This seemed like a interesting WI. Of course, there is a degree as to which you could compact a Nuclear weapon, so a 9mm nuke is something that belongs in the world of fantasy, but what about a nuclear .50 round or a Nuclear 20mm round. Of course, the cost of such as bullet would be a few hundred pounds a bullet for the Nuclear material, and the safe assembly of such a complex weapon, which would require high levels of skill to do. However, it does have several uses: A special forces teams with a few of these in wartime could use them as bunker busting weapon, or ground support aircraft could fire a few at a coluom of enemy tanks, and destroy them, as well as making a dangerous nuclear area.
What do others think?