A FRAMEWORK FOR SAFETY DECISIONMAKING GIVEN NEW SEISMIC HAZARD INFORMATION Annie Kammerer, Kevin Coppersmith, Nilesh Chokshi, Robert Budnitz INL Seismic RiskInformed Methodology Independent Review Panel SMiRT 23 August 2015
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A FRAMEWORK FOR SAFETY DECISION-‐MAKING GIVEN NEW SEISMIC HAZARD INFORMATION
Annie Kammerer, Kevin Coppersmith, Nilesh Chokshi, Robert Budnitz INL Seismic Risk-‐Informed Methodology Independent Review Panel
SMiRT 23 August 2015
MoVvaVon
¨ Earth science informaVon conVnues to evolve leading to the need for a process for reevaluaVon. The process should be applicable to periodic reevaluaVon, as well as to the assessment of new informaVon. The process must be risk-‐informed and account for the radiological risk of the facility. ¤ NRC Generic Issue 199 and resulVng major regional studies
n Central and Eastern US Seismic Source CharacterizaVon Study n Next GeneraVon A\enuaVon RelaVonships for Eastern North America)
¤ DOE order 420.1C requires a 10-‐year reevaluaVon process ¤ NRC Post-‐Fukushima 50.54(f)
n Subsumed GI-‐199 and also incorporated flooding in a reevaluaVon process ¤ NRC Near Term Task Force RecommendaVon 2.2
n Recommends 10-‐year periodic reevaluaVon n SVll under review/development
Background & Overview
¨ Developed as a convergence of early work by the authors focused on NPPs and a new project for re-‐evaluaVon of INL faciliVes (SDC-‐3)
¨ Incorporates a graded approach using Seismic Design Categories ¨ Incorporates periodic reevaluaVon requirements/guidance
under DOE Order 420.1C and the NRC 50.54(f) process. Can also be used as a framework for assessing new hazard informaVon.
¨ Incorporates the SSHAC Process with appropriate levels ¨ Can be used for other reevaluaVon of other natural hazards ¨ Detailed in SMiRT Paper: “A Framework for Safety Decision
Making Given New Seismic Hazard InformaVon” ¨ S"ll a work-‐in-‐progress. The figures have changed since the
SMiRT paper was wri<en.
Senior Seismic Hazard Analysis (SSHAC) Process
¨ Originally described in NUREG/CR-‐6372 (1989). AddiVonal guidance provided in NUREG-‐2117 (2012)
¨ The SSHAC reports described a structured approach for incorporaVng a variety of data types and expert judgment into the model development process
¨ The process objecVve is to develop a model that represents the center, body, and range of the technically defensible interpretaVons within a composite model
¨ 4 Levels of complexity described in 2 NUREG reports
¨ The objecVves are the same regardless of SSHAC Level
NUREG/CR-6372 (1989)
NUREG 2117 (2012)
SSHAC Levels
1
2
3
4
} TI confers with members of technical community to understand alternaVve viewpoints
} Gather data and informaVon from literature } TI makes assessments including uncertainty
} Expert panel responsible for making technical assessments
} TFI facilitates expert interacVons and aggregates expert assessments
} Workshops are held to discuss: ◦ Significant issues and available data ◦ AlternaVve hypotheses ◦ Feedback
} ParVcipatory peer review of process and technical } TI team responsible for technical assessments
*The above roles and levels are described in detail in NUREG-‐2117.
SSHAC Levels
1
2 } TI confers with members of technical community to understand alternaVve viewpoints
} Gather data and informaVon from literature } TI makes assessments including uncertainty
• Levels 1 and 2 are simpler, faster, and require fewer resources, but have the same objecVves as Levels 3 and 4 in terms of developing models that capture the center, body and range of the technically defensible interpretaVons.
• Level 2 studies are currently used for performing site-‐specific enhancements to Level 3 regional models (like the CEUS SSC).
• Level 1 and 2 studies conducted to the standards outlined in the SSHAC Guidance NUREGs are appropriate for assessing whether or not a new higher level study is required and for providing an interim esVmate of hazard.
3
4
} Expert panel responsible for making technical assessments
} TFI facilitates expert interacVons and aggregates expert assessments
} Workshops are held to discuss: ◦ Significant issues and available data ◦ AlternaVve hypotheses ◦ Feedback
} ParVcipatory peer review of process and technical } TI team responsible for technical assessments
• Levels 3 and 4 are used for new faciliVes and major modificaVons to exisVng faciliVes.
• Level 3 is proposed for use if it is determined that a new study in needed under the DOE Order.
• Level 3 is far more widely used than Level 4 in US. The NRC has indicated that Levels 3 and 4 provide similar levels of regulatory assurance and itself conducts Level 3 studies jointly with DOE and EPRI.
7 Criteria for Assessing Need for PSHA Update or Follow up AcVons
¨ 7 criteria were developed and used for all SDC category faciliVes ¤ The Vming in which they appear in the process differs for the SDCs to account for the level of radiological risk
¤ Criteria #1 to #4 come directly from the DOE Order and its supporVng documents and look at changes in hazard informaVon
¤ Criteria # 5 and #6 use informaVon from ASCE 43-‐05 and NRC Regulatory Guide 1.208. Compares the design basis ground moVon (DBGM) to the new esVmates of hazard from a SL1 or SL2 and the resulVng Ground MoVon Response Spectrum (GMRS) n The DBGM is the ground moVon to which the plant has been designed and is maintained. DBGM is called “AuthorizaVon Ground MoVon” in DOE faciliVes.
7 Criteria for Assessing Need for PSHA Update or Follow up AcVons
¨ Criterion #1: New data, models, and methods developed since the exisVng PSHA
¨ Criterion #2: New inputs to the PSHA model, including the SSC, GMC, and site response models ¤ Includes the treatment of aleatory and epistemic uncertainVes ¤ Does the model sVll capture the center, body, and range of technically-‐defensible interpretaVons
¨ Criterion #3: Changes in the technical bases ¤ Technical arguments and jusVficaVons for the hazard inputs and the associated treatment of uncertainVes
¨ Criterion #4: Significant changes in mean hazard ¤ Need to consider the precision or “noise” levels of hazard calculaVons
SSHAC Process ObjecVve
¨ “The fundamental goal of a SSHAC process is to properly carry out and completely document the acVviVes of evaluaVon and integraVon, defined as:
¨ EvaluaVon: The consideraVon of the complete set of data, models, and methods proposed by the larger technical community that are relevant to the hazard analysis.
¨ IntegraVon: RepresenVng the center, body, and range of technically defensible interpretaVons in light of the evaluaVon process (i.e., informed by the assessment of exisVng data, models, and methods).”
Quoted from NUREG 2117
7 Criteria for Assessing Need for PSHA Update or Follow up AcVons
¨ Criterion #5: Compare mean hazard at the annual frequency of exceedance (AFE) for specific SDC level with DBGM
¨ Criterion #6: Compare mean hazard at AFE for specific SDC level with GMRS ¤ Intended to ensure meeVng target performance goals ¤ GMRS includes a factor to account for slope of hazard curve ¤ ASCE 43-‐05 and RG 1.208 define GMRS consistently
¨ Criterion #7: Risk insights: Compare mean risk with target performance goals for SDC level; compare GMRS with HCLPF capacity
SDC-‐3 FaciliVes
For SDC-‐3 and SDC-‐4 and FaciliVes
From
DOE Order and
supp
orVn
g do
cumen
ts
Provides confident basis for applying the methodology
Intended for reevaluaVon acVviVes only
DocumentaVon requirements if no new data model or methods or if new hazard does not
exceed DBGM or GMRS
Comparison
of n
ew
hazard inform
aVon
with
de
sign basis and
GMRS
SDC-‐5 FaciliVes
SDC-‐5 FaciliVes
Consistent with 50.54(f) approach. Recognizes potenVal impact from SDC-‐5
faciliVes
Thank You
QuesVons?
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