Photon Factory Activity Report 2019 #37 (2020)

BL-27B/2018G574

Decontamination of alkali chloride baths containing nuclear material
by precipitation and distillation techniques
Jun-ya Ibe1*, Megumi Aso 1, Masayuki Watanabe 2, Sou Watanabe 2, Youko Takahatake 2,Haruaki Matsuura1
12

Tokyo City University, 1-28-1, Tamazutsumi, Setagaya-ku, Tokyo, 1588557, Japan
Japan Atomic Energy Agency, 2-4, Shirakata, Nakagun, Tokai-mura, Ibaraki, 3191195, Japan

1 Introduction
By the pyro-reprocessing of spent fuel, uranium can beelectrochemically recovered using molten salts. Since
waste salt generated from pyro-reprocessing test contains
uranium can easily capture moisture from the air andcorrode equipment and piping material, further treatment
technology for decontamination and waste stabilization
should be required. The aim of this study is to develop a
simple separation method for decontamination of salts. A
two-step process has been considered. In the first step,oxides are added as oxygen donor in the melts, and thenuranium is separated from the salt as precipitates. In thenext step, melt bath components are evaporated by avacuum distillation.
In this study, LiCl-KCl eutectic and NaCl-2CsCl salts
were used as melt baths, lithium oxide was used as aprecipitant, and cerium chloride was used as uranium
surrogate for testing the precipitation process. The amountand the procedure of addition of the precipitant andreaction condition has been optimized by the aid ofevaluation of chemical status of cerium in the precipitation.

similarity in EXAFS oscillation pattern, as alreadyreported in literature [1]. Amount of the precipitates
increased with increasing the amount of oxide, thus
recovery ratio of cerium must potentially depend on
solubility of oxychloride into the bath salts.
In the future, we will conduct distillation experiments anda detailed study of the evaluation of mass balance in eachsteps and the introduction for efficient salt recovery system
in distillation equipment will be carried out using uranyl
chloride sample for mockup examination.

2 Experiment
5 g of salts and 5 wt% of cerium chloride were added toa quartz cell and melted in an electric furnace in the argon
circulated glove box in the controlled area of the Atomic
Energy Research Lab, TCU. The temperature was set at700 °C for LiCl-KCl eutectic and 800 °C for NaCl-2CsClsalt, respectively.
Next, a continuous addition test was conducted in whichlithium oxide was added chemical stoichiometric amountof Ce in 50% increments up to 200%, and allowed to keepfor 1.5 hours each time, and using a sampling tube,
collected the supernatant bath salt. Batch tests wereconducted in which oxides were added in advance inamounts of 50%, 75%, 100%, 150%, and 200%,respectively..
After the precipitation test, the supernatant was subjected
to ICP-OES and ion chromatography analysis, and theprecipitation was subjected to XAFS analysis. XAFS
measurement was carried out at Energy Accelerator
Research Organization Photon Factory BL-27B, intransmission mode, using Ce-L3 absorption edge.

Fig.1 XANES of the cerium in precipitates generated andcomparative chemical compounds

3 Results and Discussion
As shown in Fig. 1, the valence of the cerium in
precipitates generated is equivalent to 3. As shown in Fig.
2, it is considered that oxychloride was formed by theNaCl-2CsCl C200
LiCl-KCl C200

absorption[a.u.]

CeOCl
CeO2
CeCl 3

5.7

5.725 5.75 5.775
photon energy[keV]

5.7
5.8

5.725 5.75 5.775
photon energy[keV]

CeOCl Ar
CeO2
CeCl3

FT|x(k)・k3|[arb unit]

NaCl-2CsCl C200
LiCl-KCl C200

012
3R[Å]

450

5.8

123
R[Å]

45Fig. 2 EXAFS structural function of precipitates
generated and comparative chemical compounds
References[1] Yoshiharu Sakamura et al., Central ResearchInstitute of Electric Power Industry Research Report
T96073 (1996) p.7*g2081802@tcu.ac.jp, hmatuura@tcu.ac.jp