THERMODYNAMICS OF RADIOACTIVE TRACE-ELEMENTS IN CONCENTRATED ELECTROLYTE-SOLUTIONS - HYDROLYSIS OF CM3+ IN NACL-SOLUTIONS

The hydrolysis reaction of curium has been studied by time resolved laser fluorescence spectroscopy (TRLFS) in the pH range 3-10 in NaCl solutions of varying molalities between 0.01 and 6.15 mol NaCl/kg H2O at 25 degrees C. The concentration of the Cm species present under these conditions, namely Cm3+, Cm(OH)(2+) and Cm(OH)(2)(+), are determined from the fluorescence emission spectra by peak deconvolution. The first and second hydrolysis constants are calculated at each NaCl molality from the spectroscopically quantified mole fraction of each species at given pH. The set of data is used to parameterize the ion-interaction approach (Fitter equations). Strong association reactions, as found in the system, require a combination of ion-interaction and ion-association concepts. The formation of the curium hydroxo species is included in the Fitter approach and the parameters for the interaction of the curium species with the chloride ion are derived.