We’ve established that it’s trivial to construct a dirty bomb, if you can gather together enough nuclear material. We can also assume, quite easily, that ISIS/ISIL really, really, really wants to obtain a dirty bomb and set it off somewhere. Anywhere will do. Nothing else strikes more terror into the heart of the public at large, never mind the actual facts – the majority of people still won’t drive within a mile of Three Mile Island, even though that accident released less radiation than a typical coal-fired power plant does on an average day.
Therefore, we can safely conclude that obtaining a large amount of radioactive material for a dirty bomb must be really, really hard to do. Part of the problem is that nuclear debris leaves a signature that can be traced back to its source. North Korea may be pleased as punch to aid ISIS/ISIL in nuking a small part of the planet, but they’re not so keen on getting blamed for it. Same goes for China, Pakistan, India and Russia. (The ex-Soviet states have mostly relinquished their stockpiles of weapons-grade uranium, though piles of it show up in broom closets now and again…) There’s also geography at play – Syria and N.Korea are thousands of miles apart, so how’s the material gonna get there? Send it via FedEx?
Now, it’s always possible that a lone nuclear tech somewhere with an axe to grind may co-operate with ISIS by sneaking out some glowy stuff – but that also comes with problems. First, no matter which country they’re in, these guys are watched like a hawk. So you’d need a conspiracy of two or more people, probably lots more, to defeat security measures. Then there’s getting in contact with the right people – radical Muslim fanatics and educated nuclear technicians don’t travel in the same circles, and this kind of job isn’t something you would advertise on Craigslist.
And what if they get caught? Delivering black market glowy stuff to terrorists is the worst form of treason imaginable, they would be treated worse than Jared Fogle in prison. Of course, the Russians and Chinese probably wouldn’t let him get that far – heck, even in America, such a problem might be “dealt with” by arranging a Karen Silkwood-style car accident. Or maybe by arranging a more elegant solution such as accusing them of cheating on a test, or something like that – I dunno, who knows.
But it goes without saying that in the fullness of time, somebody somewhere someday will set off a dirty bomb, or worse. I’m frankly amazed that it hasn’t happened yet – the CIA/GRU/MI6 must be putting in a ton of overtime these days.