Civil Engineering Reference
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which ranges from 0.1 to 0.5. The value of
k
d
is determined as a ratio of radionu-
clide concentrations in groundwater (see Table 2.1 and Figure 2.1) and solid phase
(see Figures 2.3, 2.4, and 2.5) recalculated to volume concentrations. It depends
on the soil and rock types reaching its maximum in the upper soil and decreasing
with depth usually by 1-2 orders of magnitude. According to our previous assess-
ments [
Shestopalov
, 2001], its value was taken as 10-100 in landscape type 1, 5-50
in landscape type 2, and 1-10 in landscape type 3. The vertical distributions of the
dispersion coefficient
D
(
z
) for three typical sections were determined during the
inverse problem solution for the calibration period 10 years (year 1996) for which
the data of groundwater sampling were available. The obtained values of
D
vary
from 0.001 m
2
/day (landscape type 1) to 0.01 m
2
/day (landscape type 3).
It is supposed that the dispersion coefficient obtained by this calibration
procedure should to some extent implicitly account for the flow and transport
heterogeneities of the geological medium.
Figure 5.1 gives an example of the model calibration plot of relative
137
Cs
concentration against depth for a typical depression area in the CEZ (landscape
type 3) with its corresponding sampling data points obtained in 1996.
137
Cs Relative concentration
0
0.2
0.4
0.6
0.8
137
Cs Observed concentration, Bq/dm
3
0.0
0.25
0.5
0.75
1.0
0
5
10
15
20
Figure 5.1
Model calibration plot of relative
137
Cs concentration against depth (forecast
time 10 years) for landscape type 3 with corresponding sampling data points obtained
from wells and soil pore solution (upper point) in a typical depression within CEZ in 1996.
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