Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 47 (2014)

Recovery of 248 Cm material from mixed Cm/Gd target
M. Murakami∗1,∗2 and H. Haba∗1∗1∗2

was fed to elute 153 Gd completely. The flow rate was
230–240 µL/min at room temperature. Each 1 mL ofthe effluent was collected in a separate PP tube andsubjected to γ-ray spectrometry at fixed geometry.
Figures 1(a)–(d) show the elution curves of the multitracer with 0.2, 0.3, 0.4, and 0.5 M HNO3 as the second eluent. 133 Ba was eluted with 5 mL of 0.1 M HNO3
with a recovery of 100.3 ± 2.5%. 30 mL of 0.2 M HNO3
(Fig. 1(a)) was used to elute 139 Ce and then 143 Pm, as
expected from the difference in the Kd values.5) 145 Sm
and 153 Gd were not eluted in these fractions. Owing to
the increase in the concentration of the second eluent,
the peaks of the elution curves of 139 Ce and 143 Pm get
shifted to lower volumes and approach to each other.
In the case of 0.5 M HNO3 , 6.2 ± 0.6% of 153 Gd waseluted until 139 Ce was completely eluted. Since Cm
is expected to be found between Ce and Pm from theorder of the Kd values,5) Cm and Gd can be separated
with the schemes shown in Fig. 1(a)–(c). However, thescheme shown in Fig. 1(a) takes a large amount of eluent, and in the case of 0.4 M HNO3 , the condition forseparation is stricter than that in the case of 0.2 M and0.3 M HNO3 , owing to the close peaks of the elution
curves. Therefore, we selected the scheme in Fig. 1(b)for the separation of 248 Cm and nat Gd.
By applying the scheme of Fig. 1(b) to the purification of 830-µg 248 Cm target material containing nat Gd(about 10 wt%), 99.3 ± 4.1% of 248 Cm was collectedin the fraction of the 12-mL 0.3 M HNO3 solution.

Recovery (%)

In the chemical experiments on superheavy elements(SHEs), the lighter homologue elements in the periodic
table are simultaneously produced, and their chemical behaviors are compared to those of SHEs underidentical experimental conditions. For this purpose, amixed 248 Cm/Gd target deposited on a thin metallic
backing foil has been often used.1,2) The target as wellas the backing material are gradually damaged by theirradiation with the intense heavy-ion beams. Since
the available amount of 248 Cm is limited, its recovery, which involves purification from the used target,
is essential to produce a new target.
Bis(2-ethylhexyl)phosphoric acid (HDEHP) is one of
the widely used extractants for separating lanthanide
ions.3) Separation of lanthanide and actinide throughextraction chromatography using an HDEHP-laden
resin has been studied.4,5) Using the HDEHP resin,
one can perform stepwise separation of lanthanide andactinide elements by simply changing the concentration of the HNO3 eluents. The distribution coefficients(Kd ) of these elements strongly depend on the HNO3
concentration: The Kd values for +3 ions are inverse
third power dependent on the mean activity of the hydrogen ion.4) Therefore, in this work, we investigatedseveral schemes to effectively separate Cm and Gd withthe HDEHP resin using a multitracer of lanthanide elements. Further, we separated the 248 Cm material fromnat
Gd with the optimized scheme.
The commercially available Ln Resin (Eichrom), theHDEHP-laden hydrophobic resin with the particle sizeof 100–150 µm, was packed into a polyethylene column(5 mm i.d. × 50 mm height; column volume: ≈1 mL).
The multitracer was produced by bombarding a nat Hftarget with a 135-MeV/nucleon 14 N beam from theRIKEN Ring Cyclotron. After the irradiation, the rareearth elements were separated from the target materialby an establised procedure, detailed in Ref. 6. The
multitracer including 133 Ba, 139 Ce, 143 Pm, 145 Sm, and153
Gd in 0.1 M HNO3 was stocked in a polypropylene(PP) tube. The Kd values are reported to be in theorder Ba  Ce < Cm < Pm < Sm < Gd in the Ln
Resin–HNO3 system.5) After the conditioning of thecolumn with 3.0 mL of 0.1 M HNO3 solution, 1 mLof the stock solution was loaded onto the column. 4mL of 0.1 M HNO3 was then fed onto the column asa first eluent. According to the reported Kd values,5)most of the +1 and +2 metal ions such as 133 Baelute in this fraction. As a second eluent, 0.2–0.5 M
HNO3 solutions were fed until 143 Pm was completely
eluted from the column. Finally, 6 mL of 1.0 M HNO3RIKEN Nishina Center
Department of Chemistry, Niigata University- 277 -100

0.1 M 0.2 M

50

139

0133

0133

5000145

Ce

143

100.1 M

100153

Ba

Pm

1.0 M
Gd(a)

2030

0.3 M
139

Ba

5Ce40
1.0 M
153

143

Pm

10145

1330Gd

200Ce

1.0 M
143Pm

145

153

SmGd(c)5100.1 M
13350(b)0.4 M
139Ba0100

Sm150.1 M

100
50Sm0.5 M
143

Ba139015Pm
145Ce

5201.0 M
Sm153

Gd(d)

1015

Volume (mL)

133

Fig. 1. Elution curves ofBa, 139 Ce, 143 Pm, 145 Sm, and153
Gd. The concentrations of the second eluents are (a)0.2 M, (b) 0.3 M, (c) 0.4 M, and (d) 0.5 M.

References
1) K. Tsukada et al.: Radiochim. Acta 97, 83 (2009).
2) Z. J. Li et al.: Radiochim. Acta 100, 157 (2012).
3) S. Cotton: Lanthanide and Actinide Chemistry (JohnWiley & Sons, 2006).
4) E. P. Horwitz et al.: J. Inorg. Nucl. Chem. 31, 3255
(1969).
5) E. P. Horwitz and C. A. A. Bloomquist: J. Inorg. Nucl.
Chem. 37, 425 (1975).
6) Y. Ezaki et al.: J. Nucl. Radiochem. Sci. 10 Suppl., 123(2009) (In Japanese).