Environmental Engineering Reference
In-Depth Information
TABLE 18.1
Emission (in %) from the Total Activity of Radioactive Substances Saved up in the 
Core during the Operating Period of the Fourth Block of Chernobyl NPP
According to Data from the USSR for the 
International Atomic Agency (August 1986) [1]
According to Results of the 
Study at the End of 2000 [2]
Radionuclide
133 Xe, 85 Kr
∼100
∼100
131 I
20 ± 10
55 ± 5
134 Cs
10 ± 5
33 ± 10
137 Cs
13 ± 7
33 ± 10
Uranium and transuranium
elements a
3 ± 1.5
3 ± 1
a Taking into account the fragments of the reactor active zone, ejected around the fourth block.
materials), the accurate determination of the dynamics of radioactive substances entering the
atmosphere was dificult to assess. Two assessments of the composition of the emission rejection
are shown in Table 18.1.
In the initial period after the accident, most radionuclides were ejected from the destroyed reactor
in the form of dispersed fuel (mainly with a UO 2 matrix). During lava formation of the fuel materials,
which took place at a temperature of about 2000°C, only volatile and light fusible substances, like
Te and alkaline metals, evaporated from the fuel. More than 95% of nuclear fuel (more than 180 t)
remained inside the “Shelter,” which was built above the destroyed block at the end of November 1986.
The integral ejection of radionuclides with a half-time of T 1/2 >20 h, without taking into account
inert gases from the destroyed reactor, was around 3 × 10 18 Bq [2].
18.3  GLOBAL TRANSFER OF THE ACCIDENT PRODUCTS
At the moment of the accident, winds near the earth's surface were weak and without special
direction. Still, at altitudes of more than 1500 m the wind was mostly in the southeast direction, with
a speed around 8-10 m/s. Part of the radioactivity was raised to this level and moved throughout
the western regions of the USSR to Finland and Sweden. There, on April 27, radioactive aerosols
from the Chernobyl accident were discovered [3] for the irst time outside the USSR. Over the end
of April and the beginning of May, radioactive aerosols, including I and Cs, were detected in the
upper troposphere and lower stratosphere (up to 15 km) above the territory of Poland [4]. The fallout
of refractory elements such as Ce, Zr, Np, and Sr was detected mainly on USSR territory.
Changing meteorological conditions, especially wind direction, and also the continuous ejection
of a large mass of radioactive aerosols and gases for 10 days resulted in a very complicated picture
of the distribution of radionuclides in the atmosphere. Part of the nuclides was shifted on the low
highs to Poland and Germany. By April 29 and 30, radioactive clouds reached other countries of
Eastern and Central Europe. Radioactive substances were in the north of Italy by April 30, and in
Central and South Italy the next day. In France, Belgium, and the Netherlands, radioactive contami-
nation was detected on May 1, and in Great Britain the next day. Gases and aerosol products from
the Chernobyl accident reached the north of Greece on May 2 and the south of Greece by May 3. At
the beginning of May, radioactive substances were detected in Israel, Kuwait, and Turkey.
The observation of aerosol and gaseous components of radioactive iodine was provided in 19
stations in Europe, with sampling and analysis of 171 samples. Only aerosol components of radio-
nuclides were studied on 1892 samples from 85 sites [5].
The transfer of radioactive products in the eastern direction took place very fast. Already by
May 2, the irst aerosol and gaseous samples of 131 I were found in Japan, May 4 in China, May 5
 
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