In a nutshell it’s easier to achieve critical mass with a larger mass.
***True enough. One could build essentially a nuke truck bomb. And the Ukes have some very radioactive soil at Chernobyl they could just pile into some of their missiles & fire at Russian ammo dumps.
Russia does not believe in self total destruction.
The very notion of introducing nukes is off the table. Why nuke Ukraine, enrage the world and then die a quick and horrible death.
Nukes ain’t gonna happen i
Putin is nuke rattling same as Kim Jung Un.