WITH the dismantlement of thousands of nuclear weapons and the demilitarization of millions of conventional munitions, the Departments of Energy and Defense face the problem of disposing of large quantities of energetic materials, including high explosives, propellants, and pyrotechnics. Some energetic materials can be recycled and reused, but others must be destroyed. Open burning, open detonation, and incineration have been the most commonly used destruction methods. Although in some cases the traditional methods are still the best, the trend today is toward alternative destruction processes.|
A team at Lawrence Livermore National Laboratory, led by Ravi Upadhye, recently completed development of an environmentally friendly method for destroying these energetic materials from conventional and nuclear weapons. The process involves a crucible of molten salt in which the high explosives and propellants are reduced to carbon dioxide, nitrogen, and water. Depending upon the material being destroyed and the environmental regulations under which the user is operating, the gas by-product, or "off-gas," from the molten salt process may be sent through a cold trap or filter to remove small quantities of salt carried in the off-gas before it is released to the atmosphere. (See the photo and the diagram below.)
Livermore scientists have received two patents for their process and have two more patent applications pending. In 1995, the Northern California Section of the American Institute of Chemical Engineers named the team's molten salt destruction process their Project of the Year.
The Molten Salt Process
From R&D to Field Use|
The concept of using molten salt to destroy high explosives has been around for more than 20 years, but it took the end of the Cold War to prompt development of a usable system. In 1991, building on decades of experience with high explosives, Lawrence Livermore scientists began to do the chemical engineering necessary to take the molten salt method from theory to reality. They had at their disposal Livermore's state-of-the-art High-Explosives Applications Facility.
Livermore's initial laboratory-scale unit, with a capacity of 1 kilogram per hour (12,000 pounds per year), had a small side feeder and was used at first to destroy pure explosive powders. Then, a larger-diameter top injector was installed for feeding in real-world waste simulants such as machine shavings and sump sludge, including rust, metal parts, string, wood, sand, and floor sweepings. In every case, the waste simulants ran through the peristaltic pumps without clogging, and explosives were completely destroyed.
The 5-kilogram-per-hour unit was built in 1995 and has successfully completed a "shakedown run." In late 1996, it is scheduled to be dismantled and installed at Eglin Air Force Base in Florida for field demonstrations. Once the unit at Eglin is in full operation, it will be the first molten salt destruction system in the world that has proceeded past R&D and into field use.
Upadhye also noted, "Our process is safe, effective, and easy to use. We have built process controls and safety equipment into the system so that the unit can be operated after just minimal training." Ease of use is important because there is a huge job ahead--the Departments of Energy and Defense alone have hundreds of millions of pounds of energetic wastes to recycle or destroy.
Key Words: dismantlement, high explosives, incineration, molten salt destruction, open burning. open detonation.