SOKHUMI, Abkhazia - It's the stuff from which nightmares are made.
Ignoring the ominous graffiti scrawled on the rusting steel doors - "Radiation! Danger!! Stop! Cancer!" - three men broke into a masonry bungalow at a medical research institute here in May 2002. They fished seven lead-lined capsules out of a containment pool.
The thieves took the containers, shaped like coffee cans, back to a garage, stripped the lead out of at least one, and planned to melt down the metal to make shotgun pellets.
But these were not ordinary canisters. Lerry Meskhi, head of nuclear and radiation safety for the former Soviet republic of Georgia, said they contained a small but potent amount of cesium 137, emitting about 33,000 curies of radioactivity - enough to cause radiation sickness or death.
The three thieves quickly fell ill. Abkhazia's de-facto government - rebels who led a successful revolt against Georgia in 1993 - had the cesium moved to the ruins of a nearby physics institute for safer storage.
But the danger posed by this deadly cache, and thousands of others like it scattered through the former Soviet empire, has by no means disappeared.
When the Soviet Union and its satellite regimes collapsed, Cold War fears of mutual annihilation were replaced by fears that Soviet-era stockpiles of plutonium and highly enriched uranium could, through bribery or theft, fall into the hands of rogue states or terrorists.
But those fears now extend to relatively common radioactive materials, including those used in medical research, agriculture and navigation devices.
Cesium 137 and these other common materials can't detonate. But an ounce or so - the weight matters less than the level of radioactivity, measured in curies - could be used to make a "dirty bomb," a conventional high-explosive salted with radioactive matter.
Such a device would have no more explosive power than a conventional bomb. But it would spread a cloud of radioactive particles that could cause additional injuries or deaths. It would certainly trigger panic.
A recent study by the U.S. National Defense University in Washington, D.C., estimated that the cleanup after detonation of one large device in Lower Manhattan would cost $40 billion.
No one has ever used a dirty bomb. But after the defeat of the Taliban in Afghanistan, U.S. troops scouring caves used by al-Qaida discovered the blueprints for one. Justice Department officials said in June 2002 that they had foiled a plot to use such a device in a major American city.
The radioactive ingredients for a dirty bomb can be found in just about every country in the world. But nowhere, it seems, are more of them kept under poor security than in the former Soviet Union.
And probably nowhere in the wreckage of the U.S.S.R. is the material less secure than in Abkhazia and other rebel-controlled bits of post-Soviet states where corruption is endemic, the rule of law weak and smuggling a mainstay of the economy.
If the three Abkhazian thieves had known what they had, they might have tried to smuggle the cesium to Turkey with a shipload of lumber. Or tried to carry it in a car through Georgia and south toward Iran.
In recent years, hunters and farmers in Georgia have stumbled on radioactive devices scattered through the countryside. They have used the hot cores to make hot water or keep them warm while camping in the mountains. This month, the Georgian government said it had found tiny amounts of cesium 137 at 30 gasoline stations across the country, used to measure the level of gas in tanks.
Abkhazia is a breakaway part of Georgia where separatists routed government troops in the fall of 1993, after a civil war that killed 10,000 people.
Today Abkhazia is one of four ethnic enclaves - the others are Chechnya, Nagorno-Karabakh and Trans-Dniester - to claim independence. Most have become havens for smugglers and criminal groups.
With its palm-fringed beaches, orange groves and sunny Mediterranean climate, Abkhazia seems like a dreamy refuge from the world of war and terrorist threats. That appearance masks a different reality.
The country is carved up among four criminal gangs who smuggle everything from timber and hazelnuts to hashish and stolen cars, according to a draft report by American University's Transnational Crime and Corruption Center. Kidnapping and assassination are common. Police are ineffective.
"The distinction among official security and police forces, criminals [and] various armed formations is totally blurred," the report says.
During the war, the medical research institute in Sokhumi was ransacked. But its radioactive cesium, used in leukemia research, was untouched.
Theft and recovery
The institute's director, Sergei K. Ardzinba, resisted foreign pressure to move the material to a more secure storage site. He hoped, he said in a recent interview, to resume radiological experiments one day.
After the theft and recovery of the cesium in May 2002, Ardzinba relinquished the material. The rebel government moved it to a vault at a former nuclear weapons lab called the Sokhumi Institute of Physics and Technology. There, it was stored with about 240 other samples of radioactive material.
Unfortunately, the Sokhumi physics institute has a poor record of protecting nuclear materials. According to Western experts, in spring 1993 it held between 1.4 and 4.4 pounds of highly enriched uranium, suitable for a nuclear bomb. Sometime after that, nonproliferation experts say, the uranium vanished.
Since the fall of the Soviet Union, there have been at least 18 reports of stolen plutonium or highly enriched uranium. But the theft in Sokhumi is unique.
"It represents, to the best of my knowledge, the only confirmed instance of missing or diverted highly enriched uranium or plutonium that was not recovered," said William Potter, a nonproliferation scholar with the Monterey Institute of International Studies in California.
For several years after the war with Georgia, Abkhaz officials barred international inspectors from visiting the physics institute. Experts with Russia's atomic energy agency, Minatom, finally gained access in December 1997. They found most buildings vacant. Any highly enriched uranium was gone.
Abkhazian officials insist they haven't lost any nuclear bomb materials. Anatolia I. Markolia, director of Sokhumi's physics institute, says he has no evidence the facility ever had highly enriched uranium. "Nothing went missing during the war," he said.
But most foreign experts believe otherwise. Valter G. Kashia, a former researcher at the institute, said in an interview he personally used 655 grams - 1.4 pounds - of highly enriched uranium at the institute to test designs of nuclear-powered electric generators for spacecraft. Kashia fled Abkhazia in 1992 and now lives in exile in Tbilisi, the Georgian capital.
Abkhazia's security chief turned down requests to visit the Sokhumi physics institute and see the vault where the radioactive materials are held.
Lack of security
Nonproliferation experts say they think cesium 137 from the medical research center is still safely stored there. But some still worry about what might happen to the material.
"Even if [radioactive material] is under lock and key and guarded, how reliable is that under the Abkhaz regime?" asked Scott Parish, a proliferation researcher at the Monterey Institute, who has been to Abkhazia.
Vilmos Friedrich, an official with the International Atomic Energy Agency in Vienna, helps run that agency's program to clean up radioactive materials in the former Soviet Union. Among the most troublesome regions for regulators, he said, are those where central governments have little or no control.
"Of course, where the political structure is not well established, where smuggling and illicit trafficking of any kind of materials is going on, there is much higher probability that this illicit activity also includes radioactivity," he said.
Georgian authorities have caught several people attempting to smuggle materials that might be used in a dirty bomb. Last May, a taxi driver was caught headed for Tbilisi's main railroad station carrying a trunk loaded with containers of highly radioactive cesium 137 and strontium 90.
A month later, an Armenian man was arrested in a border town, on his way south to the Armenian capital, Yerevan. American-supplied radioactivity detectors set up at the roadside sounded an alarm, and border guards discovered a 4.4-pound disc of uranium hidden a shopping bag filled with tea.
Lt. Gen. Valeri Chkheidze, chief of the Georgian border guards, said Abkhazia's long coastline on the Black Sea makes it difficult to control what goes in and what comes out.
"Contraband is widespread," he said. "Drugs are being trafficked. Where there is no control, it is easy to smuggle radioactive materials as well."