NRC Review of PG&E’s March 2015Probabilistic Seismic HazardProbabilistic Seismic Hazard

Analysis for the Diablo Canyon Power Plant CaliforniaPower Plant, California

Dr Brittain HillDr. Brittain HillSenior Level Advisor, Office of New Reactors

Division of Site Safety & Environmental AnalysisDivision of Site Safety & Environmental Analysis

Most Important Points

• NRC is in the process of conducting an independent review of PG&E’s March 2015independent review of PG&E s March 2015 probabilistic seismic hazards assessment for Diablo Canyon.

• Current information shows that Diablo Canyon can shut-down safely even if a 1 in 10,000 year y , yearthquake occurs.

• If new information questions the ability of Diablo• If new information questions the ability of Diablo Canyon to operate safely, NRC will take immediate regulatory action to protect public g y p psafety and the environment.

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What is NRC Reviewing?

• 50.54(f) request: All licensees conduct a probabilistic seismic hazard analysis (PSHA) using current NRCseismic hazard analysis (PSHA) using current NRC regulations and guidance

• PG&E’s March 11 2015 PSHA submittal:PG&E s March 11, 2015 PSHA submittal:– Seismic Source Characterization report + Supporting reports– Ground Motion Characterization report + Supporting reports– Participatory Peer Review Panel documentation

• Responses to NRC questions and Requests for Additi l I f tiAdditional Information

• Informed by other information, including AB-1632 t I d d t P R i P l treport, Independent Peer-Review Panel reports

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What is SSHAC?

• SSHAC = Senior Seismic Hazards Analysis CommitteeCommittee

• A process used to develop a hazard assessment that represents the center body and range ofthat represents the center, body, and range of technically defensible interpretations.– Workshops held to identify data and discuss alternativeWorkshops held to identify data and discuss alternative

models– Team integrates data and models into probabilistic

i i h d tseismic hazards assessment– Continuous review and feedback by Participatory Peer

Review PanelReview Panel– Thorough documentation of methods and assumptions

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How will NRC Review SSHAC?

• Consistency with applicable guidanceConsistency with applicable guidance

• Effectiveness of Participatory Peer Review P lPanel

• Consideration of seismic hazard data and models

Traceable integration of data and models• Traceable integration of data and models into PSHA

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How will NRC Review PSHA?

• Participated as observers in SSHAC k hworkshops

• Detailed review of documentation

• Perform independent sensitivity analyses for potentially significant topicspotentially significant topics

• Conduct public meetings and site audits

• Issue Requests for Additional Information and review responsesp

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Earthquake Recurrence

• Understanding Hosgri fault dataHosgri fault data and uncertainties

• Representing alternative models for fault geometries

• DeterminingDetermining lag-time between earthquakes

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earthquakes

Site Response

• Calculating uncertainties withuncertainties with site-term approach

R ti• Representing subsurface variations at sitevariations at site

• Evaluating site response using approach in

idguidance8

PG&E March 2015 submittal, Figure 2.3.2-4

Why is DCPP Safe Today?

LTSP margin=Minimum safety margin for weakest componentcomponent (diesel generator

t lcontrol panels)

=1.35 x LTSP load

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2015 PSHA = PG&E March 2015; DE = Design Earthquake; DDE = Double DE; HE = Hosgri Evaluation; LTSP = 1988 Long Term Seismic Program

Current NRC Review Status

• NRC expects to finish review and issue a Staff Assessment report in mid-2016Staff Assessment report in mid-2016

• Current information shows Diablo Canyon can shut-down safely even if a 1 in 10,000 year earthquake occurs

• If information questions the ability of Diablo Canyon to operate safely NRC will takeCanyon to operate safely, NRC will take immediate regulatory action to protect public safety and the environmentsafety and the environment

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