If you need something to worry about, here it is.
futurescience.com
futurescience.com
What if you try it and don't accomplish more than force a electrical grid "reboot"? Better hope we can't figure out from the isotope mix way way up there where it came from.
That's one of the big dangers from doing it in the atmosphere, you're leaving a "this bomb built here from that design and this source of fissionables". If you're smuggling it in, it's because you're not a big nation state. You won't enjoy the wrath of your target....