Environmental Engineering Reference
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100
Cs-137
Long-lived beta-activity nuclides
10
1
0.1
0.01
25.11
30.11
5.12
10.12
Date of sampling
15.12
20.12
25.12
FIGURE 18.9
Contents of aerosol carriers of
137
Cs (in Bq/m
3
) and long-living beta-active radionuclides
(in pulses per second per cubic meter) in room 207/5 of the “Shelter” in 2000.
241
Am and
154
Eu concentrations were 0.05 Bq/m
3
, and for
60
Co it was three times higher. The ratio
137
Cs/
90
Sr1. 15 was also close to that calculated for the fuel of the fourth block.
Besides monitoring aerosol characteristics, simultaneous measurements of the daughter products
(DPs) of radon and thoron also took place. From the data presented in Figure 18.10, it is clear that,
unlike accident aerosols, the concentration of natural radioactive aerosols in room 207/5 continu-
ously declined in the second decade of the month and increased in the third.
From a comparison of Figures 18.9 and 18.10, it is clear that the dynamics of changes of con-
centrations of accident products and natural radionuclides are different. The cause of the high
concentrations of the irst type of aerosols is connected to working operations, and for the second
25
Room 2007 in shelter
ORU-750
Neftebaza
20
15
10
5
0
14
16
18 20
Date of sampling
22
24
26
FIGURE 18.10
Rate of count of beta-particles of radon and thoron daughters on 50th min after the inish
of aerosol sampling in room 207/5 of the “Shelter,” and in two points near Chernobyl NPP in December
2000.
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