38
and Te, which condensed on inactive carriers (soot, etc.) (Borovoy et al. 1990).
During combustion of graphite, fuel particles depleted of volatile radionuclides
were removed from the reactor. At this stage radioactive contamination of the territory of Belarus was formed (Konoplya et al. 2007).
In the opinion of Konoplya et al. (2007), the removal of the UO 2 -based nuclear
fuel from the emergency reactor occurred at relatively low temperatures not due to
evaporation but as a result of dispersion and oxidation, proceeding with the formation of finely dispersed particles, in which uranium was partially in five and hexavalent state. Technogenic uranium is basically originated from Chernobyl, concentrated
mainly within the Polesie State Radiation-Ecological Reserve (PSRER). In the rest
of the country territory, there is mainly natural uranium, but use of mineral fertilizers, dolomite flour, and other reclaiming additives in the agro-industrial complex
leads to additional amounts of uranium entering the soil.
During the oxidation process, the structure of the fuel particle was destroyed
with the release of fission products, which stabilized in the intercrystalline space of
uranium dioxide. The dispersion of fuel particles and the proportion of uranium
oxides in higher oxidation states were mainly determined by the duration of the
oxidation process (Loshchilov et al. 1992; Kashparov et al. 1995, 2003).
The contamination of the territory with actinides (including uranium) was
extremely uneven and not only within the same region but also in the same settlement. This could be caused by the redistribution of radioactive products in the atmosphere and the peculiarities of their arrival on the Earth’s surface under unequal
meteorological conditions. Among the radionuclides emitted from the destroyed
reactor, the maximum mass is accounted for by long-lived uranium isotopes—
235
U,
236
U, and
238
U. The presence of
236
U in radioactive products, which is formed in
significant quantities by the operation of a nuclear reactor of the RBMK type, indicates the presence of Chernobyl uranium. If the content of
239
Pu in the Chernobyl
release at the time of the accident (26.04.1986) is taken as unity, then the content of
uranium isotopes with respect to
239
Pu was:
235
U, (1.9 ± 0.4) × 10
–4
;
236
U,
(1.0 ± 0.3) × 10
–3
; and
238
U, (3.1 ± 0.6) × 10
–3
(IAEA 1988) .
Under the condition of 5% fuel release from the emergency reactor, 9.5 t of uranium fell into the environment (Konoplya et al. 2007). In general, the total emission
of actinides on the territory of Belarus was approximately 2.5 times greater than
their global deposition. Approximately half of the actinides fell on the territory
immediately adjacent to the Chernobyl nuclear power plant, the rest was dispersed
practically throughout the territory of Belarus. At the territory of the PSRER, the
density of uranium deposition is from 18 to 100 Bq/m
2
. The deposition of Chernobyl
uranium on the surface of the soil could significantly affect the content and isotopic
composition of uranium in the near zone. The ratio of
235
U/
238
U and the proportion
of Chernobyl uranium in the total uranium content in the (0–5)-cm soil layer at
different distances from the destroyed nuclear reactor, established by mass spectrometric analysis by Konoplya et al. (2007), is given in Table 1.
In the surface layer of the soil of the 30-km zone of the Chernobyl NPP and
adjacent areas, the ratio of
235
U/
238
U by mass exceeds the ratio of natural isotopes of
uranium. The ratio of
235
U/
238
U by mass for natural uranium is 0.00725 and for
G. A. Sokolik et al.
and Te, which condensed on inactive carriers (soot, etc.) (Borovoy et al. 1990).
During combustion of graphite, fuel particles depleted of volatile radionuclides
were removed from the reactor. At this stage radioactive contamination of the territory of Belarus was formed (Konoplya et al. 2007).
In the opinion of Konoplya et al. (2007), the removal of the UO 2 -based nuclear
fuel from the emergency reactor occurred at relatively low temperatures not due to
evaporation but as a result of dispersion and oxidation, proceeding with the formation of finely dispersed particles, in which uranium was partially in five and hexavalent state. Technogenic uranium is basically originated from Chernobyl, concentrated
mainly within the Polesie State Radiation-Ecological Reserve (PSRER). In the rest
of the country territory, there is mainly natural uranium, but use of mineral fertilizers, dolomite flour, and other reclaiming additives in the agro-industrial complex
leads to additional amounts of uranium entering the soil.
During the oxidation process, the structure of the fuel particle was destroyed
with the release of fission products, which stabilized in the intercrystalline space of
uranium dioxide. The dispersion of fuel particles and the proportion of uranium
oxides in higher oxidation states were mainly determined by the duration of the
oxidation process (Loshchilov et al. 1992; Kashparov et al. 1995, 2003).
The contamination of the territory with actinides (including uranium) was
extremely uneven and not only within the same region but also in the same settlement. This could be caused by the redistribution of radioactive products in the atmosphere and the peculiarities of their arrival on the Earth’s surface under unequal
meteorological conditions. Among the radionuclides emitted from the destroyed
reactor, the maximum mass is accounted for by long-lived uranium isotopes—
235
U,
236
U, and
238
U. The presence of
236
U in radioactive products, which is formed in
significant quantities by the operation of a nuclear reactor of the RBMK type, indicates the presence of Chernobyl uranium. If the content of
239
Pu in the Chernobyl
release at the time of the accident (26.04.1986) is taken as unity, then the content of
uranium isotopes with respect to
239
Pu was:
235
U, (1.9 ± 0.4) × 10
–4
;
236
U,
(1.0 ± 0.3) × 10
–3
; and
238
U, (3.1 ± 0.6) × 10
–3
(IAEA 1988) .
Under the condition of 5% fuel release from the emergency reactor, 9.5 t of uranium fell into the environment (Konoplya et al. 2007). In general, the total emission
of actinides on the territory of Belarus was approximately 2.5 times greater than
their global deposition. Approximately half of the actinides fell on the territory
immediately adjacent to the Chernobyl nuclear power plant, the rest was dispersed
practically throughout the territory of Belarus. At the territory of the PSRER, the
density of uranium deposition is from 18 to 100 Bq/m
2
. The deposition of Chernobyl
uranium on the surface of the soil could significantly affect the content and isotopic
composition of uranium in the near zone. The ratio of
235
U/
238
U and the proportion
of Chernobyl uranium in the total uranium content in the (0–5)-cm soil layer at
different distances from the destroyed nuclear reactor, established by mass spectrometric analysis by Konoplya et al. (2007), is given in Table 1.
In the surface layer of the soil of the 30-km zone of the Chernobyl NPP and
adjacent areas, the ratio of
235
U/
238
U by mass exceeds the ratio of natural isotopes of
uranium. The ratio of
235
U/
238
U by mass for natural uranium is 0.00725 and for
G. A. Sokolik et al.