&gt; 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>My understanding is that dirty bombs don&#x27;t even necessarily undergo any nuclear reaction. You don&#x27;t even need the right kind of material for them. It&#x27;s just a traditional bomb with radioactive material strapped to it.