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Dry deposit
The rate of dry deposit, per unit area at point (x, y) at instant t is given by:
DDS (x, y, 0, t) = Vd x AV (x, y, 0, t) [2]
in which:
AV = activity per unit volume
Vd = apparent rate of dry deposit
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5. SITING CONSIDERATIONS
The value of Vd theoretically depends on a large number of parameters (aerosol particle
size, atmospheric conditions, ground condition etc.); in the current versions of the user's
interface of the codes, default values are proposed for Vd:
non‐organic iodine Vd = 5.10‐ 3 m/s
organic iodine Vd = 10 ‐4 m/s
aerosols (all other fission products) Vd = 5.10 ‐3 m/s
In each time interval dt, with the "source depletion" method (depletion is considered to
take place uniformly throughout the puff and not preferentially at ground level, thus
preserving the Gaussian vertical profile), for puff d, belonging to family f and initially
containing the quantity Q, depletion of the puff is:
dQ
dt
= −
+∞
∫ ∫
+∞
−∞
−∞
DDS(
x,
y,
0,
t)
dxdy
[3]
and, the quantity remaining Qis in the puff at instant t, equals, when all calculations have
been made:
Q
is
( f , b,
t
i
)
⎡
Qexp⎢−
Vd
( f )
⎣
2
π
= ∫ ti
to
2
1 ⎛ − z ⎞ ⎤ o exp ⎜
⎟
⎟dt
2 ⎥
σz
( t)
⎝ 2σ
( t)
⎠ ⎦