If the wind speed is less than the critical speed, the plume rise is calculated using Petersen and Lavdas’
Eq. A-14)

Ah =4.0F) 4875. (4.28)

Otherwise, the rise is calculated using Petersen and Lavdas’ Eq. A-13

F 13
Ah =2.6 2 : (4.29)
u(h,)S

4.5.3 Effective Release Height

If the isolated stack option is selected in STDose, the plume height is equal to an effective release height.
The effective release height has three components: stack height, plume rise, and stack down wash. It is
calculated as

h,=h,+Ah+Ah, , (4.30)

where h, is the stack height and Ah, is the stack down wash. The stack height is entered by the user, and
the calculation of plume rise is previously described. Stack down wash occurs when the stack exit
velocity is less than or approximately the same magnitude as the stack-height wind speed. It is an
aerodynamic effect that reduces the stack height by up to three stack diameters. Down wash is calculated

in Petersen and Lavdas’ Eq. A-1 as
Ww
Ah, sal f -1s] (4.31)

when the ratio between the exit velocity and stack-height wind speed is less than 1.5. Otherwise, the
down wash is set to 0.0.

If the isolated stack option is not selected, the release is treated as if it occurs from the surface of the
building. A default release height of 10 m is assumed unless another, greater release height is entered.

4.6 DEPOSITION

RASCAL 3.0 calculates deposition for iodine and particles using the dry and wet deposition models used
in MESORAD (Scherpelz, et al. 1986; Ramsdell, et al. 1988) and earlier versions of RASCAL. The
activity deposited each time step is the product of the total deposition rate and the time-step duration. At
any time, the surface contamination (activity/m?) is the sum of the activity deposited in the current time
step plus previously deposited activity.


on recycled
paper

Federal Recycling Program


2.2.1 Spent Fuel Pool

The spent fuel pool release is based on information from NUREG/CR-6451 (Travis, Davis, and Grove
1997). RASCAL assumes that the fuel in a pool must be uncovered for more than 2 h in order for the fuel
to reach 1200°F, the temperature at which cladding failures are expected. This assumption is based on the
heat-up rate of 30-day-old fuel. Because it does not give credit for heat removal by steam cooling, this
assumption is conservative. No cladding failure or releases are projected if the fuel is uncovered for less
than 2h. After 2 h the fuel is projected to rupture due to internal pressure releasing the “hot gap” fraction
of the fission products in the fuel. Only fuel that has been irradiated within the past year for a PWR or 180
days for a BWR is assumed to be able to reach 1200°F after it is uncovered. This is based on the
observation that one-year-old fuel required 10 hr or more to reach 1200°F. With steam cooling this fuel is
not expected to reach this temperature.

The user enters the number of fuel batches or assemblies that are one, two, and three years old. (No other
fuel ages are allowed.) If the reactor is a PWR, the user enters whether the density of the fuel pool racking
is high or low. The accident conditions that the user enters are the length of time the fuel is uncovered, if
and when the fuel was recovered, and if and when the pool was drained. Because it is assumed that the fuel
is uncovered, there is no fission product reduction due to scrubbing in the pool.

Fuel release fractions are shown in Table 2.6 (Travis, Davis, and Grove 1997) by STCP category. RASCAL
determines which fuel release fractions to use based on conditions in the pool, the fuel racking, and the fuel
age. If the pool is never totally drained, only fuel that has been in storage for one year or less is considered
to be damaged and the release fractions used are those for a hot-gap release. In a PWR with high-density
pool racking or in a BWR, if the pool is totally drained for at least 2 h all fuel is damaged and the release
fractions used are for a fire release. In a PWR with low-density pool racking if the pool is totally drained
for at least 2 h a fire release occurs in all fuel that has been in storage for one year or less. Fuel that has
been stored for more than one year is involved in a fire release only if there is at least one batch of fuel that
has been in storage for one year or less. If all fuel is older than one year, then hot-gap release fractions are
used for all the fuel.

A reduction factor of 0.01 is applied to non-noble gas fission products if the user specifies that the release
from the building will occur through a filtered vent. The user also specifies the duration of the release and
the percentage release rate.

2.2.2 Fuel Damaged Under Water

The spent fuel damaged under water scenario is based on NUREG/CR-6451 (Travis, Davis, and Grove
1997). Fuel that is mechanically damaged under water is assumed to remain cold but experiences cladding
failure. This results in a cold gap release. All damaged fuel is assumed to have been stored for the same
length of time. A reduction factor of 0.01 is always applied to non-noble gas fission products released from
fuel under water to account for scrubbing in the pool. In addition, a reduction factor of 0.01 is applied

2-14


AVAILABILITY OF REFERENCE MATERIALS
IN NRC PUBLICATIONS

NRC Reference Material

As of November 1999, you may electronically access
NUREG-series publications and other NRC records at
NRC's Public Electronic Reading Room at
www.nrc.gow/NRC/ADAMS/index.html.

Publicly released records include, to name a few,
NUREG-series publications; Federal Register notices;
applicant, licensee, and vendor documents and
correspondence; NRC correspondence and internal
memoranda; bulletins and information notices;
inspection and investigative reports; licensee event
reports; and Commission papers and their
attachments.

NRC publications in the NUREG series, NRC.
regulations, and Title 10, Energy, in the Code of
Federal Regulations may also be purchased from one
of these two sources.
1. The Superintendent of Documents

U.S. Govemment Printing Office

Mail Stop SSOP

Washington, DC 20402-0001

Intemet: bookstore.gpo.gov

Telephone: 202-512-1800

Fax: 202-512-2250
2. The National Technical Information Service

Springfield, VA 22161-0002

www.ntis.gov

1-800-553-6847 or, locally, 703-605-6000

Asingle copy of each NRC draft report for comment is
available free, to the extent of supply, upon written
request as follows:
Address: Office of the Chief Information Officer,
Reproduction and Distribution
Services Section
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
E-mail: DISTRIBUTION@nrc.gov
Facsimile: 301-415-2289

Some publications in the NUREG series that are
posted at NRC's Web site address
www.nre.gov/NRC/NUREGS/indexnum.htm!

are updated periodically and may differ from the last
printed version. Although references to material found
on a Web site bear the date the material was
accessed, the material available on the date cited may
subsequently be removed from the site.

Non-NRC Reference Material

Documents available from public and special technical
libraries include all open literature items, such as
books, journal articles, and transactions, Federal
Register notices, Federal and State legislation, and
congressional reports. Such documents as theses,
dissertations, foreign reports and translations, and
non-NRC conference proceedings may be purchased
from their sponsoring organization.

Copies of industry codes and standards used in a
substantive manner in the NRC regulatory process are
maintained at—

The NRC Technical Library

Two White Flint North

11545 Rockville Pike

Rockville, MD 20852-2738

These standards are available in the library for
reference use by the public. Codes and standards are
usually copyrighted and may be purchased from the
originating organization or, if they are American
National Standards, from—

American National Standards Institute

11 West 42 Street

New York, NY 10036-8002

www.ansi.org

212-642-4900

Legally binding regulatory requirements are stated
only in laws; NRC regulations; licenses, including
technical specifications; or orders, not in
NUREG-series publications. The views expressed
in contractor-prepared publications in this series
are not necessarily those of the NRC.

The NUREG series comprises (1) technical and
administrative reports and books prepared by the
‘staff (NUREG-XXXX) or agency contractors
(NUREG/CR-X00X), (2) proceedings of
conferences (NUREG/CP-XXxXxX), (3) reports
resulting from international agreements
(NUREG/A-XXXX), (4) brochures
(NUREG/BR-XXXxX), and (5) compilations of legal
decisions and orders of the Commission and
Atomic and Safety Licensing Boards and of
Directors’ decisions under Section 2.206 of NRC’s
regulations (NUREG-0750).



APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

3
g & |e
AG 2 |é fle
& a 3 2 a [4
-f oR ole fe Ode TE
S 212 = Ss o|e a
eg ra z |E i Ale |3 |3,/8
ze E|§ 2 |¢ |S life |S S218
Name & 18 2 |é 2 1é 4 lala |2 [22
(gal) ft %ld_|psi |MW(t)
Quad-Cities - Unit 1 IBWR |Mark I T24|N/A 125550] 160000] 0.5] 56] _2511| 22000] 15000|Operational
Quad-Cities - Unit 2 IBWR |Mark I T24(N/A 125550} __160000|_0.5] 56] 2511] 22000} 15000|Operational
Rancho Seco PWR |Large, Dry | 177|N/A 0} 2000000! 0.1] 59] 2772| 22000] 15000|Decommissioned
River Bend - Unit 1 BWR |Mark III 624|N/A 144700} 260000} 0.26] 15] 2894] 22000] 15000|Operational
Salem - Unit 1 PWR |Dry Ambient | 193|/U-Tube 250808} 2600000] 0.1] 47} 3411] 22000} 15000|Operational
Salem - Unit 2 PWR {Dry Ambient | 193}U-Tube 250808] 2600000} 0.1] 47| 3411] 22000/ 15000 Operational
San Onofre - Unit 1 PWR |N/A O|N/A 0} 1400000] 0.5] 47] 1347] 22000] 15000/Decommissioned
San Onofre - Unit 2 PWR {Dry Ambient | 217|/U-Tube 249265] 2300000} 0.3} 60] 3390] 22000] 15000|Operational
San Onofre - Unit 3 PWR |Dry Ambient | 217/U-Tube 249265] 2300000] 0.3] 60} 3390] 22000} 15000/Operational
Seabrook - Unit 1 PWR |Dry Ambient | 193|U-Tube 250808] 2700000} 0.5] 65| 3411] 22000] 15000|Operational
Sequoyah - Unit 1 [PWR |Ice Condenser] 193/U-Tube 250808} 1200000] 0.5] 11} —3411{ 22000} 15000|Operational
Sequoyah - Unit 2 PWR [Ice Condenser} 193|U-Tube 250808] 1200000) 0.5] 11] 3411] 22000} 15000|Operational
Shearon Harris - Unit 1 [PWR [Dry Ambient | 157|U-Tube 204044} 2500000) 0.3| 45] 2775] 22000] 15000|Operational
South Texas Project -
Unit 1 PWR [Dry Ambient | 193]U-Tube 279412] 3300000} 0.3} 56] 3800] 22000] 15000|Operational



where

D'(y) = plume dose rate ,

y = distance from the ground-level projection of the center of the plume,
Cy = finite line correction factor,

N, = number of line sources (36 or 100),

i,j = line source indices,

D’\(y,) = infinite line, line-source dose rate.

The finite-line source correction factor is included in Eq. (4.46) to account for the fact that the plume
does not extend upwind of the release point. A correction factor could be calculated by numerical
integration of a rather complex equation. However, an approximate correction factor of adequate
accuracy for emergency response dose calculations can be calculated using

x

C, =05]1 :
. “@any

> (4.47)

where

x = downwind distance (m) to a point beneath the plume centerline at the intersection of the
plume centerline and a perpendicular line passing through the receptor,

R = distance (m) from the release point to the receptor,

h, = effective release height.

In the case of a ground-level release and a receptor on the plume centerline, the correction factor will be
one. However, generally the correction factor is less than one. For a 0.7 MeV photon, the correction
factor given by Eq. (4.47) corresponds to a receptor at a position approximately 100 m off of the plume
centerline. Doses will be slightly over estimated for receptors that are closer than 100 m and slightly
under estimated for receptors that are farther than 100 m from the centerline.

When the horizontal dispersion parameter exceeds 400 m, TADPLUME shifts from a line-source based,
finite-plume model to an infinite-plane model. The infinite-plane model used by TADPLUME is similar
to the model used by TADPUFF. The differences between the two models are associated with the
calculation of concentrations, not with the cloud-shine calculation. Thus, Eq. (4.43) for TADPUFF
becomes

2

“ 110
} (1+ kpz; exp (—1z,) (4.48)
isl

01 VDF,
PO

T
y GO,

exp) -0
y

for TADPLUME.
Finally, when the vertical extent of the plume is sufficient (6, = 400 m, or a uniformly mixed plume

with a 600 m vertical extent), TADPLUME shifts to a semi-infinite plume, cloud-shine model.
Equation (4.44) for TADPUFF becomes

423


K, =exp(2.3884.0T;" 51.2393) (5.19)

K, =exp(40319.67," 87.1927) . (5.20)

With self association, the effective molecular weight for HF for vapor-phase densities and mole fractions
is greater than the molecular weight of the HF monomer. It is

[Posey MWe, +K Pian, M Wa, +K Pin, M Wain, ]

MWap = (5.21)
Pur
5.2.8 Partial Vapor Pressures of HF
If a condensed phase exists in the HF-H,O system, the vapor pressure of HF is calculated using
‘relationships of the form
Pur =exp(ATy! +B), (5.22)

where the model parameters are a function of the weight fraction of HF in the condensed phase.
Williams (1985) gives estimates of the coefficient values based on a figure supplied by Allied Chemical
(Brian C. Rogers). The differences between partial vapor pressures estimated using the model and the
figure, range from about 1% for weight fractions near 1.0 to a maximum of 5% at weight fractions
below 0.5. If a condensed phase does not exist, the partial vapor pressure of HF is calculated using an
iterative procedure along with estimation of the effective molecular weight.

5.2.9 Partial Vapor Pressure of H,O

As long as UF, continues to exist in the vapor phase, all water entering the plume will be used by the
UF,/H,O reaction to form HF and UO,F,. Under these conditions, the partial vapor pressure in the HF-
H,0 system will be zero. Following conversion of all of the UF,, an initial estimate is made of the H,O
partial vapor pressure from the mass of water in the plume using the ideal gas law. The phase
composition of the HF-H,O system is determined by comparing the sum of the HF partial pressure and
the initial estimate of the HO partial pressure with the total pressure of HF and H,O for an azeotropic
mixture. If the sum is less than the total pressure for the azeotropic mixture, there is no condensation
phase and the initial H,O partial pressure estimate is used. If condensation occurs, an iterative procedure
is used to determine the partial pressure of H,O. The procedure is described in detail by Williams
(1985).

5.2.10 Enthalpy of HF-H,O Vapor Mixtures

The enthalpy of HF-H,O vapor mixtures is given by

5-7


Table 2.2 Nuclear Power Plant Core Inventory and Coolant Concentrations

PWR BWR} PWR BWR
Inventory’| coolant} _coolant4 Inventory*| _coolant’| _ coolant”

Nuclide_ | CivmMwa | Cie Cilg | Nuclide_| Ci/MWiy_| C/MW(D | C/MWOD
Ba-140 | 5.30e+04} _1.30e-08} _4.00e-10]Mo-99 5.30e+04| _6.40e-09] _ 2.00e-09
Ce-144_ | 2.80e+04]  4.00e-09] _3.00e-12[Np-239 | 5.50e+05] 2.20e-09| _ 8.00e-09
Co-58 Of 4.60¢-09] 1.00e-10fRu-103 | 3.70e+04] 7.50e-09]  2.00e-11
Co-60 Ol 5.30e-10] _2.00e-10JRu-106 | 8.00e+03] _9.00e-08] _3.00e-12
Cs-134 | 2.50e+03] _3.70e-11] _3.00e-11]Sb-127 | 2.00e +03 0 ol
Cs-136 | 1.00e+03| _8.70e-10] _2.00e-11]Sb-129 | 1.10e+04 0 0
Cs-137 1.60e+03] _5.30e-11] _8.00e-11]Sr-89 3.10e+04| _1.40e-10] _1.00e-10
H-3 O} _1.00e-06] _1.00e-08]Sr-90 1.20e+03| _1.20e-11| _7.00e-12
1-131 2.80e+04] _2.00e-09[ _ 2.20e-09]Sr-91 3.70e+04| _9.60e-10] _4.00e-09)
1-132 4.00e+04] —6.00e-08] _ 2.20e-08]Tc-99m O| _4.70e-09] — 2.00e-09
1-133 5.70e+04| —2.60e-08] _1.50¢-08|Te-129m | 1.80e+03] 1.90e-10] _4.00e-11
1-134 6.30€+04|  1.00e-06} _4.30e-08]Te-131m | 4.00e+03] _1.50e-09] 1.00e-10
1-135 5.00e+04] 5.50e-08| _2.20e-08]Te-132_ [| 4.00e+04] 1.70e-09] _1.00e-11
Kr-85 1.90e+02] _ 4.30e-07 Xe-131m | 3.30e+02] _7.30e-07 0
Kr-85m_| 8.00e+03] _ 1.60e-07| Ofxe-133_[ 5.70e+04] _2.90e-08 ol
Kr-87 1.60e+04] _ 1.70e-08 O[xe-133m | 2.00e+03| _7.00e-08 0
Kr-88 2.30e+04] _ 1.80e-08) Ofxe-135_ | 1.10e+04| _6.70e-08 dl
La-140__| 5.30e+04]  2.50e-08] _4.00e-10[Xe-138 | 5.70e+04]| _6.10e-08] 0.00e+00)
Mn-54 Of 1.60e-09] _3.50e-11] ¥-91 4.00e+04| 5.20e-12]4.00R-11

“The inventories are from NUREG-1228, Table 2.2 (McKenna and Gitter 1988).

“Coolant concentrations are from ANSI 1999.

where

D, = the current core uncovery duration (h),

Devs = the core uncovery duration (h) at the beginning of core damage state CDS,

Dens = the total duration that core damage state CDS is expected to occur.

In the example given above, Dy is 1.75 h, Dens, is 0.5 h and Dep, is 1.5h. So Fops is (1.75-0.5)/1.5 or

0.833 h.

If the user has entered a time at which the core is recovered, then core damage and release of material
from the core stops, and the core-damage state remains the same.

If the reactor core has never been uncovered, only coolant activity may be released. Note that rapid
increases in the iodine and other fission-product concentrations in the coolant as high as 3 orders of

2-4


where

Avg = cross-sectional area (m°),
Q'ue = UF, release rate (g/s),
Pug = UF, density (g/m*),

u = wind speed at 10m (m/s).

4. There is no diffusion of the UF, plume.
5. Deformation of the UF, control volume is determined by gravitational slumping of the UF,.

6. The rate of change of the UF, control volume width is given by

dW ute -le (Pers Par) y «| , (5.3)
dt Pure

where

Was =UF, control volume width (m),

t = time (s),

k = a slumping constant (dimensionless),
& = gravitational constant (m/s’),

Pa, = density of air (g/m*),

Hyg = thickness of the control volume (m).

7. The slumping constant has a theoretical value of 1.4 but may be given a lower value to account for
surface resistance or to tune the model. A value of 1.3 is used as default in the current version of
the UF, model in RASCAL.

8. Air is entrained into the UF, control volume only through the top. Entrainment through the sides
is negligible because after only a few seconds the area of the top of the volume is much larger than
the area of the sides.

9. The rate of entrainment of air into the UF, control volume is given by

dv
i SW Wag, (5.4)

= air entrainment rate (m’/s),
w, = an entrainment velocity (m/s).



McKenna, T. J., et al. 1996. Response Technical Manual: RTM-96. Vol. 1, Rev. 4, _NUREG/BR-
0150, U.S. Nuclear Regulatory Commission.

Sjoreen A. L., T. J. McKenna, and J. Julius. 1987. Source Term Estimation Using MENU-TACT.
NUREG/CR-4722, U.S. Nuclear Regulatory Commission.

Soffer, L., et al. 1992. Accident Source Terms for Light-Water Nuclear Power Plants, Draft Report for
Comment. NUREG-1465, U.S. Nuclear Regulatory Commission.

Travis, R. J., R. E. Davis, and E. J. Grove. 1997. A Safety and Regulatory Assessment of Generic
BWR and PWR Permanently Shutdown Nuclear Power Plants. NUREG/CR-6451, BNL-NUREG-52498,
U.S. Nuclear Regulatory Commission.

U.S. Nuclear Regulatory Commission (NRC). 1990. Severe Accident Risks: An Assessment for Five
U.S. Nuclear Power Plants. NUREG-1150. U.S. Nuclear Regulatory Commission.

2-21


7 DOSE CALCULATIONS IN FMDOSE

FMDose is designed to compute doses after a radiological emergency has begun. It allows field
measurement data to be used in decision making regarding measures taken to protect the health of the
public and emergency workers. FMDose computes doses, derived intervention levels (DILs), and
emergency-worker turn-back guidance at a single field measurement location. Doses are to people
standing outdoors. Calculational methods are based on the FRMAC Assessment Manual (DOE 1995).
All calculations require the user to enter at least one air or ground concentration and a meter reading.

The dose factors used are not listed in this document. They are available within the RASCAL 3.0
radionuclide help files. The air-submersion and ground-shine dose factors are for effective dose from
Federal Guidance Report No. 12 (EPA 1993). The 50-year committed-effective-dose equivalent and
thyroid inhalation dose factors are from Federal Guidance Report No. 11 (EPA 1991). Four-day bone
marrow, lung, and small-intestine wall inhalation dose factors are for an adult and were computed using
the methods described in the previous reference. The committed effective dose equivalent is a weighted
sum of selected organ doses and is defined in ]CRP Publication 26 (ICRP 1977).

For emergency worker guidance and early-phase doses based on air concentrations, all radionuclide
concentrations are assumed to be constant over the exposure period. All other dose and DIL calculations
include decay and decay-product ingrowth. Weathering is included in decay of ground concentrations.
FMDose uses different weathering functions in computing the amount of material resuspended from the
ground and the amount of material remaining on the ground. For clarity, the equations for doses and
DILs presented here do not explicitly include the decay integral or daughter ingrowth.

If data are entered in mass units, their specific activity is used to compute the activity present. If
enriched uranium is included in the measurements, its specific activity is computed based on its
enrichment as described in Section 3.1.1.

Because the user chooses the input and output units used, the calculations all include factors to convert
the units of the data to match the output units. This factor is not explicitly included in the following
discussion.

7.1 EARLY-PHASE DOSES

The early phase dose extends from before a major release until the risk of a major release has ended and
the areas with major contamination have been identified. Early-phase doses include up to 4 days of
exposure to ground shine and the actual time of exposure to contaminated air as the plume passes.
Early-phase doses are used to project where early-phase protective action guides (PAGs) may be
exceeded and where early health effects are possible.

The early-phase doses that FMDose computes are total effective dose equivalent (TEDE), total acute

7-1


When isotopic concentrations are entered, the user also enters an overall release rate. The amount of
activity released is computed as the concentration times the rate times the release duration. Up to three
sets of concentrations and rates may be entered. The isotopic concentrations may be decayed over a
selected time period prior to release, and decay is calculated over the duration of the release.

Table 3.5 Activity (Ci) Released in Criticality

of 10"? Fissions’
Activity Activity

Radionuclide { (Ci) Radionuclide | (Ci)

Kr-83m 1.5E2 1-131 7.3E0
Kr-85m 8.9E1 1-132 1.0E3
Kr-85 1.3E-5 1-133 1.7E2
Kr-87 1.1E3 1-134 4.2E3
Kr-88 6.6E2 1-135 5.0E2
Kr-89 4.6E4 Sr-91 3.2E2
Xe-133m 1.9E-2 Sr-92 1.2E3
Xe-133 2.7E-3 Ru-106 2.0E-2
Xe-135m 3.3E2 Cs-137 1.0E-2
Xe-135 5.2E0 Ba-139 2.4E3
Xe-137 2.454 Ba-140 1.1E1
Xe-138 1.0E4 Ce-143 1.0E2

*Source: SAIC 1998.

Ina fire release, the user enters the amount of each radionuclide present. The amount of material
released is reduced by the fire reduction factors. No other types of reduction are allowed. The default
values for these fire reduction factors are from NUREG/BR-0150 (McKenna, et al. 1996). They are
shown in Tables 3.6 and 3.7. The default fire release fractions are supplied for each element. The user
can also enter these fractions directly.

For all types of isotopic releases, if the user selects release units in mass, rather than activity, the source
term is converted to Curies using the specific activity of each radionuclide. The user may specify the
enrichment level for enriched uranium. The enrichment level for natural uranium is assumed to be 0.7%
(McKenna, et al. 1996, Table E-5). Specific activity is computed as described in Section 3.1.1. For
natural and enriched uranium, radiological decay and dose are calculated assuming the properties of U7*

3-7


where

D,'(p) = dose rate in (rem/h)/Ci,

p = distance from point source,

f, = fraction of disintegrations producing ys of energy, E,,
B,(u,,P) = buildup factor for air,

#4, = linear attenuation factor for air,

E, = gamma energy,

T, = mass energy absorption coefficient for tissue (#,,/p,),
W, = ratio of whole body dose to surface dose.

The constant 2.13 x 10° is a collection of unit conversion constants to give dose rate in (rem/h)/Ci. The
components of the constant are described following Eq. 19 in Scherpelz, et al. (1986). Previous
versions of RASCAL used a constant value of 592, which gives dose rates in (rem/s)/Ci.

The mode! then calculates the dose rate at ground level as a function of horizontal distance from the
ground-level position of center of the puff. This calculation involves summation over volume elements
distributed throughout the puff.

DO=AYY YY Ma » (4.37)
i j ork

where

D‘(1) = dose rate at r,

1 = distance from the receptor to the projection of the puff center on the ground,
i,j,k = indices associated with the volume elements,

D’,(Pix) = dose rate at distance p from a point source in volume element ijk,

Py = distance from the center of the volume element ijk to the receptor,

Mj, = fraction of the total puff activity in volume element ijk.

For purposes of cloud-shine calculation, puffs were assumed to be circular cylinders with three layers.
The volume elements were defined in 3, 5, or 8 annular rings with either 6 or 16 sectors. The fraction
of activity in volume elements varied by annulus and level. Finally, the dose at a receptor for a period is
accumulated by summing the product of dose rates and the time step for all puffs for all time steps in the
period.

In RASCAL 3.0, this process has been modified by eliminating the calculation of composite

characteristics from the gamma energies. In its place, the TADPUFF calculates the dose rate vs distance
from a point source that has all of the activity in the puff. Thus, Eq. (4.36) is replaced by

N
D',(P) = 5, Q,D' (0) (4.38)

419


In both cases, the user enters the uranium enrichment level. STDose converts the mass of UF, to
activity using the enrichment level and the specific activity. This conversion is done by interpolation
using a spline fit to the data in Table E-4 of NUREG/BR-0150 (McKenna, et. al 1996).

No radiological decay is computed in UF, accident scenarios.
3.1.2 Fires and Explosions Involving Uranium Oxide

In STDose, accidents involving uranium oxide can be modeled as either fires or as explosions. The
scenarios available in STDose were selected to span a wide range of possible accidents. Uranium oxide
fires may occur in several different types of facilities. In the milling of uranium ore, a fire can occur in
a drum of milled ore or during the process of extracting solvent. After the ore is milled, the production
of reactor fuel begins with creating a powder from the UO,. Both wet and dry processes are used to
produce this powder. Uranium-oxide-contaminated waste can be stored in several forms, and any of
these can be involved in a fire. Uranium oxide explosions are characterized as (1) those caused by the
detonation of high explosives in contact with the material, (2) those caused by a fire (deflagration), and
(3) those caused by a sudden pressure change in the material container (venting). The UO, in the
explosion may be in liquid, solid, or powder form, or it simply may be surface contamination.

For all cases, the user enters the amount of material (UO,) at risk and its enrichment level. For all cases,
the user chooses among a variety of accident conditions. These accident conditions are listed in Tables
3.2 and 3.3 (DOE 1994). Each set of accident conditions is associated with a default set of airborne
Telease fractions (ARFs) and inhalation fractions (IFs). The ARFs and IFs are considered to be
conservative. The IF is the fraction of the material released that is expected to be inhaled. The material
is defined as all vapors and any particulate material that has a diameter of < 10 pm. (Note that the IFs
are not used in the source term calculation. They are used in the calculation of inhalation dose to reduce
the amount of material inhaled.) The default values for the ARFs and Is are shown in Tables 3.2 and
3.3 (DOE 1994).

STDose calculates the source term by first converting the mass of UO, to U by multiplying by 0.88.
Then the amount of material is converted from mass to activity as described in Section 3.1.1. The source
term is the product of this activity times the ARF value.

3.1.3 Criticality Accidents

A criticality accident results from the uncontrolled release of energy from an assemblage of fissile
material. In RASCAL 3.0, a criticality accident may be modeled using the assumptions in NUREG/CR-
6410 (SAIC 1998). In addition, the criticality data may be entered directly by the user. The physical
systems modeled are listed in Table 3.4 (SAIC 1998). This table also presents the assumed number of
fissions in the first burst of the criticality and the total yield. The assumed amounts of each radionuclide
released per 10” fissions are listed in Table 3.5 (SAIC 1998). These values are based on ORIGEN
calculations (ORNL 1989).


Dir) [x0 QTY Q, DF yee , (4.44)

where [x(r)/Q] is calculated using Eq. (4.2) or a variation thereof, as appropriate. The semi-infinite
dose factors from Federal Guidance Report No. 12 (Eckerman and Ryman 1993) are used in this
calculation.

4.9.3.2. TADPLUME Cloud-Shine Dose Calculations

A new set of models has been developed for cloud-shine dose calculations in TADPLUME. These
calculations proceed in a manner similar to the calculations in TADPUFF. Near the source, the plume is
divided into a large number of equal-strength line sources spaced to properly represent the distribution of
activity in the plume. The dose rates from these line sources are used to calculate the ground-level dose
rate as a function of horizontal distance from the plume axis. This relationship is then used to calculate
dose rates and 15-min doses at receptor locations. When the width of the plume is sufficient (o, = 400
m), TADPLUME switches from the line-source model to an infinite-slab model. Finally, when the
vertical dimensions of the plume are sufficient to make the semi-infinite cloud model appropriate (o, =
400 m or a uniformly-mixed plume with a thickness of 600 m), TADPLUME switches to a semi-infinite
cloud model.

Dose rates from line sources are calculated using

XN
Dip) =F 0'.D",(p) , (4.45)
ost

where

D‘(e) = dose rate (rem/s) at a distance p from and infinite line source of Q', (Ci/m),
Q’;, = line-source strength (Ci/m), Q’,,= Q’, /u where Q’, is in Ci/s,
D‘,(p) = line-source dose rate factor [(rem/s)/(Ci/m)] for radionuclide n.

Equation (4.45) is analogous to Eq. (4.38) with changes in the definitions of source term and dose
factors.

The line-source dose rates are combined to get the plume dose rate by summing over all line sources,
just as the point-source dose rates were combined to get a puff dose rate. The number of line sources
used is determined by the horizontal dispersion parameter, o,. If o, > 200 m, 100 lines (10X10) are
used to describe the concentration distribution in the plume. Otherwise, the concentration distribution is
described by 36 lines (6X6). In either case, the lines are spaced horizontally and vertically such that all
lines represent the same fraction of the activity in the plume. The plume dose rate is given by

Diy) -2YYdiG,) . (4.46)
! }

4-22


dose, and several organ-specific inhalation doses. TEDE is the sum of 4-day ground shine, air
submersion, and 50-year committed effective dose equivalent (CEDE) from inhalation. Total acute bone
dose is the sum of ground shine over the selected exposure period, air submersion, and 4-day red bone
marrow inhalation doses over the exposure period selected by the user.

7.1.1 Inhalation Doses

Inhalation dose results from inhaling contaminated air. The inhalation doses that FMDose calculates are
for 50-year CEDE and thyroid and 4-day bone, lung, and small-intestine wall. In addition a 50-year
thyroid dose is calculated using only the air concentrations of isotopes of iodine. This dose is used in the
decision to administer KI. The inhalation dose, D,,. is computed as

N
Dio =BR xTa x) Cai XDCFiei . (7.1)

isl

where

BR = breathing rate (1.2 m*/h),

T, = selected exposure time for air,

N = number of radionuclides,

cai = emtered air concentration of radionuclide i,

DCF,,, = inhalation dose factor for radionuclide i and organ o.

If the user does not enter air concentration measurements, FMDose uses the activity resuspended from
the ground instead. This calculation is described in Section 7.7.

7.1.2 Cloud-Submersion Dose

The cloud-submersion dose results from standing in contaminated air. The cloud-submersion dose, Ds,
is

x
Ds=Ta x)’ CaixDCFsi ; (7.2)

isl
where DCF,, is the effective submersion dose factor for radionuclide i.

If the user does not enter air concentration measurements, the activity resuspended from the ground is
used in their place. This calculation is described in Section 7.7.

7.1.3 Ground-Shine Dose
The ground-shine dose is the gamma dose from standing on contaminated ground. FMDose computes
ground shine at 1 m above the ground surface. The dose is reduced by a correction factor to account for

ground surface roughness. The early-phase, ground-shine dose for all radionuclides, Dg, is

7-2


CCC-371. Oak Ridge National Laboratory, Oak Ridge, Tenn.

Powers, D. A., L. N. Kmetyk, and R. C. Schmidt. 1994. A Review of the Technical Issue of Air
Ingression During Severe Reactor Accidents. NUREG/CR-6218, SAND-94-0731, U.S. Nuclear
Regulatory Commission.

Science Applications International Corp. (SAIC). 1998. Nuclear Fuel Cycle Facility Accident Analysis
Handbook. NUREG/CR-6410, Science Applications International Corp., Reston, VA.

U. S. Department of Energy (DOE). 1994. Airborne Release Fractions/Rates and Respirable Fractions

for Non-Reactor Nuclear Facilities: DOE Handbook. Vol. 1, DOE-HDBK-3010094, U.S. Department
of Energy.

3-13


6.3.1 Surface Winds

The surface winds are made up of the wind direction (the direction from which the wind is blowing) and
the wind speed. Wind directions must be entered in degrees. Wind speed can be entered as m/s, mph,
or knots. The wind-speed and wind speed unit are passed to the meteorological data processing program
in the observation file. METPROC converts all wind speeds to m/s. Both a wind direction and wind
speed are required. The acceptable range for wind directions is 0 through 360°. The acceptable range
for wind speeds is 0 through 30 m/s. A wind speed of 0.4 m/s will be answered in UF6PLUME if the
wind speed is less than 0.4 m/s.

6.3.2 Atmospheric Stability Class

Aumospheric stability may be entered either as a stability class (A—extremely unstable through G—
extremely stable) based on the general classification scheme discussed by Pasquill (1961), Gifford
(1961), and Turner(1964) or as temperature variation with height (dT/dz). If dT/dz is entered, it will
be converted to a stability class by METPROC using the conversion table shown in Table 6.1 (NRC,
1972). If the temperature difference measurement is over a height interval different from those shown in
Table 6.1, the measurement is adjusted to the appropriate interval.

Table 6.1 Estimated Pasquill-Gifford Stability
Class Based on NRC Delta TM Method

Stability dT/dz dT/dz
Class (°C/100 m) | (°F/100 ft)
A <-1.9 <-l

B <-1.7 <-0.9

Cc <-1.5 <-0.8

D <-0.5 <-0.3

E < 1.5 < 0.8

F <4 <2.2

G 24 22.2

METPROC has two options related to modification of station stability classes. The first option allows
METPROC to replace a missing stability class with an estimate based on the time of day, the wind speed
at the station, and whether there is precipitation or not. The second option allows METPROC to
compare the entered stability class with ranges of stability classes that would be expected given the time

6-4


ANSI/ANS

ARF

BWR

CEDE

CDS

DIL

FRMAC

LRF

MFR

NRC

PAG

PWR

RDF

STCP

TEDE

LIST OF ABBREVIATIONS

American National Standard Institute/American Nuclear Society
activity release fractions

boiling water reactor

committed effective dose equivalent

core damage state

derived intervention levels

Federal Radiological Monitoring and Assessment Center
inhalation fractions

leakage rate fraction

mass flow rate

Nuclear Regulatory Commission

protective action guide

pressurized water reactor

reduction factors

Source Term Code Package

total effective dose equivalent

xii


CONTENTS

Page
ABSTRACT 1.00... nen e en eee eee ene tebe n teen eens iii
LIST OF FIGURES .. 6... 0.0.0 cece cece net e eter ene e ete ee eens ix
LIST OF TABLES . 21.1.0. o eee cnet e eee tnt e eter cent ne x

1 INTRODUCTION ...
1.1 STDOSE ...
1.2 FMDOSE .
1.3 DECAY CALCULATIONS .
1.4 REFERENCES

2 REACTOR AND SPENT FUEL SOURCE TERM CALCULATIONS IN STDOSE ............ 2-1
2.1 CALCULATION OF THE AMOUNT OF ACTIVITY AVAILABLE FOR RELEASE

IN NUCLEAR POWER PLANT ACCIDENTS ...
2.1.1 Core Cooling Status
2.1.2 Containment Radiation Monitor . .
2.1.3 Coolant Sample ..........
2.1.4 Containment Air Sample .......
2.1.5 User-defined Core Damage Estimate
2.1.6 Monitored Releases — Mixtures ..
2.1.7 Effluent Source Terms

2.2.1 Spent Fuel Pool
2.2.2 Fuel Damaged Under Water ...
2.2.3 Release from a Dry Storage Cask . . . 2-15

2.3 CALCULATION OF RELEASE REDUCTION FOR REACTOR RELEASE PATHWAYS. . 2-16

2.4 CALCULATION OF LEAKAGE FACTORS FOR REACTOR ACCIDENTS ...
2.4.1 Percent Per Hour
2.4.2 Containment Pressure and Hole Size
2.4.3 Flow Rate 2.0.0.0... ccc cece cece nent e teen teen teen eens
2.44 Direct ....

2.5 REFERENCES

3 FUEL CYCLE AND MATERIALS SOURCE TERM CALCULATIONS IN STDOSE.......... 3-1
3.1 CALCULATION OF THE AMOUNT OF ACTIVITY AVAILABLE FOR RELEASE IN

FUEL CYCLE AND MATERIALS SOURCE TERMS

3.1.1 UF, Releases from Cylinders and Cascade Systems

3.1.2 Fires and Explosions Involving Uranium Oxide ..

3.1.3 Criticality Accidents


Table 3.7 Fire Release Fractions by Element’

Release Release Release Release
Element’ | fraction’ | Element | fraction |} Element | fraction | Element | fraction
H(gas) 0.5 Se 0.01 I 0.5 Ww 0.01
Cc 0.01 Kr 1.0 Xe 1.0 Ir 0.001
Na 0.01 Rb 0.01 Cs 0.01 Au 0.01
P 0.5 Sr 0.01 Ba 0.01 Hg 0.01
Ss 0.5 Y 0.01 La 0.01 Tl 0.01
cl 0.5 Zr 0.01 Ce 0.01 Pb 0.01
K 0.01 Nb 0.01 Pr 0.01 Bi 0.01
Ca 0.01 Mo 0.01 Pm 0.01 Po 0.01
Sc 0.01 Te 0.01 Sm 0..01 Ra 0.001
Ti 0.01 Ru 0.1 Eu 0.01 Ac 0.001
v 0.01 Rh 0.01 Gd 0.01 Th 0.001
Cr 0.01 Ag 0.01 Tb 0.01 Pa 0.001
Mn 0.01 Cd 0.01 Ho 0.01 U 0.001
Fe 0.01 In 0.01 Tm 0.01 Np 0.001
Co 0.001 Sn 0.01 Yb 0.01 Pu 0.001
Zn 0.01 Sb 0.01 Hf 0.01 Am 0.001
Ge 0.01 Te 0.01 Ta 0.001

*Table F-3 from McKenna et al. 1996. The release fraction for ruthenium was changed from the value of
0.01 in NUREG-1140 to a value of 0.1. NUREG-1140 assumed that ruthenium was nonvolatile
(McGuire 1998). However, research in NUREG/CR-6218 (Power, Kmetyk, and Schmidt 1994) indicates
(in Table 5) that at high temperatures ruthenium starts to become volatile. The ruthenium release fraction
of 0.1 is less than the value of 0.5 used in NUREG-1140 for volatile compounds because ruthenium is less
volatile than other volatile compounds. becoming highly volatile only at temperatures not normally reached
in building fires. The carbon release fraction is appropriate for carbon compounds other than CO;. Those
compounds deliver most of the dose. The dose conversion factors used for carbon are for those carbon
compounds.

"If the specific compound form of the isotope is known, Table 3.5 should be used.

“The fire release fraction is the fraction of the isotope released when the material is involved in a fire, and
equals the total activity released (Ci), users should divide by the activity involved in fire (Ci).

3-10



5 UF, MODEL

UF6PLUME is a special version of TADPLUME developed to treat potential releases of UF,, HF, and
UO,F,, or a combination of UF,, HF, and UO,F,. Modifications to TADPLUME include the
introduction of a dense gas model to treat the gravitationally driven spread of UF, releases, a
chemical/thermodynamic model to treat the reaction of UF, with water vapor in the atmosphere, and a
plume rise model to treat the vertical displacement of HF/UO,F, plumes when their densities becomes
less than the density of air. Minor modifications were also made to input and output routines to
accommodate the additional information required by UF6PLUME.

The dense gas and chemical/thermodynamic models are implemented in control volumes that move
downwind at the 10-m level wind speed. The control volumes are initially defined by the release rates of
UF,, HF, and UO,F,. As the control volumes move downwind, the volume of UF, is deformed by
gravitational settling, and air and water vapor are mixed into the UF, volume. The chemical reaction

UF, +2H,0 >UO,F, +4HF +heat (5.1)

is assumed to occur instantaneously as the mixing takes place. The result of the reaction is a decrease of
mass and volume of the control volume containing UF, and increase in the mass and volume in the
HF/UO,F, control volume. The temperatures of these two control volumes are assumed to be identical
and are determined from the initial temperature of the released material, the air temperature, and the heat
reaction of UF, and water vapor.

The output of the dense gas and chemical/thermodynamic model calculations is used as input to
atmospheric dispersion and deposition calculations. This input is a function of distance from the release

point to the point at which all UF, has been converted to HF and UO,F,. Beyond this point, the HF and
UO,F, source terms remain constant with correction for deposition and decay as described in Section 4.

5.1 UF, MODEL ASSUMPTIONS AND EQUATIONS
The following assumptions were made in development of the UF, model.

1. The UF, plume is released at or near ground level.

2. An initial UF, control volume is defined by the UF, release rate and density.
3. The initial cross section of the UF, control volume is square with
Ag = Sue, (6.2)
Parolt

5-1


wind speed increases to 4 m/s, and to 0.5 s when the speed exceeds 8 m/s. As the control volume
moves downwind, plume rise is calculated using the stable plume equations discussed in Section 4.5.2.
In addition, transition plume rise is calculated using

Ah, =16F/?x?3u7t (5.31)
where Ah, is the transition rise (Briggs 1984). The smaller of the transition and final rise is selected as
the plume rise.

Dispersion of the HF and UO,F, plumes is calculated using the dispersion parameters that are used in
TADPLUME. As long as there is UF, present, the HF and UO,F, plumes are assumed to be uniformly

mixed in the vertical because the plumes are being fed by the UF,—H.O reaction. Normalized HF and
UO,F, concentrations in this range are given by

xi Q’=— exp (2) ; 6.32)
- 0.

where H is the thickness of the plume. The thickness of the plume is equal to the plume rise plus the
vertical dispersion (39,).

At the point that the last UF, is converted to HF and UO,F,, the plume is assumed to become elevated.

The effective release height at this point is calculated assuming that the ground-level concentrations of
the uniformly-mixed and elevated plumes are equal. The effective release height, Ah,, is

} 2
Ah, =-2.007 Ee] (5.33)

This effective release height is assumed for the remainder of the dispersion calculations.

Assuming the mixing-layer thickness is significantly greater than the vertical dimension of the plume, the
normalized concentrations of HF and UO,F, are calculated as

2 2
1 exp) 411%] Jexp -{2 2) (5.34)
TUG, S, 2\o, 2 o,

after all UF, has been converted to HF and UO,F,. The receptor height, z, is assumed to be 1 m.

X1V=

UF6PLUME generates the following products:

. airborne uranium exposure (g-s)/m’,
. inhaled uranium (mg),
. dose commitment from inhaled uranium (rem),

5-10


NUREG-1741

RASCAL 3.0: Description of
Models and Methods

U.S. Nuclear Regulatory Commission os
Washington, DC 20555-0001 A }



7.6 GROUND EXPOSURE AND WEATHERING
Ground-shine doses and DILs are dependent on ground contamination. They include the explicit

calculation of radiological decay and daughter ingrowth and weathering of the material on the ground.
The exposure to radionuclide i on the ground, E,,, is computed as (EPA 1992)

To To
Eci=0.37x JCoixe 28-5 +0.63 x JCoixe 3108-3 , (7.11)
j=0 jro

where
L = number of daughters in radionuclide chain i,
C,, = concentration of radionuclide i on the ground.
7.7 AIR CONCENTRATION DUE TO RESUSPENSION
Intermediate-phase doses from inhalation and air immersion are always computed from the activity
assumed to be resuspended from the ground. FMDose computes early-phase doses from resuspended

activity when the user has not entered any air concentration measurements. The concentration of activity
in the air that results from material resuspended from the ground is computed as (NCRP 1999)

Cai=Coix(R xe 410-9) , (7.12)

where R is the resuspension rate entered by the user.

Note that because the computed resuspension factor is a function of time, the resuspension calculation is
included in the decay calculation.

7.8 REFERENCES

International Commission on Radiological Protection (CRP). 1977. “Recommendations of the
International Commission of Radiological Protection.” ICRP Publication 26, Pergamon Press, Oxford.

National Council on Radiation Protection and Measurements (NCRP). 1999. Recommended Screening
Limits for Contaminated Surface Soil and Review of Factors Relevant to Site-Specific Studies. NCRP
Report 129, NCRP, Bethesda, Md.

U.S. Department of Energy (DOE). 1995. FRMAC Assessment Manual for Interim Use and Comment.
U.S. Department of Energy.

7-6


ABSTRACT

The Radiologic Assessment System for Consequence AnaLysis (RASCAL) 3.0 is the latest version of the
RASCAL series of codes. RASCAL was developed for use by U.S. Nuclear Regulatory Commission
personnel who conduct an independent assessment of radiological accidents to prepare dose projections.
It includes three sets of tools for use in consequence analysis STDose, FMDose, and DecayCalc.
STDose estimates (1) source terms for radiological accidents, (2) atmospheric transport, diffusion, and
deposition of effluents from the accidents, and (3) doses from exposure to the effluents. FMDose
calculates doses from environmental measurements of activity in the air and on the ground. DecayCalc
calculates activity of radionuclides present at a future time following decay and ingrowth. The current
version of RASCAL includes computational techniques that are substantially modified from those used in
the prior versions of RASCAL and significantly expands the capabilities of STDose. The major changes
to STDose are (1) the inclusion of time-dependent source terms and source terms for fuel cycle and
materials accidents, (2) the inclusion of radiological decay during atmospheric transport, (3) the addition
of a UF, atmospheric transport model, and (4) the ability to include meteorological data from multiple
stations and the effects of terrain. The major changes to FMDose are the addition of emergency-worker
guidance and derived intervention-level calculations.

iti


U.S. Environmental Protection Agency (EPA). 1988. “Limiting Values of Radionuclide Intake and Air
Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion.” Federal
Guidance Report No. 11. EPA-520/11-88-020, U.S. Environmental Protection Agency.

U.S. Environmental Protection Agency (EPA). 1992. “Manual of Protective Action Guides and
Protective Actions for Nuclear Incidents.” EPA-520/1-75-001A, U.S. Environmental Protection
Agency.

U.S. Environmental Protection Agency (EPA). 1993. “External Exposure to Radionuclides in Air
Water, and Soil.” Federal Guidance Report No. 12. EPA-402-R-93-081, U.S. Environmental
Protection Agency.


Table 2.9 Leak Rate Types Available in each Reactor Release Pathway

Containment

pressure and | cfm, kg/s,
Pathway %fh | hole size gam Direct
Bypass xX x x
Containment leakage x xX
Wet well x x xX
Dry well x x
Steam generator tube rupture x
Reactor Effluent x

2.4.1 Percent per Hour

The %/h release rate releases a fixed fraction of the source term per unit time. The actual leakage rate
fraction used is computed based on the length of the time step entered by the user. This release rate

results in the source term being released at a constant rate over time.

2.4.2 Containment Pressure and Hole Size

The containment pressure and hole size option is available only for a facility with a design pressure and
containment volume. In this case, the equation (Blevins 1984) for the mass flow rate, MER, is

2
MFR =C(2>) Ap (Pi-Pag ,

where

C = 0.63,

D = hole diam,

p = density of containment atmosphere,
P, = pressure in containment,

P, = atmospheric pressure,

g = acceleration of gravity.

(2.9)


Table 6.3 Limits of Atmospheric Stability Classes Based on
Time of Day, Wind Speed, and Precipitation

No or Light Moderate or Heavy
Wind Speed (m/s) Precipitation Precipitation
Daytime
< 3.0 1-5 3-5
3.1-5.0 2-4 3-4
> 5.0 3-4 3-4
Nighttime
< 3.0 3-7 3-5
3.1-5.0 4-6 4-5
5.1- 6.0 45 45
> 6.0 4 4

6.3.4 Mixing Height

TADPLUME and TADPUFF use the mixing height to limit vertical dispersion. Mixing heights may be
entered with the other meteorological data for a station. However, this information is generally not
available. Consequently, unless the option of entering mixing-height data is specifically selected,
METPROC will estimate mixing heights from wind speed and stability. There is also an option of using
climatological mixing-height estimates in place of measured or calculated values.

6.3.5 Temperature

The ambient air temperature should be entered for the first meteorological station. If the meteorological
data are to be used for consequence analysis for a ground-level release not involving UF,, and it is not
snowing, the temperature may be omitted without affecting doses.

6.3.6 Pressure

The station atmospheric pressure (not sea-level pressure at the station) is needed for thermodynamic
calculations in UF6PLUME. However, the calculations are not particularly sensitive to the pressure as
long as the pressure is within a few percent of the actual value. METPROC includes default pressures
for fuel-cycle facilities that should be adequate for most purposes because atmospheric pressures rarely
vary by more than +5%. METPROC will convert pressures entered in other units to millibars.

6-6


6 METEOROLOGICAL DATA PROCESSOR

The meteorological data processor, METPROC, is the STDose module used for entering meteorological
data and preparing the data for use by the atmospheric transport and diffusion models in RASCAL 3.0.

In earlier RASCAL versions, this function was handled directly by the user interface. It was necessary

to separate the function from the interface to expand capabilities of TADPLUME and TADPUFF.

Meteorological data for the site (event location) and as many as 35 additional meteorological stations
may be entered and processed for use by the RASCAL 3.0 atmospheric models using METPROC. All
data must be entered manually at the present time. Future version of the meteorological data processor
may include options for importing meteorological data files.

The following sections describe the technical aspects of the meteorological data requirements and the
meteorological data processing.

6.1 MODEL DOMAIN

Model domain refers to the area covered by the dose calculations in STDose. The model domain for
TADPUFF is square. In RASCAL 3.0, STDose has three options for the TADPUFF model domain.
They are squares that are 20, 50, and 100 miles (32, 80, and 160 km) ona side. The model domain is
selected when dose calculations are started. METPROC creates a meteorological file for each domain
for use by TADPUFF. These files describe the spatial and temporal variation of meteorological
conditions at nodes on a Cartesian grid. METPROC also creates a smaller file of meteorological data
for the release point for use by TADPLUME and UF6PLUME. This file describes the temporal
variation of meteorological conditions at the center of the polar grid used by these straight-line models.

Meteorological data must be entered for at least one location, generally the release site. If data are
entered for only one location, the data will be assumed to be representative for the center of the domain.

6.2 METEOROLOGICAL STATIONS

Locations for which meteorological data are entered are called meteorological stations. Meteorological
stations may be within or near the model domain. Spatial fields of winds, stability, etc., are produced
from the station meteorological data. Section 6.3 discusses the meteorological data input.

Information on each station must be available to METPROC before METPROC can use station
meteorological data in generating the meteorological fields needed by TADPUFF. Files containing the
required information for potential release sites are included with RASCAL 3.0. Each file contains the
information for the location of the site and for other meteorological stations near the site. However, the
file for a specific site may not include information for all meteorological stations near the site, or the

61


2 REACTOR AND SPENT FUEL SOURCE TERM CALCULATIONS IN
STDOSE

The source term calculations in STDose estimate the amount of radioactive (or hazardous) material
released based on a wide variety of potential radiological accident scenarios. The source term
calculations performed that pertain to reactor sites generally can be categorized as (1) nuclear power
plant accidents, (2) spent reactor fuel accidents, and (3) effluent releases that can be characterized by an
isotopic mix. These calculations are performed using an extension of the method of estimating source
terms from reactor accident conditions described in NUREG-1228 (McKenna and Giitter 1988).

STDose divides the source term calculation into three parts: first, it calculates the amount of activity
available for release based on the source term type; second, this activity is reduced, based on the
reduction mechanisms that the user has selected for the release pathway; and third, the activity is
released according to the release rate selected. This can be shown as

Si=liXARFGX] | RDFa LF; (2.1)
k
where

S,, = total amount of radionuclide i released under accident conditions j,

I, = inventory of radionuclide i,

ARF,, = airborne release fraction of radionuclide i under accident conditions j,
RDF, = reduction factor that applies to radionuclide i for reduction mechanism k,
LF, = leakage fraction selected under accident conditions j.

In RASCAL 3.0, nuclear power plant accidents and effluent source terms may change with time. Source
terms are recomputed at intervals of varying length, called time steps. A new time step starts whenever
the user changes any of the time-dependent data or every 15 min, whichever is less. At the end of each
time step, the inventory of activity is decremented for the amount of activity released or removed by
reduction and the effects of radiological decay, so that no more than the total inventory can be released.
Time steps may be no less than 1 min and must be an integral number of minutes. Before passing the
source term to the atmospheric transport model, STDose converts the user-selected time steps to the 15-
min time steps used by the atmospheric transport models. Note that neither the type of source term
calculation nor release pathway may change with time. The minimum amount of activity of any one
nuclide that will be passed to atmospheric transport models in one time-step is 10° Ci.

STDose includes six release pathways for nuclear power plant accidents. Only those pathways that are
appropriate to the accident type, location, and method of source calculation are available to the user in
any assessment. Data specific to each reactor site are shown in Appendix A. Spent fuel accidents have a
single release pathway available. All release pathways only allow those reduction mechanisms that are
possible for that type of accident. Table 2.1 shows the relationships among the types of source terms
and release pathways.

2-1


Table 4.1 Constant Values for Calculation of Atmospheric Dispersion Parameters

Stability Class
Distance Range (m) A B Cc D E F G
a, allx 0.3658 0.2751 0.2089 0.1471 0.1046 0.0722 0.0481
a x< 100m 0.192 0.156 0.116 0.079 0.063 0.053 0.032
100m <x < 1000mm _ 0.00066 = 0.0382 0.113 0.222 0.211 0.086 0.052
1000 m < x 0.00024 0.055 0.113 1.26 6.73 18.05 10.83
b, x< 100m 0.936 0.922 0.905 0.881 0.871 0.814 0.814
100m < x < 1000m 1.941 1.149 0.911 0.725 0.678 0.74 0.74
1000 m < x 2.094 1.098 0.911 0.516 0.305 0.18 0.18
¢ x< 100m 0.0 0.0 0.0 0.0 0.0 0.0 0.0
100m < x <1000m 9.27 3.3 0.0 1.7 -13 0.35 0.21
1000 m_ < x 9.6 2.0 0.0 -13.0 -34.0 -48.6 -29.2

Atmospheric dispersion experiments did not stop after development of the Pasquill-Gifford curves.
However, the emphasis of the experiments did shift. For example, there have been experiments that
examined dispersion in the vicinity of buildings and other experiments that examined dispersion under
low wind-speed conditions. Ramsdell (1990) describes corrections to the basic dispersion parameter
relationships in Eq. (4.11) and (4.12) that improve the dispersion parameter estimates in the vicinity of
buildings. These corrections are included in RASCAL 3.0 as an option for ground-level releases.

Enhanced dispersion parameters, 4, and X,, are defined as

%, =(63 +407)”

where the enhancement terms, Ao,? and Aa,’ have the form

Ao’(t) =A[I-(1+t/T)exp(-W/T)] ,

where

(4.13)

(4.14)

(4.15)

t = transport time (distance divided by the wind speed in TADPLUME and time since release in

TADPUFF),

Ay = 0.5T? (T is the horizontal time scale for wake turbulence),

4-9


The local time is defined as

Tt -(Se-r.) . (6.10)

where

t,. = time at the prime meridian,
A, = longitude (in radians) of the station.

Sunrise and sunset are calculated by setting the solar elevation angle to -0.833° (the sun appears to rise
and set when it is 0.833° below the horizon) and solving for T, using Eq. (6.10). Sunset is 24 h - Ty.
The equations for sunrise and sunset do not take into account the ellipticity of the earth’s orbit, but it is
accurate to about +16 min.

6.4.4 Dry Air and Water Vapor Density

UF6PLUME requires estimates of the air density and water content of the atmosphere. These two
variables are estimated from the air temperature, station pressure, and humidity for the event site. (The
event site is assumed to be at the location of the first meteorological station. The method used to
calculate the dry air density and water-vapor density depends upon the variables used for humidity and
whether the temperature, pressure, and moisture variables exist.

The water vapor density is given by

G
=o 6.11
p, RT (6.11)
where
Py = water vapor density (kg/m*),
€ = vapor pressure (Pa),
R, = gas constant = 461.5 J/kg K,
T = temperature (K),
and the dry air density can be estimated by
--¢) 6.12
Cor (6.12)

where

Pa = dry air density (kg/m3),


10. The entrainment velocity is given by

p, iu?
w= (5.5)
(Pars — Pair) 8B are

where u, is a scaling velocity (m/s) associated with atmospheric turbulence.

11. The water available for reaction with UF, is determined by a combination of the water vapor in the
entrained air and precipitation entering the UF, control volume.

12. The water available for reaction is given by

Ma20 =Ph20Vair Pr ut6¥Pr201 > 6.6)

where

My, = the rate at which water becomes available for reaction (g/s),
Pizoy = density of water vapor in the ambient air (g/m*),

P, = precipitation rate (m/s),

Piso = density of liquid water (g/m).

13. The reaction between UF, and water is assumed to occur at the top of the UF, control volume.
The volume of UF, involved in the reaction is subtracted from the UF, control volume, and the
masses of air, HF, and UO,F, are added to the HF/UO,F, control volume. The volume of the
HF/UO,F, control volume is increased by the volumes of the air and HF. The UO,F, formed in
the UF,/H,0 reaction is present as small particles that are assumed to have negligible volume. The
temperature and volumes of the control volumes are adjusted to conserve enthalpy in constant
pressure reaction.

14. Potential heat exchange with the ground and possible reaction of UF, with water on the ground
surface are assumed to be negligible. However, these phenomena could be added to the model at a
later date.

15. The ground is assumed to be a sink for UF, that may be deposited on the ground. Any UF,
condensing in the UF, control volume is assumed to deposit on the ground. Wet deposition of UF,
is not modeled because all water entering the UF, control volume is assumed to react with UF, to
produce HF and UO,F,.

5.2 CHEMICAL/THERMODYNAMIC MODEL

The chemical/thermodynamic model in UF6PLUME is based on the description contained in
NUREG/CR-4360, Calculational Methods for Analysis of Postulated UF, Releases (Williams 1985).
The initial release for UF6PLUME may be UF, or a mixture of UF,, HF, and UO,F,. However, the
chemical/thermodynamic model is only invoked when the release includes UF,. A release of HF or
UO,F,, or a combination of HF and UO,F, is treated as a release of passive contaminants.

5-3


Table 3.2 Airborne Release Fractions and Respiration Fractions

Used in Uranium Oxide Fires’
Type of fire Condition ARF IF
Production process Dry process 1x10° 1
Wet process 3x10° 1
HEPA filter At high temperature 1x10* 1
Failure 1 1
Incinerator exhaust 4x10 1
Waste fire Solid packaged in drums 5x10* 1
Solid loosely packed 5x10? 1
Combustible liquid 3x10? 1
Non-combustible liquid 2x10° 1
Uranium mill Drum in a fire 1x10° 1
Solvent extraction 3x10 1

“Source: DOE 1994.

The activity released in a criticality occurs in discrete bursts. In the predefined scenarios, the bursts are
assumed to be 10 min apart. The fission may not continue for more than 48 bursts. The number of
fissions in all except the first burst is

patio”!
(48-1)

(3.2)

where

Y, = the total yield of the criticality (column 3 in Table 3.4),
Y, = the yield of the initial burst (column 2 in Table 3.4).

To calculate the source term, STDose first determines the initial activity of each radionuclide present as
the product of the yield of the first burst (in 10'° fissions) and the activity per 10" fissions listed in Table
3.5. For each following time step, STDose: (1) determines if the criticality is still occurring and if
enough time has passed for one or more bursts to have occurred, and if so, adds the appropriate activity,
(2) reduces the amount of activity for the amount released, and (3) applies radiological decay to the
result. A criticality will end when either the total number of allowed bursts have been accounted for or
when the “end of criticality” time entered by the user has been reached. Note that if the user selects a
release duration that is not long enough to include all 48 bursts, the total activity released will be less
than the total yield listed in Table 3.5.

3-4


distributed in the vertical. With this last assumption, the puff model becomes

2
x(TV/Q “Tal of (2) | , (43)

where H is the mixing layer thickness. RASCAL switches to the uniformly mixed model when
6, > 1.05H.

4.1.2 Straight-Line Gaussian Plume Models

Puff models represent plumes as a series of puffs. Concentrations at a point in the plume are calculated
by adding the concentrations at the point associated with all puffs in the vicinity of the point. In effect,
the puff models perform a numerical time integration of concentration as puffs pass by the point. Near a
telease point, the meteorological conditions may be assumed to be constant as the puff moves from the
source to the receptor. If the wind speed is assumed to be much greater than zero and the point for
which the concentration is to be calculated is sufficiently far down wind that the change in dispersion
parameters with distance as puffs pass the point can be neglected, then the puff model can be integrated
analytically to give a plume model.

Assuming that the x-axis is aligned with the mean transport direction and that the mean wind speed is u,
then the average concentration during plume passage is given by

xoy2)= fo QF, exp (=) t, (4.4)
(27)? o,@)o,(x)6,«) | 2,0)

where

X = average concentration,

Q’ = release rate,

F,, F, = lateral and vertical exponential terms, shown above,
x = down-wind distance at which o,, 0, and o, are evaluated,
u = wind speed,

t = time.

On integration, the plume model becomes

1 F, F,
X(x,y,2)/Q'=———— _ , (4.5)

2NUG,6,

which is a simplified version of TADPLUME, the straight-line Gaussian model used in RASCAL. The
straight-line Gaussian plume model for ground-level releases is frequently given as

43


APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

5 |e
g 3 |g
& g [2 2 & |e
& a 2
»-e bE bE ela ie |
e 313 2 5 S a
7 ro} z = =
SE 3 |o = |& ca: é /8 |3./8
Bolg 3 5 3 & 15 a 18
3 8 E |g 2 {2 le l2iz |e [eg
Name IS 216 & ald lz |2¢g
(gal) [fe %Id {psi |MW(t)
Limerick - Unit 2 BWR [Mark II 764|N/A 172900} 240000] 0.5] 56] 3293} 22000] 15000|Operational
Maine Yankee PWR [Dry Ambient | 217|U-Tube 0} 1900000] 0.1] 55 2700} 22000] 15000|Decommissioned
McGuire - Unit 1 IPWR |Ice Condenser! 193|U-Tube 250808] _1200000|_0.2| 28] 3411] 22000] 15000| Operational
McGuire - Unit 2 PWR |Ice Condenser] 193|U-Tube 250808] 1200000] 0.2} 28] _3411| 22000} 15000|Operational
Millstone - Unit 1 BWR [Mark I 580|N/A Oj 150000] _ 0.5] 62{ 2011} 22000] 15000|Decommissioned
Millstone - Unit 2 PWR |Dry Ambient_| 217|/U-Tube 198529] 1900000] __3| 54] 2700|_ 22000} 15000|Operational
Sub-
Millstone - Unit 3 PWR {atmospheric _| 193|U-Tube 250808] 10000000| 0.9} 45| 3411] 22000] 15000|Operational
Monticello IBWR [Mark I 484|N/A 83500] 130000] 0.5] 56] 1670] 22000} 15000|Operational
Nine Mile Point - Unit 1 BWR {Mark I 532|N/A 92500} 180000 0.5] 62| _1850| 22000] 15000|Operational
Nine Mile Point- Unit2 [BWR |Mark II T64(N/A 173350|__300000|_ 1.1] 45] 3323] 22000] 15000|Operational
Sub-
North Anna - Unit 1 PWR |atmospheric | 157|U-Tube 212721) 1800000] 0.1] 45] 2893] 22000] 15000|Operational
Sub-
North Anna - Unit 2 [PWR |atmospheric _| 157|U-Tube 212721] 1800000) 0.1] 45] 2893| 22000] 15000|Operational
Oconee - Unit 1 PWR |Dry Ambient | 177|Once-Through | 188824] 1900000] 0.5] 59] _2568| 22000|15000|Operational



4.3 DISPERSION PARAMETERS

The horizontal dispersion parameters (0, and o,) used in TADPLUME and TADPUFF are based on the
results of a large number of dispersion experiments conducted in the 1950s and 1960s. The
experiments, which were conducted over relatively flat terrain, typically involved tracer releases ranging
from about 10 min to 1 h in duration with ground-level concentration measurements at distances ranging
from 100 m to several kilometers. Only a few direct measurements of vertical dispersion parameters
(o,) were made. Consequently, vertical dispersion parameters have been estimated with dispersion
models using measured values of the horizontal dispersion parameter and measured concentrations.
Dispersion parameters have been summarized in many forms. Perhaps the best known summary is the
set of dispersion parameter curves called the Pasquill~Gifford curves (Gifford 1976).

Regulatory guidance published by the NRC includes graphic depiction of these curves, and numerical
approximations to the curves are included in many computer codes used by the NRC. In RASCAL 3.0,
dispersion parameters are estimated using the same basic algorithms that were used in earlier RASCAL
versions and are used in other NRC codes including PAVAN (Bander 1982) and XOQDOQ (Sagendorf,
Goll, and Sandusky 1982). These parameterizations have generally been attributed to Eimutis and
Konicek (1972). However, the 0, parameterization is properly attributed to Tadmor and Gur (1969),
and the o, parameterization is properly attributed to Martin and Tikvart (1968).

The basic dispersion parameter relationships used in the NRC codes are

6, a, x0 (4.11)

©, =3,(x)-x°TM +e,(x) , (4.12)

where

x = the distance from the release point, in meters,
a, = a function of stability class,
a,, b,, and c, = functions of stability class and distance.

Table 4.1 gives values for a, a,, b,, and c,. Note that 0.9031, a,, a,, b, and c, are empirical constants
evaluated by fitting curves. Of these constants, 0.9031 and b, are dimensionless; c, has dimensions of

meters; and a, and a, have dimensions of m“°°%” and m''~*! , respectively.


ig — fy
x10 Tu 0,6, “xp {2} , a6

where F, in Eq. (4.5) is the exponential term in Eq. (4.6). When the the release and receptor are at
ground level and H is large, the sum of exponential terms that comprise F, has a value af 2. Hence, the
constant 2 in Eq. (4.5) does not appear in Eq. (4.6).

Another assumption that deserves comment is that the meteorological conditions are assumed to be
horizontally homogeneous and stationary. This means that the wind direction and speed responsible for
transporting the plume from the release point to the receptor and the turbulence responsible for diffusion
are assumed not to change with location throughout the model domain. It also means that the
meteorological conditions do not change as a function of time during the release and time required for
transport. Together, these assumptions constrain the usefulness of the straight-line plume model to
estimating concentrations and doses at receptors near the release point for short-duration releases; at
longer distances another model is required.

4.1.3 Treatment of Calm Winds

The Gaussian puff model behaves well in calm winds. If the dispersion parameters are a function of
time, as they are in many models, the material in the puff continues to disperse even though it isn’t
moving. If, as in RASCAL 3.0, the dispersion parameters are calculated as the function of travel
distance, dispersion ceases during calm winds, and the material distribution remains unchanged as long
as the wind is calm. In either case, deposition, depletion, exposures, and doses are calculated just as
they are during windy conditions.

The straight-line Gaussian plume model in Eq. (4.5) tends to over estimate concentrations and doses
during low-wind speed conditions and becomes undefined for calm wind conditions because wind speed
is in the denominator. This behavior is the result of the derivation of the straight-line Gaussian plume
model assumes that the wind speed is significantly greater than zero thus eliminating a portion of the
solution of the dispersion equation that deals with low-wind speed diffusion. To compensate for the
missing part of the solution, many straight-line models assume a wind speed of 0.5 to 1 m/s when calm
winds are encountered. However, this assumption does not address the other aspect of calm winds —
the lack of a well-defined wind direction. No entirely satisfactory wind direction assumption exists for
calm winds for a model such as RASCAL.

When the wind speed falls below 0.447 m/s (1 mph), TADPLUME switches from the standard Gaussian
plume model previously described to a plume model derived by Frenkiel (1953). In this model,
described by Csanady (1973) and Kao (1984), the dispersion parameters (0,, 0,, 0,) are assumed to be
functions of along wind, cross wind, and vertical turbulence levels (o,, 6,, 0,,) and travel time (e.g.,
6,=0,t). With this assumption,

o.c -] y2y2 1 7
HQ = S11 4 By? PRexpf SA rtef 2 |) a7
“oo,r 2 oO,r 205r° 2°" Or



where

Hye, = the enthalpy,

P = the atmospheric pressure (psia),

P* = the vapor pressure over liquid UF, (psia),
P, = the density of the liquid (Ib,/ft).

The last term in this relationship is a correction for supersaturated liquids, assuming an incompressible
fluid. Finally, the enthalpy for UF, vapor is given by

H geoy =43.2614 +9.21307 X107T, +6.26265 X10°T? +2951L71T 5.17
43.0939 x10°T, (Zlpr —Ziis 21) 61)
The last term in this relationship is a compressibility correction. This term is small in the atmosphere
because atmospheric pressure is always near 14.7 psia.

5.2.5 Uranium Enrichment

William’s (1985) model includes correction terms for the molecular weight to account for enrichment.
The correction terms are retained in UF6PLUME. The molecular weight of enriched uranium is input
to UF6PLUME along with the release rates. However, the corrections terms have only a small effect on
the results of model computations.

5.2.6 HF-H,O System

William’s (1985) model treats HF and H,O as a system for computation of vapor pressures and enthalpy
assuming that the HF and H.O are vapors in equilibrium with a condensed phase. It is unlikely that a
condensed phase will occur in the atmosphere because of the exothermic nature of the UF,/H,O reaction.
However, the equations for the condensed phase are included in UF6PLUME for completeness. HF
vapor in the atmosphere is assumed to exist as a set of polymers linked by hydrogen bonding. The
effects of this self association are included in the HF vapor pressure and enthalpy calculations.

5.2.7 HF Self Association
According to Williams (1985), Beckerdrite, Powell, and Adams (1983) report that the self association of

HF is reasonably modeled by assuming equilibrium among an HF monomer (HF),, an HF trimer (HF),,
and an HF hexamer (HF),. The partial pressure of HF is given by

Pur =Piu,, +K Piney +K Piney, + (5.18)

where the second and third terms on the right are the partial pressures of the polymers and K, and K, are
equilibrium coefficients. The equilibrium coefficients have been determined experimentally by
Strohmeier and Briegleb (Beckerdrite, Powell. and Adams 1983). Using these data, Williams (1985)
derived the following relationships to estimate the coefficients

5-6


of day and meteorological conditions and replace values that are out of the expected range with more
likely values.

When the first option is selected, Table 6.2 is used to estimate the stability class from wind speed,
precipitation type, and the time of day. Factors discussed by Turner (1964) were used in selecting the
stability classes for the table. Daytime is defined as one hour after sunrise to one hour before sunset.
Nighttime is defined as one hour before sunset to one hour after sunrise.

Table 6.2 Estimated Atmospheric Stability Class for

Missing Stability Classes
No or Light Moderate or Heavy
Wind Speed (m/s) Precipitation Precipitation

Daytime

< 6.0 3 3

> 6.0 4 4
Nighttime

< 3.0 6 5

3.1-5.0 5 5

> 5.0 4 4

When the second option is selected, Table 6.3 is used to determine the reasonable range of stability
classes given the time of day, wind speed, and precipitation type. These ranges are based on factors
discussed by Turner (1964). If a meteorological station stability class falls within the reasonable range,
the stability class is not modified. But if the stability class falls outside the range, the stability class is
changed to the closest stability class within the range.

6.3.3 Precipitation Class

Wet deposition in TADPLUME, TADPUFF, and UF6PLUME and the reaction between UF, and
water in UF6PLUME are affected by precipitation. Information on precipitation may be entered for
each station during meteorological data entry by selecting one of seven precipitation classes, or
unknown, if appropriate. In addition to none, the precipitation classes are light, moderate, and heavy
rain; and light, moderate and heavy snow. In the context of RASCAL 3.0, rain includes drizzle,
freezing rain, and freezing drizzle; and snow includes snow grains, snow pellets, ice pellets, ice crystals,
and hail. METPROC estimates precipitation rates from precipitation classes. Estimation of precipitation
rates is covered in Section 6.4.6.

6-5


Table 3.8 Reduction Factors Available in Each
Fuel Cycle and Materials Release Pathway

Pathway
§
2/2 ]2 3
¢|e]8 5
. . s$i/2}/2/s °
Reduction mechanism 2/518 ]8 z
Fire x?
Filters x’ x
Sprays x
Building retention x? | x? xX
Other x

“Isotopes and materials in a fire only
° Factors used may be modified by the user

Table 3.9 Reduction Factors for Fuel Cycle and Materials

Halogen and Ref.

Reduction Noble gas _| Other NUREG
Filters 1 0.01 1228
Sprays 1 h factor | /CR-4722
(exponential time dependence) <0.25 ev (Fig. 5)

20.25 eft
Containment holdup 1 h factor | 1150
(exponential time dependence) <2 el?" | App. B

22 e 1St
Other reduction 1 1 N/A
Minimum reduction, except for filters 0 0.001 1228
Minimum reduction, sprays only 0 0.03 /CR-4722

(Fig. 5)



APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE

3
, z |é
EI 2 2 a. o
Beja |e id |e le |e
ae: ae: s | |g |g | |4 |,
ef ole le ie lege E laa
3 g § g 2 8 eo le oo) 30 £/a
Name & (é 2 \é 2 18 Ala E < |2é8
(gal) fe %Id_|psi|MW(t)
Arkansas - Unit 1 PWR |Dry Ambient | 177/Once-Through | 188824] 2100000| 0.2| 59] 2568] 22000] 15000|Operational
Arkansas - Unit 2 PWR |Dry Ambient | 177|/U-Tube 206985| 1800000] 0.1] 54} 2815] 22000] 15000|Operational
Sub-
Beaver Valley - Unit 1 [PWR jatmospheric | 157]U-Tube 195000] 1800000] 0.1) 54| 2652] 22000] 15000|Operational
Sub-
Beaver Valley - Unit 2 [PWR jatmospheric | 157}U-Tube 195000] 1800000] 0.1] 54 2652} 22000] 15000/Operational
Big Rock Point BWR {Dry Ambient | 84|N/A 0} 1200000} 0.5] 27] 240} 22000] 15000|Decommissioned
Braidwood - Unit 1 PWR [Dry Ambient _| 193|U-Tube 250808} 2900000} 0.1] 61] 3411] 22000] 15000|Operational
Braidwood - Unit 2 PWR [Dry Ambient | 193|U-Tube 250808| 2900000} 0.1] 61) 3411] 22000] 15000|Operational
Browns Ferry - Unit 1 BWR [Mark I T64|N/A 164650} 160000) 0.5] 56] 3293] 22000] 15000|Operational
Browns Ferry - Unit 2 BWR [Mark I T64|N/A 164650] 160000) 0.5] 56] 3293] 22000] 15000|Operational
Browns Ferry - Unit 3 BWR {Mark I 764|N/A 164650] 160000] 0.5] 56} 3293} 22000} 15000/Operational
Brunswick - Unit 1 IBWR [Mark I S60|N/A 127900{ 160000) 0.5] 62] 2436] 22000] 15000|Operational
Brunswick - Unit 2 IBWR {Mark I 560|N/A. 121800] 160000} 0.5] 62] 2436} 22000} 15000/Operational
Byron - Unit 1 PWR [Dry Ambient | 193/U-Tube 250808] 2900000] 0.1] 61] 3411) 22000] 15000|Operational
Byron - Unit 2 PWR [Dry Ambient | 193/U-Tube 250808] 2900000} 0.1] 61] 3411] 22000] 15000|Operational



— —
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION | 1. REPORT NUMBER
Kaan 1102, (Assigned by NAC, Add Vol. Supp., Rev.,
}3201, 3202 BIBLIOGRAPHIC DATA SHEET end Addendum Numbers, f any.)
(See instructions on the reverse)
2. TITLE AND SUBTITLE NUREG-1741 1

RASCAL 3.0: Description of Models and Methods

3.___ DATE REPORT PUBLISHED

MONTH ] YEAR
March 2001
/4. FIN OR GRANT NUMBER
L1565
5. AUTHOR(S) 6. TYPE OF REPORT
A.L. Sjoreen, ORNL (a), J. V. Ramsdell, Jr., PNNL (b), T. J. McKenna, IAEA (c), S. A. Technical
McGuire, NRC (d), C. Fosmire, Innovative Emergency Management (e), and G. F. Athey, Athey c
Consulting (f) 7. PERIOD COVERED (inclusive Dates)

8, PERFORMING ORGANIZATION - NAME AND ADDRESS (i! NAC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and ‘mailing address; if contractor,
provide name and mailing adores.)

(a) Oak Ridge Nationa! Laboratory, PO Box 2008, Oak Ridge, TN 37831; (b) Pacific Northwest National Laboratories, PO Box 999,
Richland, WA 99352; (c) Intemational Atomic Energy Agency, Wagramerstrasse 5, PO Box 100, A-1400, Vienna, Austria; 1
(d) U. S. Nuclear Regulatory Commission, Incident Response Operations, Washingt on, DC 20555; (e) Innovative Emergency
Management, 8555 United Plaza Blvd., Baton Rouge, LA 70809; (f) Athey Consulting, PO Box 178, Charlestown, WV 25414

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (I NAC, type "Same as above’; if contractor, provide NRC Division, Office or Region, U.S. Nuclear Regulatory Commission,
and mailing address.)

Incident Response Operations, U. S. Nuclear Regulatory Commission, Washington D C-20555-0001

10. SUPPLEMENTARY NOTES.
Stephen. A. McGuire, NRC Project Manager

14. ABSTRACT (200 words or fess)

The Radiological Assessment System for Consequence AnaLysis (RASCAL) 3.0 is the latest version of the RASCAL series of
codes. RASCAL was developed for use by U. S. Nuclear Regulatory Commission per sonnel who conduct independent
assessment of radiological accidents to prepare dose Projections. It includes three sets of tools for use in consequence
analysis: STDose, FMDose, and DecayCalc. StDose estimates: (1) source terms for radiological accidents, (2) atmospheric
transport, diffusion, and deposition of effluents from the accidents, and (3) d oses from exposures to the effluents. FMDose
calculates doses from environmental measurements of activity in the air and on the ground. DecayCalc calculates activity of |
radionuclides present at a future time following decay and ingrowth. The curre nt version of RASCAL includes computational
techniques that are substantially modified from those used in the prior version of RASCAL and significantly expands the
capabilities of STDose. The major changes to STDose are: (1) the inclusion of time-dependent source terms and source
terms for fuel cycle and materials accidents, (2) the inclusion of tadiological decay during atmospheric transport, (3) the
addition of a UF6 atmospheric transport model, and (4) the ability to include m eteorological data from multiple stations and the
effects of terrain.

12. KEY WORDS/DESCRIPTORS (List words or phrases that wil assist researchers in locating the report.) 13. AVAILABILITY STATEMENT
Emergency response unlimited
Source term calculations 14, SECURITY CLASSIFICATION
Atmospheric transport (his Page)

Dose calculations unclassified
(This Report)
unclassified

15. NUMBER OF PAGES 1

16. PRICE

NRC FORM 335 (2-89)


NUREG-1741

RASCAL 3.0: Description of
Models and Methods

Manuscript Completed: February 2001
Date Published: March 2001

Prepared by

A. L. Sjoreen*

J. V. Ramsdell, Jr.”
T. J. McKenna‘
S.A. McGuire*

C. Fosmire*

G. F. Athey‘

*Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN 37831

*Pacific Northwest National Laboratories
P.O. Box 999
Richland, WA 99352

‘International Atomic Energy Agency
Wagramerstrasse 5

P.O. Box 100

A-1400, Vienna, Austria

S. A. McGuire, NRC Project Manager

Prepared for

Incident Response Operations

U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

A REG,
tea,
3 2,

£
f
5
8
“,

*
be tad

woo

89,

te,

“Incident Response Operations
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

‘Innovative Emergency Management
8555 United Plaza Boulevard
Baton Rouge, LA 70809

fAthey Consulting
P.O. Box 178
Charlestown, WV 25414


When KI is taken, FMDose reduces the inhalation dose by 95% of the contribution of the thyroid dose to
effective dose (0.03) for all the isotopes of iodine. FMDose writes a table that includes the results of the
calculations both with and without KI taken and with and without respiratory protection.

The turn-back limits used in the calculations are shown in Table 7.1

Table 7.1 Emergency Worker Turn-Back Limits?

Emergency Worker Activity Limit (rem)
All 5
Protecting valuable property 10
Life saving 250
Life saving: to exceed this limit the worker >250
should be a volunteer and be trained on the

impact of radiation exposure

* Source: EPA 1992.

7.3 EARLY-PHASE EXPOSURE-RATE DILs

Early-phase DILs are used to promptly assess deposition to identify locations where the early-phase
TEDE PAG may be exceeded after the plume passes. DILs are calculated from both air and ground
concentrations, if the user has entered both. FMDose also computes a ground-only DIL that includes an
estimate of the air concentrations that resulted from resuspension of activity on the ground. Both total
DIL and radionuclide-specific DILs are calculated. This calculation is from Method M.3.2 of the
FRMAC assessment manual (DOE 1995).

The total DIL is computed as
MR

DiLec =P, x :
Dreve

(7.7)

where P, is the early-phase PAG for this DIL.

The Dygpg includes 4 days of ground shine and 1 h of air submersion and inhalation. Doses used in the
early-phase DIL calculations are computed as described in Section 7.1.4.

The radionuclide specific DILs are computed as
Cai
Drtepe

DILeG =Pgg X (7.8)

7-4


boundaries. Signs of heights that are negative are changed to positive, and heights (h,) that are above the
mixing layer are replaced by 2H-h,.

The dose rate at ground level from a slab is calculated as

015°Q,DF, 2
D', (1,2) =—-_,—exp {2} 1+kpz)exp(—pz) , (4.41)
270, oO,

y y

where

z = height of the slab above the receptor, which is assumed to be at 1 m (m),
DF,,, = dose factor radionuclide n for an infinite plane {(rem/s)/(Ci/m?)],

# = total gamma ray absorption coefficient for air (m"),

k = ratio of energy in scattered photons to absorbed energy.

The infinite plane dose factor is approximated by

DF yy =DFiigg/ 241.2, (4.42)

where DF,,., is the semi-infinite cloud dose factor [(rem/s)/(Ci/m*)] and 241.2 is a constant with units of
meters evaluated by comparing dose rates calculated by Eq. (4.35) with semi-infinite cloud dose rates in
plumes for which the semi-infinite cloud model is appropriate. Semi-infinite cloud dose factors
contained in Federal Guidance Report No. 12 (Eckerman and Ryman 1993) are used to estimate the
infinite-plane dose factors. These calculations were carried out for 30 radionuclides that are typically
released in reactor accidents involving fuel damage. The standard deviation of the estimates of the
constant value was 0.04.

In Eq. (4.41), the term (1+kyz) represents the buildup factor due to scattered photons, and exp(-pz)
represents the absorption of energy by the air. These terms are discussed by Healy and Baker (1968)
and Healy (1984). In RASCAL 3.0, » and k are assumed to be constants with values appropriate for
~0.7 MeV photons (4 =0.01, k=1.4) based on Figure 16.4 of Healy (1984).

Ultimately, the dose rate at a receptor is

013° Q,DF,.
D',(r) -—Te

y

2 10
exp) -of } (1+kpz,)exp(—pz,) , (4.43)

Tt
G,

where the summation is over all slabs.
When the vertical extent of the puff is sufficient for the semi-infinite cloud mode | to be appropriate
(o, > 400 m, or a uniformly-mixed plume with a vertical depth > 600 m), the cloud-shine dose rate is

calculated using the semi-infinite cloud model

4-21


modified to force the centers of puffs to pass directly over the receptor nodes. As a result, when the
wind direction is constant, TADPUFF may not calculate centerline concentrations and doses. However,
as time goes by and wind directions change, TADPUFF will give more realistic concentration and dose
patterns than TADPLUME. In addition, TADPUFF may give more realistic concentration and dose
patterns than TADPLUME when topography modifies the winds because the wind fields used by
TADPUFF can be modified to account for topography. The wind data used by TADPLUME are not
modified to account for topography.

The movement of puffs is controlled by the wind at the center of the puff as the puffs move through the
model domain. The spatial variation of winds is represented in TADPUFF by two-dimensional fields of
vectors that give the direction and speed of puff movement. These fields are prepared by the
meteorological model discussed in Section 6 and are updated at 15-min intervals based on the available
wind data.

Calculation of puff movement is a six-step process. In sequence, the steps are

1. Make an initial estimate of the direction and speed of the puff movement given the current puff
position and height above ground using bilinear interpolation (Press, et al. 1986) of the vectors at
the nearest nodes of the field;

2. Make an initial estimate of the puff position at the end of the period using the the initial estimates
of direction and speed;

3. | Make a second estimate of the direction and speed of puff movement using the estimated puff
position at the end of the period;

4. Make a second estimate of the puff position at the end of the period using the estimate of direction
and speed from step 3;

5. Average the end points calculated in steps 2 and 4;

6. Calculate the final estimate of direction and speed of puff movement using the puff’s initial
position and the average end point calculated in step 5.

The actual puff movement for the period may take place in one or several steps. The step size is
adjusted to ensure adequate accuracy in the integration of concentrations that takes place at receptors.
Errors in the integration should be less than 5% at common wind speeds. Larger errors may occur near
the release point and in high wind speed conditions, because the minimum step size is 30 s. These larger
errors should not be a problem because the plume model output should be used for receptors near the
release point.

The vector fields prepared by the meteorological program are for a height of 10 m above ground. These
vectors are used for puffs that represent ground-level releases. If the release height is greater than 12 m,
a wind-speed profile is used to adjust the transport speed from 10 m to the puff transport height. The
profile used to adjust the wind speed considers both surface friction and atmospheric stability (see
Section 6.4.2 or Panofsky and Dutton 1984, Sections 6.4-6.6).

47


U.S. Nuclear Regulator Commission (NRC). 1972. “Onsite Meteorological Programs.” Regulatory
Guide 1.23.

Panofsky, H. A., and J. A. Dutton. 1984. Atmospheric Turbulence. J. Wiley & Sons, New York.

Pasquill, F. 1961. “The Estimation of the Dispersion of Windborne Material.” The Meteorological
Magazine, 90:33-49.

Paulson, C. A. 1970. “The Mathematical Representation of Wind Speed and Temperature Profiles in
the Unstable Atmospheric Surface Layer.” J. of Applied Meteorology, 9:1884-89.

Ramsédell, Jr., J. V., G. F. Athey, and C. S. Glantz. 1983. MESOI Version 2.0: An Interactive
Mesoscale Lagrangian Puff Dispersion Model With Deposition and Decay. NUREG/CR-3344, U.S.
Nuclear Regulatory Commission.

Ramsdell, Jr., J. V., etal. 1988. The MESORAD Dose Assessment Model, Volume 2: Computer Code.
Vol. 2., NUREG/CR-4000, U.S. Nuclear Regulatory Commission.

Ramsdell, Jr., J. V., C. A. Simonen, and K. W. Burk. 1994. Regional Atmospheric Transport Code
Sor Hanford Emission Tracking (RATCHET). PNWD-2224 HEDR, Battelle, Pacific Northwest
Laboratories, Richland, Wash.

Rogers, R. R., and M. K. Yau. 1989. A Short Course in Cloud Physics. Pergamon Press, New York.

Ross, D. G. 1988. “Diagnostic Wind Field Modeling for Complex Terrain: Model Development and
Testing.” J. of Applied Meteorology, 27:785-96.

Scherpelz, R. I., et al. 1986. The Mesorad Dose Assessment Model. Vol. 1., NUREG/CR-4000, U.S.
Nuclear Regulatory Commission.

Snedecor, G. W., and W. G. Cochran. 1980. Statistical Methods. 7® Edition, Iowa State University
Press, Ames, Iowa.

Stull, R. B. 1988. An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers,
Dordrecht, Netherlands.

Turner, D. B. 1964. “A Diffusion Model for an Urban Area.” J. of Applied Meteorology,
3(1):83-91.

U.S. Environmental Protection Agency. 1999. PCRAMMET User’s Guide. EPA-454/B-96-001
(Revised June 1999), Research Triangle Park, N.C.

6-18


Table 2.6 Fuel Release Fractions Used in Spent Fuel Accidents*

STCP category Fire’ Hot gap | Cold gap

Noble gases 1 0.4 0.4
Halogens 0.7 3x10? 3x10°
Alkali metals 0.3 3x10? | 3x10°

Tellurium group | 6x10? | 1x10° 1x10

Barium, strontium | 6X10* | 6x10 | 6x107

Noble metals 6x10* |6x10* | 6x10"
Cerium group 2x10* |6x10* |6x10’
Lanthanides 2x10* | 6x10* 6x10"

“Source: First three columns from Table 3.2 in NUREG/CR-

6451 (Travis. Davis, and Grove 1997).

‘The fire release from a spent fuel pool values are the geometric
mean of the high and low fractions presented in the referenced

NUREG/CR-6451.

to non-noble gas fission products if the user specifies that the release will be through a filtered vent. The
user specifies the duration of the release and the percentage release rate.

2.2.3 Release from a Dry Storage Cask

A release is assumed to occur if an accident causes damage to the cladding of the fuel stored in the cask and
causes the integrity of the fuel cask to be lost. It is assumed that only one cask is involved in the accident.
The user can define the number of assemblies involved in the accident by selecting the type of fuel cask or
by directly entering the number of assemblies. Activity can be released from the cask if there is either major
damage to the cask and the fuel elements inside of it or if there is a loss of cooling for more than the thermal
limit (24 h). If assemblies are damaged without heating cold gap release fractions in Table 2.6 are used.
Loss of cooling results in a hot gap release. The hot gap spent fuel pool release fractions in Table 2.6 are
used. In calculating the activities, all fuel in the cask is assumed to have been in storage for the same amount
of time. There are no reduction mechanisms to reduce the amount of activity released. The user specifies
the duration of the release and the percentage release rate.

No release is assumed to occur if cooling is lost for less than the thermal limit or the cask is engulfed ina
fire because the casks are designed to maintain their integrity in those situations.

2-15


1E+05,

mo a

:
g 1E+02
5 1E+01 F
S  1B+00
°
3 101
2 1B-02
2
g 1E03
2 1E-04
1E-05 f-
16-06 1 1 4 1 1 1 4 1
ib dh ry mb 1b 2b th an
In-Vesse! Melt Gap Spiked Coolant Normal Coolant

CORE DAMAGE AND TME AFTER REACTOR SHUTCOWN

Figure 2.6 BWR Mark III Dry Well Containment Monitor Response (sprays on).

1E+05
tne i

1E+

§
a é

an mun im us th un an us
Tae Vessel Matt op Spiked Cootaat ‘Normal Coolant

1E+

g
T

1E+

8
T

1 TO 100% RELEASE TO CONTAINMENT (R/h)

PEGE

CORE DAMAGE AND TIME AFTER REACTOR SHUTOOWN:

Figure 2.7 BWR Mark III Dry Well Containment Monitor Response (sprays off).

2-11


N
Do =Gcorr x} (DCFeixEsi) > (7.3)
i=l

where

Gcorr = Selected ground surface correction factor (default: 0.7),
DCF, = effective dose factor from exposure to contaminated ground for radionuclide i,
Eg = exposure to the ground over the selected exposure period.

7.1.4 TEDE Dose

TEDE is an estimate of the total dose from all pathways. The TEDE is used to compare to early-phase
PAGs. TEDE, is

TEDE =De+Ds+De . (7.4)
where

De = 50-year committed effective dose equivalent from inhalation [Eq. (7.1)],
Dg = effective dose equivalent from air submersion [Eq. (7.2)],
Dg = effective dose equivalent from ground shine over 4 days [Eq. (7.3)].

7.2 EMERGENCY WORKER TURN-BACK GUIDANCE

Emergency worker turn-back guidance defines the self-reading dosimeter reading that should result in
acceptable doses to workers who perform various kinds of emergency services. This calculation is from
Method M.2.2 of the FRMAC assessment manual (DOE 1995). Emergency worker guidance values,
EWyp, are computed as

Lew (7.5)

1+ 10—ER xe)
MR

EWre=

where

Lew = specific turn-back limit,
ER = respiratory protection efficiency entered by the user,
Dy = 50-year committed effective dose equivalent rate (rem/h) computed as the dose from 1 h of

exposure [Eq. (7.3)],
MR = meter reading.


3.1 CALCULATION OF THE AMOUNT OF ACTIVITY AVAILABLE FOR
RELEASE IN FUEL CYCLE AND MATERIALS SOURCE TERMS

3.1.1 UF, Releases from Cylinders and Cascade Systems

Two types of source term scenarios are available that release UF,: cascade releases and cylinder
releases. Only gaseous diffusion plants have cascades. Cylinder releases can occur at any facility that
stores UF,.

In the cascade scenario, the user enters the amount of UF, in the cascade. This amount may be entered
(1) directly or (2) as a total mass, in the pounds of UF, per cell and the number of units or cells in the
cascade that are involved in the release. STDose assumes that there are ten cells per unit. When the
number of cells is entered, the amount of material available is the product of the number of cells times
their inventory. When the number of units is entered, this result is divided by ten. The user also enters
the maximum fraction of the mass of material in the cascade that is available for release and the rate at
which the material escapes from the cascade to its building.

In the cylinder scenario, the user enters the amount of UF, in a cylinder release as the mass of the
available inventory or as the number of 14-ton, 10-ton, and 2.5-ton cylinders involved. The 2.5-ton
cylinder is assumed to contain 2277 kg UF,, the 10-ton cylinder is assumed to contain 9539 kg, and the
14-ton cylinder, 12,338 kg. The initial amount of material is the sum of the number of each type of
cylinder times the amount of UF, in that type of cylinder. The user also enters the rate at which material
is escaping from the cylinder. The user enters a maximum fraction of the cylinder that can be released,
unless the UF, is liquid and the release is caused by a valve failure. In this case, the valve location is
used to set the maximum release fraction. The relationship between valve position and release fraction is
shown in Table 3.1. (All cylinders are assumed to have the same maximum release fraction and release
rate.) All UF, releases through a building (or filters) are assumed to convert to UO,F, and HF prior to
release to the atmosphere. All releases of UF, that are solid in their cylinders are converted to UO,F,
and HF prior to release to the atmosphere, unless the cylinder is ina fire. UF, is converted as 1 kg of
UF, = 0.88 kg UO,F, +0.23 kg HF.

Table 3.1 UF, Release Fractions Based

on Valve Location
Maximum release
Valve position fraction
360° — facing up 1.00

270° — facing the side | 0.50

180° — facing down 0.25

3-2


APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

; s |e
&

2/8 _ de £12

2 Pas g |2 |e |, s |g

& <8 g |s a je) je |é

2 |: g g |s gs |eie |e [2 als
2 |s g | § 2 a @ |erg |e Te ee
Name = 1d Z 1a £8 A léls |2 [22
(gal) ft? %Id_|psi |MW(t)

Dresden - Unit 2 IBWR |Mark I T2AIN/A. 126350|__ 160000} 0.5] 62| 2527] 22000] 15000|Operational
Dresden - Unit 3 IBWR |Mark I TR4|N/A 126350|__160000| 0.5} 62] 2527] 22000] 15000|Operational
Duane Arnold BWR [Mark I 368|N/A 82900} 130000) 0.5] 56] _3430|_ 22000] 15000|Operational
Edwin I. Hatch - Unit 1 BWR [Mark I 560|N/A 127900] 150000} _1.2{ 56] _2436| 22000} 15000|Operational
Edwin I. Hatch - Unit 2 BWR |Mark I 560|N/A 127900] 150000} 1.2] 56] 2436] 22000] 15000|Operational
Fermi - Unit 2 BWR [Mark I 764|N/A 171500] 160000} 0.5] 56] _3430| 22000] 15000/Operational
Fort Calhoun PWR [Dry Ambient | 133]U-Tube 110294] 1100000] 0.2] 56] 1500] 22000] 15000] Operational
Generic BWR Mark I IBWR [Mark I 550|N/A 170000} _ 250000] 0.54] 60] _2500| 22000] 15000|Generic
Generic BWR Mark II IBWR [Mark II 55S0|N/A. 170000} 350000] 0.58] 50} 3000} 22000] 15000|Generic
Generic BWR Mark III BWR |Mark Ill 700|N/A 170000] 1250000} 0.36] 15] __3400|_ 22000] 15000|Generic
Generic PWR with Ice
Condenser Containment PWR |Ice Condenser} 200|U-Tube 250000} 1200000} 0.25] 15] 3500] 22000/ 15000|Generic
Generic PWR with Large,
Dry Containment [PWR {Dry Ambient | 200]U-Tube 250000} 2500000} 0.1} 50] 3800} 22000] 15000|Generic



Ah =38.71F)Su(h)” , (4.23)

again depending on the value F,. Equation (4.22) is used when F, is less than 55, otherwise Eq. (4.23)
is used.

4.5.2 Stable Atmospheric Conditions

As in unstable and neutral conditions, plume rise is dominated by momentum if the atmospheric
temperature exceeds the effluent temperature. If the effluent temperature is greater than the ambient
temperature, a At, is calculated to differentiate between momentum- and buoyancy- dominated plumes.
The At, is given by Petersen and Lavdas’ Eq. A-11

At, =0.0196w,T,S'? , (4.24)

where S is a stability parameter associated with the frequency of vertical oscillation of air parcels in a
stable atmosphere. The square root of this parameter is known as the Brunt-Vaisala frequency discussed
in texts on the atmospheric boundary layer, e.g., Panofsky and Dutton (1984) or Stull (1988). It is
defined by

s=et'S (4.25)

where 06/z is the potential temperature lapse rate shown in Petersen and Lavdas’ Eq. A-10.
Following Petersen and Lavdas, potential temperature lapse rates of 0.02°K/m and 0.035 °K/m are
assumed in TADPLUME and TADPUFF for Pasquill-Gifford stability classes E and F, respectively. A
lapse rate of 0.05°K/m is assumed for G stability class following Ramsdell, Simonen, and Burk (1994).

In stable conditions when the temperature difference is less than At,, plume rise is momentum dominated

and a plume rise estimate is made using Eq. (4.18). The plume rise is also estimated using Petersen and
Lavdas’ Eq. A-16

te}

15 { F,w,T,

a= 3(2e | 429)
slop

where F, is the stack flow (m°*/s). The two plume rise estimates are compared, and the smaller value is
selected.

When plume rise is determined to be buoyancy dominated in stable conditions, the stack-height wind
speed is compared with a critical wind speed to determine whether conditions are calm or windy. The
critical wind speed, u,, is calculated using Petersen and Lavdas’ Eq. A-15

u, =0.2746F!48"5 (4.27)

4-13


results are multiplied by the actual activity of the parent. The activities of short-lived daughters are not
automatically set equal to their parents, as is done in STDose and DecayCalc.

8.3 REFERENCES
U. S. Environmental Protection Agency (EPA). 1993. “External Exposure to Radionuclide in Air

Water, and Soil.” Federal Guidance Report No. 12, EPA-402-R-93-081, U.S. Environmental
Protection Agency.

8-3


Air, water vapor, and HF are assumed to be ideal gases; a compressibility factor is used to account for
deviation of UF, behavior from that of an ideal gas. Although UF, cannot exist as a liquid at
atmospheric pressures, equations for the density, vapor pressure, and enthalpy of liquid UF, are
included in UF6PLUME because they were included in the computer code published by Williams
(1985).

5.2.1 Compressibility Factor

Dewitt (1960) cites work by D. W. Magnuson in Presenting the following relationship for UF,
compressibility factor

= L

© (1) +4892 x10) , 6.7

where
Z = the compressibility factor,
T, = the temperature (°R),
P = the pressure (psia).
5.2.2 UF, Density
The density of UF, is given by the following relationships. The relationships for the UF, liquid and

vapor are based on the work of Dewitt (1960), and the relationship for the density of UF, solid was
derived by Williams (1985) based on data presented by Dewitt. The density of solid UF, is given by

MW
Pures =330.0 oreo (22) . (5.8)

where
Pures = the density of the solid (Ib,,/ft),
t = the temperature (°F),
MW = the molecular weight.

The density of liquid UF, is given by

Parsi = (2506 —0.1241t, +2.620 xo (Se) (5.9)
and the density of UF, vapor is given by
_MW-P-Z

Puss =o (5.10)

5-4


Table 2.7 Reduction Factors Available in Each Reactor

Release Pathway
Pathway
2
2
a
2
Sle 2
s a o o 3
B/E) 2] 2] 5
zel/ze/slsle
S/s/2/]s]5
€ = =J=o {5
& a °° 3 i)
8s Ss Es = E
: . 5 5 3 >| s
Reduction mechanism O10 Slala
Fire
Filters xe |X |X
Sprays x =| x? x
Containment holdup x xX [XxX
Plate out (bypass only) x?
Sub-cooled or saturated pool x
Ice condenser x
Steam generator—partitioned or x?
not partitioned
Steam jet air ejector release x?
“Only when through a building

*Only if no other reduction is active
“PWR with ice condenser only
4PWR only

After the amount of time that the reduction mechanism is active has passed the initial time interval, T,,
the RDF is

RDF se ~*T ee -¥(T-TTM 2.8)

Since the user can enter release and reduction data that changes with time, it is possible to turn the sprays
on and off several times. The initial spray, A,, applies to (1) all the activity in containment the first time
the sprays are turned on, and (2) all the activity that enters the containment the first time that sprays are
active. If the sprays are turned off and then turned back on, only the continuing A, is used. The initial
4, for holdup applies only if the sprays were never turned on. Otherwise the continuing A, is used.

2-17


from current meteorological data is preferable to estimating the mixing height from climatological data,
if sufficient data are available.

METPROC uses algorithms developed by Ramsdell, Simonen, and Burk (1994 ) for estimating mixing
height from current meteorological data. The algorithms are based relationships derived by Zilitinkevich
(1972) for stable and neutral conditions. For stable atmospheric conditions, the relationship is

V2
H -1(2*) . (6.5)

where

H = mixing height (m),

k = von Karman constant (0.4),
u. = friction velocity (m/s),

L = Monin-Obukhov length (m),
f = Coriolis parameter (1/s).

A 50-m mixing height is used if the mixing height calculated by Equation 6.5 is less than 50 m.
Similarly, if the calculated mixing height is greater than 2000 m, the mixing height is set to 2000 m.

For neutral and unstable conditions, the mixing height is calculated by
Het (6.6)

where f is a constant set to 0.2. If the mixing height calculated by Equation 6.6 is less than 250 m, the
mixing height is set to 250 m, and if the calculated mixing height is greater than 2000 m, the mixing
height is set to 2000 m.

The mixing-layer thickness may also be estimated from climatological data. When this option is
selected, the mixing-layer thickness is estimated from typical morning and afternoon thicknesses for each
month using the method used in the Environmental Protection Agency’s meteorological Preprocessor
code, PCRAMMET (EPA 1999). The monthly morning and afternoon mixing-layer thicknesses were
calculated from daily data obtained from the Environmental Protection Agency’s Support Center for
Regulatory Air Models (http:/www.epa.gov/scram001/). The following rules are used in estimating
mixing-layer thicknesses from the monthly values.

@ — From midnight to sunrise—use the morning mixing height.
© — From sunrise to 1400—linearly interpolate between morning and afternoon mixing heights.
© — From 1400 to sunset—use the afternoon mixing height.

6-11


1 INTRODUCTION

The Radiological Assessment System for Consequence AnaLysis (RASCAL) 3.0 is the latest version of
RASCAL (Athey, Sjoreen, and McKenna 1989; Athey et al. 1993, Sjoreen et al. 1994, Athey, Sjoreen,
and Ramsdell 1997). RASCAL was developed for use by U.S. Nuclear Regulatory Commission (NRC)
personnel who conduct an independent assessment of radiological accidents to prepare dose projections.
RASCAL includes three sets of tools for use in consequence analysis STDose, FMDose, and DecayCalc.
STDose estimates (1) source terms for radiological accidents, (2) atmospheric transport, diffusion, and
deposition of effluents from the accidents, and (3) doses from exposure to the effluents. FMDose
calculates doses from environmental measurements of activity in the air and on the ground at a single
location. DecayCalc calculates activity of radionuclides present at a future time following radiological
decay and ingrowth.

Documentation for the earlier versions of RASCAL has generally been limited to user’s guides (Athey,
Sjoreen, and McKenna 1989, Athey et al. 1993, Sjoreen et al. 1994, Athey, Sjoreen, and Ramsdell
1997) and workbooks (Athey, Sjoreen, and McKenna 1993, Athey and McKenna 1994). The user’s
guides have contained brief technical descriptions of the computational models implemented in the
consequence assessment tools and have referred readers to other documents for details. The current
version of RASCAL includes computational techniques that are substantially modified from those used in
the prior versions of RASCAL and significantly expands the capabilities of STDose. Therefore we are
publishing this compilation of the technical bases for the RASCAL 3.0 tools.

1.1 STDOSE

STDose is the primary tool for consequence analysis. It includes five computational modules —
STCALC, TADPLUME, TADPUFF, UF6PLUME, and METPROC. The technical bases for these
modules are presented in this document. The sixth STDose module, VIEWMET, is used by STDose to
display meteorological data and does not perform any computations. VIEWMET is not discussed further
in this document.

STCALC estimates the amount of radioactive (or hazardous) material released from a wide variety of
potential radiological accident scenarios. The source term calculations performed can be generally
categorized as (1) nuclear power plant accidents, (2) spent reactor fuel accidents, (3) fuel cycle
facility/UF, accidents, (4) uranium fires and explosions, (5) criticality accidents, and (6) isotopic releases
(e.g., transportation, materials). The source terms estimated are time dependent and are intended to be
somewhat conservative but in general to be “best guess” estimates. The technical bases for STCALC
estimates for reactor and spent fuel accidents are presented in Section 2. The technical bases for
STCALLC estimates for fuel cycle and materials accidents are presented in Section 3.

TADPLUME and TADPUFF perform atmospheric transport, diffusion, and dose calculations for
releases in which the activity released can be treated as a passive atmospheric constituent. For RASCAL
3.0 these codes have been modified to permit temporal variation of release rates by radionuclide and to
track deposition by radionuclide. TADPUFF has been modified to accept spatial as well as temporal
variation of winds, atmospheric stability, precipitation, and mixing-layer thickness. The codes now

1-1


where R is the universal gas constant, 10.73 (psia -ft°)/(Ib-mol °R).
5.2.3 UF, Vapor Pressure

The following relationships, based on the work of Dewitt (1960), describe the vapor pressure of UF,.
The constants in the relationships assume English units for pressure, temperature, and volume. From
32°F to the tiple point of 147.3°F, the vapor pressure of UF, the solid phase is

39010?

S.11
(t, +298.1) em

Pures of 0.44 +9.642 x10 t,

where Ps, is the vapor pressure (psia) and tf is the temperature (°F). From the triple point (147.3°F)
to 240°F, the vapor pressure is given by

4.668 x10°
Puro = 12.16 ——_____ 5.12
uf 6vl on (i; oar] (5.12)
and from 276°F to the critical temperature (446°F) the vapor pressure is given by
6.976 x10?
Paroyn = XP] 13.76 -————_ |. 5.13
uf6vh a ee ¢ )
Between 250°F and 276°F, the vapor pressure is estimated by a weighted average of Py, and Prrovn
t, —240.0
Puro = Paton (160-4) +P SSO] : (5.14)

5.2.4 UF, Enthalpy
Williams (1985) provides the following equations for the enthalpy of UF, using 25°C (77°F) as a base.

The equations are to a large extent based on data of Dewitt (1960). For solid UF,, the enthalpy is given
by

_ 2 472 4
H yegs =50-446 ~5.70531 x10 T, +1.27509 x10 1? — 9645637! , (5.15)

where Hyg, is the enthalpy (Bru/Ib,,). For liquid UF,, the enthalpy is given by

H ror = 30.6133 + 5.100577107 T, + 5.13165210°T?

P-Pe .
-6.139.34T,1+ canned OP) : 6-16)
y

5-5


. deposited uranium (g/m’),

. average HF concentration (ppm by volume),
. 1-h equivalent HF concentration (ppm by volume), and
. HF deposition (g/m’).

The airborne uranium exposure and uranium deposition are calculated, accounting for deposition and
depletion. The inhaled uranium and the dose commitment are calculated from the airborne uranium
exposure. Similarly, an HF exposure and HF deposition are calculated, accounting for deposition and
depletion. The average HF concentration is calculated from HF exposure. The 1-h equivalent HF
concentration is an effective concentration calculated for short-duration releases for comparison with
toxicity limits. It is calculated as

ut
t
=c(pf 5.35
Cube cols) , (5.35)

where
C,,. = 1-h equivalent concentration (ppm),
C(t) = average concentration for duration t (ppm),
t = duration of the exposure to concentration C(t) (s).

UF6PLUME does not calculate cloud-shine or ground-shine doses.

5.4 REFERENCES

Beckerdrite, J. M., D. R. Powell, and E. T. Adams. 1983. “Self-Association of Gases, 2: The
Association of Hydrogen Fluoride.” J. Chem. Eng. Data, 28:287-93.

Briggs, G. A. 1984. “Plume Rise and Buoyancy Effects.” Atmospheric Science and Power Production.
Ed. D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Dewitt, R. 1960. Uranium Hexafluoride: A Survey of the Physico-Chemical Properties. GAT-280,
Goodyear Atomic Corporation, Portsmouth, Ohio.

Williams, W. R. 1985. Calculational Methods for Analysis of Postulated UF6 Releases. 2 Vols.,
NUREG/CR-4360, U. S. Nuclear Regulatory Commission.


LIST OF FIGURES

Figure Page

2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8

PWR Containment Monitor Response (sprays on) .......--.-- 200s cece e eee eee eee 2-8
PWR Containment Monitor Response (sprays off) ........--...... :

BWR Mark I & II Dry Well Containment Monitor Response (sprays on) .
BWR Mark I & II Dry Well Containment Monitor Response (sprays off) . .
BWR Mark I & II Wet Well Containment Monitor Response (sprays on)
BWR Mark III Dry Well Containment Monitor Response (sprays on) .....
BWR Mark III Dry Well Containment Monitor Response (sprays off) . . -
BWR Mark IIT Wet Well Containment Monitor Response



decay data using a binary search and then sum it for 1 h, then for 5 min twice, then for 1 min twice.

STDose extracts the required 5-min and 15-min decay data for the radionuclides in the source term and
passes them in a file to TADPUFF or TADPLUME for the calculation of decay during atmospheric
transport.

In STDose only, the activities of the short-lived daughters are initially set equal to their parents. These
are listed in Table 8.1. (Note that only 0.16 of the I is set to °"Xe.) The activities of the parents and
daughters may not remain equal throughout the accident because reduction mechanisms may affect them
differently.

Table 8.1 Short-lived Daughters Whose
Activities are Set Equal to-Their
Parents’ Activities

Parent Daughter
“Ti “Sc

“Ge “Ga

Kr Rb

Mo TC
Ru 2Rh
195Cq 105m A g
"Sn 13mIp
Sn 126285 Sb
10Te Te

57 (x 0.16) 135mXe
BICS piaBa
Ce “pr

8.2.2 FMDose

FMDose calculates decay directly. The Chain program has been modified to be called as a subroutine.
FMDose calls Chain for each parent radionuclide. Depending on the calculation being performed, it

returns either the activity remaining after the decay period or the amount of integrated activity for each
parent and its daughters integrated over the decay period and assuming an initial activity of one. These

8-2


The UF,-H,0 reaction is limited by one constituent or the other. If the available water is the limiting
factor, the heat of reaction is calculated as

Hy, =25.199 x10? Be : (5.26)

blo

where

H,,. = heat of reaction,
M2. = mass of water available for the reaction,
MW,,, = molecular weight of water.

Otherwise, the heat of reaction is calculated as

H gy = 50.398 x10?
t x10 (8.27

With completion of the UF,-H,O reaction, the enthalpy of the plume in the control volume is

H = AH ji, + AH roy + AB ye + AH nro +A yore? tHe - (5.28)

plume

The change in enthalpy of air is
4H ,,, =0.24037m,,, (tase -17.0) (5.29)

and, the change in enthalpy associated with entrained water is
AH ,,, =(0.99783m yo4¢ $0.472 My rove tie -77.0) (5.30)

Finally, an iterative procedure is used to arrive at a plume temperature that gives the same mixture
enthalpy. During this procedure, the phase composition of the HF-H,O mixture and UF, are adjusted as
the temperature changes. The plume temperature is used in plume-rise calculations.

5.3 DISPERSION AND DEPOSITION OF HF AND UO,F,

The UF, model works in two stages. In the first stage, the model calculates the spread of UF,, the
conversion of UF, to HF, and UO,F,, and the plume rise of the HF and UO,F,. The products of this
stage are UF,, HF, and UO,F, source terms and the plume rise of HF and UO,F,, all as a function of
distance from the release point. In the second stage, a straight-line Gaussian model based on
TADPLUME is used to calculate airborne concentrations and deposition of HF and UO,F, at receptors
ona polar grid. The distance-dependent source terms calculated in the first stage are used as long as UF,
is present. After the UF, is gone, the HF and UO,F, source terms are depleted to account for
deposition.

The UF, chemical and thermodynamics models are run in the first stage while the control volume moves
downwind in small time steps. The maximum time step is 2 s. Time steps decrease to 1 s when the

5-9


7.4 INTERMEDIATE-PHASE DOSES

The intermediate phase begins after the source of a major release is under control. FMDose computes
ground-shine dose and inhalation dose from resuspension. The intermediate-phase doses that FMDose
computes are for the first year, the second year, and fifty years. Note that the second year
intermediate-phase dose is the dose from the first 2 years minus the dose from the first year. The
intermediate-phase TEDE does not include an air submersion dose because it is assumed that the plume
has passed before the intermediate phase begins.

FMDose computes the intermediate-phase ground-shine dose as shown in Eq. (7.3), using the
appropriate exposure periods. The inhalation dose is computed as shown in Eq. (7.1), with the air
concentration being estimated from resuspension using the appropriate exposure period as described in
Section 7.7.

If the user enters a re-entry delay time, FMDose computes first- and second-year doses with delay.
Dose with re-entry delay, Dyp is computed as

Dwo =D(t+p)—Dpb (7.9)
where

Dcr+p) = dose for the selected period plus the re-entry delay,
Dp = dose for the re-entry delay period.

In addition, the first-year dose from a meter reading is computed. This value is used to estimate the
first-year dose from a meter reading taken 1 m above the ground. It is valid for only the mix entered. It
is computed as
Dries = Dist + Dies ; (7.10)
14 xDorr

7.5 INTERMEDIATE-PHASE DEPOSITION DILs

Intermediate-phase DILs are used to assess deposition to identify locations where the relocation PAG and
long-term objectives may be exceeded after the plume passes. FMDose computes the intermediate-phase
deposition exposure-rate total DIL the same way as the early-phase total DILs [Eq. (7.6)] using the
intermediate-phase exposure periods, except that the external dose is always used to estimate the meter
reading. FMDose assumes that there is no air submersion dose in the intermediate phase. The
intermediate-phase deposition marker radionuclide DILs are computed the same way as the early-phase,
radionuclide-specific DILs [Eq. (7.7)]. The DILs for first year, second year, and 50 years are computed
for a range of times from 0 to 100 days since the release or contamination event. FMDose presents the
Tesults both graphically and as a table.


values for all times up to the time of the forecast.

For each station, data for all times before the first date and time with an entered value are assumed to be
missing. Likewise, data for all dates and times past the entered value are assumed to be missing.

6.4 OTHER METEOROLOGICAL PARAMETERS

Meteorological data entered for a station are used to evaluate additional parameters. The following
subsections describe these additional parameters.

6.4.1 Monin-Obukhov Length

The Monin-Obukhov length (L) is a scaling length for vertical motions in atmospheric boundary layer
studies that is used as a measure of atmospheric stability. It is used in wind profile, turbulence, and
mixing-layer depth calculations. Golder (1972) provides a graphical means for converting from
Pasquill-Gifford stability classes to Monin-Obukhov lengths using the surface roughness length

(Section 6.4.2). METPROC uses a procedure to convert stability classes to Monin-Obukhov lengths that
was developed by Ramsdell, Simonen, and Burk (1994) based on Golder’s work.

6.4.2 Winds

The RASCAL 3.0 atmospheric dispersion models are measured at 10 m above ground level for ground-
level release calculations and release height winds for elevated release calculations. Wind measurements
are not always made at these heights. Therefore, METPROC adjusts wind speeds for the difference
between the measurement height and the height required for model calculations. A diabatic wind-profile
model, which accounts for the effects of surface roughness and atmospheric stability on variation of
wind speed with height, is used for this adjustment. No attempt is made to model the variation of wind
direction with height.

The diabatic profile model is derived from atmospheric boundary layer similarity theory proposed by
Monin and Obukhov (1954). The basic hypothesis of similarity theory is that a number of parameters in
the atmospheric layer near the ground, including wind profiles, should be universal functions of the
friction velocity, a length scale, and the height above the ground. The length scale is referred to as the
Monin-Obukhov length and the ratio z/L is related to atmospheric stability.

ue) =}-(2)] ; 6.3)

6-9

The diabatic wind profile is


The dry deposition rate is calculated using a constant deposition velocity of 0.003 m/s (0.3 cm/s). This
deposition velocity is used because data summarized by Sehmel (1984) indicate that it is a reasonable
value for iodine assuming that about one-third of the iodine in the atmosphere is associated with
particles, another one-third is in the from of reactive gases (e.g., I, or HI) and the remaining one-third is
in the form of non reactive gases (e.g., CHI). A deposition velocity of 0.003 m/s is slightly high for 1
um particles of other materials. The dry deposition rate is given by

OVX , (4.32)

where w’, is the deposition rate in (activity/m*)/s and v, is the dry deposition velocity.

The wet deposition rate is calculated using a washout model. In the washout model, the wet deposition
rate is

a, =, fade : (4.33)

where A, is a washout coefficient that is a function of the precipitation type. The washout coefficients
used in RASCAL are listed in Table 4.2. These coefficients, which were used in previous versions of
RASCAL, are based on analyses of experimental data by Engelmann (1968). TADPLUME and
TADPUFF convert the washout coefficients to s for use in the models. Hanna, Briggs, and Hosker
(1982) and Slinn (1984) point out that the washout model is appropriate only for monodisperse aerosols
and highly reactive gases.

The total deposition rate at any point is the sum of the dry and wet deposition rates at that point. In
TADPLUME, the total deposition rate is a function of position only because the concentration in the
plume is a function of position. In TADPUFF, the total deposition rate is a function of position because
the concentration varies in space, and meteorological conditions may vary in space. In both models, the
total deposition rate is a function of time at a point because both the concentration and precipitation may
change with time.

Table 4.2, RASCAL Washout Coefficients"

Precipitation Type © Washout

Coefficient (bh)
1 (light rain) 0.79
2 (moderate rain) 2.2
3 (heavy rain) 4.0
4 (light snow) 0.36
5 (moderate snow) 12
6 (heavy snow) 2.3

“Source: Engelmann 1968.

4-15


3. Calculate the new dispersion parameters using the sums calculated in step 2; and
4. Add the enhancement term, if appropriate.

Separate virtual distances are required for the horizontal and vertical dispersion parameters because the
dispersion parameters increase at different rates. The equations for the virtual distances are

6 1/0.9031
hy -(=} (4.16)
ay

1 (x)
-(2="| (4.17)

a(x)

Xe

Note that these equations are the same as Eqs. (4.11) and (4.12) solved for x rather than o.

4.4 MIXING LAYER THICKNESS

The mixing layer thickness is included in all RASCAL 3.0 dispersion calculations. The thickness is
passed to the atmospheric dispersion programs in the meteorological data files that are created by the
meteorological data processing program. The meteorological data processing program has three options
for determining the mixing layer thickness for each station. The thickness may be estimated from
meteorological data and surface roughness; it may be estimated from climatological data; or it may be
entered directly. See Section 6.4.3 for details related to estimation of mixing layer thickness.

4.5 STACK PLUME RISE

RASCAL estimates final plume rise for stacks using Briggs’ equations (1969, 1975, and 1984) as
implemented by Petersen and Lavdas (1986) in the INPUFF 2.0 code and Ramsdell, Simonen, and Burk
(1994) in the RATCHET code. In general, the numerical constants in the equations are dimensional,
and the appropriate metric (SI) units should be assumed.

Plume rise is caused by vertical momentum of the exhaust gases in a stack and buoyancy due to
difference in density between the exhaust gases and the atmosphere. Equations for both momentum- and
buoyancy- dominated plume rise are included in TADPLUME and TADPUFF. In general, one factor or
the other will dominate. For a given set of stack and atmospheric conditions, the temperature difference
between the stack effluent and the atmosphere determines which factor is dominant. The initial step in
the plume- rise calculation is to determine the critical temperature difference given the stack effluent and
atmospheric conditions. If the difference in temperature is less than the critical temperature, plume rise
is calculated using momentum-rise equations; otherwise, it is calculated using buoyancy-rise equations.
Plume rise is corrected for stack downwash, when the stack exit velocity is less than five times the wind
speed.

4-11


include data for 1 h and 24 h of hold-up in the containment, STDose adjusts these data for the

actual hold-up time entered by the user. If the hold-up time entered is less than 1 h or greater than 24 h,
the data for the respective time is used as shown. If the holdup time is between 1 h and 24 h, then
STDose does a linear interpolation to determine the data to use at the time selected.

After the correct data are selected, STDose scales the monitor reading entered by the user to account for
the difference in the reactor power used to produce the figure and the reactor power entered by the user
in the accident scenario. This scaled monitor reading, R, is calculated by

—3000xMR (2.4)
Power

R

where

MR = the containment monitor reading entered,
Power = the reactor power [MW(t)].

STDose then determines which of the core-damage states or coolant conditions fall between the 1 and
100% level. Containment monitor readings can represent either(1) in-vessel melt or gap core-damage
states, or (2) normal or spiked coolant conditions. If no other data are available, STDose assumes that
any reading that falls between 100% of spiked coolant and 1% of vessel melt represents gap activity. A
reading greater than 1% vessel melt is assumed to be vessel melt. A reading representing between 1%
and 100% spiked coolant is assumed to be spiked coolant. A reading of less than 1% spiked coolant is
assumed to be normal coolant. If the user enters a core uncovery time, it can be used to distinguish
between the overlapping scales of the gap and in-vessel core-damage states. For example, if the core of
a PWR has been uncovered less than 30 min, the reading must represent gap activity.

When STDose determines that the estimated core-damage state is gap or in-vessel melt, it then computes
the fraction of either state that the reading represents. This percentage cannot be more than 100%. The
percentage, P, of the damage state selected is calculated by

P=100x , @.5)
1D

where

P,p = the meter reading assumed for 1% of the core-damage state for a 3000 MW(t) reactor.
If the monitor reading represents spiked coolant, STDose uses a spiking factor of 100. This factor is
used because it is the factor used in determining the monitor responses to spiked coolant shown in

Figures 2.1-2.8,

The calculations based on monitor readings should provide the maximum reading expected under the
conditions stated. The calculations assume (1) a prompt release to containment of all the fission products

2-7


4.1.1 Gaussian Puff Model

The one-dimensional solution of the diffusion equation can be expanded to three dimensions using the
principle of superposition to get the basic Gaussian puff model. In a Cartesian coordinate system with x
and y axes in a horizontal plane and z in the vertical, the normalized concentration in the vicinity of the
puff is

; 1 lf{x—x, ’ Ify-y, ' 1f{z-z, ,
wo teense | te) heey) «

This equation, when combined with a transport mechanism to move the center of the puff (x,, Yor Zo)» iS
a simplified version of TADPUFF, the puff model in RASCAL 3.0. The dispersion parameters are
shown as functions of direction from the puff center. However, in most implementations of the puff
model, the puff is assumed to be symmetrical in the x and y directions. Hence, x and y may be replaced
by the horizontal distance r from the center of the puff.

As shown previously, the height of the center of the puff is sufficient for vertical dispersion to proceed
unimpeded either by the ground or by an elevated layer of the atmosphere. Unimpeded vertical
dispersion is generally not the case. Typically, the earth’s surface and the top of the atmospheric mixing
layer are assumed to be reflective surfaces. When these assumptions are made, the vertical exponential

term
ex _l(z-z, \
5 9,

is replaced by a sum of exponential terms that account for reflection. This sum is

— 1/2nH —h—-z P 1/2nH +h—z P
> exp y ————_ }|_ + exp) --} ————__ +
=< 9, 2 oO,

where H is the height of the top of the mixing layer, and h is the release height. In practice, only a
small number of terms need be considered. In RASCAL 3.0, as in MESORAD (Scherpelz et al. 1986;
Ramsdell, et al. 1988) and earlier versions of RASCAL, the summation is carried out from n = -2 to 2.
This term can be simplified if one or more of H, h, or z equals zero. For example if H is large
compared to 9, and z is zero, the summation may be replaced by

“LG))

At long down-wind distances where the vertical dispersion parameter is the same magnitude as the
mixing layer thickness, the puff model can be further simplified by assuming that material is uniformly

4-2


polar grid with receptor nodes at 10° intervals on circles at eight radial distances that may be adjusted to
suit the problem at hand. The TADPUFF domain consists of a square Cartesian grid with receptor
nodes uniformly spaced throughout the domain. The polar grid has a higher node density near the
release point than the Cartesian grid, and conversely, the Cartesian grid has a higher node density in the
far field than the polar grid.

In general, the receptor nodes for the two grids do not coincide. This fact leads to apparent
discrepancies in the doses reported in the maximum value tables in the model output for the two models
for wind directions other than north, east, south, or west. The doses reported for TADPLUME are for
the plume centerline at each distance. The doses reported for TADPUFFE are the highest doses calculated
at nodes at about the nominal distance -- for example, 5 miles. The node with the highest dose may or
may not be on plume centerline, and may be nearer or farther from the release point than the nominal
distance. When a direct comparison of doses calculated by the two models is desired, the wind direction
for the period of calculations should be north, east, south, or west. For these wind directions, both
TADPLUME and TADPUFF calculate plume centerline concentrations and doses.

4.2: TRANSPORT

Atmospheric transport refers to the movement of material from the source to downwind receptors. The
following two sections describe the treatment of atmospheric transport in RASCAL 3.0.

4.2.1 TADPLUME Transport

TADPLUME is a straight-line Gaussian model. As this name implies, the model assumes straight-line
transport based on the wind direction at the time and place of release. TADPLUME rounds the wind
direction to the closest 10° as it calculates the transport direction to ensure that the axis of the plume
passes directly over receptors. As is common in straight-line Gaussian models, transit time is not
considered in determining when material arrives at receptors; material arrives at receptors at the time of
Telease. As a result, dose rates calculated by TADPLUME cannot be used to estimate the time of arrival
of a plume at a receptor and are not likely to correspond with dose rates measured in the field. Transit
time, calculated using the wind speed at the release height, is used to calculate the decay of radionuclides
between the source and the receptors. It is also used to calculate depletion of material in the plume due to
wet deposition. Decay calculations are performed at 5-min intervals; depletion is calculated for the full
transit time.

4.2.2 TADPUFF Transport

Unlike TADPLUME, TADPUFF explicitly accounts for transit time in all calculations because the
model tracks the movement of individual puffs and calculates concentrations and doses based on puff
Positions. As a result, dose rates calculated by TADPUFF may be used to estimate the time of arrival of
a plume and may be compared with dose rates measured in the field. Decay and ingrowth of
radionuclides and depletion of the puffs as a result of wet and dry deposition are calculated at 5-min
intervals.

TADPUFF differs significantly from TADPLUME in that neither the wind data nor the wind fields are

4-6


H a mpoy =1051.0+0472T, -[prs0 +0136T, #790642 Wie), +667 358W ip i : (5.23)

where

Wars and Wary = the weight fractions of the HF polymers with respect to total HF,
Wary = the weight fraction of HF in the HF-H,O vapor.

The heat of association for (HF); is -790.642 Btu/Ib,, (HF); formed, and the heat of association of
(HF), is -667.358 Btu/Ib,, formed.

5.2.11 Enthalpy of HF-H,O Liquid Mixtures

The enthalpy of liquid HF-H,O mixture is given by a relationship of the form
Hym2o1 =A, +BiWaer tC, War» (5.24)

where the coefficients A,, B,, and C, are functions of the weight fraction Wy, of HF in the HF-H,O
liquid mixture. Williams (1985) provides correlations for estimating the coefficients that are based on an
enthalpy-concentration diagram provided by Brian C. Rogers at Allied Chemical.

5.2.12 UO,F, Enthalpy

UO,F, is formed as a product of the UF6-H,0 reaction. It is a solid with a heat capacity of 0.0821
Btu/(Ib,, °F). The enthalpy at any temperature, relative to a reference temperature is

Hj oor> =0.0821(t, ty) (5.25)
uo2f2 f ref

where t, the UO,F, temperature, and t,,, the reference temperature, are in °F or Rankine. The
reference temperature is 77°F in UF6PLUME.

5.2.13. Mixture Enthalpies and Plume Temperature

Mixing and reactions in UF6PLUME are assumed to take place under constant pressure. The following
reference conditions are assumed for enthalpy calculations: a pressure of 1013.25 mb (1 atmosphere, 760
mm Hg, or 14.696 psia), a temperature of 25°C (77°F); a vapor state for UF,, H,0, and air;
monomeric vapor for HF; and solid for UO,F,.

In UF6PLUME, the enthalpy of the plume is calculated for the control volume as the control volume
moves downwind. The control volume initially consists of the volume of the UF, plus the volume of the
entrained air and water vapor and has an enthalpy equal to the sum of enthalpies of the UF,, air, and
H,O. With the UF,-H,0 reaction, the enthalpy of the control volume increases because of the heat
release and the changes in the masses of the plume constituents.


Table 2.1 Relationship of Reactor and Spent Fuel Source Terms to Release Pathways

Event type

Source term

Release pathways available

Nuclear power plant

Coolant sample

Steam generator tube rupture
Containment bypass

Nuclear power plant

Containment air sample
Containment radiation monitor

Containment leakage or failure

Nuclear power plant

Effluent gross concentrations release rate

Direct

Nuclear power plant
Pressurized water
teactor (PWR) only

Core cooling status
User-defined core damage estimate

Containment leakage or failure
Steam generator tube rupture
Containment bypass

Nuclear power plant
Boiling water reactor
(BWR) only

Core cooling status
User-defined core damage estimate

Wet well
Dry well
Containment bypass

Reactor spent fuel

Pool storage - uncovered fuel

Pool storage - damaged assembly under
water

Dry storage cask event

Spent fuel release

Effluent

Effluent Release Rates
Effluent Concentrations

Direct

The following discussion of the STDose calculations is divided into three parts. First, all the source
term calculations are presented. These are followed by discussions of the reductions possible according
to the release pathway. Finally, the calculation of leakage factor is presented.

2.1 CALCULATION OF THE AMOUNT OF ACTIVITY AVAILABLE FOR
RELEASE IN NUCLEAR POWER PLANT ACCIDENTS

Seven types of source term data can be used to estimate the source term for a nuclear power plant
accident: (1) core cooling status, (2) containment radiation monitor, (3) coolant sample, (4) containment
air sample, (5) user-defined core damage estimate, (6) effluent releases measured directly, and (7)
effluent gross concentrations release rates. In the core cooling status and containment radiation monitor,
the user enters data that are used to estimate the core damage state or the activity in the coolant. In all
other source term types, the user enters a direct estimate of activity available for release. The
calculations performed for each of these types of data are discussed in the following sections.

2-2



A, = 0.5T?(2+2z/L),

T = But,

B = projected building area,

u* = scaling wind speed (friction velocity) calculated from the wind speed, stability, and surface

roughness using the wind-profile relationships discussed in Section 6.4.2 ,

z = release height (all releases are assumed to be 210 m),

L = Monin-Obukov length which is a function of stability. Evaluation of L is described in
Section 6.4.1

Near the release point, the enhancement terms are primarily functions of wind speed and distance; they
are weakly dependent on stability; and they are independent of building dimensions. The enhancement
terms increase with increasing distance from the release point until they reach an asymptotic limit that is
a function of the building area. The terms are large for low wind speeds and decrease as the wind speed
increases. They are negligible for wind speeds above about 4 m/s. This behavior is supported by a
recent analysis of dispersion and turbulence data (Ramsdell and Fosmire 1998). The results of that
analysis also suggests that the enhanced dispersion noted in the vicinity of buildings at low wind speeds
in wake dispersion experiments may be as much an artifact caused by underestimation of dispersion by
the basic dispersion algorithms (Eqs. 4.11 and 4.12) as it is due to increased turbulence in the vicinity of
buildings. Consequently, use of the building wake correction option is recommended for all releases
other than isolated stacks.

4.3.1 TADPLUME Dispersion Parameters

The computational algorithms used in TADPLUME calculate dispersion parameters directly from Eqs.
(4.11) through (4.15) as the parameters are needed. Equations (4.11) and (4.12) are used for plume
releases from isolated stacks and for other releases if the building wake correction is not selected. If the
building wake options is selected, all five equations are used.

4.3.2. TADPUFF Dispersion Parameters

In TADPUFF, the wind direction, wind speed, and stability are permitted to change as a function of
time and position. As a result, puffs may follow curved trajectories and even return to the release point,
and stability may change along the puff’s trajectory. If dispersion parameters were calculated directly,
as in TADPLUME, discontinuities in the dispersion parameters and possible reduction in plume
dimensions with increasing time could occur. Neither condition is consistent with the known
characteristics of atmospheric dispersion. Consequently, dispersion parameters for TADPUFF cannot be
directly calculated from Eqs. (4.11) through (4.15) as is done in TADPLUME.

In TADPUFF, dispersion parameters are calculated in a four-step process as the puffs move through the
model domain.

1. Calculate virtual distances from the puff center to the release point based on the current puff
dimensions and the meteorological conditions at the position of the puff. The virtual distances are
imaginary distance that, if used in Eq. (4.11) (x,,) and Eq. (4.12) (x,,) with the meteorological
conditions at the puff position, would give the current dispersion parameters;

2. Add the distance to be moved during the next time step to the virtual distances;

4-10


CONTENTS (continued)

Page
3.1.4 Isotopic Source Terms ........ 26.000 e teens 3-6
3.2 CALCULATION OF RELEASE REDUCTION FOR EACH FUEL CYCLE AND
MATERIALS RELEASE PATHWAY ..........-0 0000 cece cece cece nee n ences eens 3-8
3.3 CALCULATION OF LEAKAGE FACTORS FOR FUEL CYCLE AND
MATERIALS ACCIDENTS

3.3.1 Percent per Hour
3.3.2 Flow Rate
3.3.3 Direct...
3.4 REFERENCES

4 TRANSPORT, DIFFUSION, AND DOSE CALCULATIONS
4.1 THEORETICAL BASES FOR GAUSSIAN MODELS ..
4.1.1 Gaussian Puff Model ...................

4.1.2. Straight-Line Gaussian Plume Models .
4.1.3 Treatment of Calm Winds ........
4.1.4 Model Domains .......
4.2 TRANSPORT ............
4.2.1 TADPLUME Transport .
4.2.2 TADPUFF Transport ..
4.3 DISPERSION PARAMETERS .......
4.3.1 TADPLUME Dispersion Parameters
4.3.2 TADPUFF Dispersion Parameters
4.4 MIXING LAYER THICKNESS ......
4.5 STACK PLUME RISE ................
4.5.1 Unstable and Neutral Atmospheric Conditions .
4.5.2 Stable Atmospheric Conditions ........
4.5.3 Effective Release Height ....
4.6 DEPOSITION ............
4.7 DEPLETION ...........
4.8 DECAY AND INGROWTH
4.9 DOSE CALCULATIONS
4.9.1 Organ Committed Dose Equivalents Due to Inhalation
4.9.2 Ground-Shine Doses
4.9.3 Cloud-Shine Doses .
4.9.4 Open- and Closed- Window ‘Dose Rates
4.10 REFERENCES

5 UF, MODEL .... 2.2.6.6 eee te ete n ett nett tenn eee eees 5-1
5.1 UF, MODEL ASSUMPTIONS AND EQUATIONS . 5-1
5.2 CHEMICAL/THERMODYNAMIC MODEL .... 5-3

5.2.1 Compressibility Factor ........... 5-4
5.2.2 UF, Density ....... 5-4
5.2.3 UF, Vapor Pressure .. 0.2.0.0 cence nett nee e ee eeee 5-5

vi


Slinn, W. G. N. 1984. “Precipitation Scavenging.” Atmospheric Science and Power Production. Ed.
D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Tadmor, J., and Y. Gur. 1969. “Analytical Expressions for Vertical and Lateral Dispersion
Coefficients in Atmospheric Diffusion.” Atmospheric Environment, 3:688-98.

4-27


2.3 CALCULATION OF RELEASE REDUCTION FOR REACTOR
RELEASE PATHWAYS

Reactor accident release pathways allow consideration of the reduction due to the physical systems that
are present. The release pathway selected limits the available reduction mechanisms and the way in
which the leak rate can be defined. In nuclear power plant releases, the reduction mechanisms available
are dependent on the source term calculation type and the release pathway chosen. Each of the release
pathways and reduction mechanisms, and the data used for them, are discussed in more detail below.
Six types of release pathways have been defined. Table 2.7 shows which reduction mechanisms are
available for each pathway.

Reduction factors (RDF in Eq. 2.1) are applied as scaling factors, as described in NUREG-1228
(McKenna and Giitter 1988). All reduction factors, except fire reduction, are defined for three
categories: noble gases (STCP category 1), halogens (STCP category 2), and other particles. Noble
gas factors all default to one. RASCAL 3.0 assumes that halogens and other particles have the same
reduction. The default values for all reduction factors and their references are included in Table 2.8. In
some cases the user can turn reduction mechanisms on and off as the accident progresses. Also, the
reduction factors themselves may be modified for filters.

STDose reactor source term calculations include a maximum effectiveness for sprays and a maximum
effectiveness for all reduction, excluding filters. See Table 2.8. For each, the appropriate reduction
factor or product of reduction factors computed at each time step is compared to the maximum and is not
allowed to surpass it.

Steam generator condition does not affect the total amount of activity present; it only reduces the amount
of activity released. Activity removed by all other mechanisms is made permanently unavailable for
release. Sprays and holdup in containment will not be applied simultaneously, and

holdup applies only in large containment or auxiliary buildings. Plate-out apply only to bypass accidents
and will not be combined with any other reduction mechanism.

All reduction mechanisms are be characterized by a constant factor except sprays and hold-up. The
RDFs for sprays and holdup are computed at each time step as an exponential function of time. Two
factors each are used, an “initial” A, that is applied only for the initial time interval listed in Table 2.7
and a “continuing” A, that is applied thereafter. The reduction factors used for sprays and hold-up are
dependent on the total amount of time that each mechanism has been acting. So initially the RDF for
sprays or hold-up is

RDF=e-T . (2.7)
where

T = the total amount of time (h) the sprays or holdup have been acting.


Bander, T. J. 1982. PAVAN: An Atmospheric Dispersion Program for Evaluating Design Basis
Accidental Releases for Radioactive Materials from Nuclear Power Stations. NUREG/CR-2858, U.S.
Nuclear Regulatory Commission.

Briggs, G. A. 1969. Plume Rise, TID-25075, U.S. Atomic Energy Commission.

Briggs, G. A. 1975. “Plume Rise Predictions,” Lectures on Air Pollution and Environmental Impact
Analyses. American Meteorological Society, Boston, Mass.

Briggs, G. A. 1984. “Plume Rise and Buoyancy Effects.” Atmospheric Science and Power
Production. Ed. D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Csanady, G. T. 1973. Turbulent Diffusion in the Environment. D. Reidel, Boston, Mass.

Draxler, R. R. 1984. “Diffusion and Transport Experiments.” Atmospheric Science and Power
Production. Ed. D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Eckerman, K. F., A. B. Wolbarst, and A. B. C. Richardson. 1988. Federal Guidance Report No. 11.
Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for
Inhalation, Submersion, and Ingestion. U. S. Environmental Protection Agency.

Eckerman, K. F., and J. C. Ryman. 1993. Federal Guidance Report No. 12. External Exposure to
Radionuclides in Air, Water, and Soil. U. S. Environmental Protection Agency.

Eimutis, E. C., and M. G. Konicek. 1972. “Derivations of Continuous Functions for the Lateral and
Vertical Atmospheric Dispersion Coefficients.” Atmospheric Environment, 6:859-63.

Englemann, R. J. 1968. “Calculation of Precipitation Scavenging.” Meteorology and Atomic Energy
1968. Ed. D. Slade, TID-24190, U.S. Atomic Energy Agency.

Frenkiel, F. N. 1953. “Turbulent Diffusion: Mean Concentration in a Flow Field of Homogeneous
Turbulence.” Advances in Applied Mechanics, 3:61-107.

Gifford, F. A. 1976. “Turbulent Diffusion-Typing Schemes: A Review.” Nuclear Safety, 17 No. 1:
68-86.

Hanna, S. R., G. A. Briggs, and R. P. Hosker. 1982. Handbook on Atmospheric Diffusion. DOE/TIC-
11223, U.S. Department of Energy.

Healy, J. W., and R. E. Baker. 1968. “Radioactive Cloud-Dose Calculations.” Meteorology and Atomic
Energy 1968. Ed. D. Slade, TID-24190, U.S. Atomic Energy Agency.

Healy, J. W. 1984. “Radioactive Cloud-Dose Calculations.” Atmospheric Science and Power
Production. Ed. D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Kao, S. K. 1984. “Theories of Atmospheric Transport and Diffusion.” Atmospheric Science and Power
Production. Ed. D. Randerson, DOE/TIC-27601, U.S. Department of Energy.

425


zero at the beginning of the period. After the surface is contaminated, ground-shine doses can be
incurred, even if airborne material is not present.

4.9.3, Cloud-Shine Doses

Earlier versions of RASCAL calculated cloud-shine doses using either a semi-infinite cloud model or a
finite-plume model based on the model developed for MESORAD (Scherpelz, et al. 1986). The first
of these models assumes that activity is uniformly distributed through a large volume, and the second
assumes that activity is concentrated in a finite number of points distributed through a volume to
represent the actual activity distribution. The use of the semi-infinite cloud model is usually
inappropriate in the immediate vicinity of the release point, and application of the MESORAD finite-
plume model to cloud-shine dose estimates near the release point in TADPLUME did not prove
satisfactory. Consequently, the cloud-shine dose models in RASCAL 3.0 have been significantly revised
from those used in earlier RASCAL versions.

Cloud-shine models based on line sources and plane sources have been developed that are analogous to
the point-source model used in MESORAD. These models are used, along with the point-source model,
until plumes and puffs grow to sufficient size that the assumptions associated with the semi-infinite cloud
model are met. In the MESORAD point-source model, point-source dose rates were calculated as a
function of distance for each radionuclide from gamma energies. This calculation, which was repetitive
and time consuming, has been deleted. The finite-plume, cloud-shine models in RASCAL 3.0 make use
of precalculated dose rate vs distance curves. These curves are provided in the radionuclide database for
each radionuclide for a 1 Ci (0.01 Sv) point source, and a 1 Ci/m (0.01 Sv/m) infinite-line source. The
remainder of this section describes the RASCAL 3.0 cloud-shine models.

4.9.3.1 TADPUFF Cloud-Shine Dose Calculations

There are three stages in TADPUFF cloud-shine dose calculations. Near the source where puff
dimensions are small compared to the mean path length of photons, TADPUFF uses a revised version of
the point-kernel dose model used in previous versions of RASCAL. When the puff radius becomes
sufficient (0,=400 m), cloud-shine dose rates beneath the centerline of the plume are calculated using an
infinite-slab model. The dose rate at ground level is calculated assuming that the activity in the plume is
equally divided among ten horizontal slabs with slab heights determined by the release height and vertical
dispersion coefficients. The change in dose rate with distance from slabs is due only to buildup and
absorption of photons; the change in dose rate across the plume is proportional to the crosswind variation
of activity concentration in the slab. This model will be discussed further. Finally, when the vertical
dimensions of the plume become sufficient (6,=400 m), cloud-shine is calculated using a semi-infinite
cloud model.

Previous versions of RASCAL used the MESORAD finite-puff, cloud-shine model (Scherpelz et al.
1986, Ramsdell et al. 1988). This model first calculates composite characteristics (photon energies,
photons per disintegration, etc.) of the gamma radiation from the radionuclide mix in a puff. Next, the
model calculates the dose rate vs distance from a point source having the composite characteristics using

213x10°

Dy(p)= L[fBtunre ELT Wy] (4.36)
Y

4-18


1 TO 100% RELEASE TO CONTAINMENT (Rh)

15406

1 TO 100% RELEASE TO CONTAINMENT (R/h)

PERERELER

1E+06
1£+05
1B +06
1E+03
1E+@2
1E+01

1E+00

1E-O1

1E-2
1E-03
1E-O4

1E-05

n 1 n 1 1 n
db mn ih mb ib mb th un
‘Io-Vessel Melt Gp ‘Spiked Coolant ‘Normal Coolant

CORE DAMAGE AND TIME AFTER REACTOR SHUTDOWN

Figure 2.2 PWR Containment Monitor Response (sprays off).

L 1 1 1
ib ub ib Mb 1b mh
In-Veseel Mek Cap Spiked Coolant Normal Coolant

n 1 1 L
ib ma

‘CORE DAMAGE AND TIME AFTER REACTOR SHUTDOWN

Figure 2.3 BWR Mark I & II Dry Well Containment Monitor Response (sprays on).


Table 3.3 Airborne Release Fractions and Respiration Fractions

Used in Uranium Explosions*
Explosion
characteristics Material form ARF IF
Detonation Liquid 1 1
Solid 1 2x10"
Powder 1 2x10"
Surface contamination | 1x10 | 1
Deflagration Liquid 1x10* | 1
Solid 0 0
Powder 5x10? | 1x10°
Surface contamination | 3x10"
Venting Liquid 2x10? | 1
Solid 0 0
Powder 1x10? | 7x10?
Surface contamination | 110° | 1

* Source: DOE 1994.

For criticality accidents, the criticality-shine dose is computed with the source term. The shielding
thicknesses entered by the user are used only in this calculation. The dose in rem, D,,;, at 10 ft is
computed as (Hopper and Broadhead 1998)

Derit =D gamma + Doeutron (3.3)
Dgamma =1 x10 “15 eB ye 7 (0.586 x8 +0147 xC +0092 x W) (3.4)
Dacusron =1 X10 ~ "4 x F xe ~ 0258 XS +9240 XC #0277 XW) (3.5)


4.5.1 Unstable and Neutral Atmospheric Conditions

In unstable and neutral atmospheric conditions, plume rise is dominated by momentum if the atmospheric
temperature is greater than the effluent. When plume rise is dominated by momentum, the plume rise is
estimated using Petersen and Lavdas’ Eq. A-9 (1986).

Ah =6r,wu(h)TM . (4.18)

where

Ah = plume rise estimate (m),

T, = stack radius (m),

w, = effluent initial vertical velocity (m/s),
u(h) = = stack height wind speed (m/s).

If the ambient air temperature is less than the effluent temperature, a critical temperature is calculated
from either Petersen and Lavdas’ Eq. A-3

< 0.0187 w 9°T, 177 (4.19)

or Petersen and Lavdas’ Eq. A-4

y\t3
a <osoesd ®} T, (4.20)
I

where At, is the critical temperature difference (K) and T, is the effluent temperature (K). The choice
between Eq. (4.19) and (4.20) is based on the value of a buoyancy-flux parameter, F,. The buoyancy-
flux parameter is defined by Petersen and Lavdas’ Eq. A-2 as

F=al(t,-T.) 7, Jon (4.21)

where g is gravitational acceleration (9.8 m/s*), and T, is the air temperature (°K). If F, is less than 55,
the critical temperature is given by Eq. (4.19), otherwise it is given by Eq. (4.20). Equation (4.18) is
used as long as the temperature difference, T, - T, , is less than At,.

When the temperature difference is greater than At,, the plume rise is calculated using either Petersen
and Lavdas’ Eq. A-7
Ah =21.42F)*u(h,)7 (4.22)

or Petersen and Lavdas’ Eq. A-8

4-12


ero a
1E+@

1 TO 100% RELEASE TO CONTAINMENT (ht)

1 7 1 4 1 1 4
1b ws in unr in wb 1a ua
‘Tr Vessel Mets Gap ‘Spiked Coolant ‘Normal Coolant

CORE DAMAGE AND TIME AFTER REACTOR SHUTDOWN

1E+00

vol
vet | |

nel ia
i il
vs ,

Figure 2.8 BWR Mark III Wet Well Containment Monitor Response.

2.1.5 User-Defined Core Damage Estimate

The user can select a core-damage state directly. The state selected may be “none,” increased fuel pin
leakage, 1 to 100% of cladding failure, 1 to 100% of core melt, or 100% vessel melt through. If the user
selects “none,” there is no source term and no calculations are performed. Increased fuel pin leakage results
in a coolant release. The user may enter a coolant spiking factor from 1 to 1000. The core damage activity
release fractions (ARFs) used for each of the other states are shown in Tables 2.3 and 2.4 (Soffer et al.
1992). The source term, S;,_ is then computed as

Sy =Ti XARFy (2.6)

where I; is the inventory of radionuclide i.
2.1.6 Monitored Release — Mixtures

The effluent gross concentrations release rate source term calculation is intended for assessments when the
user can enter an activity release rate (i.e., a stack monitor reading) and a release duration and can estimate
the radionuclide mix. The user can enter the estimated mix either of two ways: (1) as a core damage state
or (2) as the percentages of the release that are represented by each of the eight STCP categories. When the
user has selected the mix as a core-damage state, then the mix can be modified by the effects of filters,
sprays, retention in a pool, or 2 h of holdup. These factors will change the mix because they affect only the
non-noble gases.

2-12


6.3.7 Humidity

Information on humidity is needed for chemical reaction and thermodynamic calculations in
UF6PLUME. Humidity information may be entered for the first station as dew point temperature,
relative humidity, or wet bulb temperature. METPROC includes default humidity information based on
climatological data for fuel-cycle facilities. However, actual data should be entered whenever possible
because the calculations are very sensitive to humidity, and humidities have a wide range of variation in
the atmosphere.

6.3.8 Temporal Interpolation of Input Values

The atmospheric models in RASCAL 3.0 expect meteorological data on the 15-min time interval
typically used to record meteorological data at U.S. nuclear facilities. Data from other meteorological
stations are not likely to be available on that interval. Consequently, METPROC will estimate missing
15-min data for each station by linear interpolation between observed values. For example, if 10:00 and
11:00 observations are entered for a station, METPROC will estimate values for 10:15, 10:30, and
10:45. METPROC will not interpolate between observed and forecast values, or between two forecast
values.

The interpolation procedures are as follows:
Winds

. If the wind (either speed or direction) is missing for the earlier observation, the winds at all times
between the two observations are also assumed to be missing.

. If the wind is missing for the later observation but not for the earlier observation, the winds are set
to the wind of the earlier for times within 12 h of the earlier observation, otherwise they are
assumed to be missing.

. If the winds for both the earlier and later observation are valid, the winds are interpolated as

follows:

1. The wind speed and direction are converted to U (east-west) and V (north-south)
components.

2. The U and V component are linearly interpolated (i.e., U(t) = (U, - Ud{(-t)Mtrt)} +
U, where U,, U,, §, t, are the U component and time of the later and earlier
observations, respectively).

3. The U and V components are converted back to speed and direction.

67


Table 3.10 Leak Rate Types Available in Each Fuel Cycle

and Materials Release Pathway
efm, kg/s,

Pathway %lh gal/m Direct
UF, cylinder x x
UF, cascade x x
Criticality x
UO, fire or explosion
Isotopic x

3.3.2 Flow Rate

When a flow rate is entered by the user, the leakage rate fraction is computed as the flow rate divided by
the total building volume that contains the source term.

3.3.3 Direct

In a “direct” release, the user only enters the release duration. The leakage rate fraction is computed
differently, depending on the source term type. For the UF, cascade and the UO, fire or explosion, the
leakage rate fraction is set at 100% divided by the release duration. For isotopic releases, those rates are
entered by the user. No leakage rate fraction is needed, so none is computed.

3.4 REFERENCES

Hopper, C. M., and B. L. Broadhead. 1998. An Updated Nuclear Criticality Slide Rule. Vol.2,
NUREG/CR-6504, ORNL/TM-13322/Vol.2, U.S. Nuclear Regulatory Commission.

McGuire, S. A. 1998. A Regulatory Analysis on Emergency Preparedness for Fuel Cycle and Other
Radioactive Material Licensees (Final Report). NUREG-1140, U.S. Nuclear Regulatory Commission.

McKenna, T. J. McKenna, and J. Giitter. 1988. Source Term Estimation During Incident Response to
Severe Nuclear Power Plant Accidents, NUREG-1228, U.S. Nuclear Regulatory Commission.

McKenna, T. et al. 1996. Response Technical Manual: RTM-96. Vol. 1, Rev. 4, NUREG/BR-0150,
U.S. Nuclear Regulatory Commission.

Oak Ridge National Laboratory (ORNL). 1989. ORIGEN2 Isotope Generation and Depletion Code,
3-12


information for a meteorological station may become outdated. Therefore, METPROC provides the
means to add meteorological stations to the file or update information in the file.

The following information is needed for each meteorological station

e A station identification. The station identification can be any 10 letter character; the release site
ID is appropriate for the first station in the station list; FAA or ICAO location indicators are
appropriate for national weather service or other stations that have them.

e The latitude (positive north of the equator and negative south of the equator) and longitude
(positive east of the prime meridian and negative west of the prime meridian) of the station in
decimal degrees.

e The elevation of the station (m). The elevation should be the height of the station above mean
sea level.
e The surface roughness for the station (m). Meteorological texts such as Panofsky and Dutton

(1984) and Stull (1988) provide guidance on estimating surface roughness. If no other
information is available, a surface roughness of 0.2 m may be used.

e The height at which the wind measurements are made (m). The instrument height should be
height above ground level.

METPROC uses station positions to place station data in the proper locations in the modeling domain;
station elevations are used in the potential flow model that adjusts wind fields for topographic effects
(Section 6.5.1), and the surface roughness and height of wind measurement are used in calculating wind
speed variation with height (Section 6.4.2). The following information is used to identify the
engineering units associated with the meteorological data for the station and permit METPROC to
convert data value to units used in model calculations

e stability data type (Pasquill-Gifford stability class, dT/dz in °C/100 m, or dT/dz in °F/100 ft,
e height interval for dT/dz,

e units of height interval for dT/dz (1=m, 2= ft, 9=undefined),

e units for wind speed (1 =m/s, 2=mph, 3=knots),

e units for temperature (1=°C, 2=°F) for the first station, not used for other stations.

A longer station name may be included for each station for better identification.
The first station in the station file is the station at the source of the release (the site). The latitude and

longitude of the first station will define the coordinates of the center of the model domain grid.
Distances from the center of the grid to the other stations are calculated using

X,, =, AA,, cos, (6.1)

6-2


4.9.1 Organ Committed Dose Equivalents Due to Inhalation

Organ committed dose equivalents and committed effective dose equivalents are calculated for 15-min
periods in both TADPLUME and TADPUFF. These dose equivalents are the sums over all
radionuclides of products of the exposure to the radionuclide during the 15-min period times a
radionuclide and organ specific dose factor and the breathing rate. The general expression for the
organ-committed dose equivalents is

is
Dis Shor J 2.0 . (4.34)
0

where

D,s = organ-committed dose equivalent due to inhalation during a 15-min period,
v, = breathing rate,

F, = radionuclide n and organ specific dose factor,

%_ = radionuclide n concentration,

t = time.

Dose factors used in RASCAL 3.0 are from Federal Guidance Report No. 11 (Eckerman, Wolbarst, and
Richardson 1988).

At the end of each 15-min period, the committed dose equivalents at each receptor node are written to
TADPLUME and TADPUFF output files. They are then set to zero prior to beginning model
calculations for the next 15-min period.

4.9.2 Ground-Shine Doses

TADPLUME and TADPUFF calculate ground-shine dose equivalents as the sum over all radionuclides
of product of the surface contamination by the radionuclide and a radionuclide-specific dose factor. The
general expression for the ground-shine dose equivalent is

t415
0B) Pr jauou| . (4.35)

where

D,, = dose equivalent during the period,

DF, = radionuclide n specific ground-shine dose factor,
©, = radionuclide n surface concentration,

t = time.

Note that the integration in Eq. (4.35) is from t to t+15 min. These integration times are used because
the surface concentration at any time is cumulative from the beginning of the event but the dose is set to

4-17


Ys =TAd,, » 6.2)

where

X, = distance of the station east (+) or west (-) of the source (center of the grid) (km),
y,, = distance of the station north (+) or south (-) of the source (center of the grid) (km),
I, = radius of the earth (= 6370 km),

, = latitude of the center of the grid (first station),

Aj,, = longitude difference between the station and the source (center of the grid) (radians),

A@,, = latitude difference between the station and the source (center of the grid) (radians).

6.3 METEOROLOGICAL DATA INPUT

Station meteorological data are entered for specific dates and times. The data may be actual observations
(measurements) or they may be taken from meteorological forecasts. If available, the following data
should be entered for each station:

surface-level wind direction and speed,
estimated atmospheric stability,
precipitation class, and

estimated mixing height.

All of these data are used in the transport, diffusion, and deposition calculations. In addition, the
following data should be entered for the first station (center of the grid):

e ambient air temperature,

e pressure (station), and

@ humidity measurement (dew point temperature, relatively humidity, or wet bulb temperature).
The air temperature is used in plume rise calculations in TADPLUME, TADPUFF, and UF6PLUME.
The air temperature, station pressure, and humidity are used in the thermodynamic calculations in
UF6PLUME. Station pressure and humidity are used only by UF6PLUME.

The following subsections describe the meteorological variables in more detail.

6-3


6-V

APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

Es g ig
2 |8 . {2 z |e
& 2's & {2 2], a |S
6 <\¢ 8 | a |§ —- |é
a 1 gio 9 g % | 8ls 5 5
> a ©ls ‘sS cy els i) 2)
n= ~ 18 ¢ g 3218 |Js [ells
> i= c i= Oo 3 Bs o/|e
2 ls Bie 3 ‘3 & |hlo |i |E bls
3 18 E|3 - |& slg |e |es|?
Name gid Z18 < 8 A idle |e laa
(gal) [ft ld \psi |MW(t)
Vogtle - Unit 1 PWR [Dry Ambient _| 193|/U-Tube 262132} 2700000] 0.1| 52] 3565] 22000) 15000/Operational
Vogtle - Unit 2 IPWR [Dry Ambient | 193|]U-Tube 262132} 2700000] 0.1] 52| 3565) 22000] 15000/Operational
‘Washington Nuclear Power
- Unit 2 BWR |Mark II 764|N/A 174300} 200000] 0.5] 45) 3323} 22000) 15000/Operational
| Waterford - Unit 3 PWR |Dry Ambient | 217/U-Tube. 249268] 2700000; 0.5} 44; 3390] 22000) 15000|Operational
Watts Bar - Unit 1 PWR |Ice Condenser| 193|U-Tube _ |. 250808) 920000) 0.5] 15) 3411] 22000] 15000/Operational
Wolf Creek - Unit 1. PWR [Dry Ambient _| 193/U-Tube 262132) 2500000} 0.1) 60} 3565] 22000) 15000/Operational
Yankee- Rowe PWR |Large, Dry 76|U-Tube 0} 1000000} 3] 34 600] 22000] 15000|Decommissioned
Zion - Unit 1 [PWR [Dry Ambient | 193}U-Tube 0} 2900000] 0.1] 47] 3250] 22000) 15000|Decommissioned|
Zion - Unit 2 PWR [Dry Ambient _| 193|U-Tube O| 2900000] 0.1] 47] 3250] 22000] 15000|Decommissioned



UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, DC 20555-0001

OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE, $300


The leakage rate fraction, LRF, of the containment volume atmosphere released, then is

MER xD
RE = . (2.10)

where

D, = the release duration,
Vc. = the containment volume.

When the user enters a containment pressure that is less than atmospheric pressure, STDose sets LRF to
zero. STDose does not compute the change in containment pressure. The user may enter changing
containment pressures as the assessment proceeds.

2.4.3 Flow Rate

When a flow rate is entered by the user, the leakage rate fraction is computed as the flow rate divided by
the total volume that contains the source term. This volume may be the containment volume, a building
volume, or the coolant volume, depending on the source term type.

2.4.4 Direct

In a “direct” release, the leakage rate fraction is computed differently, depending on the source term
type. In a bypass release when the activity being released is coolant, the release duration is assumed to
be 15 min. In a bypass release when core activity is being released, the release duration is assumed to be
the amount of time needed to release all the activity in that core damage state, as listed in Table 2.3.

The leakage fraction is set to allow for a release to occur only during the duration selected. For effluent
releases the release rates are used as entered by the user. No leakage rate fraction is needed, so none is
computed.

2.5 REFERENCES

American National Standard Institute (ANSI/ANS). 1999. Radioactive Source Term for Normal
Operation of Light Water Reactors. ANSI/ANS-18.1-1999, American Nuclear Society, La Grange Park,
Illinois.

Blevins, Robert D. 1984. Applied Fluid Dynamics Handbook. Krieger Publishing Company, Malabar,
FL, 1984.

McKenna, T. J.. and J. Giitter. 1988. Source Term Estimation During Incident Response to Severe
Nuclear Power Plant Accidents. NUREG-1228, U.S. Nuclear Regulatory Commission.

2-20


ACKNOWLEDGMENTS

We would like to thank the many people who reviewed the draft versions of RASCAL 3.0 and this
document. We especially appreciate the efforts of Gary Bethke, Dennis Damon, Tom Essig, Paul Lane,
Steve LaVie, Trish Milligan, Jocelyn Mitchell, Aby Mohseni, and Don Stout. Steve Stage, Innovative
Emergency Management, developed the wind field modification module used in the meteorological data
processor program while at PNNL.

xi


4 TRANSPORT, DIFFUSION, AND DOSE CALCULATIONS

RASCAL 3.0 uses Gaussian models to describe the atmospheric dispersion of radioactive and chemical
effluents from nuclear facilities. These models have frequently been used in licensing and emergency
Tesponse calculations made by the NRC staff, [e.g., PAVAN (Bander 1982), XOQDOQ (Sagendorf,
Goll, and Sandusky 1982), MESORAD (Scherpelz et al.1986; Ramsdell et al. 1988), and RASCAL
Version 2.0 (Athey et al. 1993)], because they quickly provide reasonable estimates of atmospheric
concentrations, deposition, and doses given relatively limited information on topography and
meteorology. A straight-line Gaussian plume model, TADPLUME, is used near the release point
where travel times are short and plume depletion associated with dry deposition is small. A Lagrangian-
trajectory Gaussian puff model, TADPUFF, is used at longer distances where temporal or spatial
variations in meteorological conditions or depletion of the plume due to dry deposition may be
significant.

This section describes TADPLUME and TADPUFF. It begins with a short theoretical derivation of
Gaussian plume and puff models, and then describes the implementation of those models in
TADPLUME and TADPUFF. The section concludes with a description of the dose calculations that are
embedded in TADPLUME and TADPUFF. Section 5 describes UF6PLUME, a straight-line Gaussian
plume model developed to handle the complexities associated with releases of UF,.

4.1 THEORETICAL BASES FOR GAUSSIAN MODELS

The derivation of the Gaussian models used to describe atmospheric dispersion is discussed in many
texts. Various texts including Slade (1968), Csanady (1973), Randerson (1984), and Seinfeld (1986)
provide the bases for the following discussion. They may be consulted where additional detail is
desired.

Atmospheric dispersion is governed, in part, by a differential equation called the diffusion equation.
With a set of assumptions that can reasonably be applied to atmospheric processes, the diffusion equation
has a specific, closed-form algebraic solution that is Gaussian. In one dimension, the solution is

_ ol 1fx—x, .
Xx) /Q cacaaeece > (4.1)

where

x(x) = concentration at a distance x from the center, x,, of the concentration distribution,
Q = amount of material released,
© = dispersion parameter.

Atmospheric dispersion parameters are functions of either distance from the release point or time since
release. They may also be functions of atmospheric stability and surface roughness. Numerous
atmospheric dispersion experiments have been conducted to evaluate dispersion parameters and to
develop methods to predict dispersion-parameter estimates from readily available data. A number of
these experiments are described by Draxler (1984).

41


LIST OF TABLES

Table Page
2.1 Relationship of Reactor and Spent Fuel Source Terms to Release Pathways ................
2.2. Nuclear Power Plant Core Inventory and Coolant Concentrations .....
2.3. BWR Core Activity Release Fractions ...................
2.4 PWR Core Activity Release Fractions ...............
2.5 Elements in STCP Categories ...........
2.6 Fuel Release Fractions used in Spent Fuel Accidents .................
2.7 Reduction Factors Available in each Reactor and Spent Fuel Release Pathway .
2.8 Reactor Reduction Factors .. 22.0.2... eee eee eee cnn eee eee
2.9 Leak Rate Types Available in each Reactor Release Pathway .
3.1 UF, Release Fractions Based on Valve Location
3.2 Airborne Release Fractions and Respiration Fractions Used in Uranium Oxide Fires .
3.3 Airborne Release Fractions and Respiration Fractions Used in Uranium Explosions
3.4 Fission Yields Used in Criticality Calculations ............0..-0.000020005
3.5 Activity (Ci) Released in Criticality of 10'° Fissions
3.6 Fire Release Fractions by Compound Form. .
3.7 Fire Release Fractions by Element
3.8 Reduction Factors Available in each Fuel Cycle and Materials Release Pathway ...........
3.9 Reduction Factors for Fuel Cycle and Materials .
3.10 Leak Rate Types Available in each Fuel Cycle and Materials Release Pathway .
4.1 Constant Values for Calculation of Atmospheric Dispersion Parameters ..................-
4.2, RASCAL Wash-out Coefficients . .
6.1 Estimated Pasquill-Guifford Stability Class Based on NRC Delta TM Method . .
6.2 Estimated Atmospheric Stability Class for Missing Stability Classes...............0......
6.3 Limits of Atmospheric Stability Classes Based on Time of Day, Wind Speed, and
Precipitation
6.4 Precipitation Rates as a Function of Precipitation Climate Zone ..............-.0.0.0005 6-15
7.1 Emergency Worker Turn-Back Limits .. 0.00.00. 0 200k e ee 7-4
8.1 Short-lived Daughters Whose Activities Are Set Equal to their Parents’ Activities ........... 8-2


and UTM, respectively. UTM is used rather than U*> because U** has a specific activity about 3 orders of
magnitude higher than that of U**.

Table 3.6 Fire Release Fractions by Compound Form’

Form of compound? Release fraction‘
Noble gas 1.0
Very mobile form 1.0
Volatile or combustible compound 0.5
Carbon 0.01
Semivolatile compound 0.01
Nonvolatile compound 0.001
U and Pu metal 0.001
Nonvolatile in a flammable liquid 0.005
Nonvolatile in a non-flammable liquid 0.001
Nonvolatile solid 0.0001

Source: *Table F-2, McKenna et al. 1996.
*lf the compound form is not known, the user enters the fire release
fractions in Table 3.6.
‘The fire release fraction is the fraction of the isotope released when the
material is involved in a fire; it equals the total activity released (Ci)
divided by the activity involved in fire (Ci).

3.2 CALCULATION OF RELEASE REDUCTION FOR EACH FUEL CYCLE
AND MATERIALS RELEASE PATHWAY

Most fuel cycle and materials accident release pathways allow consideration of the reduction caused by
the physical systems that are present. The release pathways limit the available reduction mechanisms and
the way in which the leak rate can be defined. Each of the release pathways and reduction mechanisms
and the data used for them are discussed in more detail below. Five types of release pathways have been
defined. Table 3.8 shows which reduction mechanisms are available for each pathway.

Reduction factors (RDF in Eq. 3.1) are applied as scaling factors, as described in NUREG-1228
(McKenna and Giitter 1988). All reduction factors, except fire reduction, are defined for three
categories: noble gases (STCP category 1), halogens (STCP category 2), and other particles. Noble gas
factors all default to one. RASCAL 3.0 assumes that halogens and other particles have the same


8-V

APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

3
2 s |6
2 g 5
Pa . le 2 |é
& Pa g [2 |e a |&
2 |e <5 g i (2 el, |e |g
& |e Elé rn cd
> |s Py g « a 3 Seles
2 |g = |§ 2 2 |e ise |s |Sel4
Name & 18 Z16 2 (8 (4 |alg lz lz
(gal) —_|ft? %Id_\psi |MW(t)
South Texas Project - Unit 2;PWR |Dry Ambient _| 193|U-Tube 279412) 3300000] 0.3] 56} 3800} 22000/ 15000|Operational
St. Lucie - Unit 1 PWR [Dry Ambient | 217/U-Tube 198529} 2500000| 0.5] 44) 2700) 22000] 15000|Operational
St. Lucie - Unit 2 PWR |Dry Ambient | 217/U-Tube 198529} 2500000| 0.5] 44! 2700] 22000] 15000|Operational
Summer PWR [Dry Ambient _| 157/U-Tube 213235] 1800000| 0.2| 55|_2775} 22000! 15000|Operational
Sub-
Surry - Unit 1 PWR [atmospheric | 157|U-Tube 187206] 1800000) 0.1] 60| 2441) 22000] 15000|Operational
Sub-
Surry - Unit 2. PWR |atmospheric | 157|U-Tube __ 187206] 1800000) 0.1} 60|_2441| 22000] 15000)Operational
Susquehanna - Unit 1 BWR |Mark II 764|N/A 172050|__ 240000) 0.5] 53] 3293} 22000) 15000| Operational
Susquehanna - Unit 2 _ BWR |Mark II 764|U-Tube 172050] 240000) 0.5] 53} 3293} 22000] 15000|Operational
Three Mile Island - Unit 1_|PWR_|Dry Ambient _| 177|Once-Through | 188824] 2000000] 0.1] 55|__2568] 22000] 15000|Operational
Trojan ___|PWR |N/A 193|N/A 0} 2000000] 0.2) 60) 3411} 22000) 15000|/Decommissioned
Turkey Point - Unit 3 PWR [Dry Ambient | 157|U-Tube 169118] 1600000 0.25] 59| 2200 22000} 15000|Operational
Turkey Point - Unit 4 PWR |Dry Ambient _| 157)U-Tube 169118} 1600000} 0.25} 59] 2200} 22000/15000/Operational |
‘Vermont Yankee BWR [Mark I 368|N/A. 79650! 130000} 0.5) 56] 1593] 22000 15000/Operational



in the coolant, spiked coolant, gap, or in-vessel melt; (2) uniform mixing in the containment; and (3) an
unshielded monitor that can see a large fraction of the containment volume. Because the mix is most
likely different from that assumed in the calibration of the monitor, the actual reading at the upper end of
the scale could differ by a factor of 10-100 if a shielded detector is used for the higher radiation
measurements.

The levels of damage indicated in the figures should be considered minimum levels unless there are
inconsistent monitor readings. Inconsistent readings may be caused by uneven mixing in containment
[e.g., steam rising to top of dome or not enough time for uniform mixing to occur (it may take hours)].

2.1.3 Coolant Sample

When the user enters the activity in a coolant sample, it completely defines the activity available for
release. No further calculations are performed. It cannot be used to estimate the core-damage state. The
activity can be released only through a steam generator tube rupture or containment bypass.

2.1.4 Containment Air Sample

When the user enters the activity in a containment air sample, it completely defines the activity available
for release. No further calculations are performed. It cannot be used to estimate the core-damage state.
A containment air sample cannot be used to define the activity released in a steam generator tube rupture
or containment bypass.

1E+06

Monifor
1E+08 [— TM w—

oo i

1B+03
1£4+02 |
1E+01

1E+00

marr |
mat |
a

1 TO 100% RELEASE TO CONTAINMENT (f/h)

1B03

1B-04 L 1 1 1 1 1 L

in wh oth Mh th mh th th
In-Vense! Meit Gop Spiked Coolant Normal

‘CORE DAMAGE AND TIME AFTER REACTOR SHUTDOWN

Figure 2.1 PWR Containment Monitor Response (sprays on).

2-8


Nuclear power plant nuclide inventory data are used in computing nuclear power plant and spent fuel
accidents. The inventories used for pressurized water reactors (PWRs) and boiling water reactors
(BWRs) are from NUREG-1150 (NRC 1990). Normal coolant concentrations are from (ANSI 1999).
Due to limitations in the number of nuclides that can be transported in the atmosphere, only those
nuclides that are expected to be significant contributors to dose are included in the coolant inventory.
These data are shown in Table 2.2. Default inventories assume a burn-up of 18,000 MWD/MTU. In
all calculations, the inventories are adjusted for the actual burnup. All radionuclides in the initial
inventory that have a half-life of more than one year are computed as

BURNUPactuat (2.2)

INVa =INV1 x———____—._ ,
BURNUPassumen

where the assumed burnup is 18,000 MWD/MTU.

In all cases, if the reactor is shut down prior to the start of the release, the inventory or coolant activity
is decayed over the shutdown period prior to any other calculations being performed.

2.1.1 Core Cooling Status

STDose can use data on the core cooling status to estimate the core damage state or coolant activity. The
core damage state is based on the amount of time the core is uncovered. The resulting amount of core
activity available in containment or coolant are based on the core release fractions in Tables 3-12 and
3-13 in NUREG-1465 (Soffer et al. 1992). The core release fractions are shown in the following
Tables 2.3 and 2.4. Note that the fractions shown in these tables are cumulative; that is, the fraction
released in a vessel melt-through is the sum of the cladding failure, core melt, and vessel melt-through
fractions. The fractions are listed according to Source Term Code Package (STCP) categories as revised
in NUREG-1465 (Soffer et al. 1992). The chemical elements in each of the STCP categories are listed
in Table 2.5. The isotopes of all elements not listed in this table are not included in the initial source
term calculations. When a daughter grows in during the scenario, its release fraction is that of its STCP
category, not that of its parent.

STDose recomputes the core-damage state every time step or 15 min, whichever is less. First it
computes the core uncovery duration, based on the core uncovery time entered by the user and the
current time in the scenario calculations. The core-damage state selected is the one into which the
current core uncovery duration falls. For example, when a BWR core has been uncovered for 1 h and 45
min, it has a core-damage state of “core melt”; that is 1.75 h is greater than the total cladding failure
duration (0.5 h) and less than the total cladding failure plus core melt durations (0.5 h +1.5 h). The
fraction of that core-damage state, Fp, that has been released from the core at any time is determined as

Du —Deps-: (2.3)
Deps ,

Feos =


CONTENTS (continued)

5.2.4 UF, Enthalpy
5.2.5 Uranium Enrichment ....... 2.60.00 cece eect e nee en eee
5.2.6 HF-H,O System . .
5.2.7 HF Self Association ......

5.2.8 Partial Vapor Pressure of HF .
5.2.9 Partial Vapor Pressure of H,O
5.2.10 Enthalpy of HF-H,O Vapor Mixtures... 2.2.0.0. 00.0 cece cece eee eee e ees 5-7

5.2.11 Enthalpy of HF-H,O Liquid Mixtures . 5-8
5.2.12 UO,F, Enthalpy ..................0.. - 5-8
5.2.13 Mixture Enthalpies and Plume Temperature . 5-8
5.3 DISPERSION AND DEPOSITION OF HF AND UO,F, . - 5-9
5.4 REFERENCES ..... 20.0.0. 0 cece eee e tent n ene e eee tenenees 5-11

6 METEOROLOGICAL DATA PROCESSOR .
6.1 MODEL DOMAIN ................
6.2 METEOROLOGICAL STATIONS .
6.3 METEOROLOGICAL DATA INPUT .

6.3.1 Surface Winds ...
6.3.2 Atmospheric Stability Class
6.3.3 Precipitation Class ......
6.3.4 Mixing Height ............ 0... cece cece eee eee
6.3.5 Temperature
6.3.6 Pressure ...
6.3.7 Humidity .......
6.3.8 Interpolated Values ...

6.4 OTHER METEOROLOGICAL PARAME’
6.4.1 Monin-Obukhov Length . .
6.4.2 Winds ...........
6.4.3 Mixing Height .
6.4.4 Dry Air and Water Vapor
6.4.5 Precipitation Rate .

6.5 CALCULATING SPATIALLY VARYING METEOROLOGICAL CONDITIONS ........ 6-15
6.5.1 Winds ....
6.5.2 Stability and Precipitation
6.5.3 Mixing Height ......... 00.00. :

6.6 CALCULATING METEOROLOGICAL CONDITIONS AT THE SOURCE ............. 6-17

6.7 REFERENCES ...

7 DOSE CALCULATIONS IN FMDOSE

7.1 EARLY-PHASE DOSES
7.1.1 Inhalation Doses

7.1.2 Cloud-Submersion Dose ...

vii


8 DECAY CALCULATIONS

Almost all modules in RASCAL 3.0 require some kind of decay calculation. All use the same data and
basic method of calculation. Because STDose requires that decay calculations be performed at least
every 15 min, it was determined that a significant amount of calculation time could be saved by
precalculating decay over that period for all of the radionuclides in RASCAL. Since the STDose
calculations may also require decay over longer or shorter periods, decay was also precomputed for 1
and 5 min, 1h, and 1, 14, and 182 days. One implication of this is that in RASCAL 3.0, decay cannot
be calculated for less than 1 min. Only FMDose calculates decay directly. In FMDose, the decay
equations had to be modified to include the weathering of material on the ground. For this reason the
precalculated decay file could not be used.

8.1 DECAY DATA FILES

The decay data used in RASCAL 3.0 is the decay data used in creating the dose factors in Federal
Guidance Report No. 12 (USEPA 1993). FMDose reads this file directly. The decay data file used by
STDose and decay was created by running a program called Chain, that was originally written by K. F.
Eckerman to read the decay data used in creating the dose factors in Federal Guidance Report No. 12
and to solve the Bateman equations.

The precalculated decay data is stored in two binary, direct-access files called DECAY.DAT and
INTDECAY.DAT. These files contain data for all 825 radionuclides in Federal Guidance Report No.
12, sorted in alphabetical order. Decay has been precomputed for 1, 5, and 15 min, 1 h, and 1, 14,
and 182 days. Each line in the file contains the names and resulting activities of the parent nuclide and its
daughters. DECAY.DAT contains the activity (Ci) of each radionuclide remaining after the decay
period. INTDECAY.DAT contains the integrated activity (Ci sec) of each radionuclide calculated over
the decay period.

8.2 IMPLEMENTATION

This section discusses the implementation of the decay calculations in STDose, FMDose, and
DecayCalc. The calculation of decay in TADPUFF and TADPLUME are discussed in Section 4.8.

8.2.1 STDose and DecayCalc

The decay calculations for the source term calculation of STDose and DecayCalc are performed by the
same subroutines. These subroutines compute decay incrementally, starting with the longest time period
for which decay data have been precalculated and stored. For each time period, the activity of the parent
and its daughter products are summed. The process is repeated until the correct decay time is reached.
For example, assuming that 72 min of decay are required, the subroutines find the required nuclide

8-1


Dir) =[XVQTY VDF ace» (4.49)

where x(r)/Q’ is calculated using Eq. (4.5) or a variation thereof, as appropriate.
4.9.4 Open- and Closed-Window Dose Rates

Calculation of open- and closed-window dose rates is a new feature in RASCAL 3.0. These dose rates,
which are reported in mrad/h, are intended for use in comparisons with field radiation measurements.
The open-window dose rate has four components. These components are gamma and beta radiation from
airborne activity and gamma and beta radiation from surface contamination. The closed-window dose
rates have only the gamma radiation components.

The gamma dose rate from airborne activity is calculated using the same algorithms used in TADPUFF
and TADPLUME for finite-plume, cloud-shine doses with adjustment for the difference in energy
absorption coefficients of tissue and air. The gamma dose rate is calculated as

DF,
D'yyig = DP Esicnie 50
air DF (4.50)

sictissue

where D’ is the cloud-shine dose rate calculated by TADPLUME or TADPUFF for tissue. Semi-infinite
cloud-dose factors for tissue from Federal Guidance Report No. 12 (Eckerman and Ryman 1993) are
used in this calculation along with semi-infinite cloud-dose factors for air calculated by A. L. Sjoreen
using the methods listed in (Scherpelz 1986). The semi-infinite dose factors for air are included in the
RASCAL 3.0 radionuclide database. They are passed to TADPLUME and TADPUFF as needed.

The beta dose rates from airborne activity are calculated using the semi-infinite cloud model with
appropriate dose factors. Beta semi-infinite cloud dose factors, which were extracted from the original
data used in producing Federal Guidance Report No. 12 by its authors, are included in the RASCAL 3.0
radionuclide database and passed to TADPLUME and TADPUFF as needed.

The gamma and beta ground-shine dose rates are calculated using the same models used to calculate
external doses to the body, with dose factors for air in place of dose factors for tissue. These dose
factors, which were extracted from the original data used in producing Federal Guidance Report No. 12
by its authors, are included in the RASCAL 3.0 radionuclide database and passed to TADPLUME and
TADPUFF as needed.

4.10 REFERENCES

Athey, G. F., etal. 1993. RASCAL Version 2.0 User’s Guide. Vol. 1., Rev. 1., NUREG/CR-5247,
U.S. Nuclear Regulatory Commission.

4-24


When the sample is taken at a time that is later than the start of the release, the nuclide concentrations are
first computed at the sample time. Then they are adjusted back to the values they would have had at the start
of release time, due to the effects of radiological decay. Daughter ingrowth is not considered here.

STDose computes the source term using Eq. (2.1) without the leakage fraction. First STDose determines
the source term that would result for a reactor with a power of 1 MW(t) using the selected radionuclide mix.
Tf the core-damage state is entered, the fractions from Tables 2.3. or 2.4 for that state are used. STDose
then scales all activities in the computed mix up (or down) so that they sum to the total amount of activity
released. The activity released is determined by the product of the release rate and duration that were
entered by the user.

2.1.7 Effluent Source Terms

Two other types of effluent source terms are available: effluent release rates and effluent concentrations.
Effluent release rates are simply used as entered. The user is not given the opportunity to enter reduction
factors since this option assumes that the user knows what is being released. Up to three sets of rates may
be entered along with their start and end times. No decay is calculated in the source term calculation. When
effluent concentrations are entered, the user also enters an overall release rate. The amount of activity
released is computed as the concentration times the rate times the release duration. Up to three sets of
concentrations and rates may be entered. The effluent concentrations may be decayed over a selected time
period prior to release to the environment, and decay is calculated over the duration of the release.

2.2 ACTIVITY RELEASED IN SPENT FUEL STORAGE ACCIDENTS

RASCAL calculates releases for three types of spent fuel storage accidents: (1) releases when the fuel stored
in a pool is uncovered, the fuel overheats, and the cladding is damaged, (2) releases when the fuel stored
in a pool is damaged under water, and (3) releases when an accident causes damage to the cladding of the
fuel stored in a dry storage cask and causes the integrity of the dry storage cask to be lost.

For each accident, the activity in the damaged fuel elements is calculated as follows. The activity in the fuel
involved at the time of reactor shutdown is first computed. This activity is computed as the number of
batches (or assemblies) involved times the fraction of a reactor core that one batch (or assembly) represents
times the activity in a full reactor core. By definition, a batch is defined as one-third of the fuel in any core.
The number of assemblies per core is specific to the plant selected and is included in the facility database
and may be adjusted by the user. The activity in a full reactor core is computed as the reactor power in
MW<(t) from the database or entered by the user times the core inventory per MW(t) listed in Table 2.2
(McKenna and Giitter 1988) adjusted for the actual burn-up of the fuel as described in Eq. (2.2). Note that
the burn-up of the spent fuel may be different than the burn-up of the reactor core. Finally, the activity is
reduced to account for radiological decay during the storage period.

2-13


report '"'I air concentrations and open- and closed-window dose rates in addition to the doses reported in
earlier versions of RASCAL. All results are reported at 15-min intervals. The technical bases for
TADPLUME and TADPUFF are presented in Section 4.

TADPLUME and TADPUFF do not adequately model the processes that are important when UF, is
released to the atmosphere. UF, is initially a dense gas, and it reacts chemically with the water in the
atmosphere to give HF and UO.F,. UF6PLUME is a version of TADPLUME that has been modified to
treat the dense gas dispersion and chemical reactions associated with UF,. The technical bases for
UF6PLUME are presented in Section 5.

As indicated above, one of the areas in which RASCAL 3.0 has expanded capabilities is in the treatment
of the meteorological conditions. In earlier versions of RASCAL, variation in meteorological conditions
was limited; data could be entered only four times at a single location. Therefore, TADPLUME and
TADPUFF could run using the same meteorological data. TADPUFF now has the capability to use
spatially and temporally varying meteorological conditions. To support this increased capability, the
meteorological data entry component of earlier versions of RASCAL has been moved to a separate
module, METPROC, that can be run either from STDose or as a stand-alone program. This module
includes meteorological data entry, conversion of the data to engineering units used by TADPLUME and
TADPUFF, and preparation of input files for TADPLUME and TADPUFF. The TADPUFF files
contain fields that describe the spatial variation of meteorological conditions. Meteorological data may
be entered for as many as 36 locations, and the number of observations is not limited. METPROC has
options that, if selected, evaluate stability data for consistency with season and time of day, estimate
mixing-layer height from meteorological data or climatology, substitute climatological estimates for
missing data, and modify the wind field for topographic effects. The technical bases for METPROC are
presented in Section 6.

1.2 FMDOSE

FMDose is a stand-alone program that calculates doses, derived intervention levels (DILs), and
emergency-worker turn-back guidance at a single field measurement location. It calculates doses and
DILs for both the early phase and the intermediate phase of the accident. Calculational methods are
based on the Federal Radiological Monitoring and Assessment Center (FRMAC) Assessment Manual
(DOE 1995). All calculations require the user to enter at least one air or ground concentration and a
meter reading. For emergency worker guidance and early-phase doses based on air concentrations,
FMDose assumes that all radionuclide concentrations are constant over the exposure period. All other
dose and DIL calculations include decay and decay-product ingrowth. The calculation of the decay of
ground concentrations includes weathering. The technical bases for FMDose are presented in Section 7.

1.3 DECAY CALCULATIONS
Almost all modules in RASCAL 3 require some kind of decay calculation. All use the same data and

basic method of calculation. DecayCalc is a stand-alone program that only calculates radiological decay
and daughter ingrowth. The technical bases for the decay calculations are presented in Section 8.


Table 2.8 Reactor Reduction Factors

Noble | Halogen or Ref.
Reduction gas Other NUREG
Filters 1 0.01 1228
Sub-cooled pool 1 0.01 1228
Saturated pool 1 0.05 1228
Sprays 1 h_ factor | /CR-4722
(exponential time dependence) <0.25 e?! (Figure 5)

20.25 7!
Containment hold-up 1 h factor 1150
(exponential time dependence) <2 el# App. B
22 e° St
Plate out (containment bypass only) 1 0.4 1228
Ice condenser—no fans or recirculation 1 0.5 1228
Ice condenser - 1 h or more recirculation 1 0.25 1228
Steam generator tube rupture—to secondary 1 0.02 1228
Steam generator tube rupture—not partitioned or 1 0.5 1228
solid
Steam generator tube rupture—steam jet air ejector | 1 0.05 1228
release
Minimum reduction, except for filters 0 0.001 1228
Minimum reduction, sprays only 0 0.03 /CR-4722
(Figure 5)

2.4 CALCULATION OF LEAKAGE FACTORS FOR REACTOR ACCIDENTS

Four types of reactor leak rates are used in RASCAL 3.0: (1) percent of total amount per unit time, (2)
based on containment pressure and hole size, (3) flow rate (volume or mass per unit time), and (4) a
“direct” release, with all activity released during the selected release duration. The types of flow rates
available in each type of release pathway are shown in Table 2.9. Because the atmospheric transport
models expect the source term to be in terms of a rate, rather than a total amount, the leakage data that

the user enters is always converted to a leakage rate fraction (LRF) by STDose.

2-18



6.4.5 Precipitation Rate

The RASCAL 3.0 atmospheric codes use precipitation rate to calculate wet deposition rate. When the
precipitation class for a station is other than none or unknown, METPROC estimates a precipitation rate
(mm/h) for the station using the precipitation class and a precipitation rate zone. Each site in the
RASCAL 3.0 database is assigned to one of three precipitation rate zones. The precipitation zones,
originally defined in Ramsdell, Simonen, and Burk (1994) are based on annual precipitation. Zone 1 is
for areas where the annual precipitation is less than 10 in., zone 2 is for areas where the annual
precipitation is between 10 and 20 in., and zone 3 is for areas where the annual precipitation exceeds 20
in. Generic sites and sites not known to RASCAL 3.0 are assigned to precipitation rate zone 3. The
precipitation rates assigned by METPROC are listed in Table 6.4. These rates, based on data collected
in the Pacific northwest, should be conservative for most nuclear facilities in the United States.

Table 6.4 Precipitation Rates as a Function of Precipitation Climate Zone

Precipitation Precipitation Rate (mm/h)
Class Zone 1 Zone 2 Zone 3
1 0.4 0.6 0.7

2 3.8 3.8 3.8

3 3.8 3.8 8.5

4 0.3 0.3 0.7

5 17 17 3.8

6 17 17 3.8

6.5 CALCULATING SPATIALLY VARYING METEOROLOGICAL CONDITIONS

TADPUFF takes into account both spatial and temporal variations in the atmospheric conditions.
METPROC provides gridded fields of the atmospheric stability class, the inverse Monin-Obukhov
length, the east-west (u) and north-south (v) components of the wind, the mixing height, and the
precipitation class and precipitation rate for each of the three TADPUFF model domains. The following
subsections describe the preparation of the fields from the station data.

6.5.1 Winds
TADPUFF uses wind fields to calculate movement of puffs. These are fields of u (east-west) and v
(north-south) components of the wind vector. The wind fields are created from station wind data using a

1/1? interpolation scheme, where r is the distance from the grid point to the station. This interpolation

6-15


Atmospheric Stability

If the atmospheric stability for the earlier observation is missing, the atmospheric stabilities at all
times between the two observations are assumed to be missing.

If the atmospheric stability for the later observation is missing but not for the earlier observation,
then the atmospheric stabilities are set to the value of the earlier observation as long as the elapsed
time from the earlier observation is less than 12 h. After 12 h, the stabilities are set to missing.

If both observations have valid atmospheric stabilities, the atmospheric stability is estimated using
linear interpolation between the two observations. If the atmospheric stability is given by a
Pasquill-Gifford stability class (1-7), then the interpolation is rounded to the nearest integer.

Precipitation Class

If the precipitation class for the earlier observation is missing, the precipitation class for all times
between the two observations will be set to missing.

If the precipitation class for the later observation is missing but not for the earlier observation,
then precipitation classes are set to the precipitation class of the earlier observation as long as the
elapsed time from the earlier observation is less than 12 h. After 12 h, the precipitation classes are
Set to missing.

If both observations have valid precipitation classes, then the precipitation class for the earlier
observation is used when the time is less than or equal to half way between the two observations.
If the time is greater than half way between the two observations, the precipitation class of the
later observation is used.

Mixing Height

Unless the mixing height is being entered directly (not calculated from the meteorological data or
from climatology), the method of estimating mixing heights being used for the earlier observation
will continue to be used.

If the mixing heights are being entered directly, the technique used to interpolate stability is used
to estimate the missing mixing heights (see previous statement).

Temperature, Pressure, and Moisture

The same technique previously explained used to estimate missing stabilities is used for
temperature, pressure, and humidity.

If data are missing between observed and forecast values, persistence will be used to estimate missing

6-8


1.4 REFERENCES

Athey, G. F., A. L. Sjoreen, and T. J. McKenna. 1989. RASCAL Version 1.3 User’s Guide.
NUREG/CR-5247, U.S. Nuclear Regulatory Commission.

Athey, G. F., et al. 1993. RASCAL Version 2.0 User’s Guide. Vol. 1, Rev. 1, NUREG/CR-5247,
U.S. Nuclear Regulatory Commission.

Athey, G. F., A. L. Sjoreen, and T. J. McKenna. 1993. RASCAL Version 2.1 Workbook. Vol. 2,
NUREG/CR-5247, U.S. Nuclear Regulatory Commission.

Athey, G. F., and T. J. McKenna. 1994. RASCAL Version 2.0 Workbook. Vol. 2, Rev. 2, NUREG/CR-
5247, U.S. Nuclear Regulatory Commission.

Athey, G. F., A. L. Sjoreen, and J. V. Ramsdell. 1997. RASCAL Version 2.2 User’s Guide. Vol 1,
Rev. 2, Supp. 1, NUREG/CR-5247, U.S. Nuclear Regulatory Commission.

U.S. Department of Energy (DOE). 1995. FRMAC Assessment Manual for Interim Use and Comment,
1995.

Sjoreen, A. L., et al. 1994. RASCAL Version 2.1 User’s Guide. Vol 1, Rev. 2, NUREG/CR-5247,
U.S. Nuclear Regulatory Commission.


Pp = total station pressure (Pa),
R = gas constant for dry air = 287.0 J/kg K.

The method used to calculate the vapor pressure (e) depends upon the moisture variable. If the moisture
variable is the dew point and precipitation is not occurring, then the vapor pressure is given by
e=e,(ty) , (6.13)

where e,(t) [mb] is the saturation vapor pressure at temperature t (°C). According to Rogers and Yau
(1989), the saturation vapor pressure is given by

t
e,(t)=6.112 exp{ 17.67—t— } 6.14
() no aa) (o14)

If the moisture is defined by the relative humidity and precipitation is not occurring, then the vapor
pressure is given by

_RH-e,(t)
100

e (6.15)

where RH is the relative humidity (percent) and e,(t) is given by Eq. (6.14).

If the moisture is given by the wet bulb temperature and precipitation is not occurring, then the vapor

pressure is given by
Pp 1004(t-1, )
=e,(t)—| —— |} —+—_" | , 1

e=e,(t) (2s) 25E6 6.16)

where t, is the wet bulb temperature [°C].

If precipitation is occurring, the air is assumed to be 95% saturated, so the vapor pressure is given by

e=0.95e,(t) , (6.17)

where e,(t) is given by Eq. (6.14). During precipitation, Eq. (6.17) is used regardless of the moisture
variable.

If the temperature is missing, a climatological temperature estimate will be taken from the site
climatology file, if available. A temperature of 15°C will be assumed if a climatology file is not
available. If the pressure is missing, a pressure of 1000 mb is assumed. Finally, if the moisture
variable is missing, a relative humidity of 60% is assumed unless there is precipitation. During periods
of precipitation, the relative humidity is assumed to be 95%.

6-14


Zilitinkevich, S. S. 1972. “On the Determination of the Height of the Ekman Boundary Layer.”
Boundary-Layer Meteorology, 3(2):141-5.

6-19


9-V

APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

3
5 7]
g 3 |g
Ae : (8
& 5 3 2 a |e
Bie Ss 2
B < 3 S$ 2
= 3 2 8 a a ale E E
Bg ae: s | (lg |zg |e |e
SIs 5 (8 2 8 “| |3 |3e/8
Ea & 3 € i m7 7 3 Sole
= |g a 3 So | & |B2a
& |s g|3 B |& g\)e |e |es|%
Name £ 18 Z 1a <5 alalé |< |<¢%
(gal) _|fe %Id_|psi|MW(t)
Oconee - Unit 2 PWR |Large, Dry 177/Once-Through | 188824] 1900000] 0.5] 59] 2568] 22000] 15000|Operational
Oconee - Unit 3 PWR |Large, Dry 177/Once-Through | 188824] 1900000] _0.5| 59| 2568] 22000] 15000|Operational
Oyster Creek BWR [Mark I 560|N/A 96500| 180000] 0.5] 62| 1930] 22000] 15000|Operational
Palisades PWR |Dry Ambient | 204/U-Tube 186029] 1600000] 0.2| 55] 2530] 22000] 15000|Operational
Palo Verde - Unit 1 PWR [Dry Ambient | 241|/U-Tube 279412] 2600000] 0] 60] 3800} 22000] 15000/Operational
Palo Verde - Unit 2 PWR |Large, Dry _| 241/U-Tube 285000) 2600000) 0} 60} 3800] 22000} 15000|Operational
Palo Verde - Unit 3 PWR |Large, Dry __| 241]U-Tube 285000] 2600000} 0.1] 60} 3800] 22000} 15000|Operational
Peach Bottom - Unit 2 BWR |Mark I T64|N/A 172900] 180000} 0.5] 58} 3293] 22000) 15000|Operational
Peach Bottom - Unit 3 BWR |Mark I 764|N/A 172900] 180000} 0.5] 58] 3293} 22000] 15000/Operational
Perry - Unit 1 BWR [Mark III 748|N/A 178950} 280000] 0.2} 15} 3579] 22000] 15000/Operational
Pilgrim - Unit 1 BWR [Mark I 580|N/A 99900|__150000|_0.5] 56] 1998] 22000} 15000|Operational
Point Beach - Unit 1 PWR {Dry Ambient | 121/U-Tube 111691] 1000000] 0.4] 60] 1518] 22000] 15000|Operational
Point Beach - Unit 2 PWR |Dry Ambient | 121|U-Tube 111691] 1000000] _0.4| 60] 1518] 22000] 15000|Operational
Prairie Island - Unit 1 PWR [Dry Ambient | 121|U-Tube 121322} 1300000] 0.5] 41] 1650] 22000} 15000|Operational
Prairie Island - Unit 2 PWR |Dry Ambient | 121/U-Tube 121322] 1300000] _0.5] 41] _1650| 22000] 15000|Operational



where

N = number of radionuclides,
Q, = activity of radionuclide n in the puff,
D’,.(P) = dose rate at distance p from a 1-Ci point source of radionuclide n.

The overall puff geometry remains the same in TADPUFF as it was in earlier versions of RASCAL.
However, the internal geometry has changed. In TADPUFF, the puff is divided into ten layers with
each layer containing one-tenth of the activity. The number of annular rings has been fixed at six, with
each ring containing one-sixth of the puff activity, and the number of sectors has been fixed at 12. With
these changes, the number of volume elements has been increased, and the fraction of activity in each
volume element becomes 1/720 of the total activity. In TADPUFF, Eq. (4.37) becomes

DIN=L TY YD (Py) (4.39)
T20  o

As before, symmetry is used to reduce the computational load.

When the horizontal dispersion parameter reaches 400 m, the puff radius is large enough that the
horizontal variations in the cloud-shine dose rate are directly proportional to the horizontal variation in
concentration in the puff. At this point, MESORAD changed to a semi-infinite cloud model, and
previous versions of RASCAL changed to calculating dose rates beneath the center of the puff using the
finite-puff model and dose rates elsewhere using the horizontal variation in concentration. TADPUFF
changes from the point-source based cloud-shine model used in earlier versions of RASCAL to a new
plane-source based model. The plane-source model assumes that the puff is a vertical cylinder as is
assumed in the point-source model. However, rather than assuming that activity is distributed among
volume elements, the activity is assumed to be concentrated on ten horizontal slabs (planes).

To calculate the activity in each slab, the concentration at the center of the puff (y=0) is first integrated
vertically from the bottom of the puff to the top. This is similar to the integration done in calculating the

depletion from wet deposition
ry) h, Q 1)
exp} 0.5} — Z=—+exp| 0.5] — ; 4.40)
<] ‘| (=) i Ino, P [=] 40)

where (x), is the vertically integrated concentration of radionuclide n at the center of the puff. This
concentration is then divided by the number of slabs (ten) to get the concentration in each slab.

Within the cylinder, the vertical position of the slabs is determined by the effective release height, the
mixing-layer thickness, and the vertical-dispersion coefficient. When a Gaussian distribution is
Partitioned so the area under the curve is divided into ten equal parts and the center of mass of each part
is determined, these centers of mass fall at +0.1270, +0.3850, +0.6740, +1.0370, and +1.6450.
Using this as a basis, the slab heights are initially estimated as h,+0.1270,, h,+0.3850,, h,£0.6749,,
h, £1.0370,, and h,+1.6450,. The initial heights may lie below ground level or above the top of the
mixing layer. Any heights that fall outside these bounds are adjusted to account for reflection by the

4-20


Martin, D. O., and J. A. Tikvart, 1968. “A General Atmospheric Diffusion Model for Estimating the
Effects on Air Quality of One or More Source.” 67° Annual Meeting of the Air Pollution Control
Association for NAPCA, St. Paul, Minnesota.

Panofsky, H. A., and J. A. Dutton. 1984. Atmospheric Turbulence. J. Wiley & Sons, New York.

Petersen, W. B., and L. G. Lavdas. 1986. INPUFF 2.0-A Multiple Source Gaussian Puff Dispersion
Algorithm User’s Guide. EPA/600/8-86/024, Atmospheric Sciences Research Laboratory, U.S.
Environmental Protection Agency, Research Triangle Park, N.C.

Press, W. H., et al. 1986. Numerical Recipes: the An of Scientific Computing. Cambridge University
Press, Cambridge, United Kingdom.

Ramsdell, Jr., J. V., et al. 1988. The MESORAD Dose Assessment Model, Volume 2: Computer Code.
Vol. 2., NUREG/CR-4000, U.S. Nuclear Regulatory Commission.

Ramsdell, Jr., J. V. 1990. “Diffusion in Building Wakes for Ground-Level Releases.” Atmospheric
Environment, 24B:377-88.

Ramsdell, Jr, J. V., C. A. Simonen, and K. W. Burk. 1994. Regional Atmospheric Transport Code for
Hanford Emission Tracking (RATCHET). PNWD-2224 HEDR, Battelle, Pacific Northwest Laboratories,
Richland, Wash.

Ramsdell, Jr., J. V., and C. J. Fosmire. 1998. “Estimating Concentrations in Plumes Released in the
Vicinity of Buildings: Model Development.” Atmospheric Environment, 32:1663-17.

Randerson, D. 1984. Atmospheric Science and Power Production. DOE/TIC-27601, U. S. Department
of Energy.

Sagendorf, J. F., J. T. Goll, and W. F. Sandusky. 1982. XOQDOQ: Computer Program for the
Meteorological Evaluation of Routine Effluent Releases at Nuclear Power Stations. NUREG/CR-4380,
U.S. Nuclear Regulatory Commission.

Scherpelz, R. I., et al. 1986. The Mesorad Dose Assessment Model. Vol. 1., NUREG/CR-4000, U.S.
Nuclear Regulatory Commission.

Sehmel, G. A. 1984. “Deposition and Resuspension.” Atmospheric Science and Power Production. Ed.
D. Randerson, DOE/TIC-27601, U. S. Department of Energy.

Seinfeld, J. H. 1986. Armospheric Chemistry and Physics of Air Pollution. John Wiley & Sons, New
York.

Stull, R. B. 1988. An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers,
Dordrecht, Netherlands.

Slade, D. H. 1968. Meteorology and Atomic Energy 1968. TID-24190, U.S. Atomic Energy Agency.

4-26


magnitude may be seen following reactor shutdown, startup, rapid power change, and reactor coolant
system depressurization. Such increases are referred to as iodine spikes. The user may select a spiking
factor from 1 to 1000. The activity of all radionuclides in the coolant except noble gases are multiplied
by this spiking factor.

Table 2.3 BWR Core Activity Release Fractions

Cladding Core melt | Vessel melt-

failure through
Duration of core damage state (h) | 0.5 1.5 3.0
Core uncovery duration at which | 0.0 0.5 2.0
this core damage state begins (h)
Noble gases 0.05 0.95 0
Halogens 0.05 0.25 0.30
Alkali metals 0.05 0.20 0.35
Tellurium group 0 0.05 0.25
Barium, strontium 0 0.02 0.1
Noble metals 0 0.0025 0.0025
Cerium group 0 0.0005 0.005
Lanthanides 0 0.0002 0.005

‘Source: Table 3-12 from NUREG-1465 (Soffer et al. 1992)
2.1.2 Containment Radiation Monitor

STDose can use a containment radiation monitor reading to estimate the core damage state or the
amount of activity in the coolant. The user can enter changes in the monitor readings with time, so this
calculation can result in a time-varying source term. The fractional core-damage state or coolant
condition is determined based on the data in Figs. A.5 — A.12 in RTM-96 (McKenna, et al. 1996), that
are shown as Figures 2.1—2.8 below. The bars in these figures represent the range from 1 to 100% of
the'labeled core-damage state. The data in these figures were calculated assuming a reactor power of
3000 MW(t). Note that these figures use the older terminology “gap” and “in-vessel melt” to refer to
cladding failure and core melt, respectively. In this section only, the older terms are used for ease of
comparison with the figures.

To estimate the core-damage state, STDose first determines which set of data in the figures should be

used. It selects the figure to use, based on the containment type and whether or not containment sprays
are operating and, for BWRs, whether the monitor is in the wet well or dry well. Since the figures

2-5


scheme, which was used in earlier NRC codes such as MESOI (Ramsdell, Athey, and Glantz 1983) and
MESORAD (Scherpelz, et al. 1986; Ramsdell et al. 1988), is common in spatial interpolation of the
wind fields (Hanna, Briggs, and Hosker 1982).

If the meteorological stations reporting data are well placed with respect to major topographic features,
the wind fields developed by interpolation will give reasonable puff trajectories. However, with one
meteorological station or a small number of stations, the wind fields may not properly reflect the effects
of topography. METPROC includes an option to use a simple one-layer model to adjust wind fields for
topography based on site topographic data. Topographic data are included in RASCAL 3.0 for all sites
in the database. The wind-field model is a two-dimensional adaption of the wind fitting program
described by Ross et al. (1988) that is used in the NUATMOS and MATTHEW codes.

The wind-field model uses the wind fields created by interpolation as a starting point. The thickness of
the mixing layer is calculated for each node in the model domain by computing the difference between
the top of the boundary layer and the terrain elevation. For those nodes where the terrain rises above the
top of the boundary layer, the program assumes that the boundary-layer thickness is 0.01 m and sets the
wind to zero. This technique is simple to implement and has proven effective at generating flows that
avoid obstacles such as mountain ridges.

The initial wind field is adjusted using methods of variational calculus to produce a non-divergent wind
field in the boundary layer, subject to the constraint of minimum difference between the initial wind field
and the adjusted wind field. The equation for adjusting the wind field involves solving Poisson’s
equation. The code uses a nine-point Laplacian operator and a simultaneous relaxation technique to
obtain the solution.

The model has been tested and shows that the winds produced by the model flow around obstacles that
are well resolved by the grid. Obstacles having width of three grid points or greater are considered well
resolved. Smaller obstacles may or may not be resolved, depending on their shape and orientation
relative to the grid. For example, a ridge one grid point wide is well resolved if it runs in the x or y
direction, but if that same ridge is at 45° to the grid, it is not resolved.

The adjusted wind field is most accurate near stations and along trajectories that pass near stations.
Wind fields are less accurate elsewhere. Thus, it is desirable to have wind data near the release point
and, if possible, at downwind locations.

Sites not included in the RASCAL 3.0 database and the generic site do not have topographic data files.
Therefore, the option of modifying wind fields for topographic effects is not available for these sites.

6.5.2 Stability and Precipitation
The stability class and precipitation fields (precipitation class and precipitation rate) are based on data for
the closest meteorological station. Fields created in this manner include stability class, inverse Monin-

Obukhov length, precipitation class, and precipitation rate. This procedure avoids averaging that would

6-16


von L a
wea F a
weas | | |

1b ub 1b uh Ih wa ib ub
In-Vessel Meit Gap ‘Spiked Coolest Normal Coolant

CORE DAMAGE AND TIME AFTER REACTOR SHUTDOWN

1 TO 100% RELEASE TO CONTAINMENT (Rh)
a
bi
2
T

Figure 2.4 BWR Mark I & II Dry Well Containment Monitor Response (sprays off).

1E+06
1E+03

al |
—TMiin

1E+@ |

1E+01

L n L 1 1 1 4 ‘

ih 4m 1k wh ih ua ih 24h
In Vessel Me Gap ‘Spiked Coola Noxmal Coolant

CORE DAMAGE AND TIME AFTER REACTOR SHUTOOWN

1 TO 100% RELEASE TO CONTAINMENT (hn)

FEEEEES

Figure 2.5 BWR Mark I & Il Wet Well Containment Monitor Response (sprays on).

2-10


where r is a pseudo-diagonal distance from a point directly above the release point to the intake.

2 2
Pax? (2) y? (&) ze, (4.8)
oO, oO,

x = the downwind distance,
y = the cross wind distance from the plume center line,
z = the vertical distance from the plume center line.

The definition of r is
where

For positions under the center line of a plume, y = 0.0, and z = h,+Ah, thus

2
? = «(&] (h, +h)? . (4.9)

Oy

TADPLUME assumes that 6,=0,=0.4 m/s and that 0, =0.04 m/s based on a cursory review of
atmospheric turbulence data.

Equation (4.7) is well behaved in low-wind speed conditions and gives finite x/Q values for calm wind
(mean wind velocity = 0). As wind speed increases, x/Q values increase to a maximum value for a
wind speed in the 1 to 2 m/s range and then decrease as the wind speed continues to increase. The
equation is used in TADPLUME for wind speeds between 0.1 and 0.4 m/s. The direction of the x axis
(plume center line) is determined by the wind direction at the release point. During these periods this
direction may be the last reported direction.

For calm winds, Eq. (4.7) has a simple form that is similar to the standard Gaussian puff model. It is

= oO,
Qn) oo,

xX/Q (4.10)

This equation is used for wind speeds < 0.1 m/s. In this calculation, y is assumed to be zero, and the
resulting x/Q’ is a function only of x and z. The x/Q’ calculated at each distance is applied in all
directions.

In TADPLUME use of Eq. (4.9) and Eq. (4.10) is limited to receptors less than 16.1 km (10 mi) from
the release point. Calculations are not made for greater distances.

4.1.4 Model Domains

TADPLUME and TADPUFF use different model domains. The TADPLUME domain consists of a

4-5


@ From sunset to midnight—use exponential interpolation between the afternoon and morning mixing
heights. For the last day of the month, use the morning of the next month.

The exponential interpolation of the mixing height is given by

bt
H(t)=a- -——|, 6.7
(t) ee | 6.7)

where

H(t) = mixing height at time t (m),
a = H,,,,/exp(-b),

b = 24 In(Hyq/Henorn)(24 ~ thunseds
Hyom = Morning mixing height (m),
Hy, = afternoon mixing height (m),
Lunset = time of sunset (h).

The following equations (Stull 1988) are used in calculating sunset and sunrise times

sin v=sin osin 8, —cosdcos6, cos(Ty) , (6.8)

where

v = local elevation of the sun,

& = latitude of the station,

5, = solar declination angle (angle of the sun above the equator),
Tp = local time.

The solar declination angle is calculated using

5, =9, oo( 780") 5 (6.9)

y
where

¢, = latitude of the tropic of Cancer (23.45°),

d = Julian calendar day of the year,

d, = Julian calendar day of the summer solstice (173),
d, = average number of days per year (365.25).

6-12


3 FUEL CYCLE AND MATERIALS SOURCE TERM CALCULATIONS IN
STDOSE

The source term calculations in STDose estimate the amount of radioactive (or hazardous) material
released based on a wide variety of potential radiological accident scenarios. The source term
calculations performed that pertain to fuel-cycle facility and materials accidents can be generally
categorized as (1) fuel-cycle facility/UF, accidents, (2) uranium fires and explosions, (3) criticality
accidents, and (4) isotopic releases (e.g., transportation, materials).

STDose divides the source term calculation into three parts: first, it calculates the amount of activity
available for release based on the source term type; second, this activity is reduced, based on the
reduction mechanisms that the user has selected for the release pathway; and third, the activity is
released according to the release rate selected. This can be shown as

Si =i XARFGx] | RDFit LF; . (3.1)
¥
where

Sj, = is total amount of radionuclide i released under accident conditions j,

J, = is inventory of radionuclide i,

ARF, = is airborne release fraction of radionuclide i under accident conditions j,
RDF, = is reduction factor that applies to radionuclide i for reduction mechanism k,
LF, = is leakage fraction selected for accident conditions j.

In RASCAL 3.0, source terms may change with time. Source terms are recomputed at intervals of
varying length, called time steps. A new time step starts whenever the user changes any of the time-
dependent data or every 15 min, whichever is less. At the end of each time step, the inventory of
activity is decremented for the amount of activity released or removed by reduction and the effects of
radiological decay, so that no more than the total inventory can be released. Time steps may be no less
than 1 min and must be an integral number of minutes. Before passing the source term to the
atmospheric transport model, STDose converts the user-selected time steps to the 15-min time steps used
by the atmospheric transport models. Note that the type of source term calculation may not change with
time. The minimum amount of activity of any one nuclide that will be passed to atmospheric transport
models in one time step is 10° Ci.

STDose allows a single release pathway for each of the fuel-cycle and materials accident types. The
release pathways only allow those reduction mechanisms that are possible for that type of accident.

The following discussion of the fuel-cycle and materials STDose calculations is divided into three parts.

First all the source term calculations are presented. These are followed by discussions of the reductions
possible according to the release pathway. Finally, the calculation of leakage factor is presented.

3-1


Table 2.4 PWR Core Activity Release Fractions

Cladding Core melt | Vessel melt

failure through
Duration of core damage state (h) | 0.5 1.3 2.0
Core uncovery duration at which 0.0 0.5 1.8
this core damage state begins (h)
Noble gases 0.05 0.95 0
Halogens 0.05 0.35 0.25
Alkali metals 0.05 0.25 0.35
Tellurium group 0 0.05 0.25
Barium, strontium 0 0.02 0.1
Noble metals 0 0.0025 0.0025
Cerium group 0 0.0005 0.005
Lanthanides 0 0.0002 0.005

Source: Table 3-13 from NUREG-1465 (Soffer et al. 1992)

Table 2.5 Elements in Revised STCP Categories

STCP Category name Elements

Category

1 Noble gases Xe, Kr

2 Halogens I, Br

3 Alkali metals Cs, Rb

4 Tellurium group Te, Sb, Se

5 Barium, strontium | Ba, Sr

6 Noble metals Ru, Rh, Pd, Mo, Tc, Co

7 Cerium group La, Zr, Nd, Eu, Nb, Pm, Pr, Sm, Y, Cm, Am
8 Lanthanides Ce, Pu, Np

Source: Table 3-8 trom NUREG-1465 (Soffer et al. 1992)

2-6



RASCAL calculates and stores deposition by radionuclide for all radionuclides except noble gases.
Noble gases are assumed not to deposit. However, RASCAL 3.0 does calculate the surface
contamination from Xe isotopes that result from decay of iodine, assuming that the Xe is trapped within
the remaining iodine. The Xe isotopes are not included in ground-shine dose calculations, but the Cs
daughters of Xe are included in the ground-shine dose calculations. In general, the contribution of these
daughters to the total dose is small.

4.7 DEPLETION

Both atmospheric models in RASCAL 3.0 calculate depletion caused by wet deposition; only TADPUFF
accounts for depletion from dry deposition. TADPLUME does not account for depletion from dry
deposition because the calculation is relatively time consuming, and dry deposition generally does not
result in significant depletion of the plume near the source.

In TADPUFF, the activity in the puffs (Q) is updated every 5 min. The activity removed from each
puff is determined by integrating the total deposition rate under the puff in space and time. In
TADPLUME, the fraction of activity remaining in the plume at each distance during periods of
precipitation is estimated assuming an exponential decrease in activity with travel time, i.e., Q(x) =

Q.exp(-A,x/u).

4.8 DECAY AND INGROWTH

TADPLUME and TADPUFF calculate decay and ingrowth at 5-min intervals for both airborne and
deposited radionuclides. The decay schemes used include as many as four progeny and account for
branched decay chains. The 5-min decay and ingrowth calculations continue to the end of the calculation
period specified by the user. If the duration of the calculation period specified by the user is less than 96
h (4 days), TADPLUME and TADPUFF will continue ground-shine dose calculations until 96 h have
elapsed from the beginning of the model run specified by the user. Decay and ingrowth calculations
during this extended period are made at 1-h intervals.

4.9 DOSE CALCULATIONS

One of the areas in which RASCAL 3.0 differs significantly from earlier RASCAL versions is dose
calculations. The calculation of dose commitments from inhalation of activity (Section 4.9.1) and the
calculation of ground-shine doses (Section 4.9.2) are generally unchanged, except that the dose
calculations can now treat temporal variations in the activity release rate and radionuclide mix. The
cloud-shine calculations have been revised to improve consistency between the TADPLUME and
TADPUFF cloud-shine dose estimates and to decrease TADPUFF computational time. Calculation of
open- and closed- window dose rates has been added to both TADPLUME and TADPUFF. The cloud-
shine calculations are discussed in Section 4.9.3, and the calculations of open- and closed-window dose
tates is discussed in Section 4.9.4.

4-16


APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

g & |e
#8 . ie a |e
8 aa 5 2 2h, 2 a
& <=|§ 3 s a |§ e |é
B lg 2g s |é alee 4 |e
@ |E Pat = |£ fie |2 |3./8
2 lq 3 5 3 & |§ & © o/s
3 a § § 2 a 2 3 3 iy wo 1A
Name é {8 Z21¢ & 18 a lalg |< |2é8
(gal) ft %id_\psi |MW(t)
Callaway PWR |Dry Ambient | 193/U-Tube 262132| 2500000] 0.1] 60] 3565} 22000] 15000|Operational
Calvert Cliffs - Unit 1 PWR |Dry Ambient | 217|U-Tube 198529] 2000000} 0.33] 50] 2700} 22000] 15000|Operational
Calvert Cliffs - Unit 2 PWR [Dry Ambient | 217/U-Tube 198529} 2000000] 0.33] 50} 2700] 22000) 15000|Operational
Catawba - Unit 1 PWR Ice Condenser| 193}U-Tube 250808] 1200000] 0.2} 30| 3411] 22000] 15000|Operational
Catawba - Unit 2 PWR |Ice Condenser| 193}U-Tube 250808] 1200000] 0.2} 30] 3411} 22000] 15000/Operational
Clinton BWR |Mark III 624|N/A 144700] 250000] 0.65] 15} 2894} 22000} 15000|Operational
Comanche Peak - Unit! [PWR |Dry Ambient | 193/U-Tube 250808] 3000000} 0.1} 50} 3411] 22000] 15000/Operational
Comanche Peak - Unit2__ |PWR |Dry Ambient | 193/U-Tube 250808] 3000000} 0.1] 50] 3411] 22000} 15000/Operational
Cooper BWR |Mark I 548/N/A 119050] 150000} 0.5] 56} 2381} 22000) 15000|Operational
Crystal River - Unit 3 PWR |Dry Ambient | 177|Once-Through | 187059] 2000000] 0.25] 55} 2544] 22000] 15000|Operational
D. C. Cook - Unit 1 PWR {Ice Condenser| 193]U-Tube 238971] 1200000] 0.25] 12} 3250] 22000] 15000|Operational
D.C. Cook - Unit 2 PWR |Ice Condenser| 193}U-Tube 250808] 1200000] 0.25} 12| 3411] 22000} 15000|Operational
Davis-Besse PWR |Dry Ambient | 177|Once-Through | 203823] 2900000] 0.5} 40| 2772] 22000] 15000|Operational
Diablo Canyon - Unit 1 PWR |Dry Ambient | 193/U-Tube 245441] 2600000] 0.1] 47] 3338} 22000] 15000|Operational
Diablo Canyon - Unit 2 PWR |Dry Ambient | 193/U-Tube 250808} 2600000} 0.1] 47] 3411] 22000} 15000|Operational



a-V

APPENDIX. NUCLEAR REACTOR FACILITY DATA USED IN STDOSE (cont.)

g i é
S e
a |B e |e
Bel - 8 (als) |e |e
RB 1g 2) 8 g |é aes 4 |e
SE Pat z |& Ale |3 |3,/8
2 \q 3 2 (8 Slalg |= [Ras
g |5 5 \§ - |& eles |e |e)
Name g 1d 215 £ S a lald lz 25
(gal) ft? %Id_|psi|MW(t)
Ginna PWR {Dry Ambient | 121]U-Tube 111765] 1000000} 0.1} 60] 1520] 22000| 15000/Operational
Grand Gulf - Unit 1 BWR [Mark III 800|N/A 191650} 270000] 0.35] 15} 3833} 22000) 15000|Operational
H. B. Robinson - Unit2__ |PWR [Dry Ambient | 157/U-Tube 169118} 2100000) 0.1] 42} 2300} 22000] 15000|Operational
Haddam Neck PWR [Dry Ambient | 157/U-Tube 0} 1700000 0.1] 40} _1825|_ 22000] 15000|/Decommissioned
Hope Creek - Unit 1 IBWR |Mark I 764(N/A 164650] 170000] 0.5] 62] 3293} 22000] 15000)Operational
Indian Point - Unit 2 [PWR |Dry Ambient | 193]U-Tube 225809| 2600000] 0.1] 47] 3071} 22000] 15000|/Operational
Indian Point - Unit 3 PWR [Dry Ambient | 193|U-Tube 222426| 2600000} 0.1] 47| 3025] 22000] 15000|Operational
James A. Fitzpatrick BWR [Mark I 560/N/A. 126800} 110000} 0.5] 56} 2436] 22000] 15000]Operational
Joseph M. Farley - Unit 1_|PWR |Dry Ambient | 157/U-Tube 195000} 2000000} 0.3] 54] 2652] 22000] 15000/Operational
Joseph M. Farley - Unit2__|PWR |Dry Ambient | 157/U-Tube 70000| 2000000} 0.3] 54] 2652] 22000} 15000|Operational
Kewaunee PWR {Dry Ambient | 121]U-Tube 121324] 1300000] 0.5] 46] 1650} 22000] 15000|Operational
LaCrosse BWR {Mark I O|N/A 70000 i) a ke) 165] 22000] 15000|Decommissioned
LaSalle - Unit 1 BWR [Mark II 764|N/A 166150} 200000} 0.5} 45} 3323] 22000] 15000|Operational
LaSalle - Unit 2 BWR [Mark II T64(N/A 166150] 200000} 0.5) 45] 3323] 22000] 15000|Operational
Limerick - Unit 1 [BWR |Mark II 764|N/A 172900|__240000] 0.5] 56} 3293} 22000} 15000[Operational



CONTENTS (continued)

7.1.3 Ground-Shine Dose .......0 00.0.0 e ence eens 7-2
7.1.4 TEDE Dose ........... 0.0000
7.2 EMERGENCY WORKER TURN-BACK GUIDANCE .....
7.3 EARLY-PHASE EXPOSURE-RATE DILs .......
7.4 INTERMEDIATE-PHASE DOSES ........
7.5 INTERMEDIATE-PHASE DEPOSITION DILs ..

7.6 GROUND EXPOSURE AND WEATHERING .... 7-6
7.17 AIR CONCENTRATION DUE TO RESUSPENSION - 7-6
7.8 REFERENCES .... 1.2.0.0 6000s eos ece cece eee ete eee tenet e cence 7-6

8 DECAY CALCULATIONS
8.1 DECAY DATA FILES . :
8.2 IMPLEMENTATION ............ 00020 c eee cece eee . 8-1

8.2.1 STDose and DecayCale ..............00.00000% . 8-1
8.2.2 FMDose..........
8.3 REFERENCES

APPENDIX «2.2.22. n eee n ene e teenies A-l

viii


where

u(z) = wind speed at height z (m/s),

u. = friction velocity (boundary-layer scaling velocity) (m/s),
k = von Karman constant (=0.4),

2) = surface roughness length (m),

(z/L) = stability correction factor,

L = Monin-Obukhov length (m).

The surface roughness length is associated with small-scale topographic features. It arises as a constant
of integration in the derivation of the wind profile equations and is used in several boundary-layer
relationships. Texts on atmospheric diffusion, air pollution and boundary-layer meteorology (Panofsky
and Dutton 1984, Stull 1988) contain tables that give approximate relationships between surface
roughness and land use, vegetation type, and topographic roughness.

The term ¥(z/L) accounts for the effects of stability on the wind profile. In stable atmospheric
conditions, ¥(z/L) has the form -az/L where « has a value of 5. In neutral conditions P(z/L) is equal
to zero, and the diabatic profile simplifies to a logarithmic profile.

In unstable air, ¥(z/L) is more complicated. According to Panofsky and Dutton (1984), the most
common form of (z/L) for unstable conditions, based on the work of Businger et al. (Paulson 1970) is

v(z)-m Ay} tan” ()+% (6.4)

where x = (1-16z/L)"*. Equation (6.4) is used to estimate the friction velocity (u.) from the wind
speed, surface roughness, and Monin-Obukhov length. In unstable and neutral conditions, the use of
Eq. (6.4) is limited to the lowest 100 m of the atmosphere. In stable conditions, the upper limit for
application of Eq. (6.4) is the smaller of 100 m or three times the Monin-Obukhov length.

6.4.3. Mixing Height

Heating of the surface and surface friction combine to generate turbulence that mixes material released at
or near ground level through a layer that varies in thickness from a few meters to a few kilometers in
thickness. This layer is referred to as the mixing layer. The atmospheric models in RASCAL 3.0 use
the mixing height (also referred to as the mixing-layer depth and mixing-layer thickness) to limit vertical
diffusion.

METPROC has three methods for obtaining estimates of the mixing height at meteorological stations.

The mixing height may be entered directly, or it may be estimated by the program from either current
meteorological data or climatological information. Of the later two options, estimation of mixing height

6-10


Table 3.4 Fission Yields Used in Criticality Calculations*

System modeled in the Initial burst yield | Total yield
scenario (fissions) (fissions)
Solution < 100 gal 1x10" 3x10"
Solution > 100 gal 1x10% 3x10”
Liquid/powder 3x10” 3x10”
Liquid/metal pieces 3x 108 1x10%
Solid uranium 3x10" 3x10"
Solid plutonium 1x108 1x10%
Large storage arrays below None 1x10”
prompt critical

Large storage arrays above 3x10” 3x10”
prompt critical

“Source: SAIC 1998.

where
F = the total number of fissions,
S = the thickness of steel shielding in inches,
W = the thickness of water shielding in inches,
C = the thickness of concrete shielding in inches.

Doses, D,is, (rem) at other distances, D, are computed as:

Deri = (FJ XD crit
Di

3.1.4 Isotopic Source Terms

(3.6)

Three types of isotopic source terms are available: (1) isotopic release rates, (2) isotopic concentrations,

and (3) sources and materials in a fire. Uranium oxide fires were discussed in Section 3.1.2.

Isotopic release rates are simply used as entered. The user may not enter reduction factors, since this
calculation assumes that the user knows exactly what is being released. Up to three sets of rates may be

entered along with their start and end times. No decay is calculated in the source term calculation.

3-6


minimize the effects of extreme stability or instability. It also provides maximum detail in treating
isolated precipitation events.

6.5.3 Mixing Height

Estimates of station mixing height are not considered particularly reliable. Therefore, the spatial
variation of the mixing height is modeled using two steps. The initial step is create a mixing height field
using the mixing height for the closest station for each point in the field. If there is only one station the
process is terminated after this step. The second step is taken when there are two or more stations. In
this step, the mixing height at each point in the field is replaced by an average of the initial mixing height
and the mixing heights at 24 surrounding points. This second step smooths the mixing height field.

6.6 CALCULATING METEOROLOGICAL CONDITIONS AT THE SOURCE

All of the RASCAL 3.0 atmospheric dispersion models require information about the wind speed, wind
direction, atmospheric stability, precipitation class, precipitation rate, mixing-layer depth, and
temperature at the source. If these meteorological data are available for the first station, which is
considered to be at the source, then those data are used. If no data are available for the first station, the
wind speed, wind direction, atmospheric stability, current weather, precipitation rate, and mixing-layer
depth will be estimated from the spatial meteorological data field. For the temperature, a default
climatological value will be used if it exists. The default climatological temperature varies by month and
is obtained from the climate file. If the climate file does not exists for the site, the temperature will be
set to 15°C.

6.7 REFERENCES

Environmental Protection Agency (EPA), 1995. PCRAMMET User's Guide, Office of Air Quality
Planning and Standards, Emissions, Monitoring, and Analysis Division, Research Triangle Park, N.C.

Gifford, F. A. 1961. “Use of Routine Meteorological Observations for Estimating Atmospheric
Dispersion.” Nuclear Safety, 2(4):47-51.

Golder, D. 1972. “Relations Among Stability Parameters in the Surface Layer.” Boundary-Layer
Meteorology, 3(1):47-58, 1972.

Hanna, S. R., G. A. Briggs, and R. P. Hosker. 1982. Handbook on Atmospheric Diffusion. DOE/TIC-
11223, U.S. Department of Energy.

Monin, A. S., and A. M. Obukhov. 1954. “Basic Laws of Turbulent Mixing in the Ground Layer of the
Atmosphere.” Trans. Geophys. Inst. Akad. Nauk, USSR, 151:163-87.

6-17


reduction. Fire release fractions are element specific. The fire reduction factors are shown in Tables 3.6
and 3.7 and are from NUREG-1140 (McGuire 1998). The default values for all other reduction factors
and their references are included in Table 3.8. The default reduction factors for filters and “other”
reduction may be modified by the user.

The calculation of the total reduction factor includes a maximum.effectiveness for sprays and a maximum
effectiveness for all reduction, excluding filters (see Table 3.9). For each, the appropriate reduction
factor or product of reduction factors computed at each time step is compared to the maximum and is not
allowed to surpass it.

All reduction mechanisms are constant factors except for the reduction due to the action of sprays. The
RDF for sprays is computed at each time step as an exponential function of time. Two factors each are
used, an “initial” 4,, which is only applied for the initial time interval listed in Table 3.9, and a
“continuing” 1, which is applied thereafter. The reduction factor used for sprays is dependent on the
total amount of time that the sprays have been acting. So initially the RDF for sprays is

RDF=e-*7 , GB.)
where T is the total amount of time (h) the sprays have been acting.

After the amount of time that the reduction mechanism is active has exceeded the initial time interval, T,,
the RDF is

RDF =e -AT ye -Ac(T-T) G.8)

3.3 CALCULATION OF LEAKAGE FACTORS FOR FUEL CYCLE AND
MATERIALS ACCIDENTS

Three types of leak rates are used in fuel-cycle and materials releases in RASCAL 3.0. They are (1)
percent of total amount per unit time, (2) flow rate (volume or mass per unit time), and (3) a “direct”
release, with all activity released during the selected release duration. The types of flow rates available in
each type of release pathway are shown in Table 3.10. Because the atmospheric transport models expect
the source term to be in terms of a rate, rather than a total amount, the leakage data that the user enters is
always converted to a leakage rate fraction (LRF) by STDose.

3.3.1 Percent per Hour
The percent per hour (%/h) release rate releases a fixed fraction of the source term per unit time. The

actual leakage rate fraction used is computed based on the length of the time step entered by the user.
This release rate results in the source term being released at a constant rate over time.