Tests were made to investigate flowsheet modifications which might improve the expected performance of the reference Submerged Demineralizer System (SDS) flowsheet for decontaminating the high-activity-level water at the Three Mile Island Nuclear Power Station, Unit 2. The tests included one series designed to show the effects of aging time, temperature, and pH on reduction of the concentrations of residual /sup 137/Cs and /sup 90/Sr, and a second series designed to evaluate the physical sorption of /sup 125/Sb on silica gel or other inorganic sorbents. Results of the tests indicated that the most promising method for reducing /sup 137/Cs and /sup 90/Sr concentrations below 10/sup -4/ .mu. Ci/mL is to age the effluent water from the zeolite columns for at least 2 h at 75/sup 0/C prior to its passage through another zeolite column. Sorption of the /sup 125/Sb on silica gel or other inorganic sorbents did not show sufficient promise to be considered for practical use. A previously identified method for removal of /sup 125/Sb requires deionization of the water by removal of the sodium on a cation exchange resin prior to sorption of /sup 125/Sb on anion exchange resin; however, this method would generate a relatively large amount of low-activity-level solid waste (ion exchange resin).

This report discusses the Submerged Demineralizer System (SDS) flowsheet for decontamination of the high-activity-level water at the Three Mile Island Unit 2 Nuclear Power Station was evaluated at Oak Ridge National Laboratory in a study that included filtration tests, ion exchange column tests, and ion exchange distribution tests. The contaminated waters, the SDS flowsheet, and the experiments made are described. The experimental results were used to predict the SDS performance and to indicate potential improvements.