RADIOCHEMICAL APPROACHES TO THE MIGRATION OF ELEMENTS FROM A RADWASTEREPOSITORY

Underground HLW or IL alpha radwaste repositories will contain tons to hundreds of tons of anthropogenic elements. According to our understa nding of chemistry in anoxic conditions, it is predicted that the rele ase of the elements into the far field will be mainly dependent upon t he ''solubilities'', sums of the concentrations of soluble species and colloidal/pseudo colloidal forms, of expected near field compounds. O n the other hand, safety assessments, based on computation models of m igration, show that elements in the discharged water into the biospher e will be at tracer level, or at least, at trace levels. Kinetic and t hermodynamic aspects of the processes in which elements will be involv ed during their migration are discussed together with the change in th eir concentrations, over several order of magnitude. It is shown that special attention must be given to predict the behaviour of the elemen ts in the far field from what we know from classical chemistry, and th at more experimental data must be obtained to improve the models.