Ground Zero

Energy Department scientists are working to perfect an immobilization system, which would store surplus plutonium in a form that makes it impossible for potential terrorists to use the material.

The first step is to mill the plutonium into a talc-like powder and use pressure to force it and a ceramic mixture into a puck that is 3.5 inches in diameter. A machine now under development would then remotely insert 20 pucks into a can; four of these cans would be inserted into a vertical rack, and seven of those racks would be placed into a stainless-steel, high-level-waste canister. The canister is 10 feet tall, 2 feet in diameter and three-eighths of an inch thick.

At that point, technicians would pour 4,000 pounds of molten glass, roughly 400 pounds of which is radioactive sludge, into the canister. Today's off-the-shelf sludge-the stuff that SRS technicians have been pouring into canisters roughly every other day since 1996-consists of uranium, plutonium and other fissionable products that came from previous bomb-building operations at SRS. Officials say the really radioactive stuff-cesium-won't be used until the Russian-U.S. program kicks off in 2008.

Some observers note a history of sludge-related technical problems at SRS, but they add that the puck-and-canister system seems to be in good shape. SRS engineers acknowledge that they are still working out the system's kinks, but they say that tests have been promising. Recently, after filling up a test canister with nonradioactive glass, Clyde R. Ward, an advisory robotics engineer from Westinghouse, and his colleagues tried to cut it open, to see how well the internal mechanics were working. "Just doing a cross section took several saws," Ward says. "First we used eight 10-foot, diamond-tipped saws, but that failed. Then we went to plan B-a company in Ohio that uses wire-cable saws. That worked, but the difficulty we had demonstrated another good antiproliferation feature."

Once the glass settles and cools, the nearly 3-ton canister is moved in an enormous, specialized vehicle that drives no more than three miles per hour to a long-term interim storage facility a couple hundred yards away. Although the structure above the facility doesn't look especially imposing, getting to the plutonium-filled canisters beneath will be none too easy. The canisters are laid upright into underground concrete vaults, then topped and sealed by a 4.5-foot-thick plug. The plug shields the radiation so effectively that a person standing on top of the vault gets only normal background levels, officials say. To foil earthquakes, the 2,286 vaults are seismically reinforced; to foil interlopers, the vaults are being filled with canisters in random order. They are then left unmarked, so that a visitor can't tell whether a vault is full or empty.