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2
BGCAPP and PCAPP Process Descriptions and Secondary Waste Generation
This chapter provides an overview of the processes currently planned to destroy the stockpiles of chemical weapons stored at Blue Grass Army Depot (BGAD) and Pueblo Chemical Depot (PCD). They are presented primarily to indicate how the various waste streams are generated. The description of the process for BGCAPP is organized to take into account the trio of agents and the three munition types that will be processed in several types of munition destruction campaigns. In contrast, the description of the process for PCAPP, where a large number of similar munitions containing only one type of agent will be processed, is largely described in terms of the sequential operations that will be used.
BGCAPP PROCESS DESCRIPTION
Insight into the secondary waste streams that will be produced during operation of BGCAPP can be gained through an understanding of the processes for agent and munitions destruction and the waste materials generated by each of those processes. Different handling approaches are necessary for the various types of munitions that require disposal at BGCAPP. Figure 2-1 provides a flow plan of the BGCAPP processes that reflects the three types of munitions: 1
8-inch projectiles filled with GB and 155-mm projectiles filled with VX;
155-mm projectiles filled with mustard agent H; and
M55 rockets (and M56 rocket warheads) filled with VX or GB.
Processing of these munitions is discussed serially in the following sections. In many cases, similar operations are used for all three types of munitions. To avoid repetition, the greatest detail is provided for the processing of the GB- and VX-filled projectiles. Figure 2-1 reflects the BGCAPP design configuration made available to the committee when this report was being prepared.
The stored munitions are first delivered from storage igloos to the unpack area. Before leaving the unpack area, all packing material (dunnage) is removed. In addition to the munitions themselves, there is a substantial amount of nonprocess waste (dunnage and miscellaneous waste) that will contribute to the secondary waste generated and disposed of by BGCAPP. Monitoring is performed during the transport from storage and unpacking operations to ensure the safety of workers in recognition that some of these nonprocess wastes have the potential for being agent-contaminated.
GB and VX Projectiles
Neither the 8-inch GB projectiles nor the 155-mm VX projectiles stored at BGAD are charged with energetics. Hence, separation of the burster from the agent-filled portion of the rounds is not needed (as is the case for the H-filled munitions discussed later). After being unpacked, these GB and VX projectiles are initially sent to the nose closure removal station, where the lifting plugs are separated from the projectile bodies. The lifting plugs are fed to the metal parts treater (MPT), and the projectile bodies are sent to the munitions washout station (MWS) (see Figure 2-2).
At the MWS, agent is accessed by puncturing the projectile bodies, which are then drained by inverting the munitions. The residue remaining in the agent cavity is then washed out with a high-pressure spray nozzle using water at 110°F and 10,000 psig (NRC, 2005b). The rinse-out process is important to remove whatever fraction of the agent may have gelled and cannot be readily decanted from the perforated projectiles. The MWS process generates two process
1
Note that the actual order of the munitions processing schedule calls for all GB munitions to be processed first, followed by all VX munitions and, finally, all mustard agent H munitions. Changeover periods of 12 weeks between processing GB and VX munitions and 20 weeks between processing VX and H munitions are scheduled. Sam Hariri, lead process engineer, BGCAPP, “BGCAPP throughput and availability analysis (TAA),” presentation to the committee, January 23, 2008.
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FIGURE 2-1 Process and waste stream diagram for BGCAPP.
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FIGURE 2-2 Munitions washout system. SOURCE: PMACWA, May 20, 2008.
streams: (1) liquid agent and rinse water and (2) solid metal munition casings. In addition, the atmosphere from the MWS process is filtered by the main munitions demilitarization building heating, ventilation, and air conditioning (HVAC) system, which is discussed later in the process description.
Treatment of Liquid Agent and Rinse Water from the MWS
The liquid agent and rinse water from the MWS is sent to the agent collection/toxic storage tanks and subsequently to the agent neutralization reactors (ANRs), which have been charged with demineralized water and sodium hydroxide to maintain the desired caustic pH level.2 The resulting solution, now termed agent hydrolysate, is then transferred to a sampling tank, where the contents are analyzed to ensure that at least 99.9999 percent (160 ppb for VX, 75 ppb for GB, and 86 ppb for H) of the agent has been destroyed.3 Hydrolysis of GB produces isopropylmethyl phosphonic acid and neutralized hydrofluoric acid. The hydrolysis products of VX are more complex. The principal products from the VX hydrolysis reaction are bis(diisopropylamino) ethanethiol and ethylmethyl phosphonic acid. A less prevalent but competing hydrolysis reaction forms S-2-(diisopropylamino)ethyl methylphosphonothioic acid, also known as compound EA-2192, which retains much of the toxicity of VX itself (Yang, 1999). Secondary reactions of the hydrolysis products, stabilizers, and impurities form additional chemical products during VX hydrolysis. Upon verification of 99.9999 percent agent destruction, the agent hydrolysate is transferred to an agent hydrolysate storage tank, where it is blended with energetics hydrolysate prior to secondary treatment. Additional details on the chemistry and analysis of the hydrolysate are discussed in Chapter 3 and Appendix B.
Secondary treatment of agent hydrolysate is mandated by the Chemical Weapons Convention treaty to ensure irreversible destruction of the chemical agents. The BGCAPP design, as described in the record of decision of February 7, 2003, incorporates the use of supercritical water oxidation (SCWO) for secondary destruction of the hydrolysate. SCWO essentially mineralizes the organic constituents, effectively degrading any traces of the residual agent and also destroying hydrolysis products. The SCWO system for BGCAPP is expected to be fairly tolerant in its ability to process hydrolysate feed streams containing two or more liquid phases. At BGCAPP, the feed for the SCWO reactor will be a mixture of agent and energetic hydrolysates. The reactor will operate at a temperature of 1200°F and a pressure of 3,400 psig.4This environment is highly oxidizing and converts most elements to their most stable oxidation states (e.g., carbon is oxidized to form carbon dioxide, hydrogen to form water, sulfur to form sulfates, and so on). However, the caustic hydrolysate feed stream is extremely corrosive under SCWO conditions:
2
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
3
A destruction efficiency of 99.9999 percent is somewhat higher than the values given; however, these values are used to ensure that the variance range in the analyses results is taken into account.
4
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
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Salts can precipitate and plug the SCWO equipment, making maintenance of the reactors problematic.
The SCWO system in turn produces its own waste streams, which must be appropriately managed. The extremely corrosive SCWO environment results in limited lifetimes for the SCWO reactor liners, which will likely require frequent replacement during runs with VX and GB (NRC, 2005b). Thus, a secondary waste will be produced in the form of titanium SCWO reactor liners that have experienced significant corrosion. The SCWO operation produces several other effluents. The offgas from the unit is separated from the liquid stream, and the gaseous effluent is then processed in the HVAC system for the SCWO processing building.5 The condensed-phase SCWO effluents are a mixture of liquid and solid material that flow into the water recovery system (WRS). The SCWO process also produces salts (e.g., sodium sulfate) that are insoluble in supercritical water but emerge as a slurry and are separated from the liquid in serial multimedia and canister filters. These filters constitute a secondary waste stream. The residual liquid goes to the reverse osmosis (RO) system, which recovers 70 percent of the water. The other 30 percent of the RO separation is a rejectate brine.6 This constitutes a secondary waste stream and may contain agent below the detection limit. The RO rejectate brine is intended for offsite disposal, provided nondetect levels of agent can be verified.7
Treatment of Metal Munition Casings
The drained metal projectile casings from treatment in the MWS are decontaminated in the MPT (see Figure 2-3), which will treat wastes both during munitions destruction campaigns and during facility closure operations. The MPT will treat munitions casings and other metal wastes, as well as plastics such as polyvinyl chloride (PVC), teflon, butyl rubber, cellulosic materials, sludge, concrete, the lifting plugs, wooden pallets, and demilitarization protective ensemble (DPE) suits. The objective of MPT treatment is to ensure that metal parts and other secondary wastes processed through it attain a temperature of 1000°F throughout for at least 15 minutes, which will allow their unrestricted release or disposal. The same conditions are used at all other chemical weapons destruction facilities to achieve agent decontamination of such materials.8
Offgases from the MPT are sent to the MPT offgas treatment system (OTM), which consists of a flameless bulk oxidizer unit, a cyclone particulate separator, and a venturi scrubber.9 The OTM is a critical system, because its throughput limits the amount of waste that can be processed per MPT batch. Within the flameless bulk oxidizer, heated air and natural gas are mixed with the offgas to ensure oxidation of the entrained organics. The bulk oxidizer operates at 2000°F, with a gas residence time of 1 second to ensure destruction of dioxins and furans. Particulates present in the effluent from the bulk oxidizer are removed by a cyclone particulate separator, and the particles are recycled back into the MPT for further destruction. The gaseous effluent is sent to a venturi scrubber, which removes particulate matter >14 µm in diameter and neutralizes the acid gases by caustic scrubbing. The venturi scrubber also treats offgas from the ANRs and the agent hydrolysate storage tanks (NRC, 2005b). The liquid effluent from the venturi scrubber is sent to agent hydrolysate storage, where it is combined with agent hydrolysate.10 However, if agent is detected, then the liquid is recycled to the ANRs for further treatment.
Finding 2-1. Continued recycling of the particulates into the metal parts treater from the cyclone particulate separator of the metal parts treater offgas treatment system may cause solids buildup, which could impede operation of the metal parts treater.
Recommendation 2-1. The operation of the metal parts treater should be modified to avoid solids buildup and the attendant creation of a particulate waste stream that could impede its operation.
The overhead gases from the venturi scrubber are then passed through an additional particulate filter. The particulate filter medium constitutes a secondary waste stream from the venturi scrubber and is one of the larger secondary waste streams. The filtered venturi offgas is heated to 120°F to lower the relative humidity and then sent to the munitions demilitarization building HVAC, where it flows through activated carbon filters.11
Mustard Agent H Projectiles
The mustard agent H-filled 155-mm projectile rounds differ from those filled with nerve agent VX in that they are explosively configured (i.e., they contain both the agent fill and a burster), and hence the energetics must be separated before the chemical agent fill can be removed for neutralization. In the BGCAPP design, the burster is separated from the main body of the munition, which contains the chemical
5
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
6
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
7
“Nondetect levels” refers to trace (parts per billion) amounts of a particular agent that may be present but that are below the value of the approved analytical procedure being used for that agent to quantify with precision.
8
See also the discussion on management of scrap metal under environmental regulations in Chapter 3.
9
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
10
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
11
Sam Hariri, lead process engineer, BGCAPP, “Overview of MPT and SCWO process design,” presentation to the committee, January 23, 2008.
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FIGURE 2-3 Metal parts treater. SOURCE: NRC, 2008.
fill, by the linear projectile/mortar disassembly (LPMD) machine.12 The agent fill is then emptied from the energetics-free munition at the MWS.
Liquids from H-Filled 155-mm Projectiles
Following treatment in the MWS, the process at BGCAPP for treating the agent removed from the H-filled 155-mm munitions is identical to that for the VX-filled 155-mm munitions, with the exception that H is first hydrolyzed using hot water (194°F) and then treated with 50 percent sodium hydroxide (NRC, 2005b). This treatment converts mustard agent H principally to chloride and thiodiglycol; however, the resultant hydrolysate may also contain residual quantities of other chemical compounds that were present in the agent or that are hydrolyzed mustard agent impurities. A fraction of these are characterized as higher molecular weight heels that exist in either the solid or the gelled state within the munition (Yang et al., 1997).13 The heels are made up of sulfonium ions formed from dimerization of mustard agent in the munitions (Yang et al., 1997)14 and are effectively dissolved and hence removed from the munition bodies by the MWS. The salts produced from mustard agent hydrolysis are primarily sodium chloride, while the offgas contains some minimal amounts of hydrocarbons.
Bursters from H-Filled 155-mm Projectiles
The separated bursters are treated in the energetics batch hydrolyzer (EBH) (see Figure 2-4), where hot caustic (50 percent sodium hydroxide) is added to degrade the tetrytol high explosive. The EBH produces solid material, liquid energetics hydrolysate, and offgas. The solid product of the EBH consists of metal from the bursters, which is then heated in the MPT (BPBGT, 2007).15 The decontaminated metal parts constitute a secondary waste that is very similar to the decontaminated projectile casings described earlier. Gaseous effluent from the OTM is likewise treated as described in the section on GB and VX projectiles.
12
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
13
Yu-Chu Yang, Assembled Chemical Weapons Alternatives program, “Chemical compositions of liquid HT, solid HT, liquid H and solid H,” presentation to the Mustard Working Group Meeting, September 23, 2003.
14
Yu-Chu Yang, ACWA program, “Chemical compositions of liquid HT, solid HT, liquid H and solid H,” presentation to the Mustard Working Group Meeting, September 23, 2003.
15
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
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FIGURE 2-4 Energetics batch hydrolyzer. SOURCE: PMACWA, May 20, 2008.
The energetics hydrolysate produced by the EBH consists of a highly alkaline solution containing nitrate, nitrite, acetate, and formate salts (and glycerol as well when propellant from M55 rockets [see next section] is being processed). After separation of the solids, the energetics hydrolysate is moved to an energetics neutralization system (ENS) (BPBGT, 2007).16 It is likely that all energetics will be destroyed in the EBH, and differential scanning calorimetry is to be performed on the energetics hydrolysate once it is in the ENS reactor to ascertain that this is the case (NRC, 2005b). Once the energetics hydrolysate within the ENS has been cleared, it is sent to energetics hydrolysate storage before going through an aluminum filtration system (AFS),17 from which the liquid effluent then goes to the SCWO reactor.
Gaseous Effluent from Energetics Processing
Processing units dedicated to treatment of the projectile bursters produce offgas, which is an important effluent stream that requires processing. Offgas is produced by the EBH, the ENS reactor, and the bulk oxidizer unit. These three streams are fed into the energetics offgas treatment system (OTE), which consists of a venturi scrubber tower system that uses acid to remove ammonia. Effluent from the energetics OTS includes excess scrubber water, which constitutes a secondary waste, and offgas. The offgas is sent through a particulate filter, and the particulate filter medium is another secondary waste. After the gaseous effluent has traversed a heater and a scrubber, a blower forces it through filter banks consisting of activated carbon and a high-efficiency particulate air (HEPA) filter, both of which become a secondary waste.
GB- or VX-Filled M55 Rockets
The M55 rockets are filled with either GB or VX and are configured with the propellant-filled rocket motors and the rocket warhead. Each rocket is in its own shipping and
16
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
17
The AFS is covered in the next section, on M55 rockets with GB and VX fills.
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FIGURE 2-5 Rocket cutting machine. SOURCE: PMACWA, May 20, 2008.
firing tube (SFT) when delivered from storage to the munitions demilitarization building of BGCAPP. The warhead contains both energetic bursters and chemical agent fill. With the rocket still in the SFT, the warhead is separated from the rocket motor by the rocket cutting machine (see Figure 2-5), which uses a pipe-cutter-type mechanism to effect the separation. The section of the SFT that houses the warhead is also removed at this point. Noncontaminated rocket motors, which comprise a secondary waste stream, are sent to storage for shipment offsite and subsequent disposal. Noncontaminated SFTs will be disposed of offsite at a Toxic Substances Control Act (TSCA)-permitted commercial facility.18
The warheads are sent to the rocket shear machine (RSM) (see Figure 2-6), where they are first punched in the top and bottom of the rocket agent cavity to drain the agent, and a high-pressure warm-water stream is used to remove any solidified heels or residuals. The agent and washout water are then sent to the agent collection storage. The drained rockets’ warheads (and, where applicable, contaminated rocket motors) are then chopped at three additional locations by the guillotine-like blade of the RSM (NRC, 2005b). Process water is used during this cutting.
Only about 200 of the M55 rockets stored at BGAD are expected to have rocket motors that are contaminated with agent due to leakage.19 The motors and warheads of contaminated rockets are fed to the RSM, where they are sectioned such that they fit into the MPT. The contaminated SFTs are sent to the MPT for further treatment, generating solid and gaseous product streams similar to those described previously.20
After the agent has been drained, the rocket warhead components are fed to the EBH in a fashion similar to that for the projectiles, bursters, and empty agent cavities. Energetics are from the rockets’ warhead segments, burster charge segments, and fuzes, and when necessary, contaminated motor segments. The burster energetics for the M55 rockets are much different from the tetrytol found in the mustard agent H munitions: They include lead styphnate, lead azide, barium nitrate, antimony sulfide, tetracene, lead azide, RDX, calcium resinate-graphite, and TNT. The propellants are usually processed separately from other energetics and are expected to be effectively hydrolyzed by the EBH. In addition to the energetics, there will be other materials, including the firing tubes and rocket cavities.
The operational sequence of the EBH is as follows: Motor segments from contaminated rockets are separated from the warhead and tailfin pieces and delivered to an EBH. Then water and a caustic solution are added to the EBH, after which the rocket motor segments are added and processed for 2 hours. Warhead and tailfin segments are then added and processed for 4 hours. Undissolved materials consisting of SFT pieces, burster walls, and metal parts from the rockets are then removed from the EBH. After all the solids have been removed, EBH rotation speed is increased to remove hydrolysate, which is sent to the ENS reactor. Hydrolysate in the ENS reactor is sampled and tested by differential scanning calorimetry to verify that organics have been destroyed to acceptably low levels. When the energetic materials are determined to be well below the level at which the hydrolysate would pose an explosion hazard, the hydrolysate is transferred to storage tanks. Metal parts from the EBHs are sent to the MPT, where they are heated to 1000°F for at least
18
The use, storage, and disposal of PCBs are regulated by the Environmental Protection Agency (EPA) under the Toxic Substances Control Act and 40 CFR, Part 761. PCB waste handlers, including some generators, transporters, commercial storers, and disposers of PCB wastes, must notify EPA of their PCB waste activities, and each receives a unique identification number. Any PCB disposal facility must obtain approval of the EPA regional administrator for the region in which the facility is located (40 CFR 761.77).
19
Roger Dickerman, systemization manager, BGCAPP, “Secondary waste streams,” presentation to the committee, January 23, 2008.
20
At the time this report was prepared, BGCAPP did not have approval from EPA Region 4 to treat PCBs and is not included under the national approval granted by the EPA for the incinerators at the four other stockpile disposal facilities under the U.S. Army’s Chemical Materials Agency (CMA).
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FIGURE 2-6 Rocket shear machine. SOURCE: PMACWA, May 20, 2008.
15 minutes, then cooled and sent to storage for offsite disposal. The secondary waste stream that is the solid product of the MPT may contain the toxic metals lead, barium, and antimony.
Before the energetics hydrolysate is treated by SCWO, it is first sent to the AFS, where 75 percent phosphoric acid, 35 percent hydrochloric acid, and 93 percent sulfuric acid are added to precipitate the aluminum. The treated rocket components account for the largest fraction of aluminum-bearing wastes, but energetics hydrolysate from other H-containing rounds is also sent through the AFS.21 Most of the aluminum must be removed before treatment in the SCWO reactor because it generates solids that would precipitate in the SCWO reactor and interfere with its operation. The precipitated aluminates are separated by filtration, and the filtrate cake residue from the AFS is also a secondary waste. The separated liquid is sent to the energetics hydrolysate blend tank and then to the SCWO reactor for final treatment.
Nonprocess Secondary Wastes
Substantial dunnage will be generated by operation of BGCAPP. Dunnage includes wood pallets, other combustible solids, and metallic solids. Dunnage and other nonprocess secondary wastes will be segregated into contaminated and noncontaminated materials, as determined by enhanced onsite container monitoring prior to opening. Noncontaminated wood pallets will be shipped offsite without treatment for disposal by appropriate methods to minimize waste. All wood pallets and other dunnage associated with leaking munitions will be treated as agent-contaminated dunnage and will be decontaminated to meet the airborne exposure limits (BPBGT, 2004) set in an approved waste analysis plan (WAP) (BPBGT, 2007).22 Additional waste streams include DPE suits and spent carbon filters from the offgas treatment described above. Agent-contaminated (i.e., spent) activated carbon is to be shipped offsite for further treatment and disposal at a permitted treatment, storage, and disposal facility (TSDF). Activated carbon that is not contaminated with agent will be managed by appropriate methods to minimize waste (BPBGT, 2007).23
PCAPP PROCESS DESCRIPTION
This section describes the PCAPP process being designed by Bechtel National, Inc., to destroy the chemical weapons stockpiled at PCD according to the configuration
21
Sam Hariri, lead process engineer, BGCAPP, “Process design overview,” presentation to the committee, January 23, 2008.
22
Specifically, see Sections 3.1.5 and 4.3 of the cited reference.
23
Specifically, see Sections 3.1.5 and 4.3 of the cited reference.
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information available to the committee when this report was being prepared. A process flow diagram is given in Figure 2-7. It is worthwhile noting that PCAPP will process only munitions filled with mustard agent HD or HT. No munitions containing nerve agent are stored at PCD.
The destruction processes for chemical munitions at PCAPP will involve (1) transfer and disassembly of munitions to access the chemical agent and energetic materials, (2) core processes that destroy the agent, and (3) residuals treatment processes that decontaminate the munitions bodies and other materials associated with the munitions. These processes are accomplished in the major steps described in the following sections. The equipment used for projectile disassembly and removal of the agent is the same as that used for the mustard agent munitions at BGCAPP.
The munitions are disassembled to separate the agent-containing portions from the energetic materials and their associated metal parts. Energetics that are not contaminated with agent will be separated and prepared for shipment to appropriate offsite destruction and disposal facilities. Agent is drained from the munition bodies using hot, high-pressure water in the MWS. Contaminated energetics will be destroyed through an explosive destruction technology (EDT) that remains to be selected.24
During disassembly of the munitions, the main waste streams that call for further processing are as follows:
The chemical agent drained from the munition cavities;
The energetic materials, which may include propellants, bursters, igniters, and fuzes, and their associated metal parts;
Metal munitions casings and their associated metal parts;
Dunnage, most of which is not contaminated with agent;
Process offgas streams and air from the facility’s HVAC system; and
Filters used during offgas treatment (carbon, HEPA, etc.).
In the core disposal operations that follow disassembly, the chemical agents are destroyed by hydrolysis, which is in turn followed by a secondary biotreatment process in immobilized cell bioreactors (ICBs) to treat the streams resulting from the hydrolysis (the hydrolysates) to meet Chemical Weapons Convention requirements and produce environmentally acceptable wastes.
Metal parts such as the projectile casings are treated by being heated in the munitions treatment unit (MTU) to a set temperature (at least 1000°F) for a specific duration (at least 15 minutes) to decompose any residual agent and energetics.
Most agent-contaminated secondary wastes will be treated in an autoclave or supplemental decontamination unit (SDU) to destroy the agent. All offgases from PCAPP processes, including the offgases from storage vessels used during these processes, will be treated to ensure that the offgas streams are at or below regulated levels for agent and other contaminants before release directly to the atmosphere.
Unless otherwise noted, the following discussion is based on the RCRA Stage III, Class 3, permit modification request and the associated WAP (PMACWA, 2006). The plan has been filed with, but not yet approved by, the Colorado Department of Public Health and Environment (CDPHE) as of the preparation of this report (see Chapter 3 for further discussion of the PCAPP WAP).
Energetics Removal, Treatment, and Shipment
The projectiles (105- and 155-mm) and 4.2-inch mortar rounds stored at PCD contain HD and some mortar rounds contain HT. Some 105-mm projectiles have been reconfigured to remove the propellant and fuze but retain a burster and nose plug. Unreconfigured 105-mm projectiles with integral fuzes and bursters are contained in sealed tubes with bags of propellant, two tubes to a box. All of the 155-mm projectiles have been reconfigured to contain lifting plug and burster but no fuze. The 4.2-inch mortar with integral fuze, burster, propellant wafers, and ignition cartridge are contained in sealed tubes, two tubes to a box (NRC, 2005a).
The munitions are brought from storage to the energetics reconfiguration building (ERB) in overpack (enclosed) pallets via the munitions service magazine. The air in each overpack pallet is monitored after transport to determine whether there are any leaks. If no leak is found, the pallets are removed from the overpack and moved by a forklift into the ERB. The pallets are manually unpacked; the boxes of the unreconfigured 105-mm projectiles and the 4.2-inch mortars are opened; the munitions, contained in sealed fiber shipping tubes, are then removed from the boxes. The interior of each tube is monitored for agent. If a leak is found, the munitions are overpacked and returned to storage for later onsite treatment by the yet-to-be-selected EDT. Munitions determined to be leaking in storage or during transport to the ERB will also be processed by the EDT.
Munitions that are found not to be leaking are manually removed from the shipping tubes. In the case of the 105-mm projectiles, the propellant bags are separated from the munitions. The 4.2-inch mortars are disassembled to remove the ignition cartridge, propellant wafers, and miscellaneous metal parts. Secondary wastes from this operation will include uncontaminated propellant bags and wafers, ignition cartridges, and miscellaneous metal parts.
24
An EDT involves using controlled explosive charges in an enclosed chamber. There are several versions of this technology. The Resource Conservation and Recovery Act (RCRA) permit for PCAPP provides for the use of an EDT. A forthcoming National Research Council report will examine the applicability of the various types of EDTs for use at PCAPP and, possibly, BGCAPP. The secondary waste from these EDTs is outside the scope of this report.
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FIGURE 2-7 Process and waste stream diagram for PCAPP.
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The previously reconfigured munitions (no fuzes) and the partially reconfigured munitions (as described above, with fuzes) are moved into an explosive containment room, where nose plugs, fuzes, boosters, and bursters are removed by the LPMD machine robot. The empty burster well is sampled to determine if a leak has occurred; if no leak has occurred, the bursters and fuzes will be shipped offsite to a commercial TSDF. If a leak has occurred in the burster well, the munitions are overpacked for treatment by the EDT.25 Munitions that cannot be processed successfully by the LPMD machine robot—that is, rejects—will be containerized and treated by the EDT.
The ERB HVAC will be vented downstream of the OTS to the agent filter area (AFA).
Agent Hydrolysis and Munitions Body Treatment
A munitions body, having been separated from the energetics, still contains agent sealed in its agent cavity by the burster well. The munitions are next moved to the cavity access machine in the agent processing building (APB). There, the burster well of each projectile is buckled (or, in the case of mortar shells, the mortar base is cut) to access the agent. The agent is drained and the cavity washed with warm, high-pressure water to rinse out any gelled agent or residue. The munitions bodies are then sent to the MTU (see Figure 2-8), where they are heated to at least 1000°F by external heating coils.
Drained agent, wash water, and any suspended solids are fed to agent/water separators. The separated water is recycled to the washout station, and the concentrated agent is sent to a hydrolysis reactor, where it is neutralized with hot (194°F) water. Hydrolysis is completed by the addition of NaOH. The neutralized solution is then sent to a storage tank, where it will be sampled for the presence of residual mustard. The clearance criterion is “nondetect,” which is defined as ≤20 ppb for HD and ≤200 ppb for HT. If the batch is not accepted, the hydrolysate is recycled to the hydrolysis reactor. The agent collection and neutralization components are vented to the OTS.
Spent decontamination solution is generated throughout the APB for decontamination of equipment and personnel. The spent decontamination solution is collected in sumps and pumped to the agent hydrolyzers.
The SDU and the Autoclave
The SDU is used to treat secondary wastes from various activities, including general maintenance, equipment maintenance, worker safety measures, and sampling. Typical secondary waste streams treated are DPE suits and other personal protective equipment; sampling equipment; tools, drums, and other containers; and dunnage. The SDU is a large electrically heated chamber approximately 12 feet wide, 6.5 feet deep, and 8 feet high (interior dimensions). Once it has been loaded, the operators select the correct operating conditions (time and temperature) for the materials. The temperature can be varied from 195°F to the design temperature of 600°F. During treatment, any agent that volatilizes but does not decompose is treated in the OTS along with other gases. After the SDU has cooled, the decontamination level of the treated material is confirmed by monitoring. It is then unloaded from the SDU and packaged for offsite shipment. The monitoring capability of the SDU will be used to evaluate some wastes for suitability for offsite shipment. The criterion for reclassification as “clean” for offsite shipment is a vapor screening level (VSL) of less than 1.0, whether determined in the SDU or by container headspace monitoring (PMACWA, 2006).26
The autoclave is another PCAPP component used to treat wastes from the same kinds of activities. As this report was being prepared, a descision on which wastes would go to the SDU and which to the autoclave had still not been made. The autoclave has a working space approximately 4 feet wide, 7 feet deep, and 7 feet high. Once it has been loaded, the operators select the correct operating conditions (time and temperature) for the materials. Air is evacuated during preheat cycles to promote the vaporization of liquids (BPT, 2007). The autoclave is heated by steam at approximately 350°F to promote hydrolysis of the agent. During treatment, any agent that volatilizes but does not decompose, along with other gases, is treated in the OTS. After treatment, the autoclave is cooled and dried by a vacuum pump. If the treatment is successful, as indicated by monitoring, the material is unloaded from the SDU and packaged for shipment offsite.
OTS and AFA
The purpose of the OTS is to quench and neutralize acidic gases and remove particulates from the offgas streams of the MTUs, the APB tanks, the SDU, and the autoclave. The OTS consists of a venturi scrubber tower, offgas filter, offgas reheater, and offgas blower. Offgases treated in the OTS are directed to the AFA for further treatment before discharge to the atmosphere. The MTUs vent gases at approximately 650°F. The gases are rapidly quenched by caustic solution to approximately 120°F in the venturi. Some particulates are removed from the gas in the venturi discharge liquid. The cooled gas and the discharge liquid flow to the scrubber tower, where the acid gases are absorbed and neutralized by a counterflow stream of water and caustic. The offgas from the SDU and the autoclave are also treated in the scrubber tower. Spent scrubber liquid (containing particulates) is pumped to the spent decontamination solution tanks. The scrubber offgas is filtered by the offgas filter to remove particulates
25
Discussion of PCAPP secondary wastes with Craig Myler, chief process engineer, Bechtel Pueblo Team, February 12, 2008.
26
Specifically, see Section C-2b-1, page C-13, of the cited reference.
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FIGURE 2-8 Munitions treatment unit. SOURCE: PMACWA, May 20, 2008.
greater than 0.5 micron. To prevent condensed droplets from entering the offgas blower, the filtered offgas is heated to reduce the relative humidity. The blower sends the treated offgas to the AFA.
The AFA is common to the ERB and the APB and consists of 10 filter units, 8 in operation and 2 in standby. Each filter unit consists of a particulate prefilter, a HEPA filter, an activated carbon filter for removal of agent vapor and volatile organic compounds (VOCs), five backup activated carbon filters in the event of breakthrough, and a final HEPA filter. Filtered air is exhausted into a common header and ducted to a common stack. There will be secondary waste in the form of spent activated carbon and filter media.
Biotreatment
Hydrolysate that has been cleared for agent content, various condensates, and process water is collected in one of three 30-day storage tanks. The pH is adjusted with sodium hydroxide as needed, and nutrients (principally nitrogen in the form of ammonium salts or urea, as well as phosphorus) are added before the hydrolysate is fed to one of six ICB module feed tanks. Each module consists of four ICB units. The principal product of mustard agent hydrolysis is thiodiglycol, and the ICB system biodegrades thiodiglycol and other organic constituents to innocuous end products, principally carbon dioxide, water, sulfate, and other oxidized mineral chemicals.
Important ICB environmental conditions include nutrient concentration, feed rate, temperature, pH (adjusted with nitric acid or sodium hydroxide), and dissolved oxygen (supplied by compressed air blowers). Each ICB module will discharge to an associated ICB effluent tank, where the discharge will be sampled to verify the satisfactory performance of the biotreatment. Acceptable performance for the biodegradation process is the removal of more than 95 percent of thiodiglycol, with the goal being to remove 99 percent or more of thiodiglycol and an average of 90 percent or more of total organic compounds (PMACWA, 2006).27 If biodegradation is insufficient, the effluent will be recycled to the ICB module feed tank for further treatment; otherwise, the effluent will be discharged to the water recovery system (WRS). The ICB discharges are gases to the biotreatment area (BTA) OTS, liquids to the WRS, and secondary waste solids (sludges and other residues), which will be periodically removed.
The 30-day storage tanks vent through dedicated local activated carbon filters to the atmosphere. The remaining biotreatment tanks, including the ICBs, vent to the BTA OTS. The ICB liquid phase contains odiferous components that partition to the gas phase and vent to the BTA OTS. The BTA OTS (not shown in Figure 2-7) will have six trains, one for each ICB module. The principal components of each train are (1) two iron sponge absorbers to remove volatile odorous inorganic and organic sulfur compounds such as hydrogen sulfide, mercaptans, and thiols; (2) a heater to lower the relative humidity before the carbon adsorption system; (3) an activated carbon system consisting of a prefilter (to remove solid particles in order to extend the activity and life of the carbon adsorption bed), two activated carbon filters in series to remove potentially odorous gaseous compounds and other VOCs not removed by the iron sponges, and a final HEPA
27
Specifically, see page C-11 of cited reference.
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filter (to prevent carbon particles from escaping the unit); (4) an exhaust blower and stack; and (5) two iron sponge absorber condensate pumps to pump condensate to the clarifiers of the WRS via the ICB effluent tanks. The BTA OTS produces secondary waste from the iron sponge absorber and secondary wastes from the prefilter, the HEPA filter, and the activated charcoal filter secondary wastes.
Water Recovery and Brine Reduction
The cleared ICB effluent is approximately 98 wt percent water, 0.8 wt percent sodium sulfate, 0.7 wt percent sodium chloride, and traces of agent impurities and degradation products (PMACWA, 2006). The WRS and the brine reduction system (BRS) reclaim water from the biotreatment system effluent and the blowdown from both the cooling tower and the steam boiler. In addition, some process water passes through an RO system to feed the steam boilers and munitions washout system; the retentate is fed to the WRS.
The WRS includes two clarifiers, two thickeners, two filter presses, and auxiliary equipment. The ICB effluent is transferred to the WRS clarifiers, where a polymer will be injected to provide chemical coagulant for enhancing removal of suspended solids. The clarified effluent will be transferred to the BRS. The clarifier sludge will be pumped to the WRS thickeners, where a polymer may be added to enhance thickening. Thickener overflow is recycled to the clarifiers, and underflow is pumped to the dewatering filter presses. The filter press separates the solids from the liquid stream. The liquid is recirculated to the clarifiers, and the filter cake, containing 20-25 percent dry weight solids, is a secondary waste.
The BRS includes a feed conditioning system, two brine concentrators, two evaporator/crystallizers, two distillate liquid-phase carbon filters, three solids dewatering units, and an offgas treatment system (BRS OTS) (not shown in Figure 2-7). The BRS feed conditioning system converts carbonate salts to carbon dioxide, which is then removed so that carbonate scale does not form and foul downstream process equipment. Feed is conditioned by heating and acidifying it, followed by steam stripping of the carbon dioxide, noncondensable gases, and some VOCs. The stripped gases are transferred to the BRS OTS, and the liquid effluent is transferred to caustic mixing tanks, where the pH is increased by the addition of sodium hydroxide to reduce corrosion in downstream equipment. The effluent from the mixing tanks is distilled in the brine concentrator, and about 80 percent of the fed effluent is distillate transferred to the liquid-phase carbon filter unit and, finally, to the process water tanks. The brine concentrator vapor effluent comprises steam and noncondensable gases, which are combined with the steam stripper overhead and vented to the BRS OTS. The brine concentrator underflow contains essentially all of the nonvolatile material, salts, residual organic compounds, and suspended solids. These materials are extracted by the evaporator/crystallizer units: Water is transferred to the liquid-phase carbon filters and finally to the process water tanks, noncondensable vapor is transferred to the BRS OTS, and the solids (as a slurry) are dewatered to produce a solid cake for shipment to an offsite TSDF as a secondary waste.
In summary, the WRS and BRS produce process water, vapor to the BRS OTS, and secondary waste in the form of a solid cake for shipment to an offsite TSDF. It is planned that the BRS OTS filter cake will be analyzed for toxicity characteristic leaching procedure (TCLP) organics (volatile and semivolatile constituents) and metals. In addition, the filter cake is planned to be tested for free liquids to ensure the dewatering has removed liquids in accordance with land disposal restrictions (PMACWA, 2006).28 The BRS OTS is, for the purposes of this report, identical to the BTA OTS except that there are no iron sponge absorbers or condensate pumps. The BRS OTS produces prefilter, HEPA, and charcoal filter secondary wastes.
28
Specifically, see page C-14.