This study investigated the behavior of phosphate in uranium-bearing organo phosphorus solvents under pyrolysis and combustion conditions. The volatilization characteristics of phosphate and the reaction between uranium oxide and phosphate oxide were established based on the results of a thermogravimetric analysis of tributyl phosphate (TBP) and uranium-bearing TBP-dodecane solutions. Uranium dioxide, UO2, functioned as a sorbent for the capture of vaporized phosphate oxide, P4O10(g). A significant fraction of phosphate remained in the form of uranium pyrophosphate (UP2O7) and uranium metaphosphate (U(PO3)4). The P4O10(g) capturing capacity of UO2 was 0.96-0.84 g/g for pyrolysis and 0.60 g/g for combustion, respectively. The relatively low phosphate-capturing capacity of combustion was due to the dissociation of P4O10(g) from (U(PO3)4) at flame temperatures higher than 1300K. Pyrolysis appears to be a better method than combustion for a thermal destruction of uranium-bearing TBP solutions while affording minimized problems associated with the condensation of corrosive phosphoric acid.
Final report for FY 1965 on tungsten--uranium dioxide materials for NASA. Part I. Preparation of high purity uranium oxide powders. Part II. Cladding and joining of tungsten cermets by plasma spraying. Part III. Tungsten coating of uranium dioxide particles