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INL Seismic 10 Year Re-evaluation Process for Existing Nuclear Facilities

Following a Risk-Informed Methodology

Justin Coleman

INL/MIS-14-33483

Department of Energy Order 420.1C for Reevaluation of Existing Facilities

• Requires a review of natural phenomena hazards (NPH)

assessments at least every ten years to evaluate the need for an update based on “significant” change in data, criteria, and assessment methods

• For SDC-3 to SDC-5 facilities
• Order points to DOE-STD-1020-2012 for criteria and

guidance to be considered in the 10-year evaluation – DOE-STD-1020-2012 points to ANSI/ ANS-2.29-2008 and NUREG-2117 for consideration

• f hazard adequacy and guidance.
• DOE Order 420.1C establishes nuclear facility and

programmatic safety of nuclear facilities—function of both hazard (seismic) as well as the facility capacity—

DOE Order 420.1C

• Confinement/Containment of hazardous materials
• Protection of occupants, co-located workers, and the public
• Continued operation of essential facilities and equipment
• Safe shutdown of hazardous facilities and equipment
• Maintaining personnel access responding to accidents during NPH

events

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DOE-STD-1020-2012

• 9.2.1 At a frequency not to exceed ten years, the following aspects of NPH assessments shall

be reviewed for changes that would warrant updating the assessments: NPH data and data collection methods; NPH modeling techniques, either generic or specific to the region of interest; and NPH assessment methods.

• 9.2.2 Consistent with DOE 420.1C, a preliminary estimate of whether changes to data, models,
• r methods are “significant” and warrant updating the assessments should be performed and

consider the following criteria:

– Are the changes to data, models, or methods likely to cause a change in the estimates of the major inputs to hazard calculations? – Given potential changes to the hazard inputs, by what magnitude might the calculated hazard results change, and how might the results impact current site design standards?

• 9.2.3 The preliminary estimate of how hazard results might change from new inputs will likely

be imprecise. An expected significant increase in the hazard results would clearly favor completion of a new assessment. However, even if hazard results are not expected to change significantly, large changes to the input parameters may warrant a new assessment to ensure the NPH assessment continues to have a viable technical basis.

• 9.2.4 In the case of seismic hazard assessments, a determination of whether an existing

assessment remains adequate for future use should consider the criteria in Section 4.1 of ANSI/ANS-2.29-2008 for the suitability of existing studies. Additional guidance on the bases for updating existing seismic assessments can be obtained from NUREG-2117, Practical Implementation Guidelines for SSHAC Level 3 and 4 Hazard Studies.

• 9.2.5 A decision on updating an NPH assessment should consider the intended

application of the assessment results.

DOE-STD-1020-2012

• 9.2.1 At a frequency not to exceed ten years, the following aspects of NPH assessments shall

be reviewed for changes that would warrant updating the assessments: NPH data and data collection methods; NPH modeling techniques, either generic or specific to the region of interest; and NPH assessment methods.

• 9.2.2 Consistent with DOE 420.1C, a preliminary estimate of whether changes to data, models,
• r methods are “significant” and warrant updating the assessments should be performed and

consider the following criteria:

– Are the changes to data, models, or methods likely to cause a change in the estimates of the major inputs to hazard calculations? – Given potential changes to the hazard inputs, by what magnitude might the calculated hazard results change, and how might the results impact current site design standards?

• 9.2.3 The preliminary estimate of how hazard results might change from new inputs will likely

be imprecise. An expected significant increase in the hazard results would clearly favor completion of a new assessment. However, even if hazard results are not expected to change significantly, large changes to the input parameters may warrant a new assessment to ensure the NPH assessment continues to have a viable technical basis.

• 9.2.4 In the case of seismic hazard assessments, a determination of whether an existing

assessment remains adequate for future use should consider the criteria in Section 4.1 of ANSI/ANS-2.29-2008 for the suitability of existing studies. Additional guidance on the bases for updating existing seismic assessments can be obtained from NUREG-2117, Practical Implementation Guidelines for SSHAC Level 3 and 4 Hazard Studies.

• 9.2.5 A decision on updating an NPH assessment should consider the intended application of

the assessment results.

INL Risk-Informed Methodology

• Develop methodology for quantifying if there is

a “significant” change in nuclear facility risk – Meets intent of DOE Order 420.1C

• Determines SDC-3 or greater nuclear facilities
• Produces a defensible estimate of the site-

specific seismic hazard – Estimates changes in seismic hazard data, models and methods – Uses SSHAC level 1 process

• Calculates fragilities for facilities of concern
• Quantifies systems
• Calculates risk
• Inclusion of risk information meets the spirit and
• bjectives of DOE Order 420.1C

INL Nuclear Facility Seismic Risk Informed Process

Seismic Risk Seismic Hazard Component Fragilities Systems Evaluation Consequence Analysis

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Quantification

Peer Review of technical elements and adherence to Risk-Informed Process

Seismic Design Categories

ANSI/ ANS-2.26-2004; Reaffirmed 2010

Seismic Design Category (SDC): A category assigned to an SSC, which is a function of the severity of adverse radiological and toxicological effects of the hazards that may result from the seismic failure of the SSC on workers, the public, and the environment. SSCs may be assigned to Seismic Design Categories that range from 1 to 5.

Senior Seismic Hazard Analysis (SSHAC) Process

• Originally described in NUREG/CR-6372 (1989) and

Additional guidance provided in NUREG-2117 (2012) – Describes a structured approach for incorporating data types and expert judgment into the model development process – 4 Levels of complexity described in 2 NUREG reports

• For all SSHAC levels the goal is the same: to capture the

center, body and range of the technically defensible interpretations through a combined hazard model

• For each SSHAC level increase the level of engagement of

the broader seismic technical community grows – Increasing SSHAC level generally provides greater assurance of the hazard results, and generally reduces uncertainty and increases regulatory assurance

• Moving from SSHAC 1 to 3 increases schedule by ~3x and

cost ~10x.

NUREG/CR-6372 (1989) NUREG 2117 (2012)

From Peer Review Panel Report

“Because a confident basis is needed for applying the criteria (and that basis should include an assessment of all associated uncertainties), it is recommended that a site-specific SSHAC Level 1 or 2 study be conducted. The study should include a participatory or in-process peer review. If conducted properly and according to regulatory guidance (i.e., NUREG/CR-6372 and NUREG-2117), the hazard assessment activities and the hazard products developed will provide a defensible, well-documented basis to make comparisons with the existing technical underpinnings of the current design or licensing bases for the facility

• f interest. It should be noted that the SL1 or SL2 study will

provide a reliable basis to evaluate the need for an update of a PSHA, and will provide an estimate of the updated hazard values to be used in the broader SHPRM activities; however, the SL1 or SL2 study is not, in itself, an update.”

ASCE/SEI 43-05 Seismic Hazard Guidance

• Performance-based approach to

ensure facility achieves desired performance

• Provides guidance on where to

enter the mean hazard curve to achieve a desired performance

• bjective and, in turn, to mitigate

defined dose consequence

• Works with RG1.208 to define

performance-based GMRS used for new NPPs in the US and for post-Fukushima reevaluation

DOE Performance Criteria

• DOE-STD-3009 set deterministic targets

– 25 rem at site boundary – 100 rem for co-located worker

• ASCE-43-05 sets seismic structural performance targets

toed to appropriate hazard levels

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Flowchart of Approach

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Possible Outcomes

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Acknowledgments

• Risk Informed Method Peer Review Team
• White Paper Authors
• Bob Budnitz
• Nilesh Chokshi
• Kevin Coppersmith
• Annie Kammerer

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Questions

• Process possible Outcomes

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INL Risk-Informed Methodology to Quantify Existing Nuclear Facility Risk

• Defensible estimate of seismic hazard at MFC
• Evaluate nuclear facility structure, system, and component fragilities
• Quantify facility risk
• Perform independent peer review

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Path Forward

• Execute work scope in PLN-2856
• By end of FY-15, update project execution plan to consider all factors

defined by DOE STD-1020-2012

• Possible outcomes:

– Take action on identified facilities to mitigate seismic risk. AND – Probabilistic Seismic Hazard Assessment update not necessary for existing facilities. OR – Continue work on Probabilistic Seismic Hazard Assessment

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IMPROVED, EARLY UNDERSTANDING OF RISK

DOE-STD-1020-2012

• Evaluation at least every ten years
• Data, models, and methods
• “Significant” change in the estimates of the major inputs
• r hazard that may impact current site design standards
• Points to NUREG-2117 (the SSHAC guidelines), Practical

Implementation Guidelines for

• A decision on updating an NPH assessment should

consider the intended application of the assessment results.