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ARTICLE
Year : 2011  |  Volume : 34  |  Issue : 2  |  Page : 104-109  

Study of atmospheric stagnation, recirculation, and ventilation potential at Narora Atomic Power Station site


1 Environmental Survey Laboratory, Environmental Studies Section, Health Physics Division, Bhabha Atomic Research Centre, Narora Atomic Power Station, P.O. NAPP Township, Narora, District Bulandshahr, Uttar Pradesh, India
2 Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India

Date of Web Publication12-Jul-2012

Correspondence Address:
Deepak Kumar
Environmental Survey Laboratory, Environmental Studies Section, Health Physics Division, Bhabha Atomic Research Centre, Narora Atomic Power Station, P.O. NAPP Township, Narora, District Bulandshahr, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


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  Abstract 

Atmosphere is an important pathway to be considered in assessment of the environmental impact of radioactivity releases from nuclear facilities. Estimation of concentration of released effluents in air and possible ground contamination needs an understanding of relevant atmospheric dispersion. This article describes the meteorological characteristics of Narora Atomic Power Station (NAPS) site by using the integral parameters developed by Allwine and Whiteman. Meteorological data measured during the period 2006-2010 were analyzed. The integral quantities related to the occurrence of stagnation, recirculation, and ventilation characteristics were studied for NAPS site to assess the dilution potential of the atmosphere. Wind run and recirculation factors were calculated for a 24-h transport time using 5 years of hourly surface measurements of wind speed and direction. The occurrence of stagnation, recirculation, and ventilation characteristics during 2006-2010 at NAPS site is observed to be 33.8% of the time, 19.5% of the time, and 34.7% of the time, respectively. The presence of strong winds with predominant wind direction NW and WNW during winter and summer seasons leads to higher ventilation (48.1% and 44.3%) and recirculation (32.6% of the summer season). The presence of light winds and more dispersed winds during prewinter season with predominant wind directions W and WNW results in more stagnation (59.7% of the prewinter season). Thus, this study will serve as an essential meteorological tool to understand the transport mechanism of atmospheric radioactive effluent releases from any nuclear industry.

Keywords: Atmospheric dispersion, contamination, radioactivity, recirculation, stagnation, ventilation


How to cite this article:
Kumar D, Kumar A, Kumar V, Rao K S, Kumar J, Ravi P M. Study of atmospheric stagnation, recirculation, and ventilation potential at Narora Atomic Power Station site. Radiat Prot Environ 2011;34:104-9

How to cite this URL:
Kumar D, Kumar A, Kumar V, Rao K S, Kumar J, Ravi P M. Study of atmospheric stagnation, recirculation, and ventilation potential at Narora Atomic Power Station site. Radiat Prot Environ [serial online] 2011 [cited 2020 Aug 12];34:104-9. Available from: http://www.rpe.org.in/text.asp?2011/34/2/104/98395


  1. Introduction Top


Narora Atomic Power Station (NAPS) site is an inland site situated on the right bank of Lower Ganga Canal (LGC) and Parallel Lower Ganga Canal (PLGC) at a distance of 3.5 km from Narora Barrage. The area of the plant site is fairly flat terrain with dense farming activities around the site. The site lies in Indo-Gangetic alluvium, bordered on the north by the Shivalic foothills, which is about 60 km away from Aligarh, Uttar Pradesh, India (Latitude 28° 10' 00" North and longitude 78°24' 09"East). At NAPS, two pressurized heavy water reactors having capacity of each 220 MWe are operating since the year 1991. Study of meteorological parameters of nuclear power plant site form an integral part of the program of environmental safety and impact assessment of gaseous radioactive effluents released or estimated to be released from the nuclear power plants. Site meteorological characteristics are used as input at various phases of nuclear power plant evolution, i.e., site selection, design and construction, and operation and maintenance. During site selection, three terms such as stagnation, recirculation, and ventilation are useful indicators for specifying the type of airflow condition. Stagnations are events where atmospheric flow decreases in speed, or stops altogether, allowing pollutants to build up in stagnant air in the vicinity of pollutant source. Recirculations are events in which polluted air is initially carried away from the source but later return to produce a high pollution near the source. Ventilations, on the other hand, are events in which polluted air is replaced or diluted by fresh air. Allwine and Whiteman defined integral quantities which may be used to identify "stagnation" and "recirculation" conditions during a certain period using the surface wind data measured at a meteorological station [1] to assess the transport of pollutants in air at a given place. Ventilation coefficient (product of mixing height and average wind speed) is also an important index to analyze the meteorological conditions of any site.

An attempt was made for the first time to study the integral quantities such as stagnation, recirculation, and ventilation using the wind characteristics available in the Environmental Survey Laboratory at NAPS site, Uttar Pradesh, India.

The assimilative capacity of the atmosphere can be studied using this index. The assimilative capacity of the atmosphere determines the maximum pollutant load that can be discharged into the atmosphere without violating the prescribed limits. [2] Integral parameter such as stagnation mostly depends on wind speed and recirculation depends on changes of wind direction. So stagnation, recirculation, and ventilation are useful indices to study the specific characteristics of a site.


  2. Experimental Top


2.1. Methodology

At Environmental Survey Laboratory, NAPS, the meteorological data such as wind speed and wind direction were collected using anemometer and wind vane sensors mounted on a meteorological tower at 7 and 30 m height. The primary source of meteorological information is 1 h averaged values, i.e., 1 h average wind speed and wind direction. Gaussian plume model is recommended to predict the transport of radioactive releases from 145 m high stack at NAPS during normal operation. The double gaussian plume model proposed by Pasquill adopts the assumption of a constant wind direction, which might result in disagreement with the real phenomenon. To compensate the disagreement, US Nuclear Regulatory Commission recommends the standard default correction factor or the factor derived by a field experiment. [3] The correction factor is applied to reflect the effect of a plume stagnation, recirculation, and sea breeze. Allwine and Whiteman proposed an approach to study site-specific atmospheric transport and diffusion conditions by means of "stagnation" and "recirculation" concepts. [1] In this method, the representative integral quantities for stagnation and recirculation are calculated on the basis of the observed wind speed (U) and wind direction (θ).

This method considers a time series of N data pairs (U; θ) (where θ is the direction from which the wind is blowing, measured clockwise from north) and it proposes to resolve the wind vector into east-west (positive toward the east) and north-south (positive toward the north) components, respectively, in the following way:



where i = 1, 2… N.

By summing Eqs. (1) and (2) over 24 h, we can calculate the transportation distance of the effluents in the directions of east-west and north-south, respectively.



where ε is the sampling intervals and p = 24 h/ε

The straight-line distance (Li) from the release point is calculated as given below:



The real transport distance, which is also, known as the wind run (Si) is calculated as given below:



Also the recirculation factor (Ri) is computed at each time step t i by the following equation:



The wind run is the total distance a parcel would travel, regardless of direction, over the transport time ε. The wind run is used as a measure of stagnation. Total stagnation exists when S = 0. This occurs when winds are calm and thus the result is no net transport. The resultant transport distance represents the net distance a parcel will travel over the transport time ε. The resultant transport direction (measured clockwise from north) represents the direction a parcel will travel during the transport time ε. The recirculation factor provides an indication of the presence of local recirculations on the time scale comparable with ε. When R = 0, straight-line transport will occur and when R = 1, 0 net transport will occur over time interval ε and as a result there will be complete recirculation. Ventilation is characterized by high values of S and low values of R.

Allwine and Whiteman [1] proposed an approach for classifying the atmosphere of different sites by comparing the mean values of the wind run (S) and the recirculation factor (R) with predetermined critical values. If the mean value of S is lower than the critical value, the local atmosphere shows a tendency toward stagnation of the air. If the mean value of R is greater than the corresponding critical value, the local air flow will have a tendency toward recirculation. For a site prone to ventilation, the mean value of S is greater than a critical value of S and the mean value of R is lower than a critical value of R. A second procedure for classifying stagnation, recirculation,n and ventilation potential is based on computations of the percent occurrence of Si < Sc (stagnation), Ri > Rc (recirculation), and simultaneously Si>Scv and Ri < Rcv (ventilation), where Sc and Rc are the average daily critical transport indices (CTIs) for stagnation and recirculation, respectively, and Scv and Rcv are the average daily CTIs for ventilation.


  3. Results and Discussion Top


3.1. Meteorological characteristics of NAPS site

At NAPS site, wind speed and wind direction were measured at 7 and 30 m heights of a meteorological tower. [Figure 1] shows the annual wind roses at 30 m height during 2006-2010. This figure represents the prevailing wind directions and the distribution of wind speeds. From the annual wind roses, it is observed that the predominant wind directions are NW, WNW, W, and WSW. A NAPS is an inland site with plane topography extended up to few kilometers. Because of the plane terrain in all directions up to few kilometers, it is assumed that the wind field (wind speed and direction) is homogeneous throughout the study area. Only one micro-meteorological station (30 m tower) is operational in NAPS site. The predominant wind directions such as NW, WNW, and W are observed due to NW winds during summer and winter seasons. Wind speed of NAPS site at 30 m height during the year 2006-2010 was varying from <0.2 to 19 m/s with an average value of 2.2 m/s.
Figure 1: Wind rose during the year 2006-2010

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3.2. Variation of straight-line distance in km (Li) from the release point during 2006-2010

The straight-line distance from the release point during 2006-2010 is given in [Table 1]. The straight-line distance from the release point was found to be varying from 4 to 917 km with an average value of 185 km. The variation of daily average straight-line distance from the release point is shown in [Figure 2]: The daily average straight-line distance from the release point was observed to be minimum (4 km) on 23/09/2010 and maximum (917 km) on 25/01/2006 [Figure 2]. The day on which Li was minimum, the hourly average wind speed was fluctuating from to <0.20 to 3.2 m/s with daily average wind speed of 1.7 m/s and the maximum fluctuation of wind direction was 310°. As a result, the wind parcel has traveled less straight-line distance from the release point. The day on which Li was maximum, the hourly average wind speed was fluctuating from 2.7 to 15.8 m/s with daily average wind speed of 10.6 m/s and the maximum fluctuation of wind direction was 16°. As a result, the wind parcel has traveled maximum straight-line distance from the release point. Thus, the daily average straight-line distance is dependent on both wind speed and direction.
Figure 2: Variation of straight-line distance from release point during 2006-2010

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Table 1: Variation of daily straight-line distance in km (Li) from the release point during 2006-2010

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3.3. Variation of wind run in km (Si) during 2006-2010

The wind run during 2006-2010 is given in [Table 2]. The wind run is found to be varying from 19 to 919 km with an average value of 224 km. Kim et al. [4] reported the mean values of wind run of four nuclear power sites in the Republic of Korea as 225-449 km. Venegas and Mazzeo [5] reported the mean values of wind run of several sites in Argentina as 125-787 km.
Table 2: Variations of daily wind run in km (Si) during 2006-2010

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The variation of daily average wind run is shown in [Figure 3]. The daily average wind run was observed to be minimum (19 km) on 07/12/2010 and maximum (919.48 km) on 25/01/2006 [Figure 3]. The day on which minimum wind run was observed, the hourly average wind speed was fluctuating from 0.7 to 1.08 m/s with daily average wind speed of 0.8 m/s, and as a result, the wind parcel has traveled less real transport distance. The day, on which maximum wind run was observed, the hourly average wind speed was fluctuating from 9.7 to 56.9 m/s with daily average wind speed of 38.3 m/s, and as a result, the wind parcel has traveled maximum real transport distance. Thus, the daily average wind run is only dependent on wind speed.
Figure 3: Variation of wind run point during 2006-2010

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From [Figure 1], the occurrence of minimum and maximum calm conditions was found to be 4.72% (during 2007) and 21.5% (during 2010), respectively. The average wind run was observed to be 257 km during 2007 and 173 km during 2010. A negative correlation was observed between the percentage occurrences of calm condition with the real transport distance (wind run).

3.4. Variation of recirculation factor (Ri) during 2006-2010

The daily average recirculation factor during 2006-2010 is given in [Table 3]. The daily average recirculation factor was found to vary from 0.001 to 0.96 with an average value of 0.21. The variation of daily average recirculation factor is shown in [Figure 4].
Figure 4: Variation of recirculation factor during 2006-2010

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Table 3: Variation of daily recirculation factor (Ri) during 2006-2010

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The daily average recirculation factor was observed to be minimum (0.0014) on 12/12/2010 and maximum (0.96) on 22/02/2010 [Figure 4]. The day on which Ri is 0.002, the hourly average wind speed was fluctuating from 1.08 to 2.88 m/s with daily average wind speed of 1.8 m/s. The day on which Ri is 0.96, the hourly average wind speed was fluctuating from 2.16 to 11.16 m/s with daily average wind speed of 4.96 m/s.

3.5. Atmospheric stagnation, recirculation, and ventilation potential during 2006-2010

At NAPS site, the average wind speed at 30 m height during the year 2006-2010 was found to be 2.2 m/s, which is very close to that of Grand Canyon region. [1] Since no CTI values are available in the literature on Indian climate, the CTI values given by Allwine and Whiteman are used in this study.

Following Allwine and Whiteman, we estimated the occurrence of stagnation (Si < Sc) by assuming Sc=170 km (2.2 m/s average daily wind speed for NAPS site), recirculation (Ri > Rc) by assuming Rc=0.4, and ventilation (Si > Scv and Ri < Rcv) by assuming Scv=220 km and Rcv=0.2. The occurrence of stagnation, recirculation, and ventilation characteristics at NAPS site during 2006-2010 was found to be 33.8% of the time, 19.5% of the time, and 34.7% of the time, respectively. It is observed that the sum of percentage occurrence of stagnation, recirculation, and ventilation was found to be 88.0%.The sum of the observed percentage occurrence of stagnation, recirculation, and ventilation is not equal to 100%, because some wind flow conditions did not show any of these features, and in some cases, the stagnation and recirculation phenomenon was observed simultaneously. Allwine and Whiteman [1] utilized the integral measures of atmospheric stagnation, recirculation, and ventilation to study Colorado plateaus basin region of Arizona and reported as 62% stagnation, 34% recirculation, and 8% ventilation at surface station of Bullfrog basin. A radar profiler station at Page, Arizona, experienced as 20% stagnation, 25% recirculation, and the frequency of ventilation ranged 40-70%. Kim et al. [4] studied the site characteristics of four nuclear power plant sites of Republic of Korea and reported as 0.4-18.7% stagnation, 8.0-14.8% recirculation. and 19.8-57.2% ventilation. Venegas and Mazzeo [5] studied the atmospheric stagnation, recirculation, and ventilation potential of several sites in Argentina and reported as 2-45% stagnation, 4-10% recirculation, and 18-58% ventilation. Nankar and Patra [6] studied and reported as 19.2% stagnation, 21.0% recirculation. and 40.0% ventilation at KAPS site.

The Li, Si, and Ri data of NAPS site were grouped in different seasons such as summer (March, April, and May), monsoon (June, July, August, and September), prewinter (October and November), and winter (December, January, and February), respectively. The seasonal variation of Li, Si, and Ri during 2006-2010 is studied and the respective percentage occurrence of stagnation, recirculation, and ventilation characteristics at NAPS site in different seasons is given in [Figure 5]. The overall percentage occurrence of stagnation, recirculation, and ventilation characteristics during 2006-2010 is also compared with the seasonal variation as shown in [Figure 5]. It is observed that the occurrence of stagnation is comparatively more in prewinter and monsoon season (59.7% and 38.2%, respectively), recirculation in summer season (32.6%), and ventilation is comparatively more in winter and summer season (48.1% and 44.3%, respectively). The frequency of occurrence of higher wind speeds is comparatively more in the summer season (3.3-5.3 m/s: 29.2%; > 5.3 m/s: 6.49%). The NW and WNW wind predominates during this season. Therefore, throughout winter and summer season, suitable transport conditions are available for the wind parcel to travel in the downwind directions. This is one of the reasons of occurrence of higher ventilation during winter and summer season. The frequency of occurrence of light winds is comparatively more in the prewinter season (0.8-1.4 m/s: 29.0%; > 1.4-3 m/s: 44.8%) and wind direction showed more dispersion of wind with predominant wind directions NW and WNW. As a result, more stagnation was observed during prewinter season.
Figure 5: Seasonal variation of stagnation, recirculation, and ventilation characteristics of Narora site

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  4. Conclusions Top


From this study, it is revealed that the dilution potential of NAPS site is prone to more ventilation than stagnation and recirculation. The presence of strong winds during winter and summer season leads to higher ventilation (48.1% of winter season and 44.3 % of summer season). The presence of light winds and more dispersed winds with predominant wind directions NW and WNW during prewinter season results in more stagnation (59.7% of prewinter season). Thus, the summer and winter season show better dilution than prewinter season. Thus, this study will serve as an essential meteorological tool to understand the transport mechanism of atmospheric radioactive effluent releases from any nuclear industry.


  5. Acknowledgements Top


The authors would like to thank Shri A K Ghosh, Director, HS and E group, Shri P K Sarkar, Head, HPD, BAR,C for their keen interest and encouragement. The continuous support given by Shri P.M Ravi, Head, ESS, HPD, BARC, is gratefully acknowledged. Dr. A K Patra and Shri D. P Nankar ESL, KAPS, are gratefully acknowledged for providing technical suggestions. Thanks are also due to Shri J P Singh and Shri S Ahmed, ESL, NAPS, for their help and co-operation during collection of meteorological data.

 
  References Top

1.Allwine KJ, Whiteman CD. Single-station integral measures of atmospheric stagnation, recirculation and ventilation. Atmos Environ 1994;28:713-21.  Back to cited text no. 1
    
2.Rama Krishna TV, Reddy MK, Reddy RC, Singh RN. Assimilative capacity and dispersion of pollutants due to industrial sources in Visakhapatnam bowl area. Atmos Environ 2004;38:6775-87.  Back to cited text no. 2
    
3.Reg. Guide 1.111. Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents Routine Release from Light-water Cooled Reactors, US Nuclear Regulatory Commission, 1977.  Back to cited text no. 3
    
4.Kim EH, Suh KS, Hwang WT, Jeong HJ, Han MH, Moon JY. Analysis of the site characteristics of Korean nuclear power sites from the meteorological aspects. Ann Nucl Energy 2007;34:719-23.   Back to cited text no. 4
    
5.Venegas LE, Mazzeo NA. Atmospheric stagnation, recirculation and ventilation potential of several sites in Argentina. Atmos Res 1999;52:43-57.  Back to cited text no. 5
    
6.Nankar DP, Patra AK. Atmospheric stagnation, recirculation and ventilation potential of KAPS in India. Anal Nucl Energy 2009;36:475-80.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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  In this article
Abstract
1. Introduction
2. Experimental
3. Results and D...
4. Conclusions
5. Acknowledgements
References
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