I believe it is mostly about producing the right ratio of materials to either compress to create the explosion or to build a shotgun type device. The actual physical parts are probably beyond for a few years, but building a 5-8 pound nuclear device is probably possible.
No, I am not a nuclear physicist, just a guy who reads a lot of stuff. Most of it way beyond me...lol
There are limits for a fission device. The smallest you can do with plutonium (hottest) is about a 4” ball. With a fusion device, set off with lasers rather than a fission trigger..... interesting.
Very tiny H-bomb, almost no radiation to deal with.
Interesting.
I don’t believe a true nuke explosion device can be that miniaturized.
Implosion is method to reduce the amount of core material, but it uses shaped charges to get past sub critical mass reaction.
Dirty bombs? Yes.
True nuclear explosion, no.
Not going to happen.