Patent Number: 054240425
Section: description

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In the following description similar components are referred to by the same reference numeral in order to simplify the understanding of the sequential aspect of the drawings. Referring now to FIG. 1, the radioactive waste processing system 20 in its preferred embodiment is comprised of a number of subsystems: a feed conditioning subsystem 22, a waste preparation subsystem 24, a melting/combustion subsystem having a two-zone melter chamber 26, a glass handling subsystem 28, and an off-gas cleaning and control subsystem having an off-gas control component 32 and a pollution control component 34. Radioactive waste from a plant 36, such as a nuclear power plant but which could be a hospital or other radioactive waste generator, can usually be characterized as coming from one of three main waste streams or types of waste: dry active waste (DAW) 38, ion exchange resin and wet waste or sludge 42, and liquid waste having organics and inorganics, a substantial portion of which is aqueous waste 44. Prior to any vitrification activity, each type of waste is preferably conditioned before it is blended with the other wastes from that generator and glass formers for feeding into melter chamber 26. The goal of waste preparation is to form a waste feed that has a uniform BTU content through blending, drying or size reduction. The first type of waste, DAW 38, is typically comprised of wooden boards and metal fragments, low level protective clothing such as rubber or plastic booties and gloves, paper and the like, and is usually packaged for handling in the form of bales, drums or plastic bags containing semi-compacted or non-compacted DAW 38. DAW 38 is conditioned preferably by shredding with a shredder 46 (discussed more fully below) to reduce the size of pieces of DAW 38. Shredding DAW 38 with shredder 46 allows DAW 38 to blend more easily with the various constituents of DAW and the wastes from the other waste streams, as well as to increase surface area and oxidation kinetics in the melter. Instead of compacting at the generator's facility, DAW 38 can simply be packed into drums, bales and similar containers for transporting to waste preparation subsystem 24, which can be on-site but is preferably part of a centralized, waste processing facility located off-site. The resins in resins and sludges 42 that are generated by plant 36 typically exist in granular or powdered form and are usually introduced into processing system 20 in any packaging that is desirable for efficient handling and transport. The sludges in resins and sludges 42 are usually floor drain tank bottoms and storage tank bottoms. Resins and sludges 42 are conditioned preferably by dewatering (drying) to remove the slurry and interstitial water, or "free" water between resin beads. Such dewatering does not necessarily include significant removal of water in the resin beads themselves. Preferably, resins and sludges 42 are dewatered using a resin dryer 48, which can be any suitable dryer that removes the free or standing water from resins and sludges 42 efficiently. Most preferably, resin dryer 48 is of the kind taught in commonly-assigned U.S. Pat. No. 4,952,339, whose disclosure is incorporated herein by reference. Once the interstitial water has been removed from resins and sludges 42 using the necessary resin dryer 48, resins and sludges 42 are stored in containers suitable for transporting in shielded casks to waste preparation subsystem 24. The remaining waste is generally referred to as liquid waste, however, it consists predominately of aqueous waste 44, and to a lesser extent, of organic liquid waste. Constituents of liquid waste other than aqueous waste 44 include combustible organics, lube oil, antifreeze, inorganic acids and salts, boron and the like, and make up a very small proportion of the liquid waste compared to the proportion of aqueous waste 44. Conditioning of aqueous waste 44 usually occurs through concentration processes involving filtration technologies and/or liquid volume reduction, both of which are shown as 52. Filtration/liquid volume reducer 52 can be comprised of any desirable combination of filters, evaporators, dryers, and the like as needed. Preferably, filtration/liquid volume reducer 52 comprises prefiltration and microfiltration membranes, reverse osmosis (hyperfiltration) membranes, and an evaporator/concentrator tank followed by a vacuum dryer. All aspects of filtering and liquid volume reduction used in filtration/liquid volume reducer 52 can be accomplished using selective microfiltration and reverse osmosis with aqueous volume reduction to treat streams of liquid or aqueous waste 44. These technologies are known individually but their combination with vitrification is new and cost-effective in concentrating aqueous waste 44, and particularly aqueous waste 44 having a high conductivity, such as wastes from laundries and floor and equipment drains. Also, these technologies generate much less waste volume than conventional filtration. The initial stage of concentration uses reverse osmosis whereby water is forced from a more concentrated solution through a selective or semipermeable membrane into a less concentrated solution by exerting high pressure on the concentrated solution. Particulate matter and dissolved material in the concentrated stream do not pass through the selective membrane; only clean water passes through the selective membrane. Most of the selective membranes used for reverse osmosis are made from either cellulose diacetate and cellulose triacetate blends, aramid hollow fiber, or are based on polyamide chemistry. Typically, the membranes have pore sizes less than 10.degree. Angstroms (10.sup.-7 cm) and can retain organic materials in the range of 100 to 200 molecular weight. Preferably, aqueous waste 44 is pretreated using conventional filtration, microfiltration, pH adjustments, surfactants and the like prior to using reverse osmosis processes. Pretreatment is often necessary to prevent membrane fouling caused by material in suspension or low solubility salts in aqueous waste 44 that precipitate upon concentration. Microfiltration membranes are similar to membranes used for reverse osmosis except that the pores on microfiltration membranes are significantly larger, usually between 400.degree. and 10,000.degree. Angstroms. Obviously, the degree and quantity of separation depends on the respective pore sizes and the particular contents of aqueous waste 44 being filtered. However, typical microfiltration is suited to remove organics (oils and the like) and colloidal material from various types of aqueous waste 44. The final stage of the conditioning of aqueous waste further separates the liquid portion of aqueous waste 44 from the solid residue while either reusing or discharging the clean water. This system is suitable for processing aqueous waste 44 having both dissolved and suspended solids, as well as sludges. The system uses a blender/dryer to evaporate water from aqueous waste 44, resulting in concentrated aqueous waste 44 having approximately 5-90% by volume solids. Depending on the particular initial concentration of waste 44, the system can be used without prior filtration processes such as those previously described. However, although the system is capable of handling aqueous waste 44 having very low solids, its efficiency improves when prior filtration processes have been performed. Preferably, reverse osmosis processes are included with the blender/dryer system in a portable, multiple skid-mounted assembly for easy handling. In this manner, the prefiltration and microfiltration units preferably comprise the first skid, while the reverse osmosis component is mounted on the second skid and the blender dryer system is mounted on the third and fourth skids. The blender/dryer system is typically operated under vacuum conditions to improve heat transfer and reduce fouling of blender/dryer surfaces. In the preferred operation of the reverse osmosis/filtration system, assuming aqueous waste 44 is of a typical constituency, a 50 gallon per minute (gpm) pump feeds aqueous waste 44 to a single-stage cartridge filter (prefilter) and microfilter that are aligned in series. The concentrate from the microfiltration is directed to the inlet of the blender dryer system. The permeate from the microfiltration is directed to the inlet of the reverse osmosis component. The concentrate from the reverse osmosis component is directed to the inlet of the blender dryer while the clean water permeates from the reverse osmosis component is reused or discharged. The blender dryer preferably comprises a steam heated evaporator/concentrator tank connected to a vacuum dryer. The water vapor from both the concentrator tank and the vacuum dryer is condensed and may be returned to the prefilter inlet for recycling. The dry product in the dryer is discharged to a waste drum or to the melt chamber. The reverse osmosis/filtration system is designed for continuous operation with a 95% to 98% recovery rate of the feed water. It is possible to adjust the recycling of the microfiltration permeate and concentrate depending on the particular characteristics of aqueous waste 44. Typically, with a 50 gpm feed rate to the microfiltration and reverse osmosis stage of the system, approximately 0.5 to 1.0 gpm of concentrate will flow to the blender dryer. The remainder of aqueous waste 44 is clean and can be reused or discharged. The condensate can be reused also, thus providing close to 100% recovery of water if desired. However, because melter 26 can accommodate aqueous waste 44 having 5-20% by volume solids, such recovery rates are unnecessary. Waste from feed conditioning subsystem 22, whether in the form of shredded DAW 38, dried resins and sludges 42 or concentrated aqueous waste 44, is transported to waste preparation subsystem 24 for blending with glass formers and possibly other wastes to form a waste feed stream for melter chamber 26. Waste preparation subsystem 24 is shown in FIGS. 2a-2b and described below in more detail. Melter chamber 26 converts the waste feed stream into molten glass and off-gas, as shown in FIGS. 3-4 and described below in more detail. The molten glass passes to glass handling subsystem 28, which is described in more detail below. Similarly, the off-gas passes to exhaust control component 32 and eventually pollution control component 34 of the off-gas cleaning and control subsystem, which is shown in FIGS. 5a-5b and discussed more fully below. In FIGS. 2a-2b, portions of feed conditioning subsystem 22 and waste preparation subsystem 24 are shown schematically. Waste preparation subsystem 24 is used for mixing and blending all forms of waste discussed above and for delivering a consistent waste feed stream to melter chamber 26. Waste preparation subsystem 24 preferably comprises a hydraulic shredder/classifier 54 fed by a conveyor 56 through an air lock 58, a main rotary screw melter feeder 62, a resin hopper 64 with a first metering auger 66, and a glass former hopper 68 with a second metering auger 72. First and second metering augers 66, 72 are used to blend resins and sludges 42 from resin hopper 64 and glass formers from glass former hopper 68 together with the shredded waste from shredder/classifier 54 for feeding directly into melter chamber 26 (shown in FIG. 1). Shredder/classifier 54 is preferably similar to feed conditioning shredder 46, as shown in FIG. 1, and can be used in lieu of feed conditioning shredder 46 in most instances. The shredding portion of shredder/classifier 54 is an integrated material processor capable of processing drums, bales, concrete blocks, liquids, loose waste and the like. The classifier portion (not shown) of shredder/classifier 54 removes large metallic objects from shredder/classifier 54 that could possibly damage the overall feeding system of shredder/classifier 54. Shredder/classifier 54 is operated in a facility under a negative pressure with a chemically inert gas or nitrogen blanket to reduce the threat of fire caused by high volume shredding by shredder/classifier 54 of certain products in DAW 38. Nitrogen can be supplied by external means, but is preferably extracted from off-gas from melter chamber 26, the operation of which is discussed more fully below. Since the shredding portion of shredder/classifier 54 (and ultimately melter chamber 26) can process many metal objects, concrete, sand and other noncombustibles, the classifier portion of shredder/classifier 54 removes objects that cannot be processed by the shredding portion of shredder/classifier 54 such as thick steel plate, motors, valves and the like. Although shredder/classifier 54 is used mainly for shredding DAW 38, liquid waste and/or aqueous waste 44 can be mixed with an adsorbent, packaged and fed into shredder/classifier 54 by conveyor 56 or some other appropriate means. Also, dried resins and sludges 42 can be packaged and fed into shredder/classifier 54 via conveyor 56. Thus, in this manner, shredder/classifier 54 can be used to begin blending all waste types together for feeding to melter chamber 26. In the preferred operation of shredder/classifier 54, a plurality of waste drums 74 is loaded sequentially onto conveyor 56 by appropriate means. Drums 74 may contain compacted DAW 38, dried resins and sludges 42, aqueous liquid adsorbents and the like. As the first of waste drums 74 approaches air lock 58, an inner door 76 of air lock 58 closes and seals, air lock 58 is purged preferably with nitrogen, an outer door 78 of air lock 58 opens, a second conveyor 82 brings the drum into air lock 58, and then outer door 78 of air lock 58 closes and seals. Once outer door 78 of air lock 58 is closed and sealed and air lock 58 is purged, inner door 76 of air lock 58 opens. Second conveyor 82 then loads the drum onto an elevator (not shown) within air lock 58 that drops the drum into shredder/classifier 54. Once waste drums 74 have passed the classifier portion and are in the shredding portion of shredder/classifier 54, the waste contained in waste drums 74, as well as waste drums 74 themselves, are reduced to pieces preferably approximately 7.50 cm.times.7.50 cm. The contents of the waste at this time is normally composed substantially of DAW 38, however, it may also contain aqueous waste 44, adsorbents containing aqueous waste 44, concentrated aqueous waste 44, resins and sludges 42 and the like. Upon completion of shredding and, to a certain extent mixing, the contents of shredder/classifier 54 are fed into main rotary screw melter feeder 62, which pushes the waste material into melter chamber 26. As the shredded waste material from shredder/classifier 54 moves through main rotary screw melter feeder 62 toward melter chamber 26, resins and sludges 42 from resin hopper 64 are preferably blended together therewith using first metering auger 66. Similarly, glass formers from glass former hopper 68 are also released into second metering auger 72 to blend in rotary screw melter feeder 62 with shredded waste material from shredder/classifier 54. The mixing rate and overall composition of the waste being fed into melter chamber 26 can be adjusted depending on the composition of the wastes being blended together and the ultimate feed composition desired. Blending several waste types together prior to entry into melter chamber 26 produces a more consistent melter feed, thus eliminating potential thermal spikes within melter chamber 26 and off-gas emissions in off-gas control component 32 and pollution control component 34 and allowing more efficient operation of melter chamber 26. Also, different waste types can be stored temporarily until desirable blending ratios are possible. This is useful for batch processing operations, especially in view of pending legislation that may require processed waste to be returned, curie-for-curie to the plant from which it came. In FIG. 3, a schematic view of the preferred embodiment of the melter/combustion subsystem and glass handling subsystem 28 (both shown generally in FIG. 1) of waste processing system 20 is shown. The melter/combustion subsystem preferably comprises a two-zone melter chamber 26 having an upper or thermal zone 84, a lower or melting zone 86 and a disconnect mechanism 87. Upper or thermal zone 84 is where the bulk of the volume reduction and off-gas separation of entering waste occurs. Lower zone 86, which houses a melter chamber 88 heated by electric induction heating coils 92, is where waste and glass formers are melted together to form a glassy pool. Both upper zone 84 and lower zone 86 are preferably cylindrical water-cooled vessels with inner and outer liners. However, other forms of cooling and liners made of several suitable materials can be used. For example, chamber 88 could have a silicon carbide, inconel, alumina or zirconia liner. Also, upper zone 84 can be lined with a removable metal radiation barrier or with optional refractory material; lower zone 86 is not lined. Lower zone 86 is adapted for use with disconnect mechanism 87 and can comprise any one of a number of known melting zone designs, including refractory lined, Joule heated electrode melters; induction heated cold wall crucibles; induction heated warm or hot wall crucibles; in-can melter chambers; and slagging chambers. Cold wall crucibles feature a segmented wall, preferably made of non-suscepting Inconel, cooled by a surrounding water wall. Also, the crucible has a water jacket (or cold wall) "disc" bottom and induction heating coils surrounding the crucible and water wall that operate within the frequency range of approximately 30-50 kHz. Warm and hot wall crucibles feature a cylindrical crucible with a cold wall bottom. Typically, warm wall crucibles are made of non-suscepting alumina or zirconia, although a suscepting crucible liner is optional. Hot wall crucibles are made of silicon carbide or Inconel. The induction heating coils normally operate in the range of approximately 30-50 kHz for warm wall crucibles and 1-3 kHz for hot wall crucibles. In-can melter chambers are cylindrical canisters with an optional refractory lining. The canisters are surrounded by induction heating coils or a resistive heating element. Slagging chambers use the buildup of glass on the inside of the chamber walls to restrict heat loss that, along with water cooled walls, eliminate the need for refractory lining and controls the temperature of the chamber by removing heat quickly. Preferably, the top of upper zone 84 has a plurality of pipes, shown generally as 94, 96, attached thereto for air, oxygen and water feeds, instrumentation, camera view ports and the like. Also, a larger pipe 98 is attached to the top of upper zone 84 for gas recirculation (discussed in greater detail below). Waste is fed into upper zone 84 via rotary screw melter feeder 62 (shown in FIGS. 2a-2b) through a first side port 102. A second side port 104 is a gas outlet port connecting melter chamber 26 with the off-gas cleaning and control subsystem. Waste fed into melter chamber 26 from shredder/classifier 54 of waste preparation subsystem 24 (see FIGS. 1, 2a-2b) falls onto the molten glass pool within melt chamber 88 formed by glass formers, noncombustible waste and ash from combustible waste. Organic constituents present in the waste are consumed by the intense heat maintained within thermal zone 84 and burned off. Combustibles within the waste become off-gas, which passes through outlet port 104, and ash, which dissolves into the molten glass pool in chamber 88. The non-organic constituents in the waste also dissolve or settle into glass thereby becoming incorporated into the glass melt. Alternatively, aqueous waste 44 can be fed directly into melter chamber 26 without prior conditioning or blending with other types of waste. Similarly, resins and sludges 42 and adsorbents containing resins and sludges 42 or liquid waste can be fed directly into melter chamber 26 without affecting greatly the final glass product produced. Controlled amounts of oxygen, preferably mixtures containing approximately 20-90% oxygen, are injected into melter chamber 26 through one of the pipes 94, 96 to aid in processing and volume reduction of the contents of reciter chamber 26. The high oxygen content minimizes the off-gas volume and improves oxidation kinetics in melter chamber 26, thus greatly reducing nitrogen in the off-gas. Off-gas formed in melter chamber 26 is exhausted through second port 104, which passes to exhaust control component 32 of the off-gas cleaning and control subsystem (discussed in greater detail below). Alternatively, an immersion thermocouple (not shown) can be used to verify the maintenance of off-gas and refractory temperatures in melter chamber 26. A bottom induction nozzle 106 taps molten glass produced in melter chamber 26, preferably cooling the molten glass during tapping to stop flow as required. From nozzle 106, the molten glass proceeds to glass handling subsystem 28. Preferably, remote power supplies (not shown) provide approximately 400 kw of power at approximately 1-50 kHz to induction coils 92 through a lower port 107. Generally, 1-3 kHz is used for hot wall induction heating and in-can melter applications and approximately 30-50 kHz for warm and cold wall induction heated applications (both discussed above). The heat generated by induction heating melts and ultimately vitrifies the glass formers with the noncombustible waste contents and ash that have been fed into melter chamber 26. Induction heating provides much more efficient heating and stirring than conventional vitrification heating applications using electrodes. As a result, the consistency and homogeneity of the molten glass matrix and ultimately the final glass product is improved. The consistency of the final glass product is typically measured by the leach and solubility characteristics of the final glass composite. That is, when vitrified, metals in the waste contents dissolve in the glass in the form of metal oxides rather than the glass encapsulating the metal particles. The use of enriched oxygen (discussed below) enhances oxidation of metals to oxides thereby improving incorporation of metals into a glass matrix. A particulate filter 108 is remotely loaded in front of second port 104 to minimize particulate matter formed in thermal zone 84 from passing to the off-gas cleaning and control subsystem. Filter 108 also serves as a radiant heat barrier for thermal zone 84. Preferably, the differential pressure across filter 108 is monitored and, as the pressure increases--indicating that cleaning or replacement is necessary--filter 108 can be back flushed with gas to clean filter 108 or, alternatively, filter 108 can be pushed into melter chamber 26 and a new filter can be loaded. Glass handling subsystem 28 receives, solidifies and packages the stabilized liquid glass waste for eventual transport. Preferably, a portion of glass handling subsystem 28 includes a sealed enclosure 112 positioned under melt chamber 26 and nozzle 106. Enclosure 112 is dimensioned to house a bulk storage canister 114 that is to be filled with molten glass tapped from nozzle 106. Once canister 114 is filled with molten glass, it is cooled, capped and washed within enclosure 112. Canister 114 is then removed for positioning of the next canister to be filled. In FIG. 4, a schematic view of an alternative embodiment of melter/combustion subsystem and glass handling subsystem 28 (both shown generally in FIG. 1) of waste processing system 20 is shown. In this alternative embodiment, molten glass is tapped from nozzle 106 directly into a water-cooled glass solidification unit 116 where the glass is cooled into globules that can then be handled like marbles for ease of storage and handling. Solidification unit 116 is preferably a cooled, metal conveyor 118 that moves molten glass tapped from nozzle 106 to a waste glass hold-up bin 122 while simultaneously cooling the molten glass. Preferably, water is used as the cooling liquid and sprays on the bottom side of metal conveyor 118 and, optionally, as a mist on top of conveyor 118 through spray jets 123. With this relatively rapid solidification, the molten glass forms small, solid globules. In this embodiment, by the time the molten glass reaches the end of liquid-cooled conveyor 118, the glass will be fully solidified and cooled to less than approximately 250.degree. C. The glass globules will fall into holding bin 122 through a tube 124 connecting liquid-cooled conveyor 118 to holding bin 122. A waste glass fill chamber 126, which is sealed against an outlet 128 of holding bin 122, houses a waste container 132 for filling with the glass marbles as required. Preferably, any fine glass particulates exiting liquid-cooled conveyor 118 will be returned to melt chamber 26 by appropriate means. The alternative embodiment shown in FIG. 4 allows the glass globules to be stored in a wide variety of container sizes and shapes without the need for complex fill port arrangements. This is advantageous, particularly in the United States, because the glass marbles produced can be directly placed in high density, crosslinked polyethylene containers or other appropriate containers for final disposal. FIGS. 5a-5b show the off-gas cleaning and control subsystem, that is also shown diagrammatically in FIG. 1. As mentioned previously, the off-gas cleaning and control subsystem has an exhaust control component 32 and a pollution control component 34. Exhaust control component 32 is preferably a carbon monoxide control chamber 142 for oxidizing volatile organics and vapor products to carbon dioxide and water. Control chamber 142 is preferably a cylindrical, vertically-oriented vessel constructed with an inconel or other alloy inner shell lined with a high temperature refractory designed for long-term operation. The refractory can be a remotely applied, gunite cement that eliminates manual replacement of refractory. Control chamber 142 has an inlet port 144 in connection with outlet port 104 of melter chamber 26 for receiving off-gas therefrom. Inlet port 144 is preferably oriented so that off-gas enters control chamber 142 at an angle to increase gas flow and mixture. Also, control chamber 142 has mounted around its upper area a plurality of electrical resistance heaters 148 for keeping control chamber 142 at proper operating temperatures. Preferably, resistance heaters 148 are rated at a total power of approximately 160 kw. Control chamber 142 is designed to provide high turbulence, preferably greater than a Reynolds number of approximately 8,000 for off-gas having a residence time of approximately 2-3 seconds with a temperature of 1000.degree.-1200.degree. C. Such turbulence is preferably sufficient to completely oxidize organics in the off-gas from melter chamber 26. An injection port 152, shown in FIG. 5b, tangentially penetrates control chamber 142 for injecting an air/oxygen mixture at an angle to increase mixing of the gas and to assist in the conversion of carbon monoxide to carbon dioxide and water. An air/oxygen mixture is used instead of air alone to reduce the gas volume and formation of NO.sub.x, both of which would be higher if air alone were used since air is approximately 78% nitrogen. Also, an outlet port 154 located at the bottom of control chamber 142 connects to ductwork 156, which directs off-gas from control chamber 142 forward to pollution control component (shown generally as 34) of the off-gas cleaning and control subsystem. Prior to pollution control component 34, a pressure control and containment system is connected to ductwork 156. The pressure control and containment system preferably comprises an overpressure control chamber 157 connected to ductwork 156 through piping 158 and an overpressure control device 159. The pressure control and containment system is used for capturing releases by the entire waste processing system 20 due to large pressure spikes, thus preventing uncontrolled releases to the environment. Overpressure control chamber 157 is preferably an expansion tank for containing vented gases during excessive overpressure conditions. Also, overpressure control chamber 157 may contain water spray cooling devices (not shown) to assist in cooling gases released into chamber 157. Overpressure control device 159 is used to separate overpressure control chamber 157 from ductwork 156 and the normal operation of waste processing system 20, and usually in the form of a burst disk that connects overpressure control chamber 157 to ductwork 156 when an excessive overpressure condition forms within waste processing system 20. Also, the pressure control and containment system contains emergency exhaust (not shown) in case of explosion, backfire or flareup. Pollution control component 34 of the off-gas cleaning and control subsystem can include any of a number of elements but the specific configuration of pollution control component 34 will depend on factors such as emissions regulations, locality, public opinion and cost. The ability to properly clean off-gas from melter chamber 26 is required not only to license and legally operate systems such as the waste processing system 20, but also to protect public health and the environment. Preferably, a wet scrubbing pollution control component 34 is used in the off-gas cleaning and control subsystem of waste processing system 20. Such a configuration preferably contains a gas quencher 172, a venturi scrubber 174, a cyclone mist separator 176, a packed bed scrubber 178, an electric heater 182, a pair of HEPA filters 184 and 186, and an induced draft fan 188. One advantage of a wet scrubbing configuration is the high removal efficiency for particulate metals and acid gases such as SO.sub.x, HCl and HF. Another advantage is that particulates in the off-gas are intercepted by water droplets in venturi scrubber 174 and contained in the scrubbing liquid. Thus, the particulates are not produced as fly ash. Gas quencher 172 connects to ductwork 156 from control chamber 142 and is the first element of pollution control component 34. Gases exiting control chamber 142 potentially contain a variety of gases and vaporized metals that require treatment and/or removal prior to release to the atmosphere. Such pollutants include CO, SO.sub.2, SO.sub.3, NO.sub.x, HCl, HF, HBr.sub.2, heavy metals and radioisotopes (in particular C.sub.14, H.sub.3, and Cesium). Gas quencher 172 rapidly cools passing off-gas by injecting a solution of sodium hydroxide and water into the off-gas. The water mist initially absorbs the sensible heat and then absorbs latent heat as it is vaporized. By rapidly cooling the off-gas, gas quencher 172 reduces the possibility of downstream components being damaged by excessive heat. Secondly, gas quencher 172 reduces the gas load by a factor of 3--cool gas occupies less space than hot gas--thus reducing the necessary size of downstream components. Also, gas quencher 172 decreases any potential formations of Dioxins and Furans since the off-gas does not remain in gas quencher 172 long enough nor is the temperature range (approximately 200.degree.-300.degree. F.) appropriate for their formation. Finally, gas quencher 172 causes the initiation of particulate and acid gas absorption. Venturi scrubber 174 is used to remove both particulates and acid gases from the off-gas stream at very high efficiencies. Venturi scrubber 174 has a converging section, a throat section and an expansion section. In operation, gases are accelerated in the converging section and pass through the throat section where the scrubbing liquid solution is injected. As the gas passes through the throat and expansion sections, the sudden expansion atomizes the scrubbing liquid thereby providing a large surface area for the collection of particulate and acid gases. The wet, mist-laden gas from venturi scrubber 174 enters cyclone mist separator 176 tangentially through a horizontal tangential inlet 194. The cyclonic entrainment uses inlet 194 to induce a centrifugal force on the entering gases. Liquid drops are forced to the internal walls of separator 176 where the drops coalesce and drain into a collection sump 196. From collection sump 196, the coalesced liquid is preferably recirculated back to gas quencher 172 via a scrubber pump 198 and piping 202. Alternatively, the scrubber liquid is directed to a volume reduction system (not shown) such as the blender/dryer system described above. Unlike the liquid drops, the mist-free gases exit cyclone mist separator 176 and enter packed bed scrubber 178. Packed bed scrubber 178 removes acid gas at high efficiencies. In operation, the entering gas stream flows through a nonmetallic packing material that provides a high wetted surface area. A scrubbing solution is injected counter-currently to the gas stream, that is, down through a packed bed. The scrubbing solution, which is preferably a water solution adjusted with sodium hydroxide to a pH of approximately 6-8, drips down through the packed bed and fully wets all the available surface area. As the gas stream flows up through the packed bed, the particulates and acid gases from the gas stream impinge on the wetted packing and are absorbed and neutralized by the scrubber liquid. The scrubbing solution then drains down through the cyclone mist separator 176 and into collection sump 196. Approximately 50-150% of the stack off-gas is recycled using a blower unit 162 contained within a segment of recycling pipe 164 in connection with the rear end of pollution control component 34. Since 90% oxygen is injected into reciter chamber 26 (see pipes 96, 98 in FIGS. 3-4 and related discussion above) to greatly reduce nitrogen, a portion of the off-gas produced in melter chamber 26 can be recycled after passing through packed bed scrubber 178. A carbon dioxide removal unit 179 and a nitrogen removal unit 181 can be installed along recycling pipe 164 after blower unit 162. In this configuration, carbon dioxide removal unit can be any known removal unit suitable for this application but is preferably a liquification/refrigeration unit or an adsorber/scrubber unit. Similarly, nitrogen removal unit 181 can be any suitable unit but is preferably a nitrogen removal adsorber. Heater 182, preferably an electric resistance heater rated at approximately 50 kw, can be placed between packed bed scrubber 178 and filters 184, 186 for reducing the humidity of the gas as required for efficient operation of HEPA filters 184 and 186. Also, heater 182 could be sized to suppress the stack plume as desired, that is, to reduce the water vapor plume of the stack gas. Such reduction may be driven by public sensitivity to stack plumes. HEPA filters 184 and 186 are preferably high efficiency particulate absorbing filters capable of removing particles approximately 0.30 micrometers and larger at approximately 99.97% efficiency. The filter cartridge (not shown) for HEPA filters 184 and 186 is preferably a glass fiber media. Preferably, filter housings facilitate removal of the filter cartridge so that nothing is released to the environment. Preferably, HEPA filters 184 and 186 are configured in parallel so that pollution control component 34 remains in operation while either one of filters 184, 186 is being changed out. Filters 184, 186 can be housed in a stainless steel housing (not shown) along with pre-filters and the like as necessary. Induced draft fan 188, preferably a centrifugal, radial blade fan, is positioned just before a plurality of Continuous Emission Monitors 189 and an emission stack 204. Induced draft fan 188 is used to pull gas through the off-gas cleaning and control subsystem and to maintain a negative pressure inside melter chamber 26 in the range of approximately -2.9 to -4.9 KPa. Alternatively, carbon dioxide removal unit 179 and nitrogen removal unit 181 can be used downstream of HEPA filters 184 and 186 for removal of carbon dioxide and nitrogen thereby leaving almost no stack emissions. Preferably, collection sump 196 is a scrubbing liquid recirculation system, similar to a closed water cooling system. Collection sump 196 has a tank, dual pumps, filters, a heat exchanger and various piping and valves (none of which are shown). Collection sump 196 differs from a closed water cooling system in that the tank is a holding tank acting as a sump for the removal of sludge returned from the scrubber 178. Also, incorporated into the collection sump 196 is a scrubber-solution, pH adjustment subsystem (not shown) with dual metering pumps and a controller. Preferably, this subsystem continuously monitors and adjusts the pH of the scrubber solution between approximately 6-8 by the addition of sodium hydroxide, shown generally as 206, or other suitable substance. Also, fresh make-up water can be added as required. Normally, scrubber sludge is comprised principally of NaCl from neutralized HCl (from PVC plastics) and Na.sub.2 SO.sub.4 from neutralization of SO.sub.x from cation ion exchange resins. In use, waste processing system 20 vitrifies radioactive waste, comprised essentially of DAW 38, resins and sludges 42 and aqueous waste 44, that is generated by plant 36 and conditioned and blended with glass formers for vitrification. DAW 38 is conditioned by shredding. Resins and sludges 42 are conditioned by drying of interstitial, "free" water. Aqueous waste 44 is conditioned by concentration using filtration, adsorbents, and dryers so that aqueous waste 44 is approximately 5-90% by volume solids, but usually 70-90% by volume solids. Preferably, the DAW and conditioned resin and aqueous wastes are packaged in suitable containers and transported off-site to a centralized facility that houses waste preparation subsystem 24, the melting combustion subsystem, glass handling subsystem 28 and the off-gas cleaning and control subsystem. Resins and sludges 42 are then placed in hopper 64 and the remaining waste is fed into shredder/classifier 54. Alternatively, some of the waste can be fed directly into melter chamber 26 depending on its constituency. Then, all of the waste types are blended together depending on their particular constituents to produce a waste feed stream that will yield a constant BTU value when combusted. Shredder/classifier 54 and feeder 62 can be used to assist in blending the waste types, as can hoppers 64, 68. Once waste feed is fed into melter chamber 26, either continuously or in a batch mode, the combustible constituents of the waste feed are combusted in upper zone 84 and lower zone 86 to form an off-gas and an ash. The ash settles or dissolves along with the noncombustible constituents of the waste feed and the glass formers into the glass matrix. The ash, noncombustibles and the glass formers melt together to form a molten glass matrix using chamber 88. The molten glass matrix is dispensed to glass handling subsystem 28, where it is stored in suitable containers for solidification. The molten glass can be cooled as small blocks or large monoliths, depending on the size and shape of the storage containers, which can be high integrity containers or other suitable packages. Also, the molten glass can be cooled in the shape of marbles or crushed into a frit for storage in containers of various sizes and shapes. The off-gas produced in thermal zone 84 of melter 26 is processed through the off-gas cleaning and control subsystem, where it cleaned, partially recycled and eventually passed through a filtered emissions stack 204 into the environment. It will be apparent to those skilled in the art that the present invention is applicable to the processing of all types of waste, including but not limited to radioactive, toxic, industrial, household and the like, and that the examples discussed herein above are exemplary only. It will be apparent to those skilled in the art that many changes and substitutions can be made to the preferred embodiment herein described without departing from the spirit and scope of the present invention as defined by the appended claims.