Kinetics and mechanism of Eu(III) transfer in tributyl phosphate microdroplet/HNO aqueous solution system revealed by fluorescence microspectroscopy

Miyagawa, Akihisa*; Kusano, Yuka*; Nagatomo, Shigenori*; Sano, Yuichi; Nakatani, Kiyoharu*

Analytical Sciences, 38(7), p.955 - 961, 2022/07

https://doi.org/10.1007/s44211-022-00117-3

In this study, we reveal an Eu(III) extraction mechanism at the interface between HNO and tributyl phosphate (TBP) solutions using fluorescence microspectroscopy. The mass transfer rate constant at the interface is obtained from the analysis of fluorescence intensity changes during the forward and backward extractions at various HNO and TBP concentrations to investigate the reaction mechanism. This result indicates that one nitrate ion reacts with Eu(III) at the interface, whereas TBP molecules are not involved in the interfacial reaction, which is different from the results obtained using the NaNO solution in our previous study. We demonstrate that the chemical species of Eu(III) complex with nitrate ion and TBP in the aqueous solution play an important role for the extraction mechanism.

Mechanism of phase transfer of uranyl ions; A Vibrational sum frequency generation spectroscopy study on solvent extraction in nuclear reprocessing

Kusaka, Ryoji; Watanabe, Masayuki

Physical Chemistry Chemical Physics, 20(47), p.29588 - 29590, 2018/12

https://doi.org/10.1039/C8CP04558E

Mechanistic understanding of solvent extraction of uranyl ions (UO) by tributyl phosphate (TBP) will help improve the technology for the treatment and disposal of spent nuclear fuels. So far, it has been believed that uranyl ions in the aqueous phase are adsorbed to a TBP-enriched organic/aqueous interface, form complexes with TBP at the interface, and are extracted into the organic phase. Here we show that uranyl-TBP complex formation does not take place at the interface using vibrational sum frequency generation (VSFG) spectroscopy and propose an alternative extraction mechanism that uranyl nitrate, UO(NO), passes through the interface and forms the uranyl-TBP complex, UO(NO)(TBP), in the organic phase.

Technetium separation for future reprocessing

Asakura, Toshihide; Hotoku, Shinobu; Ban, Yasutoshi; Matsumura, Masakazu; Morita, Yasuji

Journal of Nuclear and Radiochemical Sciences, 6(3), p.271 - 274, 2005/12

https://doi.org/10.14494/jnrs2000.6.3_271

Tc extraction and separation experiments were performed basing on PUREX technique with using spent UO fuel with burn-up of 44 GWd/t. The experimental results were examined with performing calculations by a simulation code ESSCAR (Extraction System Simulation Code for Advanced Reprocessing). It was demonstrated that Tc can be almost quantitatively extracted from a dissolver solution and that Tc can also be almost quantitatively recovered by scrubbing. Further, it was clearly presented from the calculation results of ESSCAR that the extraction mechanism of Tc is dominated by the synergistic effect of Zr and U.

Structural analysis of Co-extracted heptavalent technetium and rhenium complexes by EXAFS

Suzuki, Shinichi; Yaita, Tsuyoshi; Okamoto, Yoshihiro; Shiwaku, Hideaki; Motohashi, Haruhiko*

Physica Scripta, T115, p.306 - 307, 2005/00

In spent fuel reprocessing, distribution behavior of technetium in tri- butyl phosphate (TBP) extraction system is a very complicated. Especially, in the presence of metallic ions, i.e., U(VI), Pu(IV)and Zr(IV)in the TBP extraction system, the extraction of technetium is enhanced by the co- extraction with U, Pu and Zr. The mechanism of co-extraction mechanism of technetium is performed by exchange with nitric acid ion and per-technetate ion. In this research, we perform the structural analysis of technetium complexes in ethanol solution compared with rhenium and manganese complexes by EXAFS. Furthermore we measured some organic complexes and co-extracted complexes of technetium with uranium and zirconium extracted by TBP as compared with those of rhenium.

Removal and recovery of uranium from solid wastes by supercritical carbon dioxide fluid leaching method

Meguro, Yoshihiro; Tomioka, Osamu; Imai, Tomoki*; Fujimoto, Shigeyuki*; Nakashima, Mikio; Yoshida, Zenko; Honda, Tadashi*; Koya, Fumio*; Kitamura, Nobu*; Wada, Ryutaro*; et al.

Proceedings of International Waste Management Symposium 2004 (WM '04) (CD-ROM), 8 Pages, 2004/03

Supercritical CO fluid leaching (SFL) method using supercritical CO fluid containing a complex of HNO - tri-n-butyl phosphate (TBP) was applied to removal of uranium from radioactive solid wastes. Sea sands, incineration ashes and porous alumina bricks were employed as matrixes of simulated solid wastes. Real radioactive incineration ash wastes and firebrick wastes were also subjected to the SFL treatment. It was found that uranium could be efficiently removed from both of the simulated wastes and real wastes by the SFL method. The removal efficiency of uranium from the real waste was lower than that from the corresponding artificial waste. About 1 g and 35 mg of uranium were recovered from 10 g of the real ash waste and 37 g of the real firebrick waste, respectively.

Luminescence study on the inner-sphere hydration number of lanthanide(III) ions in neutral organo-phosphorus complexes

Zhang, P.*; Kimura, Takaumi; Yoshida, Zenko

Solvent Extraction and Ion Exchange, 22(6), p.933 - 945, 2004/00

https://doi.org/10.1081/SEI-200037439

no abstracts in English

Structural and electronic investigation of TbPdAl by means of EXAFS and XANES measurements

Mizumaki, Masaichiro*; Yoshii, Kenji; Kitazawa, Hideaki*; Tanida, Hajime*

Journal of Solid State Chemistry, 171(1-2), p.291 - 294, 2003/02

https://doi.org/10.1016/S0022-4596(02)00179-2

no abstracts in English

Effect of U(VI) concentration on equilibrium and kinetics in flow-extraction of U(VI) in HNO/supercritical CO+TBP system

Meguro, Yoshihiro; Iso, Shuichi; Yoshida, Zenko

Proceedings of International Solvent Extraction Conference 2002 (CD-ROM), p.1131 - 1136, 2002/00

no abstracts in English

Modelling of the extraction of uranium with supercritical carbon dioxide

Clifford, A. A.*; Zhu, S.*; Smart, N. G.*; Lin, Y.*; Wai, C. M.*; Yoshida, Zenko; Meguro, Yoshihiro; Iso, Shuichi

Journal of Nuclear Science and Technology, 38(6), p.433 - 438, 2001/06

https://doi.org/10.3327/jnst.38.433

no abstracts in English

A Study on modeling and numerical simulation of extraction in the CMPO-TBP system

; ;

JNC TN8400 2001-022, 60 Pages, 2001/03

JNC-TN8400-2001-022.pdf:1.31MB

A numerical simulation code for the TRUEX (Transuranium Extraction) process was developed. Concentration profiles of americium and europium were calculated for some experiments of the counter current extraction system those were carried out in CPF (Chemical Processing Facility) by using the code. Calculation profiles were in agreement with the experimental results. Operational conditions were also examinted for the americium recovery experiment by the TRUEX process carried out in the Plutonium Fuel Center. It was shown that lowering the concentration of nitric acid in the scrub solution and decreasing the flow rate of solvent and strip solution was effective for improving the performance of the stripping step and reducing the volume of the waste solution. In order to find the optimum conditions for various experiments, this simulation code was modified to calculate the concentration profiles of other metal elements such as zirconium and iron and the effect of oxalic acid on the extraction behavior of the metal elements. The calculated concentration profiles of americium and europium were varied by this modification. In the experiment at CPF, the calculations were carried out to obtain recovery ratio of americium in the product stream with the amount of oxalic acid added to the process. This calculation result showed that it was possible to improve the performance of decontamination of fission products by increasing oxalic acid concentration added to the process. The calculation was also carried out for finding the optimum conditions of oxalic acid concentration added to the europium recovery process.