Photon Factory Activity Report 2017 #35 (2018)

BL-27B/2017G623

XAFS measurement on radioactive waste simulants in various disposal glasses
Kei Shiina1, Yuri Tajimi1, Takafumi Uchiyama1, Toshiaki Kakihara2, Yasutomo Tajiri2,and Haruaki Matsuura1
1

Cooperative Major in Nuclear Engineering, Tokyo City University,
1-28-1, Tamazutsumi, Setagaya-ku, Tokyo, 1588557, Japan
2IHI Corp, 1, Shin-nakahara-cho, Isogo-ku, Yokohama, 2358501, Japan

2 Experiment
1 g of various glass samples with different Si/B ratio,
alkali and alkaline earth metal contents, which also
contained all simulated waste liquid components, werepulverized. These samples were installed in-between two
alumina plates with 0.5 mm gaps. An alumina cell wasinstalled in an electric furnace placed in-between two ion
chambers to obtain the EXAFS oscillation in the moltenstate, i.e.at 1200 oC and 800 oC. EXAFS oscillation atroom temperature has been also collected. The obtained
data has been analyzed by the program of WinXAS
version 3.02. An EXAFS oscillation was extracted using
the cubic spline method and the structure function wasobtained by the Fourier transformation. Structuralparameters were derived from fitting based on EXAFS
equation.
3 Results and Discussion
Comparing the EXAFS oscillations at the molten state
and those at room temperature, it can be considered thatthe glass having a small deviation in the distance between
Mo - O would be a stable glass from local structural pointof view. Since the glass at high temperature has adisordered structure, the peak becomes small. The
structural functions of glasses containing both Ca and Mg
have been modified significantly depending ontemperature. On the other hand, samples containing single
alkaline-earth element have larger temperaturedependency than those containing double elements.

0.3

FT|x(k)・k3|[arb unit]

1 Introduction
In Japan, high-level radioactive liquid waste generated
from reprocessing of spent nuclear fuel is planning to bemixed with glass matrix, filled in a stainless steel canister,cooled down well and put into deep disposal site. At themoment, borosilicate glass is considered to be one of thebest candidates of vitrified glass. Furthermore, in order toreduce the cost required for stable preserving vitrified
glass for a long period, there is a demand for a techniquefor increasing packing ratio of wastes in the vitrified glass.
In this case, molybdates tend to crystallize out fromvitrified glass as a yellow phase (YP) and may affecthomogeneity of vitrified glass. Therefore, in order toinvestigate the optimum composition ratio of vanadiumadded borosilicate glass [1,2] which is supposed to suppress
YP generation in the case of highly molybdenum filled, Si/ B ratio, the alkali content, the alkaline earth metal
content have been modified and the local structuralchange around molybdenum and zirconium in simulated
glass has been evaluated by the EXAFS analysis.

0.2
RT800℃

0.1

1200℃
001

23
R[Å]

45Fig.1 Structural functions of Mo-O depending on theaddition of both Mg and Ca.
4 Conclusion
Since the oxygen coordination number of Mo did notchange, it does not contribute to the matrix network
structure of glass. Also the alkaline-earth metal plays arole of charge compensation, and it becomes more stable
glass with double elements addition. By evaluating thelocal structures of molten and solidified glass, it can makeclarify the guidelines of searching optimum glass
composition.
References[1] T. Nabemoto, T. Oniki., Molten salt and hightemperature chemistry, 59, 20-24 (2016).
[2] H. Kawashima, T. Hashimoto, T. Kakihara, T. Fukui
The fall meeting of the Atomic Energy Society ofJapan, 1E03 (2016).
* g1781008@tcu.ac.jp