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Journal Articles

Electrochemical recovery of Zr and Cd from molten chloride salts for reprocessing of used nitride fuels

Murakami, Tsuyoshi*; Hayashi, Hirokazu

Journal of Nuclear Materials, 558, p.153330_1 - 153330_7, 2022/01

Excess amounts of dissolution agents, CdCl$$_2$$ and ZrCl$$_4$$, are required to dissolve transuranium (TRU: Pu and minor actinides) nitrides into LiCl-KCl melts at the chemical dissolution step, which is the first step in the reprocessing of used nitride fuels. We propose an electrochemical process where the remaining Zr and Cd are recovered from the melts to be recycled as dissolution agents for the chemical dissolution step, leaving TRU in the melts. Since the initial concentration ratio of CdCl$$_2$$/ZrCl$$_4$$ remaining in the melts would depend on the condition of the chemical dissolution step and would vary during the proposed electrochemical recovery process, electrochemical behaviors of Zr and Cd were investigated in LiCl-KCl melts with various concentration ratios of CdCl$$_2$$/ZrCl$$_4$$ at 723 K to confirm the basic feasibility of the proposed process. Potentiostatic electrolysis was performed using a liquid Cd cathode at -1.05 V (vs. Ag/AgCl), which was a more positive potential than the redox potentials of TRU on the liquid Cd electrode. The obtained results showed that the current efficiency for recovering Zr and Cd from the melts was as high as 100% regardless of the CdCl$$_2$$/ZrCl$$_4$$ concentration ratio in the melts.

Journal Articles

Separation behaviors of actinides from rare-earths in molten salt electrorefining using saturated liquid cadmium cathode

Kato, Tetsuya*; Inoue, Tadashi*; Iwai, Takashi; Arai, Yasuo

Journal of Nuclear Materials, 357(1-3), p.105 - 114, 2006/10

 Times Cited Count:90 Percentile:98.63(Materials Science, Multidisciplinary)

Electrorefining in the molten LiCl-KCl eutectic salt containing actinides(An) and rare-earths(RE) was conducted to recover up to 10 wt% An into liquid Cd cathode, which is much higher than the solubility of An in liquid Cd at the experimental temperature. In the saturated Cd cathode, An and RE were recovered to form a compound of the PuCd$$_{11}$$ lattice, MCd$$_{11}$$. The separation factors of RE against Pu were defined as (RE/Pu in the Cd cathode)/(RE/Pu in the salt) and calculated for the saturated Cd alloy including MCd$$_{11}$$. The separation factors for the Cd cathodes were a little larger than the equilibrium values.

Journal Articles

Stability of lanthanide oxides in LiCl-KCl eutectic melt

Hayashi, Hirokazu; Minato, Kazuo

Journal of Physics and Chemistry of Solids, 66(2-4), p.422 - 426, 2005/02

 Times Cited Count:28 Percentile:72.74(Chemistry, Multidisciplinary)

Stability of lanthanide sesquioxides (Ln$$_2$$O$$_3$$; Ln=La, Nd, Gd) in LiCl-KCl eutectic melt is studied. Some lanthanide oxides have been pointed out to form oxide chlorides (LnOCl) in the chloride melts, according to the reaction, Ln$$_2$$O$$_3$$ + 2Cl$$^-$$ = 2LnOCl +O$$^{2-}$$. Equilibrium of the reaction for Ln = La, Nd, Gd in LiCl-KCl eutectic melt were studied. Entire La$$_2$$O$$_3$$ and a part of Nd$$_2$$O$$_3$$ converted to LaOCl and NdOCl respectively, though Gd$$_2$$O$$_3$$ remained with a trace amount of GdOCl for 2wt % of Ln$$_2$$O$$_3$$ in LiCl-KCl eutectic melt. The equilibrium depends on the free energies of formation of the solid compounds, Ln$$_2$$O$$_3$$ and LnOCl, and that of oxide ion (O$$^{2-}$$) in the melt. We derive the chemical potential of the oxide ion from the equilibrium using the reported thermochemical data of Ln$$_2$$O$$_3$$ and LnOCl.

Journal Articles

Electrode reaction of the Np$$^{3+}$$/Np couple at liquid Cd and Bi electrodes in LiCl-KCl eutectic melts

Shirai, Osamu; Uozumi, Koichi*; Iwai, Takashi; Arai, Yasuo

Journal of Applied Electrochemistry, 34(3), p.323 - 330, 2004/03

 Times Cited Count:26 Percentile:52.18(Electrochemistry)

The electrode reactions of the Np$$^{3+}$$/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in LiCl-KCl eutectic melt. It was found that the diffusion of Np$$^{3+}$$ in the salt phase was a rate-determining step in the cathodic reaction when the concentration of NpCl$$_{3}$$ was less than about 1 wt.% and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np$$^{3+}$$/Np couple at liquid Cd electrode at 723, 773 and 823 K were observed more positively than those at Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift would result from a lowering of activity of Np in Cd phase according to the alloy formation of NpCd$$_{11}$$ at 723 K and NpCd$$_{6}$$ at 773 and 823 K. The redox potentials of the Np$$^{3+}$$/Np couple at liquid Bi electrode at 723, 773 and 823 K were more positive than those at Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which would be attributable to a lowering of activity of Np in Bi phase according to the formation of NpBi$$_{2}$$.

Journal Articles

Recovery of U by electrolysis of UN in LiCl-KCl eutectic melts

Shirai, Osamu; Uozumi, Koichi*; Iwai, Takashi; Arai, Yasuo

Journal of Nuclear Science and Technology, 39(Suppl.3), p.745 - 748, 2002/11

no abstracts in English

Journal Articles

Behavior of plutonium and americium at liquid cadmium cathode in molten LiCl-KCl electrolyte

Iizuka, Masatoshi*; Uozumi, Koichi*; Inoue, Tadashi*; Iwai, Takashi; Shirai, Osamu; Arai, Yasuo

Journal of Nuclear Materials, 299(1), p.32 - 42, 2001/10

 Times Cited Count:74 Percentile:97.77(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Electrode reaction of the Np$$^{3+}$$/Np couple in LiCl-KCl eutectic melts

Shirai, Osamu; Iizuka, Masatoshi*; Iwai, Takashi; Arai, Yasuo

Journal of Applied Electrochemistry, 31(9), p.1055 - 1060, 2001/09

 Times Cited Count:20 Percentile:47(Electrochemistry)

no abstracts in English

Journal Articles

Recovery of Neptunium by electrolysis of NpN in LiCl-KCl eutectic melts

Shirai, Osamu; Iizuka, Masatoshi*; Iwai, Takashi; Suzuki, Yasufumi; Arai, Yasuo

Journal of Nuclear Science and Technology, 37(8), p.676 - 681, 2000/08

no abstracts in English

Journal Articles

Electrolysis of plutonium nitride in LiCl-KCl eutectic melts

Shirai, Osamu; Iwai, Takashi; Shiozawa, Kenichi; Suzuki, Yasufumi; Sakamura, Y.*; Inoue, Tadashi*

Journal of Nuclear Materials, 277(2-3), p.226 - 230, 2000/02

 Times Cited Count:23 Percentile:81.29(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Development of plutonium recovery process by molten salt electrorefining with liquid cadmium cathode

Iizuka, Masatoshi*; Uozumi, Koichi*; Inoue, Tadashi*; Iwai, Takashi; Shirai, Osamu; Arai, Yasuo

Proceedings of 6th International Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation (CD-ROM), p.327 - 341, 2000/00

no abstracts in English

Journal Articles

Studies on pyrochemical reprocessing for metallic and nitride fuels; Behavior of transuranium elements in LiCl-KCl/liquid metal systems

Sakamura, Y.*; Inoue, Tadashi*; Shirai, Osamu; Iwai, Takashi; Arai, Yasuo; Suzuki, Yasufumi

Proc. of the Int. Conf. on Future Nuclear Systems (GLOBAL'99)(CD-ROM), 8 Pages, 1999/00

no abstracts in English

Journal Articles

Molten salt electrolytes for high energy density cells

; H.Shimotake*

New Mater.New Processes, 2, p.283 - 288, 1983/00

no abstracts in English

Journal Articles

Performance of high temperature LiAl/LiCl-KCl/FeS cells

; *

Yoyuen, 23(2), p.117 - 134, 1980/00

no abstracts in English

Oral presentation

Oral presentation

Decontamination of alkali chloride baths containing nuclear material by precipitation and distillation techniques

Ibe, Junya*; Aso, Megumi*; Takahatake, Yoko; Watanabe, So; Watanabe, Masayuki; Matsuura, Haruaki*

no journal, , 

Since waste salt generated from pyro-reprocessing test which contains uranium can easily capture moisture and corrode equipment, further treatment technology for decontamination. Oxides are added as oxygen donor in the melts, and then uranium is separated from the salt as precipitates. In the next step, melt bath components are evaporated by a vacuum distillation. First, LiCl-KCl eutectic and NaCl-2CsCl salts were used as melt baths, lithium oxide was used as a precipitant, and cerium chloride was used as uranium surrogate for testing the precipitation process. Next, a distillation line has been constructed and the best condition for distillation has been searched. Amount of the precipitates increased with increasing the amount of oxide, and recovery ratio of cerium must potentially depend on solubility of oxychloride into the bath salts. It is considered that oxychloride was formed by the similarity in EXAFS oscillation and X-ray diffraction patterns.

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