Radioactive Aerosols of Chernobyl Accident - Aerosols: Measurement, Dosimetry, and Health Effects - page 482

0.3

106 Ru

0.2

103 Ru

0.1

137 Cs

134 Cs

0

August September

FIGURE 18.5 Relative contribution of radionuclides with volatile components in total gamma-radiation of
the aerosols sampled from ground layer of atmosphere (1 m above a surface of ground) near destroyed reactor
in 1986.

between aerosol and gaseous components of radionuclides was determined according to the dis-
tribution in layers of the package. It was assumed that the sorption deposition of I, Te, and Ru was
near 100%.
The layer-by-layer distribution of volatile nuclides in SFM-I, which was used for air sampling
above the destroyed reactor, is present in Table 18.4.
In middle of May 1986, in gaseous form, it was 0.6%-13% 103 Ru, 2.7%-16% 106 Ru, and
1%-8% 132 Te.
The similarity of distribution for both isotopes of Ru showed that they are present in air in the
same gaseous compounds, and their absence in the second layer shows that sorption was good. Even
with high iltration velocity, the eficiency of gaseous compounds of Te was also good.
Radioactive iodine was found in the second sorption ilter. So the gaseous compound in which
it was, sorbed worse than that with Ru and Te. Only in samples taken above the reactor on May 8
and 14 (Table 18.4) was iodine found in the upper facing and in the irst sorption layer. This can be
explained by the fact that iodine was in the form of vapors of I 2 . These measurements point out that
from May 15 to 19, new gaseous iodine compounds were in the atmosphere with smaller coeficients
of dynamic sorption, that is, possible organic forms (CH 3 I, etc.).
Measurements of radioactive components of I and Ru were provided also at a great distance from
Chernobyl NPP [26] from aircraft at a distance of 100-300 km north of Chernobyl above Ukraine,
Belarus, and Russia at a height of 1200 m, and from a research ship 4000 km in the Atlantic ocean.
The results of measurements of concentrations of 131 I and the ratio of aerosol and gaseous compo-
nents of I and Ru are shown in Table 18.5.
As we can see from Table 18.5, gaseous 131 I was present in all samples, and gaseous Ru in the
majority of samples. Based on date and site of sampling (near 4000 km from Chernobyl), samples
from May 4 to 5 belong to the irst ejection of radioactive materials from the exploded reactor.
Measurements provided in May 1986 showed a weak dependence of gaseous 131 I from the distance
of the Chernobyl NPP—the lowest near the reactor and the highest in the Atlantic, North, and
Baltic Sea.
Unfortunately, in the majority of countries around the world, atmosphere monitoring was pro-
vided only by aerosol ilters [5]. It is, however, necessary to pay attention to the measurements