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Stephen A. Vigeant, CCM and Carl A. Mazzola, CCM Shaw Environmental & Infrastructure

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. DMCC Meeting, San Francisco, CA, May 4, 2009. Outline. Introduction

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Stephen A. Vigeant, CCM and Carl A. Mazzola, CCM Shaw Environmental & Infrastructure

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  1. 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 DMCC Meeting, San Francisco, CA, May 4, 2009

  2. Outline • Introduction • Objective of the Study • Technical Approach • Sensible heat and moisture flux • Atmospheric dilution and dispersion • Results • Conclusions

  3. Introduction • Overseas nuclear power station meteorological monitoring program consists of two towers • 58 meters • 10 meters • Cooling system includes two 12 m x 12 m cooling ponds with elevated water temperatures • Cooling ponds located 62 meters from 10-m tower • Nuclear regulatory agency concerned about possible effects of cooling ponds on 10-m tower measurements

  4. Objective of the Study • Devise an analytical technique to estimate the potential impact of the cooling ponds on the 10-m tower temperature and relative humidity measurements • Estimate heat and moisture fluxes from the cooling ponds • Determine the impacts of fluxes on 10-m tower measurements using dispersion modeling • Use 1-year of onsite measurements to estimate heat and moisture fluxes and dispersion

  5. Technical Approach:Heat and Moisture Fluxes • Bulk aerodynamic formulas of Friehe and Schmitt, 1976 chosen to estimate sensible heat and moisture fluxes from the cooling ponds • Fluxes primarily due to differences in water and air temperatures

  6. Technical Approach:Heat and Moisture Fluxes Sensible heat flux: Hs = rCpCHU(Ts – Ta) where: Hs = sensible heat flux (cal m-2 sec-1) r = air density (g m-3) Cp = heat capacity of air (cal g-1 °K-1) CH = sensible heat transfer coefficient (dimensionless) U = mean wind speed (m sec-1) at reference height (10 meters) Ts = mean water temperature (°K) Ta = mean air temperature at reference height (10 meters) (°K)

  7. Technical Approach:Heat and Moisture Fluxes Moisture flux: E = CeU(Qs – Qa) where: E = moisture flux (g m-2 sec-1) Ce = moisture transfer coefficient (dimensionless) U = mean wind speed (m sec-1) at reference height (10 meters) Qs = mean water vapor density (g/m3) near the water surface (assumed to be saturated) Qa = mean water vapor density (g/m3) at reference height (10 meters)

  8. Technical Approach:Heat and Moisture Fluxes Water vapor densities Qs and Qa calculated by: Qs and Qa = r[(RH x Ws) / (1 + RH x Ws)] where: r = air density (g m-3) Ws = saturation mixing ratio (dimensionless) RH = relative humidity (dimensionless) Qs based on water temperature Qa based on air temperature

  9. Technical Approach:Heat and Moisture Fluxes • Sensible heat and moisture fluxes calculated using one year of hourly onsite measurements • Sensible heat transfer coefficients based on seasonal values obtained from site specific study • Moisture transfer coefficient is taken from Friehe and Schmitt • Seasonal intake water temperature measurements used along with assumed pond temperature 7 °C higher • Fluxes assumed to be homogeneous over the ponds • Multiply fluxes (cal m-2 sec-1 and g m-2 sec-1) by pond surface area to obtain sensible heat and moisture “source terms”

  10. Technical Approach:Atmospheric Dilution and Dispersion • Dispersion or mixing of sensible heat and moisture “source term” with ambient air determined using U. S. NRC dispersion model ARCON96 • Normalized concentrations (C/Qs) calculated at the 10-m tower located 62 meters from the cooling ponds • Hourly onsite data from the 10-m tower used to calculate hourly C/Q values • Sensible heat (cal sec-1) and moisture (g sec-1) transfer rates are multiplied by the calculated X/Q values in sec m-3 to obtain hourly values of sensible heat and water vapor concentration

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