COPRECIPITATION PHENOMENA DURING SPENT FUEL DISSOLUTION .1. EXPERIMENTAL PROCEDURE AND INITIAL RESULTS ON TRIVALENT ION BEHAVIOR

Coprecipitation may be a significant process in controlling radionucli de release during spent fuel dissolution in geological disposal. The c oprecipitation behaviour of the trivalent elements Am, Cm and Eu with Na-polyuranates is studied in saline solutions. Experimental data are obtained by precipitation from a supersaturated solution of dissolved high burnup spent fuel in 5 m NaCl solution at pH values between 5.7 t o 12. The resulting concentrations of dissolved Am, Cm and Eu were fou nd similar to those observed in spent fuel leaching experiments and we re found to be considerably lower than expected, if the formation of p ure Am(OH)(3), Cm(OH)(3) and Eu(OH)(3) solid phases is assumed. Coprec ipitation phenomena and formation of solid solutions are suggested to be responsible for the lower solubility concentrations.