The Present Baseline System
BASELINE SYSTEM IMPLEMENTATION
In this section, the baseline system as it is implemented in a second generation form at Tooele Army Depot is briefly described. The first generation, the Johnston Atoll Chemical Agent Disposal System (JACADS), is now operating on Johnston Island, having successfully completed Operational Verification Testing (OVT) in March 1993. This chapter is intended not only to describe the present system, but also to provide a base to which the technologies in the next chapter can be compared. It also serves to indicate that disposal of chemical agents and munitions requires an extensive and rather complex system . The concerns that have motivated a search for alternative technologies appear to address only a portion of that system. Figure 5-1 shows the major system components of the baseline system.
Storage, Transportation, And Unloading Of Munitions And Containers
Munitions are stored in vented igloos. The igloo area is monitored for agent. Most bulk containers are stored in the open or in monitored warehouses. Prior to transport of munitions and containers, the area is checked for any signs of leakage. If agent contamination is found, special procedures are followed to contain leaking munitions and to decontaminate the area. The munitions or ton containers are then loaded into a robust, vapor-tight, transport container that is designed to withstand impacts and fire exposures. (A transport container for spray tanks is yet to be designed.) The transport container is moved from the storage area to the unpacking area within the disposal building. Munitions and agent containers are unpacked manually. Packing materials (dunnage) are transported to the dunnage furnace.
Disassembly and Draining
Munitions are moved into an explosive containment room that is maintained below atmospheric pressure (to prevent any leakage of agent) and is designed to withstand overpressures that might result from the explosion of munitions during processing. Ventilation air from this room is passed sequentially through six charcoal filter beds, with agent monitors after the first, second, and fourth beds. Agent traces were rarely found after the first bed and were never detected beyond the second bed throughout the OVT at JACADS.
Bulk storage containers are taken to a bulk drain station where they are punched and drained within a ventilated enclosure that also feeds to the charcoal bed filter banks.
Agent is removed from munitions and containers by automated machinery using one of two processes. Where possible, containers (M55 rockets, land mines, bombs, spray tanks, and ton containers) are simply punched and drained of agent. Heavy-walled steel artillery projectiles are disassembled to be drained of agent. Disassembly begins with removal of explosive elements in the case of armed projectiles. In all cases, mechanical extraction of a press-fit burster tube is the means to gain access to the agent. Agent drainage (and subsequent destruction) can be complicated by gelling or solidification of the material, particularly in the case of mustard, some of which then does not drain from the munition or ton container.
These operations result in three separate streams of material that are fed to specially designed destruction systems: an agent stream that is stored in a feed tank prior to injection into the liquid incinerator; a mixed stream of energetics, small metal components, and residual agent to be fed to the rotary kiln deactivation furnace system; and large metal parts (e.g., ton containers, spray tanks, artillery projectiles) with residual agent but no energetics, to be fed to the metal parts furnace. The separation of these three streams is an important safety feature of the baseline system. This provides the designer the freedom to tailor the design of each disposal system to the properties of the separate (and quite different) materials to ensure safe, controllable operations. As a result, most agent is treated in liquid form, separate from the energetics and metal parts. The energetics and metal parts, with only residual agent present, are then treated separately.
The only alternative to these baseline operations that has been considered extensively is the cryofracture process, in which assembled munitions are crushed after being cryogenically cooled in a liquid nitrogen bath. The resultant mixture of agents, energetics, and metal fragments is then fed, without separation, into a single rotary kiln, similar to but larger than the baseline deactivation furnace system. The Stockpile Committee has not recommended this process (NRC, 1989b, 1991a-c).
The drained agent at Tooele will be stored in a 500-gallon tank inside a room designed to contain toxic substances. The volume of agent storage has been greatly reduced at Tooele (by about a factor of 5 less than at JACADS) because of higher earthquake risks there. This tank represents the largest single volume of agent on-site. A larger emergency dump tank is also provided at Tooele but is not intended to be used for normal operations.
The liquid incinerator consists of two sequential combustion chambers and a pollution abatement system (discussed below). The first or "primary" combustion chamber is preheated to an operating temperature of 2700ºF with fuel before agent is injected. As agent flow increases, the fuel flow is decreased to maintain the desired temperature for effective agent destruction. Agent flow to the burner is stopped if this temperature drops below 2550ºF. Gases from the first chamber are sent to a secondary chamber, also preheated with fuel, for a final burn stage at 2200ºF. Some slag produced during nerve agent destruction was deposited on the lower-temperature walls of the secondary chamber. Spent decontamination fluid is also injected into the secondary chamber for destruction of any residual agent in the solution as well as for evaporation and discharge of the water. This fluid also contains salts that deposit in the bottom of the secondary chamber. The liquid incinerator had to be shut down periodically for manual removal of glasslike solidified salts. A better slag removal system is being developed to discharge molten salts during operation. Its effectiveness needs to be demonstrated during pre-agent testing at Tooele.
Energetic materials (fuses, boosters, bursters, and solid rocket propellant) are burned in a counterflow rotary kiln (deactivation furnace system). Energetic materials are all contained in thin-walled metallic housings that must be punched or cut into pieces prior to burning, since confined energetics would detonate rather than burn in the kiln. M55 rockets, after being drained of agent, are sliced into seven pieces to expose enough energetic material surface area to allow burning without detonating. Draining and slicing both occur while the rocket is in its fiberglass launch tube. Bursters from artillery projectiles are similarly sliced after removal from the projectile. Explosive elements in land mines are punched in place to expose the explosive and are not removed from the munition. Properly exposed energetic elements, typically wetted with agent, are fed into the downstream end of the kiln (downstream in the sense of gas flow) in a controlled sequence to avoid excessive explosive concentrations within the kiln. Solid elements move
upstream (against the gas flow) as the energetic materials burn and then exit onto an electrically heated discharge conveyor where their temperature is maintained at 1000ºF for 15 minutes. This results in a 5X decontaminated material that is suitable for release to the general public, although the mixture of light steel components, melted aluminum, and glass fibers is of no commercial value. Gases discharged from the rotary kiln pass through an afterburner where they are subjected to a temperature of 2200ºF for 2 seconds. These conditions are more stringent than those at JACADS (2000ºF for 1 second) and should allow the furnace to fully comply with removal efficiency requirements for destruction of polychlorinated biphenyls (PCBs). (Some fiberglass launch tubes contain small quantities of PCB.) The gases then are treated in the pollution abatement system described below.
Metal Parts Decontamination
Metal parts, drained of agent (ton containers, bombs, spray tanks, artillery projectiles and their burster wells, which were pulled to release the agent) are heated to 1000ºF and maintained at that temperature for 15 minutes in a fuel-fired metal parts furnace, producing 5X metal suitable for release as scrap. Residual or undrained (including gelled) agent that was not removed from these elements is vaporized and burned within the furnace. This process takes additional time and can limit the system's throughput. At JACADS, special procedures were implemented to allow increased quantities (over the design limit of 5 percent residual per projectile) of agent processing in the metal parts furnace. This procedure ensured compliance with the overall feed restriction contained in the Resource Conservation and Recovery Act permit. After successful testing and with proper monitoring and control, this is an acceptable practice, but the regulatory treatment of these conditions should be clarified so that waivers will not be required for operation.
Gases discharged from the metal parts furnace are passed through an afterburner, maintained at of 2200ºF, before being treated in the pollution abatement system described below.
Pollution Abatement Systems
The liquid incinerator, deactivation furnace system, and metal parts furnace employ identical and dedicated pollution abatement systems. Gases leaving the secondary chamber of the liquid incinerator or the metal parts furnace afterburner flow to separate dedicated pollution abatement systems for removal of gaseous pollutants and particles to meet emission standards. Hot gases leaving the deactivation furnace system kiln flow to a refractory-
lined cyclone that removes large particles (rocket launch tube glass fibers), enter the afterburner, and then flow to a similar pollution abatement system.
Each pollution abatement system consists of a quench tower, a venturi scrubber, a packed bed scrubber, a candle mist-eliminator vessel, brine or quench recycle pumps, and an induced draft (ID) blower. Figure 5-2 shows a schematic of a pollution abatement system.
The exhaust gas stream enters the quench tower near the bottom, where it is cooled by contact with a countercurrent spray of brine pumped from the packed bed scrubber sump. Acidic gases (e.g., hydrogen chloride, hydrogen fluoride, nitrogen oxides, carbon dioxide, and sulfur dioxide, depending on the chemical agent incinerated) in the exhaust gas react with caustic brine to form salts, which remain in solution in the brine. The cooled gas stream exits from the top of the quench tower and enters a variable throat venturi where it is scrubbed to remove particulates. The venturi uses a variable throat to maintain a constant pressure drop independent of the flow of exhaust gases. The brine streams from the quench and venturi scrubber are returned to the scrubber tower sump. Process water is added to the packed bed scrubber sump to make up for water evaporated in the quench tower. An 18 percent caustic (sodium hydroxide) solution is added as necessary to the sump to maintain the brine pH above 7.0.
The exhaust gas stream from the venturi scrubber enters the scrubber tower below the clear liquor reservoir tray, moves upward through the packed bed section, and exits at the top of the tower after passing through a mist eliminator pad. In the packed bed section, the gas stream contacts a brine solution flowing countercurrently through the bed. Acidic gases that remain in the exhaust gas stream are further scrubbed with caustic brine. The brine solution from the packed bed falls back to the reservoir tray and is recycled back to the top of the packed bed section. Excess brine overflows into the tower sump. Brine density is controlled by pumping a brine stream into the brine reduction area (BRA) storage tanks and replacing it with processing water.
The scrubbed gases enter a candle mist-eliminator vessel. Mist-eliminator candles (i.e., candle-shaped fabric filters) remove very fine mist and submicron particulate matter not removed in the venturi scrubber. The cooled and cleaned exhaust gases are pulled through an induced draft blower located downstream of the stack shared by the three furnace systems' pollution abatement systems.
Particulate emissions from the liquid incinerator, deactivation furnace system, and metal parts furnace were consistently low in tests at JACADS (the dunnage furnace was not tested). The mean for all trial burns for each incinerator was less than 5mg/m3 at 7 percent dioxygen, with a maximum measured value of 10.9 mg/m3. Permit requirement is less than 180 mg/m3.
Consequently, metal emissions (covered in Appendix VII of Environmental Protection Agency regulations) are extremely low, frequently below detectable limits.
The dunnage furnace and its pollution abatement system consist of a feed handling system, a primary chamber, an afterburner, a quench tower, a baghouse separator, an induced draft blower, and a separate exhaust stack. It is designed to burn noncontaminated and contaminated dunnage from the munitions processing operations, as well as charcoal and HEPA (high-efficiency particulate air) filter media from the air filters. Exhaust gases from the afterburner flow into the dunnage pollution abatement system quench tower. A water quench is used for cooling the exhaust gases, and a baghouse is used to remove particles. This pollution abatement system does not include acid gas scrubbing. The exhaust gases are maintained above the saturation temperature to prevent moisture condensation in downstream equipment. Gases exhaust to the atmosphere through a separate stack via the dunnage furnace induced draft blower.
To date, problems in demonstrating performance of this unit at JACADS have prevented incineration of most of the dunnage generated there. The alternative for JACADS has been disposal of decontaminated materials as hazardous waste. A dunnage incinerator is provided at Tooele and must be proven satisfactory, or else an alternative dunnage waste disposal strategy must be developed and proven prior to agent operations there. The Army has decided not to bum demilitarization protective ensemble suits (containing polyvinyl chloride) from Tooele operations in the dunnage furnace to avoid concerns about dioxins and furans.
The brine reduction area collects, stores, and evaporates discarded process brines and dries the salts produced by the three furnace pollution abatement systems. Operation of the brine reduction area produces salt that contains 10 percent or less water by weight. The brine reduction area consists of four subsystems: (1) steam generation (boilers) (2) brine evaporation (3) brine drying and, (4) pollution abatement. Entrained particles from the brines are collected in a baghouse before the exhaust is discharged to the atmosphere. The brine reduction area pollution abatement system consists of a heated, dual-module baghouse dust collection system. A fan pulls the exhaust gas through the baghouse modules prior to discharge to the atmosphere through a stack. A fuel-fired superheater heats the brine reduction area exhaust so that it remains above the dew point as it passes through the filters in the baghouse modules. The baghouse modules are equipped with a pulse air jet system to provide continuous cleaning of the
bags. Solids accumulate in drums under the baghouse for packaging and storage prior to shipping for land disposal as hazardous waste.
The satisfactory operation of the brine reduction area was not demonstrated during the OVT. This must be done prior to agent operations at Tooele, or some alternative brine handling system must be developed and proven.
Agent Monitoring Systems
The agent monitoring systems to be installed at Tooele are the same as those in use at JACADS. There are two types of analyzers: (1) the ACAMS (Automated Continuous Agent Monitoring System), which is capable of detecting agent at concentrations well below those that present an immediate threat to plant personnel or the surrounding population, with 3-to-8 minute response time; and (2) the DAAMS (Depot Area Air Monitoring System) for collection of longer, time-averaged samples for more selective subsequent analysis in the laboratory. The ACAMS monitors in personnel areas and in the stack are set to give a warning alarm at 20 percent of permissible agent levels (Table 3-1). Plant operations are shut down upon an alarm at the 20 percent level. The DAAMS samples are analyzed for the much lower permissible general population levels (Table 3-1). Many ACAMS and DAAMS monitoring points are distributed throughout the facility at appropriate locations.
In the event of agent release, the ACAMS monitors provide alarms and automatic corrective actions such as stopping the processing of agent until the nature of the problem is determined. The DAAMS system serves the dual purpose of providing samples that are used to confirm or refute indications of the presence of agent from the ACAMS and of documenting any concentrations of agent at much lower levels of detection sensitivity. Both systems use the principle of drawing gas through a gas chromatograph equipped with a flame photometric detector. The detection of any agent present is interpreted by computer analysis.
These systems must be readjusted for each agent type. The ACAMS generates frequent false alarms because it cannot adequately differentiate agent from other commonly encountered organic contaminants (e.g., fuel contaminants, diesel exhaust, antifreeze). For example, during OVT4, there were 55 alarms suggesting that allowable stack concentrations had been exceeded during 151 days of testing. All were determined to be false positive alarms. Further, when an alarm sounds, the retrieval and laboratory analysis of the DAAMS collection tubes to verify conditions typically require half an hour or more. Frequent false alarms can make operators complacent and
reluctant to stop operations, particularly when faced with production goals. At continental U.S. sites, such false alarms would erode public confidence in system safety.
The Stockpile Committee has prepared a special report on monitoring systems (NRC, 1994a), which recommends improvements to the Tooele system to allow more timely and agent-specific identification in the event of agent releases. The Army has begun development and testing of improved instrumentation.
BASELINE PERFORMANCE AT JACADS DURING OVT
To gain operational experience with the baseline system, and to confirm its ability to safely dispose of chemical agents and munitions, the JACADS facility was subjected to Operational Verification Testing, conducted in four campaigns (phases), from July 16, 1990, through March 6, 1993. The testing included a representative variety of munitions and containers and all three principal agents. The testing phases included
OVT1—M55 rockets containing agent GB (7,490 destroyed over a seven month period);
OVT2—M55 rockets containing agent VX (13,889 destroyed over a 19-week period);
OVT3—Ton (bulk) containers of blister agent HD (67 destroyed over a 4-week period); and
OVT4—105 mm M60 projectiles containing blister agent HD (18,949 destroyed over a 22-week period).
From the beginning of OVT, the MITRE Corporation, a not-for-profit corporation, was under contract to the Army to evaluate and report on each of the four campaigns (MITRE, 1991, 1992, 1993a, b) and to produce an overall OVT summary evaluation report (MITRE, 1993c). Based on these reports, its multiple visits to JACADS and other disposal sites, and its long-term study and examination of the baseline system, the Stockpile Committee evaluated OVT in two reports.
In July 1993, the Stockpile Committee issued a preliminary report: Evaluation of the Johnston Atoll Chemical Agent Disposal System Operational Verification Testing: Part I (NRC, 1993b). This report found that OVT ''has provided additional assurance that the baseline system is capable of the safe disposal of the Army's chemical stockpile,'' and recommended that the Army initiate systemization of the almost completed Tooele Chemical Disposal Facility. Systemization will consist of a thorough testing of the plant using agent surrogates to ensure proper operation before beginning operations with
agents. Additionally, the committee found that OVT identified some system deficiencies and indicated opportunities for improvements in operations and performance with regard to safety, environmental performance, and plant efficiency. The committee recommended that systemization at Tooele be used to implement these improvements prior to beginning the destruction of agent and munitions.
The Stockpile Committee has issued a more comprehensive follow-up report: Evaluation of the Johnston Atoll Chemical Agent Disposal System Operational Verification Testing: Part II (NRC, 1994b). This report details the committee's specific recommendations that should be implemented during the systemization at Tooele. For those recommendations requiring testing with agent (not possible yet at the Tooele facility), such as improved agent monitoring systems, testing can be conducted in parallel at JACADS or at the Chemical Agent Munitions Disposal System at Tooele.
The types of problems encountered during OVT show the importance of conducting full-scale demonstration tests on any complex prototype system to identify and correct any unanticipated weaknesses.
For example, during OVT, the lining of the liquid incinerator (LIC) deteriorated more rapidly than expected, requiring replacement with a more durable firebrick. Glassy slag accumulated in the secondary combustion chamber, and the system had to be shut down periodically for manual slag removal. A continuous system for molten slag removal has now been designed and will be tested during systemization at Tooele.
Other systems also encountered problems during OVT, requiring modifications to ensure safe operation. For example, several failures of munitions tracking systems allowed improperly processed munitions to be fed to furnaces. Also, unanticipated problems with gelled mustard required suited operators to perform tasks that were intended to be automated.
Some mishaps were indicative of deficiencies in training (e.g., operator errors, safety violations) or administrative procedures (e.g., poor recordkeeping, late incident reporting). These management issues are independent of the specific technology or system employed.
In the operation and maintenance of any complex system, safety is ultimately dependent upon effective management and trained operators. Public perception of the safety of a facility is heavily influenced by the performance and responsiveness of facility management. The OVT was important both because it revealed system and management weaknesses and because it demonstrated that management was generally able to respond to these incidents. Management's response has been a combination of equipment modifications, improved training for operators and maintenance personnel, and more realistic standard operating procedures.
In summary, though there were mishaps and mistakes during these startup tests, the multiple layers of safety designed into the facility avoided
hazards to workers and to the surrounding community. There were no "showstopper" incidents during OVT. The Stockpile Committee, therefore, judged the baseline system capable of safe disposal of the chemical stockpile. As noted, the committee's second OVT report contains specific recommendations for improvements that can and should be made before destruction of agents begins at Tooele. These are discussed in the report by the Stockpile Committee, Evaluation of the Johnston Atoll Chemical Agent Disposal System Operational Verification Testing: Part II (NRC, 1994b).
The main recommendations from that report are as follows:
Give safety considerations priority over production goals.
Proceed with Tooele systemization, and during systemization, conduct needed testing and improvement activities, including the following:
develop and demonstrate an improved agent monitoring and identification system;
complete the brine reduction area and pollution abatement system performance tests, or develop a satisfactory brine disposal alternative;
demonstrate the dunnage furnace performance with various levels of chlorinated waste; if needed, either modify the pollution abatement system design (e.g., add acid gas scrubbing) or limit feed materials to those that can be handled by the existing design (alternatively, satisfactory land disposal options must be' identified);
review the probable levels of NOx production from VX destruction and the allowable emission levels at the other continental U.S. sites requiring VX destruction; if appropriate, develop needed NOx abatement systems;
develop and demonstrate the proposed hot-slag removal system for the liquid incinerator system;
eliminate furnace feed errors by improved monitoring and control of the deactivation furnace and metal parts furnace feed systems and by improved methods for tracking the various types of munitions; and
address all problems associated with residual gelled mustard, in particular, the use of suited personnel to perform functions that were intended to be automated.
Establish and maintain close working relationships with permitting agencies, and support these efforts with careful analysis of operating parameters to ensure that permits provide for safe destruction of agent, adherence to regulatory requirements, and effective plant operations.
Establish programs, procedures, and management oversight to ensure continuing compliance with all environmental regulations.
Develop systems to improve overall management of safety.
Complete the risk assessment for the Tooele Chemical Disposal Facility during the systemization period.
Note that most of these recommendations are not specific to the agent destruction process.
The Stockpile Committee believes that the baseline system is fundamentally sound but that these improvements will provide worthwhile enhancement of the baseline system and will, if satisfactorily implemented, support safe and efficient operations at Tooele. This belief requires final confirmation after review of the results of the Tooele risk assessment.
As the first fully integrated baseline system, the JACADS facility was subject to startup problems, which would be the case for any complex system. As might be expected, these problems were often made more difficult by the remote location of the facility. Beyond these expected problems however, and as noted in its OVT reports, the Stockpile Committee believes that the Chemical Stockpile Disposal Program has been understaffed in view of the many major technical, regulatory, and public communications issues involved. This has led to administrative oversights and even to short-term technical modifications where longer-term solutions are necessary. If the program is now to include parallel efforts for alternative technologies, and if these alternatives are to be aggressively pursued, overall program staffing must be significantly increased.