The chances, that the Russians will throw a nuke at the Ukraine are pretty small. It would bring no benefit.
You are making the same mistake as all Western politicians. You are trying to think rationally. It's not applicable here.
Yes. I think rationally. Because I've read a lot about nuclear warfare. There are people in Japan even nowadays suffering from sicknesses after those two nukes thrown at hiroshima and nagasaki. I doubt that anyone, how stupid they may be, would launch a nuke near their own borders.
Thinking back of Tschernobyl: That radiation even reached western europe. Bavaria for example..
Launching a nuke would not only contaminate the Ukraine but also large parts of russia and europe. That would probably kick of a third world war. And if that's happening, well then we're all f***'ed..
I really try to keep calm on that subject. But... *sigh* It's hard to do that. Keeping my rationallity is probably my last resort not running around in panic...