Photon Factory Activity Report 2004 #22 Part B (2005)
Chemistry

27B/2004G064

Chlorination of polyvalent metal oxide in molten salts
Yoshihiro OKAMOTO*1, Tsuyoshi YAITA1, Kazuo MINATO1, Noriko USAMI2,Katsumi KOBAYASHI2
1
Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki 319-1195, Japan
2
KEK-PF, Tsukuba, Ibaraki 305-0801, Japan

Experimental
The Y K-edge (E0=17.080keV)) XAFS measurementsof Y2O3 and YCl3 were performed in transmission method
at the BL27B station in the KEK-PF. The Zr K-edge(E0=17.998keV) XAFS data was also obtained byextending the Y K-edge XAFS measurement. Thestarting sample was a mixture of Y2O3-ZrCl4(1:2) in LiClKCl eutectic. The samples were sealed off in a quartz cellunder reduced pressure.
Details of the XAFS
measurement of molten salts are described in ref.[2]. The
XAFS data was analyzed by using WinXAS code[3].
Results and discussions
Fig.1 shows raw XAFS spectra of the LiCl-KCl-Y2O3ZrCl4 mixture sample before and after heating. There are
two XAFS data in each curve. They are Y K-edge and ZrK-edge(E0=17.998keV) XAFS, respectively. The Y Kedge XAFS curve before heating is clearly different fromthat after heating. An edge jump of the Zr K-edge XAFS

Absorbance, µt

0.8became very weak after the heating. It suggests that Y2O3
changed to YCl3 and ZrCl4 disappeared by the heating.
3Fourier transform magnitude functions |FT(k χ(k)| ofthe mixture sample before and after heating are shown inFig.2. Chemical state of Y can be evaluated fromdifference in the distance between Y-O and Y-Clcorrelation. At 500°C, the Y-O correlation is predominant,although the sample is in molten state. On the other hand,the 1st peak shows the Y-Cl correlation at 550°C. It canbe concluded that the reaction occurs between 500 and550°C. The XAFS result after cooling to 500°C wasalmost the same as that of LiCl-KCl-YCl3 mixture melt[4].
0.5
Y-O Y-Cl

0.4(1) before heating|FT(k3χ(k)|Introduction
In the pyrochemial reprocessing of spent nuclear fuels,chlorination of polyvalent oxides like UO2 etc. is an
important reaction. Recently, a chlorination reaction
using ZrCl4 with LiCl-KCl eutectic melt was proposed by
Sakamura et al.[1]. For example, the chlorination ofyttrium oxide is expressed as following chemical reaction,
Y2O3 + (3/2)ZrCl4 → 2YCl3 + (3/2)ZrO2
It is very significant to know nature of the chlorination
reaction, for example, a temperature dependence etc. In
the present work, the chlorination reaction of Y2O3 wasobserved by using in situ XAFS measurement.

0.3(2) heating to 500°C0.2(3) heating to 550°C

0.1(4) cooling to 500°C0012r(Å)

3Fig.2 Fourier transform magnitude |FT(k χ(k)| of theLiCl-KCl-Y2O3-ZrCl4 sample before and afterheating. Dashed line shows XAFS result of molten
15%YCl3 in LiCl-KCl eutectic[4].
3after
heat

0.6
be0.4

ing
foreheat ing

Y K-edge

17Zr K-edge

18E(keV)

19Fig.1 Raw XAFS spectra of the LiCl-KCl-Y2O3-ZrCl4
sample before and after heating.

References[1]Y.Sakamura et al., J.Nucl.Mater., 340(2005)39.
[2]Y.Okamoto et al., Nucl.Inst.Meth.Phys.Res. A, 487(2002)605.
[3]T.Ressler, J.Synchrotron Rad., 5(1998)118.
[4]Y.Okamoto et al., J.Synchrotron Rad., 8(2001)1191.
* okamoto@molten.tokai.jaeri.go.jp

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