Over 270 kg of high-temperature borosilicate glass have been produced in a series of three short-term tests in the High-Temperature Ceramic Melter vitrification system at PNL. The glass produced was formulated to vitrify simulated Hanford residual-liquid waste. The tests were designed to 1) demonstrate the feasibility of utilizing high-temperature, continuous-vitrification technology for the immobilization of the residual-liquid waste, 2) test the airlift draining technique utilized by the high-temperature melter, 3) compare glass produced in this process to residual-liquid glass produced under laboratory conditions, 4) investigate cesium volatility from the melter during waste processing, and 5) determine the maximum residual-liquid glass production rate in the high-temperature melter.The three tests with the residual-liquid composition confirmed the viabilityof the continuous-melting vitrification technique for the immobilization of this waste. Although minor processing difficulties (e.g., the formation of fused aggregates of unreacted feed) were encountered in the earlier tests, slight modification of the vitrification system and proper feed preparation produced excellent results in the later tests.The airlift draining technique was demonstrated in these tests and the glass produced from the melter was shown to be less porous than the laboratoryproduced glass. The airlift also was shown to be capable of satisfactorily draining glass from the melter during periods of discharge heater failure.The final glass produced from the second test was compared to a glass of the same composition produced under laboratory conditions. A number of glass characteristics were compared, including porosity, softening and transition temperatures, heat capacity, leaching rate, thermal conductivity, and electrical resistivity. The comparative tests found the glasses to be indistinguishable, as the small differences in the test results fell within the precision range of the characterization testing equipment.iii The cesium volatility was examined in the final test. Two melter effluent scrubbing systems were utilized to determine the cesium volatilization rate during processing. This examination showed that 0.44 wt% of the cesium (assumed to be cesium oxide) was volatilized, which translates to a volatilization rate of 115 mg/cm 2 -h.During later stages of the final residual-liquid test, the cold cap of unreacted feed in the melting cavity was accumulating, indicating that the maximum glass production rate had been achieved. This processing rate was found to be 18 kg/h of glass, representing a melting flux of 160 kg/m 2 -h for the residual-liquid feed. iv • ,"