Radioactive Aerosols of Chernobyl Accident - Aerosols: Measurement, Dosimetry, and Health Effects - page 494

Science of Ukraine. Round the clock sampling was executed at all three aspiration installations AU,
located in the northern (AU-1), the northwestern (AU-2) and the southern (AU-3) sectors of the area.
FPP-15-1.5 iltering material with the surface 0.8 m 2 was used and exposed for 2 weeks. Air low
rate was 400-500 m 3 /h. The material was placed on a horizontal cage screen, its axis being situated
1 m above the ground. A small roof made of rooing iron was erected over the installation at the
height of 1.8 m to protect it from rain and snow. The installation was enclosed in a metal mesh. After
sampling had been over the iltering material was delivered to Chernobyl for conducting gamma-ray
spectrometric and radiochemical analysis.
A convincing illustration of the inluence of “Shelter” on the composition and concentration
of radioactive aerosols near Chernobyl NPP was the ire in room 805/3 of January 14, 1993 [43].
During the ire, concentration of Σβ in VT-2 stack exceeded the usually observed level by approxi-
mately 30 times.
Figure 18.15 presents the monthly results of monitoring close to the earth's layer of air in the area
of AU-1, AU-2, and AU-3 in 2000.
In 2000, the aspiration in the area of AU-1 and AU-2 showed the same concentration values for
137 Cs—1-3 mBq/m 3 and for 241 Am—0.02-0.06 mBq/m 3 . During wintertime, the values were a little
lower than in the summer. In the south ilter installation (AU-3) they are usually higher than for the
north and northwest, which can be explained only by the higher density of pollution of the soil in
this site.
A substantial concentration growth took place in the spring of 2000, when at a distance of
300-500 m from the “Shelter” building activity took place. Figure 18.15 reveals that in this period
aerosol concentration increased substantially. It should also be mentioned that the 137 Cs/ 241 Am ratio
increased at the beginning and end of 2000 (Figure 18.16)
This can be explained as a result of changing the ratio between contributions of aerosols due to
dust raising in the territory and release from the “Shelter” [47-49]. In the limit situation, when dust
raising is minimum, for example, in the case of a stable snow layer, the 137 Cs/ 241 Am ratio can be
close to 200, which is typical for aerosols ejected from cracks in the walls [46].
The average annual concentration of aerosol carriers of total beta-radiating nuclides
dynamic in 1993-2008 is given on Figure 18.17. As products of the Chernobyl accident with a

1

Am-241, North
Cs-137, North

Am-241, North-west
Cs-137, North-west

Am-241, South
Cs-137, South

0.1

0.01

0.001

0.0001

0.00001

0.000001

January March May July September November

FIGURE 18.15 Concentration of radioactive aerosols of 137 Cs and 241 Am in ground layer of atmosphere near
the “Shelter” in 2000. Sampling was executed in three points.