Civil Engineering Reference
In-Depth Information
Chernobyl
NPP
150-300 kBq/m
2
100-150 kBq/m
2
50-100 kBq/m
2
0
5 0
km
Figure 2.8
Zones of assessed
137
Cs accumulation recalculated per unit area for the
Quaternary deposits of the CEZ by data of 2001.
In the central zone of maximum contamination (close to Chernobyl NPP),
the accumulation per unit area reaches 120-300 kBq/m
2
, in the intermediate zone
it is about 100-150 kBq/m
2
, and in the rest of the area it is 50-100 kBq/m
2
.
An important factor is the annual increase of radionuclide accumulation in
the geological medium. As observations show, the accumulation process proceeds
with variable intensity determined by variation of atmospheric precipitation,
radionuclide forms, etc. In spite of these uncertainties, the average assessment of
the accumulation rate can be determined. For
137
Cs, at average
K
d
= 20 dm
3
/kg, for
the entire CEZ area it comprises about 500 Ci/year (see Table 2.2). If also consid-
ering the above-mentioned temporary locations of radioactive wastes and the
Chernobyl NPP operation site, then the assessed amount of
137
Cs, which annually
comes from the surface to the geological environment, can reach about 1000 Ci.
Based on the available data, in the same way as for
137
Cs, an assessment of
accumulation of
90
Sr can be obtained reaching the same order of value. As a
result, the total assessed accumulation in the geological environment of
137
Cs and
90
Sr appears to be exceeding 4-23 times the annual flushing out of these radionu-
clides from the CEZ with water of the river Pripyat [
Kholosha et al
., 1999].
Assuming that this process continues with the same intensity, then during
30 years (one half-life period) about 30% of the initial amount of
137
Cs and
90
Sr
should be accumulated in the geological environment.
In reality, this process is rather variable over the area. Its intensity is higher
within the PFMZ locations. In such locations, the rate of areal redistribution and
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