'Failure in Nuclear Security': The Moldova Wake-Up Call

— -- Dramatic video released overnight shows what authorities say are the early stages of a nightmare scenario for the U.S.: Criminal gangs with access to nuclear material from Russia, prepared to sell to ISIS.

The videos, covering two raids conducted in Moldova in the last 10 months, show the plots as they were foiled by Moldovan authorities reportedly working with the FBI -- the latest in a series of troubling incidents involving some material that could be used in the construction of a deadly dirty bomb.

“It’s undeniable evidence of a failure in nuclear security. Material that was supposed to be under authorized control was found outside of it,” Will Tobey of Harvard’s Belfer Center for Science and International Affairs told ABC News.

As reported in an investigation by The Associated Press, ISIS never got close to the nuclear material in the Moldovan operations, and the buyers were really undercover agents. The amount of radioactive material sold was said to be small and of low quality.

Analysts and nuclear security observers told ABC News today that the threat from black market nuclear material has been relatively low-level but constant since the break-up of the Soviet Union, and has recently taken an even more challenging turn as the relationship between the U.S. and Russia has just about reached its nadir in terms of nuclear security.

Russia announced in November that it will not send diplomats to the 2016 Nuclear Security Summit in Washington, the first time the Russians have shunned the summit in years.

“The U.S. and, frankly, the Russian activities in this issue have been very significant over two decades,” Tobey told ABC News. “But unfortunately, the Russians have decided to end the cooperation, and it leaves us with very little opportunity to affect nuclear security in Russia.”

A list compiled by the Terrorism Research Initiative details more than 360 smuggling and security “incidents” in the Black Sea region from 1990 to 2011 -- by far the most stemming from Russia.

The former head of the U.S. National Counterterrorism Center, Matthew Olsen, said that if the Russians “aren’t helping, it makes the smuggling market that much more lucrative and that much harder to stop.”

“It’s very difficult to be confident we are stopping every one of these types of smuggling operations,” said Olsen, now an ABC News consultant.

Representatives for the Russian government at its embassy in Washington did not respond to request for comment today.

Several U.S. counter-terrorism officials downplayed the Moldovan busts – the most recent of which took place in December 2014 and February 2015 -- saying that the country’s security services were going public now to show they’ve been serious about cracking down on the black market for nuclear material in order to discourage smugglers.

The criminal gangs selling the material to buyers tried to drive up the price of the illicit material by claiming it was powerful and radioactive, and that there were competing buyers from a Middle Eastern terrorist group, a law enforcement official told ABC News.

"Our assessment was that the sellers were financially motivated not ideologically-driven," the official said, echoing comments by other counter-terrorism officials today.

Of the handful of Moldovan stings leading to arrests, the FBI was involved in the two cases they deemed most serious, officials said. In the case in February involving cesium, the sample sold to the undercover officers wasn't radioactive, as the sellers had claimed, officials said.

The FBI was "unable to determine" whether there were any criminal kingpins from large networks who got away and still have radioactive material, one official said, adding that those arrested may have been the only individuals directly involved.

“President Obama has made preventing nuclear terrorism one of the United States’ top foreign policy priorities, labeling it in his 2009 Prague speech 'the single most important threat' to U.S. national security," the White House National Security Council said in a statement. The statement referenced the 2016 Nuclear Security Summit “where global leaders will discuss the evolving threat of nuclear terrorism and highlight steps that can be taken together to counter nuclear smuggling and deter, detect and disrupt attempts at nuclear terrorism,” but did not mention Russia’s expected absence.

Olsen and other experts told ABC News today that while the threat of nuclear terrorism is very low relative to the day-to-day threats the U.S. faces, the consequences of an attack would be “catastrophic.”

“I worry about it every night,” said Sharon Squassoni, Director and Senior Fellow at the Center for Strategic and International Studies (CSIS) Proliferation Prevention Program. “You have to look at the consequence versus probability. If you look at the probability of a terrorist group either acquiring or putting together a full-up nuclear weapon, the probability is low. But the consequence is off the charts.”

Squassoni was specifically referring to a fully-formed nuclear device -- believed well beyond ISIS’s capabilities -- but said the math gets scarier for dirty bombs, which can use conventional explosives in combination with highly radioactive material.

“The probability of a terrorist organization getting its hands on radioactive material is much higher,” she told ABC News. “It doesn’t have the kind of catastrophic effect a nuclear detonation would have, but it is still something that we completely want to prevent a group like ISIS from getting... You could imagine an explosive device with radioactive material detonated in any American city – that’s truly a weapon of terror.”

ISIS rarely discusses even an interest in nuclear material -– outside of an admittedly “far-fetched” scenario when a British captive held by the group once purportedly ruminated about ISIS buying a nuke from Pakistan -– and top current and former U.S. counter-terrorism officials told ABC News other threats are more immediately concerning, such as ISIS’s reported possession of chemical weapons.

Olsen said that he suspects even a dirty bomb is likely beyond ISIS at this point, but it was hardly a reassuring thought.

“I think it’s clear that they have the resources, they have the money to buy and apparently there are circles of gangs in eastern Europe willing to sell,” he said. “The intention itself is quite concerning.”