WASHINGTON • On the day the Islamic State in Iraq and Syria (ISIS) overran the Iraqi city of Mosul in 2014, it laid claim to one of the greatest weapons bonanzas 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.
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 the militants 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, earlier 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.
Why ISIS failed to take advantage of its windfall is not clear. United States 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.
More certain is the fact that the danger has not entirely passed. With dozens of ISIS stragglers still loose in the city, US officials asked that details about the cobalt's current whereabouts not be revealed.
They also acknowledged that their worries extend far beyond Mosul. Similar equipment exists in hundreds of cities around the world, some of them in conflict zones.
The worries began within hours of the ISIS' stunning blitz into Iraq's second-largest city. As TV networks showed footage of triumphant terrorists parading through Mosul's main thoroughfares, intelligence agencies took quiet inventory of the vast array of military and material wealth the militants had suddenly acquired.
The list included three Iraqi military bases, each supplied with US-made weapons and vehicles. It also included bank vaults containing hundreds of millions of dollars in hard currency, as well as factories for making munitions and university laboratories for mixing chemicals used in explosives or as precursors for poison gas.
The Institute for Science and International Security, a non-profit group in Washington that monitors global nuclear threats, has obtained documents showing that two different medical centres in Mosul had obtained cobalt-60 machines in the 1980s. The institute quietly shared its findings with US intelligence and military officials in late 2015 but declined to publish its report, fearing that ISIS occupiers would benefit from the information.
The institute's president, Mr David Albright, noted that groups such as ISIS have long discussed the possibility of using such material in a dirty bomb, a simple device that uses conventional explosives to spread radioactive debris across densely populated urban terrain.
Such a bomb would probably not cause large numbers of casualties, but it can be enormously effective, he said, as a weapon of terrorism.
WASHINGTON POST
