On Wednesday, the Associated Press published a horrifying report about criminal networks in the former Soviet Union trying to sell “radioactive material to Middle Eastern extremists.” At the center of these cases, of which the AP learned of four in the past five years, was a “thriving black market in nuclear materials” in a “tiny and impoverished Eastern European country”: Moldova.

It’s a new iteration of an old problem with a familiar geography. The breakup of the Soviet Union left a superpower’s worth of nuclear weapons scattered across several countries without a superpower’s capacity to keep track of them. When Harvard’s Graham Allison flagged this problem in 1996, he wrote that the collapse of Russia’s “command-and-control society” left nothing secure. To wit:

The Russian nuclear weapons archipelago includes hundreds of sites over one-seventh of the Earth’s land mass, sites at which 1,000 tons of highly enriched uranium, 100 tons of plutonium and some 30,000 nuclear warheads are at risk.

Specifically, as described in Foreign Policy by the journalist Douglas Birch:

Russia inherited [the Soviet Union’s] vast stores of nuclear, chemical, and biological weapons. And they were a mess. Western visitors to weapons depots and labs were shocked to find AWOL guards, broken fences and unlocked doors. Two million nerve gas shells were discovered sitting in rotting barns in a patch of forest in western Siberia.

In the intervening years, the United States has spent billions to help Russia upgrade its nuclear facilities and improve security, helping decommission or destroy thousands of nuclear warheads until that cooperation ended in late 2014. But nuclear materials remain accessible, and certain estimates about their prevalence are classified. While it would be hard to steal a nuclear warhead, radioactive components for a “dirty bomb” are significantly easier to obtain and transport. Radiation sickness isn’t necessarily a deterrent for a suicide bomber.

Because the AP’s investigation focused on sting operations by the FBI and Moldovan authorities, in which undercover informants broke up transactions they themselves may have played a role in initiating, the report left open questions about the real likelihood of terrorists obtaining large quantities of nuclear materials. “[I]n most of the operations arrests were made after samples of nuclear material had been obtained rather than the larger quantities,” the AP wrote. “That means that if smugglers did have access to the bulk of material they offered, it remains in criminal hands.”

Alternatively, it’s in nobody’s hands. In a case from February, for example, a smuggler tried convince a representative of ISIS to buy enough cesium 137 to, in the AP’s words, “contaminate several city blocks.” (Cesium is not one of the key elements used to make nuclear weapons; rather, it has medical and industrial applications.) Only the ISIS representative was actually an undercover informant, and “investigators said the one vial [of cesium] they ultimately recovered was a less radioactive form of cesium than the smugglers originally had advertised, and not suitable for making a dirty bomb.” On the other hand, in a 2011 case, an informant was able to buy highly enriched uranium in a “green sack” from out of a Lexus parked near a circus in Moldova’s capital. The AP reported that tests revealed it “was high-grade material that could be used in a nuclear bomb.”

More disturbing than the revelations are the unknowns:

Moldovan investigators can’t be sure that the suspects who fled didn’t hold on to the bulk of the nuclear materials. Nor do they know whether the groups, which are pursuing buyers who are enemies of the West, may have succeeded in selling deadly nuclear material to extremists at a time when the Islamic State has made clear its ambition to use weapons of mass destruction.

Reports such as these surface periodically from the former Soviet Union and Pakistan and, perhaps because the implications are too terrible to think about and the solutions are too hard to find, they fade more quickly than their severity warrants. The underlying issues are largely the same as they were 20 years ago: The black market exists because there’s a supply of the material and a demand for it. As one Moldovan investigator told the AP: “As long as the smugglers think they can make big money without getting caught, they will keep doing it.”