How Isis nearly had ‘dirty bomb'

A key element for a devastating weapon was missing in Mosul

On the day Isis overran the Iraqi city of Mosul in 2014, it laid claim to one of the greatest weapons bonanzas ever to fall to a terrorist group: a large metropolis dotted with military bases and garrisons stocked with guns, bombs, rockets and even battle tanks.

But the most fearsome weapon in Mosul on that day was never used by the terrorists. Only now is it becoming clear what happened to it.

Locked away in a storage room on a Mosul college campus were two caches of cobalt-60, a metallic substance with lethally high levels of radiation. When contained within the heavy shielding of a radiotherapy machine, cobalt-60 is used to kill cancer cells. In terrorists’ hands, it is the core ingredient of a “dirty bomb,” a weapon that could be used to spread radiation and panic.

Western intelligence agencies were aware of the cobalt and watched anxiously for three years for signs that the militants might try to use it. Those concerns intensified in late 2014 when Isis (Islamic State) officials boasted of obtaining radioactive material, and again early last year when the terrorists took over laboratories at the same Mosul college campus with the apparent aim of building new kinds of weapons.

In Washington, independent nuclear experts drafted papers and ran calculations about the potency of the cobalt and the extent of the damage it could do. The details were kept under wraps on the chance that Mosul’s occupiers might not be fully aware of what they had.

Iraqi military commanders were apprised of the potential threat as they battled Isis fighters block by block through the sprawling complex where the cobalt was last seen. Finally, this year, government officials entered the bullet-pocked campus building and peered into the storage room where the cobalt machines were kept.

They were still there, exactly as they were when Isis seized the campus in 2014. The cobalt apparently had never been touched. “They are not that smart,” a relieved Health Ministry official said.

Why Isis failed to take advantage of their windfall is not clear. US officials and nuclear experts speculate that the terrorists may have been stymied by a practical concern: how to dismantle the machines’ thick cladding without exposing themselves to a burst of deadly radiation.

US officials acknowledged that their worries extend far beyond Mosul. Similar equipment exists in hundreds of cities around the world. “Nearly every country in the world either has them, or is a transit country” through which high-level radiological equipment passes, said Andrew Bieniawski, a vicepresident for the Nuclear Threat Initiative.

Because cobalt-60 decays over time, the potency of the Mosul machines’ 30-year-old cobalt cores would have been far less than when the equipment was new, but still enough to deliver a lethal dose at close range.

David Albright, president of the Institute for Science and International Security, said: “The worst case would have been [Isis] widely dispersing the radioactive cobalt in a city, causing panic and an expensive, disruptive cleanup. There would likely not have been that many deaths.”

Iraqi officials said that both machines had been placed out of commission for several years because of a lack of parts and had been put in storage in a building owned by the University of Mosul, in the city's eastern side. The machines are now in secure storage, a health official said.