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Separation of cesium-137 from fission products by means of a Kel-F column supporting dipicrylamine
JOURNAL
594
OF CHROMATOGRAPNY
OF CESIUM-137 FROM FISSION PRODUCTS SEPARATION A KEL-F COLUMN SUPPORTING DIPICRYLAMINE
BY MEANS
OF
C. TESTA* AND C. CESARANO”* Casaccia Nuclear Center of C.N.E.N., Rome (Italy) (Received January XQth,x965) _
INTRODUCTION
Cesium-137 has been separated already by reversed-phase chromatography on a column of Kel-F supporting tetraphenylboron l. l!Iowever, this method had the clrawback that the column could be used only for one cycle owing to the considerable solubility of tetraphenylboron (TPB) in the aqueous solutions; moreover a IOO o/o cesium recovery was obtained only by washing the column with a mixture of I M FtCl-acetone, which removed all the supported organic material. Therefore another compound was tried which would selectively retain cesium and be less soluble than TPB ; from the papers by KYRS et ~1.2and BRAY AND RWIZRTS~ on the solvent extraction of cesium dipicryiamine, it seemed that a solution of dipicrylamine in nitrobenzene would meet these two requirements. In fact, by using a column of Kel-F supporting a dipicrylamine-nitrobenzene solution a complete separation of cesium from fission products was achieved and the column could be used again for more than fifteen cycles without losing its properties; with prolonged washing a decontamination factor greater than 103 was obtained. EXPERIMENTAL
Reagents
AND
RESULTS
and eq&@nent
Dipicrylamine, 40 y. in water, nitrobenzene and all the other chemical reagents of analytical grade were supplied by Sot. Carlo Erba (Milan), PolytriAuorochl.oroetl~ylene (Kel-F) , low density, grade 300, was supplied by Minnesota Mining Manufactury (U.S.A.). After grinding in an electric mill, only the fraction ranging from IOO to 170 mesh was used. The column had .a dia.meter of 10 mm and ended with a fritted glass disk. Counting of cesium and other fission products was performed by means of a 400 channel analyzer model T.MC. Pre$wation of Kel-F-&PicryZamine colztmn 0.5 g of 40 o/o dipicrylamine were shaken for IO min with 15 ml of nitrobenzene; after centrifugation 4 ml of the organic phase were mixed with 6 g of Kel-F roo-170 mesh, and the mixture was suspended in 50 ml of 0.01 lW EDTA (pw[ 7) and poured * Industrial Hygiene and Medical Department. * * Hot Operation Laboratory. J’. ChYOtVZUt0~.,.IQ
(1965)594-598
SEPARATION
OF
KEL-l? SUPPORTING
13'cS ON
595
DLPICRYLAMENE
into the column. After gentle pressure with a glass rod, the bed reached a height of 15 cm. Sdme glass wool was finally added and the column washed with 50 ml of 0.01 M EDTA (#I 7). Se@aratiom of cesizm from @ssion prodtick
From the studies on the solvent extraction of cesium by dipicrylamine2p3, it appears that the extraction coefficient increases rapidly from pH o to pH 7, and then it remains almost constant. Therefore, after the addition of the complexing agent, the pH was always kept at 7. A few milligrams of uranium, which had been irradiated about two years before, were dissolved in nitric acid and the solution diluted to 50 ml with water; to x ml of the final solution xo ml of 0.01 Jl EDTA and I A4 NaOH was added to give a pH of 5; after boiling for IO min to complex cerium, zirconium, niobium,, ruthenium etc. completely, the pH was brought to 7 with L ll4 NaOH. The solution was then passed through the column at a flow-rate of 0.5 ml/min; after washing with 30 ml of 0.01 lkf EDTA to remove completely the activity of the other fission products, cesium was quantitatively eluted with 15 ml of 0.5 M HN03 (Fig. I), 1. EPln O.OlM EOTA (PH -7.0 p
OlM &
EO A washing
OS M
IdNO3
16 m 0 3 14 d u 2 12
El?
S
free from %8
7-
E 4 10 6 6 4 2 0
1 Q
4
a
Fig. I. Separation 0.5 ml/min.
12
of
16
I
20
cesium-137
24
20
from fission products.
Bed dimensions
10 x
x50 mm ; fiow-rate
Two similar experiments were carried out with the same column at a flow-rate of I and 2 ml/min, and no significant change was noticed either in the shape of the elution curve or in the recovery of cesium; therefore a flow-rate ranging from I to 2 ml/min was used in the successive experiments. To obtain the accuracy and reproducibility of the method the initial activity of cesium-137 was determined by precipitating with ItC1044 and the same column, suitably regenerated with 50 ml of 0.01 Al EDTA (pH 7), was used for 15 consecutive cycles; Table I shows that an average recovery of 99.95 0/O& 0.3~ y0 was obtained. J. C?zromaiog.,‘Ig
(x965)
5g4-5g8
C. TESTA,
596 TABLE
I
RECOVERY
Initial
OP CESIUM-137
activity
FROM
of cc$ium-137
CyGh
A GtiVity
nzumber
fowd (G.$.rn.)
ww68 143,095 143,997 143,100 144,046 r43,=o I438232 I431293 143,392 143,698 342,858 143,245 143,693 142,394 142,527 Average
C. CESARANO
143,328
=
FLSSION
PRODUCTS
BY
THE
ICEL-F-DIPICRYLAMLNE
METISOD
343,385 c.p.m.
(%I
(%)
99-71 99.79 100.42 99.80 lOO.4G 100.34 99.89 99.93 100.35
-0.29 -0.21 + 0.42 -0.20 -I- 0.46 -k 0.34 -0.11 -0.07
100.21 99.63
99.30 99.40
-O.IO + 0.21 -0.70 -0.60
99.95
&0.3X
99.90
IOO.21
Determination of decontaminatio% factors A recently irradiated sample and a new column were used to determine the decontamination factors; 1.4 g of uranium, which had been irradiated about four months before, were dissolved in concentrated nitric acid and the solution diluted to 106 ml with water. Of this final solution 0.1 ml (1.4 mg U) was added to 5 ml of 0.01 M EDNA containing IOO pg of cesium as’a carrier. The pH was brought to 5 and the solution boiled for IO min; after cooling the pH was brought to 7 and the solution passed through the column as usual. From the spectrum of original fission products and that of purified cesium-x3.7, a decontamination factor for zirconium of about IOO was obtained. To improve the decontamination factor a second experiment was carried out in which a wash of IOO ml (instead of 30 ml) of 0.01 lU EDNA (pH 7) was used. Fig. z shows the spectrum of the original fission products (discontinuous line) where the presence of cesium-137 was not distinguishable, and that of isolated cesium-137 (continuous line), obtained by counting TOOtimes longer. It is very difficult to distinguish the presence of 244Ce-‘441?rand of i03Ru-i00Ru, whilst the peak of TZr-DSNb is still visible. From the ratio of the activities a decontamination factor > 103 for zirconium can be obtained; greater values are expected for the other radionuclides. CONCLUSLONS
From the results obtained it appears that a quantitative and reproducible separation of cesium-137 from fission products can be achieved by employing a column of Kel-Fsupporting dipicrylamine. The method is simple and the,column can be used again for several cycles. The decontamination factors are good and sufficient J. Cltromatog., 19 (x963) 394-398
SEPARATION
OF 137cS
ON
KEL-F
SUPPORTING
597
DIPICRYLAMINE
_’ .
4opoc
‘4nCe,‘44 Pr
‘J7CS
5, z 5 I= Y
30,oo
20,oc
‘03~u, "'Ru !7
QSZr i
‘1. 10
20
30
40
50
60
70
80
CHA6&L6
100
Fig. 2. Gamma spectrum of the original fission products, obtained b-v counting 4 min (discontinuous line), and of isolated cesium-137, obtained by counting 400 min (continuous line).
J. Chromatog.,
rg (196.5)
594-598
C. TESTA, C. CESARANO
598
for the method to be used for burn-up measurements, for cesium-137 determinations in fall-out samples and in general health physics work. ACKNOWLEDGEMENT
The authors are grateful to Mr. U, GALLUCCI for his accurate
experimental
work. SUMMARY
The separation of cesium-137 from fission products by a column of Kel-F (polytriffuorochloroethylene) supporting dipicrylamine is described, The average recovery ,of cesium is 99.95 yO & 0.31 y0 and the decontamination factors are greater than IO3; the column can be regenerated and used for more than 15 consecutive cycles. REFERENCES I’C. CESARANO, G. PTJGNETZX AND C. TESEA,J. Chromatog., Ig (1965) 589. 2 M. KYRS, J. PERCZK AND I?.POLANSKY, Collectiofl Cxmh. Chem. Commun., 25 (Ig6o) 2642. 3 L. ,A. BRAN AND F. P. ROBERTS, U.S. At. Energy Comm., HW-76222 (rg63). 4 L. E. GLXENDENIN AND C. M. NELSON, PevchZovale Methodfov the Detevmination of Cesiwm Activity in Eissio~ Pvoduck, National Nuclear Energy Series, Div. IV, Vol. g, McGraw Hill, New York, 1931, pp. 1642-3645. J. Chomatog.,
rg (1965)
5g+sg8
594
OF CHROMATOGRAPNY
OF CESIUM-137 FROM FISSION PRODUCTS SEPARATION A KEL-F COLUMN SUPPORTING DIPICRYLAMINE
BY MEANS
OF
C. TESTA* AND C. CESARANO”* Casaccia Nuclear Center of C.N.E.N., Rome (Italy) (Received January XQth,x965) _
INTRODUCTION
Cesium-137 has been separated already by reversed-phase chromatography on a column of Kel-F supporting tetraphenylboron l. l!Iowever, this method had the clrawback that the column could be used only for one cycle owing to the considerable solubility of tetraphenylboron (TPB) in the aqueous solutions; moreover a IOO o/o cesium recovery was obtained only by washing the column with a mixture of I M FtCl-acetone, which removed all the supported organic material. Therefore another compound was tried which would selectively retain cesium and be less soluble than TPB ; from the papers by KYRS et ~1.2and BRAY AND RWIZRTS~ on the solvent extraction of cesium dipicryiamine, it seemed that a solution of dipicrylamine in nitrobenzene would meet these two requirements. In fact, by using a column of Kel-F supporting a dipicrylamine-nitrobenzene solution a complete separation of cesium from fission products was achieved and the column could be used again for more than fifteen cycles without losing its properties; with prolonged washing a decontamination factor greater than 103 was obtained. EXPERIMENTAL
Reagents
AND
RESULTS
and eq&@nent
Dipicrylamine, 40 y. in water, nitrobenzene and all the other chemical reagents of analytical grade were supplied by Sot. Carlo Erba (Milan), PolytriAuorochl.oroetl~ylene (Kel-F) , low density, grade 300, was supplied by Minnesota Mining Manufactury (U.S.A.). After grinding in an electric mill, only the fraction ranging from IOO to 170 mesh was used. The column had .a dia.meter of 10 mm and ended with a fritted glass disk. Counting of cesium and other fission products was performed by means of a 400 channel analyzer model T.MC. Pre$wation of Kel-F-&PicryZamine colztmn 0.5 g of 40 o/o dipicrylamine were shaken for IO min with 15 ml of nitrobenzene; after centrifugation 4 ml of the organic phase were mixed with 6 g of Kel-F roo-170 mesh, and the mixture was suspended in 50 ml of 0.01 lW EDTA (pw[ 7) and poured * Industrial Hygiene and Medical Department. * * Hot Operation Laboratory. J’. ChYOtVZUt0~.,.IQ
(1965)594-598
SEPARATION
OF
KEL-l? SUPPORTING
13'cS ON
595
DLPICRYLAMENE
into the column. After gentle pressure with a glass rod, the bed reached a height of 15 cm. Sdme glass wool was finally added and the column washed with 50 ml of 0.01 M EDTA (#I 7). Se@aratiom of cesizm from @ssion prodtick
From the studies on the solvent extraction of cesium by dipicrylamine2p3, it appears that the extraction coefficient increases rapidly from pH o to pH 7, and then it remains almost constant. Therefore, after the addition of the complexing agent, the pH was always kept at 7. A few milligrams of uranium, which had been irradiated about two years before, were dissolved in nitric acid and the solution diluted to 50 ml with water; to x ml of the final solution xo ml of 0.01 Jl EDTA and I A4 NaOH was added to give a pH of 5; after boiling for IO min to complex cerium, zirconium, niobium,, ruthenium etc. completely, the pH was brought to 7 with L ll4 NaOH. The solution was then passed through the column at a flow-rate of 0.5 ml/min; after washing with 30 ml of 0.01 lkf EDTA to remove completely the activity of the other fission products, cesium was quantitatively eluted with 15 ml of 0.5 M HN03 (Fig. I), 1. EPln O.OlM EOTA (PH -7.0 p
OlM &
EO A washing
OS M
IdNO3
16 m 0 3 14 d u 2 12
El?
S
free from %8
7-
E 4 10 6 6 4 2 0
1 Q
4
a
Fig. I. Separation 0.5 ml/min.
12
of
16
I
20
cesium-137
24
20
from fission products.
Bed dimensions
10 x
x50 mm ; fiow-rate
Two similar experiments were carried out with the same column at a flow-rate of I and 2 ml/min, and no significant change was noticed either in the shape of the elution curve or in the recovery of cesium; therefore a flow-rate ranging from I to 2 ml/min was used in the successive experiments. To obtain the accuracy and reproducibility of the method the initial activity of cesium-137 was determined by precipitating with ItC1044 and the same column, suitably regenerated with 50 ml of 0.01 Al EDTA (pH 7), was used for 15 consecutive cycles; Table I shows that an average recovery of 99.95 0/O& 0.3~ y0 was obtained. J. C?zromaiog.,‘Ig
(x965)
5g4-5g8
C. TESTA,
596 TABLE
I
RECOVERY
Initial
OP CESIUM-137
activity
FROM
of cc$ium-137
CyGh
A GtiVity
nzumber
fowd (G.$.rn.)
ww68 143,095 143,997 143,100 144,046 r43,=o I438232 I431293 143,392 143,698 342,858 143,245 143,693 142,394 142,527 Average
C. CESARANO
143,328
=
FLSSION
PRODUCTS
BY
THE
ICEL-F-DIPICRYLAMLNE
METISOD
343,385 c.p.m.
(%I
(%)
99-71 99.79 100.42 99.80 lOO.4G 100.34 99.89 99.93 100.35
-0.29 -0.21 + 0.42 -0.20 -I- 0.46 -k 0.34 -0.11 -0.07
100.21 99.63
99.30 99.40
-O.IO + 0.21 -0.70 -0.60
99.95
&0.3X
99.90
IOO.21
Determination of decontaminatio% factors A recently irradiated sample and a new column were used to determine the decontamination factors; 1.4 g of uranium, which had been irradiated about four months before, were dissolved in concentrated nitric acid and the solution diluted to 106 ml with water. Of this final solution 0.1 ml (1.4 mg U) was added to 5 ml of 0.01 M EDNA containing IOO pg of cesium as’a carrier. The pH was brought to 5 and the solution boiled for IO min; after cooling the pH was brought to 7 and the solution passed through the column as usual. From the spectrum of original fission products and that of purified cesium-x3.7, a decontamination factor for zirconium of about IOO was obtained. To improve the decontamination factor a second experiment was carried out in which a wash of IOO ml (instead of 30 ml) of 0.01 lU EDNA (pH 7) was used. Fig. z shows the spectrum of the original fission products (discontinuous line) where the presence of cesium-137 was not distinguishable, and that of isolated cesium-137 (continuous line), obtained by counting TOOtimes longer. It is very difficult to distinguish the presence of 244Ce-‘441?rand of i03Ru-i00Ru, whilst the peak of TZr-DSNb is still visible. From the ratio of the activities a decontamination factor > 103 for zirconium can be obtained; greater values are expected for the other radionuclides. CONCLUSLONS
From the results obtained it appears that a quantitative and reproducible separation of cesium-137 from fission products can be achieved by employing a column of Kel-Fsupporting dipicrylamine. The method is simple and the,column can be used again for several cycles. The decontamination factors are good and sufficient J. Cltromatog., 19 (x963) 394-398
SEPARATION
OF 137cS
ON
KEL-F
SUPPORTING
597
DIPICRYLAMINE
_’ .
4opoc
‘4nCe,‘44 Pr
‘J7CS
5, z 5 I= Y
30,oo
20,oc
‘03~u, "'Ru !7
QSZr i
‘1. 10
20
30
40
50
60
70
80
CHA6&L6
100
Fig. 2. Gamma spectrum of the original fission products, obtained b-v counting 4 min (discontinuous line), and of isolated cesium-137, obtained by counting 400 min (continuous line).
J. Chromatog.,
rg (196.5)
594-598
C. TESTA, C. CESARANO
598
for the method to be used for burn-up measurements, for cesium-137 determinations in fall-out samples and in general health physics work. ACKNOWLEDGEMENT
The authors are grateful to Mr. U, GALLUCCI for his accurate
experimental
work. SUMMARY
The separation of cesium-137 from fission products by a column of Kel-F (polytriffuorochloroethylene) supporting dipicrylamine is described, The average recovery ,of cesium is 99.95 yO & 0.31 y0 and the decontamination factors are greater than IO3; the column can be regenerated and used for more than 15 consecutive cycles. REFERENCES I’C. CESARANO, G. PTJGNETZX AND C. TESEA,J. Chromatog., Ig (1965) 589. 2 M. KYRS, J. PERCZK AND I?.POLANSKY, Collectiofl Cxmh. Chem. Commun., 25 (Ig6o) 2642. 3 L. ,A. BRAN AND F. P. ROBERTS, U.S. At. Energy Comm., HW-76222 (rg63). 4 L. E. GLXENDENIN AND C. M. NELSON, PevchZovale Methodfov the Detevmination of Cesiwm Activity in Eissio~ Pvoduck, National Nuclear Energy Series, Div. IV, Vol. g, McGraw Hill, New York, 1931, pp. 1642-3645. J. Chomatog.,
rg (1965)
5g+sg8