I wonder if Russia would have invaded if Ukraine had nuclear weapons.
Pavlo Rizanenko, a member of the Ukrainian parliament told USA Today that Ukraine may have to arm themselves with their own nuclear weapons if the United States and other world leaders do not hold up their end of the agreement. He said "We gave up nuclear weapons because of this agreement. Now, there's a strong sentiment in Ukraine that we made a big mistake." He also said that, "In the future, no matter how the situation is resolved in Crimea, we need a much stronger Ukraine. If you have nuclear weapons, people don't invade you."
Ukraine operates 4 nuclear reactors and Soviet-era expertise on nuclear weapons is likely still present in the form of (retired) engineers and scientists, so they are likely able to develop it again.
This said, building a credible nuclear deterrence also requires at least one element of the nuclear triad, i.e. the capability to "deliver the gadget". In practical terms, more expertise to gain and more investments to do.
This is probably laughably unpractical, I just don't know why. Radiation? Maintenance? Just the fact that you can only use them, not threaten with them?
IMO this. The real reason of existence of nuclear weapons is deterrence, not actual retaliation. If you reach the point of nuclear retaliation, then you only get MAD (mutual assured destruction) and no one wins.
> For delivery, I've always wondered if it was possible to smuggle them in, say, by car. No need for a rocket or anything.
If you're interested on this possibility, a good movie I can recommend is "The Sum of All Fears" (2002).
Rent a warehouse or storage unit and just keep the nukes there.
The destruction on site is of course horrific, but far afield the concerns are fairly minimal, unless you’re actively trying to cause fallout.