Physical and chemical characterization of synthetic calcined sludge

Calcined synthetic sludge was chemically characterized in support of engineering studies to design a processing plant to solidify highly radioactive waste at the Savannah River Plant. An analytical technique is described which provides quantitative data by mass spectrometric analysis of gases evolved during thermogravimetric analysis without measurements of gas flow rates or mass spectrometer sensitivities. Scanning electron microprobe analysis, Mossbauer spectroscopy, and several other common analytical methods were also used. Calcined sludge consists primarily of amorphous particles of hydrous oxides with iron, manganese, nickel, and calcium distributed fairly uniformly throughout the powder. Iron, manganese, nickel, and calcium exist in forms that are highly insoluble in water, but aluminum, sulfate, nitrate, and sodium exhibit relative water solubilities that increase in the given order from 60% to 94%. Evolved gas analysis in a helium atmosphere showed that calcined sludge is completely dehydrated by heating to 400/sup 0/C, carbon dioxide is evolved between 100 to 700/sup 0/C with maximum evolution at 500/sup 0/C, and oxygen is evolved between 400 and 1000/sup 0/C. Evolved gas analyses are also reported for uncalcined sludge. A spinel-type oxide similar to NiFe/sub 2/O/sub 4/ was detected by x-ray diffraction analysis at very low-level in calcined sludge