Last I heard, we had them as small as 10T and 20t, variables you can adjust to requirements.
You want to be at least a quarter mile away for the small ones.
Well radiation detectors in the short term, and two-headed rodents in the longer term
400 yards danger close for 10kt? Nooooo thanks. A rule of thumb for standing in the open is about a yard per pound.
We had “ dial a nuke “ tactical weapons when I was in the AF in the 80s. Variable yield.
We used to practice a “nuke lay down “ delivery where we came screaming in at 600kts at treetop and would drop a drougue retarded bomb on a 45 second delay to give us time to exit the blast area. For hardened command bunkers.