ML20079F916
| ML20079F916 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 04/14/1982 |
| From: | Wang H DAMES & MOORE |
| To: | |
| Shared Package | |
| ML20079F902 | List: |
| References | |
| NUDOCS 8206080260 | |
| Download: ML20079F916 (30) | |
Text
Enclosure (6) I I
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TECHNICAL MEMORANDUM SITE-SPECIFIC ATMUSPHERIC DIFFUSION AND DOSE PROJECTION MODELS FOR MIDLAND NUCLEAR POWER PLANT MIDLAND, MICHIGAN Dames & Moore USM Job No. 5697-040-07 h April 14, 1982 8206080260 920601 PDR ADOCK 05000329 PDR
Dames & Moore- l5 = g n i, g (312) 297-6C0 l --
TWX: 910-253-4097 Cable address: DAMEMORE 1
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April 14,1982 Consumers Power Company Safety and Licensing Department Midland Project 1945 West Parnall Road Jackson, Michigan 49201 Attention: Mr. James M. Toszer Nuclear Engineer ,
Gentlemen:
, Re: Technical Memorandum Site-Specific Atmospheric Diffusion and Dose Projection Models Midland Nuclear Power Plant For Consumers Power Company Enclosed please find tnree (3) copies of our technical memorandum pertaining to the development of atmospheric diffusion and dose projection models for the Midland Nuclear Power Plant. The technical memorandum nas incorporated tne comments from Consumers Power Company in your April 5,1982 letter. If you nave any questions concerning the contents of this technical memorandum, please do not hesitate to contact me at your convenience.
Very truly yours, DAMES &M00RJ _
g/sv Hua Wang, P .
Senior En eer/Meteorologi st HW: Jag Enclosure cc: George Nicholas - Dames & Moore u
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TECHNICAL MEMORANDUM SITE-SPECIFIC ATMOSPHERIC DIFFUSION AND DOSE PROJECTION MODELS ,
FOR MIDLAND NUCLEAR POWER PLANT MIDLAND, MICHIGAN SUBMITTED TO CONSUMERS POWER COMPANY 1945 WEST PARNALL ROAD JACKSON, MICHIGAN 49201 PREPARED BY DAMES & MOORE 1550 NORTHWEST HIGHWAY PARK RIDGE, ILLINDIS 60068 Job No. 5697-040-07 Revision 0 April 14, 1982
TABLE OF CONTENTS
. PAGE
1.0 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . I 2.0 REGULATORY REQUIREMENTS. . . . . . . . . . . . . . . . . . . . . . . 2
3.0 DESCRIPTION
OF ATMOSPHERIC DIFFUSION MODEL . . . . . . . . . . . r . 5 3.1 THEORETICAL BASIS OF THE SEGMENT-PLUME MODEL. . . . . . . . . . 5 3.2 MAJOR FEATURES OF MODELING ALGORITHMS . . . . . . . . . . . . . 10 .
3.2.1 Release Mode . . . . . . . . . . . . . . . . . . . . . . 10 3.2.2 Bu i l di n g Wa k e Adj u s tmen t . . . . . . . . . . . . . . . . 10 3.2.3 P l u me Me a n de r . . . . . . . . . . . . . . . . . . . . . . 11 3.2.4 Effective Plume Height . ................ 12 0 3.2.5 Vertical Variation of Wind Speed . . . . . . . . . . . . 15 5
6 3.2.6 Plume Depletion by Dry Deposition. . . . . . . . . . . . 15 9
7 3.3 INPUT PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . 16 b 3.4 OUTPUT PF.CSENTATION . . . . . . . . . . . . . . . . . . . . . . 17 4
0
4.0 DESCRIPTION
OF DOSE PROJECTION MODEL . . . . . . . . . . . . . . . . 18 b 4.1 METHODOLOGIES FOR RADIOLOGICAL DOSE CALCULATIONS. . . . . . . . 18 7
l 4.1.1 Radioactive Decay. . . . . . . . . . . . . . . . . . . . 18 P 4.1.2 Total Body Dose for Noble Gas Releases . . . . . . . . . 19 C
0 4.1.3 Thyroid Inhalation Dose from Atmospheric Releases
- of Radioiocines and Utner Radionuclides. . . . . . . . . 20 2
6 4.2 INPUT PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . 21 4.3 OUTPUT PRESENTATION . . . . . . . . . . . . . . . . . . . . . . 21 l
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1.0 INTRODUCTION
The Midland Nuclear Power Plant (Plant) owned by Consumers Power Company is located in Midland, Michigan. The plant site is bordered to the north and east by the Tittabawassee River. The area north of the Plant and across the river is occupied by Dow Chemical Company's industrial complex, as shown in Figure 1-1. The approximately 1,235-acre site is situated on level terrain of the lower peninsula of Michigan.
The Plant, currently under construction, consists of two units.
Each unit employs a pressurized water reactor (PWR) as the source of heat for steam generation. The design gross electric output is 505 MWe for Unit 1 and 852 MWe for Unit 2. The schedule date of commercial operation for the Plant 0
5 is December 1983 for Unit 2 and July 1984 for Unit 1.
ti 9 To comply witn the Nuclear Regulatory Comission (NRC) requirements 7
for emergency response plans and preparedness at the Plant, Consumers Power
. 0 4 Company has retained Dames & Moore to develop site-specific atmospheric 0
- diffusion and dose projection models which will be installed at Plant's 0
7 Technical Support Center (TSC) computer. These models will be designed C to provide near real-time predictions of the atmospheric transport and P
C dispersion and radiological doses in the event of an accidental release of 0
- gaseous effluents into the atmosphere. This technical memorandum presents a 2
6 brief review of the regulatory requi rements and a detailed description of the models currently being developed by Dames & Moore.
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l 2.0 REGULATORY REOUIREMENTS As specified in 10 CFR 50.47, the emergency response plans for nuclear power plants shall provide adequate methods, systems, and equipment for assessing and monitoring actual or potential off-site consequences of a radiological emergency condition within the Emergency Planning Zones (EPZ).
Generally, the plume exposure pathway EPZ consists of an area of approximately 10 miles in radius and the ingestion pathway EPZ consists of an area of approximately 50 miles in radius. One of the key elements in detailed emergency plan implementation procedures is the ability to assess the actual or potential consequences in the event of an accidental release of radioactive effluents. To gain this capability, on-site meteorological and radiological 0
5 programs are required to provide near real-time data and calculations for 6
9 determining the area of affected population, the dimension, travel time and 7
position of radioactive plumes, and the radiological impact on public health 0
4 and safety.
0 The NRC document, " Criteria for Preparation and Evaluation of 0
7 Radiological Emergency Response Plans and Preparedness in Support of Nuclear C Power Plants, Appendix 2" (NUREG-0654, November 1980), specifies that the P
C compliance of the meteorological aspects of emergency preparedness at 0
operating nuclear power plants is determined by the following three functional 2
6 elements:
- 1. On-site meteorological measurement program;
- 2. Near real-time predictions of the atmospheric transport and dispersion of effluents and radiological doses; and
- 3. Remote interrogation of the atmospheric measurement and prediction systems.
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- Concerning near real-time atmospheric dif fusion estimates and radiological dose assessments, the following two classes of models are identified in NUREG-0654:
- 1. A Class A model which can provide initial transport and diffusion estimates for plume exposure EPZ witnin 15 minutes following the classification of an incident using actual IS-minute average, on-site meteorological data; and
- 2. A Class B model which can provide estimates of relative concentrati on , deposition, and radiological doses of gaseous ,
effluents within the plume exposure and ingestion pathway EPZs for the duration of the release, taking into account spatial and temporal variations of meteorological conditions.
The models should include site-specific, local climatological effects on plume trajectory, source cnaracteristics (release mode and cuilding complex influence), and terrain conditions. The scnedule for implementing 0
5 the Class B model at operating nuclear generating stations has not been 6
9 firmly establisned.. However, it is anticipated that the NRC will accept a 7
- site-specific augmented Class A model, in lieu of the Class B model, for 0
4 atmospheric diffusion estimates and- radiological dose assessment for both 0
- plume exposure and ingestion pathway EPZs.
0 7 At present, the NRC considers variable-trajectory Gaussian " segment-C plume" or " puff" modeling approaches to provide acceptable bases for a Class P
C A, augmented Class A, or Class B model . A suitably enhanced, site-specific 0
- straight-line, steady-state Gaussian plume model may be considered adequate as 2
6 a Class A model only. Conceptually, the Gaussian " segment-plume" model simulates a continuous plume by dividing it into contiguous segments, each describing a portion of plume behavior between successive time periods.
Average relative concentrations and depositions at selected sampling points are calculated by determining the contribution of eacn plume segment whicn passes over it. The Gaussian "puf f" model differs f rom the " segment-plume"
[3] Revision 0 OcmeN$$1coro
model in that the model simulates a continuous point source by superimposing a series of discrete puffs at successive time periods. Under a uniform, steady-state wind field, both models have the ability to reproduce the results of the straight-line Gaussian plume model.
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3.0 DESCRIPTION
OF ATMOSPHERIC DIFFUSION MODEL Ine site-specific atmospheric diffusion model will be designed to provide diffusion estimates for gaseous effluent releases from the Plant using actual 15-minute average, on-site meteorological data. The base model is a Gaussian " segment-plume" model.
The " segment-plume" model is a variable trajectory model based on the statistical approach to diffusion. The model allows the deformation of a -
continuous plume by dividing tne plume into a number of contiguous segments, as shown in Figure 3-1. Each plume segment describes a portion of plume behavior between successive time intervals, advects by the local wind field, and diffuses in a Gaussian fashion. Concentration averages are calculated by 0
5 determining the contribution each plume segment makes to the grid of receptors 6
9 over which it passes.
7
- The " segment-plume" model is one class of the plume element models 0
4 identified in NRC Regulatory Guide 1.111. The basic model formulation 0
- will be modified to account for various modes of effluent releases, buoyancy 0
7 and momentum plume rise, buidling wake in fluence, plume meander, te rain C interaction, and dry deposition. Detailed description of the " segment-plume" P
C concept and modeling algoritnms are presented below.
0 2
6 3.1 THEORETICAL BASIS OF THE SEGMENT-PLUME MODEL The fundamental basis for the " segment-plume" model is an integral mass balance over a finite plume segment. Matnematically, the conservation of mass over a plume segment of length as can be expressed by the following mass l
balance equation:
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SOURCE O PLUME INCREMENT
- 1
- PLUME SEN s
FIGURE 3-1 THE VARIABLE-TRAJECTORY SEGMENT-PLUME MODELING APPROACH
aQ = f /, {u(s,r,z) dr dz }as
+// u X dr dz -I I u X dr dz (3-1) o= s+as 0 " s wnere s, r, and z are the longitudinal, lateral, and vertical plume coordi-nates, G(s,r,z) is the rate of change (gain-loss) of effluent concentration X(s,r,z) by decay and removal processes, aQ is the resultant rate of change of effluent mass, and u is the wind speed. Assuming a quasi-steady state, G(s r,z) and u are considered to be constant from s to s + as, where s is the current distance of a plume segment endpoint from the release point, measured along the plume axis.
0 5 Two possible vertical concentration distribution functions can 6
9 be chosen in the model for diffusion estimates: (1) a vertical Gaussian 7
profile, ignoring any effects of the mixing deptn; or (2) a uniform vertical
. 0 4 distribution below the mixing lid.
0 For Case 1, the ground-level axial plume concentration x(s r,0) is 0
7 defined at tne upwind edge of a plume segment by the expression:
C
-r d -h,2 -
X(s,r,0) = Q(s) exp ,,p (3-2)
U u az (s) oy(s) ,2cy 2 , 20z -
2 wnere Q(s) is the effluent mass flux, he is the effective plume height, 6
and oy (s) and oz(s) are, respectively, the lateral and vertical dispersion coefficients at downwind distance s. Full reflection from the ground is assumed.
For Case 2, if the effective plume height lies below the mixea lid H, tne grouna-level axial concentration is expressed at the upwind edge of tne plume segment oy tne expression for uniform vertical mixing:
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(3-U X(s .r ,0) = /E u Hm oy(s) exp ,2a 2 y
where Hm is the maximum mixing depth encountered by the plume segment. If, ratner, the plume centerline lies above the mixing lid, no ground-levei concentrations are calculated.
The computational scheme of .tne " segment-plume" model has three distinct functional e.lements: (1) a Lagrangian plume trajectory functi on , ,
, (2) a plume dispersion function, and (3) a plume sampling function.
. The Lagrangian plume trajectory function is used to advect the endpoints of each plume segment during a basic time step; the resultant distance between consecutive end points defines the length of each plume 0 segment. In a spatial varying but spatially-homogeneous meteorological field, 5
6 the position of the endpoint from the source can be expressed mathematically 9
by the following equation:
[
. 0 4
0 s(t + At) = s(t) + .u(t+At) At (3-4)
The plume dispersion function determines the horizontal spread of a 0
7 plume along the plume trajectory by the following equation:
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oy(s+As) = oy(s) + As J (3-5)
U ds s+As/2 2
6 Similar equations for oz are used. These terms allow for spatial and temporal changes in stability class to be included, without violating the entropy principle (centerline concentrations cannot increase with downwind distance).
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_ _ _ _ - ___._ _ -______m_ _ _ _ _ _ _ _ _
Each plume segment resident on tne grid (at the end of evEry G1me '
step at) is sampled, using the plume sampling . function, to evaluate the average concentration experienced at each sampling and intersection during the previous time step. For example, consider the hypothetical plume segment in a Cartesian coordinate depicted in Figure 3-2. The plume segment centerline at time t+ at extends from (x,y) to (x+ ax,y+ay), the positions of the two consecutive plume segment endpoints at time t+at. The plume segment length ,
is as = (ax2 + ay2)1/2 The lateral extent of a plume segment is considered
- to be truncated at +3ay. This is a reasonable simplification--much less tnan 1% of tne area under the Gaussian distribution function lies beyond +3 oy from its center. In tnis example, plume segment radii of size 3cy (s) at 0 the upwind edge (x,y) of the segment and of size 3a (s+as) y at the cownw1nd 5
6 edge (x+ax,y+ay) are indicated.' At time t+at, each grid point impacted by the 9 ~,
7 hypothetical plume segment is assigned a certain average concentration
. O x(1,j) resulting from the presence of tne plume segment over at. This 4
0 evaluation is illustrated as follows.
O Suppose the grid point concentration x(1,j) is to be calculated.
7 First, tne ground-level concentrations x(x,y) and x (x+ax, y+ay) ara computed C
P using Equations (3-2) and (3-4) for the case of a vertical Gaussian C
0 concentration profile. Next, a point (x',y') is found such that the line 2 segment of length r constructed from (x',y') to the grid point (1,j) is 6
perpendicular to the plume segment cer.terline. Tne ground-level concentration at tne point (x',y')is then computed by linear interpolation:
x(x' ,y') = x(x ,y) as2 + x(X+aX. Y+ay) AS1 (3-6) asl t as2
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9
Tne lateral plume dispersion coefficient ey(x,y) is similarly interpolated from:
, ,, ,) , o (x,y) y as2 + Cy(x+ax, y+ay) Asl (3-7) asi + as2 Finally, tne grid point concentration x(1.j) is computed as:
x(1.j) = X(x',y') exp -r (3-8) ,
$ 20y 2( xi,y * ),
If tne grid point lies within more than one plume segment at the end of a time step (for example, because plumes of multiple sources overlap), tne total concentration at the grid point )T(1,j ) is computed as the sum of the 0 individual contributions:
5 6
mT 9 XT(i J)
- I Xm(i.j) (3-9) 7 m=1 0
4 where mT is the total number of segments impacting the grid intersection 0
(i,j) during the time step of interest.
0 7
C P
C The set of equations (3-1) through (3-9) provides the theoretical 0
framework of tne " segment-plume" model under a temporally-varying but 2
6 spatially-homogeneous meteorological field. Under steady-state conditions, the model should yield the same results as tne straight-line Gaussian dispersion model . This concept will be used to design test cases for the verification of tne " segment-plume" model.
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3.2 MAJ0.4 FEATURES OF MODELING ALGORITHMS The site-specific atmospheric diffusion model for the Plant is based on the Gaussian " segment-plume" concept. The model combines and ennances various dispersion modeling algorithms into the computer program that can be used to provide diffusion estimates during a radiological emergency condition and to determine the dimension and location of the plume, and. the location, magnitude and arrival time of the peak concentration for each 15-minute time interval. Because only one point on-site meteological measurements will be available at tne Plant, the model will use a time-dependent, homogeneous wind field as meteorological input. Major features of the modeling algorithms tnat will be incorporated into the model are described below.
0 5
6 9 3.2.1 Release Mode 7
b Two kinds of source release mode will be considered: elevated 4
0 release and ground-level release. The elevated release consists of any b release in wnich the effective release height is higher than twice the height 7
of an adjacent solid structure. The ground-level release includes all C
P releases with a release height of less than twice the height of the tallest C
0 adjacent structure. In practice, tne release neignt for the ground-level 2 release is assumed to be at the 10-meter level above the ground.
6 3.2.2 Building Wake Adjustment the building wake adjustment will oe applied to ground-level releases only and follows tne formulation stipulated in NkC Regulatory Guide 1.111. Tnis formulation is expressed by:
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, o Izj(x) = (a zj (x) 2
+ 0.502f,)1/2 < Noz j(x) (3-10) where Dz is the maximum adjacent building height either up- or downwind from the release point; x is the distance from the release point to the receptor, measured from the lee edge of the complex of adjacent buildings; oz j(x) is the vertical dispersion coef ficient of the plume at -
distance, x, for atmospheric stability class, j; and I zj(x) is the vertical dispersion coefficient of tne plume, with the correction for additional dispersion within the building wake cavity.
3.2.3 plume Meander U
5 j At low wind speeds under stable and neutral atmospneric conditions, f tne effect of plume meanaer is significant and often results in greater f horizontal plume dif fusion. This effect will De included in the atmospheric dif fusion model using tne acceptable method described in NRC Regula' tory Guide
{ 1.145. Specifically, when the wind speed at the 10-meter level is less 7
than 6 meters per second, the following equations will be used to determine C
p enhanced horizontal diffusion due to the plume meander effect:
C U
[Moy ; x < 800m
~
I
} (3-11) 6 y =(I'IH-1) 1800m + y; x > 800n wnere Iy is tne enhanced horizontal dispersion coefficient due to plume meander; o is the horizontal dispersion coef ficient determined at 800 J800m meters downwind f rom the release point; and H is tne correction factor for plume meander taken from Figure 3 of f4RC Regulatory Guide 1.145.
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3.2.4 Effective Plume Height For elevated releases, the effective plume height will be calculated from:
he=h5 + Ah - ht-c (3-12) c is the correction for stack downwash; ne is the effective plume heignt; ,
ah is the rise of the plume above the release point; h5 is the physical stack / vent heignt; and ht is the terrain height between the re' lease point and the point for wnich the calculation is made (ht must De greater than or equal to zero).
0 Note tnat the effective release height is a function of the distance 5
6 Detween the release point and the location where tne concentration is being 9
7 calculated.
U When the vertical exit velocity is less than 1.5 times tne 4
0 horizontal wind speed, a correction for stack downwash is substracted from 0 Equation (3-12) by the following equation:
7 C c = 3(1.5 - W/u)d (3-13)
P C where 0
- d is the inside diameter of the stack or other release point; 2
6 u is the mean windspeed at the height of release; and W is the vertical exit velocity of the plume.
Both the momentum and buoyancy aspects of the plume rise will be incorporated into tne model by the following equation:
Ah = (Ahm 3 + anb3 )l/3 (3-14)
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. o wnere an m is the plume rise due to the momentum of the plume; and ahb is the plume rise due to the buoyancy of the plume.
l For nuetral or unstable conditions, Ahm is given by:
l l Anm = min (4hi , ah2) (3-15) wnere ahl = 1.44 (w/u)2/3 (xfo)1/3 o f
Ah2 = 3.0 (w/u) d (3-16)
For stable conditions, Ahm is defined by:
O ah m = min (ah l , ah2 , ah3 , ah4) (3-17) 5 6 wnere 9 ah 3 = 4 (Fm /s)l/4 7
0 ah 4 = 1.5 (Fm/u)1/3 s-1/6 4 (3-18) 0 Em = 0.25 (wd)2 0
7 C s=yh P
C where U
Fm is the momentum flux parameter; 2
6 s is the stability parameter; T is the ambient temperature; g is tne acceleration of gravity; and e is the ambient potential temperature.
[13] Revision 0 3amMEAsore ;
I -
The stability parameter, s, taken on the following values for stability classes E, F, and G, respectively: 8.7 x 10-4, 1.75 x 10-3, and l . 2.45 x 10-3 (sec-2),
For unstable or neutral conditions, the buoyant plume rise, ho, is defined by:
- f(x) ; x < x*
abb=< f(x*) g(x) : x* < x < 5x* (3-19) ,
, f(x*) g(x*) ; 5x* < x where f(x) = 1.6 F1/3 x 2/3 g-1 F = 4.3 10-3 Oh 0
5 6 g(x) , 0.4 + 0.64 (x/x*) + 2.2 (x/x*)2 (3-20) 9 (1 + 0.8 (x/x*)2 0
(0.52 FO.4 hs0 .6 ;hs < 1000 (ft) 4 and x* =J (3-21) 0 (33.0 FO.4 ;hs )_ 1000 (ft)
U wnere h5 is the stack or vent height (ft);
, P Qh is effluent heat flux (cal /sec); and C
0 F is the buoyancy flux parameter (m4 /sec3 ).
2 6 Under stable conditions, Abb is defined by:
[f(x) : x < x' abb=< (3-22) 2.9(F/Us)1/3 ; x > x i
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wnere x' = 2.4 u s -0.5 (3-23) 2.3.5 Vertical Variation of Wind Speed The vertical variation of wind speed with height will be assumed by tne f ollowing power-law relationship:
u=u m (h) where u is the wind speed at height z; um is the wind speed at the sensor heignt Zm; and 0
5 p is the power law exponent which is stability dependent.
6 9 Values of p as a function of atmospheric stability which will De 7
- used in the model are given in Table 3-1.
0 4
0 3.2.6 Plume Depletion by Dry Deposition 0
, 7 Radioactive material may be removed from the plume when the plume C
P touches vegetation or other surfaces. These physical removal processes will C
0 De included in the plume dispersion calculation by means of a correction 2 factor for dry deposition. NRC Regulatory Guide 1.111 recommends a model for 6
plume depletion by dry deposition whicn depenas on Pasquill stability class, elevation of release, and downwind distance of plume travel. The correction factors are expressed as the fraction of material released which remains in the plume. When the appropriate correction f actor is multiplied by tne effluent concentration assuming no dry deposition, the effective plume concentration is calculated.
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o O TABLE 3-1 POWER LAW EXPONENTS FOR VERTICAL WIND SPEED PROFILE PASQUILL-GIFFURD STABILITY CLASS POWER LAW EXPONENT
- A 0.11 B 0.11 C 0.11 '
D 0.13 E 0.33 F 0.47 G 0.56 0
5
- Based on an analysis of onsite 9
meteorological data at the Midland 7
site for the perioa 1975-80 by Consumers Power Company.
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Plume depletion by dry deposition will be incorporated into the atmospheric diffusion model using the acceptable values of relative deposition rates described in NRC Regulatory Guide 1.111.
3.3 INPUT PARAMETERS The si te-speci fic atmospheric diffusion model will be designed to accept both real and hypothetical 15-minute average meteorological data as model input. The real-time meteorological data required for model input will be processed by the data acquisition system installed at the onsite primary meteorological tower. These processed 15-minute average meteorological data will be entered into a data verification computer program ,
6 to perform data validity check and substitution. The resulting wind speed, 6
9 wind direction, ambient temperature, and atmospheric stability (determined by 7
delta-temperature or sigma-theta method) will then be used in the model 0
4 calculations. The hypothetical meteorological data which can be entered 0
manually into the model are intended for model performance evaluation and 0
7 emergency planning purposes.
C The model will be capable of treating multi-point effluent releases P
C at specific points within the Plant. The real-time effluent characteristics 0
at each release point, in terms of flow rate and effluent exit temperature 2
6 will be provided by the onsite radiological monitoring system. Again, hypothetical effluent release data may be entered manually into the model for emergency planning purposes.
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3.4 OUTPUT PRESENTATION The results of model calculations will include relative concen-trations and depositions in both tabular and graphic forms. Tabulated results will contain both 15-minute average and cumulative values at all specified radial distances from the Plant, as well as all input parameters used in the model calculations. Graphic displays of the shape and area extent of the effluent plume at each 15-minute time interval will be generated by color graphics terminals located within the TSC and other designated facilities.
The calculated relative concentration and deposition values will also be stored as established data files in the computer for use as input parameters
, to the dose projection model.
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4.0 DESCRIPTION
OF DOSE PROJECTION MODEL The site-specific dose projection model for the Plant will be designed to estimate radiation doses to man from gaseous effluent releases witnin the injection pathway EPZ (50 miles). The model will include the following two types of radiological doses:
- 1) Total body dose from noble gases; and Thyroid inhalation dose commitment from gaseous releases of 2) radioiodines and other radionuclides.
The methodologies for the radiological dose calculations will be based primarily on the assumptions, parameters, and methods describec in NRC Regulatory Guide 1.109. The model will be capable of performing instantaneous 0 (15-minute) and cumulative short-term (up to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />) calculations at S
6 specified radial distances within the ingestion pathway EPA from the Plant.
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0 4.1 METHODOLOGIES FOR RADIOLOGICAL DOSE CALCULATIONS 4
0
- 4.1.1. Radioactive Decay 0
7 The radioactive properties of individual radioisotopes or particular C
P mixtures of radioisotopes are of importance in determining the quantity and C
0 nature of the radioactive materials reaching the receptor as well as the 2 resulting radiation dose. Tne concentrations of radioactive material in the 6
plume can change due to radioactive decay while the plume is traveling from tne release site to the receptor site. The decay time can be determined from the calculated time of travel Detween the source and receptor based on the atmospheric diffusion model described in Section 3.0.
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The following equation will be used to estimate radioactive decay for the time tnat elapses after tne release:
QD , gj e- Ajt l where 0 = Decayed source term of radionuclide 1 (pCi/sec);
9 Qj = Initial source term of radionuclide i at the time of release (pC1/sec);
t = time after Qj was released from the stack (sec);
Ai = In2(T1/2)1 = decay constant for radionuclide 1 (sec-1); and (T1/2)j = half life for rsdionuclide 1 (sec).
4.1.2 Total Body Dose From Noble Gas Releases 0
i 5 6 The total body dose will be calculated f rom noble gases at al.1 9
7 receptors using the following equation:
0 4 UT. 3p p D (X/Q) DFB4 (1.142x10-4 yr/hr) 0 0
where DT = Total body dose (mrem /hr);
7 SF = 0.7 = Structure shielding factor; C
p DFBj = Total gody dose ' conversion factor for radionuclide i C
(mrem-m /pCi-yr);
qD = Decayed source term for radionuclide 1 (pCi/sec);
2 0
X/Q = Average dispersion factor (sec/m3 ).
All noble gases, their half lives, and DFBj that are to be used in the model can be found in Table 4-1. The real time dose will be calculated (i.e., dose from all releases taking into account all meteorological data for the numoer of plume segments used) ano the cumulative total body dose wnich is tne dose that a particular location received for the entire releases.
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I TABLE 4-1 NOBLE GASES FOR TOTAL BODY DOSE IS0 TOPE HALF LIFE DFBj (tirem m/PCi yr)
KR-83m 1.83 h 7.56E-08 KR-85m 4.48 h 1.17E-03 KR-85 10.72 yr 1.61E-05 KR-87 76.3 m 5. 92E-03 KR-88 2.84 h 1.47E-02 KH-89 3.17 m 1.66E-02 XE-131m 11.9 d 9.15E-05 XE .33m 2.19 d 2.51E-04 0
5 XE-133m 5.245 d 2.94E-04 9
- XE-135m 15.29 m 3.12E-03 XE-135 9.09 n 1.81E-03 4
XE-137 3.83 m 1.42E-03 0
XE-138 14.17 m 8.83E-03 7
AR-41 1.827 h 8.84E-03 C
P
REFERENCE:
U.S. NRC Regulatory Guide 1.109, C
Revision 1,1977 (Table B-1).
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4.1.3 Thyroid Inhalation Dose From Atmospheric Releases of Radiciodines and Other Radionuclides The thyroid inhalation dose f'om r radiciodines and otner ra dio-nuclides released into tne atmosphere will be calculated using the following equation:
E D,Tn = R, j Q (X/D)D OFAj ,T where T
Un = Dose commitment to the thyroid in an age group for a specific period (mrem /hr);
Ra = Breath rate for individuals in an age group (m3/sec);
g0
= Decayed source term (pCi/sec);
5 (X/Q)0 = Dispersion factor corrected for dapletion (sec/m3 ).
6 f DFAi a = Inhalation dose conversion factor for radionuclide i in an age group (mrem /pCi); and U
3 T = Period for dose commitraent (sec).
O Isotopes which will be included in tne thyroid innalation dose, their half 0
lives, and DFAi a are given in Table 4-2. Both the thyroid dose comitment C
f r each 15-minute plume segment and the total thyroid commitment for all plume segments will be calculated. Values of Ra for four different age groups, according to NRC Regulatory Guide 1.109, are provided below:
2 6
Age Group Ra (m3 fyr)
Adults (17 years and older) 8,000 Teenage (11 to 17 years) 8,000 Children (1 to 11 years) 3,700 Infants (1 to 1 year) 1,400
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o o TABLE 4-2 ISOTOPES FOR THYROID IhHALATION DOSE UFAia (mrem /PC1)
ISOTOPE HALF LIFE ADULT TEEf4AGEK CHILD li4FAl4T H-3 12.35 yr 1.58E-07 1.59E-07 3.04E-07 4.62E-07 C-14 5730 yr 4.26E-07 6.09E-07 1.82E-06 3.79E-06 fia-24 15.00 h 1.28E-06 1.72E-06 4.35E-06 7.54E-06 ,
CR-51 27.704 d 7.44E-09 9.37E-09 2.31E-08 4.11E-08 TE-125m 58 d 1.31E-07 1.75E-07 5.20E-07 1.16E-06 TE-127m 109 d 4.11E-07 5.48E-07 1.64E-06 3.48E-06 TE-127 9.35 n 1.32E-10 1.77E-10 5.30E-10 1.32E-09 0 TE-129m 33.6 d 4.30E-07 5.72E-07 1,71E-06 3.91E-06 6 TE-129 69.6 h 4.87E-12 6.48E-12 1.93E-11 4.82E-11 9
7 TE-131m 30 h 6.88E-09 9.06E-09 2.64E-08 6.38E-08 0 TE-131 25.0 m 1.17E-12 1.55E-12' 4.59E-12 1.13E-11 0 TE-132 78.2 h 2.37E-08 3.07E-08 8.58E-08 1.99E-07 0 1-130 12.36 h 1.42E-04 1.86E-04 4.99E-04 1.14E-03 7
I-131 8.04 d 1.49E-03 1.83E-03 4.39E-03 1.06E-02 P I-132 2.3 h 1.43E-05 1.89E-05 5.23E-05 1.21E-04 C
0 I-133 20.8 h 2.69E-04 3.65E-04 1.04E-03 2.54E-03 2 I-134 52.6 m 3.73E-06 4.94E-06 1.37E-05 3.18E-05 I-135 6.61 h 5.60E-05 7.76E-05 2.14E-04 4.97E-04
REFERENCE:
U.S. fiRC Regulatory Guide 1.109, Revision 1,1977, (Tables E-7 Througn E-10).
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