ML15117A226

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Nuclear Regulatory Commission April 28, 2015, Public Meeting Slides for Diablo Canyon Seismic Hazard Reevaluation
ML15117A226
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 04/28/2015
From:
Japan Lessons-Learned Division
To:
DiFrancesco N, NRR/JLD, 415-1115
References
Download: ML15117A226 (23)
v • d • e


Text

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

References and Logistics

  • Meeting Feedback Form (request from njd2@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

7 NTTF2.3-SeismicWalkdowns - COMPLETEDreviewsJune2014 Licenseesidentifyandaddressdegraded,nonconforming,orunanalyzedconditionsrelativeto aplantscurrentlicensinganddesignbases.

NTTF2.1-InterimExpeditedApproach(ESEP)CEUS:12/31/2014;WUS:1/16 Ifthedesignbasisdoesnotboundreevaluatedhazard:Licenseesperforminterimevaluationto demonstratekeypiecesofequipmentforcorecoolingatahigherhazardusinginstalledFLEXequipment upto2xSSE.Evaluateneedformodificationswhilelongertermriskevaluationisperformed.

NTTF2.1-HazardReevaluations:SUBMITTEDCEUS:3/2014;WUS:3/2015 Licenseesreevaluatehazardbasedonpresentdayguidance/methodsusedtodefinethedesignbasisfornew reactors.

RegulatoryActions NRCstaffdetermineswhetheradditionalregulatoryactionsarenecessarytoprovide additionalprotectionagainsttheupdatedhazards.

NTTF2.1-InterimEvaluation:COMPLETEDCEUS:4/2014;WUS:4/2015 Ifthedesignbasisdoesnotboundreevaluatedhazard:Licenseesevaluatedtheneedforinterimevaluations usingnewseismicsourcesandgroundmotionwitholdhazardwhilethelongertermriskevaluationis performed.

NTTF2.1-SeismicRiskEvaluations:June2017-2020 Ifthedesignbasisdoesnotboundreevaluatedhazard:Licenseesdetermineperformaseismicrisk evaluation.

Tiered-approach to Seismic Activities

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

  • CEUSlicensees(96units/59sites)

- PreviouslyapprovedSSHACLevel3Models

- Plantspecificsiteanalyses

  • WUSlicensees(6units/3sites)

- Regionalsourceandgroundmotionmodelsdevelopedbyeach LicenseeusingSSHACLevel3Studies

- Plantspecificsiteanalyses 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

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

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?

12

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?

14

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

WUS Group 2 Risk Evaluations plant mods plant mods

Staff Assessment or response Staff acknowledgement to use GMRS for risk evaluation Expedited Interim Evaluations Schedule for Seismic Hazard and Risk Evaluations 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-CentralandEasternUnitedStates GMRS-GroundMotionResponseSpectrum NRC-U.S.NuclearRegulatoryCommission NPP-NuclearPowerPlant NTTF-NearTermTaskForce SFP-SpentFuelPool SMA-SeismicMarginsAnalysis SPID Screening,Prioritization,andImplementationDetailsSPID SPRA-SeismicProbabilisticRiskAssessment SSC-Structures,SystemsandComponents SSHAC-SeniorSeismicHazardAnalysisCommittee SSE-SafeShutdownEarthquake SPID-Screening,Prioritization,andImplementationDetails WUS-WesternUnitedStates 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

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 23 NRC makes Regulatory Decisions as Needed

  • Safety Enhancements
  • Modify Plant License PHASE 2 DECISION-MAKING Interact with Industry on Hazard and Risk Evaluation Guidance CEUS Licensees submit Site Response (9/2013 &

3/2014)

Licensees submit Hazard Reevaluations and Interim Evaluations, as needed (3/2014, CEUS; 3/2015, WUS)

Screen and prioritize plants for Risk Evaluation.

Review Interim Evaluations, as needed (CEUS:5/2014; WUS:5/2015)

Screened-in plants complete Expedited Approach Interim (CEUS:12/31/2014;WUS:1/2016) and Risk Evaluation (Group 1: 2017)

NRC reviews Risk Evaluation PHASE 1 STAGE 1 STAGE 2 INFORMATION GATHERING

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