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Stability of Novel Cyclic Monoamide Extractants for U(VI)against γ-Ray Irradiation in HNO3

Graduate School of Science and Engineering Research,Kinki University
1

Faculty of Science and Engineering, Kinki University
Research Reactor Institute, Kyoto University

2INTRODUCTION: Uranium is the predominantly major
component of spent fuels, and extractants with high selectivity and capacity to U(VI) and radiation stability innitric acid media are desired in the world. Monoamide
extractants have been studied for the purpose due to very
little generation of the secondary waste resulting from thespent extractants. Above all, “branched monoamodes”
have been studied almost exclusively so far, probably
because of relatively easy synthesis[1]. On the other hand,extensive studies on pyrrolidone and its related derivatives,
which are categorized into “ring monoam-ides”, convinced
us that some ring monoamides with high symmetry would
exceed branched monoamodes on the above-mentioned
properties[2,3]. Based on the back-ground, we focused on
1,3-dialkyl-2-pyrrolidone (DRP) (Fig. 1). In this study,
fundamental stability of two DRPs, 1,3-dibuthyl-2pyrrolidone (DBP) and 1,3- dihex-yl-2-pyrrolidone (DHP),against γ-ray irradiation was investigated.

3 M HNO3 (Fig. 2(a)), the residual ratios calculated
through (A) to (C) in DHP show an identical trend, where
nearly no decomposition occurred after irradiation at ca.
0.8 MGy. This suggests that the stability of DHP in 3 M
HNO3 is better than that of water-soluble N-butyl- pyrrolidone (NBP) with the residual ratio of ca. 85 % at 0.8
MGy, although the solution conditions of both compounds during irradiation are different in a precise sensewith each other[3]. On the other hand, for the sample
irradiated in 6 M HNO3 (Fig. 2(b)), the calculated residual ratios were found to differ depending on the position ofhydrogen atom in DHP. While the residual ratio calculated from hydrogen of the side chain (A) remains nearly
100 % after irradiation at ca. 0.75 MGy, those calculated
from hydrogen in the ring ((B) and (C)) decrease down to40 through 60 %. The residual ratios of ca. 50 % werein accordance with the results for NBP. These facts indicate that DHP possesses satisfying radiation stability ataround 3 M HNO3. Further detailed investigations areongoing.
Residual ratio / %Y. Uemoto, Y. Makino1, K. Matsumoto1, M. Nogami1 andN. Sato2

10080ABC

60
40
0.0(a)
0.2

0.4
0.6
Dose / MGy

O
R'

0.8

1.0

R
Residual ratio / %N(R, R’: hydrocarbon group)
Fig. 1. Chemical structure of DRP.
EXPERIMENTS: DBP and DHP were synthesized bymodifying the method shown in the reference[4]. For
the sample for γ-ray irradiation to DBP and DHP, solutions consisting of 30 vol% DBP or DHP in n-dodecane
as the organic phase and 3 or 6 mol/dm3 (= M) HNO3 as
the aqueous phase were prepared in a Pyrex tube. Irradiation was carried out by the 60Co source up to 1.14
MGy at room temperature under ambient atmosphere,
similarly to the earlier study[5]. Irradiated samples
were analyzed by 1H NMR. CDCl3 containing a known
weight of TMS which is a standard material was used as
the NMR solvent for the organic phase. The residual
ratio of MEC was calculated by the area ratio of eachsignal with that of TMS.
RESULTS: No distinguished appearance changes wereobserved for the irradiated samples. In a 1H NMR spectrum, neat DRP shows several signals. The calculated
residual ratios for DHP irradiated in 3 and 6 M HNO3 areshown in Fig. 2, respectively, together with the relationship between the position of hydrogen in the structure ofDHP and that of the signal. For the sample irradiated in100AB
C80
60
40
0.0(b)
0.2

0.4
0.6
Dose / MGy

0.8

1.0(A)(A)(B) (C)

Fig.2. Dependence of residual ratio of DHP on dose;(a) 3 M HNO3, (b) 6 M HNO3.
REFERENCES:[1] S. Suzuki, et al., Proc. ATALANTE 2004, Nimes,France (2004), P1-63 (CD-ROM).
[2] M. Nogami, et al., Prog. Nucl. Energy, 53 (2011)948-951.
[3] M. Nogami, et al., Sci. China Chem., 55 (2012)
1739-1745.
[4] K. Matsui, et al., JP1990-017128 (1990).
[5] T. Nishida, et al., KURRI Progress Report 2013(2014) 295.

27057

- 100 -Search for the Ultraviolet Photons Emitted from 229mTh in its Deexcitation ProcessGraduate School of Science, Osaka University
Research Reactor Institute, Kyoto University

1INTRODUCTION: Thorium-229m lies in the first excited state of the 229Th nucleus and this excitation energy
is extremely low to be 7.8 ± 0.5 eV [1] corresponding tovacuum ultraviolet (VUV) photon of which the wavelength is about 160 nm. Thorium-229m is expected todecay by the gamma transition and/or the internal conversion (IC) process. Because its excitation energy value
is in the same energy scale with that of the chemical bond,229m
Th would decay by IC process in some chemicalforms and in the other forms, the IC may be hindered.
Consequently, the decay process of 229mTh is able to varydepending on its chemical form. This phenomenon is
unique to 229mTh and makes 229mTh nucleus very fascinating. Recently, photon emissions from the 229mTh sample implanted into MgF2 glass were reported and its
half-life was evaluated to be about 6 h [2]. However, it iscontroversial [3]. In our study, the results of the photon
detection for the hydroxide and fluoride precipitates of229m
Th grown for 2 h or 13 h were previously reported[4]: decaying photons were observed for 13-h growthsamples. Here, the results of the photon detection for the229m
Th precipitates after purified and the 229mTh samples
implanted into the MgF2 glass are reported.
EXPERIMENTS: Thorium-229m precipitated samples
were prepared by the method reported previously [4]. In
this study the additional procedure to purify the 229mTh
was performed before 229mTh was coprecipitated with Sm,
assuming that the half-life of 229mTh would be long: about
several hours. After 229mTh was separated from 233U, the229mTh eluent was heated to dryness. Then, 8 M HNO3solution was added and 229mTh was adsorbed on the anion-exchange resin (Muromac 1×8 200-400 mesh, 1 mL).
The daughter nuclides of 229Th were removed by pouring
8 M HNO3 solution. After that, 2 M HCl solution waspassed through the 229mTh column and 229mTh was eluted.
In the case of the 229mTh samples implanted into MgF2glass, 229mTh was collected as the recoil product from theelectrodeposited sample of 233U in vacuum.
RESULTS: On the results of the photon detection forthe 229mTh samples after purified, there was no decaying
photon emission. In addition, on the result of thelong-time measurement, the count rate of photons increased as time passed. This result is shown in Fig. 1.
These growing photons agreed with the growth of thedaughter nucleus 212Bi. Taking into account the result inref. 4, we concluded that no significant photons from229m
Th were observed although we used about 200 mg of233
U: this amount was about 400 times larger than that in
the study in ref. 2.
Because in the experiment on the 229mTh precipitates,

VUV photons deriving only from the daughter nuclides
were observed, we measured the photons emitted fromthe same 229mTh samples as those in ref. 2 to search thephotons derived from 229mTh in MgF2. On the result of
the MgF2 glass samples, decaying photons probablyoriginating from multiple components including thedaughter nuclides were observed. This result is shown inFig. 2. We are precisely analyzing these data to elucidate
these origins.
2Count rate [cps]Y. Yasuda, Y. Kasamatsu, Y. Shigekawa, T. Ohtsuki1,K. Takamiya1 and A. Shinohara●：229m Th sample―：212 Bi growth…：Background1002
3
Time [s][×105]
229m
Fig. 1. The photon count for theTh precipitate (hydroxide form) grown for about 13 h. Black dots denotethe photon count rate of the 229mTh sample, solid curve
describes the growth of 212Bi and dotted line describes
the count rate of background.
5Count rate [cps]

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● : 229m Th sample… : Background32
1001
Time [s]2[×106]
Fig. 2. The photon count for theTh implanted into
the MgF2 glass for about 26 h. Black dots denote thephoton count rate of the 229mTh sample and the solid
curve describes the fitted decay curve consisted of two
decaying components: these half-lives are about 10 h
and 7 d.
229m

REFERENCES:[1] B. R. Beck et al., LLNL-PROC (2009) 415170.
[2] X. Zhao et al., Phys. Rev. Lett. 109 (2012) 160801/1-4.
[3] E. Peik et al., Phys. Rev. Lett. 111 (2013) 018901/1.
[4] Y. Yasuda et al., KURRI Progress Report 2014 (2015)
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