Sandia LabNews

Explosive Destruction System keeps pace with changing mission


John Didlake, Don Golling, Tom Raber, and Bob Crocker
The EDS P2P team of John Didlake, Don Golling (both 8123), Tom Raber (8131), and Bob Crocker (8125) with models of the P2P (left) and P2 (on right). Improvements to the P2P cut the processing time in half. (Photo by Dino Vournas)

The Explosive Destruction System (EDS), developed by Sandia for the US Army, is a modern technology that is being used to deal with remnants of our military history. Those remnants — in the form of recovered chemical munitions — continue to emerge in unusual places. Even though the battles of World War I and World War II were fought on foreign soil, munitions from those two wars continue to surface all over the country at current and formerly used defense sites and at burial sites.

EDS was developed in response to the need for a mobile system to safely destroy World War I-era chemical mortars and shells found in the Spring Valley neighborhood of Washington, D.C. The Spring Valley munitions were World War I artifacts, left behind when American University conducted chemical weapons research for the US Army.

EDS was first used in 2001 at Rocky Mountain Arsenal in Colorado and then at other locations including Spring Valley. Sandia next created a larger version of EDS, capable of destroying more munitions at once and handling munitions with a higher explosive charge.

Two of the larger systems were used from 2006 to 2010 to destroy more than 1,200 munitions, including 450 German Traktor rockets at the Army’s Pine Bluff Arsenal in Arkansas (see the July 30, 2010 issue of Sandia Lab News). This enabled the Army to complete its mission to destroy all non-stockpile materiel declared when the United States entered into the 1993 Chemical Weapons Convention, an international treaty mandating the destruction of chemical warfare materiel.

Almost as soon as that mission was complete, Brent Haroldsen, John Didlake (both 8123), and other Sandia engineers went to work modifying the existing EDS design to increase speed. Called the Phase 2 Pilot, or P2P, this model incorporates several design changes that halved the processing time, from two days to one.

“When we first designed EDS, speed was not a priority,” explains Brent. For the original application of safely destroying munitions in populated areas, the design emphasized transportability, flexibility, redundancy, certainty of destruction, and simplicity of manual operation.

Significantly reduced processing time

But the EDS process is not inherently slow. By changing the heating and cooling system and design of the door clamps, the researchers were able to significantly reduce processing time without sacrificing any of the attributes and strengths that have made EDS successful.

Now EDS may be used to clean up burial sites in places like Alaska’s Fort Glenn, a World War II-era secret airfield that played a critical role in the Aleutian Islands Campaign. Records indicate that during the war munitions may have been buried there, but it isn’t known if those munitions were ever recovered.

“A burial site remediation could take several years and in a remote place like Fort Glenn, the costs really add up,” says Brent. “So if we can cut the processing time in half, that’s a huge savings.” Fort Glenn is just one of many suspected burial sites all over the country.

The core of EDS is a leak-tight vessel, in which munitions are placed. An explosive shaped charge opens the metal shell, exposing the chemical agent and burster, a small explosive that disperses the agent. The burster explodes or deflagrates safely inside the vessel. A reagent is then pumped into the chamber to neutralize the chemical agent. The chamber is heated and turned to mix the chemicals and facilitate the reaction.

Heating and cooling the vessel is the most time consuming part of the whole process. One of the biggest changes was a switch from heating the entire vessel from the outside in to pumping in steam to heat the vessel from the inside out. That reduced the heating time down from about 90 minutes to about 20 minutes, a total savings of more than two hours, since the vessel is heated in two stages.

“This was a significant change,” says Brent. “Commercial steam fittings usually allow a little leakage, which is not acceptable for our process. And the whole vessel rotates as the steam is injected, adding another layer of complexity. It’s more difficult to maintain the integrity of the seals with the big shifts in temperature that occur when the steam is turned on and off. So it took some time and work to develop fittings and valves that met our safety requirements.”

“Not all of the safety issues were intuitively obvious,” adds John. “The EDS is housed inside a vapor containment structure with a carbon filtration system that provides an extra layer of defense against an agent release. The filtration system does not like water, so we had to think about accident scenarios that might release steam into the building.”

Cooling the vessel rapidly posed another problem. The vessel can’t be opened until it has cooled to 60 degrees C, which used to take overnight. The researchers built an intermediate holding container, so the hot effluent can be drained as soon as the operation finishes. Cold water is then pumped into the vessel to accelerate cooling. Injecting steam actually made it easier to cool the vessel because the vessel walls don’t get as hot.

Testing at Aberdeen Proving Grounds

The researchers also changed the clamps on the door of the vessel. In the Phase 1 and Phase 2 EDS, the clamp on the door was attached to the trailer when the vessel door was opened. “As you closed the door, you had to disconnect the clamp from the trailer to allow the vessel to rotate during operation,” explains Brent. “The nuts on those clamps had to be tightened by hand.”

The Phase 2 vessel is about 3 feet in diameter and the clamps weigh about 1,500 pounds each. Tightening the clamps required nearly an hour’s worth of brute, physical work. The new design uses a clamp designed for undersea operations in the oil industry. Using a pneumatic wrench, the new door design can be closed in about five minutes.

Since February, the Army has been testing the P2P with live mustard agent at the Aberdeen Proving Ground in Maryland. The Sandia researchers are also working on additional modifications that will further reduce processing time and simplify the operation.

Before the vessel can be drained, liquid and gas samples must be collected and analyzed in a lab to confirm destruction of the agent. “We’re working on gas and liquid monitoring systems based on MicroChemLab technology that will take regular samples throughout the process to give continuous feedback,” says Brent. “Automating these two processes could save another two to three hours.”

The P2P performed well in the Aberdeen Proving Grounds tests earlier this year. The Army is now considering if it is better to retrofit the existing EDS units or create a Phase 3 system. Brent expects work on either option to start sometime next year.