The Evaluation of Uranium-236 Isotopic Dilution with the Addition of Depleted Uranium to Supernatant Liquid Waste

This paper describes laboratory-scale results on experiments performed to examine the feasibility of isotopic dilution of uranium-235 in supernatant liquid storage tanks at the Savannah River Site. The isotopic dilution tests were accomplished by adding an alkaline depleted uranium solution to small portions of simulated and actual storage tank waste solutions with enriched U-235 compositions. Based on the laboratory observations, recommendations were made, which involved the addition of significant quantities of uranyl carbonate solution to over four million liters of U-235 enriched waste stored in Tank 43H at SRS to reduce the risk for criticality. A post-uranyl carbonate addition analysis on the tank supernate confirmed the effectiveness of depleted uranium in isotopic dilution of U-235. The U-235 enrichment in the Tank 43H was isotopically diluted from an original high of over 4 wt percent down to less than 0.5 wt percent as predicted from the laboratory investigations