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PNC TN8410 93-006, 38 Pages, 1992/12
Elimination of the ionic platinum group metals (palladium, rhodium, ruthenium) and technetium from dissolver solution seems to be an effective method to improve the stability, reliability and operability of the extraction process in spent nuclear fuel reprocessing. Some fundamental experiments were conducted for the purpose of establishing this new method. A method of electrolytic extraction to separate and recover such metals from Purex process solutions was investigated. Potentiostatic investigations of platinum group metals were carried out to identify deposition starting potential and rate in a nitric acid condition. As the results, it was found that the deposition rate depended on the electrode material, temperature, nitric acid concentration and coexistence ions. The deposition rate were found to be related to the polalization potential, and the optimum deposition potential was specified for each of platinum group metals.
; ; Kawata, Tomio
PNC TN8410 92-153, 16 Pages, 1992/05
Platinum group metals (palladium, rhodium, ruthenium) and technetium are key nuclides which dominate the overall decontamination factors of the Purex Process. They are also precious metals which can be potential resources in the future. Electrolytic deposition (or extraction) is likely to separate and recover such metals from Purex process solutions. Potentiostatic investigation for platinum group metals were carried out to identify the deposition starting potential and deposition velocity in nitric acid condition. As the results, it was found that there was an optimum deposition potential specific to each platinum elements. Palladium tended to deposit on the cathode electrode surface from modified HLLW with high efficiency even in the high acid concentration.
Nakayoshi, Akira; Kitawaki, Shinichi; Kofuji, Hirohide; Sakamura, Yoshiharu*; Murakami, Tsuyoshi*; Uruga, Kazuyoshi*; Ando, Hidekazu*
no journal, ,
no abstracts in English
Sakamura, Yoshiharu*; Uruga, Kazuyoshi*; Ando, Hidekazu*; Kitawaki, Shinichi; Nakayoshi, Akira; Kofuji, Hirohide
no journal, ,
no abstracts in English
Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Kihara, Sorin*
no journal, ,
We have studied electrolytic redox behaviours of U ions under weak acidic conditions. UO
is reduced to UO
reversibly. The UO ion disproportionates to produce U
and UO in an acid solution, and the reaction rate of the disproportionation is lower in weaker acidic solution up to pH ca. 2.1. It was found that reduction current of UO increased abruptly after the induction period of several minutes. Acceleration of UO reduction coincides to adsorption of reduction product on the electrode surface which was observed by the electrochemical quartz crystal microbalance. As a result of electrolytic reduction of UO to U(IV), black fine particles were formed both on the surface of the electrode and in the solution. The size of the U(IV)-containing particles formed in a solution of pH 2.5 was analysed to be ca. 10 nm. The particles in the colloid solution were filtered after aging the colloidal particles, and filtrate was analysed by X-ray diffraction measurement system. Characteristic diffraction peaks of XRD pattern of the U-containing particles can be assigned to be poorly crystallized UO of fluorite structure. These facts suggest that the aggregated U(IV) work as catalyst for the electrolytic reduction and the disproportionation of UO.
Kitatsuji, Yoshihiro; Ouchi, Kazuki; Otobe, Haruyoshi; Kihara, Sorin*
no journal, ,
Electrolytic reduction of neptunium ion in the weak acidic solution was investigated. On the cyclic voltammogram of Np(V) in the solution of pH 3.8, reduction and deposition of Np was observed. Stripping current due to oxidation of deposited Np was also appeared. Stripping voltammetry after preelectrolysis at definite potential was carried out. Stripping currents were almost constant despite variation of preelectrolysis time and concentration of Np(V). Difference of reduction-deposition behavior between U and Np was discussed.
Kitatsuji, Yoshihiro; Ouchi, Kazuki; Otobe, Haruyoshi
no journal, ,
Redox behaviors of actinide ions in a low-acid solution are complicated and have been unclear, because they tend to form hydroxide complexes, colloids and precipitates. Recently, autocatalysis of the reduction of U(V) to U(IV) in the solution where U(IV) forms hydroxide colloid was reported; U(IV) colloid formed as reduction product catalyzes the electrolytic reduction of U(V). In this study, possibility of catalysis of Zr(IV) colloid which was analogous of U(IV) colloid on the reduction of U(V) was investigated. When U(VI) was electrolyzed at a constant potential in order to reduce to U(V) in the solution of pH 3.0 containing 10 mM Zr(IV), the increase of the reduction current was observed in initial stage of electrolysis. This results indicates that U(VI) was reduced further to U(IV) without catalysis of U(IV) colloid, and that Zr(IV) colloid also acts as catalyst. Intensity of catalysis depends on concentration of Zr(IV), condition of preparing colloid and acidity of the solution.
reduction test using cathode shroudSakamura, Yoshiharu*; Iizuka, Masatoshi*; Kofuji, Hirohide
no journal, ,
no abstracts in English
Tada, Kohei; Kofuji, Hirohide; Murakami, Tsuyoshi*
no journal, ,
no abstracts in English
Ouchi, Kazuki; Matsumura, Daiju; Tsuji, Takuya; Kobayashi, Toru; Otobe, Haruyoshi; Kitatsuji, Yoshihiro
no journal, ,
We analyzed electrodeposited U compounds by X-ray absorption fine structure (XAFS) and impedance spectra measurements. The XAFS spectrum of the deposits was similar to that of U(IV) hydroxide formed by neutralizing U(IV) ion. The electrical resistances obtained from the impedance spectra of U deposits at 4 to 80 minutes after stopping electrodeposition were increased with time. These results indicate that U deposits forms U(IV) hydroxide as an intermediate and finally transforms into U(IV) oxide having generally a larger electrical resistance than a hydroxide.
O meltsSakamura, Yoshiharu*; Iizuka, Masatoshi*; Kofuji, Hirohide
no journal, ,
no abstracts in English
O meltsSakamura, Yoshiharu*; Iizuka, Masatoshi*; Kofuji, Hirohide
no journal, ,
no abstracts in English
using Ni anode in LiCl-LiO meltSakamura, Yoshiharu*; Murakami, Tsuyoshi*; Iizuka, Masatoshi*; Kofuji, Hirohide
no journal, ,
no abstracts in English
