Structural determination of neptunium species in aqueous solutions by EXAFS and quantum chemical calculations

Ikeda, Atsushi  ; Yaita, Tsuyoshi; Okamoto, Yoshihiro  ; Shiwaku, Hideaki   ; Tsushima, Satoru*; Hennig, C.*

Neptunium (93Np) is one of the most problematic nuclides in the nuclear fuel reprocessing process and the following radioactive waste disposal. Proper understanding of the Np behavior 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 various aqueous solutions, and the complex structure of Np species in the sample solutions are determined by EXAFS spectroscopy, partly with the help of DFT calculations.