Appendix A Selected Chemical Weapon Destruction Techniques facility, minute quantities of agent were detected in the CHEMICAL NEUTRALIZATION: brine. At Rocky Mountain Arsenal the neutralization THE ARMY’S EXPERIENCE brine was considered agent-free if a 5 percent excess sodium hydroxide level was achieved. At CAMDS a more In a 1969 report, the National Research Council (NRC) strict criterion was used of less than 20 parts per billion recommended chemical neutralization for the destruction (ppb) agent (the Army’s soldier drinking water standard). of the chemical weapons (CW) agent GB and incineration Difficulties in certifying this level of destruction at for mustard agents H and HD. After research and CAMDS may have come from occlusion of GB in rust or development work on chemical neutralization at the other particulate, formation of GB during analysis, or Chemical Agent Munitions Disposal System (CAMDS) false positives resulting from some unidentified interfer- (Tooele, Utah) and Rocky Mountain Arsenal (Denver, ence in the complex neutralization mixture (l). Agent Colorado) in the 1970s, the Army concluded that inciner- emissions at the facility during brine spraying at Rocky ation was the best method for the destruction of all Mountain Arsenal often exceeded the action level (0.0003 chemical weapons. The NRC Committee on Chemical 3 milligram per cubic meter (mg/m )) and occasionally the Weapons Disposal has recently been asked by the Army 3 shutdown level (0.003 mg/m ). These levels were promul- to reevaluate incineration and alternatives for CW dis- gated by the Department of Health and Human Services posal. (DHHS) and the Army’s Surgeon General. However, perimeter monitors showed that the emission standard for Chemical Neutralization of Nerve Agents the general population was not exceeded (l). Most of the Army’s experience with large-scale chemi- cal neutralization of chemical weapons was with the After being drained of GB, the empty munition bodies organophosphorus ester agent GB. This agent was suc- were moved to a deactivation furnace where explosives cessfully neutralized using aqueous sodium hydroxide on and propellants were incinerated and metal parts ther- a scale compatible with destruction of the current U.S. mally decontaminated, i.e., incinerated. Empty ton con- CW stockpile. Approximately 8.4 million pounds of tainers were similarly incinerated in separate furnaces. GB-taken from underground storage tanks, GB ton Thus, “chemical neutralization” actually applied only to containers, M139 bomblets (Honest John Warhead), M34 the drained agent and treatment of the remaining waste cluster bombs, M55 rockets, and 155/105-mm projectiles, depended on incineration. However, disposal of the M34 were neutralized at Rocky Mountain Arsenal from 1974 cluster bomblets and ton containers used a caustic to 1976 and at CAMDS between 1979 and 1982. By (aqueous sodium hydroxide) wash to treat the drained weight, this represents 17 percent of the 25,000 tons of container by neutralizing any residual agent. For some agent to be destroyed in the current program. reason—possibly a lack of confidence in the efficacy of GB is stable at neutral pH but is hydrolyzed rapidly at this process-the caustic wash treatment was also fol- alkaline pH. The half-life of GB at 300 C in aqueous lowed by thermal decontamination (incineration). solution is 146 hours at pH 7 (neutral conditions) but decreases to 0.4 hour at pH 9 (alkaline conditions) (l). From 1979 to 1981,13,951 M55 rockets containing GB Presumably at higher pH and temperature, the hydrolysis (2.9 percent of the current M55 rocket stockpile) were rate would be even more rapid. The suggestion has been destroyed by this combined chemical neutralization/ made that the addition of a catalyst could speed up this incineration process (l). The Army also reported prob- hydrolysis reaction even more (2). lems with re-formation of GB during the brine drying process, although it is not clear why the corrective actions As part of the Army’s program, after GB neutralization described above were not applied to solve the problem in was determined to be complete, the resulting brine was evaporated by spray drying and the salts were packed into this instance. The reaction was also reported to take longer drums for disposal. There were some problems with the than expected. Adding excess sodium hydroxide to spray-drying process, including the possibility that GB accelerate the reaction created a larger amount of salt for might re-form under certain conditions. This re-formation disposal. Given the intrinsically rapid hydrolysis rate of could be successfully avoided by adjusting the pH and GB under alkaline conditions (corresponding to a short brine flow rate, and by reducing the operating temperature half life), the apparent slow reaction encountered in this (l). situation may have been due to problems associated with the large scale of the demonstration such as complete and Difficulties were also encountered in confirming that thorough mixing of the organic material with the aqueous the brine was agent-free. Particularly at the CAMDS sodium hydroxide. –31- 32 ● Disposal of Chemical Weapons: Alternative Technologies Although the agent VX, which is structurally similar to lead to re-formation of the agent. In some situa- GB, can also be chemically neutralized, this was never tions, the rate of neutralization in large-scale tests of demonstrated by the Army on a large scale. Acid chemical agents was much slower than had been chlorinolysis (chlorination in an aqueous acidic medium predicted. Very large amounts of impurities in followed by caustic neutralization) rather than alkaline certain grades of mustard agent also made neutrali- hydrolysis was suggested by the Army as the best method zation difficult to monitor adequately. However, it for chemical destruction of VX (l). However, VX was is not clear that the problems encountered with shown to be neutralized on a small scale by hydrolysis ‘‘industrial scale-up” of chemical neutralization are with sodium hydroxide. The problems encountered with insurmountable, and the scale of a chemical neutral- the neutralization of GB led the Army to abandon plans ization program is similar to or smaller than that of to test the large-scale neutralization of VX. The Army industrial large-scale processes. indicated that a poor water volubility, mixing problems, 3. The quantity and nature of the waste produced by and the presence of a “bis” impurity (with unspecified neutralization are more problematic than those susceptibility to alkaline hydrolysis) made alkaline hy- produced by incineration. Calculations by the Army drolysis of VX difficult (l). As with GB, neutralization indicated that 1 pound of GB will produce 1.5 was apparently intended only for the liquid chemical pounds of salt, compared to a salt yield of 1.4 agent. Incineration was to be used for destruction of the pounds from incineration. In practice, the excess explosives and propellant components, and for thermal caustic added to speed up the reaction led to 2.6 decontamination of munition cavities and metal parts. In pounds at Rocky Mountain and 3 to 6 pounds at addition, lack of a reliable low-level monitoring capabil- CAMDS of salt per pound of agent hydrolyzed. The ity for VX in the neutralization brine at the time of the Army speculated that the sometimes heterogeneous Army’s research program led it to conclude that DHHS form of some agents (partially gelled, mixed with would never approve chemical hydrolysis (l). solid particles such as rust) may have contributed to the variation in results obtained with chemical Chemical Neutralization of Mustard Agents neutralization. These types of technical problems Mustard agent has also been shown in the Army’s encountered in the transformation of industrial research to be hydrolyzed under alkaline conditions on a processes from bench-scale demonstrations may not small scale, although only slowly at ambient temperature. be insurmountable given sufficient motivation to The corresponding reaction rates with alkaline hydrolysis reach a solution. Also, it has been argued that at elevated temperature were not reported. The products producing larger amounts of salts from neutraliza- of mustard hydrolysis with sodium hydroxide were not tion may be relatively more acceptable than some of identified and their toxicities were not assessed. Alkaline the perceived problems of incineration, such as the hydrolysis of mustard agents on a pilot-plant scale was formation of dioxins. reported, using the base monomethanolamine instead of 4. The capital and operating costs of chemical neutral- sodium hydroxide, to produce a homogeneous nontoxic ization were estimated to be higher than those of organic waste. Calcium hypochlorite slurry or aqueous incineration (1). This cost comparison might have bleach (sodium hypochlorite) was used to oxidize rather to be considerably revised now in light of the than hydrolyze mustard agents, but there was “uncer- unanticipated cost increases in the Army’s inciner- tainty about the completeness of the reaction” (l). ation program, which are due in part to technical problems encountered by the Army after 1987 (3). Summary of the Army’s Neutralization 5. The analytical problems encountered in certifying Process Experience that the waste materials of chemical neutralization were agent-free. This must be compared to the In the Army’s summary of its experience with chemical analytical problems faced in demonstrating that neutralization, the following