The Department of Energy (DOE) has reactivated a Cold War technology called sticky foam to tighten security at sites that store bomb-grade processed uranium and plutonium.

Sticky foam is a hydrocarbon solution held in pressurized containers built into steel doors. Should attackers attempt to break through a sticky foam door, they will rupture the container and expose the solution to air. Air transforms the liquid solution into a solid, and the sticky foam explodes out of the door, expanding by a 40-to-1 ratio. “It has a very sticky consistency, gets all over attackers, and slows them down dramatically,” says Ronald E. Timm, president of RETA Security, Lemont, Ill. Primarily a consulting firm, RETA Security manufactures and installs doors and other barriers containing sticky foam under a technology transfer agreement with Sandia National Laboratories.

Security tacticians call sticky foam a force multiplier that delays attackers, gives defenders a better chance in a fight, and allows time for reinforcements to arrive and mount a counterattack. “Sticky foam provides an extremely long time delay that can be crucial in terms of responding to an attack,” says Gary Batte, a security analyst with Argonne National Laboratory in Idaho Falls, Idaho.

Threat estimates conducted after the Sept. 11 attacks led the DOE to determine that storage sites for nuclear materials might have to deal with larger numbers of attackers than existing defensive plans anticipated. But budgets have not permitted the deployment of more security people.

An alternative to more people is a force multiplying and delaying technology such as sticky foam. Developed in the 1980s by Sandia Laboratories, sticky foam was originally designed to protect sites storing nuclear materials. “After the Cold War, it just fell off the map,” Timm says.

Terrorism has led to a comeback for sticky foam. The DOE has installed the technology at several sites, although neither Timm nor Batte will say how many or where. Timm also believes that the Nuclear Regulatory Commission (NRC), U.S. embassies and other facilities guarded by small defending forces may find the material useful.

To prove the capabilities of sticky foam for a variety of facilities, RETA and Argonne recently conducted a series of tests with the material. “We attacked sticky foam barriers with platter charges, shaped charges and ballistic means,” Timm says.

In the first test, RETA attached 40 pounds of C4 explosives to a large, heavy metal disk, called a platter charge. The disk was then fired at a Class 5 vault door at a range of 100 feet. Moving at 6,000 feet per second, the platter charge blew a hole the size of the disk through the door. “The sticky foam instantly deployed on both sides of the door,” Timm says. “We never lost the barrier.”

Another charge of C4 was set around the frame of a vault door. Such a shape charge, as it is called, doesn't explode, but it will burn large holes in barriers. In this case, the charge cut a hole that was instantly refilled with sticky foam.

For the ballistics test, an M-16 rifle was used to shoot a hole in a door. The sticky foam expanded to fill a hallway on each side of the door. This test was designed to test the intentional deployment of the material by a defender. “If you're on the high security side of a door and attackers are attempting to break through, you can use your weapon to shoot the door,” Timm says. “The sticky foam will deploy, delay the attackers, and give you time to call for help.”

According to Batte, use by a defender is unique to sticky foam. “There are competitive technologies,” he says. “Some manufacturers have developed doors designed with coiled springs inside of a hollow door. When you poke a hole through this kind of door, the springs close up the opening. We've found that this technology works against platter charges and shape charges. But you can't initiate the metal springs with a rifle shot.”

A report describing these tests and their results in detail is available from RETA Security, at