Radioactive Aerosols of Chernobyl Accident - Aerosols: Measurement, Dosimetry, and Health Effects - page 480

144 Ce

0.3

95 Nb

0.2

95 Zr

0.1

141 Ce

0

June July

FIGURE 18.4 Concentration of the sum of gamma-radioactive nuclides in the aerosols sampled in June-July
1986 on territory of Chernobyl NPP.

137 Cs, 2.83 ± 0.26 μm for 144 Ce, and 3.00 ± 0.28 μm for isotopes of Pu. At the same time, isotopes of
103 Ru, 106 Ru were discovered on smaller particle carriers (AMAD = 2.57 ± 1.01 μm) with the great-
est variation from average size. This can be explained by the desorption of volatile compounds Ru
from particle carriers, and subsequently their deposition on aerosol particles of submicron range.
On some days, the portions of small disperse fractions of Ru were near 40%.
Observation in the 1986 summer-autumnal period showed that AMAD values of aerosols near
the earth's surface began to increase, which was conirmed by later studies.
Table 18.3 shows typical aerosol concentrations, based on samples that were taken in the middle
of June in the machine room of the third block (neighboring the destroyed fourth block) by means
of packets of iber and sorption ilter materials [21].
It is clear from these data that day concentrations were substantially higher than night concentra-
tions due to extensive activity in the daytime, resulting in the formation of higher dust concentrations.
The sizes of aerosol particles at night (AMAD = 0.75 μm) were smaller than in the daytime
(AMAD = 1 μm), and all radionuclides were on the same carriers. In the “day” sample A, Ru was
found in both aerosol (70%) and gaseous form (30%). But in the “night” sample C, Ru in gas form
did not exceed 2%, possibly due to differences in air temperature. At the same time, in samples
A and C, the portion of gaseous 131 I was 98%.

TABLE 18.3
Concentrations of Radionuclides in the Third Block of the Chernobyl NPP (Bq/m 3 )

Sample Sampling Date and Time

144 Ce 141 Ce 131 I 103 Ru 106 Ru 95 Zr 95 Nb 137 Cs 134 Cs

A July 13, 18:15-19:07 437 156 1 210 — — — 40.7 25.9

B July 13, 18:15-19:07 465 175 — 124 79 334 516 46.7 24.2

C July 13-14, 19:10-10:10 51.8 18.5 8.5 15.8 12.2 36 54 5.9 2.9

D July 13-14, 19:10-10:10 54.1 23.3 — 17.4 14.1 46.3 70.4 6.4 2.5