Code Manual for CONTAIN 2.0 - Federation of American Scientists

where V~ is the drop volume, which can change because of condensation or evaporation of water
as the drop falls; V is the atmosphere volume; and SIis obtained from the mass balance equations
and is expressed as
(8-10)
where lq~is the mass transfer coefficient in the spray drop for either 12or CHqIas given below; and
k~,Iis the mass transfer coefficient in the gas phase for either Izor CHqIas given below.
The gas-phase mass transfer coefficients, based on mass density difference, are obtained from
(8-11)
where DI,,, is the diffusivity of the iodine species I in a steam-air mixture, which is defined below;
D is the drop diameter; Nm = v~D pl/p~, where v~is the terminal velocity and ~, is the atmosphere
viscosity; and N~c= Ua/(paDI,W), here p, is the atmosphere density.
The difl%sivity of iodine in a steam-air mixture used in Equation (8-11) is
‘lsa= [5+(’J)I”’
(8-12)
where Y, equals P$P, (Pvis the partial pressure of the water vapor in the atmosphere, and P, is the
atmosphere pressure); DI,,is the diffusivity in a steam atmosphere at temperature T and pressure P
for either 12or CHql and DI,,is the diffusivity in air at temperature T and pressure P for either Iz or
CH~I. These diffusivities (in S1units) are given by
DJ2,s
=
D
MLs =
3.2801 X 10-4T15
P 0.7075 + 45;72
[
4.3306 X 10-4T 15
P 0.7075 + y
(
)
)
(8-13)
(8-14)
Rev O 8-28 6/30/97