Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field
The spatial redistribution of the ²³⁵U isotope of natural uranium in a gradient temperature field along the height of the reactor in supercritical carbon dioxide has been experimentally investigated. The scheme of the reactor is given and the principle of operation of the reactor is described. The m...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2021
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| Цитувати: | Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field / B.V. Borts, S.F. Skoromnaya, Yu.G. Kazarinov, I.M. Neklyudov, V.I. Tkachenko // Problems of Atomic Science and Technology. — 2021. — № 5. — С. 98-103. — Бібліогр.: 24 назв. — англ. |
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irk-123456789-1954432023-12-05T12:33:49Z Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field Borts, B.V. Skoromnaya, S.F. Kazarinov, Yu.G. Neklyudov, I.M. Tkachenko, V.I. Thermal and fast reactor materials The spatial redistribution of the ²³⁵U isotope of natural uranium in a gradient temperature field along the height of the reactor in supercritical carbon dioxide has been experimentally investigated. The scheme of the reactor is given and the principle of operation of the reactor is described. The method of preparation of initial samples from granite samples containing natural uranium and the procedure of extraction are described. The conclusion about the spatial redistribution of ²³⁵U isotopes in supercritical carbon dioxide is based on the analysis of gamma spectra of extracts. It is shown that the concentration of the ²³⁵U isotope in a supercritical fluid is maximal near the lower heated flange of the reactor, and decreases with approaching the upper, cooled flange. It was concluded that the separation factor of the ²³⁵U isotope in supercritical carbon dioxide can be about 1.2 ± 0.12. Експериментально досліджено просторовий перерозподіл ізотопу ²³⁵U природного урану в градієнтному полі температури по висоті реактора в надкритичному діоксиді вуглецю. Наведено схему і описаний принцип роботи реактора. Описані метод підготовки вихідних зразків із зразків гранітів, що містять природний уран, і порядок проведення екстракції. Висновок про просторовий перерозподілі ізотопів ²³⁵U в надкритичному діоксиді вуглецю заснований на аналізі гамма-спектрів екстрактів. Показано, що в надкритичному флюїді концентрація ізотопу ²³⁵U максимальна поблизу нижнього фланця реактора, що підігрівається, і зменшується з наближенням до верхнього охолоджуваного фланця. Зроблено висновок про те, що коефіцієнт поділу ізотопу ²³⁵U в надкритичному діоксиді вуглецю може становити величину близько 1.2 ± 0.12. Экспериментально исследовано пространственное перераспределение изотопа ²³⁵U природного урана в градиентном поле температуры по высоте реактора в сверхкритическом диоксиде углерода. Приведена схема и описан принцип работы реактора. Описаны метод подготовки исходных образцов из образцов гранитов, содержащих природный уран, и порядок проведения экстракции. Вывод о пространственном перераспределении изотопов ²³⁵U в сверхкритическом диоксиде углерода основан на анализе гамма-спектров экстрактов. Показано, что в сверхкритическом флюиде концентрация изотопа ²³⁵U максимальна вблизи нижнего подогреваемого фланца реактора, и уменьшается с приближением к верхнему, охлаждаемому фланцу. Сделан вывод о том, что коэффициент разделения изотопа ²³⁵U в сверхкритическом диоксиде углерода может составлять величину около 1.2 ± 0.12. 2021 Article Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field / B.V. Borts, S.F. Skoromnaya, Yu.G. Kazarinov, I.M. Neklyudov, V.I. Tkachenko // Problems of Atomic Science and Technology. — 2021. — № 5. — С. 98-103. — Бібліогр.: 24 назв. — англ. 1562-6016 https://doi.org/10.46813/2021-135-098 http://dspace.nbuv.gov.ua/handle/123456789/195443 542.61 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
Thermal and fast reactor materials Thermal and fast reactor materials |
| spellingShingle |
Thermal and fast reactor materials Thermal and fast reactor materials Borts, B.V. Skoromnaya, S.F. Kazarinov, Yu.G. Neklyudov, I.M. Tkachenko, V.I. Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field Вопросы атомной науки и техники |
| description |
The spatial redistribution of the ²³⁵U isotope of natural uranium in a gradient temperature field along the height of the reactor in supercritical carbon dioxide has been experimentally investigated. The scheme of the reactor is given and the principle of operation of the reactor is described. The method of preparation of initial samples from granite samples containing natural uranium and the procedure of extraction are described. The conclusion about the spatial redistribution of ²³⁵U isotopes in supercritical carbon dioxide is based on the analysis of gamma spectra of extracts. It is shown that the concentration of the ²³⁵U isotope in a supercritical fluid is maximal near the lower heated flange of the reactor, and decreases with approaching the upper, cooled flange. It was concluded that the separation factor of the ²³⁵U isotope in supercritical carbon dioxide can be about 1.2 ± 0.12. |
| format |
Article |
| author |
Borts, B.V. Skoromnaya, S.F. Kazarinov, Yu.G. Neklyudov, I.M. Tkachenko, V.I. |
| author_facet |
Borts, B.V. Skoromnaya, S.F. Kazarinov, Yu.G. Neklyudov, I.M. Tkachenko, V.I. |
| author_sort |
Borts, B.V. |
| title |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| title_short |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| title_full |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| title_fullStr |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| title_full_unstemmed |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| title_sort |
spatial nonuniform distribution of ²³⁵u isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2021 |
| topic_facet |
Thermal and fast reactor materials |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/195443 |
| citation_txt |
Spatial nonuniform distribution of ²³⁵U isotope at supercritical fluid extraction with carbon dioxide in a gradient temperature field / B.V. Borts, S.F. Skoromnaya, Yu.G. Kazarinov, I.M. Neklyudov, V.I. Tkachenko // Problems of Atomic Science and Technology. — 2021. — № 5. — С. 98-103. — Бібліогр.: 24 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-16T23:26:43Z |
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2025-07-16T23:26:43Z |
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1837847967850037248 |
| fulltext |
ISSN 1562-6016. PASТ. 2021. №5(135), p. 98-103.
https://doi.org/10.46813/2021-135-098
UDC 542.61
SPATIAL NONUNIFORM DISTRIBUTION OF
235
U ISOTOPE
AT SUPERCRITICAL FLUID EXTRACTION WITH CARBON DIOXIDE
IN A GRADIENT TEMPERATURE FIELD
B.V. Borts
1
, S.F. Skoromnaya
1
,
Yu. G. Kazarinov
1,2
, I.M. Neklyudov
1,2
, V.I. Tkachenko
1,2,3
1
NSC “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine;
2
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
3
E-mail: tkachenko@kipt.kharkov.ua
The spatial redistribution of the
235
U isotope of natural uranium in a gradient temperature field along the height of
the reactor in supercritical carbon dioxide has been experimentally investigated. The scheme of the reactor is given
and the principle of operation of the reactor is described. The method of preparation of initial samples from granite
samples containing natural uranium and the procedure of extraction are described. The conclusion about the spatial
redistribution of
235
U isotopes in supercritical carbon dioxide is based on the analysis of gamma spectra of extracts. It
is shown that the concentration of the
235
U isotope in a supercritical fluid is maximal near the lower heated flange of
the reactor, and decreases with approaching the upper, cooled flange. It was concluded that the separation factor of the
235
U isotope in supercritical carbon dioxide can be about 1.2 ± 0.12.
ENERGY URANIUM ISOTOPE.
METHODS FOR URANIUM EXTRACTION
FROM NUCLEAR MATERIALS
The main fuel isotope in open-cycle uranium-fueled
thermal reactors is
235
U. Since the world nuclear energy
uses this uranium isotope, then, naturally, its production
and depletion rate in the world are growing [1].
Generation of
235
U isotope is based on its separation
from the bulk of natural uranium, which mainly consists
of
238
U isotope in an approximate ratio
99.2745%
238
U:0.7200%
235
U [2].
Production of uranium compounds for the needs of
nuclear power is carried out by direct mining and
refining of uranium from uranium deposits [1, 3], as well
as by spent nuclear fuel reprocessing (SNF) using well-
developed methods (bismuth-phosphate process, liquid
extraction in the form of redox and purex processes)
[4–9].
The disadvantage of uranium production by
processing of uranium ores is its incomplete (up to
95…97%) extraction from the feedstock. Therefore, a
large amount of waste uranium has accumulated in
Ukraine in the form of tailing dumps, which form
technogenic deposits of a total area of about 2.5 mln m
2
and a mass of about 40 mln t. Waste heaps of coal mines
of a total volume of coal rocks of the order of
1056.52 mln m
3
can be also counted as technogenic
deposits containing heavy metals, uranium and thorium.
Therefore, search for new alternative, low-waste
technologies for processing technogenic deposits should
be considered as one of the most important tasks in the
development of nuclear energy.
One of these technologies satisfied the selective, deep
and low-waste processing of feedstock is the physical
method of supercritical fluid extraction by carbon
dioxide (SFE-CO2) [10] of uranyl nitrate complexes with
organophosphorus compounds. According to this method
a supercritical fluid with an uranium complex dissolved
in it is generated in a reactor at a high pressure (more
than 7.38 MPa) and a relatively low temperature (more
than 31.06 ºС). Experiments proved that up to 62% of
uranium complexes are extracted at a pressure of 9 MPa
and a temperature of 38 ºС [11]. Relatively low
indicators of extraction efficiency in [11] were obtained
at low pressures, low temperatures and using tributyl
phosphate (TBP) as an organophosphorus reagent. The
use of higher pressures (up to 30 MPa) and additional
complexing agents make it possible to increase the
extraction efficiency up to 100% [12].
A theoretical estimate has shown that the maximum
extraction efficiency of the uranium complex is about
96% [13].
Since, uranium complexes are in the volume of the
fluid in the process of SFE-CO2, there is a certain
possibility to carry out local changes in the ratio of the
amount of isotopes by the effect of some external factors.
An example is the Rank-Hilsch vortex tubes [14] used to
separate
36
Ar/
40
Ar isotopes in the fossil gases Н2 or
СF3Сl, which can be considered as an external factor. In
the case of SFE-CO2 for uranium complexes a change in
the ratio of the amount of isotopes can be implemented
in the process of fluid extraction from the reaction
volume on condition that the flow and temperature
scenarios similar to the Zippe centrifuge are realized.
In the case of SFE-CO2 the supercritical fluid
containing uranium complexes is under high pressure.
Such a medium is quite sensitive to the temperature
differential at its boundaries: even small temperature
gradients (at the level of 0.1…0.2 С/cm) can start the
convective mechanism of mass transfer, which has been
experimentally confirmed in [15]. Therefore, it is of
great interest to study the effect of the temperature
gradient on the spatial distribution of a supercritical fluid
containing complexes of uranium isotopes, which may
arise even due to a small temperature difference in the
probabilities of their transitions between energy levels
[13].
As one of the examples of the possible redistribution
of uranium isotopes under natural conditions, in our
mailto:tkachenko@kipt.kharkov.ua
opinion, is a natural nuclear reactor that operated for
more than tens of thousands of years about two billion
years ago in Gabon, West Africa [16]. To initiate chain
fission reaction in such a natural reactor it is necessary to
have
235
U enrichment at least 3%, as it is provided in
modern commercial nuclear reactors. For example, light
water reactors operate at pressures of about 15.0 MPa
and temperatures of about 300 ºС [17]. At such
parameters the water is in a liquid state (Tsc = 374 ºC,
Psc = 21.77 MPa) and carbon dioxide, as noted above,
goes into a supercritical state and turns into a good
organic solvent [10, 11]. Under such conditions, at low
water content, when there is no moderator and fission
reactions cease, the dissolution of uranium complexes in
supercritical carbon dioxide is possible. The
aforementioned uranium enrichment to a level of 3% can
be observed in the field of a spatial temperature gradient
due to the temperature difference in probabilities of
transitions of uranium isotope complexes between
energy levels [13].
This paper presents the results of an experimental
study of the change in the spatial distribution of
235
U
isotope in a volume of supercritical carbon dioxide
heated from below and cooled from above.
DESCRIPTION OF THE TRIAL SETUP
REACTOR
Experiments for investigation of spatial distribution
of uranium isotopes
235
U and
238
U in the reactor were
carried out on the upgraded laboratory setup for
supercritical fluid extraction “SFE-U” [11, 18]. The
setup allows raising the pressure of supercritical carbon
dioxide up to 20.0 MPa and maintaining the temperature
from room temperature to 50 ºC. Control of pressure and
temperature at different points of the reactor is provided
by digital barostats and thermostats, which allow such
control in automatic, semi-automatic and manual modes.
When carrying out the extractions, Carbon dioxide
meeting the requirements of GOST 8050-85 with a
volumetric CO2 content of 99.8% was used for
extractions.
The updating of the laboratory setup was carried out
only for the reactor, which in its original form was a
cylinder 9 cm high and 2.6 cm in diameter. In the
upgraded reactor its height was increased to 21.8 cm. Its
lower and upper flanges were maintained at specified
temperatures by means of adjustable heaters and the
temperature of the lower flange was set higher than the
temperature of the upper one.
The internal arrangement of the upgraded reactor is
presented in Fig 1.
A specific feature of this upgraded reactor is a sealed
axial mounting of a stainless steel tube of a diameter of
6.1 mm and a wall thickness of 1 mm. At the end of the
tube there is a intake device 10 (see the fragment of
section A in Fig. 1) in the form of an umbrella, which
doses removing a part of the extract from the volume of
the reactor by lowering the pressure in it. Decreasing the
pressure is carried out stepwise, starting from the initial
pressure release by about 4.0 MPa and subsequent
pressure release in total by an amount within the range of
9.6…10.0 MPa from the initial one. As shown in [11],
the bulk of the uranium complex containing
235
U isotope
is recovered during the first pressure release. The
fraction of the primary recovered extract volume was
estimated by the same ratio as the primary pressure
release, 0.25 of the total volume, and basically
corresponded to the area located below the intake device.
Fig. 1. Internal arrangement of the elements of the
upgraded reactor:
1 – bolt; 2 – middle flange; 3 – fitting;
4 – sealer; 5 – case; 6 – insert;
7 – bottom flange; 8 – bolt; 9 – tube; 10 – intake device;
11 – lower flange temperature sensor;
12 – lower flange heating element;
13 – upper flange temperature sensor;
14 – upper flange heating element
The intake device was located at a given distance
from the lower flange of the reactor in each series of
experiments.
SAMPLE PREPARATION
Sample preparation is necessary to impart to the
initial samples the properties of solubility in supercritical
carbon dioxide. Sample preparation was carried out
similarly to that described in [19], where samples of
granites with uranium content from 0.13 to 667 µg/g
were used as the initial material containing natural
uranium. The uranium content in the initial samples was
determined by gamma spectrometry using SEG-50 (P)
spectrometer based on a semiconductor germanium-
lithium diffusion-drift detector DGDK-60V.
A granite sample with the highest natural uranium
content was used for the experiments. The original
sample was crushed and grinded to powder of a grain
size of less than 50 μm. Then 10 g of powder was poured
with 20 ml of 40% nitric acid and kept for a day. The
resulting solution was filtered. After filtration the
solution was mixed with 6 ml of 30% TBP solution in
kerosene and was shaken. After stratification the organic
phase was filtered through a paper filter. Thus, under the
assumption that the efficiency of all sample preparation
procedures is close to 100%, the uranium content in 1 ml
of solution was estimated to be no more than 1.1 mg.
EXTRACTION PROCEDURE
The extraction on the upgraded SFE-U unit was
carried out in the following order:
– a glass container (short test tube) containing 2 ml of
the obtained organic extract was placed in the reactor;
– the upper flange of the reactor was heated up to
35 ºС, the lower flange – up to 40 ºС;
– injection of carbon dioxide by means of a
compressor up to a pressure of 16.0 MPa;
– exposition of the extract for 30 min;
– discharge of the extract (~ 1 ml) into a glass jar for
5 min while releasing pressure from 16 to 12 MPa;
– discharge of the extract (~ 1 ml) into a glass beaker
for 5 min while releasing pressure from 12 to 6 MPa;
– after releasing the pressure to atmospheric, the
extract residue was removed from the reactor.
The extraction procedures described above were
carried out three times at three different points along the
height of the reactor: I, II, and III. At point I the distance
from the lower flange of the reactor to the intake device
(see item 10 in Fig. 1) was – 5 cm; at point II – 10 cm; at
point III – 15 cm.
PROCESSING OF THE OBTAINED
EXPERIMENTAL RESULTS
The initial samples of the solution (before CFE-СО2
carrying out) and the samples obtained as a result of
CFE-СО2 were analyzed for the content of uranium
235
U
isotope according to the spectra obtained on the gamma-
ray detector.
A detector based on high-purity germanium was used
as a gamma-ray detector – a coaxial germanium detector
GC 1818 (Germanium Coaxial) with a relative detection
efficiency отн = 18%, an energy resolution Е = 180 keV
at an energy of gamma quanta Е = 1.33 MeV.
Table 1
The results of the analysis of
235
U isotope content
in natural uranium using the FRAM program
Sample No.
(Volume)
Content
235
U, %
Error; +/-,
%
0 (2 ml) initial 0.69 0.012; (1.75)
0 (6 ml) initial 0.64 0.007; (1.03)
I.1 (2 ml) 0.91 0.018; (1.95)
I.2 (2 ml) 1.35 0.101; (7.5)
I.3 (2 ml) 1.4 0.062; (4.44)
II.1 (2 ml) 1.57 0.352; (2.44)
II.2 (2 ml) 1.00 0.056; (5.62)
II.3 (2 ml) 1.07 0.055; (5.17)
III.1 (2 ml) 0.98 0.061; (6.19)
III.2 (2 ml) 0.97 0.030; (3.16)
III.3 (2 ml) 0.96 0.063; (6.27)
The residue (2 ml)
in point III
0.63 0.017; (2.70)
When using the detector, gamma spectra were
measured with their subsequent analysis by the FRAM
program [20] which was developed at the Los Alamos
National Laboratory. The sample was placed directly in
front of the detector window.
The standard exposure time was about 2 days.
A special feature of the FRAM software is that
results are obtained using only spectral data and known
nuclear constants. In this case, calibration of the
spectrometric system using standard samples is not
required.
The results of the analysis of
235
U isotope content in
natural uranium using the FRAM program are presented
in Table1.
RESULTS AND DISCUSSION
Based on the results presented in Table 1 the
following conclusions can be drawn.
The content of the uranium isotope
235
U in the initial
samples does not exceed the values corresponding to
natural uranium – 0.711…0.7200% [2].
As a result of SFE-CO2 complexes of uranium from
the region located at a distance of 5 cm from the lower
flange (point I)
235
U isotope content varied from 0.91 %
to 1.4 %.
235
U isotope content decreased to a level of
1.0 % with increasing the distance from the lower flange
of the reactor (point II) up to 10 cm.
235
U content
decreases to an average value of 0.97 %, but remains
above the natural level with a further increase in the
distance from the lower flange of the reactor up to
15 cm.
The excess of
235
U isotope concentration over the
natural level at points I–III, in our opinion, was due to
the experimental conditions: at each point of extract
separation the
235
U concentration corresponded to its
local average content in the removed volume, the value
of which was estimated to be about 0.45 of the total
volume.
The location of the experimental points of
235
U
isotope concentration over the height of the reactor
(black squares) is shown in Fig. 2. The X-axis direction
is chosen from the cold reactor flange to the warm
flange. The experimental points are well described by the
linear dependence of the uranium isotope concentration
expy x on the normalized length x (the straight line in
Fig. 2 passing through the experimental points), which
was plotted using the least squares method:
0.67 0.85expy x x . (1)
The real distribution of the uranium isotope
concentration is described by the lower straight line in
Fig. 2, which is obtained from expression (1) after its
normalization to the entire volume of the reactor:
0.3 0.85realy x x . (2)
The validity of the expression (2) is confirmed by
calculating the average percentage of
235
U isotope over
the height of the reactor
1
0
0.725real realy x y x dx ,
which approximately corresponds to the natural.
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
C
o
n
c
e
n
tr
a
ti
o
n
,
2
3
5
U
(
%
)
Normalized lenght (Arb. un.)
Fig. 2. Dependence of
235
U isotope concentration on the
reactor normalized length. Solid line – formula (1),
dashed line – (2)
Both straight lines in Fig. 2 characterize the uneven
distribution of
235
U isotope over the reactor height.
To check the correspondence between the content of
235
U isotope in the initial sample and its total content in
the extract and in the residue after extraction we
measured its content in the reactor after sample
acquisition at point III. The measurements showed that
the content of this isotope was below the natural level
and corresponded to a value of 0.63% (see Table 1). The
balance equation for the uranium isotope content in the
extract and in the residue in the reactor is as follows:
0.97 0.63 1 0.72x x , (3)
where x – part of the volume of the supercritical fluid
extracted from the reactor; the numerical coefficient for
the first term is the amount of isotope extracted from the
reactor at point III; the numerical coefficient for the
second term is the amount of isotope remaining in the
reactor; on the right side – the value of the natural
amount of the isotope.
It follows from (3) that part of the volume of the
supercritical fluid extracted from the reactor is equal to
0.264x , which corresponds to the value of the
primary pressure release – 4.22 MPa.
Thus, as a result of the experiments it was shown
that at certain parameters of the supercritical fluid in a
spatially inhomogeneous temperature field the
235
U
isotope content is unevenly distributed over the reactor
height: maximum at a distance of 5 cm from the lower
flange (hotter) and decreases with a distance from it.
COMPARATIVE ASSESMENT OF THE
EFFICIENCY OF URANIUM ISOTOPE
REDISTRIBUTION
The spatial redistribution of the isotopic composition
of natural uranium obtained in this work as a result of
supercritical fluid extraction with carbon dioxide has an
analogy with the problems of separating isotopes of
various chemical elements. A series of such elements
start from light elements Ar, Li [14, 21] and end with
heavy ones – U, Pu [22, 23]. One of the parameters
determined the efficiency of isotope separation is the
separation factor [22, 23].
The separation factor for a mixture of two isotopes
is determined by the expression:
1
,
1 1
c c
c c
(4)
where c and 1 c – concentration of light and heavy
isotopes in the enriched mixture, respectively; c and
1 c – the same in the original mixture.
From expression (2) it follows that at the height of the
reactor 0.67x the content of
235
U is equals to 0.861%.
This uranium content corresponds to the separation factor
with taking into account the measurement error (see Fig. 2):
0.8695 0.72 1.2 0.12 .
Separation factors for uranium isotopes when using
different separation methods are presented in Table 2.
Table 2
Separation factors
235
U and
238
U in different separation
methods [23]
Separation method
Separation factor,
Chemical enrichment [24] 1.0013…1.0030
Gas–diffusion enrichment 1.00429
Centrifugation (250 m/s) 1.026
Centrifugation (600 m/s) 1.233
Isotope separation in a system of
opposite, axially symmetric
magnetic fields [21]
30–40
СFE-СО2 1.2 ± 0.12
Analyzing the results of the experiments it can be
concluded that the separation factor of
235
U isotope is
about 1.2 ± 0.12 in the SFE-U setup.
CONCLUSIONS
Redistribution of
235
U isotope of natural uranium in a
supercritical dioxide medium with a spatial temperature
gradient is shown by experiments in the paper. The
diagram of the reactor of the experimental setup is
presented and the principle of its operation is described.
The method of sample preparation and the procedure for
the extraction of natural uranium from granite samples
are described. The isotopic composition of uranium in
the obtained extracts is determined using the method of
gamma spectrometry. It is shown that at certain
parameters of the supercritical fluid the concentration of
235
U isotope is nonuniformly distributed over the height
of the reactor: its concentration is maximum near the
lower heated flange of the reactor and decreases with
approaching the upper, colder flange of the reactor. The
separation factor of
235
U isotope in supercritical carbon
dioxide is determined; it is equal to 1.2 ± 0.12.
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Article received 30.06.2021
ПРОСТРАНСТВЕННО-НЕОДНОРОДНОЕ РАСПРЕДЕЛЕНИЕ ИЗОТОПА
235
U
ПРИ СВЕРХКРИТИЧЕСКОЙ ФЛЮИДНОЙ ЭКСТРАКЦИИ ДИОКСИДОМ УГЛЕРОДА
В ГРАДИЕНТНОМ ПОЛЕ ТЕМПЕРАТУР
Б.В. Борц, С.Ф. Скоромная,
Ю.Г. Казаринов, И.М. Неклюдов, В.И. Ткаченко
Экспериментально исследовано пространственное перераспределение изотопа
235
U природного урана в
градиентном поле температуры по высоте реактора в сверхкритическом диоксиде углерода. Приведена схема
и описан принцип работы реактора. Описаны метод подготовки исходных образцов из образцов гранитов,
содержащих природный уран, и порядок проведения экстракции. Вывод о пространственном
перераспределении изотопов
235
U в сверхкритическом диоксиде углерода основан на анализе гамма-спектров
экстрактов. Показано, что в сверхкритическом флюиде концентрация изотопа
235
U максимальна вблизи
нижнего подогреваемого фланца реактора, и уменьшается с приближением к верхнему, охлаждаемому
фланцу. Сделан вывод о том, что коэффициент разделения изотопа
235
U в сверхкритическом диоксиде
углерода может составлять величину около 1.2 ± 0.12.
ПРОСТОРОВО-НЕОДНОРІДНИЙ РОЗПОДІЛ ІЗОТОПІВ
235
U
ПРИ НАДКРИТИЧНІЙ ФЛЮЇДНІЙ ЕКСТРАКЦІЇ
ДІОКСИДОМ ВУГЛЕЦЮ В ГРАДІЄНТНОМУ ПОЛІ ТЕМПЕРАТУР
Б.В. Борц, С.Ф. Скоромна,
Ю.Г. Казарінов, І.М. Неклюдов, В.І. Ткаченко
Експериментально досліджено просторовий перерозподіл ізотопу
235
U природного урану в градієнтному
полі температури по висоті реактора в надкритичному діоксиді вуглецю. Наведено схему і описаний принцип
роботи реактора. Описані метод підготовки вихідних зразків із зразків гранітів, що містять природний уран, і
порядок проведення екстракції. Висновок про просторовий перерозподілі ізотопів
235
U в надкритичному
діоксиді вуглецю заснований на аналізі гамма-спектрів екстрактів. Показано, що в надкритичному флюїді
концентрація ізотопу
235
U максимальна поблизу нижнього фланця реактора, що підігрівається, і зменшується з
наближенням до верхнього охолоджуваного фланця. Зроблено висновок про те, що коефіцієнт поділу ізотопу
235
U в надкритичному діоксиді вуглецю може становити величину близько 1.2 ± 0.12.
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