No one in their right mind would sell material to a client who seems mad enough to deploy it because they (the seller) can have no way of knowing where the buyer is planning to set it off; if they are enjoying their life in a major conurbation then there is a serious possibility that it will become the target.
As for any potential buyer, mad as they may be I just hope that they are not also ignorant: about the planet's prevailing winds running from west to east, for example. Wherever they live, the radioactivity will be coming their way. If not airborne, it will spread via the oceans. Their deity will not magically intervene to save them from its effects.
And, yes, the maddest thing about the concept of mutually assured destruction was the idea that shelters would deliver anyone safely back to a remotely habitable planet, where farming or fishing might still be viable.