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THERMAL TREATMENT AND PREPROCESSING AND POSTPROCESSING OPERATIONS 95 off-site shipment. It also addresses thermal treatment that could reduce waste gas volumes. The following types of operations are reviewed in this chapter: ⢠preprocessing unit operations: cryoprocessing and mechanical removal of energetics; ⢠heat treating of contaminated parts: pyrolysis and oxidation; and ⢠postprocessing and pollution control unit operations: drying, activated-carbon adsorption beds, and stack gas holdup. The postprocessing and pollution control operations examined here are more demanding than normal industrial applications because chemical weapons destruction must consider the potential extreme toxicity of any residual chemical agent in the waste stream. Commercial preprocessing and postprocessing liquid and solid handling, holdup, and pollution control processes do not. need special evaluation to be considered for use. (The pollution abatement system that removes acid gases and particulates was examined at a pollution abatement workshop held by the National Research Council's Committee on Review and Evaluation of the Army Chemical Stockpile Disposal Program on May 15-17, 1991.) PREPROCESSING OPERATIONS Although the development of alternative approaches has generally assumed the use of a front-end reverse assembly facility similar to that now being demonstrated at the Johnston Atoll Chemical Agent Disposal System (JACADS), certain variations of this front-end operation are possible. Cryoprocessing There are several possible cryogenic processes that would use liquified nitrogen to cool the still-assembled weapon below its brittle fracture temperature, which would be followed by the use of a mechanical method to break up the weapon. The resulting mixture of frozen agent and fractured metal parts and energetics would then be fed into a single rotary kiln incinerator. The NRC recently completed a separate study on this technology (NRC, 1991). One conclusion was that ''...although there exists a reasonably good chance that the cryofracture process can eventually be made to operate satisfactorily, the start up time for the proposed full-scale facility at Tooele might be extended over several years, and major modifications or even a
