I&#x27;d imagine that building a proper bomb, i.e. large and efficient one, is quite hard --- the geometry and timing of the implosion charges is complex, fiddly, and difficult to get right the first time.<p>However, building something which squibs, i.e. undergoes a partial criticality and goes bang in a reasonably large but not city-killing way, and spreading a bunch of radioactive material about, is probably much easier. (This is the &#x27;dirty bomb&#x27; thing that was getting the press excited a couple of years back.)<p>(Fun fact: if you&#x27;re locked in a room with a nuke on a timer, your best option is probably to beat the shit out of it with an axe. Provided you can physically damage it enough to upset the implosion geometry, it won&#x27;t go off properly. Of course, <i>you&#x27;ll</i> still die, but...)