ML19331B241
| ML19331B241 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 09/23/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19331B231 | List: |
| References | |
| REGGD-01.XXX, REGGD-1.XXX, NUDOCS 8007280834 | |
| Download: ML19331B241 (26) | |
Text
_
SEP 2 3 $77 REGULATORY GUIDE 1.XXX ATMOSPHERIC DISPERSION MODELS FOR POTENTIAL CONSEQUENCE ASSESSMENTS AT NUCLEAR P0kT.R PL A.
INTRODUCTION Section 50.34 of 10 CTR Part 50 requires that each applicant for a construction permit or operating license provide an analysis and evalu of the design and performance of structures, systems and compon e
facility with the objective of assessing the risk to public health a d n
safety resulting from the operation of the facility.
Section 50.34 of 10 CTR Part 50 further states that the site evaluation e
in 10 CIR Part 100 shall be included in the analysis and evaluatio n
described above.
Section 100.10 of 10 CFR Part 50 states that meteoro logical conditions at the site and surrounding area are to be include the factors to be considered in assessing the consequences of p t o ential reactor accidents.
This guide provides acceptable procedures and assumptions that m used to determine appropriate atmospheric dispersion conditions for as ng the consequences of potectial nuclear power plant reactor accidents which are made as required by Section 100.11 of 10 CFR Part 50.
The Regulatory Position presented in this guide represents a. substan-tial change 2.s procedures used to determine atmospheric dispersio n condi-tions appropriate for use in assessing the potential offsite radiolo i g cal e
1.XXX-1 8007280 h
o n
n
~
~
DMFT consequences resulting from a range of postulated accidental releases of radiological material to the atmosphere.
This guide provides an acceptable methodology for determining site specific relative concentrations (X/Q) and replaces portions of Regulatory Guide 1.3, Revision 2, " Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling ~Jater Reactors," Regulatory Guide 1.4, Revision 2, " Assumptions Used fo-Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors," Regulatory Guide 1.5, " Assumptions Used for Evaluating the Potential Radiological Consequences cf a Steam Line Break Accident for Boiling Water Beactors," Regulatory Guide 1.24, " Assumptions Used for Evaluating the Potential Consequences of a Pressurized Water
~
Reactor Radioactive Gas Storage Tank Failure," Regulatory Guide 1.25,
" Assumptions Used for Evaluating the Potential Radiological Consequences of l
a Fuel Handling Accident in the Fuel Handling and Storage Facility for i
i Boiling and Pressurized Water Reactors," Regulatory Guide 1.77, "Assump-l tions Used for Evaluating a Control Rod Ejection Accident for Pressurized Water Reactors," and Regulatory Guide 1.98, " Assumptions Used for Evaluating the Potential Radiological Consequences of a Radioactive Offgas System Failure in a Boiling Water Reactor."
3.
DISCUSSICN l
The procedural changes contained in this guide are based on a review of recent experimental data on diffusion frem ground-level releases.yithout buildings present and from releases at various locations on reactor" facility 1.III-2
buildings durirg stable atmospheric conditions with light wind speeds (Refs.1-6), and a recognition that meteorological evaluation procedures should provide estimates of the variations in atmospheric dispersion that occur as a function of wind direction and distance from the source to receptor.
The procedures described in this pide incorporate the results of the atmospheric tests referred to above which verify the existence of effluent plume " meander" under stable (E, F and G) atmospheric conditions, as defined by the AT criteria in Regulatory Guide 1.23 (Ref. 7), when wind speeds are light. Effluent concentrations measured over a period of one hour under such conditions have been shown to be substantially lower than would be predicted using the traditional curves (Ref. 8) of lateral and vertical plume spread, based upon current atmospheric stability criteria.
The procedures in this guide also recognize that atmospheric dispersion con-ditions are frequently directionally dependent; that is, certain air flow directions can exhibit substantially more or less favorable diffusion conditions than others, and the wind can transport effluents in certain directions more frequently than in others.
C.
REGUI.ATORY POSITION l
This section identifies the atmospheric transport and diffusion models, methods of evaluating boundary distances for the exclusion area and the outer boundary of the low population zone for purposes of estimating disper-sion values, and the methods of establishing X/Q value distributions and selecting x/Q values to be used in consequence assessments that are accept-able to the NRC staff.
1.XXX-3
~
~
m 1.
Calculation of Relative Atmospheric Concentration y/Q Values x/Q values should be calculated at appropriate distances (see C.2 below) for each vind direction (16 compass points; 22-1/2 degree sectors centered on true north, etc.) based on vind speed and atmospheric stability class indicated by vertical temperature gradient (AT), as defined in Regula-tory Guide 1.23 for distances to 80 km (50 mi) from the site., Either hourly averaged data or joint frequency distributions of hourly data may be used. klen joint frequency distributions are used, the wind speed for x/Q calculations shoul'd be the maximum value in the vind speed class interval so that the individual x/Q values are calculated to represent the minimum value in the cu=ulative frequency class interval. The distribution is then enveloped by the maximal x/Q values. Thus, when the cumulative probability distributions of x/Q are assessed, each x/Q value represents that which is l
l equaled or exceeded within the class interval (Ref. 9). klen hourly data l
are used, the wind speed for x/Q calculation should be the "nourly averaged" i
vind speed as defined in Regulatory Guide 1.23 Cal =s should be defined as hourly average vind speeds belov the starting speed of the anemeneter, and should be assigned a wind speed equal to that of the acenometer or vane starting speed, whichever is higher. klen joint frequency distributions are used, vind directions during calm conditions should be assigned in proportion to the directional distribution of the lowest non-cala vind speed class. klen hourly data are used, vind directions during calm condi-tions should be assigned in proportion to the directional distribution of non-cals conditions with a vind speed less than 0.7 meters per second (z/s)
(the vind speed class limit, i.e., 1.5 mph).
l 1.III-4
g
_s a
Formulae and parameters presented in this section should be used in the absence of site specific diffusion data unless unusual siting, meteoro-logical or terrain conditions dictate the use of other models or considera-tions.
For example, quality controlled, site-specific atmospheric diffusion tests may be used as a basis for modifying the formulae and parameters Short-term (< 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) release period calculations '
a.
Acceptable mathematical models for calculating x/Q values appro-priate for short time period atmospheric dispersion calculations are presented below.
Meteorological data and calculations for the one hour time period are assumed to apply over the entire two hour release period.
This assumption has been confirmed as reasonably conservative, considering the variation with time of postulated accidental releases.
If releases associated with a given postulated event ara estimated to occur in a period substantially less than one hour (i.e., less than 20 minutes), the applicability of the models should be evaluated on a case-by-case basis.
(1)
Releases through vents or other building penetrations This class of release modes includes all release points or areas which are lower than two and one half times the height of adjacent solid structures (Ref. 10).
The formulae and assumptions are:
(a)
During conditions of neutral (D) and stable (E, F and G) stability when the speed at the 10 meter level is less than 6 m/s, credit for horizontal plume meander can be considered such that X
1 9:
ulo " y #z
~(
1.XXX-5
O.
^
l whenever the x/Q value, calculated using Equation 1, is less than the i
greater value calculated from either 1
(2)
X, 9
lo (* 'y#z + A/2) u i
i l
or -
X, 1
(3) 9 lo (3" "y "z) u where 3
X/Q is the relative concentration (sec/m ) at ground level, n
is 3.14159, "10 is the wind speed (m/s) at 10 meters above grade, 1
is the lateral plume spread (m), a function of atmospheric 7
stability, wind speed I and downwind distance from release.
10 For distances to 800 meters, I = Ma ; M being a function of y
y atmospheric stability and wind speed (see Figure 3). For distr.cces greater than 800 meters, I = (M-1)ay800m * #y' y
is the lateral plume spread (m), a function of atmospheric ey stability and distance (Figure 1),
S 1.XXI-6
.-_..,.-,,.__-._,,r..
/%
is the vertical plume spread (m), a function of atmospheric og stability and distance (Figure 2), and A
is the smallest vertical plane, cross-sectional area (a ) of the 2
building from which the effluent is released.
Otherwise x/Q is the greater value calculated from either Equation 2 or 3.
In other words, calculate x/Q values based on Equations 1, 2, and 3.
Compare the values computed from Equations 2 and 3, and select the higher value.
Compare this higher value with the value calculated through use of Equation 1, and select the lower of these two values to represent the x/Q value for postulated release and atmospheric conditions.
Examples and a detaileo explanation of the rationale are given in Appendix A.
(b) During all other atmospheric stability and/or wind speed conditions, x/Q is the greater value calculated from either Equa-tion 2 or 3.
(2) Stack Releases A stack release is assumed when the effluent is exhausted from a release point that is higher than two and one half times the height of adjacent solid structures (Ref. 10).
The general formula and assumptions are:
-h'2 I
=-
exp (4) n uh a o 2a y g g
where i
is the wind speed (m/s) which represents conditions at se release u3
- height, 1.III-7
@F1 h,
is the effective height (m) determined from h,.= h, - h,
g h,
is the height of the release point above plant grade, and h
is the maximum terrain height above plant grade'between the g
release point and the point for which the calculation is made, but should not be allowed to exceed h,.
The other parameters in Equation 4 have been defined previously.
Atmospheric stability for determination of a and e, is obtained from the vertical temperature differences (AT) between the release height and the 10-meter level as described in Regulatory Guide 1.23.
For those cases where fumigation conditions are to be evaluated for elevated releases, the formula and assumptions are:
X=
1 (5) 9 (2n)1/2 Ee h,
y where E
is wind speed (m/s) representative of the layer, h,,
for which a value of 2 m/s is a reasonably conservative assumption in most cases, c
is the lateral plume spread (m) at a given distance which is 7
usually assumed for a moderately stable (F) atmospheric stability condition which normally precedes the onset of-fumigation, and 1.XXX-8
'O
+
,m h,
is as defined above for elevated releases.
1 The'x/Q value calculated by Equation 5 should not exceed nu e a,
7 b.
Release periods greater than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> The average x/Q values should be calculated for appropriate time periods during the course of the postulated accident as described below.
The time periods for averaging should represent intra-diurnal, diurnal and synoptic meteorological regimes (e.g., 8 and 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> and 3 and 26 days as presented in Section 2.3.4 of Regulatory Guide 1.70) (Ref. 11). The x/Q value for each appropriate time period at the distance of interest in each direction sector should be obtained by a logarithmic interpolation between the calculated value that is selected using the procedure described in Section C.3.a below, assumed as a "2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />" value, and the annual average (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />) value at the distance of interest in that direction sector (Ref. 9).
The annual average x/Q value should be calculated using the method described in Regulatory Guide 1.111, Section C.l.c. (Ref. 12), but with h, determined as described in Section C.1.a.(2) above.
2.
Determination of Distances for x/Q Calculations In order to take into consideration the possibility of airflow trajec-tory deviations, plume segmentation (particularly in light wind, stable j
conditions), and the potential for wind speed and direction frequency shifts from year to year, the following procedure should be used to determinethedistancefromwhichthecalculationsofrelativeconce[n-trations (x/Q) are made.
1.XII-9
-e-em---
n--,-
--e--
r-
-w,,,-,,m-*
s-
,-m--,---
-,,-w-c-pe
n
~'
For each wind direction sector, the minimum distance (exclusion area or LPZ) to be assumed for the sector of interest should be defined as the miniibum distance within that sector and one-half of the width of the direction sector on either side of the sector of interest. Effectively, this distance is the minimum distance of either the exclusion area or LPZ within a 45 degree direr. tion sector, centered on the direction sector of interest. However, should there not be a well defined exclusion boundary in a sector (e.g., a sector extending seaward at a coastal site) then the distance for that se-tor should be taken as that distance over which the applicant or licensee intends to have control.
l 3.
Determination of x/Q Values by Sector Assessment of t/Q's at the exclusion distance a.
Acceptable procedures for selecting the x/Q values to be used in the consequence assessment analyses for both the " conservative" and " realistic" accident conditions (see Section 2.3.4 of Ref. 11) are described below.
For the realistic assessment, fumigation conditions may be ignored.
(1) Non-fumigation conditions Cumulative probability distributions of the x/Q values, as determined from Section C.I.a above at the distances determined from Section C.2 above, excluding fumigation from elevated releases, shoula be 1
constructed for each of the 16 cardinal compass point directions (22-1/2 i
degree direction sectors). Each directional probability distribution should be normalized to 100"..
If joint frequency table data are used to calculate the x/Q values, the cumulative probability distribution function should be computed such as to envelope the data points.
i 1.XII-10 l
DRUT The effective probability level (P,) for the selection of the y/Q first value in each direction sector should be detenined (Ref. 9) by i
valtiplying the probability level (P), selected as 5". for the conservat ve
) having accident assessment, by the ratio of the total number of hours (N (1 year =
valid wind and stability data in the meteorologier.1 data record 8760 hours0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />) to the number of those hours (n) in which the sind and then lividing this' product by into the direction sector of interest, For the the total number of sectors (S) (15 for sectors of 22\\ degrees).
realistic accident assessment X/Q detemination as describ 2.3.4 of Regulatory Guide 1.70 (Ref.11), P should be selected as 50"..
This procedure, in equation form may be stated as:
P (N/n) _
(6) p,
S e
b It where the individual terms in the equation are described as a ove.
In should be noted that P, can exceed 100*. if n is sufficiently small.
d unless the those directions, the selection of a x/Q value may be ignore x/Q values for that sector are very high when compared with x/Q val P, in other direction sectors.
For each assessment, the x/Q values that are selected, as describ is selected.
above, for the 16 directions are compared and the highest value Fumigation conditions - conservative assessment (2)
In the absence of information which i.sdicates that fumigation
/Q ccaditions occur substantially less than five percent of the time, X h of values should be calculated, assuming fumigation conditions, for eac the 16 directions sectors using Equation 5 1.33%-11 7
--.,.p,,
a
- - - ~.
(a) Inland sites For elevated releases at sites located at distances equal to
-or greater than 3200 meters f ce large bodies of water (e.g., oceans or a Great Lake), a fumigation condition at the exclusion distance should be assumed to exist at the time of the accident and continue for one-half hour (Kef. 13).
In this case, two x/Q values, one for the O to 1/2-hour time period and the other for the 1/2 to 2-hour time period following the accident, should be selected for the accident consequence analysis using the following procedures.
For the O to 1/2-hour time period x/Q values should be determined, using Equation 5 for sectors in which the effective height of release (h,) is 3r.'ter than 0, or using Equation 4 and the selection procedure described in Section C.3.a.(1) above for sectors in which h, = 0, for each of the 16 direction sectors.,
For the 1/2 to 2-hour time period, x/Q values for each of the 16 direction sectors should be determined using Equation 4 and the selection procedure described in Section C.3.a.(1) above.
(b) Coastal sites For elevated releases at sites located less than 3200 meters from large bodies of water, a fumigation condition at the exclusion distance should be assuned to exist at the time of the accident and continue for four hours CRef.13) in each of the onshore and along shore airflow directions.
The x/Q value to be used in the accident consequence analysis for the 0 to l
l 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> period following an accident, in this case, is the maximum ef the 16 1
t l
individual direction sector I/Q values, calculated and selected as described 1
1.III-12
A Therefore, two-hour X/Q values above for the O to 1/2-hour time period.
ditions.
for exclusion distances should be based entirely on fumigation con i
This conservative assessment does not consider f,requency an If information direction.
of fumigation conditions as a function of airflow ence can be presented to substantiate the actual directional occurr h
mptions of and duration of fuwsgation conditions at a site, t e assu h lf hour fumigation in all appropriate directions and of duration of one-a Then fumigation need only be considered and four hours may be modified.
ll occur for airflow directions in which fumigation has been determined wi For example, evamin. 1on and of a duration determined from the study.
ed river valley may of site-specific informatio'n at a location in a pronounc i
the down-valley indicate that fumigation conditions occur predominatly dur ng half hour.
" drainage flow" regime and persist for durations of about one-lley Therefore, in this case airflow directions other than the dowc-va ditiens, and directions can be excluded from consii.:ation of fumigation con On idered as one half hour.
the duration of fumigation would still be cons tal) say show no directional the other hand, sites in open terrain (non-coas i s much less than preference for fumigation conditions, but may shaw durat on In this case, fumigation should be considered for all one half hour.
directions, but with durations rach less than one-half hour.
Assessments of t/Q's at the LP_2 d in b.
Acceptable procedures for selecting the X/Q values to be l
the consequence assessments are described be ow.
i In most cases, the highest X/Q values for the appropriate direction sector.
periods will all occur within the same 22-1/2 degree 1.III-13 v----
t DRIiFT
~
for the various However, for those sites at which the highest.x/Q values same direction setter, an evalua-h time periods do not all occur within t ei l accident should be made fo tien of the consequences of the potent a urse of the accident h
sector using the x/Q values in that sector for t e co st The x/Q values, for that sector which produces the greate blic (i.e., the highest analysis.
potential risk to the health and safety of the pu dose estinate), should be considered controlling.
h'on-fumigation conditions (1) l The 16 sets of x/Q values obtained by us4.ng the interpo C.1.b above should be co= pared, and the tion procedure described in Section b d above, should be considered values for the sector, evaluated as descri e d
This procedure may be used for both the conservative an controlling.
realistic accident assessments.
Tumigation conditions - conservative assessment l to (2)
For elevated releases at sites located at distances equa s
dies of water, the x/Q value for or greater than 3200 =eters from large bo hour and 1/2 to 2 hou each sector, at the LPZ, for the 0 to 1/2 d as described for this i
periods following the accident should be deter = ne l
case in Section C.3.a.(2) above.
0 meters For elevated releases at sites located less tor, at the L?Z, for from large bodies of water, the x/Q value for each se the O to 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> period following an acc for this case in Section C.2.a.(2) above.
I f
1.XII-14
.t
~~
.m 3.=
DRet I IMPLEMENTATION D.
information to applicants d
The purpose of this section is to provi eing this regula regarding the NRC staff's plans for us t d by the Commission.
This guide reflects current practice accep et proposes an l
ative i
Except in those cases in which the appl cand portions of method for complying with specifiewill be used in the evalu f subdittals the method described herein it applications docketed after for operating license or construction perm idered for licensing The method described herein will be cons If an appli-
- L s on an individual basis.
actions concerning operating reactor ide in developing submittals for cant wishes to use this regulatory gupermit applications do before i
valuated operating license or construct ontions of the application will be e
_, the pertinent por on the basis of this guide.
nt.
_*Date 4 months after publication for public comme l
1.xxX-15 G
,n.,..,,,...-,..,,,n-
,,.m,,.,,,
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a n
l REFERENCES h i Van der Hoven, I., " A Survey of Field Measurements of Atmosp er c
- Safety, 1.
Diffusion Under Low-Wind Speed Inversion Conditions," Nuclear March-April 1976, Vol. 17 No. 4.
Atmo' spheric Start, G. E. et al., " Rancho Seco Building Wake Effects On
), Air 2.
Diffusion," NOAA Technical Memorandum ERL ARL-XX (in draft from Publi-Resources Laboratory, Idaho Falls, Idaho, 1977, available i
National Oceanic cation Services, Environmental Research Laborator es, d 80302.
and Atmospheric Administration, Boulder, Colora o Conditions Near Wilson, R. B., et al., " Diffusion Under Low Windspeed ARL-61, Air 3
Oak Ridge, Tennessee," NOAA Technical Memorandum ERL from Publi-Resources Laboratory, Idaho Falls, Idaho, 1976, available National Oceanic i
cation Services, Environmental Research Laborator es, l
d 80302.
and Atmospheric Administration, Boulder, Co ora o Windspeed, Sagendorf, J. F. and C. R. Dickson, " Diffusion Under Low 52, Air 4.
Inversion Conditions," NOAA Technical Memorandum *,RL ARL l from Resources Laboratory, Idaho Falls, Idaho, 1974, availab e National Publication Services, Environmental Research Laboratories, l
d 80302.
Oceanic and Atmospheric Administration, Boulder, Co ora o m
O 1.XXI-16
a REFERENCES (Cont'd.)
Gulf States Utilities Company, " Dispersion of Tracer Gas at the Proposed 5.
l River Bend Nuclear Power Station," Preliminary Safety Analysis Report, i
i Amendment 24, Docket Numbers 50-458 and 50-459, 1974
/
Metropolitan Edison Company, " Atmospheric Diffusion Experiments with 6.
Tracer Gas at Three Mile Island Nuclear Station Under Low W SF6 Speed Inversion Conditions," Final Safety Analysis Report, Amendment 24, Docket Number 50-289, 1972 Regulatory Guide 1.23 (Safety Guide 23), "Onsite Meteorological Prog 7.
U.S. Nuclear Regulatory Commission, Washington, D.C.
Gifford, F.
A., Jr., "An Outline of Theories of Diffusion in the Lower 8.
Layers of the Atmosphere," Chapter 3 in Meteorology and Atomic Energy 1968 (D. H. Slade, Ed), available as TID-24190 from the National t
Technical Information Service, Springfield, VA 22151.
Markee, E. H., Jr. and J. R. Levine, "Probabilistic Evaluations of 9.
Atmospheric Diffusion Conditions for Nuclear Facility Design and Siting," Paper in Proceedings of the American Meteorological Society Conference on Probability and Statistics in Atmospheric Sciences, Las Vegas, Neveda, November 1977_. (in draft) e 1.2%X-17
i i
=
3 BRUT' REFERENCES (Cont'd.)
f Synder, W. H. and R. E. Lawson, Jr., " Determination of a Necessary 10.
Height for a Stack Close To A Building-A Wind Tunnel Study,"
Pergamon Press, 1976 Atmospheric Environment, Vol. 10, pp 683-691, 1
1 salysis Regulatory Guide 1.70, " Standard Format and Content of Safety 11.
- LWR Idition," U.S. Nuclear Regulatory Reports for Nuclear Power Plant:
Commission, Washington, D.C.
Regulatory Guide 1.111, " Methods for Estimating Atmospheric T 12.
from Light-Water-andDispersionofGyseousEffluentsinRoutineReleases D.C.
Cooled Reactors," U.S. Nuclear Regulatory Commission, Washington, Van der Hoven, I., " Atmospheric Transport and Diffusion at Coastal 13.
Sites," Nuclear Safetv, Vol. 8, pp 490-499, 1967 l
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Lacara.1 di.ffusion, c, vs. dev=vi=d distanca frem 7
source for Pasqud11's turbulance types (Raf. 8).
duri=g extre=ely stable (G)
Tor purposes of esti=ati=g e7 conditions, vicheut plu=e meander or other lateral enhancement...the follevi=g approx 1=ation is appropriate:
ey(G)= fey (7) 1.III-19
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Vertical diffusion, e, vs. downwind distance fron
' Figure 2.
z source for Pasquill's turbulance types (Ref. 8).
l l
Tor purposes of esti=ating e duri=g extremely. stable (G) g conditions, the fo11cvi=g approxi=atics is appropriate:
l
'z(G)"f8 (I) 2 W
1.III-20 1
[
10" G
e 6
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3 4
5 6
10
'aTfD SPEED (m/sec)
Figura 3.
Correction factors for Pasquill-Gifford e values.
7 dasedona=alysesofRef.2) 1.III-21
. ~. ---
m ATMOSPHERIC DIFFUSION MODEL FOR REI. EASES THROUGH VENTS AND BUILDING PENETRATIONS Rationale The effects of building wake mixing and ambient plume meander on atmos-pheric dispersion is expressed in this guide in tems of conditional use of Equations 1, 2 and 3.
Equation 1 is an empirica'l formulation based on atmospheric diffusion experiment results (Reference 2) and includes the combined effects of increased plume meander and of building wake in the horizontal crosswind direction over time periods of one hour when the wind speed is light. Although the results could not be quantified, these experi-ments also indicate that vertical building wake mixing is not as complete during light wind, stable atmospheric conditions as during moderate wind, unstable conditions. Equations 2 and 3 are fomulations which have had widespread acceptance within the meteorological community over a period of many years (Ref. 8), but have been recently found to provide estimates which are too conservative at least for the light wind, stable atmospheric conditions (Ref.1 and 2).
Therefore, based on the principles that horizon-tal plume meander dominates dispersion during light wind, stable conditions and that meander diminishes as the wind speed increases and the atmospheric stability decreases while building wake mixing becomes more effective in dilution of effluents, th'e conditional use of Equations 1, 2 and 3 is appropriate for providing reasonable X/Q estimates.
g,t-
o m
i Example Figure A-1 shows plots of X/Q times the wind speed u versus downwind lo distance for Equations 1, 2 and 3 for atmospheric stability class G.
Equation 1 is plotted for M = 2, 3 and 6.
Figure A-2 shows plots of x/Q times u versus downwind distance based on the conditional use of Equations lo 1, 2 and 3 as described in the Regulatory Position for wind speed conditions appropriate for M = 2, 3 and 6.
Comparison of Figure A-1 to Figure A-2 shows that for M = 6, Equation 1 is used for all distances since the X u /0 l0 for Equation 1 is less than the values calculated for the greater value produced by either Equation 2 or Equation 3 at all distances. For M = 3, the values from Equation 1 are used for distances beyond 0.8 km since the greater value produced by either Equation 2 or Equation 3 is greater than
~
l the value produced by Equation 1.
However, for distances less than 0.8 km, Equation 1 equals Equation 3.
Therefore, the appropriate x/Q value is determined from Equation 3 since Equation 1 is n:t less than Equation 3, and Equation 3 produces the higher value when compared with Equation 2.
k' hen M = 2, Equation 1 will not be used at all since it is never less than the greater value produced by either Equation 2 or Equation 3.
- Instead, Equation 3 will be used up to 0.8 km and Equation 2 will be used beyond 0.8 l
km.
e O
I A-2
.L m
10-2.,
h
}Eq.1,M=3 Eq.1, M=2 Eq.1, M=6 10'3 -
Eq.2 N.
N
[
\\
~
3
\\
e
\\
e-x
\\
e M
10 \\
\\
Eq. 1, M=3
\\
Eq. 1. M=6 Eq.3
\\
N
)
10-5.-
0.1 1.0 10 PLUME TRAVEL DISTANCE (Kilcmeters) 71gure A-1.
x T /9 48 A function f Plume travel distance for G 0
stability condition using Equations 1, 2 and 3.
A-3
10 ~2
~
' " ~ '
Oh[I Eq.3 10~3 g
=
I o
!=~
Eq.1 Eq.2 x
NM A'
10 52 53 W6 10-5 0.1
'1 '. 0
'lb _
20 PLUME TMVEL DISTANCE (Xiler.eters)
~
Figure A-2.
Regulatory Positi.cn on x IT /0 ** *
- EI"'
10 l
travel distance fbr G stability condition.
A,- 4
,n ENCLOSURE 2 OUTSTANDING RESPONSES THROUGH REVISION 12 ASB MTEB-Mat Int QAB 121.1.1 010.7 121.14 421.2 010.8 010.34 RSB QAB:C0 CSB 211.35 422.7 211.54 022.1 211.83 EPB 022.2 022.14 CPB - Fuel Design 432.9 022.19 432.11 022.21 231.8 432.12 231.10 432.15 ISCSB 231.13 231.16 031.2 231.22 PSB AAB 040.13 312.11 040.16 312.12 040.18 312.29
.040.19 312.36 040.33 312.41 040.37 040.57 ETSB~~
040.60 040.62 321.3 040.63 040.66 GSB MEB 361.3 361.4 110.6 361.5 110.369 110.15 GTEB 110.21 110.23 362.2 110.25 362.8 1110.26 110.30(2)
M[
372.2 372.7
.