Joe Bellini, Exelon Drew Miller Exelon April 6, 2012 Evaluation Guidance Joe Bellini, Exelon Drew Miller Exelon April 6, 2012

Draft prioritization scheme sent to the NRC Current Status Draft prioritization scheme sent to the NRC March 14 Draft evaluation guidance sent to NRC April 2 NRC meetings to discuss comments Apr 11, Apr 25, May 16 Evaluation guidance is not required by 50.54(f) letter

Purpose Summarize 50.54(f) letter, enclosure entitled ‘Recommendation 2.1: Flooding’ Provide overview of new plant flood hazard evaluation methods in NUREG/CR-7046, including the Hierarchical Hazard Assessment (HHA) Approach Review flooding mechanisms Establish industry-wide priorities Develop scoping strategies (with examples) Overview & clarify technical requirements Provide technical references for evaluations

Guideline Content Introduction Purpose Definitions Categorization/Prioritization Scheme Scoping Strategy Detailed Evaluation Considerations

Introduction Actions Requested by 50.54(f) Letter Evaluate all relevant flooding mechanisms using present-day regulations, methodologies, engineering practices, and modeling software. Where the reevaluated flood exceeds the design basis, submit an interim action plan that documents actions planned or taken to address safety issues (if any) at the new hazard levels. Perform an integrated assessment to identify vulnerabilities and corrective actions under full power operations and other plant configurations.

Introduction Information Requested by 50.54(f) Letter Hazard Reevaluation Report – Documents the results of the new evaluations for all relevant flooding mechanisms. Integrated Assessment Report – Documents corrective actions (completed and/or planned) for plants where the current design basis floods do not bound the reevaluated hazard for relevant mechanisms and the entire duration of the flood.

Introduction Overview of RG 1.59 and NUREG/CR-7046 Compare Deterministic versus Probabilistic Methods Hierarchical Hazard Assessment (HHA) Approach Start with conservative simplifying assumptions for relevant hazards If any safety-related SSC is adversely affected, use site-specific data to provide more refined analysis

Purpose Give utility staff general information on the various flooding mechanisms, establish industry-wide priorities, develop scoping strategies, and provide technical references & considerations. Supplement NUREG/CR-7046. Not intended to be a comprehensive technical reference for completing the evaluations.

Prioritization Scheme Flood hazard evaluations are estimated to require an average of 2600 utility manhours and 6100 vendor manhours. Evaluations require specialized expertise. Limited resources will not allow all sites to perform evaluations at the same time. Prioritization will facilitate organization and submittal in an appropriate manner.

Prioritization Scheme NRC scheme according to draft letters Industry has engaged the NRC on an approach “Priority” based on proximity of sites to one or multiple flooding mechanisms and complexity of analysis Seek NRC agreement on concept (conducted webinar with NRC to discuss scheme on March 29) NEI to solicit utilities for input parameters to obtain ratings Target: 60 days after 50.54(f) letters (May 8) for NRC to finalize priorities

Prioritization Scheme License Vintage (select one) Rating Co-Located Sites (select one) 1969 - 1975 13 Yes 3 1976 - 1984 8 No 6 1985 - 1996 Recent Evaluations, after 1995 (select one) Location/Hazard (select all that apply) Comprehensive/Detailed 2 River 5 Mixed Detailed/Approx. Lake Nothing Recent 10 Coastal 7 Upstream Dams Size of Watershed (select one) Onsite Reservoir > 20,000 sq. miles Local Intense Precipitation < 20,000 sq. miles Location/Hazard Summation 2 to 28 Not applicable Licensing Basis (select one) Wet 14 Dry 4 Category 1 – Most complex evaluations (59 to 81) Category 2 – Average evaluation complexity (37 to 58) Category 3 – Simplest evaluation (14 to 36)

Prioritization Scheme Criteria: License vintage Relevant flooding mechanisms Licensing basis (wet or dry) Co-located sites Recent evaluations Size of watershed (> or < 20,000 sq. mi.)

Scoping Strategy Compile available information that could be leveraged for the evaluation Identify major physical and operational changes to assess the need for new or supplemental surveys Identify relevant (screen) flooding mechanisms Assess extent of evaluation for each flooding mechanism (can include HHA approach) Develop site-specific scope for flooding evaluation

Technical Considerations Guidance based on NUREG/CR-7046 and 6966 Deterministic Evaluate each applicable hazard Local intense precipitation River flooding Upstream dam failure Storm surge Seiche Tsunami Ice-induced flooding Wind-generated waves Channel migration or diversion Combinations of flooding mechanisms Technical references

NRC / Industry Agreements Prioritization scheme Acceptable approach and references Other issues Gap analysis for co-located existing / new plant sites Hazard screening criteria Others as identified

Technical and Consistency Issues Insights from evaluations Inquiries on evaluation process NEI will maintain a web board with new information

Estimated Schedule for Guidance Submit final prioritization scheme to NRC Late April NRC issue of prioritization scheme May 8 Submit final draft of evaluation guidance to NRC and industry Late May Utility schedule for evaluation if > 3y (90 day response) June 10