Effect of ionizing radiation on the extraction of Am(III) with p-tert-butylthiacalix[4]arene from alkaline carbonate solutions

Article abstract of DOI:10.1134/S1066362217040087

The effect of γ-irradiation of tert-butylthiacalix[4]arene (TCA) solutions in m-nitrobenzotrifluoride (NBTF) and tetrachloroethylene (TCE) on the extraction of ²⁴¹Am from alkaline carbonate solutions was studied. TCA itself remains stable upon γ-irradiation of its solutions in NBTF to a dose of 200 kGy, but the diluent undergoes strong degradation. The radiation resistance of TCA in TCE is considerably lower: A dose of 70 kGy causes complete degradation of TCA. In the TCA–TCE–aqueous phase system, sulfate ions appear upon γ-irradiation as the final product of the extractant radiolysis. A large number of γ-radiolysis products of TCE and TCA were detected by HPLC and GCMS. The products of radiolysis of TCA in TCE, compared to the initial extractant, have lower molecular mass and higher polarity. The results show that chlorinated diluents are not promising diluents for thiacalixarene in extraction processing of alkaline high-level waste.

Full text of DOI:10.1134/S1066362217040087

ISSN 1066-3622, Radiochemistry, 2017, Vol. 59, No. 4, pp. 365–371. © Pleiades Publishing, Inc., 2017.
Original Russian Text © I.V. Smirnov, E.S. Stepanova, M.Yu. Tyupina, N.M. Ivenskaya, I.G. Tananaev, S.R. Zaripov, S.R. Kleshnina, S.E. Solov’eva,
I.S. Antipin, 2017, published in Radiokhimiya, 2017, Vol. 59, No. 4, pp. 319–324.
Effect of Ionizing Radiation on the Extraction
of Am(III) with p-tert-Butylthiacalix[4]arene
from Alkaline Carbonate Solutions
I. V. Smirnov*а–c, E. S. Stepanovaа,b, M. Yu. Tyupinaа, N. M. Ivenskayab, I. G. Tananaevb,d,
S. R. Zaripove, S. R. Kleshninaf, S. E. Solov’evae,f, and I. S. Antipine,f
а Khlopin Radium Institute, 2-i Murinskii pr. 28, St. Petersburg, 194021 Russia
b Ozersk Institute of Technology, pr. Pobedy 48, Ozersk, Chelyabinsk oblast, 456783 Russia
c St. Petersburg State University, Universitetskaya nab. 7–9, St. Petersburg, 199034 Russia
d Far Eastern Federal University, ul. Sukhanova 8, Vladivostok, 690091 Russia
e Kazan (Volga Region) Federal University, ul. Kremlevskaya 18, Kazan, Tatarstan, 420008 Russia
f Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences,
ul. Arbuzova 8, Kazan, Tatarstan, 420088 Russia
*e-mail: igor_smirnov@khlopin.ru
Received December 12, 2016
Abstract—The effect of γ-irradiation of tert-butylthiacalix[4]arene (TCA) solutions in m-nitrobenzotrifluoride
(NBTF) and tetrachloroethylene (TCE) on the extraction of 241Am from alkaline carbonate solutions was stud-
ied. TCA itself remains stable upon γ-irradiation of its solutions in NBTF to a dose of 200 kGy, but the diluent
undergoes strong degradation. The radiation resistance of TCA in TCE is considerably lower: A dose of
70 kGy causes complete degradation of TCA. In the TCA–TCE–aqueous phase system, sulfate ions appear
upon γ-irradiation as the final product of the extractant radiolysis. A large number of γ-radiolysis products of
TCE and TCA were detected by HPLC and GCMS. The products of radiolysis of TCA in TCE, compared to
the initial extractant, have lower molecular mass and higher polarity. The results show that chlorinated diluents
are not promising diluents for thiacalixarene in extraction processing of alkaline high-level waste.
Keywords: extraction, americium-241, thiaxalix[4]arene, alkaline media, γ-radiolysis, radiolysis products
DOI: 10.1134/S1066362217040087
ponent HLW should involve recovery of hazardous
radionuclides from the liquid phase of the heterogene-
ous medium by one or another procedure. This study
was aimed at developing a process for extraction
preconcentration and separation of 241,243Am from mul-
ticomponent alkaline media using high-performance
macrocyclic compounds. We have shown that Am(III)
is efficiently extracted from alkaline carbonate solu-
tions with substituted thiacalix[4]arenes. p-Bromo-
thiacalix[4]arene at pH 12 showed the highest ability
to extract Am (distribution ratio DАm > 100) and the
highest selectivity [selectivity factor βmax(Am/Eu) =
18] [4].
One of the most important problems of modern ap-
plied radiochemistry is final liquidation of so-called
“nuclear heritage.” Active efforts are made at nuclear
objects for remediation of contaminated territories,
decommissioning of large nuclear facilities, and final
removal and disposal of the accumulated radioactive
waste. One of the aspects of this problem is processing
of high-level waste (HLW) accumulated in the course
of implementation of the USSR Nuclear Project at the
Mayak Production Association. This HLW has a vol-
ume of more than 18000 m3. It is in the form of multi-
component slurries containing sodium hydroxide, car-
bonate, nitrite, and nitrate in combination with such
hazardous radionuclides as 137Сs, 90Sr, and transura-
nium nuclides [1–3].
The suggested promising extraction system for re-
covering radionuclides from alkaline carbonate media
should be adapted to real conditions by performing
The first step of processing of complex multicom-
365

366
SMIRNOV et al.
stirred at 180°С for 6 h. After cooling to room tem-
perature, 20 mL of hexane was added to the solidified
mixture. The undissolved residue consisting of un-
changed phenol and sulfur was filtered off, and hexane
was removed from the filter on a rotary evaporator.
The residue was dried in a vacuum for several hours,
and TCA/2 was obtained as a beige powder in 51%
yield. The product purity was checked by TLC
(chloroform/hexane, 2 : 1, Rf 0.1). The spectroscopic
data and melting point of the sample agreed with the
published data [8].
trials with simulated HLW solutions under the action
of ionizing radiation. First, it is necessary to evaluate
the radiation resistance of the extractants and diluents
used in the experiments, taking into account contradic-
tory data published in the literature. For example,
Kikuchi et al. [5] reported high radiation resistance of
p-tert-butylthiacalix[4]arene: After irradiation to an
absorbed dose of up to 1 MGy, the degree of degrada-
tion was as low as 1%. Furthermore, under definite
conditions (рН 2–4) the ability of thiacalix[4]arene for
coordination to Am(III) was enhanced, which was at-
tributed to oxidation of sulfide bridges to sulfone
groups in the course of irradiation. On the contrary,
Špendlíková et al. [6] noted low radiation resistance
of p-tert-butylthiacalix[4]arene in 1,2-dichloroethane:
The degree of degradation was up to 99% at a dose of
10 kGy, whereas in cyclohexanone at a dose of
100 kGy under equal other conditions only 60% of the
thiacalixarene decomposed.
Calix[4]arene sulfone was prepared by the known
procedure [9].
CAS/2 was synthesized by oxidation of TCA/2 dis-
solved in chloroform with a mixture of 30% H2O2 and
glacial acetic acid on heating on a glycerol bath (Tbath
=
100°С) for 2 h. CAS/2 was isolated from the reaction
mixture in the form of a beige crystalline precipitate in
1
82% yield by extraction with chloroform. H NMR
In this study, we examined the effect of γ-ir-
radiation on the extraction of Am(III) with solutions of
p-tert-butylthiacalix[4]arene in m-nitrobenzotrifluoride
and tetrachloroethylene from alkaline carbonate solu-
tions.
spectrum (CDCl3), δ, ppm: 1.26 s (18Н, t-Bu), 5.90 s
(2Н, OH), 6.95 d (3J = 8 Hz, 2Н, ArH), 7.50 d.d (3J =
4
8 Hz, J = 4 Hz, 2Н, ArH), 7.60 d (4J = 4 Hz, 2H,
ArH). IR spectrum, ν, cm–1: 3415 (OH), 2962 (СН),
1308, 1134 (SO2). Mass spectrum (electrospray ioniza-
tion): m/z 361.1 [M– – 1]. Found, %: С 66.38, H 7.06,
S 8.26. C20H26O4S. Calculated, %: C 66.27, H 7.23, S
8.85. Melting point 210°С.
EXPERIMENTAL
As diluents in solvent extraction and extractant irra-
diation experiments we used m-nitrobenzotrifluoride
(NBTF) (Rhodia, France) and pure grade tetrachloro-
ethylene (TCE) (Vekton, St. Petersburg, Russia),
washed with a sodium carbonate solution and with wa-
ter. Solutions of p-tert-butylthiacalix[4]arene in these
diluents were prepared from the accurately weighed
portion of the substance. Inorganic chemicals were of
no worse than analytically pure grade (Vekton) and
were used without additional purification. Solvents for
HPLC and GPC (Acros Organics) were used without
additional purification. 241Am containing 99.9% main
isotope was produced at the Khlopin Radium Institute.
The formulas and designations of the extractants
studied are given below.
TCA/2
TCA
p-tert-Butylthiacalix[4]arene sample containing 95%
main substance was synthesized and characterized by
the known procedure [7]. p-tert-Butylphenol (99%) and
sulfur (98%) used in the synthesis were produced by
Acros Organics. All the chemicals and solvents were
used in the synthesis without additional purification.
TCA/2 was synthesized as follows: A round-
bottomed flask was charged with 5.00 g (33.33 mmol)
of p-tert-butylphenol, 0.11 g (3.33 mmol) of sulfur,
and 0.02 g (0.42 mmol) of NaOH. The mixture was
CAS
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EFFECT OF IONIZING RADIATION ON THE EXTRACTION OF Am(III)
367
rate in the column 1.98 mL min–1, linear velocity
51.3 cm s–1, purging rate 5.0 mL min–1, flow split ratio
50.0; thermostat temperature program: 2 min at 60°C,
heating to 180°С at a rate of 10°C min–1, 10 min at
180°C, and heating to 200°С at a rate of 10°C min–1;
MS parameters: ion source temperature 210°C, inter-
face temperature 220°C, solvent subtraction time
2.50 min, detector amplification 0.96 kV, and scanned
mass range 44–800.
CAS/2
Experimental Procedures
1H and 13C NMR spectra. The H and 13C NMR
1
Determination of the concentration. The concen-
tration of sulfate ions in the aqueous phase after the
irradiation was determined on a Staier ion chromato-
graph equipped with a TS10 column thermostat, a con-
ductometric detector, and Mul’tiKhrom program–
apparatus complex. The detection limit of sulfate ions
was 0.2 mg L–1 (0.002 mM).
spectra were recorded with a Bruker AVANCE 400
spectrometer. The mass spectra were taken on a Bruker
amaZon X mass spectrometer with electrospray ioniza-
tion (ESI) and recording of negatively charged ions.
The IR spectra were measured with a Bruker Alpha
FT–IR spectrometer from KBr pellets in the interval
500–4000 cm–1. The melting points of the substances
were determined on a Boetius small heating table with
a PHMK 0.5 visual device. Elemental analysis was
performed with a Perkin Elmer PE 2400 series 2
СHNS/О analyzer.
pH of solutions was determined with an HI-8314
digital pH meter (Hanna Instruments) using an
I-1330B microelectrode allowing the measurements to
be performed in the extraction micro test tubes. The
pH meter was calibrated using standard buffer solu-
tions with pH 7.01 and 10.01.
HPLC separation was performed with a Thermo
Dionex UltiMate 3000 HPLC system. A Zorbax
Eclipse Plus C18 RR column (particle size 3.5 μm,
length 100 mm, inside diameter 4.6 mm) was used.
Column temperature 35°C, flow rate 1.0 mL min–1.
The separation was performed in the isocratic mode in
the acetonitrile/tetrahydrofuran (75 : 25) solvent sys-
tem. The sample volume was 0.01 mL, and the concen-
tration was 0.1 mg mL–1.
Extraction of Am(III). The distribution ratios of
radionuclides were determined as follows: A 1.5-mL
centrifugal polypropylene micro test tube was charged
with 0.6 mL of an aqueous phase of preset composi-
tion. The aqueous phases with a preset pH value were
prepared by mixing 1 M NaHCO3 and NaOH solutions
in appropriate ratio; constant ionic strength of the solu-
tions was thus ensured. The equilibrium pH value was
determined directly in the test tube. After that, a radio-
active tracer was added, the components were mixed,
and the mixture was allowed to stand for 15 min. Then,
0.6 mL of the organic phase was added, and the phases
were stirred at 21–23°С for 15 min. Preliminary ex-
periments showed that this time was sufficient to attain
the equilibrium in the system. The phase separation
was performed by centrifugation at 3000 rpm for
10 min. We took for measurements 0.4-mL samples of
the organic and aqueous phases. The Am content was
determined radiometrically from the γ-radiation of
241Am. The distribution ratios were calculated by the
formula DАm = Аorg/Аaq, where А is the activity concen-
tration of the radionuclide in the corresponding phase.
The extraction was studied with tracer amounts of
241Am. Radiometric measurements were performed
with a DeskTop InSpector scintillation γ-ray spec-
trometer (Canberra) based on a well-type 51 × 51 mm
NaI detector. The measurement time was chosen so as
Separation by gel permeation chromatography
(GPC) was performed on an Agilent 1260 Infinity
GPC device with an RI detector using two PLgel Mini-
Mix-E columns (particle size 3 μm, length 250 mm,
inside diameter 4.6 mm) with a PLgel MiniMix-E
Guard protective column. THF for HPLC was used as
a mobile phase at a flow rate of 0.3 mL min–1. The
sample concentration was ~1.0 mg mL–1, and the sam-
ple volume, 0.02 mL. GPC analysis of the products
was performed after 8-point calibration using polysty-
rene reference samples with narrow molecular-mass
distribution in the molecular mass range from 580 to
10 100.
Studies by gas chromatography–mass spec-
trometry (GCMS) were performed with a Shimadzu
GCMS-2010 Ultra device under the following condi-
tions: column thermostat temperature 60°C, injector
temperature 250°C, injection with flow splitting, pres-
sure 34.8 kPa, total flow rate 106.0 mL min–1, flow
RADIOCHEMISTRY Vol. 59 No. 4 2017

368
SMIRNOV et al.
Table 1. List of irradiated samples and compositions of the
mixed. After the emulsion separation, we took from
each test tube 4.5 mL of the aqueous phase to deter-
mine the concentration of sulfate ions and 4.5 mL of
the organic phase for further studies.
aqueous and organic phases
Sample Absorbed Aqueous
Organic phase
no.
dose, kGy
phasea
1
2
3
4
5
6
7
8
9
10
11
12
13
14
–
H2O
1
2
3
–
–
H2O
1
2
3
1
2
3
RESULTS AND DISCUSSION
70
1 mM TCA in TCE
Pure TCE
One of factors limiting the use of calixarenes in
extraction processes is their low solubility in organic
solvents used in solvent extraction. However, low
solubility of tert-butylthiacalix[4]arene in NBTF
(~10–4 M) does not prevent the use of this reagent for
efficient extraction of Am(III) from an alkaline car-
bonate medium (Fig. 1). As can be seen, the Am(III)
extraction maximum is at pH in the interval from 12 to
13, i.e., TCA in NBTF can be used for extracting ra-
dionuclides from alkaline HLW.
1 mM TCA in TCE
200
Pure TCE
Preliminary experiments on γ-irradiation of a solu-
tion of TCA in NBTF demonstrated high radiation re-
sistance of the thiacalixarene, in agreement with the
data of [5]. In the two-phase system consisting of 2 ×
10–4 M TCA in NBTF and 1 M NaOH + 1 M Na2CO3
in the aqueous phase, at an absorbed dose of 200 kGy,
the TCA concentration (according to HPLC data) did
not change noticeably. γ-Irradiation of NBTF in con-
tact with an alkaline aqueous phase leads to accumula-
tion of black radiolysis products in the organic phase
and complicates determination of the Am(III) distribu-
tion ratios in extraction from alkaline carbonate solu-
tions. Therefore, further experiments on TCA radioly-
sis were performed using TCE as diluent. This choice
is due to high solubility of the reagent and convenience
of studying the mixtures by spectroscopic and chroma-
tographic methods. In addition, TCE is structurally
similar to hexachlorobutadiene, a commercial diluent
that was used at the Mayak Production Association for
HLW processing.
а
(1) 0.6 M NaOH + 0.4 M NaHCO3, (2) 0.45 M NaOH +
0.3 M NaHCO3 + 0.25 M NaNO3, and (3) 0.45 M NaOH +
0.3 M NaHCO3 + 0.25 M NaNO2.
to ensure no more than 10% uncertainty of radiometric
measurements.
Extractant irradiation. Irradiation was performed
in glass test tubes with stoppers equipped with gas re-
lease tubes. The volume of each phase in the test tube
was 5 mL. Prior to irradiation, the phases were thor-
oughly mixed. Irradiation was performed to absorbed
doses of 70 and 200 kGy. The irradiated samples are
listed in Table 1. The extractants were irradiated on an
Issledovatel’ γ-ray installation (Mayak Production As-
sociation) using a 60Co source with the total activity of
6.1 × 1014 Bq and maximal γ-radiation dose in the cen-
ter of the working chamber of 14 kGy h–1.
After the irradiation completion, the phases were
In the next step of the study, a 1 mM solution of
TCA in TCE and two-phase systems containing in the
aqueous phase sodium hydroxide, carbonate, nitrate,
and nitrite (components of alkaline HLW) were sub-
jected to γ-irradiation (Table 1). The γ-irradiation dose
in the experiment was chosen so as to reach the ab-
sorbed dose of 70 kGy, corresponding to the radiation
load on the solvent in industrial processing of HLW
before withdrawal from the cycle. After irradiation to
a dose of 200 kGy, both the TCA–TCE organic phase
and aqueous phases of all the compositions acquire
yellow color. The color of the extractant samples
obtained without contact with the aqueous phase and
Fig. 1. Extraction of Am(III) from alkaline carbonate solu-
tions with a 2 × 10–4 M solution of TCA in NBTF.
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EFFECT OF IONIZING RADIATION ON THE EXTRACTION OF Am(III)
369
Table 2. 241Am distribution ratios in extraction with a 1 mM solution of TCA in TCE from alkaline carbonate solution (1 M
of the sum NaOH + NaHCO3, pH 13.44)
Irradiation dose, kGy
Sample no.
Aqueous phase, M
Unwashed organic phase
Without contact with aqueous phase
0
70
200
1
2
3
4
5
1.63
1.75
2.67
1.65
1.01
1.1
28.46
2.5
H2O
–
–
–
–
0.6 NaOH + 0.4 NaHCO3
0.45 NaOH + 0.3 NaHCO3 + 0.25 NaNO2
0.45 NaOH + 0.3 NaHCO3 + 0.25 NaNO3
1.96
0.86
1.72
Organic phase washed with two portions of 0.5 M Na2CO3
6
7
8
9
10
Without contact with aqueous phase
H2O
0.6 NaOH + 0.4 NaHCO3
0.45 NaOH + 0.3 NaHCO3 + 0.25 NaNO2
0.45 NaOH + 0.3 NaHCO3 + 0.25 NaNO3
2.2
–
–
–
–
1.94
1.08
1.45
0.67
1.18
1.27
0.61
2.56
1.3
1.78
Table 3. Content of SO42– in the equilibrium aqueous phase after γ-irradiation of a 1 mM solution of TCA in TCE
Concentration of SO42– in equilibrium aqueous phase after irradiation, mM
Aqueous phase, M
70 kGy
0.035
0.48
200 kGy
0.11
0.37
0.6 NaOH + 0.4 NaHCO3
0.5 NaOH + 0.3 NaHCO3 + 0.25 NaNO2
0.45 NaOH + 0.3 NaHCO3 + 0.25 NaNO3
0.83
0.75
in contact with pure water was the most intense.
aqueous phases after the TCA irradiation revealed the
presence of sulfate ion, the final product of TCA radio-
lysis (Table 3). As can be seen, the maximal yield of
sulfate ions in the aqueous phase does not exceed 20%
of the theoretically possible yield. Hence, complete
degradation of TCA does not occur even at an irradia-
tion dose exceeding by a factor of 3 the dose reached
in the course of industrial extraction processing of
HLW.
For the irradiated and nonirradiated samples of the
organic phase, we determined DAm under similar con-
ditions. Some of the experiments were performed with
unwashed samples of the irradiated organic phases,
and other experiments, with the organic phases washed
after irradiation with two portions of a 0.5 M Na2CO3
solution at the phase volume ratio of 1 : 1. Data on the
extraction of Am(III) from alkaline carbonate solutions
with nonirradiated and irradiated samples of TCA so-
lutions in TCE are given in Table 2. As can be seen, in
many cases DAm increased after irradiation of the or-
ganic phase. For example, after irradiation of a TCA
solution without contact with the aqueous phase to a
dose of 200 kGy (sample 1 in Table 2), DAm increased
by a factor of 20 compared to the unirradiated sample
of the same composition. On the contrary, washing of
the irradiated organic phase with a Na2CO3 solution in
most cases decreased DAm. Presumably, TCA degrada-
tion products extract Am(III) more efficiently than
TCA itself does, but are partially washed out from the
organic phase in the course of sodium carbonate wash-
ing, which is confirmed by the data noted in [5].
Because the formation of calixarene sulfone (CAS)
and its degradation products (CAS/2) in the course of
the TCA radiolysis via oxidation of sulfide bridges
could be expected, we have studied the extraction of
Am(III) with these compounds (Fig. 2).
As can be seen, CAS and CAS/2 extract Am from
alkaline solutions with the distribution ratios that are
lower than those in extraction with TCA by a factor of
several thousands. Thus, in alkaline solutions oxidation
of TCA to CAS cannot cause an increase in DAm, in
contrast to weakly acidic solutions [5].
Another possible pathway of TCA radiolysis is the
TCA macroring opening with the formation of linear
products. To confirm this assumption, we studied the
Am extraction from alkaline solutions with a solution
Chemical analysis of some samples taken from the
RADIOCHEMISTRY Vol. 59 No. 4 2017

370
SMIRNOV et al.
Fig. 5. Chromatograms (GPC) of a solution of TCA in TCE
Fig. 2. Extraction of 241Am with 1 mM solutions of
(1) TCA and (2) CAS and (3) with a 2 mM solution of
CAS/2 in TCE from alkaline carbonate solutions in relation
to pH of the aqueous phase.
(1) before irradiation and (2) after irradiation to a dose of
200 kGy.
In the final step of the study, we studied the TCA
and TCE radiolysis products by HPLC and GCMS. We
studied irradiated solutions of TCA in TCE by HPLC
using a reversed-phase column. As we found, TCA is
absent in these samples, and the retention times of the
radiolysis products are shorter than that of the initial
TCA, suggesting their higher polarity. The chroma-
tograms are shown in Fig. 4.
To evaluate the molecular masses of products
formed by radiolysis of solutions of TCA in TCE, the
irradiated solutions were analyzed by GPC. We have
found that the irradiated TCA solutions do not contain
substances with the relative molecular mass higher
than 300 amu (Fig. 5).
Fig. 3. Extraction of Am(III) from alkaline carbonate solu-
tions with (1) 0.001 M solution of TCA and (2) 0.002 M
solution of TCA/2 in TCE.
A GCMS analysis of irradiated solutions of TCA in
TCE revealed the presence of products formed by
radiolysis of TCE itself and by subsequent trans-
formation of the primary radiolysis products: penta-
and hexachloroethane, perchloro-1,3-butadiene, octa-
chloropropane, and hexachloropropene, which could
be formed by transformations of highly reactive radical
intermediates (Cl·, CCl2=CCl·) generated by radiolysis
of С–Сl bonds. In the case of thiacalixarene, the for-
mation of various chlorinated phenols and thiobisphe-
nols is observed.
Fig. 4. Chromatograms (reversed-phase HPLC) of a solu-
tion of TCA in TCE (1) before irradiation and (2) after
irradiation to a dose of 200 kGy.
The γ-irradiation-induced transformations of lower
unsaturated chlorocarbons presumably consist in de-
tachment of chlorine atoms and their addition to mole-
cules of the substance being irradiated. The radicals
formed upon detachment of chlorine atoms probably
recombine or undergo addition to the initial substance
with the subsequent detachment of chlorine atoms [6,
10–12]. However, the processes occurring upon TCE
irradiation are insufficiently understood yet.
of TCA and its nonmacrocyclic analog, TCA/2, which
is a “half” of the thiacalixarene molecule (Fig. 3). As
can be seen, TCA/2 exhibits very high extraction abil-
ity, quantitatively extracting Am from the aqueous
phase at its pH up to 13. The Am distribution ratios at
high pH values in the extraction with thiacalixarene
and its nonmacrocyclic analog, TCA/2, differ insignifi-
cantly (Fig. 3).
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EFFECT OF IONIZING RADIATION ON THE EXTRACTION OF Am(III)
371
ACKNOWLEDGMENTS
Thus, we have demonstrated the stability of TCA
upon γ-irradiation of its solution in nitrobenzotri-
fluoride in the presence of an alkaline aqueous phase
to an absorbed dose of up to 200 kGy. In the process,
nitrobenzotrifluoride undergoes significant radiolysis.
After irradiation of a TCA solution in TCE, DAm in the
extraction of Am(III) increases, although TCA is not
detected in the organic phase. Probably, TCA degrada-
tion products extract Am(III) more efficiently than
TCA itself does.
The study was supported by the Russian Science
Foundation (project no. 15-13-20 017).
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the subsequent chemical transformations of the pri-
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The diluents checked in this study are unsuitable
for extraction processing of alkaline HLW: NBTF un-
dergoes strong radiation degradation, and TCE radioly-
sis products cause the TCA degradation.
Translated by G. Sidorenko
RADIOCHEMISTRY Vol. 59 No. 4 2017