After the euphoric ring of sledgehammer blows on the Berlin Wall echoed away in 1989 and diplomats from the West and the collapsing Soviet Union signed agreements trimming nuclear arsenals, physicists and engineers east and west were left with the daunting task of shifting production smoothly from forward to reverse.

A major challenge was dealing with the bits and pieces left when nuclear weapons were retired and taken apart. Production had occurred steadily over four decades, but suddenly that routine had to be changed as thousands of US weapons were scheduled for dismantlement and began to flow back to the Pantex plant near Amarillo, Texas.

The volume of material was the major issue to be dealt with, but of concern as well was the speed with which some very delicate operations had to be accomplished. Sandia's robotics group began looking for safe ways to handle pits, gas generators, and other components faster than people could, and those robotic work cells designed for specific operations are now at Pantex - two in production use and one in the installation and approval process.

The already installed Automated Gas Generator Disassembly System (AGGDIS) was successfully demonstrated at Pantex last month and project team members began work two days later tearing down the Weighing and Leak Check System (WALS) equipment in the Albuquerque lab for shipment to Pantex. It will be installed and integrated into the plant's operation, operational procedures will be developed this summer, it will be evaluated by the end of the year, and it should be operational by next summer.

The robotics staff and Pantex engineers did an outstanding job implementing three projects that comprise a significant change in the older processes, says Al Jones, manager of Sandia's Manufacturing Systems Department.

Gas generators require delicacy
Gas generators, roughly the size and shape of small cans of frozen orange juice concentrate, contain explosive powder which, when detonated, deploys the parachute in a laydown bomb. Disarming and dismantling them is not heavy work, "but they're old so the binder in the powder is degraded and handling them may be a little dicey," says Jones. "You want to keep people out of the operation, if possible."

He says the team got a lot of help from Vince Loyola of the Explosive Subsystems and Materials Department, "who suggested the project and provided technical guidance to see it through."

The generators' igniters are more explosive than the powder charges, he says, and several thousand of these devices must be dealt with. Even though they are small, they contain a number of components and must be handled according to very specific procedures.

AGGDIS picks up the generator, inserts it into a stationary socket, and turns it to unscrew the part that locks it closed. It then pours the powder into a container and in a series of operations, uses a brush and puff of air to clean out residue, removes the igniter, deposits various parts in individual containers, and moves on to the next generator.

"Experience says a person could average about one a day," Jones says. "Our robot did three the first afternoon and we think it can do about 24 a day when it's in full production - about three an hour during an eight-hour shift."

It doesn't have to stop for breaks or meals, he points out with a slight smile. Intelligent Systems and Robotics Center Director Pat Eicker says the AGGDIS system now operational at Pantex is a "proof of concept" for other customers. He says Sandia is working with the Department of Defense to develop similar technology for the dismantlement of conventional and chemical munitions.

WALS relieves people of the radiation exposure from removing pits from storage containers, checking their weight and the integrity of their casings, then returning them to the containers. The exposure is slight and is monitored, but it is accumulative so people can spend only specific amounts of time performing such work. There is no such sensitivity for robots. WALS is able to adjust its grippers and other movements to handle the seven kinds of pits and four kinds of containers it will encounter in its work, Jones says.

Already busy at Pantex for a year, Stage Right began as a standard forklift vehicle. Sandia engineers added sensors and controls that allow an operator to manipulate it from a remote location to move pallets of pit containers into and out of storage facilities, relieving people of the necessity to absorb even minimal radiation exposures.

All three systems - AGGDIS, WALS, and Stage Right - were designed as integral to the agility of Pantex's new Special Nuclear Material Consolidated Storage Facility, expected to become operational in May 1998. It will incorporate all three robotic functions in a single building, which is part of the plan to make Pantex significantly smaller within the next five years, says Jones.

Sandia is a multiprogram Department of Energy laboratory operated by a subsidiary of Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has broad-based research and development programs contributing to national security, energy and environmental technologies, and economic competitiveness.