Nuclear Techniques ›› 2019, Vol. 42 ›› Issue (7): 0-070101-7.doi: 10.11889/j.0253-3219.2019.hjs.42.070101

• SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS •    

Lattice modification of U3O8 matrix induced by cerium substitution

Hanjie CAO1,2,Hongliang BAO1,Haisheng YU1,Yuying HUANG1,3(),Jianqiang WANG1()   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
  • Received:2019-03-05 Revised:2019-04-28 Online:2019-07-10 Published:2019-07-16
  • Contact: Yuying HUANG,Jianqiang WANG E-mail:huangyuying@sinap.ac.cn;wangjianqiang@sinap.ac.cn
  • About author:Fisrt author: CAO Hanjie, male, born in 1991, graduated from University of Science and Technology of China in 2014, doctoral student, focusing on the applications in inorganic chemistry by XAFS technique
  • Supported by:
    Supported by National Natural Science Foundation of China(No.U1532259, No.21701183, No.11175244)

Abstract: Background

Cerium is one of the important products of the mixed oxide (MOX) reaction, and CeO2 forms U1- x Ce x O2 solid solution with UO2. In the post-treatment of spent fuel, UO2 may be oxidized to U3O8 resulting in an increase in spent fuel volume. The structure and volume of spent fuel are concerned with the solubility, valence and electronic structure of uranium-cerium solid solutions.

Purpose

This paper aims to study the local structure of Ce-substituted U3O8 by X-ray absorption fine structure (XAFS) technique.

Methods

First of all, (U1- y Ce y )3O8- δ (y=0, 0.05, 0.20) mixed oxides were prepared by coprecipitation method. Then, powder X-ray diffraction (XRD) and X-ray absorption fine spectroscopy (XAFS) characterizations at U L3 edge and Ce K edge have been undertaken to study the chemical changes of uranium-cerium oxides.

Results

The XRD data shows that the Ce-substituted U3O8 has the P 62 ˉ m space group which is different with α-U3O8. The U L3-edge X-ray absorption near edge structure (XANES) data of Ce-substituted U3O8 shows a slight increase in the uranium average valance. The X-ray absorption near edge structure (EXAFS) data shows that the neighboring atoms of Ce cations are far away from those of U cations.

Conclusions

The Ce cations replaced the U site in U3O8, and the U3O8 sample was changed from the original C2mm to P 62 ˉ m space group. The lattice volume was increased and the local structure around U cation was changed by adjusting the atomic distance and increasing the valence of U.

Key words: Synchrotron radiation X-ray absorption fine structure, Cerium doping, Uranium oxide, Local structure

CLC Number: 

  • TL99