Photon Factory Activity Report 2017 #35 (2018)

BL-27B/2017G081

Structural Analysis of Waste Generated by Pyroprocess in Iron Phosphate GlassYuri Tajimi 1, Hirohide Kofuji 2, Sou Watanabe 2, Tetsuji Yano 3, Rikiya Kado 3,Takuhiro Miyawaki 3, Motoshi Iwanaga 3, and Haruaki Matsuura 1
1

Cooperative Major in Nuclear Engineering, Tokyo City University, 1-28-1, Tamazutsumi,Setagaya-ku, Tokyo, 1588557, Japan
2
Japan Atomic Energy Agency, 2-4, Shirakata, Nakagun,Toukai-mura, Ibaraki, 3191195, Japan
3
Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo, 1528552, Japan
1 Introduction
For the vitrification of high-level radioactive wastefrom pyroprocess, fission products are separated fromspent salt as phosphates and the rest of them is vitrified asiron phosphate glass. The glass has high affinity tocontain waste salts as main constituents of glass. This fact
attracts attention to this system as suitable vitrification
media, because this glass system is also known to havehigh loading capacity of nuclear wastes.
Among fission products, zirconium has been considered
to be difficult to dissolve into iron phosphate glass.
According to the previous study, Zr ions in glass arestabilized by the coexistence of alkali ions, Cs2O, whichis also one of radwastes generated from the nuclear powerplant. Moreover, the chemical stability of the glasses
depends in the concentration of these waste elements. [1]In this study, the coordination structure around the Zrand Cs atoms in iron-phosphate glass have been evaluatedby EXAFS structural analysis of the glass samples withdifferent Cs2O concentration in order to clarify the role ofthese elements in the glass properties.
2 Experiment2 mass% of ZrO2 with 2, 4, 8 and 16 mass% of Cs2O,
as well as 4 mass% of ZrO2 with 0, 2, 4, 8, 16, 25 and 40
mass% of Cs2O were added to the iron phosphate glass
matrix i.e., 1Cr2O3-3(CoO)2-4.5Al2O3-28Fe2O3-65P2O5(in mol%). EXAFS measurement of these samples havebeen carried out by transmission or fluorescence mode atKEK.
The obtained data have been analysed by EXAFS
analysis program WinXAS version 3.02. An EXAFS
oscillation was extracted using the cubic spline methodand the structure function was obtained by the Fouriertransformation. Structural parameters were derived fromfitting based on EXAFS equation.
3 Results and Discussion
In the EXAFS oscillation of Zr, there is no remarkable difference depending on ZrO2 concentration. Zr-O distanceshows certain dependency on Cs2Oconcentration below
16 mass%. When Cs2O concentration is higher than 16mass%, oscillations become identical.

It is considered that the influence of Cs addition on thelocal structure of Zr almost disappears at high Cs2O
concentration region more than 16 mass%.
EXAFS analysis of Cs shows that the distance of thenearest neighbor (Cs-O) gradually becomes shorter withincreasing Cs2O concentration. Particularly in the case ofthe glasses with 2 mass% of ZrO2 concentration, Cs-O
peak shifted greatly between 8 and 16 mass% of Cs2O
concentration. In the case of 4 mass% of ZrO2 glasses,
the great shift is found between 16 and 25 mass% of Cs2Oconcentration. It can be said that local structural
correlation between Zr and Cs exists in iron-phosphateglass, which is related to the solubility and stability of Zrand Cs in this glass system.

Fig. 1: EXAFS oscillations of Zr in iron phosphate glasses
with various Cs2O concentration（0, 2, 4, 8, 16, 25, 40 mass%）.

4 SummaryCorrelation of local structure between Zr and Cs exists
in iron-phosphate glass at structural variation of Zr-O
coordination below 16 mass% of Cs2O concentration.
.
References[1] T. Yano, T. Kishi, Y. Nakata, H. Kofuji, M. Takeuchi, Proc.
of ICG2015, Bangkok, 2015

* g1781010@tcu.ac.jp