WO2009045611A2

WO2009045611A2 - Chemical weapons treatment

Info

Publication number: WO2009045611A2
Application number: PCT/US2008/071145
Authority: WO
Inventors: Donald A. Fraser; Kevin G. Finucane
Original assignee: Amec Earth & Environmental, Inc.
Priority date: 2007-07-27
Filing date: 2008-07-25
Publication date: 2009-04-09
Also published as: WO2009045611A3

Abstract

Methods for treatment of a munition containing a chemical agent and at least one explosive component are provided. In certain embodiments a method for treating a munition containing a chemical agent and an explosive component is provided. The munition is heated to thermally decompose the explosive component and the chemical agent and the remnants of the munition are treated. In certain embodiments, heating the munition to thermally decompose the explosive component comprises wrapping the munition with a heat trace, applying power to the heat trace, heating the munition to a critical temperature, and maintaining the critical temperature for a time period sufficient to thermally decompose the explosive component. In certain embodiments, the critical temperature is below a flash point and an auto-ignition temperature of the explosive component. In certain embodiments, treating the chemical agent and the remnants of the munition comprises performing a vitrification process.

Description

CHEMICAL WEAPONS TREATMENT

BACKGROUND OF THE INVENTION Field of the Invention toooi] Embodiments of the invention as recited in the claims generally relate to the treatment of chemical weapons. More specifically, the claims generally relate to the treatment of munitions containing chemical agents and explosive components.

Description of the Related Art

[0002] Approximately 70 different chemicals have been used or stockpiled as chemical weapons agents ("chemical agents") during the 20^th century. Chemical weapons are classified as weapons of mass destruction by the United Nations, and their production and stockpiling was outlawed by the Chemical Weapons Convention of 1993 (the "CWC"). The CWC also required that stockpiles be destroyed within ten years. Chemical agents may be in liquid, gas, or solid form. Liquid agents are generally designed to be highly volatile so they can be dispersed over a large area quickly.

[0003] The most important factor in the effectiveness of chemical weapons is the efficiency of its delivery, or dissemination to a target. The most common dissemination techniques include munitions (such as bombs, projectiles such as artillery and mortar shells, and warheads) that allow dissemination at a distance. These munitions generally contain the chemical agent, a fuse, and a central "burster" charge. When the "burster" charge detonates, the agent is expelled laterally. The use of burster charges was developed during World War I and was used by most nations in the early stages of chemical weapon development, in part because standard munitions could be used to carry the chemical agent.

[0004] Unexploded World War I munitions are frequently uncovered in former battle and depot storage areas and thus continue to pose a threat to civilian populations. Vitrification methods have been used for safely disposing contaminated soil, waste material, and chemical agents. Examples of such methods are provided in United States patent numbers: 4,376,598, 5,024,556, 5,443,618, 5,536,114, RE35,782, 6,120.430, and 7,211 ,038. The disclosures of these patents are incorporated herein by reference.

[0005] Generally, the known vitrification methods involve placement of the material to be treated into a vitrification chamber or vessel. An electrical current is supplied between electrodes. Application of the current is continued until the temperature of the material is raised to the point where the material begins to melt and is continued until the material is completely melted. In certain cases, other additives may be required to provide an initial electrically conductive resistance path through the material to be treated if such material is not capable of adequate current conduction. Once the resistance path is initiated and melting of the material begins, the molten material itself will continue current conduction.

[0006] In batch vitrification processes, once the material is sufficiently melted and all hydrocarbon components or other waste species such as toxic materials are treated, the electricity supply is terminated and the molten material is allowed to cool within the vitrification chamber or vessel. In continuous vitrification processes, the molten material is poured into receptacles and allowed to cool and solidify. The cooling step then results in a vitrified and/or crystallized solid material. In this manner, contaminants are immobilized within a solid, vitrified mass thereby ensuring containment of the contaminants and facilitating disposal of same.

[0007] In the course of melting the material, hydrocarbon components are destroyed or vaporized and the gases are normally vented through a suitable scrubber, quencher, filter or other known device or method.

[0008] Although current vitrification technologies are able to accommodate and render harmless chemical agents, currently available vitrification technologies are challenged with energetic materials such as explosives.

[0009] Therefore, there is a need for a method for treating and rendering harmless munitions containing chemical agents and explosives in a safe and efficient manner. SUMMARY OF THE INVENTION

[0010] Methods for treatment of a munition containing a chemical agent and at least one explosive component are provided. In certain embodiments a method for treating a munition containing a chemical agent and an explosive component is provided. The munition is heated to thermally decompose the explosive component and the chemical agent and the remnants of the munition are treated. In certain embodiments, heating the munition to thermally decompose the explosive component comprises wrapping the munition with a heat trace, applying power to the heat trace, heating the munition to a critical temperature, and maintaining the critical temperature for a time period sufficient to thermally decompose the explosive component. In certain embodiments, the critical temperature is below a flash point and an auto-ignition temperature of the explosive component. In certain embodiments, treating the chemical agent and the remnants of the munition comprises performing a vitrification process.

[0011] In certain embodiments a method for treating a munition containing a chemical agent and an explosive component is provided. The method comprises placing the munition in a treatment cell, covering the munition with soil to a predetermined level, positioning a starter path in the treatment cell, heating the munition to a critical temperature, maintaining the munition at the critical temperature for a period of time in order to thermally decompose the explosive component under the soil cover, and subsequently vitrifying the chemical agent. In certain embodiments, the method further comprises wrapping the munition in a heat trace prior to placing the munition in a treatment cell. In certain embodiments, the method further comprises surrounding the munition with a refractory material prior to covering the munition with a soil to a predetermined level. In certain embodiments, the predetermined level comprises a level of soil cover sufficient to achieve camouflet conditions.

[0012] In certain embodiments a method for treating a munition containing a chemical agent and an explosive component is provided. The munition is placed in a treatment cell. The munition is heated to a temperature to thermally decompose the explosive component. The remaining chemical agent, the remnants of the munition, and the soil are treated within the treatment cell. In certain embodiments, heating the munition to a temperature to thermally decompose the explosive component comprises performing a heat ramp for a first period of time to heat the munition to a critical temperature and soaking the munition at a critical temperature for a second period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0014] FIG. 1 is a process flow diagram illustrating one embodiment of the present invention;

[0015] FIG. 2 is a schematic side view of a treatment cell according to one embodiment of the present invention;

[0016] FIG. 3 is a schematic top view of the treatment cell of FIG. 2;

[0017] FIG. 4 is a plot depicting temperature (⁰C) versus time (hours) for a planned heating ramp according to one embodiment of the present invention;

[0018] FIG. 5 is a plot depicting temperature (⁰C) versus time (hours) for an actual heating ramp according to one embodiment of the present invention;

[0019] FIG. 6 is a plot depicting NO_x emissions and temperature within a test artillery shell during heating;

[0020] FIG. 7 is a plot depicting the internal pressure and temperature of a test shell during actual heating and vitrification treatment; [0021] FIG. 8 is a plot depicting temperature (⁰C) versus elapsed time (hours) for the response of a thermocouple located at a refractory interface with the base of the melt during the actual vitrification treatment of a test shell;

[0022] FIG. 9 is a plot depicting total power (kW) versus elapsed time (hours) for the actual vitrification treatment of a test shell;

[0023] FIG. 10 is a plot depicting electrical current (amps) versus time (hours) for the actual vitrification treatment of a test shell; and

[0024] FIG. 11 is a plot depicting electrical potential (voltage) versus time (hours) for the actual vitrification treatment of a test shell.

[0025] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and/or process steps or one or more embodiments may be beneficially incorporated in one or more other embodiments without additional recitation.

DETAILED DESCRIPTION

[0026] As discussed above, traditional vitrification processes are able to render harmless chemical agents but have difficulty with confined or concentrated energetic materials such as explosives. Embodiments of the present invention, however, provide a two stage treatment process including a heating step during which the explosive component is thermally decomposed prior to treating the chemical agent. Moreover, the method of treatment is designed to treat the munition in one process sequence and thus no secondary waste treatment or decontamination is required and personnel and environmental safety hazards that are otherwise present when implementing conventional treatment methods are minimized.

[0027] Chemical agents that may be treated with the method of the current invention include but are not limited to nerve agents, for example, Cyclosarin (GF), Sarin (GB), Soman (GD), Tabun (GA), VX, insecticides, and Novichok agents, Asphyxiant/ Blood agents, such as, Arsine, Cyanogen chloride, Hydrogen cyanide, Vesicant/blister agents, such as, Sulfur mustard (HD, H), Nitrogen mustard (HN-1 , HN-2, HN-3), Lewisite (L), Adamsite, Clark I, Clark II, Phosgene oxime (CX), Choking/Pulmonary agents, such as, Chlorine, Hydrogen chloride, Nitrogen oxides, Phosgene/diphosgene (CG), Lachrymatory agents, such as Tear gas or Pepper spray, Incapacitating agents, such as, Agent 15 (BZ), Cytoxic proteins, such as, Ricin and Abrin, and Incendiaries such as white phosphorous.

[0028] Explosive components include but are not limited to: picric acid, trinitrotoluene (TNT), and other energetic materials Energetic materials include Mercury Fulminate, Lead Azide, Lead Styphnate, Diazodinitrophenol (DDNP), Silver Azide, Tetrazene, Nitrocellulose (guncotton), Nitroglycerin, PETN [Pentaerythritol tetranitrate], EGDN [ethylene glycol dinitrate], RDX [Research Department Explosive or Royal Demolition Explosive; Hexahydro-1 ,3,5-trinitro-1 ,3,5-triazine], HMX [High Melting Explosive; Octahydro-1 ,3,5,7-tetranitro-1 ,3,5,7-tetrazocine ], Tetryl (2,4,6- trinitrophenyl-methylnitramine), TATB (1 ,3,5-triamino-2,4,6-trinitrobenzene), Picric Acid (2,4,6-trinitrophenol), Ammonium Picrate (Yellow D / Explosive D), Nitroguanidine (picrite), CH-6, Composition A-5, Amatol, Baratol, Composition A, Composition B / Comp B, Composition B-3, Composition C-3, and Composition C-4 / Comp C-4 Plastic Explosive.

[0029] The method of the current invention may be used in virtually all types of vitrification processes including, for example, the GeoMelt^® In Container Vitrification (ICV)™ and Subsurface Planar Vitrification (SPV)™ both of which are available from AMEC Earth and Environmental, Inc. (AMEC), among others. The method of the current invention could also be adapted for use with other types of thermal treatment methods to include the heating step followed by thermal desorption, incineration, or other types of vitrification including plasma, induction heating, and various types of joule or resistive heating vitrification processes. The method of the current invention may also be used to treat other waste material associated with explosive components. For example, the method of the current invention may be used to treat organic compounds, such as solvents, dioxins, pesticides, and polychlorinated biphenyls (PCBs), heavy metals, radionuclides, and inorganic compounds. The method of the current invention may be performed either in-situ, which avoids the risk and expense of excavation or in containers, which can then be transferred to long term storage. Concentration of the contaminants can be of a wide range. Further, the invention can be used with all soil types such as, for example, sands, silts, clays, etc. The soil to be treated may be wet or comprise sludge, sediments, or ash.

[0030] The GeoMelt^® process is a group of vitrification technologies that can be configured in various ways to meet a wide range of treatment requirements. In GeoMelt^® applications, a waste and soil mixture is electrically melted to destroy, remove, or permanently immobilize contaminants. Melt temperatures generally are between 1200°C and 2000⁰C, depending on the composition of the waste/soil mixture. Organic materials are destroyed and/or removed during the melting process. The byproduct of the GeoMelt^® process is semi-crystalline glass, which immobilizes heavy metals and radionuclides in a geologically durable waste form suitable for disposal without any further treatment.

[0031] Organic compounds such as dioxins, pesticides, and polychlorinated biphenyls (PCBs) are destroyed via pyrolysis and dechlorination reactions at elevated temperatures in reducing conditions around the melt. No organic compounds remain in the melt, because they cannot exist at such high temperatures for sustained periods of time. A broad range of organic compounds have been successfully treated in commercial operations. The destruction and removal efficiencies (DRE) achieved during commercial operations for organic species are greater than 99.9999%. The DRE includes the percentage destroyed by the melt (typically 90-99.9%) and the percentage destroyed and/or removed by the off-gas treatment equipment.

[0032] Subsurface Planar Vitrification (SPV)™ allows for in-place treatment of waste materials in the ground, thus minimizing potential exposure pathways and eliminating the cost of waste relocation that is required to implement other thermal treatment technologies. In SPV, electrodes are staged within the treatment area in a configuration resulting in two separate vertical planar melts that propagate downward as they merge together, resulting in one coalesced melt encompassing the treatment area. SPV also can be applied within large in-ground treatment cells to treat large volumes of staged waste materials.

[0033] In Container Vitrification (ICV)™ involves the use of a refractory-lined container, into which waste and soil are staged and the vitrification process is applied. The melt container is either re-used after removal of vitrified material, or in some cases, the entire package is disposed.

[0034] FIG. 1 is a process flow diagram 100 illustrating one embodiment of the present invention. FIG. 2 and FIG. 3 show schematic views of one embodiment of the present invention as applied to munitions such as a 77-mm chemical artillery shell 202. In step 110, the shell 202 containing a chemical agent and an explosive component is wrapped with a heat trace. In step 120, the shell 202 is placed in a treatment cell 200. In step 130, the shell 202 is surrounded with a refractory material. In step 140, the shell 202 and refractory material are covered with soil to a predetermined level to achieve camouflet conditions. In step 150, a starter path is positioned in the treatment cell 200. In step 155, the off-gas containment hood is secured to the top of the container to seal the treatment vessel and connections are made to the off-gas treatment system. In step 160, the shell 202 is heated to a critical temperature. In step 170, the shell 202 is maintained at the critical temperature for a period of time to thermally decompose the explosive component. At step 180, the remaining chemical agent and the remnants of the shell 202 and soil are treated using vitrification. Although discussed with reference to shells, it should be understood that this process may be used to treat other munitions including but not limited to bombs, projectiles such as artillery and mortar shells, and warheads.

[0035] In step 110, the shell 202 containing a chemical agent and an explosive component is wrapped with a heat trace configured to heat the shell 202. In certain embodiments, the heat trace may comprise insulated heat tape with a maximum operating temperature above the thermal decomposition temperature of the specific explosive component to be treated. In certain embodiments, the heat tape has a maximum operating temperature of up to about 760⁰C. In certain embodiments, after wrapping the heat trace around the shell 102, the shell 202 is covered with a layer of insulation. In certain embodiments, the layer of insulation comprises a layer of ceramic insulation, such as, for example Kaowool insulation. In certain embodiments, the layer of insulation is between about 2 mm and about 10 mm thick, for example, about 6.35 mm thick. The length and thickness of the heat trace is a function of the shell size and the explosive charge. The heat trace may be connected with a feedback controller (not shown) which may be configured to monitor and adjust the temperature of the heat trace based on a pre-programmed process recipe for heating the shell 202. In certain embodiments, other methods such as microwave heating, inductive heating, radio frequency heating, other types of resistive heating, or combinations thereof may be used to heat the munition.

[0036] In certain embodiments, the treatment cell 200 may be replaced by another container containing the chemical agent and explosive component. Other containers include roll-off boxes, metal drums, such as standard 55 gallon steel drums, projectiles, bombs, and custom made boxes of indeterminate size. The container may be either reusable or consumable. In certain embodiments, the use of containers approved for transportation by the proper governmental authorities allows for both treatment and shipping to a disposal site within the same container

[0037] In step 120, the shell 202 is placed in a treatment cell 200. In certain embodiments, the treatment cell 200 comprises an exterior container 204 coupled with an off-gas hood 206. In certain embodiments, an interior container (not shown) is placed within the exterior container 204. In certain embodiments, the exterior container 204 is a cylindrical steel cylinder. In certain embodiments, the exterior container 204 measures between about 1000 mm and about 2000 mm in diameter, for example, about 1829 mm in diameter. An interior container 208 is disposed within the exterior container 204. In certain embodiments, the interior container 208 comprises a steel cylinder. In certain embodiments, the interior container 208 is between about 500 mm and about 1500 mm in diameter, for example, about 1219 mm in diameter and about 1372 mm in height. The interior container 208 has sidewalls 210 and a base 212. In certain embodiments, the interior container 208 contains a protective liner 214. In certain embodiments, the protective liner 214 comprises an insulating material 216 and a refractory material 218. The insulating material 216 lines each of the sidewalls 210 and the base 212 of the interior container 208. The insulating material 216 may be selected from ceramic blankets, felt, or paper material composed of in part or whole temperature resistant materials or combinations of materials such as but not limited to alumina, silica, and kaolin. After placement of the insulating material 216, the interior container 208 is lined with the refractory material 218 so as to line the sidewalls 210 as well as the base 212 of the interior container 208. The refractory material 218 may comprise any material that contains the molten material undergoing vitrification during the vitrification treatment stage. The refractory material may be selected from cobble, gravel, wire mesh, granular aggregate, castable shaple, or brick composed of in part of temperature resistant materials or combinations of materials such as but not limited to alumina, silica (pure), silica (sand), silicon carbide, kaolin, anorthite, corundum, spinel, and magnesia. In certain embodiments, the protective liner 214 may be kept in place by a removable slipform 220. In certain embodiments, the cylindrical removable slipform 220 comprises cardboard. In other embodiments, the removable slipform may comprise steel or wool.

[0038] After the insulating material 216 and the refractory material 218 are placed in the interior container 208, the shell 202 is placed into the interior container 208. In embodiments without the interior container 208, the refractory material 218 is placed in the interior container 208. In certain embodiments, a metal container 230 is used to lower the shell 202 into the interior container 208. The shell 202 is then covered with earthen material 232 used in the vitrification process to disperse energy released during thermal decomposition. The material may be soil, gravel, any other granular material suitable for vitrification, and combinations thereof.

[0039] In step 140, the shell and refractory material are covered with a layer of soil 234 to a predetermined level. The amount of soil or earthen materials covering the shell is designed to achieve camouflet conditions (Ae. a condition whereby the mass of the soil 234 above the shell 202 is sufficient to suppress and contain the maximum possible force of the thermal decomposition such that there will be no surface cratering). The mass and depth of the soil 234 placed above the shell 202 is therefore a function of the size of the explosive charge. In certain embodiments other materials may be used in addition to the earthen materials to achieve camouflet conditions, for example, a heavy movable plate may be placed on top of the column of soil, gravel, or other earthen material to minimize the amount of overburden required. In other embodiments, engineered systems including fabric, mats, or grates could be incorporated within the soil layers to improve the shear strength of the soil.

[0040] Next, the plurality of electrodes 224 is placed in the treatment cell 200. In certain embodiments, with reference to FIG. 3, the plurality of electrodes 224 is positioned to create one horizontal planar melt above the munition. In other embodiments the plurality of electrodes 224 may be used to create a horizontal planar melt below the munition. In another embodiment the plurality of electrodes 224 may be used to create two separate vertical planar melts on either side of the munition. The plurality of electrodes 224 may comprise any even number of electrodes. In certain embodiments the plurality of electrodes 224 comprises four electrodes. The plurality of electrodes 224 may comprise any material suitable for conducting electric current. In certain embodiments, each of the plurality of electrodes 224 comprises a graphite material. In certain embodiments, each of the plurality of electrodes 224 is between about 20 mm and 300 mm in diameter, for example, about 51 mm in diameter. The plurality of electrodes 224 may be supported by a series of individual support structures (not shown) that allow for fixed and mobile vertical positioning with pneumatic gripper/motor assemblies.

[0041] In step 150, a starter path 236 is positioned in the treatment cell 200 between the plurality of electrodes 224. The starter path 236 may comprise any material or combination of materials that is moderately conductive and suitable for commencing the melt process. In certain embodiments, the starter path 236 comprises a non-conductive material combined with a conductive material. Once the non-conductive portion of the starter path 236 melts, the non-conductive portion becomes conductive and the melt commences.

[0042] In step 155, an off-gas hood is secured to the top of the treatment cell 200. The off-gas hood 206 is positioned over and coupled with the exterior container 204. The off-gas hood 206 has a plurality of openings 222 through which extend a plurality of electrodes 224. The hood 206 also has an air inlet 226 and an outlet 228 which leads to an off-gas treatment system (not shown).

[0043] In step 160, the shell 202 is heated to a critical temperature in order to thermally decompose the explosive component. The critical temperature is based upon the decomposition temperature of the particular explosive component. Although discussed with particular reference to picric acid it should be understood that the thermal decomposition may be modified for use with other explosive components. Step 160 will be discussed with reference to FIG. 4. FIG. 4 is a plot 400 depicting temperature (⁰C) versus time (hours) for a planned heating ramp of one embodiment of the present invention where the explosive component within an artillery shell is picric acid. Power is applied to the heat trace in order to heat the shell 202 to the critical temperature. In one exemplary process, with reference to FIG. 4, where picric acid is used as the explosive charge, a heat ramp design is used in which the internal shell 202 temperature is elevated from ambient temperature (30⁰C) to 140⁰C at a rate of 2 degrees per minute.

[0044] In step 170, the shell 202 is maintained at the critical temperature for a period of time. In the case where picric acid is the explosive being decomposed, at 140⁰C, a two hour soak is performed. At a temperature of 140⁰C the liquid picric acid would decompose (the melting point of picric acid is 123°C) which is slightly below its flash point (150⁰C) and well below its auto-ignition temperature (300⁰C). In certain embodiments, after the critical temperature is achieved, the temperature may be increased using a slow ramp. [0045] In certain embodiments, the treatment cell 200 also comprises a monitoring system for monitoring the thermal decomposition of the explosive component. The monitoring system may comprise a series of thermocouples 240 in order to monitor melt progress during vitrification operations. In certain embodiments, the monitoring system may comprise a length of stainless steel tubing 242 connected to polyethylene tubing to allow for NO_x analysis and for recording the internal munition pressure using a pressure transducer. The presence of NO_x gases may be used to identify the thermal decomposition of explosive components containing nitrates. The monitoring system may be used to identify the presence of other gases emitted during the thermal decomposition of explosive components. In certain embodiments, an accelerometer 244 is coupled to the side of the interior container 208 to measure vibrations caused by detonation of the explosive component during controlled heating if detonation is the mode at which decomposition takes place. All instruments are connected to a controller that may comprise a PC-based data acquisition system for automatic data logging.

[0046] At step 180, the remaining chemical agent and the remnants of the munition and soil are treated with vitrification. The treatment process may include many types of batch vitrification processes including, for example, the GeoMelt^® In Container Vitrification (ICV)™ and Subsurface Planar Vitrification (SPV)™ both of which are discussed above.

Example

[0047] Embodiments of the invention will be described with reference to a specific test example using a 70 mm test shell containing 25 g of picric acid as its explosive component and no chemical agent. The purpose of this test was to verify decomposition of picric acid by controlled heating and to demonstrate the successful application of heating followed by vitrification. It should be understood that the example is not intended to limit the scope of the invention in any way.

[0048] The test shell was installed 152 mm above the base silica sand layer, in the center of a 1219 mm diameter container, and was surrounded on all sides by 152 mm of vesicular basalt gravel. The gravel and test shell were contained in a metal basket in order to facilitate loading into the interior container. The depth of burial for the test shell with respect to the starter path position was 833 mm. An additional 102 mm of gravel was staged on top of the gravel basket. Soil was loaded around and on top of the gravel to a height of 991 mm above the refractory silica sand base layer. The starter path was installed between the four 51 mm diameter graphite electrodes and buried under 152 mm of cover soil.

[0049] FIG. 5 is a plot 500 depicting temperature (⁰C) versus time (hours) for the actual heating ramp of the test example. The heat tape controller achieved the desired rate and soak time by pre-programming a 55-minute ramp to 140⁰C at a rate of 2°C/minute, followed by a second program calling for an additional 10-degree ramp lasting two hours. The second ramp is the soak. Thermometric data was recorded every 16 seconds. The 140⁰C soak was suspended after 1.25 hours because NO_x emissions levels had decreased markedly after approximately 30 minutes of soaking. The remainder of the controlled heating involved periodic 10- degree increases with 30-minute soaks (until 180⁰C) followed by a 10-degree increase with 15-minute soaks until 250⁰C had been attained. This approach was based on NO_x analyzer response, which indicated minimal NO_x emissions levels after 150⁰C had been attained. The importance of NO_x emissions are discussed further in the next section.

[0050] The difference between internal and external shell temperatures averaged 9.5 ⁰C up until about 250⁰C. At this temperature, after approximately 5.5 hours of heating, the test shell temperature increased rapidly to 42O⁰C in the course of two minutes. This rapid temperature increase coincided with the sudden failure of NO_x tubing. After this, the heat temperature controller failed to control the internal thermocouple, although it was still registering temperature. The heat tape still appeared operable, as indicated by the ability to adjust the power output. This may have indicated that the internal thermocouple (or heat tape, or both) had shifted position enough so that an increase in power to the heat tape failed to register on the thermocouple. [0051] FIG. 6 is a plot 600 depicting NO_x emissions within the test shell during heating. The gas analyzer recorded NO, NO₂, and NO_x emissions within the test shell during heating via tubing installed through the side of the shell. The NO_x analyzer data was recorded every 4 seconds. At approximately 5.5 hours, the NO_x level spiked to the instrument detection limit of 5000 ppm. NO and NO₂ emissions also reached the 5000 ppm level at this time, indicating that total NO_x levels were much higher than recorded during the final moments of controlled heating. The data depicted in FIG. 6 indicated picric acid decomposition during the 140⁰C soak period, and also after the internal test shell temperature reached 150⁰C and 189°C. It is notable that 150⁰C is the flash point of picric acid, and that 189°C is near the temperature (183°C) at which a long induction period is reported in picric acid. The NO, NO₂, and NO_x emissions indicated the decomposition of picric acid to expected combustion products.

[0052] FIG. 7 is a plot 700 depicting the internal pressure of the test shell during heating. Further indication of complete decomposition of picric acid was recorded by the pressure transducer connected to the same tubing from which the NO_x analyzer received samples. The pressure was approximately 20 kPa during the 140⁰C soak and until the final decomposition event at approximately 5.5 hours. At this time, the pressure decreased momentarily to 13 kPa, and then increased in the course of 2 seconds to 257 kPa (FIG. 5). This is the highest recorded pressure before the polyethylene tubing ruptured. The pressure data was automatically recorded in 1 -second intervals. The accelerometer fastened to the inner steel container did not register any vibration during the heating period.

[0053] After completion of controlled heating activities, the surface of the cover soil above the starter path was examined. There was no indication of surface cratering. Electrical resistance through the starter path between phase electrodes was measured and found to be essentially unchanged from the preheat conditions, ranging from 1.1 ohms to 1 -6 (ohms), indicating that the starter path was not disrupted. [0054] Vitrification operations subsequently commenced. Each graphite electrode was pre-marked at 25.4 mm intervals to allow for monitoring of downward progress as the melt progressed from the top of the staged soil column, to the final depth of 991 mm relative to the electrode starting position. Power to the melt was terminated approximately 28.5 hours later. Electrode descent rate (used as an indication of processing rate) was 35 vertical mm/hour, which was within the target rate of 25-38 mm/hour for this test.

[0055] The vitrified monolith was removed from the container after six days of cooling. The monolith measured approximately 813 mm in height and 1041 mm in diameter. The initial staged diameter was 914 mm, indicating a general thickening as the melt migrated into the sand and as it incorporated silica sand as a fused rind into the melt periphery. The base of the melt included approximately 64 mm of fused silica sand at the center. Overall, the volume reduction owing to the densification of the staged material was approximately 30%.

[0056] The vitrified monolith was split open to observe the interior glass and to determine the fate of the test shell, gravel, and gravel basket. The gravel was no longer present, indicating complete incorporation into the melt as constituent oxides. The metal basket melted completely. Remnants of the test shell were observed at the base of the glass block in the center. The exposed test shell remnant embedded in the glass measured approximately 152 mm in length and approximately 76 mm in width. The remnant was roughly concave but mostly irregular in shape. The position of the test shell remnant at the base of the center of the melt indicates that controlled heating operations did not result in significant lateral movement of the shell and it is likely that the shell, having remained in position during controlled heating descended due to its higher density as it was being melted to rest on the base of the silica sand layer.

[0057] The heating and vitrification tests were successful. The heat tape achieved target temperatures as the desired rates and maintained the 140⁰C soak well. The soak/ramp approach, as modified to allow for periodic temperature increases bases on NO_x analyzer response, effectively decomposed the picric acid in a safe and reasonable amount of time (about 5.5 hours).

[0058] A method for treating and rendering harmless munitions containing chemical agents and an explosive component has been provided. Decomposition of the picric acid did not damage either the ICV treatment container or starter path. There was no surface disruption associated with picric acid decomposition and the subsequent melting operation was successful. The melt was completed in approximately 28.5 hours. There were no safety or operational problems during controlled heating or melting operations.

[0059] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims:

1. A method for treating a munition containing a chemical agent and an explosive component, comprising: heating the munition to thermally decompose the explosive component; and treating the chemical agent and the remnants of the munition.

2. The method of claim 1 , wherein the heating the munition to thermally decompose the explosive component comprises: wrapping the munition with a heat trace; applying power to the heat trace; heating the munition to a critical temperature; and maintaining the critical temperature for a time period sufficient to thermally decompose the explosive component.

3. The method of claim 2, wherein the heating the munition to a critical temperature comprises heating the munition using a heat ramp.

4. The method of claim 1 , wherein the critical temperature is below a flash point and an auto-ignition temperature of the explosive component.

5. The method of claim 1 , wherein the treating the chemical agent and the remnants of the munition comprises a vitrification process.

6. The method of claim 1 , wherein the treating the chemical agent and the remnants of the munition comprises performing a subsurface planar vitrification process.

7. The method of claim 1 , wherein the treating the chemical agent and the remnants of the munition comprises performing an in container vitrification process.

8. The method of claim 1 , wherein the chemical agent is selected from the group comprising: Phosgene, VX, sulfur mustard, Lewisite, Adamsite, Clark I, Clark Il and white phosphorous.

9. The method of claim 1 , wherein the explosive component is selected from the group comprising: picric acid, trinitrotoluene (TNT), Mercury Fulminate, Lead Azide, Lead Styphnate, Diazodinitrophenol (DDNP), Silver Azide, Tetrazene, Nitrocellulose (guncotton), Nitroglycerin, PETN [Pentaerythritol tetranitrate], EGDN [ethylene glycol dinitrate], RDX [Research Department Explosive or Royal Demolition Explosive; Hexahydro-1 ,3,5-trinitro-1 ,3,5-triazine], HMX [High Melting Explosive; Octahydro- 1 ,3,5,7-tetranitro-1 ,3,5,7-tetrazocine ], Tetryl (2,4,6-trinitrophenyl-methylnitramine), TATB (1 ,3,5-triamino-2,4,6-trinitrobenzene), Picric Acid (2,4,6-trinitrophenol), Ammonium Picrate (Yellow D / Explosive D), Nitroguanidine (picrite), CH-6, Composition A-5, Amatol, Baratol, Composition A, Composition B / Comp B, Composition B-3, Composition C-3, and Composition C-4 / Comp C-4 Plastic Explosive.

10. A method for treating a munition containing a chemical agent and an explosive component, comprising: placing the munition in a treatment cell; covering the munition with soil to a predetermined level; positioning a starter path in the treatment cell; heating the munition to a critical temperature; maintaining the munition at the critical temperature for a period of time in order to thermally decompose the explosive component; and

V /iIttrifying residual components including the remaining soil and chemical agent.

11. The method of claim 10, further comprising wrapping the munition in a heat trace prior to placing the munition in the treatment cell.

12. The method of claim 10, further comprising surrounding the munition with a refractory material prior to covering the munition with earthen material to a predetermined level.

13. The method of claim 10, wherein the predetermined level comprises a level sufficient to achieve camouflet conditions.

14. The method of claim 10, wherein the chemical agent is selected from a group comprising: phosgene, VX, mustard gas, lewisite, and white phosphorous.

15. The method of claim 10, wherein the explosive component is selected from the group comprising: picric acid, trinitrotoluene (TNT), Mercury Fulminate, Lead Azide, Lead Styphnate, Diazodinitrophenol (DDNP), Silver Azide, Tetrazene, Nitrocellulose (guncotton), Nitroglycerin, PETN [Pentaerythritol tetranitrate], EGDN [ethylene glycol dinitrate], RDX [Research Department Explosive or Royal Demolition Explosive; Hexahydro-1 ,3,5-trinitro-1 ,3,5-triazine], HMX [High Melting Explosive; Octahydro- 1 ,3,5,7-tetranitro-1 ,3,5,7-tetrazocine ], Tetryl (2,4,6-trinitrophenyl-methylnitramine), TATB (1 ,3,5-triamino-2,4,6-trinitrobenzene), Picric Acid (2,4,6-trinitrophenol), Ammonium Picrate (Yellow D / Explosive D), Nitroguanidine (picrite), CH-6, Composition A-5, Amatol, Baratol, Composition A, Composition B / Comp B, Composition B-3, Composition C-3, and Composition C-4 / Comp C-4 Plastic Explosive.

16. The method of claim 10, wherein the treatment cell comprises: an exterior container coupled with an off-gas hood, wherein the off-gas hood has a plurality of opening through which extend a plurality of electrodes; and an interior container disposed within the exterior container.

17. The method of claim 10, wherein the critical temperature is a temperature range below a flash point and an auto-ignition temperature of the explosive component.

18. The method of claim 1 , wherein the treating the chemical agent and the remnants of the munition comprises performing a subsurface planar vitrification process.

19. A method for treating a munition containing a chemical agent and an explosive component, comprising: placing the munition in a treatment cell; heating the munition to a temperature to thermally decompose the explosive component; and treating the remaining chemical agent and the remnants of the munition and soil within the treatment cell.

20. The method of claim 19, wherein the heating the munition to a temperature to thermally decompose the explosive component comprises: performing a heat ramp for a first period of time to heat the munition to a critical temperature; soaking the munition at the critical temperature for a second period of time; and vitrifying the chemical agent.