Large boxes of powdered Caesium 137, a powerfully radioactive substance that can be used to make dirty bombs, have been lost in the former Soviet Union. Unlike the solid Strontium-90 used in nuclear power plants that has been misplaced in Russia in the recent past, the Caesium was powdered, so it would be easy to pack into a dirty bomb.

Russian sources originally claimed that the Caesium was spread on fields in secret Soviet agricultural experiments, but Melissa Fleming, spokesperson for the International Atomic Energy Agency in Vienna, says this isn?t true. That would have caused vast tracts of farmland to become contaminated, and probably considerable human exposure as well. The ceasium was in fact kept inside shielded boxes, and used as a source of gamma rays to irradiate grain, to keep it from germinating in storage, says Abel Gonzales, director of radiation and waste safety at the IAEA. The gamma rays were also used to induce mutations in seeds, which was a common method for generating improved crop varieties.

Because the Caesium was used only as a source of radiation, it hasn?t self-destructed and is out there somewhere. It has a half-life of 32 years, so most of it is still very radioactive. “We have no idea how many of these (Caesium) sources there are,” says Gonzales.

Each shielded box contained 3,500 Curies of Caesium. “That is very, very big,” says Gonzales. By comparison, a Caesium source containing only a few hundred Curies, lost from a hospital in Goiania, Brazil in 1987, killed four people immediately and exposed dozens many more to heavy doses of radiation.

Besides Stronium 90 and Caesium, radioactive uranium is missing in Russia as well. Recently, Russian police and the Federal Security Service seized two kilograms of uranium that were found in a car in central Russia. They also discovered a fragment of a combustible bar used in nuclear reactors inside the car, which was found in the Russian town of Izhevsk.

In light of the above, it?s a relief to hear that Russia, the U.S. and the International Atomic Energy Agency in Vienna have agreed to mount a joint search for “lost” radioactive material throughout the former Soviet Union. In the next few weeks, experts will fan out across central Asia, trying to find scattered quantities of Cesium-137, Strontium-90 and other dirty bomb ingredients before the terrorists do.

“After September 11, we started looking at where terrorists might get the material for a dirty bomb,” says Jack Caravelli of the U.S. Department of Energy. “Then we realized how many sources of radioactive material there are out there.”

Now the hunt is underway for 100 abandoned Strontium-powered thermal generators scattered along arctic waterways and flight paths. They originally powered lighthouses and radio navigation beacons, and each contains up to 40,000 Curies of radioactivity.

Georgia alone had eight of these batteries. Four were found on military bases in 1997, and two more were found abandoned in woodland in February (the men who found them are still under medical care). A search has just been started for the remaining two. 280 other radioactive sources have also turned up in Georgia.

Russian and U.S. experts will start by searching old Soviet records and sending teams to talk to regional authorities, most of whom are extremely anxious to get rid of the material, if they could only figure out where it is.

Wonder what else they?re not telling us? Read ?Into the Buzzsaw? by Kristina Borjesson, click here.

To learn about the missing caesium, click here. To learn about the discovered uranium, click here.

To learn about the search for other missing radioactive materials,click here.

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