Message:When I ran the calculation in college, I found it took about eighty pounds of fissionable matter like 235 to reach critical mass. Less and it slowly just decays. 238 is pretty much crap. Pluto-stuff is dealy poison and hard to work with. So eighty pounds from tons and tons of rocks spun in a centrifuge. You'd still need to implode that U mass and that's extra weight and know-how (exceeds most except nation states).
Fiction is a suitcase bomb. Reality is a carbomb w/ nuclear material. Either obtaining fission or spreading poison. Five miles of go away or five miles of coughing slow death.
Backpack power plant is actually easier. We send them into space as permanent reactors on explorers. Any amount of matter can be made into a DC source. The casing determines voltage, not the amount. Amount determines battery life. Five pounds probably powers Most for a century+. Heat source in middle (fission decay) produces current through thermocouples. Just need mass at center and dissimilar metals around the core and on the outside. The whole produces a potential.
I no longer own the textbook with the equations, but there is an interwebs.
All for post apocalyptic gaming (of course). My mad scientist days were...well never. Life is good, long. Work while you'er strong and young. Game until your eyes and ears fail. Switching focus, I have no patience for people that leapt at the life of Logan's Run, did nothing but party in their twenties. Then by mid thirties left with no skills and tired. That parasite sleeps on the streets of LA, cause it never gets freezing cold here. There they lie, all day, complaining they are no longer twenty-five and feeling invincible. At thirty they should have RENEWED, but they became runners. Where are the Sandmen?
But said for game purposes of course. Maybe I'll find those equations on the interwebs? Kidding.
Yours,
IronRed
17-Jan-2021