Environmental Engineering Reference
In-Depth Information
10
1
0.1
December-02
December-03
December-04
December-05
December-06
December-07
FIGURE 18.19
Concentration of aerosol carriers of
212
Pb at the “Bypass” system in 2002-2007.
1
0.1
0.01
December-02
December-03
December-04
December-05
December-06
December-07
FIGURE 18.20
AMAD of aerosols carriers of
212
Pb at the “Bypass” system in 2002-2007.
Carriers of radon and thoron DPs both in the “Bypass” system and in the territory of the
“Shelter” object are aerosol particles with AMAD of 0.05-0.4 μm (Figure 18.20). Average value of
AMAD = 0.15 μm, which is characteristic for carriers of radon and thoron DPs in other regions both
in the environment and inside premises [50].
Researches demonstrated that radon and thoron DPs as well as their mother substances can
accumulate in a number of premises of the “Shelter” when air low through the “Bypass” system is
stopped. Usually this happens in the second half of the spring when during the daytime the air in the
vicinity of the Chernobyl NPP warms up to 30°C and above and the premises inside the “Shelter”
still remain cold after the winter time. Such situations were recorded, for example, in premise No.
207/5 in the third week of May 2003, and on May 23 and 24, 2007. Concentration of
212
Pb reached
in the irst case 15 Bq/m
3
, and in the second one 12-13 Bq/m
3
.
DPs of radon and thoron represent the main danger while inhaling air that contains them. First,
some of them radiate α-particles. Secondly, being placed on submicron aerosols they intrude the
lowest parts of lungs—bronchi and alveolus.
Discovering the radon concentration over 100 Bq/m
3
and thoron over 6 Bq/m
3
in the premises
of the “Shelter” is a negative factor, which has not been taken into account while monitoring the
radiation environment. Due to inhalation of aerosol carriers of DPs of natural noble gases the
average radiation dose for personnel of the “Shelter” object may reach 20 mSv/g, that is, the value
of the effective radiation dose limit.
Search WWH ::
Custom Search