ML070670331

Site Status, NuStart-NEI Seismic Workshop

ML070670331
Person / Time
Site:	Harris, Bellefonte, PROJ0740
Issue date:	03/01/2007
From:	Progress Energy Carolinas
To:	Office of Nuclear Reactor Regulation
References
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Download: ML070670331 (20)

Text

Progress Energy Harris Site Status NuStart-NEI Seismic Workshop March 1, 2007 1

Harris Project Summary

• Existing Harris Nuclear Plant (HNP Unit 1) located 20 miles SW of Raleigh, NC

• Two new AP1000 Units (HAR 2 and HAR

3) are planned adjacent (North) of HNP Unit 1

• Site Investigation performed April through December 2006

• PSHA and SSE work ongoing

• COLA submittal in late 2007 2

Harris Site Location 3

Harris Location of New Units HAR 2 HAR 3 South 4

Harris Geotechnical Boring Layout SiteView NI 5

Harris Geotechnical Investigation Summary Soil & Rock Borings -50 at AP1000 Structures

-18 General Characterization

-15 at CTs and Conveyance Groundwater Monitoring Wells 20 P-S Suspension Logging (Compression 7 Boreholes (~150-200 ft depth) and shear wave velocity [Vp and Vs])

Downhole Logging (Vp and Vs) 2 Boreholes (~200 ft depth)

SASW Surveys (Vs) 4 Pairs of Profiles (depth < 100 ft)

MASW Surveys (Vs) 5 Profiles (depth < 70 ft)

Seismic Refraction Surveys (Vp) ~3200 Feet 6

Harris Existing Subsurface Profile (Typical)

HAR-2 HAR-3 Residual Soils - Reddish Brown. 0 - 10 0 - 25 Typically lean clays (CL), sandy silts (ML) and silty sand (SM)

Top of Weathered Rock - 0 - 10 10 - 25 Transition Zone from Residual Soil to Sound Rock Top of Sound Rock 5 - 20 15 - 40 7

Harris - Unit 2 Fence Diagram with S-Wave Velocity Profiles 8

Harris - Unit 3 Fence Diagram with S-Wave Velocity Profiles 9

Harris - Unit 2 - S-Wave Velocity Profiles - Adjusted Elevations 10

Harris - Unit 3 - S-Wave Velocity Profiles - Adjusted Elevations 11

Harris Rock Shear Wave Velocity

• Shear Wave Velocity (VS) below Reactor Island Basemat Elevation (220 feet above MSL) -

based on 7 suspension logging profiles to depth of ~200 feet bgs.

Unit Average Vs Standard (fps) Deviation HAR-2 6,227 779 HAR-3 6,079 981 12

Harris Preliminary Construction Plans

• Plant Site Grades

- Establish Plant Grade at Elevation = 260 feet.

- Establish Nuclear Island Basemat Subgrade on Competent Rock at Elevation = 220 feet.

• Nuclear Island:

- HAR-2: Rock Excavation (~1H:2V) to basemat subgrade.

- HAR-3: Plan to excavate as soil (~2H:1V) to basemat subgrade.

Overexcavate clay seams at basemat subgrade, backfill/grout with concrete fill.

• Other Structures:

- HAR-2: Excavate to Competent Rock and place Engineered Backfill (typically only 5 to 10 feet needed).

- HAR-3: Overexcavate and place Structural Backfill (up to 30 feet needed), OR construct deep foundations (caissons). To be finalized during detailed design.

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Harris Site Seismicity Giles County Central Virginia

• Site sits in a region of relatively low seismicity

• Sources related to Charleston, East Tennessee, Giles County, and Central Virginia at distances >

Harris Site

~ 100 km contribute to Charleston site hazard East Tennessee 14

Harris Regional Physiographic Setting 15

Harris Site PSHA

• Use UCSS (Vogtle) update of Charleston seismic source

- Overlay reoccurring Charleston mb > ~6.5 earthquakes

- Limit Mmax to mb 6.5 for EPRI-SOG Charleston sources to prevent double counting

• Use EPRI-SOG expert team assessments for all other seismic sources

- No adjustments in rates needed

- Minor adjustments in Mmax and source combinations 16

Harris Site PSHA (Contd)

• Use EPRI (2004) Ground Motion Models

• Use EPRI (2006) (G1.3) Aleatory Variability (Sigma)

• Consider use of EPRI (2006) CAV filter (G1.2)

- Not expected to produce a large change in hazard

- Implementation will incorporate site response 17

Harris Site Geology

• Site sits in Durham subbasin of the Deep River basin

• Approximately 5,000 ft of Triassic sediments

• Shallow sediments consist of interbedded siltstones and sandstones

• VS 4,000-5000 ft/sec at foundation level, quickly rising to 6,000-7,000 ft/sec 18

Harris Site Response

• Compute amplification of Triassic sediments using NUREG/CR 6728 method 2B

• Shallow velocity profile based on site data to a depth of ~200 ft

• Deeper profile based on nearby deep bore hole and refraction lines 19

Harris Site SSE Ground Motions

• Use performance-based ASCE 43-05 methodology

• Define SSE at outcrop of weathered Triassic rocks - elevation ~250 ft

• Simultaneously compute motions at foundation level - elevation 220 ft 20