The experience was summarized as follows (NRC, 2007, p. 60):

The micronization process proved difficult to operate, and throughputs were much lower than expected. In addition, while being transported in pipes from the micronizer to the deactivation furnace system, the resulting powder could under some circumstances become an explosive mixture. Fortunately, no explosive event happened at JACADS, but the possibility is real and must be considered. A prudent course now would be for the Chemical Materials Agency to immediately pursue alternative disposal options for treating spent activated carbon resulting from current operations as well as for the large amounts of spent activated carbon that will [be] generated during closure operations.

On p. 45 the same report stated that “depending on the organic contaminants adsorbed, spent carbon may be classified as hazardous or nonhazardous.” In this context, “spent carbon” is a more generalized term than “exposed carbon” because it refers to activated carbon that has been exposed either to agent or to other airborne contaminants.

The JACADS experience demonstrated that activated carbon exposed to agent can be incinerated. As well as oxidizing the carbon, this process destroys any agent that may be present. However, use of the micronization process to prepare the carbon for incineration created an explosion hazard associated with the handling of the finely divided carbon. The carbon dust also created operational problems that extended JACADS’ operating time and necessitated additional maintenance. Also, CMS processing required many demilitarization protective ensemble (DPE) entries by personnel to conduct maintenance operations. At times, CMS maintenance operations accounted for 85 percent of DPE entries, which increased the risk to personnel and created additional secondary waste for disposal. Used DPE suits were a major source of secondary waste. This had a direct impact on closure decontamination operations and schedule.


Finding 7-1. The micronization of carbon before it is incinerated in the deactivation furnace system is a hazardous operation with operational problems and a lot of maintenance. Fine pulverized carbon is susceptible to dust explosions.


Recommendation 7-1. If a chemical agent disposal facility must dispose of any carbon on-site, micronization should not be used to prepare the carbon for incineration.

Disposal of Used Carbon at ABCDF

At ABCDF, after their removal from service, the used carbon filters were double bagged in polyethylene. The vapor space in the bag was then sampled for agent. Bags with >1 vapor screening level (VSL)1 agent levels of mustard agent HD were placed in 95-gallon polyethylene drums and shipped by truck to the Veolia Environmental Services Facility in Port Arthur, Texas, where the used carbon was incinerated without opening the drums. There were 482 drums with >1 VSL contamination.

The remaining filter trays from the heating, ventilation, and air conditioning (HVAC) Banks 2 through 6 were placed in bags and shipped without drumming since they had agent levels <1 VSL. The total weight of carbon filters with <1 VSL contamination was 94,720 lb.

Since the polyethylene drums and bagged filters were not to be opened before being fed to a rotary kiln and incinerated at the Veolia facility, the metal filter frames became part of the kiln discharge solid residue. Kiln flue gases were processed through the Veolia facility’s gas scrubbing system. Carbon at ABCDF was contaminated only with mustard agent HD, with the worst-case loading of HD estimated to be 16 weight percent, the HD saturation level.2 The waste was transported based on a transportation risk assessment (TRA).


Finding 7-2. The use of a transportation risk assessment provides a methodology to assist the permitting regulatory authority in making a determination of whether the proposed method of shipment is safe.


Recommendation 7-2. The Chemical Materials Agency should explore with the appropriate regulatory

1

 Vapor screening levels (VSLs) and short-term limits (STLs) are names for equivalent measurements (specified in RCRA operating permits) for control limits used to help plan for waste transport and disposal. They also supplement short-term exposure limits (STELs) for protecting workers’ health during plant operations as waste is generated and moved to storage areas within the plant. VSL/STL concentrations vary by agent and are the same values as STELs except that VSL is measured in air sampled for about 5 minutes instead of 15 minutes for STELs. For GB, VX, and HD, 1 VSL is equivalent to 0.0001 mg/m3, 0.00001 mg/m3, and 0.003 mg/m3, respectively.

2

 Brian O’Donnell, Chief, Secondary Waste and Closure Team, CMA, “CMA carbon management,” Presentation to the committee, June 4, 2008.



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