Selective electromagnetic heating for rate control in electrically heated melters

Abstract

Embodiments described herein relate to methods and systems for controllably delivering radiation into one or more discrete locations within a cold cap of hot material on a molten portion contained within a processing chamber of a directed energy melter. The one or more discrete locations include a foam within the cold cap at an interface with the molten portion.

Description

SELECTIVE ELECTROMAGNETIC HEATING FOR RATE CONTROL IN ELECTRICALLY HEATED MELTERSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 673,070 filed on July 18, 2024, the disclosure of which is incorporated herein in its entirety by this reference.BACKGROUND

[0002] The technology selected to process and stabilize radioactive waste from reprocessing of spent reactor fuel in defense programs in the United States and also from reprocessing of commercial reactor spent fuel in other countries involves the use of electrically heated glass melter technology for the incorporation of radioactive material into highly engineered glass products. The processing of high-level waste (HLW) and some Low Activity Waste (LAW) typically involves vitrification of the residual fission products generated during the reprocessing of the spent nuclear fuel. In the United States, HLW was produced from the processing of spent or partially spent fuel where the primary objective was production of nuclear material for defense programs. Much of the HLW generated from the nuclear defense complex operations is stored in tanks at United States Department of Energy (DOE) facilities at Hanford, Savannah River and Idaho. In addition to HLW there are large quantities of low-level waste (LLW) or low activity waste (LAW) that glass melters can immobilize in a vitreous waste form for long term storage. Joule (electrically) heated glass melting technology has been used for processing most of the HLW and a significant fraction of the LLW in the US and elsewhere.

[0003] The Hanford site near Richland, Washington has 177 carbon steel tanks with over 200,000 cubic meters of radioactive waste material generated during the cold war. The Waste Treatment and Immobilization Plant (WTP) has initiated operation of the LAW melters and is now planning for the commissioning of the HLW melters.

[0004] The vitrification rates of these and other facilities employing liquid or slurry- fed joule-heated melter (JHM) technology are limited by the rate at which the incoming feed mixture can be incorporated into the glass melt.SUMMARY

[0005] In an embodiment, a system for selectively melting material is disclosed. The system includes a processing chamber configured to hold hot material therein, wherein the- Page 1 - Docket No. 57003-00431hot material includes a molten portion and a cold cap disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion. The system includes at least one EM radiation source configured to selectively generate electromagnetic (EM) radiation in one or more of a microwave or a millimeter wave frequency. The system includes one or more waveguides operably coupled to the at least one EM radiation source and configured to guide the EM radiation into at least the foam of the cold cap in the processing chamber. The system includes a controller operably coupled to the at least one EM radiation source, wherein the controller is configured to selectively adjust one or more of a power or a frequency of the EM radiation to selectively eliminate at least some of the foam, control a temperature profile in the cold cap, and prevent emissions of volatile components from the cold cap from exceeding a selected level.

[0006] In an embodiment, the at least one EM radiation source is configured to generate and emit one or more of microwave radiation or millimeter wave radiation. In an embodiment, the at least one EM radiation source is located outside of the processing chamber. In an embodiment, the one or more waveguides are configured to change locations of the output orifices thereof within the processing chamber in any of an x, y, or z plane, or combinations thereof.

[0007] In an embodiment, the system includes one or more sensors positioned and configured to sense a temperature of at least a portion of the cold cap, positioned and configured to measure emissions from a surface of the cold cap, or both.

[0008] In an embodiment, the controller is configured to receive a sensed temperature of the at least a portion of cold cap and in response thereto, selectively adjust the power, frequency, or the location of the application of the EM radiation.

[0009] In an embodiment, system includes one or more of joule heating electrodes, plasma heating electrodes, or induction heating means. In an embodiment, the at least one EM radiation source is the sole source of heating for the processing chamber.

[0010] In an embodiment, a method for melting material is disclosed. The method includes producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein the EM radiation includes one or more of microwave or millimeter wave radiation. The method includes directing the EM radiation into at least the foam of the cold cap.- Page 2 - Docket No. 57003-00431Producing the EM radiation outside of the processing chamber and directing the EM radiation into at least the foam of the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap, to eliminate at least some of the foam, and prevent emissions of one or more components of the hot material in the cold cap from exceeding a selected level.

[0011] In an embodiment, the method includes adding hot material into the processing chamber, wherein the hot material includes radioactive waste particles and glass particles, wherein adding the hot material into the processing chamber includes adding the hot material via a waste inlet operably coupled to the processing chamber.

[0012] In an embodiment, the method includes varying one or more of a power, a frequency, or a location of the application of the EM radiation effective to provide one or more of a selected EM radiation penetration depth into the foam of the cold cap or selected temperature profile in the cold cap.

[0013] In an embodiment, the method includes determining a temperature of one or more of the solid portion, the calcined portion, or the foam of the cold cap with one or more sensors and adjusting a frequency of the EM radiation responsive to determining the temperature.

[0014] In an embodiment, the method includes heating the molten portion via one or more of joule heating, plasma heating, or induction heating, wherein a first amount of power supplied by the EM radiation is less than a second amount of power supplied by the one or more of joule heating, plasma heating, or induction heating.

[0015] In an embodiment, a method for melting material is disclosed. The method includes producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, wherein the cold cap includes a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein a frequency of the EM radiation is between 0.8 GHz and 10 GHz. The method includes guiding the EM radiation into the processing chamber. The method includes directing the EM radiation into the foam of the cold cap. The method includes sensing a temperature of the cold cap. The method includes adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap.- Page 3 - Docket No. 57003-00431

[0016] In an embodiment, directing the EM radiation into the foam includes varying one or more of the frequency, power, or location of application of the EM radiation over a duration.

[0017] In an embodiment, the processing chamber is configured to contain radioactive material and the hot material includes radioactive material.

[0018] In an embodiment, the method includes selective dynamic control of one or more of frequency, power, or location of application of the EM radiation in the cold cap or portions thereof.

[0019] In an embodiment, the method includes microwave or millimeter wave heating with power and frequency selected to penetrate through the cold cap and be absorbed in a top layer of molten material in the glass bath. The transfer of heat from the microwave or millimeter wave heated top layer of the molten glass to the bottom layer of the cold cap can further increase the vitrification processing rate.

[0020] Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the embodiments of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0022] FIG. 1A is a schematic of a system for melting material, according to at least some embodiments.

[0023] FIG. IB shows a close-up view of region A of FIG. 1A, according to at least some embodiments.

[0024] FIG. 1C is a schematic of an example collimating device, according to at least some embodiments.

[0025] FIG. ID is a schematic of an example collimating device, according to at least some embodiments.- Page 4 - Docket No. 57003-00431

[0026] FIG. 2 is a schematic of a system for melting material, according to at least some embodiments.

[0027] FIG. 3 is a schematic of a system for melting material, according to at least some embodiments.

[0028] FIG. 4 is a schematic of a mobile system for melting material, according to an embodiment.

[0029] FIG. 5 is a flow chart of a method for melting material, according to at least some embodiments.

[0030] FIG. 6 is a flow chart of a method for melting material, according to at least some embodiments.

[0031] FIG. 7 is a schematic of a controller for executing any of the example methods disclosed herein, according to at least some embodiments.DETAILED DESCRIPTION

[0032] Embodiments described herein relate to systems and methods for selectively melting material in a melter. The systems and methods controllably deliver electromagnetic (EM) radiation into one or more discrete locations within a cold cap of hot material that sits on a molten portion all contained within a processing chamber of a directed energy melter. The one or more discrete locations include a foam layer within the cold cap. The foam is disposed below a calcined layer and an uppermost solid layer of the cold cap, at an interface of the cold cap with the molten portion.

[0033] Selective dynamic spatial and temporal control of the directed EM radiation (e.g., power and / or frequency) can provide an effective means of providing cold cap heating in targeted locations and in the selected amounts to enhance vitrification process rates. For even more efficient incorporation of cold cap material into the molten portion, the systems and methods disclosed herein provide dynamic heating of cold cap material using variation of the frequency of EM radiation (e.g., microwave and / or millimeter wave). Such variation may be carried out as a function of one or more of time or position of the end of at least one waveguide for emitting the EM radiation. The systems and methods disclosed herein, including the selective dynamic spatial and temporal control of EM radiation, can provide a substantial increase in vitrification process rates while maintaining cold cap emissions below a selected threshold amount and maintaining glass quality.

[0034] Melter processing rates are limited by the temperature of the cold cap. An experimental study and computational studies of the beneficial effects of increasing cold- Page 5 - Docket No. 57003-00431cap temperatures was carried out by using a glass melter that operated with a relatively high molten glass temperature, such as in the range of 1,000 °C to 1,650 °C. By using higher glass temperatures, substantially higher processing rates (e.g., a factor of around 2x faster) may thus be obtained in existing melters. However, because use of higher temperatures in the molten glass reduces glass quality, this approach has not been used for melters. The use of selective heating with EM radiation into the foam in a cold cap, dynamic EM radiation heating, or both makes it possible to obtain substantial rate processing gains without the drawback of having a higher temperature throughout the glass melter. Such solutions limit emissions of radioactive material from the glass material and the cold cap and also maintain the quality of the glass material generated from the melter.

[0035] Increasing the rate of conversion of radioactive waste into vitrified material provides an important solution for addressing the challenge of isolating radioactive waste from the environment for long periods of time. New technology is needed to reduce the time and cost for addressing this need. For example, in the United States there is an urgent need to accelerate the vitrification of radioactive defense waste, such as at the Department of Energy Hanford site. The methods and systems herein address an urgent need to accelerate the processing rate in melters (e.g., joule-heated melters) that are employed for waste vitrification (e.g., vitrifying radioactive waste in a highly stable glass). It is estimated that, using present glass melter technology, vitrification of present stocks of radioactive waste will take many decades under even the most optimistic assumptions.

[0036] The processing rate in joule-heated melters is limited by the amount of heating at the interface of the newly added material that has not melted (the "cold cap") and become incorporated into the molten portion in the melter. This is because the primary mode of thermal energy transfer into the cold cap is conduction from the molten glass pool (e.g., molten portion or molten material) below the cold cap. Additional heating is useful at this interface in order to remove this processing rate limitation. However, it may also be necessary to prevent overheating of the cold cap in order to prevent and / or reduce emissions of radioactive material from the surface of the cold cap that faces the plenum of the processing chamber of the melter and to also avoid increasing the bulk glass bulk temperature in the melter in or to avoid creating undesired glass characteristics.

[0037] Examples of methods and systems herein utilize EM energy (e.g., microwave radiation) to aid in melting the introduced hot material (e.g., waste material and glass particles) in the cold cap. For example, the methods and systems described herein direct EM radiation into the cold cap to the interface between the cold cap and the molten portion- Page 6 - Docket No. 57003-00431to selectively accelerate heating subsurface portions of the cold cap. In some examples, the EM radiation is controlled to penetrate to a selected depth within the cold cap to aid melting / vitrification of waste material in the hot material. For example, the EM radiation may supplement the heat in a joule-heated melter so as to accelerate heating of the cold cap and increase the processing rate of new material without causing emissions of radioactive material from the surface of the cold cap to exceed a selected level or compromise the integrity of the resulting glass material with the vitrified waste therein. The melting rate improvements provided by the embodiments disclosed herein are estimated to potentially save tens of billions of dollars and reduce the amount of time needed to clean-up current stocks of radioactive materials in the United States. It is estimated that the rate enhancements provided by embodiments disclosed herein are expected to be at least two times faster than current melting techniques and possibly more than four times faster than current melting techniques.

[0038] Example methods and systems described herein may accelerate melting of the cold cap (e.g., incorporation of the cold cap into the molten portion) without raising the temperature of the material on the surface (e.g., surface opposite the molten portion) of the cold cap above a volatilization temperature of the material or without raising the bulk average temperature of the molten glass bath. Thus, the examples of methods and systems disclosed herein may allow for faster vitrification of material into a molten bath than conventional melters while preventing volatilization (e.g., vaporization) of the material. Accordingly, radioactive materials may be quickly and safely processed (e.g., vitrified) to isolate the radioactive materials from the environment.

[0039] FIG. 1A is a schematic of a system 100 for melting material, according to at least some embodiments. The system 100 includes a processing chamber 110, at least one EM radiation source 120, one or more waveguides 122 operably coupled to the at least one EM radiation source 120, a waste inlet 130, and a controller 140 operably coupled to the at least one EM radiation source 120 and the waste inlet 130. The processing chamber 110 may include a container with a wall thickness and material composition sufficient to contain a molten portion therein. For example, the processing chamber 110 may include a waste processing chamber (e.g., melter), such as a radioactive waste processing chamber. The processing chamber 110 may include an interior region 112 configured to contain a hot material 132 therein, such as radioactive waste in a molten glass bath, and to receive the radioactive waste in solid form. For example, the processing chamber 110 may include a refractory metal lining disposed within a housing (e.g., ceramic body) or a refractory- Page 7 - Docket No. 57003-00431ceramic lining disposed in a metal housing. In some examples, the processing chamber may have a relatively long shallow design to aid volumetric heating from the at least one EM radiation source 120.

[0040] The hot material 132 may include a waste material such as radioactive waste or any other material to be incorporated into a molten glass. The hot material 132 may initially include the waste material, one or more solvents (e.g., water, an acid), and one or more dissolved portions of the waste material. The hot material 132 may include a slurry of the waste material and the one or more solvents. The hot material 132 may include glass particles for forming a molten portion 139 (e.g., molten glass bath), such as glass forming particles (e.g., oxides), borosilicate glass beads, alumina phosphate glass, alkalialuminosilicate glass, high silica glass, sodium phosphate glass, iron enriched basalt, iron phosphate glass, lead iron glass, or any other glass forming material suitable for vitrifying (radioactive) materials. For example, the slurry may include the glass particles. The molten portion 139 (e.g., molten material such as glass) may incorporate or encapsulate (e.g., vitrify) the waste materials therein upon melting. Accordingly, the waste material in the hot material 132 may be vitrified using the system 100.

[0041] The hot material 132 may be processed in the processing chamber 110 to include a molten portion 139 and a cold cap 134 disposed on the molten portion 139. FIG. IB shows a close-up view of region A of FIG. 1 A, according to at least some embodiments. As shown, the cold cap 134 may be at least semi-solid and includes an uppermost solid portion 136, a calcined portion 138 below the solid portion 136, and a foam 137 below the calcined portion 138. The foam 137 may have an interface with the molten portion 139 where the foam 137 is incorporated into the molten portion 139. The solid portion 136 may include the hot material 132 having solid glass-making particles that are not yet melted, the waste material (e.g., radioactive material), and carrier material (e.g., solvent, soil, sand, or the like). The solid portion 136 may not be completely solid, but components therein such as the glass making material may be solid. For example, the solid portion 136 may include a slurry containing the waste material and one or more of a solvent (e.g., water), glass forming material(s), and other carrier material(s).

[0042] The operation of a joule-heated vitrification methods includes introduction of a slurry containing HLW or LAW mixed with glass forming constituents into the (glass melter) processing chamber 110. The slurry feed accumulates on the surface of the molten portion 139 (e.g., molten glass or glass bath) and undergoes a series of chemical and- Page 8 - Docket No. 57003-00431physical processes eventually resulting in the incorporation of oxides of the radioactive materials into the final glass product.

[0043] The three primary zones in the (joule-heated) melter are the plenum, the cold cap, and the molten pool of glass. Above the cold cap, the plenum generally operates in a temperature range of 200-300 °C. Slurry containing waste and glass forming additives is introduced into the plenum of the processing chamber 110 where evaporation of the aqueous phase of the slurry takes place. The slurry mixture forms a layer on the surface of the bulk molten glass bath where boiling and initial drying takes place. The energy required to drive the steady state boiling process is primarily derived from the electrical energy passing through the molten portion 139. In some melter systems, plenum heaters may be added to enhance the rate of evaporation and drying on the upper surface of the cold cap 134.

[0044] The chemical and physical changes in the cold cap involve complex sets of chemical reactions where nitrates, nitrites, carbonates, hydroxides, and various other chemical compounds are all eventually converted into oxides that are assimilated into the molten portion (e.g., glass melt).

[0045] Incorporation of the cold cap 134 into the molten portion 139 (e.g., melting the hot material) may include at least four distinct processing zones, the solid portion 136 where drying of the hot material 132 occurs (e.g., liquid components of the waste slurry are evaporated); the calcined portion 138 where calcining and other reactions of the components of the hot material takes place; the foam 137 where final calcining and gas evolution processes produce small bubbles in the partially vitrified hot material 132 to form the foam 137; and where melting and dissolution of the foam 137 into the larger molten portion 139 (e.g., glass bath) takes place. Each of these processing zones may absorb thermal energy (e.g., EM radiation) at different rates. For example, the solid portion 136 includes significant absorption of EM radiation, the calcined portion 138 includes partial to good transmission of EM radiation as the calcined portion 138 dries, the foam 137 has variable absorption of EM radiation based on the amount of bubbles therein, and the molten portion has significant absorption of the EM radiation.

[0046] The solid portion 136 of the cold cap 134 contains raw feedstock (e.g., hot material 132) with high water content and is where vigorous boiling and initial drying of the hot material 132 occurs. As noted above, in this zone the interaction of the microwave energy absorbed is significant and a large percentage of the microwave energy is absorbed which increases the evaporation rate of the water from the cold cap 134.- Page 9 - Docket No. 57003-00431

[0047] Without utilizing the at least one EM radiation source 120, the latent heat of vaporization energy required to boil off the water fraction of the feed is via conduction from the high temperature molten glass bath below and a combination of radiation, conduction, and convection from the melter surfaces and the gases in the plenum space above the cold cap 134. The EM energy (e.g., microwave power) can be employed (e.g., focused and varied as a function of time and spatial location) to provide selective internal heating of one or more portions of the cold cap 134 resulting in a selectively controlled rate increase of the drying and calcining of the incoming waste as it transitions through the various layers of the cold cap 134. The amount of EM power and the length of time it is used is controlled (e.g., by controller 140) to meet selected drying and calcining objectives and to prevent emissions of gaseous radioactive material (e.g., cesium) beyond an acceptable level.

[0048] The calcined portion 138 of the cold cap 134 is characterized by further drying where both free water and chemically bound water are driven off the reacting components of the hot material 132. Depending on the composition of the hot material 132, the gases that evolve from the calcined portion 138 are composed of water vapor, carbon dioxide, oxides of nitrogen, oxides of sulfur, and other gases. The calcined portion 138 is relatively porous allowing the gases to evolve from the drying and reacting hot material 132 therein through the boiling solid portion 136 above. The calcined portion 138 will absorb the EM radiation (e.g., microwave energy) but will have a finite transparency due to the absence of water in the liquid phase. The use of a range of EM (e.g., microwave and or millimeter wave) frequencies and the control of the EM power that is employed as a function of time facilitates the tuned deposition of EM radiation and enhances the desired transmission of a certain fraction of the microwaves to regions in and below the calcined portion 138.

[0049] The primary mode of thermal energy transfer into the cold cap 134 is conduction from the molten portion 139 (e.g., molten glass bath) below the cold cap 134. This conduction is the rate limiting step of the incorporation (e.g., melting) of the unmelted material (cold cap) into the molten portion 139. The small bubbles forming the foam 137 are created in a semi-vitreous zone where some of the glass-like material exhibits lower dielectric absorption and therefore is less opaque to microwaves. The foam 137 also creates discontinuities in the interface between the cold cap 134 and the molten portion 139, which inhibits thermal energy transfer from the molten portion 139 into the cold cap 134. Localized absorption of the microwave energy causes the layers of glassy material to become less viscous allowing the gas within the foam 137 (e.g., small bubbles) to be- Page 10 - Docket No. 57003-00431released to the upper porous portion of the cold cap 134 and restoring continuous thermal contact between components of the thermal system (e.g., cold cap 134 and molten portion 139). Accordingly, localized heating of one or more of the foam 137 or calcined portion 138 thereabove would also increase thermal energy transfer into the cold cap 134.

[0050] Additional heating (aside from thermal energy transfer from the molten portion) may be provided at the interface of the foam 137 and the molten portion 139 in order to remove processing rate limitation presented by the foam 137. However, it may be desirable to only enhance melting and dissolution as this may be the rate limiting step in melting, such as in a joule-heated or induction-heated melter process. Applying excess heat to the solid portion 136 or the calcined portion 138 may result in higher volatilization of hot material (e.g., waste feed components) into gas phase within the processing chamber 110 which may be unintentionally removed or vented with other gas phase constituents within the processing chamber to prevent overpressure. When such hot material includes radioactive components, such as barium, cesium, iodine, strontium, technetium, xenon, rhenium, etc., it is important to prevent such radioactive components or carrier materials from being volatilized. Accordingly, EM radiation 125 may be input directly into one or more discrete layers or regions of the cold cap, such as into the foam 137.

[0051] Returning to FIG. 1 A, increasing the bulk temperature of the molten portion 139 may increase the wear of melter components such as the refractory lining and electrodes that supply the electric current into the molten portion 139. It may be desirable to prevent overheating of the cold cap 134 and thereby prevent and / or reduce emission of waste material (e.g., radioactive material) from the surface of the cold cap 134 that faces the plenum (e.g., unfilled space of the interior region 112) of the processing chamber 110. Using a directed beam of EM radiation 125 can provide the localized heating of the foam 137 and / or in the interface region between the foam 137 and the surface of the molten portion 139 (e.g., glass bath). The localized beam(s) of EM radiation from one or more EM radiation sources may be provided at a high enough frequency to concentrate most of the heating in one or more selected portions of the cold cap but be a low enough frequency to prevent volatilization of the cold cap due to overheating of the upper surface or portions of the cold cap. The frequency of the EM radiation from the one or more sources of EM radiation may be varied as a function of time to most effectively meet the above-stated objectives as they change over time, such as when the composition of the material in the cold cap changes over time (e.g., one or mor portions of the cold cap have solvent removed therefrom). The variation in frequency may be obtained by selectively using more the one- Page 11 - Docket No. 57003-00431EM radiation source where the sources differ in the frequency of EM radiation that they generate. The molten glass in the molten portion 139 may be conductive and may readily absorb the EM radiation to rapidly heat. Accordingly, the frequency of the EM radiation may be limited to prevent penetration of the EM radiation into the molten glass bath to prevent emissions of volatilized waste material caused by overheating of the molten glass bath.

[0052] In some examples, EM radiation may be directed into a discrete layer or region of the molten portion 139. For example, the systems and methods therein provide for operation of the EM radiation (e.g., microwave or millimeter wave) heating so that the EM radiation penetrates through the cold cap 134 and is absorbed in the top region of molten portion 139 (e.g., at or below the interface between the molten portion 139 and the cold cap 134). This heating may be facilitated by use of at least one EM radiation source (e.g., microwave source) configured to emit EM radiation at a low microwave frequency (e.g., 800 to 900 GHz) effective to penetrate through the cold cap 134 due to relatively little absorption of the low frequency EM radiation. This may also be facilitated by timing of the use of this EM radiation such that the absorption of the low frequency EM radiation by the material(s) in the cold cap 134 has been diminished by EM radiation heating at earlier times (e.g., limited absorption by water due to prior drying with microwave heating). The transfer of heat from the EM radiation heated top layer of the molten portion 139 to the bottom layer of the cold cap 134 can further increase the vitrification processing rate.

[0053] The EM heating systems can be used with melters where one or both of joule heating or induction heating is used to heat the molten portion, and the EM radiation (e.g., microwave) heating power is less than the joule heating or induction heating power because the volume of material in the cold cap is much less than the volume of molten portion. For example, the volume of the hot material in the cold cap may be less than one tenth, one eighth, one fifth, one quarter, or one third of the volume of the material in the molten portion.

[0054] The at least one EM radiation source 120 may be configured to selectively generate EM radiation in one or more of a microwave or a millimeter wave frequency. The at least one EM radiation source 120 generates and emits EM radiation at various frequencies, such as at least 0.8 GHz, 0.8 GHz to 10 GHz, 0.8 GHZ to 0.9 GHZ, 0.8 GHz to 2.5 GHz, 0.9 GHz to 10 GHz, 0.9 GHz to 3 GHz, 3 GHz to 6 GHz, 6 GHz to 10 GHz, 0.9 GHz to 5 GHz, or 5 GHz to 10 GHz. The frequency may be preset or may be varied during processing. Under certain circumstances, the EM radiation heating range may- Page 12 - Docket No. 57003-00431extend to the 10 GHz to 30 GHz microwave range. In some examples, the at least one EM radiation source 120 may include a microwave generator or emitter. An advantage of the systems disclosed herein is that there are EM radiation sources (e.g., microwave generators) in the 0.8 GHz to 10 GHz frequency range which provide a relatively low-cost radiation source and for which there is a large amount of commercial experience. The at least one EM radiation source 120 may emit one or more (e.g., varying) frequencies of the EM radiation during a discrete duration, such as in one or more frequencies in any of the ranges disclosed above. In some examples, two or more EM radiation sources 120 may be employed for selective heating of various portions (e.g., layers) in the cold cap at various times, such as two or more EM radiation sources configured to provide radiation with different frequencies for selective heating of various portions (e.g., layers) in the cold cap 134 at various times.

[0055] The at least one EM radiation source 120 may be positioned outside of the processing chamber 110. For example, in examples where the processing chamber is a radioactive waste processing chamber, the life of the at least one EM radiation source 120 can be prolonged by shielding the at least one EM radiation source 120 from harmful radiation (e.g., from the radioactive materials) inside of the processing chamber 110. Such a configuration reduces the amount of equipment that would need to be located within the controlled high dose rate zone. For example, only the waveguides and their spatial control arms would need to be located in this zone. In some examples, the at least one EM radiation source 120 may be isolated from the radiation in the processing chamber 110 by shielding (of the processing chamber) and by one or more bends in the one or more waveguides. The at least one EM radiation source 120 generates and emits EM radiation at various powers, such as 1 kW to 700 kW, 2 kW to 600 kW, 2 kW to 40 kW, 3 kW to 30 kW, 10 kW to 100 kW, or 20 kW to 600 kW. The power may be preset or may be varied during processing.

[0056] By controlling on or more of the power or frequency of the EM radiation (e.g., generally, as a function of time, or as a function of spatial position of a waveguide), the penetration depth of the EM radiation may be selectively customized to reach into and through the calcined portion 138 to the interface between the molten portion 139 and the foam 137. For example, in the frequency range of 0.8 GHz to 10 GHz, the penetration lengths of the EM radiation can be more than ten times greater than those in the millimeter wave frequency range and can be well matched to penetrate a selected depth into a cold cap. For example, the penetration depth can be 1 cm or more, such as 1 cm to 20 cm, 1 cm to 3 cm, 3 cm to 6 cm, 6 cm to 10 cm, 10 cm to 15 cm, 15 cm to 20 cm, 1 cm to 15 cm, 1- Page 13 - Docket No. 57003-00431cm to 5 cm, 5 cm to 10 cm, 5 cm to 15 cm, more than 2 cm, more than 5 cm, less than 20 cm, less than 10 cm, or less than 5 cm. Moreover, since the penetration depth can be increased by around a factor of ten as the frequency is decreased from 10 GHz to 0.9 GHz, the systems and methods herein provide capability for selective adjustment of penetration depth for different processing conditions or hot materials.

[0057] Radiation in the 0.8 GHz to 10 GHz frequency range is well suited to obtaining desired penetration lengths in the 1 cm to 10 cm range in water-soaked cold caps. Such radiation may also be well suited to penetrating to the selected penetration depths in cold caps with little to no water content. The selected penetration depth may be adjusted by choice of the EM radiation power or frequency. For example, as the frequency is decreased, the penetration depth will increase. When there is a relatively lower water content in the hot material it may be advantageous to use EM radiation in the 10 GHz to 30 GHz range, such as 10 GHz to 20 GHz, 20 GHz to 30 GHz, 10 GHz to 20 GHz, 15 GHz to 25 GHz, less than 30 GHz, less than 25 GHz, or less than 20 GHz. Such penetration depths may also be adjusted by positioning of the waveguide or output orifice thereof in relation to the cold cap 134, such as being closer to, or within a portion of, the cold cap in a vertical direction.

[0058] Further adjustment of radiation penetration depth may be obtained by using higher frequencies of radiation, such as millimeter wave radiation (e.g., greater than 30 GHZ). In addition, the spatial location of microwave or millimeter wave heating may also be determined by waveguides that are positioned so that a wave guide end (e.g., output orifice) is below the top of the cold cap. Further spatial heating variation may be obtained by adjustment of the vertical positions of these waveguides. The vertical position of waveguide ends can be preset or varied as function of time during the introduction of radioactive waste material into the reaction chamber.

[0059] The systems and methods described herein may selectively control the frequency, power, and other parameters of EM radiation heating, including the water content of the radioactive material that is introduced to the processing chamber (e.g., melter), so as to selectively control and increase the processing rate while keeping cold cap surface emissions at a sufficiently low level (e.g., below a threshold level). For example, EM (e.g., microwave) heating may be used to increase the processing rate of melting in a processing chamber, such as a joule-heated melter or an induction-heated melter, while limiting surface heating of the cold cap 134 to limit or prevent surface emissions of material therefrom. The EM radiation heating can be employed on existing melters (e.g., systems) as well as on new melters.- Page 14 - Docket No. 57003-00431

[0060] The systems and methods disclosed herein may overcome limitations of utilizing directed beams of higher frequency (e.g., millimeter) wave EM radiation to aid in melting the hot material. For example, because of the relatively short wavelength of the EM radiation in the 30 GHz to 300 GHz range, it may have a penetration depth in the cold cap that is much shorter than the thickness of the cold cap 134, especially if there is a substantial water content in the hot material (e.g., waste). Accordingly, EM radiation in the 30 GHz to 300 GHz range can cause excess heating at the surface of the cold cap. This can result in poor heating of the cold cap 134 at the interface with the molten portion 139 and elevated emissions of one or more components of the hot material 132 from the surface of the cold cap 134 (that faces the plenum of the processing chamber 110). The relatively short penetration depth of the EM radiation with the frequency of 30 GHz to 300 GHz can be due to the chemistry of the cold cap and / or the presence of water therein.

[0061] In some examples, the systems and methods disclosed herein includes using millimeter wave radiation in addition or alternatively to using microwave radiation. For example, in embodiments where a selected temperature profile in the cold cap, or portions thereof, includes heating one or more of the solid portion 136 or the calcined portion 138 of the cold cap, millimeter wave heating may be selectively utilized to apply at least a portion of the EM radiation into those portions of the cold cap. As noted above, the millimeter wave heating may include EM radiation in the 30 GHz to 300 GHz range, such as 30 GHz to 100 GHz, 100 GHz to 200 GHz, 200 GHz to 300 GHz, or less than 150 GHz. In such examples, the millimeter wave EM radiation may not penetrate as deeply into the cold cap 134 as microwave radiation. For example, microwave radiation may be used to penetrate the calcined portion 138 and / or the foam 137 to a selected depth below the surface of the cold cap 134. In some examples, millimeter wave radiation may be introduced by waveguides with ends that are below the top of the cold cap.

[0062] The systems and methods disclosed herein may overcome the limitations of purposefully bubbling a gas (e.g., larger bubbles of externally produced gases forced into and) through the molten portion 139 to heat the interface between the cold cap 134 and the molten portion 139 (e.g., glass bath). For example, utilizing EM radiation in a frequency range of 0.9 GHz to 10 GHz as disclosed herein does not cause emission of material from the surface of the cold cap 134, whereas providing a bubbling gas (not to be confused with small bubbles forming the foam 137) through the molten portion 139 causes volatilization and carries one or more components of the hot material 132 (e.g., radioactive waste material) to be carried in the bubbling gas. The example EM (e.g., microwave) heating- Page 15 - Docket No. 57003-00431systems and methods described herein can achieve cold cap modification-enabled processing rate enhancement without the issues that have prevented rate enhancement by purposeful bubbling and may thereby increase the processing rate of hot material therein by a factor of at least two (e.g., a factor of three or four in some cases) for a joule-heated melter. Further, the elimination of foam 137 (e.g., bubble layer in the cold cap) by selective application of EM radiation thereto increases the processing rate of hot material 132 into the molten portion 139.

[0063] The EM radiation 125 may be directed into the interior region 112 of the processing chamber 110 via one or more waveguides 122. For example, the one or more waveguides 122 may be operably coupled to the at least one EM radiation source 120. The one or more waveguides may guide the EM radiation into one on or more portions of the cold cap 134 in the processing chamber 110, such as into at least the foam 137. For example, each of the one or more waveguides 122 may include a conduit with one or more bends therein. The conduit may have a circular, square, or rectangular cross-sectional profile. The conduit may have one or more bends or curves therein. An advantage of using microwaves (e.g., EM radiation in the 0.9 GHz to 10 GHz range) may be that the requirement on window material in the waveguides would be less demanding than in the millimeter radiation frequency range (e.g., 30 GHz to 300 GHz radiation). For example, the window may be made of ceramic rather than a diamond. In some examples, the one or more waveguides may be translatable, such as being movable in one or more of lateral, vertical, or angular direction.

[0064] In some examples, the system 100 may include one or more collimating devices124 operably coupled to the one or more waveguides 122. The one or more collimating devices 124 may collimate and direct (e.g., guide) the EM radiation 125 into one or more beams. For example, the one or more collimating devices 124 may direct the EM radiation125 at one or more selected portions of the hot material 132 (e.g., interface below the cold cap 134). The one or more collimating devices 124 may collimate the EM radiation 125 to a selected beam width. FIG. 1C is a schematic of an example collimating device, according to at least some embodiments. As shown, the one or more collimating devices 124 may include a horn 124a, such as a radiative horn. FIG. ID is a schematic of an example collimating device, according to at least some embodiments. As shown, the one or more collimating devices 124 may include a phased array 124b. The horn 124a or phased array 124b may direct the EM radiation 125 at one or more discrete portions of the hot material 132 (e.g., the interface of the cold cap 134 and the molten portion 139). In some examples,- Page 16 - Docket No. 57003-00431the EM radiation generator may use a frequency source in combination with a klystron amplifier system which may send the EM radiation (e.g., microwave radiation) into a phased array of waveguides that protrude into the processing chamber.

[0065] Returning to FIG. 1A, with use of example systems and methods disclosed herein, EM radiation (e.g., microwave radiation having a frequency of 0.9 GHz to 10 GHz) can be introduced into the processing chamber 110 with a significant amount of collimation and spatial localization. For example, the one or more waveguides 122 and one or more collimating devices 124 may provide localized and directed heating of selected discrete portion(s) (e.g., the interface between the foam 137 and the molten portion 139, and / or any lateral portions of the cold cap 134) of the hot material 132. The one or more waveguides 122 may include or be moved by spatial control arms. The use of a translating divergent beam of EM radiation may result in a more controlled rate of evaporation and heating to minimize the vaporization of certain constituents of the hot material 132.

[0066] The waveguide(s) 122 may be configured move within the processing chamber in any of an x, y, or z plane, or combinations thereof to deliver EM radiation to one or more selected regions of the cold cap 134. Such regions may include a selected depth within the cold cap 134 or selected lateral regions of the cold cap 134. By translating the microwave deposition across the surface of the cold cap 134 while at the same time varying the frequency and microwave power as a function of time, selectively controlled volumetric heating of all layers in the cold cap 134 is possible using the systems and methods disclosed herein. Such volumetric heating provides faster incorporation of the hot material 132 in the cold cap 134 into the molten portion 139.

[0067] The systems and methods described herein may selectively control the position(s) of the EM radiation output (e.g., waveguide(s)), so as to selectively control and increase the processing rate while keeping cold cap 134 surface emissions at a sufficiently low level (e.g., below a threshold level). For example, translational movement or positioning of the EM (e.g., microwave) heating may be used to increase the processing rate of melting the hot material 132 in the processing chamber, while limiting surface heating of the cold cap 134 to limit or prevent surface emissions of material therefrom. The translational emission of EM radiation can be employed on existing melters (e.g., systems) as well as on new melters.

[0068] Control of EM radiation frequency, power, or emission position(s) may be utilized to more evenly and efficiently heat and incorporate the hot material 132 in the cold cap 134 into the molten portion 139 than systems and processes without such control.- Page 17 - Docket No. 57003-00431

[0069] The translational movement and application of the EM radiation may be carried out using movable waveguides 122. For example, the waveguide 122 may be configured to be moved in an x-y plane relative to the surface of the cold cap 134. Such translational movement may be carried out using telescoping components, such as telescoping tubes (e.g., ceramic cylinders). The translational movement may be carried out by ball screws and encoders, or the like.

[0070] Additionally or alternatively, the application of EM radiation across the lateral area of the cold cap 134 may be carried out by including tiltable waveguides. Such tiltable waveguides may be selectively tilted to apply EM radiation to more than one area of the cold cap 134, such as a second area of the cold cap 134 after applying EM radiation to a first area of the cold cap 134.

[0071] The system 100 includes the controller 140. The controller 140 may be operably coupled to one or more components of the system 100 via one or more connections 144 (e.g., wireless or hardwired connections) to control the system 100. The controller 140 may be operably coupled to the at least one EM radiation source 120, the waveguide(s) 122, and the waste inlet 130 via the connections 144. The controller 140 is configured to selectively adjust one or more of a power or a frequency of the EM radiation to selectively eliminate at least some of the foam, control a temperature profile in the cold cap, and prevent emissions of volatile components from the cold cap from exceeding a selected level.

[0072] The controller 140 may be configured (e.g., including programming) to selectively adjust one or more of the power or the frequency of the EM radiation or the position of the waveguide(s) 122 to selectively control a temperature profile in the cold cap and at least partially eliminate the foam 137, while preventing emissions of volatile components from the cold cap 134 from exceeding a selected level (e.g., below a threshold level). For example, the controller 140 may direct the at least one EM radiation source 120 to initiate generation or alter the power or frequency of the EM radiation 125. The controller 140 may cause the at least one EM radiation source 120 to vary the power or frequency of EM radiation 125 emitted into and at least partially through the cold cap 134 during a selected duration. For example, the controller 140 may direct the at least one EM radiation source 120 to vary the power or the frequency of the EM radiation 125 every second or more (e.g., 1 second, 10 seconds, 30 seconds, 1 minute, 10 minutes, 3 minutes, etc.). Such variation may be according to a pattern, such as a sinusoidal increase and decrease of frequency or wavelength of the EM radiation 125 over time. The variations may include at least two (e.g., three or more) discrete frequencies and / or wavelengths of EM radiation,- Page 18 - Docket No. 57003-00431such as to deliver the EM radiation to a depth within the cold cap 134 to reach into the solid portion 136, the calcined portion 138, the foam 137, the molten portion 139, or interfaces between any of the foregoing.

[0073] The controller 140 may be operably coupled to the waveguide(s) 122 or the one or more collimating devices. In such examples, the controller 140 may control the waveguide or the one or more collimating devices to direct the EM radiation to a selected depth and / or lateral location within the processing chamber 110. The controller 140 may actively control the target location of the EM radiation to coincide with a dry section (e.g., calcined portion 138) of the cold cap 134, the foam 137, the interface of the foam 137 with the molten portion 139, or the solid portion 136 (e.g., a newly added portion of the hot material). For example, the controller 140 may cause the waveguide 122 and the one or more collimating devices to direct the EM radiation to move locations in the cold cap, such as to areas of the cold cap 134 not yet treated by EM radiation.

[0074] The controller 140 can use preset characteristics or vary characteristics of the EM radiation such as EM radiation power or frequency; amount of drying of the hot material in the cold cap; processing rate; or spatial positioning of the EM radiation using sensed information such as cold cap portion temperature, molten portion temperature, and emissions of material from the cold cap 134. Sensed information on material emissions from the cold cap can be used to keep radioactive material emissions from the melting / vitrification process below selected levels. The controller 140 can use closed loop or real time monitoring of these and other parameters and / or open loop control using a lookup table. The look-up table can make use of experimental measurements of the impact of EM power, frequency, and other parameters on processing rate enhancement, emissions from the cold cap and other characteristics of melter operation.

[0075] In some examples, the system 100 may include one or more sensors 150 positioned and configured to sense a temperature of one or more portions of the hot material 132, one or more portions of the cold cap 134 (e.g., the foam 137, the calcined portion 138, or the solid portion 136), or the molten portion 139. The one or more sensors 150 may include a millimeter wave pyrometer, a scanning (e.g., infrared) thermometer, a laser thermometer, a thermocouple, or any other suitable temperature sensor. The one or more sensors 150 may include radiation detectors (e.g., Geiger counter), spectrometers (e.g., atomic absorption spectrometer, inductively coupled plasma atomic emission spectrometer), or any other suitable sensor for detecting the presence or amount of a specific material. The one or more sensors 150 may be positioned and configured to- Page 19 - Docket No. 57003-00431measure a volatile material (e.g., cesium or technetium) in gases emitted from the processing chamber (e.g., from the cold cap). The one or more sensors 150 may be positioned to measure the temperature of one or more portions of the cold cap 134 (the solid portion 136, the calcined portion 138, the foam 137), chemical emissions of one or more components from the cold cap 134, or the temperature of emissions from the cold cap 134. The one or more sensors 150 may be operably coupled to the controller 140. The controller 140 may receive the sensed temperature(s) or amounts of radioactive material detected from the one or more sensors 150 (e.g., of the cold cap) and responsive thereto, selectively adjust one or more of the power or the frequency of the EM radiation, such as to maintain or vary a selected penetration depth of the EM radiation or a selected material processing (e.g., melting) rate. The controller 140 may receive the sensed temperature(s) or amounts of radioactive material detected from the one or more sensors 150 (e.g., of the cold cap) and responsive thereto, selectively adjust the position of the waveguides 122 or output orifices associated therewith (e.g., collimating device), such as to maintain or vary a selected penetration depth of the EM radiation, a selected area of EM radiation application, or a selected material processing (e.g., melting) rate. Such selective control can be according to one or more operational programs stored in the controller 140.

[0076] In some examples, the system 100 includes one or more joule heating electrodes 160 positioned to heat the molten portion 139. For example, one or more joule heating electrodes 160 may be positioned in the lower region of the processing chamber 110 to heat the molten portion 139 to a selected temperature (e.g., maintain the molten portion in a molten state). The processing chamber 110 may be a joule-heated melter. The one or more joule heating electrodes 160 may melt the hot material and vitrify the waste in the hot material or maintain the hot material in a molten state where the heating is provided by the passage of current between the joule heating electrodes 160. The one or more joule heating electrodes 160 may be operably coupled to the controller 140. The controller 140 may direct the joule heating electrodes 160 to heat the molten portion 139 in the processing chamber 110 to a selected temperature.

[0077] In some examples, the system 100 may include one or more induction heating elements 180, such as an induction coil or electromagnet disposed about one or more portions of the processing chamber 110 (e.g., the lower region). The induction coil or electromagnet may be operably coupled to an electronic oscillator. The one or more induction heating elements 180 may be operably coupled to the controller 140. The- Page 20 - Docket No. 57003-00431controller 140 may direct the induction heating elements 180 to heat the molten portion 139 in the processing chamber 110 to a selected temperature.

[0078] In some examples, the controller 140 may be operably coupled to the waste inlet 130. The controller 140 may control the flow rate of the hot material 132 into the processing chamber 110. For example, the controller 140 may increase or decrease the flow rate of hot material 132 into the processing chamber 110 to achieve a selected processing rate, a cold cap thickness, or a penetration depth of the EM radiation into the cold cap. The controller 140 may be operably coupled to a pre-dryer (e.g., evaporator or heater) to control predrying of the hot material that is introduced into the processing chamber (e.g., melter) based on one or more of temperature or emissions detected by the one or more sensors 150.

[0079] The system 100 may include an outlet 170 for removing the molten portion 139 (e.g., vitrified waste) from the processing chamber 110. For example, the outlet 170 may be located in the bottom of the processing chamber 110. The outlet 170 may be operably coupled to the controller 140. The outlet 170 may be selectively opened, closed, or partially restricted to control the rate of removal of the molten portion 139 therefrom.

[0080] The system 100 may include a gas vent 175 for removing gases from the processing chamber 110. For example, the gas vent 175 may be located in upper portion of the processing chamber 110. The gas vent 175 may be used to remove steam, volatilized components of the waste material, or any other process gases. The gas vent 175 may be operably coupled to the controller 140. The gas vent 175 may be selectively opened, closed, or partially restricted to control the rate of removal of one or more gases from the processing chamber 110. The gas vent 175 may be operably coupled to a downstream gas cleaning apparatus, such as an apparatus for cleaning one or more chemicals or radioactive materials from the one or more gases.

[0081] In some examples, the system 100 may include a containment structure 190, such as cladding or shielding to contain one or more emissions from the processing chamber 110. For example, the containment structure 190 may include a sealed enclosure disposed about one or more portions of the system 100. The containment structure 190 may prevent leaks of fluids (e.g., off gases) and / or radioactivity from the system 100. In some examples, the containment structure 190 may include lead, depleted uranium, depleted thorium, barium sulfate, tungsten, iron, alloys of any of the foregoing, or high-density concrete typically used in radioactive processing facilities.

[0082] The system 100 may include a power source (not shown). The power source may be operably coupled to any of the components of the system 100 to supply electrical- Page 21 - Docket No. 57003-00431energy thereto. The power source may include at least one of a motor, generator, batteries, solar cells, wind turbines, or any other source of electrical energy.

[0083] The EM generation devices (e.g., at least one EM radiation source 120), waveguides, collimating devices, controllers, and other components of the example systems disclosed herein can be used on existing melters or on new melters. For example, the EM generation devices, waveguides, collimating devices, controllers, and other components of the example systems disclosed herein can be retrofit onto existing waste melters.

[0084] In some examples, the at least one EM radiation source 120 can serve as the sole source of heating. Such examples can be of particular interest for small melters with molten glass bath depths in a range of 1 cm to 15 cm. For example, low volume melters for processing radioactive material may be used where the volume of fissile material (e.g., barium, cesium, iodine, strontium, technetium, xenon, etc.) being melted is limited in order to avoid a critical mass that would result in a nuclear criticality event.

[0085] In some examples, systems for melting material may include more than one EM radiation source and / or waveguide, such as a plurality of waveguides or EM radiation sources. For example, multiple waveguides may be placed in the areas over which the hot material (e.g., radioactive waste) is deposited and the power from the EM radiation sources may thereby be distributed and varied over the areas.

[0086] FIG. 2 is a schematic of a system 200 for melting material, according to at least some embodiments. The system 200 includes a processing chamber 210 defining an interior region 212. The processing chamber 210 defines a waste inlet 230 configured to provide hot material 232 to the interior region 212. The processing chamber 210 may include a molten portion 239 disposed therein. The hot material 232 provided to the processing chamber 210 may form a cold cap 234 on the molten portion 239. The system 200 is configured to incorporate the cold cap 234 into the molten portion 239. The system 200 may also include a controller 240 that is configured to control one or more components of the system 200, as previously discussed. Components of the system 200 may be similar or identical to the like numbered components of the system 100 in one or more aspects. For example, the processing chamber 210 may be similar or identical to the processing chamber 110 in one or more aspects. The cold cap 234 may be similar or identical to the cold cap 134 in one or more aspects, such as including the solid portion 236, the calcined portion 238, and the foam 237.

[0087] The system 200 includes a plurality of EM radiation sources, such as at least one first EM radiation source 220a and at least one second EM radiation source 220b. The- Page 22 - Docket No. 57003-00431first and second EM radiation sources 220a, 220b may be the same as or substantially similar to any of the EM radiation sources disclosed herein. For example, the first and second EM radiation sources 220a, 220b may be positioned external to the interior region 212 and configured to provide EM radiation (e.g., microwave or millimeter wave radiation) into selected portions of the interior region 212, for instance, using one or more waveguides 222 and / or collimating devices 224.

[0088] The amount of EM radiation (e.g., energy) that is deposited in different layers in the cold cap 234 may also be selectively controlled by use of the waveguides 222 whose ends are located in various locations, such as within the cold cap 234 when the hot material (e.g., radioactive waste) is added. These ends of these waveguides 222 may be positioned either before hot material 232 is introduced or while hot material 232 is being processed. The ends of the waveguides 222 may be positioned at various locations below the top of the cold cap 234. The waveguides 222 and collimating devices 224 may be configured to emit EM radiation into one or more selected portions of the cold cap 234. For example, the waveguides 222 may be configured to extend vertically toward or into the cold cap 234 to deliver EM radiation into a selected portion thereof, such as the foam 237, the calcined portion 238, the solid portion 236, or to an interface of any of the portions. As shown in FIG. 2, the waveguides 222 may terminate at or near the cold cap 234, such as positioning the collimating device 224 in or near the cold cap 234. The waveguides 222 may be constructed to move at least vertically (e.g., in a z direction) toward the cold cap 234. In some examples, the waveguides 222 may be configured to move laterally (e.g., in the x-y plane) with respect to the cold cap 234. Such control of the vertical position and lateral position of the waveguides 222 may be performed by the controller 240. The control may be responsive to the sensed characteristics of one or more of the hot material 232, cold cap 234, or molten portion 239. Such sensed characteristics may be detected by at least one sensor 250. The at least one sensor 250 may be operably coupled to the controller 240 to communicate the sensed information thereto.

[0089] The absorption of EM energy in the foam 237 and other layers in the cold cap 234 may be closed loop controlled by measurements of cold cap temperature at various heights above the molten portion 239 (e.g., glass bath) or beneath it. These measurements may be used to vary the level (e.g., frequency, wavelength, or power) of the EM radiation that is used as a function of time. The frequencies of the EM radiation may be in the 0.8 GHz to 30 GHz microwave range and / or in the 30 GHz to 200 GHz millimeter wave range.- Page 23 - Docket No. 57003-00431

[0090] The orientation of the waveguides 222 may be perpendicular to the level of the molten material or at a range of angles relative to perpendicular, including a 90 degree angle, a 60 degree angle, a 45 degree angle, a 30 degree angle, or the like. The position of the ends of the waveguides 222 may either be fixed or moveable as disclosed above. When the end of a waveguide 222 is moveable, its position may be varied in closed loop control as a function of measurements of temperature at various spatial locations in the cold cap 234 and / or as a function of time.

[0091] The position of the ends of a waveguide 222 can also be varied by use of open loop control where the open loop control may use information that includes experimentally determined levels of vitrification rate control as functions of waveguide end position; EM radiation power level; and / or time after the beginning of the introduction of a batch of hot material 232 into the processing chamber 210 (e.g., glass melter).

[0092] In order to facilitate positioning of the waveguides 222, the waveguides 222 may include telescoping tubes constructed of materials composed to resist heat inside the plenum of the processing chamber 210. Such material may include a refractory ceramic (e.g., high temperature ceramic), a refractory metal, or the like. The output orifices (e.g., windows) of the waveguides 222 may be made of high temperature ceramic materials composed to withstand high temperatures and to be transparent to radiation that impinges on them from the microwave and / or millimeter wave EM radiation sources. The waveguides may also be surrounded by cladding or a protective layer such as ceramic cylinders configured to resist the temperatures in the processing chamber 210.

[0093] Selective EM radiation heating of different regions in the cold cap 234 may be provided by control of parameters that include the power level of EM radiation as noted above, and also as a function of both time and spatial positioning of a waveguide or multiple waveguides located a various positions across the top of the cold cap 234 and / or may include waveguide output orifices immersed at one or more locations within the cold cap 234.

[0094] In some examples, the first EM radiation source 220a is configured to emit EM radiation into a first portion of the cold cap 234 (e.g., the calcined portion 238) and the second EM radiation source 220b is configured to emit EM radiation into a second portion of the cold cap 234 (e.g., the foam 237). In such an embodiment, the first and second EM radiation sources 220a, 220b may allow the system 200 to provide EM radiation into different portions of the hot material 232 contemporaneously (e.g., substantially simultaneously).- Page 24 - Docket No. 57003-00431

[0095] In some examples, the first EM radiation source 220a e.g., via the waveguide 222 or the collimating device 224 connected to the first EM radiation source 220a) is configured to emit EM radiation towards a first location of the hot material 232 and the second EM radiation source 220b (e.g., via the waveguide 222 or the collimating device 224 connected to the second EM radiation source 220b) is configured to emit EM radiation towards a second location of the hot material 232. The first and second locations of the hot material 232 may be different from each other. In some examples, the first location may be laterally spaced from the second location on an x-y plane relative to the surface of the cold cap 234. In such examples, the different locations on the cold cap 234 may be heated by EM radiation separately by the first and second EM radiations sources 220a and 220b. Additionally, the frequency, power, or wavelength of the EM radiation emitted from the first and second EM radiations sources 220a and 220b may be selectively controlled (e.g., varied) to reach selected parts of the hot material 232 in the cold cap 234, such as the solid portion 236, the calcined portion 238, the foam 237, or interfaces of any of the same.

[0096] In some examples, the incoming hot material 232 may be heated prior to addition to the cold cap 234. For example, the first location may be positioned upstream from the second location relative to the flow of the hot material 232. In such an example, the EM radiation from the first EM radiation source 220a may at least partially calcine the hot material 232 before the hot material 232 reaches the second location where it is exposed to the EM radiation from the second EM radiation source 220b. In some examples, the first location may be closer to the gas vent 275 than the second location. In such examples, at least some of the steam generated by the EM radiation from the first EM radiation source 220a does not flow into the path of EM radiation from the second EM radiation source 220b thereby minimizing any absorption of the primary EM radiation by the steam before the (second) EM radiation reaches the cold cap 234. The first EM radiation source 220a and the second EM radiation source 220b may be used when the waste inlet 230 continuously provides the hot material 232 or provides the hot material 232 in batches. The first and second EM radiation sources 220a, 220b may be independently operated or operated in sync.

[0097] The first EM radiation source 220a and the second EM radiation source 220b are each configured to emit one or both of microwave radiation or millimeter wave radiation. In such examples, using the first and second EM radiation sources 220a, 220b to simultaneously emit the same type of EM radiation may facilitate more uniform heating or temperature profiles of different parts of the cold cap 234, simultaneously heating (e.g.,- Page 25 - Docket No. 57003-00431calcining) a larger percentage of the hot material 232, contemporaneously eliminating foam 237, or actively facilitating incorporation of a larger percentage of the cold cap 234 into the molten portion 239. Using the first and second EM radiation sources 220a, 220b to simultaneously emit the EM radiation into different portions of the cold cap 234 may be beneficial when relatively large quantities of the hot material 232 are provided to the processing chamber 210 and / or the processing chamber 210 is relatively large.

[0098] The system 200 may include one or more EM radiation sources in addition to the first EM radiation source 220a and the second EM radiation source 220b, such as any number of additional EM radiation sources. In such examples, each EM radiation source and corresponding waveguides may be positioned and configured to apply EM radiation to different areas of the cold cap 234 spaced laterally from each other in the x-y plane and / or spaced vertically from each other in the cold cap 234.

[0099] The instantaneous rate of feeding the hot material 232 (e.g., radioactive waste) into the cold cap 234 on top of the molten portion 239 (e.g., glass bath) may also be varied at various locations of waveguide 222 ends in order to adjust EM radiation heating of the hot material 232 at various cold cap portions above the molten portion 239. This variation in feeding rate may be used as an additional means to selectively control cold cap heating to increase the vitrification rate of the hot material 232.

[0100] An additional option for selective heating of the cold cap is to locate the end of a waveguide so as to heat the highly conductive top region of the molten portion 239. The molten material in the molten portion 239 will strongly absorb the EM radiation. Moreover, the molten portion 239 is an excellent conductor of heat to the areas of the cold cap 234 on the molten portion. This heating can transfer heat into the cold cap 234 above the molten portion 239 (e.g., into the foam 237 and calcined portion 238) and thereby increase the vitrification rate.

[0101] The use of both microwave and millimeter wave heating may be used to provide a wide range of absorption lengths of the EM radiation under changing conditions. The use of both microwave and millimeter wave heating may be used to provide a wide range of absorption levels with very low frequency microwaves (e.g., as low as 0.8 to 0.9 GHz) and the lowest absorption levels (characterized by relatively low value of the imaginary part of the dielectric constant). Millimeter waves, which can provide frequencies that are 30 to 100 times higher than very low frequency microwaves, have much greater absorption levels (characterized by high values of the imaginary part of the dielectric constant). The absorption length of the EM radiation will typically decrease with increasing frequency.- Page 26 - Docket No. 57003-00431High power EM radiation sources that may be employed as the EM radiation source 220a or 220b include magnetrons at 2.45 GHz and gyrotrons at 28 GHz as well as at higher frequencies. These EM radiation sources can provide a wide range of absorption lengths.

[0102] In some examples, selective heating may be provided by use of low frequency microwaves (e.g., 0.8 to 2.5 GHz) which may have sufficiently low absorption levels to penetrate through the entire cold cap with low power loss. Such EM radiation provides effective heating of the top layer of the electrically conductive molten glass that is right beneath the cold cap (e.g., at the interface therewith. Selective heating of this layer of the hot molten portion (e.g., glass) provides a highly effective means to provide substantial additional heating of the lower part of the foam by heat transfer from the molten portion.

[0103] An application of selective EM heating due to the choice of the EM radiation frequency is the use of high frequency microwave or millimeter wave power (e.g., microwave power provided by klystron sources or millimeter wave power provided by gyrotrons) to provide very short absorption length radiation in the cold cap. For example, very strong absorption may be provided near the end of a waveguide that is immersed in the cold cap.

[0104] In some examples, plasma that is directed to or produced within the cold cap by various means may be used to increase EM radiation absorption in various regions of the cold cap. The plasma may be produced by high voltages between inserted plasma electrodes or by creating regions of high electric field intensity using EM (e.g., microwave or millimeter wave) radiation.

[0105] FIG. 3 is a schematic of a system 300 for melting material, according to at least some embodiments. The system 300 is an example of a plasma enhanced melter. The system 300 includes a processing chamber 310 defining an interior region 312. The processing chamber 310 defines a waste inlet 330 configured to provide hot material 332 to the interior region 312. The processing chamber 310 may include a molten portion 339 disposed therein. The hot material 332 provided to the processing chamber 310 may form a cold cap 334 on the molten portion 339. The system 300 is configured to incorporate the cold cap 334 into the molten portion 339. The system 300 may also include a controller 340 that is configured to control one or more components of the system 300. Except as otherwise disclosed herein, the system 300 may be the same as or substantially similar to any of the systems disclosed herein. Components of the system 300 may be similar or identical to the like numbered components of the system 100 or 200 in one or more aspects. For example, the processing chamber 310 may be similar or identical to the processing- Page 27 - Docket No. 57003-00431chamber 110 or 210 in one or more aspects. The cold cap 334 may be similar or identical to the cold cap 134 in one or more aspects, such as including the solid portion 336, the calcined portion 338, and the foam 337.

[0106] The system 300 includes one or more plasma electrodes 362, such as a first plasma electrode and a second plasma electrode. The plasma electrodes 362 of the system 300 are configured to introduce energy into the processing chamber 310. For example, the system 300 is configured to provide electrical energy to the plasma electrodes 362 (e.g., responsive to direction from the controller 340). The electrical energy provided to the plasma electrodes 362 may provide plasma heating to the processing chamber 310 (e.g., plenum) or hot material 332 therein. The plasma heating may facilitate calcining of the hot material 332 and facilitate heating of the hot material 332 and the molten portion 339 which, in turn, facilitates incorporation of the cold cap 334 into the molten portion 339. The plasma heating may also induce reactions between any organic material in the hot material 332 and oxygen in the processing chamber 310 to form synthesis gas. Further examples of the structures of the plasma enhanced melters and methods of using plasma enhanced melters are disclosed in U.S. Patent No. 9,771,532 issued on September 26, 2017, the disclosure of which is incorporated herein, in its entirety, by this reference.

[0107] The system 300 includes at least one EM radiation source 320. Similar to the other EM radiation sources disclosed herein, the at least one EM radiation source 320 may be used to heat the hot material 332, such as heating the foam 337, the calcined portion 338, the solid portion 336, or an interface of any of the foregoing. The at least one EM radiation source 320 may also be used to heat at least one of the cold cap 334 (e.g., the foam 337, the calcined portion 338, the solid portion 336, or an interface of any of the foregoing) or the molten portion 339 to facilitate incorporation of the hot material in the cold cap 334 into the molten portion 339. It is currently believed that use of the at least one EM radiation source(s) 320 in a plasma enhanced melter facilitates maintaining a sufficiently high and uniform temperature in cold cap 334 within the melter. Further, dynamic heating based on variation of the location of the waveguide(s) 322 or variation of the characteristics of the EM radiation emitted therethrough may further increase heating speed to create a selected temperature profile and temperature uniformity within the cold cap 334, such as across lateral dimensions thereof. Such temperature control can be achieved using less joule heating than is possible without the EM radiation. Less joule heating in-glass within the molten portion 339 avoids the potential for over current and avoids overheating of the glass which otherwise results in damaged refractory materials- Page 28 - Docket No. 57003-00431within the processing chamber 310, as can be the case if only joule heating is applied as the only means of “defrosting” a melter (e.g., a plasma enhanced melter).

[0108] In some examples, the at least one EM radiation source 320 may be used to facilitate start-up of the system 300 (e.g., the melter) from an idle, such as a cold or hot idle. For example, while idling the system 300, the molten portion 339 may cool and, optionally, may at least partially solidify at or near a surface thereof due to radiative cooling. Just using the non-EM radiation heat sources of the system 300 (e.g., one or more of the joule heating electrodes 360, the plasma electrodes 362, or the induction heating elements 380) to restart the system 300 from the idle may take considerable time and energy. However, the EM radiation provided by the at least one EM radiation source 320 may more quickly increase the temperature of the molten portion 339 thereby quickening restart of the system 300 in an efficient manner. The EM radiation provided by the at least one EM radiation source 320 may be especially effective at melting any solidified portions of the molten portion 339 since the solidified portions may absorb the EM radiation (e.g., the solidified portions that are spaced from a top surface to avoid emission of the molten portion 339) and / or the EM radiation may reach and heat the liquid portions of the molten portion 339 that are adjacent to the solidified portions.

[0109] In some examples, example systems disclosed herein may be implemented in mobile apparatus. For example, mobile systems (e.g., waste melters) that provide onsite immobilization of radioactive material resulting from medical use, nuclear power production, a nuclear reactor accident, or malicious use radioactive material may be used.

[0110] FIG. 4 is a schematic of a mobile system 400 for melting material, according to an embodiment. The mobile system 400 may include a carriage 404 for supporting and moving a processing chamber 410, at least one EM radiation source 120, a controller 140, or any other components of the mobile system 400. The mobile system 400 may include the carriage 404 that has wheels 408 for moving the mobile system 400 from one location to another. The carriage 404 may include a frame having a plurality of legs 405 and a table 407 disposed on the legs 405. The table 407 may include one or more cross members positioned to support one or more components of the mobile system 400. The frame of the carriage 404 may include one or more cross-members or connections positioned to support the processing chamber 410.

[0111] The carriage 404 includes the wheels 408 at the end of the legs 405. In some examples, the carriage may include skids or tracks in addition or alternative to the wheels 408. In some examples, the carriage 404 may include a drive mechanism (e.g., motor,- Page 29 - Docket No. 57003-00431transmission, drive shafts, axles, etc.). In some examples, the carriage 404 may have a connection (e.g., hitch) that allows the carriage 404 to be towed by a vehicle.

[0112] The mobile system 400 may include one or more components of the system 100. For example, the mobile system 400 may include the processing chamber 410, which may be similar or identical to the processing chamber 110 in one or more aspects. The processing chamber 410 may have any dimensions such as a relatively shallow container (e.g., 1 cm to 15 cm maximum depth) or a relatively deep container. The relatively shallow container may allow faster processing of materials using solely EM heating and may prevent critical mass of radioactive materials therein (and prevent an associated critical nuclear event). The processing chamber 410 may contain hot material 132 therein. The processing chamber 410 may be sealed to contain the hot material 132 and fluids therein in a closed environment. In some examples, the processing chamber 410 may be operably coupled to a hot material 132 (e.g., radioactive waste feed slurry) supply via the inlet 155.

[0113] The mobile system 400 includes the at least one EM radiation source 120. The at least one EM radiation source 120 may be supported by the carriage 404. The at least one EM radiation source 120 may be disposed outside of the processing chamber 410, such as outside of a containment structure (not shown) around the processing chamber 410 or between the processing chamber 410 and the at least one EM radiation source 120. The containment structure may be similar or identical to the containment structure 190 (FIG. 1 A) in one or more aspects, such as having a cladding or shielding to contain one or more emissions from the processing chamber 410. The EM radiation source 120 may be shielded from emissions (e.g., radiation and / or heat) from the material in the processing chamber 410.

[0114] The at least one EM radiation source 120 may be operably coupled to the one or more waveguides 122 which may be operably coupled to the one or more collimating devices 124. The at least one EM radiation source 120, the one or more waveguides 122, and the one or more collimating devices 124 may be positioned to emit the EM radiation 125 into the cold cap 134, through the solid portion 136 and calcined portion 138 to the foam 137 or interface between the molten portion 139 and the foam 137 of the hot material 132 as described herein. The one or more waveguides 122 and the one or more collimating devices 124 may be movable to emit the EM radiation 125 into the cold cap 134 at one or more lateral locations thereof and / or one or more discrete positions (e.g., depths or layers) within the cold cap 134, at an interface between the molten portion 139 and the cold cap 134, or into the molten portion 139.- Page 30 - Docket No. 57003-00431

[0115] The mobile system 400 may include the gas vent 175 operably coupled to the processing chamber 410. The gas vent 175 may be operably coupled to one or more gas cleaning apparatuses as described herein. The one or more gas cleaning apparatuses may be used to clean the gas emitted from the processing chamber 410, such as removing radioactive material therefrom or encapsulating radioactive material therein. A moveable containment structure in which the processing would occur might also be used. The containment structure may be similar or identical to the containment structure 190 disclosed herein. Such a containment structure may include off-gas treatment systems such as scrubbers, etc., disposed therein or thereon.

[0116] The processing chamber 410 may include an outlet 170, such as in a lower portion of the processing chamber. The outlet 170 may be used to remove the molten portion 139 (e.g., vitrified radioactive waste) from the processing chamber 410.

[0117] The mobile system 400 may include the controller 140. The controller 140 may be operably coupled to one or more of any of the components of the mobile system 400. The controller 140 may include programming stored therein to automatically direct and control any aspects of operation of the mobile system 400. For example, the controller 140 may be operably coupled to the at least one EM radiation source 120 and may selectively control the initiation and frequency of the EM radiation produced therein or variations of the frequency of the EM radiation. The controller 140 may be operably coupled to the waveguide(s) 122 to control translational movement thereof within the processing chamber 410. In some examples, the controller 140 may be configured to a drive system (not shown) on the carriage 404 to control movement of the mobile system 400. The controller 140 may be used to control the mobile system according to any of the example methods disclosed herein, in one or more aspects.

[0118] The mobile system 400 may include one or more sensors (not shown) for measuring the temperature of the hot material (e.g., cold cap 134) measuring emissions from the hot material (e.g., volatilized radioactive material), as disclosed herein with respect to the sensors 150.

[0119] In some examples, the sole source of heating in the processing chamber 410 may be from the EM radiation 125. In some examples, the mobile system 400 may include one or more of joule electrodes, plasma electrodes, or induction heating elements, as disclosed herein with respect to the systems 100, 200, and 300 to heat the hot material therein.- Page 31 - Docket No. 57003-00431

[0120] The mobile system 400 may include a power source (not shown). The power source may be operably coupled to any of the components of the mobile system 400 to supply electrical energy thereto. The power source may include at least one of a motor, generator, batteries, solar cells, or any other source of electrical energy. For example, the power source may include an internal combustion engine positioned and attached to the carriage 404 to move the carriage 404. The power source may include an alternator or generator operably coupled to, and powered by, the motor.

[0121] The mobile system 400 may be used to provide local waste processing at different sites, such as the Department of Energy Hanford site, or any nuclear power plant or waste site.

[0122] Components or features from any of the systems disclosed herein may be utilized with any of the other systems disclosed herein.

[0123] The systems and methods disclosed herein may dramatically increase the production rate of joule-heated melters without unwanted increases in emissions of volatile radioactive species such as cesium or the like in HLW and LAW. For example, the systems described herein can conservatively increase the waste processing rate of a joule-heated melter by a factor of at least two and possibly greater than four.

[0124] The EM radiation heating techniques described in this disclosure may complement other production rate technologies such as the introduction of air bubblers, operating at higher melt tank temperatures or modified glass formulations.

[0125] FIG. 5 is a flow chart of a method 500 for melting material, according to at least some embodiments. The example method 500 includes an act 510 of producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein the EM radiation includes one or more of microwave or millimeter wave radiation and an act 520 of directing the EM radiation into at least the foam of the cold cap, wherein producing the EM radiation outside of the processing chamber and directing the EM radiation into at least the foam of the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap, to eliminate at least some of the foam, and prevent emissions of one or more components of the hot material in the cold cap from exceeding a selected level. In some examples, the method 500 may be performed using any components of the systems 100-400 disclosed herein. In some examples, the method 500 may include- Page 32 - Docket No. 57003-00431more or fewer acts than the acts 510 and 520. For example, any of the acts 510 or 520 may be combined or split into separate acts. In some examples, additional acts may be added to the acts 510 and 520.

[0126] The act 510 of producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein the EM radiation includes one or more of microwave or millimeter wave radiation may include producing EM radiation with any suitable EM radiation generator device such as a microwave radiation source (e.g., generator) or millimeter wave radiation source. The EM radiation source may be located outside of the processing chamber as described above with respect to FIG. 1A. The act 510 of producing EM radiation outside of a processing chamber configured to hold hot material therein may include producing EM radiation with a frequency of 0.9 GHz to 10 GHz, 10 GHz to 30 GHz, or 30 GHz to 300 GHz, such as in any of the frequency ranges disclosed herein. The act 510 of producing EM radiation outside of a processing chamber configured to hold hot material therein may include producing EM radiation with a varying frequency between 0.9 GHz to 10 GHz, 10 GHz to 30 GHz, or 30 GHz to 300 GHz. The act 510 of producing EM radiation outside of a processing chamber configured to hold hot material therein may include producing EM radiation with a varying power between 20 kW and 600 kW.

[0127] In some examples, producing EM radiation outside of a processing chamber and directing the EM radiation into the cold cap of the hot material are effective to cause the EM radiation to heat the foam effective to at least partially eliminate the foam. In some examples, producing EM radiation outside of a processing chamber and directing the EM radiation into the cold cap of the hot material are effective to cause the EM radiation to heat the calcined portion of the cold cap without heating the solid portion to a temperature in excess of a vaporization temperature of the hot material (e.g., waste material or glass particles therein).

[0128] One or more of the frequency or power level of the EM radiation may be such that the surface temperature of the newly added material is maintained at or adjusted to at least 90 °C, such as less than 150 °C when liquid is present on the cold cap surface for borosilicate glass typically used for vitrifying radioactive waste materials. The temperature ranges may vary depending on the composition of the hot material slurry being fed to the processing chamber (e.g., melter). For portions of the cold cap that are dry and free of- Page 33 - Docket No. 57003-00431liquids, the temperature can be locally raised to higher temperatures in the range of 150 °C to 500 °C, or greater. One or more of the frequency or power level of the EM radiation should be selected to keep surface emissions of the hot material (e.g., cold cap) below a selected level (e.g., below a threshold level), such as where volatilization of radioactive species (e.g., barium, cesium, iodine, strontium, technetium, xenon, etc.) are limited to below the selected level or even prevented.

[0129] Producing the EM radiation may include producing the EM radiation at a power level (or power supplied to the EM radiation generator) or frequency effective to cause heating of one or more portions of the cold cap (e.g., foam, calcined portion, or solid portion) without overheating the cold cap to cause emissions of one or more components of the hot material to exceed a selected level. The power level may be controlled by a controller. The power level or frequency may be controlled responsive to sensed information, such as temperature of the cold cap, emissions from the cold cap, feed rate of the hot material, etc. A suitable level power of the EM radiation to heat the cold cap without causing emissions above the selected level may be preset or may vary depending upon on one or more of the geometry of the processing chamber, the chemical composition of the hot material, the thickness of the cold cap (or portions therein), the thickness of the molten portion, an acceptable level of emissions of the one or more components, the dryness of the hot material, the frequency of the EM radiation, the temperature of the cold cap, the temperature of the molten portion, etc. The suitable level of power may include any of the levels of power disclosed herein, such as 2 kW to 600 kW.

[0130] Producing the EM radiation may include producing the EM radiation at a power level effective to produce a selected penetration depth of EM radiation into the cold cap, such as in the range of 1 cm to 15 cm.

[0131] In some examples, the selected level of emissions of the one or more components of the hot material (e.g., cesium, technetium, etc.) may depend on one or more of the chemical composition of the hot material, the species of the one or more components of the hot material that is emitted, the rate of processing of the hot material, the amount of hot material in the processing chamber, the duration of time that the hot material resides in the processing chamber, the power of the EM radiation applied to the hot material, the frequency of the EM radiation applied to the hot material, environmental regulations, safety standards, etc. The selected level may be based on a rate of emission, such as parts per million per minute or hour.- Page 34 - Docket No. 57003-00431

[0132] The act 520 of directing the EM radiation into at least the foam of the cold cap may include directing the EM radiation into the foam of the cold cap with one or more waveguides. For example, one or more waveguides may be operably coupled to the EM radiation generator and protrude to (e.g., into) the interior region of the processing chamber. In some examples, directing the EM radiation into the foam of the cold cap is carried out without causing volatilization of the hot material in the cold cap. Such direction of the EM radiation may include directing the EM radiation into one or more of the foam portion, the calcined portion, or the solid portion, such as to the interface between the foam and the molten portion of the hot material in the processing chamber.

[0133] In some examples, directing the EM radiation into the cold cap without causing volatilization of the hot material in the cold cap may include directing the EM radiation into the cold cap effective to cause the cold cap to have a selected temperature profile. The selected temperature profile may include a temperature at the upper surface of the cold cap that is below the volatilization temperature of the hot material (e.g., waste material therein). The selected temperature profile may include a temperature at the interface of the foam and the molten portion that is higher than the temperature where the EM radiation is not emitted therein. The selected temperature profile may include a temperature in the calcined portion that is higher than the temperature where the EM radiation is not emitted therein. The selected temperature profile may include a temperature in the solid portion that is higher than the temperature where the EM radiation is not emitted therein.

[0134] The acts of the example method 500 may be effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap, to eliminate at least some of the foam, and prevent emissions of one or more components of the hot material in the cold cap from exceeding a selected level. For example, producing EM radiation outside of a processing chamber and directing the EM radiation into the foam of the cold cap may be effective to cause the EM radiation to heat the foam, calcined portion, or solid portion without heating the solid portion to a temperature in excess of a vaporization temperature of the one or more components of the hot material.

[0135] In some examples, the method 500 may include adding hot material into the processing chamber. The hot materials may include radioactive material(s) such as barium, cesium, iodine, strontium, technetium, xenon, rhenium, etc. Adding hot material into the processing chamber may include adding any of the hot materials disclosed herein into the processing chamber via a waste inlet operably coupled thereto. The hot material may include one or more of waste particles (e.g., radioactive waste particles), dissolving agents- Page 35 - Docket No. 57003-00431(e.g., acids), glass forming particles, or dissolved particles of any of the foregoing. For example, adding hot material into the processing chamber may include adding radioactive waste particles and glass particles into the processing chamber via a waste inlet operably coupled thereto, such as in a slurry.

[0136] In some examples, the hot material (e.g., slurry waste feed stream) may be fed spatially in a predefined pattern so that the directed EM radiation is aimed at a dry section of the cold cap to ensure the additional heating effect of the EM radiation is at the interface between the cold cap and the molten portion (e.g., molten glass surface).

[0137] In some examples, adding hot material into the processing chamber may include adding hot material into the processing chamber so as to control the thickness of the cold cap and thus vary the ratio of the radiation penetration depth to the cold cap thickness or discrete portions therein. The cold cap thickness may be controlled so as to achieve a selected ratio of radiation penetration depth to thickness for a given power and / or frequency. For a selected ratio, this may enable selecting the power and / or frequency of the EM radiation so as to meet objectives that may include availability and cost of the at least one EM radiation source and ease of transmitting and collimating the radiation. The ratio of the radiation penetration depth to cold cap thickness may be chosen so as to achieve a selected hot material processing (e.g., vitrification) rate or meet some other objective while limiting or eliminating emissions from the surface of the cold cap that faces the plenum.

[0138] In some examples, the method 500 may include determining a temperature of one or more portions of the cold cap with one or more sensors. In some examples, determining the temperature of one or more portions of the cold cap with one or more sensors may include determining the temperature of the foam, calcined portion, solid portion, or materials emitted therefrom.

[0139] In some examples, the method 500 may include adjusting one or more of the power, the frequency, the location, or the area of application of the EM radiation responsive to determining the temperature. For example, adjusting one or more of the power, the frequency, the location, or area of application of the EM radiation responsive to determining the temperature may include adjusting one or more of the power, the frequency, the location, or the area of application of the EM radiation to cause the cold cap or portions thereof to exhibit a selected temperature profile, a vitrification rate of the hot material (e.g., the waste material therein), or a selected penetration depth into the cold cap or portions thereof (e.g., a penetration depth into the foam, the solid portion, or the calcined portion). Adjusting the location of application of the EM radiation may include moving one- Page 36 - Docket No. 57003-00431or more waveguides in a first location (e.g., any location in the x, y, or z planes) of the cold cap to at least a second location effective to apply EM radiation into the one or more portions of the cold cap at the second location. Adjusting the location of application of the EM radiation may include activating one or more waveguides in the first location and activating one or more waveguides in at least the second location. Such translational adjustments of spatial application of the EM radiation may be carried out according to a pattern or to targeted sensor feedback of specific portions of the cold cap. Such translational adjustments and variations may be carried out in combination with power or frequency adjustments. By dynamically adjusting one or more of power, frequency, or location of application of the EM radiation, a selected temperature profile may be created and maintained throughout the cold cap and higher process rates may be achieved while preventing unwanted levels of emissions of radioactive materials from the cold cap and molten portion.

[0140] In some examples, the method 500 may include drying the slurry. In some examples, the method 500 may include calcining the dried slurry. In some examples, the method 500 may include melting the calcined and dried slurry. In some examples, the method 500 may include pre-drying the hot material (e.g., radioactive waste slurry). Such pre-drying may allow selective adjustment of the penetration length of the EM radiation at a selected power and / or frequency.

[0141] In some examples, the method 500 may include collimating the EM radiation with one or more of a phased array or a radiative horn. Collimating the EM radiation with one or more of the phased array or the radiative horn may include collimating the EM radiation into one or more beams of a selected width. Collimating the EM radiation with one or more of the phased array or the radiative horn may include directing the collimated beam in one or more directions in the processing chamber. Collimating the EM radiation with one or more of the phased array or the radiative horn may include collimating the EM radiation effective to cause the EM radiation into the cold cap to a selected depth.

[0142] The collimation of the EM radiation may allow use of the example systems and methods herein in cold crucible batch processing. In some examples, the sole source of heating of the hot material may be the EM radiation from the at least one EM radiation source. For example, the longer penetration length of microwaves relative to millimeter wave radiation may allow examples where EM radiation is the only form of heating in the system.- Page 37 - Docket No. 57003-00431

[0143] In some examples, the method 500 may include joule heating the hot material in the processing chamber. In some examples, the method 500 may include induction heating the hot material in the processing chamber. In some examples, the method 500 may include plasma heating the hot material in the processing chamber. In some examples, heating the hot material in the processing chamber may include controlling one or more joule heaters (e.g., joule electrodes), induction heaters, or plasma heaters (e.g., plasma electrodes) to control the temperature of the hot material, such as to exhibit a selected temperature profile in the cold cap or process the hot material at a selected rate. In some examples, the method 500 may include heating the molten portion via one or more of joule heating, induction heating, or plasma heating, wherein the power (e.g., heating energy) supplied by the EM radiation is less than the power (e.g., heating energy) supplied by the joule heating, plasma heating, or induction heating. For example, the power applied to joule heating electrodes of a joule-heated melter may be in a range of 100 kW to 3,000 kW and the power applied to the at least one EM radiation source may be 20 kW to 600 kW (or about 4 kW to 150 kW). In some examples, the power applied to induction heating elements of an induction heating melter may be in a range of 10 kW to 200 kW and the power applied to the at least one EM radiation source may be 2 kW to 40 kW (or about 0.5 kW to 10 kW).

[0144] Any of the characteristics (e.g., parameters) of the EM radiation disclosed herein may be controlled, such as EM power, EM frequency, waveguide positions, or duration(s) of heating at various powers, frequencies, waveguide positions, and times after initiation of the EM heating. In some examples, the method 500 may include controlling one or more characteristics of the EM radiation (e.g., microwave radiation), such as with one or more of the controller, the at least one EM radiation source, the one or more waveguides, or the one or more collimating devices. These characteristics may include one or more of power, frequency, or spatial location (e.g., depth or lateral location) of the EM radiation. For example, when heating from EM radiation is introduced from above the cold cap, the power level which is used may be adjusted as a function of time after the initiation of EM heating to selectively heat the various layers of the cold cap, such as in a sinusoidal pattern of increasing and decreasing EM power and / or frequency levels. These changes in EM power and / or frequency may be used to vaporize water in the waste material (e.g., solid portion (e.g., slurry) or calcined portion) and thereby allow a greater amount of subsequent microwave radiation to heat the foam underneath the solid portion and calcined portion.

[0145] In some examples, controlling one or more characteristics of the EM radiation may be responsive to sensor information detected by one or more sensors. The sensor- Page 38 - Docket No. 57003-00431information may include measurements of the temperature(s) in one or more portions of the cold cap or emissions from heating of the surface of the molten portion. Such measurements may be taken at selected intervals over time. In some examples, controlling one or more characteristics of the EM radiation may include directing the EM radiation to one or more locations (e.g., laterally or to a depth) that have not been treated with EM radiation (e.g., for a selected amount of time). Accordingly, controlling the one or more characteristics of the EM radiation may include varying one or more of the location, the frequency, or the power of the EM radiation over a selected duration of time, such as continuously or intermittently.

[0146] In some examples, the method 500 may include varying the frequency of the EM radiation, such as with the controller. In some examples, the method 500 may include adjusting one or more of the power or the frequency of the EM radiation to achieve a selected temperature profile in the cold cap. In some examples, the method 500 may include adjusting one or more of the power or the frequency of the EM radiation to a power or frequency that is effective to provide a selected EM radiation penetration depth into the cold cap, such as into the foam. In some examples, the selected EM radiation penetration depth into the cold cap may be to the calcined portion, to the foam, or to the interface between the foam and the molten portion.

[0147] The controllers disclosed herein may be utilized to perform any of the acts disclosed herein, such as controlling the hot material feed rate into the processing chamber based on information from sensors, such as temperature or emissions.

[0148] FIG. 6 is a flow chart of a method 600 for melting a material, according to an embodiment. The method 600 includes an act 610 of producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, wherein the cold cap includes a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein a frequency of the EM radiation is between 0.9 GHz and 10 GHz. The method 600 includes the act 620 of guiding the EM radiation into the processing chamber. The method 600 includes the act 630 of directing the EM radiation into the foam of the cold cap. The method 600 includes the act 640 of sensing a temperature of the cold cap. The method 600 includes the act 650 of adjusting one or more of a frequency, a power, or a location of application of the EM radiation responsive to the temperature of the cold cap. The method 600 may include more or fewer acts than the acts 610-650. For example, any of the acts 610-650 may be combined or split- Page 39 - Docket No. 57003-00431into more than one act. The method 600 may be carried out using any of the examples of systems disclosed herein.

[0149] The method 600 includes an act 610 of producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, wherein the cold cap includes a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein a frequency of the EM radiation is between 0.9 GHz and 10 GHz may be similar or identical to the act 510 described above, in one or more aspects. For example, the act 610 may include producing EM radiation with any suitable EM radiation source (e.g., generator) such as a microwave or millimeter wave radiation generator.

[0150] The at least one EM radiation source (e.g., generator) may be located outside of the processing chamber as described above with respect to the systems 100-400. In some examples, producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, wherein the cold cap includes a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein a frequency of the EM radiation is between 0.9 GHz and 10 GHz may include producing EM radiation with any of the frequencies or power levels disclosed herein. The act 610 may include varying one or more of the frequency, the power, or the location of application of the EM radiation, over a duration. For example, producing EM radiation outside of a processing chamber configured to hold hot material therein may include producing EM radiation with a varying frequency between 0.9 GHz and 10 GHz, 10 GHz to 30 GHz, or 30 GHz to 300 GHz; or a varying power between 1 kW and 700 kW. Such variation may include a sinusoidal or other pattern of changes of the frequency and / or power of the EM radiation as disclosed herein.

[0151] In some examples, producing EM radiation outside of a processing chamber configured to hold hot material therein, wherein a frequency of the EM radiation is between 0.9 GHz and 10 GHz, is effective to cause the EM radiation to heat the calcined portion of the cold cap without heating the solid portion to a temperature in excess of a vaporization temperature of the hot material (e.g., the waste material or glass particles therein).

[0152] The method 600 includes the act 620 of guiding the EM radiation into the processing chamber. The act 620 of guiding the EM radiation into the processing chamber may include using one or more waveguides to guide the EM radiation into the processing- Page 40 - Docket No. 57003-00431chamber. For example, the act 620 may include using any of the waveguides disclosed herein to guide the EM radiation from the at least one EM radiation source to the interior region of the processing chamber. In some examples, guiding the EM radiation into the processing chamber may include using a plurality of waveguides to guide the EM radiation into the processing chamber.

[0153] The method 600 includes the act 630 of directing the EM radiation into the foam of the cold cap. Directing the EM radiation into the foam of the cold cap may include directing EM radiation into one or more portions of the cold cap (e.g., solid portion, calcined portion, foam). Directing the EM radiation into the foam of the cold cap may include producing a localized beam of EM radiation in the processing chamber. In some examples, directing the EM radiation into the calcined portion of the cold cap may include directing varying frequencies of EM radiation into the hot material above the cold cap (e.g., feed) over a duration. Directing the EM radiation into the foam may include varying the position or location of application of the EM radiation over a duration. Directing the EM radiation into the foam of the cold cap may include directing the EM radiation using one or more collimating devices. The one or more collimating devices may include one or more horns or one or more phased arrays. Directing the EM radiation into the foam may include varying the area (e.g., wider or focused beam) of application of the EM radiation, such as with a collimating device. In some examples, directing the EM radiation into the foam of the cold cap may include directing the EM radiation into the cold cap without causing volatilization of the hot material in the cold cap. For example, one or more collimating devices may be operably coupled to the waveguides operably coupled to the at least one EM radiation source and protrude at least into the plenum of the processing chamber, such as to or into the cold cap. In some examples, the act 630 may include collimating the EM radiation with one or more of a phased array or a radiative horn. Collimating the EM radiation may include collimating the EM radiation into one or more beams of a selected width. Collimating the EM radiation may include directing the collimated beam in one or more directions in the processing chamber. Collimating the EM radiation may include collimating the EM radiation effective to cause the EM radiation into the cold cap to a selected depth therein or therethrough.

[0154] In some examples, directing the EM radiation into the foam of the cold cap may include directing the EM radiation into the cold cap without causing volatilization of the hot material in the cold cap. For example, directing the EM radiation into the foam of the- Page 41 - Docket No. 57003-00431cold cap may include directing the EM radiation to the interface between the foam and the molten portion in the processing chamber.

[0155] In some examples, directing the EM radiation into the foam of the cold cap may include directing the EM radiation into the cold cap effective to cause the cold cap, or one or more portions thereof, to have a selected temperature profile. The selected temperature profile may include a temperature at the upper surface of the cold cap that is below the volatilization temperature of the hot material (e.g., radioactive waste material therein). The selected temperature profile may include a temperature at the interface of the foam and the molten portion that is higher than the temperature where the EM radiation is not emitted therein. The selected temperature profile may include a temperature at the interface of the foam and the molten portion that is effective to eliminate at least some of the foam.

[0156] In some examples, directing the EM radiation into the foam of the cold cap may include moving the location of the EM radiation in the cold cap, such as to a different lateral location or penetration depth, with the one or more collimating devices or one or more waveguides. For example, directing the EM radiation into the foam of the cold cap may include continuously or intermittently moving the EM radiation over a duration. In some examples, directing the EM radiation into the foam of the cold cap may include directing or altering a target location of the EM radiation with the controller, such as responsive to one or more temperature measurements of at least a portion of the cold cap.

[0157] In some examples, directing the EM radiation into the foam of the cold cap may additionally include directing the EM radiation into one or more of the solid portion or the calcined portion.

[0158] The method 600 includes the act 640 of sensing a temperature of the cold cap. In some examples, sensing a temperature of the cold cap may include sensing the temperature of one or more portions of the cold cap with one or more sensors. The one or more sensors may be similar or identical to any of the sensors disclosed herein. In some examples, sensing a temperature of the cold cap may include determining the temperature of the cold cap or materials (e.g., cesium or technetium) emitted therefrom. In some examples, sensing a temperature of the cold cap may include sensing the temperature of the cold cap with an infrared scanning thermometer or a thermocouple. The sensed temperature may be used to selectively control one or more aspects of the operation of the system, such as controlling (adjusting or varying) the frequency of the EM radiation, the rate of addition of hot material into the processing chamber, the rate of removal of the molten portion from the processing chamber, the heat added by the joule electrodes, the heat added by an- Page 42 - Docket No. 57003-00431induction heater (e.g., power applied to one or more induction heating elements), or the target location of the EM radiation in the cold cap.

[0159] The method 600 includes the act 650 of adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap. In some examples, adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap may include increasing or decreasing the frequency of the EM radiation to achieve a selected penetration depth. The penetration depth may be adjusted to increase heat at the interface between the cold cap and the molten portion. In some examples, adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap may include adjusting the power or the frequency of the EM radiation to cause one or more portions of the cold cap to exhibit a selected temperature profile, a vitrification rate of the hot material (e.g., the waste material therein), or a selected penetration depth. In some examples, adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap may include continuously or intermittently adjusting the power, frequency, or location of application of the EM radiation over a duration, such as according to a pattern or to the location of the sensed temperature. In some examples, adjusting the power, frequency, or location of application of the EM radiation may be responsive to pre-drying of the radioactive material.

[0160] In some embodiments, adjusting one or more of the frequency, power, or location of application of the EM radiation responsive to the temperature of a portion of the cold cap may include using the controller to adjust the power, the frequency, or the location of application of the EM radiation. For example, the controller may receive, as input, the sensed temperature(s) of the portions(s) of the cold cap or amount of component(s) of the hot material in the gas phase and responsive thereto may provide instructions to the at least one EM radiation source and / or waveguides to alter the EM radiation to a selected power, frequency, or location. The controller may adjust the power, the frequency, or location based upon one or more parameters, such as EM power or frequency, depth of penetration, hot material composition, selected emission level, selected processing rate, amount of predrying of the material before it is introduced to the cold cap, spatial location, molten portion temperature, or selected cold cap temperature. The controller may utilize closed loop or real-time monitoring of any parameters and or / open loop control using a look-up table. The look-up table can make use of experimental measurements of the impact of EM power or- Page 43 - Docket No. 57003-00431frequency or any other parameters on processing rate enhancement, emissions from the cold cap, or other characteristics of processing the hot material. The controller may adjust one or more of the frequency of EM radiation, the power of EM radiation (or supplied to the at least one EM radiation source), the location of application of the EM radiation, the feed rate of hot material into the processing chamber, the power applied to the joule heating electrodes or the induction coil to maintain or adjust the temperature of the cold cap (e.g., surface temperature or average temperature) to above or below a selected temperature or below a selected emission level.

[0161] The method 600 may be used to process radioactive material. For example, the processing chamber may be configured to contain radioactive material, and the hot material includes radioactive material. In such examples, the EM radiation frequency may be selected to penetrate the radioactive (waste) material, such as to a selected depth or through the cold cap.

[0162] In some examples, the method 600 may include directing the EM radiation responsive to material emissions from the cold cap. For example, the system 100-400 may include one or more sensors for detecting emissions of the material from the cold cap, such as Geiger counters or one or more spectrometers (not shown) disposed in a gaseous component outlet (not shown) of the processing chamber. In such examples, detected material emissions or an amount thereof from the cold cap can be used to monitor and limit radioactive material emissions from the melting process to below selected levels.

[0163] In some examples, the method 600 may include any acts or aspects of the method 500. For example, the method 600 may include adding hot material into the processing chamber as disclosed above with respect to the method 500. The hot material may include one or more of radioactive waste particles, dissolving agents, glass particles, or dissolved particles of any of the foregoing.

[0164] In some examples, the method 600 may include drying or pre-drying (e.g., dewatering) the hot material, such as drying the slurry of the hot material. In some examples, the hot material may be fed spatially in a predefined pattern so that the directed EM radiation is focused on a dry section of the cold cap to ensure the additional heating effect of the EM radiation is at the interface between the cold cap and the molten portion. In some examples, adding hot material into the processing chamber may include adding hot material into the processing chamber to achieve one or more processing properties or characteristics.- Page 44 - Docket No. 57003-00431

[0165] In some examples, the method 600 may include joule heating the hot material in the processing chamber as disclosed above with respect to the method 500. In some examples, the method 600 may include automatically controlling one or more characteristics of the EM radiation (e.g., microwave radiation), such as with one or more of the controller, the at least one EM radiation source, the one or more waveguides, or the one or more collimating devices as disclosed above with respect to the method 500. Controlling one or more characteristics of the EM radiation may be effective to control one or more characteristics of the hot material in the processing chamber or the processing characteristics.

[0166] Any of the example systems disclosed herein may be used to carry out any of the acts or methods of melting material disclosed herein, such as using a controller. The controller may carry out any of the acts or portions of the methods disclosed herein.

[0167] FIG. 7 is a schematic of a controller 700 for executing any of the example methods disclosed herein, according to at least some embodiments. The controller 700 may be configured to implement any of the example methods disclosed herein, such as the method 500 or 600. The controller 700 may be used for any of the controllers 140-340 disclosed herein. The controller 700 includes at least one computing device 710. The at least one computing device 710 is an exemplary computing device that may be configured to perform one or more of the acts described above, such as of the method 500 or 600. The at least one computing device 710 can include one or more servers, one or more computers (e.g., desk-top computer, lap-top computer), or one or more mobile computing devices (e.g., smartphone, tablet, etc.). The computing device 710 can comprise at least one processor 720, memory 730, a storage device 740, an input / output (“I / O”) device / interface 750, and a communication interface 760. While an example computing device 710 is shown in FIG. 7, the components illustrated in FIG. 7 are not intended to be limiting of the controller 700 or computing device 710. Additional or alternative components may be used in some examples. Further, in some examples, the controller 700 or the computing device 710 can include fewer components than those shown in FIG. 7. For example, the controller 700 may not include the one or more additional computing devices 712. In some examples, the at least one computing device 710 may include a plurality of computing devices, such as a server farm, computational network, or cluster of computing devices. Components of computing device 710 shown in FIG. 7 are described in additional detail below.

[0168] In some examples, the processor(s) 720 includes hardware for executing instructions (e.g., adjusting power or frequency of EM radiation), such as those making up- Page 45 - Docket No. 57003-00431a computer program. For example, to execute instructions, the processor(s) 720 may retrieve (or fetch) the instructions from an internal register, an internal cache, the memory 730, or a storage device 740 and decode and execute them. In particular examples, processor(s) 720 may include one or more internal caches for data such as look-up tables. As an example, the processor(s) 720 may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory 730 or storage device 740. In some examples, the processor 720 may be configured (e.g., include programming stored thereon or executed thereby) to carry out one or more portions of any of the example methods disclosed herein.

[0169] In some examples, the processor 720 is configured to perform any of the acts disclosed herein such as in method 500 or 600 or cause one or more portions of the computing device 710 or controller 700 to perform at least one of the acts disclosed herein. Such configuration can include one or more operational programs (e.g., computer program products) that are executable by the at least one processor 720. For example, the processor 720 may be configured to automatically adjust one or more of the power, frequency, or location of application of the EM radiation responsive to a sensed temperature or level (e.g., rate) of emission of one or more components of the hot material.

[0170] The at least one computing device 710 (e.g., a server) may include at least one memory storage medium (e.g., memory 730 and / or storage device 740). The computing device 710 may include memory 730, which is operably coupled to the processor(s) 720. The memory 730 may be used for storing data, metadata, and programs for execution by the processor(s) 720. The memory 730 may include one or more of volatile and non-volatile memories, such as Random Access Memory (RAM), Read Only Memory (ROM), a solid- state disk (SSD), Flash, Phase Change Memory (PCM), or other types of data storage. The memory 730 may be internal or distributed memory.

[0171] The computing device 710 may include the storage device 740 having storage for storing data or instructions. The storage device 740 may be operably coupled to the at least one processor 720. In some examples, the storage device 740 can comprise a non- transitory memory storage medium, such as any of those described above. The storage device 740 (e.g., non-transitory storage medium) may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage device 740 may include removable or non-removable (or fixed) media. Storage device 740- Page 46 - Docket No. 57003-00431may be internal or external to the computing device 710. In some examples, storage device 740 may include non-volatile, solid-state memory. In some examples, storage device 740 may include read-only memory (ROM). Where appropriate, this ROM may be mask programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. In some examples, one or more portions of the memory 730 and / or storage device 740 (e.g., memory storage medium(s)) may store one or more databases thereon. At least some of the databases may be used to store one or more of look-up tables, operation programs, threshold levels of components in gas phase, correlations of frequencies or power levels to materials in hot materials or thicknesses thereof, etc., as disclosed herein.

[0172] In some examples, one or more of look-up tables, operation programs, threshold levels of components in gas phase, correlations of frequencies or power levels to materials in hot materials or thicknesses thereof, etc., may be stored in a memory storage medium such as one or more of the at least one processor 720 (e.g., internal cache of the processor), memory 730, or the storage device 740. In some examples, the at least one processor 720 may be configured to access (e.g., via bus 770) the memory storage medium(s) such as one or more of the memory 730 or the storage device 740. For example, the at least one processor 720 may receive and store the data (e.g., look-up tables) as a plurality of data points in the memory storage medium(s). The at least one processor 720 may execute programming stored therein adapted access the data in the memory storage medium(s) to automatically adjust the power or frequency of the EM radiation. For example, the at least one processor 720 may access one or more look-up tables in the memory storage medium(s) such as memory 730 or storage device 740.

[0173] The computing device 710 also includes one or more I / O devices / interfaces 750, which are provided to allow a user to provide input to, receive output from, and otherwise transfer data to and from the computing device 710. These I / O devices / interfaces 750 may include a mouse, keypad or a keyboard, a touch screen, camera, optical scanner, network interface, web-based access, modem, a port, other known I / O devices or a combination of such VO devices / interfaces 750. The touch screen may be activated with a stylus or a finger.

[0174] The I / O devices / interfaces 750 may include one or more devices for presenting output to a user, including, but not limited to, a graphics engine, a display (e.g., a display screen or monitor), one or more output drivers (e.g., display drivers), one or more audio speakers, and one or more audio drivers. In some examples, I / O devices / interfaces 750 are- Page 47 - Docket No. 57003-00431configured to provide graphical data to a display for presentation to a user. The graphical data may be representative of one or more graphical user interfaces and / or any other graphical content as may serve a particular implementation.

[0175] The computing device 710 can further include a communication interface 760. The communication interface 760 can include hardware, software, or both. The communication interface 760 can provide one or more interfaces for communication (such as, for example, packet-based communication) between the computing device 710 and one or more additional computing devices 712 or one or more networks. For example, communication interface 760 may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI.

[0176] Any suitable network and any suitable communication interface 760 may be used. For example, computing device 710 may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, one or more portions of controller 700 or computing device 710 may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WLMAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination thereof. Computing device 710 may include any suitable communication interface 760 for any of these networks, where appropriate.

[0177] The computing device 710 may include a bus 770. The bus 770 can include hardware, software, or both that couples components of computing device 710 to each other. For example, bus 770 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination thereof.- Page 48 - Docket No. 57003-00431

[0178] The systems and methods disclosed herein, including the selective dynamic spatial and temporal control of EM radiation, provide a substantial increase in vitrification process rates while maintaining cold cap emissions below a selected threshold amount and maintaining glass quality.

[0179] The systems and methods of providing selective dynamic spatial and temporal application of EM radiation into cold caps disclosed herein can be readily added to existing melters, such as at the Hanford and other facilities.

[0180] While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.- Page 49 - Docket No. 57003-00431

Claims

CLAIMSWhat is claimed is:

1. A system for selectively melting material, the system comprising: a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion; at least one EM radiation source configured to selectively generate electromagnetic (EM) radiation in one or more of a microwave or a millimeter wave frequency; one or more waveguides operably coupled to the at least one EM radiation source and configured to guide the EM radiation into at least the foam of the cold cap in the processing chamber; and a controller operably coupled to the at least one EM radiation source, wherein the controller is configured to selectively adjust one or more of a power or a frequency of the EM radiation to selectively eliminate at least some of the foam, control a temperature profile in the cold cap, and prevent emissions of volatile components from the cold cap from exceeding a selected level.

2. The system of claim 1, wherein the processing chamber is configured to contain radioactive waste in a molten glass bath and to receive the radioactive waste in a solid form.

3. The system of claim 1, wherein the at least one EM radiation source is configured to selectively generate the EM radiation with a frequency between 0.8 GHz and 10 GHz.

4. The system of claim 1, wherein the at least one EM radiation source located outside of the processing chamber.

5. The system of claim 1, wherein an output orifice of at least one of the one or more waveguides is disposed within the cold cap.

6. The system of claim 1, wherein the one or more waveguides are configured move within the processing chamber in any of an x, y, or z plane, or combinations thereof.

7. The system of claim 1, further comprising one or more sensors positioned and configured to sense a temperature of at least a portion of the cold cap or positioned and configured to measure emissions from a surface of the cold cap.- Page 50 - Docket No. 57003-004318. The system of claim 7, wherein the at least a portion of the cold cap includes the foam.

9. The system of claim 7, wherein the controller is configured to receive a sensed temperature of the at least a portion of cold cap and in response thereto, selectively adjust the power of the EM radiation.

10. The system of claim 7, wherein the controller is configured to receive a sensed temperature of the at least a portion of the cold cap and in response thereto, selectively adjust a frequency of the EM radiation emitted from the at least one EM radiation source.

11. The system of claim 1, further comprising one or more joule heating electrodes positioned and configured to heat the molten portion.

12. The system of claim 1, further comprising one or more plasma heating electrodes positioned and configured to heat a plenum of the processing chamber.

13. The system of claim 1 wherein the at least one EM radiation source is a sole source of heating for the processing chamber.

14. A method for melting material, the method comprising: producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, the cold cap including a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein the EM radiation includes one or more of microwave or millimeter wave radiation; and directing the EM radiation into at least the foam of the cold cap; wherein producing the EM radiation outside of the processing chamber and directing the EM radiation into at least the foam of the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap, to eliminate at least some of the foam, and prevent emissions of one or more components of the hot material in the cold cap from exceeding a selected level.

15. The method of claim 14, further comprising adding the hot material into the processing chamber, wherein the hot material includes radioactive waste particles and glass particles; wherein adding the hot material into the processing chamber includes adding the hot material via a waste inlet operably coupled to the processing chamber.- Page 51 - Docket No. 57003-0043116. The method of claim 14, further comprising varying a frequency of the EM radiation effective to provide a selected EM radiation penetration depth into the foam of the cold cap.

17. The method of claim 14, further comprising adjusting a frequency of the EM radiation to achieve the selected temperature profile in the cold cap.

18. The method of claim 14, further comprising: determining a temperature of one or more of the solid portion, the calcined portion, or the foam of the cold cap with one or more sensors; and adjusting a frequency of the EM radiation responsive to determining the temperature.

19. The method of claim 17, further comprising heating the molten portion via one or more of joule heating or induction heating, wherein a first amount of power supplied by the EM radiation is less than a second amount of power supplied by the one or more of joule heating or induction heating.

20. A method for melting material, the method comprising: producing electromagnetic (EM) radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion, wherein the cold cap includes a solid portion, a calcined portion under the solid portion, and a foam under the calcined portion, and wherein a frequency of the EM radiation is between 0.8 GHz and 10 GHz; guiding the EM radiation into the processing chamber; directing the EM radiation into the foam of the cold cap; sensing a temperature of the cold cap; and adjusting one or more of a frequency, a power, or a location of application of the EM radiation responsive to the temperature of a portion of the cold cap.

21. The method of claim 20, wherein directing the EM radiation into the foam includes varying one or more of the frequency, power, or location of application of the EM radiation, over a duration.

22. The method of claim 20, wherein: the processing chamber is configured to contain radioactive material; and the hot material includes the radioactive material.- Page 52 - Docket No. 57003-00431