tva clinch river smr seismic approach - nrc · 2016. 1. 12. · • to provide an overview of...

TVA Clinch River SMR Seismic Approach

January 13, 2016

Purpose of Meeting

• To provide an overview of TVA’s approach to

Geology and Seismology for the Clinch River

Early Site Permit Application (ESPA)

• To address the observations and describe the

actions taken as a result of the September

2015 Readiness Review

• To address the specific comments regarding

the Clinch River Site Seismic Analysis made

regarding the Readiness Review described in

the November 19, 2015 memorandum to TVA

(ML15303A480)

SEISMIC ANALYSIS | 2

Agenda

• Introductions

• Readiness Review Summary

• Geological, Geotechnical and Geophysical Site

Characterization Overview

• GMRS Development (Nov 19th letter, Bullet 2)

- Site data availability

- Site response analysis

• 2D Sensitivity Analysis Development (Nov 19th

letter, Bullet 1)


Clinch River Site Project Description

• The Clinch River Small Modular Reactor

Project is preparing an Early Site Permit

Application

• The ESPA is based on a “Surrogate Plant”

that represents 2 or more reactor units,

based on current US LWR SMR designs

• The Clinch River Site is located in Oak

Ridge, Tennessee


Opening Comments

• We appreciate the feedback obtained during

the Readiness Review and also received in the

November 19th letter

• TVA had not completed the GMRS calculation

and had not developed detailed descriptions on

our approach for the readiness review

• We made substantial progress in this area and

are looking forward to presenting it to you and

hearing your feedback

• We want your feedback on our effectiveness in

resolving your concerns that rose to the

“significant” level SEISMIC ANALYSIS | 5

Readiness Review Summary

• The September Readiness Review resulted in

66 documented Observations and Issues:

- 46 O&I’s for Geological

- 20 O&I’s for Seismic

• 21 O&I’s closed during Review

- (19 Geological and 2 Seismic)

• All remaining O&I’s have been resolved in the

ESP SSAR


Specific November 19, 2015 Letter Topics

• Ground Motion Response Spectra (GMRS)

development technical concerns

- The availability of site data used in the

analysis

- Sufficient justification for key site

response parameters

• The inclusion of 2D model sensitivity

analysis results in the ESPA submittal


Discussion Topic

• Introductions


• Geological, Geotechnical and Geophysical

Site Characterization Overview





letter, Bullet 1)


Overview of Clinch River Site

Characteristics Geology and Seismology (1 of 2)

• The site region is defined as the area within a 200 mi

radius of the Clinch River Nuclear Site

• The Clinch River Site is located in the Valley and Ridge

physiographic province. The area within a 200 mi

radius of the CRN Site includes six physiographic

provinces.

• The Clinch River Site is located near the northwest

edge of the generally accepted boundary of the

previously defined East Tennessee Seismic Zone

(ETSZ)


Clinch River Site Location


Local Physiography


Bedrock

physiography is

characterized by a

well-developed

valley and ridge

system with the

Clinch River

incised through

some ridges

Readiness Review Observations and Issues for Geology

• We received 46 observations and issues on

the geological characterization portion of the

SSAR during the September 2015

Readiness Review.

• 19 of the observations were considered

closed during the course of the 2 day

review.

• The remaining 27 issues have been

resolved in their respective SSAR sections


Questions?

Discussion Topic

• Introductions




• GMRS Development (Nov 19th letter, Bullet

2)




letter, Bullet 1)


Seismicity (1 of 2)


Plot of Regional Seismicity from the Updated

CEUS SSC Earthquake Catalog

Seismicity (2 of 2)


East Tennessee Seismic Zone Geometry

(As Defined by USGS) *NOT DEFINED IN CEUS-SSC MODEL

Location of Area A

and B Boreholes

Borehole Location


Geologic Cross-Section


GMRS Development (1 of 2)

• The GMRS was developed using the following

NRC guidance:

- NRC Regulatory Guide 1.208, A Performance-Based

Approach to Define the Site-Specific Earthquake

Ground Motion

- NUREG/CR-6728, Technical Basis for Revision of

Regulatory Guidance on Design Ground Motions:

Hazard- and Risk-Consistent Ground Motion Spectra

Guidelines

• No exceptions were taken


GMRS Development (2 of 2)

Page

20

Review Site Information

Hard Rock Hazard

Evaluate Kappa to

Constrain Low Strain

Damping

Develop Site Vs Profiles

and Select Dynamic

Properties

Develop Suite of Amplification

Factors

Develop GMRS Using Approach 3 Review

Perform 2D analysis to

address dipping strata

Approach 3 Site Response Analysis (1 of 2)

• Fully probabilistic

- Preserves hazard levels

- Hazard at a specified datum is computed by

integrating of hard rock hazard with

probability distribution of site amplification

- Properly accommodates aleatory variability

and epistemic uncertainty

- Results in complete hazard curves at ground

surface at desired exceedance frequency

• Endorsed in NUREG/CR-6728


Approach 3 Site Response Analysis (2 of 2)

• Basic Steps in Approach 3

- Characterization of epistemic uncertainty in

dynamic material properties, multiple models,

logic tree approach

- Randomization of site dynamic material

properties

- Computation of amplification factors using

Random Vibration Theory

- Integration of hard rock hazard curves with

amplification factors


Discussion Topic

• Introductions








letter, Bullet 1)


Use of Site-Specific Data

• Shallow site-specific geologic, geotechnical, and

geophysical data collected as part of site

investigations were used in the development of the

GMRS.

• The SPID guidelines were not used as a basis for

developing the GMRS because there was a

significant amount of site-specific data at the site in

addition to data in the vicinity of the site.

• However, there are some site response analysis

procedures (e.g., assessment and incorporation of

epistemic uncertainty in dynamic material

properties, randomization) that are consistent with

NUREG/CR-6728 and the SPID that were used. SEISMIC ANALYSIS | 24

Geologic Cross-Section Showing Borehole Locations and VS Profiles


Clinch River Geologic Cross Section


Vs Profile for Clinch River Area A - OYO Suspension Data


Vs Profiles for Clinch River Area B - OYO Suspension Data


Geologic and Velocity Profiles for Area A


Basecase VS Profiles Area A


Geologic and Velocity Profiles for Area B



Basecase VS Profiles Area B

Kappa Estimation (1 of 2)

• Empirical kappa estimates used to constrain

low-strain hysteretic damping

- Tellico Dam site used as analog for Clinch River

> Located 10 miles from Clinch River

> Geologic structure similar in style

> ~ 12,000 ft to Precambrian basement

> Average shear-wave velocities (surface to

basement) are similar

> Tellico instrumented with strong motion recorder

- Tellico strong motion recordings

> Processed 59 recordings from 2004 to 2008

> 20 earthquakes between M 0.9 to 3.3


Kappa Estimation (2 of 2)

• Methods used to estimate kappa

- Acceleration response spectral shapes (5%

damped)

- Direct measurement of high frequency

decay of S-wave Fourier amplitude spectrum (FAS)

• Each method corrected for site amplification

based on suspension log profile

• Characterize epistemic uncertainty in kappa

• Empirical range in kappa 0.006 to 0.016 sec


• Express uncertainty in kappa with three base cases

- LR 0.006 sec, BE 0.010 sec, UR 0.016 sec

- Relative weights 0.2, 0.6, 0.2

• Profile and kappa associations are based on geology

and VS(30)

- Profile Kappa

LR UR

BE BE

UR LR

• Total effective kappa used to constrain low-strain

damping


Incorporating Kappa into Site Response Analysis (1 of 2)

• Kappa contributions

- VS and damping in each layer

- Wave scattering in random profiles

• Distribute damping within profile

• Both nonlinear and linear behavior in the top 500 ft were

assumed to be equally likely

• Nonlinear analysis low-strain damping set at 2%, and linear

analysis at 1.25% in top 500 ft

• Below 500 ft damping (Q) taken proportional to VS

• Adjusted to maintain total effective kappa at the surface

• In summary, site-specific kappa values were used


Incorporating Kappa into Site Response Analysis (2 of 2)

• Nonlinear dynamic material properties

- Equivalent-linear and linear analyses were

performed for the top 500 ft equally

weighted.

- Linear analyses below 500 ft

• Equivalent linear analyses

- Updated EPRI rock curves were used that

reflect upper range nonlinearity


Site Response Analysis

Summary of GMRS Development


Mean Hard Rock Hazard Curves


• Results of the deaggregation of the PSHA results indicate the controlling earthquake were a M 7.5 at 380 km (long period) and a M 5.9 at 16 km at 10-4 AFE

• Three basecase velocity profiles were used in the analysis to address the epistemic uncertainty particularly below the measurement depths.

• The range in basecase velocities also accommodates potential 2D effects due to the dipping structure beneath the site.


Inputs

Inputs and Weights Used for Site Response Analyses for Areas A and B


Velocity Profile Kappa(sec)

P1 0.010

P2 0.016

P3 0.006

Weights

P1 0.6

P2 0.2

P3 0.2

G/Gmax and Hysteretic Damping Curves

M1 0.5

M2 0.5

Randomization

• To account for the aleatory variability across the site, 60 random velocity profiles were developed from each of the smoothed basecase profiles.

• Correlation of Vs between layers was modeled using the footprint model (developed by Gabriel Toro).


Development of Amplifications Functions

• Amplification factors (5%-damped pseudo-absolute response spectra) are represented in terms of a median estimate and an associated standard deviation (sigma) for each oscillator frequency and input rock amplitude.


Amplification

Factors, 5%-

Damped

Pseudo-

Absolute

Spectra


Vertical GMRS V/H Ratios

• For the firm to hard rock conditions at the site the NRC has produced appropriate design V/H ratios (NUREG/CR-6728). The ratios accommodate potential magnitude and distance dependencies based on three levels of expected horizontal PGA: < 0.2g, 0.2g to 0.5g, > 0.5g.

• Epistemic uncertainty in V/H ratios was assessed by examining the range in available models appropriate for firm to hard rock site conditions.


GMRS Results


GMRS Area A


Horizontal PGA = 0.49 g

Vertical PGA = 0.68 g

GMRS Area B




GMRS Envelope




Technical Advisory Group Review

• An Independent Review was performed of

the GMRS work by our Technical Advisory

Group (TAG)

• The TAG provided comments and advice on

the analytical approach, as well as a review

of the results and the response to their

comments


GMRS Conclusions

• The Site Response Analysis contains the

applicable attributes required to fully define

the site hazard and associated GMRS

• The applicable SSAR sections have been

updated to reflect this information


Questions?

Discussion Topic

• Introductions







• 2D Sensitivity Analysis (Nov 19th letter,

Bullet 1)


2D Sensitivity Analysis (1 of 3)

• Due to the dipping nature of the underlying

stratigraphy (about 33 degrees) beneath the

site, potential 2D effects on ground motions are

being evaluated in a sensitivity analysis.

• In the development of the GMRS using

Approach 3, a 1D equivalent-linear site

response analysis was performed.

• Potential 2D effects were addressed in the 1D

analysis by evaluating the epistemic

uncertainties in shear-wave velocities beneath

the site and surrounding area.



• A primary objective of the 2D sensitivity

analysis is to evaluate how simplifying the

dipping stratigraphy to a 1D model for site

response impacts the GMRS.

• The 2D sensitivity analysis is being performed

using an expanded version of the computer

program SDE-SASSI version 2.0.

• The mesh was based on the geologic cross-

section developed by Dr. Bob Hatcher.

• Velocities, damping, and densities were

adopted from the 1D analysis.



• The influence of the dipping stratigraphy will be

evaluated by comparing the amplification

computed by the 2D and 1D analyses.

• Results of the 2D sensitivity analysis are a

series of time history responses, response

spectra (5%-damped) and amplification

functions for several specified locations on the

surface.


2D Sensitivity Analysis Conclusions

• Preliminary Results

• The description and results of the 2D

sensitivity analysis will be included in the

ESPA


Future Hazards Updates

• TVA will follow NUREG-0800 2.5.2 and

Regulatory Guide 1.208 for guidance and

direction on how to incorporate updates to

hazards information for the submitted

seismic analysis


Questions?

Regulatory Compliance

• The ESPA has been developed consistent

with the applicable regulatory guidance

identified in the acceptance criteria sections

of NUREG 0800 Sections 2.5.1 through

2.5.5.

• No exception have been taken to this

guidance.

• Meeting this extensive guidance provides

confidence in the completeness and quality

of the ESPA.


Overall Conclusions

• Based on our internal reviews and our actions to

address the issues identified in the NRC readiness

review, the ESP Application will be complete, with

necessary reference material and data to support NRC

review.

• TVA appreciates the opportunity to participate in the

Readiness Review Process to facilitate the submittal of

the Clinch River Early Site Permit Application.

• TVA is prepared to support timely review; we have the

necessary resources and are ready to provide timely

responses to NRC questions that arise during the

review.


Acknowledgement and Disclaimer

Acknowledgment: “This material is based upon work supported by

the Department of Energy under Award Number DE-NE0008336.”

Disclaimer: “This presentation was prepared as an account of work

sponsored by an agency of the United States Government. Neither

the United States Government nor any agency thereof, nor any of their

employees, makes any warranty, express or implied, or assumes any

legal liability or responsibility for the accuracy, completeness, or

usefulness of any information, apparatus, product, or process

disclosed, or represents that its use would not infringe privately owned

rights. Reference herein to any specific commercial product, process,

or service by trade name, trademark, manufacturer, or otherwise does

not necessarily constitute or imply its endorsement, recommendation,

or favoring by the United States Government or any agency thereof.

The views and opinions of authors expressed herein do not

necessarily state or reflect those of the United States Government or

any agency thereof.”


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