Everyone is in an anti-nuke PANIC MODE! Quit worrying!
My dad worked on the PROJECT GNOME back around 1961. When that nuke was set off, it blew some radiation out the shaft to the surface and containment barriers were quickly set up.
In just a very short time the radioactivity had decayed to where it was safe to go into the blast area and go into the mine.
Gnome was a cool test.