ML092640177

Environmental Science and Engineering

ML092640177
Person / Time
Site:	Indian Point
Issue date:	08/28/2009
From:	Heinke G, Henry J Univ of Toronto, Canada
To:	Atomic Safety and Licensing Board Panel
SECY RAS
References
50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01, RAS 284
Download: ML092640177 (3)

Text

ENVIRONMENTAL SCIENCE AND ENGINEERING J. Glynn Henry and Gary W. Heinke with contrfibutions by other staff members.

of the University.of Toronto:

[an Burton William 1. Moroz E Kenneth .Hare R. Ted Munn Thonmas C. Hutchinson 0. J. C. Runnalls Donald Mackay Prentice Hail, Engjewood Cliffs. NJ. 0763Z

Soc. 13.5 Predicting Air Pollutant Concentrations. 527 Stc . ... CenterlineeIof imaginary plume-X

,_S- HZ+

Figure 13--20 Definition sktetch showingJ plume dispersion inthe vertical dirocilon adthe reliection of polluanits at ground level C, ,and C, - concenntialon due to real and knaglnar aowrcea, re.speoively..

point (as a location Z + I') is added to the concentration in the real plume. The plume.

diffusion equation, in its most commion form, then becomes

• (13.28) where,

• C is the polhutant concentatfion (kg/n*)az a receptor locate.d ac (t, y, :)

• .c% and a7, are diffusion coefllcieat* in the y and z directions, respectively*(in), and are functions oU"the downwind distance x from the souree;

• " is the mean wind speed through the layer in which diffusion takes place (m/s);

Air Pollution Chap. 13.

• x, y, and z are spatial coordinates of the receptor (in) relative to the source (the x-:ý axis is oriented in the direction of the mean wind, y is at fight angle to x in thc:

horizontal plane, z is in the vertical plane, and Z is the vertical coordinate reladi.e to ground level);

• H is the effective height of tie pollutant release (m); and

• Q is the source emission rae (kgls)

Some of the assumptions made to develop this equation are as follows:

1. All of the polluta]nts are emitted from a point source of infinite strength.

2. The wind is uniform through the layer in which -dispersion occurs, and an iverage or mean wind can be used in the equation. In practice, the wind used in the equation is taken to be the wind at the top of a stack for an elevated source, estimated using Equation 13.25.

3. The concentration distribution across the width and depth of the plume is Gaussian.

4. The edges of the plume are where the concentration of pollutant has decreased to one-tenth of the plume centerline value.

5. The pollutant under consideration is not lost by decay, chemical reaction, or deposition; i.e., it is conservative. The method of images is used to assure that pollutants are not lost to the ground. (It is supposed that all of the pollutant which impinges at the.

earth's surface is fully "reflected.")

6. The equation is to be used over relatively flat, homogeneous terrain. It should not be used routinely in coastal or mountainous areas, in any area where building profiles are highly irregular, or where the plure travels over warm bare soil and then over colder snow or ice-covered surfaces.

7. The equation represents a steady state solution (8QtSt = 0) over the averaging period.

8. The pollutants have the same density as the air surrounding them. This assumption is remarkably close for the case of stack gases from fossil-fuel-fired combustion processes. It is satisfaL-tory for small particles, but not. for particles which have a finite and significant fall velocity.

Note how the equation reduces to a simpler form for concentrations at specific ground-level locations, such as at a distance y from the centerline (Z = 0) or on the centerline of the plume (y = 0, Z = 0).

The values of a-, and or. have been determined empirically and are conveniently graphed as functions of x and atmospheric turbulence or stability categories in Figure 13-21. Table 13-17 describes the method for determining the stability categories based on wind speed, time of day (radiation), and cloud cover. Category A corresponds to an extremely unstable atmosphere. F to a very stable atmosphere. and D to a near-neiMral atmosphere.

The curves in Figure 13-21 are for continuous point-source plumes over averaging periods of 10 minutes or so. They should not be used to describe the diffusion of a puff in three dimensions. Using data from Figure 13-21, Equation 13.28 gives the .10-minute average