Environmental Engineering Reference
In-Depth Information
this level indicative for area of AU-1 and AU-2 for 7 years. But in 2008 a sharp rise of the concentra-
tion up to 0.06 Bq/m
3
was observed in the area of AU-3. This value proved to be the highest for 15
previous years. A higher concentration of about 0.08 Bq/m
3
took place in the area of AU-2 only in
1993, as it follows from Figure 18.17.
A detailed concentration dynamic of aerosol carriers
137
Cs and
241
Am as a result of the 15 day
sampling in 1993-2007 is presented in Figure 18.18. It is evident that
137
Cs and
241
Am concen-
trations are very close in the area of AU-1, AU-2, and AU-3 positions. But some considerable
luctuations (up to 2 orders of magnitude) are observed sometimes at a general tendency of con-
centration decline.
Although the nuclear-physical origins of
137
Cs and
241
Am are different (the irst one is a product
of uranium ission, the second appears at beta-decay of
241
Pu (
T
1/2
= 15.2 years), the dynamic of their
concentrations in the air of local areas is practically identical for the period of 1993-2007 (see
Figure 18.18). As it follows from the results of measurements about 900 samples, concentrations of
241
Am were prevalent in the range of 0.01-0.1 mBq/m
3
. Minimal concentration was not lower than
0.002 mBq/m
3
and maximal approached 1 mBq/m
3
in several cases only.
Concentration increase was caused by works conducted in the local zone or in its vicinity. Let us
consider some of the reasons.
One of the highest concentrations of
137
Cs (0.06 Bq/m
3
) was registered in the period from March
24 to April 3, 1998, in the southern installation area (AU-3). At that time a lifting crane “Demag”
used at construction of the “Shelter” in 1986 was being dismantled and decontaminated.
Concentrations of
137
Cs and
241
Am increased several fold at AU-3 in the spring and summer,
2000, because of site preparation works for construction of an irradiated fuel storage facility
10
-1
10
0
10
-2
10
-2
10
-3
10
-4
10
-4
10
-5
10
-6
10
-6
(a)
(b)
10
0
10
-2
10
-4
10
-6
(c)
FIGURE 18.18
Concentration of aerosol carriers of
137
Cs (—) and
241
Am (-⚫-) by 1992-2007 samples at the
northern (a), northwestern (b), and southern (c) installations in the local zone of the “Shelter.”
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