DEMONSTRATION OF PACKAGING OF FERNALD SILO I WASTE IN CHEMICALLY BONDED PHOSPHATE CERAMIC

This paper summarizes our experience in bench-scale packaging of Fernald Silo I waste in chemically bonded phosphate ceramics. The waste was received from the Fernald Environmental Management Project (FEMP), and its treatability was studied in our laboratory. This waste contained As5+, Ba, Cr6+, Ni, Pb, Se4+, and Zn as the hazardous contaminants. In addition, the total specific activity of all the radioactive isotopes in the waste was 3.85 µCi/g, of which that of radium alone was 0.477 µCi/g. This indicated that radon (a daughter product of the radium) in the waste could present a serious handling problem during this study. For this reason, the waste was handled and stored in a flowing-air glovebox. We made waste form samples with an actual waste loading of 66.05 wt.% and subjected them to the Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure (TCLP). The results showed excellent stabilization of all contaminants. Actual levels detected in the leachate were well below the EPA's most stringent Universal Treatment Standards and in almost all cases were one order of magnitude below this limit. Radioactivity in the leachate was also very low. Alpha activity was 25 ± 2.5 pCi/mL, while beta activity was 9.81 ± 0.98 pCi/mL. This very low activity was attributed to the efficient stabilization of radium as insoluble radium phosphate in the waste form, thus prohibiting its leaching. This study indicates that the chemically bonded phosphate ceramic process may be a very suitable way to package Silo I waste for transportation and storage or disposal.