Bench-scale crossflow filtration of Hanford tank C-106, C-107, B-110, and U-110 sludge slurries

Pacific Northwest National Laboratory has a bench-scale crossflow filter installed in a shielded hot cell for testing radioactive feeds. During FY97 experiments were conducted on slurries from radioactive Hanford waste from tanks C-106, C-107, B-110, and U-110. Each tank was tested at three slurry concentrations (8, 1.5, and 0.05 wt% solids). A two-parameter central composite design which tested transmembrane pressure from 5 to 40 psig and axial velocity from 3 to 9 ft/s was used for all feeds. Crossflow filtration was found to remove solids effectively, as judged by filtrate clarity and radiochemical analysis. If the filtrates from these tests were immobilized in a glass matrix, the resulting transuranic and ({sup 90}Sr) activity would not breach low activity waste glass limits of 100nCi/g (TRU) and 20 {mu}Ci/ml ({sup 90}Sr). Two exceptions were the transuranic activity in filtrates from processing 1.5 and 8 wt% C-106 tank waste. Subsequent analyses indicated that the source of the TRU activity in the filtrate was most likely due to soluble activity, but obviously proved ineffective at removing the soluble plutonium species. Re-testing of the C-106 supported this hypothesis. These data suggest the need to control carbonate and pH when processing tank wastes for immobilization