Radioactive Aerosols of Chernobyl Accident - Aerosols: Measurement, Dosimetry, and Health Effects - page 493

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FIGURE 18.13 AMAD of aerosol carriers of Σβ-radiating nuclides—Chernobyl accident products (⚪, sam-
pling during the dust suppression operation; ⚫, sampling in absence of the dust suppression operation), and of
radon and thoron daughters (Δ) at the “Bypass” system of the “Shelter” in 2005.

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FIGURE 18.14 AMAD of aerosol carriers of Chernobyl accident products (◻) and DPs of radon and thoron
(×) at the “Bypass” system of the “Shelter” in 2010: samples with AMAD over 8 μm are displayed by mark.

Processing of results demonstrated that in 2002-2006 radio nuclides—products of the accident
practically always had the AMAD in the range of 1-10 μm at s values from 1.1 to 3.5. For example,
the AMAD values for 80 samples taken in 2003-2004 were presented in logarithmic-normal coor-
dinates. It was established that 50% interval fell at the AMAD = 3.8 μm and 67% of all samples had
the AMAD from 1.7 to 8.5 μm. Fractionating of 90 Sr, 137 Cs, 154 Eu, 241 Am by particles of different
size was not observed.
At the same time DPs of radon and thoron had the AMAD in the range 0.02-0.8 μm, the 50%
interval falling to the AMAD = 0.15 μm. Consequently, radio nuclide carriers of the Chernobyl
genesis had appeared as a rule because of dispersion and DPs of radon and thoron as a result of
condensation. The similar data were received in 2005 and 2006 (Figure 18.13).
Particles with AMAD over 2 μm continued, as a rule, being radio nuclide carriers—Chernobyl
accident products in the “Bypass” system in 2010 (Figure 18.14). AMAD exceeded 5 μm in the
majority of samples and in four samples exceeded even 8 μm, DPs of radon and thoron being associ-
ated, as before, with aerosol particles with AMAD in the range of 0.08-0.4 μm.

18.10 RADIOACTIVE AEROSOLS CLOSE TO THE SURFACE LAYER
OF THE ATMOSPHERE NEAR THE “SHELTER”
After 1992, monitoring radioactive aerosols in the vicinity of the “Shelter” has been continued by
specialists of Nuclear and Radiation Safety Department of ISTC “Shelter” of National Academy of