|Year : 2011 | Volume
| Issue : 4 | Page : 240-241
Estimation of atmospheric dilution factors for trombay site using the air pollution model
R Shrivastava, SP Indumati, MB Pote, RB Oza, VD Puranik
Department of Environmental Assessment Division, Bhabha Atomic Research Centre, Mumbai, India
|Date of Web Publication||17-Jan-2013|
Department of Environmental Assessment Division, Bhabha Atomic Research Centre, Mumbai
Source of Support: None, Conflict of Interest: None
This paper presents the application of The Air Pollution Model (TAPM) in estimation of atmospheric dilution factors for Trombay site for unit release rate in different wind sectors. The values obtained from the model are compared with those obtained from routinely collected meteorological data at 10 m height. The measurement carried out at 10 m height is extrapolated to the release height using power laws with stability-dependent coefficient. The maximum value of dilution factor at 1.6 km, computed using model data is 0.1039E-06 s/m 3 while that obtained using measured data is 0.1238E-06 s/m 3 ; however, the two are occurring in different sectors. Thus, model-generated dilution factors can be used in case if only the maximum impact of the releases need to be studied and no measured data are available. In general, it was found that except few sectors, model-generated dilution factors remain within a factor of two as compared to that generated using measured data. The main application of this study is for upcoming sites where representative measured meteorological data may not be available; however, computation of atmospheric dilution factors is required for environmental impact assessment.
Keywords: Atmospheric dilution factor, TAPM, NCEP-FNL
|How to cite this article:|
Shrivastava R, Indumati S P, Pote M B, Oza R B, Puranik V D. Estimation of atmospheric dilution factors for trombay site using the air pollution model. Radiat Prot Environ 2011;34:240-1
|How to cite this URL:|
Shrivastava R, Indumati S P, Pote M B, Oza R B, Puranik V D. Estimation of atmospheric dilution factors for trombay site using the air pollution model. Radiat Prot Environ [serial online] 2011 [cited 2020 Jun 6];34:240-1. Available from: http://www.rpe.org.in/text.asp?2011/34/4/240/106096
| 1. Introduction|| |
Various nuclear facilities are operational at the Bhabha Atomic Research Centre (BARC) located at Trombay. The routine operation of these facilities lead to the release of small amount of radioactivity in the atmosphere which gets dispersed depending upon the prevailing meteorological conditions at the site. The atmospheric dilution factors are important indicators of diffusive properties of the site. They are useful for estimating the annual averaged concentration distribution of gaseous effluents released from nuclear facilities. Routinely measured hourly meteorological data are used in the preparation of diffusion climatology of the site which in turn is used to estimate the dilution factors. However, measured data may be incomplete due to the occurrence of missing hours on account of instrument failure. Also, the wind measurements are carried out at 10 m height and need to be extrapolated to stack height using wind profile laws. The prognostic meteorological models can give meteorological parameters at desired height. The Air Pollution Model (TAPM, Hurley, 2005)  is a prognostic model which can provide hourly output of meteorological parameters like wind, temperature, relative humidity, and other meteorological parameters. These parameters are used to estimate the dilution factors for Trombay site and the results are compared with the same obtained using measured data. The results of this study are presented in this paper.
| 2. Materials and Methods|| |
TAPM is a meteorological model coupled with dispersion algorithms. The model solves momentum equations for horizontal wind components, the incompressible continuity equation for vertical velocity, and scalar equations for virtual potential temperature and specific humidity. The turbulence terms are determined using the K-ε model by solving prognostic equations for turbulent kinetic energy and eddy dissipation rate. In this study, the meteorological data generated by TAPM model for the year 2009 at 100 m altitude are used to estimate the dilution factors for Trombay site. The initial and boundary conditions data for TAPM were generated using the analyzed meteorological data from the National Centers for Environmental Prediction (NCEP) Final Analysis (FNL) at 1° resolution and processed using Conformal Cubic Atmospheric Model (CCAM, Thatcher, 2008).  TAPM output values of hourly wind speed, solar and net radiation are used in the computation of atmospheric stability (50-SG-S3, 1980).  These data along with the model-generated wind data are used to estimate dilution factors for unit release rate in different wind sectors. The same computation is also carried out using measured meteorological data wherein wind speed data collected at 10 m height are extrapolated to stack height using wind profile laws. In this case, the atmospheric stability is estimated using wind speed at 10 m height, solar radiation and cloud cover.
| 3. Results and Discussion|| |
[Figure 1] shows the wind rose obtained using TAPM-generated data and that using measured data for the year 2009. According to the wind rose generated using measured data, predominant wind directions for Trombay site are West North West (WNW) and North (N) with the annual average wind speed of 2.52 m/s. From the model generated wind rose, it is seen that the predominant directions are South West (SW) and North West (NW) with the annual average wind speed of 5.44 m/s. One of the reasons for differences in the wind rose could be the presence of missing data in observations. [Figure 2] shows the dilution factors calculated at 1.6 km using model-generated and measured meteorological data. Also plotted in the same Figure in blue color is the ratio between the dilution factors computed using the two methods. Except few sectors, the ratio remains within a factor of two. The same information is presented in [Table 1]. It should be noted that in case of dilution factor calculation using TAPM, stability is estimated using wind speed, solar and net radiation, whereas in the case of dilution factor calculation using measured data, it is estimated based on wind speed, solar radiation and cloud cover.
|Figure 2: Dilution factors at 1.6 km obtained using TAPM data and measured data|
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|Table 1: Comparison of dilution factors estimated using TAPM data and measured data|
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| 4. Conclusion|| |
The maximum value of dilution factor computed using model data is 0.1039E-06 s/m 3 while that obtained using measured data is 0.1238E-06 s/m 3 at 1.6 km distance; however, the two are occurring in different sectors. Many a times, representative measured meteorological data for the site may not be available; however, for impact assessment studies, estimation of atmospheric dilution factors is required. In such situations, a prognostic model like TAPM may be used. Also, the use of net radiation in the estimation of atmospheric stability removes the uncertainty associated with manual observation of cloud cover. Using similar methodology to estimate the dilution factors, this model will be validated at other sites like Kaiga and Vishakhapatnam.
| 5. Acknowledgements|| |
The authors express their gratitude to Dr. A. K. Ghosh, Director, HSEG and Dr. D. N. Sharma Associate Director, HSEG, BARC, for their interest and encouragement during the course of this study. Thanks are also due to Dr. R. N. Nair, Head EMS, EAD, for useful suggestions and discussion.
| References|| |
|1.||Hurley PJ. TAPM: A practical approach to prognostic meteorological and air pollution modeling; Environmental Modeling and Software, 20, p. 737-752 |
|2.||Thatcher Marcus. CCAM GUI Instructions for TAPM Users v810t. |
|3.||Safety Series No. 50-SG-S3, 1980. Atmospheric Dispersion in Nuclear Power Plant Siting A Safety Guide. |
[Figure 1], [Figure 2]