ML15142A395

NRR E-mail Capture - NRC Technical Focus Areas in Support of Public Meeting on June 4

ML15142A395
Person / Time
Site:	Columbia
Issue date:	05/21/2015
From:	Nicholas Difrancesco Japan Lessons-Learned Division
To:	Linda Williams Energy Northwest
References
Download: ML15142A395 (3)

Text

NRR-PMDAPEm Resource From: DiFrancesco, Nicholas Sent: Thursday, May 21, 2015 3:53 PM To: Williams, Lisa L.

Cc: Rogalski, Richard J.; Shams, Mohamed; Jackson, Diane; Vega, Frankie

Subject:

NRC Technical Focus Areas in Support of Public Meeting on June 4 Ms. Williams, In support of the public meeting scheduled for June 4, 2015, the NRC staff would like to gain additional technical understanding in several areas to support productive public meeting discussions. In addition to providing a general overview of the SSC and GMC SSHAC Reports and March 2015 50.54(f) response for Columbia Generating Station, please provide additional clarification on the following topics.

Seismic Source Characterization

1. Summarize the information used to constrain the slip rates on the YFTB faults, including:

a. Methodology used to evaluate fault slip from topography including associated uncertainties in the ages and offsets.

b. Rationale for excluding thin skinned seismo-tectonic models.

c. How potential effects of surficial erosion were accounted for in the use of an average topographic profile to represent structural relief in individual faults.

d. Bases for excluding listric fault geometries or potential for backthrust structures in structural relief model.

2. Summarize the information use to define the areal seismic source zones, including:

a. Bases for zone boundaries

b. Seismicity rate calculations, smoothing, and how uncertainty was captured as part of logic tree.

c. Bases for Mmax distributions Ground Motion Characterization

1. Provide additional detail on the process used to define the target site kappa values and their uncertainties, including the rationale for logic tree weightings.

2. Provide additional detail on the Vs-Kappa corrections applied to the scaled backbone GMPEs, including:

a. Rational for not applying a kappa correction for the subduction zone GMMs

b. Comparison of the Vs-kappa scaled median GMPEs and NGA-West 2 models

c. Whether any observational data from the region was used to assess the Vs-kappa corrected GMPEs

3. Provide additional discussion regarding bases for bump seen at T=0.1sec in the mean tau values for the NGA-West2 models and the decision for smoothing through this peak in developing single-station sigma.

Site Response

1. Provide additional detail regarding the characterization of the uncertainty in the site response analyses, specifically:

a. Bases for only a single profile for the upper 525 ft

b. Bases for two Vs profiles and their associated weights for the SMB stack 1

c. Thickness of the interbed deposits including their lateral extent

d. Adequacy of EPRI and Peninsular curves for covering range of nonlinear behavior for the Pasco Gravel

e. Bases for randomizing the small strain damping for the basalt layers in the SMB stack in view of the uncertainty already incorporated into the determination of the site kappa

2. In view of the relatively high shear wave velocities (> 760 m/s) and high confining stresses in the interbed layers, provide the rationale for not considering linear behavior of these materials and instead using a single sand curve which demonstrates significant non-linear behavior.

3. Provide additional detail regarding the decision not to implement a minimum site amplification value and the effect of this decision on the development of the uncertainty in the site amplification function as well as on the final hazard curves for the site.

Please let me know if you have any questions on the above focus areas.

Thanks, Nick DiFrancesco Senior Project Manager - Seismic Reevaluation Activities U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Japan Lesson Learned Project Division nicholas.difrancesco@nrc.gov l Tel: (301) 415-1115 2

Hearing Identifier: NRR_PMDA Email Number: 2100 Mail Envelope Properties (Nicholas.DiFrancesco@nrc.gov20150521155300)

Subject:

NRC Technical Focus Areas in Support of Public Meeting on June 4 Sent Date: 5/21/2015 3:53:14 PM Received Date: 5/21/2015 3:53:00 PM From: DiFrancesco, Nicholas Created By: Nicholas.DiFrancesco@nrc.gov Recipients:

"Rogalski, Richard J." <rjrogalski@energy-northwest.com>

Tracking Status: None "Shams, Mohamed" <Mohamed.Shams@nrc.gov>

Tracking Status: None "Jackson, Diane" <Diane.Jackson@nrc.gov>

Tracking Status: None "Vega, Frankie" <Frankie.Vega@nrc.gov>

Tracking Status: None "Williams, Lisa L." <llwilliams@energy-northwest.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 3790 5/21/2015 3:53:00 PM Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received: