.96E-03 1.15E-03 1.74E-03 3.02E-03 4.68E-03 6.03E-03 1.00E-01 1.94E-03 5.89E-04 9.77E-04 1.86E-03 3.16E-03 4.27E-03 2.00E-01 7.33E-04 1.23E-04 2.40E-04 5.89E-04 1.26E-03 1.95E-03 3.00E-01 3.54E-04 3.98E-05 8.32E-05 2.40E-04 6.17E-04 1.10E-03 S.OOE-01 1.15E-04 7.08E-06 1.59E-05 5.62E-05 1.91 E-04 4.27E-04

?.OOE-01 4.48E-05 1.78E-06 4.37E-06 1.74E-05 6.92E-05 1.82E-04 1.00E+OO 1.32E-05 3.16E-07 8.32E-07 3.80E-06 1.74E-05 5.25E-05 2.00E+OO 8.90E-07 4.57E-09 1.82E-08 1.29E-07 9.12E-07 3.16E-06 3.00E+OO 1.63E-07 2.88E-10 1.91 E-09 2.04E-08 1.66E-07 5.89E-07 5.00E+OO 2.24E-08 9.55E-12 1.38E-10 2.29E-09 2.40E-08 8.91E-08 1.00E+01 1.71E-09 9.33E-14 3.55E-12 1.00E-10 1.55E-09 7.08E-09 2.00E+01 1.06E-1 0 4.68E-16 5.62E-14 2.63E-12 6.17E-11 3.72E-10

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-5 Table A-4: Soil Hazard Results for 5Hz Spectral Acceleration (5% Damping) for Elevation 226ft.

5Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-03 9.56E-02 5.75E-02 7.08E-02 9.33E-02 1.15E-01 1.29E-01 2.00E-03 7.07E-02 4.07E-02 5.01 E-02 6.92E-02 8.91E-02 1.02E-01 3.00E-03 5.71 E-02 3.24E-02 4.07E-02 5.62E-02 7.41E-02 8.51E-02 5.00E-03 4.23E-02 2.40E-02 3.02E-02 4.37E-02 5.75E-02 6.61E-02 1.00E-02 2.67E-02 1.59E-02 1.95E-02 2.82E-02 3.89E-02 4.57E-02 2.00E-02 1.55E-02 9.12E-03 1.20E-02 1.66E-02 2.34E-02 2.75E-02 3.00E-02 1.06E-02 6.17E-03 8.32E-03 1.18E-02 1.59E-02 1.95E-02 5.00E-02 6.22E-03 3.39E-03 4.68E-03 6.92E-03 9.55E-03 1.18E-02 7.00E-02 4.30E-03 2.09E-03 2.95E-03 4.57E-03 6.76E-03 8.51E-03 1.00E-01 2.84E-03 1.18E-03 1.74E-03 2.88E-03 4.47E-03 5.75E-03 2.00E-01 1.12E-03 2.75E-04 4.68E-04 9.77E-04 1.86E-03 2.69E-03 3.00E-01 5.54E-04 9 .55E-05 1.74E-04 4.27E-04 9.55E-04 1.51E-03 S.OOE-01 1.74E-04 1.82E-05 3.80E-05 1.07E-04 2.95E-04 5.75E-04 7.00E-01 6.93E-05 4.79E-06 1.12E-05 3.63E-05 1.12E-04 2.46E-04 1.00E+OO 2.16E-05 8.91E-07 2.46E-06 9.55E-06 3.31E-05 7.94E-05 2.00E+OO 1.39E-06 1.95E-08 6.76E-08 4.68E-07 2.14E-06 5.25E-06 3.00E+OO 2.67E-07 1.66E-09 7.41 E-09 7.94E-08 4.27E-07 1.05E-06 5.00E+OO 4.13E-08 5.75E-11 4.27E-10 9.77E-09 6.46E-08 1.78E-07 1.00E+01 3.45E-09 3.89E-13 6.92E-12 4.79E-10 4.57E-09 1.55E-08 2.00E+01 2.12E-10 1.51E-15 5.62E-14 1.41 E-11 1.95E-10 8.71E-10

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-6 Table A-5: Soil Hazard Results for 10 Hz Spectral Acceleration (5% Damping) for Elev. 226ft.

10Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-03 8.24E-02 4.90E-02 6.03E-02 8.13E-02 1.00E-01 1.15E-01 2.00E-03 5.97E-02 3.39E-02 4.27E-02 6.03E-02 7.59E-02 8.71E-02 3.00E-03 4.85E-02 2.75E-02 3.47E-02 5.01E-02 6.31E-02 7.41 E-02 S.OOE-03 3.68E-02 2.14E-02 2.69E-02 3.89E-02 5.01E-02 5.89E-02 1.00E-02 2.43E-02 1.45E-02 1.82E-02 2.63E-02 3.55E-02 4.27E-02 2.00E-02 1.48E-02 8.91E-03 1.15E-02 1.62E-02 2.19E-02 2.75E-02 3.00E-02 1.06E-02 6.03E-03 7.94E-03 1.18E-02 1.59E-02 2.04E-02 S.OOE-02 6.61E-03 3.31 E-03 4.68E-03 7.24E-03 1.02E-02 1.35E-02 7.00E-02 4 .71 E-03 2.04E-03 3.02E-03 5.01E-03 7.59E-03 1.00E-02 1.00E-01 3.14E-03 1.12E-03 1.74E-03 3.16E-03 5.13E-03 6.92E-03 2.00E-01 1.23E-03 2.34E-04 4.47E-04 1.05E-03 2.09E-03 3.16E-03 3.00E-01 6.14E-04 7.76E-05 1.66E-04 4.57E-04 1.07E-03 1.78E-03 S.OOE-01 1.92E-04 1.23E-05 3.24E-05 1.12E-04 3.39E-04 6.61E-04 7.00E-01 7.52E-05 3.16E-06 9.33E-06 3.72E-05 1.26E-04 2.75E-04 1.00E+OO 2.29E-05 7.76E-07 2.14E-06 9.55E-06 3.72E-05 8.51E-05 2.00E+OO 1.36E-06 3.09E-08 8.91 E-08 4.07E-07 2.19E-06 S.SOE-06 3.00E+OO 2.31 E-07 3.80E-09 1.29E-08 6.61 E-08 3.72E-07 9.77E-07 S.OOE+OO 3.33E-08 2.29E-10 1.00E-09 7.08E-09 5.25E-08 1.48E-07 1.00E+01 2.61 E-09 3.16E-12 2.09E-11 2.51 E-1 0 3.47E-09 1.20E-08 2.00E+01 1.45E-10 1.86E-14 2.00E-13 4.68E-12 1.32E-10 6.17E-10 0

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-7 Table A-6: Soil Hazard Results for 25Hz Spectral Acceleration (5% Damping) for Elev. 226ft.

25Hz Annual Frequency of Exceedance Spectral Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-03 6.36E-02 3.31 E-02 4.37E-02 6.31E-02 8.32E-02 9.55E-02 2.00E-03 4.49E-02 2.40E-02 3.09E-02 4.68E-02 6.03E-02 7.24E-02 3.00E-03 3.63E-02 2.00E-02 2.51E-02 3.89E-02 5.01 E-02 6.03E-02 5.00E-03 2.73E-02 1.59E-02 2.00E-02 2.95E-02 3.89E-02 4.79E-02 1.00E-02 1.78E-02 1.05E-02 1.41 E-02 1.95E-02 2.57E-02 3.39E-02 2.00E-02 1.09E-02 6.17E-03 8.32E-03 1.18E-02 1.59E-02 2.24E-02 3.00E-02 7.79E-03 4.07E-03 5.62E-03 8.32E-03 1.18E-02 1.66E-02 5.00E-02 4.88E-03 2.14E-03 3.09E-03 4.90E-03 7.59E-03 1.12E-02 7.00E-02 3.42E-03 1.20E-03 1.86E-03 3.31E-03 5.50E-03 8.13E-03 1.00E-01 2.19E-03 5.50E-04 9.55E-04 1.95E-03 3.63E-03 5.50E-03 2.00E-01 7.43E-04 8.71E-05 1.86E-04 5.25E-04 1.32E-03 2.29E-03 3.00E-01 2.97E-04 2.40E-05 5.13E-05 1.66E-04 5.25E-04 1.05E-03 5.00E-01 7.23E-05 4.90E-06 1.02E-05 3.31E-05 1.15E-04 2.69E-04 7.00E-01 2.63E-05 1.82E-06 3.80E-06 1.15E-05 3.98E-05 9.33E-05 1.00E+OO 8.26E-06 5.62E-07 1.29E-06 3.80E-06 1.23E-05 2.82E-05 2.00E+OO 6.45E-07 4.37E-08 1.23E-07 3.89E-07 1.07E-06 2.14E-06 3.00E+OO 1.57E-07 8.13E-09 2.29E-08 8.91E-08 2.69E-07 5.62E-07 5.00E+OO 2.60E-08 6.92E-10 2.24E-09 1.18E-08 4.37E-08 1.07E-07 1.00E+01 1.59E-09 1.29E-11 5.50E-11 4.27E-10 2.34E-09 7.41 E-09 2.00E+01 5.61 E-11 1.07E-13 6.03E-13 7.24E-12 6.61 E-11 2.88E-10

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page A-8 Table A-7: Soil Hazard Results for Peak Ground Acceleration for Elevation 226ft.

Peak Annual Frequency of Exceedance Ground Acceleration Mean 5th% 16th% 50th% 84th% 95th%

(g) 1.00E-03 5.70E-02 2.75E-02 3.80E-02 5.62E-02 7.59E-02 8.91E-02 2.00E-03 3.87E-02 1.95E-02 2.63E-02 4.07E-02 S.SOE-02 6.46E-02 3.00E-03 3.03E-02 1.59E-02 2.14E-02 3.24E-02 4.37E-02 5.25E-02 S.OOE-03 2.17E-02 1.18E-02 1.62E-02 2.34E-02 3.16E-02 3.98E-02 1.00E-02 1.29E-02 6.92E-03 9.77E-03 1.41 E-02 1.91 E-02 2.63E-02 2.00E-02 6.95E-03 3.31E-03 4.68E-03 7.24E-03 1.05E-02 1.59E-02 3.00E-02 4.70E-03 1.91E-03 2.82E-03 4.68E-03 7.41 E-03 1.18E-02 S.OOE-02 2.73E-03 7.59E-04 1.26E-03 2.46E-03 4.47E-03 7.24E-03 7.00E-02 1.81E-03 3.63E-04 6.46E-04 1.48E-03 3.09E-03 5.13E-03 1.00E-01 1.08E-03 1.45E-04 2.82E-04 7.59E-04 1.95E-03 3.39E-03 2.00E-01 2.64E-04 1.62E-05 3.63E-05 1.20E-04 4.57E-04 1.05E-03 3.00E-01 8.93E-05 3.89E-06 9.33E-06 3.31E-05 1.35E-04 3.63E-04 S.OOE-01 1.75E-05 5.62E-07 1.48E-06 5.89E-06 2.40E-05 6.46E-05 7.00E-01 5.08E-06 1.38E-07 3.98E-07 1.62E-06 7.08E-06 1.86E-05 1.00E+OO 1.24E-06 2.82E-08 9.12E-08 4.17E-07 1.86E-06 4.47E-06 2.00E+OO 6.72E-08 8.91E-10 3.39E-09 2.24E-08 1.07E-07 2.82E-07 3.00E+OO 1.43E-08 7.76E-11 3.55E-10 3.31 E-09 2.14E-08 6.46E-08 S.OOE+OO 1.72E-09 2.51E-12 1.51E-11 2.14E-10 2.19E-09 8.13E-09 1.00E+01 6.03E-11 8.71E-15 8.13E-14 2.24E-12 5.13E-11 2.40E-10 2.00E+01 1.15E-12 9.33E-18 1.48E-16 8.71E-15 5.37E-13 3.09E-12

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 8-1 Appendix B:

Site-Specific Shear Modulus Degradation and Damping Curves

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page B-2 1.10 1.00 -

0.90 -

0.80 -

0 .70

- Layer 1 (Ali Prof les) 0.60 I

- Layer 2 (Profiles A and B)

.. 0.50

- Layer 3A (Profiles A and B) and Layer E

(!)

2 (Profile C) 0.40

- Layer 3B (Profil s A and B) and Layer 3 (Profile G) 0.30 0.00 -l-----.;._-.........;_ _ _ _ _ _......._ _ _ _...;...._........_ _ _ _ ___,

0.0001 0.0010 0.0100 0.1000 1.0000 Shear Strain, y (%)

Figure B-1:

Computed Modulus Reduction Curves Sand Behavior

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page 8-3 30 24 - Layer 3A (Profile~ A and B) and Laye~

r 2= --+---+----i----..-t-------,-,,_._....,.,.r-1 (Profil~ C) 22

- Layer 3B (Profile A and B) and Layer 3

I

{Profile C)

- 20 18 16 14 12 10 8

6 I I 4

2 0

0.0001 0.0010 0.0100 0.1000 1.0000 Shear Strain, y (%)

Figure B-2:

Computed Damping Variation Curves Sand Behavior

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page B-4 0.60

"'E

(!)

0.50

- Layer 1 (All Pro iles) 0.40

- Layer 2 (Profile A and B) 0.30

- Layer 3A (Profil sA and B) and Layer 2 (Profile )

0.20 0.10 I I I 0.00 0.0001 0.0010 0 .0100 0.1000 1.0000 Shear Strain, y (%)

Figure B-3:

Computed Modulus Reduction Curves Clay Behavior

Seismic Hazard and Screening Report H.B. Robinson Steam Electric Plant (HBRSEP) Page B-5 30

- Layer 1 (All Profil s) 28 -

- Layer 2 (Profiles Aand B) 26

- Layer 3A (Profile A and B) and 24 Layer 2 (Profile C~

I I

- Layer 3B (Profiles A and B) a~ '

I 22 -

Layer 3 (Profile C 20 -

--c::.e 0

18 -

0 i

0::

16 - -

Cl r::: 14 . -

Q.

E I'll 0 12 .

(ij "i:

E Cl)

I'll 10 8

6 4

2 0 +-------------~------------_.------------~------------~

0.0001 0.0010 0.0100 0.1000 1.0000 Shear Strain, y (%)

Figure B-4:

Computed Damping Variation Curves Clay Behavior

Seismic Hazard and Screening Report H. B. Robinson Steam Electric Plant (HBRSEP) Page 8-6 Table B-1: Peninsular Range (0- 50ft) Shear Modulus Degradation and Damping Data Strain(%) G/Gmax D 0.000001 1 1 0.0001 1 1 0.000316 1 1 0.001 1 1.2 0.00316 0.97 1.64 0.01 0.87 2.8 0.0316 0.68 5.49 0.1 0.43 10.2 0.316 0.22 16.5 1 0.09 22.9 3.16 0.05 27 30 0.05 27

v t e Letter Sequence Request
CAC:MF0720, (Approved, Closed)
Initiation Request, Request Acceptance... Administration Questions Answers Results Approval Other: ML13252A243, RNP-RA/14-0008, Second Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049), RNP-RA/14-0083, Third Six-Month Status Report in Response to March 12, 2012, Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049), RNP-RA/15-0009, Fourth Six-Month Status Report in Response to March 12, 2012, Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)
MONTHYEAR2015-02-23 [Table View]

RNP-RA/15-0045, Submits Revision to Seismic Hazard Evaluation to Include New Ground Motion Response Spectra (GMRS) Using New Geotechnical Data and Shear-Wave Testing

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RNP-RA/15-0045, Submits Revision to Seismic Hazard Evaluation to Include New Ground Motion Response Spectra (GMRS) Using New Geotechnical Data and Shear-Wave Testing

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