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Suzuki, Shinichi; Yaita, Tsuyoshi; Okamoto, Yoshihiro; Shiwaku, Hideaki
no journal, ,
Recovery of uranium with high decontamination factor from the spent nuclear fuels that includes about 95% uranium for LWR and about 85% uranium for FBR is a key technique for a reprocessing during the transition periods from LWR to FBR cycle. However, the requirements for process development are gradually becoming severe as time progresses, e.g., economic efficiency, environmental loading, nuclear proliferation etc. On the background, we have focused on the local structures around the metal in various kinds of extracted complexes to understand extraction mechanism and design new separation process. In this presentation, following three topics will be introduced. (1) U(VI)-Tc(VII)-TBP extraction system, (2) U(VI)-N,N-di-alkyl monoamides extraction system, (3) Th(IV) -N,N-di-alkyl monoamides extraction system. In this talk, coordination structure of Th(IV)-NO
- system will be also discussed.
Ikeda, Atsushi; Hennig, C.*; Tsushima, Satoru*; Rossberg, A.*; Scheinost, A. C.*; Bernhard, G.*; Yaita, Tsuyoshi
no journal, ,
Neptunium (93Np) is one of the most problematic nuclides in the nuclear fuel reprocessing process and the following radioactive waste disposal because of its chemical similarity to the fissile nuclides of uranium (U) and plutonium (Pu). Proper understanding of the behavior of Np in the reprocessing process or in the migration process on the geological disposal of radioactive wastes requires vast fundamental information about the chemical properties of Np in solutions. In the present study, Np solution samples with different oxidation states are electrochemically prepared in aqueous perchlorate, nitrate, and carbonate solutions, and the complex structure of Np species in the sample solutions are determined by EXAFS spectroscopy and DFT calculations. The obtained results reveal the structural difference between different Np oxidation states, as well as the different coordination behavior in each solution system.