ML16154A030

R2.1 Seismic -- PVNGS Data Request and Draft Request for Additional Information

ML16154A030
Person / Time
Site:	Palo Verde
Issue date:	06/24/2015
From:	DiFrancesco N Japan Lessons-Learned Division
To:	Weber T N Arizona Public Service Co
References
Download: ML16154A030 (2)

Text

From: DiFrancesco, Nicholas To: Thomas.N.Weber@aps.com Cc: Shams, Mohamed

Christopher.Wandell@aps.com

Carl.Stephenson@aps.com

Watford, Margaret

Jackson, Diane; Devlin-Gill, Stephanie

Subject:

R2.1 Seismic -- PVNGS Data Request and Draft Request for Additional Information Date: Wednesday, June 24, 2015 5:19:02 PM Mr. Weber, As a follow-on to the discussion yesterday on screening status. The staff is continuing its

review of the reevaluated seismic hazard for Palo Verde Nuclear Generating Station.

Below is an data request for review in the ePortal.

Data Request

In support of a confirmatory review, please provide the PVNGS composite

earthquake catalog prior to the declustering analysis, meaning the catalog with

1,941 events in it as mentioned in "Palo Verde Nuclear Generating Station Seismic

Source Characterization" report on page 6-7 and 6-10.

The staff requests the

catalog be provided in the tabular form.

Separately, the NRC staff is planning to issue one set of request for additional information (RAI) prior to making a final screening decision.

The staff has identified one RAI thus far.

The RAI request should be finalized during the first full week of July. Below is a draft RAI

question. Please let me know if you would like a clarification call on the below request.

Request for Additional Information The southwestern United States (SWUS) Ground Motion Characterization (GMC)

project used the partially non-ergodic sigma model, which implies the use of a

single station sigma model.

For the partially non-ergodic approach, the site term (dS2S s) is assumed to be known and as such its standard deviation (f S2S) is excluded from the single station sigma model.

Use of the single station sigma

approach assumes that the epistemic uncertainty for the site term is captured by

the epistemic uncertainty in the Vs-kappa correction and the uncertainty in the site

amplification factor.

Section 2.3.6 of the Seismic Hazard and Screening Report for

Palo Verde Nuclear Generating Station Units 1, 2, and 3, states that "the variability

in the amplification factors results from variability in shear wave velocity, depth to

hard rock, modulus reduction curves, hysteretic damping curves, and application of

the nine Fourier adjustment functions to account for uncertainty in the kappa and

the deep site Vs profile."

In order for the staff to better understand how the uncertainty in the site term is

captured for the Palo Verde site; please provide a more detailed description, including all equations used for the total standard deviation of the site amplification

factor. As part of the response, describe how the various epistemic and aleatory

portions are combined to determine the total amplification factor uncertainty.

In addition, provide a justification for including the epistemic uncertainty associated

with the Vs-kappa correction as part of the uncertainty in the site amplification

factor rather than as part of the logic tree for the median ground motion models and whether this decision impacts the final control point hazard curves and GMRS.

Please let me know if you have any questions or concerns.

Thanks,

Nick

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