NRC Activities Related to the

Fukushima Task Force Flooding and

Seismic Hazard Recommendations

Christopher Cook, Ph.D.

Chief, Geoscience and Geotechnical Engineering Branch

Division of Site Safety and Environmental Analysis

Office of New Reactors

21 March 2012

2

Outline

• Background

• Scope

• Overall Approach

• Hazard Reevaluation

• Walkdowns

• Schedules

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Background

• NRC established the Near-Term Task Force (NTTF) in response to events at Fukushima Dai-ichi in March 2011

• NTTF developed a set of twelve overarching recommendations

• Recommendation Two included:

– Flooding Hazard Reevaluations and Walkdowns

– Seismic Hazard Reevaluations and Walkdowns

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Scope: NTTF Recommendation 2.1

• Reevaluate hazards at all operating reactor sites

• Collect information to facilitate NRC’s determination if there is a need for additional regulatory actions

• Gather information to address ongoing Generic Issues related to:

– Updated seismic hazards since the plant was licensed (GI-199)

– New information on plant safety following upstream dam failures (GI-204)

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Scope: NTTF Recommendation 2.3

• Develop seismic and flooding walkdown procedures

• Perform walkdowns using NRC-endorsed walkdown methodology

• Identify and address degraded, non-conforming or unanalyzed conditions

• For flooding hazards only, identify and address any cliff-edge effects

NTTF defined “Cliff-Edge” effect: safety consequence of a flooding event may increase sharply with a small increase in flooding level.

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Overall Approach: R2.1

• Recommendation 2.1 will be implemented in two phases: – Phase 1:

• Licensees reevaluate flooding and seismic hazards using present-day regulatory guidance and methodologies

• If necessary, perform an integrated/risk assessment following the hazard reevaluation

– Phase 2:

• Based on results of Phase 1, NRC will determine if further regulatory actions are necessary to protect against the updated hazard

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Recommendation 2.1 Evaluation

Licensees Conduct

Hazard Reevaluation

NRC & Stakeholders

Interact on

Integrated/Risk

Assessment Guidance

NRC Reviews Hazard

Reevaluation and Near-

Term Actions

Licensees Conduct

Integrated/Risk

Assessment, as needed

NRC Reviews

Integrated/Risk

Assessment and

Additional Actions

NRC to make Regulatory

Decisions, as needed:

* Safety Enhancements

* Backfit Analysis

* Modify Plant License

PHASE 1

STAGE 1 STAGE 2

PHASE 2

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R 2.1: Flooding Hazard Reevaluation • Hazard reevaluation should be consistent with

regulatory guidance and methodologies used for Early Site Permit (ESP) and Combined License (COL) reviews – NUREG-0800, “Standard Review Plan” Section 2.4

– NUREG/CR-7046, “Design Basis Flood Estimate for Site Characterization of Nuclear Power Plants in the USA”

• Evaluation should discuss all flood-causing mechanisms.

• Mechanisms that are not applicable at a site may be screened-out; however, a justification should be provided.

Use this elevation for this

causal mechanism in Step 3 Yes

Is the reevaluated flood

hazard elevation greater

than the current design

elevation?

No

No

No

Yes

Yes

Re-evaluate flood hazard based on present day guidance and methodology

(HHA) for each flood causing mechanism (e.g. local intense precipitation)

2a

1

2

Select one flood causing mechanism for analysis

2b

Develop conservative estimate for site-related parameters using simplifying

assumptions for a flood causing mechanism

Can parameter and/or

variables in analysis be

further refined?

Use site-specific data to refine

analysis

Compile data for site flood hazard

To Page 2

Have all flood causing

mechanisms identified in

Step 2 been addressed?

9

10

3

Submit the final report

No

Yes

Compare the final flood

elevations for all re-evaluated

flood causing mechanisms to

current design basis flood.

Does the design basis flood

elevation bound the

reevaluated flood hazard for all

mechanisms?

Submit hazard re-evaluation reports and plan for

conducting an integrated assessment

Perform an integrated assessment of the plant

performance

Identify vulnerabilities, if any, and actions planned

or taken during the re-evaluation

Submit hazard re-evaluation results

Phase 2

6

7

8

4

5

9

10

From Page 1

No further action

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R2.1: Seismic Hazard Reevaluation

• Determine Ground Motion Response

Spectrum (GMRS) for Site

– Use Probabilistic Method (PSHA)

• Seismic Source Models

• Seismic Ground Motion Models

• Site Response Evaluation

• Compare GMRS with Safe Shutdown

Earthquake (SSE) with Plant

Spectrum 11

R2.1 Seismic Hazard Reevaluation

• New seismic source models for Central

and Eastern United States of America

(CEUS) developed jointly by NRC, Dept

of Energy, and Electric Power Research

Institute (EPRI)

www.ceus-ssc.com

• EPRI (2004, 2006) ground motion

prediction equations for CEUS

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R2.1: Seismic Risk Evaluation

• Depending on Screening Criteria perform

– Seismic Margin Analysis (SMA) or

– Seismic Probabilistic Risk Assessment (SPRA)

• SMA method is NRC SMA (NUREG/CR-

4334) with enhancements.

• SPRA approach is Level 1 with estimate of

Large Early Release Frequency (LERF)

described in RG 1.200.

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R2.1 Seismic

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Overall Approach: R2.3 Walkdowns • Licensees and staff interact to develop walkdown methodology

– Procedures

– Training

– Staffing

• Integrate the combined effects of flooding along with other adverse weather conditions, such as high winds, hail, lightning, etc, that could simultaneously occur.

• Integrate insights from any new and relevant flood hazard information, as well as recent flood-related walkdowns.

• Identify any changes since the original licensing (security improvements/temporary structures) and review flood protection/mitigation features.

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Overall Approach: R2.3 (continued)

• Licensees perform the walkdowns using NRC-endorsed walkdown methodology

• Identify and address degraded, non-conforming or unanalyzed conditions addressed by licensee’s corrective action program

• Identify and address cliff-edge effects for flooding only. Addressed by licensee’s corrective action program.

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Flooding Recommendations Schedules

• Recommendation 2.1: hazard – Develop approach for Integrated Assessment by

approximately November 2012.

– Complete Hazard Evaluations within 1 to 3 years. Include plans for Integrated Assessment, if necessary.

– Complete Integrated Assessment within 2 years following Hazard Evaluation, if necessary.

• Recommendation 2.3: walkdown – Inform within 90-days of walkdown procedure.

– Complete and submit walkdown response by approximately November 2012.

All dates are from 12 March 2012

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Seismic Recommendations Schedules

• Recommendation 2.1: hazard – Develop approach for Risk Assessment by approximately

November 2012.

– Complete Hazard Evaluations within 1.5 years for Central and Eastern USA sites. For Western USA sites, complete within 3 years. Include plans for Risk Assessment, if necessary.

– Complete Risk Assessment within 3-4 years following Hazard Evaluation, if necessary.

• Recommendation 2.3: walkdown – Inform within 120-days of selected walkdown procedure.

– Complete and submit walkdown response by approximately November 2012.

All dates are from 12 March 2012

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Questions ?