There's little doubt that given sufficient materials and funding such a device can be built, particularly given Kydaffi's previous attempts at doing so. Better questions would be directed as to how compact such a device can be built, and how *leaky* and otherwise susceptable to detection methods it might be.
See the Paräparat neutron trigger details of the *Virus House* device described in post #9, above....
As the bomb sphere drives itself down onto the armored nose cap, a plunger crushes the "Paräparat", and neutrons spray into the mass of uranium...
About the size of a washing machine.
Neutron triggering could get you up to 80 Ktons.
Of course, if you were really smart, yield is limited only by your imagination. You simply, oh, nevermind, loose lips and all that.
Given the fact the world is awash in U-235, anthrax , smallpox , and god-knows what else, we had better hope that our enemy is dumber than our intelligence agencies.
Of course, in the future, I expect WMD will become democratized like every weapons technology before it.
We are going to have an extremely polite society or an extremely dead one.