ML20062C859

ODCM Atmospheric Diffusion & Deposition Factors

ML20062C859
Person / Time
Site:	Seabrook
Issue date:	01/31/1990
From:	Harvey R YANKEE ATOMIC ELECTRIC CO.
To:
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ML20062C849	List: ML20062C846 ML20062C855 ML20062C859
References
PROC-900131, NUDOCS 9011020198
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Text

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i e

l SEABROCK STATION OTTSITE DOSE CALCULATION MANUAL ATMOSPHERIC DITTUSION AND DEPOSITION TACTORS by Robert 8. Harvey, Jr.

l l

January 1990 Yankee Atomic Electric Company Nuclear Services Division 580 Main Street Bolton, MA 01740 1398 j

f01100o19g 901026 f,DR ADOCK 05000.ia:3 PDC l

I

{

4 SEABROOK $TATION OTTSITE DOSE CALCULATION MANUAL ATMOSPHERIC DITTUSION AND DEPOSITION TACTORS by 4

l l

Robert 8. Harvey, Jr.

1 January 1990 l

4 Yankee Atomic Electric company Nuclear Services Division 580 Main Street Bolton, MA 01740 1398-p?O11020198 901974, p,DR ADOCK 05000443 PDC

SEA 3R00K STATION OTTSITE DOSE CALCULATION MANUAL ATMOSPHERIC DIFITSION AND DEPOSITION TACTOR $

TABLE OF CONTENTS Section ZAgg

1.0 INTRODUCTION

1 2.0 DETAILS OF CALCULATION 2

2.1 Meteorological Data Joint Frequency Distributions 5

l 2.1.1 Atmospheric Stability Class 5

2.1.2 Wind Speed Groups 5

2.1.3 Vind Direction Sectors 6

2.1.4 TIAL Conditions 6

2.2 Diffusion and Deposition Tactor Averages 8

t 2.3 Diffusion and Deposition Factor Models 9

2.3.1 Undepleted CHI /Q 9

2.3.2 Depleted CHI /Q 11 2.3.3 D/Q 12 l

2.3.4 Camma CHI /Q 13 l

2.3.5 Plume Standard Deviations and Building Wake 15' Effects 2.3.6 Entrainment 16 2.3.7 Effective Plume Height 17 2.3.8 Mixing Depths 19 2.3.9 Recirculation Correction Factors 20 3.0 RESULTING DITTUSION AND DEPOSITION FACTOR VALLT1 21

4.0 REFERENCES

24 11

l SEABROOK STATION OTTSITE DOSE CALCULATION %WAL ATMOSPHERIC DITTUSION AND DEPOSITION TACTORS LIST OF TABLES Number g

g 1

Seabrook Station ODCM Atmospheric 26 Diffusion and Deposition Factors I

'e l

l LLL e

SEASROCK !TATION OFTSITE DOSE CA* JLATION MANUAL ATMOSPHERIC DITTUSION AND DEPOSITION TACTORS LIST OF EXHIBITS Humhit lilla ZA&R 1

Projected Annual Noble cas Effluent 27 Releases 2

Regu' story Guide 1.111 (Rev. 0) Open 28 Terrain Recirculation Correction Factors 3

Site Map Showing Locations of the

$9 Administration Building / Turbine Building Complex and the Site Boundary 4

Site Map Showing Locations of the Prisary 30 Vent Sta:k and the Site Boundary 5

Receptor Locations 31 0

e M

iv

~

i I

I 1,0 INTR 0Bt'cT 0N The purpose of the Seabrook Station Offsite Dese Calculation Manual (CDCM) is to identify the equipment, methods, equations, and data used to verify compliance with the effluent release limits specified in the Seabrook Station Technical Specifications.

Included as part of Section 7.0 of the ODCM is a table of the atmospheric diffusion and deposition f actors used to calculate the offsite doses and radionuclide concentrations necessary to determine compliance with the dose and dose rate requirements of the Technical Specifications which implement 10Cm20 and 10cm$0 Appendix I dose criteria.

The intent of this document is to present a technical description of the methor'. ology used to generate the Seabrook Station ODCM atmospheric diffusion and deposition factors.

/

1 i

c 4

1 1

1

l I

i 2.0 DETAILS OF CALCULATION Seabrook Station Offsite Dose Calculation Manual (CDCM) atmospheric l

diffusion and deposition factors were computed for routine continuous and randomly distributed batch releases using the AEOLUS 2 computer code l

l (Reference 1).

AEOLUS.2 is based, in part, on the constant mean wind I

direction model with Caussian diffusion as presented in Regulatory Guide 1.111 1

(Reference 2) and as implemented by the NRC X0QD0Q computer code (Reference 3).

Tour types of atmospheric diffusion and deposition factors were generated by AE0LUS.2 for use within the Seabrook Station ODCM:

1.

Undepleced C#f/Q faccors which convert noble release rates (C1/sec) 3 to ground level concentrations (C1/m ),

t 2.

Deplaced CNI/Q factors which convert iodine and particulate release 3

races (CL/sec) to ground level concentrations (CL/m ).

3.

D/Q faccors which convert iodine and particulate releases (C1) to 2

i ground deposition per unit area (C1/m ).

I 4

Camma CNI/Q faccors which are used to convert noble gas release rates (Ci/sec) to whole body gamma dose rates (ares /sec) utilizing the sector average gamma dose model presented in Section 7 5 of Meteorology and Atomic Energy 1968 (Reference 4).

[The standard gamma dose rate equation for a semi-infinite cloud can be converted to a finite cloud gamma dose race equation by replacing undeplaced CHI /Q factors in the seni. infinite cloud dose rate equation with ganas CHI /Q factors.)

Two categories of potential release pathways were considered: (i) a

' generic' ground level telease pathway (indicative of Condenser Air Evacuation 1

and Chemistry Lab Hood Vents releases); and, (ii) a Primary Vent Stack release pathway.

The following assumptions were - used in generating diffusion and 2

~

_, _.,... - +.

1 s

1 a

deposition factors for each of the two release pathways:

Sector average atmospheric diffusion and deposition factors were used (e.g., the plume was assumed to be distributed evenly horizontally across a 22.5 degree vide direction sector).

P,ecirculation correction factors were applied to consider the effects of spatial and temporal variations in airflow which can occur during prolonged periods of atmospheric stagnation and during the onset and i

i decay of seabreezes.

The ground level release pathway was treated as a Regulatory Guide 1.111 ground mode release occurring below the height of adjacent buildings.

The Primary Vent Stack release pathway was created as a, Regulatory Guide 1.111 mix mode release occurring above (but less than 2 times above) the height of adjacent buildings.

Onsite lower level wind speed data were used to evaluate diffusion and deposition conditions for both release pathways.

These data were used 'as is' to disperse the plume for the ground level release pathway and the ground node portion of the Primary Vent Stack release I

pathway.

These data were extrapolated upwards to the Primary Vent Stack release height for evaluating the potential for plume entrainment and for determining plume rise and dispersion for the elevated mode portion of the Primary Vent Stack release pathway.

Ons! ' ) lower level wind direction data were used to determine plume transport (e.g., affected downwind sector) for both release pathways.

i Atmospheric stability was determined as a function of vertical temperature difference using the onsite 209'.43' delta temperature l'

measurements.

3

~

l The effect of the Thermal Internal Boundary Layer (TISL) coastal si:e phenomenon on plume dispersion was evaluated for both release pathways. TIBLs were assumed to occur from April through September between the hours of 08:00,and 18:00 whenever solar radiation was above 0.35 langley /ain, wind speed was between 2 and 10 m/sec, and the wind was from the northeast clockwise through south southeast.

The Regulatory Guide 1.111 depletion / deposition model was used for determining depleted CHI /Q and D/Q values for both release pathways.

Vet depletion / deposition and decay.in transit were not considered.

The gamma energy spectrum used to generate the gamma CHI /Q values was i

derived using the gamma energy spectrum associated with the projected i

annual noble gas release rates for each release pathway as presented I

in Section 3.5 of the Seabrook Station Environmental Report.

[

i Operating License Stage (ER.0LS).

Average diffusion and deposition factors were generated using on site meteorological data from the six year period January 1980 through December 1983 and January 1987 through December 1988 (with the exception that April 1980 and May 1980 data were substituted with April 1979 and May 1979 data e,

because of low data recovery races) by compiling a joint frequency distribution of wind speed, wind direction, and atmospheric stability for both i

TIBL and TIBL/non 11BL conditions.

Corresponding diffusion and deposition factors for each wind speed / wind direction / stability class combination were generated.

Average diffusion and deposition factors were then calculated for each receptor as a function of the frequency of wind speed /vind direction / stability combinations applicable to the receptor's location.

Specific details on the compilation of the meteorological data joint-frequency distributions and the resulting average diffusion and deposition factors are provided in the subsect'.ons which follow.-

i 4

(

b

l. - _ _ _ _ _ _ _ _ _. _ _ _ _. _ _ _ _ _ _ _.. _ _ _ _

2.1 Meteorelerical Data Joint Freeuanev Distributions Hourly meteorological data records consisting of lower level wind speed.

lower level wind directicn. and 209'.43' vertical temperature difference (delta t.emperature) data were used to generate joint frequency summaries of I

stability class 1, wind speed group j, and wind direction sector k for both TIBL and TIAL/non TIAL conditions as follows:

I 2.1.1 Atmeatharie stability Clamaan Atmospheric stability classes (Pasquill Categories A through C) were t

determined as a function of vertical temperature difference using the onsite 209'.43' delta temperature measurements and the atmospheric stability I

classification criteria outlined in Regulatory Guide 1.23 (Reference 5).

2.1.2 Wind sened crouca Lower level wind speed data were utilized to generate wind speed frequency distributions for both the ground level and Primary Vent Stack I

release pathways.

In accordance with Regulatory Guide 1.111 guidance, the l

wind speed data were divided into 12 wind speed classes which approximated the Beafort wind scale.

The lowest wind speed group represented cala conditions, defined as wind speeds less than the anemometer /vind vano threshold wind speed of 0.5 mph.

A group. average wind speed of 0.25 mph (half the anemometer /vind threshold wind speed) was assigned to this first vind speed group.

For vane all other wind speed groups, the average wind speed was determined for each wind speed group j as a function of stability class 1.

These group. average ground level wind speeds u (i.j) were used to disperse the plume for the g

ground. level release pathway and the ground. node portion of the Primary Vent Stack mix mode release pathway.

In order to perform dispersion analysis for the elevated mode portion of 5

1

the Primary Vent Stack release pathway, the group average ground. level wind speeds u (1,j) were extrapolated to the Primary Vent Stack release hei he of g

l

$7.9 m above plant grade as follows:

u,(i.j) - u (1,j) * [57.9m/10.0s)9(1) g where u,(1.j ) is the group. average elevated wind speed (considered to be representative of conditions at the Primary Vent Stack release hei5ht) and q(i) is a stability dependent power coefficient.

In line with the XOQD0Q i

computer code, q(i) was defined as 0.25 for stability classes A, B, C, and D and 0.50 for stability classes E. F, and G.

2.1.3 Vind Direction Sectore The hourly wind direction data were classified into 16 compass point sectors (e.g.,

22.5. degree wide sectors) centered on true north, north.

northeast, etc. Wind directions during cala conditions (e.g., hours with wind speeds less than 0.5 mph) for any given stability were distributed to the various sectors in proportion to the sector. dependent observatiens in the second wind speed Croup for that stability.

2.1.4 TIBL conditions For coastal sites such as Seabrook, a Thermal Internal Boundary Layer (TIBL) can form under conditions of seabreese or onshore stadient flow which can limit the vertical mixing depth of the plume. During certain times of the year when offshore water temperatures are relatively low, a cool and stable air mass can form over the cold water surface.

Duting an onshore flow, this cool and stable marine air can be heated from below by a warmer land surface and become unstable in the lower levels.

The layer of unstable air beneath the stable marine air is known as the TIBL and tends to increase in depth with 6

4 i

i inland distance.

For rolesses occurring within the TIBL, the material is

,l l

trapped within the TIBL.

This lid will limit the mixing volume to a greater extent than the average mixing depth for the area around the site and can result in higher ground level concentrations.

The following criteria were established for the formation of TIBL4:

TIBLs were assumed to occur only during the time of year when the

[

land water temperature difference was assumed suitable for TIBL formation. A TIBL season from April through September was assumed 1

appropriate for the Seabrook site.

TIBLs can occur only during daytime when there is sufficient solar intensity to generate a TIBL.

Consequently. TIBL occurrence was limited to between the hours of 08:00 and 18:00.

t The wind direction must be onshore with an overwater fetch sufficiently lon5 to stabilize et marine air mass.

Consequently.

TIBL occurrence was limited to time periods where the wind direction was from the northeast clockwise to south southeast sectors.

The wind spesd must be in an appropriate range. Too low a wind speed will not support a TIBL; too high a wind speed will result in e

generating mechanical turbulence which will overcome any thermal effects resulting in a TIBL.

Consequently TIBL occurrence was limited to time periods where wind speeds were between 2 and 10 4

m/sec.

(Note that the check on wind speed for the identification of TIBLs was applied to the data in the hourly meteorological file, not to the group average wind speed values).

Solar radiation sust be sufficiently strong since it is the heating of the land which causes the development of a TIBL.

Consequently, TIBL occurrence was limited to time periods when a minimum of 0.35 langley / min vers recorded.

7

A separate joint frequency distribution f,(1.j,k) representing the number of observations of stability class 1, wind speed group j, and wind direction sector k during TIBL conditions was compiled.

$1nce one of the parameters needed in TIBL analysis is the intensity of solar radiation for determining TIBL hei&ht, average solar radiation values were compiled for each array position in the f,(i.j,k) joint frequency distribution.

2.2 Diffusion and Danonition Facter Avermana Average diffusion and deposition factors for each receptor location were I

determined as follows:

I E(k,x)

(C(x)/f ]

( ( f(i,j,k) f,(i j,k))

• DF(i.j,k',x) )

=

g 1,j

{

( f,(1,j,k)

• DF,(i.j,k,x))

+ (C(x)/f ]

g 1.j l

where:

E(k,x) average diffusion factor of interest (e.g., undepleted CHI /Q, depleted Cha/Q, D/Q, or gamma CHI /Q) for receptor located at in directional sector k at downwind distance x C(x) recirculatica correction factor for downwind distance x total number of observations in the joint frequency f

=

e distribution f(1.j,k) number of observations in the joint frequency distribution l

f(i.j,k) with stability class 1, wind speed group j, and wind direction sector k (TIBL and non.TIBL conditions) number of observations in the joint frequency distribution I

f,(i.j,k)

=

with stability class 1, wind speed group j, and wind 8

i

'i 1

j direction sector k (TIBL conditions only) diffusion factor of interest in directional sector k at i

Dr(i,j,k,x) downwind distance x in directional sector k for stability L

class i and wind speed group j during non TIBL conditions diffusion factor of interest at downwind distance x in DT,(i.j,k,x) directional sector k for stability class i and wind speed group j during TIBL conditions The fundamental equations used to determine the diffusion f actors DT(i.j,k,x) and DT,(i.j,k,x) are described in the subsections which follow.

A description of the recirculation correction factors C(x) is provided in Subsection 2.3.9.

I 2.3 Diffusion and Danonition raeter Medala l

l 2.3.1 Undanlated CHI /O The equation used to determine undepleted diffusion factors 3

CHI /Qu(i j,k,x) (sec/m ) in direction sector k at a downwind distance x for stability class i and wind speed class j was as follows:

E (1,j)

• CHI /Qug(i.j,k,x) l CHI /Qu(i.j,k,x) g (1.E (i.j)) *. CHI /Que(1,j,k,x)

+

g where the subscripts "g" and "a" stand for " ground. node" and " elevated mode" releases, and E (i.j) is the plume entrainment coefficient.

The. ground. mode g

and elevated. node undepleted diffusion factors CHI /Qu g( i. j, k, x) and CHI /Que(i.j,k,x) were defined as follows:

2,032 CHI /Qug(i.j,k,x) u (1,j )*E,(1,x)*x g

9

5 exp - ([21,5*J*L(1,j,k,x)/I,(1,x))2 0

2.032 CHI /Que(i j,k,x) 5

{ exp - ((2).0.S*h,(i j,k,x)/a (1,x) + [2)0.5*J*L(1,j,k,x)/a (1,x))2 g

g s..,

where:

downwind distance (a) from the release point x

group average ground level wind speed (a/sec) Ior stability u (i j) g class i and wind speed group j group average elevated wind speed (m/sec) for stability l

u,(i.j )

class i and wind speed group j (representative of conditions at the Primary Vent Stack release height) vertical plume standard deviation (a) at downwind distance a,(1,x) x and stability class i vertical plume standard deviation (a) at downwind distance I (i,x) g x and stability class i corrected for building wake effects effective plume hei ht above ground (a) as a function of h,(i j,k,x) 5 stability class i and wind speed class j in direction sector k at a downwind distance x mixing layer depth (a) as a function of stability class i L(i.j,k,x) and wind speed class j in direction sector k at a downwind l

distance x i

The generation of the group average wind speeds u (L'd)

""d "*(i'd) ""*

S 10

~, -

discussed in Section 2.1.2.

Details on the definitions of the remaining para:teters ar* Siven in the subsections that follow.

2. 3. 't Deelated CMT /O The equation used to determine depleted diffusion factors CHI /Q (i j,k,x) d 3

(sec/m ) for downwind distance x in direction sector k for stability class i and wind speed group j was as follows:

CHI /Q (1,j,k,x)

E (i.j)

• CHI /Qug(i j,k,x)

• D (x)

=

d i

g g

(1 E (i.j)]

• CHI /Que(i j,k)

• D (1.j,k,x)

+

t i

where D (x) and D,(1,j,k,x) were the dry depletion factors for ground. node and g

elevated modo portions of the plume, respectively, for downwind distance x in direction sector k for stability class i and wind speed group j.,

'na dry depletion factors O (x) and D,(i.j,k,x) used were based on the g

dry depletion factors presented in Figures 2 through 5 of Regulatory cuide 1.111 as represented by analytical expressions provided in the XOqD0Q computer code. (Regulatory Guide 1.111 Tigures 2 through 5 repressnt depletion factors for release heights of 0 m, 30 m, 60 m, and 100 m, respectively.)

A description of the procedure employed for determining the appropriate depletion correction factors D (x) and D,(i.j,k,x) from Regulatory Guide 1.111 5

Tigures 2 through 5 fo11cws.

The ground mode dry deposition correction factors D (*) "*** * "P"**d **

E the downwind distance of interesc x using a stability independent analytical expression corresponding to the single curve in Figure 2 of Regulatory Guide 1.111.

I The elevated aode dry deposition correction factors D,(i j,k,x) were computed at downwind distance x in direction sector k for stability class i l

and wind speed group j using a modified effective plume hei ht h,'(1,j,k,x)

{

i 11 i

I i

i l

defined as:

(h, + hpr(i j,x) c(i.j))

0.5*h (k,x) h,'(i.j k,x)

=

g where the parameters stack height h,, plume rise hpr(i,j,x),

downwash correction factor c(i.j), and maximum terrain height h (k,x) are discussed in g

Subsection 2.3.7.

The above expression represents the use of an average terrain height between the release point and the receptor. This expression was used with the limiting conditions that 0 m s h,'(i j,k,x) s 100 m.

Dry depletion correction factors for three different plume heights h were computed for the downwind distance of interest x using the stability dependent analytical expressions for rigures 2 through 5 of Regulatory Guide 1.111 as follows:

I 0, 30, and 60 m if h,'(i j,k,x) $ 30 m, h

30, 60, and 100 m if h,'(i.j,k,x) > 30 m.

h The three computed depletion correction factors were then converted to logarithms and subjected to parabolic interpolation for computation of the correct factor D (f j,k,x) at the desired height h,' (i.j,k,x).

Due to the limiting condition that h,' (i.j,k,x) s 100 m, extrapolation of the data to effective plume heights greater than 100 m was not allowed.

2.3.3 D/.Q 2

The ' equation used to determine deposition factors D/Q(i.j,k,x) (1/m ) in direction sector k at dowr. wind distance x for atmospheric stability class i and wind speed group j was as follows:

8- * (E (1,j)*P (x) + (1.E (i j)}*P,(1,j,k,x))

D/Q(i.j,k,x)

=

. g g

g w*x l

1 12

-#e-i+--2 v

~

y

,,v-,

. ~,

-w.ew-e.e----e-e-.c.-e

-w se T

w

4 I

1 are the relative deposition rates (1/m) for

]

where P (x) and P,(1,j,k,x) g i

ground mode and elevated. node portions of the plume, respectively, for downwind distance x in direction sector k for stability class i and wind speed group j.

The relative deposition rates P (x) and P,(i j,k,x) used were based g

1 I

on the relative deposition rates presented in Figures 6 through 9 of Regulatory Guide 1.111 as represented by analytical expressions provf.ded in i

che X0QD0Q computer code. (Regulatory Guide 1.111 Figures 6 through 9 j

represent relative deposition rates for release heights of 0 m, 30 m, 60 m, j

and 100 m,

respectively.)

The procedure employed for datermining the l

i appropriate relative deposition rates F (x) and P,(1,j,k,x) from Regulatory g

Guide 1.111 Figures 6 through 9 was similar to the procedure used to determine the appropriate dry deposition factors D (x) and D,(1,j,k,x) from Regulatory g

Cuide 1.111 Figures 2 through 5 as described in Section 2.3.2.

l 2.3.4 C==== CHI /0 I

were generated for downwind l

Canna diffusion factors CHI /g(i.j,k,x) i distance x in direction sector k for stability class i and wind speed group j t

I using the following expression:

1 f

E(r)

• A(r)

• CHI /Q (i.j,k,r,x) 7 r

l CHI /Q,(1,j,k,x)

{E(r)*A(r) r i

Q'(n)

• A(r.n) n A(r)

=

Q'(n) n 13-i i

l l

t I

where:

1 release rate (e.g., C1/yr) of nuclide n (used to indicate the

(

Q'(n) l relative concentration of nuclide n in the plume) median energy level (Mev) of gamma photon energy group r E(r) i photon yield (photo / dis) of gamma ray photons in energy group r A(r.n) i due to the decay of nuclide n in the plume photon yield (photo / dis) of gamma ray photons in energy group r A(r)

=

due to the decay of all nuclides in the plume (used to indicate the relative abundance of energy group r photons in the plume)

The plume nuclidermixture was derived from the estimates of annual noble gas releases sa presented in section 3.5 of the seabrook 'itation Environmental l

Operating License Stage (ER.0LS ).

These annual isotopic release Report rates (C1/yr) are provided in Exhibit 1.

A table of isotope. dependent photon production rates for 16 different energy groups was then used along with the plume's estimated nuclide sixture to determine the relative abundance A(r) of I

l each energy group's photons in the plume.

The resulting 16 energy group spectrum was then reduced to an eight group energy spectrue for the purposes of calculating the energy dependent gamma diffusion factor CHI /Q (i,j,k,r,x).

y The energy d* pendent gamma diffusion factors CHI /Q,(i.j,k, r,x) were determined as follows:

e E (1,j)

• CHI /Q7s(i.j,k, r,x)

CHI /Q (i j,k,r,x) g 7

(1 E (i.j)]

• CHI /Q,,(i.j,k,r,x)

+

where the ground noda and elevated. node energy dependent gasmsa diffusion factors CHI /Q7s(i.j,k,r,x) and CHI /Q,(i.j,k,r,x) were defined as:

y 2

• y,(r) * (I1g(1,r,x) + K(r)*I2g(i*)I CHI /Q,g(i.j,k,r,x)

(wjo.5

• u (1,j)

• x * (w/8) g 14 a

5 exp - ([2]0.5*J*L(1,j,k,x)/I (1,x))2 g

2

• y,(r) * [I,(i.j,k, r,x) + K(r)*1 (1,j,k, r, x))

t 2

CHI /Q,,(1.j,k, r x)

[wlo.5

• u,(1,j)

• x * [r/8)

• exp ([2].0.5*h,(i j,k,x)/a (i,x))

g 5

j

{ exp

([2].0.5*h,(i j,k,x)/a (i,x) + [2]0.5*J*L(i j,k,x)/a (1,x))2 g

g s..s where y,(r) is the linear energy absorption coefficient for sir (1/a) at energy E(r) and K(r) is the buildup factor for air defined as [p(r).

u,(r)]/u,(r) where g(r) is the linear attenuation coefficient for air (1/a) at energy E(r).

(

Paraesters Ig (1,r,x), 12g(i' #'*)' Ile(1,j,k,r,x), and 12e(l'3'N'#'X) ***

g integrals defined by Healy and Baker in Section 7 5.2.5 in Meteorology and Atomic Energy - 1968 (Reference 4).

These integrals account for the dispersion of the plume and are functions of vertical plume standard deviation

('z f'T I and 1 lg 2g3 E f** Ile

""d 12e),

effective P ume hei ht h, and l

5 s

photon energy E(r).

Further details on the derivation of the gamma diffusion factor and the calculation of the It and 12 intervals can be found in References 1 and 6.

2.3.$

Plu== Standard Deviatiana and Ruildine Valem Effaata The algorithms used to determine vertical plume standard deviation a (1,x) were the same as those utilized by computer code X0QD0Q for non desert z

15

conditions.

l Tor ground mode portion of any release, consideration was also given to i

additional dispersion of the effluent plume within the vaka causad by the

{

buildings adjacent to the release point.

In such cases, use was made of an l

adjusted vertical standard deviation I (1,x) defined as:

g i

(a (i.x)2

+ 0.5*h /*l

• l I (i.x) b g

l where h is the height of the building causing additional dispersion. A value b

i of 23.8 m was used representing the Heater Bay and Control Building roof heights. The maximum value of I (1,x) was restricted by the condition:

l 1

I (1,x) $

(3]O.S.,g(g,,)

g i

1 1

2.1.6 Entrainment i

According to Regulatory Guide 1.111, effluents can be considered to be I

ground. mode releases (E (i.j) - 1), elevated mode releases (E (i.j) = 0), or g

g mixed mode releases (0 < E (i j) < 1) depending on: (a) the elevation of the g

release point relative to the height of adjacent solid structures, and (b) the effluent vertical exit velocity relative to the speed of the prevailing wind l

at the height of release.

Releases from the ground level release pathway were assumed to occur below the tops of adjacent buildings.

Conseguently, E (i,j) - 1 for ground-g level releases.

Primary Vent Stack releases occur at a height of approximately 3.4 m above the height of the containment snructure, the highest building on site.

Consequently, Primary Vent Stack releases qualified as a mixed. node release pathway based on Regulacory Guide 1.111 criteria. The entrainment coefficient for Primary Vent Stack releases was therefore defined as follows:

i 16 i

l l

l l

l 1.0 vhen V,/u,(1,j) s 1.0 E (i.j) g

2. 5 8

1. 5 8 V,/u,(i.j )

when 1.0 < V,/u,(i,j) $ 1.5 E (i.j) g 0.30 0.06 V,/u,(i j )

when 1.5 < V,/u,(i.j) s 5.0 E (i,j) g l

0.0 when 5.0 < V,/u,(i.j)

E (1,j) g l

where V, is the Prisary Vent Stack effluent exit velocity.

An exit velocity i

of 12.9 m/sec (representing a flow rate of 272,665 cfa) was used to represent N*

1 o

l I

2.3.7 Ef fec tiva P1"== Hainht Ground level releases.nd the ground modo portion of the Primary Vent Stack releases were assumed to have effective plume he18 ts equal to zero.

In h

l accordance with Regulatory Guide 1.111, the effective plume he}ght for the elevated portion of Primary Vent Stack release was defined as:

c(i.j) h (k,x)

+ hpr(1, j, x) h,(1,j,k, x) h, g

where:

I effective plume height (a above receptor grade) at distance h,(i.j,k,x) l x in downwind sector k for stability class i and wind speed e

group j Primary Vent Stack height (57.9 a above plant grade) h, l

hpr(iej,X) = plume rise above the release point (a) at distance x for stability class i and wind speed group j h (k,x) - maximum terrain height (a above plant grade) between the g

release point and the receptor located at downwind distance x in direction sector k [hg20) c(i.j) - downwash correction factor (a) for low relative exit velocity as a function of stability class i and wind speed group j 17

.r

-,e..

y

l

?

i The downvash correction factor c(i.j) is defined as:

i 3*(1. 5 W,/u,(i.j )]*d when V,/u,(1, j ) < 1. 5 c(i.j) 0 when V,/u,(1,j ) ;t 1.5 c(i.j) where d is the effective inside diameter of the Primary Vent Stack (3.57 m).

Only non buoyant plumes were assumed to emanate from the Primary Vent l

Stack. Consequently, the momentua jet equations adopted from the X0QD0Q computer code were utilized as outlined below to determine plume rise hpr' l

For neutral and unstable conditions, plume rise was computed from the i

following two equations:

l'"

• IV /"e(l'd)) 667 * (x/d)0.333

• d hpr(l'd'*)

o I

hpr(i'd) 3

• IW /"e(i'd)I

• d o

and the lesser (more conservative) value used.

For stable conditions, the results of the previous two equations were compared with the results from the following two equations:

4 * (F,/S,(i)]0.25 hpr(i.j)

=

1.5 * [F,/u,(1.j))0.333, g (i).0.167 hpr(i.j)

=

a and the smallest valua of h was used.

In the last two equations. F,is the pr momentum flux parameter defined as:

(W,*d/2)2 F,

=

and 5,(1) is the restoring acceleration per unit vertical displacement for adiabatic action in the atmosphere (sec'2).

In line with the X0QD0Q computer code, 5,(i) is defined as 8. 7 x 10*' for E stability, 1.75 x 10*3 for F 18

-I-

stability, and 2.45 x 10*3 for C stability.

2.3.8 Mixin Deeths Vertical diffusion of the plume can be inhibited by the existence of a stable atmospheric layer (an elevated inversion) aloft.

The rate of vertical mixing is reduced in such cases and the stable layer can be considered as an effective lid on vertical transport of pollutants.

For the determination of diffusion factors during non.TIBL conditions, the mixing layer height L(i.j,k,x) was assigned a value of 900 m based on the average of the mean annual morning and mean annual af ternoon mixing layer heights for the Seabrook site region as reported by Holzworth (Reference 7).

For TIBL conditions, the mixing layer height L(i.j,k,x) was assigned a i

value equal to the height of the TIBL as predicted by the following relationship:

heib1(i.j,k,x)

L(i j,k,x) 1.79 ((x+x,(k))

• SR(i.j,k))0.5 + g3,33 where heib1(i.j,k, x) is the height (a) of the TIBL layer above ground in direction sector k at distance x for stability class i and wind speed group j, x,(k) is the upwind distance from the shoreline to the release point whenever l

the wind is blowing towards direction sector k, and SR(i.j,k) is the average solar radiation intensity (langley / min) for stability class i, wind speed l

group j, and direction sector k.

was derived from a field study This relationship for heib1(i j,k,x) conducted by Lebeis and Toltaan at the Forst 2 Nuclear Power Plar.t site on the western shore of -Ida Erie (References 8 and 9).

14beis and Foltaan tested several different parameters to account for observed TIBL height variation (including overland fetch, land / water temperature differences, solar i

19

1 1

l l

radiation, wind direction, wind direction standard deviation, wind speed, i

l frictional velocity, and ovetvater vertical temperature gradient) and found 1

l that overland fetch and solar radiation, were the top ranked parameters.

Support for an equation of this form can also be found in NUREC/CR.3542 (Reference 10).

Note that the above equation defines a TIBL height of 83.33 m at the coastline, due to the heating of the onshore flow by warmer water near the I

coastline.

Consequently, all releases (including those from the 57.9 m high Primary Vent Stack) are assumed to occur beneath the TIBL.

The plume is not i

allowed to punch through the TIBL even though the plume rise equations may i

predict so.

Also note that TIBiJ are assume to follow the terrain and are not

{

allowed to exceed the 900 m mixing layer height discussed previously.

2.3.9 Racirculation cerrcetien Factern In order to consider the effects of spacial and temporal variations in airflow such as recirculation which can occur during prolonged periods of atmospheric stagnation and during the onset and decay of seabreezes, recirculation correction factors C(x) were applied in defining each type of i

diffusion factor as a function of downwind distance x.

The recirculation l

l correction factors used were based on the 'open terrain' correction factors published in Rev. O to Regulatory cuide 1.111 (Reference 11) (See Exhibit 2).

These recirculation correction factors are compatible with site specific factors generated at other coastal sites (e.g., perry and St. Lucie No. 2).

I 20

3.0 REEMTINc Dirrvst0N MD _ DEPOSITION FACTORE Diffusion and deposition factors for the ground. level and Primary Vent Stack release pathways were calculated fer the Site Boundary and two onsite locations: 'The Rocks' and the Ed' Center.

In order to determina the maximum offsite diffusion and deposition factors for the mixed node Primary vent Stack release pathway, diffusion and deposition factors were also calculated at 0.25 mile increments from the stack starting beyond the site boundary out to five miles.

The ft.11owing criteria were used to determine receptor downwind distances and dire' tion sectors:

1.

Ground Level Release Pathway

'The Rocks" and Ed Concer: The minimum distances from the nearest 1

point on the Administration Building / Turbine Building complex to

'The Rocks' and Ed Center as measured from a site aerial photograph were used.

Sice Soundary: For the south southeast clockwise to north downwind sectors, the minimum distances from the nearest point on the Administration Building / Turbine Building complex to the site boundary within a 45. degree sector centered on the cespass direction of interest as measured from Seabrook Station FSAR Figure 2.14A were used (see Exhibit 3).

The site boundary for the remaining six sectors, north northeast clockwise to i

southeas t, is located over marsh. Consequently, for these remaining six sectors, the minimum distances from the center of the Unit 1 containment Building ?e the nearest dry land beyond the site boundary as asasured fram a site aerial photograph were i

used.

21

2.

Primary Vent Stack Release Fathway

'The-Rocks' and Ed Concer: The minimum distances from the center of the Unit 1 Containment Building to 'The Rocks' and Ed Center 1

as measured from a site aerial photograph were used.

Sice Boundary: For the south southeast clockwise to north downwind sectors, the minimum distances from the center of the Unit 1 Containment Building to the site boundary within a 45-j degree sector centered on the cospass' direction of interest as measured from Seabrook Station FSAR Figure 2.1 4A were used (see Exhibit 4).

The site boundary for the remaining six-sectors,-

i north northeast clockwise.to southeast..is locatt3 over marsh.-

Consequently, for these remaining six sectors, the nipinum distances from the center of the Unit 1 Containment Building to the nearest dry land beyond the site boundary as measured from a site aerial photograph were used.

A list of the resulting receptor coordinates (downwind distance and sector) is provided in Exhibit 5.

Six year average diffusion and deposition factors were ; talculated for e

'The Rocks' and the Ed Center - during the tin.e per;iod January 1980 through December 1983 and January 1987 throu6h December 1988.

For the site boundary

(

and offsite receptors, both six year growing season (April through September) and year round (January through December) diffusion and deposition factors -

were generated, with the hit er of the two chosen to represent the site h

boundary and offsite receptor diffusion and deposition factors.

The resulting diffusion and deposition factors for the two onsite-receptors ('The Rocks' and Ed Center) and the location and resulting

^

diffusion and deposition factors for the highest. site boundary /offsite receptors are provided in Table 1 for both the ground level and.the Primary 22

h Vent Stack release pathways.

These are the diffusion and deposition values incorporated into the Seabrook Station offsite Dose Calculation Manual.

r i

I t

l l

l t

23

~~

I l

4.0 REFERENCES

i 1.

JN Hamavi. "AEOLUS.2 - Technical Description" Entsch Engineering P100 R13.A datsd March 1988.

2.

US Nuclear' Regulatory Commission, " Methods for Estimating Atmospheric Transport and Dispersion of Caseous Effluents in Routine Releases from Light Water Cooled Reactors", Regulatory Guide 1.111, Rev.1, dated July 1977.

3.

JF Sagendorf, JT Coll, and VF Sandusky, "X0QD0Q: Computer Program for the i

Meteorological Evaluation of Routine Effluent Releases at Nuclear Power Stations", NUREC/CR 2919, dated September 1982.

4 JV Healy and RE Baker, " Radioactive Cloud dose Calculations", Chapter 7 of Macaorolony and Atomie Knarry - 1968, DH Slade. Editor, US Atomic.

Energy Commission, dated July 1968.

5.

US Nuclear Regulatory Commission, "Onsite Meteorological Programs".,

Regulatory Guide 1.23 (Safety Guide 23), Rev. O, dated February 1972.

f0#

6.

JN Hamavi, "A Method for Computer the Gamma Dose' Integrals It and I2 the Finite Cloud Sect 1r. Average Model", Yankee Atomic Electric Report YAEC 1105, dated Maren 1975.

CC Holzworth, " Mixing Hei hts,' Wind Speeds, and Potential for Urban Air 7.

5 Pollution throughout the Continuous United States" US EPA Office of Air Programs PB-207 103, dated January 1972.

8.

MP Lebeis and RA Foltaan, " Development of a Site Specific Empirical l

Equation to Fatinate TIBL He1 hts at the Ferai 2 Power Plant Site", Paper 5

85 25A.3 presented at the 78th Annual Meeting of the Air Pollution-a control Association, Detroit, Michigan, Juna 16 21, 1985.

9.

MP Lebeis, "Use of Monostatic Acoustic Radars to Determine Thermal Internal Boundary Layer Hei hts Along the Western Lake-Erie Shoreline",

5 24

t Paper 85 258.4 presented at the 78th Annual Meeting of the Air Pollution-Control Association, Detroit, Michigan, June 16 21, 1985.

10. WA Lyons, CS Keen, and JA Schuh, "Modeling Mesoscale Diffusion and i

Transport Processes for Release's within Coastal Zones During u nd/ Sea-Breezes", NUREC/CR.3542, dated December 1983.

11.

US Nuclear Regulatory Commission, "Mathods for Estimating Atmospheric Transport and Dispersion of Caseous Effluents in Routine Releases from Light Water Cooled Reactors", Regulatory Guide 1.111, Rev. O, dated March 1976.

I i

)

)

i F

25 a

.. -. ~.. -.-_- -..

i TABLE 1 Saabrook Station ODCM Atmoscharie Diffusion and Danesition Factors A. Ground Level Release Pathway Raean ear Diffusion Factor The Rocka Ed.Cantar Sita Endv(*)

'I 3

1.6 x 10*'

2.3 x 10 5 t,o x to 5-Undeplaced CHI /Q, sec/m (244a ENE)

(406a SW)

(823a W) 3 1.5 x 10*'

2.1 x 10 5 9,4 x to 6 Deplaced CHI /Q, sec/m (244a EFE)

(406a SW)

(823a W) f I

D/Q, m*2 5.1 x 10*7 1.0 x 10*7' 5.1 x 10 8

'l (244m ENE)

(406a SV)

(8A3m W) 3 2.6 x 10 5 5.3 x 10 6 3,4 x to 6 Gamma CHI /Q, sec/m (244a ERE)

(406a SW)

(823a W) i

2. Primary Vent Stack Release Pathway l

Raeant or Diffusion Factor The Rocka Ed Cantar

-Sita Endv(*)-

3 1.7 x 10-5 1.6 x 10 6 8.2 x 10*7 l

Undepleted CHI /Q, sec/m (244a ENE)

(488a SW)

(974m W) 3 1.6 x 10-5 1.5 x 10-6 7.5 x 10*7' Depleted CHI /Q, sec/m l

(244a ENE)

(488a.SW)

(974a W)

D/Q, a 2 1.1 x 10*7 2.7 x 10*3 1.5 x 10 8-(244a ENE)

(488a SW)

(914a NW) 3 5.0 x 10 6 1.1 x 10 6 8.5 x'10*7 Gamma CHI /Q, sec/m (244a ENE).

(488a SW)

.(974a W)

(*)The highest site boundary diffusion and deposition factors occurred during the Apr Sep growing season. Note that for the Primary Vent Stack Release Pathway, none of the offsite receptor diffusion and deposition factors (located at 0.25 mile increments beyond the.si.e boundary) exceeded the site boundary diffusion and deposition factors.

l 26

?

-,_,._,.._.m..,

EXHIBIT 1 l

l Preiaeted Annual Noble Can Effluent Releases (Ci/vri l

Ground Level Primary Vent Stack Radionuelida Relaana Pathway Relaama Pathway 1

Ar 41 O(*)

2.5 x 10

(

i Kr 83M 0(*)

O(a) 0 1

Kr 85M 1.0 x 10 1.0 x 10 2

I Kr 85 0(*)

2.6 x 10 0

[

Kr 87 O(*)

3.0'x 10 0

1 Kr 88 2.0 x 10 1.6 x 10 Kr 89 O(a)

O(*)

1 Xe 131M 0(*)

2.3 x 10 1

Xe 133M O(a) 1.6 x 10 1

2 l

Xe 133 2.1 x 10 9.9 x 10

~

Xe 135M 0(*)

O(*)

0 1

Xe 135 3.0 x 10 3.8 x 10 -

Xe 137 O(a) 0(*)

0 Xe 138 0(*)

1.0 x'10

(*)Less'than 1.0 Ci/yr.

Reference:

Seabrook Station ER OLS Table 3.5 10 4

i 27 l

l

t I

l t

EXHIBIT 2-l l

Recalaterv Guide 1.111 (Rev. 0)

Q g _ Terrain Recirculation correction Factors

(

L i

i 10

..~

i i

f h

h h h e 4 f h

h I

~

t i

t i i e I e I

l l

l l l ll l !

l

~~

~

l l

l l liii l

i 4

l l

I I

N A

8 i

i A

g 3.,

.2 4

,.i I

l l l

~

i i

i-l v

I l l

'll T

I I

i l

l l I.

,r

'L I

l S

4 i

0.1 0.1 1.0 10 100 DISTANCE (Kit.QMETERS) u 28 1

-r l'

EXHIBIT 3 I

l Site Man Showine Locations of the i

t l

Administration Buildinn/ Turbine Buildine Camelax l

l and the site Roundarv l

t w,.....,,-

......u n.. :

9 m

s A,.i; -

'. x 1

5

-y e

l j

gn,g ---^

y.

,.. g j

'a.

( a }. : # U "

s1 p

}

},4 I

47 -

~

.. -t p

u L

<.: A.:. j.:

1 i

'.]'./l?I #f T' YQ 1

,g i., *.Uf"'g.{ g,.'

h.'

.erW7?.

?.;..g p=

l

?

&* "=L,%:(y,,

ie g

g<

g-k. E,

bj'y ESE

' S" N

[

l i

,.(

a.;!

d y

a a

s

.. ', ;3:

./

. le K

vy.

' n

'.'{.(ie f.

s afsE f,}s 4,. -

rr

.ts,.

. a s '

2 p.~.

u...

sse-

'g S

2,

~]

y

..--m (x 4~

= _ = =...

-- m. -

. !!,'Af.,

ev.uciew a e =,A-o

- w =

ufi

...s SEASA008t ifAT100.

• Wenf1,8 4 3 740sALSAfffY A8eALY185 AG 0AT

)

1. 4ynt a.i.4a s

29 4

_.u._.-

..a,

.... -.. ~ -...

EXHIBIT 4~

Site Man Showina Locations of the l

Primary Vent Stack and the Site Boundarv-N I

a...... e - i m.

w.:

.it

.. i l

/

i

)

HW g

' ' *. i....

4

[

NE

5p.;.'l'-..

N.-

1.-

l s

5 k-

[

ENE

.)

r ='-

i m_N

• C 4

7, s,sh -

? - __,;.3T ~ ~ # -

- /"

l w

/

e w

w =~-_ _ > ~ ~ - -

.t 1I W f.%,

'===

i

?,'

/

'"p l

D..- t

%E J. 56

& L\\

l l

N l

.j/'E$E b

WSW

/

r' ' - '..

./

.,4 q

t

/

2 l>

Ab. -

r, n.

,'v,

.(.

!l.,.

p:(

,4:;;

d a

m,

,$w

M.h kll 5

• f.. y':; j$ ',

/ \\

t.

i c.

55E

/.

i g "====

1

= gggs y

s

.s.

= = = = = =..

c.

= =...,

N - :mm...

\\I1

'\\

. 'f.'Al.i.

pusucsaavice cowaav op newmaurumas sitt sounoaadt -

$4Aga00st STAfl0N Usuft i 4 3 '

N""# U "

l

1. icuat 2 n 4a i

4 i

).

30 f

3

EXHIBIT 5

{

l Racaneer locations r

Ground Level Primary Vent Stack Receetor Ralamaa Pathway

@ama Pathway The Rocks 244a ENE 244a NE 204a ENE Ed Center 406a SW 48Sa SW Site Bndy 780s N 914e N 2926a NN (a) 2926,3 NN (*)'

2276sNE{*)

2276u NE{*(*))-

I 2276a}E)(*)

2276a.qE 2438a E *{")

2438a E *) }

2276a ES 2276mES{')-

2276a SE *)

2276m SE 952s SSE-914e SSE 968a S 930s-S 968a SSW 990s SSW-I 941m SW 1022m.SW 871m WSW 1022m WSW i

823a W 974a W i

775m WNU 930s WW 775m NW 914a NW-775a NNW 914e NNW l

2 Offsite None (b) i h

(*)The site boundary in the NNE through SE sectors is-located over marsh I

(e.g., water).

Consequently, the site boundary distances for these six.

direction sectors represent the nearest dry land beyond the site boundary.

(b)Because the maximum offsite dispersion and deposition factors for the Primary Vent Stack Release Pathway may occur beyond the site boundary, diffusion and deposition factors were determined' at 0.25 mile increments from the stack starting beyond the site boundary out to five miles.

4 31 q

m m.

~

-ar - y

_,.r

-