JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Alpha-radiolysis of Organic Extractants for
Separation of Actinides
Y. Sugo a) , M. Taguchi b) , Y. Sasaki a) , K. Hirota b) and Y. Morita a)
a) Division of Fuels and Materials Engineering, NSED, JAEA,
b) Environment and Industrial Materials Research Division, QuBS, JAEA
1. Introduction
Alpha-radiolysis study of organic extractants for the
separation of actinides using an actinide radionuclide has
some experimental problems as follows; a long-term
exposure to actinides is required, and the extractants are
contaminated with the radionuclide. In the previous work 1) ,
these problems were solved by irradiation with helium ions.
It was also found that the radiation chemical yield for the
degradation of N,N,N',N'-tetraoctyldiglycolamide (TODGA)
in n-dodecane by helium ions was less than that by
gamma-rays.
In this study, the influence of coexisting oxygen on the
radiolysis of TODGA was investigated with helium ions
provided by a cyclotron accelerator in the TIARA facility.
2. Experimental
TODGA was dissolved in n-dodecane, and purged with
nitrogen or oxygen gas. The solution was irradiated with
helium ions according to the previous report 2) under various
atmospheres. The irradiated sample was diluted in acetone
containing tri-n-butyl phosphate (TBP), which was used for
the internal standard, and analyzed using a capillary gas
chromatograph (GC) equipped with a flame ionization
detector (FID) or a mass spectrometer (MS).
3. Results and Discussion
The concentration of TODGA in n-dodecane after
irradiation with 48.6 MeV helium ions under air, oxygen,
and nitrogen is logarithmically plotted against dose in Fig. 1.
It was observed the yield for the degradation of TODGA in
the presence of oxygen was slightly less than that in the
nitrogen-saturated system.
Next, a difference in the degradation products according
to the existence of oxygen was examined by GC/MS
Concentration of TODGA
[mmol/L]
10
Air
O
2
N
2
1
0 100 200 300
Dose [kGy]
Fig. 1 Degradation of TODGA in n-dodecane by
irradiation with 48.6 MeV helium ions under various
atmospheres.
JAEA-Review 2010-065
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analysis. Figure 2 shows the changes in gas
chromatograms before and after irradiation under air,
oxygen, and nitrogen conditions. The peaks at the
retention time of 5.6 and 14.2 min are assigned to TBP and
TODGA, respectively. A number of new peaks appeared
after irradiation in the range of 3.9-4.2 and 7.9-9.2 min are
both assigned to the degradation products of n-dodecane.
The former large peaks at 3.9-4.2 min, which are assigned to
the oxidation products of n-dodecane such as ketones and
alcohols, were appeared only in the presence of oxygen.
This result suggests the intermediate species of
n-dodecane such as radical cations are liable to react with
oxygen. It is therefore considered that the yield for the
degradation of TODGA is slightly reduced in the presence
of oxygen.
Relative Intensity
Relative Intensity
Relative Intensity
Relative Intensity
1.0
0.5
0.0
1.0
0.5
0.0
1.0
0.5
0.0
1.0
0.5
0.0
4 6 8 10 12 14
Retention time [min]
4 6 8 10 12 14
Retention time [min]
4 6 8 10 12 14
Retention time [min]
4 6 8 10 12 14
Retention time [min]
Fig. 2 Changes in the gas chromatograms (a) before
and after irradiation under (b) air, (c) O2, and (d) N 2
conditions.
References
1) Y. Sugo et al., Radiat. Phys. Chem., 78(12) (2009)
1140-1144.
2) Y. Sugo et al., JAEA Takasaki Ann. Rep. 2007 (2008)
161.
(a)
(b)
(c)
(d)