ML20151V865

Reg Guide,Rev 1, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants. Reissued Feb 1983 to Correct Page 1.145-7

ML20151V865
Person / Time
Issue date:	11/30/1982
From:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:
References
REGGD-01.145, REGGD-1.145, NUDOCS 8808230038
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• o y,, Revidon 1 49 U.S. NUCLEAR REGULATORY COMMISSION November 1982

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REGULATORY OFFICE OF NUCLEAR REGULATORY RESEARCH GU DE (Reissued February 1983 to correct page 1.145 7)

REGULATORY GUIDE 1,145 ATMOSPHERIC DISPERSION MODELS FOR POTENTIAL ACCIDENT CONSEQUENCE ASSESSMENTS AT NUCLEAR POWER PLANTS A. INTRODUCTION Reactors," and Regulatory Guide 1.4, "Assumptions Used for Esaluating the Potential Radiological Consequences of a Section 100.10 of 10 CFR Part 100, "Reac:or Site Loss of Coolant Accident for Pressurized Water Reactors."

Criteria " states that meteorological conditions at the site A number of other regulatory guides also include recorn-and surrounding area should be considered ir determining mendations for or references to radiological analyses of the acceptability of a site for a power rea tor, Section potential accidents. The applicabiSty of the specific criteria 50.34 of 10 CFR Part 50, "Domestic Ucersing of Produc- discussed herein to these other analyses will be considered tion and Utilization Facilities," requires that rach appLcant on a case-by-case basis. Until such time as generic guidelines for a construction pstmit or operating license provide an are developed for such analyses, the methodology provided an:Jysis and culua' ion of the design and performance of in this guide is acceptable to the NRC staff, structures, systems, and components of the facility with the objective of assessing the risk to public health and safety The Advisory Committee on Reactor Safeguards has

• resulting from the operation of the facility. Section 50.34 been consulted concerning this guide and has concurred in of 10 CFR Part 50 also states that special uttention should the regulatory position.

be directed to the site evaluation factors identified in 10 CFR Part 100 in the assessment of the site. B. DISCtJSSION The regulatory positions presented in this guide repre- The atmospheric diffusion2 models described in this sent a substantial change from procedures previously used guide reflect review of becent experimental data on diffu-to determine relative concertrations for assessing the sion from retc.ees at ground level at open sites and from potential offsite radiological consequences for a range of releases st various locations on reactor facility buildings pc:tulated accidental releases of radionetive material to the during stable atmospheric conditions with low windspeeds ttmosphere. These procedures now include consideration of (Refs. I through 6). These tests confirm the existence of plume meander, directional dependence of dispersion effluent plume "meander" during low windspeed condi.

conditions, and wind frequencies for various locations tions and neutral (D) and stable (E, F, and G) atmospheric eround actual exchsion area and low population zone stability conditions (as defined by the temperature differ.

(I PZ) tmundanes) ence (,1T) criteria in Regulatory Guide 1.23, "Onsite Meteorological Programs," and provide bases for quantify-The direction-dependent approach provides an improved ing the effects of plume meander on effluent concentra-basis for relating the Part 100-relate I review of a proposed tiens. Effluent concentrations measured over a period of reactor to specific site considerations. Accordingly, this I hout under such conditions have been shown to be guide provides an acceptable methodology for deter- substantially lower than would be predicted using the mining site-specific relative concentrations (t/Q) and traditional curves (Ref. 7) of lateral knd vertical plume should Ic used in determining x/Q values for the evalua- spread.

tions discussed in Regulatory Guide 1.3, "Assumptions , '

Lines indicate substantive chanses from previous ts.ae. -

Used for Lyaluating the Potential Radiological Conse-quences of a Ims of Coolant Accident for Boiling Water 2 in discussions throu hout this retulatory guide, statogheric Aspersio>i wati be cons cred as conaisting of twti components:

demospheric transport due to organized or mean airftow Whin the I for additional informatioi concernmg the bases for the teruta. atmosphere and atmospherk d Wose due to disorganized or random air motions, thime de etion and surface deposition of tory luastions presented in this rulde, see N U REG /C R.2 2 60, airborne materials are not inc Jed in the daspersion models "Technical t$ asis foe Hegulatory Guide I.la$." descibed in this guide.

USNRC REGULATORY GUIDES Comments sho ind be sent to the Sacretary of the Comrsission, U . $. Nuclea r R e9ula t ory Cornmission W asMngt on, D.C. a0sss, Regulatory Gu6aes are 6ssued to describe and make avaliable to the Attentions DoCheting and $erv6ce Branck pu boc m et h arts ec c ep t able to the NRC staff of 4m p6emen t 6ng spec ivir parts on the commission's ragu6ations, to dwneate tech- The guides are issued in tne following ten broad div6sJons:

n# oves med by the staff 6n evaluatsrw specifk proo6 ems or postu-6at ed oc c idents or 1. Power Reactors g. Products Guioes are nol out.tostitutes providefor evidarwe to appieceats.

reeuiat6ons, Re9ulatory and compliance with 2. Research and Test Hesctors r. Transportation them as not ieoutred. Methods ans solut6ons ditteeent from anose set 3. F uels and Materials P acuittee 4. Occupat6onal Health i

r out en the oueon wesi de ecceptable 6f they prov6ae a basis for tr e a. E nvironmentai and Seting 9. Antitrust and F6nanc6a4 Rev6ew fin'ines teouisite to the 6 nuance oe continuance of a permit of 6. Mater 6a6s and fiant Fvotect6on 10 General

6. cense my the commession, cooles of issued gu.oes may be purchased at the current Government This eusoe was 4ssued atte consideestion of comments reconved from ev6ntens othce peke. A subscription serv 6ce for future suloes in soo-divisions 4s a t.he u6aput.o.c. c c.mmen.tsd and ai swe,eestions fo.e emproveme.nts 6n.these u may app opn

, encourae sii i mn, and uion m < em d. n cific,ma.i.on de ot,ta ned ov on into sui.h.vadatdo nt20m o

n.scrio. tionNuci ihauenann, us through serme the Govet anR eeuiaio sment Print 6nLo non o n.a.i.. t.oe.uc ommodate e -m.nti and io r.nui r.ew in.orma- a nnineton, p.n nc o.C. n,d curreni,opo p,euencanons com m ui

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l The procedures in this guide also recognize that atmos- conservative evaluation of alms, taking into account the  ;

pheric dispersion conditions and wind frequencies are limitations of the windspeed sneasurement system, will be usually directionally dependent; that is, certain airflow neceuary. Wind directions during calm conditions shcald directions can exhibit substantially more or less favorable be assigned in proportion to the directional distribution of diffusion conditions than others, and the wind can trans- noncalm winds with apeeds less than 1.$ meters per second.3 i port effluents in certain directions more frequently than in '

othen. The procedures also allow evaluations of atmos- 1,2 Determination of DLstances for x/Q Calculations phenc dispersion for directionally variab'e datances such as a noncircular exclusion area boundary. For each wind direction sector, x/Q values for each s4nificant release point should be calculated at an appro-C. REGULATORY POSITION priate exclusion area boundary distance and outer low population zone (LPZ) boundary distance, The following

~17 tis section identifies acceptable methods for (1) procedure should be used to determine these distances. The calculating strnospheric relative concentration (x/Q) values, procedure takes into consideration the possibility of curved (2) determining x/Q values on a directional basis,(3) deter. airflow trajectories, plume segmentation (particularly in mhing x/Q values on an overall site basis, and (4) choosing low wind, stable conditions), and the potential for wind-x/Q values to be used in rvaluations of the types of events speed and wind direction frequency shifts from year to described in Regulatory Guides 1.3 and 1.4. year, Selection of conservative, Icss detailed site parameters For each of the 16 sectors, the distance for exclusion for the evaluation may be sufficient to establish compliance area boundary or outer LPZ boundary x/Q calculation with regulatory guidelines, should be the minimum distance from the stack or,in the case of rdcases through vents or building penetrations, the

1. CALCULATION OF ATMOSPilERIC RELATIVE CON. nearest point on the building to the exclusion area bound-CENT R ATION (x/Q) V ALU ES ary or outer LPZ bour.Jary within a 45-degree sector centered on the compass direction of interest, Equations and parameten presented in this section should be used unless unusual siting, meteorological, or For stack releases, the maximum ground-level s oncentra-terrain conditions dictate the use of other models or tion in a sector rnay occur beyond the exclusion area considerations. Site-specific atmospheric diffusion tests boundary distance or oute: LPZ boundey distance, There-covering a full range of conditions may be used as a basis fore, for tack releases, g/Q calculations should be made in for modifying the equations and parameters. cach sector at each minimu'm boundarv distance and at various distances beyond the exclusion area boundary 1.1 Meteorological Data Input distance to determine the maximum relative concentration for consideration in subsequent calculations.

The meteorological datt. needed for x/Q calculations include windspeed, wmd direction, and a measure of atmos- 1.3 Calculation of x/Q Values at Exclusion Area Bound-phene stabtlity.These data should represent hourly averages ary Distances as defined in Regulatory Guide 1.23.

Relative concentrations thai can ba :. armed to apply at Wind direction should oe classed into 16 compass direc- the exclusion area boundary for 2 houts immediately tions (22.5-defree sectors centered on true north, north- following an accident should be determined.' Calculations northeast, etc.), based on meteorological data representing r.1 hout average should be assumed to apply for the entire 2-hour period.

Atmospheric stabtlity should be determined by vertical This assumption is reasonably conservative considering the

.1T between the release height and the 10-meter level, small variation of /Q X values with ateraging time s:(ef. 8).

Acceptable stability classes are given in Regulatory Guide if releases associated with a postulated event are estimated 1.23 If other well documented parameten are used to to occur in a period oflen than 20 minutes, the applicabil- 1 determine plume dispersion (with appropriate ju:tification), ity of these models should be evaluated on a case-by-case the models described in this guide may require modifica- basis. l tion. A well-documented parameter is one that is substan- I tiated by diffusion data collected in terrain conditions P:ocedures for calculating "2-hour" x/Q values depend similar to those at the nuclear power plant site being on the mode of release. The procedures are described considered, below, Calms should be defined as hourly average windspeeds below the vane or anemometer starting speed, whichever is l I

higher (to reflect limitations in instrumentation). If the instrumer.tation program conforms to the regulatory 3 position in Regulatory Guide 1.23, cairns should be assigned M Ws a u mters per second rrwtae a resumble ranse rue defknins the a windspeed equal te the vane or anemometer starting d'""b"*"* *I'$"J destion durins luht winds.

\ speed, whichever is tigher. Otherwise, consideration of a "See I 800.18 of 10 CIR Part too.

1.145 2 l

1.3.1 Releases Through Ven ts or Other Building xfQ values should be calculated using Equations 1,2, Penetrations and 3. The values from Equations 1 and 2 should be com-D This class of release modes includes all release points or areas that are effectively lower than two and one-half times the height of adjacent solid structures (Ref. 9). Within this pared and the higher value selected. This value should be compared with the value from Equation 3, and the lower value of these two should then be selected as the appro-priate X/Q value. Examples and a detailed explanation of class, two sets of meteorological conditions are treated the rationale for determining the controlling conditions are differently

• foUows: given in Aprendix A to this guide.

a. During neutral (D) or stable (E, F, or G) atmos-pheric sta*vility conditions when the windspeed at the b. During all other meteorological conditions, plume 10-meter level is less than 6 meters per second, horizontal meander should not be considered. The appropriate X/Q plume meander may be considered X/Q values may be value for these conditiois is the higher value calculated determined through selective use of the fouowing set of from Equation 1 or 2.

equations for ground-level relative concentrations at the plume centerline: 1.3.2 Stack Releases t This class of release modes includes all release points at X/Q= (1)

U,g(noyg a + A/2' leve:s that are two and one-hai! times the height of adjacent solid stn.ctures or higher (Ref. 9). Nonfumigation condi-tions are treated separately.

I X/0=

10(3royg a) (2) a. For nonfumigatior, conditions, the equation for ground-level relative concentration at the plume center-line for stack releases is:

_1 -

gg = _U gnE yz a (3) 1 -h 2'

e X/O =nU ~ aa exp (4) hyz 20 z where . .

I X/Q is relative concentration,in sec/m3 , where n is 3.14159. Uh is windspeed representing conditions at the release height,in m/see, Dg is windspeed at 10 meters above plant grade,5 in m/sec, h, is effective stack height, in m: h, = h, - ht '

ay is latwl plume spread, in m, a function of atmos- h, is the initial height of the plume (usually the pheric str.bility and distance (sce Fig.1), stacx height) 9bove plant grade, in m, and og is vertical plume spread, in m, a function of h t

is the maximum terrain height above plant atmospheric stability and distance (see Fig. 2), grade between the release point and the point for which the calculation is made, in m. If Ey is lateral plume spread with meander and building - htis greater than hs , then h, = 0.

wake effects, in m, a_ function of atmospheric stability, windspeed U g, and distance [for For those cases in which t:ee applicant can demon-distances of CN) meters or less, E = hia y, where strate that the vertical velocity of effluent plumes from the hf is determined from Fig. 3; for dstances greater plant (because of either buoyarcy or mx' r_.sa! jet effects) than 800 meters, Zy = (ht - 1) oy 800m + 0y],and wiu be maintained during the course of the accident, this additional velocity may be considered in the determination A is the smallest vertical-plano cross-sectional area of of the effective stack height (h,)using the same procedures the reactor building, in m 2 (Other structures described in regulatory position 2.a of Regulatory Guide or a directional consideration may be justified 1.111, "hfethods for Estimating Atmospheric Transport when appropriate.) and Dispersion of Gaseous EfGuents in Routine Releases from Light-Water-Cooled Reactors."

b. For fumigation conditions, a "fumigation X/Q" should be calculated for each sector as fouow? The equa-D ,$oNhNch h tayer p ume nl cd when su7fe7 e bui tion for ground-level relative concentration et the plume enterline for stack releases during fumigation conditions wske errects. 1s 1.145 3

- m

I 2. DETERMINATION OF MAXIMUM SECTOR X/Q x/Q = ,he>0 (5) VALUES (2rr)%Ugyeoh The X/Q values calculated in regulatory position 1 are {

used to determine "sector x/Q values" and "maximum sector x/Q values" for the exclusion area boundary and the outer LPZ boundary, where 2.1 Exclusion Area Boundary

_Uh* is windspeed representative of the fumigation layer of depth he , in m/sec;in lieu ofinforma- 2.1.1 &neralNethod tion to the contrary, the NRC staff considers a value of 2 meters per second as a reasonably Using the X/Q vales calculated for each hour of data conservative assumption for eh of about 100 according to regulatory peition 1.3, a cumulative proba-meters, and bility distribution of /Q X values :hould be constructed for ec;h of the 16 sectors. Each distrii,ution should be de-oy is the lateral plume spread, in m, that is repre- scribed in terms of probabilities of given x/Q values being sentative of the layer at a given distance; a exceeded in that sector during the total time. A plot of X/Q moderately stable (F) atmospheric stability versus probability of being exceeded should be made for condition is usually assumed. each sector, and a smooth curve should be drawn to fonc an upper bound of the computed points. For each of the 16 7

Equation 5 cannot be applied indiscriminately because curves, the x/Q value that is exceeded 0.5 percent of the the x/Q values calculated, using this equation, become total num'oer of hours in the data set should be selected unrealistically large as he becomes small (on the order of (Ref.10). These are the sector x/Q values. The highest of 10 meters). The X/Q values calculated using Equation 5 the 16 sector values is defined as the maximum sector x/Q must therefore be limited by certain physical restrictions, value.

The highest ground-level x/Q values from devated releases are expected to occur during stable conditions with low 2.1.2 Fumigation Conditionsfor Stc;k Releases windspeeds when the effluent plume impacts on a terrain obstruction (i.e., h#= 0). Ilowever, elevated plumes diffuse Regulatory position 1.3.2 describes procedures for upward through the stable layer aloft as well u downward calculating a fumigation X/Q for each sector. These sector through the fumigation layer. Thus ground-level relative fumigation values, and the general (nonfumigation) sector concentrations for elevated releases under fumigation values obtained in regulatory position 2.1.1, are used lI conditions cannot be higher than those produced by to determine appropriate sector fumigation X/Qs. Conserva-nonfumigation, stable atmospheric conditions with h, = 0. tive assumptions for fumigation conditions, which differ for For the fumigstion case that assumes F stability and a inland and coastal sites, are described below. Modifications windspeed of 2 meters per second, Equation 4 should be may be appropriate for specific sites, used instead of Equation 5 at distances greater than the distance at which the x/Q values determined using Equa- a. Inland Sites: For stack releases at sites located 3.2 tion 4 with h, = 0 and Equation 5 sre equal. kilometers or more from large bodies of water (e.g., oceans or Great Lakes), a fumigation condition should be assumed 1.4 Calculation of X/Q Values at Outer LPZ Boundary to exist at the time of the accident av i continue for 1/2 Distances hour (Ref. I1). For each sector, if the sector fumigation X/Q exceeds the sector nonfumigation X/Q, use the fumiga-Two-nour X/Q values should also be calculated at outer tion value for the 0 to 1/2-hour time period and the non-LPZ boundary distances. The procedures described above fumigation value for the 1/2-heur to 2-hour time period, for exclusion area boundary distances (see regulatory Otherwise, use the nonfumigation sector value for the position 1.3) should be used. entire 0 to 2-hour time period. The 16 (sets of) values thus determined should be used in dose assessments requiring An annual average (8760-hour) X/Q should be calculated time-integrated concentration considerations.

for each sector at the outer LPZ boundary distance for that sector, using the method described in regulatory posi- b. Coastal Sites: For stack releases at sites located less tion 1.c of Regulatory Guide 1.111. For stack releases, h e than 3.2 kilometers from large bodies of water, a fumiga-should be determined as describ:d in regulatory posi- tion condition should be assumed to erist at the exclusion tion 1.3.2 above. area boundary at the time of the accident and continue for the entire 2-hour period. For each sector, the larger of the These calculated 2-hour and annual average values are used in regulatory position 2.2 to determine sector X/Q ~ 7 selection of the 0.5 values at outer LPZ boundary distances for various inter- without consideration of p5reent level is based me meander, onthe between an sequality, rercent mediate time periods *6 directionally independent evaluation of X/Q (the pre tous evaluation procedure) and tne o.s percent directionally dependent evalustion of y/O araged over a reasonably representative number of existing 6 nuciens gower plant sites. See NUREG/CR 226o for additional See 100.11 of to CFR Part too. information.

1.145-4 l

sector fumigation x/Q and the sector nonfumigation x/Q These are then the maximum sector x/Q values. Ilowever,if should be used for the 2-hour periud. Of these 16 sector the highest sector X/Qs do not all occurin the same sector, D values, the highest is the maximum sector x/Q value.

c. Modifications: nese conse. e assumptions do not the 16 (sets of) values will be used in dose assessments requiring time-integrated concentration considerations.

The set of X/Q values resulting in the highest time-consider frequency and duration of fumigation conditions integrated dose within a sector should be considered the as a function of airflow direction. l' information can be maximum sector X/Q values.

presented to substantiata the likely directional occurrence and duration of fumigation conditions at a site, the assump- 2.2.2 Fumigation Conditions for Stack Releases tions of fumigation in all directions and of duration of 1/2 hour and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for the exclusion area boundary may be Determination of sector x/Q values for fumigation modified. Then fumigation need only be considered for conditions at the outer LPZ boundary involves the follow-airflow directions in which fumigation has been determined ing assumptions concerning the duration of fumigation for to occur and of a duration determined from the study of inland and coastal sites:

site conditions.s

a. Inland Sites: For stack releases at sites located 3.2

2. 2 Outer LPZ Boundary kilometers or more from large bodies of water, a fumigation condition should be assumed to exist at the outer LPZ 2.2.1 GeneralMethod t " .> at the time of the accident and continue for 1/2 h+ ator x/Q values for fu.nigation should be deter-Sector X/Q Values for the outer LPZ boundary should be mineu as for the exclusion area boundary in regulatory determined for various time position 2.1.2.

of the postulated .ccident.geriods The timethroughout periods should the course represent appropriate meteorological regimes, e.g., 8 and b. Coastal Sites: For stack releases at sites located less 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 than 3.2 kilometers from large bodies of water, a fumiga-Regulatory Guide 1.70, "Standard Format and Content of tion condition should be assumed to exist at the outer LPZ Safety Analysis Reports for Nuclear Power Plants--LWR boundary following the arrival of the plume and continue Edition," or other time periods appropriate to release for a 4-hour period (Ref. I1). Sector X/Q values for fumiga-durations. tion should be determined as for the exclusion area bound-ary in regulatory position 2.1.2.

l For a given sector, the average x/Q values for the various time periods may be approximated by a logarithmic inter- c. The modifications discussed in regulatory posi-polation between the 2-hour IO sector x/Q and the annual tion 2.1.2 may also be considered for the outer LPZ average (8760-hour) X/Q for the same sector. De 2-hour boundary.

sector x/Q for the outer LPZ boundary is determined using the general method given for the exclusion area boundary 3. DETERMINATION OF 5 PERCENT OVERALL SITE in regulatory position 2.1. The annual average X/Q for a given X/Q VALUE sector is determined as described in regulatory position 1.4 The x/Q values that are exceeded no more than 5 per-The logarithmic interpolation procedure produces results cent of the total number of hours in the data set around the that are consistent with studies of variations of average exclusion area boundary and around the outer LPZ bound-concentrations with time perioos up to 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (Ref. 8). ary should bo determined as follows (Ref.10):

Alternative methods should also be consistent with these studies and should produce results that provide a mono- Using the X/Q values calculated acccrding to regulatory tonic decrease in average x/Q with time. position 1, an overall cumulative probability distribution for all directions combined should be constructed. A plot For each time period, the highest of the 16 sector X/Q of xlQ versus probability of bemg exceeded should be values should be identified. In most cases, these highest made, and an upper bound curve should be drawn. The

v. dues will occur in the same sector for all time periods. 2-hour X/Q value that is exceeded 5 percent of the time should be selected from this curve as representing the dispersion condition indicative of the type of release being 8

For example, examination of site-specific information at a considered. In addition, for the outer LPZ boundary the

" ' " maximum of the 16 annual average x/Q values should be NrfNionY *oc@rYtly duttEg he ow nval e y " ra ag i w e rp"ime* and persist for durations of about 1/2 hour. Therefore,in used along with the 5 percent 2-hour x/Q value to deter-may be exhu$d ffor# n r$derNioho$furnigst o1 on#dift n's and mine X/Q values for the intermediate time periods by the duration of fumigation would still be considered as 1/2 hour, logarithmic interpolation.

On the other hand, data from sites in open terrain (noncoastal) may indicate rno directional preference for fumigation conditions but may indicate durations much less than 1/2 hour. In this case, 4* SELECT 10N OF X/Q VALUES TO BE USED IN fumigauon should be considered for all directions, but with dura-EVALUATIONS D tions of less than 1/2 hour.

'See in 10o.11 of t o C FR Part 10o, The X/Q value for exclusion area boundary or outer LPZ g are bawd on 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> aversted data but are assumed gg g gggg ggg 1.145-5

(regulatory position 2) or the 5 percent overall site X/Q incorporating or referencing a duplicate plant design I (regulatory position 3), whichever is higher. All direction- and those submitted under the replicate plant option dependent sector values should be presented for considera- of the Commission's standardization program),

tion of the appropriateness of the exclusion area and outer LPZ boundaries. Where the basic meteorological data 3. Operating license applications.

necessary for the analyses described herein substantially deviate from the regulatory position stated in Regulatory For operating reactors, the licensee may use the method Guide 1.23, consideration should be given to the resulting described in this guide or may continue to use the method uncertainties in dispersion estimates. previously contained or referenced in the FSAR for such facilities.

D. IMPLEMENTATION This guide does not apply to the following options The purpose of this section is to provide information to specified in the Commission's standardization policy under applic' ants regarding the NRC staff plans for using this the reference system concept:

regulatory guide.

1. Preliminary design approval applications.

Except in those cases in which an applicant proposes an acceptable alternative method for complying with specified 2. Final design approval, Type 1, applications, portions of the Commission's regulations, the method described herein will be used in the evaluation of the 3. Final design approval, Type 2, applications, following:

4. Manufacturinglicense applications.

l. For early site rey;ew applications.

The implementation date for this guide is December 30,

2. For construction permit applications (including those 1982.

l I

1.145-6

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2 5 lo' 2 S 10' 2 5 lo' OISTANCE FROM SoVRcE tml D Figure 1. Lateral diffusion without meander and building wake effects, oy, vs. down-wind distance from source for Pasquill's turbulence types (atmospheric stability) (Ref. 7).

The sigmi values preanted above are for unrestricted flow over relatively flat, uniform terrain. They may require modificatiors before tpplication in situations in which rough terrain or restricted flow conditions (e.g.,

within the confines of a narrow valley) must be considered or in coastal and desert areas. (See Hef.12 for additional information.)

l For purposes of estimating oy during extremely stable (G) atmospheric stability conditions,without plume l meander or othet lateral enhancement, the following approximation is appropriate:

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10 8

10 2 5 10 3 2 5 10' 2 5 10' DISTANCE FROM SOURCE (m) l Figure 2. Vertical diffusion without meander and building wake effects, az, vs. downwind distance from source for Pasquill's turbulence types (atrnospheric stability) (Ref. 7).

The sigma values presented above are for unrestricted flow over relatively flat, uniform terrain They may require modification before application in situations in which rough terrain or restricted flow conditions (e.g., within the confines of a narrow valley) must be considered or in coastal and desert areas. (See Ref.12 for additional information.)

For purposes of estimating ogduring extremely stable (G) atmospheric stability conditions, the following approximation is appropriate:

OW: Z

1. 5z 1.145-8

10 -- -- - . . _ _

7 -- - - -

t Stability Class .

l l

6 6 i _ _ _

l J .

I i x I i

, 4  ! .

g '

1 t;

E g 3, ,

p '

l e t E

8  :

s D 2 - - -

l -

l I

I 1

I l -~ 1 i i- i i, 1 2 3 4 5 6 10 WIN DSPE ED (m/sec)

FlyJre 3. Correction factors for o values y by atmospheric stability class (see Appendix A to this guide),

i 1,145-9

APPENDIX A ATMOSPHERIC DIFFUSION MODEL FOR RELEASE THROUGH VENTS AND BUILDING PENETRATIONS Rationale vertical plume meander is shown to be virtually nonexistent during light wind, stable conditions, liowever, the experi- l The effects of building wake mixing and ambient plume mental results for both situations could not ba cuantified j meander on atmospheric dispersion are expressed in this for generel application at this time. I guide in terms of conditional use of Equations 1,2, and 3.3 I The conditional use of Equations 1,2, and 3 is consid-Equations 1 and 2 are formulations that have been ered appropriate because (1) horizontal plume meander acceptable for evaluating nuclear power plant sites over a tends to dominate dispersion during light wind and stable period of many years (Ref. 7 and Regulatory Guides 1.3 or neutral conditions and (2) building wake mixing becomes and 1.4). He conditional use of Equations 1 and 2 provides more effective in dispersing effluents than meander effects an assessment of atmospheric diffusion, including only the as the windspeed increases and the atmosphere becomes less effects of building wake mixing that occur during moderate stable, windspeed conditions (>3 m/sec). These equations have recently been found to provide estimates of ground-level Examples of Conditional Use of Diffusion Equations concentrations that are consistently too high during light wind and stable or neutral atmospheric conditions for Figures A-1, A-2, and A-3 show plots of XU _ o/Q (X/Q 1-hour release durations (Refs. I through 6). versus downwin,d distance multiplied based on theby the windspeed conditional use U,g(a)s described in regu Equation 3 is an empirical formulation based on NRC position 1.3.1) of Equat'ons 1, 2, and 3 during atmos-staff analysis of atmospheric diffusion experiment results pheric stability class G. De variable M for Equation 3 (Ref. 2). De NRC staff examined values of lateral plume equals 6,3, and 2 respectively in Figures A-1, A-2,and A 3 spread with rneander and building wake effects (Zy ) by (M is as defined in regulatory position 1.3.1).

atmospheric stability class (based on AT), calculated from measured ground-level concentrations from the expen- In Figure A-1, the xUto/Q from Equation 3 (M = 6)is mental results, Plots of the computed Zyvalues by atmos- less than the higher value from Equation 1 or 2 at all pheric stability class and downwind distance were analyzed distances. Herefore, for M = 6, Equation 3 is used for all conservatively but within the scatter of the data points by distances, virtually enveloping most test data. He resultant analysis is the basis for the correction factors spplied to the oyvalues In Figure A 2, the xD,o/Q from Equation 3 (M = 3)is (see Fig. 3 of this guide). Rus, Equation 3 identities con- less than the higher value from Equation 1 or 2 beyond 0.8 servatively the combined effects ofincreased plume meander km. Herefore, fer M = 3, Equation 3 is used beyond 0.8 and building wake on diffusion in the horizontal crosswind km. For distances less than 0.8 km, the value from Equa-direction under light wind and stable or neutral atmos- tion 3 equals that from Equation 2. Equation 2 is therefore pheric conditions, as quantified in Figure 3. Rese experi- ur rd 'or distances less than 0.8 km.

ments also indicate that vertical building wake mixing during light wind and stable conditions is not as complete In Figure A 3, the XUno/Q from Equation 3 (M = 2)is l as during moderate wind, unstable conditions, in addition, never less than the higher value from Equation 1 or 2.

Therefore, for M = 2, Equation 3 is not used at all. Instead, Equation 2 is used up to 0.8 km, and Equation 1 is used I ,For additionalinformation see NUREGlCR-2260. beyond 0.8 km.

1.145-10

l

' 4 I 10 j i

-Eq. 2, -

\ I  !

\

l

\

l l

\ ,

i , -

-Eq. 3 (M=6) \

\ i l i l

\ '

10 : - Eq. l -

; l j i

.$ N( l  ! I

\l N  ! l E \ N  !

i g N i[

~

\ \ \

\

l

\\ ,

x 4 \

10

.N \ Eq. 1

~

\ Eq 3 (M=6)-

! _ \

\

Eq. 2 D ~

t t

l.

.s  ! '

10 . . -

O.1 1.0 10 PLUME TRAVEL DISTANCE (km) 1 Figure A 1. xU /O 10 as a function of plume travel distance for G stability condition using Equations 1,2, and 3 (M = 6).

l l ,

D 1.145-11

f

-2 f 10

Eq. 3 (M=3)

Eq. 2 i\

i

~ i t (

i

! \ i 10

- Eq . 1 \ ll l

~ ~ N )\ l  ! i  !

! I i e*

! !h N \'

B - \ s i

\ (\ .

\ \l

\

\ Eq.1 10"- Ni '

3

\l --Eq. 3 (M=3) _

\

Eq.'2 1

in 5 ,

0.1 1.0 jo PLUME TRAVEL DISTANCE (km)

Figure A 2. x0 /O 10 as a function of plume travel distance for G stability condition using Equations 1,2, and 3 (M = 3). .

4 1.145-12 (

l l

( q. 3 M l 10 2 _

- Eq. 2 \

\\

I Il

\  ! 11 I ( \, ll

,I \ l iI Eq. 1  !  !

\

' '3 ~

I~ ' ' mL I!

2 2

i

\

\ N l

o' -

\

\

h N \Eq.i 30 ~- \l K l i Eq. 3 (M 2)-

\

\

\

~

Eq. 2 l

10

01 1.0 10 PLUME TRAVEL DISTANCE (km)

Figure A 3. x039/O as a function of plume travel distance for G stability condition using Equations 1,2, and 3 (M = 2).

I 1.145-13 s

REFERENCES

1. I. Van der lloven, "A Survey of Field Measurements sion Experiments with SF, Tracer Gas at Three hiile of Atmospheric Diffusion Under Low-Wind Speed Island Nuclear Station Under Low Wind Speed Inversion Conditions," Nuclear Safety, Vol.17, inversion Conditions," Final Safety Analysis Report, No. 4, March-April 1976. Amendment 24, Docket Number 50-289, 1972.

2. G. E. Start et al., "Ramho Seco Building Wake 7. F. A. Gifford, Jr., "An Outline of Theories of Diffu-Effects on Atmospheric Diffusion," NOAA Technical sien in the Lower Layers of the Atmosphere,"

Memorandurn ERL ARL-69, Air Resources Labora- Chapter 3 in Meteorology and Atomic Energy-1968 tory, Idaho Falls, Idaho, November 1977. Available (D. IL Slade, Ed.). Available as TID-24190 from the from Publication Services, Environmental Research National Technical Information Service, Springfield, Laboratories. National Oceanic and Atmospheric Virginia 22151. l Administration, Boulder, Colorado 80302. l

8. F. Gifford, "Atmospheric Dispersion Models for

3. R. B. Wilson et al., "Diffusion Under Low Windspeed Environmental Pollution Applications," Lectures on Conditions Near Oak Ridge, Tennessee," NOAA Air Pollution and Environmental Impact Analyses, Technical Memorandum ERL ARL-61, Air Resources American Meteorological Society, pp. 35-38, 1975.

Laboratory, Idaho Falls, Idaho,1976. Available from Publication Services, Environmental Research Labora- 9. W.11. Snyder and R. E. Lawson, Jr.,"Determination tories, National Oceanic and Atmospheric Administra- of a Necessary lleight for a Stack Close to a Building-tion, Boulder, Colorado 80302. A Wind Tunnel Study," Atmospheric Environment, Vol.10, pp. 683-691, Pergamon Press,1976.

4. J. E. Sagendorf and C. R. Dickson,"Diffusion Under Low Windspeed, inversion Conditions," NOAA 10. D. R. Muller memorandum to 11. R. Denton,"Meteoro-Technical Memorandum ERL ARL 52, Air Resources logical Model for Part 100 Evaluations," July 25, Laboratory, Idaho Falls, Idaho,1974. Available from 1978, and August 2,1978 reply.

Publication Services, Environmental Research Labora-tories, National Oceanic and Atmospheric Administra- 11. 1. Van der lloven, "Atmospheric Transport and tion, Boulder, Colorado 80302. Diffusion at Coastal Sites," Nuclear Safety, Vol. 8, pp. 490-499,1967.

5. Gulf States Utilities Company, "Dispersion of Tracer Gas at the Proposed River Bend Nuclear Power 12. International Atomic Energy Agency, "Atmosrheric Stetion," Preliminary Safety Analysis Report, Amend. Dispersion in Nuclear Power Plant Siting-A Safety ment 24, Docket Numbers 50-458 and 50-459,1974. Guide," Safety Series No. 50-SO-S3, Vicnaa, Austria, 1980. Available from UNIPUB, 345 Park Avenue

6. Metropolitan Edison Company, "Atmospheric Diffu- South, New York, N.Y.10010.

1.145 14

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