In situ speciation of actinides with a newly developed spectro-electrochemical cell

Natural aquatic and terrestrial environments exert large variations in redox state due to oxygen diffusion on one hand and microbial processes on the other hand. Actinides with their large number of oxidation states are especially susceptible to these redox changes, forming different aqueous complexes which may greatly differ by solubility and mobility. These complexes are often difficult to investigate due to their thermodynamic metastability. Therefore, we developed a new spectro-electrochemical cell, which allows to study the structure and speciation of aqueous actinide complexes in situ by X-ray absorption spectroscopy, while applying and maintaining a constant potential. Due to the specific safety requirements for handling of radioactive materials the electrochemical cell is gas tight. The spectro-electrochemical cell comprises two safety compartments and a special electrode arrangement. First U LIII-edge X-ray absorption spectra have been obtained from aqueous solutions of U(VI) and U(IV) in high concentrated chloride solutions.