For a number of years, researchers at the Pacific Northwest Laboratory have been developing processes and equipment for converting high-level liquid • wastes to solid forms. One of these processes is the Spray Calciner/ln-Can ~'elter system. To irrmobilize high-level liquid wastes, this system must be operated remotely, and the calcine must be reliably conveyed from the calciner to the melting furnace. A concept for such a remote conveyance system was developed at the Pacific Northwest Laboratory, and equipment was tested under full-scale, nonradioactive conditions. The report here describes this concept and the design of demonstration equipment and presents the results of equipment operation during experimental runs of 7 d. The design includes a connecting section and its associated systems--a canister support and alignment concept and a weight-monitoring system for the melting furnace.Remote coupling of the connecting section to the canister and modified canister handling were demonstrated during the runs. No misalignment problems were encountered. The retraction mechanism of the connecting section was not as reliable as desired as a result of the accumulation of calcine. However, all canister exchanges were completed as necessary for the continuity of the runs.The connecting section maintained the process envelope during the fill and canister exchange activities as well as can be determined by the process instrumentation. Some calcine leakage was noted at the spout/cone valve interface, probably due to warping of the cone valve. Airflow through this small leak was not noticeable by process offgas instrumentation.In this design, the canister sits on the bottom of the furnace. To monitor fill of the canister, the whole furnace is weighed by two systems, one which monitors small weight gains for instantaneous fill rate and one which monitors total furnace weight. The instantaneous weight-gain system produced too much noise to monitor the small weight changes that occurred. However, all side torques, thermal expansion and misalignment problems were isolated from the total weight system so that the long-term changes were quite visible.iii During these runs, the flow of batch and offgasses through the delivery tube assembly of the connecting section was unhindered during the operating periods. The spout and cone-valve cooling system, after modification, provided better temperature control although the cooling was still not adequate for dependable operation.
Three full-scale vitrification processes at the Pacific Northwest Laboratory produced over 67,000 kg of simulated nuclear-waste glass from March 1979 to August 1980. Samples were analyzed to monitor process operation and evaluate the resulting glass product. These processes are: • Spray Calciner/ln-Can Melter (SC/ICM) • Spray Calciner/Calcine-Fed Ceramic Melter (SC/CFCM) • Liquid-Fed Ceramic Melter (LFCM). Waste components in the process feed varied less than +10%. The SC/ICM and SC/CFCM which use separate waste and frit feed systems showed larger glass compositional variation than the LFCM, which processed only premixed feed during this period. The SC/ICM and SC/CFCM product contained significant amounts of acmite crystals, while the LFCM product was largely amorphous. In addition, the lower portion of all SC/ICM-filled canisters contained a zone rich in waste components. A product chemical durability as determined by pH4 and soxhlet leach tests varied considerably. Aside from increased durability under pH4 conditions with decreasing waste content, glass composition, microstructure and melting process did not correlate with glass durability. For all samples analyzed, the weight loss under pH4 conditions ranged from 17.7 to 85.2 wt%. Soxhlet conditions produced weight losses from 1.78 to 3.56 wt%.
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