| Samples of low-activity-level (10('-6) (mu)Ci/ml) spent lubricating oils generated at Carolina Power and Light in two of their nuclear plants were decontaminated by employing four unit processes: adsorption; ion-exchange; ultrafiltration; solvent extraction. About 85 to 98% activity removal was achieved, depending on the process. The contaminants are apparently organometallic polymeric compounds dissolved and suspended in the oils. Relatively slow adsorption and ion-exchange processes were found to be suitable but were ones which would offer problems if used on an industrial scale. However, these polymeric activity-containing compounds were easily retained by uncharged, cross-linked ultrafiltration membranes. The retention of impurities by these membranes was in the range of 50-70%, depending on their porosity. They could be used in series to achieve at least 92% activity removal at 90 C and 110 psig. Also, at these temperatures the radioactive metals were well dissociated from their complexes. Metal-containing low molecular weight compounds were found to be water-soluble and could be removed by solvent extraction. Consequently, oils with low-level activities could be treated by ultrafiltration and solvent extraction successfully, and these were found to be the most practical of the four methods of decontamination studied. Oils with higher levels of activity would generate large volumes of low-activity-level aqueous wastes if treated by the solvent extraction process, too voluminous to render the process practical. Thus, ultrafiltration appeared to be the best process for the decontamination of used lube oils, at the rather low operating cost estimated to be of the order of... |
PDF Full Text Request