Photon Factory Activity Report 2022 #40 (2023)

BL-27B/2020G606, 2022G618

XAFS analysis on manganese in molten salt precipitation method
Yuri YAMAMOTO1,*, Youko TAKAHATAKE2, Sou WATANABE2 Masayuki WATANABE2and Haruaki MATSUURA1
1
Tokyo City University, 1-28-1, Tamazutsumi, Setagaya-ku, Tokyo, 158-8557, Japan
2
Japan Atomic Energy Agency, 2-4, Shirakata, Nakagun, Toukai-mura, Ibaraki, 319-1195, Japan

3 Results and Discussion
Figure 1 shows the EXAFS radial structure functions ofthe precipitate, and Figure 2 shows the XANES spectra.
The EXAFS radial structure functions of the sediments
have very close feature of that of manganese(II) oxide thanto manganese(II) chloride. From this fact, it can be seenthat the added manganese(II) chloride was precipitated asan oxide due to the reaction with lithium oxide. Also, theXANES spectrum confirmed that the precipitate wassimilar to the manganese oxide. This indicates that the024R [Å]

6MnCl2
MnO
Li-K precipitate
Na-Cs precipitate

FT|χ(k)・k3| [a. u.]

FT|χ(k)・k3| [a. u.]

MnCl2
MnO
Li-K precipitate
Na-Cs precipitate

8024R [Å]68Figure 1 EXAFS radial structure functions ofprecipitates generated by 1.5 and 2 times larger molar
amount of Li2O to chemical stoichiometric MnCl2

6.53

MnCl2MnO
Li-K precipitate
Na-Cs precepitate

6.54
6.55
6.56
Photon energy [keV]

Absorbance [a. u.]

2 Experiment
A mixture of LiCl-KCl eutectic composition salt or
NaCl-2CsCl salt, manganese(II) chloride and lithium oxide
was placed in a quartz tube in a glove box. Manganese (II)chloride was added at 10wt% to the bath salt, and lithiumoxide was added at a stoichiometric amount of 150% or
200% to the amount of manganese. The prepared samples
were melted at 700°C for LiCl-KCl bath and 800°C for
NaCl-2CsCl bath for about 4.5 hours using an electric
furnace in a glove box. After heating, the sample wassolidified together with the quartz tube, and salt bath andsediment were separately collected. In this study, only abatch test was conducted in which a precipitant was added
in advance before molten.
The collected sample was pulverized and mixed withboron nitride. The mixture was divided into 80 mg and 120
mg and subjected to XAFS measurement by thetransmission method at Photon Factory BL-27B of KEK.
The EXAFS radial structure function and XANES spectra
were analyzed by the measured data, and the coordination
structure and valence of the precipitates were investigated.

precipitate is divalent. Even though manganese(II)chloride is melted after adding lithium oxide, it precipitates
as a divalent oxide with the same valence.

Absorbance [a. u.]

1 Introduction
The spent salt bath generated in the research anddevelopment relating to the pyro reprocessing method ofspent fuel has a risk of residual unrecovered nuclear fuelmaterial and corrosion of equipment and piping due tochloride ions. Therefore, appropriate processing isrequired. In research on the process development of saltbath, analogous simulants are used as substitutes fornuclear fuel materials. However, the cerium used in theprevious research has a lower valence than the uranium inthe actual bath salt, and is less likely to form an oxyanion.
Therefore, the nuclear fuel material cannot be fully
simulated. Based on the above discussion, we focus on
manganese alternatively, which exists up to 7 valences, andcompare it with cerium by conducting the same experiment
procedure as in the previous research [1].

6.57 6.53

MnCl2
MnO
Li-K precipitate
Na-Cs precipitate

6.54
6.55
6.56
Photon energy [keV]

6.57

Figure 2 XANES spectrum of the manganese inprecipitates generated by 1.5 and 2 times larger molar
amount of Li2O to chemical stoichiometric MnCl2
Acknowledgement
This research is part of the results of joint research withTokyo City University and Japan Atomic Energy Agency.
References[1] Jun-ya Ibe et al. Decontamination of alkali chloride
baths containing nuclear material by precipitationand distillation techniques ~distillation experiment~.
Atomic Energy Society of Japan Fall Meeting. 2021,
3B05,* g2381815@tcu.ac.jp