Environmental Engineering Reference
In-Depth Information
it is due to gas emissions from building materials and constructions of the destroyed block, air
exchange, and atmospheric pressure.
One important cause of sharp increasing aerosol concentrations in “Shelter” is ire inside the
building. Over a period of 16 years, in the room of “Shelter” seven ires were recorded. During the
ire: (1) the formation of radioactive aerosols takes place, and these aerosols are transported with
smoke and hot air; and (2) inside the “Shelter” a very intensive movement of air mass takes place,
which overwhelms the usual ventilation low. This results in additional ejection of radioactive
aerosols into the free atmosphere.
During the 4 h ire on January 14, 1993, around 33 MBq of radioactive material was ejected
additionally into the atmosphere. The normal ejection for that period was approximately 1.4 MBq.
The average concentration of gamma-radioactive nuclides through the ventilation stack increased
140 times.
18.9.3 a
erosol
c
oncentration
in
tHe
“b
yPass
”
oF
tHe
“s
Helter
”
in
2002-2009
Construction of the “Shelter” had been completed in November 1986. Thereafter, monitoring
radioactive aerosols emission was conducted in the “Bypass” system connecting the former central
hall of the fourth power-generating unit with the high level elevated ventilation stack VT-2. The
last remaining power-generating unit of the Chernobyl NPP was stopped in December 2000, and
decommissioning of the station started. All that required carrying out more profound monitoring of
aerosols coming out of the “Shelter” into its environment.
Some 400 aerosol samples were taken at the “Bypass” system during 2002-2009 with the help
of three-layer ilter packages. As a rule, concentration of total β-activity (Σβ) of aerosol carriers of
Chernobyl accident products was in the range of 1-10 Bq/m
3
as shown in Figure 18.11, about 30%
of the activity being accounted for
137
Cs.
It was established that signiicant inluence on the aerosol content in the former central hall
of the fourth power-generating unit had been exercised by wind presence in the environment. So,
Σβ = 165 Bq/m
3
(Figure 18.11) was registered on December 8, 2003, when maximal wind gusts
reached 12-13 m/s. An identical situation was observed on April 8, 2008, when Σβ = 100 Bq/m
3
at
wind gusts of 14 m/s.
10,000
1,000
100
10
1
0.1
0.01
16.9.03
3.4.04
20.10.04
8.5.05
24.11.05 12.6.06 29.12.06 17.7.07
2.2.08
20.8.08
FIGURE 18.11
Concentration of total β-activity (Σβ) of aerosol carriers of Chernobyl accident products at
the “Bypass” system of the “Shelter” in 2003-2008.
Search WWH ::
Custom Search