Photon Factory Activity Report 2005 #23 Part B (2006)
Chemistry

27B/2006G090

XAFS measurement on molten chlorides containing yttrium chloride
1Haruaki MATSUURA*1, Yoshihiro OKAMOTO2Res. Lab. for Nucl. Reactors, Tokyo Tech., Ookayama, Meguro-ku, Tokyo, 152-8550, Japan
2Synchr. Rad. Res. Center, JAEA, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan

Introduction
During the course of development of pyrochemical
reprocessing of oxide nuclear fuels, one of the several
critical issues is how to make realization of the uraniumplutonium oxides (MOX) co-electrodeposition process.
To electrodeposit MOX fuel effectively, one has to clarify
the relationship between local structure around actinide
species and electrochemical behaviour depending uponchlorine – oxygen gas ratio, melt bath composition,
temperature, co-existing fission and cladding elements etc.
In a real process, these materials are usually diluted inmolten chloride baths. In such condition, the localstructure around rare earths depending upon various meltbaths should be much importantly evaluated. First, wehave targeted yttrium in molten alkali chlorides before
using actinide compounds because rare earths have beenutilized as prototypes of actinides in some cases ofelectrochemical studies.

(xYCl3=0.1). Due to large amount of co-existence of high
X-ray absorbing atom, i.e. Cs, we have only choice offluorescence mode. Figure1(a) and (b) show extracted
χ(k) XAFS spectra of solid and molten samples,
respectively. We have tested fluorescence measurement
using yttrium water solution with quartz containers andthe same furnace several times beforehand, but luckily,
even in molten phase at high temperature, we haveobtained one of the best spectra ever. As shown in Fig. 1(a), we have obtained well recognizable oscillation until
15 Å-1. Probably this would be the first time of obtaining
excellent resolution data of fluorescence XAFS spectra inmolten phase at high temperature. The local environment
around a rare earth ion in various melt composition andelements can be evaluated by this way, thus thesetechniques are applicable to arrange new processes inpyrochemical treatment for not only oxide fuels but also
another compound types of nuclear fuels.

Experimental
The YCl3 with various melt baths were prepared in adried argon circulated glove box. A certain amount of thesamples were sealed in specially designed quartz cells.
The electric furnace used was the similar to that originallydesigned for the laboratory XAFS equipment, but slightly
modifying to improve thermal homogeneity as well as
vacuum tightness. We have carried out the XAFS
measurement of yttrium chlorides and mixture with alkali
chlorides at molten and solid phases, using Si (111)
double crystal monochromator at Y-K X-ray absorption
edge.
Results and discussion
These quartz cells have successfully sealed the samples
during performing the experiments at high temperaturesin whole experiments, thus this type of confinement
would be transferable to perform XAFS measurement on
actinide compounds in molten state. XAFS spectra ofboth molten and solidified NaCl-KCl (1:1molar ratio) –YCl3 (xYCl3=0.5, 0.1, and 0.01) have been obtained usingtransmission mode. Similar to the results on pure YCl3
and LiCl-KCl (eutectic)-YCl3 [1], phase shift in XAFS
spectra between solid and molten phases are relativelysmall, as compared to LaCl3 and its alkali chloride
mixtures cases. These facts imply that the local
environment around a yttrium ion in molten states does
not drastically change from that in solid phases, i.e., 6coordinated structure. The most striking result isperforming SSD fluorescence XAFS measurement formolten NaCl-CsCl (1:2 molar ratio) – YCl3 mixture

Fig. 1(a), (b) Extracted oscillation of fluorescence
XAFS of NaCl-CsCl (1:2 molar ratio) – YCl3mixture.
References[1] Y. Okamoto et al., J. Synchr. Rad. 8, 1191 (2001).
*hmatsuur@nr.titech.ac.jp

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