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21M062007D The Shaw Group Inc. ® An Analytical Screening Technique to Estimate the Effect of Cooling Ponds on Meteorological Measurements – A Case Study.

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Presentation on theme: "21M062007D The Shaw Group Inc. ® An Analytical Screening Technique to Estimate the Effect of Cooling Ponds on Meteorological Measurements – A Case Study."— Presentation transcript:

1 21M062007D The Shaw Group Inc. ® An Analytical Screening Technique to Estimate the Effect of Cooling Ponds on Meteorological Measurements – A Case Study Stephen A. Vigeant, CCM and Carl A. Mazzola, CCM Shaw Environmental & Infrastructure PAMS Mini-Conference, Columbia, SC; April 3, 2009

2 21M062007D The Shaw Group Inc. ® Outline Introduction Study Objective Technical Approach –Sensible heat and moisture flux source terms –Atmospheric transport and diffusion Results Conclusions

3 21M062007D The Shaw Group Inc. ® Introduction Situation: Overseas nuclear power station meteorological monitoring program with 2 instrumented towers (58-meter; 10-meter) Cooling system: Includes two 12 m x 12 m cooling ponds with elevated water temperatures Ponds: Located 62 meters from 10-meter tower instrumentation Issue: Nuclear regulatory agency concerned about possible effects of cooling ponds on 10- meter tower measurements

4 21M062007D The Shaw Group Inc. ® Study Objective Develop analytical technique to estimate potential impact of cooling ponds on 10-meter tower temperature and RH measurements –Source Terms: Estimate sensible heat and moisture fluxes from cooling ponds –Atmospheric Transport and Diffusion: Determine impacts of fluxes on 10-meter tower measurements using appropriate model Use 1-year of onsite data to estimate source term and atmospheric transport and diffusion Calculate temperature and moisture impacts to 10-meter tower instrumentation

5 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Fluxes Bulk aerodynamic formulae of Friehe and Schmitt (1976) selected to estimate sensible heat and moisture fluxes from cooling ponds Fluxes primarily driven by –Water and air temperature differences –Wind speed above ponds

6 21M062007D The Shaw Group Inc. ® 6 Sensible Heat and Moisture Fluxes Discharge Pond T s Wind Sensible Heat & Moisture Fluxes TaTa

7 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Fluxes Sensible Heat FluxH s = C p C H U(T s – T a ) where: H s = sensible heat flux (cal m -2 sec -1 ) = air density (g m -3 ) C p = heat capacity of air (cal g -1 °K -1 ) C H = sensible heat transfer coefficient (dimensionless) U = mean wind speed (m sec -1 ) at reference height (10 meters) T s = mean water temperature (°K) T a = mean air temperature at reference height (10 meters) (°K)

8 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Fluxes Moisture FluxE = C e U(Q s – Q a ) where: E = moisture flux (g m -2 sec -1 ) C e = moisture transfer coefficient (dimensionless) U = mean wind speed (m sec -1 ) at reference height (10 meters) Q s = mean water vapor density (g/m 3 ) near the water surface assume saturation (assume saturation) Q a = mean water vapor density (g/m 3 ) at reference height (10 meters)

9 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Fluxes Water vapor densities (Q s and Q a ) Q s and Q a = [(RH x W s ) / (1 + RH x W s )] where: = air density (g m -3 ) W s = saturation mixing ratio (dimensionless) RH = relative humidity (dimensionless) Q s (based on water temperature) Q a (based on air temperature)

10 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Flux Source Terms Calculate hourly sensible heat and moisture fluxes using one year of onsite measurements –Base sensible heat transfer coefficients (C H ) on seasonal values obtained from site-specific study –Base moisture transfer coefficient (C e ) on Friehe & Schmitt –Use seasonal intake water temperature measurements –Assume pond temperature is 7°C higher –Assume flux homogeneity over entire pond surface Multiply calculated fluxes (cal m -2 sec -1 ; g m -2 sec -1 ) by pond surface area Obtain sensible heat and moisture source terms (cal sec -1 ; g sec -1 )

11 21M062007D The Shaw Group Inc. ® Technical Approach: Atmospheric Transport and Diffusion Determine transport and diffusion of sensible heat and moisture source terms Calculate normalized concentrations Qs) at 10-meter tower located 62 meters from cooling ponds Use NRC ARCON96 code due to close proximity of source and receptor –Horizontal and vertical diffusion coefficients adjusted for plume meander and aerodynamic building wake –Empirical adjustments based on many wind tunnel and atmospheric tracer studies –NUREG/CR-6331 Revision 1 Use hourly onsite data from 10-m tower: ARCON96 input

12 21M062007D The Shaw Group Inc. ® Technical Approach: Atmospheric Transport and Diffusion ARCON96 Code Description Straight-line Eulerian Gaussian plume Ground-level, vent, and elevated releases Incorporates low wind speed plume meander Incorporates aerodynamic building wake effects Valid at source-receptor distances as close as 10 meters Recommended by NRC for use in control room habitability analyses in Regulatory Guide 1.194

13 21M062007D The Shaw Group Inc. ® Technical Approach: Atmospheric Transport and Diffusion ARCON96 Code Input Options Area source (virtual point) option used for cooling ponds Sector averaging constant (4.3) Wind direction sector width (90 degrees azimuth) Surface roughness length (0.2 m) One year of hourly onsite meteorological data

14 21M062007D The Shaw Group Inc. ® Technical Approach: Sensible Heat and Moisture Concentrations Multiply sensible heat (cal sec -1 ) and moisture (g sec -1 ) fluxes by calculated ARCON96 /Q values (sec m -3 ) Obtain hourly values of sensible heat (X H ) (cal m -3 ) and moisture concentration (X w ) (g m -3 ) at 10-m tower instruments X H = H s ( /Q)Sensible Heat Concentration X W = E ( /Q)Water Vapor Concentration

15 21M062007D The Shaw Group Inc. ® Technical Approach: Pond Sensible Heat and Moisture Impact Calculations Calculate increase in temperature ( T a ) at 10-meter tower T a = X H /C p T a = X H /C p Calculate increase in RH ( RH) at 10-meter tower RH = 100 x [X W (g m -3 ) / W (g m -3 )] RH = 100 x [X W (g m -3 ) / W (g m -3 )]

16 21M062007D The Shaw Group Inc. ® Results Temperature Impact –Largest hourly temperature impact: + 0.2°C –Increase between 0.10°C °C (0.3% of time) –Increase between 0.01°C °C (24% of time) –Increase of < 0.01°C (14% of time) –No impact when wind direction outside of 90-degree azimuth ARCON96 window (62% of time) RH Impact –Largest hourly RH impact: + 0.7% ANSI/ANS-3.11 (2005) and NRC Regulatory Guide 1.23 Revision 1 accuracy requirements –Air temperature± 0.5 °C –RH± 4%

17 21M062007D The Shaw Group Inc. ® Conclusions Temperature and moisture increases due to presence of discharge ponds at 10-meter tower not significant Slight increases Much smaller than ANSI/ANS-3.11 accuracy standard for each parameter Have no meaningful effect on meteorological data used to evaluate environmental impacts of nuclear power plant No effect of discharge pond on wind speed and wind direction is expected


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