13 th Nuclear Utility Meteorological Data Users Group Meeting Lessons Learned From Establishing Design- and Operating-Basis Regional Meteorological Conditions For Permitting New Nuclear Power Plants in the United States Ping K Wan Bechtel Power Corporation October 2009

2 Introduction Highlight significant climate characteristics Establish Design- & Operating-Basis Meteorological Criteria Discuss Lessons Learned – Areas of concern – Guidance needed to fill gaps – Ways could expedite/improve application review process

3 Significant Site Climate Characteristics Ambient temperature & humidity statistics Maximum rainfall rates Maximum snowfall rates Tornado parameters Basic wind The UHS Meteorological conditions Regional Air Quality

4 Establishing Design Criteria Design-Basis for SSCs (safety-related) Consider the most severe natural phenomena historically reported for the site and surrounding area with margin sufficient to account for the limited accuracy, quantity, and period of time which the data have been accumulated. Operating-Basis for SSCs (nonsafety-related) Consider the statistic of meteorological averages and extremes collected onsite and/or at nearby representative stations with sufficient length of reliable records available.

5 Plant Heat Dissipation System Design Ambient Temperature & Humidity The 0%, 1%, and 2% Annual/Seasonal Exceedance Values for: Minimum ambient dry bulb temperature Maximum ambient – Dry-bulb temperature – Wet-bulb temperature (coincident) – Wet-bulb temperature (non-coincident)

6 Building Roof Design Maximum Rainfall & Snowfall Rates Maximum Rainfall Rate Maximum Short-Term Rainfall Rate Maximum Snowfall Rates & Snowpack 48-Hour Probable Maximum Winter Precipitation

7 Structural Design Tornado and Extreme Wind Tornado Parameters – Maximum wind speed (maximum rotational & translational speed) – Radius of maximum rotational speed – Pressure drop & rate of pressure drop Basic Wind Speed – 3-Sec Wind Gust – Fastest Mile

8 Ultimate Heat Sink (UHS) Design Meteorological Conditions resulting in: Maximum evaporation and drift loss of water, Minimum water cooling Potential for water freezing in the UHS water storage facility, if applicable

9 Requests for Additional Information SER documents NRC’s technical review of an applicant’s SAR RAIs are a tool to help the NRC Staff reach the conclusions presented in the SER Technical Reviewer Technical Editor and Licensing Assistant Office of General Counsel NRC Project Manager COL Applicant Branch Chief NRC Project Manager NRC June 2008

10 Meteorology-Related RAIs Repetitive requests for information in 3 basic areas identify a need for additional guidance: Information and analysis deficiencies – Incomplete data – Unidentified data sources – Inconsistent application of values – Questionable technical approach

11 Meteorology-Related RAIs (cont.) Data quality & representativeness deficiencies – Representativeness for specific site – Interpretation of data – Misapplication of NCDC storm events database Deviation from guidance or inconsistency with DCD – Seasonal versus annual exceedance for temperatures – Site characteristic values versus DCD values

12 Meteorology-Related RAIs (cont.) Potential Climate Change Impacts – Related to meteorological site characterization for establishing site suitability for possible future construction/operation of a NPP at the site – Early Site Permits are valid for 10 to 20 years and can be renewed for an additional 10 to 20 years. – ACRS and NRC were specifically interested in the impacts of climate change on design-basis hurricane and design- basis temperatures – In general, just analyzing past trends is not sufficient. Forecasts of climate change need to be examined.

13 Guidance—In Progress COL/DC-ISG-7 (draft) issued to identify combinations of winter precipitation to assume for determining snow loads on building roof.

14 Guidance—In Progress ANS 2.21 (in development) to provide criteria for assessing atmospheric effects on the ultimate heat sink.

15 Guidance—Still Needed Appropriateness of non-site specific data sets for use in applications Risk-based approach to exceedance of meteorological parameters for plant design PPE-type approach to guide site selection efforts Seasonal vs. annual exceedance values for dry- and wet-bulb temperatures Climate change impacts—identifying and applying trends

16 Selection of Reactor Type Guided By Meteorological Parameters Site Values ABWRAP1000ESBWRU.S. EPR APWR Extreme Wind Basic Wind Speed:  100-yr mean recurrence interval for SR  50-yr mean recurrence interval for NSR Tornado  Max rotational speed  Max translational speed  Max pressure drop  Rate of Pressure Drop  Radius Precipitation  Maximum rainfall rate  Maximum snow load  Weight of 48-hour PMWP Ambient Design Temperature 0%, 1%, 2% Exceedance  Maximum Dry Bulb  Maximum Wet Bulb – coincident – non-coincident)  Minimum Dry Bulb

17 Expedite/Improve Review Process Adherence to regulatory guidance Avoidance of weakness identified in previous applications Guidance development – Cooperation between industry & NRC with respect to scope and approach – Consistency in content and conclusions

18 In Closing Adherence to regulatory and industry guidance. Design- and Operating-basis regional meteorological conditions must be complete and sufficiently conservative. Consistently apply the established parameters for the chosen reactor technology. Leverage RAIs Lessons Learned Experience fully. Guidance development should be closely coordinated between industry and U.S. NRC.