GBOCHEMICAL ASSESSMENT OF NUCLEAR WASTE ISOLATION

Measurement of the solubilities of certain waste radionuclide compounds .. will be necessary to adequately assess and predict the ability of potential underground waste storage facilities to meet federally established performance , . ' criteria. During such measurements,' it is usually necessary to physically separate solid and solution phases. Experiments have been conducted to test and compare the relative efficacy of three' com~only used separation methods, i.e. gravity settling, centrifugation and fi~tration. The results indicated that sorption of solution species onto filters can occur and could potentially lead to erroneous results in solubility measurements when one is dealing with trace amounts of radionuclides in solution. ~he degree of retention by filters depended on the solutibnpH and the nature of the filter material. Of the three methods, centrifugation appeared to give the most reliable and consistent results. Filtration was found to give results comparable to centrifugation if care is taken in the selection of filter type •