ML15117A226

Nuclear Regulatory Commission April 28, 2015, Public Meeting Slides for Diablo Canyon Seismic Hazard Reevaluation

ML15117A226
Person / Time
Site:	Diablo Canyon
Issue date:	04/28/2015
From:	Japan Lessons-Learned Division
To:
DiFrancesco N, NRR/JLD, 415-1115
References
Download: ML15117A226 (23)

Text

Near-term Task Force Recommendation 2.1 Seismic Hazard Evaluation Pacific Gas & Electric Company Public Meeting April 28, 2015

References and Logistics

• Public Meeting Agenda - ML15105A528

• NRC Presentation Slides - ML15117A226

• Licensee Presentation Slides - ML15117A069

• Licensee Hazard Report - ML15070A607 and ML15070A608

• Meeting Feedback Form (request from njd2@nrc.gov)

• Webcast Archive at http://video.nrc.gov

• Meeting Summary to be issued within 30-day 2

Meeting Purposes

• Gather additional information based on early identification of areas where additional technical information will support the staffs review

• Gain a better understanding of how the licensee conducted their evaluation 3

Outline

• Background of NRC Near-term Task Force Recommendation 2.1 (NTTF R2.1)

• Current NRC approach to seismic hazard characterization

• Hazard characterization for NTTF R2.1

• Potential outcomes

• Focus questions for NRC review

• Timeline 4

NTTF Report and Recommendations 5

NRC 50.54(f) activities to address NTTF Seismic Recommendations 50.54(f) Request for Information Letter issued March 12, 2012

• Enclosure 1 (or R2.1):

Seismic hazard and risk reevaluation

• Enclosure 3 (or R2.3):

Seismic Walkdowns

• Other enclosures addressed flooding and emergency response 6

Tiered-approach to Seismic Activities NTTF 2.3 - Seismic Walkdowns - COMPLETED reviews June 2014 Licensees identify and address degraded, nonconforming, or unanalyzed conditions relative to a plants current licensing and design bases.

NTTF 2.1 - Hazard Reevaluations: SUBMITTED CEUS:3/2014; WUS:3/2015 Licensees reevaluate hazard based on present day guidance/methods used to define the design basis for new reactors.

NTTF 2.1 - Interim Evaluation: COMPLETED CEUS: 4/2014; WUS: 4/2015 If the design basis does not bound reevaluated hazard: Licensees evaluated the need for interim evaluations using new seismic sources and ground motion with old hazard while the longerterm risk evaluation is performed.

NTTF 2.1 - Interim Expedited Approach (ESEP) CEUS: 12/31/2014; WUS: 1/16 If the design basis does not bound reevaluated hazard: Licensees perform interim evaluation to demonstrate key pieces of equipment for core cooling at a higher hazard using installed FLEX equipment up to 2 x SSE. Evaluate need for modifications while longerterm risk evaluation is performed.

NTTF 2.1 - Seismic Risk Evaluations: June 2017 - 2020 If the design basis does not bound reevaluated hazard: Licensees determine perform a seismic risk evaluation.

Regulatory Actions NRC staff determines whether additional regulatory actions are necessary to provide additional protection against the updated hazards.

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Probabilistic Approach

• Previous studies such as 2011 Shoreline Fault Report and 2014 Coastal Commission Report were deterministic

- Few selected scenario earthquakes

- Limited treatment of uncertainty

• NTTF Recommendation 2.1 calls for seismic hazard reevaluations at each nuclear power plant using current NRC regulations

• Current NRC regulations and guidance specify a probabilistic approach for developing design ground motions

• Probabilistic ground motion hazards are characterized by a Ground Motion Response Spectrum or GMRS 8

Development of Seismic Hazard for R2.1 Reevaluations

• Licensees perform probabilistic seismic hazard analyses following NRC guidance (Regulatory Guide 1.208)

• CEUS licensees (96 units/59 sites)

- Previously approved SSHAC Level 3 Models

- Plantspecific site analyses

• WUS licensees (6 units/3 sites)

- Regional source and ground motion models developed by each Licensee using SSHAC Level 3 Studies

- Plantspecific site analyses 9

Screening Approach for R2.1 Reevaluations

• Screening approach specified in Industry Screening, Prioritization, and Implementation Details (SPID)

Guidance

• SPID provides detailed guidance for

- Development of GMRS

- Seismic Risk Evaluations & Limited Scope Evaluations (high frequency, SFP)

• Plants with GMRS > SSE Screen In for

- Interim Evaluations (and actions, as needed)

- Expedited Interim Evaluations (and actions, as needed)

- Seismic Risk Evaluations 10

Potential Outcomes for R2.1 Reevaluations Outcome 1 Outcome 3 No Further Analysis Outcome 2 Industry Testing Program for High Frequency Sensitive components 11

NRC Review of SSHAC Studies for WUS Sites

• Did SSHAC process follow NRC guidance?

• How effective was the peer review panel?

• Have all applicable data been considered?

• Were data uncertainties identified and considered?

• Was an appropriate range of applicable models considered?

• How were models selected and weighted in the analysis?

• How were models assembled into the PSHA?

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NRC Review of Source Models for WUS Sites

• How were seismic sources identified?

- Geologic mapping

- Geophysical observations

- Earthquake catalog

• How were seismic sources characterized?

- Geometry (location, length, dip)

- Range of magnitudes

- Faulting style (normal, reverse, strike-slip)

- Slip rate and recurrence models

- Complex rupture scenarios 13

NRC Review of Ground Motion Models and Site Response for WUS Sites

• Do final ground motion models capture a reasonable range of alternative models?

• How were sources of uncertainty captured in model development?

• How were ground motion models adjusted for local site geology?

• Does site response analysis cover a reasonable range of alternative soil/rock properties?

• How was uncertainty in site response analysis incorporated into final probabilistic hazard curves?

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Schedule for Seismic Hazard and Risk Evaluations 2012 2013 2014 2015 2016 2017 2018 2019 2020 CEUS Hazard All plants Development WUS CEUS plant mods Expedited Interim plant mods Only plants WUS with new Evaluations seismic hazard exceeding Risk Evaluations design basis Group 1 Higher Priority Group 2 Group 3 (as needed)

Lower Priority Hazard Analyses Risk Evaluations Staff Assessment or Expedited Interim Staff acknowledgement to response Evaluations use GMRS for risk evaluation 15

Forthcoming Seismic Screening Letter

• Issuance of letter for WUS sites in ~ 2 weeks

• Diablo Canyon has screened-in for further risk evaluations and is a review priority

• No immediate safety issues identified

• Information supports safety assurance allowing additional time to complete the seismic risk evaluation 16

List of Acronyms

• CEUS - Central and Eastern United States

• GMRS - Ground Motion Response Spectrum

• NRC - U.S. Nuclear Regulatory Commission

• NPP - Nuclear Power Plant

• NTTF - NearTerm Task Force

• SFP - Spent Fuel Pool

• SMA - Seismic Margins Analysis

• SPID Screening, Prioritization, and Implementation Details SPID

• SPRA - Seismic Probabilistic Risk Assessment

• SSC - Structures, Systems and Components

• SSHAC - Senior Seismic Hazard Analysis Committee

• SSE - Safe Shutdown Earthquake

• SPID - Screening, Prioritization, and Implementation Details

• WUS - Western United States 17

Break for NRC Staff Alignment

• 15 - 20 minute planned break for NRC staff alignment to support meeting wrap-up

• Meeting to resume at 4:00pm (Eastern) or 1:00pm (Western) 18

Opportunity for Public Questions or Comments

• Additional Questions?

Please ask us at:

JLD_PublicResource@nrc.gov 19

Backup Slides 20

Additional WUS Seismic Hazard Reports Public SSHAC Reports

• Diablo Canyon http://www.pge.com/en/safety/systemworks/

dcpp/sshac/index.page 21

Guidance Documents

• Two main guidance documents proposed by industry and endorsed by the NRC

• Screening, Prioritization, and Implementation Details (SPID)

- Submitted by EPRI on November 2012

- Endorsed by NRC on February 15, 2013

- EPRI-1025287 (ML12333A170)

• Seismic Evaluation Guidance: Augmented Approach (aka Expedited Approach)

- Submitted by EPRI on April 9, 2013

- Endorsed by NRC on May 7, 2013

- EPRI-3002000704 (ML13102A142) 22

Seismic 2.1 Process Ensures Clarity, Consistency, and Risk-Informed Regulatory Decisions PHASE 1 INFORMATION GATHERING STAGE 1 STAGE 2 PHASE 2 Screen and prioritize plants DECISION-MAKING Interact with Industry on for Risk Evaluation.

Hazard and Risk Review Interim Evaluation Guidance Evaluations, as needed NRC makes Regulatory (CEUS:5/2014; WUS:5/2015)

Decisions as Needed CEUS Licensees submit Screened-in plants Site Response (9/2013 &

• Safety Enhancements complete Expedited 3/2014)

• Backfit Analysis Approach Interim (CEUS:12/31/2014;WUS:1/2016)

• Modify Plant License and Risk Evaluation Licensees submit Hazard (Group 1: 2017)

Reevaluations and Interim Evaluations, as needed (3/2014, CEUS; NRC reviews Risk 3/2015, WUS) Evaluation 23