Incineration/vitrification of simulated low-level institutional wastes in a joule-heated glass melter

Abstract

The purpose of this study was to determine the feasibility of reducing the volume of low-level institutional wastes by incineration and then converting the residual solids into glass with a single-step process. Experimental test results with simulated waste show that a joule-heated ceramic melter originally developed for high-level waste vitrification can be used for the low-level waste volume reduction process. Off gas analysis from the experiment shows that incineration of combustible solids was essentially complete. This is attributable to high combustion temperatures (>950 °C) and the introduction of excess combustion air or oxygen at the melter's glass surface. The only instance where a pyrolysis product (hydrogen) was detected was when the oxygen concentration in the process off gas depleted to 7.8%. An insulating blanket over the glass surface, which would have reduced incineration temperatures, never formed. In addition, calculations show that for scaled-up processing rates, incineration temperatures will remain high because the medicinal waste provides much of its own heat for combustion, vitrification, and process heat losses. Results of the incineration experiment indicate that process scale-up for higher capacities is quite feasible. Although feed rates in this experiment through the pilot-scale melter were low (0.5 kg/ h), they could be increased as much as tenfold, even for the laboratory-scaled unit tested here, by use of an improved feed system. The overall test results were so encouraging that we recommend further tests aimed at adapting high-level waste vitrification technology to the management of both institutional wastes and low-level wastes generated from the nuclear fuel cycle.