13th Nuclear Utility Meteorological Data Users Group Meeting

Lessons Learned From Establishing Design- and Operating-Basis

Regional Meteorological ConditionsFor Permitting New Nuclear Power Plants

in the United States

Ping K WanBechtel 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 DesignAmbient 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 DesignTornado 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 Applican

t

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

ABWR AP1000 ESBWR U.S. EPR

APWR

Extreme WindBasic Wind Speed:100-yr mean recurrence interval for SR 50-yr mean recurrence interval for NSR

- - - - - -

TornadoMax rotational speedMax translational speedMax pressure dropRate of Pressure DropRadius

- - - - - -

PrecipitationMaximum rainfall rateMaximum snow loadWeight of 48-hour PMWP

- - - - - -

Ambient Design Temperature0%, 1%, 2% ExceedanceMaximum Dry BulbMaximum 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.