Destroying Chemical Weapons: US Army Reviews Technology

09-Feb-2010 11:50 EST

To destroy chemical weapons, the US Army can’t just throw them in an incinerator. They have to be destroyed carefully so that no harmful chemicals are released into the air or water supplies.

In 2009, the US Army, working with the National Research Council (NRC), tested 4 technologies – 3 private-vendor systems and 1 Army-developed explosive destruction system (EDS) – to destroy chemical weapons. Tests were conducted at the Blue Grass Army Depot in Kentucky and the Pueblo Chemical Depot in Colorado.

The developers of one of the systems tested – US-based Versar and Japan’s Kobe Steel – announced [pdf] Feb 9/10 that they received a $13 million subcontract from URS Corp. to deliver their Detonation in a Vacuum Assisted Chamber (DAVINCH) system to the Deseret Chemical Depot in Tooele, UT for chemical weapons destruction. In addition to supplying the system, Versar will provide project management at the depot.

The Army testing revealed some interesting facts about the DAVINCH system…

The 3 private-vendor systems tested by Army and the NRC were the DAVINCH system developed by Kobe Steel and Versar, the transportable detonation chamber T-60 model supplied by US-based CH2M Hill, and the static detonation chamber SDC2000 model from Sweden’s Dynasafe.

A report prepared on the testing by the Board on Army Science and Technology describes how each system works:

• DAVINCH: “The process uses a detonation chamber in which chemical munitions are destroyed when donor charges surrounding the munitions are detonated. Offgases are produced that require secondary treatment….The offgases resulting from agent destruction in the DAVINCH vessel are filtered to remove particulates and, with oxygen from an external supply, are pumped into the cold plasma oxidizer, which oxidizes CO to CO2. Condensate water is then recovered from the exhaust gas; the gas is passed through activated carbon and exhausted to the atmosphere.”

• T-60: “The TC-60 has three main components: a detonation chamber, an expansion chamber, and an emissions control system. A munition wrapped in explosive is mounted in the detonation chamber. The floor of the chamber is covered with pea gravel, which absorbs some of the blast energy. Bags containing water are suspended near the projectile to help absorb blast energy and to produce steam, which reacts with agent vapors. Oxygen is added when destroying munitions containing mustard agent. After the explosive is detonated, the gases are vented to an expansion chamber, then to the emissions control system. The offgas treatment system includes a reactive-bed ceramic filter to remove acidic gases and to collect particulates such as soot and dust from the pea gravel. A catalytic oxidation (CATOX) unit oxidizes hydrogen, carbon monoxide, and organic vapors from the gas stream before the stream is vented through a carbon adsorption bed and released to the atmosphere.”

• SDC2000: “The detonation chamber is a nearly spherical, armored, high-alloy stainless steel vessel. The vessel is double-walled, with the inner wall considered to be armored….Chemical munitions are placed in a cardboard box or carrier, which is transported to the top of the system. The boxed munitions are fed into the detonation chamber through two sequential loading chambers. The boxed munitions are dropped onto a heated (550°C-600°C) shrapnel (scrap) bed at the bottom of the detonation chamber, resulting in deflagration, detonation, or burning of the munition’s explosive fill. The chemical agent in the munitions is destroyed by the shock wave from the detonation or by decomposition due to the high heat in the chamber. The offgas treatment system includes a cyclone for removal of large particulates and a flameless thermal oxidizer that converts carbon monoxide and hydrogen to carbon dioxide and water. This is followed by a fast quench system to minimize dioxin and furan formation, acidic and basic (caustic) scrubbers, and an absorber/particulate filter system that uses Sorbalite, a mixture of calcium oxides and carbonates with activated carbon.”

• Army EDS: “The U.S. Army’s EDSs are trailer-mounted mobile systems originally intended to destroy explosively configured chemical munitions that are deemed unsafe to transport. The system has been used to destroy chemical munitions with or without explosive components. At the heart of the EDS system is an explosion containment vessel. The EDS Phase 2 (EDS-2) containment vessel is designed to handle munitions containing up to 4.8 lb TNT-equivalent of explosives. The EDS uses explosive shaped charges to access the agent cavity and to destroy any energetics in the munition. After detonation of the shaped charges, reagents appropriate to the agent to be neutralized are pumped into the vessel and the vessel contents are mixed until the treatment goal has been attained. After the concentration of chemical agent falls below the treatment goal, as determined by sampling the contents of the chamber, the liquid waste solution is transferred out of the chamber into a waste drum. The drummed EDS liquid waste is normally treated further at a commercial hazardous waste treatment, storage, and disposal facility.”

For destruction of 155-mm mustard gas munitions, the report determined that the DAVINCH and SDC2000 were the most effective. For destruction of M55 rocket motors, the report found that the T-60 was most effective.