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

2. 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

3. 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

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

5. 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.

6. 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.

7. 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

8. 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.

9. 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.

10. 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

11. Prioritization Scheme
License Vintage (select one)
Rating
Co-Located Sites (select one) 13
Yes 3 8 No 6
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)

12. 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.)

13. 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

14. 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

15. 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

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

17. 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