The one thing going in the would-be nuclear terrorists favor is that nuclear weapons have a lot of “slack” built into their design. IE, they can be ridiculously “inefficient” and still be devastating. Even a rough-implosion sub-kiloton warhead is still a much hotter, radioactive version of this:

But that’s it. Everything else works against them. There’s a lot of attention paid to nuclear material ever since the 1940s for obvious reasons. The materials require specialized personnel and are hazardous (radiation is the least of the worries-both uranium and plutonium are extremely flammable, for one). I used the analogy of Y2K in my review of the best book on the subject that I’ve read.

While reading Brian Michael Jenkins’ own book, one passage jumped at me. This was Jenkins, a renowned terrorism and security expert, talking about how the yields increased.

We have too easily slid from the scientists’ first estimates of terrorist nuclear devices with yields likely to be in the tenths of a kiloton range to a now-assumed standard of a ten-kiloton terrorist bomb. The worst case has become the baseline assessment.

-Brian Michael Jenkins. Will Terrorists Go Nuclear? (Kindle Locations 3611-3612). Kindle Edition.

And yet, both seem valid. Ten kilotons is slightly less than Little Boy, an extremely simple “bang two chunks of HEU together” design whose biggest limiter is that it requires a lot of fissile material. Less than a kiloton is what’s often theorized for a very basic implosion design, necessary with plutonium as the explosive material. Since in the 1970s there was justified fear around the glut of plutonium, that is not an unreasonable assumption. Likewise, it’s also not unreasonable to assume that with access to Little Boy levels of material (Cold War “Surplus”?) one could make a Little Boy level bomb.

There are no real case studies to go on. Aum Shinrikyo conducted the only known and most credible attempt to acquire nuclear weapons by a terror group. It never got beyond basic theoretical designs, as has every other terror daydream. With a (thankful) sample size of zero, all planners can do is base the possibilities on theory.